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Sample records for visible light sensitive

  1. Development of Visible Light-Responsive Sensitized Photocatalysts

    Directory of Open Access Journals (Sweden)

    Donghua Pei

    2012-01-01

    Full Text Available The paper presents a review of studies about the visible-light-promoted photodegradation of the contaminants and energy conversion with sensitized photocatalysts. Herein we studied mechanism, physical properties, and synergism effect of the sensitized photocatalysts as well as the method for enhancing the photosensitized effect. According to the reported studies in the literature, inorganic sensitizers, organic dyes, and coordination metal complexes were very effective sensitizers that were studied mostly, of which organic dyes photosensitization is the most widely studied modified method. Photosensitization is an important way to extend the excitation wavelength to the visible range, and therefore sensitized photocatalysts play an important role in the development of visible light-responsive photocatalysts for future industrialized applications. This paper mainly describes the types, modification, photocatalytic performance, application, and the developments of photosensitization for environmental application.

  2. Mechanochemical Synthesis of Visible Light Sensitive Titanium Dioxide Photocatalyst

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    Jan Šubrt

    2011-01-01

    Full Text Available Phase transition of anatase nanoparticles into the phases TiO2-II and rutile under grinding was studied. The addition of ammonium carbamate to the reaction mixture inhibits the phase conversion and the cold welding of particles. The UV-visible absorption spectrum showed narrowing the band gap width after grinding with an ammonium carbamate additive resulting in shift of the light absorption of the ground sample towards the visible region. By EPR, intensive formation of OH• radical at irradiation of the sample with both UV (λ > 300 nm and visible (λ > 435 nm light was observed. High photocatalytic activity of the ground sample in visible light region was demonstrated also by measurement of kinetics of the photocatalytic decomposition of 4-chlorophenol.

  3. Preparation of sensitized ZnS and its photocatalytic activity under visible light irradiation

    International Nuclear Information System (INIS)

    Zhang Haitao; Chen Xinyi; Li Zhaosheng; Kou Jiahui; Yu Tao; Zou Zhigang

    2007-01-01

    In this paper, sensitized ZnS with visible light driven photocatlytic ability was successfully prepared. The obtained ZnS was characterized by x-ray diffraction, UV-visible diffuse reflectance spectra and Fourier transform infrared spectra. The photocatalytic property of the prepared ZnS was evaluated by decomposing methyl orange (MO). These sensitized ZnS powders with a proper molar ratio showed higher photocatalytic activity than TiO 2 (P25) under visible light (λ > 420 nm) irradiation. A possible explanation for the visible light activity of the prepared ZnS was proposed

  4. Visible-light sensitization of boron-doped nanocrystalline diamond through non-covalent surface modification

    Czech Academy of Sciences Publication Activity Database

    Krýsová, Hana; Vlčková Živcová, Zuzana; Bartoň, Jan; Petrák, Václav; Nesladek, M.; Cígler, Petr; Kavan, Ladislav

    2015-01-01

    Roč. 17, č. 2 (2015), s. 1165-1172 ISSN 1463-9076 R&D Projects: GA ČR GA13-31783S Institutional support: RVO:61388955 ; RVO:61388963 ; RVO:68378271 Keywords : nanocrystallines * visible-light sensitization * boron-doped diamond Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.449, year: 2015

  5. Origin of visible-light sensitivity in N-doped TiO2 films

    International Nuclear Information System (INIS)

    Nakano, Yoshitaka; Morikawa, Takeshi; Ohwaki, Takeshi; Taga, Yasunori

    2007-01-01

    We report on visible-light sensitivity in N-doped TiO 2 (TiO 2 :N) films that were deposited on n + -GaN/Al 2 O 3 substrates by reactive magnetron sputtering and subsequently crystallized by annealing at 550 deg. C in flowing N 2 gas. The N-doping concentration was ∼8.8%, as determined by X-ray photoelectron spectroscopy measurements. From transmission electron microscopic observations and optical absorption measurements, yellow-colored TiO 2 :N samples showed an enhanced granular structure and strong absorption in the visible-light region. Photoelectron spectroscopy in air measurements showed a noticeable decrease in ionization energy of TiO 2 by the N doping. Deep-level optical spectroscopy measurements revealed two characteristic deep levels located at ∼1.18 and ∼2.48 eV below the conduction band. The 1.18 eV level is probably attributable to the O vacancy state and can be active as an efficient generation-recombination center. The pronounced 2.48 eV band is newly introduced by the N doping and contributes to band-gap narrowing of TiO 2 by mixing with the O 2p valence band. Therefore, this localized intraband is probably one origin of visible-light sensitivity in TiO 2 :N

  6. Visible light induced photoelectrochemical biosensing based on oxygen-sensitive quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Wang Wenjing; Bao Lei [State Key Laboratory of Analytical Chemistry for Life Science, Department of Chemistry, Nanjing University, Nanjing 210093 (China); Lei Jianping, E-mail: jpl@nju.edu.cn [State Key Laboratory of Analytical Chemistry for Life Science, Department of Chemistry, Nanjing University, Nanjing 210093 (China); Tu Wenwen [State Key Laboratory of Analytical Chemistry for Life Science, Department of Chemistry, Nanjing University, Nanjing 210093 (China); Ju Huangxian, E-mail: hxju@nju.edu.cn [State Key Laboratory of Analytical Chemistry for Life Science, Department of Chemistry, Nanjing University, Nanjing 210093 (China)

    2012-09-26

    Highlights: Black-Right-Pointing-Pointer The near-infrared QDs are synthesized in an aqueous solution. Black-Right-Pointing-Pointer QDs-based biosensor exhibits visible-light induced cathodic photocurrent. Black-Right-Pointing-Pointer The oxygen dependency of the photocurrent is verified. Black-Right-Pointing-Pointer A photoelectrochemical strategy is established by coupling with enzymatic reaction. Black-Right-Pointing-Pointer Photoelectrochemical sensor shows high upper detection limit, acceptable stability and accuracy. - Abstract: A visible light induced photoelectrochemical biosensing platform based on oxygen-sensitive near-infrared quantum dots (NIR QDs) was developed for detection of glucose. The NIR QDs were synthesized in an aqueous solution, and characterized with scanning electron microscopy and X-ray photoelectron spectroscopy. The as-prepared NIR QDs were employed to construct oxygen-sensitive photoelectrochemical biosensor on a fluorine-doped tin oxide (FTO) electrode. The oxygen dependency of the photocurrent was investigated at as-prepared electrode, which demonstrated the signal of photocurrent is suppressed with the decreasing of oxygen. Coupling with the consumption of oxygen during enzymatic reaction, a photoelectrochemical strategy was proposed for the detection of substrate. Using glucose oxidase (GOx) as a model enzyme, that is, GOx was covalently attached to the surface of CdTe QDs, the resulting biosensor showed the sensitive response to glucose. Under the irradiation of visible light of a wavelength at 505 nm, the proposed photoelectrochemical method could detect glucose ranging from 0.1 mM to 11 mM with a detection limit of 0.04 mM. The photoelectrochemical biosensor showed a good performance with high upper detection limit, acceptable stability and accuracy, providing an alternative method for monitoring biomolecules and extending the application of near-infrared QDs.

  7. PHOTOPOLYMERIZATION INITIATED BY DIMETHYLAMINOCHALCONE/DIPHENYL-IODONIUM SALT COMBINATION SYSTEM SENSITIVE TO VISIBLE LIGHT

    Institute of Scientific and Technical Information of China (English)

    LI Jun; LI Miaozhen; SONG Huaihai; YANG Yongyuan; WANG Erjian

    1993-01-01

    Several dimethylamino-substituted chalcone (I.e.dimethylaminobenzal acetophenone) (DBA) derivatives with intramolecular charge transfer transition character were used as visible light sensitizers for radical photopolymerization initiated by iodonium salt (DPIO). Initiating radical species is produced from DBA sensitized photolysis of DPIO through the single electron transfer,accompanying the bleaching of DBA.The activity of DBA decreases as a function of substituent attached to phenyl ring in the order:DBA-2(OCH3)>DBA-1(H)>DBA-3(Cl).The kinetic study on photopolymerization of MMA was carried out in CH3CN solution at 30℃ by dilatometry.The polymerization rate was determined to be proportional to the concentration with exponents of 0.42,0.25 and 0.86 for DPIO,DBA-1and MMA,respectively.

  8. Nanostructure sensitization of transition metal oxides for visible-light photocatalysis

    Directory of Open Access Journals (Sweden)

    Hongjun Chen

    2014-05-01

    Full Text Available To better utilize the sunlight for efficient solar energy conversion, the research on visible-light active photocatalysts has recently attracted a lot of interest. The photosensitization of transition metal oxides is a promising approach for achieving effective visible-light photocatalysis. This review article primarily discusses the recent progress in the realm of a variety of nanostructured photosensitizers such as quantum dots, plasmonic metal nanostructures, and carbon nanostructures for coupling with wide-bandgap transition metal oxides to design better visible-light active photocatalysts. The underlying mechanisms of the composite photocatalysts, e.g., the light-induced charge separation and the subsequent visible-light photocatalytic reaction processes in environmental remediation and solar fuel generation fields, are also introduced. A brief outlook on the nanostructure photosensitization is also given.

  9. Selective oxidation with nanoporous silica supported sensitizers: An environment friendly process using air and visible light

    Energy Technology Data Exchange (ETDEWEB)

    Saint-Cricq, Philippe; Pigot, Thierry; Blanc, Sylvie [Institut des Sciences Analytiques et de Physicochimie pour l' Environnement et les Materiaux, Universite de Pau et des Pays de l' Adour, Helioparc-2 Av. du President Angot, F-64053 Pau Cedex 09 (France); Lacombe, Sylvie, E-mail: sylvie.lacombe@univ-pau.fr [Institut des Sciences Analytiques et de Physicochimie pour l' Environnement et les Materiaux, Universite de Pau et des Pays de l' Adour, Helioparc-2 Av. du President Angot, F-64053 Pau Cedex 09 (France)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Photo-sensitizers were covalently grafted on silica matrices. Black-Right-Pointing-Pointer Grafted powdered silica was characterized by diffuse reflectance and emission spectroscopy. Black-Right-Pointing-Pointer Selective solvent-free photo-oxygenation was carried out with air under visible light. Black-Right-Pointing-Pointer Singlet generation and reactivity at the gas-solid interface was demonstrated. - Abstract: Transparent and porous silica xerogels containing various grafted photosensitizers (PSs) such as anthraquinone derivatives, Neutral Red, Acridine Yellow and a laboratory-made dicyano aromatics (DBTP) were prepared. In most cases, the xerogels were shown to be mainly microporous by porosimetry. The PSs were characterized in the powdered monoliths (form, aggregation, concentration) by electronic spectroscopy which also proved to be a useful tool for monitoring the material evolution after irradiation. These nanoporous xerogels were used as microreactors for gas/solid solvent-free photo-oxygenation of dimethylsulfide (DMS) using visible light and air as the sole reactant. All these PSs containing monoliths were efficient for gas-solid DMS oxidation, leading to sulfoxide and sulfone in varying ratios. As these polar oxidation products remained strongly adsorbed on the silica matrix, the gaseous flow at the outlet of the reactor was totally free of sulfide and odorless. The best results in term of yield and initial rate of degradation of DMS were obtained with DBTP containing xerogels. Moreover, as these materials were reusable without loss of efficiency and sensitizer photobleaching after a washing regeneration step, the concept of recyclable sensitizing materials was approved, opening the way to green process.

  10. Facile preparation of squarylium dye sensitized TiO{sub 2} nanoparticles and their enhanced visible-light photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhongyu, E-mail: zhongyuli@mail.tsinghua.edu.cn [Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164 (China); Changzhou Expansion New Stuff Technology Limited Company, Changzhou 213122 (China); Fang, Yongling [Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164 (China); Zhan, Xueqiu [Department of Basic Courses, Wuxi Institute of Technology, Wuxi 214121 (China); Xu, Song [Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164 (China)

    2013-07-05

    Highlights: •ISQ dye sensitized TiO{sub 2} nanoparticles were prepared via a facile solution method. •ISQ/TiO{sub 2} nanoparticles exhibited significantly enhanced visible light activity. •ISQ/TiO{sub 2} showed high visible light photocatalytic activity over MB decomposition. •ISQ/TiO{sub 2} nanoparticles exhibited good photocatalytic stability. -- Abstract: A squarylium dye, 1,3-bis[(3,3-dimethylindolin-2-ylidene)methyl]squaraine (ISQ) sensitized TiO{sub 2} nanoparticles photocatalysts with different mass ratio of ISQ to TiO{sub 2} were facilely prepared by blending ISQ and TiO{sub 2} in ethanol solution. The resulting composite photocatalysts were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR) and UV–vis diffuse reflectance spectroscope (DRS). The visible light photocatalytic activities of ISQ sensitized TiO{sub 2} nanoparticles were evaluated using the degradation of methylene blue (MB) as a photodegradation target. The results showed that photo-response of the ISQ sensitized TiO{sub 2} nanoparticles were remarkably extended to visible-light region, and the ISQ dye sensitized TiO{sub 2} exhibited significantly enhanced photocatalytic activity under visible light irradiation. The maximum photocatalytic activity of the ISQ sensitized TiO{sub 2} was found at a composite photocatalyst (mass ratio of ISQ to TiO{sub 2} was 1:3), and its degradation efficiency of MB reached approximately 98% in 2 h under visible light irradiation. Furthermore, a possible mechanism for the photocatalytic oxidative degradation was also proposed.

  11. Non-sensitized selective photochemical reduction of CO2 to CO under visible light with an iron molecular catalyst.

    Science.gov (United States)

    Rao, Heng; Bonin, Julien; Robert, Marc

    2017-03-02

    A substituted tetraphenyl iron porphyrin, bearing positively charged trimethylammonio groups at the para position of each phenyl ring, demonstrates its ability as a homogeneous molecular catalyst to selectively reduce CO 2 to CO under visible light irradiation in organic media without the assistance of a sensitizer and no competitive hydrogen evolution for several days.

  12. Graphene oxide quantum dot-sensitized porous titanium dioxide microsphere: Visible-light-driven photocatalyst based on energy band engineering.

    Science.gov (United States)

    Zhang, Yu; Qi, Fuyuan; Li, Ying; Zhou, Xin; Sun, Hongfeng; Zhang, Wei; Liu, Daliang; Song, Xi-Ming

    2017-07-15

    We report a novel graphene oxide quantum dot (GOQD)-sensitized porous TiO 2 microsphere for efficient photoelectric conversion. Electro-chemical analysis along with the Mott-Schottky equation reveals conductivity type and energy band structure of the two semiconductors. Based on their energy band structures, visible light-induced electrons can transfer from the p-type GOQD to the n-type TiO 2 . Enhanced photocurrent and photocatalytic activity in visible light further confirm the enhanced separation of electrons and holes in the nanocomposite. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Sensitization of Perovskite Strontium Stannate SrSnO3 towards Visible-Light Absorption by Doping

    Directory of Open Access Journals (Sweden)

    Hungru Chen

    2014-01-01

    Full Text Available Perovskite strontium stannate SrSnO3 is a promising photocatalyst. However, its band gap is too large for efficient solar energy conversion. In order to sensitize SrSnO3 toward visible-light activities, the effects of doping with various selected cations and anions are investigated by using hybrid density functional calculations. Results show that doping can result in dopant level to conduction band transitions which lie lower in energy compared to the original band gap transition. Therefore, it is expected that doping SrSnO3 can induce visible-light absorption.

  14. Preparation and spectroscopic characterization of visible light sensitized N doped TiO2 (rutile)

    International Nuclear Information System (INIS)

    Livraghi, S.; Czoska, A.M.; Paganini, M.C.; Giamello, E.

    2009-01-01

    Nitrogen doped TiO 2 represents one of the most promising material for photocatalitic degradation of environmental pollutants with visible light. However, at present, a great deal of activity is devoted to the anatase polymorph while few data about rutile are available. In the present paper we report an experimental characterization of N doped polycrystalline rutile TiO 2 prepared via sol-gel synthesis. Nitrogen doping does not affect the valence band to conduction band separation but, generates intra band gap localized states which are responsible of the on set of visible light absorption. The intra band gap states correspond to a nitrogen containing defect similar but not coincident with that recently reported for N doped anatase. - Graphical abstract: Nitrogen doped TiO 2 represents one of the most promising material for photocatalitic degradation of environmental pollutants with visible light. However, at present, a great deal of activity is devoted to the anatase polymorph while few data about rutile are available. In the present paper we report an experimental characterization of N doped polycrystalline rutile TiO 2 prepared via sol-gel synthesis

  15. Bactericidal activity under UV and visible light of cotton fabrics coated with anthraquinone-sensitized TiO2

    KAUST Repository

    Rahal, Raed

    2013-06-01

    This study describes a method derived from ISO/TC 206/SC specifications to assess the bactericidal activity against a bacterial strain, Pseudomonas fluorescens, of various photocatalytic fabrics, under UVA and filtered visible light. The experimental method allowed the accurate quantification of bacteria survival on photoactive surfaces and films under UVA and UV-free visible irradiation. Cotton fabrics coated with TiO2, anthraquinone or anthraquinone-sensitized TiO2 display a significant bactericidal efficiency. TiO2-coated fabrics are very efficient against P. fluorescens after 4 h UVA irradiation (bacteria survival below the detection limit). Under UVA-free visible light, anthraquinone-sensitized TiO2 coated fabrics induced a significant bactericidal activity after 2 h irradiation, while anthraquinone alone-coated fabrics were not as efficient and TiO2 coated fabrics were almost inefficient. These results show that although exhibiting a weak n-π* band in the 350-420 nm range, anthraquinone is a good candidate as an efficient visible light photosensitizer. A synergy effect between anthraquinone and TiO2 was demonstrated. A possible reaction mechanism, involving a synergy effect for singlet oxygen formation with anthraquinone-sensitized TiO2 is proposed to account for these results. © 2012 Elsevier B.V. All rights reserved.

  16. CdS nanoparticle sensitized titanium dioxide decorated graphene for enhancing visible light induced photoanode

    International Nuclear Information System (INIS)

    Yousefzadeh, S.; Faraji, M.; Nien, Y.T.; Moshfegh, A.Z.

    2014-01-01

    Highlights: • CdS nanoparticles were deposited on TiO 2 /graphene film by different SILAR cycles. • The visible light absorption increased due to graphene and CdS nanoparticles. • The highest photocurrent density was achieved for nanocomposite with 30 CdS cycles. • A mechanism has been suggested for nanocomposite photoanodes, significantly. - Abstract: CdS/TiO 2 /graphene (CTG) nanocomposite thin films were synthesized by a facile production route. The TiO 2 /graphene (TG) nanocomposite was initially fabricated by sol-gel method in such a way that TiO 2 nanoparticles loaded on graphene oxide (GO) sheet via photocatalytic process. Then, CdS nanoparticles were deposited on the TG thin film by successive ion layer adsorption and reaction process (SILAR) approach. Based on atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses, the TG thin film possessed a larger surface area as compared with the pure TiO 2 thin film due to presence of graphene sheet. UV/visible spectroscopy exhibited that visible absorption of the CTG samples increased with increasing CdS SILAR deposition cycle (n). Enhanced photocurrent response of the CTG(n) photoanodes measured as compared with the TG and T photoanodes due to good electrical conductivity and large surface area of graphene as well as the visible light-harvesting ability of CdS nanoparticles. Maximum photocurrent density of about 4.5 A/m 2 and electron life time of about 5 s was measured for the CTG(30) photoanodes

  17. CdS nanoparticle sensitized titanium dioxide decorated graphene for enhancing visible light induced photoanode

    Energy Technology Data Exchange (ETDEWEB)

    Yousefzadeh, S.; Faraji, M. [Physics Department, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Nien, Y.T. [Department of Materials Science and Engineering, National Formosa University, Taiwan (China); Moshfegh, A.Z., E-mail: moshfegh@sharif.edu [Physics Department, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of)

    2014-11-30

    Highlights: • CdS nanoparticles were deposited on TiO{sub 2}/graphene film by different SILAR cycles. • The visible light absorption increased due to graphene and CdS nanoparticles. • The highest photocurrent density was achieved for nanocomposite with 30 CdS cycles. • A mechanism has been suggested for nanocomposite photoanodes, significantly. - Abstract: CdS/TiO{sub 2}/graphene (CTG) nanocomposite thin films were synthesized by a facile production route. The TiO{sub 2}/graphene (TG) nanocomposite was initially fabricated by sol-gel method in such a way that TiO{sub 2} nanoparticles loaded on graphene oxide (GO) sheet via photocatalytic process. Then, CdS nanoparticles were deposited on the TG thin film by successive ion layer adsorption and reaction process (SILAR) approach. Based on atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses, the TG thin film possessed a larger surface area as compared with the pure TiO{sub 2} thin film due to presence of graphene sheet. UV/visible spectroscopy exhibited that visible absorption of the CTG samples increased with increasing CdS SILAR deposition cycle (n). Enhanced photocurrent response of the CTG(n) photoanodes measured as compared with the TG and T photoanodes due to good electrical conductivity and large surface area of graphene as well as the visible light-harvesting ability of CdS nanoparticles. Maximum photocurrent density of about 4.5 A/m{sup 2} and electron life time of about 5 s was measured for the CTG(30) photoanodes.

  18. Visible-Light-Driven, Dye-Sensitized TiO2 Photo-Catalyst for Self-Cleaning Cotton Fabrics

    Directory of Open Access Journals (Sweden)

    Ishaq Ahmad

    2017-11-01

    Full Text Available We report here the photo-catalytic properties of dye-sensitized TiO2-coated cotton fabrics. In this study, visible-light-driven, self-cleaning cotton fabrics were developed by coating the cotton fabrics with dye-sensitized TiO2. TiO2 nano-sol was prepared via the sol-gel method and the cotton fabric was coated with this nano-sol by the dip-pad–dry-cure method. In order to enhance the photo-catalytic properties of this TiO2-coated cotton fabric under visible light irradiation, the TiO2-coated cotton fabric was dyed with a phthalocyanine-based reactive dye, C.I. Reactive Blue 25 (RB-25, as a dye sensitizer for TiO2. The photo-catalytic self-cleaning efficiency of the resulting dye/TiO2-coated cotton fabrics was evaluated by degradation of Rhodamine B (RhB and color co-ordinate measurements. Dye/TiO2-coated cotton fabrics show very good photo-catalytic properties under visible light.

  19. Ubiquitous quantum dot-sensitized nanoporous film for hydrogen production under visible-light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Miyauchi, Masahiro, E-mail: mmiyauchi@ceram.titech.ac.jp [Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552 (Japan); JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Shiga, Yuhiro; Srinivasan, Nagarajan; Atarashi, Daiki; Sakai, Etsuo [Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552 (Japan)

    2015-06-15

    To develop the efficient photocatalytic hydrogen production device, tin monosulfide (SnS) quantum dots (QDs) were deposited onto a nanoporous TiO{sub 2} electrode by the successive ionic layer adsorption and reaction (SILAR) method. When Pt nanoparticles as co-catalysts were modified at the interface between the electroconductive glass substrate and nanoporous SnS QDs/TiO{sub 2} layer, hydrogen molecules were produced under visible-light irradiation without applying a bias potential. In addition, the size and color of SnS QDs could be tailored using SILAR method, and the optimal structure of the SnS QDs was determined for efficient photocurrent generation and hydrogen production. The photocatalysis device developed in the present study was constructed as a simple single plate consisting of non-toxic elements. - Highlights: • Unique photo-electrochemical thin film device without application of a bias potential. • Non-toxic and inexpensive SnS quantum dot for visible-light harvesting. • Tailored SnS quantum dots using the SILAR method for efficient hydrogen production.

  20. Ubiquitous quantum dot-sensitized nanoporous film for hydrogen production under visible-light irradiation

    International Nuclear Information System (INIS)

    Miyauchi, Masahiro; Shiga, Yuhiro; Srinivasan, Nagarajan; Atarashi, Daiki; Sakai, Etsuo

    2015-01-01

    To develop the efficient photocatalytic hydrogen production device, tin monosulfide (SnS) quantum dots (QDs) were deposited onto a nanoporous TiO 2 electrode by the successive ionic layer adsorption and reaction (SILAR) method. When Pt nanoparticles as co-catalysts were modified at the interface between the electroconductive glass substrate and nanoporous SnS QDs/TiO 2 layer, hydrogen molecules were produced under visible-light irradiation without applying a bias potential. In addition, the size and color of SnS QDs could be tailored using SILAR method, and the optimal structure of the SnS QDs was determined for efficient photocurrent generation and hydrogen production. The photocatalysis device developed in the present study was constructed as a simple single plate consisting of non-toxic elements. - Highlights: • Unique photo-electrochemical thin film device without application of a bias potential. • Non-toxic and inexpensive SnS quantum dot for visible-light harvesting. • Tailored SnS quantum dots using the SILAR method for efficient hydrogen production

  1. Visible-light self-cleaning cotton by metalloporphyrin-sensitized photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Afzal, Shabana [School of Applied Sciences and Engineering, Monash University, Churchill 3842 (Australia); Daoud, Walid A., E-mail: wdaoud@cityu.edu.hk [School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Langford, Steven J. [School of Chemistry, Monash University, Clayton 3800 (Australia)

    2013-06-15

    Thin films of meso-tetra(4-carboxyphenyl)porphyrin with different metal centres (MTCPP, M = Fe, Co and Zn) in combination with anatase TiO{sub 2} have been formed on cotton fabric. Their self-cleaning properties have been evaluated by conducting the photocatalytic degradation of methylene blue under visible-light irradiation. All MTCPP/TiO{sub 2}-coated cotton fabrics showed superior self-cleaning performance as compared to the bare TiO{sub 2}-coated cotton. Among the three metal porphyrins, FeTCPP showed the highest photocatalytic activity with complete degradation of methylene blue in 180 min. The fabrics were characterized by FESEM, XRD, UV–vis and fluorescence spectroscopy.

  2. White LED visible light communication technology research

    Science.gov (United States)

    Yang, Chao

    2017-03-01

    Visible light communication is a new type of wireless optical communication technology. White LED to the success of development, the LED lighting technology is facing a new revolution. Because the LED has high sensitivity, modulation, the advantages of good performance, large transmission power, can make it in light transmission light signal at the same time. Use white LED light-emitting characteristics, on the modulation signals to the visible light transmission, can constitute a LED visible light communication system. We built a small visible optical communication system. The system composition and structure has certain value in the field of practical application, and we also research the key technology of transmitters and receivers, the key problem has been resolved. By studying on the optical and LED the characteristics of a high speed modulation driving circuit and a high sensitive receiving circuit was designed. And information transmission through the single chip microcomputer test, a preliminary verification has realized the data transmission function.

  3. High sensitivity ethanol gas sensor based on Sn - doped ZnO under visible light irradiation at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Peishuo; Pan, Guofeng; Zhang, Bingqiang; Zhen, Jiali; Sun, Yicai, E-mail: pgf@hebut.edu.cn [Institute of Microelectronic, Hebei University of Technology, Tianjin (China)

    2014-07-15

    Pure ZnO and 5at%, 7at%, 9at% Sn - doped ZnO materials are prepared by the chemical co - precipitation method. They were annealed by furnace at temperature range of 300 - 700ºC in air for 1h. The ZnO materials are characterized by X - ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the Sn - doped ZnO materials appear rough porous structures. The maximum sensitivity can be achieved by doping the amount of 7 at%. It has much better sensing performance towards ethanol vapor under visible light irradiation. The response and recovery time are ~1s and ~5s, respectively. The mechanism for the improvement in the sensing properties can be explained with the surface adsorption theory and the photoactivation theory. (author)

  4. Sacrificial hydrogen generation from aqueous triethanolamine with Eosin Y-sensitized Pt/TiO2 photocatalyst in UV, visible and solar light irradiation.

    Science.gov (United States)

    Chowdhury, Pankaj; Gomaa, Hassan; Ray, Ajay K

    2015-02-01

    In this paper, we have studied Eosin Y-sensitized sacrificial hydrogen generation with triethanolamine as electron donor in UV, visible, and solar light irradiation. Aeroxide TiO2 was loaded with platinum metal via solar photo-deposition method to reduce the electron hole recombination process. Photocatalytic sacrificial hydrogen generation was influenced by several factors such as platinum loading (wt%) on TiO2, solution pH, Eosin Y to Pt/TiO2 mass ratio, triethanolamine concentration, and light (UV, visible and solar) intensities. Detailed reaction mechanisms in visible and solar light irradiation were established. Oxidation of triethanolamine and formaldehyde formation was correlated with hydrogen generation in both visible and solar lights. Hydrogen generation kinetics followed a Langmuir-type isotherm with reaction rate constant and adsorption constant of 6.77×10(-6) mol min(-1) and 14.45 M(-1), respectively. Sacrificial hydrogen generation and charge recombination processes were studied as a function of light intensities. Apparent quantum yields (QYs) were compared for UV, visible, and solar light at four different light intensities. Highest QYs were attained at lower light intensity because of trivial charge recombination. At 30 mW cm(-2) we achieved QYs of 10.82%, 12.23% and 11.33% in UV, visible and solar light respectively. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Eosin Y-sensitized nanosheet-stacked hollow-sphere TiO2 for efficient photocatalytic H2 production under visible-light irradiation

    Science.gov (United States)

    Shi, Jinwen; Guan, Xiangjiu; Zhou, Zhaohui; Liu, Haipei; Guo, Liejin

    2015-06-01

    Nanosheet (with around 20 nm in thickness)-stacked hollow-sphere TiO2 was synthesized via a modified solvothermal reaction for different times followed by calcination treatment at different temperatures. After surface modification by different cations (H+ or Fe3+) and further sensitization by Eosin Y, the obtained photocatalysts achieved remarkably enhanced H2-production activity (about 4.2 times of that for Eosin Y-sensitized P25) and stability under visible-light irradiation. The improved photocatalytic performance was synergistically caused by the enhanced Eosin Y sensitization (due to the enlarged surface area and electropositively modified surface), the optimized crystal structure (well-crystallized anatase phase), and the unique micro/nanostructure (nanosheet-stacked hollow spheres). This work presented an effective route to explore new visible-light-driven H2-production photocatalysts by coupling nanomaterials with special morphologies and metal-free dyes with visible-light absorption.

  6. Eosin Y-sensitized nanosheet-stacked hollow-sphere TiO2 for efficient photocatalytic H2 production under visible-light irradiation

    International Nuclear Information System (INIS)

    Shi, Jinwen; Guan, Xiangjiu; Zhou, Zhaohui; Liu, Haipei; Guo, Liejin

    2015-01-01

    Nanosheet (with around 20 nm in thickness)-stacked hollow-sphere TiO 2 was synthesized via a modified solvothermal reaction for different times followed by calcination treatment at different temperatures. After surface modification by different cations (H + or Fe 3+ ) and further sensitization by Eosin Y, the obtained photocatalysts achieved remarkably enhanced H 2 -production activity (about 4.2 times of that for Eosin Y-sensitized P25) and stability under visible-light irradiation. The improved photocatalytic performance was synergistically caused by the enhanced Eosin Y sensitization (due to the enlarged surface area and electropositively modified surface), the optimized crystal structure (well-crystallized anatase phase), and the unique micro/nanostructure (nanosheet-stacked hollow spheres). This work presented an effective route to explore new visible-light-driven H 2 -production photocatalysts by coupling nanomaterials with special morphologies and metal-free dyes with visible-light absorption

  7. Formation of multilayer-Eosin Y-sensitized TiO{sub 2} via Fe{sup 3+} coupling for efficient visible-light photocatalytic hydrogen evolution

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuexiang; Guo, Miaomiao; Peng, Shaoqin [Department of Chemistry, Nanchang University, Nanchang 330031 (China); Lu, Gongxuan; Li, Shuben [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2009-07-15

    An efficient visible-light active photocatalyst of multilayer-Eosin Y-sensitized TiO{sub 2} is prepared through linkage of Fe{sup 3+} between not only TiO{sub 2} and Eosin Y but also different Eosin Y molecules to form three-dimensional polymeric dye structure. The multilayer-dye-sensitized photocatalyst is found to have high light harvesting efficiency and photocatalytic activity for hydrogen evolution under visible light irradiation ({lambda} > 420 nm). On the optimum conditions (1:1 initial molar ratio of Eosin Y to Fe(NO{sub 3}){sub 3}, initial 10 x 10{sup -3} M Eosin Y, and 1.0 wt% Pt deposited by in situ photoreduction), its maximal apparent quantum yield for hydrogen evolution is 19.1% from aqueous triethanolamine solution (TEOA aq). The present study highlights linking between dye molecules via metal ions as a general way to develop efficient visible-light photocatalyst. (author)

  8. Antibacterial Activity of Hydrophobic Composite Materials Containing a Visible-Light-Sensitive Photocatalyst

    Directory of Open Access Journals (Sweden)

    Kentaro Yamauchi

    2011-01-01

    Full Text Available The conventional superhydrophobic surface offered by PTFE provides no sterilization performance and is not sufficiently repellent against organic liquids. These limit PTFE's application in the field of disinfection and result a lack of durability. N-doped TiO2 photocatalyst added PTFE composite material was developed to remedy these shortcomings. This paper reports the surface characteristics, and the bactericidal and self-cleaning performance of the newly-developed composite material. The material exhibited a contact angle exceeding 150 degrees consistent with its hydrophobicity despite the inclusion of the hydrophilic N-doped TiO2. The surface free energy obtained for this composite was 5.8 mN/m. Even when exposed to a weak fluorescent light intensity (100 lx for 24 hours, the viable cells of gram-negative E. coli on the 12% N-doped TiO2-PTFE film were reduced 5 logs. The higher bactericidal activity was also confirmed on the gram-positive MRSA. Compared with the N-doped TiO2 coating only, the inactivation rate of the composite material was significantly enhanced. Utilizing the N-doped TiO2 with the PTFE composite coating could successfully remove, by UV illumination, oleic acid adsorbed on its surface. These results demonstrate the potential applicability of the novel N-doped TiO2 photocatalyst hydrophobic composite material for both indoor antibacterial action and outdoor contamination prevention.

  9. An efficient dye-sensitized BiOCl photocatalyst for air and water purification under visible light irradiation.

    Science.gov (United States)

    Li, Guisheng; Jiang, Bo; Xiao, Shuning; Lian, Zichao; Zhang, Dieqing; Yu, Jimmy C; Li, Hexing

    2014-08-01

    A photosensitized BiOCl catalyst was found to be effective for photocatalytic water purification and air remediation under visible light irradiation (λ > 420 nm). Prepared by a solvothermal method, the BiOCl crystals possessed a 3D hierarchical spherical structure with the highly active facets exposed. When sensitized by Rhodamine B (RhB), the photocatalyst system was more active than N-doped TiO2 for breaking down 4-chlorophenol (4-CP, 200 ppm) and nitric monoxide (NO, 500 ppb). The high activity could be attributed to the hierarchical structure (supplying feasible reaction tunnels for adsorption and transition of reactants or products) and the efficient exposure of the {001} facets. The former provides an enriched oxygen atom density that promotes adsorption of cationic dye RhB, and creates an oxygen vacancy state. The HO˙ and ˙O2(-) radicals produced from the injected electrons from the excited dye molecule (RhB*) into the conduction band of BiOCl were responsible for the excellent photocatalytic performance of the RhB-BiOCl system.

  10. Nitrogen complex species and its chemical nature in TiO2 for visible-light sensitized photocatalysis

    International Nuclear Information System (INIS)

    Asahi, Ryoji; Morikawa, Takeshi

    2007-01-01

    A photocatalyst with high reactivity under visible-light has been desired to utilize solar irradiation or interior lighting efficiently. Nitrogen-doped TiO 2 revealed significant improvement in optical absorption and photocatalytic activity over TiO 2 under visible light. We have performed the first-principles calculations to study the detailed N complex species introduced in TiO 2 . The results include stable geometries, densities of states, formation energies, and core levels. The present systematic studies account for the long-term controversial issue on N-doped TiO 2 , in particular, regarding the detailed assignment of N 1s binding energies observed in the XPS measurement. The detailed analyses of the formation energies show that introducing the N species more in a controlled way via process conditions is crucial to achieve the optimized photocatalytic performance

  11. Bactericidal activity under UV and visible light of cotton fabrics coated with anthraquinone-sensitized TiO2

    KAUST Repository

    Rahal, Raed; Le Bé chec, Mickaë l; Guyoneaud, Ré my; Pigot, Thierry; Paolacci, H.; Lacombe, Sylvie M.

    2013-01-01

    . The experimental method allowed the accurate quantification of bacteria survival on photoactive surfaces and films under UVA and UV-free visible irradiation. Cotton fabrics coated with TiO2, anthraquinone or anthraquinone-sensitized TiO2 display a significant

  12. Visible light broadband perfect absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Jia, X. L.; Meng, Q. X.; Yuan, C. X.; Zhou, Z. X.; Wang, X. O., E-mail: wxo@hit.edu.cn [School of Science, Harbin Institute of Technology, Harbin 150001 (China)

    2016-03-15

    The visible light broadband perfect absorbers based on the silver (Ag) nano elliptical disks and holes array are studied using finite difference time domain simulations. The semiconducting indium silicon dioxide thin film is introduced as the space layer in this sandwiched structure. Utilizing the asymmetrical geometry of the structures, polarization sensitivity for transverse electric wave (TE)/transverse magnetic wave (TM) and left circular polarization wave (LCP)/right circular polarization wave (RCP) of the broadband absorption are gained. The absorbers with Ag nano disks and holes array show several peaks absorbance of 100% by numerical simulation. These simple and flexible perfect absorbers are particularly desirable for various potential applications including the solar energy absorber.

  13. A highly uniform ZnO/NaTaO3 nanocomposite: Enhanced self-sensitized degradation of colored pollutants under visible light

    International Nuclear Information System (INIS)

    Xing, Guanjie; Tang, Changhe; Zhang, Bo; Zhao, Lanxiao; Su, Yiguo; Wang, Xiaojing

    2015-01-01

    In this study, a highly uniform ZnO/NaTaO 3 composite was prepared via simple hydrothermal synthesis. XRD confirmed the composite was constructed by pure cubic phase of NaTaO 3 and hexagonal phase of ZnO. SEM analysis showed that as-prepared ZnO/NaTaO 3 shaped as an irregular ginger with an obviously smaller size than that of pure ZnO without obvious agglomeration. EDS mapping demonstrated that the four elements (Na, Ta, O, Zn) in the composite were very uniformly distributed. The photocatalytic behaviors of as-prepared composites were studied in the degradation of methylene blue both under UV and visible irradiation. The bare ZnO showed the highest activity with 99.8% methylene blue (MB) photodegraded in 70 min under UV light irradiation whereas 94% photodegraded rate was achieved for ZnO/NaTaO 3 . More importantly, the uniform composite of ZnO/NaTaO 3 exhibited effective degradation of methylene blue under visible light which can be attributed to the well dyes adsorption abilities and the high efficiency of electron separation, induced by the synergistic effect between ZnO and NaTaO 3 . It is confirmed the dye rather than a semiconductor is excited under visible light irradiation and a self-sensitized photocatalytic mechanism was then proposed based on the experimental results. - Graphical abstract: Visible light photocatalytic activity of ZnO/NaTaO 3 and proposed schematic of self-sensitization directed photogradation of MB. - Highlights: • Highly uniform ZnO/NaTaO 3 photocatalysts were fabricated by hydrothermal method. • ZnO/NaTaO 3 composite exhibited effective degradation of MB under visible light. • ZnO/NaTaO 3 composite effectively promoted dye adsorption and electrons separation. • A self-sensitized photocatalytic mechanism was proposed for the degradation of dye

  14. Visible-light sensitization of TiO2 photocatalysts via wet chemical N-doping for the degradation of dissolved organic compounds in wastewater treatment: a review

    Science.gov (United States)

    Zhang, Wei; Jia, Baoping; Wang, Qiuze; Dionysiou, Dionysois

    2015-05-01

    Increased pollution of ground and surface water and emerging new micropollutants from a wide variety of industrial, municipal, and agricultural sources has increased demand on the development of innovative new technologies and materials whereby challenges associated with the provision of safe potable water can be addressed. Heterogeneous photocatalysis using visible-light sensitized TiO2 photocatalysts has attracted a lot of attention as it can effectively remove dissolved organic compound in water without generating harmful by-products. On this note, recent progress on visible-light sensitive TiO2 synthesis via wet chemical N-doping method is reviewed. In a typical visible-light sensitive TiO2 preparation via wet chemical methods, the chemical (e.g., N-doping content and states) and morphological properties (e.g., particle size, surface area, and crystal phase) of TiO2 in as-prepared resultants are sensitively dependent on many experimental variables during the synthesis. This has also made it very difficult to provide a universal guidance at this stage with a certainty for each variable of N-doping preparation. Instead of one-factor-at-a-time style investigation, a statistically valid parameter optimization investigation for general optima of photocatalytic activity will be certainly useful. Optimization of the preparation technique is envisaged to be beneficial to many environmental applications, i.e., dissolved organic compounds removal in wastewater treatment.

  15. Visible-light sensitization of TiO2 photocatalysts via wet chemical N-doping for the degradation of dissolved organic compounds in wastewater treatment: a review

    International Nuclear Information System (INIS)

    Zhang, Wei; Jia, Baoping; Wang, Qiuze; Dionysiou, Dionysois

    2015-01-01

    Increased pollution of ground and surface water and emerging new micropollutants from a wide variety of industrial, municipal, and agricultural sources has increased demand on the development of innovative new technologies and materials whereby challenges associated with the provision of safe potable water can be addressed. Heterogeneous photocatalysis using visible-light sensitized TiO 2 photocatalysts has attracted a lot of attention as it can effectively remove dissolved organic compound in water without generating harmful by-products. On this note, recent progress on visible-light sensitive TiO 2 synthesis via wet chemical N-doping method is reviewed. In a typical visible-light sensitive TiO 2 preparation via wet chemical methods, the chemical (e.g., N-doping content and states) and morphological properties (e.g., particle size, surface area, and crystal phase) of TiO 2 in as-prepared resultants are sensitively dependent on many experimental variables during the synthesis. This has also made it very difficult to provide a universal guidance at this stage with a certainty for each variable of N-doping preparation. Instead of one-factor-at-a-time style investigation, a statistically valid parameter optimization investigation for general optima of photocatalytic activity will be certainly useful. Optimization of the preparation technique is envisaged to be beneficial to many environmental applications, i.e., dissolved organic compounds removal in wastewater treatment

  16. Inactivation of normal and mutant Neurospora crassa conidia by visible light and near-UV: role of 1O2, carotenoid composition and sensitizer location

    International Nuclear Information System (INIS)

    Thomas, S.A.; Sargent, M.L.; Tuveson, R.W.

    1981-01-01

    Inactivation of Neurospora crassa conidia from wild-type and mutant strains by visible and near-ultraviolet light was investigated in the presence and absence of photosensitizing dyes. Inactivation by near-UV was virtually unchanged by the presence of deuterium oxide or azide suggesting that, contrary to the situation with visible light and photosensitizing dyes, 1 O 2 is not involved in any substantial way in the formation of lethal lesions. Carotenoid deficient strains were similar to wild-type strains in sensitivity to near-UV inactivation which is consistent with 1 O 2 not being involved. Photodynamic inactivation of conidia by visible light occurred in the presence of methylene blue (MB), toluidine blue O (TB), or acridine orange (AO). Carotenoid deficient strains were more sensitive to such inactivation only when MB and TB were used. This suggests that MB and TB mediated damage involves the cell membrane where carotenoids are available for quenching, whereas AO mediated damage occurs in the nucleus sequestered from the protective influence of carotenoids. A newly isolated, lemon-yellow mutant exhibited sensitivities to photodynamic inactivation similar to other pure-white mutants. The sensitivity of this pigmented mutant is apparently related to insufficient unsaturation of the two coloured carotenoids produced by the mutant. (author)

  17. Eosin Y-sensitized nanosheet-stacked hollow-sphere TiO{sub 2} for efficient photocatalytic H{sub 2} production under visible-light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Jinwen, E-mail: jinwen-shi@mail.xjtu.edu.cn; Guan, Xiangjiu; Zhou, Zhaohui; Liu, Haipei; Guo, Liejin [Xi’an Jiaotong University (XJTU), State Key Laboratory of Multiphase Flow in Power Engineering (MFPE), International Research Center for Renewable Energy IRCRE (China)

    2015-06-15

    Nanosheet (with around 20 nm in thickness)-stacked hollow-sphere TiO{sub 2} was synthesized via a modified solvothermal reaction for different times followed by calcination treatment at different temperatures. After surface modification by different cations (H{sup +} or Fe{sup 3+}) and further sensitization by Eosin Y, the obtained photocatalysts achieved remarkably enhanced H{sub 2}-production activity (about 4.2 times of that for Eosin Y-sensitized P25) and stability under visible-light irradiation. The improved photocatalytic performance was synergistically caused by the enhanced Eosin Y sensitization (due to the enlarged surface area and electropositively modified surface), the optimized crystal structure (well-crystallized anatase phase), and the unique micro/nanostructure (nanosheet-stacked hollow spheres). This work presented an effective route to explore new visible-light-driven H{sub 2}-production photocatalysts by coupling nanomaterials with special morphologies and metal-free dyes with visible-light absorption.

  18. Visible light reduces C. elegans longevity.

    Science.gov (United States)

    De Magalhaes Filho, C Daniel; Henriquez, Brian; Seah, Nicole E; Evans, Ronald M; Lapierre, Louis R; Dillin, Andrew

    2018-03-02

    The transparent nematode Caenorhabditis elegans can sense UV and blue-violet light to alter behavior. Because high-dose UV and blue-violet light are not a common feature outside of the laboratory setting, we asked what role, if any, could low-intensity visible light play in C. elegans physiology and longevity. Here, we show that C. elegans lifespan is inversely correlated to the time worms were exposed to visible light. While circadian control, lite-1 and tax-2 do not contribute to the lifespan reduction, we demonstrate that visible light creates photooxidative stress along with a general unfolded-protein response that decreases the lifespan. Finally, we find that long-lived mutants are more resistant to light stress, as well as wild-type worms supplemented pharmacologically with antioxidants. This study reveals that transparent nematodes are sensitive to visible light radiation and highlights the need to standardize methods for controlling the unrecognized biased effect of light during lifespan studies in laboratory conditions.

  19. Ag3PO4/ZnO: An efficient visible-light-sensitized composite with its application in photocatalytic degradation of Rhodamine B

    International Nuclear Information System (INIS)

    Liu, Wei; Wang, Mingliang; Xu, Chunxiang; Chen, Shifu; Fu, Xianliang

    2013-01-01

    Graphical abstract: The free OH radicals generated in the VB of ZnO play the primary role in the visible-light photocatalytic degradation of RhB in Ag 3 PO 4 /ZnO system. The accumulated electrons in the CB of Ag 3 PO 4 can be transferred to O 2 adsorbed on the surface of the composite semiconductors and H 2 O 2 yields. H 2 O 2 reacts with electrons in succession to produce active ·OH to some extent. Display Omitted Highlights: ► Efficient visible-light-sensitized Ag 3 PO 4 /ZnO composites were successfully prepared. ► Effect of Ag 3 PO 4 content on the catalytic activity of Ag 3 PO 4 /ZnO is studied in detail. ► Rate constant of RhB degradation over Ag 3 PO 4 (3.0 wt.%)/ZnO is 3 times that of Ag 3 PO 4 . ► The active species in RhB degradation are examined by adding a series of scavengers. ► Visible light degradation mechanism of RhB over Ag 3 PO 4 /ZnO is systematically studied. -- Abstract: The efficient visible-light-sensitized Ag 3 PO 4 /ZnO composites with various weight percents of Ag 3 PO 4 were prepared by a facile ball milling method. The photocatalysts were characterized by XRD, DRS, SEM, EDS, XPS, and BET specific area. The ·OH radicals produced during the photocatalytic reaction was detected by the TA–PL technique. The photocatalytic property of Ag 3 PO 4 /ZnO was evaluated by photocatalytic degradation of Rhodamine B under visible light irradiation. Significantly, the results revealed that the photocatalytic activity of the composites was much higher than that of pure Ag 3 PO 4 and ZnO. The rate constant of RhB degradation over Ag 3 PO 4 (3.0 wt.%)/ZnO is 3 times that of single-phase Ag 3 PO 4 . The optimal percentage of Ag 3 PO 4 in the composite is 3.0 wt.%. It is proposed that the ·OH radicals produced in the valence band of ZnO play the leading role in the photocatalytic degradation of Rhodamine B by Ag 3 PO 4 /ZnO systems under visible light irradiation.

  20. CdTe and graphene co-sensitized TiO2 nanotube array photoanodes for protection of 304SS under visible light

    International Nuclear Information System (INIS)

    Li, Hong; Wang, Xiutong; Hou, Baorong; Zhang, Liang

    2015-01-01

    CdTe/graphene/TiO 2 films that served as photoanodes for cathodic protection application were prepared by an electrochemical deposition method. The deposition of graphene and CdTe nanoparticles (NPs) on the surface of the TiO 2 nanotubes was confirmed by scanning electron microscope and transmission electron microscopy. The composites exhibited high light absorption in both the UV and visible light region. The results indicated that TiO 2 nanotube photoelectrodes sensitized by 20-cycle graphene and 30-cycle CdTe NPs exhibited effective photocathodic protection properties for 304 stainless steel (304SS) under the visible-light illumination, with an photopotential of −750 mV versus saturated calomel electrode and a current density of 560 μA cm −2 . Due to the efficient photogenerated charge separation, the three-component CdTe/graphene/TiO 2 showed stronger photoresponse than pure TiO 2 under visible-light illumination. In summary, the CdTe/graphene could improve the photocathodic protection properties of TiO 2 films. (paper)

  1. A highly uniform ZnO/NaTaO{sub 3} nanocomposite: Enhanced self-sensitized degradation of colored pollutants under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Guanjie; Tang, Changhe [School of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot, Inner Mongolia, 010021 (China); Zhang, Bo [College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei, 430072 (China); Zhao, Lanxiao; Su, Yiguo [School of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot, Inner Mongolia, 010021 (China); Wang, Xiaojing, E-mail: wang_xiao_jing@hotmail.com [School of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot, Inner Mongolia, 010021 (China)

    2015-10-25

    In this study, a highly uniform ZnO/NaTaO{sub 3} composite was prepared via simple hydrothermal synthesis. XRD confirmed the composite was constructed by pure cubic phase of NaTaO{sub 3} and hexagonal phase of ZnO. SEM analysis showed that as-prepared ZnO/NaTaO{sub 3} shaped as an irregular ginger with an obviously smaller size than that of pure ZnO without obvious agglomeration. EDS mapping demonstrated that the four elements (Na, Ta, O, Zn) in the composite were very uniformly distributed. The photocatalytic behaviors of as-prepared composites were studied in the degradation of methylene blue both under UV and visible irradiation. The bare ZnO showed the highest activity with 99.8% methylene blue (MB) photodegraded in 70 min under UV light irradiation whereas 94% photodegraded rate was achieved for ZnO/NaTaO{sub 3}. More importantly, the uniform composite of ZnO/NaTaO{sub 3} exhibited effective degradation of methylene blue under visible light which can be attributed to the well dyes adsorption abilities and the high efficiency of electron separation, induced by the synergistic effect between ZnO and NaTaO{sub 3}. It is confirmed the dye rather than a semiconductor is excited under visible light irradiation and a self-sensitized photocatalytic mechanism was then proposed based on the experimental results. - Graphical abstract: Visible light photocatalytic activity of ZnO/NaTaO{sub 3} and proposed schematic of self-sensitization directed photogradation of MB. - Highlights: • Highly uniform ZnO/NaTaO{sub 3} photocatalysts were fabricated by hydrothermal method. • ZnO/NaTaO{sub 3} composite exhibited effective degradation of MB under visible light. • ZnO/NaTaO{sub 3} composite effectively promoted dye adsorption and electrons separation. • A self-sensitized photocatalytic mechanism was proposed for the degradation of dye.

  2. Uniformly dispersed CdS nanoparticles sensitized TiO{sub 2} nanotube arrays with enhanced visible-light photocatalytic activity and stability

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lingjuan [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices, Hefei 230009 (China); Lv, Jun, E-mail: lvjun117@126.com [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices, Hefei 230009 (China); Xu, Guangqing; Wang, Yan; Xie, Kui [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices, Hefei 230009 (China); Chen, Zhong [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue 639798 (Singapore); Wu, Yucheng, E-mail: ycwu@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices, Hefei 230009 (China)

    2013-12-15

    In this study, TiO{sub 2} nanotube arrays (TiO{sub 2}-NTs) with various intertube spaces were fabricated in the electrolyte with different water contents and the CdS nanoparticles (CdS NPs) were further deposited onto the TiO{sub 2}-NTs as a sensitizer via a sequential chemical bath deposition (S-CBD) method. The FE-SEM, TEM, XRD and XPS results demonstrated that the CdS NPs were uniformly deposited onto the surface of TiO{sub 2}-NTs. It was found that higher water content in electrolyte was in favor of large intertube space and pore size and the uniform deposition of CdS NPs. The photocatalytic degradation of methyl orange was tested with the as-prepared CdS/TiO{sub 2}-NTs under visible light (λ>400 nm). It was found that the photodegradation rate reached as high as 96.7% under visible irradiation for 180 min. In addition, a reasonable degradation rate of 75.8% was achieved even after 5 cycles, suggesting a good photocatalytic stability of the as-prepared CdS/TiO{sub 2}-NTs. - Graphical abstract: The whole sheet of CdS NPs sensitized TiO{sub 2}-NTs with the Ti subtract was used for degradation of methyl orange under visible light (λ>400 nm) on a XPA-7 photochemical reactor. - Highlights: • Intertube space, pore size were controlled by changing water content in electrolyte. • CdS nanoparticles were uniformly deposited onto the surface of TiO{sub 2} nanotubes. • The catalyst with Ti substrate used as a whole was very convenient for recycling. • Visible-light photocatalytic activity and stability were highly enhanced.

  3. Visible light photocatalytic disinfection of E. coli with TiO_2–graphene nanocomposite sensitized with tetrakis(4-carboxyphenyl)porphyrin

    International Nuclear Information System (INIS)

    Rahimi, Rahmatollah; Zargari, Solmaz; Yousefi, Azam; Yaghoubi Berijani, Marzieh; Ghaffarinejad, Ali; Morsali, Ali

    2015-01-01

    Graphical abstract: TiO_2–graphene nanocomposites with different content of graphene were synthesized via a facile one-step solvothermal method. Photoelectrochemical responses of prepared photocatalysts were measured to determine the optimum content of graphene in TG nanocomposites. The results show that the TG nanocomposite with 3% of graphene has the highest photoactivity. This compound was sensitized with tetrakis(4-carboxyphenyl)porphyrin (TGP). The prepared photocatalysts were used for photocatalytic disinfection of E. coli. The results showed that the photocatalytic disinfection of the TG nanocomposite was increased after sensitization with porphyrin. The enhanced photocatalytic performance could be attributed to the synergistic effect between TiO_2, graphene and porphyrin sensitizer in the TGP photocatalyst. - Highlights: • TiO_2–graphene nanocomposites (TG) were synthesized with different content of graphene. • The TG nanocomposite with different content of graphene was sensitized with porphyrin (TGP). • The disinfection of E. coli using TGP was investigated in the visible light. • Porphyrin sensitizer increases effectively the photocatalytic disinfection efficiency of TGP. - Abstract: The present research deals with the development of a new heterogeneous photocatalysis system for disinfection of bacteria from wastewater by using TiO_2–graphene (TG) nanocomposite sensitized with tetrakis(4-carboxyphenyl)porphyrin (TCPP). The disinfection of wastewater using this photocatalyst is not reported in the literature yet. All the synthesized materials were thoroughly characterized by Raman, XRD, DRS, BET, and SEM analysis. The optimum content of graphene in the TiO_2–graphene nanocomposite was determined by photocurrent responses of prepared photocatalysts. Subsequently, the photocurrent measurements demonstrate that the TiO_2–graphene nanocomposite with 3% graphene content has higher photoactivity. Furthermore, sensitization of the TiO_2

  4. Novel lanthanide pH fluorescent probes based on multiple emissions and its visible-light-sensitized feature

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jintai [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Zheng, Yuhui, E-mail: yhzheng78@scnu.edu.cn [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Wang, Qianming, E-mail: qmwang@scnu.edu.cn [Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Guangzhou Key Laboratory of Materials for Energy Conversion and Storage, Guangzhou 510006 (China); State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082 (China); Zeng, Zhi [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Zhang, Cheng Cheng [Departments of Physiology and Developmental Biology, University of Texas Southwestern Medical Center, Dallas (United States)

    2014-08-11

    Graphical abstract: A new type of Eu(III) ofloxacin complex as the fluorescent pH indicator has been reported. Compared to pure ligand, the complex offers more distinguished color changes (green–red–blue) derived from both lanthanide line emissions and the secondary ionization steps of ofloxacin. - Highlights: • The pH probe offers a very wide working range in water (pH 1–14). • The emission changes have multiple colors. • Long-lived excited state lifetimes of Eu(III) has been used. • Two types of pH sensitive hydrogels were fabricated. - Abstract: A new type of Eu(III) ofloxacin complex as the fluorescent pH indicator has been presented. Compared to pure ligand, the complex offers more distinguished color changes (green–red–blue) derived from both lanthanide line emissions and the secondary ionization steps of ofloxacin. During the concentration dependence experiments, the photoluminescence studies on the complex showed that the excitation of this pH probe can occur at a very long wavelength which extends to visible range (Ex = 427 nm). Furthermore, the functional complex was successfully incorporated into soft networks and two novel luminescent hydrogels (rod and film) were fabricated. The soft materials also exhibited specific responses towards the pH variation. Finally, the onion cell-stain experiments were carried out to further confirm the validity of pH dependence and the results support the idea that the material will be suitable for monitoring biological samples in the future.

  5. MoS{sub 2}-coated microspheres of self-sensitized carbon nitride for efficient photocatalytic hydrogen generation under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Quan [Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, 710062 (China); School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Sun, Huaming; Xie, Zunyuan; Gao, Ziwei [Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, 710062 (China); Xue, Can, E-mail: cxue@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2017-02-28

    Highlights: • Successful coating of MoS{sub 2} onto self-sensitized carbon nitride microspheres. • The carbon nitride@MoS{sub 2} core-shell structure show enhanced H{sub 2} generation in visible light. • Synergistic effect of surface dyes and MoS{sub 2} coating enhances photocatalytic activities. - Abstract: We have successfully coated the self-sensitized carbon nitride (SSCN) microspheres with a layer of MoS{sub 2} through a facile one-pot hydrothermal method by using (NH{sub 4}){sub 2}MoS{sub 4} as the precursor. The resulted MoS{sub 2}-coated SSCN photocatalyst appears as a core-shell structure and exhibits enhanced visible-light activities for photocatalytic H{sub 2} generation as compared to the un-coated SSCN and the standard g-C{sub 3}N{sub 4} reference with MoS{sub 2} coating. The photocatalytic test results suggest that the oligomeric s-triazine dyes on the SSCN surface can provide additional light-harvesting capability and photogenerated charge carriers, and the coated MoS{sub 2} layer can serve as active sites for proton reduction towards H{sub 2} evolution. This synergistic effect of surface triazine dyes and MoS{sub 2} coating greatly promotes the activity of carbon nitride microspheres for vishible-light-driven H{sub 2} generation. This work provides a new way of future development of low-cost noble-metal-free photocatalysts for efficient solar-driven hydrogen production.

  6. Visible light photocatalytic disinfection of E. coli with TiO2-graphene nanocomposite sensitized with tetrakis(4-carboxyphenyl)porphyrin

    Science.gov (United States)

    Rahimi, Rahmatollah; Zargari, Solmaz; Yousefi, Azam; Yaghoubi Berijani, Marzieh; Ghaffarinejad, Ali; Morsali, Ali

    2015-11-01

    The present research deals with the development of a new heterogeneous photocatalysis system for disinfection of bacteria from wastewater by using TiO2-graphene (TG) nanocomposite sensitized with tetrakis(4-carboxyphenyl)porphyrin (TCPP). The disinfection of wastewater using this photocatalyst is not reported in the literature yet. All the synthesized materials were thoroughly characterized by Raman, XRD, DRS, BET, and SEM analysis. The optimum content of graphene in the TiO2-graphene nanocomposite was determined by photocurrent responses of prepared photocatalysts. Subsequently, the photocurrent measurements demonstrate that the TiO2-graphene nanocomposite with 3% graphene content has higher photoactivity. Furthermore, sensitization of the TiO2-graphene nanocomposite with porphyrin (TGP) is successfully capable to develop a new type of photocatalyst system for disinfection of bacteria with moderate to high yields in visible light irradiation.

  7. Well-crystalline porous ZnO-SnO2 nanosheets: an effective visible-light driven photocatalyst and highly sensitive smart sensor material.

    Science.gov (United States)

    Lamba, Randeep; Umar, Ahmad; Mehta, S K; Kansal, Sushil Kumar

    2015-01-01

    This work demonstrates the synthesis and characterization of porous ZnO-SnO2 nanosheets prepared by the simple and facile hydrothermal method at low-temperature. The prepared nanosheets were characterized by several techniques which revealed the well-crystallinity, porous and well-defined nanosheet morphology for the prepared material. The synthesized porous ZnO-SnO2 nanosheets were used as an efficient photocatalyst for the photocatalytic degradation of highly hazardous dye, i.e., direct blue 15 (DB 15), under visible-light irradiation. The excellent photocatalytic degradation of prepared material towards DB 15 dye could be ascribed to the formation of ZnO-SnO2 heterojunction which effectively separates the photogenerated electron-hole pairs and possess high surface area. Further, the prepared porous ZnO-SnO2 nanosheets were utilized to fabricate a robust chemical sensor to detect 4-nitrophenol in aqueous medium. The fabricated sensor exhibited extremely high sensitivity of ~ 1285.76 µA/mmol L(-1)cm(-2) and an experimental detection limit of 0.078 mmol L(-1) with a linear dynamic range of 0.078-1.25 mmol L(-1). The obtained results confirmed that the prepared porous ZnO-SnO2 nanosheets are potential material for the removal of organic pollutants under visible light irradiation and efficient chemical sensing applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Visible light photocatalytic disinfection of E. coli with TiO{sub 2}–graphene nanocomposite sensitized with tetrakis(4-carboxyphenyl)porphyrin

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Rahmatollah, E-mail: rahimi_rah@iust.ac.ir [Department of Chemistry, Iran University of Science and Technology, Tehran 16846-13114 (Iran, Islamic Republic of); Zargari, Solmaz [Department of Chemistry, Iran University of Science and Technology, Tehran 16846-13114 (Iran, Islamic Republic of); Yousefi, Azam [School of Chemical Engineering, Iran University of Science and Technology, Tehran 16846-13114 (Iran, Islamic Republic of); Yaghoubi Berijani, Marzieh; Ghaffarinejad, Ali [Department of Chemistry, Iran University of Science and Technology, Tehran 16846-13114 (Iran, Islamic Republic of); Morsali, Ali [Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, Tehran 14115-175 (Iran, Islamic Republic of)

    2015-11-15

    Graphical abstract: TiO{sub 2}–graphene nanocomposites with different content of graphene were synthesized via a facile one-step solvothermal method. Photoelectrochemical responses of prepared photocatalysts were measured to determine the optimum content of graphene in TG nanocomposites. The results show that the TG nanocomposite with 3% of graphene has the highest photoactivity. This compound was sensitized with tetrakis(4-carboxyphenyl)porphyrin (TGP). The prepared photocatalysts were used for photocatalytic disinfection of E. coli. The results showed that the photocatalytic disinfection of the TG nanocomposite was increased after sensitization with porphyrin. The enhanced photocatalytic performance could be attributed to the synergistic effect between TiO{sub 2}, graphene and porphyrin sensitizer in the TGP photocatalyst. - Highlights: • TiO{sub 2}–graphene nanocomposites (TG) were synthesized with different content of graphene. • The TG nanocomposite with different content of graphene was sensitized with porphyrin (TGP). • The disinfection of E. coli using TGP was investigated in the visible light. • Porphyrin sensitizer increases effectively the photocatalytic disinfection efficiency of TGP. - Abstract: The present research deals with the development of a new heterogeneous photocatalysis system for disinfection of bacteria from wastewater by using TiO{sub 2}–graphene (TG) nanocomposite sensitized with tetrakis(4-carboxyphenyl)porphyrin (TCPP). The disinfection of wastewater using this photocatalyst is not reported in the literature yet. All the synthesized materials were thoroughly characterized by Raman, XRD, DRS, BET, and SEM analysis. The optimum content of graphene in the TiO{sub 2}–graphene nanocomposite was determined by photocurrent responses of prepared photocatalysts. Subsequently, the photocurrent measurements demonstrate that the TiO{sub 2}–graphene nanocomposite with 3% graphene content has higher photoactivity. Furthermore

  9. Dye-sensitized MIL-101 metal organic frameworks loaded with Ni/NiO{sub x} nanoparticles for efficient visible-light-driven hydrogen generation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xin-Ling; Wang, Rong; Yuan, Yu-Peng, E-mail: yupengyuan@ahu.edu.cn, E-mail: cxue@ntu.edu.sg [School of Chemistry and Chemical Engineering, and Innovation Lab for Clean Energy and Green Catalysis, Anhui University, Hefei 230036 (China); Zhang, Ming-Yi [Key Laboratory for Photonic and Electronic Bandgap Materials, Ministry of Education, School of Physics and Electronic Engineering, Harbin Normal University, Harbin 150025 (China); Xue, Can, E-mail: yupengyuan@ahu.edu.cn, E-mail: cxue@ntu.edu.sg [Solar Fuels Lab, School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2015-10-01

    The Ni/NiO{sub x} particles were in situ photodeposited on MIL-101 metal organic frameworks as catalysts for boosting H{sub 2} generation from Erythrosin B dye sensitization under visible-light irradiation. The highest H{sub 2} production rate of 125 μmol h{sup −1} was achieved from the system containing 5 wt. % Ni-loaded MIL-101 (20 mg) and 30 mg Erythrosin B dye. Moreover, the Ni/NiO{sub x} catalysts show excellent stability for long-term photocatalytic reaction. The enhancement on H{sub 2} generation is attributed to the efficient charge transfer from photoexcited dye to the Ni catalyst via MIL-101. Our results demonstrate that the economical Ni/NiO{sub x} particles are durable and active catalysts for photocatalytic H{sub 2} generation.

  10. Dye-sensitized MIL-101 metal organic frameworks loaded with Ni/NiOx nanoparticles for efficient visible-light-driven hydrogen generation

    Directory of Open Access Journals (Sweden)

    Xin-Ling Liu

    2015-10-01

    Full Text Available The Ni/NiOx particles were in situ photodeposited on MIL-101 metal organic frameworks as catalysts for boosting H2 generation from Erythrosin B dye sensitization under visible-light irradiation. The highest H2 production rate of 125 μmol h−1 was achieved from the system containing 5 wt. % Ni-loaded MIL-101 (20 mg and 30 mg Erythrosin B dye. Moreover, the Ni/NiOx catalysts show excellent stability for long-term photocatalytic reaction. The enhancement on H2 generation is attributed to the efficient charge transfer from photoexcited dye to the Ni catalyst via MIL-101. Our results demonstrate that the economical Ni/NiOx particles are durable and active catalysts for photocatalytic H2 generation.

  11. Hydrogen production from water splitting over Eosin Y-sensitized mesoporous-assembled perovskite titanate nanocrystal photocatalysts under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Puangpetch, Tarawipa [Department of Chemical Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakhon Pathom 73000 (Thailand); Sommakettarin, Pichayaon [The Petroleum and Petrochemical College, Chulalongkorn University, Soi Chula 12, Phyathai Road, Pathumwan, Bangkok 10330 (Thailand); Chavadej, Sumaeth; Sreethawong, Thammanoon [The Petroleum and Petrochemical College, Chulalongkorn University, Soi Chula 12, Phyathai Road, Pathumwan, Bangkok 10330 (Thailand); Center for Petroleum, Petrochemicals, and Advanced Materials, Chulalongkorn University, Bangkok 10330 (Thailand)

    2010-11-15

    The photocatalytic water splitting is a promising process for producing H{sub 2} from two abundant renewable sources of water and solar light, with the aid of a suitable photocatalyst. In this work, a combination of sensitizer addition and noble metal loading was employed to modify perovskite photocatalysts in order to achieve the enhancement of photocatalytic H{sub 2} production under visible light irradiation. The dependence of the H{sub 2} production on type of mesoporous-assembled perovskite titanate nanocrystal photocatalysts (MgTiO{sub 3}, CaTiO{sub 3}, and SrTiO{sub 3}), calcination temperature of photocatalyst, Pt loading, type and concentration of electron donor (diethanolamine, DEA; and triethanolamine, TEA), concentration of sensitizer (Eosin Y, E.Y.), photocatalyst dosage, and initial solution pH, was systematically studied. The experimental results showed that the 0.5 wt.% Pt-loaded mesoporous-assembled SrTiO{sub 3} nanocrystal synthesized by a single-step sol-gel method and calcined at 650 C exhibited the highest photocatalytic H{sub 2} production activity from a 15 vol% DEA aqueous solution with dissolved 0.5 mM E.Y. Moreover, the optimum photocatalyst dosage and initial solution pH for the maximum photocatalytic H{sub 2} production activity were found to be 6 g/l and 11.6, respectively. (author)

  12. Controlled synthesis of {001} facets-dominated dye-sensitized BiOCl with high photocatalytic efficiency under visible-light irradiation

    International Nuclear Information System (INIS)

    Chen, Hongbin; Yu, Xiang; Zhu, Yi; Fu, Xionghui; Zhang, Yuanming

    2016-01-01

    High-quality BiOCl with {001} facets were successfully synthesized via a facile solvothermal method by controlling the volume ratio of ethanol (ET) and ethylene glycol (EG). The diameters of BiOCl nanosheets with {001} facets varied from 600 to 50 nm with the increase of EG content while the thickness nearly remained the same (∼20 nm). In the meantime, the morphologies of BiOCl turned into 3D hierarchical microspheres from 2D nanosheets. The 91.84 % {001} facets-exposed BiOCl nanosheets with diameter of 300–600 nm exhibited the best photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation on account of the strong adsorption property of the effective electron injection as well as the sequent reactive radical formation. More importantly, the RhB-sensitized BiOCl nanosheets showed effective photocatalytic property for breaking down methylene blue (MB) and methyl orange (MO) while RhB keeping almost intact until MB and MO had been photodegraded. It was found that the sensitizer radical cation (·RhB"+) could react with MB and MO and their suitable redox potential confirms that as well. These findings may provide a promising approach method for synthesizing other metal oxyhalide materials with controllable diameters of nanosheets and deepen our comprehending for the role of the semiconductor in the sensitization process.

  13. Photocatalytic H 2 production from water splitting under visible light irradiation using Eosin Y-sensitized mesoporous-assembled Pt/TiO 2 nanocrystal photocatalyst

    Science.gov (United States)

    Sreethawong, Thammanoon; Junbua, Chompoonuch; Chavadej, Sumaeth

    Sensitized photocatalytic production of hydrogen from water splitting is investigated under visible light irradiation over mesoporous-assembled titanium dioxide (TiO 2) nanocrystal photocatalysts, without and with Pt loading. The photocatalysts are synthesized by a sol-gel process with the aid of a structure-directing surfactant and are characterized by N 2 adsorption-desorption analysis, X-ray diffraction, UV-vis spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray analysis. The dependence of hydrogen production on the type of TiO 2 photocatalyst (synthesized mesoporous-assembled and commercial non-mesoporous-assembled TiO 2 without and with Pt loading), the calcination temperature of the synthesized photocatalyst, the sensitizer (Eosin Y) concentration, the electron donor (diethanolamine) concentration, the photocatalyst dosage and the initial solution pH is systematically studied. The results show that in the presence of the Eosin Y sensitizer, the Pt-loaded mesoporous-assembled TiO 2 synthesized by a single-step sol-gel process and calcined at 500 °C exhibits the highest photocatalytic activity for hydrogen production from a 30 vol.% diethanolamine aqueous solution with dissolved 2 mM Eosin Y. Moreover, the optimum photocatalyst dosage and initial solution pH for the maximum photocatalytic activity for hydrogen production are 3.33 g dm -3 and 11.5, respectively.

  14. Enhanced photoelectrochemical performance of PbS sensitized Sb–SnO{sub 2}/TiO{sub 2} nanotube arrays electrode under visible light illumination

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jia; Tang, Chengli [Department of Environmental Science and Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Xu, Hao, E-mail: xuhao@mail.xjtu.edu.cn [Department of Environmental Science and Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Yan, Wei, E-mail: yanwei@mail.xjtu.edu.cn [Department of Environmental Science and Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049 (China)

    2015-06-05

    Highlights: • Sb–SnO{sub 2} is used to modify TiO{sub 2} NTAs by microwave method. • PbS is employed to sensitive Sb–SnO{sub 2}/TiO{sub 2} NTAs by S-SILAR method. • Sb–SnO{sub 2} improves electrons transfer and PbS enhances visible light absorption. • The composite electrode shows enhanced photoelectrochemical properties. • The composite electrode exhibits high hydrogen evolution and high QE. - Abstract: The novel PbS sensitized Sb–SnO{sub 2}/TiO{sub 2} nanotube arrays (NTAs) composite electrode (PbS/Sb–SnO{sub 2}/TiO{sub 2} NTAs) was fabricated by microwave combined with sonication-assisted successive ionic layer adsorption and reaction technique (S-SILAR). The obtained electrodes were characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–Vis diffuse reflectance absorption spectra techniques. Enhanced photocurrent (15.52 mA/cm{sup 2}) of the PbS/Sb–SnO{sub 2}/TiO{sub 2} NTAs electrode was observed and can be attributed to the facile photo-generated electrons transfer and enhanced charge separation efficiency. Furthermore, the PbS/Sb–SnO{sub 2}/TiO{sub 2} NTAs composite electrode shows a higher H{sub 2} production rate than the Sb–SnO{sub 2}/TiO{sub 2} NTAs electrode and PbS/TiO{sub 2} NTAs electrode. The results indicate that the PbS/Sb–SnO{sub 2}/TiO{sub 2} NTAs electrode is a promising photoanode in visible photocatalytic water splitting.

  15. Visible light alters yeast metabolic rhythms by inhibiting respiration.

    Science.gov (United States)

    Robertson, James Brian; Davis, Chris R; Johnson, Carl Hirschie

    2013-12-24

    Exposure of cells to visible light in nature or in fluorescence microscopy often is considered to be relatively innocuous. However, using the yeast respiratory oscillation (YRO) as a sensitive measurement of metabolism, we find that non-UV visible light has a significant impact on yeast metabolism. Blue/green wavelengths of visible light shorten the period and dampen the amplitude of the YRO, which is an ultradian rhythm of cell metabolism and transcription. The wavelengths of light that have the greatest effect coincide with the peak absorption regions of cytochromes. Moreover, treating yeast with the electron transport inhibitor sodium azide has similar effects on the YRO as visible light. Because impairment of respiration by light would change several state variables believed to play vital roles in the YRO (e.g., oxygen tension and ATP levels), we tested oxygen's role in YRO stability and found that externally induced oxygen depletion can reset the phase of the oscillation, demonstrating that respiratory capacity plays a role in the oscillation's period and phase. Light-induced damage to the cytochromes also produces reactive oxygen species that up-regulate the oxidative stress response gene TRX2 that is involved in pathways that enable sustained growth in bright visible light. Therefore, visible light can modulate cellular rhythmicity and metabolism through unexpectedly photosensitive pathways.

  16. A facile approach to pure-phase Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles sensitive to visible light

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X., E-mail: xiongwang@njust.edu.cn [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, 117543 (Singapore); Zhang, M.; Tian, P. [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Chin, W.S. [Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, 117543 (Singapore); Zhang, C.M. [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2014-12-01

    Graphical abstract: - Highlights: • Pure-phase Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles were prepared by a facile and environmentally benign sol–gel method. • The multiband characteristic of the nanoparticles greatly expands the visible light absorption. • The visible-light-driven photocatalytic activity of the obtained nanoparticles was improved by 30-fold as compared to the bulk. - Abstract: Pure-phase Bi{sub 2}Fe{sub 4}O{sub 9} nanoparticles with mullite-type structure were successfully fabricated through a facile and environmentally benign sol–gel process. According to the UV–Vis diffuse reflection spectrum, the multiband structure and the band edge position of the nanoparticles were confirmed, indicating the prominent absorption in the expanded visible-light region. As compared to the bulk, the visible-light-driven photocatalytic activity of the obtained nanoparticles was improved by 30-fold. The much improved photocatalytic efficiency of the sample mainly owed to the small crystal size and the multiband characteristic as well as the adding of H{sub 2}O{sub 2} as electron scavenger and a source of hydroxide free radicals instead of Fenton-like reaction, leading to a low recombination of the photogenerated e{sup −}/h{sup +} pairs.

  17. Synergic phototoxic effect of visible light or Gallium-Arsenide laser in the presence of different photo-sensitizers on Porphyromonas gingivalis and Fusobacterium nucleatum

    Directory of Open Access Journals (Sweden)

    Habibollah Ghanbari

    2015-01-01

    Conclusion: Within the limitations of this study, the synergic phototoxic effect of visible light in combination with each of the photosensitizers on P. gingivalis and F. nucleatum. However, the synergic phototoxic effect of laser exposure and hydrogen peroxide and curcumin as photosensitizers on F. nucleatum was not shown.

  18. Visible Light Communication Systems Conception and VIDAS

    OpenAIRE

    Kumar, Navin; Lourenço, Nuno; Spiez, Michal; Aguiar, Rui L

    2008-01-01

    Visible Light Communication (VLC) using LEDs is emerging as a key technology for a ubiquitous communication system, because LED has the advantages of fast switching, long life expectancy, being less expensive and being visible light that is safe for the human body. The VLC system is expected to undergo rapid progress, inspiring numerous indoor and outdoor applications; however, many technical issues need to be addressed, especially in outdoor environment. In order to provide a better understa...

  19. A cocatalyst-free Eosin Y-sensitized p-type of Co₃O₄ quantum dot for highly efficient and stable visible-light-driven water reduction and hydrogen production.

    Science.gov (United States)

    Zhang, Ning; Shi, Jinwen; Niu, Fujun; Wang, Jian; Guo, Liejin

    2015-09-07

    Owing to the effect of energy band bending, p-type Co3O4 quantum dots sensitized by Eosin Y showed a high and stable photocatalytic activity (∼13,440 μmol h(-1) g(-1)(cat)) for water reduction and hydrogen production under visible-light irradiation without any cocatalyst.

  20. [VISIBLE LIGHT AND HUMAN SKIN (REVIEW)].

    Science.gov (United States)

    Tsibadze, A; Chikvaidze, E; Katsitadze, A; Kvachadze, I; Tskhvediani, N; Chikviladze, A

    2015-09-01

    Biological effect of a visible light depends on extend of its property to penetrate into the tissues: the greater is a wavelength the more is an effect of a radiation. An impact of a visible light on the skin is evident by wave and quantum effects. Quanta of a visible radiation carry more energy than infrared radiation, although an influence of such radiation on the skin is produced by the light spectrum on the boarder of the ultraviolet and the infrared rays and is manifested by thermal and chemical effects. It is determined that large doses of a visible light (405-436 nm) can cause skin erythema. At this time, the ratio of generation of free radicals in the skin during an exposure to the ultraviolet and the visible light range from 67-33% respectively. Visible rays of 400-500 nm length of wave cause an increase of the concentration of oxygen's active form and mutation of DNA and proteins in the skin. The urticaria in 4-18% of young people induced by photodermatosis is described. As a result of a direct exposure to sunlight photosensitive eczema is more common in elderly. Special place holds a hereditary disease - porphyria, caused by a visible light. In recent years, dermatologists widely use phototherapy. The method uses polychromatic, non-coherent (wavelength of 515-1200 nm) pulsating beam. During phototherapy/light treatment a patient is being exposed to sunlight or bright artificial light. Sources of visible light are lasers, LEDs and fluorescent lamps which have the full range of a visible light. Phototherapy is used in the treatment of acne vulgaris, seasonal affective disorders, depression, psoriasis, eczema and neurodermities. LED of the red and near infrared range also is characterized by the therapeutic effect. They have an ability to influence cromatophores and enhance ATP synthesis in mitochondria. To speed up the healing of wounds and stimulate hair growth light sources of a weak intensity are used. The light of blue-green spectrum is widely used for

  1. Built-in hyperspectral camera for smartphone in visible, near-infrared and middle-infrared lights region (second report): sensitivity improvement of Fourier-spectroscopic imaging to detect diffuse reflection lights from internal human tissues for healthcare sensors

    Science.gov (United States)

    Kawashima, Natsumi; Hosono, Satsuki; Ishimaru, Ichiro

    2016-05-01

    We proposed the snapshot-type Fourier spectroscopic imaging for smartphone that was mentioned in 1st. report in this conference. For spectroscopic components analysis, such as non-invasive blood glucose sensors, the diffuse reflection lights from internal human skins are very weak for conventional hyperspectral cameras, such as AOTF (Acousto-Optic Tunable Filter) type. Furthermore, it is well known that the spectral absorption of mid-infrared lights or Raman spectroscopy especially in long wavelength region is effective to distinguish specific biomedical components quantitatively, such as glucose concentration. But the main issue was that photon energies of middle infrared lights and light intensities of Raman scattering are extremely weak. For improving sensitivity of our spectroscopic imager, the wide-field-stop & beam-expansion method was proposed. Our line spectroscopic imager introduced a single slit for field stop on the conjugate objective plane. Obviously to increase detected light intensities, the wider slit width of the field stop makes light intensities higher, regardless of deterioration of spatial resolutions. Because our method is based on wavefront-division interferometry, it becomes problems that the wider width of single slit makes the diffraction angle narrower. This means that the narrower diameter of collimated objective beams deteriorates visibilities of interferograms. By installing the relative inclined phaseshifter onto optical Fourier transform plane of infinity corrected optical systems, the collimated half flux of objective beams derived from single-bright points on objective surface penetrate through the wedge prism and the cuboid glass respectively. These two beams interfere each other and form the infererogram as spatial fringe patterns. Thus, we installed concave-cylindrical lens between the wider slit and objective lens as a beam expander. We successfully obtained the spectroscopic characters of hemoglobin from reflected lights from

  2. Microtruss structures with enhanced elasticity fabricated through visible light photocuring

    Directory of Open Access Journals (Sweden)

    Hari Nanthakumar

    Full Text Available We report on the fabrication of an open cellular solid structure using visible light photocuring in combination with light-induced self-writing. A visible light sensitive photopolymer is irradiated with multiple arrays of microscale optical beams, which are generated from LEDs. These beams undergo self-trapping and elicit the inscription of microscale, solid struts into the medium. This process creates a structure consisting of multiple, intersecting struts that form a microtruss structure. Such structures retain their elasticity at higher temperatures as compared to a bulk film of the same thickness. This is the first demonstration of visible light photocuring of photopolymers into a microtruss structure, as well as investigation into their elastic properties under tension. Keywords: Polymers, Self-trapping, Microstructures, Cellular solids

  3. Visible light alters yeast metabolic rhythms by inhibiting respiration

    OpenAIRE

    Robertson, James Brian; Davis, Chris R.; Johnson, Carl Hirschie

    2013-01-01

    In some organisms, respiration fluctuates cyclically, and these rhythms can be a sensitive gauge of metabolism. Constant or pulsatile exposure of yeast to visible wavelengths of light significantly alters and/or initiates these respiratory oscillations, revealing a further dimension of the challenges to yeast living in natural environments. Our results also have implications for the use of light as research tools—e.g., for excitation of fluorescence microscopically—even in organisms such as y...

  4. Photodetector Characteristics in Visible Light Communication

    KAUST Repository

    Ho, Kang-Ting

    2016-04-01

    Typically, in the semiconductor industry pn heterojunctions have been used as either light-emitting diodes (LED) or photodiodes by applying forward current bias or reverse voltage bias, respectively. However, since both devices use the same structure, the light emitting and detecting properties could be combine in one single device, namely LED-based photodetector. Therefore, by integrating LED-based photodetectors as either transmitter or receiver, optical wireless communication could be easily implemented for bidirectional visible light communication networks at low-cost. Therefore, this dissertation focus on the investigation of the photodetection characteristics of InGaN LED-based photodetectors for visible light communication in the blue region. In this regard, we obtain external quantum efficiency of 10 % and photoresponse rise time of 71 μs at 405-nm illumination, revealing high-performance photodetection characteristics. Furthermore, we use orthogonal frequency division multiplexing quadrature amplitude modulation codification scheme to enlarge the operational bandwidth. Consequently, the transmission rate of the communication is efficiently enhanced up to 420 Mbit/s in visible light communication.

  5. Visible light communications modulation and signal processing

    CERN Document Server

    Wang, Zhaocheng; Huang, Wei; Xu, Zhengyuan

    2018-01-01

    This informative new book on state-of-the-art visible light communication (VLC) provides, for the first time, a systematical and advanced treatment of modulation and signal processing for VLC. Visible Light Communications: Modulation and Signal Processing offers a practical guide to designing VLC, linking academic research with commercial applications. In recent years, VLC has attracted attention from academia and industry since it has many advantages over the traditional radio frequency, including wide unregulated bandwidth, high security, and low cost. It is a promising complementary technique in 5G and beyond wireless communications, especially in indoor applications. However, lighting constraints have not been fully considered in the open literature when considering VLC system design, and its importance has been underestimated. That’s why this book—written by a team of experts with both academic research experience and industrial development experience in the field—is so welcome. To help readers u...

  6. Advances and prospects in visible light communications

    International Nuclear Information System (INIS)

    Chen Hongda; Wu Chunhui; Li Honglei; Chen Xiongbin; Gao Zongyu; Cui Shigang; Wang Qin

    2016-01-01

    Visible light communication (VLC) is an emerging technology in optical wireless communication (OWC) that has attracted worldwide research in recent years. VLC can combine communication and illumination together, which could be applied in many application scenarios such as visible light communication local area networks (VLANs), indoor localization, and intelligent lighting. In recent years, pioneering and significant work have been made in the field of VLC. In this paper, an overview of the recent progress in VLC is presented. We also demonstrate our recent experiment results including bidirectional 100 Mbit/s VLAN or Li-Fi system based on OOK modulation without blue filter. The VLC systems that we proposed are good solutions for high-speed VLC application systems with low-cost and low-complexity. VLC technology shows a bright future due to its inherent advantages, shortage of RF spectra and ever increasing popularity of white LEDs. (review)

  7. Visible Lasers and Emerging Color Converters for Lighting and Visible Light Communications

    KAUST Repository

    Shen, Chao

    2017-10-30

    GaN-based lasers are promising for white lighting and visible-light communication (VLC). The advances of III-nitride photonic integration, and the application of YAG crystal and perovskite-based phosphors to lighting and VLC will be discussed.

  8. Visible Lasers and Emerging Color Converters for Lighting and Visible Light Communications

    KAUST Repository

    Shen, Chao

    2017-01-01

    GaN-based lasers are promising for white lighting and visible-light communication (VLC). The advances of III-nitride photonic integration, and the application of YAG crystal and perovskite-based phosphors to lighting and VLC will be discussed.

  9. [Spectral Analysis of CdZnSe Ternary Quantum Dots Sensitized TiO2 Tubes and Its Application in Visible-Light Photocatalysis].

    Science.gov (United States)

    Han, Zhi-zhong; Ren, Li-li; Pan, Hai-bo; Li, Chun-yan; Chen, Jing-hua; Chen, Jian-zhong

    2015-11-01

    In this work, cadmium nitrate hexahydrate [Cd(NO₃)₂ · 6H₂O] is as a source of cadmium, zinc nitrate [Zn(NO₃)₂] as a source of zinc source, and NaHSe as a source of selenium which was prepared through reducing the elemental selenium with sodium borohydride (NaBH₄). Then water-soluble Cd₁₋xZnxSe ternary quantum dots with different component were prepared by colloid chemistry. The as-prepared Cd₁₋xZnx Se ternary quantum dots exhibit stable fluorescent property in aqueous solution, and can still maintain good dispersivity at room temperature for four months. Powder X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM) were used to analyze crystal structure and morphology of the prepared Cd₁₋xZnxSe. It is found that the as-prepared ternary quantum dots are cubic phase, show as sphere, and the average of particle size is approximate 4 nm. The spectral properties and energy band structure of the as-prepared ternary quantum dots were modulated through changing the atom ratio of elements Zn and Cd. Compared with binary quantum dots CdSe and ZnSe, the ultraviolet-visible (UV-Visible) absorption spectrum and fluorescence (FL) emission spectrum of ternary quantum dots are both red-shift. The composites (Cd₀.₅ Zn₀.₅ Se@TNTs) of Cd₀.₅ Zn₀.₅ Se ternary quantum dots and TiO₂ nanotubes (TNTs) were prepared by directly immerging TNTs into quantum dots dispersive solution for 5 hours. TEM image shows that the Cd₀.₅ Zn₀.₅ Se ternary quantum dots were closely combined to nanotube surface. The infrared spectra show that the Ti-Se bond was formed between Cd₀.₅ Zn₀.₅ Se ternary quantum dots and TiO₂ nanotubes, which improve the stability of the composite. Compared to pristine TNTs, UV-Visible absorption spectrum of the composites is significantly enhanced in the visible region of light. And the absorption band edge of Cd₀.₅Zn₀.₅ Se@TNTs red-shift from 400 to 700 nm. The recombination of the

  10. Design for The Indoor Visible Light Communication Application System Based on LED Visible Light

    Directory of Open Access Journals (Sweden)

    Lian Wenyu

    2017-01-01

    Full Text Available This paper designs an indoor visible light communication application system based on LED. The system can modulate the original signal one or more times, move to a specific frequency band, transmit on the power line, in the LED terminal use this module to decode, restore the Ethernet signals. This design is applicable to the simplicity of the LED visible light communication applications, which provide the premise and guarantee for the construction of smart home network.

  11. Preparation, characterization and visible-light-driven photocatalytic activity of a novel Fe(III) porphyrin-sensitized TiO{sub 2} nanotube photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Meng [National Engineering Lab of Textile Fiber Materials & Processing Technology, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Wan, Junmin, E-mail: wwjm2001@126.com [National Engineering Lab of Textile Fiber Materials & Processing Technology, Zhejiang Sci-Tech University, Hangzhou 310018 (China); State Key Laboratory of advanced Textiles Materials and Manufacture Technology, MOE, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Hu, Zhiwen; Peng, Zhiqin; Wang, Bing [National Engineering Lab of Textile Fiber Materials & Processing Technology, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Wang, Huigang [State Key Laboratory of advanced Textiles Materials and Manufacture Technology, MOE, Zhejiang Sci-Tech University, Hangzhou 310018 (China)

    2017-01-01

    Highlights: • FeTCPP-TNT photocatalysts are synthesized. • FeTCPP and tube-like structure are helpful to induce interfacial charge transfer at surface junction. • FeTCPP and tube-like structure are favorable for enhancing photocatalytic activity. • The photocatalytic mechanism of FeTCPP-TNT is proposed. • The photocatalyst are proven to be effective and chemically-stable catalysts. - Abstract: Iron(III) meso-tetra(4-carboxyphenyl) porphyrin (FeTCPP) loaded on the surface of TiO{sub 2} nanotubes (TNTs) has been successfully prepared through improved hydrothermal and heating reflux process. The new photocatalyst has been characterized and analyzed by TEM/EDS, BET, XRD, FT-IR, DRS, PL, XPS and EPR. The photocatalytic activity of FeTCPP/TNT nanocomposite was evaluated by the photodegradation of MB under visible light irradiation. The degradation results showed a purification of more than 90% MB in simulating wastewater, and confirmed that the prepared FeTCPP/TNT nanocomposite has acquired superior photocatalytic activitiy. The 6 times cycled results suggested the great stability of the photocatalyst. These results confirmed the FeTCPP played an important role in capturing photons and expanding the absorption wavelength to the visible light region, and the FeTCPP/TNT photocatalyst is also beneficial for the electron transfer and long-distance transmission, and could efficiently increase the separation of the electron-hole pairs, and accelerate the decomposition of organic pollutants. In addition, nano-sized structures can increase adsorption capability.

  12. Visible light emission from porous silicon carbide

    DEFF Research Database (Denmark)

    Ou, Haiyan; Lu, Weifang

    2017-01-01

    Light-emitting silicon carbide is emerging as an environment-friendly wavelength converter in the application of light-emitting diode based white light source for two main reasons. Firstly, SiC has very good thermal conductivity and therefore a good substrate for GaN growth in addition to the small...... lattice mismatch. Secondly, SiC material is abundant, containing no rear-earth element material as commercial phosphor. In this paper, fabrication of porous SiC is introduced, and their morphology and photoluminescence are characterized. Additionally, the carrier lifetime of the porous SiC is measured...... by time-resolved photoluminescence. The ultrashort lifetime in the order of ~70ps indicates porous SiC is very promising for the application in the ultrafast visible light communications....

  13. Synergetic Enhancement of the Photocatalytic Activity of TiO2 with Visible Light by Sensitization Using a Novel Push-Pull Zinc Phthalocyanine

    Directory of Open Access Journals (Sweden)

    A. Luna-Flores

    2017-01-01

    Full Text Available A new one-pot synthesis of a novel A3B-type asymmetric zinc phthalocyanine (AZnPc was developed. The phthalocyanine complex was characterized unambiguously and used to prepare a TiO2 hybrid photocatalyst to enhance its photocatalytic activity in the visible range. Different compositions of the phthalocyanine dye were tested in order to find the optimum amount of sensitizer to get the highest activity during the photocatalytic tests. The hybrid photocatalyst was characterized by UV-Vis diffuse reflectance (DRS and Fourier transform infrared spectroscopy (FT-IR and its photocatalytic activity was compared with that of the individual components considering the effects of sensitization on their efficiency to degrade Rhodamine B as a model reaction. A synergic improvement of the photocatalytic activity for the hybrid system was explained in terms of an improved electron injection from the photo-activated phthalocyanine to the TiO2. Considering the structural features of the phthalocyanine sensitizer and their effect on aggregation, some mechanistic aspects of its binding to TiO2 are suggested to account for the photocatalytic activity enhancement. Finally, the inhibitory effect on the sprouting of chia seeds (Salvia hispanica was evaluated in order to test the toxicity of the water effluent obtained after the photodegradation process. According to our growth inhibition assays, it was found that the Rh-B degradation by-products do not lead to an acute toxicity.

  14. Visible light communication applications in healthcare.

    Science.gov (United States)

    Muhammad, Shoaib; Qasid, Syed Hussain Ahmed; Rehman, Shafia; Rai, Aitzaz Bin Sulltan

    2016-01-01

    With the development in science, methods of communication are also improved, replacing old ones with new advanced ways in an attempt to make data transfer more secure, safer for health, and time as well as cost efficient. One of such methods is Visible Light Communication, as the name implies data is transferred through a light equipment such as incandescent or florescent bulb having speed of 10 Kb/s or LEDs approaching speed of 500 Mb/s [1]. VLC uses visible light between 384 and 789 THz [2,3]. Though range is limitation of VLC, however data transfer up-to distance of 1 to 2 km although at lower transfer rate has been reached.The VLC system comprises of light source like LED and receiver equipment, however, with advancement, now LEDs are used for both sending and receiving data. LED remains on all the time, and there is no change in brightness level during the whole process, making it safe for eyes. Currently, VLC system is facing some serious technical challenges before it could be applied in daily life.

  15. Switching Diarylethenes Reliably in Both Directions with Visible Light.

    Science.gov (United States)

    Fredrich, Sebastian; Göstl, Robert; Herder, Martin; Grubert, Lutz; Hecht, Stefan

    2016-01-18

    A diarylethene photoswitch was covalently connected to two small triplet sensitizer moieties in a conjugated and nonconjugated fashion and the photochromic performance of the resulting compounds was investigated. In comparison with the parent diarylethene (without sensitizers) and one featuring saturated linkages, the conjugated photoswitch offers superior fatigue resistance upon visible-light excitation due to effective triplet energy transfer from the biacetyl termini to the diarylethene core. Our design makes it possible to switch diarylethenes with visible light in both directions in a highly efficient and robust fashion based on extending π-conjugation and by-product-free ring-closure via the triplet manifold. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Indoor visible light communication with smart lighting technology

    Science.gov (United States)

    Das Barman, Abhirup; Halder, Alak

    2017-02-01

    An indoor visible-light communication performance is investigated utilizing energy efficient white light by 2D LED arrays. Enabled by recent advances in LED technology, IEEE 802.15.7 standardizes high-data-rate visible light communication and advocates for colour shift keying (CSK) modulation to overcome flicker and to support dimming. Voronoi segmentation is employed for decoding N-CSK constellation which has superior performance compared to other existing decoding methods. The two chief performance degrading effects of inter-symbol interference and LED nonlinearity is jointly mitigated using LMS post equalization at the receiver which improves the symbol error rate performance and increases field of view of the receiver. It is found that LMS post equalization symbol at 250MHz offers 7dB SNR improvement at SER10-6

  17. SILAR BiOI-Sensitized TiO2 Films for Visible-Light Photocatalytic Degradation of Rhodamine B and 4-Chlorophenol.

    Science.gov (United States)

    Odling, Gylen; Robertson, Neil

    2017-04-05

    BiOI nanoplates were deposited upon a film of TiO 2 nanoparticles derived from a commercial source using a simple room temperature sequential ionic layer adsorption and reaction (SILAR) method. X-ray diffraction, X-ray photoelectron spectroscopy and electron microscopies have been used to confirm the crystal phase, chemical states of key elements and morphology of the BiOI nanoplate-TiO 2 composites. Using both valence band X-ray photoelectron spectroscopy and UV/Vis diffuse reflectance measurements the band structure of the composites is determined to be that of a type II heterojunction. Through initial screening of the photocatalytic activity of the SILAR-modified films it was determined that five SILAR cycles are optimal in the photocatalytic degradation of rhodamine B. The visible-light sensitisation effect of BiOI was then proven by examination of the photocatalytic degradation of the colourless organic pollutant 4-chlorophenol, showing a large enhancement over an equivalent TiO 2 film. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Simulating Visibility Under Reduced Acuity and Contrast Sensitivity

    Science.gov (United States)

    Thompson, William B.; Legge, Gordon E.; Kersten, Daniel J.; Shakespeare, Robert A.; Lei, Quan

    2017-01-01

    Architects and lighting designers have difficulty designing spaces that are accessible to those with low vision, since the complex nature of most architectural spaces requires a site-specific analysis of the visibility of mobility hazards and key landmarks needed for navigation. We describe a method that can be utilized in the architectural design process for simulating the effects of reduced acuity and contrast on visibility. The key contribution is the development of a way to parameterize the simulation using standard clinical measures of acuity and contrast sensitivity. While these measures are known to be imperfect predictors of visual function, they provide a way of characterizing general levels of visual performance that is familiar to both those working in low vision and our target end-users in the architectural and lighting design communities. We validate the simulation using a letter recognition task. PMID:28375328

  19. Opsin expression in Limulus eyes: a UV opsin is expressed in each eye type and co-expressed with a visible light-sensitive opsin in ventral larval eyes.

    Science.gov (United States)

    Battelle, Barbara-Anne; Kempler, Karen E; Harrison, Alexandra; Dugger, Donald R; Payne, Richard

    2014-09-01

    The eyes of the horseshoe crab, Limulus polyphemus, are a model for studies of visual function and the visual systems of euarthropods. Much is known about the structure and function of L. polyphemus photoreceptors, much less about their photopigments. Three visible-light-sensitive L. polyphemus opsins were characterized previously (LpOps1, 2 and 5). Here we characterize a UV opsin (LpUVOps1) that is expressed in all three types of L. polyphemus eyes. It is expressed in most photoreceptors in median ocelli, the only L. polyphemus eyes in which UV sensitivity was previously detected, and in the dendrite of eccentric cells in lateral compound eyes. Therefore, eccentric cells, previously thought to be non-photosensitive second-order neurons, may actually be UV-sensitive photoreceptors. LpUVOps1 is also expressed in small photoreceptors in L. polyphemus ventral larval eyes, and intracellular recordings from these photoreceptors confirm that LpUVOps1 is an active, UV-sensitive photopigment. These photoreceptors also express LpOps5, which we demonstrate is an active, long-wavelength-sensitive photopigment. Thus small photoreceptors in ventral larval eyes, and probably those of the other larval eyes, have dual sensitivity to UV and visible light. Interestingly, the spectral tuning of small ventral photoreceptors may change day to night, because the level of LpOps5 in their rhabdoms is lower during the day than during the night, whereas LpUVOps1 levels show no diurnal change. These and previous findings show that opsin co-expression and the differential regulation of co-expressed opsins in rhabdoms is a common feature of L. polyphemus photoreceptors. © 2014. Published by The Company of Biologists Ltd.

  20. Visible Light Communications towards 5G

    Directory of Open Access Journals (Sweden)

    S. Zvanovec

    2015-04-01

    Full Text Available 5G networks have to offer extremely high capacity for novel streaming applications. One of the most promising approaches is to embed large numbers of co-operating small cells into the macro-cell coverage area. Alternatively, optical wireless based technologies can be adopted as an alternative physical layer offering higher data rates. Visible light communications (VLC is an emerging technology for future high capacity communication links (it has been accepted to 5GPP in the visible range of the electromagnetic spectrum (~370–780 nm utilizing light-emitting diodes (LEDs simultaneously provide data transmission and room illumination. A major challenge in VLC is the LED modulation bandwidths, which are limited to a few MHz. However, myriad gigabit speed transmission links have already been demonstrated. Non line-of-sight (NLOS optical wireless is resistant to blocking by people and obstacles and is capable of adapting its’ throughput according to the current channel state information. Concurrently, organic polymer LEDs (PLEDs have become the focus of enormous attention for solid-state lighting applications due to their advantages over conventional white LEDs such as ultra-low costs, low heating temperature, mechanical flexibility and large photoactive areas when produced with wet processing methods. This paper discusses development of such VLC links with a view to implementing ubiquitous broadcasting networks featuring advanced modulation formats such as orthogonal frequency division multiplexing (OFDM or carrier-less amplitude and phase modulation (CAP in conjunction with equalization techniques. Finally, this paper will also summarize the results of the European project ICT COST IC1101 OPTICWISE (Optical Wireless Communications - An Emerging Technology dealing VLC and OLEDs towards 5G networks.

  1. PAPR analysis for OFDM visible light communication.

    Science.gov (United States)

    Wang, Jiaheng; Xu, Yang; Ling, Xintong; Zhang, Rong; Ding, Zhi; Zhao, Chunming

    2016-11-28

    Orthogonal frequency-division multiplexing (OFDM) is a practical technology in visible light communication (VLC) for high-speed transmissions. However, one of its operational limitations is the peak-to-average power ratio (PAPR) of the transmitted signal. In this paper, we analyze the PAPR distributions of four VLC OFDM schemes, namely DC-biased optical OFDM (DCO-OFDM), asymmetrically clipped optical OFDM (ACO-OFDM), pulse amplitude modulated discrete multitone (PAM-DMT), and Flip-OFDM. Both lower and upper clippings are considered. We analytically derive the complementary cumulative distribution functions (CCDFs) of the PAPRs of the clipped VLC OFDM signals, and investigate the impact of lower and upper clippings on PAPR distributions. Our analytical results, as verified by numerical simulations, provide useful insights and guidelines for VLC OFDM system designs.

  2. Unidirectional visible light communication and illumination with LEDs

    NARCIS (Netherlands)

    Li, S.; Pandharipande, A.; Willems, F.M.J.

    2016-01-01

    Visible light communication (VLC) with light emitting diodes (LEDs) has attracted interest for interactive and networked lighting control, and consumer infotainment applications. In this paper, we propose an LED system for jointly achieving unidirectional VLC while providing flicker-free

  3. Visible light photoreduction of CO.sub.2 using heterostructured catalysts

    Science.gov (United States)

    Matranga, Christopher; Thompson, Robert L; Wang, Congjun

    2015-03-24

    The method provides for use of sensitized photocatalyst for the photocatalytic reduction of CO.sub.2 under visible light illumination. The photosensitized catalyst is comprised of a wide band gap semiconductor material, a transition metal co-catalyst, and a semiconductor sensitizer. The semiconductor sensitizer is photoexcited by visible light and forms a Type II band alignment with the wide band gap semiconductor material. The wide band gap semiconductor material and the semiconductor sensitizer may be a plurality of particles, and the particle diameters may be selected to accomplish desired band widths and optimize charge injection under visible light illumination by utilizing quantum size effects. In a particular embodiment, CO.sub.2 is reduced under visible light illumination using a CdSe/Pt/TiO2 sensitized photocatalyst with H.sub.2O as a hydrogen source.

  4. Visible Light Responsive Catalyst for Air Water Purification Project

    Science.gov (United States)

    Wheeler, Raymond M.

    2014-01-01

    Investigate and develop viable approaches to render the normally UV-activated TIO2 catalyst visible light responsive (VLR) and achieve high and sustaining catalytic activity under the visible region of the solar spectrum.

  5. Indigoid Photoswitches: Visible Light Responsive Molecular Tools.

    Science.gov (United States)

    Petermayer, Christian; Dube, Henry

    2018-05-15

    Indigoid photoswitches comprise a class of chromophores that are derived from the parent and well-known indigo dye. Different from most photoswitches their core structures absorb in the visible region of the spectrum in both isomeric states even without substitutions, which makes them especially interesting for applications not tolerant of high-energy UV light. Also different from most current photoswitching systems, they provide highly rigid structures that undergo large yet precisely controllable geometry changes upon photoisomerization. The favorable combination of pronounced photochromism, fast and efficient photoreactions, and high thermal bistability have led to a strongly increased interest in indigoid photoswitches over the last years. As a result, intriguing applications of these chromophores as reversible triggering units in supramolecular and biological chemistry, the field of molecular machines, or smart molecules have been put forward. In this Account current developments in the synthesis, mechanistic understanding of light responsiveness, advantageous properties as phototools, and new applications of indigoid photoswitches are summarized with the focus on hemithioindigo, hemiindigo, and indigo as key examples. Many methods for the synthesis of hemithioindigos are known, but derivatives with a fourth substituent at the double bond could not easily be prepared because of the resulting increased steric hindrance in the products. Recent efforts in our laboratory have provided two different methods to prepare these highly promising photoswitches in very efficient ways. One method is especially designed for the introduction of sterically hindered ketones while the second one allows rapid structural diversification in only three high-yielding synthetic steps. Given the lesser prominence of indigoid photoswitches, mechanistic understanding of their excited state behavior and therefore rational design opportunities for photophysical properties are also much

  6. Nanopatterned organic semiconductors for visible light communications

    Science.gov (United States)

    Yang, Xilu; Dong, Yurong; Zeng, Pan; Yu, Yan; Xie, Yujun; Gong, Junyi; Shi, Meng; Liang, Rongqing; Ou, Qiongrong; Chi, Nan; Zhang, Shuyu

    2018-03-01

    Visible light communication (VLC) is becoming an important and promising supplement to the existing Wi-Fi network for the coming 5G communications. Organic light-emitting semiconductors present much fast fluorescent decay rates compared to those of conventional colour-converting phosphors, therefore capable of achieving much higher bandwidths. Here we explore how nanopatterned organic semiconductors can further enhance the data rates of VLC links by improving bandwidths and signal-to-noise ratios (SNRs) and by supporting spatial multiplexing. We first demonstrate a colour-converting VLC system based on nanopatterned hyperbolic metamaterials (HMM), the bandwidth of which is enhanced by 50%. With regard to enhancing SNRs, we achieve a tripling of optical gain by integrating a nanopatterned luminescent concentrator to a signal receiver. In addition, we demonstrate highly directional fluorescent VLC antennas based on nanoimprinted polymer films, paving the way to achieving parallel VLC communications via spatialmultiplexing. These results indicate nanopatterned organic semiconductors provide a promising route to high speed VLC links.

  7. Catadioptric lenses in Visible Light Communications

    Science.gov (United States)

    Garcia-Marquez, J.; Valencia, J. C.; Perez, H.; Topsu, S.

    2015-04-01

    Since few years ago, visible light communications (VLC) have experience an accelerated interest from a research point of view. The beginning of this decade has seen many improvements in VLC at an electronic level. High rates of transmission at low bit error ratios (BER) have been reported. A few numbers of start-ups have initiated activities to offer a variety of applications ranging from indoor geo-localization to internet, but in spite of these advancements, some other problems arise. Long-range transmissions mean a high BER which reduce the number of applications. In this sense, new redesigned optical collectors or in some cases, optical reflectors must be considered to ensure a low BER at higher distance transmissions. Here we also expose a preliminary design of a catadioptric and monolithical lens for a LI-FI receiver with two rotationally symmetrical main piecewise surfaces za and zb. These surfaces are represented in a system of cylindrical coordinates with an anterior surface za with a central and refractive sector surrounded by a peripheral reflective sector and a back piecewise surface zb with a central refractive sector and a reflective sector, both characterized as ideal for capturing light within large acceptance angles.

  8. Precoded generalized space shift keying for indoor visible light communications

    KAUST Repository

    Kadampot, Ishaque Ashar; Park, Kihong; Alouini, Mohamed-Slim

    2014-01-01

    We consider a visible light communication system with 2 transmit light emitting diodes (LED) and nr receive photodiodes. An optical generalized space shift keying modulation scheme is considered for the transmission of bits where each LED can

  9. Efficient resource allocation scheme for visible-light communication system

    Science.gov (United States)

    Kim, Woo-Chan; Bae, Chi-Sung; Cho, Dong-Ho; Shin, Hong-Seok; Jung, D. K.; Oh, Y. J.

    2009-01-01

    A visible-light communication utilizing LED has many advantagies such as visibility of information, high SNR (Signal to Noise Ratio), low installation cost, usage of existing illuminators, and high security. Furthermore, exponentially increasing needs and quality of LED have helped the development of visible-light communication. The visibility is the most attractive property in visible-light communication system, but it is difficult to ensure visibility and transmission efficiency simultaneously during initial access because of the small amount of initial access process signals. In this paper, we propose an efficient resource allocation scheme at initial access for ensuring visibility with high resource utilization rate and low data transmission failure rate. The performance has been evaluated through the numerical analysis and simulation results.

  10. Photocatalytic H{sub 2} production from water splitting under visible light irradiation using Eosin Y-sensitized mesoporous-assembled Pt/TiO{sub 2} nanocrystal photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Sreethawong, Thammanoon; Chavadej, Sumaeth [The Petroleum and Petrochemical College, Chulalongkorn University, Soi Chula 12, Phyathai Road, Pathumwan, Bangkok 10330 (Thailand); Center for Petroleum, Petrochemicals, and Advanced Materials, Chulalongkorn University, Bangkok 10330 (Thailand); Junbua, Chompoonuch [The Petroleum and Petrochemical College, Chulalongkorn University, Soi Chula 12, Phyathai Road, Pathumwan, Bangkok 10330 (Thailand)

    2009-05-15

    Sensitized photocatalytic production of hydrogen from water splitting is investigated under visible light irradiation over mesoporous-assembled titanium dioxide (TiO{sub 2}) nanocrystal photocatalysts, without and with Pt loading. The photocatalysts are synthesized by a sol-gel process with the aid of a structure-directing surfactant and are characterized by N{sub 2} adsorption-desorption analysis, X-ray diffraction, UV-vis spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray analysis. The dependence of hydrogen production on the type of TiO{sub 2} photocatalyst (synthesized mesoporous-assembled and commercial non-mesoporous-assembled TiO{sub 2} without and with Pt loading), the calcination temperature of the synthesized photocatalyst, the sensitizer (Eosin Y) concentration, the electron donor (diethanolamine) concentration, the photocatalyst dosage and the initial solution pH is systematically studied. The results show that in the presence of the Eosin Y sensitizer, the Pt-loaded mesoporous-assembled TiO{sub 2} synthesized by a single-step sol-gel process and calcined at 500 C exhibits the highest photocatalytic activity for hydrogen production from a 30 vol.% diethanolamine aqueous solution with dissolved 2 mM Eosin Y. Moreover, the optimum photocatalyst dosage and initial solution pH for the maximum photocatalytic activity for hydrogen production are 3.33 g dm{sup -3} and 11.5, respectively. (author)

  11. Two-way visible light communication and illumination with LEDs

    NARCIS (Netherlands)

    Li, S.; Pandharipande, A.; Willems, F.M.J.

    2017-01-01

    Visible light communications (VLC) with light-emitting diodes (LEDs) has attracted applications, such as data communications, lighting control, and light interaction. In this paper, we propose a system by which two LED devices are used for two-way VLC while also providing illumination. We consider

  12. The Development of Visible-Light Photoredox Catalysis in Flow.

    Science.gov (United States)

    Garlets, Zachary J; Nguyen, John D; Stephenson, Corey R J

    2014-04-01

    Visible-light photoredox catalysis has recently emerged as a viable alternative for radical reactions otherwise carried out with tin and boron reagents. It has been recognized that by merging photoredox catalysis with flow chemistry, slow reaction times, lower yields, and safety concerns may be obviated. While flow reactors have been successfully applied to reactions carried out with UV light, only recent developments have demonstrated the same potential of flow reactors for the improvement of visible-light-mediated reactions. This review examines the initial and continuing development of visible-light-mediated photoredox flow chemistry by exemplifying the benefits of flow chemistry compared with conventional batch techniques.

  13. Integrating visible light 3D scanning into the everyday world

    Science.gov (United States)

    Straub, Jeremy

    2015-05-01

    Visible light 3D scanning offers the potential to non-invasively and nearly non-perceptibly incorporate 3D imaging into the everyday world. This paper considers the various possible uses of visible light 3D scanning technology. It discusses multiple possible usage scenarios including in hospitals, security perimeter settings and retail environments. The paper presents a framework for assessing the efficacy of visible light 3D scanning for a given application (and compares this to other scanning approaches such as those using blue light or lasers). It also discusses ethical and legal considerations relevant to real-world use and concludes by presenting a decision making framework.

  14. PtNi Alloy Cocatalyst Modification of Eosin Y-Sensitized g-C3N4/GO Hybrid for Efficient Visible-Light Photocatalytic Hydrogen Evolution

    Science.gov (United States)

    Wang, Peng; Zong, Lanlan; Guan, Zhongjie; Li, Qiuye; Yang, Jianjun

    2018-02-01

    An economic and effective Pt-based alloy cocatalyst has attracted considerable attention due to their excellent catalytic activity and reducing Pt usage. In this study, PtNi alloy cocatalyst was successfully decorated on the g-C3N4/GO hybrid photocatalyst via a facile chemical reduction method. The Eosin Y-sensitized g-C3N4/PtNi/GO-0.5% composite photocatalyst yields about 1.54 and 1178 times higher hydrogen evolution rate than the Eosin Y-sensitized g-C3N4/Pt/GO-0.5% and g-C3N4/Ni/GO-0.5% samples, respectively. Mechanism of enhanced performance for the g-C3N4/PtNi/GO composite was also investigated by different characterization, such as photoluminescence, transient photocurrent response, and TEM. These results indicated that enhanced charge separation efficiency and more reactive sites are responsible for the improved hydrogen evolution performance due to the positive synergetic effect between Pt and Ni. This study suggests that PtNi alloy can be used as an economic and effective cocatalyst for hydrogen evolution reaction. [Figure not available: see fulltext.

  15. Driving Unidirectional Molecular Rotary Motors with Visible Light by Intra- And Intermolecular Energy Transfer from Palladium Porphyrin

    NARCIS (Netherlands)

    Cnossen, Arjen; Hou, Lili; Pollard, Michael M.; Wesenhagen, Philana V.; Browne, Wesley R.; Feringa, Ben L.

    2012-01-01

    Driving molecular rotary motors using visible light (530-550 nm) instead of UV light was achieved using palladium tetraphenylporphyrin as a triplet sensitizer. Visible light driven rotation was confirmed by UV/vis absorption, circular dichroism and H-1 NMR spectroscopy and the rotation was confirmed

  16. Au/La{sub 2}Ti{sub 2}O{sub 7} nanostructures sensitized with black phosphorus for plasmon-enhanced photocatalytic hydrogen production in visible and near-infrared light

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Mingshan; Fujitsuka, Mamoru; Majima, Tetsuro [The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki (Japan); Cai, Xiaoyan [The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki (Japan); Department of Physics, Beihang University, Beijing (China); Zhang, Junying [Department of Physics, Beihang University, Beijing (China)

    2017-02-13

    Efficient utilization of solar energy is a high-priority target and the search for suitable materials as photocatalysts that not only can harvest the broad wavelength of solar light, from UV to near-infrared (NIR) region, but also can achieve high and efficient solar-to-hydrogen conversion is one of the most challenging missions. Herein, using Au/La{sub 2}Ti{sub 2}O{sub 7} (BP-Au/LTO) sensitized with black phosphorus (BP), a broadband solar response photocatalyst was designed and used as efficient photocatalyst for H{sub 2} production. The optimum H{sub 2} production rates of BP-Au/LTO were about 0.74 and 0.30 mmol g{sup -1} h{sup -1} at wavelengths longer than 420 nm and 780 nm, respectively. The broad absorption of BP and plasmonic Au contribute to the enhanced photocatalytic activity in the visible and NIR light regions. Time-resolved diffuse reflectance spectroscopy revealed efficient interfacial electron transfer from excited BP and Au to LTO which is in accordance with the observed high photoactivities. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. W18O49 nanorods decorated with Ag/AgCl nanoparticles as highly-sensitive gas-sensing material and visible-light-driven photocatalyst

    International Nuclear Information System (INIS)

    Sun Shibin; Chang Xueting; Dong Lihua; Zhang Yidong; Li Zhenjiang; Qiu Yanyan

    2011-01-01

    A novel gas-sensing material and photocatalyst was successfully obtained by decorating Ag/AgCl nanoparticles on the W 18 O 49 nanorods through a clean photochemical route. The as-prepared samples were characterized using combined techniques of X-ray diffractometry, electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Gas-sensing measurements indicate that the Ag/AgCl/W 18 O 49 NRs sensors exhibit superior reducing gas-sensing properties to those of bare W 18 O 49 NRs, and they are highly selective and sensitive to NH 3 , acetone, and H 2 S with short response and recovery times. The Ag/AgCl/W 18 O 49 NRs photocatlysts also possess higher photocatalytic performance than bare W 18 O 49 NRs for degradation of methyl orange under simulated sunlight irradiation. Possible mechanisms concerning the enhancement of gas-sensing and photocatalytic activities of the Ag/AgCl/W 18 O 49 NRs composite were proposed. - Graphical Abstract: The Ag/AgCl nanoparticles adhered well to the W 18 O 49 nanorod. The Ag could act as transfer center of the photoexcited carriers, prohibiting their recombinations in both W 18 O 49 and AgCl. Highlights: → Ag/AgCl/W 18 O 49 NRs were successfully obtained via a clean photochemical route. → The Ag/AgCl nanoparticles decorated on the W 18 O 49 NRs possessed cladding structure. → The Ag/AgCl/W 18 O 49 NRs exhibited excellent gas-sensing and photocatalytic properties.

  18. Visible light emission from porous silicon carbide

    DEFF Research Database (Denmark)

    Ou, Haiyan; Lu, Weifang

    2017-01-01

    Light-emitting silicon carbide is emerging as an environment-friendly wavelength converter in the application of light-emitting diode based white light source for two main reasons. Firstly, SiC has very good thermal conductivity and therefore a good substrate for GaN growth in addition to the small...

  19. High visibility temporal ghost imaging with classical light

    Science.gov (United States)

    Liu, Jianbin; Wang, Jingjing; Chen, Hui; Zheng, Huaibin; Liu, Yanyan; Zhou, Yu; Li, Fu-li; Xu, Zhuo

    2018-03-01

    High visibility temporal ghost imaging with classical light is possible when superbunching pseudothermal light is employed. In the numerical simulation, the visibility of temporal ghost imaging with pseudothermal light, equaling (4 . 7 ± 0 . 2)%, can be increased to (75 ± 8)% in the same scheme with superbunching pseudothermal light. The reasons for that the retrieved images are different for superbunching pseudothermal light with different values of degree of second-order coherence are discussed in detail. It is concluded that high visibility and high quality temporal ghost image can be obtained by collecting sufficient number of data points. The results are helpful to understand the difference between ghost imaging with classical light and entangled photon pairs. The superbunching pseudothermal light can be employed to improve the image quality in ghost imaging applications.

  20. On the Secrecy Capacity of MISO Visible Light Communication Channels

    KAUST Repository

    Arfaoui, Mohamed Amine; Rezki, Zouheir; Ghrayeb, Ali; Alouini, Mohamed-Slim

    2017-01-01

    We study the secrecy capacity of the multiple- input single-output (MISO) Gaussian wiretap visible light communication (VLC) channel. We study a typical VLC scenario with one transmitter, one legitimate receiver, and one eavesdropper. Specifically

  1. Discrete Input Signaling for MISO Visible Light Communication Channels

    KAUST Repository

    Arfaoui, Mohamed Amine; Rezki, Zouheir; Ghrayeb, Ali; Alouini, Mohamed-Slim

    2017-01-01

    In this paper, we study the achievable secrecy rate of visible light communication (VLC) links for discrete input distributions. We consider single user single eavesdropper multiple-input single-output (MISO) links. In addition, both beamforming

  2. Visible Light Responsive Catalyst for Air & Water Purification

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective for this project was to investigate and develop viable approaches to render the normally UV-activated titanium dioxide (TiO2) catalyst visible light...

  3. Visible Light Communication: An Emerging Area in Wireless

    Indian Academy of Sciences (India)

    A. Chockalingam

    infrared to ultraviolet. • includes visible light wavelengths (380 to 780 nm). Concluding remarks. NH ... low power, high data rate systems in satellites, portable devices, etc. .... improve spectral efficiency and performance. • Issues. • channel ...

  4. A novel mirror diversity receiver for indoor MIMO visible light

    KAUST Repository

    Park, Ki-Hong; Alheadary, Wael G.; Alouini, Mohamed-Slim

    2016-01-01

    In this paper, we propose and study a non-imaging receiver design reducing the correlation of channel matrix for indoor multiple-input multiple-output (MIMO) visible light communication (VLC) systems. Contrary to previous works, our proposed mirror

  5. Visible Light Communications (VLC) for Ambient Assisted Living

    DEFF Research Database (Denmark)

    Kumar, Ambuj; Mihovska, Albena D.; Kyriazakos, Sofoklis

    2014-01-01

    and a conceptual supporting architecture for its deployment. Further, the technical challenges and possible roadmap for the actual deployment are analyzed for the particular case of an eHealth scenario where the utilization of VLC technology is the enabler of the costefficient rollout of the required...... (WLANs) can take upon part of the indoor traffic, the ever increasing demand for such data, and users, calls for either use of licensed or novel unlicensed wireless communication technologies as part of the smart home enablers. This paper focuses on the potentials of visible light communications (VLC......), jointly with radio and fiber communications, to support very dense low and high data rate connectivity, while enabling deployment of secure-sensitive indoor applications, including indoor tracking and localization. The paper proposes a scenario for integrating VLC into the smart home scenario...

  6. FY 1998 report on the results of R and D projects by local consortiums for immediate effects. Development of titanium dioxide thin film photocatalysts sensitive to visible light and their applications to cleaning systems; 1998 nendo kashiko kasseina sanka chintan hikari shokubai usumaku no kaihatsu to sono system oyo seika hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    The R and D project has been implemented for developing the thin film-making process techniques which can increase areas of titanium oxide (TiO{sub 2}) photocatalysts sensitive to visible light and their mass production. The fundamental investigations are directed to elucidation of the mechanisms involved in manifestation of activity in visible light of the visible light-sensitive thin film doped with the Cr, V or other ions. The sputtering involving no ion implantation is devised for producing the thin films, to realize the highest visible light sensitivity recorded for the thin TiO{sub 2} film. The sputtering process is investigated in detail for the film-making conditions, e.g., Ar pressure, effects of coexisting O{sub 2} gas, and power gap. The conditions under which the thin film serviceable under commercial conditions can be produced are not established yet, but it is confirmed that the coating film shows superhydrophilicity and photocatalytic activity for, e.g., sterilization, when irradiated with ultraviolet ray. The method has been established for evaluating deodorizing and contamination-preventive functions of the thin films in ultraviolet and visible rays. The project has also confirmed applicability of the techniques to the commercial products, and established the self-cleanable catalyst by combining the oxide catalytic function with the photocatalytic function. (NEDO)

  7. Photodetector Characteristics in Visible Light Communication

    KAUST Repository

    Ho, Kang-Ting

    2016-01-01

    Typically, in the semiconductor industry pn heterojunctions have been used as either light-emitting diodes (LED) or photodiodes by applying forward current bias or reverse voltage bias, respectively. However, since both devices use the same

  8. Security in Visible Light Communication: Novel Challenges and Opportunities

    Directory of Open Access Journals (Sweden)

    Christian ROHNER

    2015-09-01

    Full Text Available As LED lighting becomes increasingly ubiquitous, Visible Light Communication is attracting the interest of academia and industry as a complement to RF as the physical layer for the Internet of Things. Aside from its much greater spectral availability compared to RF, visible light has several attractive properties that may promote its uptake: its lack of health risks, its opportunities for spatial reuse, its relative immunity to multipath fading, its lack of electromagnetic interference, and its inherently secure nature: differently from RF, light does not penetrate through walls. In this paper, we outline the security implications of Visible Light Communication, review the existing contributions to this under-explored space, and survey the research opportunities that we envision for the near future.

  9. Visible-light optical coherence tomography: a review

    Science.gov (United States)

    Shu, Xiao; Beckmann, Lisa; Zhang, Hao F.

    2017-12-01

    Visible-light optical coherence tomography (vis-OCT) is an emerging imaging modality, providing new capabilities in both anatomical and functional imaging of biological tissue. It relies on visible light illumination, whereas most commercial and investigational OCTs use near-infrared light. As a result, vis-OCT requires different considerations in engineering design and implementation but brings unique potential benefits to both fundamental research and clinical care of several diseases. Here, we intend to provide a summary of the development of vis-OCT and its demonstrated applications. We also provide perspectives on future technology improvement and applications.

  10. Orbital Angular Momentum Multiplexing over Visible Light Communication Systems

    Science.gov (United States)

    Tripathi, Hardik Rameshchandra

    This thesis proposes and explores the possibility of using Orbital Angular Momentum multiplexing in Visible Light Communication system. Orbital Angular Momentum is mainly applied for laser and optical fiber transmissions, while Visible Light Communication is a technology using the light as a carrier for wireless communication. In this research, the study of the state of art and experiments showing some results on multiplexing based on Orbital Angular Momentum over Visible Light Communication system were done. After completion of the initial stage; research work and simulations were performed on spatial multiplexing over Li-Fi channel modeling. Simulation scenarios which allowed to evaluate the Signal-to-Noise Ratio, Received Power Distribution, Intensity and Illuminance were defined and developed.

  11. Ultraviolet and visible light penetration of epidermis

    International Nuclear Information System (INIS)

    Eggset, G.; Kavli, G.; Volden, G.; Krokan, H.

    1984-01-01

    Light penetration in untanned skin and skin tanned with UVB (middlewave ultraviolet light) or PUVA (Psoralen photochemotherapy) was compared. Transmission at different wavelengths was measured through sheets of intact epidermis isolated by a suction blister technique. Thick epidermis was collected from a newly formed palmar friction bulla. For these studies a monochromator was used and the range of wavelengths examined was 280-700 nm. The transmission was considerably lower in tanned skin and the difference was most pronounced in the UV range. In the UVB range (290-320 nm), transmission was 13-43% for untanned epidermis, 8-12% for UVB tanned and slightly lower for PUVA tanned epidermis. At wavelengths below 325 nm only a few per cent of light penetrate through thick palmar epidermis. Both UVB and PUVA induce increased melanin content and thickening of the epidermis. Our results indicate that melanin is the most efficient protection against UVA while thickening of epidermis may be as important as the increased melanin content for the protection of living basal cells against the harmful UVB rays. (Auth)

  12. Improved spring model-based collaborative indoor visible light positioning

    Science.gov (United States)

    Luo, Zhijie; Zhang, WeiNan; Zhou, GuoFu

    2016-06-01

    Gaining accuracy with indoor positioning of individuals is important as many location-based services rely on the user's current position to provide them with useful services. Many researchers have studied indoor positioning techniques based on WiFi and Bluetooth. However, they have disadvantages such as low accuracy or high cost. In this paper, we propose an indoor positioning system in which visible light radiated from light-emitting diodes is used to locate the position of receivers. Compared with existing methods using light-emitting diode light, we present a high-precision and simple implementation collaborative indoor visible light positioning system based on an improved spring model. We first estimate coordinate position information using the visible light positioning system, and then use the spring model to correct positioning errors. The system can be employed easily because it does not require additional sensors and the occlusion problem of visible light would be alleviated. We also describe simulation experiments, which confirm the feasibility of our proposed method.

  13. Mechanisms of interaction of monochromatic visible light with cells

    Science.gov (United States)

    Karu, Tiina I.

    1996-01-01

    Biological responses of cells to visible and near IR (laser) radiation occur due to physical and/or chemical changes in photoacceptor molecules, components of respiratory chains (cyt a/a3 in mitochondria). As a result of the photoexcitation of electronic states, the following physical and/or chemical changes can occur: alteration of redox properties and acceleration of electron transfer, changes in biochemical activity due to local transient heating of chromophores, one-electron auto-oxidation and O'2- production, and photodynamic action and 1O2 production. Different reaction channels can be activated to achieve the photobiological macroeffect. The primary physical and/or chemical changes induced by light in photoacceptor molecules are followed by a cascade of biochemical reactions in the cell that do not need further light activation and occur in the dark (photosignal transduction and amplification chains). These reactions are connected with changes in cellular homeostasis parameters. The crucial step here is thought to be an alteration of the cellular redox state: a shift towards oxidation is associated with stimulation of cellular vitality, and a shift towards reduction is linked to inhibition. Cells with a lower than normal pH, where the redox state is shifted in the reduced direction, are considered to be more sensitive to the stimulative action of light than those with the respective parameters being optimal or near optimal. This circumstance explains the possible variations in observed magnitudes of low- power laser effects. Light action on the redox state of a cell via the respiratory chain also explains the diversity of low-power laser effects. Besides explaining many controversies in the field of low-power laser effects (i.e., the diversity of effects, the variable magnitude or absence of effects in certain studies), the proposed redox-regulation mechanism may be a fundamental explanation for some clinical effects of irradiation, for example the positive

  14. Visible light communication: Applications, architecture, standardization and research challenges

    OpenAIRE

    Khan, Latif Ullah

    2016-01-01

    The Radio Frequency (RF) communication suffers from interference and high latency issues. Along with this, RF communication requires a separate setup for transmission and reception of RF waves. Overcoming the above limitations, Visible Light Communication (VLC) is a preferred communication technique because of its high bandwidth and immunity to interference from electromagnetic sources. The revolution in the field of solid state lighting leads to the replacement of florescent lamps by Light E...

  15. Design of Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} nanocomponent photocatalysts for hydrogen evolution under visible light irradiation using water-soluble Erythrosin B dye sensitization

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Piyong; Wang, Tingting; Zeng, Heping, E-mail: hpzeng@scut.edu.cn

    2017-01-01

    Highlights: • A novel photocatalyst Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} was designed, synthesized and characterized. • Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} was sensitized by Erythrosin B and a significant enhancement of H{sub 2} evolution rate was achieved. • Electrochemical properties were measured and a possible mechanism of H{sub 2} evolution was proposed. - Abstract: Cu-Cu{sub 2}O nanoparticles (NPs) decorated porous graphitic carbon nitride (g-C{sub 3}N{sub 4}) (Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4}) photocatalysts were prepared. When investment of copper source materials in the experiment increased to 7 wt%, the highest H{sub 2} evolution rate (400 μmol g{sup −1} h{sup −1}) was obtained under visible light irradiation in triethanolamine solution. This is about triple of pure g-C{sub 3}N{sub 4} (140 μmol g{sup −1} h{sup −1}). Moreover, various amount of Erythrosin B dye was added into Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} photoreaction solution and a significant enhancement of H{sub 2} production rate was achieved. The highest H{sub 2} production rate was 5000 μmol g{sup −1} h{sup −1} with 5 mg Erythrosin B in photoreaction system. Erythrosin B dye sensitized Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} presented stable photocatalytic H{sub 2} evolution ability and no noticeable degradation or change of photocatalyst were detected after six recycles. A possible photocatalytic mechanism of Erythrosin B dye sensitized Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} for the enhancement of photocatalytic H{sub 2} evolution is proposed.

  16. Preparation of TiO2-Fullerene Composites and Their Photocatalytic Activity under Visible Light

    Directory of Open Access Journals (Sweden)

    Ken-ichi Katsumata

    2012-01-01

    Full Text Available The development of visible light-sensitive photocatalytic materials is being investigated. In this study, the anatase and rutile-C60 composites were prepared by solution process. The characterization of the samples was conducted by using XRD, UV-vis, FT-IR, Raman, and TEM. The photocatalytic activity of the samples was evaluated by the decolorization of the methylene blue. From the results of the Raman, FT-IR, and XRD, the existence of the C60 was confirmed in the samples. The C60 was modified on the anatase or rutile particle as a cluster. The C60 didn't have the photocatalytic activity under UV and visible light. The anatase and rutile-C60 composites exhibited lower photocatalytic activity than the anatase and rutile under UV light. The anatase-C60 exhibited also lower activity than the anatase under visible light. On the other hand, the rutile-C60 exhibited higher activity than the rutile under visible light. It is considered that the photogenerated electrons can transfer from the C60 to the rutile under visible light irradiation.

  17. Inactivation of bacterial biofilms using visible-light-activated unmodified ZnO nanorods

    Science.gov (United States)

    Aponiene, Kristina; Serevičius, Tomas; Luksiene, Zivile; Juršėnas, Saulius

    2017-09-01

    Various zinc oxide (ZnO) nanostructures are widely used for photocatalytic antibacterial applications. Since ZnO possesses a wide bandgap, it is believed that only UV light may efficiently assist bacterial inactivation, and diverse crystal lattice modifications should be applied in order to narrow the bandgap for efficient visible-light absorption. In this work we show that even unmodified ZnO nanorods grown by an aqueous chemical growth technique are found to possess intrinsic defects that can be activated by visible light (λ = 405 nm) and successfully applied for total inactivation of various highly resistant bacterial biofilms rather than more sensitive planktonic bacteria. Time-resolved fluorescence analysis has revealed that visible-light excitation creates long-lived charge carriers (τ > 1 μs), which might be crucial for destructive biochemical reactions achieving significant bacterial biofilm inactivation. ZnO nanorods covered with bacterial biofilms of Enterococcus faecalis MSCL 302 after illumination by visible light (λ = 405 nm) were inactivated by 2 log, and Listeria monocytogenes ATCL3C 7644 and Escherichia coli O157:H7 biofilms by 4 log. Heterogenic waste-water microbial biofilms, consisting of a mixed population of mesophilic bacteria after illumination with visible light were also completely destroyed.

  18. (meth)acrylates on in situ visible light polymerization of ...

    Indian Academy of Sciences (India)

    60

    ... faster to be cured using a visible light source with a Tungsten-Halogen lamp ... ranging from 350 to 1100 nm, which even covers some UV and near IR region. .... incorporation of the acid-containing and/or acrylate-containing monomer led to.

  19. Using Polarization features of visible light for automatic landmine detection

    NARCIS (Netherlands)

    Jong, W. de; Schavemaker, J.G.M.

    2007-01-01

    This chapter describes the usage of polarization features of visible light for automatic landmine detection. The first section gives an introduction to land-mine detection and the usage of camera systems. In section 2 detection concepts and methods that use polarization features are described.

  20. Hybrid bilayer plasmonic metasurface efficiently manipulates visible light

    Science.gov (United States)

    Qin, Fei; Ding, Lu; Zhang, Lei; Monticone, Francesco; Chum, Chan Choy; Deng, Jie; Mei, Shengtao; Li, Ying; Teng, Jinghua; Hong, Minghui; Zhang, Shuang; Alù, Andrea; Qiu, Cheng-Wei

    2016-01-01

    Metasurfaces operating in the cross-polarization scheme have shown an interesting degree of control over the wavefront of transmitted light. Nevertheless, their inherently low efficiency in visible light raises certain concerns for practical applications. Without sacrificing the ultrathin flat design, we propose a bilayer plasmonic metasurface operating at visible frequencies, obtained by coupling a nanoantenna-based metasurface with its complementary Babinet-inverted copy. By breaking the radiation symmetry because of the finite, yet small, thickness of the proposed structure and benefitting from properly tailored intra- and interlayer couplings, such coupled bilayer metasurface experimentally yields a conversion efficiency of 17%, significantly larger than that of earlier single-layer designs, as well as an extinction ratio larger than 0 dB, meaning that anomalous refraction dominates the transmission response. Our finding shows that metallic metasurface can counterintuitively manipulate the visible light as efficiently as dielectric metasurface (~20% in conversion efficiency in Lin et al.’s study), although the metal’s ohmic loss is much higher than dielectrics. Our hybrid bilayer design, still being ultrathin (~λ/6), is found to obey generalized Snell’s law even in the presence of strong couplings. It is capable of efficiently manipulating visible light over a broad bandwidth and can be realized with a facile one-step nanofabrication process. PMID:26767195

  1. Studies of the ECR plasma in the visible light range

    International Nuclear Information System (INIS)

    Biri, S.; Racz, R.; Palinkas, J.

    2012-01-01

    High resolution visible light (VL) plasma photographs were taken at the ATOMKI-ECRIS by an 8 mega-pixel digital camera. Plasmas were generated from gases of He, methane, N, O, Ne, Ar, Kr, Xe and from their mixtures. The analysis of the photo series gave many qualitative and numerous valuable physical information on the nature of ECR plasmas. VL photos convey information mainly on the cold electron component of the plasma. Cold electrons are confined in the central part of the plasma. It is a further challenging task to understand the colors of this special type of plasmas. The colors can be determined by the VL electron transitions of the plasma atoms and ions combined with the human eye sensitivity. There is a good visual agreement between the calculated normalized color and the real color of the plasmas. Through the examples of He and Xe we analyze the physical processes which affect the characteristic colors of these plasmas. The paper is followed by the slides of the presentation. (authors)

  2. Design of a visible-light-communication enhanced WiFi system

    OpenAIRE

    Shao, Sihua; Khreishah, Abdallah; Ayyash, Moussa; Rahaim, Michael B.; Elgala, Hany; Jungnickel, Volker; Schulz, Dominic; Little, Thomas D. C.

    2015-01-01

    Visible light communication (VLC) has wide unlicensed bandwidth, enables communication in radio frequency (RF) sensitive environments, realizes energy-efficient data transmission, and has the potential to boost the capacity of wireless access networks through spatial reuse. On the other hand, WiFi provides more coverage than VLC and does not suffer from the likelihood of blockage due to the light of sight (LOS) requirement of VLC. In order to take the advantages of both WiFi and VLC, we propo...

  3. Resource allocation for multichannel broadcasting visible light communication

    Science.gov (United States)

    Le, Nam-Tuan; Jang, Yeong Min

    2015-11-01

    Visible light communication (VLC), which offers the possibility of using light sources for both illumination and data communications simultaneously, will be a promising incorporation technique with lighting applications. However, it still remains some challenges especially coverage because of field-of-view limitation. In this paper, we focus on this issue by suggesting a resource allocation scheme for VLC broadcasting system. By using frame synchronization and a network calculus QoS approximation, as well as diversity technology, the proposed VLC architecture and QoS resource allocation for the multichannel-broadcasting MAC (medium access control) protocol can solve the coverage limitation problem and the link switching problem of exhibition service.

  4. Visible light communication: Applications, architecture, standardization and research challenges

    Directory of Open Access Journals (Sweden)

    Latif Ullah Khan

    2017-05-01

    Full Text Available The Radio Frequency (RF communication suffers from interference and high latency issues. Along with this, RF communication requires a separate setup for transmission and reception of RF waves. Overcoming the above limitations, Visible Light Communication (VLC is a preferred communication technique because of its high bandwidth and immunity to interference from electromagnetic sources. The revolution in the field of solid state lighting leads to the replacement of florescent lamps by Light Emitting Diodes (LEDs which further motivates the usage of VLC. This paper presents a survey of the potential applications, architecture, modulation techniques, standardization and research challenges in VLC.

  5. Strategies of making TiO2 and ZnO visible light active

    International Nuclear Information System (INIS)

    Rehman, Shama; Ullah, Ruh; Butt, A.M.; Gohar, N.D.

    2009-01-01

    In modern purification techniques employing semiconductor mediated photooxidation of toxic substances, zinc oxide (ZnO) and titanium dioxide (TiO 2 ) are the most widely used metal oxides due to their unique blend of properties. However, the band edges of these semiconductors lie in the UV region which makes them inactive under visible light irradiation. Researchers have been interested in the modification of electronic and optical properties of these metal oxides for their efficient use in water and air purification under visible light irradiation. Visible light activity has been induced in TiO 2 and ZnO by surface modification via organic materials/semiconductor coupling and band gap modification by doping with metals and nonmetals, co-doping with nonmetals, creation of oxygen vacancies and oxygen sub-stoichiometry. This paper encompasses the progress and developments made so far through these techniques in the visible light photocatalysis with TiO 2 and ZnO. Recently, nitrogen doping in titania has been extensively carried out and therefore somewhat detailed discussion in this respect has been presented. Visible light activation of titania clusters encapsulated in zeolite-Y by nitrogen doping and incorporation of dye or organic sensitizers inside the zeolite framework, has also been highlighted in this review.

  6. A visible light-curable yet visible wavelength-transparent resin for stereolithography 3D printing

    Science.gov (United States)

    Park, Hong Key; Shin, Mikyung; Kim, Bongkyun; Park, Jin Woo; Lee, Haeshin

    2018-04-01

    Herein, a new polymeric resin for stereolithography (SLA) three-dimensional printing (SLA-3DP) is reported. An ultraviolet (UV) or visible (VIS) light source is critical for SLA printing technology. UV light can be used to manufacture 3D objects in SLA-3DP, but there are significant occupational safety and health issues (particularly for eyes). These issues prevent the widespread use of SLA-3DP at home or in the office. Through the use of VIS light, the safety and health issues can largely be solved, but only non-transparent 3D objects can be manufactured, which prevents the application of 3DP to the production of various common transparent consumer products. For these reasons, we developed a VIS light-curable yet visibly transparent resin for SLA-3DP, which also retains UV curability. The key was to identify the photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (DPTBP). DPTBP was originally designed as a UV photoinitiator, but we found that VIS light irradiation is sufficient to split DPTBP and generate radicals due to its slight VIS light absorption up to 420 nm. The cured resin displays high transparency and beautiful transparent colors by incorporating various dyes; additionally, its mechanical properties are superior to those of commercial resins (Arario 410) and photoinitiators (Irgacure 2959).

  7. Rapid Prototyping of Standard Compliant Visible Light Communications System

    OpenAIRE

    Gavrincea, Ciprian; Baranda, Jorge; Henarejos, Pol

    2014-01-01

    This article describes the implementation of a prototype visible light communications system based on the IEEE 802.15.7 standard using low-cost commercial off-the-shelf analog devices. The aim of this article is to show that this standard provides a framework that could promote the introduction of applications into the market. Thus, these specifications could be further developed, reducing the gap between the industry and research communities. The implemented prototype makes use of software d...

  8. Optical Non-Orthogonal Multiple Access for Visible Light Communication

    OpenAIRE

    Marshoud, Hanaa; Muhaidat, Sami; Sofotasios, Paschalis C.; Hussain, Sajjad; Imran, Muhammad Ali; Sharif, Bayan S.

    2017-01-01

    The proliferation of mobile Internet and connected devices, offering a variety of services at different levels of performance, represents a major challenge for the fifth generation wireless networks and beyond. This requires a paradigm shift towards the development of key enabling techniques for the next generation wireless networks. In this respect, visible light communication (VLC) has recently emerged as a new communication paradigm that is capable of providing ubiquitous connectivity by c...

  9. Nanosecond high-power dense microplasma switch for visible light

    Energy Technology Data Exchange (ETDEWEB)

    Bataller, A., E-mail: bataller@physics.ucla.edu; Koulakis, J.; Pree, S.; Putterman, S. [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095 (United States)

    2014-12-01

    Spark discharges in high-pressure gas are known to emit a broadband spectrum during the first 10 s of nanoseconds. We present calibrated spectra of high-pressure discharges in xenon and show that the resulting plasma is optically thick. Laser transmission data show that such a body is opaque to visible light, as expected from Kirchoff's law of thermal radiation. Nanosecond framing images of the spark absorbing high-power laser light are presented. The sparks are ideal candidates for nanosecond, high-power laser switches.

  10. Vehicular Visible Light Networks for Urban Mobile Crowd Sensing

    Directory of Open Access Journals (Sweden)

    Barbara M. Masini

    2018-04-01

    Full Text Available Crowd sensing is a powerful tool to map and predict interests and events. In the future, it could be boosted by an increasing number of connected vehicles sharing information and intentions. This will be made available by on board wireless connected devices able to continuously communicate with other vehicles and with the environment. Among the enabling technologies, visible light communication (VLC represents a low cost solution in the short term. In spite of the fact that vehicular communications cannot rely on the sole VLC due to the limitation provided by the light which allows communications in visibility only, VLC can however be considered to complement other wireless communication technologies which could be overloaded in dense scenarios. In this paper we evaluate the performance of VLC connected vehicles when urban crowd sensing is addressed and we compare the performance of sole vehicular visible light networks with that of VLC as a complementary technology of IEEE 802.11p. Results, obtained through a realistic simulation tool taking into account both the roadmap constraints and the technologies protocols, help to understand when VLC provides the major improvement in terms of delivered data varying the number and position of RSUs and the FOV of the receiver.

  11. Vehicular Visible Light Networks for Urban Mobile Crowd Sensing.

    Science.gov (United States)

    Masini, Barbara M; Bazzi, Alessandro; Zanella, Alberto

    2018-04-12

    Crowd sensing is a powerful tool to map and predict interests and events. In the future, it could be boosted by an increasing number of connected vehicles sharing information and intentions. This will be made available by on board wireless connected devices able to continuously communicate with other vehicles and with the environment. Among the enabling technologies, visible light communication (VLC) represents a low cost solution in the short term. In spite of the fact that vehicular communications cannot rely on the sole VLC due to the limitation provided by the light which allows communications in visibility only, VLC can however be considered to complement other wireless communication technologies which could be overloaded in dense scenarios. In this paper we evaluate the performance of VLC connected vehicles when urban crowd sensing is addressed and we compare the performance of sole vehicular visible light networks with that of VLC as a complementary technology of IEEE 802.11p. Results, obtained through a realistic simulation tool taking into account both the roadmap constraints and the technologies protocols, help to understand when VLC provides the major improvement in terms of delivered data varying the number and position of RSUs and the FOV of the receiver.

  12. LED-based high-speed visible light communications

    Science.gov (United States)

    Chi, Nan; Shi, Meng; Zhao, Yiheng; Wang, Fumin; Shi, Jianyang; Zhou, Yingjun; Lu, Xingyu; Qiao, Liang

    2018-01-01

    We are seeing a growing use of light emitting diodes (LEDs) in a range of applications including lighting, TV and backlight board screen, display etc. In comparison with the traditional incandescent and fluorescent light bulbs, LEDs offer long life-space, much higher energy efficiency, high performance cost ratio and above all very fast switching capability. LED based Visible Light Communications (VLC) is an emerging field of optical communications that focuses on the part of the electromagnetic spectrum that humans can see. Depending on the transmission distance, we can divide the whole optical network into two categories, long haul and short haul. Visible light communication can be a promising candidate for short haul applications. In this paper, we outline the configuration of VLC, its unique benefits, and describe the state of the art research contributions consisting of advanced modulation formats including adaptive bit loading OFDM, carrierless amplitude and phase (CAP), pulse amplitude modulation (PAM) and single carrier Nyquist, linear equalization and nonlinear distortion mitigation based on machine learning, quasi-balanced coding and phase-shifted Manchester coding. These enabling technologies can support VLC up to 10Gb/s class free space transmission.

  13. Visible Discrimination of Broadband Infrared Light by Dye-Enhanced Upconversion in Lanthanide-Doped Nanocrystals

    Directory of Open Access Journals (Sweden)

    Charles G. Dupuy

    2014-01-01

    Full Text Available Optical upconversion of near infrared light to visible light is an attractive way to capture the optical energy or optical information contained in low-energy photons that is otherwise lost to the human eye or to certain photodetectors and solar cells. Until the recent application of broadband absorbing optical antennas, upconversion efficiency in lanthanide-doped nanocrystals was limited by the weak, narrow atomic absorption of a handful of sensitizer elements. In this work, we extend the role of the optical antenna to provide false-color, visible discrimination between bands of infrared radiation. By pairing different optical antenna dyes to specific nanoparticle compositions, unique visible emission is associated with different bands of infrared excitation. In one material set, the peak emission was increased 10-fold, and the width of the spectral response was increased more than 10-fold.

  14. Luminescence- and nanoparticle-mediated increase of light absorption by photoreceptor cells: Converting UV light to visible light

    OpenAIRE

    Li, Lei; Sahi, Sunil K.; Peng, Mingying; Lee, Eric B.; Ma, Lun; Wojtowicz, Jennifer L.; Malin, John H.; Chen, Wei

    2016-01-01

    We developed new optic devices ? singly-doped luminescence glasses and nanoparticle-coated lenses that convert UV light to visible light ? for improvement of visual system functions. Tb3+ or Eu3+ singly-doped borate glasses or CdS-quantum dot (CdS-QD) coated lenses efficiently convert UV light to 542?nm or 613?nm wavelength narrow-band green or red light, or wide-spectrum white light, and thereby provide extra visible light to the eye. In zebrafish (wild-type larvae and adult control animals,...

  15. Melanin photosensitization and the effect of visible light on epithelial cells.

    Directory of Open Access Journals (Sweden)

    Orlando Chiarelli-Neto

    Full Text Available Protecting human skin from sun exposure is a complex issue that involves unclear aspects of the interaction between light and tissue. A persistent misconception is that visible light is safe for the skin, although several lines of evidence suggest otherwise. Here, we show that visible light can damage melanocytes through melanin photosensitization and singlet oxygen (1O2 generation, thus decreasing cell viability, increasing membrane permeability, and causing both DNA photo-oxidation and necro-apoptotic cell death. UVA (355 nm and visible (532 nm light photosensitize 1O2 with similar yields, and pheomelanin is more efficient than eumelanin at generating 1O2 and resisting photobleaching. Although melanin can protect against the cellular damage induced by UVB, exposure to visible light leads to pre-mutagenic DNA lesions (i.e., Fpg- and Endo III-sensitive modifications; these DNA lesions may be mutagenic and may cause photoaging, as well as other health problems, such as skin cancer.

  16. Perovskite Nanocrystals as a Color Converter for Visible Light Communication

    KAUST Repository

    Dursun, Ibrahim; Shen, Chao; Parida, Manas R.; Pan, Jun; Sarmah, Smritakshi P.; Priante, Davide; AlYami, Noktan; Liu, Jiakai; Saidaminov, Makhsud I.; Alias, Mohd Sharizal; Abdelhady, Ahmed L.; Ng, Tien Khee; Mohammed, Omar F.; Ooi, Boon S.; Bakr, Osman

    2016-01-01

    Visible light communication (VLC) is an emerging technology that uses light-emitting diodes (LEDs) or laser diodes for simultaneous illumination and data communication. This technology is envisioned to be a major part of the solution to the current bottlenecks in data and wireless communication. However, the conventional lighting phosphors that are typically integrated with LEDs have limited modulation bandwidth and thus cannot provide the bandwidth required to realize the potential of VLC. In this work, we present a promising light converter for VLC by designing solution-processed CsPbBr3 perovskite nanocrystals (NCs) with a conventional red phosphor. The fabricated CsPbBr3 NCs phosphor-based white light converter exhibits an unprecedented modulation bandwidth of 491 MHz, which is ~ 40 times greater than that of conventional phosphors, and the capability to transmit a high data rate of up to 2 Gbit/s. Moreover, this perovskite enhanced white light source combines ultrafast response characteristics with a high color rendering index of 89 and a low correlated color temperature of 3236 K, thereby enabling dual VLC and solid-state lighting functionalities.

  17. Perovskite Nanocrystals as a Color Converter for Visible Light Communication

    KAUST Repository

    Dursun, Ibrahim

    2016-05-31

    Visible light communication (VLC) is an emerging technology that uses light-emitting diodes (LEDs) or laser diodes for simultaneous illumination and data communication. This technology is envisioned to be a major part of the solution to the current bottlenecks in data and wireless communication. However, the conventional lighting phosphors that are typically integrated with LEDs have limited modulation bandwidth and thus cannot provide the bandwidth required to realize the potential of VLC. In this work, we present a promising light converter for VLC by designing solution-processed CsPbBr3 perovskite nanocrystals (NCs) with a conventional red phosphor. The fabricated CsPbBr3 NCs phosphor-based white light converter exhibits an unprecedented modulation bandwidth of 491 MHz, which is ~ 40 times greater than that of conventional phosphors, and the capability to transmit a high data rate of up to 2 Gbit/s. Moreover, this perovskite enhanced white light source combines ultrafast response characteristics with a high color rendering index of 89 and a low correlated color temperature of 3236 K, thereby enabling dual VLC and solid-state lighting functionalities.

  18. A novel mirror diversity receiver for indoor MIMO visible light

    KAUST Repository

    Park, Ki-Hong

    2016-03-01

    In this paper, we propose and study a non-imaging receiver design reducing the correlation of channel matrix for indoor multiple-input multiple-output (MIMO) visible light communication (VLC) systems. Contrary to previous works, our proposed mirror diversity receiver (MDR) not only blocks the reception of light on one specific direction but also improves the channel gain on the other direction by receiving the light reflected by a mirror deployed between the photodetectors. We analyze the channel capacity and optimal height of mirror in terms of maximum channel capacity for a 2 -by-2 MIMO-VLC system in a 2-dimensional geometric model.We prove that this constructive and destructive effects in channel matrix resulting from our proposed MDR are more beneficial to obtain well-conditioned channel matrix which is suitable for implementing spatial-multiplexing MIMO-VLC systems in order to support high data rate.

  19. Fullerene C70 decorated TiO2 nanowires for visible-light-responsive photocatalyst

    International Nuclear Information System (INIS)

    Cho, Er-Chieh; Ciou, Jing-Hao; Zheng, Jia-Huei; Pan, Job; Hsiao, Yu-Sheng; Lee, Kuen-Chan; Huang, Jen-Hsien

    2015-01-01

    Graphical abstract: - Highlights: • TiO 2 nanowire decorated with C 60 and C 70 derivatives has been synthesized. • The fullerenes impede the charge recombination due to its high electron affinity. • The fullerenes expand the utilization of solar light from UV to visible light. • The modified-TiO 2 has great biocompatibility. - Abstract: In this study, we have synthesized C 60 and C 70 -modified TiO 2 nanowire (NW) through interfacial chemical bonding. The results indicate that the fullerenes (C 60 and C 70 derivatives) can act as sinks for photogenerated electrons in TiO 2 , while the fullerene/TiO 2 is illuminated under ultraviolet (UV) light. Therefore, in comparison to the pure TiO 2 NWs, the modified TiO 2 NWs display a higher photocatalytic activity under UV irradiation. Moreover, the fullerenes also can function as a sensitizer to TiO 2 which expand the utilization of solar light from UV to visible light. The results reveal that the C 70 /TiO 2 NWs show a significant photocatalytic activity for degradation of methylene blue (MB) in visible light region. To better understand the mechanism responsible for the effect of fullerenes on the photocatalytic properties of TiO 2 , the electron only devices and photoelectrochemical cells based on fullerenes/TiO 2 are also fabricated and evaluated.

  20. Performance comparison of binary modulation schemes for visible light communication

    KAUST Repository

    Park, Kihong

    2015-09-11

    In this paper, we investigate the power spectral density of several binary modulation schemes including variable on-off keying, variable pulse position modulation, and pulse dual slope modulation which were previously proposed for visible light communication with dimming control. We also propose a novel slope-based modulation called differential chip slope modulation (DCSM) and develop a chip-based hard-decision receiver to demodulate the resulting signal, detect the chip sequence, and decode the input bit sequence. We show that the DCSM scheme can exploit spectrum density more efficiently than the reference schemes while providing an error rate performance comparable to them. © 2015 IEEE.

  1. Optical antenna for a visible light communications receiver

    Science.gov (United States)

    Valencia-Estrada, Juan Camilo; García-Márquez, Jorge; Topsu, Suat; Chassagne, Luc

    2018-01-01

    Visible Light Communications (VLC) receivers adapted to be used in high transmission rates will eventually use either, high aperture lenses or non-linear optical elements capable of converting light arriving to the receiver into an electric signal. The high aperture lens case, reveals a challenge from an optical designers point-of-view. As a matter of fact, the lens must collect a wide aperture intensity flux using a limited aperture as its use is intended to portable devices. This last also limits both, lens thickness and its focal length. Here, we show a first design to be adapted to a VLC receiver that take these constraints into account. This paper describes a method to design catadioptric and monolithic lenses to be used as an optical collector of light entering from a near point light source as a spherical fan L with a wide acceptance angle α° and high efficiency. These lenses can be mass produced and therefore one can find many practical applications in VLC equipped devices. We show a first design for a near light source without magnification, and second one with a detector's magnification in a meridional section. We utilize rigorous geometric optics, vector analysis and ordinary differential equations.

  2. Optimal linear precoding for indoor visible light communication system

    KAUST Repository

    Sifaou, Houssem

    2017-07-31

    Visible light communication (VLC) is an emerging technique that uses light-emitting diodes (LED) to combine communication and illumination. It is considered as a promising scheme for indoor wireless communication that can be deployed at reduced costs while offering high data rate performance. In this paper, we focus on the design of the downlink of a multi-user VLC system. Inherent to multi-user systems is the interference caused by the broadcast nature of the medium. Linear precoding based schemes are among the most popular solutions that have recently been proposed to mitigate inter-user interference. This paper focuses on the design of the optimal linear precoding scheme that solves the max-min signal-to-interference-plus-noise ratio (SINR) problem. The performance of the proposed precoding scheme is studied under different working conditions and compared with the classical zero-forcing precoding. Simulations have been provided to illustrate the high gain of the proposed scheme.

  3. Precoded generalized space shift keying for indoor visible light communications

    KAUST Repository

    Kadampot, Ishaque Ashar

    2014-09-01

    We consider a visible light communication system with 2 transmit light emitting diodes (LED) and nr receive photodiodes. An optical generalized space shift keying modulation scheme is considered for the transmission of bits where each LED can be either in ON state or OFF state at a given time. With this set-up, we design in this paper a precoder for this modulation scheme given the channel state information to improve the bit error rate performance of the system. As conventional precoding techniques for radio frequency at the transmitter cannot be applied to the optical intensity channel, we formulate an optimization problem with constraints for this specific channel. An analytical solution for the precoder is derived and the system performance is compared with and without precoder.

  4. A Reversible Photoacid Functioning in PBS Buffer under Visible Light.

    Science.gov (United States)

    Abeyrathna, Nawodi; Liao, Yi

    2015-09-09

    A metastable-state photoacid that can reversibly release a proton in PBS buffer (pH = 7.4) under visible light is reported. The design is based on the dual acid-base property and tautomerization of indazole. The quantum yield was as high as 0.73, and moderate light intensity (10(2) μmol·m(2)·s(-1)) is sufficient for the photoreaction. Reversible pH change of 1.7 units was demonstrated using a 0.1 mM aqueous solution. This type of photoacid is promising for control of proton-transfer processes in physiological conditions and may find applications in biomedical areas.

  5. Disparity in Cutaneous Pigmentary Response to LED vs Halogen Incandescent Visible Light: Results from a Single Center, Investigational Clinical Trial Determining a Minimal Pigmentary Visible Light Dose.

    Science.gov (United States)

    Soleymani, Teo; Cohen, David E; Folan, Lorcan M; Okereke, Uchenna R; Elbuluk, Nada; Soter, Nicholas A

    2017-11-01

    Background: While most of the attention regarding skin pigmentation has focused on the effects of ultraviolet radiation, the cutaneous effects of visible light (400 to 700nm) are rarely reported. The purpose of this study was to investigate the cutaneous pigmentary response to pure visible light irradiation, examine the difference in response to different sources of visible light irradiation, and determine a minimal pigmentary dose of visible light irradiation in melanocompetent subjects with Fitzpatrick skin type III - VI. The study was designed as a single arm, non-blinded, split-side dual intervention study in which subjects underwent visible light irradiation using LED and halogen incandescent light sources delivered at a fluence of 0.14 Watts/cm2 with incremental dose progression from 20 J/cm2 to 320 J/cm2. Pigmentation was assessed by clinical examination, cross-polarized digital photography, and analytic colorimetry. Immediate, dose-responsive pigment darkening was seen with LED light exposure in 80% of subjects, beginning at 60 Joules. No pigmentary changes were seen with halogen incandescent light exposure at any dose in any subject. This study is the first to report a distinct difference in cutaneous pigmentary response to different sources of visible light, and the first to demonstrate cutaneous pigment darkening from visible LED light exposure. Our findings raise the concern that our increasing daily artificial light surroundings may have clandestine effects on skin biology. J Drugs Dermatol. 2017;16(11):1105-1110..

  6. Invisibility Cloaking Based on Geometrical Optics for Visible Light

    Science.gov (United States)

    Ichikawa, H.; Oura, M.; Taoda, T.

    2013-06-01

    Optical cloaking has been one of unattainable dreams and just a subject in fiction until recently. Several different approaches to cloaking have been proposed and demonstrated: stealth technology, active camouflage and transformation optics. The last one would be the most formal approach modifying electromagnetic field around an object to be cloaked with metamaterials. While cloaking based on transformation optics, though valid only at single frequency, is experimentally demonstrated in microwave region, its operation in visible spectrum is still distant from realisation mainly owing to difficulty in fabricating metamaterial structure whose elements are much smaller than wavelength of light. Here we show that achromatic optical cloaking in visible spectrum is possible with the mere principle based on geometrical optics. In combining a pair of polarising beam splitters and right-angled prisms, rays of light to be obstructed by an object can make a detour to an observer, while unobstructed rays go straight through two polarising beam splitters. What is observed eventually through the device is simply background image as if nothing exists in between.

  7. Bismuth titanate nanorods and their visible light photocatalytic properties

    International Nuclear Information System (INIS)

    Pei, L.Z.; Liu, H.D.; Lin, N.; Yu, H.Y.

    2015-01-01

    Highlights: • Bismuth titanate nanorods have been synthesized by a simple hydrothermal process. • The size of bismuth titanate nanorods can be controlled by growth conditions. • Bismuth titanate nanorods show good photocatalytic activities of methylene blue and Rhodamine B. - Abstract: Bismuth titanate nanorods have been prepared using a facile hydrothermal process without additives. The bismuth titanate products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and UV-vis diffusion reflectance spectrum. XRD pattern shows that the bismuth titanate nanorods are composed of cubic Bi 2 Ti 2 O 7 phase. Electron microscopy images show that the length and diameter of the bismuth titanate nanorods are 50-200 nm and 2 μm, respectively. Hydrothermal temperature and reaction time play important roles on the formation and size of the bismuth titanate nanorods. UV-vis diffusion reflectance spectrum indicates that bismuth titanate nanorods have a band gap of 2.58 eV. The bismuth titanate nanorods exhibit good photocatalytic activities in the photocatalytic degradation of methylene blue (MB) and Rhodamine B (RB) under visible light irradiation. The bismuth titanate nanorods with cubic Bi 2 Ti 2 O 7 phase are a promising candidate as a visible light photocatalyst

  8. Design of a visible-light spectroscopy clinical tissue oximeter.

    Science.gov (United States)

    Benaron, David A; Parachikov, Ilian H; Cheong, Wai-Fung; Friedland, Shai; Rubinsky, Boris E; Otten, David M; Liu, Frank W H; Levinson, Carl J; Murphy, Aileen L; Price, John W; Talmi, Yair; Weersing, James P; Duckworth, Joshua L; Hörchner, Uwe B; Kermit, Eben L

    2005-01-01

    We develop a clinical visible-light spectroscopy (VLS) tissue oximeter. Unlike currently approved near-infrared spectroscopy (NIRS) or pulse oximetry (SpO2%), VLS relies on locally absorbed, shallow-penetrating visible light (475 to 625 nm) for the monitoring of microvascular hemoglobin oxygen saturation (StO2%), allowing incorporation into therapeutic catheters and probes. A range of probes is developed, including noncontact wands, invasive catheters, and penetrating needles with injection ports. Data are collected from: 1. probes, standards, and reference solutions to optimize each component; 2. ex vivo hemoglobin solutions analyzed for StO2% and pO2 during deoxygenation; and 3. human subject skin and mucosal tissue surfaces. Results show that differential VLS allows extraction of features and minimization of scattering effects, in vitro VLS oximetry reproduces the expected sigmoid hemoglobin binding curve, and in vivo VLS spectroscopy of human tissue allows for real-time monitoring (e.g., gastrointestinal mucosal saturation 69+/-4%, n=804; gastrointestinal tumor saturation 45+/-23%, n=14; and p<0.0001), with reproducible values and small standard deviations (SDs) in normal tissues. FDA approved VLS systems began shipping earlier this year. We conclude that VLS is suitable for the real-time collection of spectroscopic and oximetric data from human tissues, and that a VLS oximeter has application to the monitoring of localized subsurface hemoglobin oxygen saturation in the microvascular tissue spaces of human subjects.

  9. Visible-light system for detecting doxorubicin contamination on skin and surfaces.

    Science.gov (United States)

    Van Raalte, J; Rice, C; Moss, C E

    1990-05-01

    A portable system that uses fluorescence stimulated by visible light to identify doxorubicin contamination on skin and surfaces was studied. When activated by violet-blue light in the 465-nm range, doxorubicin fluoresces, emitting orange-red light in the 580-nm range. The light source to stimulate fluorescence was a slide projector with a filter to selectively pass short-wave (blue) visible light. Fluorescence was both observed visually with viewing spectacles and photographed. Solutions of doxorubicin in sterile 0.9% sodium chloride injection were prepared in nine standard concentrations ranging from 2 to 0.001 mg/mL. Droplets of each admixture were placed on stainless steel, laboratory coat cloth, pieces of latex examination glove, bench-top absorbent padding, and other materials on which antineoplastics might spill or leak. These materials then were stored for up to eight weeks and photographed weekly. The relative ability of water, household bleach, hydrogen peroxide solution, and soap solution to deactivate doxorubicin was also measured. Finally, this system was used to inspect the antineoplastic-drug preparation and administration areas of three outpatient cancer clinics for doxorubicin contamination. Doxorubicin fluorescence was easily detectable with viewing spectacles when a slide projector was used as the light source. The photographic method was sensitive for doxorubicin concentrations from 2.0 to 0.001 mg/mL. Immersion of study materials in bleach for one minute eliminated detectable fluorescence. Doxorubicin contamination is detectable for at least eight weeks in the ambient environment. Probable doxorubicin contamination was detected in two of the three clinics surveyed. A safe, portable system that uses fluorescence stimulated by visible light is a sensitive method for detecting doxorubicin on skin and surfaces.

  10. Exquisite light sensitivity of Drosophila melanogaster cryptochrome.

    Directory of Open Access Journals (Sweden)

    Pooja Vinayak

    Full Text Available Drosophila melanogaster shows exquisite light sensitivity for modulation of circadian functions in vivo, yet the activities of the Drosophila circadian photopigment cryptochrome (CRY have only been observed at high light levels. We studied intensity/duration parameters for light pulse induced circadian phase shifts under dim light conditions in vivo. Flies show far greater light sensitivity than previously appreciated, and show a surprising sensitivity increase with pulse duration, implying a process of photic integration active up to at least 6 hours. The CRY target timeless (TIM shows dim light dependent degradation in circadian pacemaker neurons that parallels phase shift amplitude, indicating that integration occurs at this step, with the strongest effect in a single identified pacemaker neuron. Our findings indicate that CRY compensates for limited light sensitivity in vivo by photon integration over extraordinarily long times, and point to select circadian pacemaker neurons as having important roles.

  11. Forward and correctional OFDM-based visible light positioning

    Science.gov (United States)

    Li, Wei; Huang, Zhitong; Zhao, Runmei; He, Peixuan; Ji, Yuefeng

    2017-09-01

    Visible light positioning (VLP) has attracted much attention in both academic and industrial areas due to the extensive deployment of light-emitting diodes (LEDs) as next-generation green lighting. Generally, the coverage of a single LED lamp is limited, so LED arrays are always utilized to achieve uniform illumination within the large-scale indoor environment. However, in such dense LED deployment scenario, the superposition of the light signals becomes an important challenge for accurate VLP. To solve this problem, we propose a forward and correctional orthogonal frequency division multiplexing (OFDM)-based VLP (FCO-VLP) scheme with low complexity in generating and processing of signals. In the first forward procedure of FCO-VLP, an initial position is obtained by the trilateration method based on OFDM-subcarriers. The positioning accuracy will be further improved in the second correctional procedure based on the database of reference points. As demonstrated in our experiments, our approach yields an improved average positioning error of 4.65 cm and an enhanced positioning accuracy by 24.2% compared with trilateration method.

  12. Light-sensitive brain pathways and aging.

    Science.gov (United States)

    Daneault, V; Dumont, M; Massé, É; Vandewalle, G; Carrier, J

    2016-03-15

    Notwithstanding its effects on the classical visual system allowing image formation, light acts upon several non-image-forming (NIF) functions including body temperature, hormonal secretions, sleep-wake cycle, alertness, and cognitive performance. Studies have shown that NIF functions are maximally sensitive to blue wavelengths (460-480 nm), in comparison to longer light wavelengths. Higher blue light sensitivity has been reported for melatonin suppression, pupillary constriction, vigilance, and performance improvement but also for modulation of cognitive brain functions. Studies investigating acute stimulating effects of light on brain activity during the execution of cognitive tasks have suggested that brain activations progress from subcortical regions involved in alertness, such as the thalamus, the hypothalamus, and the brainstem, before reaching cortical regions associated with the ongoing task. In the course of aging, lower blue light sensitivity of some NIF functions has been reported. Here, we first describe neural pathways underlying effects of light on NIF functions and we discuss eye and cerebral mechanisms associated with aging which may affect NIF light sensitivity. Thereafter, we report results of investigations on pupillary constriction and cognitive brain sensitivity to light in the course of aging. Whereas the impact of light on cognitive brain responses appears to decrease substantially, pupillary constriction seems to remain more intact over the lifespan. Altogether, these results demonstrate that aging research should take into account the diversity of the pathways underlying the effects of light on specific NIF functions which may explain their differences in light sensitivity.

  13. Visualization of light propagation in visible Chinese human head for functional near-infrared spectroscopy

    Science.gov (United States)

    Li, Ting; Gong, Hui; Luo, Qingming

    2011-04-01

    Using the visible Chinese human data set, which faithfully represents human anatomy, we visualize the light propagation in the head in detail based on Monte Carlo simulation. The simulation is verified to agree with published experimental results in terms of a differential path-length factor. The spatial sensitivity profile turns out to seem like a fat tropical fish with strong distortion along the folding cerebral surface. The sensitive brain region covers the gray matter and extends to the superficial white matter, leading to a large penetration depth (>3 cm). Finally, the optimal source-detector separation is suggested to be narrowed down to 3-3.5 cm, while the sensitivity of the detected signal to brain activation reaches the peak of 8%. These results indicate that the cerebral cortex folding geometry actually has substantial effects on light propagation, which should be necessarily considered for applications of functional near-infrared spectroscopy.

  14. Blood pulsation measurement using cameras operating in visible light: limitations.

    Science.gov (United States)

    Koprowski, Robert

    2016-10-03

    The paper presents an automatic method for analysis and processing of images from a camera operating in visible light. This analysis applies to images containing the human facial area (body) and enables to measure the blood pulse rate. Special attention was paid to the limitations of this measurement method taking into account the possibility of using consumer cameras in real conditions (different types of lighting, different camera resolution, camera movement). The proposed new method of image analysis and processing was associated with three stages: (1) image pre-processing-allowing for the image filtration and stabilization (object location tracking); (2) main image processing-allowing for segmentation of human skin areas, acquisition of brightness changes; (3) signal analysis-filtration, FFT (Fast Fourier Transformation) analysis, pulse calculation. The presented algorithm and method for measuring the pulse rate has the following advantages: (1) it allows for non-contact and non-invasive measurement; (2) it can be carried out using almost any camera, including webcams; (3) it enables to track the object on the stage, which allows for the measurement of the heart rate when the patient is moving; (4) for a minimum of 40,000 pixels, it provides a measurement error of less than ±2 beats per minute for p lighting; (5) analysis of a single image takes about 40 ms in Matlab Version 7.11.0.584 (R2010b) with Image Processing Toolbox Version 7.1 (R2010b).

  15. Mobile health-monitoring system through visible light communication.

    Science.gov (United States)

    Tan, Yee-Yong; Chung, Wan-Young

    2014-01-01

    Promising development in the light emitting diode (LED) technology has spurred the interest to adapt LED for both illumination and data transmission. This has fostered the growth of interest in visible light communication (VLC), with on-going research to utilize VLC in various applications. This paper presents a mobile-health monitoring system, where healthcare information such as biomedical signals and patient information are transmitted via the LED lighting. A small and portable receiver module is designed and developed to be attached to the mobile device, providing a seamless monitoring environment. Three different healthcare information including ECG, PPG signals and HL7 text information is transmitted simultaneously, using a single channel VLC. This allows for a more precise and accurate monitoring and diagnosis. The data packet size is carefully designed, to transmit information in a minimal packet error rate. A comprehensive monitoring application is designed and developed through the use of a tablet computer in our study. Monitoring and evaluation such as heart rate and arterial blood pressure measurement can be performed concurrently. Real-time monitoring is demonstrated through experiment, where non-hazardous transmission method can be implemented alongside a portable device for better and safer healthcare service.

  16. Visibility of changes in light intensity caused by voltage leaps

    International Nuclear Information System (INIS)

    Seljeseth, Helge; Mogstad, Olve

    2006-05-01

    Sintef Energy Research was engaged by NVE to evaluate the official requirements on voltage leaps in regulations concerning quality of delivery, and simultaneously conduct tests with a panel of test persons in order to get more detailed evaluations and recommendations to the existing requirements on voltage leaps. Tests and laboratory experiments have been performed on a total of 96 test persons, and the results reveal that voltage leaps even smaller than the 3 percent limit set by Norwegian regulations are visible to most people. The majority of the test persons consider the light conditions as unacceptably bad when light conditions are near the limit of voltage leap. Moreover, 25 percent of the test persons considered the light quality unacceptable when the voltage leap was well under half of the official limit.The results of the experiments indicates a need for narrowing the restrictions on voltage leaps in the Norwegian power network in order to limit the size and frequency of this kind of disturbance in the voltage. Recommendations for regulations are elaborated in chapter 3 (ml)

  17. Preparation of mesoporous CdS-containing TiO{sub 2} film and enhanced visible light photocatalytic property

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Yanmei; Wang, Renliang, E-mail: rlwang@tsmc.edu.cn; Zhang, Wenping; Ge, Haiyan; Wang, Xiaopeng; Li, Li

    2015-01-15

    Highlights: • Well-dispersed distribution of CdS nanoparticles inside of TiO{sub 2} mesoporous structures was fabricated. • The sensitization of CdS nanoparticles significantly extends the response of TiO{sub 2} mesoporous film in the visible region. • An improved visible light photocatalytic activity was observed by the CdS–MTF. - Abstract: Mesoporous TiO{sub 2} films containing CdS nanocrystals were successfully fabricated by a two-step process of successive ionic layer adsorption and reaction (SILAR) technique and a solvothermal method followed by annealing. The distribution of CdS nanoparticles in the inner structures of the TiO{sub 2} mesoporous films is confirmed by field emission scanning electron microscope. The CdS modification of the mesoporous films results in an increase in the visible light adsorption, and exhibits more excellent photocatalytic degradation of methyl orange (MO) under visible light irradiation.

  18. Downlink resource allocation for multichannel TDMA visible light communications

    KAUST Repository

    Abdelhady, Amr Mohamed Abdelaziz

    2017-05-12

    Optical wireless communications (OWC) in general and resource allocation in OWC networks particularly have gained lots of attention recently. In this work, we consider the resource allocation problem of a visible light communication downlink transmission system based on time division multiple access with the objective of maximizing spectral efficiency (SE). As for the operational conditions, we impose constraints on the average optical intensity, the energy consumption and the quality-of-service. To solve the non-convex problem, we transform the objective function into a difference of concave functions by solving a second order differential inequality. Then, we propose a low-complexity algorithm to solve the resource allocation problem. Finally, we show by simulations the SE performance gains achieved by optimizing the power allocation over equal power allocation in the considered system. Numerical results show the SE gains achieved by using this solution.

  19. Downlink resource allocation for multichannel TDMA visible light communications

    KAUST Repository

    Abdelhady, Amr Mohamed Abdelaziz; Amin, Osama; Chaaban, Anas; Alouini, Mohamed-Slim

    2017-01-01

    Optical wireless communications (OWC) in general and resource allocation in OWC networks particularly have gained lots of attention recently. In this work, we consider the resource allocation problem of a visible light communication downlink transmission system based on time division multiple access with the objective of maximizing spectral efficiency (SE). As for the operational conditions, we impose constraints on the average optical intensity, the energy consumption and the quality-of-service. To solve the non-convex problem, we transform the objective function into a difference of concave functions by solving a second order differential inequality. Then, we propose a low-complexity algorithm to solve the resource allocation problem. Finally, we show by simulations the SE performance gains achieved by optimizing the power allocation over equal power allocation in the considered system. Numerical results show the SE gains achieved by using this solution.

  20. Discrete Input Signaling for MISO Visible Light Communication Channels

    KAUST Repository

    Arfaoui, Mohamed Amine

    2017-05-12

    In this paper, we study the achievable secrecy rate of visible light communication (VLC) links for discrete input distributions. We consider single user single eavesdropper multiple-input single-output (MISO) links. In addition, both beamforming and robust beamforming are considered. In the former case, the location of the eavesdropper is assumed to be known, whereas in the latter case, the location of the eavesdropper is unknown. We compare the obtained results with those achieved by some continuous distributions including the truncated generalized normal (TGN) distribution and the uniform distribution. We numerically show that the secrecy rate achieved by the discrete input distribution with a finite support is significantly improved as compared to those achieved by the TGN and the uniform distributions.

  1. Colposcopic imaging using visible-light optical coherence tomography

    Science.gov (United States)

    Duan, Lian; McRaven, Michael D.; Liu, Wenzhong; Shu, Xiao; Hu, Jianmin; Sun, Cheng; Veazey, Ronald S.; Hope, Thomas J.; Zhang, Hao F.

    2017-05-01

    High-resolution colposcopic optical coherence tomography (OCT) provides key anatomical measures, such as thickness and minor traumatic injury of vaginal epithelium, of the female reproductive tract noninvasively. This information can be helpful in both fundamental investigations in animal models and disease screenings in humans. We present a fiber-based visible-light OCT and two probe designs for colposcopic application. One probe conducts circular scanning using a DC motor, and the other probe is capable of three-dimensional imaging over a 4.6×4.6-mm2 area using a pair of galvo scanners. Using this colposcopic vis-OCT with both probes, we acquired high-resolution images from whole isolated macaque vaginal samples and identified biopsy lesions.

  2. Imaging of Biological Tissues by Visible Light CDI

    Science.gov (United States)

    Karpov, Dmitry; Dos Santos Rolo, Tomy; Rich, Hannah; Fohtung, Edwin

    Recent advances in the use of synchrotron and X-ray free electron laser (XFEL) based coherent diffraction imaging (CDI) with application to material sciences and medicine proved the technique to be efficient in recovering information about the samples encoded in the phase domain. The current state-of-the-art algorithms of reconstruction are transferable to optical frequencies, which makes laser sources a reasonable milestone both in technique development and applications. Here we present first results from table-top laser CDI system for imaging of biological tissues and reconstruction algorithms development and discuss approaches that are complimenting the data quality improvement that is applicable to visible light frequencies due to it's properties. We demonstrate applicability of the developed methodology to a wide class of soft bio-matter and condensed matter systems. This project is funded by DOD-AFOSR under Award No FA9550-14-1-0363 and the LANSCE Professorship at LANL.

  3. Toward visible light response: Overall water splitting using heterogeneous photocatalysts

    KAUST Repository

    Takanabe, Kazuhiro

    2011-01-01

    Extensive energy conversion of solar energy can only be achieved by large-scale collection of solar flux. The technology that satisfies this requirement must be as simple as possible to reduce capital cost. Overall water splitting by powder-form photocatalysts directly produces a mixture of H 2 and O2 (chemical energy) in a single reactor, which does not require any complicated parabolic mirrors and electronic devices. Because of its simplicity and low capital cost, it has tremendous potential to become the major technology of solar energy conversion. Development of highly efficient photocatalysts is desired. This review addresses why visible light responsive photocatalysts are essential to be developed. The state of the art for the photocatalysts for overall water splitting is briefly described. Moreover, various fundamental aspects for developing efficient photocatalysts, such as particle size of photocatalysts, cocatalysts, and reaction kinetics are discussed. Copyright © 2011 De Gruyter.

  4. Visible light mediated upgrading of biomass to biofuel

    Science.gov (United States)

    AgPd@g-C3N4, comprising heterogenized Ag and Pdnanoparticles on graphitic carbon nitride, g-C3N4, has beensynthesized and used for the upgrading of biofuel as exemplifiedby the hydrodeoxygenation of lignin-derived vanillin underphotochemical conditions using formic acid. The bimetallicframework is found to be highly active due to the synergisticeffects of Ag and Pd with the graphitic carbon nitride support andtheir mutual interaction.This dataset is associated with the following publication:Varma , R., M. Nadagouda , S. Verma, and R.B. Nasir Baig. Visible light mediated upgrading of biomass to biofuel. Energy & Environmental Science. RSC Publishing, Cambridge, UK, 18(5): 1327-1333, (2016).

  5. Network coding multiuser scheme for indoor visible light communications

    Science.gov (United States)

    Zhang, Jiankun; Dang, Anhong

    2017-12-01

    Visible light communication (VLC) is a unique alternative for indoor data transfer and developing beyond point-to-point. However, for realizing high-capacity networks, VLC is facing challenges including the constrained bandwidth of the optical access point and random occlusion. A network coding scheme for VLC (NC-VLC) is proposed, with increased throughput and system robustness. Based on the Lambertian illumination model, theoretical decoding failure probability of the multiuser NC-VLC system is derived, and the impact of the system parameters on the performance is analyzed. Experiments demonstrate the proposed scheme successfully in the indoor multiuser scenario. These results indicate that the NC-VLC system shows a good performance under the link loss and random occlusion.

  6. Turn on the lights: leveraging visible light for communications and positioning

    Science.gov (United States)

    Hranilovic, Steve

    2015-01-01

    The need for ubiquitous broadband connectivity is continually growing, however, radio spectrum is increasingly scarce and limited by interference. In addition, the energy efficiency of many radio transmitters is low and most input energy is converted to heat. A widely overlooked resource for positioning and broadband access is optical wireless communication reusing existing illumination installations. As many of the 14 billion incandescent bulbs in use worldwide are converted to energy efficient LED lighting, a unique opportunity exists to augment them with visible light communications (VLC) and visible light positioning (VLP). VLC- and VLP- enabled LED lighting is not only energy efficient but enables a host of new use cases such as location-aware ubiquitous high-speed wireless communication links. This talk presents the recent work of the Free-space Optical Communication Algorithms Laboratory (FOCAL) at McMaster University in Hamilton, Canada in developing novel signaling and indoor localization techniques using illumination devices. Developments in the signaling design for VLC systems will be presented along with several prototype VLC communication systems. Novel approaches to the integration of VLC networks with power line communications (PLC) are discussed. The role of visible light communications and ranging for automotive safety will also be highlighted. Several approaches to indoor positioning using illumination devices and simple smartphone-based receivers will be presented. Finally, a vision for VLC and VLP technologies will be presented along with our ongoing research directions.

  7. Photocatalytic Surface Patterning of Cellulose using Diazonium Salts and Visible Light

    OpenAIRE

    Schroll, Peter; Fehl, Charlie; Dankesreiter, Stephan; König, Burkhard

    2013-01-01

    Coumarin-functionalized cellulose sheets were chemically modified using a visible light catalyzed “Photo-Meerwein” arylation. Use of a photomask to pattern the surface resulted in directly visible images.

  8. On the Secrecy Capacity of MISO Visible Light Communication Channels

    KAUST Repository

    Arfaoui, Mohamed Amine

    2017-02-07

    We study the secrecy capacity of the multiple- input single-output (MISO) Gaussian wiretap visible light communication (VLC) channel. We study a typical VLC scenario with one transmitter, one legitimate receiver, and one eavesdropper. Specifically, we compute the achievable secrecy rate for various input signaling distributions, including the truncated generalized normal (TGN) and uniform distributions. The transmitter is equipped with multiple light sources, while the legitimate and unauthorized receivers are each equipped with a single photodetector. We analyze the achievable secrecy rates via transmit beamforming and artificial noise. In addition, both zero-forcing beamforming and robust beamforming are considered. In the former case, the location of the eavesdropper is assumed to be known, whereas in the latter case, the location of the eavesdropper is unknown. Our numerical results show that the secrecy rate achieved by the TGN distribution is significantly improved as compared to those achieved by the truncated Gaussian and uniform distributions, for both zero-forcing beamforming and robust beamforming. We also derive an upper bound on the achievable secrecy capacity that we used to assess the closeness of the achievable secrecy rates to the derived bound.

  9. Spectroscopic Doppler analysis for visible-light optical coherence tomography

    Science.gov (United States)

    Shu, Xiao; Liu, Wenzhong; Duan, Lian; Zhang, Hao F.

    2017-12-01

    Retinal oxygen metabolic rate can be effectively measured by visible-light optical coherence tomography (vis-OCT), which simultaneously quantifies oxygen saturation and blood flow rate in retinal vessels through spectroscopic analysis and Doppler measurement, respectively. Doppler OCT relates phase variation between sequential A-lines to the axial flow velocity of the scattering medium. The detectable phase shift is between -π and π due to its periodicity, which limits the maximum measurable unambiguous velocity without phase unwrapping. Using shorter wavelengths, vis-OCT is more vulnerable to phase ambiguity since flow induced phase variation is linearly related to the center wavenumber of the probing light. We eliminated the need for phase unwrapping using spectroscopic Doppler analysis. We split the whole vis-OCT spectrum into a series of narrow subbands and reconstructed vis-OCT images to extract corresponding Doppler phase shifts in all the subbands. Then, we quantified flow velocity by analyzing subband-dependent phase shift using linear regression. In the phantom experiment, we showed that spectroscopic Doppler analysis extended the measurable absolute phase shift range without conducting phase unwrapping. We also tested this method to quantify retinal blood flow in rodents in vivo.

  10. Switchable polarization rotation of visible light using a plasmonic metasurface

    Directory of Open Access Journals (Sweden)

    Stuart K. Earl

    2017-01-01

    Full Text Available A metasurface comprising an array of silver nanorods supported by a thin film of the phase change material vanadium dioxide is used to rotate the primary polarization axis of visible light at a pre-determined wavelength. The dimensions of the rods were selected such that, across the two phases of vanadium dioxide, the two lateral localized plasmon resonances (in the plane of the metasurface occur at the same wavelength. Illumination with linearly polarized light at 45° to the principal axes of the rod metasurface enables excitation of both of these resonances. Modulating the phase of the underlying substrate, we show that it is possible to reversibly switch which axis of the metasurface is resonant at the operating wavelength. Analysis of the resulting Stokes parameters indicates that the orientation of the principal linear polarization axis of the reflected signal is rotated by 90° around these wavelengths. Dynamic metasurfaces such as these have the potential to form the basis of an ultra-compact, low-energy multiplexer or router for an optical signal.

  11. Visible light communication technology for fine-grained indoor localization

    Science.gov (United States)

    Vieira, M.; Vieira, M. A.; Louro, P.; Fantoni, A.; Vieira, P.

    2018-02-01

    This paper focuses on designing and analysing a visible light based communication and positioning system. The indoor positioning system uses trichromatic white Light Emitting Diodes (LEDs), both for illumination purposes and as transmitters, and an optical processor, based on a-SiC:H technology, as mobile receiver. On-Off Keying (OOK) modulation scheme is used, proving a good trade-off between system performance and implementation complexity. In the following, the relationship between the transmitted data and the received output levels is decoded. LED bulbs work as transmitters, sending information together with different identifiers, IDs, related to their physical locations. Square and diamond topologies for the unit cell are analyzed, and a 2D localization design, demonstrated by a prototype implementation, is presented. Fine-grained indoor localization is tested. The received signal is used in coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel. The location and motion information is found by mapping the position and estimating the location areas.

  12. Luminescence- and nanoparticle-mediated increase of light absorption by photoreceptor cells: Converting UV light to visible light.

    Science.gov (United States)

    Li, Lei; Sahi, Sunil K; Peng, Mingying; Lee, Eric B; Ma, Lun; Wojtowicz, Jennifer L; Malin, John H; Chen, Wei

    2016-02-10

    We developed new optic devices - singly-doped luminescence glasses and nanoparticle-coated lenses that convert UV light to visible light - for improvement of visual system functions. Tb(3+) or Eu(3+) singly-doped borate glasses or CdS-quantum dot (CdS-QD) coated lenses efficiently convert UV light to 542 nm or 613 nm wavelength narrow-band green or red light, or wide-spectrum white light, and thereby provide extra visible light to the eye. In zebrafish (wild-type larvae and adult control animals, retinal degeneration mutants, and light-induced photoreceptor cell degeneration models), the use of Tb(3+) or Eu(3+) doped luminescence glass or CdS-QD coated glass lenses provide additional visible light to the rod and cone photoreceptor cells, and thereby improve the visual system functions. The data provide proof-of-concept for the future development of optic devices for improvement of visual system functions in patients who suffer from photoreceptor cell degeneration or related retinal diseases.

  13. UV Blocking Glass: Low Cost Filters for Visible Light Photocatalytic Assessment

    OpenAIRE

    Dunnill, Charles W.

    2014-01-01

    A number of commercially available art protection products have been compared and assessed for their suitability as UV blocking filters in the application of “visible light” photocatalytic research. Many groups claiming visible light photocatalytic success employ filters to block out stray UV radiation in order to justify that their photocatalysts are indeed visible light photocatalysts and not UV light photocatalysts. These filters come in varying degrees of ability and price and many author...

  14. On-off keying transmitter design for navigation by visible light communication

    Science.gov (United States)

    Louro, P.; Vieira, M.; Costa, J.; Vieira, M. A.

    2018-02-01

    White LEDS revolutionized the field of illumination technology mainly due to the energy saving effects. Besides lighting purposes LEDs can also be used in wireless communication systems when integrated in Visible Light Communication (VLC) systems. Indoor positioning for navigation in large buildings is currently under research to overcome the difficulties associated with the use of GPS in such environments. The motivation for this application is also supported by the possibility of taking advantage of an existing lighting and WiFi infrastructure. In this work it is proposed an indoor navigation system based on the use of VLC technology. The proposed system includes trichromatic white LEDs with the red and blue chips modulated at different frequencies and a pinpin photodetector with selective spectral sensitivity. Optoelectronic features of both optical sources and photodetector device are analyzed. The photodetector device consists two pin structures based on a-SiC:H and a-Si:H with geometrical configuration optimized for the detection of short and large wavelengths in the visible range. Its sensitivity is externally tuned by steady state optical bias. The localization algorithm makes use of the Fourier transform to identify the frequencies present in the photocurrent signal and the wavelength filtering properties of the sensor under front and back optical bias to detect the existing red and blue signals. The viability of the system was demonstrated through the implementation of an automatic algorithm to infer the photodetector cardinal direction. A capacitive optoelectronic model supports the experimental results and explains the device operation.

  15. Visible Light Induces Melanogenesis in Human Skin through a Photoadaptive Response

    Science.gov (United States)

    Randhawa, Manpreet; Seo, InSeok; Liebel, Frank; Southall, Michael D.; Kollias, Nikiforos; Ruvolo, Eduardo

    2015-01-01

    Visible light (400–700 nm) lies outside of the spectral range of what photobiologists define as deleterious radiation and as a result few studies have studied the effects of visible light range of wavelengths on skin. This oversight is important considering that during outdoors activities skin is exposed to the full solar spectrum, including visible light, and to multiple exposures at different times and doses. Although the contribution of the UV component of sunlight to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology in terms of inflammation, and limited information is available regarding the role of visible light on pigmentation. The purpose of this study was to determine the effect of visible light on the pro-pigmentation pathways and melanin formation in skin. Exposure to visible light in ex-vivo and clinical studies demonstrated an induction of pigmentation in skin by visible light. Results showed that a single exposure to visible light induced very little pigmentation whereas multiple exposures with visible light resulted in darker and sustained pigmentation. These findings have potential implications on the management of photo-aggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions. PMID:26121474

  16. Visible Light Induces Melanogenesis in Human Skin through a Photoadaptive Response.

    Science.gov (United States)

    Randhawa, Manpreet; Seo, InSeok; Liebel, Frank; Southall, Michael D; Kollias, Nikiforos; Ruvolo, Eduardo

    2015-01-01

    Visible light (400-700 nm) lies outside of the spectral range of what photobiologists define as deleterious radiation and as a result few studies have studied the effects of visible light range of wavelengths on skin. This oversight is important considering that during outdoors activities skin is exposed to the full solar spectrum, including visible light, and to multiple exposures at different times and doses. Although the contribution of the UV component of sunlight to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology in terms of inflammation, and limited information is available regarding the role of visible light on pigmentation. The purpose of this study was to determine the effect of visible light on the pro-pigmentation pathways and melanin formation in skin. Exposure to visible light in ex-vivo and clinical studies demonstrated an induction of pigmentation in skin by visible light. Results showed that a single exposure to visible light induced very little pigmentation whereas multiple exposures with visible light resulted in darker and sustained pigmentation. These findings have potential implications on the management of photo-aggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions.

  17. Visible Light Induces Melanogenesis in Human Skin through a Photoadaptive Response.

    Directory of Open Access Journals (Sweden)

    Manpreet Randhawa

    Full Text Available Visible light (400-700 nm lies outside of the spectral range of what photobiologists define as deleterious radiation and as a result few studies have studied the effects of visible light range of wavelengths on skin. This oversight is important considering that during outdoors activities skin is exposed to the full solar spectrum, including visible light, and to multiple exposures at different times and doses. Although the contribution of the UV component of sunlight to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology in terms of inflammation, and limited information is available regarding the role of visible light on pigmentation. The purpose of this study was to determine the effect of visible light on the pro-pigmentation pathways and melanin formation in skin. Exposure to visible light in ex-vivo and clinical studies demonstrated an induction of pigmentation in skin by visible light. Results showed that a single exposure to visible light induced very little pigmentation whereas multiple exposures with visible light resulted in darker and sustained pigmentation. These findings have potential implications on the management of photo-aggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions.

  18. UV-B sensitivity of plant photosynthesis as influenced by visible irradiation

    International Nuclear Information System (INIS)

    Caldwell, M.M.; Warner, C.W.

    1982-01-01

    Experiments were made to separate the effects of preconditioning and concomitant visible irradiation and to investigate this with respect to both light-limited and light-saturated photosynthesis. (orig./AJ)

  19. Mobile User Connectivity in Relay-Assisted Visible Light Communications

    Directory of Open Access Journals (Sweden)

    Petr Pešek

    2018-04-01

    Full Text Available In this paper, we investigate relay-assisted visible light communications (VLC where a mobile user acts as a relay and forwards data from a transmitter to the end mobile user. We analyse the utilization of the amplify-and-forward (AF and decode-and-forward (DF relaying schemes. The focus of the paper is on analysis of the behavior of the mobile user acting as a relay while considering a realistic locations of the receivers and transmitters on a standard mobile phone, more specifically with two photodetectors on both sides of a mobile phone and a transmitting LED array located upright. We also investigate dependency of the bit error rate (BER performance on the azimuth and elevation angles of the mobile relay device within a typical office environment. We provide a new analytical description of BER for AF and DF-based relays in VLC. In addition we compare AF and DF-based systems and show that DF offers a marginal improvement in the coverage area with a BER < 10–3 and a data rate of 100 Mb/s. Numerical results also illustrate that relay-based systems offer a significant improvement in terms of the coverage compared to direct non-line of sight VLC links.

  20. Aspheric lens based imaging receiver for MIMO visible light communication

    Science.gov (United States)

    Ju, Qiuqi; Liang, Zhongcheng; Liu, Xueming; Yang, Tingting; Wang, Jin

    2014-10-01

    Visible light communication (VLC) has been regarded as a promising solution in short-range intelligent communication system. Nowadays, the research is focused on integrating the multi-input multi-output (MIMO) technique in the VLC system, to achieve a larger transmission capacity and stronger transmission reliability. However, one important issue should be addressed due to the use of MIMO technology: the multipath inter-symbol interference. The multipath intersymbol interference comes from the reflection of the signal in the room and channel crosstalk between different channels. In this paper, we propose a novel optical system used in the MIMO VLC system to reduce multipath interference dramatically. Signals from different LEDs can be separated by using parabolic lens plated with reflecting film. This structure can reduce the reflection effect effectively as well. We present the simulation results to observe the distribution of optical power on the imaging plane for various receiving positions and low correlation between all channels. We can find that the optical power density becomes stronger than non-imaging system and the interference is sharply decreased, thus the SNR and BER are also optimized. Analysis about the optical system is given in this paper.

  1. Visible light to electrical energy conversion using photoelectrochemical cells

    Science.gov (United States)

    Wrighton, Mark S. (Inventor); Ellis, Arthur B. (Inventor); Kaiser, Steven W. (Inventor)

    1983-01-01

    Sustained conversion of low energy visible or near i.r. light (>1.25 eV) to electrical energy has been obtained using wet photoelectrochemical cells where there are no net chemical changes in the system. Stabilization of n-type semi-conductor anodes of CdS, CdSe, CdTe, GaP, GaAs and InP to photoanodic dissolution is achieved by employing selected alkaline solutions of Na.sub.2 S, Na.sub.2 S/S, Na.sub.2 Se, Na.sub.2 Se/Se, Na.sub.2 Te and Na.sub.2 Te/Te as the electrolyte. The oxidation of (poly) sulfide, (poly)selenide or (poly)telluride species occurs at the irradiated anode, and reduction of polysulfide, polyselenide or polytelluride species occurs at the dark Pt cathode of the photoelectrochemical cell. Optical to electrical energy conversion efficiencies approaching 15% at selected frequencies have been observed in some cells. The wavelength for the onset of photocurrent corresponds to the band gap of the particular anode material used in the cell.

  2. Continuous zoom antenna for mobile visible light communication.

    Science.gov (United States)

    Zhang, Xuebin; Tang, Yi; Cui, Lu; Bai, Tingzhu

    2015-11-10

    In this paper, we design a continuous zoom antenna for mobile visible light communication (VLC). In the design, a right-angle reflecting prism was adopted to fold the space optical path, thus decreasing the antenna thickness. The surface of each lens in the antenna is spherical, and the system cost is relatively low. Simulation results indicated that the designed system achieved the following performance: zoom ratio of 2.44, field of view (FOV) range of 18°-48°, system gain of 16.8, and system size of 18 mm×6  mm. Finally, we established an indoor VLC system model in a room the size of 5  m ×5  m ×3  m and compared the detection results of the zoom antenna and fixed-focus antenna obtained in a multisource communication environment, a mobile VLC environment, and a multiple-input multiple-output communication environment. The simulation results indicated that the continuous zoom antenna could realize large FOV and high gain. Moreover, the system showed improved stability, mobility, and environmental applicability.

  3. The route to visible light photolithography using hyperlens

    Science.gov (United States)

    Sun, Jingbo; Litchinitser, Natalia M.

    2018-04-01

    Hyperlens, a curved hyperbolic metamaterials-based device, first emerged as a promising way of overcoming the diffraction limit for subwavelength imaging applications. In addition, it was recently realized that it can be used for sub-wavelength de-magnification. The magnification/de-magnification rate of the hyperlens is directly related to the thickness of the hyperbolic metamaterial. In this paper, we perform a systematic study on the de-magnification properties in different types of the hyperlens. We optimize the de-magnifying properties of a hyperlens to facilitate its potential applications for sub-wavelength photolithography. In order to achieve the required de-magnification properties, we developed a multi-step multi-layer deposition method to fabricate high-quality, thick hyperbolic metamaterials, advancing the state-of-the-art magnification and/or de-magnification properties of the hyperlens. The application of such a high de-magnification rate hyperlens in the photolithography technique may open up a new approach to the nanolithography using visible light, addressing growing demands for inexpensive, all-optical nanoscale pattern recording.

  4. Subcarrier intensity modulation for MIMO visible light communications

    Science.gov (United States)

    Celik, Yasin; Akan, Aydin

    2018-04-01

    In this paper, subcarrier intensity modulation (SIM) is investigated for multiple-input multiple-output (MIMO) visible light communication (VLC) systems. A new modulation scheme called DC-aid SIM (DCA-SIM) is proposed for the spatial modulation (SM) transmission plan. Then, DCA-SIM is extended for multiple subcarrier case which is called DC-aid Multiple Subcarrier Modulation (DCA-MSM). Bit error rate (BER) performances of the considered system are analyzed for different MIMO schemes. The power efficiencies of DCA-SIM and DCA-MSM are shown in correlated MIMO VLC channels. The upper bound BER performances of the proposed models are obtained analytically for PSK and QAM modulation types in order to validate the simulation results. Additionally, the effect of power imbalance method on the performance of SIM is studied and remarkable power gains are obtained compared to the non-power imbalanced cases. In this work, Pulse amplitude modulation (PAM) and MSM-Index are used as benchmarks for single carrier and multiple carrier cases, respectively. And the results show that the proposed schemes outperform PAM and MSM-Index for considered single carrier and multiple carrier communication scenarios.

  5. Unequal error control scheme for dimmable visible light communication systems

    Science.gov (United States)

    Deng, Keyan; Yuan, Lei; Wan, Yi; Li, Huaan

    2017-01-01

    Visible light communication (VLC), which has the advantages of a very large bandwidth, high security, and freedom from license-related restrictions and electromagnetic-interference, has attracted much interest. Because a VLC system simultaneously performs illumination and communication functions, dimming control, efficiency, and reliable transmission are significant and challenging issues of such systems. In this paper, we propose a novel unequal error control (UEC) scheme in which expanding window fountain (EWF) codes in an on-off keying (OOK)-based VLC system are used to support different dimming target values. To evaluate the performance of the scheme for various dimming target values, we apply it to H.264 scalable video coding bitstreams in a VLC system. The results of the simulations that are performed using additive white Gaussian noises (AWGNs) with different signal-to-noise ratios (SNRs) are used to compare the performance of the proposed scheme for various dimming target values. It is found that the proposed UEC scheme enables earlier base layer recovery compared to the use of the equal error control (EEC) scheme for different dimming target values and therefore afford robust transmission for scalable video multicast over optical wireless channels. This is because of the unequal error protection (UEP) and unequal recovery time (URT) of the EWF code in the proposed scheme.

  6. A visible-light-driven composite photocatalyst of TiO2 nanotube arrays and graphene quantum dots

    Directory of Open Access Journals (Sweden)

    Donald K. L. Chan

    2014-05-01

    Full Text Available TiO2 nanotube arrays are well-known efficient UV-driven photocatalysts. The incorporation of graphene quantum dots could extend the photo-response of the nanotubes to the visible-light range. Graphene quantum dot-sensitized TiO2 nanotube arrays were synthesized by covalently coupling these two materials. The product was characterized by Fourier-transform infrared spectrometry (FTIR, scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray diffraction (XRD, thermogravimetric analysis (TGA and UV–vis absorption spectroscopy. The product exhibited high photocatalytic performance in the photodegradation of methylene blue and enhanced photocurrent under visible light irradiation.

  7. Enhanced visible-light photocatalysis and gas sensor properties of polythiophene supported tin doped titanium nanocomposite

    Science.gov (United States)

    Chandra, M. Ravi; Siva Prasada Reddy, P.; Rao, T. Siva; Pammi, S. V. N.; Siva Kumar, K.; Vijay Babu, K.; Kiran Kumar, Ch.; Hemalatha, K. P. J.

    2017-06-01

    The polythiophene supported tin doped titanium nanocomposites (PTh/Sn-TiO2) were synthesized by modified sol-gel process through oxidative polymerization of thiophene. The fourier transform infrared spectroscopy (FT-IR) and UV-Vis diffuse reflectance spectroscopy (UV-DRS) analysis confirms the existence of synergetic interaction between metal oxide and polymer along with extension of absorption edge to visible region. The composites are found to be in spherical form with core-shell structure, which is confirmed by scanning electron spectroscopy (SEM) and transmission electron microscopy (TEM) images, the presence of all respective elements of composite are proven by energy-dispersive X-ray spectroscopy (EDX) analysis. The importance of polythiophene on surface of metal oxide has been were studied as a function of photocatalytic activity for degradation of organic pollutant congo red and gas sensor behavior towards liquid petroleum gas (LPG). All the composites are photocatalytically active and the composite with 1.5 wt% thiophene degrades the pollutant congo red within 120 min when compared to remaining catalysts under visible light irradiation. On the other hand, same composite have shown potential gas sensor properties towards LPG at 300 °C. Considering all the results, it can be noted that polythiophene acts as good sensitizer towards LPG and supporter for the tin doped titania that improve the photocatalytic activity under visible light.

  8. Intimate Coupling of Photocatalysis and Biodegradation for Degrading Phenol Using Different Light Types: Visible Light vs UV Light.

    Science.gov (United States)

    Zhou, Dandan; Xu, Zhengxue; Dong, Shanshan; Huo, Mingxin; Dong, Shuangshi; Tian, Xiadi; Cui, Bin; Xiong, Houfeng; Li, Tingting; Ma, Dongmei

    2015-07-07

    Intimate coupling of photocatalysis and biodegradation (ICPB) technology is attractive for phenolic wastewater treatment, but has only been investigated using UV light (called UPCB). We examined the intimate coupling of visible-light-induced photocatalysis and biodegradation (VPCB) for the first time. Our catalyst was prepared doping both of Er(3+) and YAlO3 into TiO2 which were supported on macroporous carriers. The macroporous carriers was used to support for the biofilms as well. 99.8% removal efficiency of phenol was achieved in the VPCB, and this was 32.6% higher than that in the UPCB. Mineralization capability of UPCB was even worse, due to less adsorbable intermediates and cell lysis induced soluble microbial products release. The lower phenol degradation in the UPCB was due to the serious detachment of the biofilms, and then the microbes responsible for phenol degradation were insufficient due to disinfection by UV irradiation. In contrast, microbial communities in the carriers were well protected under visible light irradiation and extracellular polymeric substances secretion was enhanced. Thus, we found that the photocatalytic reaction and biodegradation were intimately coupled in the VPCB, resulting in 64.0% removal of dissolved organic carbon. Therefore, we found visible light has some advantages over UV light in the ICPB technology.

  9. Characterization and mechanism analysis of N doped TiO2 with visible light response and its enhanced visible activity

    International Nuclear Information System (INIS)

    Cheng Xiuwen; Yu Xiujuan; Xing Zipeng

    2012-01-01

    Nitrogen doped TiO 2 nanoparticles were synthesized through a hydrolysis-precipitation process using ammonia water as the doping species. The resulting materials were characterized by XRD, DRS, SPS, XPS and FT-IR. Further, the activity enhanced-mechanism was discussed in detail. XRD results showed that doping with nitrogen could effectively retard the phase transformation of TiO 2 from anatase to rutile and increase the anatase crystallinity. DRS and SPS results indicated that the light absorbance edge of nitrogen doped TiO 2 nanoparticle was obviously red-shifted to visible light region and the separation rates of photogenerated charge carriers were greatly improved, respectively. XPS and FT-IR analysis implied that the contents of surface hydroxyl groups were improved significantly and the VBM (valance bond maximum) of O2p was 2.3 eV. Under the visible light irradiation with 120 min, a 65.3% degradation rate of phenol could be achieved. The photocatalytic activity of nitrogen doped TiO 2 was 2.08 and 1.97 times than that of pure TiO 2 and P25 TiO 2 , respectively. The enhanced visible light activity was attributed to the well anatase crystallinity, small crystallite size, intense light absorbance edge in visible region, more content of surface hydroxyl groups and high separation efficiency of photogenerated charge carriers.

  10. Semipolar InGaN-based superluminescent diodes for solid-state lighting and visible light communications

    KAUST Repository

    Shen, Chao

    2017-02-16

    III-nitride light emitters, such as light-emitting diodes (LEDs) and laser diodes (LDs), have been demonstrated and studied for solid-state lighting (SSL) and visible-light communication (VLC) applications. However, for III-nitride LEDbased SSL-VLC system, its efficiency is limited by the

  11. Semipolar InGaN-based superluminescent diodes for solid-state lighting and visible light communications

    KAUST Repository

    Shen, Chao; Ng, Tien Khee; Lee, Changmin; Leonard, John T.; Nakamura, Shuji; Speck, James S.; Denbaars, Steven P.; Alyamani, Ahmed Y.; El-Desouki, Munir M.; Ooi, Boon S.

    2017-01-01

    III-nitride light emitters, such as light-emitting diodes (LEDs) and laser diodes (LDs), have been demonstrated and studied for solid-state lighting (SSL) and visible-light communication (VLC) applications. However, for III-nitride LEDbased SSL

  12. Visible light assisted photodegradation of halocarbons on the dye modified TiO{sub 2} surface using visible light

    Energy Technology Data Exchange (ETDEWEB)

    Chatterjee, Debabrata; Dasgupta, Shimanti [Chemistry Section, Central Mechanical Engineering Research Institute, Durgapur 713209 (India); N Rao, Nageswar [Wastewater Technology Division, National Environmental Engineering Research Institute, Nagpur 400020 (India)

    2006-05-05

    Visible light assisted photodegradation of various halocarbons, viz. chloro-phenols, trichloroethylene, 1,2-dichloroethane and 1,4-dichlorobenzene, has been achieved on the surface of dye-modified TiO{sub 2} semiconductor. Thionine, eosinY, rhodamineB, methyleneblue, nileblueA and safranineO were used for the modification of TiO{sub 2} semiconductor photocatalyst. After 5h of irradiation with a 150W Xenon lamp, over 55-72% degradation of pollutants has been achieved. A working mechanism involving excitation of surface adsorbed dye, followed by charge injection into the TiO{sub 2} conduction band and formation of reactive {sup *}O{sub 2}{sup -}/{sup *}HO{sub 2} radicals, is proposed for the degradation of the enlisted organics to carbon dioxide. Efficacy of the photocatalytic system towards halocarbon degradation has been discussed in regard to excited state redox properties of the dyes selected for this study. Formation of {sup *}O{sub 2}{sup -} radical has been substantiated by using a chemiluminescent probe luminol. (author)

  13. Joint illumination and visible-light communication systems : data rates and extra power consumption

    NARCIS (Netherlands)

    Tsiatmas, Anagnostis; Willems, Frans; Linnartz, Jean-Paul; Baggen, C.P.M.J.; Bergmans, Jan

    2015-01-01

    Visible Light Communications (VLC) have been promoted as an energy-efficient Gb/s-technology for indoor settings, since VLC can be merged with the illumination functionality. As a result, Joint Illumination and visible-light Communication (JIC) systems are perceived as a green technology and the

  14. Enhanced visible-light activity of titania via confinement inside carbon nanotubes

    KAUST Repository

    Chen, Wei; Fan, Zhongli; Zhang, Bei; Ma, Guijun; Takanabe, Kazuhiro; Zhang, Xixiang; Lai, Zhiping

    2011-01-01

    O 2 in comparison with nanoparticles dispersed on the outer surface of CNTs, extending the photoresponse of TiO 2 from the UV to the visible-light region. The CNT-confined TiO 2 exhibited improved visible-light activity in the degradation of methylene

  15. Visible Light Photocatalysis of [2+2] Styrene Cycloadditions via Energy Transfer

    Science.gov (United States)

    Lu, Zhan; Yoon, Tehshik P.

    2012-01-01

    Hip to be square: Styrenes participate in [2+2] cycloadditions upon irradiation with visible light in the presence of an iridium(III) polypyridyl complex. In contrast to previous reports of visible light photoredox catalysis, the mechanism of this process involves photosensitization by energy transfer and not electron transfer. PMID:22965321

  16. Toxic effect of visible light on Drosophila lifespan depending upon diet protein content.

    Science.gov (United States)

    Shen, Jie; Zhu, Xiang; Gu, Yitian; Zhang, Chiqian; Huang, Jiahong; Qing, Xiao

    2018-03-01

    We investigated the toxic effect of visible light on Drosophila lifespan in both sexes. The toxic effect of ultraviolet (UV) light on organisms is well known. However, the effects of illumination with visible light remain unclear. Here, we found that visible light could be toxic to Drosophila survival, depending on the protein content in diet. In addition, further analysis revealed significant interaction between light and sex, and showed that strong light shortened life span by causing opposite direction changes in mortality rate parameters in females versus males. Our findings suggest that photoageing may be a general phenomenon, and support the theory of sexual antagonistic pleiotropy in aging intervention. The results caution that exposure to visible light could be hazardous to life span and suggest that identification of the underlying mechanism would allow better understanding of aging intervention.

  17. Immunological aspects of light radiation sensitivity

    International Nuclear Information System (INIS)

    Hellman, K.B.; Schuller, G.B.

    1981-01-01

    The immune system comprises one aspect of the host's defense mechanism against potentially harmful agents. It has become recognized as an important factor in light radiation sensitivity and light-mediated disease. The interaction of light radiation with the immune system has formed the basis for the evolving discipline of photoimmunology. A description of the multicomponent immune system, its modification by light radiation, and a discussion of how photoimmunological studies may provide data important for understanding the mechanisms involved in photosensitivity are presented in this review. Photosensitivity may be either acquired or may be genetic in nature. Acquired photosensitivity involves an individual's reaction to either light alone or light in conjunction with topically or systemically administered photosenitizing agents. The outcome of such a reaction can be benign or severe, depending on a number of factors. Genetic photosensitivity includes the reactions to light radiation of individuals carrying the genetic information for inherited diseases such as Ataxia telangiectasia (AT) and Xeroderma pigmentosum (XP). Factors associated with these conditions can lead to enhanced sensitivity to radiation-related diseases, such as cancer. In addition, there are conditions which cannot be readily placed in either of the categories just described but, nevertheless, have been correlated with immune system dysfunction. These include photoallergy, photosensitivity associated with autoimmunity, and light-induced skin cancer. Immunological studies have provided information which may aid in elucidating the problem of photosensitivity and in the development of suitable radioprotective measures

  18. Penning plasma based simultaneous light emission source of visible and VUV lights

    Energy Technology Data Exchange (ETDEWEB)

    Vyas, G. L., E-mail: glvyas27@gmail.com [Manipal University Jaipur (India); Prakash, R.; Pal, U. N. [CSIR-Central Electronics and Engineering Research Institute, Microwave Tubes Division (India); Manchanda, R. [Institute for Plasma Research (India); Halder, N. [Manipal University Jaipur (India)

    2016-06-15

    In this paper, a laboratory-based penning plasma discharge source is reported which has been developed in two anode configurations and is able to produce visible and VUV lights simultaneously. The developed source has simultaneous diagnostics facility using Langmuir probe and optical emission spectroscopy. The two anode configurations, namely, double ring and rectangular configurations, have been studied and compared for optimum use of the geometry for efficient light emissions and recording. The plasma is produced using helium gas and admixture of three noble gases including helium, neon, and argon. The source is capable to produce eight spectral lines for pure helium in the VUV range from 20 to 60 nm and total 24 spectral lines covering the wavelength range 20–106 nm for the admixture of gases. The large range of VUV lines is generated from gaseous admixture rather from the sputtered materials. The recorded spectrum shows that the plasma light radiations in both visible and VUV range are larger in double ring configuration than that of the rectangular configurations at the same discharge operating conditions. To clearly understand the difference, the imaging of the discharge using ICCD camera and particle-in-cell simulation using VORPAL have also been carried out. The effect of ion diffusion, metastable collision with the anode wall and the nonlinear effects are correlated to explain the results.

  19. Photocathodic Protection of 304 Stainless Steel by Bi2S3/TiO2 Nanotube Films Under Visible Light.

    Science.gov (United States)

    Li, Hong; Wang, Xiutong; Wei, Qinyi; Hou, Baorong

    2017-12-01

    We report the preparation of TiO 2 nanotubes coupled with a narrow bandgap semiconductor, i.e., Bi 2 S 3 , to improve the photocathodic protection property of TiO 2 for metals under visible light. Bi 2 S 3 /TiO 2 nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of Bi 2 S 3 deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO 2 and orthorhombic Bi 2 S 3 and exhibited a high visible light response. The photocurrent density of Bi 2 S 3 /TiO 2 was significantly higher than that of pure TiO 2 under visible light. The sensitization of Bi 2 S 3 enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO 2 . The Bi 2 S 3 /TiO 2 nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.

  20. Photocathodic Protection of 304 Stainless Steel by Bi2S3/TiO2 Nanotube Films Under Visible Light

    Science.gov (United States)

    Li, Hong; Wang, Xiutong; Wei, Qinyi; Hou, Baorong

    2017-01-01

    We report the preparation of TiO2 nanotubes coupled with a narrow bandgap semiconductor, i.e., Bi2S3, to improve the photocathodic protection property of TiO2 for metals under visible light. Bi2S3/TiO2 nanotube films were successfully synthesized using the successive ionic layer adsorption and reaction (SILAR) method. The morphology and structure of the composite films were studied by scanning electron microscopy and X-ray diffraction, respectively. UV-visible diffuse reflectance spectra were recorded to analyze the optical absorption property of the composite films. In addition, the influence of Bi2S3 deposition cycles on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. Results revealed that the heterostructure comprised crystalline anatase TiO2 and orthorhombic Bi2S3 and exhibited a high visible light response. The photocurrent density of Bi2S3/TiO2 was significantly higher than that of pure TiO2 under visible light. The sensitization of Bi2S3 enhanced the separation efficiency of the photogenerated charges and photocathodic protection properties of TiO2. The Bi2S3/TiO2 nanotubes prepared by SILAR deposition with 20 cycles exhibited the optimal photogenerated cathodic protection performance on the 304 stainless steel under visible light.

  1. Isotope effects in photo dissociation of ozone with visible light

    Science.gov (United States)

    Früchtl, Marion; Janssen, Christof; Röckmann, Thomas

    2014-05-01

    Ozone (O3) plays a key role for many chemical oxidation processes in the Earth's atmosphere. In these chemical reactions, ozone can transfer oxygen to other trace gases. This is particularly interesting, since O3 has a very peculiar isotope composition. Following the mass dependent fractionation equation δ17O = 0.52 * δ18O, most fractionation processes depend directly on mass. However, O3 shows an offset to the mass dependent fractionation line. Processes, which show such anomalies, are termed mass independent fractionations (MIF). A very well studied example for a chemical reaction that leads to mass independent fractionation is the O3 formation reaction. To what degree O3 destruction reactions need to be considered in order to understand the isotope composition of atmospheric O3 is still not fully understood and an open question within scientific community. We set up new experiments to investigate the isotope effect resulting from photo dissociation of O3 in the Chappuis band (R1). Initial O3 is produced by an electric discharge. After photolysis O3 is collected in a cold trap at the triple point temperature of nitrogen (63K). O3 is then converted to O2 in order to measure the oxygen isotopes of O3 using isotope ratio mass spectrometry. To isolate O3 photo dissociation (R1) from O3 decomposition (R2) and secondary O3 formation (R3), we use varying amounts of carbon monoxide (CO) as O atom quencher (R4). In this way we suppress the O + O3 reaction (R3) and determine the isotope fractionation in R1 and R2 separately. We present first results on the isotope effects in O3 photo dissociation with visible light in the presence of different bath gases. Results are interpreted based on chemical kinetics modeling. (R1) O3 + hυ → O (3P) + O2 (R2) O3 + O (3P) → 2 O2 (R3) O + O2 + M → O3 + M (R4) O (3P) + CO + M → CO2 + M

  2. Plasmonic light-sensitive skins of nanocrystal monolayers

    Science.gov (United States)

    Akhavan, Shahab; Gungor, Kivanc; Mutlugun, Evren; Demir, Hilmi Volkan

    2013-04-01

    We report plasmonically coupled light-sensitive skins of nanocrystal monolayers that exhibit sensitivity enhancement and spectral range extension with plasmonic nanostructures embedded in their photosensitive nanocrystal platforms. The deposited plasmonic silver nanoparticles of the device increase the optical absorption of a CdTe nanocrystal monolayer incorporated in the device. Controlled separation of these metallic nanoparticles in the vicinity of semiconductor nanocrystals enables optimization of the photovoltage buildup in the proposed nanostructure platform. The enhancement factor was found to depend on the excitation wavelength. We observed broadband sensitivity improvement (across 400-650 nm), with a 2.6-fold enhancement factor around the localized plasmon resonance peak. The simulation results were found to agree well with the experimental data. Such plasmonically enhanced nanocrystal skins hold great promise for large-area UV/visible sensing applications.

  3. Development of a visible light transmission (VLT) measurement system using an open-path optical method

    Science.gov (United States)

    Nurulain, S.; Manap, H.

    2017-09-01

    This paper describes about a visible light transmission (VLT) measurement system using an optical method. VLT rate plays an important role in order to determine the visibility of a medium. Current instrument to measure visibility has a gigantic set up, costly and mostly fails to function at low light condition environment. This research focuses on the development of a VLT measurement system using a simple experimental set-up and at a low cost. An open path optical technique is used to measure a few series of known-VLT thin film that act as sample of different visibilities. This measurement system is able to measure the light intensity of these thin films within the visible light region (535-540 nm) and the response time is less than 1s.

  4. Visible-light electroluminescence in Mn-doped GaAs light-emitting diodes

    International Nuclear Information System (INIS)

    Nam Hai, Pham; Maruo, Daiki; Tanaka, Masaaki

    2014-01-01

    We observed visible-light electroluminescence (EL) due to d-d transitions in light-emitting diodes with Mn-doped GaAs layers (here, referred to as GaAs:Mn). Besides the band-gap emission of GaAs, the EL spectra show two peaks at 1.89 eV and 2.16 eV, which are exactly the same as 4 A 2 ( 4 F) → 4 T 1 ( 4 G) and 4 T 1 ( 4 G) → 6 A 1 ( 6 S) transitions of Mn atoms doped in ZnS. The temperature dependence and the current-density dependence are consistent with the characteristics of d-d transitions. We explain the observed EL spectra by the p-d hybridized orbitals of the Mn d electrons in GaAs

  5. Visible-Light-Driven BiOI-Based Janus Micromotor in Pure Water.

    Science.gov (United States)

    Dong, Renfeng; Hu, Yan; Wu, Yefei; Gao, Wei; Ren, Biye; Wang, Qinglong; Cai, Yuepeng

    2017-02-08

    Light-driven synthetic micro-/nanomotors have attracted considerable attention due to their potential applications and unique performances such as remote motion control and adjustable velocity. Utilizing harmless and renewable visible light to supply energy for micro-/nanomotors in water represents a great challenge. In view of the outstanding photocatalytic performance of bismuth oxyiodide (BiOI), visible-light-driven BiOI-based Janus micromotors have been developed, which can be activated by a broad spectrum of light, including blue and green light. Such BiOI-based Janus micromotors can be propelled by photocatalytic reactions in pure water under environmentally friendly visible light without the addition of any other chemical fuels. The remote control of photocatalytic propulsion by modulating the power of visible light is characterized by velocity and mean-square displacement analysis of optical video recordings. In addition, the self-electrophoresis mechanism has been confirmed for such visible-light-driven BiOI-based Janus micromotors by demonstrating the effects of various coated layers (e.g., Al 2 O 3 , Pt, and Au) on the velocity of motors. The successful demonstration of visible-light-driven Janus micromotors holds a great promise for future biomedical and environmental applications.

  6. Irradiation of skin with visible light induces reactive oxygen species and matrix-degrading enzymes.

    Science.gov (United States)

    Liebel, Frank; Kaur, Simarna; Ruvolo, Eduardo; Kollias, Nikiforos; Southall, Michael D

    2012-07-01

    Daily skin exposure to solar radiation causes cells to produce reactive oxygen species (ROS), which are a primary factor in skin damage. Although the contribution of the UV component to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology. Solar radiation comprises UV, and thus the purpose of this study was to examine the physiological response of skin to visible light (400-700 nm). Irradiation of human skin equivalents with visible light induced production of ROS, proinflammatory cytokines, and matrix metalloproteinase (MMP)-1 expression. Commercially available sunscreens were found to have minimal effects on reducing visible light-induced ROS, suggesting that UVA/UVB sunscreens do not protect the skin from visible light-induced responses. Using clinical models to assess the generation of free radicals from oxidative stress, higher levels of free radical activity were found after visible light exposure. Pretreatment with a photostable UVA/UVB sunscreen containing an antioxidant combination significantly reduced the production of ROS, cytokines, and MMP expression in vitro, and decreased oxidative stress in human subjects after visible light irradiation. Taken together, these findings suggest that other portions of the solar spectrum aside from UV, particularly visible light, may also contribute to signs of premature photoaging in skin.

  7. High photoactive and visible-light responsive graphene/titanate nanotubes photocatalysts: preparation and characterization.

    Science.gov (United States)

    Qianqian, Zhai; Tang, Bo; Guoxin, Hu

    2011-12-30

    A series of graphene/titanate nanotubes (TNTs) photocatalysts using graphene and nanoscale TiO(2) or P25 as original materials were fabricated by hydrothermal method. Both low hydrothermal temperature and proper amount of graphene are propitious to better photoactivity. The photocatalytic activities of these nanocomposites far exceed that of P25, pure TNTs and reported TiO(2)-based nanocomposites for the degradation of Rhodamine-B under visible-light irradiation. These prepared photocatalysts were characterized by TEM, XRD, XPS, BET, FTIR and UV-vis diffuse reflection spectra, and the results indicate that the outstanding photoactivities in visible-light region result from sensitization effect of graphene rather than impurity level in the band gap of TNTs. Furthermore, large BET surface areas of these photocatalysts (almost 10 times larger than that of previously reported graphene/TiO(2) nanoparticles) evidently enhance their absorption abilities and photocatalytic performances (the rate constants of degrading Rhodamine-B are at least 5 times higher than that of previously reported photocatalysts). These photocatalysts show good stability, and their photoactivities do not obviously decrease after four times of repeated uses. A detailed photocatalytic mechanism is suggested, as well. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. Visible light communication based vehicle positioning using LED street light and rolling shutter CMOS sensors

    Science.gov (United States)

    Do, Trong Hop; Yoo, Myungsik

    2018-01-01

    This paper proposes a vehicle positioning system using LED street lights and two rolling shutter CMOS sensor cameras. In this system, identification codes for the LED street lights are transmitted to camera-equipped vehicles through a visible light communication (VLC) channel. Given that the camera parameters are known, the positions of the vehicles are determined based on the geometric relationship between the coordinates of the LEDs in the images and their real world coordinates, which are obtained through the LED identification codes. The main contributions of the paper are twofold. First, the collinear arrangement of the LED street lights makes traditional camera-based positioning algorithms fail to determine the position of the vehicles. In this paper, an algorithm is proposed to fuse data received from the two cameras attached to the vehicles in order to solve the collinearity problem of the LEDs. Second, the rolling shutter mechanism of the CMOS sensors combined with the movement of the vehicles creates image artifacts that may severely degrade the positioning accuracy. This paper also proposes a method to compensate for the rolling shutter artifact, and a high positioning accuracy can be achieved even when the vehicle is moving at high speeds. The performance of the proposed positioning system corresponding to different system parameters is examined by conducting Matlab simulations. Small-scale experiments are also conducted to study the performance of the proposed algorithm in real applications.

  9. Ocular exposure to ultraviolet and visible radiation from light sources

    International Nuclear Information System (INIS)

    Hietanen, M.

    1992-01-01

    Exposure of the eyes to UV radiation and blue light of artificial light sources and the sun was evaluated. A spectroradiometer was used to determine the spectral irradiance at 1 nm intervals from 250 to 800 nm. Various groups of workers are at risk of ocular over-exposure to optical radiation, outdoor workers maintenance personnel of bright light source as and wear eye-protectors with effective filtering of UV radiation and blue light. (author)

  10. Mitigation Technique for Receiver Performance Variation of Multi-Color Channels in Visible Light Communication

    Directory of Open Access Journals (Sweden)

    Yeong Min Jang

    2011-06-01

    Full Text Available “Green” and energy-efficient wireless communication schemes have recently experienced rapid development and garnered much interest. One such scheme is visible light communication (VLC which is being touted as one of the next generation wireless communication systems. VLC allows communication using multi-color channels that provide high data rates and illumination simultaneously. Even though VLC has many advantageous features compared with RF technologies, including visibility, ubiquitousness, high speed, high security, harmlessness for the human body and freedom of RF interference, it suffers from some problems on the receiver side, one of them being photo sensitivity dissimilarity of the receiver. The photo sensitivity characteristics of a VLC receiver such as Si photo-detector depend on the wavelength variation. The performance of the VLC receiver is not uniform towards all channel colors, but it is desirable for receivers to have the same performance on each color channel. In this paper, we propose a mitigation technique for reducing the performance variation of the receiver on multi-color channels. We show received power, SNR, BER, output current, and outage probability in our simulation for different color channels. Simulation results show that, the proposed scheme can reduce the performance variation of the VLC receiver on multi-color channels.

  11. Far-ultraviolet spectral changes of titanium dioxide with gold nanoparticles by ultraviolet and visible light

    Science.gov (United States)

    Tanabe, Ichiro; Kurawaki, Yuji

    2018-05-01

    Attenuated total reflectance spectra including the far-ultraviolet (FUV, ≤ 200 nm) region of titanium dioxide (TiO2) with and without gold (Au) nanoparticles were measured. A newly developed external light-irradiation system enabled to observe spectral changes of TiO2 with Au nanoparticles upon light irradiations. Absorption in the FUV region decreased and increased by the irradiation with ultraviolet and visible light, respectively. These spectral changes may reflect photo-induced electron transfer from TiO2 to Au nanoparticles under ultraviolet light and from Au nanoparticles to TiO2 under visible light, respectively.

  12. Visible and invisible the wonders of light phenomena

    CERN Document Server

    Bisi, Olmes

    2015-01-01

    Light phenomena have intrigued humankind since prehistory. Think of the rainbow, a sunset on the sea, a game of shadows. Humans have always used light for their own needs, from cooking food to illuminating a room. However, light is not only limited to what we can see with our eyes. The invisible part of the electromagnetic spectrum is broad and dynamic. This book outlines the mysteries and wonders of electromagnetism, heat, and light. It also covers the history of our scientific understanding of light. The dark as well as the bright sides of light are fully explored in these pages, from their impact on our world to their use in cutting-edge technologies in a variety of fields. Numerous full-color images and drawings complement the text, and light phenomena are explained in a simple and engaging way.

  13. Transition metal-modified zinc oxides for UV and visible light photocatalysis.

    Science.gov (United States)

    Bloh, J Z; Dillert, R; Bahnemann, D W

    2012-11-01

    In order to use photocatalysis with solar light, finding more active and especially visible light active photocatalysts is a very important challenge. Also, studies of these photocatalysts should employ a standardized test procedure so that their results can be accurately compared and evaluated with one another. A systematic study of transition metal-modified zinc oxide was conducted to determine whether they are suitable as visible light photocatalysts. The photocatalytic activity of ZnO modified with eight different transition metals (Cu, Co, Fe, Mn, Ni, Ru, Ti, Zr) in three different concentrations (0.01, 0.1, and 1 at.%) was investigated under irradiation with UV as well as with visible light. The employed activity test is the gas-phase degradation of acetaldehyde as described by the ISO standard 22197-2. The results suggest that the UV activity can be improved with almost any modification element and that there exists an optimal modification ratio at about 0.1 at.%. Additionally, Mn- and Ru-modified ZnO display visible light activity. Especially the Ru-modified ZnO is highly active and surpasses the visible light activity of all studied titania standards. These findings suggest that modified zinc oxides may be a viable alternative to titanium dioxide-based catalysts for visible light photocatalysis. Eventually, possible underlying mechanisms are proposed and discussed.

  14. A Comprehensive Lighting Configuration for Efficient Indoor Visible Light Communication Networks

    Directory of Open Access Journals (Sweden)

    Thai-Chien Bui

    2016-01-01

    Full Text Available Design of an efficient indoor visible light communication (VLC system requires careful considerations on both illumination and communication aspects. Besides fundamental factors such as received power and signal-to-noise ratio (SNR level, studies on mobility scenarios and link switching process must be done in order to achieve good communication link quality in such systems. In this paper, a comprehensive lighting configuration for efficient indoor VLC systems for supporting mobility and link switching with constraint on illumination, received power, and SNR is proposed. Full connectivity in mobility scenarios is required to make the system more practical. However, different from other literatures, our work highlights the significance of recognizing the main influences of field of view angle on the connectivity performance in the practical indoor scenarios. A flexible link switching initiation algorithm based on the consideration of relative received power with adaptive hysteresis margin is demonstrated. In this regard, we investigate the effect of the overlap area between two light sources with respect to the point view of the receiver on the link switching performance. The simulation results show that an indoor VLC system with sufficient illumination level and high communication link quality as well as full mobility and support link switching can be achieved using our approach.

  15. Aerobic oxidation of alcohols in visible light on Pd-grafted Ti cluster

    Science.gov (United States)

    The titanium cluster with the reduced band gap has been synthesized having the palladium nanoparticles over the surface, which not only binds to the atmospheric oxygen but also catalyzes the oxidation of alcohols under visible light.

  16. Sustainable Strategy Utilizing Biomass: Visible-Light-Mediated Synthesis of gamma-Valerolactone

    Data.gov (United States)

    U.S. Environmental Protection Agency — A novel sustainable approach to valued g-valerolactone was investigated. This approach exploits the visible-light-mediated conversion of biomass-derived levulinic...

  17. Continuous Flow Science in an Undergraduate Teaching Laboratory: Photocatalytic Thiol-Ene Reaction Using Visible Light

    Science.gov (United States)

    Santandrea, Jeffrey; Kairouz, Vanessa; Collins, Shawn K.

    2018-01-01

    An undergraduate teaching laboratory experiment involving a continuous flow, photocatalytic thiol-ene reaction using visible-light irradiation is described that allows students to explore concepts of green chemistry, photochemistry, photocatalysis, and continuous flow chemistry.

  18. Robust Visible and Infrared Light Emitting Devices Using Rare-Earth-Doped GaN

    National Research Council Canada - National Science Library

    Steckl, Andrew

    2006-01-01

    Rare earth (RE) dopants (such as Er, Eu, Tm) in the wide bandgap semiconductor (WBGS) GaN are investigated for the fabrication of robust visible and infrared light emitting devices at a variety of wavelengths...

  19. Resource Allocation for Outdoor Visible Light Communications with Energy Harvesting Capabilities

    KAUST Repository

    Abdelhady, Amr Mohamed Abdelaziz; Amin, Osama; Chaaban, Anas; Alouini, Mohamed-Slim

    2018-01-01

    Visible light communication (VLC) is a promising technology that can support high data rate services for outdoor mass gathering night events while permitting energy harvesting. In this paper, a VLC system is considered where a transmitter sends data

  20. Photooxidative damage to mammalian cells and proteins by visible light

    International Nuclear Information System (INIS)

    Packer, L.; Kellogg, E.W. III

    1980-01-01

    In the present article, studies carried out in our laboratory on the effects of visible irradiation and O 2 in a variety of target systems ranging from cultured mammalian cells to purified catalase are reviewed. We will relate these studies of photooxidative damage to a scheme for the propagation of intracellular damage which traces a number of the possible pro-oxidant and anti-oxidant pathways found in the cell

  1. A high-speed, eight-wavelength visible light-infrared pyrometer for shock physics experiments

    Science.gov (United States)

    Wang, Rongbo; Li, Shengfu; Zhou, Weijun; Luo, Zhen-Xiong; Meng, Jianhua; Tian, Jianhua; He, Lihua; Cheng, Xianchao

    2017-09-01

    An eight-channel, high speed pyrometer for precise temperature measurement is designed and realized in this work. The addition of longer-wavelength channels sensitive at lower temperatures highly expands the measured temperature range, which covers the temperature of interest in shock physics from 1500K-10000K. The working wavelength range is 400-1700nm from visible light to near-infrared (NIR). Semiconductor detectors of Si and InGaAs are used as photoelectric devices, whose bandwidths are 50MHz and 150MHz respectively. Benefitting from the high responsivity and high speed of detectors, the time resolution of the pyrometer can be smaller than 10ns. By combining the high-transmittance beam-splitters and narrow-bandwidth filters, the peak spectrum transmissivity of each channel can be higher than 60%. The gray-body temperatures of NaI crystal under shock-loading are successfully measured by this pyrometer.

  2. A Femtosecond Visible/Visible and Visible/Mid-Infrared Transient Absorption Study of the Light Harvesting Complex II

    NARCIS (Netherlands)

    Stahl, A.D.; Di Donato, M.; van Stokkum, I.H.M.; van Grondelle, R.; Groot, M.L.

    2009-01-01

    Light harvesting complex II (LHCII) is the most abundant protein in the thylakoid membrane of higher plants and green algae. LHCII acts to collect solar radiation, transferring this energy mainly toward photosystem II, with a smaller amount going to photosystem I; it is then converted into a

  3. CALDER: High-sensitivity cryogenic light detectors

    International Nuclear Information System (INIS)

    Casali, N.; Bellini, F.; Cardani, L.

    2017-01-01

    The current bolometric experiments searching for rare processes such as neutrinoless double-beta decay or dark matter interaction demand for cryogenic light detectors with high sensitivity, large active area and excellent scalability and radio-purity in order to reduce their background budget. The CALDER project aims to develop such kind of light detectors implementing phonon-mediated Kinetic Inductance Detectors (KIDs). The goal for this project is the realization of a 5 × 5 cm"2 light detector working between 10 and 100mK with a baseline resolution RMS below 20 eV. In this work the characteristics and the performances of the prototype detectors developed in the first project phase will be shown.

  4. Eosin Y Catalyzed Visible-Light-Promoted Aerobic Oxidative Cyclization of 2-Aminobenzothiazole

    Directory of Open Access Journals (Sweden)

    Vishal Srivastava

    2015-12-01

    Full Text Available A mild and efficient one-pot visible light irradiated synthesis of 2-aminobenzothiazole 4(a–l from arylisothiocyanate 1(a–l and secondary amines 2 have been reported in presence of eosin Y as an organophotoredox catalyst at room temperature under aerobic condition. This synthesis includes application of air and visible light as inexpensive, readily available, high atom economy, non-toxic and sustainable regents.

  5. Synthesis and polymorphic control for visible light active titania nanoparticles

    Science.gov (United States)

    Kaewgun, Sujaree

    Titania (TiO2) is useful for many applications in photocatalysis, antimicrobials, pigment, deodorization, and decomposition of harmful organics and undesirable compounds in the air and waste water under UV irradiation. Among the three phases of TiO2, Rutile, Anatase, and Brookite, studies have been more focused on the anatase and rutile phases. Pure brookite is the most difficult phase to prepare, even under hydrothermal conditions. Predominantly brookite phase TiO2 nanoparticles were prepared by the Water-based Ambient Condition Sol (WACS) process in our laboratory. The objectives of this research were to enhance visible light active (VLA) photocatalytic properties of polymorphic brookite TiO2 by minimizing the lattice defects and narrowing band gap of titania by nitrogen and/or carbon chromophone, and to investigate the deactivation, reusability, and regeneration of the VLA titania in order to design better titania catalysts for organic compound degradation applications. In order to study the influence of hydroxyl content on photocatalytic activities (PCAs) of polymorphic titania nanoparticles, the WACS samples were post-treated by a Solvent-based Ambient Condition Sol (SACS) process in sec-butanol (sec-BuOH). All samples were characterized for phase composition, surface area, hydroxyl contamination, and particle morphology by x-ray diffraction, N2 physisorption, FT-IR, solid state 1H NMR and scanning electron microscopy, and then compared to a commercial titania, Degussa P25. Evaluation of methyl orange (MO) degradation under UV irradiation results showed that the lower lattice hydroxyl content in SACS titania enhanced the PCA. As-prepared titania and SACS samples, which have similar surface areas and crystallinity, were compared in order to prove that the superior PCA came from the reduction in the lattice hydroxyl content. To enhance PCA and VLA properties of WACS, an alternative high boiling point polar solvent, N-methylpyrrolidone (NMP), was utilized in the

  6. UV Blocking Glass: Low Cost Filters for Visible Light Photocatalytic Assessment

    Directory of Open Access Journals (Sweden)

    Charles W. Dunnill

    2014-01-01

    Full Text Available A number of commercially available art protection products have been compared and assessed for their suitability as UV blocking filters in the application of “visible light” photocatalytic research. Many groups claiming visible light photocatalytic success employ filters to block out stray UV radiation in order to justify that their photocatalysts are indeed visible light photocatalysts and not UV light photocatalysts. These filters come in varying degrees of ability and price and many authors fail to correctly characterise their filters in individual papers. The use of effective filters to prevent both false positive and false negative results is important to maintain scientific rigor and create accurate understanding of the subject. The optimum UV filter would have the highest UV blocking properties (<390 nm and simultaneously the highest visible light transmission (390–750 nm. Single and double layers of each of the glass products were assessed as well as laminate products. The conclusions show an inexpensive and highly effective setup for the conduction of visible light photochemistry that should be incorporated as a standard part in any researcher’s work where the claim of visible light activity is made.

  7. Highly Transparent, Visible-Light Photodetector Based on Oxide Semiconductors and Quantum Dots.

    Science.gov (United States)

    Shin, Seung Won; Lee, Kwang-Ho; Park, Jin-Seong; Kang, Seong Jun

    2015-09-09

    Highly transparent phototransistors that can detect visible light have been fabricated by combining indium-gallium-zinc oxide (IGZO) and quantum dots (QDs). A wide-band-gap IGZO film was used as a transparent semiconducting channel, while small-band-gap QDs were adopted to absorb and convert visible light to an electrical signal. Typical IGZO thin-film transistors (TFTs) did not show a photocurrent with illumination of visible light. However, IGZO TFTs decorated with QDs showed enhanced photocurrent upon exposure to visible light. The device showed a responsivity of 1.35×10(4) A/W and an external quantum efficiency of 2.59×10(4) under illumination by a 635 nm laser. The origin of the increased photocurrent in the visible light was the small band gap of the QDs combined with the transparent IGZO films. Therefore, transparent phototransistors based on IGZO and QDs were fabricated and characterized in detail. The result is relevant for the development of highly transparent photodetectors that can detect visible light.

  8. An ultrathin invisibility skin cloak for visible light.

    Science.gov (United States)

    Ni, Xingjie; Wong, Zi Jing; Mrejen, Michael; Wang, Yuan; Zhang, Xiang

    2015-09-18

    Metamaterial-based optical cloaks have thus far used volumetric distribution of the material properties to gradually bend light and thereby obscure the cloaked region. Hence, they are bulky and hard to scale up and, more critically, typical carpet cloaks introduce unnecessary phase shifts in the reflected light, making the cloaks detectable. Here, we demonstrate experimentally an ultrathin invisibility skin cloak wrapped over an object. This skin cloak conceals a three-dimensional arbitrarily shaped object by complete restoration of the phase of the reflected light at 730-nanometer wavelength. The skin cloak comprises a metasurface with distributed phase shifts rerouting light and rendering the object invisible. In contrast to bulky cloaks with volumetric index variation, our device is only 80 nanometer (about one-ninth of the wavelength) thick and potentially scalable for hiding macroscopic objects. Copyright © 2015, American Association for the Advancement of Science.

  9. Visible Light Neural Stimulation on graphitic-Carbon Nitride/Graphene Photocatalytic Fibers

    DEFF Research Database (Denmark)

    Zhang, Zhongyang; Xu, Ruodan; Wang, Zegao

    2017-01-01

    conversion, was for the first time investigated. Specifically, g-C3N4 was combined with graphene oxide (GO) in a 3D manner on the surfaces of electrospun polycaprolactone/gelatin (PG) fibers and functioned as a biocompatible interface for visible-light stimulating neuronal differentiation. The enhanced......Light stimulation allows remote and spatiotemporally accurate operation that has been applied as effective, non-invasive means of therapeutic interventions. Here, visible light neural stimulation of graphitic carbon nitride (g-C3N4), an emerging photocatalyst with visible-light optoelectronic...... was confirmed by the Lactate Dehydrogenase (LDH) assay, live dead staining and colorimetric cell viability assay CCK-8. Under a bidaily, monochromatic light stimulation at a wavelength of 450 nm at 10mW/cm2, a 18.5-fold increase of neurite outgrowth of PC12 was found on g-C3N4 coated fibers; while AA reduced GO...

  10. Reduced graphene oxide and Ag wrapped TiO2 photocatalyst for enhanced visible light photocatalysis

    International Nuclear Information System (INIS)

    Leong, Kah Hon; Sim, Lan Ching; Jang, Min; Ibrahim, Shaliza; Bahnemann, Detlef; Saravanan, Pichiah

    2015-01-01

    A well-organised reduced graphene oxide (RGO) and silver (Ag) wrapped TiO 2 nano-hybrid was successfully achieved through a facile and easy route. The inherent characteristics of the synthesized RGO-Ag/TiO 2 were revealed through crystalline phase, morphology, chemical composition, Raman scattering, UV-visible absorption, and photoluminescence analyses. The adopted synthesis route significantly controlled the uniform formation of silver nanoparticles and contributed for the absorption of light in the visible spectrum through localized surface plasmon resonance effects. The wrapped RGO nanosheets triggered the electron mobility and promoted visible light shift towards red spectrum. The accomplishment of synergised effect of RGO and Ag well degraded Bisphenol A under visible light irradiation with a removal efficiency of 61.9%

  11. Ag and CdS nanoparticles co-sensitized TiO2 nanotubes for enhancing visible photoelectrochemical performance

    International Nuclear Information System (INIS)

    Wang Qingyao; Yang Xiuchun; Liu Dan; Chi Lina; Hou Junwei

    2012-01-01

    Highlights: ► Ag and CdS nanoparticles co-sensitized TiO 2 nanotubes were fabricated by the SILAR method. ► The co-sensitization expands the photoresponse range of TiO 2 NTs to 668.7 nm. ► Visible light photocurrents and photocatalytic activities of CdS–Ag/TiO 2 NTs were studied. ► The electron transfer mechanism of CdS–Ag/TiO 2 NTs was proposed. - Abstract: The Ag and CdS nanoparticles co-sensitization of TiO 2 nanotubes (CdS–Ag/TiO 2 NTs) were prepared by successive ionic layer adsorption and reaction (SILAR) technique. The phase composition, morphology and optical property were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis diffusion reflection spectroscopy (DRS). The co-modification of Ag and CdS nanoparticles expanded the photoresponse range of TiO 2 NTs from ultraviolet region to 668.7 nm, and the CdS–Ag/TiO 2 NTs prepared by SILAR deposition of 5 cycles exhibited higher visible photocurrent and stability against photocorrosion. The detailed electrons transfer mechanism of CdS–Ag/TiO 2 NTs was proposed, and photocatalytic activity toward degradation of methyl orange (MO) under visible-light irradiation was also investigated.

  12. Third-order gap plasmon based metasurfaces for visible light

    DEFF Research Database (Denmark)

    Deshpande, Rucha Anil; Pors, Anders; Bozhevolnyi, Sergey I.

    2017-01-01

    with different dimensions, to operate as a polarization beam splitter for linearly polarized light. The fabricated polarization beam splitter is characterized using a super-continuum light source at normal light incidence and found to exhibit a polarization contrast ratio of up to 40 dB near the design...... of the performance of polarization beam splitters based on third-order GSP resonance as well as other potential applications of the suggested approach....... by an optically thick gold film are calculated for the operation wavelength of 633 nm. Exploiting the occurrence of the third-order GSP resonance for nanobricks having their lengths close to 300 nm, we design the phase-gradient metasurface, representing an array of (450 x 2250 nm2) supercells made of 5 nanobricks...

  13. Visible light induced photocatalytic degradation of some xanthene ...

    African Journals Online (AJOL)

    Photocatalytic degradation of eosin and erythrosin-B (xanthene dyes) has been carried out using anthracene semiconductor immobilized on polyethylene films. Effect of various parameters like pH, concentration of dyes, amount of semiconductor and light intensity have been studied on the rate of reaction. Various control ...

  14. Investigation of Light-Emitting Diode (LED) Point Light Source Color Visibility against Complex Multicolored Backgrounds

    Science.gov (United States)

    2017-11-01

    authors. Statistical analyses and analysis plots were obtained using IBM SPSS Statistics.* 5.1 Threshold Visible Illuminance by LED Color and...LED Visibility vs. Outdoor Background Illuminance Across all camouflage materials, the outdoor distances of visibility are plotted with SPSS in Fig

  15. TiO2/carbon nanotube hybrid nanostructures: Solvothermal synthesis and their visible light photocatalytic activity

    International Nuclear Information System (INIS)

    Tian Lihong; Ye Liqun; Deng Kejian; Zan Ling

    2011-01-01

    MWCNT/TiO 2 hybrid nanostructures were prepared via solvothermal synthesis and sol-gel method with benzyl alcohol as a surfactant. As-prepared hybrid materials were characterized by X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectra and X-ray photoelectron spectroscopy. The results showed that MWCNTs were uniformly decorated with anatase nanocrystals in solvothermal condition, but MWCNTs were embedded in a majority of TiO 2 nanoparticles by sol-gel method. When the weight ratio of MWCNTs to TiO 2 was 20%, MWCNT/TiO 2 hybrid nanostructures prepared by solvothermal synthesis exhibited higher visible-light-driven photocatalytic activity than that prepared by sol-gel method. Post-annealing of MWCNT/TiO 2 nanostructures at 400 deg. C resulted in the formation of the carbonaceous Ti-C bonds on the interface between TiO 2 and MWCNTs, which enhanced the photoabsorbance of the hybrid materials in the visible light region and improved the visible-light degradation efficiency of methylene blue. - Graphical abstract: MWCNT/TiO 2 nanostructures have been prepared by solvothermal method, which exhibited higher visible-light-driven photocatalytic activity than that prepared by sol-gel method. The carbonaceous Ti-C bonds on the interface between TiO 2 and MWCNTs enhanced the photoabsorbance of the hybrid materials in the visible light region. Highlights: → Anatase TiO 2 nanoparticles were anchored on CNTs surface uniformly via solvothermal method → The morphology facilitated the electron transfer between CNTs and TiO 2 → Ti-C bonds extended the absorption of MWCNT/TiO 2 to the whole visible light region. → The hybrid nanostructures showed enhanced visible-light induced photocatalytic activity.

  16. Recent progress on doped ZnO nanostructures for visible-light photocatalysis

    International Nuclear Information System (INIS)

    Samadi, Morasae; Zirak, Mohammad; Naseri, Amene; Khorashadizade, Elham; Moshfegh, Alireza Z.

    2016-01-01

    Global environmental pollution and energy supply demand have been regarded as important concerns in recent years. Metal oxide semiconductor photocatalysts is a promising approach to apply environmental remediation as well as fuel generation from water splitting and carbon dioxide reduction. ZnO nanostructures have been shown promising photocatalytic activities due to their non-toxic, inexpensive, and highly efficient nature. However, its wide band gap hinders photo-excitation for practical photocatalytic applications under solar light as an abundant, clean and safe energy source. To overcome this barrier, many strategies have been developed in the last decade to apply ZnO nanostructured photocatalysts under visible light. In this review, we have classified different approaches to activate ZnO as a photocatalyst in visible-light spectrum. Utilization of various nonmetals, transition metals and rare-earth metals for doping in ZnO crystal lattice to create visible-light-responsive doped ZnO photocatalysts is discussed. Generation of localized energy levels within the gap in doped ZnO nanostructures has played an important role in effective photocatalytic reaction under visible-light irradiation. The effect of dopant type, ionic size and its concentration on the crystal structure, electronic property and morphology of doped ZnO with a narrower band gap is reviewed systematically. Finally, a comparative study is performed to evaluate two classes of metals and nonmetals as useful dopants for ZnO nanostructured photocatalysts under visible light. - Highlights: • Metals and nonmetals used as a dopant to shift ZnO band gap toward visible-light. • Modification of electronic structure played a crucial role in doped ZnO activity. • Correlation between dopant's characteristics and ZnO visible activity was reviewed. • Photo-degradation of doped ZnO was studied and compared for different dopants.

  17. Recent progress on doped ZnO nanostructures for visible-light photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Samadi, Morasae; Zirak, Mohammad [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Naseri, Amene [Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of); Khorashadizade, Elham [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Moshfegh, Alireza Z., E-mail: moshfegh@sharif.edu [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of)

    2016-04-30

    Global environmental pollution and energy supply demand have been regarded as important concerns in recent years. Metal oxide semiconductor photocatalysts is a promising approach to apply environmental remediation as well as fuel generation from water splitting and carbon dioxide reduction. ZnO nanostructures have been shown promising photocatalytic activities due to their non-toxic, inexpensive, and highly efficient nature. However, its wide band gap hinders photo-excitation for practical photocatalytic applications under solar light as an abundant, clean and safe energy source. To overcome this barrier, many strategies have been developed in the last decade to apply ZnO nanostructured photocatalysts under visible light. In this review, we have classified different approaches to activate ZnO as a photocatalyst in visible-light spectrum. Utilization of various nonmetals, transition metals and rare-earth metals for doping in ZnO crystal lattice to create visible-light-responsive doped ZnO photocatalysts is discussed. Generation of localized energy levels within the gap in doped ZnO nanostructures has played an important role in effective photocatalytic reaction under visible-light irradiation. The effect of dopant type, ionic size and its concentration on the crystal structure, electronic property and morphology of doped ZnO with a narrower band gap is reviewed systematically. Finally, a comparative study is performed to evaluate two classes of metals and nonmetals as useful dopants for ZnO nanostructured photocatalysts under visible light. - Highlights: • Metals and nonmetals used as a dopant to shift ZnO band gap toward visible-light. • Modification of electronic structure played a crucial role in doped ZnO activity. • Correlation between dopant's characteristics and ZnO visible activity was reviewed. • Photo-degradation of doped ZnO was studied and compared for different dopants.

  18. Visible lights induced polymerization reactions: interactions between rose bengal and iron aren complex

    International Nuclear Information System (INIS)

    Burget, D.; Grotzinger, C.; Jacques, P.; Fouassier, J.P.

    1999-01-01

    The present paper is devoted to an investigation of the interactions between Rose Bengal (RB) and an Iron aren (Irg(+)) complex that are usable in visible light induced polymerization reactions. Steady state and flash photolysis experiments were performed in order to elucidate the nature of the intermediates formed after light excitation. A complete scheme of evolution of the excited states is discussed

  19. Visible Light Emission from Atomic Scale Patterns Fabricated by the Scanning Tunneling Microscope

    DEFF Research Database (Denmark)

    Thirstrup, C.; Sakurai, M.; Stokbro, Kurt

    1999-01-01

    Scanning tunneling microscope (STM) induced light emission from artificial atomic scale structures comprising silicon dangling bonds on hydrogen-terminated Si(001) surfaces has been mapped spatially and analyzed spectroscopically in the visible spectral range. The light emission is based on a novel...

  20. Visible-light Homogeneous Photocatalytic Conversion of CO2 into CO in Aqueous Solutions with an Iron Catalyst.

    Science.gov (United States)

    Rao, Heng; Bonin, Julien; Robert, Marc

    2017-11-23

    An iron-substituted tetraphenyl porphyrin bearing positively charged trimethylammonio groups at the para position of each phenyl ring catalyzes the photoinduced conversion of CO 2 . This complex is water soluble and acts as a molecular catalyst to selectively reduce CO 2 into CO under visible-light irradiation in aqueous solutions (acetonitrile/water=1:9 v/v) with the assistance of purpurin, a simple organic photosensitizer. CO is produced with a catalytic selectivity of 95 % and turnover number up to 120, illustrating the possibility of photocatalyzing the reduction of CO 2 in aqueous solution by using visible light, a simple organic sensitizer coupled to an amine as a sacrificial electron donor, and an earth-abundant metal-based molecular catalyst. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. DEEP HST /STIS VISIBLE-LIGHT IMAGING OF DEBRIS SYSTEMS AROUND SOLAR ANALOG HOSTS

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Glenn; Gaspar, Andras [Steward Observatory and the Department of Astronomy, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Grady, Carol A. [Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002 (United States); Stark, Christopher C.; Kuchner, Marc J. [NASA/Goddard Space Flight Center, Exoplanets and Stellar Astrophysics Laboratory, Code 667, Greenbelt, MD 20771 (United States); Carson, Joseph [Department of Physics and Astronomy, College of Charleston, 66 George Street, Charleston, SC 29424 (United States); Debes, John H.; Hines, Dean C.; Perrin, Marshall [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Henning, Thomas [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Jang-Condell, Hannah [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Rodigas, Timothy J. [Department of Terrestrial Magnetism, Carnegie Institute of Washington, 5241 Branch Road, NW, Washington, DC 20015 (United States); Tamura, Motohide [The University of Tokyo, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588 (Japan); Wisniewski, John P., E-mail: gschneider@as.arizona.edu [H. L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, OK 73019 (United States)

    2016-09-01

    We present new Hubble Space Telescope observations of three a priori known starlight-scattering circumstellar debris systems (CDSs) viewed at intermediate inclinations around nearby close-solar analog stars: HD 207129, HD 202628, and HD 202917. Each of these CDSs possesses ring-like components that are more massive analogs of our solar system's Edgeworth–Kuiper Belt. These systems were chosen for follow-up observations to provide imaging with higher fidelity and better sensitivity for the sparse sample of solar-analog CDSs that range over two decades in systemic ages, with HD 202628 and HD 207129 (both ∼2.3 Gyr) currently the oldest CDSs imaged in visible or near-IR light. These deep (10–14 ks) observations, made with six-roll point-spread-function template visible-light coronagraphy using the Space Telescope Imaging Spectrograph, were designed to better reveal their angularly large debris rings of diffuse/low surface brightness, and for all targets probe their exo-ring environments for starlight-scattering materials that present observational challenges for current ground-based facilities and instruments. Contemporaneously also observing with a narrower occulter position, these observations additionally probe the CDS endo-ring environments that are seen to be relatively devoid of scatterers. We discuss the morphological, geometrical, and photometric properties of these CDSs also in the context of other CDSs hosted by FGK stars that we have previously imaged as a homogeneously observed ensemble. From this combined sample we report a general decay in quiescent-disk F {sub disk}/ F {sub star} optical brightness ∼ t {sup −0.8}, similar to what is seen at thermal IR wavelengths, and CDSs with a significant diversity in scattering phase asymmetries, and spatial distributions of their starlight-scattering grains.

  2. AgBr/diatomite for the efficient visible-light-driven photocatalytic degradation of Rhodamine B

    Science.gov (United States)

    Fang, Jing; Zhao, Huamei; Liu, Qinglei; Zhang, Wang; Gu, Jiajun; Su, Yishi; Abbas, Waseem; Su, Huilan; You, Zhengwei; Zhang, Di

    2018-03-01

    The treatment of organic pollution via photocatalysis has been investigated for a few decades. However, earth-abundant, cheap, stable, and efficient substrates are still to be developed. Here, we prepare an efficient visible-light-driven photocatalyst via the deposition of Ag nanoparticles (light intensity. For comparison, AgBr/SiO2 ( κ = 0.04 min-1) and commercial AgBr nanoparticles ( κ = 0.05 min-1) were measured as well. The experimental results reveal that diatomite acted more than a substrate benefiting the dispersion of AgBr nanoparticles, as well as a cooperator to help harvest visible light and adsorb dye molecules, leading to the efficient visible-light-driven photocatalytic performance of AgBr/diatomite. Considering the low cost (10 per ton) and large-scale availability of diatomite, our study provides the possibility to prepare other types of diatomite-based efficient photocatalytic composites with low-cost but excellent photocatalytic performance.

  3. Zinc vanadate nanorods and their visible light photocatalytic activity

    International Nuclear Information System (INIS)

    Pei, L.Z.; Lin, N.; Wei, T.; Liu, H.D.; Yu, H.Y.

    2015-01-01

    Highlights: • Zinc vanadate nanorods have been synthesized by a facile hydrothermal process. • The size of zinc vanadate nanorods can be controlled by growth conditions. • Zinc vanadate nanorods show good photocatalytic activities of methylene blue under solar light. - Abstract: Zinc vanadate nanorods have been synthesized by a simple hydrothermal process using zinc acetate and sodium vanadate as the raw materials. The zinc vanadate nanorods have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and solid UV–vis diffuse reflectance spectrum. XRD pattern and HRTEM image show that the zinc vanadate nanorods are composed of single crystalline monoclinic Zn 2 V 2 O 7 phase. SEM and TEM observations show that the diameter and length of the zinc vanadate nanorods are 50–100 nm and about 5 μm, respectively. Sodium dodecyl sulfonate (SDS) has an essential role in the formation of zinc vanadate nanorods. The SDS-assisted nucleation and growth process have been proposed to explain the formation and growth of the zinc vanadate nanorods. Solid UV–vis diffuse reflectance spectrum shows that the zinc vanadate nanorods have a band gap of 2.76 eV. The photocatalytic activities of the zinc vanadate nanorods have been evaluated by the photocatalytic degradation of methylene blue (MB) under solar light irradiation. The MB with the concentration of 10 mg L −1 can be degraded totally under the solar light irradiation for 4 h. It is suggested that the zinc vanadate nanorods exhibit promising application potential for the degradation of organic pollutants under solar light irradiation

  4. Preparation, characterization and enhanced visible-light photocatalytic activities of BiPO4/BiVO4 composites

    International Nuclear Information System (INIS)

    Wu, Siyuan; Zheng, Hong; Lian, Youwei; Wu, Yiying

    2013-01-01

    Graphical abstract: - Highlights: • BiPO 4 /BiVO 4 composites were successfully prepared by the hydrothermal method. • BiPO 4 /BiVO 4 composites exhibited broad absorption in the visible region. • Visible-light photocatalytic activities of BiPO 4 /BiVO 4 composites were enhanced. • P/V molar ratio and pH value of the reaction affect photocatalytic activity. • The mechanism of enhanced visible-light photocatalytic activities was discussed. - Abstract: BiPO 4 /BiVO 4 composites with different P/V molar ratios were prepared by the hydrothermal method and the effect of pH values of hydrothermal reaction on photocatalytic activity of BiPO 4 /BiVO 4 composite was investigated. The photocatalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectroscopy. The photocatalytic property of BiPO 4 /BiVO 4 was evaluated by photocatalytic degradation of Methylene blue under visible light irradiation. The results showed that the photocatalytic activity of the composites was much higher than that of pure BiPO 4 and BiVO 4 . The rate constant of Methylene blue degradation over BiPO 4 /BiVO 4 (P/V molar ratio of 5:1 and hydrothermal reaction pH value of 1.5) is 1.7 times that of pure BiVO 4 . The photocatalytic activity enhancement of BiPO 4 /BiVO 4 composite is closely related to the BiVO 4 functioning as a sensitizer to adsorb visible light and the heterojunction of BiPO 4 /BiVO 4 acting as an active center for hindering the rapid recombination of electron–hole pairs during the photocatalytic reaction

  5. Photoelectrocatalytic activity of liquid phase deposited α-Fe2O3 films under visible light illumination

    International Nuclear Information System (INIS)

    Zhang, Man; Pu, Wenhong; Pan, Shichang; Okoth, Otieno Kevin; Yang, Changzhu; Zhang, Jingdong

    2015-01-01

    Liquid phase deposition (LPD) technique was employed to prepare α-Fe 2 O 3 films for photoelectrocatalytic degradation of pollutants. The obtained LPD films were characterized by various surface analysis techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). The results indicated that α-Fe 2 O 3 films with porous structure were successfully deposited on the titanium substrates by the LPD process. The UV–Visible diffuse reflectance spectroscopic (DRS) analysis showed that the obtained LPD α-Fe 2 O 3 film mainly absorbed visible light, which was advantageous to the utilization of solar energy. Under visible light illumination, the Fe 2 O 3 film electrodes exhibited sensitive photocurrent responses, which were affected by the calcination temperature. Consistent with the photocurrent analysis, the α-Fe 2 O 3 film calcined at 600 °C showed the best photoelectrocatalytic performance, and different organic pollutants such as methyl orange (MO) and p-nitrophenol (PNP) were effectively degraded over the LPD film electrode by photoelectrocatalytic treatment under visible light illumination. - Highlights: • α-Fe 2 O 3 film is prepared by liquid phase deposition process. • LPD α-Fe 2 O 3 film has a porous structure and absorbs visible light. • Calcination temperature shows a significant effect on the PEC performance of α-Fe 2 O 3 film. • α-Fe 2 O 3 film is efficient for photoelectrocatalytic degradation of pollutants

  6. Revised constraints and Belle II sensitivity for visible and invisible axion-like particles

    International Nuclear Information System (INIS)

    Dolan, Matthew J.; Kahlhoefer, Felix

    2017-09-01

    Light pseudoscalars interacting pre-dominantly with Standard Model gauge bosons (so-called axion-like particles or ALPs) occur frequently in extensions of the Standard Model. In this work we review and update existing constraints on ALPs in the keV to GeV mass region from colliders, beam dump experiments and astrophysics. We furthermore provide a detailed calculation of the expected sensitivity of Belle II, which can search for visibly and invisibly decaying ALPs, as well as long-lived ALPs. The Belle II sensitivity is found to be substantially better than previously estimated, covering wide ranges of relevant parameter space. In particular, Belle II can explore an interesting class of dark matter models, in which ALPs mediate the interactions between the Standard Model and dark matter. In these models, the relic abundance can be set via resonant freeze-out, leading to a highly predictive scenario consistent with all existing constraints but testable with single-photon searches at Belle II in the near future.

  7. Revised constraints and Belle II sensitivity for visible and invisible axion-like particles

    Energy Technology Data Exchange (ETDEWEB)

    Dolan, Matthew J. [Melbourne Univ. (Australia). ARC Centre of Excellence for Particle Physics at the Terascale; Ferber, Torben [British Columbia Univ., Vancouver, BC (Canada). Dept. of Physics and Astronomy; Hearty, Christopher [British Columbia Univ., Vancouver, BC (Canada). Dept. of Physics and Astronomy; Institute of Particle Physics, Vancouver, BC (Canada); Kahlhoefer, Felix [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); RWTH Aachen Univ. (Germany). Inst. for Theoretical Particle Physics and Cosmology; Schmidt-Hoberg, Kai [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2017-09-15

    Light pseudoscalars interacting pre-dominantly with Standard Model gauge bosons (so-called axion-like particles or ALPs) occur frequently in extensions of the Standard Model. In this work we review and update existing constraints on ALPs in the keV to GeV mass region from colliders, beam dump experiments and astrophysics. We furthermore provide a detailed calculation of the expected sensitivity of Belle II, which can search for visibly and invisibly decaying ALPs, as well as long-lived ALPs. The Belle II sensitivity is found to be substantially better than previously estimated, covering wide ranges of relevant parameter space. In particular, Belle II can explore an interesting class of dark matter models, in which ALPs mediate the interactions between the Standard Model and dark matter. In these models, the relic abundance can be set via resonant freeze-out, leading to a highly predictive scenario consistent with all existing constraints but testable with single-photon searches at Belle II in the near future.

  8. Automatic illumination compensation device based on a photoelectrochemical biofuel cell driven by visible light

    Science.gov (United States)

    Yu, You; Han, Yanchao; Xu, Miao; Zhang, Lingling; Dong, Shaojun

    2016-04-01

    Inverted illumination compensation is important in energy-saving projects, artificial photosynthesis and some forms of agriculture, such as hydroponics. However, only a few illumination adjustments based on self-powered biodetectors that quantitatively detect the intensity of visible light have been reported. We constructed an automatic illumination compensation device based on a photoelectrochemical biofuel cell (PBFC) driven by visible light. The PBFC consisted of a glucose dehydrogenase modified bioanode and a p-type semiconductor cuprous oxide photocathode. The PBFC had a high power output of 161.4 μW cm-2 and an open circuit potential that responded rapidly to visible light. It adjusted the amount of illumination inversely irrespective of how the external illumination was changed. This rational design of utilizing PBFCs provides new insights into automatic light adjustable devices and may be of benefit to intelligent applications.Inverted illumination compensation is important in energy-saving projects, artificial photosynthesis and some forms of agriculture, such as hydroponics. However, only a few illumination adjustments based on self-powered biodetectors that quantitatively detect the intensity of visible light have been reported. We constructed an automatic illumination compensation device based on a photoelectrochemical biofuel cell (PBFC) driven by visible light. The PBFC consisted of a glucose dehydrogenase modified bioanode and a p-type semiconductor cuprous oxide photocathode. The PBFC had a high power output of 161.4 μW cm-2 and an open circuit potential that responded rapidly to visible light. It adjusted the amount of illumination inversely irrespective of how the external illumination was changed. This rational design of utilizing PBFCs provides new insights into automatic light adjustable devices and may be of benefit to intelligent applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00759g

  9. Photooxidation of anthracene under visible light with metallocarboxyphenylporphyrins

    Directory of Open Access Journals (Sweden)

    Carlos Enrique Díaz-Uribe

    2014-01-01

    Full Text Available En este trabajo sintetizamos metalocarboxifenilporfirinas (TcPP-M, M= Cu y Zn y la carboxifenilporfirina libre de metal (TcPPH y determinamos su eficiencia en la fotooxidación de antraceno bajo luz visible a través de la generación de oxígeno singulete ( 1 O 2 . La presencia de 1 O 2 fue evidenciada por Resonancia Paramagnética Electrónica (RPE, el cual el oxígeno singulete reacciona con la 2,2,6,6-tetrametil-4-piperidona-N (TEMP para producir el radical 2,2,6,6-tetrametil-4-piperidona-N-oxil (TEMPO. Los resultados catalíticos indican que la incorporación del metal en el anillo de la porfirina afecta su eficiencia sobre la oxidación del antraceno. La TcPPH mostró la eficiencia fotónica más alta en la conversión de antraceno (31 % en comparación con la TcPPZn (13 % y TcPPCu (9 %. Estos resultados pueden ser relacionados a la distorsión de la planaridad del anillo de porfirina. Finalmente se detectó la formación de antraquinona y oxoantrona como productos de oxidación in la reacción del antraceno con 1 O 2.

  10. Cooling atomic ions with visible and infra-red light

    Science.gov (United States)

    Lindenfelser, F.; Marinelli, M.; Negnevitsky, V.; Ragg, S.; Home, J. P.

    2017-06-01

    We demonstrate the ability to load, cool and detect singly charged calcium ions in a surface electrode trap using only visible and infrared lasers for the trapped-ion control. As opposed to the standard methods of cooling using dipole-allowed transitions, we combine power broadening of a quadrupole transition at 729 nm with quenching of the upper level using a dipole allowed transition at 854 nm. By observing the resulting 393 nm fluorescence we are able to perform background-free detection of the ion. We show that this system can be used to smoothly transition between the Doppler cooling and sideband cooling regimes, and verify theoretical predictions throughout this range. We achieve scattering rates which reliably allow recooling after collision events and allow ions to be loaded from a thermal atomic beam. This work is compatible with recent advances in optical waveguides, and thus opens a path in current technologies for large-scale quantum information processing. In situations where dielectric materials are placed close to trapped ions, it carries the additional advantage of using wavelengths which do not lead to significant charging, which should facilitate high rate optical interfaces between remotely held ions.

  11. Preparation and characterization of visible light-driven AgCl/PPy photocatalyst

    International Nuclear Information System (INIS)

    Gu Shuna; Li Bing; Zhao Chongjun; Xu Yunlong; Qian Xiuzhen; Chen, Guorong

    2011-01-01

    Graphical abstract: AgCl/PPy composite exhibits improved photocatalytic performance and high stability under visible light. Display Omitted Highlights: → AgCl/(PPy) nanocomposites as visible light driven photocatalyst. → Composites exhibited high visible light-driven photocatalytic activity and stability. → Photocatalytic process on MO followed photoreduction mechanisms. → Used photocatalyst can be regenerated in aqueous FeCl 3 solution. - Abstract: Visible light photoactive AgCl/polypyrrole (PPy) composites were prepared via the reaction between excessive Ag + and Cl - ions in the presence of PPy . The AgCl/PPy composites were systematically characterized using Fourier transform infrared (FTIR) spectroscopy, Raman spectra, X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and Thermal gravity analysis (TGA). It was found that face-centered cubic AgCl nanocrystallite and 0.2 wt% PPy component existed in the composite and spherical AgCl/PPy nanoparticles were in the range of 200-600 nm. The AgCl/PPy composites showed higher visible light-driven photocatalytic activity and stability than that of AgCl. A photoreduction mechanism was postulated for AgCl/PPy photocatalyst on dye methyl orange (MO). The used AgCl/PPy photocatalyst was facilely regenerated by an oxidation process in aqueous FeCl 3 solution.

  12. Preparation and characterization of visible light-driven AgCl/PPy photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Gu Shuna; Li Bing [Key Laboratory for Ultrafine Materials of Ministry of Education, Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zhao Chongjun, E-mail: chongjunzhao@ecust.edu.cn [Key Laboratory for Ultrafine Materials of Ministry of Education, Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Xu Yunlong; Qian Xiuzhen; Chen, Guorong [Key Laboratory for Ultrafine Materials of Ministry of Education, Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2011-05-05

    Graphical abstract: AgCl/PPy composite exhibits improved photocatalytic performance and high stability under visible light. Display Omitted Highlights: > AgCl/(PPy) nanocomposites as visible light driven photocatalyst. > Composites exhibited high visible light-driven photocatalytic activity and stability. > Photocatalytic process on MO followed photoreduction mechanisms. > Used photocatalyst can be regenerated in aqueous FeCl{sub 3} solution. - Abstract: Visible light photoactive AgCl/polypyrrole (PPy) composites were prepared via the reaction between excessive Ag{sup +} and Cl{sup -} ions in the presence of PPy{sub .} The AgCl/PPy composites were systematically characterized using Fourier transform infrared (FTIR) spectroscopy, Raman spectra, X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and Thermal gravity analysis (TGA). It was found that face-centered cubic AgCl nanocrystallite and 0.2 wt% PPy component existed in the composite and spherical AgCl/PPy nanoparticles were in the range of 200-600 nm. The AgCl/PPy composites showed higher visible light-driven photocatalytic activity and stability than that of AgCl. A photoreduction mechanism was postulated for AgCl/PPy photocatalyst on dye methyl orange (MO). The used AgCl/PPy photocatalyst was facilely regenerated by an oxidation process in aqueous FeCl{sub 3} solution.

  13. Antibacterial property of Ag nanoparticle-impregnated N-doped titania films under visible light

    Science.gov (United States)

    Wong, Ming-Show; Chen, Chun-Wei; Hsieh, Chia-Chun; Hung, Shih-Che; Sun, Der-Shan; Chang, Hsin-Hou

    2015-07-01

    Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet-visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films.

  14. Protection from visible light by commonly used textiles is not predicted by ultraviolet protection.

    Science.gov (United States)

    Van den Keybus, Caroline; Laperre, Jan; Roelandts, Rik

    2006-01-01

    Interest is increasing in the prevention of acute and chronic actinic damage provided by clothing. This interest has focused mainly on protection against ultraviolet irradiation, but it has now also turned to protection against visible light. This change is mainly due to the action spectrum in the visible light range of some photodermatoses and the increasing interest in photodynamic therapy. The ultraviolet protection provided by commercially available textiles can be graded by determining an ultraviolet protection factor. Several methods have already been used to determine the ultraviolet protection factor. The fact that protection from visible light by textiles cannot be predicted by their ultraviolet protection makes the situation more complicated. This study attempts to determine whether or not the ultraviolet protection factor value of a particular textile is a good parameter for gauging its protection in the visible light range and concludes that a protection factor of textile materials against visible light needs to be developed. This development should go beyond the protection factor definition used in this article, which has some limitations, and should take into account the exact action spectrum for which the protection is needed.

  15. Au/ZnO nanoarchitectures with Au as both supporter and antenna of visible-light

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Tianyu; Chen, Wei; Hua, Yuxiang; Liu, Xiaoheng, E-mail: xhliu@mail.njust.edu.cn

    2017-01-15

    Highlights: • An inversed Au/ZnO nanostructure was fabricated with ZnO loaded onto Au. • The Au/ZnO nanocomposites showed enhanced properties in visible-light photocatalysis. • The SPR effect of Au was considered important for visible-light photocatalysis. - Abstract: In this paper, we fabricate Au/ZnO nanostructure with smaller ZnO nanoparticles loaded onto bigger gold nanoparticles via combining seed-mediated method and sol-gel method. The obtained Au/ZnO nanocomposites exhibit excellent properties in photocatalysis process like methyl orange (MO) degradation and oxidative conversion of methanol into formaldehyde under visible light irradiation. The enhanced properties were ascribed to the surface plasmon resonance (SPR) effect of Au nanoparticles, which could contribute to the separation of photo-excited electrons and holes and facilitate the process of absorbing visible light. This paper contributes to the emergence of multi-functional nanocomposites with possible applications in visible-light driven photocatalysts and makes the Au/ZnO photocatalyst an exceptional choice for practical applications such as environmental purification of organic pollutants in aqueous solution and the synthesis of fine chemicals and intermediates.

  16. Au/ZnO nanoarchitectures with Au as both supporter and antenna of visible-light

    International Nuclear Information System (INIS)

    Liu, Tianyu; Chen, Wei; Hua, Yuxiang; Liu, Xiaoheng

    2017-01-01

    Highlights: • An inversed Au/ZnO nanostructure was fabricated with ZnO loaded onto Au. • The Au/ZnO nanocomposites showed enhanced properties in visible-light photocatalysis. • The SPR effect of Au was considered important for visible-light photocatalysis. - Abstract: In this paper, we fabricate Au/ZnO nanostructure with smaller ZnO nanoparticles loaded onto bigger gold nanoparticles via combining seed-mediated method and sol-gel method. The obtained Au/ZnO nanocomposites exhibit excellent properties in photocatalysis process like methyl orange (MO) degradation and oxidative conversion of methanol into formaldehyde under visible light irradiation. The enhanced properties were ascribed to the surface plasmon resonance (SPR) effect of Au nanoparticles, which could contribute to the separation of photo-excited electrons and holes and facilitate the process of absorbing visible light. This paper contributes to the emergence of multi-functional nanocomposites with possible applications in visible-light driven photocatalysts and makes the Au/ZnO photocatalyst an exceptional choice for practical applications such as environmental purification of organic pollutants in aqueous solution and the synthesis of fine chemicals and intermediates.

  17. Structure and properties of visible-light absorbing homodisperse nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Benedict, Jason

    2018-04-05

    Broadly, the scientific progress from this award focused in two main areas: developing time-resolved X-ray diffraction methods and the synthesis and characterization of molecular systems relevant to solar energy harvesting. The knowledge of photo‐induced non‐equilibrium states is central to our understanding of processes involved in solar‐energy capture. More specifically, knowledge of the geometry changes on excitation and their relation to lifetimes and variation with adsorption of chromophores on the substrates is of importance for the design of molecular devices used in light capture.

  18. Enhanced visible light absorption and reduced charge recombination in AgNP plasmonic photoelectrochemical cell

    Directory of Open Access Journals (Sweden)

    Samaila Buda

    Full Text Available In this research work, silver nanoparticles (AgNP were synthesized using a simple solvothermal technique, the obtained AgNP were used to prepare a titania/silver (TiO2/Ag nanocomposites with varied amount of Ag contents and used to fabricated a photoanode of dye-sensitized solar cell (DSSC. X-ray photoelectron spectroscopy (XPS was used to ascertain the presence of silver in the nanocomposite. A photoluminance (PL spectra of the nanocomposite powder shows a low PL activity which indicates a reduced election- hole recombination within the material. UV–vis spectra reveal that the Ag in the DSSC photoanode enhances the light absorption of the solar cell device within the visible range between λ = 382 nm and 558 nm nm owing to its surface plasmon resonance effect. Power conversion efficiency was enhanced from 4.40% for the pure TiO2 photoanode based device to 6.56% for the device fabricated with TiO2/Ag due to the improvement of light harvesting caused by the localized surface plasmonic resonance effect of AgNP. The improvement of power conversion was also achieved due to the reduced charge recombination within the photoanode. Keywords: Nanoparticle, Silver, Plasmonic, Power, Photon

  19. A Novel Mirror-Aided Non-imaging Receiver for Indoor 2x2 MIMO Visible Light Communication Systems

    KAUST Repository

    Park, Kihong; Oubei, Hassan M.; Alheadary, Wael Ghazy; Ooi, Boon S.; Alouini, Mohamed-Slim

    2017-01-01

    Indoor visible light communication (VLC) systems are now possible because of advances in light emitting diode and laser diode technologies. These lighting technologies provide the foundation for multiple-input multiple-output (MIMO) data

  20. Visible light scatter as quantitative information source on milk constituents

    DEFF Research Database (Denmark)

    Melentiyeva, Anastasiya; Kucheryavskiy, Sergey; Bogomolov, Andrey

    2012-01-01

    analysis. The main task here is to extract individual quantitative information on milk fat and total protein content from spectral data. This is particularly challenging problem in the case of raw natural milk, where the fat globule sizes may essentially differ depending on source. Fig. 1. Spots of light...... designed set of raw milk samples with simultaneously varying fat, total protein and particle size distribution has been analyzed in the Vis spectral region. The feasibility of raw milk analysis by PLS regression on spectral data has been proved. The root mean-square errors below 0.10% and 0.04% for fat....... 3J&M Analytik AG, Willy-Messerschmitt-Strasse 8, 73457 Essingen, Germany. bogomolov@j-m.de Fat and protein are two major milk nutrients that are routinely analyzed in the dairy industry. Growing food quality requirements promote the dissemination of spectroscopic analysis, enabling real...

  1. Split and delay photon correlation spectroscopy with a visible light

    International Nuclear Information System (INIS)

    Rasch, Marten

    2016-04-01

    The development and performance of a setup constructed with the aim for the split pulse photon correlation spectroscopy is presented in this thesis. The double pulse time structure is accomplished with help of an Acusto-Optic Modulator (AOM) crystal, which mimics the splitting and delaying of photon pulses. The setup provides double pulses and allows to control the pulse width and delay and to synchronize them into one camera exposure window. The performance of the setup was successfully verified in a proof of principle experiment with a model system of polystyrene particles following Brownian motion. The measured radius of particles obtained with from the split pulse experiment (R h =(2.567±0.097) μm) is in agreement with the particle size provided by the manufacturer (R=(2.26±0.08) μm). The achieved results show higher statistics compared to a standard Dynamic Light Scattering (DLS) measurement.

  2. Visible Light Photocatalytic Properties of Modified Titanium Dioxide Nanoparticles via Aluminium Treatment

    Directory of Open Access Journals (Sweden)

    Dessy Ariyanti

    2016-03-01

    Full Text Available Titanium dioxide (TiO2 has gained much attentions for the last few decades due to its remarkable performance in photocatalysis and some other related properties. However, its wide bandgap (~3.2 eV can only absorb UV energy which is only ~5% of solar light spectrum. The objective of this research was to improve the photocatalytic activity of TiO2 by improving the optical absorption to the visible light range. Here, colored TiO2 nanoparticles range from light to dark grey were prepared via aluminium treatment at the temperatures ranging from 400 to 600 oC. The modified TiO2 is able to absorb up to 50% of visible light (400-700 nm and shows a relatively good photocatalytic activity in organic dye (Rhodamine B degradation under visible light irradiation compared with the commercial TiO2. Copyright © 2016 BCREC GROUP. All rights reserved Received: 10th November 2015; Revised: 7th January 2016; Accepted: 7th January 20 How to Cite: Ariyanti, D., Dong, J.Z., Dong, J.Y., Gao, W. (2016. Visible Light Photocatalytic Properties of Modified Titanium Dioxide Nanoparticles via Aluminium Treatment. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (1: 40-47. (doi:10.9767/bcrec.11.1.414.40-47 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.1.414.40-47

  3. Research on the Collinear Equation Model of Visual Positioning Based on Visible Light Communication

    Directory of Open Access Journals (Sweden)

    Wang Yuqi

    2015-01-01

    Full Text Available A positioning method based on visible light communication is proposed, which receiving visible light information by low-resolution photodiode array and receiving visual information by the front camera of mobile phone. The terminal position is determined by matching spot information provided by photodiode array with visual information and position information provided by visible light communication. A collinear equation model is derived which based on mobile phone front camera. A hardware-in-loop simulation has been conducted to verify the collinear equation. The three-dimensional positioning error is on the level of decimeter. Moreover, the main factors which affect the positioning accuracy are analyzed in order to further improve the positioning accuracy.

  4. Visible-Light-Responsive Catalyst Development for Volatile Organic Carbon Remediation Project

    Science.gov (United States)

    Zeitlin, Nancy; Hintze, Paul E.; Coutts, Janelle

    2015-01-01

    Photocatalysis is a process in which light energy is used to 'activate' oxidation/reduction reactions. Unmodified titanium dioxide (TiO2), a common photocatalyst, requires high-energy UV light for activation due to its large band gap (3.2 eV). Modification of TiO2 can reduce this band gap, leading to visible-light-responsive (VLR) photocatalysts. These catalysts can utilize solar and/or visible wavelength LED lamps as an activation source, replacing mercury-containing UV lamps, to create a "greener," more energy-efficient means for air and water revitalization. Recently, KSC developed several VLR catalysts that, on preliminary evaluation, possessed high catalytic activity within the visible spectrum; these samples out-performed existing commercial VLR catalysts.

  5. Design and fabrication of a TiO2/nano-silicon composite visible light photocatalyst

    International Nuclear Information System (INIS)

    Lin, C.Y.; Fang, Y.K.; Kuo, C.H.; Chen, S.F.; Lin, C.-S.; Chou, T.H.; Lee, Y.-H.; Lin, J.-C.; Hwang, S.-B.

    2006-01-01

    Nano-silicon (nc-Si) was utilized as the charges generator to promote the photocatalytic and super-hydrophilic reactivity of TiO 2 film under visible light irradiation. The photocatalytic ability of TiO 2 /nc-Si composite photocatalyst was evaluated by a set of experiments to photodecompose 100 ppm methylene blue (MB) in aqueous solution. And the super-hydrophilic property was characterized by measuring the water droplet contacts angle, under visible light irradiation in atmospheric air and at room temperature. Under 100 mW/cm 2 visible light irradiation, the droplet contact angles were reduced to 0 deg. within 4 h with nc-Si charge generator. Additionally, the rate constant of MB photo-degradation was promoted 6.6 times

  6. Enhanced visible-light activity of titania via confinement inside carbon nanotubes

    KAUST Repository

    Chen, Wei

    2011-09-28

    Titania confined inside carbon nanotubes (CNTs) was synthesized using a restrained hydrolysis method. Raman spectra and magnetic measurements using a SQUID magnetometer suggested the formation of remarkable oxygen vacancies over the encapsulated TiO 2 in comparison with nanoparticles dispersed on the outer surface of CNTs, extending the photoresponse of TiO 2 from the UV to the visible-light region. The CNT-confined TiO 2 exhibited improved visible-light activity in the degradation of methylene blue (MB) relative to the outside titania and commercial P25, which is attributed to the modification of the electronic structure of TiO 2 induced by the unique confinement inside CNTs. These results provide further insight into the effect of confinement within CNTs, and the composites are expected to be promising for applications in visible-light photocatalysis. © 2011 American Chemical Society.

  7. Effects of Curcuma extract and visible light on adults with plaque psoriasis.

    Science.gov (United States)

    Carrion-Gutierrez, Miguel; Ramirez-Bosca, Ana; Navarro-Lopez, Vicente; Martinez-Andres, Asunción; Asín-Llorca, Manuel; Bernd, August; Horga de la Parte, José Francisco

    2015-01-01

    We conducted a phase IV randomized, double-blind, placebo-controlled, pilot clinical trial to investigate the safety and efficacy of oral curcumin together with local phototherapy in patients with plaque psoriasis. Patients with moderate to severe psoriasis received Curcuma extract orally with real visible light phototherapy (VLRT) or simulated visible light phototherapy (VLST) in the experimental area, while the rest of the body surface was treated with ultraviolet A (UVA) radiation. The endpoints were the number of responders and the temporal course of the response. The secondary outcomes were related to safety and adverse events. Twenty-one patients were included in the study. In the intention-to-treat analysis, no patients included in the VLRT group showed "moderate" or "severe" plaques after the treatment, in contrast to the patients included in the VSLT group (pCurcuma if activated with visible light phototherapy, a new therapeutic method that would be safer for patients than existing treatments.

  8. Indoor anti-occlusion visible light positioning systems based on particle filtering

    Science.gov (United States)

    Jiang, Meng; Huang, Zhitong; Li, Jianfeng; Zhang, Ruqi; Ji, Yuefeng

    2015-04-01

    As one of the most popular categories of mobile services, a rapid growth of indoor location-based services has been witnessed over the past decades. Indoor positioning methods based on Wi-Fi, radio-frequency identification or Bluetooth are widely commercialized; however, they have disadvantages such as low accuracy or high cost. An emerging method using visible light is under research recently. The existed visible light positioning (VLP) schemes using carrier allocation, time allocation and multiple receivers all have limitations. This paper presents a novel mechanism using particle filtering in VLP system. By this method no additional devices are needed and the occlusion problem in visible light would be alleviated which will effectively enhance the flexibility for indoor positioning.

  9. Vertically aligned ZnO@CdS nanorod heterostructures for visible light photoinactivation of bacteria

    International Nuclear Information System (INIS)

    Zirak, M.; Akhavan, O.; Moradlou, O.; Nien, Y.T.; Moshfegh, A.Z.

    2014-01-01

    Highlights: • Synthesis of vertically aligned ZnO@CdS nanorod heterostructures. • Effective antibacterial application of the ZnO@CdS nanorods under visible light irradiation. • Determination of the optimum loading of CdS on the ZnO nanorods in the antibacterial application. -- Abstract: Vertically aligned ZnO@CdS nanorod heterostructure films with various loadings of CdS nanoparticle shell were synthesized and applied in photoinactivation of Escherichia coli bacteria under visible light irradiation. While neither the bare ZnO nanorods (with band-gap energy (E g ) of ∼3.28 eV) under visible light irradiation nor the nanorod heterostructures in dark exhibited any significant antibacterial activity, the ZnO@CdS nanorod heterostructures (with E g ∼2.5–2.6 eV) could successfully inactivate the bacteria under visible light irradiation. Furthermore, it was found that an optimum loading of the CdS shell (corresponding to the effective thickness less than ∼15 nm) is required to achieve a complete inactivation of the bacteria after 24 h visible light irradiation at room temperature. Using X-ray photoelectron spectroscopy, the lower photoinactivation efficiencies of the ZnO@CdS nanorod heterostructure at CdS thicknesses lower and higher than the optimum one were assigned to lower amounts of CdS nanoparticles and OH bonds (substantially existed on the hydrothermally synthesized ZnO nanorods) which are responsible for absorption of the visible light and production of hydroxyl radicals, respectively. Water contact angle measurements showed that the sample with more surface OH groups has a more hydrophilic surface and so more antibacterial activity

  10. Vertically aligned ZnO@CdS nanorod heterostructures for visible light photoinactivation of bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Zirak, M. [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Akhavan, O., E-mail: oakhavan@sharif.edu [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of); Moradlou, O. [Department of Chemistry, Faculty of Sciences, Alzahra University, P.O. Box 1993893973, Tehran (Iran, Islamic Republic of); Nien, Y.T. [Department of Materials Science and Engineering, National Formosa University, Huwei District, Taiwan (China); Moshfegh, A.Z. [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of)

    2014-03-25

    Highlights: • Synthesis of vertically aligned ZnO@CdS nanorod heterostructures. • Effective antibacterial application of the ZnO@CdS nanorods under visible light irradiation. • Determination of the optimum loading of CdS on the ZnO nanorods in the antibacterial application. -- Abstract: Vertically aligned ZnO@CdS nanorod heterostructure films with various loadings of CdS nanoparticle shell were synthesized and applied in photoinactivation of Escherichia coli bacteria under visible light irradiation. While neither the bare ZnO nanorods (with band-gap energy (E{sub g}) of ∼3.28 eV) under visible light irradiation nor the nanorod heterostructures in dark exhibited any significant antibacterial activity, the ZnO@CdS nanorod heterostructures (with E{sub g} ∼2.5–2.6 eV) could successfully inactivate the bacteria under visible light irradiation. Furthermore, it was found that an optimum loading of the CdS shell (corresponding to the effective thickness less than ∼15 nm) is required to achieve a complete inactivation of the bacteria after 24 h visible light irradiation at room temperature. Using X-ray photoelectron spectroscopy, the lower photoinactivation efficiencies of the ZnO@CdS nanorod heterostructure at CdS thicknesses lower and higher than the optimum one were assigned to lower amounts of CdS nanoparticles and OH bonds (substantially existed on the hydrothermally synthesized ZnO nanorods) which are responsible for absorption of the visible light and production of hydroxyl radicals, respectively. Water contact angle measurements showed that the sample with more surface OH groups has a more hydrophilic surface and so more antibacterial activity.

  11. Suomi National Polar-Orbiting Partnership Visible Infrared Imaging Radiometer Suite Polarization Sensitivity Analysis

    Science.gov (United States)

    Sun, Junqiang; Xiong, Xiaoxiong; Waluschka, Eugene; Wang, Menghua

    2016-01-01

    The Visible Infrared Imaging Radiometer Suite (VIIRS) is one of five instruments onboard the Suomi National Polar-Orbiting Partnership (SNPP) satellite that launched from Vandenberg Air Force Base, California, on October 28, 2011. It is a whiskbroom radiometer that provides +/-56.28deg scans of the Earth view. It has 22 bands, among which 14 are reflective solar bands (RSBs). The RSBs cover a wavelength range from 410 to 2250 nm. The RSBs of a remote sensor are usually sensitive to the polarization of incident light. For VIIRS, it is specified that the polarization factor should be smaller than 3% for 410 and 862 nm bands and 2.5% for other RSBs for the scan angle within +/-45deg. Several polarization sensitivity tests were performed prelaunch for SNPP VIIRS. The first few tests either had large uncertainty or were less reliable, while the last one was believed to provide the more accurate information about the polarization property of the instrument. In this paper, the measured data in the last polarization sensitivity test are analyzed, and the polarization factors and phase angles are derived from the measurements for all the RSBs. The derived polarization factors and phase angles are band, detector, and scan angle dependent. For near-infrared bands, they also depend on the half-angle mirror side. Nevertheless, the derived polarization factors are all within the specification, although the strong detector dependence of the polarization parameters was not expected. Compared to the Moderate Resolution Imaging Spectroradiometer on both Aqua and Terra satellites, the polarization effect on VIIRS RSB is much smaller.

  12. The chemistry of amine radical cations produced by visible light photoredox catalysis

    Directory of Open Access Journals (Sweden)

    Jie Hu

    2013-10-01

    Full Text Available Amine radical cations are highly useful reactive intermediates in amine synthesis. They have displayed several modes of reactivity leading to some highly sought-after synthetic intermediates including iminium ions, α-amino radicals, and distonic ions. One appealing method to access amine radical cations is through one-electron oxidation of the corresponding amines under visible light photoredox conditions. This approach and subsequent chemistries are emerging as a powerful tool in amine synthesis. This article reviews synthetic applications of amine radical cations produced by visible light photocatalysis.

  13. Optical effects of exposing intact human lenses to ultraviolet radiation and visible light

    DEFF Research Database (Denmark)

    Kessel, Line; Eskildsen, Lars; Lundeman, Jesper Holm

    2011-01-01

    region of incoming visible light. The aim of the present study was to examine the optical effects on human lenses of short wavelength visible light and ultraviolet radiation. METHODS: Naturally aged human donor lenses were irradiated with UVA (355 nm), violet (400 and 405 nm) and green (532 nm) lasers......: Irradiation with high intensity lasers caused scattering lesions in the human lenses. These effects were more likely to be seen when using pulsed lasers because of the high pulse intensity. Prolonged irradiation with UVA led to photodarkening whereas no detrimental effects were observed after irradiation...

  14. Optical effects of exposing intact human lenses to ultraviolet radiation and visible light

    DEFF Research Database (Denmark)

    Kessel, Line; Eskildsen, Lars Baunsgaard; Lundeman, Jesper Holm

    2011-01-01

    wavelength region of incoming visible light. The aim of the present study was to examine the optical effects on human lenses of short wavelength visible light and ultraviolet radiation. METHODS: Naturally aged human donor lenses were irradiated with UVA (355 nm), violet (400 and 405 nm) and green (532 nm....... RESULTS: Irradiation with high intensity lasers caused scattering lesions in the human lenses. These effects were more likely to be seen when using pulsed lasers because of the high pulse intensity. Prolonged irradiation with UVA led to photodarkening whereas no detrimental effects were observed after...

  15. Singly-resonant sum frequency generation of visible light in a semiconductor disk laser

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer; Schlosser, P.J.; Hastie, J.E.

    2009-01-01

    In this paper a generic approach for visible light generation is presented. It is based on sum frequency generation between a semiconductor disk laser and a solid-state laser, where the frequency mixing is achieved within the cavity of the semiconductor disk laser using a singlepass of the solid......-state laser light. This exploits the good beam quality and high intra-cavity power present in the semiconductor disk laser to achieve high conversion efficiency. Combining sum frequency mixing and semiconductor disk lasers in this manner allows in principle for generation of any wavelength within the visible...

  16. Enhanced photocathodic protection performance of Ag/graphene/TiO2 composite for 304SS under visible light

    Science.gov (United States)

    Li, Hong; Wang, Xiutong; Wei, Qinyi; Liu, Xueqing; Qian, Zhouhai; Hou, Baorong

    2017-06-01

    Ag and graphene co-sensitized TiO2 composites were successfully fabricated and used as photoanodes for photogenerated cathodic protection of 304 stainless steel (304SS) under visible light. Graphene films was firstly deposited onto the TiO2 nanotube (NT) films via cyclic voltammetric electrodeposition. Ag/graphene/TiO2 films were then fabricated via dipping and photoreduction method. The morphology, composition and optical response of the Ag/graphene/TiO2 NT composites were characterized by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, UV-vis diffusion reflectance spectroscopy, respectively. The photocathodic protection performance of the Ag/graphene/TiO2 composites were systematically studied through open-circuit potential and potentiodynamic polarization measurements in 3.5 wt% NaCl solution under visible light (λ > 400 nm). The composites exhibited enhanced photogenerated cathodic protection performance for 304SS under visible light irradiation compared to pure TiO2. Graphene and Ag have a synergistic effect on the enhancement of photocathodic protection performance of TiO2. The composites prepared with 30-cycle graphene film and 15 mM AgNO3 solution showed the optimal corrosion protection performance.

  17. Mitochondrial damage and cytoskeleton reorganization in human dermal fibroblasts exposed to artificial visible light similar to screen-emitted light.

    Science.gov (United States)

    Rascalou, Adeline; Lamartine, Jérôme; Poydenot, Pauline; Demarne, Frédéric; Bechetoille, Nicolas

    2018-05-05

    Artificial visible light is everywhere in modern life. Social communication confronts us with screens of all kinds, and their use is on the rise. We are therefore increasingly exposed to artificial visible light, the effects of which on skin are poorly known. The purpose of this study was to model the artificial visible light emitted by electronic devices and assess its effect on normal human fibroblasts. The spectral irradiance emitted by electronic devices was optically measured and equipment was developed to accurately reproduce such artificial visible light. Effects on normal human fibroblasts were analyzed on human genome microarray-based gene expression analysis. At cellular level, visualization and image analysis were performed on the mitochondrial network and F-actin cytoskeleton. Cell proliferation, ATP release and type I procollagen secretion were also measured. We developed a device consisting of 36 LEDs simultaneously emitting blue, green and red light at distinct wavelengths (450 nm, 525 nm and 625 nm) with narrow spectra and equivalent radiant power for the three colors. A dose of 99 J/cm 2 artificial visible light was selected so as not to induce cell mortality following exposure. Microarray analysis revealed 2984 light-modulated transcripts. Functional annotation of light-responsive genes revealed several enriched functions including, amongst others, the "mitochondria" and "integrin signaling" categories. Selected results were confirmed by real-time quantitative PCR, analyzing 24 genes representing these two categories. Analysis of micro-patterned culture plates showed marked fragmentation of the mitochondrial network and disorganization of the F-actin cytoskeleton following exposure. Functionally, there was considerable impairment of cell growth and spread, ATP release and type I procollagen secretion in exposed fibroblasts. Artificial visible light induces drastic molecular and cellular changes in normal human fibroblasts. This may impede

  18. Implementasi Sistem Penyiaran Musik Digital di Kafe menggunakan Visible Light Communication

    Directory of Open Access Journals (Sweden)

    DENNY DARLIS

    2018-03-01

    Full Text Available ABSTRAK Teknologi penyiaran dengan frekuensi radio menggunakan teknik modulasi frekuensi (FM telah dikenal sejak lama. Teknologi ini memfasilitasi pengiriman suara melalui sinyal analog dari pemancar kepada penerima. Pengembangan teknologi komunikasi menggunakan cahaya tampak yang memanfaatkan lampu LED sebagai pengirim informasi cukup banyak dilakukan. Pada penelitian ini diimplementasi sistem pengiriman dan penerimaaan siaran musik digital dengan memanfaatkan cahaya tampak yang berasal dari lampu penerangan di kafe. Sistem visible light communication (VLC diimplementasikan dengan menggunakan metoda modulasi intensitas dan deteksi langsung (IM/DD. Dari hasil pengujian dapat ditunjukkan bahwa sistem ini dapat melewatkan siaran musik digital dengan redaman rata-rata 7,77 dB pada jarak maksimal adalah 3 meter. Hasil dari sistem yang telah dirancang dan diimplementasikan menunjukan hasil yang baik sehingga layak untuk diterapkan pada system penyiaran musik digital di kafe. Kata kunci: Visible Light Communication, IM/DD, Sistem Penyiaran Musik Digital, Sistem Penerangan Kafe. ABSTRACT Broadcasting technology uses radio frequency and technique of frequency modulation (FM has been known for a long time. This technology allows the transmission of voice through analog signals from transmitter to receiver. Currently, many research on visible light communication technology utilizes LED lights as the sender. In this paper presented the results of transmitter and receiver system implementation of digital musik broadcast for use in the cafe. Visible light communication (VLC system is implemented using intensity modulation and direct detection (IM/DD method. From the test results can be shown that this system can pass digital musik broadcast with an average attenuation of 7.77 dB at maximum distance is 3 meters. Results of the system that has been designed and implemented shows good results, so it deserves to be applied to the digital musik broadcasting

  19. Implementasi Sistem Penyiaran Musik Digital di Kafe menggunakan Visible Light Communication

    Directory of Open Access Journals (Sweden)

    DENNY DARLIS

    2017-06-01

    Full Text Available ABSTRAKTeknologi penyiaran dengan frekuensi radio menggunakan teknik modulasi frekuensi (FM telah dikenal sejak lama. Teknologi ini memfasilitasi pengiriman suara melalui sinyal analog dari pemancar kepada penerima. Pengembangan teknologi komunikasi menggunakan cahaya tampak yang memanfaatkan lampu LED sebagai pengirim informasi cukup banyak dilakukan. Pada penelitian ini diimplementasi sistem pengiriman dan penerimaaan siaran musik digital dengan memanfaatkan cahaya tampak yang berasal dari lampu penerangan di kafe. Sistem visible light communication (VLC diimplementasikan dengan menggunakan metoda modulasi intensitas dan deteksi langsung (IM/DD. Dari hasil pengujian dapat ditunjukkan bahwa sistem ini dapat melewatkan siaran musik digital dengan redaman rata-rata 7,77 dB pada jarak maksimal adalah 3 meter. Hasil dari sistem yang telah dirancang dan diimplementasikan menunjukan hasil yang baik sehingga layak untuk diterapkan pada system penyiaran musik digital di kafe.Kata kunci: Visible Light Communication, IM/DD, Sistem Penyiaran Musik Digital, Sistem Penerangan Kafe.ABSTRACTBroadcasting technology uses radio frequency and technique of frequency modulation (FM has been known for a long time. This technology allows the transmission of voice through analog signals from transmitter to receiver. Currently, many research on visible light communication technology utilizes LED lights as the sender. In this paper presented the results of transmitter and receiver system implementation of digital musik broadcast for use in the cafe. Visible light communication (VLC system is implemented using intensity modulation and direct detection (IM/DD method. From the test results can be shown that this system can pass digital musik broadcast with an average attenuation of 7.77 dB at maximum distance is 3 meters. Results of the system that has been designed and implemented shows good results, so it deserves to be applied to the digital musik broadcasting system in

  20. Integrative Multi-Spectral Sensor Device for Far-Infrared and Visible Light Fusion

    Science.gov (United States)

    Qiao, Tiezhu; Chen, Lulu; Pang, Yusong; Yan, Gaowei

    2018-06-01

    Infrared and visible light image fusion technology is a hot spot in the research of multi-sensor fusion technology in recent years. Existing infrared and visible light fusion technologies need to register before fusion because of using two cameras. However, the application effect of the registration technology has yet to be improved. Hence, a novel integrative multi-spectral sensor device is proposed for infrared and visible light fusion, and by using the beam splitter prism, the coaxial light incident from the same lens is projected to the infrared charge coupled device (CCD) and visible light CCD, respectively. In this paper, the imaging mechanism of the proposed sensor device is studied with the process of the signals acquisition and fusion. The simulation experiment, which involves the entire process of the optic system, signal acquisition, and signal fusion, is constructed based on imaging effect model. Additionally, the quality evaluation index is adopted to analyze the simulation result. The experimental results demonstrate that the proposed sensor device is effective and feasible.

  1. Significantly enhanced visible light response in single TiO2 nanowire by nitrogen ion implantation

    Science.gov (United States)

    Wu, Pengcheng; Song, Xianyin; Si, Shuyao; Ke, Zunjian; Cheng, Li; Li, Wenqing; Xiao, Xiangheng; Jiang, Changzhong

    2018-05-01

    The metal-oxide semiconductor TiO2 shows enormous potential in the field of photoelectric detection; however, UV-light absorption only restricts its widespread application. It is considered that nitrogen doping can improve the visible light absorption of TiO2, but the effect of traditional chemical doping is far from being used for visible light detection. Herein, we dramatically broadened the absorption spectrum of the TiO2 nanowire (NW) by nitrogen ion implantation and apply the N-doped single TiO2 NW to visible light detection for the first time. Moreover, this novel strategy effectively modifies the surface states and thus regulates the height of Schottky barriers at the metal/semiconductor interface, which is crucial to realizing high responsivity and a fast response rate. Under the illumination of a laser with a wavelength of 457 nm, our fabricated photodetector exhibits favorable responsivity (8 A W-1) and a short response time (0.5 s). These results indicate that ion implantation is a promising method in exploring the visible light detection of TiO2.

  2. Synthesis and photocatalytic properties of visible light responsive La/TiO2-graphene composites

    International Nuclear Information System (INIS)

    Khalid, N.R.; Ahmed, E.; Hong Zhanglian; Ahmad, M.

    2012-01-01

    Highlights: ► Synthesis of La/TiO 2 -graphene composites by two-step hydrothermal method. ► Efficient charge separation due to La doping and graphene incorporation. ► Enhanced photocatalytic activity of composite catalyst for MB degradation under visible-light. - Abstract: La/TiO 2 -graphene composites used as photocatalyst were prepared by two-step hydrothermal method. The as-prepared composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). The results of optical properties of La/TiO 2 -graphene composites exhibit extended light absorption in visible-light region and possess better charge separation capability as compared to pure TiO 2 . The photocatalytic activity measurement demonstrate that La/TiO 2 -graphene composites exhibited an enhanced photocatalytic activity for methylene blue (MB) degradation under visible-light irradiation compared to pure TiO 2 , which was attributed to greater adsorptivity of dyes, extended light absorption and increased charge separation efficiency due to excellent electrical properties of graphene and the large surface contact between graphene and La/TiO 2 nanoparticles.

  3. Visible light driven multifunctional photocatalysis in TeO2-based semiconductor glass ceramics

    Science.gov (United States)

    Kushwaha, Himmat Singh; Thomas, Paramanandam; Vaish, Rahul

    2017-01-01

    Photocatalytic xCaCu3Ti4O12-(100-x)TeO2 (x=0.25 mol% to 3 mol%), glass nanocomposites were fabricated and investigated for wastewater treatment, self-cleaning surfaces, and photocatalytic hydrogen evolution. Visible light active crystals of Cu-doped TiO2 and TiTe3O8 were grown by optimized crystallization of as-quenched glasses. The visible light photocatalytic activity of glass samples was investigated for estrogenic pharmaceutical pollutants, and the degradation rate was obtained as 168.56 min-1 m-2. A higher photocatalytic H2 production rate was observed (135 μmole h-1 g-1) for the crystallized CaCu3Ti4O12-TeO2 (x=3. 0) glass plate under visible light. The self-cleaning performance was observed using contact angle measurements for water under dark and light conditions. These visible light active glass ceramics are a cost effective sustainable solution for water treatment and self-cleaning applications.

  4. Fullerene C{sub 70} decorated TiO{sub 2} nanowires for visible-light-responsive photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Er-Chieh [Department of Clinical Pharmacy, School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei 110, Taiwan (China); Ciou, Jing-Hao [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Zheng, Jia-Huei; Pan, Job [Department of Clinical Pharmacy, School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei 110, Taiwan (China); Hsiao, Yu-Sheng, E-mail: yshsiao@mail.mcut.edu.tw [Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 24301, Taiwan (China); Lee, Kuen-Chan, E-mail: kclee@kmu.edu.tw [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Huang, Jen-Hsien, E-mail: 295604@cpc.com.tw [Department of Green Material Technology, Green Technology Research Institute, CPC Corporation, Kaohsiung 30010, Taiwan (China)

    2015-11-15

    Graphical abstract: - Highlights: • TiO{sub 2} nanowire decorated with C{sub 60} and C{sub 70} derivatives has been synthesized. • The fullerenes impede the charge recombination due to its high electron affinity. • The fullerenes expand the utilization of solar light from UV to visible light. • The modified-TiO{sub 2} has great biocompatibility. - Abstract: In this study, we have synthesized C{sub 60} and C{sub 70}-modified TiO{sub 2} nanowire (NW) through interfacial chemical bonding. The results indicate that the fullerenes (C{sub 60} and C{sub 70} derivatives) can act as sinks for photogenerated electrons in TiO{sub 2}, while the fullerene/TiO{sub 2} is illuminated under ultraviolet (UV) light. Therefore, in comparison to the pure TiO{sub 2} NWs, the modified TiO{sub 2} NWs display a higher photocatalytic activity under UV irradiation. Moreover, the fullerenes also can function as a sensitizer to TiO{sub 2} which expand the utilization of solar light from UV to visible light. The results reveal that the C{sub 70}/TiO{sub 2} NWs show a significant photocatalytic activity for degradation of methylene blue (MB) in visible light region. To better understand the mechanism responsible for the effect of fullerenes on the photocatalytic properties of TiO{sub 2}, the electron only devices and photoelectrochemical cells based on fullerenes/TiO{sub 2} are also fabricated and evaluated.

  5. Evaluating potential spectral impacts of various artificial lights on melatonin suppression, photosynthesis, and star visibility.

    Directory of Open Access Journals (Sweden)

    Martin Aubé

    Full Text Available Artificial light at night can be harmful to the environment, and interferes with fauna and flora, star visibility, and human health. To estimate the relative impact of a lighting device, its radiant power, angular photometry and detailed spectral power distribution have to be considered. In this paper we focus on the spectral power distribution. While specific spectral characteristics can be considered harmful during the night, they can be considered advantageous during the day. As an example, while blue-rich Metal Halide lamps can be problematic for human health, star visibility and vegetation photosynthesis during the night, they can be highly appropriate during the day for plant growth and light therapy. In this paper we propose three new indices to characterize lamp spectra. These indices have been designed to allow a quick estimation of the potential impact of a lamp spectrum on melatonin suppression, photosynthesis, and star visibility. We used these new indices to compare various lighting technologies objectively. We also considered the transformation of such indices according to the propagation of light into the atmosphere as a function of distance to the observer. Among other results, we found that low pressure sodium, phosphor-converted amber light emitting diodes (LED and LED 2700 K lamps filtered with the new Ledtech's Equilib filter showed a lower or equivalent potential impact on melatonin suppression and star visibility in comparison to high pressure sodium lamps. Low pressure sodium, LED 5000 K-filtered and LED 2700 K-filtered lamps had a lower impact on photosynthesis than did high pressure sodium lamps. Finally, we propose these indices as new standards for the lighting industry to be used in characterizing their lighting technologies. We hope that their use will favor the design of new environmentally and health-friendly lighting technologies.

  6. Visibility of trabecular meshwork by standard and polarization-sensitive optical coherence tomography

    Science.gov (United States)

    Yasuno, Yoshiaki; Yamanari, Masahiro; Kawana, Keisuke; Miura, Masahiro; Fukuda, Shinichi; Makita, Shuichi; Sakai, Shingo; Oshika, Tetsuro

    2010-11-01

    Polarization-sensitive optical coherence tomography (PS-OCT) is known to be advantageous because of its additional tissue-specific contrast of the anterior eye. So far, this advantage has been shown only qualitatively. We evaluate the improved visibility afforded by 3-D PS corneal and anterior eye segment OCT (PS-CAS-OCT) in visualizing the trabecular meshwork (TM) based on statistical evidences. A total of 31 normal subjects participated in this study. The anterior eye segments of both the eyes of the subjects are scanned using a custom-made PS-CAS-OCT and the standard-scattering OCT (S-OCT) and polarization-sensitive phase-retardation OCT (P-OCT) images are obtained. Three graders grade the visibility of the TM using a four-leveled grading system. The intergrader agreement, intermodality differences, and interquadrant dependence of visibility are statistically examined. All three of three combinations of graders show substantial agreement in visibility with P-OCT (ρ = 0.74, 0.70, and 0.68, Spearman's correlation), while only one of three shows substantial agreement with S-OCT (ρ = 0.72). Significant dependence of the visibility on the modality (S-OCT versus P-OCT) and quadrants are found by the analysis of variance. A subsequent Wilcoxon signed-rank test reveals significantly improved visibility. PS-CAS-OCT may become a useful tool for screening angle-closure glaucoma.

  7. BODIPY star-shaped molecules as solid state colour converters for visible light communications

    Energy Technology Data Exchange (ETDEWEB)

    Vithanage, D. A.; Manousiadis, P. P.; Sajjad, M. T.; Samuel, I. D. W., E-mail: idws@st-andrews.ac.uk, E-mail: gat@st-andrews.ac.uk; Turnbull, G. A., E-mail: idws@st-andrews.ac.uk, E-mail: gat@st-andrews.ac.uk [Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, St. Andrews KY16 9SS (United Kingdom); Rajbhandari, S. [School of Computing, Electronics and Mathematics, Coventry University, Coventry, West Midlands CV1 2JH (United Kingdom); Department of Engineering Science, University of Oxford, Oxford OX1 3PJ (United Kingdom); Chun, H.; Faulkner, G.; O' Brien, D. C. [Department of Engineering Science, University of Oxford, Oxford OX1 3PJ (United Kingdom); Orofino, C.; Cortizo-Lacalle, D.; Findlay, N. J.; Skabara, P. J. [WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL (United Kingdom); Kanibolotsky, A. L. [WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL (United Kingdom); Institute of Physical-Organic Chemistry and Coal Chemistry, 02160 Kyiv (Ukraine)

    2016-07-04

    In this paper, we study a family of solid-state, organic semiconductors for visible light communications. The star-shaped molecules have a boron-dipyrromethene (BODIPY) core with a range of side arm lengths which control the photophysical properties. The molecules emit red light with photoluminescence quantum yields ranging from 22% to 56%. Thin films of the most promising BODIPY molecules were used as a red colour converter for visible light communications. The film enabled colour conversion with a modulation bandwidth of 73 MHz, which is 16 times higher than that of a typical phosphor used in LED lighting systems. A data rate of 370 Mbit/s was demonstrated using On-Off keying modulation in a free space link with a distance of ∼15 cm.

  8. E. coli inactivation by visible light irradiation using a Fe–Cd/TiO2 photocatalyst: Statistical analysis and optimization of operating parameters

    NARCIS (Netherlands)

    Feilizadeh, Mehrzad; Mul, Guido; Vossoughi, M.

    2015-01-01

    In this study, the antibacterial effect of a Fe and Cd co-doped TiO2 (Fe–Cd/TiO2) visible light sensitive photocatalyst was optimized by varying operating parameters and using a response surface methodology to evaluate the experimental data. Twenty sets of disinfection experiments were conducted by

  9. A Behavior of Strobe Light in Non-Visibility (Dense Fog) Environments

    International Nuclear Information System (INIS)

    Cho, Jai Wan; Choi, Young Soo; Jeong, Kyung Min

    2015-01-01

    In this study, a strobe light was used to understand the behavior of light in an aerosol-like non-visibility environment. Fog was injected into a vinyl pleated cylindrical fog box that is 1 m in diameter and 5.5 m in length. After the fog concentration became saturated in the fog box, the strobe light was set off at regular time intervals until the fog particles almost dissipated in the box. Images of the behavior of the light from the strobe were taken from outside of the fog box with a digital camera in line with the strobe light sync signal. In the case of a DBA (or severe accident) of the nuclear power plant accident, coolant should be injected over the reactor pressure vessel to cool the reactor core. Cold coolant that has been poured into the reactor pressure vessel would be discharged through the nozzles of the core spray system or through pipelines in the fire protection system. The discharging cold coolant would impact high temperature structures with surface temperatures of around 250 .deg. C or higher, such as the reactor pressure vessel that surrounds the reactor core, and then evaporate and turn into steam. The steam cools while forming mist (aerosol including radioactivity), which can cause a sharp drop in visibility. Assuming that a robot has been deployed to manage and mitigate the DBA (or severe accident) at the nuclear power plant, the robot must perform its task in a non-visibility environment. A color CCD/CMOS camera corresponding to visible wavelength (400 - 700 nm) can be attached to the robot for observation and navigation. The camera needs lights in order to secure a clear field of view. Generally, the aperture of a lens is correlated to the intensity of illumination. The brighter the light, the smaller the aperture can be. If the aperture becomes narrower to the size of a pin hole, a clearer image in deep focus can be obtained. As the aperture decreases in the half, the required amount of light doubles. The observed behavior of the strobe

  10. A Behavior of Strobe Light in Non-Visibility (Dense Fog) Environments

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jai Wan; Choi, Young Soo; Jeong, Kyung Min [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    In this study, a strobe light was used to understand the behavior of light in an aerosol-like non-visibility environment. Fog was injected into a vinyl pleated cylindrical fog box that is 1 m in diameter and 5.5 m in length. After the fog concentration became saturated in the fog box, the strobe light was set off at regular time intervals until the fog particles almost dissipated in the box. Images of the behavior of the light from the strobe were taken from outside of the fog box with a digital camera in line with the strobe light sync signal. In the case of a DBA (or severe accident) of the nuclear power plant accident, coolant should be injected over the reactor pressure vessel to cool the reactor core. Cold coolant that has been poured into the reactor pressure vessel would be discharged through the nozzles of the core spray system or through pipelines in the fire protection system. The discharging cold coolant would impact high temperature structures with surface temperatures of around 250 .deg. C or higher, such as the reactor pressure vessel that surrounds the reactor core, and then evaporate and turn into steam. The steam cools while forming mist (aerosol including radioactivity), which can cause a sharp drop in visibility. Assuming that a robot has been deployed to manage and mitigate the DBA (or severe accident) at the nuclear power plant, the robot must perform its task in a non-visibility environment. A color CCD/CMOS camera corresponding to visible wavelength (400 - 700 nm) can be attached to the robot for observation and navigation. The camera needs lights in order to secure a clear field of view. Generally, the aperture of a lens is correlated to the intensity of illumination. The brighter the light, the smaller the aperture can be. If the aperture becomes narrower to the size of a pin hole, a clearer image in deep focus can be obtained. As the aperture decreases in the half, the required amount of light doubles. The observed behavior of the strobe

  11. Facile synthesis of cobalt-doped zinc oxide thin films for highly efficient visible light photocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Altintas Yildirim, Ozlem, E-mail: ozlemaltintas@gmail.com [Department of Metallurgical and Materials Engineering, Selcuk University, Konya (Turkey); Arslan, Hanife; Sönmezoğlu, Savaş [Department of Metallurgical and Materials Engineering, Karamanoglu Mehmetbey University, Karaman (Turkey); Nanotechnology R& D Laboratory, Karamanoglu Mehmetbey University, Karaman (Turkey)

    2016-12-30

    Highlights: • Photocatalytically active Co-ZnO thin film was obtained by sol-gel method. • Co{sup 2+} doping narrowed the band gap of pure ZnO to an extent of 3.18 eV. • Co-ZnO was effective in MB degradation under visible light. • Optimum dopant content to show high performance was 3 at.%. - Abstract: Cobalt-doped zinc oxide (Co:ZnO) thin films with dopant contents ranging from 0 to 5 at.% were prepared using the sol–gel method, and their structural, morphological, optical, and photocatalytic properties were characterized. The effect of the dopant content on the photocatalytic properties of the films was investigated by examining the degradation behavior of methylene blue (MB) under visible light irradiation, and a detailed investigation of their photocatalytic activities was performed by determining the apparent quantum yields (AQYs). Co{sup 2+} ions were observed to be substitutionally incorporated into Zn{sup 2+} sites in the ZnO crystal, leading to lattice parameter constriction and band gap narrowing due to the photoinduced carriers produced under the visible light irradiation. Thus, the light absorption range of the Co:ZnO films was improved compared with that of the undoped ZnO film, and the Co:ZnO films exhibited highly efficient photocatalytic activity (∼92% decomposition of MB after 60-min visible light irradiation for the 3 at.% Co:ZnO film). The AQYs of the Co:ZnO films were greatly enhanced under visible light irradiation compared with that of the undoped ZnO thin film, demonstrating the effect of the Co doping level on the photocatalytic activity of the films.

  12. Mobile Multi-Gigabit Visible Light Communication System in Realistic Indoor Environment

    OpenAIRE

    Hussein, AT; Elmirghani, JMH

    2015-01-01

    The main challenges facing high data rate visible light communication (VLC) are the low-modulation bandwidth of the current transmitters (i.e., light emitting diodes), the intersymbol interference (ISI) caused by the multipath propagation and cochannel interference (CCI) due to multiple transmitters. In this paper, for the first time, to the best of our knowledge, we propose, design, and evaluate the use of laser diodes (LDs) for communication as well as illumination. In addition, we propose ...

  13. Using advertisement light-panel and CMOS image sensor with frequency-shift-keying for visible light communication.

    Science.gov (United States)

    Chow, Chi-Wai; Shiu, Ruei-Jie; Liu, Yen-Chun; Liao, Xin-Lan; Lin, Kun-Hsien; Wang, Yi-Chang; Chen, Yi-Yuan

    2018-05-14

    A frequency-shift-keying (FSK) visible light communication (VLC) system is proposed and demonstrated using advertisement light-panel as transmitter and mobile-phone image sensor as receiver. The developed application program (APP) in mobile-phone can retrieve the rolling shutter effect (RSE) pattern produced by the FSK VLC signal effectively. Here, we also define noise-ratio value (NRV) to evaluate the contrast of different advertisements displayed on the light-panel. Both mobile-phones under test can achieve success rate > 96% even when the transmission distance is up to 200 cm and the NRVs are low.

  14. Low temperature synthesis of polyaniline-crystalline TiO2-halloysite composite nanotubes with enhanced visible light photocatalytic activity.

    Science.gov (United States)

    Li, Cuiping; Wang, Jie; Guo, Hong; Ding, Shujiang

    2015-11-15

    A series of one-dimensional polyaniline-crystalline TiO2-halloysite composite nanotubes with different mass ratio of polyaniline to TiO2 are facilely prepared by employing the low-temperature synthesis of crystalline TiO2 on halloysite nanotubes. The halloysite nanotubes can adsorb TiO2/polyaniline precursors and induce TiO2 nanocrystals/polyaniline to grow on the support in situ simultaneously. By simply adjusting the acidity of reaction system, PANI-crystalline TiO2-HA composite nanotubes composed of anatase, a mixed phase TiO2 and different PANI redox state are obtained. The XRD and UV-vis results show that the surface polyaniline sensitization has no effect on the crystalline structure of halloysite and TiO2 and the light response of TiO2 is extended to visible-light regions. Photocatalysis test results reveal the photocatalytic activity will be affected by the pH value and the volume ratio of ANI to TTIP. The highest photocatalytic activity is achieved with the composite photocatalysts prepared at pH 0.5 and 1% volume ratio of ANI and TTIP owing to the sensitizing effect of polyaniline and the charge transfer from the photoexcited PANI sensitizer to TiO2. Moreover, the PANI-TiO2-HA composite nanotubes synthesized by one-step at pH 0.5 with 1% volume ratio of ANI to TTIP exhibit higher visible light photocatalytic activity than those synthesized by the two-step. Heterogeneous PANI-TiO2-HA composite nanotubes prepared at pH 0.5 exhibit a higher degradation activity than that prepared at pH 1.5. The redoped experiment proves that the PANI redox state plays the main contribution to the enhanced visible light catalytic degradation efficiency of PANI-TiO2-HA prepared at pH 0.5. Furthermore, the heterogeneous PANI-crystalline TiO2-HA nanotubes have good photocatalytic stability and can be reused four times with only gradual loss of activity under visible light irradiation. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Organocatalyzed, Visible-Light Photoredox-Mediated, One-Pot Minisci Reaction Using Carboxylic Acids via N-(Acyloxy)phthalimides.

    Science.gov (United States)

    Sherwood, Trevor C; Li, Ning; Yazdani, Aliza N; Dhar, T G Murali

    2018-03-02

    An improved, one-pot Minisci reaction has been developed using visible light, an organic photocatalyst, and carboxylic acids as radical precursors via the intermediacy of in situ-generated N-(acyloxy)phthalimides. The conditions employed are mild, demonstrate a high degree of functional group tolerance, and do not require a large excess of the carboxylic acid reactant. As a result, this reaction can be applied to drug-like scaffolds and molecules with sensitive functional groups, enabling late-stage functionalization, which is of high interest to medicinal chemistry.

  16. Inactivation of carotenoid-producing and albino strains of Neurospora crassa by visible light, blacklight, and ultraviolet radiation

    International Nuclear Information System (INIS)

    Blanc, P.L.; Tuveson, R.W.; Sargent, M.L.

    1976-01-01

    Suspensions of Neurospora crassa conidia were inactivated by blacklight (BL) radiation (300 to 425 nm) in the absence of exogenous photosensitizing compounds. Carotenoid-containing wild-type conidia were less sensitive to BL radiation than albino conidia, showing a dose enhancement factor (DEF) of 1.2 for dose levels resulting in less than 10 percent survival. The same strains were about equally sensitive to shortwave ultraviolet (uv) inactivation. The kinetics of BL inactivation are similar to those of photodynamic inactivation by visible light in the presence of a photosensitizing dye (methylene blue). Only limited inactivation by visible light in the absence of exogenous photosensitizers was observed. BL and UV inactivations are probably caused by different mechanisms since wild-type conidia are only slightly more resistant to BL radiation (DEF = 1.2 at 1.0 percent survival) than are conidia from a uv-sensitive strain (upr-1, uvs-3). The BL-induced lethal lesions are probably not cyclobutyl pyrimidine dimers since BL-inactivated Haemophilus influenzae transforming deoxyribonucleic acid is not photoreactivated by N. crassa wild-type enzyme extracts, whereas uv-inactivated transforming deoxyribonucleic acid is photoreactivable with this treatment

  17. Photocatalytic generation of hydrogen under visible light on La2CuO4

    Indian Academy of Sciences (India)

    Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry (USTHB),. B.P. 32, 16111 ... The energy diagram shows the feasibility of La2CuO4 for the H2 evolution under visible light. The best ... An efficient photocata-.

  18. Visible light catalyzed methylsulfoxidation of (het)aryl diazonium salts using DMSO.

    Science.gov (United States)

    Pramanik, Mukund M D; Rastogi, Namrata

    2016-06-30

    The visible light catalyzed methylsulfoxidation of (het)aryl diazonium salts using DMSO is illustrated. This is the first example of DMSO being used as the source of the methylsulfinyl group. The procedure tolerates a wide range of functional groups on (het)aryl diazonium salts and provides aryl methyl sulfoxides in excellent yields under mild reaction conditions.

  19. Visible-light-mediated selective arylation of cysteine in batch and flow

    NARCIS (Netherlands)

    Bottecchia, C.; Rubens, M.; Gunnoo, S.B.; Hessel, V.; Madder, A.

    2017-01-01

    A mild visible-light-mediated strategy for cysteine arylation is presented. The method relies on the use of eosin Y as a metal-free photocatalyst and aryldiazonium salts as arylating agents. The reaction can be significantly accelerated in a microflow reactor, whilst allowing the in situ formation

  20. On different photodecomposition behaviors of rhodamine B on laponite and montmorillonite clay under visible light irradiation

    KAUST Repository

    Wang, Peng; Cheng, Mingming; Zhang, Zhonghai

    2013-01-01

    In this study, laponite and montmorillonite clays were found to be able to decompose rhodamine B upon visible light irradiation (λ>420nm). Very interestingly, it was found that rhodamine B on laponite underwent a stepwise N-deethylation and its

  1. Visible light photon counters (VLPCs) for high rate tracking medical imaging and particle astrophysics

    International Nuclear Information System (INIS)

    Atac, M.

    1998-02-01

    This paper is on the operation principles of the Visible Light Photon Counters (VLPCs), application to high luminosity-high multiplicity tracking for High Energy Charged Particle Physics, and application to Medical Imaging and Particle Astrophysics. The VLPCs as Solid State Photomultipliers (SSPMS) with high quantum efficiency can detect down to single photons very efficiently with excellent time resolution and high avalanche gains

  2. Photocatalytic activity of Fe-doped CaTiO₃ under UV-visible light.

    Science.gov (United States)

    Yang, He; Han, Chong; Xue, Xiangxin

    2014-07-01

    The photocatalytic degradation of methylene blue (MB) over Fe-doped CaTiO₃ under UV-visible light was investigated. The as-prepared samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) system, Fourier transform infrared spectra (FT-IR), and UV-visible diffuse reflectance spectroscopy (DRS). The results show that the doping with Fe significantly promoted the light absorption ability of CaTiO₃ in the visible light region. The Fe-doped CaTiO₃ exhibited higher photocatalytic activity than CaTiO₃ for the degradation of MB. However, the photocatalytic activity of the Fe-doped CaTiO₃ was greatly influenced by the calcination temperature during the preparation process. The Fe-doped CaTiO₃ prepared at 500°C exhibited the best photocatalytic activity, with degradation of almost 100% MB (10ppm) under UV-visible light for 180 min. Copyright © 2014. Published by Elsevier B.V.

  3. Peculiarities of near-ultraviolet (365 nm) and visible light effects in Paramecium Caudatum cells

    International Nuclear Information System (INIS)

    Samoilova, K.A.; Sushchenko, N.B.

    1977-01-01

    After treatment with 365 nm or visible light Paramecium caudatum cells fail to divide and die shortly after irradiation; no death occurs long after irradiation, as well as after several cell cycles, unlike the situation after the action of 254 nm or 300-380 nm. Irradiation inhibits mainly the first cell cycle following which the recovery of cells starts. Thus no after-effects take place after the action of 365 nm and visible light, and the patterns of their effects are rather similar. The photoreactivation of damages induced by 365 nm is quite small, being about 2 times less than that for 254 nm and 300-380 nm. Similarity of the action of 254, 300-380, 365 nm and visible light was established by the stimulation of cell division by low doses and increase in viability of infusoria from cultures with low survival and depressed rate of multiplication. This effect of 365 nm is not eliminated by visible light; moreover, the latter promotes the 'therapeutic' effect of the 365 nm line. (author)

  4. Visible light- and radiation-induced alkylation of pyridine ring with alkanoic acid

    International Nuclear Information System (INIS)

    Sugimori, Akira; Yamada, Tetsuo

    1986-01-01

    Quinoline and 4-methylquinoline are efficiently alkylated with alkanoic acid in the presence of iron(III) sulfate upon visible light-irradiation. Iron(III) sulfate not only accelerates the photoreaction but also increases the yield of alkylation. Gamma-irradiation also brings about the alkylation. In the photo- and radiation-induced alkylation with alkanoic acid, alkyl radicals play important roles. (author)

  5. Aerobic oxidation of alcohols in visible light on Pd-grafted Ti ...

    Science.gov (United States)

    The titanium cluster with the reduced band gap has been synthesized having the palladium nanoparticles over the surface, which not only binds to the atmospheric oxygen but also catalyzes the oxidation of alcohols under visible light. Prepared as an invited article for submission to the Elsevier journal, Tetrahedron.

  6. Zinc oxide nanostructures and its nano-compounds for efficient visible light photo-catalytic processes

    Science.gov (United States)

    Adam, Rania E.; Alnoor, Hatim; Elhag, Sami; Nur, Omer; Willander, Magnus

    2017-02-01

    Zinc oxide (ZnO) in its nanostructure form is a promising material for visible light emission/absorption and utilization in different energy efficient photocatalytic processes. We will first present our recent results on the effect of varying the molar ratio of the synthesis nutrients on visible light emission. Further we will use the optimized conditions from the molar ration experiments to vary the synthesis processing parameters like stirring time etc. and the effect of all these parameters in order to optimize the efficiency and control the emission spectrum are investigated using different complementary techniques. Cathodoluminescence (CL) is combined with photoluminescence (PL) and electroluminescence (EL) as the techniques to investigate and optimizes visible light emission from ZnO/GaN light emitting diodes. We will then show and discuss our recent finding of the use of high quality ZnO nanoparticles (NPs) for efficient photo-degradation of toxic dyes using the visible spectra, namely with a wavelength up to 800 nm. In the end, we show how ZnO nanorods (NRs) are used as the first template to be transferred to bismuth zinc vanadate (BiZn2VO6). The BiZn2VO6 is then used to demonstrate efficient and cost effective hydrogen production through photoelectrochemical water splitting using solar radiation.

  7. General approach to high power, coherent visible and ultraviolet light sources

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer

    by cascaded second harmonic and sum frequency generation using periodically poled KTP and BBO for the SHG and SFG process, respectively. The 355nm light is used to promote different photo induced reactions. The main limitation of reaching any desired wavelength in the visible spectrum using sum frequency...

  8. Effects of ultraviolet radiation, visible light, and infrared radiation on erythema and pigmentation: a review.

    Science.gov (United States)

    Sklar, Lindsay R; Almutawa, Fahad; Lim, Henry W; Hamzavi, Iltefat

    2013-01-01

    The effects of ultraviolet radiation, visible light, and infrared radiation on cutaneous erythema, immediate pigment darkening, persistent pigment darkening, and delayed tanning are affected by a variety of factors. Some of these factors include the depth of cutaneous penetration of the specific wavelength, the individual skin type, and the absorption spectra of the different chromophores in the skin. UVB is an effective spectrum to induce erythema, which is followed by delayed tanning. UVA induces immediate pigment darkening, persistent pigment darkening, and delayed tanning. At high doses, UVA (primarily UVA2) can also induce erythema in individuals with skin types I-II. Visible light has been shown to induce erythema and a tanning response in dark skin, but not in fair skinned individuals. Infrared radiation produces erythema, which is probably a thermal effect. In this article we reviewed the available literature on the effects of ultraviolet radiation, visible light, and infrared radiation on the skin in regards to erythema and pigmentation. Much remains to be learned on the cutaneous effects of visible light and infrared radiation.

  9. TiO2-anatase modified by carbon as the photo catalyst under visible light

    International Nuclear Information System (INIS)

    Morawski, A.W.; Janus, M.; Tryba, B.; Kalucki, K.; Tryba, B.; Inagaki, M.

    2006-01-01

    The photo-catalytic oxidation of phenol in water under a visible light over anatase-type titanium dioxide (Tytanpol A11, Poland), modified by carbon deposited via n-hexane carbonization, was investigated. The catalysts, which had small (0-0.2 mass%) and high (0.69-0.85 mass%) contents of carbon showed a little lower catalytic photo-activity than pristine TiO 2 . However, the catalyst with high content of carbon (0.85 mass%) gave almost 14-times lower turbidity in the phenol solution after the photo-catalyst sedimentation. These two factors depend on the carbon content and have an influence on the 'practical efficiency' of the catalysts. The 'practical efficiency' of the catalyst under visible light, calculated from these two factors, was therefore 14-times higher for the catalyst containing 0.85 mass% carbon (whereas for UV radiation, it was found to be lower - 0.2 mass% -; this is the result of a previous work). The surface modification of the catalyst with 0.85% carbon seemed to be stable under visible light. The deposition of carbon on TiO 2 by carbonization of n-hexane was supposed to lead to obtain the catalyst, which could be easily used in a water-treatment system under visible light. (authors)

  10. Can visible light impact litter decomposition under pollution of ZnO nanoparticles?

    Science.gov (United States)

    Du, Jingjing; Zhang, Yuyan; Liu, Lina; Qv, Mingxiang; Lv, Yanna; Yin, Yifei; Zhou, Yinfei; Cui, Minghui; Zhu, Yanfeng; Zhang, Hongzhong

    2017-11-01

    ZnO nanoparticles is one of the most used materials in a wide range including antibacterial coating, electronic device, and personal care products. With the development of nanotechnology, ecotoxicology of ZnO nanoparticles has been received increasing attention. To assess the phototoxicity of ZnO nanoparticles in aquatic ecosystem, microcosm experiments were conducted on Populus nigra L. leaf litter decomposition under combined effect of ZnO nanoparticles and visible light radiation. Litter decomposition rate, pH value, extracellular enzyme activity, as well as the relative contributions of fungal community to litter decomposition were studied. Results showed that long-term exposure to ZnO nanoparticles and visible light led to a significant decrease in litter decomposition rate (0.26 m -1 vs 0.45 m -1 ), and visible light would increase the inhibitory effect (0.24 m -1 ), which caused significant decrease in pH value of litter cultures, fungal sporulation rate, as well as most extracellular enzyme activities. The phototoxicity of ZnO nanoparticles also showed impacts on fungal community composition, especially on the genus of Varicosporium, whose abundance was significantly and positively related to decomposition rate. In conclusion, our study provides the evidence for negatively effects of ZnO NPs photocatalysis on ecological process of litter decomposition and highlights the contribution of visible light radiation to nanoparticles toxicity in freshwater ecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Controlled Defects of Zinc Oxide Nanorods for Efficient Visible Light Photocatalytic Degradation of Phenol

    Directory of Open Access Journals (Sweden)

    Jamal Al-Sabahi

    2016-03-01

    Full Text Available Environmental pollution from human and industrial activities has received much attention as it adversely affects human health and bio-diversity. In this work we report efficient visible light photocatalytic degradation of phenol using supported zinc oxide (ZnO nanorods and explore the role of surface defects in ZnO on the visible light photocatalytic activity. ZnO nanorods were synthesized on glass substrates using a microwave-assisted hydrothermal process, while the surface defect states were controlled by annealing the nanorods at various temperatures and were characterized by photoluminescence and X-ray photoelectron spectroscopy. High performance liquid chromatography (HPLC was used for the evaluation of phenol photocatalytic degradation. ZnO nanorods with high surface defects exhibited maximum visible light photocatalytic activity, showing 50% degradation of 10 ppm phenol aqueous solution within 2.5 h, with a degradation rate almost four times higher than that of nanorods with lower surface defects. The mineralization process of phenol during degradation was also investigated, and it showed the evolution of different photocatalytic byproducts, such as benzoquinone, catechol, resorcinol and carboxylic acids, at different stages. The results from this study suggest that the presence of surface defects in ZnO nanorods is crucial for its efficient visible light photocatalytic activity, which is otherwise only active in the ultraviolet region.

  12. Effect of buck driver ripple on BER performance in visible light communication using LED

    NARCIS (Netherlands)

    Deng, X.; Linnartz, J.P.M.G.; Arulandu, K.; Zhou, G.; Wu, Y.

    2015-01-01

    This paper analyses the communication performance for visible light communication (VLC) with Manchester encoded amplitude modulation. In particular, it considers the ripple generated by the LED driver as an important noise contribution for VLC. The ripple depends on the oscillation frequency of the

  13. Broadband plasmonic perfect light absorber in the visible spectrum for solar cell applications

    Science.gov (United States)

    Mudachathi, Renilkumar; Tanaka, Takuo

    2018-03-01

    The coupling of electromagnetic waves with subwavelength metal structures results in the perfect light absorption and has been extensively explored in the recent years for many possible applications like photovoltaics, sensing, photodetectors, emitters and camouflaging systems to name a few. Herein we present the design and fabrication of a broadband plasmonic light absorber using aluminum as functional material for operation in the visible frequency range. The metal structures can be tuned in size to manipulate the plasmonic resonance; thereby light absorption at any desired wavelengths could be realized. Thus the broadband light absorber in the visible spectrum is designed using metal structures of different sizes supporting non-overlapping individual resonances at regular intervals of wavelengths. The metal structures of different sizes are grouped in to a single unit cell and the absorber is fabricated by periodically arranging these unit cells in a square lattice. Light absorption of more than 90% for over a broad wavelength range of 200 nm from 425 nm to 650 nm in the visible spectrum is demonstrated.

  14. Performance evaluation of X-ray CT using visible scintillation light

    International Nuclear Information System (INIS)

    Kodama, Kiyoyuki; Hamada, Minoru; Suzuki, Tamotsu; Hashimoto, Masatoshi; Hanada, Takashi; Ide, Tatsuya; Maruyama, Koichi

    2004-01-01

    We proposed a new method of performance evaluation for X-ray CT using visible scintillation light and examined its usefulness in this study. When we scanned a plastic scintillator disk in a gantry opening of the X-ray CT, we could observe visible scintillation light. The rotation of the light-emitting area of the disk corresponded to that of the X-ray tube. We were able to record the scintillation light by digital video camera. By analyzing the area of visible scintillation light, the rotation speed of the X-ray tube, angular spread of the X-ray beam, uniformity of the incident X-rays, and change in X-ray energy were measured. No other method is available to obtain the above parameters of X-ray CT during a single CT scan. In the measurements of the uniformity of incident X-rays and change of X-ray energy, our method showed good accuracy in detecting the attenuation caused by the couch between the X-ray tube and the plastic scintillator disc. The proposed method is inexpensive and easy-to-use. We conclude that the method is a useful tool for performance evaluation as well as a maintenance tool for X-ray CT. (author)

  15. Interactions of monochromatic visible light and near-IR radiation with cells: currently discussed mechanisms

    Science.gov (United States)

    Karu, Tiina I.

    1995-05-01

    Biological responses of cells to visible and near IR (laser) radiation occur due to physical and/or chemical changes in photoacceptor molecules, components of respiratory chains (cyt a/a3 in mitochondria, and cyt d in E. coli). As a result of the photoexcitation of electronic states, the following physical and/or chemical changes can occur: alteration of redox properties and acceleration of electron transfer, changes in biochemical activity due to local transient heating of chromophores, one-electron auto-oxidation and O2- production, and photodynamic action and 1O2 production. Different reaction channels can be activated to achieve the photobiological macroeffect. The primary physical and/or chemical changes induced by light in photoacceptor molecules are followed by a cascade of biochemical reactions in the cell that do not need further light activation and occur in the dark (photosignal transduction and amplification chains). These reactions are connected with changes in cellular homeostasis parameters. The crucial step here is thought to be an alteration of the cellular redox state: a shift towards oxidation is associated with stimulation of cellular vitality, and a shift towards reduction is linked to inhibition. Cells with a lower than normal pH, where the redox state is shifted in the reduced direction, are considered to be more sensitive to the stimulative action of light than those with the respective parameters being optimal or near optimal. This circumstance explains the possible variations in observed magnitudes of low-power laser effects. Light action on the redox state of a cell via the respiratory chain also explains the diversity of low-power laser effects. Beside explaining many controversies in the field of low-power laser effects (i.e., the diversity of effects, the variable magnitude or absence of effects in certain studies), the proposed redox-regulation mechanism may be a fundamental explanation of some clinical effects of irradiation, for

  16. Convolutional Neural Network-Based Shadow Detection in Images Using Visible Light Camera Sensor

    Directory of Open Access Journals (Sweden)

    Dong Seop Kim

    2018-03-01

    Full Text Available Recent developments in intelligence surveillance camera systems have enabled more research on the detection, tracking, and recognition of humans. Such systems typically use visible light cameras and images, in which shadows make it difficult to detect and recognize the exact human area. Near-infrared (NIR light cameras and thermal cameras are used to mitigate this problem. However, such instruments require a separate NIR illuminator, or are prohibitively expensive. Existing research on shadow detection in images captured by visible light cameras have utilized object and shadow color features for detection. Unfortunately, various environmental factors such as illumination change and brightness of background cause detection to be a difficult task. To overcome this problem, we propose a convolutional neural network-based shadow detection method. Experimental results with a database built from various outdoor surveillance camera environments, and from the context-aware vision using image-based active recognition (CAVIAR open database, show that our method outperforms previous works.

  17. An adaptive scaling and biasing scheme for OFDM-based visible light communication systems.

    Science.gov (United States)

    Wang, Zhaocheng; Wang, Qi; Chen, Sheng; Hanzo, Lajos

    2014-05-19

    Orthogonal frequency-division multiplexing (OFDM) has been widely used in visible light communication systems to achieve high-rate data transmission. Due to the nonlinear transfer characteristics of light emitting diodes (LEDs) and owing the high peak-to-average-power ratio of OFDM signals, the transmitted signal has to be scaled and biased before modulating the LEDs. In this contribution, an adaptive scaling and biasing scheme is proposed for OFDM-based visible light communication systems, which fully exploits the dynamic range of the LEDs and improves the achievable system performance. Specifically, the proposed scheme calculates near-optimal scaling and biasing factors for each specific OFDM symbol according to the distribution of the signals, which strikes an attractive trade-off between the effective signal power and the clipping-distortion power. Our simulation results demonstrate that the proposed scheme significantly improves the performance without changing the LED's emitted power, while maintaining the same receiver structure.

  18. Bottom-up production of meta-atoms for optical magnetism in visible and NIR light

    Science.gov (United States)

    Barois, Philippe; Ponsinet, Virginie; Baron, Alexandre; Richetti, Philippe

    2018-02-01

    Many unusual optical properties of metamaterials arise from the magnetic response of engineered structures of sub-wavelength size (meta-atoms) exposed to light. The top-down approach whereby engineered nanostructure of well-defined morphology are engraved on a surface proved to be successful for the generation of strong optical magnetism. It faces however the limitations of high cost and small active area in visible light where nanometre resolution is needed. The bottom-up approach whereby the fabrication metamaterials of large volume or large area results from the combination of nanochemitry and self-assembly techniques may constitute a cost-effective alternative. This approach nevertheless requires the large-scale production of functional building-blocks (meta-atoms) bearing a strong magnetic optical response. We propose in this paper a few tracks that lead to the large scale synthesis of magnetic metamaterials operating in visible or near IR light.

  19. Synthesis of supported silver nano-spheres on zinc oxide nanorods for visible light photocatalytic applications

    Energy Technology Data Exchange (ETDEWEB)

    Saoud, Khaled [Virginia Commonwealth University-Qatar, Doha (Qatar); Alsoubaihi, Rola [Virginia Commonwealth University, Richmond, VA (United States); Bensalah, Nasr [Qatar University, Doha (Qatar); Bora, Tanujjal [Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, P.O. Box 33, Al-Khoudh-123 (Oman); Bertino, Massimo [Virginia Commonwealth University, Richmond, VA (United States); Dutta, Joydeep, E-mail: dutta@squ.edu.om [Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, P.O. Box 33, Al-Khoudh-123 (Oman)

    2015-03-15

    Highlights: • Synthesis of supported Ag NPs on ZnO nanorods using open vessel microwave reactor. • Use of the Ag/ZnO NPs as an efficient visible light photocatalyst. • Complete degradation of methylene blue in 1 h with 0.5 g/L Ag/ZnO NPs. - Abstract: We report the synthesis of silver (Ag) nano-spheres (NS) supported on zinc oxide (ZnO) nanorods through two step mechanism, using open vessel microwave reactor. Direct reduction of ZnO from zinc nitrates was followed by deposition precipitation of the silver on the ZnO nanorods. The supported Ag/ZnO nanoparticles were then characterized by electron microscopy, X-ray diffraction, FTIR, photoluminescence and UV–vis spectroscopy. The visible light photocatalytic activity of Ag/ZnO system was investigated using a test contaminant, methylene blue (MB). Almost complete removal of MB in about 60 min for doses higher than 0.5 g/L of the Ag/ZnO photocatalyst was achieved. This significant improvement in the photocatalytic efficiency of Ag/ZnO photocatalyst under visible light irradiation can be attributed to the presence of Ag nanoparticles on the ZnO nanoparticles which greatly enhances absorption in the visible range of solar spectrum enabled by surface plasmon resonance effect from Ag nanoparticles.

  20. Visible light induced changes in the immune response through an eye-brain mechanism (photoneuroimmunology).

    Science.gov (United States)

    Roberts, J E

    1995-07-01

    The immune system is susceptible to a variety of stresses. Recent work in neuroimmunology has begun to define how mood alteration, stress, the seasons, and daily rhythms can have a profound effect on immune response through hormonal modifications. Central to these factors may be light through an eye-brain hormonal modulation. In adult primates, only visible light (400-700 nm) is received by the retina. This photic energy is then transduced and delivered to the visual cortex and by an alternative pathway to the suprachiasmatic nucleus (SCN). The SCN is a part of the hypothalamic region in the brain believed to direct circadian rhythm. Visible light exposure also modulates the pituitary and pineal gland which leads to neuroendocrine changes. Melatonin, norepinephrine and acetylcholine decrease with light activation, while cortisol, serotonin, gaba and dopamine levels increase. The synthesis of vasoactive intestinal polypeptide (VIP), gastrin releasing peptide (GRP) and neuropeptide Y (NPY) in rat SCN has been shown to be modified by light. These induced neuroendocrine changes can lead to alterations in mood and circadian rhythm. All of these neuroendocrine changes can lead to immune modulation. An alternative pathway for immune modulation by light is through the skin. Visible light (400-700 nm) can penetrate epidermal and dermal layers of the skin and may directly interact with circulating lymphocytes to modulate immune function. However, even in the presence of phototoxic agents such as eosin and rose bengal, visible light did not produce suppression of contact hypersensitivity with suppresser cells. In contrast to visible light, in vivo exposure to UV-B (280-320 nm) and UV-A (320-400 nm) radiation can only alter normal human immune function by a skin mediated response. Each UV subgroup (B, A) induces an immunosuppressive response but by differing mechanisms involving the regulation of differing interleukins and growth factors. Some effects observed in humans are

  1. Comparing light sensitivity, linearity and step response of electronic cameras for ophthalmology.

    Science.gov (United States)

    Kopp, O; Markert, S; Tornow, R P

    2002-01-01

    To develop and test a procedure to measure and compare light sensitivity, linearity and step response of electronic cameras. The pixel value (PV) of digitized images as a function of light intensity (I) was measured. The sensitivity was calculated from the slope of the P(I) function, the linearity was estimated from the correlation coefficient of this function. To measure the step response, a short sequence of images was acquired. During acquisition, a light source was switched on and off using a fast shutter. The resulting PV was calculated for each video field of the sequence. A CCD camera optimized for the near-infrared (IR) spectrum showed the highest sensitivity for both, visible and IR light. There are little differences in linearity. The step response depends on the procedure of integration and read out.

  2. Biological effects of blocking blue and other visible light on the mouse retina.

    Science.gov (United States)

    Narimatsu, Toshio; Ozawa, Yoko; Miyake, Seiji; Kubota, Shunsuke; Yuki, Kenya; Nagai, Norihiro; Tsubota, Kazuo

    2014-08-01

    To elucidate the biological effects of blocking fluorescent light on the retina using specific blocking materials. Seven- to 8-week-old BALB/c mice were divided into three groups and placed in one of the three boxes: one blocked ultraviolet and violet wavelengths of light (violet blockade), one blocked ultraviolet, violet, blue and some other visible wavelengths (blue-plus blockade), and one allowed most visible light to pass through (control). They were then exposed to a white fluorescent lamp for 1 h at 5.65E-05 mW/cm(2) /s. After treatment, the electroretinogram, retinal outer nuclear layer thickness and retinal outer segment length were measured. In addition, retinal apoptotic cells were quantified by TdT-mediated dUTP nick-end labelling assay and c-Fos messenger RNA, and protein levels were measured by real-time reverse-transcription polymerase chain reaction and immunoblot analyses, respectively. The blue-plus blockade group retained a significantly better electroretinogram response following light exposure than the control or violet blockade groups. The blue-plus blockade group also exhibited greater outer nuclear layer thickness and greater outer-segment length, and fewer apoptotic cells after light exposure than the other groups. The c-Fos messenger RNA and protein levels were substantially reduced in the blue-plus blockade group and reduced to a lesser extent in the violet blockade group. The blockade of blue plus additional visible wavelengths of light was most effective in protecting the retina from light-induced damage. The blockade of violet light alone was also effective in reducing intracellular molecular responses, but these effects were not sufficient for attenuating retinal degeneration. © 2013 Royal Australian and New Zealand College of Ophthalmologists.

  3. Visible-light photocatalytic performances of TiO2 nanoparticles modified by trace derivatives of PVA

    Directory of Open Access Journals (Sweden)

    Le SHI

    2016-10-01

    Full Text Available In order to study the visible-light photocatalytic activity and catalysis stability of nanocomposites, a TiO2-based visible-light photocatalyst is prepared by surface-modification of TiO2 nanoparticles using trace conjugated derivatives from polyvinyl alcohol (DPVA via a facile method. The obtained DPVA/TiO2 nanocomposites are characterized by X-ray diffraction (XRD, Fourier transform infrared Spectra (FT-IR, scanning electron microscopy (SEM, UV-vis diffuse reflection spectroscopy (DRS, and X-ray photoelectron spectroscopy (XPS. With Rhodamine B (RhB as a model pollutant, the visible-light photocatalytic activity and stability of DPVA/TiO2 nanocomposites are investigated by evaluating the RhB decomposition under visible light irradiation. The results reveal that the trace conjugated polymers on the TiO2 surface doesn’t change the crystalline and crystal size of TiO2 nanoparticles, but significantly enhances their visible-light absorbance and visible-light photocatalytic activity. The nanocomposite with the PVA and TiO2 mass ratio of 1∶200 exhibits the highest visible-light photocatalytic activity. The investigated nanocomposites exhibit well visible-light photoctatalytic stability. The photogenerated holes are thought as the main active species for the RhB photodegradation in the presence of the DPVA/TiO2 nanocomposites.

  4. Photocatalytic degradation of 2-propanol and phenol using Au loaded MnWO4 nanorod under visible light irradiation

    CSIR Research Space (South Africa)

    Chakraborty, AK

    2012-06-01

    Full Text Available ) under visible light ( = 420 nm) irradiation. The Au loading was optimized to 3.79 wt% for the highest efficiency. The enhanced photocatalytic activity originates from the absorption of visible light by MnWO4 as well as the introduction...

  5. DFT study of benzyl alcohol/TiO2 interfacial surface complex: reaction pathway and mechanism of visible light absorption.

    Science.gov (United States)

    Zhao, Lei; Gu, Feng Long; Kim, Minjae; Miao, Maosheng; Zhang, Rui-Qin

    2017-09-24

    We propose a new pathway for the adsorption of benzyl alcohol on the surface of TiO 2 and the formation of interfacial surface complex (ISC). The reaction free energies and reaction kinetics were thoroughly investigated by density functional calculations. The TiO 2 surfaces were modeled by clusters consisting of 4 Ti atoms and 18 O atoms passivated by H, OH group and H 2 O molecules. Compared with solid-state calculations utilizing the periodicity of the materials, such cluster modeling allows inclusion of the high-order correlation effects that seem to be essential for the adsorption of organic molecules onto solid surfaces. The effects of both acidity and solvation are included in our calculations, which demonstrate that the new pathway is competitive with a previous pathway. The electronic structure calculations based on the relaxed ISC structures reveal that the chemisorption of benzyl alcohol on the TiO 2 surface greatly alters the nature of the frontier molecular orbitals. The resulted reduced energy gap in ISC matches the energy of visible light, showing how the adsorption of benzyl alcohol sensitizes the TiO 2 surface. Graphical Abstract The chemisorption of benzyl alcohol on TiO 2 surface greatly alters the nature of the frontier molecular orbitals and the formed interfacial surface complex can be sensitized by visible light.

  6. Analysis of optical transmission by 400-500 nm visible light into aesthetic dental biomaterials.

    Science.gov (United States)

    Watts, D C; Cash, A J

    1994-04-01

    The penetration of visible light into dental biomaterials is an essential factor in photoinitiation of setting reactions and in the optical aspects of dental aesthetics. Light of visible blue wavelengths, 400-500 nm, has been applied at normal angles to 0.2-5.0 mm sections of human dentine and representative ceramic, polymerceramic composites and hybrid glass-polyalkenoate materials. The integrated optical transmission has been determined for each material section. The data have been converted to absorbance values and analysed to check for mathematical conformity to the Beer-Lambert Law. It is found that conformity (typically, P ratio. This factor ranges from 30% to 90% in the materials investigated. It follows that there is a high degree of inefficiency in the transmission of visible light into and through aesthetic biomaterials for the purposes of photoactivation using existing technology. Means by which this limitation and inefficiency may be reduced are discussed. While the reflectivity of aesthetic biomaterials has been perceived by dental practitioners, the magnitude of this effect and its implications in connection with light-cured materials have not been analysed and emphasized hitherto.

  7. Deep Learning-Based Iris Segmentation for Iris Recognition in Visible Light Environment

    Directory of Open Access Journals (Sweden)

    Muhammad Arsalan

    2017-11-01

    Full Text Available Existing iris recognition systems are heavily dependent on specific conditions, such as the distance of image acquisition and the stop-and-stare environment, which require significant user cooperation. In environments where user cooperation is not guaranteed, prevailing segmentation schemes of the iris region are confronted with many problems, such as heavy occlusion of eyelashes, invalid off-axis rotations, motion blurs, and non-regular reflections in the eye area. In addition, iris recognition based on visible light environment has been investigated to avoid the use of additional near-infrared (NIR light camera and NIR illuminator, which increased the difficulty of segmenting the iris region accurately owing to the environmental noise of visible light. To address these issues; this study proposes a two-stage iris segmentation scheme based on convolutional neural network (CNN; which is capable of accurate iris segmentation in severely noisy environments of iris recognition by visible light camera sensor. In the experiment; the noisy iris challenge evaluation part-II (NICE-II training database (selected from the UBIRIS.v2 database and mobile iris challenge evaluation (MICHE dataset were used. Experimental results showed that our method outperformed the existing segmentation methods.

  8. Photodegradation of aniline by goethite doped with boron under ultraviolet and visible light irradiation

    International Nuclear Information System (INIS)

    Liu, Guanglong; Liao, Shuijiao; Zhu, Duanwei; Liu, Linghua; Cheng, Dongsheng; Zhou, Huaidong

    2011-01-01

    Highlights: → Goethite modified by boron was prepared by sol-gel method in presence of boron acid at the low temperature. → B-goethite has slight red shift in the band gap transition beside their stronger light absorption compared with pristine goethite. → The results showed that semiconductor photocatalytic reaction mechanism should exist in the process of aniline degradation with goethite and B-goethite as photocatalyst. -- Abstract: In the present study, goethite and goethite doped with boron (B-goethite) were employed to detect the presence or absence of semiconductor photocatalytic reaction mechanism in the reaction systems. B-goethite was prepared by sol-gel method in presence of boron acid in order to improve its photocatalystic efficiency under the ultraviolet and visible light irradiation. The optical properties of goethite and B-goethite were characterized by ultraviolet and visible absorption spectra and the result indicated that B-goethite has slight red shift in the band gap transition beside their stronger light absorption compared with pristine goethite. Degradation of aniline was investigated in presence of goethite and B-goethite in aqueous solution. It was found that the B-goethite photocatalyst exhibited enhanced ultraviolet and visible light photocatalytic activity in degradation of aniline compared with the pristine goethite. The photocatalytic degradation mechanism of B-goethite was discussed.

  9. Visible-light-driven dynamic cancer therapy and imaging using graphitic carbon nitride nanoparticles.

    Science.gov (United States)

    Heo, Nam Su; Lee, Sun Uk; Rethinasabapathy, Muruganantham; Lee, Eun Zoo; Cho, Hye-Jin; Oh, Seo Yeong; Choe, Sang Rak; Kim, Yeonho; Hong, Won G; Krishnan, Giribabu; Hong, Won Hi; Jeon, Tae-Joon; Jun, Young-Si; Kim, Hae Jin; Huh, Yun Suk

    2018-09-01

    Organic graphitic carbon nitride nanoparticles (NP-g-CN), less than 30 nm in size, were synthesized and evaluated for photodynamic therapy (PDT) and cell imaging applications. NP-g-CN particles were prepared through an intercalation process using a rod-like melamine-cyanuric acid adduct (MCA) as the molecular precursor and a eutectic mixture of LiCl-KCl (45:55 wt%) as the reaction medium for polycondensation. The nano-dimensional NP-g-CN penetrated the malignant tumor cells with minimal hindrance and effectively generated reactive oxygen species (ROS) under visible light irradiation, which could ablate cancer cells. When excited by visible light irradiation (λ > 420 nm), NP-g-CN introduced to HeLa and cos-7 cells generated a significant amount of ROS and killed the cancerous cells selectively. The cytotoxicity of NP-g-CN was manipulated by altering the light irradiation and the BP-g-CN caused more damage to the cancer cells than normal cells at low concentrations. As a potential non-toxic organic nanomaterial, the synthesized NP-g-CN are biocompatible with less cytotoxicity than toxic inorganic materials. The combined effects of the high efficacy of ROS generation under visible light irradiation, low toxicity, and bio-compatibility highlight the potential of NP-g-CN for PDT and imaging without further modification. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Influence of non-line of sight luminescent emitters in visible light communication systems

    Science.gov (United States)

    Ghorai, Anaranya; Walvekar, Pratik; Nayak, Shreyas; Narayan, K. S.

    2018-01-01

    We introduce and demonstrate concepts which utilize the non-line of sight fraction of light incident on a detector assembly in a visible-light communication (VLC) system. In addition to ambient light, realistic enclosures where VLC is implemented consist of a sizable fraction of scattered and reflected light. We present results of VLC systems with detectors responding to contributions from the light source scattered off a surface embedded with fluorescent and phosphorescent emitters besides the direct line of sight signal. Contribution from the emitters takes a form of discernible fluctuations in the detector signal. The implication of our results from noise analysis of these fluctuations indicates the possibility of utilizing smart coatings to further tailor VLC capabilities.

  11. Effects of polychromatic visible and infrared light on biological liquid media.

    Science.gov (United States)

    Zilov, V G; Khadartsev, A A; Bitsoev, V D

    2014-08-01

    Experimental study of the effects of polychromatic visible and infrared light on biological fluids was carried out in order to validate the new approaches to phototherapy. Polychromatic light generated by Bioptron device at different modes and frequencies was released through the fiberoptic cable, including the exposure paralleled by CO2 saturation of water and exposure from a device placed 10 cm above the water surface, which ensured maximum light absorption. The effects of irradiation were recorded in 26 and 15 min, while the increase of light absorption by blood plasma in vivo was recorded 1 h after a bath with water pre-exposed to polarized light. Absorption bands corresponding to those for immunomodulatory, anti-inflammatory, and antiviral drugs, were detected. Changes in the spectra of valency oscillations, depending on the oscillation anharmonism values, were detected.

  12. Rapid water disinfection using vertically aligned MoS_2 nanofilms and visible light

    International Nuclear Information System (INIS)

    Liu, Chong; Kong, Desheng; Hsu, Po-Chun; Yuan, Hongtao; Lee, Hyun-Wook

    2016-01-01

    Here, solar energy is readily available in most climates and can be used for water purification. However, solar disinfection of drinking water (SODIS) mostly relies on ultraviolet light, which represents only 4% of total solar energy, and this leads to slow treatment speed. The development of new materials that can harvest visible light for water disinfection, and speed up solar water purification, is therefore highly desirable. Here, we show that few-layered vertically aligned MoS_2 (FLV-MoS_2) films can be used to harvest the whole spectrum of visible light (~ 50% of solar energy) and achieve highly efficient water disinfection. The bandgap of MoS_2 was increased from 1.3 eV to 1.55 eV by decreasing the domain size, which allowed the FLV-MoS_2 to generate reactive oxygen species (ROS) for bacterial inactivation in water. The FLV-MoS_2 showed ~15 times better log inactivation efficiency of indicator bacteria compared to bulk MoS_2, and much faster inactivation of bacteria under both visible light and sunlight illumination compared to widely used TiO_2. Moreover, by using a 5 nm copper film on top of the FLV-MoS_2 as a catalyst to facilitate electron-hole pair separation and promote the generation of ROS, the disinfection rate was further increased 6 fold. With our approach, we achieved water disinfection of >99.999% inactivation of bacteria in 20 minutes with a small amount of material (1.6 mg/L) under simulated visible light.

  13. Rapid water disinfection using vertically aligned MoS2 nanofilms and visible light

    International Nuclear Information System (INIS)

    Liu, Chong; Kong, Desheng; Hsu, Po-Chun; Yuan, Hongtao; Lee, Hyun-Wook

    2016-01-01

    In most climates, solar energy is readily available and can be used for water purification. But, solar disinfection of drinking water mostly relies on ultraviolet light, which represents only 4% of the total solar energy, and this leads to a slow treatment speed. Therefore, the development of new materials that can harvest visible light for water disinfection, and so speed up solar water purification, is highly desirable. Here we show that few-layered vertically aligned MoS_2 (FLV-MoS_2) films can be used to harvest the whole spectrum of visible light (~50% of solar energy) and achieve highly efficient water disinfection. The bandgap of MoS_2 was increased from 1.3 to 1.55 eV by decreasing the domain size, which allowed the FLV-MoS_2 to generate reactive oxygen species (ROS) for bacterial inactivation in the water. The FLV-MoS_2 showed a ~15 times better log inactivation efficiency of the indicator bacteria compared with that of bulk MoS_2, and a much faster inactivation of bacteria under both visible light and sunlight illumination compared with the widely used TiO_2. Moreover, by using a 5 nm copper film on top of the FLV-MoS_2 as a catalyst to facilitate electron–hole pair separation and promote the generation of ROS, the disinfection rate was increased a further sixfold. Here, we achieved water disinfection of >99.999% inactivation of bacteria in 20 min with a small amount of material (1.6 mg l–1) under simulated visible light.

  14. Catalyst-free activation of peroxides under visible LED light irradiation through photoexcitation pathway

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Yaowen [Department of Environmental Engineering, Wuhan University, Wuhan, 430079 (China); Shenzhen Research Institute of Wuhan University, Shenzhen, 518057 (China); Li, Yixi; Yao, Linyu; Li, Simiao; Liu, Jin [Department of Environmental Engineering, Wuhan University, Wuhan, 430079 (China); Zhang, Hui, E-mail: eeng@whu.edu.cn [Department of Environmental Engineering, Wuhan University, Wuhan, 430079 (China); Shenzhen Research Institute of Wuhan University, Shenzhen, 518057 (China)

    2017-05-05

    Highlights: • Persulfate could decolorize Rhodamine B (RhB) directly via non-radical reactions. • LED lamps emitting white light were utilized as the visible light source. • Dyes could activate peroxides through photoexcitation pathway. • Decolorization of dyes and production of radicals were achieved simultaneously. • The catalyst-free peroxide/dye/Vis process was effective in a broad pH range. - Abstract: Catalysts are known to activate peroxides to generate active radicals (i.e., hydroxyl radical (·OH) and sulfate radical (SO{sub 4}·{sup −})) under certain conditions, but the activation of peroxides in the absence of catalysts under visible light irradiation has been rarely reported. This work demonstrates a catalyst-free activation of peroxides for the generation of ·OH and/or SO{sub 4}·{sup −} through photoexcited electron transfer from organic dyes to peroxides under visible LED light irradiation, where Rhodamine B (RhB) and Eosin Y (EY) were selected as model dyes. The formation of ·OH and/or SO{sub 4}·{sup −} in the reactions and the electron transfer from the excited dyes to peroxides were validated via electron paramagnetic resonance (EPR), photoluminescence (PL) spectra and cyclic voltammetry (CV). The performance of the peroxide/dye/Vis process was demonstrated to be altered depending on the target substrate. Meanwhile, the peroxide/dye/Vis process was effective for simultaneous decolorization of dyes and production of active radicals under neutral even or basic conditions. The findings of this study clarified a novel photoexcitation pathway for catalyst-free activation of peroxides under visible light irradiation, which could avoid the secondary metal ion (dissolved or leached) pollution from the metal-based catalysts and expand the application range of the peroxide-based catalytic process.

  15. Visible-light wavelength matched microsphere assembly of TiO{sub 2} superfine nanorods and the enhanced photovoltaic performance

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Xiyun; Wang, Yumin; Zhang, Xiang; Sun, Hongxia; Zhang, Qingsong; Niu, Laiyou; Liu, Juan; Zhou, Xingfu, E-mail: Zhouxf@njtech.edu.cn

    2015-05-15

    Graphical abstract: A novel visible-light wavelength matched microspheres assembly of TiO{sub 2} superfine nanorods with a diameter of ∼5 nm was fabricated via a hydrothermal method. The as-prepared rutile TiO{sub 2} microspheres have a uniform diameter of ∼450 nm and show a good light-trapping performance. Dye-sensitized solar cell based on this sample shows a satisfactory energy conversion efficiency of 6.59% and is the highest PCE reported for intrinsic rutile TiO{sub 2}. The further optimized DSSC shows a conversion efficiency of 8.3%, though the internal resistance is higher and the dye absorption is lower than that of widely used anatase TiO{sub 2} nanoparticles. - Highlights: • Microsphere assembly of TiO{sub 2} nanorods with a diameter of ∼5 nm was fabricated. • TiO{sub 2} microspheres size is well matched with the visible light wavelength. • TiO{sub 2} microsphere enhances the light-scattering ability. • Rutile TiO{sub 2} microsphere shows an energy conversion efficiency of 6.59%. • The highest PCE reported for intrinsic rutile TiO{sub 2} is obtained. - Abstract: According to the Mie scattering theory, spheres with the size matched with light wavelength are most suitable for light scattering and enhance the light trapping ability. In this paper, a novel visible-light wavelength matched sphere assembly of TiO{sub 2} superfine nanorods was fabricated via a simple one-step hydrothermal method. The morphology and the structure were examined by field emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The visible subwavelength TiO{sub 2} microsphere resembling an immature chinese chestnut is composed of countless superfine TiO{sub 2} nanorods, the diameter of these building blocks of superfine TiO{sub 2} nanorods is ∼5 nm. The obtained TiO{sub 2} sphere has an average diameter of ca. 450 nm, which matches well with the visible light wavelength and cause the

  16. A Difference in Cutaneous Pigmentary Response to LED Versus Halogen Incandescent Visible Light: A Case Report from a Single Center, Investigational Clinical Trial Determining a Minimal Pigmentary Visible Light Dose.

    Science.gov (United States)

    Soleymani, Teo; Soter, Nicholas A; Folan, Lorcan M; Elbuluk, Nada; Okereke, Uchenna R; Cohen, David E

    2017-04-01

    BACKGROUND: While most of the attention regarding skin pigmentation has focused on the effects on ultraviolet radiation, the cutaneous effects of visible light (400 to 700nm) are rarely reported. In this report, we describe a case of painful erythema and induration that resulted from direct irradiation of UV-naïve skin with visible LED light in a patient with Fitzpatrick type II skin. METHODS AND RESULTS: A 24-year-old healthy woman with Fitzpatrick type II skin presented to our department to participate in a clinical study. As part of the study, the subject underwent visible light irradiation with an LED and halogen incandescent visible light source. After 5 minutes of exposure, the patient complained of appreciable pain at the LED exposed site. Evaluation demonstrated erythema and mild induration. There were no subjective or objective findings at the halogen incandescent irradiated site, which received equivalent fluence (0.55 Watts / cm2). The study was halted as the subject was unable to tolerate the full duration of visible light irradiation. CONCLUSION: This case illustrates the importance of recognizing the effects of visible light on skin. While the vast majority of investigational research has focused on ultraviolet light, the effects of visible light have been largely overlooked and must be taken into consideration, in all Fitzpatrick skin types. J Drugs Dermatol. 2017;16(4):388-392..

  17. Structured light generation by magnetic metamaterial half-wave plates at visible wavelength

    Science.gov (United States)

    Zeng, Jinwei; Luk, Ting S.; Gao, Jie; Yang, Xiaodong

    2017-12-01

    Metamaterial or metasurface unit cells functioning as half-wave plates play an essential role for realizing ideal Pancharatnam-Berry phase optical elements capable of tailoring light phase and polarization as desired. Complex light beam manipulation through these metamaterials or metasurfaces unveils new dimensions of light-matter interactions for many advances in diffraction engineering, beam shaping, structuring light, and holography. However, the realization of metamaterial or metasurface half-wave plates in visible spectrum range is still challenging mainly due to its specific requirements of strong phase anisotropy with amplitude isotropy in subwavelength scale. Here, we propose magnetic metamaterial structures which can simultaneously exploit the electric field and magnetic field of light for achieving the nanoscale half-wave plates at visible wavelength. We design and demonstrate the magnetic metamaterial half-wave plates in linear grating patterns with high polarization conversion purity in a deep subwavelength thickness. Then, we characterize the equivalent magnetic metamaterial half-wave plates in cylindrical coordinate as concentric-ring grating patterns, which act like an azimuthal half-wave plate and accordingly exhibit spatially inhomogeneous polarization and phase manipulations including spin-to-orbital angular momentum conversion and vector beam generation. Our results show potentials for realizing on-chip beam converters, compact holograms, and many other metamaterial devices for structured light beam generation, polarization control, and wavefront manipulation.

  18. Increasing of visibility on the pedestrian crossing by the additional lighting systems

    Science.gov (United States)

    Baleja, Richard; Bos, Petr; Novak, Tomas; Sokansky, Karel; Hanusek, Tomas

    2017-09-01

    Pedestrian crossings are critical places for road accidents between pedestrians and motor vehicles. For this reason, it is very important to increase attention when the pedestrian crossings are designed and it is necessary to take into account all factors that may contribute to higher safety. Additional lighting systems for pedestrian crossings are one of them and the lighting systems must fulfil the requirements for higher visibility from the point of view of car drivers from both directions. This paper describes the criteria for the suitable additional lighting system on pedestrian crossings. Generally, it means vertical illuminance on the pedestrian crossing from the driver’s view, horizontal illuminance on the crossing and horizontal illuminance both in front of and behind the crossing placed on the road and their acceptable ratios. The article also describes the choice of the colours of the light (correlated colour temperature) and its influence on visibility. As a part of the article, there are case designs of additional lighting systems for pedestrian crossings and measurements from realized additional lighting systems by luxmeters and luminance cameras and their evaluation.

  19. Comparative Evaluation of Ultraviolet and Visible Light Transmittance through Prescriptive Ophthalmic Minus Lenses

    Directory of Open Access Journals (Sweden)

    Mohammadreza Nazari

    2014-06-01

    Full Text Available Background: Wearing spectacles is the most common approach in correcting the refractive errors worldwide. Due to harmful effects of overexposure to solar ultraviolet radiations, the usage of multi-layer coatings in ophthalmic lenses has recently been increased. These lenses can reduce the reflections and hence increase the transmission of visible light; they can also decrease the transmission of ultraviolet rays. This study aims to compare the transmission of ultraviolet (A and B and visible rays through coated and uncoated prescriptive ophthalmic plastic lenses.Materials and Methods: In this study, 39 minus non-photochromic multi-coated white plastic single-vision lenses; 9 similar lenses but without any coatings were assessed by spectral transmittancemeter for evaluation of the transmission of visible and ultraviolet rays.Results: The transmission of visible light was 97.9%±1.07% for coated lenses and 93.5%±0.54% for lenses without coating. Ultraviolet-A transmission was 12.15%±8.02% for coated lenses compared to 66.27%±23.92% in lenses without coating. The transmission of ultraviolet-B rays was 1.21%±0.4% and 23.0%±15.97% for lenses with and without coatings, respectively.Conclusion: The transmission of visible light was significantly higher in multi-coated lenses compared to uncoated samples; whereas the transmissions of ultraviolet rays in multi-coated lenses were significantly lower than uncoated ones. Therefore, it is recommended that, except for particular cases, prescribed lenses be equipped with this multi-layer coating.

  20. Dictating photoreactivity through restricted bond rotations: cross-photoaddition of atropisomeric acrylimide derivatives under UV/visible-light irradiation.

    Science.gov (United States)

    Iyer, Akila; Jockusch, Steffen; Sivaguru, J

    2014-11-13

    Nonbiaryl atropisomeric acrylimides underwent facile [2 + 2] photocycloaddition leading to cross-cyclobutane adducts with very high stereospecificity (enantiomeric excess (ee): 99% and diastereomeric excess (de): 99%). The photoreactions proceeded smoothly in isotropic media for both direct and triplet sensitized irradiations. The reactions were also found to be very efficient in the solid state where the same cross-cyclobutane adduct was observed. Photophysical studies enabled us to understand the excited-state photochemistry of acrylimides. The triplet energy was found to be ∼63 kcal/mol. The reactions proceeded predominantly via a singlet excited state upon direct irradiation with very poor intersystem crossing that was ascertained by quantification of the generated singlet oxygen. The reactions progressed smoothly with triplet sensitization with UV or visible-light irradiations. Laser flash photolysis experiments established the triplet transient of atropisomeric acrylimides with a triplet lifetime at room temperature of ∼40 ns.

  1. Mesoporous cerium oxide nanospheres for the visible-light driven photocatalytic degradation of dyes

    Directory of Open Access Journals (Sweden)

    Subas K. Muduli

    2014-04-01

    Full Text Available A facile, solvothermal synthesis of mesoporous cerium oxide nanospheres is reported for the purpose of the photocatalytic degradation of organic dyes and future applications in sustainable energy research. The earth-abundant, relatively affordable, mixed valence cerium oxide sample, which consists of predominantly Ce7O12, has been characterized by powder X-ray diffraction, X-ray photoelectron and UV–vis spectroscopy, and transmission electron microscopy. Together with N2 sorption experiments, the data confirms that the new cerium oxide material is mesoporous and absorbs visible light. The photocatalytic degradation of rhodamin B is investigated with a series of radical scavengers, suggesting that the mechanism of photocatalytic activity under visible-light irradiation involves predominantly hydroxyl radicals as the active species.

  2. Enhanced photoactivity of CuPp-TiO{sub 2} photocatalysts under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Xiangfei, Lue [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xian, Shaanxi 710069 (China); Li Jun, E-mail: junli@nwu.edu.cn [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xian, Shaanxi 710069 (China); Chen, Wang; Mingyue, Duan; Yun, Luo; Guiping, Yao [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xian, Shaanxi 710069 (China); Junlong, Wang [Wei Nan Teachers University, Wei Nan, Shaanxi, 714000 (China)

    2010-11-15

    Three novel porphyrins, 5,10,15-tri-phenyl-20-[4-(3-phenoxy)-propoxy]phenyl porphyrin, 5,15-di-phenyl-10,20-di-[4-(3-phenoxy)-propoxy]phenyl porphyrin and 5-phenyl-10,15,20-tri- [4-(3-phenoxy)-propoxy]phenyl porphyrin, and their corresponding copper(II) complexes were synthesized and characterized spectroscopically. The photocatalytic effects of TiO{sub 2} samples impregnated with copper(II) porphyrins was investigated by photodegradation of 4-nitrophenol (4-NP) in aqueous solution under visible light. The photocatalysts were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis spectra and FT-IR spectra. The results indicated that CuPps were successfully loaded and interacted with the surface of TiO{sub 2} microsphere, which is crucial to enhance the activity of the catalytic composite under visible light.

  3. Trifluoroethylation of Alkynes: Synthesis of Allylic-CF3 Compounds by Visible-Light Photocatalysis

    Institute of Scientific and Technical Information of China (English)

    Geum-bee Roh; Naeem Iqbal; Eun Jin Cho

    2016-01-01

    Two types of allylic trifluoromethylated compounds were synthesized by reacting alkynes with CF3CH2I using visible-light photocatalysis.Subtle differences in the catalytic system controlled the selectivity of iodotrifluoroethylation and hydrotrifluoroethylation.The iodotrifluoroethylated products were obtained in the presence of [Ru(bpy)3]C12 and TMEDA in CH3CN under visible-light irradiation,whereas hydrotrifluoroethylated products were synthesized usingfac-[Ir(ppy)3] and a mixture of DBU and K2CO3 in DMF.The iodotrifluoroethylation reaction worked particularly well,even at gram-scale,and the synthetic utility of iodotrifluoroethylated products was proved by their coupling reactions,providing complex CF3-containing products.

  4. Method for measuring retardation of infrared wave-plate by modulated-polarized visible light

    Science.gov (United States)

    Zhang, Ying; Song, Feijun

    2012-11-01

    A new method for precisely measuring the optical phase retardation of wave-plates in the infrared spectral region is presented by using modulated-polarized visible light. An electro-optic modulator is used to accurately determine the zero point by the frequency-doubled signal of the Modulated-polarized light. A Babinet-Soleil compensator is employed to make the phase delay compensation. Based on this method, an instrument is set up to measure the retardations of the infrared wave-plates with visible region laser. Measurement results with high accuracy and sound repetition are obtained by simple calculation. Its measurement precision is less than and repetitive precision is within 0.3%.

  5. Decoding mobile-phone image sensor rolling shutter effect for visible light communications

    Science.gov (United States)

    Liu, Yang

    2016-01-01

    Optical wireless communication (OWC) using visible lights, also known as visible light communication (VLC), has attracted significant attention recently. As the traditional OWC and VLC receivers (Rxs) are based on PIN photo-diode or avalanche photo-diode, deploying the complementary metal-oxide-semiconductor (CMOS) image sensor as the VLC Rx is attractive since nowadays nearly every person has a smart phone with embedded CMOS image sensor. However, deploying the CMOS image sensor as the VLC Rx is challenging. In this work, we propose and demonstrate two simple contrast ratio (CR) enhancement schemes to improve the contrast of the rolling shutter pattern. Then we describe their processing algorithms one by one. The experimental results show that both the proposed CR enhancement schemes can significantly mitigate the high-intensity fluctuations of the rolling shutter pattern and improve the bit-error-rate performance.

  6. Oxygen-independent direct deoxyribonucleic acid backbone breakage caused by rose bengal and visible light

    Energy Technology Data Exchange (ETDEWEB)

    Peak, M J; Peak, J G; Foote, C S; Krinsky, N I

    1984-01-01

    An oxygen enhancement ratio of 10 for the induction of backbone single-strand breaks (SSBs) in purified deoxyribonucleic acid (DNA) by monochromatic 365 nm UV radiation was obtained. Similarly, a dose reduction factor of 10 was observed when the DNA was irradiated in the presence of 0.1 M diazabicyclo(2.2.2)octane (DABCO). To determine whether this breakage of DNA was due to the action of a reactive oxygen species such as singlet oxygen, we used the photosensitizing dye Rose Bengal and visible light as a system for generating singlet oxygen. Treatment of the DNA with Rose Bengal and 545 nm monochromatic light enhanced the rate of induction of SSBs six times, compared with the rate we obtained when the light was used alone. Elimination of oxygen or addition of 0.1 M DABCO during the 545 nm irradiation in the presence of Rose Bengal did not alter the enhancement of SSBs in the DNA caused by Rose Bengal and 545 nm radiation. The induction of SSBs in the DNA caused by irradiation of the DNA by 545 nm light in the presence of Rose Bengal was not enhanced by the use of D/sub 2/O instead of H/sub 2/O as a solvent. The results indicate that Rose Bengal plus visible light can cause biological damage without the intermediacy of reactive oxygen species, i.e. Rose Bengal and visible light can react directly with biological material, in reactions that appear to be type I photosensitized processes, independent of singlet oxygen as an intermediate.

  7. Visible-light-promoted redox neutral C-H amidation of heteroarenes with hydroxylamine derivatives.

    Science.gov (United States)

    Qin, Qixue; Yu, Shouyun

    2014-07-03

    A room temperature redox neutral direct C-H amidation of heteroarenes has been achieved. Hydroxylamine derivatives, which are easily accessed, have been employed as tunable nitrogen sources. These reactions were enabled by a visible-light-promoted single-electron transfer pathway without a directing group. A variety of heteroarenes, such as indoles, pyrroles, and furans, could go through this amidation with high yields (up to 98%). These reactions are highly regioselective, and all the products were isolated as a single regioisomer.

  8. Investigation on Clarified Fruit Juice Composition by Using Visible Light Micro-Raman Spectroscopy

    OpenAIRE

    Camerlingo, Carlo; Zenone, Flora; Delfino, Ines; Diano, Nadia; Mita, Damiano Gustavo; Lepore, Maria

    2007-01-01

    Liquid samples of clarified apple and apricot juices at different production stages were investigated using visible light micro-Raman spectroscopy in order to assess its potential in monitoring fruit juice production. As is well-known, pectin plays a strategic role in the production of clarified juice and the possibility of using Raman for its detection during production was therefore evaluated. The data analysis has enabled the clear identification of pectin. In particular, Raman spectra of ...

  9. N-Iodosuccinimide-Promoted Hofmann-Löffler Reactions of Sulfonimides under Visible Light.

    Science.gov (United States)

    O'Broin, Calvin Q; Fernández, Patricia; Martínez, Claudio; Muñiz, Kilian

    2016-02-05

    Conditions for an attractive and productive protocol for the position-selective intramolecular C-H amination of aliphatic groups (Hofmann-Löffler reaction) are reported employing sulfonimides as nitrogen sources. N-Iodosuccinimide is the only required promoter for this transformation, which is conveniently initiated by visible light. The overall transformation provides pyrrolidines under mild and selective conditions as demonstrated for 17 different substrates.

  10. Pseudo and true visible light photocatalytic activity of nanotube titanic acid/graphene composites

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaodong, E-mail: donguser@hotmail.com; Liu, Xiaogang; Xue, Xiaoxiao; Pan, Hui; Zhang, Min; Li, Qiuye; Yu, Laigui; Yang, Jianjun; Zhang, Zhijun [Henan University, Key Laboratory of Ministry of Education for Special Functional Materials (China)

    2013-09-15

    Nanotube titanic acid/graphene (NTA/Gr) composites were prepared by an easy hydrothermal treatment of graphene oxide (GO) and NTA in a mixed solvent of ethanol-water. As-prepared NTA/Gr composites and GO were characterized by means of Fourier transform infrared spectrometry, X-ray diffraction, diffuse-reflection spectrometry, thermal analysis, and transmission electron microscopy. Besides, the photocatalytic activities of as-prepared NTA/Gr composites were evaluated by monitoring the degradation of methyl orange (MO) under visible light irradiation. It has been found that extending hydrothermal reaction time (24 h instead of 3 h) leads to great changes in the morphology and crystal structure of as-prepared composites. Namely, the orthorhombic NTA (ca. 10 nm in diameter) in the composite transformed to anatase TiO{sub 2} particle (ca. 20-30 nm in diameter) while the Gr sheets (with micrometers-long wrinkles) in it transformed to a few Gr fragments (ca. 50 nm in diameter). Correspondingly, the NTA/Gr composite transformed to titanium dioxide/graphene (TiO{sub 2}/Gr) composite. In the meantime, pure GO only has adsorption effect but it has no photocatalytic activity in the visible light region. Nevertheless, increasing Gr ratio results in enhanced visible light absorption capability and photocatalytic activity of NTA/Gr composites as well as the TiO{sub 2}/Gr composites. This demonstrates that the true visible light photocatalytic activity of NTA/Gr composites as well as the TiO{sub 2}/Gr composites for the degradation of MO is not as excellent as expected, and their high apparent activity is attributed to the strong adsorption of MO on the composites.

  11. Pseudo and true visible light photocatalytic activity of nanotube titanic acid/graphene composites

    Science.gov (United States)

    Wang, Xiaodong; Liu, Xiaogang; Xue, Xiaoxiao; Pan, Hui; Zhang, Min; Li, Qiuye; Yu, Laigui; Yang, Jianjun; Zhang, Zhijun

    2013-09-01

    Nanotube titanic acid/graphene (NTA/Gr) composites were prepared by an easy hydrothermal treatment of graphene oxide (GO) and NTA in a mixed solvent of ethanol-water. As-prepared NTA/Gr composites and GO were characterized by means of Fourier transform infrared spectrometry, X-ray diffraction, diffuse-reflection spectrometry, thermal analysis, and transmission electron microscopy. Besides, the photocatalytic activities of as-prepared NTA/Gr composites were evaluated by monitoring the degradation of methyl orange (MO) under visible light irradiation. It has been found that extending hydrothermal reaction time (24 h instead of 3 h) leads to great changes in the morphology and crystal structure of as-prepared composites. Namely, the orthorhombic NTA (ca. 10 nm in diameter) in the composite transformed to anatase TiO2 particle (ca. 20-30 nm in diameter) while the Gr sheets (with micrometers-long wrinkles) in it transformed to a few Gr fragments (ca. 50 nm in diameter). Correspondingly, the NTA/Gr composite transformed to titanium dioxide/graphene (TiO2/Gr) composite. In the meantime, pure GO only has adsorption effect but it has no photocatalytic activity in the visible light region. Nevertheless, increasing Gr ratio results in enhanced visible light absorption capability and photocatalytic activity of NTA/Gr composites as well as the TiO2/Gr composites. This demonstrates that the true visible light photocatalytic activity of NTA/Gr composites as well as the TiO2/Gr composites for the degradation of MO is not as excellent as expected, and their high apparent activity is attributed to the strong adsorption of MO on the composites.

  12. Visible Light Organic Photoredox-Catalyzed C-H Alkoxylation of Imidazopyridine with Alcohol.

    Science.gov (United States)

    Kibriya, Golam; Samanta, Sadhanendu; Jana, Sourav; Mondal, Susmita; Hajra, Alakananda

    2017-12-15

    The visible light-mediated C-3 alkoxylation of imidazopyridines with alcohols has been achieved using rose bengal as an organic photoredox catalyst at room temperature. Widely abundant air acts as the terminal oxidant that avoids the use of a stoichiometric amount of peroxo compounds. A wide range of functional groups could be tolerated under the reaction conditions to produce C(sp 2 )-H alkoxylated products in high yields.

  13. Optical Fiber Connection Navigation System Using Visible Light Communication in Central Office with Economic Evaluation

    Science.gov (United States)

    Waki, Masaki; Uruno, Shigenori; Ohashi, Hiroyuki; Manabe, Tetsuya; Azuma, Yuji

    We propose an optical fiber connection navigation system that uses visible light communication for an integrated distribution module in a central office. The system realizes an accurate database, requires less skilled work to operate and eliminates human error. This system can achieve a working time reduction of up to 88.0% compared with the conventional work without human error for the connection/removal of optical fiber cords, and is economical as regards installation and operation.

  14. Efficient demodulation scheme for rolling-shutter-patterning of CMOS image sensor based visible light communications.

    Science.gov (United States)

    Chen, Chia-Wei; Chow, Chi-Wai; Liu, Yang; Yeh, Chien-Hung

    2017-10-02

    Recently even the low-end mobile-phones are equipped with a high-resolution complementary-metal-oxide-semiconductor (CMOS) image sensor. This motivates using a CMOS image sensor for visible light communication (VLC). Here we propose and demonstrate an efficient demodulation scheme to synchronize and demodulate the rolling shutter pattern in image sensor based VLC. The implementation algorithm is discussed. The bit-error-rate (BER) performance and processing latency are evaluated and compared with other thresholding schemes.

  15. Hydrothermal synthesis of Ca3Bi8O15 rods and their visible light photocatalytic properties

    International Nuclear Information System (INIS)

    Li, Wenjuan; Kong, Desheng; Cui, Xiaoli; Du, Dandan; Yan, Tingjiang; You, Jinmao

    2014-01-01

    Graphical abstract: The novel Ca 3 Bi 8 O 15 rods can utilize the sunlight efficiently with the small band-gap. Using methyl orange (MO) as a model organic pollutant, the photocatalysts exhibited good photocatalytic activity, with the photodegradation conversion ratio of MO being up to 90% after 2 h of visible light (420 nm < λ < 800 nm) irradiation. - Highlights: • Ca 3 Bi 8 O 15 rods were synthesized by a hydrothermal method. • They can utilize the sunlight efficiently with the small band-gap. • They showed good photocatalytic activities in the degradation of MO, RhB and 4-CP. • The conversion ratio of MO was up to 90% after 2 h of visible light irradiation. - Abstract: High efficient visible light Ca 3 Bi 8 O 15 photocatalysts were synthesized by a hydrothermal method. Characterized by X-ray diffractometer, transmission electron microscopy, and the UV–vis diffuse reflectance spectroscopy, the results showed that the novel Ca 3 Bi 8 O 15 rods can utilize the sunlight efficiently with the small band-gap. Using methyl orange (MO) as a model organic pollutant, the photocatalysts exhibited good photocatalytic activity, with the photodegradation conversion ratio of MO being up to 90% after 2 h of visible light (420 nm < λ < 800 nm) irradiation. Furthermore, they also showed good photocatalytic activities in the degradation of rhodamine B and p-chlorophenol. Through the investigation of the degraded mechanism, the main active species played important roles in the degradation process were holes, O 2 · − and ·OH

  16. Single-shot beam size measurements using visible-light interferometry at CESR

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S.T., E-mail: sw565@cornell.edu [Cornell Laboratory for Accelerator-based Science and Education, Cornell University, Ithaca, NY 14853 (United States); Holtzapple, R. [Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407 (United States); Rubin, D.L. [Cornell Laboratory for Accelerator-based Science and Education, Cornell University, Ithaca, NY 14853 (United States)

    2017-03-01

    A new primary mirror for a visible-light beam size monitor (vBSM) was designed and installed in the Cornell Electron-Positron Storage Ring (CESR). The vertical angular acceptance of the mirror was doubled to allow double-slit interferometry with large slit separation (>12 mm). In addition, the diffraction associated with the first generation mirror has been eliminated. The resolution of the vertical beam size measurements has been dramatically improved but is ultimately limited by the beam motion. Two fast-response detectors, a Photomultiplier Tube (PMT) array and a gated camera, were employed to study the beam motion. The advantages and limitations of both devices are discussed in this paper. The gated camera was also used to measure single-shot beam width and motion of each bunch in a multi-bunch train. We measured significantly more horizontal motion of electron as compared to positron bunch trains in otherwise identical machine condition. This difference may be a signature for the difference between electron cloud build-up for positron bunch trains versus ions effects characteristic of electron bunch trains. - Highlights: • A new extraction mirror for synchrotron radiation was designed and installed in CESR. • The sensitivity of interferometer was increased and the diffraction effect was eliminated. • Two fast-response detectors were employed to study the effect of beam motion. • First time single-shot bunch-by-bunch horizontal beam size measurements using interferometry was observed from gated camera. • The difference in single bunch horizontal dynamics was observed between a positron and an electron train.

  17. Indium oxide thin film as potential photoanodes for corrosion protection of stainless steel under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yan [Key Laboratory of New Fiber Materials and Modern Textile, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Yu, Jianqiang, E-mail: jianqyu@qdu.edu.cn [Key Laboratory of New Fiber Materials and Modern Textile, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Sun, Kai; Zhu, Yukun [Key Laboratory of New Fiber Materials and Modern Textile, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Bu, Yuyu; Chen, Zhuoyuan [National Engineering Center of Marine Corrosion Protection, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071 (China)

    2014-05-01

    Graphical abstract: If the conduction band potential of In{sub 2}O{sub 3} is more negative than the corrosion potential of stainless steel, photo-induced electrons will be transferred from In{sub 2}O{sub 3} to the steel, thus shifting the potential of the steel into a corrosion immunity region and preventing the steel from the corrosion. - Highlights: • Indium oxide performed novel application under visible light. • Indium oxide by sol–gel method behaved better photoelectrochemical properties. • Electrons were transferred to stainless steel from indium oxide once light on. - Abstract: This paper reports the photoelectrochemical cathodic protection of 304 stainless steel by In{sub 2}O{sub 3} thin-film under visible-light. The films were fabricated with In{sub 2}O{sub 3} powders, synthesized by both sol–gel (In{sub 2}O{sub 3}-sg) and solid-state (In{sub 2}O{sub 3}-ss) processes. The photo-induced open circuit potential and the photo-to-current efficiency measurements suggested that In{sub 2}O{sub 3} could be a promising candidate material for photoelectrochemical cathodic protection of metallic alloys under visible light. Moreover, the polarization curve experimental results indicated that In{sub 2}O{sub 3}-sg thin-film can mitigate the corrosion potential of 304 stainless steel to much more negative values with a higher photocurrent density than the In{sub 2}O{sub 3}-ss film under visible-light illumination. All the results demonstrated that the In{sub 2}O{sub 3}-sg thin-film provides a better photoelectrochemical cathodic protection for 304 stainless steel than In{sub 2}O{sub 3}-ss thin-film under visible-light illumination. The higher photoelectrochemical efficiency is possibly due to the uniform thin films produced with the smaller particle size of In{sub 2}O{sub 3}-sg, which facilitates the transfer of the photo-induced electrons from bulk to the surface and suppresses the charge recombination of the electrons and holes.

  18. Secure positioning technique based on encrypted visible light map for smart indoor service

    Science.gov (United States)

    Lee, Yong Up; Jung, Gillyoung

    2018-03-01

    Indoor visible light (VL) positioning systems for smart indoor services are negatively affected by both cochannel interference from adjacent light sources and VL reception position irregularity in the three-dimensional (3-D) VL channel. A secure positioning methodology based on a two-dimensional (2-D) encrypted VL map is proposed, implemented in prototypes of the specific positioning system, and analyzed based on performance tests. The proposed positioning technique enhances the positioning performance by more than 21.7% compared to the conventional method in real VL positioning tests. Further, the pseudonoise code is found to be the optimal encryption key for secure VL positioning for this smart indoor service.

  19. Fabrication of Tiron-TiO{sub 2} charge-transfer complex with excellent visible-light photocatalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Binghua, E-mail: bhyao@xaut.edu.cn [Department of Applied Chemistry, Xi' an University of Technology, Xi' an 710048 (China); The Key Laboratory of Northwest Water Resources and Environmental Ecology of Ministry of Education, Xi' an University of Technology, Xi' an 710048 (China); Peng, Chao; Lu, Pan; He, Yangqing [Department of Applied Chemistry, Xi' an University of Technology, Xi' an 710048 (China); Zhang, Wen, E-mail: wenzhang@uark.edu [Department of Civil Engineering, University of Arkansas, Fayetteville 72701 (United States); Zhang, Qinku [Department of Applied Chemistry, Xi' an University of Technology, Xi' an 710048 (China); The Key Laboratory of Northwest Water Resources and Environmental Ecology of Ministry of Education, Xi' an University of Technology, Xi' an 710048 (China)

    2016-12-01

    A new charge-transfer(CT) complex (Tiron-TiO{sub 2}) was prepared via the 1,2-dihydroxy-3,5-benzenedisulfonic acid disodium salt (Tiron) as chelate sensitizer. The phase structures and morphologies were measured by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results demonstrated that the as-prepared Tiron-TiO{sub 2} is of anatase microspheres with size range between 300 and 350 nm. The analysis of FT-IR and XPS revealed that the binding structure of the Tiron-TiO{sub 2} CT complex is of the characteristic of bidentate binuclear binding-bridging. UV–vis analysis showed that the formation of CT complex on the surface of TiO{sub 2} through Tiron significantly extends the photoresponse of Tiron-TiO{sub 2} nanoparticles to visible light range (400–600 nm). Compared with unmodified TiO{sub 2}, Tiron-modified TiO{sub 2}(Tiron-TiO{sub 2}) exhibited excellent photocatalytic activity for the photocatalytic degradation of methylene blue(MB) and three kind of antibiotics under visible light irradiation (λ > 400 nm). - Highlights: • The Tiron-TiO{sub 2} charge transfer complex was synthesized. • The incorporation of Tiron with TiO{sub 2} extended TiO{sub 2} response to visible light region. • Tiron-TiO{sub 2} exhibited significant photocatalytic degradation for antibiotics. • Tiron-TiO{sub 2} showed the long-term stability and reusability.

  20. In situ Sn2+-incorporation synthesis of titanate nanotubes for photocatalytic dye degradation under visible light illumination

    International Nuclear Information System (INIS)

    Tsai, Chien-Cheng; Chen, Liang-Che; Yeh, Te-Fu; Teng, Hsisheng

    2013-01-01

    Highlights: ► Sn 2+ ions sensitize titanate nanotubes for photocatalysis under visible-light illumination. ► The Sn 5s orbital replaces the O 2p orbital as the top level of the valence band of titanates. ► The presence of Sn 2+ lifts the valence band of titanate nanotubes by approximately 0.9 eV. ► The doped Sn 2+ sites are active in donating photo-induced charges to dye degradation. - Abstract: Sn 2+ -incorporated titanate nanotubes, prepared by washing a layered sodium titanate with a SnCl 2 solution for tube formation, exhibit noticeable photocatalytic activity under visible light irradiation. This in situ synthesis results in a Sn/Ti ratio of approximately 0.6. Because of the introduction of Sn 2+ ions, the Sn 5s orbital replaces the O 2p orbital as the top level of the valence band of titanate nanotubes. Optical absorption analysis shows that Sn doping reduces the bandgap of titanate nanotubes from 3.5 to 2.6 eV. Oxidation of the Sn 2+ -incorporated titanate nanotubes leads to oxidation of Sn 2+ to Sn 4+ , hence, widening the bandgap. Under visible light irradiation, Sn 2+ -incorporated titanate nanotubes effectively degrade methylene blue in an aqueous solution, whereas the bare titanate nanotubes exhibit substantially lower photocatalytic activity. Photoluminescence analysis demonstrates that the induced charges from excitation of the Sn 2+ ions tend to be relaxed through chemical interactions, rather than irradiative recombination.

  1. Visible light assisted nitrogen dioxide sensing using tungsten oxide - Graphene oxide nanocomposite sensors

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Xin [College of Mechanical Engineering, Yangzhou University, Yangzhou 225127 (China); College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); You, Jiajun; Wang, Jie [College of Mechanical Engineering, Yangzhou University, Yangzhou 225127 (China); Zhang, Chao, E-mail: zhangc@yzu.edu.cn [College of Mechanical Engineering, Yangzhou University, Yangzhou 225127 (China)

    2017-04-15

    Tungsten oxide (WO{sub 3}) coatings were deposited by solution precursor plasma spray (SPPS) on alumina substrates. In order to enhance the NO{sub 2} sensing properties of the pure WO{sub 3} coatings at room temperature, illuminating with visible light and formation of p-n heterojunction were used. The SPPS WO{sub 3} coatings were modified by immersing them into a synthesized graphene oxide (GO) suspension to obtain the WO{sub 3}-GO composites. Raman and FTIR results demonstrated that p-n heterojunctions were successfully formed in the WO{sub 3}-GO composites. The UV–Vis spectra showed that the WO{sub 3}-GO composites had a longer visible light absorption range compared with the WO{sub 3} coatings. The sensors based on the WO{sub 3}-GO coatings exhibited ultra-high responses to NO{sub 2} at room temperature performed under visible light illumination. - Highlights: • Highly porous nanostructured WO{sub 3} coatings were deposited by SPPS process. • The WO{sub 3}-GO nanocomposites with p-n heterojunctions were successfully prepared. • The WO{sub 3}-GO nanocomposites exhibited ultra-high responses to 0.9 ppm NO{sub 2}. • The enhanced performance was ascribed to the fine structure and heterojunction.

  2. Antibacterial properties of F-doped ZnO visible light photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Podporska-Carroll, Joanna, E-mail: joannapcarroll@gmail.com [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); Myles, Adam [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin St., Dublin (Ireland); Quilty, Brid [School of Biotechnology, Dublin City University, Dublin (Ireland); McCormack, Declan E.; Fagan, Rachel [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin St., Dublin (Ireland); Hinder, Steven J. [The Surface Analysis Laboratory, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Dionysiou, Dionysios D., E-mail: dionysios.d.dionysiou@uc.edu [Environmental Engineering and Science Program, Department of Biomedical, Chemical and Environmental Engineering (DBCEE), 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012 (United States); Pillai, Suresh C., E-mail: Pillai.Suresh@itsligo.ie [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); Nanotechnology Research Group, Department of Environmental Science, PEM Centre, Institute of Technology Sligo, Sligo (Ireland)

    2017-02-15

    Highlights: • F doped ZnO nano-powders were obtained by a modified sol–gel method. • These materials were found to be effective against S. aureus and E. coli. • Enhanced visible light photocatalytic and antimicrobial properties were obtained. • The toxic effect of ZnO on bacteria can be due to the release of zinc cations. • Production of reactive oxidation species influences bacterial viability. - Abstract: Nanocrystalline ZnO photocatalysts were prepared by a sol–gel method and modified with fluorine to improve their photocatalytic anti-bacterial activity in visible light. Pathogenic bacteria such as Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) were employed to evaluate the antimicrobial properties of synthesized materials. The interaction with biological systems was assessed by analysis of the antibacterial properties of bacteria suspended in 2% (w/w) powder solutions. The F-doping was found to be effective against S. aureus (99.99% antibacterial activity) and E. coli (99.87% antibacterial activity) when irradiated with visible light. Production of reactive oxygen species is one of the major factors that negatively impact bacterial growth. In addition, the nanosize of the ZnO particles can also be toxic to microorganisms. The small size and high surface-to-volume ratio of the ZnO nanoparticles are believed to play a role in enhancing antimicrobial activity.

  3. Development of visible-light responsive and mechanically enhanced "smart" UCST interpenetrating network hydrogels.

    Science.gov (United States)

    Xu, Yifei; Ghag, Onkar; Reimann, Morgan; Sitterle, Philip; Chatterjee, Prithwish; Nofen, Elizabeth; Yu, Hongyu; Jiang, Hanqing; Dai, Lenore L

    2017-12-20

    An interpenetrating polymer network (IPN), chlorophyllin-incorporated environmentally responsive hydrogel was synthesized and exhibited the following features: enhanced mechanical properties, upper critical solution temperature (UCST) swelling behavior, and promising visible-light responsiveness. Poor mechanical properties are known challenges for hydrogel-based materials. By forming an interpenetrating network between polyacrylamide (PAAm) and poly(acrylic acid) (PAAc) polymer networks, the mechanical properties of the synthesized IPN hydrogels were significantly improved compared to hydrogels made of a single network of each polymer. The formation of the interpenetrating network was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), the analysis of glass transition temperature, and a unique UCST responsive swelling behavior, which is in contrast to the more prevalent lower critical solution temperature (LCST) behaviour of environmentally responsive hydrogels. The visible-light responsiveness of the synthesized hydrogel also demonstrated a positive swelling behavior, and the effect of incorporating chlorophyllin as the chromophore unit was observed to reduce the average pore size and further enhance the mechanical properties of the hydrogel. This interpenetrating network system shows potential to serve as a new route in developing "smart" hydrogels using visible-light as a simple, inexpensive, and remotely controllable stimulus.

  4. Facile synthesis of phosphorus doped graphitic carbon nitride polymers with enhanced visible-light photocatalytic activity

    International Nuclear Information System (INIS)

    Zhang, Ligang; Chen, Xiufang; Guan, Jing; Jiang, Yijun; Hou, Tonggang; Mu, Xindong

    2013-01-01

    Graphical abstract: - Highlights: • P-doped g-C 3 N 4 has been prepared by a one-pot green synthetic approach. • The incorporation of P resulted in favorable textural and electronic properties. • Doping with P enhanced the visible-light photocatalytic activity of g-C 3 N 4 . • A postannealing treatment further enhanced the activity of P-doped g-C 3 N 4 . • Photogenerated holes were the main species responsible for the activity. - Abstract: Phosphorus-doped carbon nitride materials were prepared by a one-pot green synthetic approach using dicyandiamide monomer and a phosphorus containing ionic liquid as precursors. The as-prepared materials were subjected to several characterizations and investigated as metal-free photocatalysts for the degradation of organic pollutants (dyes like Rhodamine B, Methyl orange) in aqueous solution under visible light. Results revealed that phosphorus-doped carbon nitride have a higher photocatalytic activity for decomposing Rhodamine B and Methyl orange in aqueous solution than undoped g-C 3 N 4 , which was attributed to the favorable textural, optical and electronic properties caused by doping with phosphorus heteroatoms into carbon nitride host. A facile postannealing treatment further improved the activity of the photocatalytic system, due to the higher surface area and smaller structural size in the postcalcined catalysts. The phosphorus-doped carbon nitride showed high visible-light photocatalytic activity, making them promising materials for a wide range of potential applications in photochemistry

  5. Multiwalled Carbon Nanotube-TiO2 Nanocomposite for Visible-Light-Induced Photocatalytic Hydrogen Evolution

    Directory of Open Access Journals (Sweden)

    Ke Dai

    2014-01-01

    Full Text Available Multiwalled carbon nanotube- (MWCNT- TiO2 nanocomposite was synthesized via hydrothermal process and characterized by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, field emission scanning electron microscope, thermogravimetry analysis, and N2 adsorption-desorption isotherms. Appropriate pretreatment on MWCNTs could generate oxygen-containing groups, which is beneficial for forming intimate contact between MWCNTs and TiO2 and leads to a higher thermal stability of MWCNT-TiO2 nanocomposite. Modification with MWCNTs can extend the visible-light absorption of TiO2. 5 wt% MWCNT-TiO2 derived from hydrothermal treatment at 140°C exhibiting the highest hydrogen generation rate of 15.1 μmol·h−1 under visible-light irradiation and a wide photoresponse range from 350 to 475 nm with moderate quantum efficiency (4.4% at 420 nm and 3.7% at 475 nm. The above experimental results indicate that the MWCNT-TiO2 nanocomposite is a promising photocatalyst with good stability and visible-light-induced photoactivity.

  6. Visible-light-induced instability in amorphous metal-oxide based TFTs for transparent electronics

    Directory of Open Access Journals (Sweden)

    Tae-Jun Ha

    2014-10-01

    Full Text Available We investigate the origin of visible-light-induced instability in amorphous metal-oxide based thin film transistors (oxide-TFTs for transparent electronics by exploring the shift in threshold voltage (Vth. A large hysteresis window in amorphous indium-gallium-zinc-oxide (a-IGZO TFTs possessing large optical band-gap (≈3 eV was observed in a visible-light illuminated condition whereas no hysteresis window was shown in a dark measuring condition. We also report the instability caused by photo irradiation and prolonged gate bias stress in oxide-TFTs. Larger Vth shift was observed after photo-induced stress combined with a negative gate bias than the sum of that after only illumination stress and only negative gate bias stress. Such results can be explained by trapped charges at the interface of semiconductor/dielectric and/or in the gate dielectric which play a role in a screen effect on the electric field applied by gate voltage, for which we propose that the localized-states-assisted transitions by visible-light absorption can be responsible.

  7. Visible-light-induced instability in amorphous metal-oxide based TFTs for transparent electronics

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Tae-Jun [Department of Electronic Materials Engineering, Kwangwoon University, Seoul 139-701 (Korea, Republic of)

    2014-10-15

    We investigate the origin of visible-light-induced instability in amorphous metal-oxide based thin film transistors (oxide-TFTs) for transparent electronics by exploring the shift in threshold voltage (V{sub th}). A large hysteresis window in amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs possessing large optical band-gap (≈3 eV) was observed in a visible-light illuminated condition whereas no hysteresis window was shown in a dark measuring condition. We also report the instability caused by photo irradiation and prolonged gate bias stress in oxide-TFTs. Larger V{sub th} shift was observed after photo-induced stress combined with a negative gate bias than the sum of that after only illumination stress and only negative gate bias stress. Such results can be explained by trapped charges at the interface of semiconductor/dielectric and/or in the gate dielectric which play a role in a screen effect on the electric field applied by gate voltage, for which we propose that the localized-states-assisted transitions by visible-light absorption can be responsible.

  8. Recognizing Banknote Fitness with a Visible Light One Dimensional Line Image Sensor

    Directory of Open Access Journals (Sweden)

    Tuyen Danh Pham

    2015-08-01

    Full Text Available In general, dirty banknotes that have creases or soiled surfaces should be replaced by new banknotes, whereas clean banknotes should be recirculated. Therefore, the accurate classification of banknote fitness when sorting paper currency is an important and challenging task. Most previous research has focused on sensors that used visible, infrared, and ultraviolet light. Furthermore, there was little previous research on the fitness classification for Indian paper currency. Therefore, we propose a new method for classifying the fitness of Indian banknotes, with a one-dimensional line image sensor that uses only visible light. The fitness of banknotes is usually determined by various factors such as soiling, creases, and tears, etc. although we just consider banknote soiling in our research. This research is novel in the following four ways: first, there has been little research conducted on fitness classification for the Indian Rupee using visible-light images. Second, the classification is conducted based on the features extracted from the regions of interest (ROIs, which contain little texture. Third, 1-level discrete wavelet transformation (DWT is used to extract the features for discriminating between fit and unfit banknotes. Fourth, the optimal DWT features that represent the fitness and unfitness of banknotes are selected based on linear regression analysis with ground-truth data measured by densitometer. In addition, the selected features are used as the inputs to a support vector machine (SVM for the final classification of banknote fitness. Experimental results showed that our method outperforms other methods.

  9. Recognizing Banknote Fitness with a Visible Light One Dimensional Line Image Sensor.

    Science.gov (United States)

    Pham, Tuyen Danh; Park, Young Ho; Kwon, Seung Yong; Nguyen, Dat Tien; Vokhidov, Husan; Park, Kang Ryoung; Jeong, Dae Sik; Yoon, Sungsoo

    2015-08-27

    In general, dirty banknotes that have creases or soiled surfaces should be replaced by new banknotes, whereas clean banknotes should be recirculated. Therefore, the accurate classification of banknote fitness when sorting paper currency is an important and challenging task. Most previous research has focused on sensors that used visible, infrared, and ultraviolet light. Furthermore, there was little previous research on the fitness classification for Indian paper currency. Therefore, we propose a new method for classifying the fitness of Indian banknotes, with a one-dimensional line image sensor that uses only visible light. The fitness of banknotes is usually determined by various factors such as soiling, creases, and tears, etc. although we just consider banknote soiling in our research. This research is novel in the following four ways: first, there has been little research conducted on fitness classification for the Indian Rupee using visible-light images. Second, the classification is conducted based on the features extracted from the regions of interest (ROIs), which contain little texture. Third, 1-level discrete wavelet transformation (DWT) is used to extract the features for discriminating between fit and unfit banknotes. Fourth, the optimal DWT features that represent the fitness and unfitness of banknotes are selected based on linear regression analysis with ground-truth data measured by densitometer. In addition, the selected features are used as the inputs to a support vector machine (SVM) for the final classification of banknote fitness. Experimental results showed that our method outperforms other methods.

  10. Zinc oxide nanorod mediated visible light photoinactivation of model microbes in water

    Energy Technology Data Exchange (ETDEWEB)

    Sapkota, Ajaya; Anceno, Alfredo J; Dutta, Joydeep [Center of Excellence in Nanotechnology, Asian Institute of Technology, Klong Luang, Pathumthani 12120 (Thailand); Baruah, Sunandan; Shipin, Oleg V, E-mail: alfredo.anceno@cemagref.fr, E-mail: joy@ait.ac.th [Environmental Engineering and Management, Asian Institute of Technology, Klong Luang, Pathumthani 12120 (Thailand)

    2011-05-27

    The inactivation of model microbes in aqueous matrix by visible light photocatalysis as mediated by ZnO nanorods was investigated. ZnO nanorods were grown on glass substrate following a hydrothermal route and employed in the inactivation of gram-negative Escherichia coli and gram-positive Bacillus subtilis in MilliQ water. The concentration of Zn{sup 2+} ions in the aqueous matrix, bacterial cell membrane damage, and DNA degradation at post-exposure were also studied. The inactivation efficiencies for both organisms under light conditions were about two times higher than under dark conditions across the cell concentrations assayed. Anomalies in supernatant Zn{sup 2+} concentration were observed under both conditions as compared to control treatments, while cell membrane damage and DNA degradation were observed only under light conditions. Inactivation under dark conditions was hence attributed to the bactericidal effect of Zn{sup 2+} ions, while inactivation under light conditions was due to the combined effects of Zn{sup 2+} ions and photocatalytically mediated electron injection. The reduction of pathogenic bacterial densities by the photocatalytically active ZnO nanorods in the presence of visible light implies potential ex situ application in water decontamination at ambient conditions under sunlight.

  11. Visible light-induced OH radicals in Ga2O3: an EPR study.

    Science.gov (United States)

    Tzitrinovich, Zeev; Lipovsky, Anat; Gedanken, Aharon; Lubart, Rachel

    2013-08-21

    Reactive oxygen species (ROS) were found to exist in water suspensions of several metal oxide nanoparticles (NPs), such as CuO, TiO2 and ZnO. Visible light irradiation enhanced the capability of TiO2 and ZnO NPs to generate ROS, thus increasing their antibacterial effects. Because of the possible toxic effects on the host tissue it is desired to find nano-metal oxides which do not produce ROS under room light, but only upon a strong external stimulus. Using the technique of electron-spin resonance (ESR) coupled with spin trapping, we examined the ability of Ga2O3 submicron-particle suspensions in water to produce reactive oxygen species with and without visible light irradiation. We found that in contrast to ZnO and TiO2 NPs, no ROS are produced by Ga2O3 under room light. Nevertheless blue light induced hydroxyl radical formation in Ga2O3. This finding might suggest that NPs of Ga2O3 could be used safely for infected skin sterilization.

  12. Thickness-dependent photocatalytic performance of graphite oxide for degrading organic pollutants under visible light.

    Science.gov (United States)

    Oh, Junghoon; Chang, Yun Hee; Kim, Yong-Hyun; Park, Sungjin

    2016-04-28

    Photocatalysts use sustainable solar light energy to trigger various catalytic reactions. Metal-free nanomaterials have been suggested as cost-effective and environmentally friendly photocatalysts. In this work, we propose thickness-controlled graphite oxide (GO) as a metal-free photocatalyst, which is produced by exfoliating thick GO particles via stirring and sonication. All GO samples exhibit photocatalytic activity for degrading an organic pollutant, rhodamine B under visible light, and the thickest sample shows the best catalytic performance. UV-vis-NIR diffuse reflectance absorption spectra indicate that thicker GO samples absorb more vis-NIR light than thinner ones. Density-functional theory calculations show that GO has a much smaller band gap than that of single-layer graphene oxide, and thus suggest that the largely-reduced band gap is responsible for this trend of light absorption.

  13. The effect of external visible light on the breakdown voltage of a long discharge tube

    Science.gov (United States)

    Shishpanov, A. I.; Ionikh, Yu. Z.; Meshchanov, A. V.

    2016-06-01

    The breakdown characteristics of a discharge tube with a configuration typical of gas-discharge light sources and electric-discharge lasers (a so-called "long discharge tube") filled with argon or helium at a pressure of 1 Torr have been investigated. A breakdown has been implemented using positive and negative voltage pulses with a linear leading edge having a slope dU/ dt ~ 10-107 V/s. Visible light from an external source (halogen incandescent lamp) is found to affect the breakdown characteristics. The dependences of the dynamic breakdown voltage of the tube on dU/ dt and on the incident light intensity are measured. The breakdown voltage is found to decrease under irradiation of the high-voltage anode of the tube in a wide range of dU/ dt. A dependence of the effect magnitude on the light intensity and spectrum is obtained. Possible physical mechanisms of this phenomenon are discussed.

  14. Visible light irradiation-induced conductivity change for CVD-grown graphene on different substrates

    Science.gov (United States)

    Li, Xiangdi; Zhang, Peng; Liu, Xianming; Cao, Xueying; Lei, Xiaohua; Chen, Weimin

    2017-08-01

    This research examines the influence of lighting on the electrical properties of graphene on different substrates, including PET, glass and SiO2, which are the most widely used substrate materials representing the flexible and rigid applications. The graphene sheets were prepared by CVD and subsequently transferred to three substrates. The resistances of graphene under periodic visible light irradiation were measured inside a vacuum chamber. Results show that the resistances for graphene samples on all substrates increased slowly under lighting, while decreased slowly as well after the light was switched off. The change degree and speed were different for graphene on different substrates, which were influenced as well by the illumination time, environment atmosphere and irradiation power. Graphene on flexible PET substrate is more stable than that on other substrates.

  15. Energy, Electron Transfer and Photocatalytic Reactions of Visible Light Absorbing Transition Metal Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Schmehl, Russell H. [Tulane Univ., New Orleans, LA (United States)

    2016-03-02

    This is the final technical report for a project carried out at Tulane University of New Orleans that describes the development of light induced (solar) reactions geared toward decomposing water into its component elements : hydrogen and oxygen. Much of the work involved optimizing systems for absorbing visible light and undergoing light promoted reactions to generate very strong reducing agents that are capable of reacting with water to produce hydrogen. Additional portions of the research were collaborative efforts to put the strong reducing agents to work in reaction with hydrogen generation catalysts prepared elsewhere. Time resolved laser spectroscopic methods were used to evaluate the light induced reactions and characterize very reactive intermediate substances formed during the reactions.

  16. CdSe nanorod/TiO2 nanoparticle heterojunctions with enhanced solar- and visible-light photocatalytic activity

    Directory of Open Access Journals (Sweden)

    Fakher Laatar

    2017-12-01

    Full Text Available CdSe nanorods (NRs with an average length of ≈120 nm were prepared by a solvothermal process and associated to TiO2 nanoparticles (Aeroxide® P25 by annealing at 300 °C for 1 h. The content of CdSe NRs in CdSe/TiO2 composites was varied from 0.5 to 5 wt %. The CdSe/TiO2 heterostructured materials were characterized by XRD, TEM, SEM, XPS, UV–visible spectroscopy and Raman spectroscopy. TEM images and XRD patterns show that CdSe NRs with wurtzite structure are associated to TiO2 particles. The UV–visible spectra demonstrate that the narrow bandgap of CdSe NRs serves to increase the photoresponse of CdSe/TiO2 composites until ≈725 nm. The CdSe (2 wt %/TiO2 composite exhibits the highest photocatalytic activity for the degradation of rhodamine B in aqueous solution under simulated sunlight or visible light irradiation. The enhancement in photocatalytic activity likely originates from CdSe sensitization of TiO2 and the heterojunction between these materials which facilitates electron transfer from CdSe to TiO2. Due to its high stability (up to ten reuses without any significant loss in activity, the CdSe/TiO2 heterostructured catalysts show high potential for real water decontamination.

  17. Modifications of γ-ray sensitivity of bacterial membranes by pre-exposure to light

    International Nuclear Information System (INIS)

    Misiti-Dorello, P.; Cancelliere, G.; De Martino, G.; Quintilini, M.

    1976-01-01

    The exposure of E. coli B/r cells to ultraviolet or to visible light prior to irradiation with γ-rays modifies the sensitivity of the cell membrane to radiation damage responsible for the intracellular K + content. Exposure of bacterial cells to sublethal doses of UV radiation increases their sensitivity to γ-induced membrane damage, while exposure to visible light has the opposite effect. In combined exposures, the visible light, either given before or after the UV always produces a strong photoprotective effect. In either case, the photosensitizing effect of UV is completely suppressed. The photoprotection decays with time if cell suspensions are left in the dark before γ-irradiation. At O 0 C, the half-life of the photoprotective effect is 25 min at pH 7 and 100 min at pH 7.5. The decay is due to the presence of oxygen. The light band responsible for the induction of photoprotection has been estimated to lie in the wavelenght region between 540 and 580 nm. (orig./MG) [de

  18. Convolutional Neural Network-Based Human Detection in Nighttime Images Using Visible Light Camera Sensors.

    Science.gov (United States)

    Kim, Jong Hyun; Hong, Hyung Gil; Park, Kang Ryoung

    2017-05-08

    Because intelligent surveillance systems have recently undergone rapid growth, research on accurately detecting humans in videos captured at a long distance is growing in importance. The existing research using visible light cameras has mainly focused on methods of human detection for daytime hours when there is outside light, but human detection during nighttime hours when there is no outside light is difficult. Thus, methods that employ additional near-infrared (NIR) illuminators and NIR cameras or thermal cameras have been used. However, in the case of NIR illuminators, there are limitations in terms of the illumination angle and distance. There are also difficulties because the illuminator power must be adaptively adjusted depending on whether the object is close or far away. In the case of thermal cameras, their cost is still high, which makes it difficult to install and use them in a variety of places. Because of this, research has been conducted on nighttime human detection using visible light cameras, but this has focused on objects at a short distance in an indoor environment or the use of video-based methods to capture multiple images and process them, which causes problems related to the increase in the processing time. To resolve these problems, this paper presents a method that uses a single image captured at night on a visible light camera to detect humans in a variety of environments based on a convolutional neural network. Experimental results using a self-constructed Dongguk night-time human detection database (DNHD-DB1) and two open databases (Korea advanced institute of science and technology (KAIST) and computer vision center (CVC) databases), as well as high-accuracy human detection in a variety of environments, show that the method has excellent performance compared to existing methods.

  19. Convolutional Neural Network-Based Human Detection in Nighttime Images Using Visible Light Camera Sensors

    Directory of Open Access Journals (Sweden)

    Jong Hyun Kim

    2017-05-01

    Full Text Available Because intelligent surveillance systems have recently undergone rapid growth, research on accurately detecting humans in videos captured at a long distance is growing in importance. The existing research using visible light cameras has mainly focused on methods of human detection for daytime hours when there is outside light, but human detection during nighttime hours when there is no outside light is difficult. Thus, methods that employ additional near-infrared (NIR illuminators and NIR cameras or thermal cameras have been used. However, in the case of NIR illuminators, there are limitations in terms of the illumination angle and distance. There are also difficulties because the illuminator power must be adaptively adjusted depending on whether the object is close or far away. In the case of thermal cameras, their cost is still high, which makes it difficult to install and use them in a variety of places. Because of this, research has been conducted on nighttime human detection using visible light cameras, but this has focused on objects at a short distance in an indoor environment or the use of video-based methods to capture multiple images and process them, which causes problems related to the increase in the processing time. To resolve these problems, this paper presents a method that uses a single image captured at night on a visible light camera to detect humans in a variety of environments based on a convolutional neural network. Experimental results using a self-constructed Dongguk night-time human detection database (DNHD-DB1 and two open databases (Korea advanced institute of science and technology (KAIST and computer vision center (CVC databases, as well as high-accuracy human detection in a variety of environments, show that the method has excellent performance compared to existing methods.

  20. Graphene–Ag/ZnO nanocomposites as high performance photocatalysts under visible light irradiation

    International Nuclear Information System (INIS)

    Ahmad, M.; Ahmed, E.; Hong, Z.L.; Khalid, N.R.; Ahmed, W.; Elhissi, A.

    2013-01-01

    Highlights: •Synthesis of Graphene–Ag/ZnO composite photocatalysts by facile one-step nontoxic approach. •Enhanced visible light absorption and efficient charge separation of ZnO by graphene modification and silver doping. •Effective utilization of photo-induced conduction band electron and valance band hole to photocatalytic degradation process. •Excellent photocatalytic performance of composites over pure ZnO. •The reduction in COD and TOC confirms the destruction of the organic molecules in the effluents along with colour removal. -- Abstract: Visible-light-responsive Graphene–Ag/ZnO nanocomposites were fabricated using a facile, one-pot, nontoxic solvothermal process for the photodegradation of organic dyes. During the solvothermal process reduction of graphene oxide and loading of Ag-doped ZnO nanoparticles on two-dimensional graphene sheets were achieved. Electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray analysis, BET surface area measurements, X-ray photoelectron spectroscopy and powder X-ray diffraction were used to confirm that the Ag-doped ZnO nanoparticles as randomly dispersed and effectively decorated on graphene sheets via covalent bonds between Zn and C atoms. Optical properties studied using UV–vis diffuse reflectance spectroscopy confirmed that the absorption edge of Ag-doped ZnO shifted to visible-light region with the incorporation of graphene. The as-synthesized Graphene–Ag/ZnO nanocomposites showed unprecedented photodecomposition efficiency compared to the Ag-doped ZnO, pristine ZnO and commercial ZnO under visible-light. The textile mill effluent containing organic substances was also treated using photocatalysis and the reduction in the chemical oxygen demand (COD) of the treated effluent revealed a complete destruction of the organic molecules along with colour removal. This dramatically enhanced photoactivity of the composite which is attributed to retarded charge recombination rate

  1. Visible Light Responsive Catalysts Using Quantum Dot-Modified Ti02 for Air and Water Purification

    Science.gov (United States)

    Coutts, Janelle L.; Levine, Lanfang H.; Richards, Jeffrey T.; Hintze, paul; Clausen, Christian

    2012-01-01

    The method of photocatalysis utilizing titanium dioxide, TiO2, as the catalyst has been widely studied for trace contaminant control for both air and water applications because of its low energy consumption and use of a regenerable catalyst. Titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors and are a setback for the technology for space application due to the possibility of Hg contamination. The development of a visible light responsive (VLR) TiO2-based catalyst could lead to the use of solar energy in the visible region (approx.45% of the solar spectrum lies in the visible region; > 400 nm) or highly efficient LEDs (with wavelengths > 400 nm) to make PCO approaches more efficient, economical, and safe. Though VLR catalyst development has been an active area of research for the past two decades, there are few commercially available VLR catalysts; those that are available still have poor activity in the visible region compared to that in the UV region. Thus, this study was aimed at the further development of VLR catalysts by a new method - coupling of quantum dots (QD) of a narrow band gap semiconductor (e.g., CdS, CdSe, PbS, ZnSe, etc.) to the TiO2 by two preparation methods: 1) photodeposition and 2) mechanical alloying using a high-speed ball mill. A library of catalysts was developed and screened for gas and aqueous phase applications, using ethanol and 4-chlorophenol as the target contaminants, respectively. Both target compounds are well studied in photocatalytic systems serve as model contaminants for this research. Synthesized catalysts were compared in terms of preparation method, type of quantum dots, and dosage of quantum dots.

  2. Visible-Light Upconversion Carbon Quantum Dots Decorated TiO2 for the Photodegradation of Flowing Gaseous Acetaldehyde

    Science.gov (United States)

    Hu, Yidan; Xie, Xiaofeng; Wang, Xiao; Wang, Yan; Zeng, Yi; Pui, David Y. H.; Sun, Jing

    2018-05-01

    Carbon-modified photocatalyst has attracted extensive attentions in the field of gaseous pollutant removal, mainly due to the improved adsorption properties and electronic transport of carbon matrix, such as carbon nanotubes, graphene, and fullerene, etc. In this work, carbon quantum dots (CQDs) were employed to enhance the photocatalytic performance of TiO2-based composites for flowing gaseous acetaldehyde removal. Besides the aforementioned advantages of carbon materials, the unique up-converted photoluminescence property of CQDs is capable of extending the optical absorption to visible-light range. Moreover, the electron spin resonance (ESR) results firstly verified a stable existence of Ti3+ defect in the CQDs/TiO2 composite, which is possibly induced by the electron migration from CQDs to TiO2. And the formed Ti3+ donor energy level in the band gap could further help with the visible-light harvesting. During the photodegradation experiments, with two-hour continuous flowing gaseous acetaldehyde injection (500 ppm, 20 sccm), the CQDs/TiO2 composite remained 99% removal efficiency under fluorescent lamp irradiation (λ > 380 nm). The optimized CQDs content was obtained as 3 wt%, and the underlying mechanism was further analyzed by temperature programmed desorption (TPD) methods. This work will push forward the air purification researches by providing new insights of CQDs sensitized photocatalyst.

  3. Synthesis of visible-light responsive graphene oxide/TiO(2) composites with p/n heterojunction.

    Science.gov (United States)

    Chen, Chao; Cai, Weimin; Long, Mingce; Zhou, Baoxue; Wu, Yahui; Wu, Deyong; Feng, Yujie

    2010-11-23

    Graphene oxide/TiO(2) composites were prepared by using TiCl(3) and graphene oxide as reactants. The concentration of graphene oxide in starting solution played an important role in photoelectronic and photocatalytic performance of graphene oxide/TiO(2) composites. Either a p-type or n-type semiconductor was formed by graphene oxide in graphene oxide/TiO(2) composites. These semiconductors could be excited by visible light with wavelengths longer than 510 nm and acted as sensitizer in graphene oxide/TiO(2) composites. Visible-light driven photocatalytic performance of graphene oxide/TiO(2) composites in degradation of methyl orange was also studied. Crystalline quality and chemical states of carbon elements from graphene oxide in graphene oxide/TiO(2) composites depended on the concentration of graphene oxide in the starting solution. This study shows a possible way to fabricate graphene oxide/semiconductor composites with different properties by using a tunable semiconductor conductivity type of graphene oxide.

  4. Photodegradation of malachite green dye catalyzed by Keggin-type polyoxometalates under visible-light irradiation: Transition metal substituted effects

    Science.gov (United States)

    Liu, Chun-Guang; Zheng, Ting; Liu, Shuang; Zhang, Han-Yu

    2016-04-01

    In the present paper, Keggin-type polyoxometalates (POMs) (NH4)3[PW12O40] and its mono-transition-metal-substituted species (NH4)5[{PW11O39}MII(H2O)] (M = Mn, Fe, Co, Ni, Cu, Zn) have been synthesized and used as photocatalyst to activate O2 for the degradation of dye molecule under visible-light irradiation. Because of the strong adsorption on the surface of POM catalyst, malachite green (MG) molecule was employed as a molecular probe to test their photocatalytic activity. The photodegradation study shows that introduction of transition metal ion leads to an increase in the degradation of MG in the following order: Mn < Fe < Co < [PW12O40]3- < Ni < Cu < Zn, which indicates that the photocatalytic activity of these POMs is sensitive to the transition metal substituted effects. Electronic structure analysis based on the density functional theory calculations shows that a moderate decrease of oxidizing ability of POM catalyst may improve the photocatalytic activity in the degradation of dye molecule under visible-light irradiation. Meanwhile, intermediate products about the photocatalytic oxidation of MG molecule were proposed on the basis of gas chromatograph mass spectrometer analysis.

  5. In-Situ Generated Graphene as the Catalytic Site for Visible-Light Mediated Ethylene Epoxidation on AG Nanocatalysts

    Science.gov (United States)

    Zhang, Xueqiang Alex; Jain, Prashant

    2017-06-01

    Despite the harsh conditions for chemical conversion, ethylene oxide produced from ethylene epoxidation on Ag-based heterogeneous catalyst constitutes one of the largest volume chemicals in chemical industry. Recently, photocatalytic epoxidation of ethylene over plasmonic Ag nanoparticles enables the chemical conversion under significantly decreased temperature and ambient pressure conditions. Yet a detailed understanding of the photocatalytic process at the reactant/catalyst interface is under debate. Surface enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique that enables the localized detection of rare and/or transient chemical species with high sensitivity under in situ and ambient conditions. Using SERS, we are able to monitor at individual sites of an Ag nanocatalyst the visible-light-mediated adsorption and epoxidation of ethylene. From detected intermediates, we find that the primary step in the photoepoxidation is the transient formation of graphene catalyzed by the Ag surface. Density functional theory (DFT) simulations that model the observed SERS spectra suggest that the defective edge sites of the graphene formed on Ag constitute the active site for C2H4 adsorption and epoxidation. Further studies with pre-formed graphene/Ag catalyst composites confirm the indispensable role of graphene in visible-light-mediated ethylene epoxidation. Carbon is often thought to be either an innocent support or a poison for metallic catalysts; however our studies reveal a surprising role for crystalline carbon layers as potential co-catalysts.

  6. Self-assembly based plasmonic arrays tuned by atomic layer deposition for extreme visible light absorption.

    Science.gov (United States)

    Hägglund, Carl; Zeltzer, Gabriel; Ruiz, Ricardo; Thomann, Isabell; Lee, Han-Bo-Ram; Brongersma, Mark L; Bent, Stacey F

    2013-07-10

    Achieving complete absorption of visible light with a minimal amount of material is highly desirable for many applications, including solar energy conversion to fuel and electricity, where benefits in conversion efficiency and economy can be obtained. On a fundamental level, it is of great interest to explore whether the ultimate limits in light absorption per unit volume can be achieved by capitalizing on the advances in metamaterial science and nanosynthesis. Here, we combine block copolymer lithography and atomic layer deposition to tune the effective optical properties of a plasmonic array at the atomic scale. Critical coupling to the resulting nanocomposite layer is accomplished through guidance by a simple analytical model and measurements by spectroscopic ellipsometry. Thereby, a maximized absorption of light exceeding 99% is accomplished, of which up to about 93% occurs in a volume-equivalent thickness of gold of only 1.6 nm. This corresponds to a record effective absorption coefficient of 1.7 × 10(7) cm(-1) in the visible region, far exceeding those of solid metals, graphene, dye monolayers, and thin film solar cell materials. It is more than a factor of 2 higher than that previously obtained using a critically coupled dye J-aggregate, with a peak width exceeding the latter by 1 order of magnitude. These results thereby substantially push the limits for light harvesting in ultrathin, nanoengineered systems.

  7. Bactericidal performance of visible-light responsive titania photocatalyst with silver nanostructures.

    Directory of Open Access Journals (Sweden)

    Ming-Show Wong

    Full Text Available BACKGROUND: Titania dioxide (TiO(2 photocatalyst is primarily induced by ultraviolet light irradiation. Visible-light responsive anion-doped TiO(2 photocatalysts contain higher quantum efficiency under sunlight and can be used safely in indoor settings without exposing to biohazardous ultraviolet light. The antibacterial efficiency, however, remains to be further improved. METHODOLOGY/PRINCIPAL FINDINGS: Using thermal reduction method, here we synthesized silver-nanostructures coated TiO(2 thin films that contain a high visible-light responsive antibacterial property. Among our tested titania substrates including TiO(2, carbon-doped TiO(2 [TiO(2 (C] and nitrogen-doped TiO(2 [TiO(2 (N], TiO(2 (N showed the best performance after silver coating. The synergistic antibacterial effect results approximately 5 log reductions of surviving bacteria of Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus and Acinetobacter baumannii. Scanning electron microscope analysis indicated that crystalline silver formed unique wire-like nanostructures on TiO(2 (N substrates, while formed relatively straight and thicker rod-shaped precipitates on the other two titania materials. CONCLUSION/SIGNIFICANCE: Our results suggested that proper forms of silver on various titania materials could further influence the bactericidal property.

  8. Facile synthesis of carbon-ZnO nanocomposite with enhanced visible light photocatalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Akir, Sana [Univ. Lille, CNRS, Centrale Lille, ISEN, Univ. Valenciennes, UMR 8520 − IEMN, F-59000, Centrale Lille (France); Laboratoire de Physique des Matériaux Lamellaires et Nano-Matériaux Hybrides, Faculté des Sciences de Bizerte, Université de Carthage, 7021, Bizerte (Tunisia); Laboratoire de Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National des Recherches en Sciences des Matériaux, Technopôle de Bordj Cedria, BP73, 8027, Soliman (Tunisia); Hamdi, Abderrahmane [Univ. Lille, CNRS, Centrale Lille, ISEN, Univ. Valenciennes, UMR 8520 − IEMN, F-59000, Centrale Lille (France); Laboratoire de Physique des Matériaux Lamellaires et Nano-Matériaux Hybrides, Faculté des Sciences de Bizerte, Université de Carthage, 7021, Bizerte (Tunisia); Laboratory of Semi-conductors, Nano-structures and Advanced Technologies, Research and Technology Centre of Energy, Borj-Cedria Science and Technology Park, BP 95, 2050, Hammam-Lif (Tunisia); Addad, Ahmed [UMET, UMR CNRS 8207, Université Lille 1, 59655 Villeneuve d' Ascq Cédex (France); Coffinier, Yannick [Univ. Lille, CNRS, Centrale Lille, ISEN, Univ. Valenciennes, UMR 8520 − IEMN, F-59000, Centrale Lille (France); Boukherroub, Rabah, E-mail: rabah.boukherroub@iemn.univ-lille1.fr [Univ. Lille, CNRS, Centrale Lille, ISEN, Univ. Valenciennes, UMR 8520 − IEMN, F-59000, Centrale Lille (France); and others

    2017-04-01

    Highlights: • C-ZnO nanocomposite was successfully prepared via a facile and eco-friendly process. • C-ZnO NPs have excellent photocatalytic activity for RhB dye degradation under visible light irradiation compared with literature. • The visible photocatalytic properties originate from injection e{sup −} in CB of ZnO from RhB. - Abstract: The present study describes a facile route for synthesis of carbon-ZnO nanocomposites (C-ZnO) via hydrothermal process in presence of glucose as carbon precursor. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) measurements. The results showed carbon uniformly coated on the surface of the ZnO nanoparticles to form the C-ZnO nanocomposites. Further investigation revealed that carbon could significantly protect ZnO NPs against the coalescence during high temperature treatment. The obtained C-ZnO nanocomposite showed excellent photocatalytic activity for the degradation of rhodamine B (RhB) under visible light irradiation, which was attributed to the repressed charge carrier recombination in the nanocomposite. Quenching experiments and photocurrent measurements revealed a photocatalytic mechanism occurring through photosensitization.

  9. Novel GQD-PVP-CdS composite with enhanced visible-light-driven photocatalytic properties

    International Nuclear Information System (INIS)

    Fan, Tao; Li, Yinle; Shen, Jianfeng; Ye, Mingxin

    2016-01-01

    Graphical abstract: - Highlights: • GQD-PVP-CdS composite was prepared for the first time through a facile hydrothermal route. • GQD-PVP-CdS demonstrated outstanding photoactivity under visible light illumination. • GQDs and polymeric material are compounded with CdS nanoparticles simultaneously for the first time. • The addition of GQDs plays pivotal roles in the enhancement of the photoactivity. - Abstract: A facile one-step hydrothermal method to synthesize graphene quantum dots (GQDs)-polyvinyl pyrrolidone (PVP)-CdS nanocomposite was reported. The nanocomposite was thoroughly characterized with X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and ultraviolet–visible spectroscopy. The results confirmed the formation of GQD-PVP-CdS composite with a uniform size (5–10 nm) and a relatively low band gap (E_g = 2.23 eV). Moreover, the as-prepared composite exhibited enhanced photocatalytic activity toward the degradation of organic contaminants, with 92.3% of methyl orange (10 mg/L) removed after 3 hours of visible light illumination. This enhancement in photocatalytic activity was postulated to be attributed to the upconversion property of GQDs and a more efficient charge distribution between GQDs and CdS particles.

  10. Visible light active TiO2 films prepared by electron beam deposition of noble metals

    International Nuclear Information System (INIS)

    Hou Xinggang; Ma Jun; Liu Andong; Li Dejun; Huang Meidong; Deng Xiangyun

    2010-01-01

    TiO 2 films prepared by sol-gel method were modified by electron beam deposition of noble metals (Pt, Pd, and Ag). Effects of noble metals on the chemical and surface characteristics of the films were studied using XPS, TEM and UV-Vis spectroscopy techniques. Photocatalytic activity of modified TiO 2 films was evaluated by studying the degradation of methyl orange dye solution under visible light UV irradiation. The result of TEM reveals that most of the surface area of TiO 2 is covered by tiny particles of noble metals with diameter less than 1 nm. Broad red shift of UV-Visible absorption band of modified photocatalysts was observed. The catalytic degradation of methyl orange in aqueous solutions under visible light illumination demonstrates a significant enhancement of photocatalytic activity of these films compared with the un-loaded films. The photocatalytic efficiency of modified TiO 2 films by this method is affected by the concentration of impregnating solution.

  11. Microwave-assisted synthesis of bismuth oxybromochloride nanoflakes for visible light photodegradation of pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Bijanzad, Keyvan; Tadjarodi, Azadeh; Moghaddasi Khiavi, Mohammad [Research Laboratory of Inorganic Materials Synthesis, Department of Chemistry, Iran University of Science and Technology, Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); Akhavan, Omid, E-mail: oakhavan@sharif.ir [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of)

    2015-10-15

    BiOBr{sub x}Cl{sub 1−x} (0visible diffuse reflectance and photoluminescence (PL) spectroscopies revealed the indirect band gap of ~2.82 eV for the bismuth oxybromochloride nanoflakes. Visible light-assisted photocatalytic studies showed that the degradation efficiency of the as-prepared BiOBr{sub x}Cl{sub 1−x} for (100 mL of 10 mg L{sup −1}) Rhodamine B (RhB), Natural Red 4 (N-Red) dye solutions was 98.14% and for the colorless organic pentachlorophenol (PCP) solution was 91.09% over 150 min. The possible mechanisms involved in the visible light photodegradation of the pollutants by BiOBr{sub x}Cl{sub 1−x} photocatalyst were also discussed.

  12. Doping effect on monolayer MoS2 for visible light dye degradation - A DFT study

    Science.gov (United States)

    Cheriyan, Silpa; Balamurgan, D.; Sriram, S.

    2018-04-01

    The electronic and optical properties of, Nitrogen (N), Cobalt (Co), and Co-N co-doped monolayers of MoS2 has been studied by using density functional theory (DFT) for visible light photocatalytic activity. From the calculations, it has been observed that the band gap of monolayer MoS2 has been reduced while doping. However, the band gaps of pristine and N doped MoS2 monolayers only falls in the visible region while for Co and Co-N co-doped systems, the band gap shifted to IR region. The optical calculation also confirms the results. The formation energy values of the doped system reaveal that MoS2 monolayer drops its stability while doping. To evaluate the photocatalytic response, band edge potentials of pristine and N-MoS2 are calculated, and the observed results show that compared to N-doped MoS2 monolayer, pure MoS2 is highly suitable for visible light photocatalytic dye degradation.

  13. Sulfonated graphene oxide-ZnO-Ag photocatalyst for fast photodegradation and disinfection under visible light.

    Science.gov (United States)

    Gao, Peng; Ng, Kokseng; Sun, Darren Delai

    2013-11-15

    Synthesis of efficient visible-light-driven photocatalyst is urgent but challenging for environmental remediation. In this work, for the first time, the hierarchical plasmonic sulfonated graphene oxide-ZnO-Ag (SGO-ZnO-Ag) composites were prepared through nanocrystal-seed-directed hydrothermal method combining with polyol-reduction process. The results indicated that SGO-ZnO-Ag exhibited much faster rate in photodegradation of Rhodamine B (RhB) and disinfection of Escherichia coli (E. coli), than ZnO, SGO-ZnO and ZnO-Ag. SGO-ZnO-Ag totally degraded RhB dye and kill 99% of E. coli within 20 min under visible light irradiation. The outstanding performances of SGO-ZnO-Ag were attributed to the synergetic merits of SGO sheets, ZnO nanorod arrays and Ag nanoparticles. Firstly, the light absorption ability of SGO-ZnO-Ag composite in the visible region was enhanced due to the surface plasmon resonance of Ag. In addition, the hierarchical structure of SGO-ZnO-Ag composite improved the incident light scattering and reflection. Furthermore, SGO sheets facilitated charge transfer and reduce electron-hole recombination rate. Finally, the tentative mechanism was proposed and verified by the photoluminescence (PL) measurement as well as the theoretical finite-difference time-domain (FDTD) simulation. In view of above, this work paves the way for preparation of multi-component plasmonic composites and highlights the potential applications of SGO-ZnO-Ag in photocatalytic wastewater treatment field. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

  14. On different photodecomposition behaviors of rhodamine B on laponite and montmorillonite clay under visible light irradiation

    KAUST Repository

    Wang, Peng

    2013-12-11

    In this study, laponite and montmorillonite clays were found to be able to decompose rhodamine B upon visible light irradiation (λ>420nm). Very interestingly, it was found that rhodamine B on laponite underwent a stepwise N-deethylation and its decomposition was terminated once rhodamine 110, as a decomposition product, was formed, whereas the same phenomenon was not observed for rhodamine B on montmorillonite, whose decomposition involved chromophore destruction. Mechanistic study revealed that the different photodecomposition behaviors of rhodamine B on laponite and montmorillonite were attributed to the oxidation by different reactive oxygen species, with laponite involving HO2/O2- while montmorillonite involving OH. It was also found that the degradation pathway of rhodamine B on laponite switched from N-deethylation to chromophore destruction when solution pH was changed from 7.0 to 3.0, which was attributed to a much higher fraction of HO2 relative to O2- under pH 3.0 than under pH 7.0. Based on the results, a mechanism of rhodamine dye decomposition on clay under visible light was proposed, involving the clay as an electron acceptor, electron relay between the adsorbed dye molecules and oxygen molecules, and subsequent reactions between the generated dye radical cations and different reactive oxygen species. The results of this study shed light on how to best utilize visible light for organic pollutant degradation on clays within engineered treatment systems as well as on many of naturally occurring pollutant degradation processes in soils and air involving clay. © 2013 King Saud University.

  15. A novel mirror diversity receiver for indoor MIMO visible light communication systems

    KAUST Repository

    Park, Kihong

    2016-12-24

    In this paper, we propose and study a non-imaging receiver design reducing the correlation of channel matrix for indoor multiple-input multiple-output (MIMO) visible light communication (VLC) systems. Contrary to previous works, our proposed mirror diversity receiver (MDR) not only blocks the reception of light on one specific direction but also improves the channel gain on the other direction by receiving the light reflected by a mirror deployed between the photodetectors. We analyze the channel capacity and optimal height of mirror in terms of maximum channel capacity for a 2 × 2 MIMO-VLC system in a 2-dimensional geometric model. We prove that this constructive and destructive effects in channel matrix resulting from our proposed MDR are more beneficial to obtain well-conditioned channel matrix which is suitable for implementing spatial-multiplexing MIMO-VLC systems in order to support high data rate.

  16. Fabrication of multilayered conductive polymer structures via selective visible light photopolymerization

    Science.gov (United States)

    Cullen, Andrew T.; Price, Aaron D.

    2017-04-01

    Electropolymerization of pyrrole is commonly employed to fabricate intrinsically conductive polymer films that exhibit desirable electromechanical properties. Due to their monolithic nature, electroactive polypyrrole films produced via this process are typically limited to simple linear or bending actuation modes, which has hindered their application in complex actuation tasks. This initiative aims to develop the specialized fabrication methods and polymer formulations required to realize three-dimensional conductive polymer structures capable of more elaborate actuation modes. Our group has previously reported the application of the digital light processing additive manufacturing process for the fabrication of three-dimensional conductive polymer structures using ultraviolet radiation. In this investigation, we further expand upon this initial work and present an improved polymer formulation designed for digital light processing additive manufacturing using visible light. This technology enables the design of novel electroactive polymer sensors and actuators with enhanced capabilities and brings us one step closer to realizing more advanced electroactive polymer enabled devices.

  17. Efficient Visible Light Communication Transmitters Based on Switching-Mode dc-dc Converters

    Science.gov (United States)

    2018-01-01

    Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting diodes (LEDs) enable. The switching-mode dc-to-dc converter (SMCdc-dc) must be the cornerstone of the LED driver of VLC transmitters in order to incorporate the communication functionality into LED lighting, keeping high power efficiency. However, the new requirements related to the communication, especially the high bandwidth that the LED driver must achieve, converts the design of the SMCdc-dc into a very challenging task. In this work, three different methods for achieving such a high bandwidth with an SMCdc-dc are presented: increasing the order of the SMCdc-dc output filter, increasing the number of voltage inputs, and increasing the number of phases. These three strategies are combinable and the optimum design depends on the particular VLC application, which determines the requirements of the VLC transmitter. As an example, an experimental VLC transmitter based on a two-phase buck converter with a fourth-order output filter will demonstrate that a bandwidth of several hundred kilohertz (kHz) can be achieved with output power levels close to 10 W and power efficiencies between 85% and 90%. In conclusion, the design strategy presented allows us to incorporate VLC into SSL, achieving high bit rates without damaging the power efficiency of LED lighting. PMID:29642455

  18. Printable photonic crystals with high refractive index for applications in visible light

    International Nuclear Information System (INIS)

    Calafiore, Giuseppe; Mejia, Camilo A; Munechika, Keiko; Peroz, Christophe; Piña-Hernandez, Carlos; Fillot, Quentin; Dhuey, Scott; Sassolini, Simone; Salvadori, Filippo; Cabrini, Stefano

    2016-01-01

    Nanoimprint lithography (NIL) of functional high-refractive index materials has proved to be a powerful candidate for the inexpensive manufacturing of high-resolution photonic devices. In this paper, we demonstrate the fabrication of printable photonic crystals (PhCs) with high refractive index working in the visible wavelengths. The PhCs are replicated on a titanium dioxide-based high-refractive index hybrid material by reverse NIL with almost zero shrinkage and high-fidelity reproducibility between mold and printed devices. The optical responses of the imprinted PhCs compare very well with those fabricated by conventional nanofabrication methods. This study opens the road for a low-cost manufacturing of PhCs and other nanophotonic devices for applications in visible light. (paper)

  19. Fabrication of Micrometer- and Nanometer-Scale Polymer Structures by Visible Light Induced Dielectrophoresis (DEP Force

    Directory of Open Access Journals (Sweden)

    Wen J. Li

    2011-12-01

    Full Text Available We report in this paper a novel, inexpensive and flexible method for fabricating micrometer- and nanometer-scale three-dimensional (3D polymer structures using visible light sources instead of ultra-violet (UV light sources or lasers. This method also does not require the conventional micro-photolithographic technique (i.e., photolithographic masks for patterning and fabricating polymer structures such as hydrogels. The major materials and methods required for this novel fabrication technology are: (1 any cross-linked network of photoactive polymers (examples of fabricated poly(ethylene glycol (PEG-diacrylate hydrogel structures are shown in this paper; (2 an Optically-induced Dielectrophoresis (ODEP System which includes an “ODEP chip” (i.e., any chip that changes its surface conductivity when exposed to visible light, an optical microscope, a projector, and a computer; and (3 an animator software hosted on a computer that can generate virtual or dynamic patterns which can be projected onto the “ODEP chip” through the use of a projector and a condenser lens. Essentially, by placing a photosensitive polymer solution inside the microfluidic platform formed by the “ODEP chip” bonded to another substrate, and applying an alternating current (a.c. electrical potential across the polymer solution (typically ~20 Vp-p at 10 kHz, solid polymer micro/nano structures can then be formed on the “ODEP chip” surface when visible-light is projected onto the chip. The 2D lateral geometry (x and y dimensions and the thickness (height of the micro/nano structures are dictated by the image geometry of the visible light projected onto the “ODEP chip” and also the time duration of projection. Typically, after an image projection with intensity ranging from ~0.2 to 0.4 mW/cm2 for 10 s, ~200 nm high structures can be formed. In our current system, the thickness of these polymer structures can be controlled to form from ~200 nanometers to ~3

  20. Micro-light-emitting-diode array with dual functions of visible light communication and illumination

    International Nuclear Information System (INIS)

    Huang Yong; Guo Zhi-You; Sun Hui-Qing; Huang Hong-Yong

    2017-01-01

    We demonstrate high-speed blue 4 × 4 micro-light-emitting-diode (LED) arrays with 14 light-emitting units (two light-emitting units are used as the positive and negative electrodes for power supply, respectively) comprising multiple quantum wells formed of GaN epitaxial layers grown on a sapphire substrate, and experimentally test their applicability for being used as VLC transmitters and illuminations. The micro-LED arrays provide a maximum −3-dB frequency response of 60.5 MHz with a smooth frequency curve from 1 MHz to 500 MHz for an optical output power of 165 mW at an injection current of 30 mA, which, to our knowledge, is the highest response frequency ever reported for blue GaN-based LEDs operating at that level of optical output power. The relationship between the frequency and size of the device single pixel diameter reveals the relationship between the response frequency and diffusion capacitance of the device. (paper)

  1. Electronic structure and visible light photocatalysis water splitting property of chromium-doped SrTiO3

    International Nuclear Information System (INIS)

    Liu, J.W.; Chen, G.; Li, Z.H.; Zhang, Z.G.

    2006-01-01

    Cr-doped SrTi 1- x Cr x O 3 (x=0.00, 0.02, 0.05, 0.10) powders, prepared by solvothermal method, were further characterized by ultraviolet-visible (UV-vis) absorption spectroscopy. The UV-vis spectra indicate that the SrTi 1- x Cr x O 3 powders can absorb not only UV light like pure SrTiO 3 powder but also the visible-light spectrum (λ>420 nm). The results of density functional theory (DFT) calculation illuminate that the visible-light absorption bands in the SrTi 1- x Cr x O 3 catalyst are attributed to the band transition from the Cr 3d to the Cr 3d+Ti 3d hybrid orbital. The photocatalytic activities of chromium-doped SrTiO 3 both under UV and visible light are increased with the increase in the amounts of chromium. -- Graphical abstract: SrTi 1- x Cr x O 3 powders, prepared by solvothermal method, can absorb not only UV light like pure SrTiO 3 powder but also the visible-light spectrum (λ>420 nm). The results of DFT calculation illuminate that the visible-light absorption bands in the SrTi 1- x Cr x O 3 catalyst are attributed to the band transition from the Cr 3d to the Cr 3d+Ti 3d hybrid orbital

  2. A cooperative positioning with Kalman filters and handover mechanism for indoor microcellular visible light communication network

    Science.gov (United States)

    Xiong, Jieqing; Huang, Zhitong; Zhuang, Kaiyu; Ji, Yuefeng

    2016-08-01

    We propose a novel handover scheme for indoor microcellular visible light communication (VLC) network. With such a scheme, the room, which is fully coverage by light, is divided into several microcells according to the layout of light-emitting diodes (LEDs). However, the directionality of light arises new challenges in keeping the connectivity between the mobile devices and light source under the mobile circumstances. The simplest solution is that all LEDs broadcast data of every user simultaneously, but it wastes too much bandwidth resource, especially when the amount of users increases. To solve this key problem, we utilize the optical positioning assisting handover procedure in this paper. In the positioning stage, the network manager obtains the location information of user device via downlink and uplink signal strength information, which is white light and infrared, respectively. After that, a Kalman filter is utilized for improving the tracking performance of a mobile device. Then, the network manager decides how to initiate the handover process by the previous information. Results show that the proposed scheme can achieve low-cost, seamless data communication, and a high probability of successful handover.

  3. Double-doped TiO{sub 2} nanoparticles as an efficient visible-light-active photocatalyst and antibacterial agent under solar simulated light

    Energy Technology Data Exchange (ETDEWEB)

    Ashkarran, Ali Akbar, E-mail: ashkarran@umz.ac.ir [Department of Physics, Faculty of Basic Sciences, University of Mazandaran, Babolsar (Iran, Islamic Republic of); Hamidinezhad, Habib [Nano and Biotechnology Research Group, Faculty of Basic Sciences, University of Mazandaran, Babolsar (Iran, Islamic Republic of); Haddadi, Hedayat [Department of Chemistry, Faculty of Sciences, Shahrekord University, P.O. Box 115, Shahrekord (Iran, Islamic Republic of); Mahmoudi, Morteza [Department of Nanotechnology, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Nanotechnology Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of)

    2014-05-01

    Graphical abstract: Double doping introduces two different electronic states in the band gap of TiO{sub 2}, which increase the lifetime of the charge carriers and leads to narrower band gap and enhancement of the visible-light absorption. - Highlights: • Preparation of single and double doped TiO{sub 2} NPs using a simple sol–gel route. • Extension of light absorption spectrum toward the visible region. • Enhanced visible-light photo-induced activity and antibacterial property in double doped TiO{sub 2} NPs. - Abstract: Silver and nitrogen doped TiO{sub 2} nanoparticles (NPs) were synthesized via sol–gel method. The physicochemical properties of the achieved NPs were characterized by various methods including X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultra violet–visible absorption spectroscopy (UV–vis). Both visible-light photocatalytic activity and antimicrobial properties were successfully demonstrated for the degradation of Rhodamine B (Rh. B.), as a model dye, and inactivation of Escherichia coli (E. coli), as a representative of microorganisms. The concentration of the employed dopant was optimized and the results revealed that the silver and nitrogen doped TiO{sub 2} NPs extended the light absorption spectrum toward the visible region and significantly enhanced the photodegradation of model dye and inactivation of bacteria under visible-light irradiation while double-doped TiO{sub 2} NPs exhibited highest photocatalytic and antibacterial activity compared with single doping. The significant enhancement in the photocatalytic activity and antibacterial properties of the double doped TiO{sub 2} NPs, under visible-light irradiation, can be attributed to the generation of two different electronic states acting as electron traps in TiO{sub 2} and responsible for narrowing the band gap of TiO{sub 2} and shifting its optical response from UV to the

  4. Polymer dots grafted TiO2 nanohybrids as high performance visible light photocatalysts.

    Science.gov (United States)

    Li, Gen; Wang, Feng; Liu, Peng; Chen, Zheming; Lei, Ping; Xu, Zhongshan; Li, Zengxi; Ding, Yanfen; Zhang, Shimin; Yang, Mingshu

    2018-04-01

    As a new member of carbon dots (CDs), Polymer dots (PDs) prepared by hydrothermal treatment of polymers, usually consist of the carbon core and the connected partially degraded polymer chains. This type of CDs might possess aqueous solubility, non-toxicity, excellent stability against photo-bleaching and high visible light activity. In this research, PDs were prepared by a moderate hydrothermal treatment of polyvinyl alcohol, and PDs grafted TiO 2 (PDs-TiO 2 ) nanohybrids with TiOC bonds were prepared by a facile in-situ hydrothermal treatment of PDs and Ti (SO 4 ) 2 . Under visible light irradiation, the PDs-TiO 2 demonstrate excellent photocatalytic activity for methyl orange degradation, and the photocatalytic rate constant of PDs-TiO 2 is 3.6 and 9.5 times higher than that of pure TiO 2 and commercial P25, respectively. In addition, the PDs-TiO 2 exhibit good recycle stability under UV-Vis light irradiation. The interfacial TiOC bonds and the π-conjugated structures in PDs-TiO 2 can act as the pathways to quickly transfer the excited electrons between PDs and TiO 2 , therefore contribute to the excellent photocatalytic activity. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. INTERFACING VISIBLE LIGHT COMMUNICATION WITH GSM NETWORKS TO PREVENT THE THEFT OF THE VEHICLE

    Directory of Open Access Journals (Sweden)

    P. Prabu

    2015-09-01

    Full Text Available Visible Light Communication (VLC by means of white Light Emitting Diode (LED is an alternate and most promising technology for existing Radio Frequency (RF communication. We proposed one of the important applications of VLC to prevent the theft of the vehicle. Every year approximately 36,000 vehicles worth Rs.115 crores are stolen in India. In critical road condition, only 15,000 are traced and many spare parts of vehicle are found missing. Even the existing technologies have some disadvantages related to the problem stated. In our paper, we dealt with the data communication through LED. One of the optical wireless communication having short range is called as VLC whose visible light spectrum starts from 380 nm and ends at 780 nm and it has an incomparable data rate of 10GB/s whereas the speed is 1MB/s on Bluetooth and for Infra Red (IR the speed is 4MB/s. We try to achieve the communication through VLC between 1 car - car to prevent the accident and 2 car - tollgate and received signal from tollgate is transmitted to Global System for Mobile communication (GSM network using microcontroller to prevent the theft of vehicle. To enhance the security of VLC, Advanced Encryption Standard (AES algorithm is used and the result is illustrated with the help of LabVIEW.

  6. Visible Light Induced Green Transformation of Primary Amines to Imines Using a Silicate Supported Anatase Photocatalyst

    Directory of Open Access Journals (Sweden)

    Sifani Zavahir

    2015-01-01

    Full Text Available Catalytic oxidation of amine to imine is of intense present interest since imines are important intermediates for the synthesis of fine chemicals, pharmaceuticals, and agricultural chemicals. However, considerable efforts have been made to develop efficient methods for the oxidation of secondary amines to imines, while little attention has until recently been given to the oxidation of primary amines, presumably owing to the high reactivity of generated imines of primary amines that are easily dehydrogenated to nitriles. Herein, we report the oxidative coupling of a series of primary benzylic amines into corresponding imines with dioxygen as the benign oxidant over composite catalysts of TiO2 (anatase-silicate under visible light irradiation of λ > 460 nm. Visible light response of this system is believed to be as a result of high population of defects and contacts between silicate and anatase crystals in the composite and the strong interaction between benzylic amine and the catalyst. It is found that tuning the intensity and wavelength of the light irradiation and the reaction temperature can remarkably enhance the reaction activity. Water can also act as a green medium for the reaction with an excellent selectivity. This report contributes to the use of readily synthesized, environmentally benign, TiO2 based composite photocatalyst and solar energy to realize the transformation of primary amines to imine compounds.

  7. Visible light induced green transformation of primary amines to imines using a silicate supported anatase photocatalyst.

    Science.gov (United States)

    Zavahir, Sifani; Zhu, Huaiyong

    2015-01-26

    Catalytic oxidation of amine to imine is of intense present interest since imines are important intermediates for the synthesis of fine chemicals, pharmaceuticals, and agricultural chemicals. However, considerable efforts have been made to develop efficient methods for the oxidation of secondary amines to imines, while little attention has until recently been given to the oxidation of primary amines, presumably owing to the high reactivity of generated imines of primary amines that are easily dehydrogenated to nitriles. Herein, we report the oxidative coupling of a series of primary benzylic amines into corresponding imines with dioxygen as the benign oxidant over composite catalysts of TiO2 (anatase)-silicate under visible light irradiation of λ > 460 nm. Visible light response of this system is believed to be as a result of high population of defects and contacts between silicate and anatase crystals in the composite and the strong interaction between benzylic amine and the catalyst. It is found that tuning the intensity and wavelength of the light irradiation and the reaction temperature can remarkably enhance the reaction activity. Water can also act as a green medium for the reaction with an excellent selectivity. This report contributes to the use of readily synthesized, environmentally benign, TiO2 based composite photocatalyst and solar energy to realize the transformation of primary amines to imine compounds.

  8. The susceptibility of the retina to photochemical damage from visible light

    Science.gov (United States)

    Hunter, Jennifer J; Morgan, Jessica I W; Merigan, William H; Sliney, David H; Sparrow, Janet R; Williams, David R

    2011-01-01

    The photoreceptor/RPE complex must maintain a delicate balance between maximizing the absorption of photons for vision and retinal image quality while simultaneously minimizing the risk of photodamage when exposed to bright light. We review the recent discovery of two new effects of light exposure on the photoreceptor/RPE complex in the context of current thinking about the causes of retinal phototoxicity. These effects are autofluorescence photobleaching in which exposure to bright light reduces lipofuscin autofluorescence and, at higher light levels, RPE disruption in which the pattern of autofluorescence is permanently altered following light exposure. Both effects occur following exposure to visible light at irradiances that were previously thought to be safe. Photopigment, retinoids involved in the visual cycle, and bisretinoids in lipofuscin have been implicated as possible photosensitizers for photochemical damage. The mechanism of RPE disruption may follow either of these paths. On the other hand, autofluorescence photobleaching is likely an indicator of photooxidation of lipofuscin. The permanent changes inherent in RPE disruption might require modification of the light safety standards. AF photobleaching recovers after several hours although the mechanisms by which this occurs are not yet clear. Understanding the mechanisms of phototoxicity is all the more important given the potential for increased susceptibility in the presence of ocular diseases that affect either the visual cycle and/or lipofuscin accumulation. In addition, knowledge of photochemical mechanisms can improve our understanding of some disease processes that may be influenced by light exposure, such as some forms of Leber’s congenital amaurosis, and aid in the development of new therapies. Such treatment prior to intentional light exposures, as in ophthalmic examinations or surgeries, could provide an effective preventative strategy. PMID:22085795

  9. III-nitride Photonic Integrated Circuit: Multi-section GaN Laser Diodes for Smart Lighting and Visible Light Communication

    KAUST Repository

    Shen, Chao

    2017-01-01

    The past decade witnessed the rapid development of III-nitride light-emitting diodes (LEDs) and laser diodes (LDs), for smart lighting, visible-light communication (VLC), optical storage, and internet-of-things. Recent studies suggested that the Ga

  10. Two dimensional visible-light-active Pt-BiOI photoelectrocatalyst for efficient ethanol oxidation reaction in alkaline media

    Science.gov (United States)

    Zhai, Chunyang; Hu, Jiayue; Sun, Mingjuan; Zhu, Mingshan

    2018-02-01

    Two dimensional (2D) BiOI nanoplates were synthesized and used as support for the deposition of Pt nanoparticles. Owing to broad visible light absorption (up to 660 nm), the as-obtained Pt-BiOI electrode was used as effective photoelectrocatalyst in the application of catalytic ethanol oxidation in alkaline media under visible light irradiation. Compared to dark condition, the Pt-BiOI modified electrode displayed 3 times improved catalytic activity towards ethanol oxidation under visible light irradiation. The synergistic effect of electrocatalytic and photocatalytic, and the unique of 2D structures contribute to the improvement of catalytic activity. The mechanism of enhanced photoelectrocatalytic process is proposed. The present results suggest that 2D visible-light-activated BiOI can be served as promising support for the decoration of Pt and applied in the fields of photoelectrochemical and photo-assisted fuel cell applications

  11. The Inherent Visible Light Signature of an Intense Underwater Ultraviolet Light Source Due to Combined Raman and Fluorescence Effects

    Science.gov (United States)

    2000-01-01

    Humans cannot see ultraviolet light. The blue-sensitive cones in the retina would respond weakly to ultraviolet wavelengths if exposed to them, but...545, 1992. 3. C. S. Yentsch, and D. A. Phinney, " Autofluorescence and Raman scattering in the marine underwater environment," Ocean Optics X, SPIE

  12. Chromate enhanced visible light driven TiO2 photocatalytic mechanism on Acid Orange 7 photodegradation

    International Nuclear Information System (INIS)

    Wang, Yeoung-Sheng; Shen, Jyun-Hong; Horng, Jao-Jia

    2014-01-01

    Highlights: • Photocatalysis of Cr(VI) and TiO 2 were studied by ESR analysis on DMPO-OH signals. • Mechanism of Cr(VI)-enhanced by visible light was different from that by UV. • O 2 adsorbed on TiO 2 surfaces could react with Cr(VI) to lower photoenergy needed. • Even by UV, no TiO 2 photocatalysis was observed without O 2 solution. • Visible light and Cr(VI) redox reaction could activate TiO 2 and would yield ·OH. - Abstract: When hexavalent chromium (Cr(VI)) is added to a TiO 2 photocatalytic reaction, the decolorization and mineralization efficiencies of azo dyes Acid Orange 7 (AO7) are enhanced even though the mechanism is unclear. This study used 5,5-dimethyl-L-pyrroline-N-oxide (DMPO) as the scavenger and the analysis of Electron Spin Resonance (ESR) to investigate this enhancement effect by observing the hydroxyl radical (·OH) generation of the Cr(VI)/TiO 2 system under UV and visible light (Vis) irradiation. With Cr(VI), the decolorization efficiencies were approximately 95% and 62% under UV and Vis, and those efficiencies were 25% less in the absence of Cr(VI). The phenomena of the DMPO-OH signals during the ESR analysis under Vis 405 and 550 nm irradiation were obviously the enhancement effects of Cr(VI) in aerobic conditions. In anoxic conditions, the catalytic effects of Cr(VI) could not be achieved due to the lack of a redox reaction between Cr(VI) and the adsorbed oxygen at the oxygen vacancy sites on the TiO 2 surfaces . The results suggest that by introducing the agents of redox reactions such as chromate ions, we could lower the photoenergy of TiO 2 needed and allow Vis irradiation to activate photocatalysis

  13. Photocatalytic hydrogen generation from water under visible light using core/shell nano-catalysts.

    Science.gov (United States)

    Wang, X; Shih, K; Li, X Y

    2010-01-01

    A microemulsion technique was employed to synthesize nano-sized photocatalysts with a core (CdS)/shell (ZnS) structure. The primary particles of the photocatalysts were around 10 nm, and the mean size of the catalyst clusters in water was about 100 nm. The band gaps of the catalysts ranged from 2.25 to 2.46 eV. The experiments of photocatalytic H(2) generation showed that the catalysts (CdS)(x)/(ZnS)(1-x) with x ranging from 0.1 to 1 were able to produce hydrogen from water photolysis under visible light. The catalyst with x=0.9 had the highest rate of hydrogen production. The catalyst loading density also influenced the photo-hydrogen production rate, and the best catalyst concentration in water was 1 g L(-1). The stability of the nano-catalysts in terms of size, morphology and activity was satisfactory during an extended test period for a specific hydrogen production rate of 2.38 mmol g(-1) L(-1) h(-1) and a quantum yield of 16.1% under visible light (165 W Xe lamp, lambda>420 nm). The results demonstrate that the (CdS)/(ZnS) core/shell nano-particles are a novel photo-catalyst for renewable hydrogen generation from water under visible light. This is attributable to the large band-gap ZnS shell that separates the electron/hole pairs generated by the CdS core and hence reduces their recombinations.

  14. Visible-light-induced Ag/BiVO4 semiconductor with enhanced photocatalytic and antibacterial performance

    Science.gov (United States)

    Regmi, Chhabilal; Dhakal, Dipesh; Wohn Lee, Soo

    2018-02-01

    An Ag-loaded BiVO4 visible-light-driven photocatalyst was synthesized by the microwave hydrothermal method followed by photodeposition. The photocatalytic performance of the synthesized samples was evaluated on a mixed dye (methylene blue and rhodamine B), as well as bisphenol A in aqueous solution. Similarly, the disinfection activities of synthesized samples towards the Gram-negative Escherichia coli (E. coli) in a model cell were investigated under irradiation with visible light (λ ≥ 420 nm). The synthesized samples have monoclinic scheelite structure. Photocatalytic results showed that all Ag-loaded BiVO4 samples exhibited greater degradation and a higher mineralization rate than the pure BiVO4, probably due to the presence of surface plasmon absorption that arises due to the loading of Ag on the BiVO4 surface. The optimum Ag loading of 5 wt% has the highest photocatalytic performance and greatest stability with pseudo-first-order rate constants of 0.031 min-1 and 0.023 min-1 for the degradation of methylene blue and rhodamine B respectively in a mixture with an equal volume and concentration of each dye. The photocatalytic degradation of bisphenol A reaches 76.2% with 5 wt% Ag-doped BiVO4 within 180 min irradiation time. Similarly, the Ag-loaded BiVO4 could completely inactivate E. coli cells within 30 min under visible light irradiation. The disruption of the cell membrane as well as degradation of protein and DNA exhibited constituted evidence for antibacterial activity towards E. coli. Moreover, the bactericidal mechanisms involved in the photocatalytic disinfection process were systematically investigated.

  15. Quantum dots/silica/polymer nanocomposite films with high visible light transmission and UV shielding properties.

    Science.gov (United States)

    Mumin, Md Abdul; Xu, William Z; Charpentier, Paul A

    2015-08-07

    The dispersion of light-absorbing inorganic nanomaterials in transparent plastics such as poly(ethylene-co-vinyl acetate) (PEVA) is of enormous current interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Nanocrystalline semiconductor or quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light, which can control plant growth in greenhouses or enhance PV panel efficiencies. This work provides a new and simple approach for loading mesoporous silica-encapsulated QDs into PEVA. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm size were synthesized using a modified facile approach based on pyrolysis of the single-molecule precursors and capping the CdS QDs with a thin layer of ZnS. To make both the bare and core-shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs through a reverse microemulsion technique based on hydrophobic interactions. By careful experimental tuning, this encapsulation technique enhanced the quantum yield (∼65%) and photostability compared to the bare QDs. Both the encapsulated bare and core-shell QDs were then melt-mixed with EVA pellets using a mini twin-screw extruder and pressed into thin films with controlled thickness. The results demonstrated for the first time that mesoporous silica not only enhanced the quantum yield and photostability of the QDs but also improved the compatibility and dispersibility of QDs throughout the PEVA films. The novel light selective films show high visible light transmission (∼90%) and decreased UV transmission (∼75%).

  16. Visible light nitrogen dioxide spectrophotometer intercomparison: Mount Kobau, British Columbia, July 28 to August 10, 1991

    Science.gov (United States)

    Mcelroy, C. T.; Elokhov, A. S.; Elansky, N.; Frank, H.; Johnston, P.; Kerr, J. B.

    1994-01-01

    Under the auspices of the World Meteorological Organization, Environment Canada hosted an international comparison of visible light spectrophotometers at Mt. Kobau, British Columbia in August of 1991. Instruments from four countries were involved. The intercomparison results have indicated that some significant differences exist in the responses of the various instruments, and have provided a basis for the comparison of the historical data sets which currently exist as a result of the independent researches carried out in the past in the former Soviet Union, New Zealand, and Canada.

  17. Preparation of Hierarchical BiOBr Microspheres for Visible Light-Induced Photocatalytic Detoxification and Disinfection

    Directory of Open Access Journals (Sweden)

    Ayla Ahmad

    2016-01-01

    Full Text Available Photocatalytic degradation is a promising alternative to traditional wastewater treatment methods. Recently developed visible light-responsive photocatalyst, BiOBr, has attracted extensive attentions. Hereby, a detailed investigation of application of BiOBr to bacterial inactivation and organic pollutants degradation is reported. Hydrothermal catalyst was prepared using template-free method. While, for solvothermal synthesis, CTAB was used as a template. Results indicate a higher photocatalytic activity by the solvothermally prepared catalyst. Solvothermally prepared BiOBr exhibited high photocatalytic activities in both water detoxification and disinfection.

  18. Research Progress on Visible-light Responding ZnO-based Nanocomposite Photocatalyst

    Directory of Open Access Journals (Sweden)

    ZHAO Yan-ru

    2017-06-01

    Full Text Available In this review, different types and properties, photocatalysis and functional mechanism of ZnO-based nanocomposite were summarized. Besides, the research advances were discussed in applications of visible-light responding ZnO-based nanocomposite in fields of degradation of organic pollutants,photocatalytic hydrogen production and antibacterial agents, and the way of thinking and suggestions for further research on ZnO-based nanocomposite photocatalyst were put forward. With the developing of basic research and application, ZnO-based nanocomposite photocatalyst will be widely used in the fields of high efficiency catalyst, environmental purification, solar energy conversion and so on.

  19. Visible Light Photocatalysis via CdS/TiO2 Nanocomposite Materials

    Directory of Open Access Journals (Sweden)

    Elias K. Stefanakos

    2006-10-01

    Full Text Available Nanostructured colloidal semiconductors with heterogeneous photocatalytic behavior have drawn considerable attention over the past few years. This is due to their large surface area, high redox potential of the photogenerated charge carriers, and selective reduction/oxidation of different classes of organic compounds. In the present paper, we have carried out a systematic synthesis of nanostructured CdS-TiO2 via reverse micelle process. The structural and microstructural characterizations of the as-prepared CdS-TiO2 nanocomposites are determined using XRD and SEM-EDS techniques. The visible light assisted photocatalytic performance is monitored by means of degradation of phenol in water suspension.

  20. Experimental demonstration of multiple-inputs multiple-outputs OFDM/OQAM visible light communications

    Science.gov (United States)

    Lin, Bangjiang; Tang, Xuan; Ghassemlooy, Zabih; Lin, Chun; Zhang, Min

    2017-10-01

    We experimentally demonstrate a 2×2 optical multiple-inputs multiple-outputs (MIMO) visible light communications system based on the modified orthogonal frequency-division multiplexing/offset quadrature amplitude modulation scheme. The adjacent subcarrier frequency-domain averaging (ASFA) with the full-loaded (FL) and half-loaded (HL) preamble structures is proposed for demultiplexing and mitigating the intrinsic imaginary interference (IMI) effect. Compared with the conventional channel estimation (CE) method, ASFA offers improved transmission performance. With the FL method, we obtain more accurate MIMO CE to mitigate the IMI effect and the optical noise compared to the HL method.

  1. Controlled trifluoromethylation reactions of alkynes through visible-light photoredox catalysis.

    Science.gov (United States)

    Iqbal, Naeem; Jung, Jaehun; Park, Sehyun; Cho, Eun Jin

    2014-01-07

    The control of a reaction that can form multiple products is a highly attractive and challenging concept in synthetic chemistry. A set of valuable CF3 -containing molecules, namely trifluoromethylated alkenyl iodides, alkenes, and alkynes, were selectively generated from alkynes and CF3 I by environmentally benign and efficient visible-light photoredox catalysis. Subtle differences in the combination of catalyst, base, and solvent enabled the control of reactivity and selectivity for the reaction between an alkyne and CF3 I. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Visible-Light-Promoted Metal-Free Aerobic Oxidation of Primary Amines to Acids and Lactones.

    Science.gov (United States)

    Cheng, Xiaokai; Yang, Bo; Hu, Xingen; Xu, Qing; Lu, Zhan

    2016-12-05

    A unique metal-free aerobic oxidation of primary amines via visible light photocatalytic double carbon-carbon bonds cleavage and multi carbon-hydrogen bonds oxidation was observed. Aerobic oxidation of primary amines could be controlled to afford acids by using dioxane with 18 W CFL, and lactones by using DMF with 8 W green LEDs, respectively. A plausible mechanism was proposed based on control experiments. This observation showed direct evidences for the fragmentation in the aerobic oxidation of aliphatic primary amines. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Eosin Y Catalyzed Visible-light-promoted One –Pot Facile Synthesis of 1,3,4- Thiadiazole

    Directory of Open Access Journals (Sweden)

    Vishal Srivastava

    2015-03-01

    Full Text Available A novel one-pot visible light irradiated synthesis of 1,3,4-thiadiazole from aldehydes and thioacyl hydrazides have been reported in presence of eosin Y as an organophotoredox catalyst at room temperature under aerobic condition. This synthesis includes application of air and visible light as inexpensive, readily available, non-toxic and sustainable regents, which fulfils the basic principle of green chemistry.

  4. Pulsed, all solid-state light source in the visible spectral region based on non-linear cavity dumping

    DEFF Research Database (Denmark)

    Tidemand-Lichtenberg, Peter; Andersen, Martin; Johansson, Sandra

    We propose a novel generic approach for generation of pulsed light in the visible spectrum, based on SFG between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser.......We propose a novel generic approach for generation of pulsed light in the visible spectrum, based on SFG between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser....

  5. Limiting the impact of light pollution on human health, environment and stellar visibility.

    Science.gov (United States)

    Falchi, Fabio; Cinzano, Pierantonio; Elvidge, Christopher D; Keith, David M; Haim, Abraham

    2011-10-01

    Light pollution is one of the most rapidly increasing types of environmental degradation. Its levels have been growing exponentially over the natural nocturnal lighting levels provided by starlight and moonlight. To limit this pollution several effective practices have been defined: the use of shielding on lighting fixture to prevent direct upward light, particularly at low angles above the horizon; no over lighting, i.e. avoid using higher lighting levels than strictly needed for the task, constraining illumination to the area where it is needed and the time it will be used. Nevertheless, even after the best control of the light distribution is reached and when the proper quantity of light is used, some upward light emission remains, due to reflections from the lit surfaces and atmospheric scatter. The environmental impact of this "residual light pollution", cannot be neglected and should be limited too. Here we propose a new way to limit the effects of this residual light pollution on wildlife, human health and stellar visibility. We performed analysis of the spectra of common types of lamps for external use, including the new LEDs. We evaluated their emissions relative to the spectral response functions of human eye photoreceptors, in the photopic, scotopic and the 'meltopic' melatonin suppressing bands. We found that the amount of pollution is strongly dependent on the spectral characteristics of the lamps, with the more environmentally friendly lamps being low pressure sodium, followed by high pressure sodium. Most polluting are the lamps with a strong blue emission, like Metal Halide and white LEDs. Migration from the now widely used sodium lamps to white lamps (MH and LEDs) would produce an increase of pollution in the scotopic and melatonin suppression bands of more than five times the present levels, supposing the same photopic installed flux. This increase will exacerbate known and possible unknown effects of light pollution on human health, environment

  6. Photochemical Synthesis of Complex Carbazoles: Evaluation of Electronic Effects in Both UV- and Visible-Light Methods in Continuous Flow.

    Science.gov (United States)

    Hernandez-Perez, Augusto C; Caron, Antoine; Collins, Shawn K

    2015-11-09

    An evaluation of both a visible-light- and UV-light-mediated synthesis of carbazoles from various triarylamines with differing electronic properties under continuous-flow conditions has been conducted. In general, triarylamines bearing electron-rich groups tend to produce higher yields than triarylamines possessing electron-withdrawing groups. The incorporation of nitrogen-based heterocycles, as well as halogen-containing arenes in carbazole skeletons, was well tolerated, and often synthetically useful complementarity was observed between the UV-light and visible-light (photoredox) methods. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. All-silicon Michelson instrument on chip: Distance and surface profile measurement and prospects for visible light spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Malak, M.; Marty, F.; Bourouina, T. [Universite Paris-Est, Laboratoire ESYCOM, ESIEE Paris, Cite Descartes, 2 Boulevard Blaise Pascal, 93162 Noisy-le-Grand Cedex (France); Nouira, H.; Vailleau, G. [Laboratoire National de Metrologie et d' Essais, 1 rue Gaston Boissier, 75724 Paris Cedex 15 (France)

    2013-04-08

    A miniature Michelson interferometer is analyzed theoretically and experimentally. The fabricated micro-interferometer is incorporated at the tip of a monolithic silicon probe to achieve contactless distance measurements and surface profilometry. For infrared operation, two approaches are studied, based on the use of monochromatic light and wavelength sweep, respectively. A theoretical model is devised to depict the system characteristics taking into account Gaussian beam divergence and light spot size. Furthermore, preliminary results using visible light demonstrate operation of the probe as a visible light spectrometer, despite silicon absorbance, thanks to the micrometer thickness involved in the beam splitter.

  8. All-silicon Michelson instrument on chip: Distance and surface profile measurement and prospects for visible light spectrometry

    International Nuclear Information System (INIS)

    Malak, M.; Marty, F.; Bourouina, T.; Nouira, H.; Vailleau, G.

    2013-01-01

    A miniature Michelson interferometer is analyzed theoretically and experimentally. The fabricated micro-interferometer is incorporated at the tip of a monolithic silicon probe to achieve contactless distance measurements and surface profilometry. For infrared operation, two approaches are studied, based on the use of monochromatic light and wavelength sweep, respectively. A theoretical model is devised to depict the system characteristics taking into account Gaussian beam divergence and light spot size. Furthermore, preliminary results using visible light demonstrate operation of the probe as a visible light spectrometer, despite silicon absorbance, thanks to the micrometer thickness involved in the beam splitter.

  9. The study of photocatalysis under ultraviolet + visible two-beam light irradiation using undoped nano-titanium dioxide

    International Nuclear Information System (INIS)

    Liu Baoshun; Wen Liping; Zhao Xiujian

    2008-01-01

    The nano-TiO 2 powder was synthesized using wet chemical method and characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET), and transmission electron microscope (TEM). The photodegradation of aqueous methyl orange and phenol under the irradiation of visible, ultraviolet (UV), and UV + visible lights was used to evaluate the photocatalytic activity of nano-TiO 2 powder prepared. It is found that the photocatalysis under UV and visible light irradiation simultaneously is much faster than the sum of that solely induced by UV light and visible light. UV-vis spectroscopy, photoluminescence (PL) spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used to investigate the physical cause of the enhancement of photocatalytic activity induced by UV + visible two-beam light irradiation. A photocatalytic mechanism based on the d-d transition of photoinduced electrons on surface located at conduction band was suggested to explain the experimental result. It is considered that this is a novel method to utilize visible light in the photocatalysis by using undoped TiO 2 material

  10. Visible light induced electron transfer process over nitrogen doped TiO2 nanocrystals prepared by oxidation of titanium nitride

    International Nuclear Information System (INIS)

    Wu Zhongbiao; Dong Fan; Zhao Weirong; Guo Sen

    2008-01-01

    Nitrogen doped TiO 2 nanocrystals with anatase and rutile mixed phases were prepared by incomplete oxidation of titanium nitride at different temperatures. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), core level X-ray photoelectron spectroscopy (CL XPS), valence band X-ray photoelectron spectroscopy (VB XPS), UV-vis diffuse reflectance spectra (UV-vis DRS), and visible light excited photoluminescence (PL). The photocatalytic activity was evaluated for photocatalytic degradation of toluene in gas phase under visible light irradiation. The visible light absorption and photoactivities of these nitrogen doped TiO 2 nanocrystals can be clearly attributed to the change of the additional electronic (N - ) states above the valence band of TiO 2 modified by N dopant as revealed by the VB XPS and visible light induced PL. A band gap structure model was established to explain the electron transfer process over nitrogen doped TiO 2 nanocrystals under visible light irradiation, which was consistent with the previous theoretical and experimental results. This model can also be applied to understand visible light induced photocatalysis over other nonmetal doped TiO 2

  11. Light Sensitivity of Lactococcus lactis Thioredoxin Reductase

    DEFF Research Database (Denmark)

    Skjoldager, Nicklas

    The thioredoxin system has evolved in all kingdoms of life acting as a key antioxidant system in the defense against oxidative stress. The thioredoxin system utilizes reducing equivalents from NADPH to reduce protein disulfide targets. The reducing equivalents are shuttled via a flavin and redox...... active dithiol motif in thioredoxin reductase (TrxR) to reduce the small ubiquitous thioredoxin (Trx). Trx in turn regulates the protein dithiol/disulfide balance by reduction of protein disulfide targets in e.g. ribonucleotide reductase, peroxiredoxins and methionine sulfoxide reductase. The glutathione......, thus expected to rely mainly on the Trx system for thiol-disulfide control. L. lactis is an important industrial microorganism used as starter culture in the dairy production of cheese, buttermilk etc. and known to be sensitive to oxidative stress. The L. lactis TrxR (LlTrxR) is a homodimeric...

  12. Visible sector inflation and the right thermal history in light of Planck data

    International Nuclear Information System (INIS)

    Wang, Lingfei; Pukartas, Ernestas; Mazumdar, Anupam

    2013-01-01

    Inflation creates perturbations for the large scale structures in the universe, but it also dilutes everything. Therefore it is pertinent that the end of inflation must explain how to excite the Standard Model dof along with the dark matter. In this paper we will briefly discuss the role of visible sector inflaton candidates which are embedded within the Minimal Supersymmetric Standard Model (MSSM) and discuss their merit on how well they match the current data from the Planck. Since the inflaton carries the Standard Model charges their decay naturally produces all the relevant dof with no dark/hidden sector radiation and no isocurvature fluctuations. We will first discuss a single supersymmetric flat direction model of inflation and demonstrate what parameter space is allowed by the Planck and the LHC. We will also consider where the perturbations are created by another light field which decays after inflation, known as a curvaton. The late decay of the curvaton can create observable non-Gaussianity. In the end we will discuss the role of a spectator field whose origin may not lie within the visible sector physics, but its sheer presence during inflation can still create all the perturbations responsible for the large scale structures including possible non-Gaussianity, while the inflaton is embedded within the visible sector which creates all the relevant matter including dark matter, but no dark radiation

  13. (Gold core) at (ceria shell) nanostructures for plasmon-enhanced catalytic reactions under visible light

    KAUST Repository

    Wang, Jianfang; Li, Benxia; Gu, Ting; Ming, Tian; Wang, Junxin; Wang, Peng; Yu, Jimmy C.

    2014-01-01

    Driving catalytic reactions with sunlight is an excellent example of sustainable chemistry. A prerequisite of solar-driven catalytic reactions is the development of photocatalysts with high solar-harvesting efficiencies and catalytic activities. Herein, we describe a general approach for uniformly coating ceria on monometallic and bimetallic nanocrystals through heterogeneous nucleation and growth. The method allows for control of the shape, size, and type of the metal core as well as the thickness of the ceria shell. The plasmon shifts of the Au@CeO2 nanostructures resulting from the switching between Ce(IV) and Ce(III) are observed. The selective oxidation of benzyl alcohol to benzaldehyde, one of the fundamental reactions for organic synthesis, performed under both broad-band and monochromatic light, demonstrates the visible-light-driven catalytic activity and reveals the synergistic effect on the enhanced catalysis of the Au@CeO2 nanostructures. © 2014 American Chemical Society.

  14. Irradiation with visible light enhances the antibacterial toxicity of silver nanoparticles produced by laser ablation

    Science.gov (United States)

    Ratti, Matthew; Naddeo, J. J.; Tan, Yuying; Griepenburg, Julianne C.; Tomko, John; Trout, Cory; O'Malley, Sean M.; Bubb, Daniel M.; Klein, Eric A.

    2016-04-01

    The rise of antibiotic-resistant bacteria is a rapidly growing global health concern. According to the Center for Disease Control, approximately 2 million illnesses and 23,000 deaths per year occur in the USA due to antibiotic resistance. In recent years, there has been a surge in the use of metal nanoparticles as coatings for orthopedic implants, wound dressings, and food packaging, due to their antimicrobial properties. In this report, we demonstrate that the antibacterial efficacy of silver nanoparticles (AgNPs) is enhanced with exposure to light from the visible spectrum. We find that the increased toxicity is due to augmented silver ion release and bacterial uptake. Interestingly, silver ion toxicity does not appear to depend on the formation of reactive oxygen species. Our findings provide a novel paradigm for using light to regulate the toxicity of AgNPs which may have a significant impact in the development of new antimicrobial therapeutics.

  15. PAPR reduction based on tone reservation scheme for DCO-OFDM indoor visible light communications.

    Science.gov (United States)

    Bai, Jurong; Li, Yong; Yi, Yang; Cheng, Wei; Du, Huimin

    2017-10-02

    High peak-to-average power ratio (PAPR) leads to out-of-band power and in-band distortion in the direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) systems. In order to effectively reduce the PAPR with faster convergence and lower complexity, this paper proposes a tone reservation based scheme, which is the combination of the signal-to-clipping noise ratio (SCR) procedure and the least squares approximation (LSA) procedure. In the proposed scheme, the transmitter of the DCO-OFDM indoor visible light communication (VLC) system is designed to transform the PAPR reduced signal into real-valued positive OFDM signal without doubling the transmission bandwidth. Moreover, the communication distance and the light emitting diode (LED) irradiance angle are taking into consideration in the evaluation of the system bit error rate (BER). The PAPR reduction efficiency of the proposed scheme is remarkable for DCO-OFDM indoor VLC systems.

  16. Construction of porous covalent organic polymer as photocatalysts for RhB degradation under visible light

    Institute of Scientific and Technical Information of China (English)

    Pingxiao Liu; Lingbao Xing; Hongtao Lin; Haining Wang; Ziyan Zhou; Zhongmin Su

    2017-01-01

    In the present work,a novel porous,and chemically stable amine-based covalent organic polymer (POP-1) was designed and synthesized under solvothermal conditions.The porosity,crystallinity,chemical stability,electrochemical properties,and diffuse reflectance of POP-1 were investigated via N2 sorption experiment,power X-ray diffraction,thermogravimetric analysis,cyclic voltammetry,and ultraviolet visible near infrared spectrometry,respectively.POP-1 exhibits good chemical stability in both acidic and alkaline aqueous solutions,as well as in organic solvents.Undoped POP-1 can be directly used as a photocatalyst for rhodamine B irradiation degradation under light-emitting diode and natural light.The Ea of POP-1 for RhB degradation is 82.37 kJ/mol.Furthermore,POP-1 can be reused as a catalyst in RhB degradation without degraded catalytic activity.

  17. Secrecy Dimming Capacity in Multi-LED PAM-Based Visible Light Communications

    Directory of Open Access Journals (Sweden)

    Byung Wook Kim

    2017-01-01

    Full Text Available Recently, mobile cloud computing (MCC has gained a lot of interest for researchers building the next-generation mobile applications. Because unauthorized access may cause serious problems, security and privacy with MCC have become significant issues. This paper addresses the secrecy dimming capacity of secure transmission in MCC over visible light communication (VLC channels. By obtaining the entropy-maximizing symbol probability of multiple light emitting diode- (LED- based pulse amplitude modulation (PAM, mathematical analysis of the secrecy dimming capacity of VLC was derived. Simulation results show that the secure transmission ability of multi-LED-based VLC is determined according to the number of activated LEDs and target dimming level. This can be a guideline for practical VLC-based mobile network designers intending to secure wireless transmission and to decide on the number of activated LEDs at target dimming level to operate.

  18. Multi-band transmission color filters for multi-color white LEDs based visible light communication

    Science.gov (United States)

    Wang, Qixia; Zhu, Zhendong; Gu, Huarong; Chen, Mengzhu; Tan, Qiaofeng

    2017-11-01

    Light-emitting diodes (LEDs) based visible light communication (VLC) can provide license-free bands, high data rates, and high security levels, which is a promising technique that will be extensively applied in future. Multi-band transmission color filters with enough peak transmittance and suitable bandwidth play a pivotal role for boosting signal-noise-ratio in VLC systems. In this paper, multi-band transmission color filters with bandwidth of dozens nanometers are designed by a simple analytical method. Experiment results of one-dimensional (1D) and two-dimensional (2D) tri-band color filters demonstrate the effectiveness of the multi-band transmission color filters and the corresponding analytical method.

  19. A hybrid CATV/16-QAM-OFDM visible laser light communication system

    International Nuclear Information System (INIS)

    Lin, Chun-Yu; Li, Chung-Yi; Lu, Hai-Han; Chen, Chia-Yi; Jhang, Tai-Wei; Ruan, Sheng-Siang; Wu, Kuan-Hung

    2014-01-01

    A visible laser light communication (VLLC) system employing a vertical cavity surface emitting laser and spatial light modulator with hybrid CATV/16-QAM-OFDM modulating signals over a 5 m free-space link is proposed and demonstrated. With the assistance of a push-pull scheme, low-noise amplifier, and equalizer, good performances of composite second-order and composite triple beat are obtained, accompanied by an acceptable carrier-to-noise ratio performance for a CATV signal, and a low bit error rate value and clear constellation map are achieved for a 16-QAM-OFDM signal. Such a hybrid CATV/16-QAM-OFDM VLLC system would be attractive for providing services including CATV, Internet and telecommunication services. (paper)

  20. Dielectric Meta-Holograms Enabled with Dual Magnetic Resonances in Visible Light.

    Science.gov (United States)

    Li, Zile; Kim, Inki; Zhang, Lei; Mehmood, Muhammad Q; Anwar, Muhammad S; Saleem, Murtaza; Lee, Dasol; Nam, Ki Tae; Zhang, Shuang; Luk'yanchuk, Boris; Wang, Yu; Zheng, Guoxing; Rho, Junsuk; Qiu, Cheng-Wei

    2017-09-26

    Efficient transmission-type meta-holograms have been demonstrated using high-index dielectric nanostructures based on Huygens' principle. It is crucial that the geometry size of building blocks be judiciously optimized individually for spectral overlap of electric and magnetic dipoles. In contrast, reflection-type meta-holograms using the metal/insulator/metal scheme and geometric phase can be readily achieved with high efficiency and small thickness. Here, we demonstrate a general platform for design of dual magnetic resonance based meta-holograms based on the geometric phase using silicon nanostructures that are quarter wavelength thick for visible light. Significantly, the projected holographic image can be unambiguously observed without a receiving screen even under the illumination of natural light. Within the well-developed semiconductor industry, our ultrathin magnetic resonance-based meta-holograms may have promising applications in anticounterfeiting and information security.

  1. Conversion of visible light to electrical energy - Stable cadmium selenide photoelectrodes in aqueous electrolytes

    Science.gov (United States)

    Wrighton, M. S.; Ellis, A. B.; Kaiser, S. W.

    1977-01-01

    Stabilization of n-type CdSe to photoanodic dissolution is reported. The stabilization is accomplished by the competitive oxidation of S(--) or S(n)(--) at the CdSe photoanode in an electrochemical cell. Such stabilized cells are shown to sustain the conversion of low energy (not less than 1.7 eV) visible light to electricity with good efficiency and no deterioration of the CdSe photoelectrode or of the electrolyte. The electrolyte undergoes no net chemical change because the oxidation occurring at the photoelectrode is reversed at the cathode. Conversion of monochromatic light at 633 nm to electricity is shown to be up to approximately 9% efficient with output potentials of approximately 0.4 V. Conversion of solar energy to electricity is estimated to be approximately 2% efficient.

  2. (Gold core) at (ceria shell) nanostructures for plasmon-enhanced catalytic reactions under visible light

    KAUST Repository

    Wang, Jianfang

    2014-08-26

    Driving catalytic reactions with sunlight is an excellent example of sustainable chemistry. A prerequisite of solar-driven catalytic reactions is the development of photocatalysts with high solar-harvesting efficiencies and catalytic activities. Herein, we describe a general approach for uniformly coating ceria on monometallic and bimetallic nanocrystals through heterogeneous nucleation and growth. The method allows for control of the shape, size, and type of the metal core as well as the thickness of the ceria shell. The plasmon shifts of the Au@CeO2 nanostructures resulting from the switching between Ce(IV) and Ce(III) are observed. The selective oxidation of benzyl alcohol to benzaldehyde, one of the fundamental reactions for organic synthesis, performed under both broad-band and monochromatic light, demonstrates the visible-light-driven catalytic activity and reveals the synergistic effect on the enhanced catalysis of the Au@CeO2 nanostructures. © 2014 American Chemical Society.

  3. Performance of multiclad scintillating and clear waveguide fibers read out with visible light photon counters

    Energy Technology Data Exchange (ETDEWEB)

    Baumbaugh, B. (Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)); Erdman, J. (Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)); Gaskell, D. (Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)); Lu, Q. (Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)); Marchant, J. (Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)); Ruchti, R. (Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)); Wayne, M. (Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)); Cooper, C. (Department of Physics, Purdue University, West Lafayette, IN 47907 (United States)); Hinson, J. (Department of Physics, Purdue University, West Lafayette, IN 47907 (United States)); Koltick, D.S. (Department of Physics, Purdue University, West Lafayette, IN 47907 (United State

    1994-06-15

    Measurements have been made of the performance of scintillating fibers read out with visible light photon counters (VLPCs). The light yields of single-clad and multiclad scintillating fibers have been compared. The experiment consisted of 3 m long scintillating fibers of 830 [mu]m diameter optically coupled to 8 m long waveguide fibers of 965 [mu]m diameter read out with HISTE-IV VLPCs. For the case of multiclad scintillating fiber and waveguide, an average of 6.2 photoelectrons was detected from the far end of the scintillating fiber if the fiber end was unmirrored, and 10.2 photoelectrons if the fiber end was mirrored. With this substantial photoelectron yield, minimum-ionizing tracks can be easily detected in fiber arrays, and excellent performance characteristics are expected for the fiber trackers designed for the D0 experiment at the Fermilab Tevatron Collider and the SDC experiment at the SSC Laboratory. ((orig.))

  4. Alternative Line Coding Scheme with Fixed Dimming for Visible Light Communication

    Science.gov (United States)

    Niaz, M. T.; Imdad, F.; Kim, H. S.

    2017-01-01

    An alternative line coding scheme called fixed-dimming on/off keying (FD-OOK) is proposed for visible-light communication (VLC). FD-OOK reduces the flickering caused by a VLC transmitter and can maintain a 50% dimming level. Simple encoder and decoder are proposed which generates codes where the number of bits representing one is same as the number of bits representing zero. By keeping the number of ones and zeros equal the change in the brightness of lighting may be minimized and kept constant at 50%, thereby reducing the flickering in VLC. The performance of FD-OOK is analysed with two parameters: the spectral efficiency and power requirement.

  5. A CDMA system implementation with dimming control for visible light communication

    Science.gov (United States)

    Chen, Danyang; Wang, Jianping; Jin, Jianli; Lu, Huimin; Feng, Lifang

    2018-04-01

    Visible light communication (VLC), using solid-state lightings to transmit information, has become a complement technology to wireless radio communication. As a realistic multiple access scheme for VLC system, code division multiple access (CDMA) has attracted more and more attentions in recent years. In this paper, we address and implement an improved CDMA scheme for VLC system. The simulation results reveal that the improved CDMA scheme not only supports multi-users' transmission but also maintains dimming value at about 50% and enhances the system efficiency. It can also realize the flexible dimming control by adjusting some parameters of system structure, which rarely affects the system BER performance. A real-time experimental VLC system with improved CDMA scheme is performed based on field programmable gate array (FPGA), reaching a good BER performance.

  6. Achromatization In The 3 To 5 μm Spectral Region With Visible Light Transmitting Materials

    Science.gov (United States)

    McDowell, M. W.; Klee, H. W.

    1984-04-01

    The theoretical performances of several f/1.5 triplet lenses suitable for use in the 3 to 5um spectral region are compared. Examples are given in which all the materials used have a finite visible transmittance. As centering errors can thus be considerably reduced, it is expected that such a lens will in practice approach more closely its theoretical performance. These lenses are also considerably less sensitive to manufacturing tolerances as a result of lower index materials, and the use of low dn/dT materials offers other advantages over the more usual silicon-germanium combination.

  7. Preparation of Fe-Doped TiO2 Nanotubes and Their Photocatalytic Activities under Visible Light

    Directory of Open Access Journals (Sweden)

    Honghui Teng

    2013-01-01

    Full Text Available Fe-doped TiO2 nanotubes (Fe-TNTs have been prepared by ultrasonic-assisted hydrothermal method. The structure and composition of the as-prepared TiO2 nanotubes were characterized by transmission electron microscopy, X-ray diffraction, and UV-Visible absorption spectroscopy. Their photocatalytic activities were evaluated by the degradation of MO under visible light. The UV-visible absorption spectra of the Fe-TNT showed a red shift and an enhancement of the absorption in the visible region compared to the pure TNT. The Fe-TNTs were provided with good photocatalytic activities and photostability and under visible light irradiation, and the optimum molar ratio of Ti : Fe was found to be 100 : 1 in our experiments.

  8. Exchangeable cations-mediated photodegradation of polycyclic aromatic hydrocarbons (PAHs) on smectite surface under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Hanzhong, E-mail: jiahz@ms.xjb.ac.cn [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Li, Li [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Chen, Hongxia; Zhao, Yue [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); School of Geology and Mining Engineering, Xinjiang University, Urumqi 830046 (China); Li, Xiyou [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Wang, Chuanyi, E-mail: cywang@ms.xjb.ac.cn [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China)

    2015-04-28

    Graphical abstract: Roles of exchangeable cations in PAHs photodegradation on clay surafces under visible light. - Highlights: • Photolysis rate are strongly dependent on the type of cations on clay surface. • The strength of “cation–π” interactions governs the photodegradation rate of PAHs. • Several exchangeable cations could cause a shift in the absorption spectrum of PAHs. • Exchangeable cations influence the type and amount of reactive intermediates. - Abstract: Clay minerals saturated with different exchangeable cations are expected to play various roles in photodegradation of polycyclic aromatic hydrocarbons (PAHs) via direct and/or indirect pathways on clay surfaces. In the present study, anthracene and phenanthrene were selected as molecule probes to investigate the roles of exchangeable cations on their photodegradation under visible light irradiation. For five types of cation-modified smectite clays, the photodegradation rate of anthracene and phenanthrene follows the order: Fe{sup 3+} > Al{sup 3+} > Cu{sup 2+} >> Ca{sup 2+} > K{sup +} > Na{sup +}, which is consistent with the binding energy of cation–π interactions between PAHs and exchangeable cations. The result suggests that PAHs photolysis rate depends on cation–π interactions on clay surfaces. Meanwhile, the deposition of anthracene at the Na{sup +}-smectite and K{sup +}-smectite surface favors solar light absorption, resulting in enhanced direct photodecomposition of PAHs. On the other hand, smectite clays saturated with Fe{sup 3+}, Al{sup 3+}, and Cu{sup 2+} are highly photoreactive and can act as potential catalysts giving rise to oxidative radicals such as O{sub 2}{sup −}· , which initiate the transformation of PAHs. The present work provides valuable insights into understanding the transformation and fate of PAHs in the natural soil environment and sheds light on the development of technologies for contaminated land remediation.

  9. Exchangeable cations-mediated photodegradation of polycyclic aromatic hydrocarbons (PAHs) on smectite surface under visible light

    International Nuclear Information System (INIS)

    Jia, Hanzhong; Li, Li; Chen, Hongxia; Zhao, Yue; Li, Xiyou; Wang, Chuanyi

    2015-01-01

    Graphical abstract: Roles of exchangeable cations in PAHs photodegradation on clay surafces under visible light. - Highlights: • Photolysis rate are strongly dependent on the type of cations on clay surface. • The strength of “cation–π” interactions governs the photodegradation rate of PAHs. • Several exchangeable cations could cause a shift in the absorption spectrum of PAHs. • Exchangeable cations influence the type and amount of reactive intermediates. - Abstract: Clay minerals saturated with different exchangeable cations are expected to play various roles in photodegradation of polycyclic aromatic hydrocarbons (PAHs) via direct and/or indirect pathways on clay surfaces. In the present study, anthracene and phenanthrene were selected as molecule probes to investigate the roles of exchangeable cations on their photodegradation under visible light irradiation. For five types of cation-modified smectite clays, the photodegradation rate of anthracene and phenanthrene follows the order: Fe 3+ > Al 3+ > Cu 2+ >> Ca 2+ > K + > Na + , which is consistent with the binding energy of cation–π interactions between PAHs and exchangeable cations. The result suggests that PAHs photolysis rate depends on cation–π interactions on clay surfaces. Meanwhile, the deposition of anthracene at the Na + -smectite and K + -smectite surface favors solar light absorption, resulting in enhanced direct photodecomposition of PAHs. On the other hand, smectite clays saturated with Fe 3+ , Al 3+ , and Cu 2+ are highly photoreactive and can act as potential catalysts giving rise to oxidative radicals such as O 2 − · , which initiate the transformation of PAHs. The present work provides valuable insights into understanding the transformation and fate of PAHs in the natural soil environment and sheds light on the development of technologies for contaminated land remediation

  10. Study on the relationship between PM2.5 concentration and visibility in Beijing based on light scattering theory

    Science.gov (United States)

    Yang, YuFeng; Li, Ting

    2018-02-01

    The study of the relationship between transmittance visibility and PM2.5 concentration under the haze conditions has important theoretical significance for Free Space Optical communication (FSO). In this paper, the influence of PM2.5 concentration on the transmittance, attenuation coefficient and visibility was studied by light scattering theory, and the results by Mie theory and Monte Carlo method were analyzed. At the same time, the effect of PM2.5 particle size distribution on visibility was also analyzed, and the visibility calculated by light scattering method was compared with the visibility measured in Beijing from 2014 to 2016. The result shows that the higher PM2.5 concentration is the more obvious the multiple scattering effect is. When the mass concentration of PM2.5 is constant, the larger the geometric mean of the particle diameter is, the larger the visibility is. By comparing the visibility measured and the visibility calculated, we can see that when PM2.5 concentration is higher than 100μg/m3 , PM2.5 is the main factor affecting the visibility; and when PM2.5 concentration is lower than 100μg/m3, other factors (such as PM10, wind speed, air pressure and gas molecules) should also need to be considered.

  11. Anodic deposition-assisted photoelectrocatalytic degradation of bisphenol A at a cadmium sulfide modified electrode based on visible light-driven fuel cells

    International Nuclear Information System (INIS)

    Luo, Jin-Yuan; Chen, Lin-Lin; Liang, Xing-Hui; Zhao, Qian-Wen; Li, Hong

    2015-01-01

    Highlights: • CdS nanoparticles can largely promote anodic deposition of BPA in the dark. • Photoelectrocatalytic degradation of BPA is driven by photo-stimulated fuel cells. • CdS/ITO is regenerated in photoelectrocatalytic degradation process of BPA. • Visible light-driven BPA fuel cell exhibits several unique advantages. - Abstract: A novel photoelectrocatalytic oxidation method has been successfully developed to effectively degrade bisphenol A (BPA) using a visible light-sensitive CdS nanoparticle modified indium-tin oxide (ITO) electrode. In the present protocol, BPA is oxidized on the CdS/ITO electrode to produce a redox-active film (BPA AD ), which is subsequently degraded upon incorporation of visible light irradiation and anodic electric fields, making the CdS/ITO electrode cyclically regenerated and the BPA removed. The addition of CdS nanoparticles to the ITO electrode not only increases the anodic deposition of BPA in the dark, but also promotes the photoelectrocatalytic degradation of BPA under visible light irradiation. The CdS/ITO photoanode shows high regeneration ability, and the removal efficiency of BPA is high up to 94.1%. Meanwhile, a monopolar visible light-simulated BPA fuel cell vs. Ag/AgCl electrode with a salt bridge is fabricated to achieve the photoelectrocatalytic degradation of BPA, showing open-circuit photovoltage of 0.412 (±0.015) V and short-circuit photocurrent density of 20.52 (±1.02) μA cm −2 , respectively. The present study provides a new approach for efficient removal of phenolic pollutants and optimum utilization of renewable energy sources.

  12. Comparative studies on the lethal, mutagenic, and recombinogenic effects of ultraviolet -A, -B, -C, and visible light with and without 8-methoxypsoralen in Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Mondon, P.; Shahin, M.M.

    1992-01-01

    Genetic effects of UV-A, UV-B, UV-C and the combination of 8-methoxypsoralen (8-MOP) with UV-A or visible light were studied in the haploid strain XV185-14C and diploid strain D5 of Saccharomyces cerevisiae. The induction of his + , lys + , and hom + reverse mutations was measured in strain XV185-14C. In strain D5 we measured the induction of genetically altered colonies, particularly twin spot colonies arising from a mitotic crossing-over. UV-C and UV-B induced point mutations at the three loci in the haploid strain and mitotic crossing-over and other genetic alterations in the diploid strain. UV-C was more mutagenic and recombinogenic than UV-B. UV-A or visible light alone did not induce genotoxic effects at the doses tested. However, UV-A plus 8-MOP produced lethal and mutagenic effects in the haploid strain XV185-14C, although mutagenic activity was less than that of UV-B. Visible light plus 8-MOP also induced genotoxic effects in strain XV185-14C. In the diploid strain D5, UV-A plus 8-MOP induced a higher frequency of genetic alterations than UV-B at comparative doses. Visible light plus 8-MOP was also genetically active in strain D5. The haploid strain was more sensitive to the lethal effects of UV-C, UV-B, UV-A, and impure visible light plus 8-MOP than the diploid strain. (Author)

  13. On the combined effect of visible light and ionizing radiation on the development of plants

    International Nuclear Information System (INIS)

    Kuzin, A.M.; Vagabova, M.Eh.

    1978-01-01

    The development processes, like germination of resting lettuce seeds and anthocyan synthesis, activated in plants by red light quanta are also very sensitive to γ-quanta. The combined effect of both factors plays an essential part in stimulation of the development of seeds preirradiated with γ-rays

  14. High security chaotic multiple access scheme for visible light communication systems with advanced encryption standard interleaving

    Science.gov (United States)

    Qiu, Junchao; Zhang, Lin; Li, Diyang; Liu, Xingcheng

    2016-06-01

    Chaotic sequences can be applied to realize multiple user access and improve the system security for a visible light communication (VLC) system. However, since the map patterns of chaotic sequences are usually well known, eavesdroppers can possibly derive the key parameters of chaotic sequences and subsequently retrieve the information. We design an advanced encryption standard (AES) interleaving aided multiple user access scheme to enhance the security of a chaotic code division multiple access-based visible light communication (C-CDMA-VLC) system. We propose to spread the information with chaotic sequences, and then the spread information is interleaved by an AES algorithm and transmitted over VLC channels. Since the computation complexity of performing inverse operations to deinterleave the information is high, the eavesdroppers in a high speed VLC system cannot retrieve the information in real time; thus, the system security will be enhanced. Moreover, we build a mathematical model for the AES-aided VLC system and derive the theoretical information leakage to analyze the system security. The simulations are performed over VLC channels, and the results demonstrate the effectiveness and high security of our presented AES interleaving aided chaotic CDMA-VLC system.

  15. Hydrothermal Synthesis of Nitrogen-Doped Titanium Dioxide and Evaluation of Its Visible Light Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Junjie Qian

    2012-01-01

    Full Text Available Nitrogen-doped titanium dioxide (N-doped TiO2 photocatalyst was synthesized from nanotube titanic acid (denoted as NTA; molecular formula H2Ti2O5·H2O precursor via a hydrothermal route in ammonia solution. As-synthesized N-doped TiO2 catalysts were characterized by means of X-ray diffraction, transmission electron microscopy, diffuse reflectance spectrometry, X-ray photoelectron spectroscopy, electron spin resonance spectrometry and Fourier transform infrared spectrometry. It was found that nanotube ammonium titanate (NAT was produced as an intermediate during the preparation of N-doped TiO2 from NTA, as evidenced by the N1s X-ray photoelectron spectroscopic peak of NH4 + at 401.7 eV. The catalyst showed much higher activities to the degradation of methylene blue and p-chlorophenol under visible light irradiation than Degussa P25. This could be attributed to the enhanced absorption of N-doped TiO2 in visible light region associated with the formation of single-electron-trapped oxygen vacancies and the inhibition of recombination of photo-generated electron-hole pair by doped nitrogen.

  16. Nonlinear degradation of a visible-light communication link: A Volterra-series approach

    Science.gov (United States)

    Kamalakis, Thomas; Dede, Georgia

    2018-06-01

    Visible light communications can be used to provide illumination and data communication at the same time. In this paper, a reverse-engineering approach is presented for assessing the impact of nonlinear signal distortion in visible light communication links. The approach is based on the Volterra series expansion and has the advantage of accurately accounting for memory effects in contrast to the static nonlinear models that are popular in the literature. Volterra kernels describe the end-to-end system response and can be inferred from measurements. Consequently, this approach does not rely on any particular physical models and assumptions regarding the individual link components. We provide the necessary framework for estimating the nonlinear distortion on the symbol estimates of a discrete multitone modulated link. Various design aspects such as waveform clipping and predistortion are also incorporated in the analysis. Using this framework, the nonlinear signal-to-interference is calculated for the system at hand. It is shown that at high signal amplitudes, the nonlinear signal-to-interference can be less than 25 dB.

  17. Visible-light photocatalytic activity of nitrided TiO2 thin films

    International Nuclear Information System (INIS)

    Camps, Enrique; Escobar-Alarcon, L.; Camacho-Lopez, Marco Antonio; Casados, Dora A. Solis

    2010-01-01

    TiO 2 thin films have been applied in UV-light photocatalysis. Nevertheless visible-light photocatalytic activity would make this material more attractive for applications. In this work we present results on the modification of titanium oxide (anatase) sol-gel thin films, via a nitriding process using a microwave plasma source. After the treatment in the nitrogen plasma, the nitrogen content in the TiO 2 films varied in the range from 14 up to 28 at%. The titanium oxide films and the nitrided ones were characterized by XPS, micro-Raman spectroscopy and UV-vis spectroscopy. Photocatalytic activity tests were done using a Methylene Blue dye solution, and as catalyst TiO 2 and nitrided TiO 2 films. The irradiation of films was carried out with a lamp with emission in the visible (without UV). The results showed that the nitrided TiO 2 films had photocatalytic activity, while the unnitrided films did not.

  18. Visible light carrier generation in co-doped epitaxial titanate films

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan B.; Smolin, Sergey Y.; Kaspar, Tiffany C.; Gao, Ran; Apgar, Brent A.; Martin, Lane W.; Bowden, Mark E.; Baxter, Jason; Chambers, Scott A.

    2015-03-02

    Perovskite titanates such as SrTiO3 (STO) exhibit a wide range of important functional properties, including high electron mobility, ferroelectricity—which may be valuable in photovoltaic applications—and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications, however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr3+ dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to between 2.4 and 2.7 eV depending on doping levels. Transient reflectance measurements confirm that optically generated carriers have a recombination lifetime comparable to that of STO and are in agreement with the observations from ellipsometry. Finally, through photoelectrochemical yield measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  19. Visible light carrier generation in co-doped epitaxial titanate films

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan B., E-mail: ryan.comes@pnnl.gov; Kaspar, Tiffany C.; Chambers, Scott A. [Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354 (United States); Smolin, Sergey Y.; Baxter, Jason B. [Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Gao, Ran [Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, California 94720 (United States); Apgar, Brent A. [Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801 (United States); Martin, Lane W. [Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, California 94720 (United States); Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Bowden, Mark E. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354 (United States)

    2015-03-02

    Perovskite titanates such as SrTiO{sub 3} (STO) exhibit a wide range of important functional properties, including ferroelectricity and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications; however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr, we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr{sup 3+} dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to 2.4–2.7 eV depending on doping levels. Transient reflectance spectroscopy measurements are in agreement with the observations from ellipsometry and confirm that optically generated carriers are present for longer than 2 ns. Finally, through photoelectrochemical methylene blue degradation measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  20. Facile synthesis and enhanced visible-light photocatalysis of graphitic carbon nitride composite semiconductors.

    Science.gov (United States)

    Li, Huiquan; Liu, Yuxing; Gao, Xing; Fu, Cong; Wang, Xinchen

    2015-04-13

    The semiconductor heterojunction has been an effective architecture to enhance photocatalytic activity by promoting photogenerated charge separation. Here, graphitic carbon nitride (CN) and B-modified graphitic carbon nitride (CNB) composite semiconductors were fabricated by a facile calcination process using cheap, sustainable, and easily available sodium tetraphenylboron and urea as precursors. The synthetic CN-CNB-25 semiconductor with a suitable CNB content showed the highest visible-light activity. Its degradation ratio for methyl orange and phenol was more than twice that of CN and CNB and its H2 evolution rate was ∼3.4 and ∼1.8 times higher than that of CN and CNB, respectively. It also displayed excellent stability and reusability. The enhanced activity of CN-CNB-25 was attributed predominantly to the efficient separation of photoinduced electrons and holes. This paper describes a visible-light-responsive CN composite semiconductor with great potential in environmental and energy applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Poly-γ-Glutamic Acid Nanoparticles Based Visible Light-Curable Hydrogel for Biomedical Application

    Directory of Open Access Journals (Sweden)

    József Bakó

    2016-01-01

    Full Text Available Nanoparticles and hydrogels have gained notable attention as promising potential for fabrication of scaffolds and delivering materials. Visible light-curable systems can allow for the possibility of in situ fabrication and have the advantage of optimal applicability. In this study nanogel was created from methacrylated poly-gamma-glutamic acid nanoparticles by visible (dental blue light photopolymerization. The average size of the particles was 80 nm by DLS, and the NMR spectra showed that the methacrylation rate was 10%. Polymerization time was 3 minutes, and a stable nanogel with a swelling rate of 110% was formed. The mechanical parameters of the prepared structure (compression stress 0.73 MPa, and Young’s modulus 0.93 MPa can be as strong as necessary in a real situation, for example, in the mouth. A retaining effect of the nanogel was found for ampicillin, and the biocompatibility of this system was tested by Alamar Blue proliferation assay, while the cell morphology was examined by fluorescence and laser scanning confocal microscopy. In conclusion, the nanogel can be used for drug delivery, or it can be suitable for a control factor in different systems.

  2. Visible light optical coherence microscopy imaging of the mouse cortex with femtoliter volume resolution

    Science.gov (United States)

    Merkle, Conrad W.; Chong, Shau Poh; Kho, Aaron M.; Zhu, Jun; Kholiqov, Oybek; Dubra, Alfredo; Srinivasan, Vivek J.

    2018-02-01

    Most flying-spot Optical Coherence Tomography (OCT) and Optical Coherence Microscopy (OCM) systems use a symmetric confocal geometry, where the detection path retraces the illumination path starting from and ending with the spatial mode of a single mode optical fiber. Here, we describe a visible light OCM instrument that breaks this symmetry to improve transverse resolution without sacrificing collection efficiency in scattering tissue. This was achieved by overfilling a 0.3 numerical aperture (NA) water immersion objective on the illumination path, while maintaining a conventional Gaussian mode detection path (1/e2 intensity diameter 0.82 Airy disks), enabling 1.1 μm full-width at half-maximum (FWHM) transverse resolution. At the same time, a 0.9 μm FWHM axial resolution in tissue, achieved by a broadband visible light source, enabled femtoliter volume resolution. We characterized this instrument according to paraxial coherent microscopy theory, and then used it to image the meningeal layers, intravascular red blood cell-free layer, and myelinated axons in the mouse neocortex in vivo through the thinned skull. Finally, by introducing a 0.8 NA water immersion objective, we improved the lateral resolution to 0.44 μm FWHM, which provided a volumetric resolution of 0.2 fL, revealing cell bodies in cortical layer I of the mouse brain with OCM for the first time.

  3. Nano-ferrites for water splitting: Unprecedented high photocatalytic hydrogen production under visible light

    KAUST Repository

    Mangrulkar, Priti A.; Polshettiwar, Vivek; Labhsetwar, Nitin K.; Varma, Rajender S.; Rayalu, Sadhana Suresh

    2012-01-01

    In the present investigation, hydrogen production via water splitting by nano-ferrites was studied using ethanol as the sacrificial donor and Pt as co-catalyst. Nano-ferrite is emerging as a promising photocatalyst with a hydrogen evolution rate of 8.275 μmol h -1 and a hydrogen yield of 8275 μmol h -1 g -1 under visible light compared to 0.0046 μmol h -1 for commercial iron oxide (tested under similar experimental conditions). Nano-ferrites were tested in three different photoreactor configurations. The rate of hydrogen evolution by nano-ferrite was significantly influenced by the photoreactor configuration. Altering the reactor configuration led to sevenfold (59.55 μmol h -1) increase in the hydrogen evolution rate. Nano-ferrites have shown remarkable stability in hydrogen production up to 30 h and the cumulative hydrogen evolution rate was observed to be 98.79 μmol h -1. The hydrogen yield was seen to be influenced by several factors like photocatalyst dose, illumination intensity, irradiation time, sacrificial donor and presence of co-catalyst. These were then investigated in detail. It was evident from the experimental data that nano-ferrites under optimized reaction conditions and photoreactor configuration could lead to remarkable hydrogen evolution activity under visible light. Temperature had a significant role in enhancing the hydrogen yield. © 2012 The Royal Society of Chemistry.

  4. Two-dimensionally grown single-crystal silicon nanosheets with tunable visible-light emissions.

    Science.gov (United States)

    Kim, Sung Wook; Lee, Jaejun; Sung, Ji Ho; Seo, Dong-jae; Kim, Ilsoo; Jo, Moon-Ho; Kwon, Byoung Wook; Choi, Won Kook; Choi, Heon-Jin

    2014-07-22

    Since the discovery of graphene, growth of two-dimensional (2D) nanomaterials has greatly attracted attention. However, spontaneous growth of atomic two-dimensional (2D) materials is limitedly permitted for several layered-structure crystals, such as graphene, MoS2, and h-BN, and otherwise it is notoriously difficult. Here we report the gas-phase 2D growth of silicon (Si), that is cubic in symmetry, via dendritic growth and an interdendritic filling mechanism and to form Si nanosheets (SiNSs) of 1 to 13 nm in thickness. Thin SiNSs show strong thickness-dependent photoluminescence in visible range including red, green, and blue (RGB) emissions with the associated band gap energies ranging from 1.6 to 3.2 eV; these emission energies were greater than those from Si quantum dots (SiQDs) of the similar sizes. We also demonstrated that electrically driven white, as well as blue, emission in a conventional organic light-emitting diode (OLED) geometry with the SiNS assembly as the active emitting layers. Tunable light emissions in visible range in our observations suggest practical implications for novel 2D Si nanophotonics.

  5. Ag loading induced visible light photocatalytic activity for pervoskite SrTiO3 nanofibers

    Science.gov (United States)

    Wu, Yeqiu; He, Tao

    2018-06-01

    The synthesis and photocatalytic activities of Ag-SrTiO3 nanofibers were reported in this work. The fabricated Ag-SrTiO3 nanofibers were characterized by TG-DSC, XRD, IR, XPS, SEM, TEM, DRS and ESR techniques. The XRD and IR results show that Ag-SrTiO3 nanofibers have a perovskite structure after the heat treatment at 700 °C. The XPS result shows that Ag element exists as Ag0 in the fabricated Ag-SrTiO3 nanofibers. The SEM and TEM images indicate the obtaining of nanofibers with porous structure. The photocatalytic activity of Ag-SrTiO3 nanofibers was evaluated by degrading RhB and MB under visible light irradiation. The Ag-SrTiO3 nanofibers show excellent photocatalytic activity under visible light irradiation because of the surface plasmon resonance effect of Ag0. In the photocatalysis process of RhB and MB, lots of hydroxyl radicals were generated, which plays the key role in the decomposition of organic pollutants.

  6. Reduced graphene oxide and Ag wrapped TiO{sub 2} photocatalyst for enhanced visible light photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Leong, Kah Hon; Sim, Lan Ching; Jang, Min; Ibrahim, Shaliza [Environmental Engineering Laboratory, Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Bahnemann, Detlef [Institut fuer Technische Chemie, Leibniz Universität Hannover, Callinstrasse 3, D-30167 Hannover (Germany); Saravanan, Pichiah, E-mail: pichiahsaravanan@gmail.com [Environmental Engineering Laboratory, Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Nanotechnology & Catalysis Research Center (NANOCAT), University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2015-10-01

    A well-organised reduced graphene oxide (RGO) and silver (Ag) wrapped TiO{sub 2} nano-hybrid was successfully achieved through a facile and easy route. The inherent characteristics of the synthesized RGO-Ag/TiO{sub 2} were revealed through crystalline phase, morphology, chemical composition, Raman scattering, UV-visible absorption, and photoluminescence analyses. The adopted synthesis route significantly controlled the uniform formation of silver nanoparticles and contributed for the absorption of light in the visible spectrum through localized surface plasmon resonance effects. The wrapped RGO nanosheets triggered the electron mobility and promoted visible light shift towards red spectrum. The accomplishment of synergised effect of RGO and Ag well degraded Bisphenol A under visible light irradiation with a removal efficiency of 61.9%.

  7. Postmodification of MOF-5 using secondary complex formation using 8- hydroxyquinoline (HOQ) for the development of visible light active photocatalysts

    Science.gov (United States)

    Thakare, Sanjay R.; Ramteke, Shruti M.

    2018-05-01

    A novel HOQ@MOF-5 compound photocatalyst was successfully constructed by interacting 8- Hydroxyquinoline with MOF-5 synthesized through a room temperature method. The secondary complex formation between the Zn cluster with 8-Hydroxyquinoline harnessed visible light and acted as a mediator to transfer photoinduced electrons to MOF-5 for enhancing the photocatalytic reaction rate with visible light. HOQ@MOF-5 was characterized by various spectroscopic techniques, such as XRD showing the crystalline nature of compound, UV-Visible spectroscopy showing the 2.54 eV band gap of HOQ@MOF-5 and morphological analysis tools, such as the nanoparticle nature of the compound with 9.561 nm particle size. The photocatalytic effect was estimated using the photocatalytic degradation of phenol as a representative organic pollutant under visible light irradiation. This work provides a new compound acting as source of electrons transfer for the development of efficient photocatalysts for remediation of environmental pollution.

  8. Amorphous TiO2 doped with carbon for visible light photodegradation of rhodamine B and 4-chlorophenol

    International Nuclear Information System (INIS)

    Shao, Penghui; Tian, Jiayu; Zhao, Zhiwei; Shi, Wenxin; Gao, Shanshan; Cui, Fuyi

    2015-01-01

    Graphical abstract: - Highlights: • Amorphous TiO 2 doped with carbon is prepared as a visible photocatalyst. • RhB and 4-chlorophenol are decomposed effectively by carbon-doped amorphous TiO 2 . • The mechanism for visible light photocatalysis is discussed detailedly. - Abstract: Visible light photocatalytic activity of amorphous TiO 2 doped with carbon is prepared by a facile sol-gel route for the first time. The most active sample with mesostructure of amorphous phase, high surface area (273 m 2 g −1 ) and large pore volume (0.33 cm 3 g −1 ) is identified by X-ray diffractometer, Raman spectrometer, transmission electron microscope and N 2 adsorption–desorption isotherms. In addition, the most active sample is characterized by Fourier transform-infrared spectrometer, X-ray photoelectron spectrometer, UV–vis diffuse reflectance spectrometer and luminescence spectrometer. The results show that the most active sample with oxygenic groups has a narrower bandgap and lower recombination of electron–hole, due to the carbon doping and phase of amorphous. Effective photodegradation capability and stability of rhodamine B and colorless 4-chlorophenol are verified by photocatalytic tests under visible light irradiation. A possible mechanism of amorphous TiO 2 doped with carbon for visible light photocatalysis is proposed. The findings of this paper will provide new insights to design visible light-induced photocatalyst based on amorphous TiO 2 for organic removal

  9. Photocatalysis-Based Nanoprobes Using Noble Metal-Semiconductor Heterostructure for Visible Light-Driven in Vivo Detection of Mercury.

    Science.gov (United States)

    Zhi, Lihua; Zeng, Xiaofan; Wang, Hao; Hai, Jun; Yang, Xiangliang; Wang, Baodui; Zhu, Yanhong

    2017-07-18

    The development of sensitive and reliable methods to monitor the presence of mercuric ions in cells and organisms is of great importance to biological research and biomedical applications. In this work, we propose a strategy to construct a solar-driven nanoprobe using a 3D Au@MoS 2 heterostructure as a photocatalyst and rhodamine B (RB) as a fluorescent and color change reporter molecule for monitoring Hg 2+ in living cells and animals. The sensing mechanism is based on the photoinduced electron formation of gold amalgam in the 3D Au@MoS 2 heterostructure under visible light illumination. This formation is able to remarkably inhibit the photocatalytic activity of the heterostructure toward RB decomposition. As a result, "OFF-ON" fluorescence and color change are produced. Such characteristics enable this new sensing platform to sensitively and selectively detect Hg 2+ in water by fluorescence and colorimetric methods. The detection limits of the fluorescence assay and colorimetric assay are 0.22 and 0.038 nM for Hg 2+ , respectively; these values are well below the acceptable limits in drinking water standards (10 nM). For the first time, such photocatalysis-based sensing platform is successfully used to monitor Hg 2+ in live cells and mice. Our work therefore opens a promising photocatalysis-based analysis methodology for highly sensitive and selective in vivo Hg 2+ bioimaging studies.

  10. Biomimetic fabrication of WO3 for water splitting under visible light with high performance

    International Nuclear Information System (INIS)

    Yin, Chao; Zhu, Shenmin; Yao, Fan; Gu, Jiajun; Zhang, Wang; Chen, Zhixin; Zhang, Di

    2013-01-01

    Inspired by the high light-harvesting properties of typical butterfly wings, ceramic WO 3 butterfly wings with hierarchical structures of bio-butterfly wings was fabricated using a template of PapilioParis butterfly wings through a sol–gel method. The effect of calcination temperatures on the structures of the ceramic butterfly wings was investigated and the results showed that the WO 3 butterfly wing replica calcined at 550 °C (WO 3 replica-550) is a single phase and has a high crystallinity and relatively fine hierarchical structure. The average grain size of WO 3 replica-550 and WO 3 powder are around 32.6 and 42.2 nm, respectively. Compared with pure WO 3 powder, WO 3 replica-550 demonstrated a higher light-harvesting capability in the region from 460 to 700 nm and more importantly the higher charge separation rate, as evidenced by electron paramagnetic resonance measurements. Photocatalytic O 2 evolutions from water were investigated on the ceramic butterfly wings and pure WO 3 powder under visible light (λ > 420 nm). The results showed that the amount of O 2 produced from WO 3 replica-550 is 50 % higher than that of the pure WO 3 powder. The improved photocatalytic performance of WO 3 replica-550 is attributed to the quasi-honeycomb structure inherited from the PapilioParis butterfly wings, providing both high light-harvesting efficiency and efficient charge transport through the WO 3

  11. A visible light imaging device for cardiac rate detection with reduced effect of body movement

    Science.gov (United States)

    Jiang, Xiaotian; Liu, Ming; Zhao, Yuejin

    2014-09-01

    A visible light imaging system to detect human cardiac rate is proposed in this paper. A color camera and several LEDs, acting as lighting source, were used to avoid the interference of ambient light. From people's forehead, the cardiac rate could be acquired based on photoplethysmography (PPG) theory. The template matching method was used after the capture of video. The video signal was discomposed into three signal channels (RGB) and the region of interest was chosen to take the average gray value. The green channel signal could provide an excellent waveform of pulse wave on the account of green lights' absorptive characteristics of blood. Through the fast Fourier transform, the cardiac rate was exactly achieved. But the research goal was not just to achieve the cardiac rate accurately. With the template matching method, the effects of body movement are reduced to a large extent, therefore the pulse wave can be detected even while people are in the moving state and the waveform is largely optimized. Several experiments are conducted on volunteers, and the results are compared with the ones gained by a finger clamped pulse oximeter. The contrast results between these two ways are exactly agreeable. This method to detect the cardiac rate and the pulse wave largely reduces the effects of body movement and can probably be widely used in the future.

  12. Photocatalytic Properties of g-C₃N₄-TiO₂ Heterojunctions under UV and Visible Light Conditions.

    Science.gov (United States)

    Fagan, Rachel; McCormack, Declan E; Hinder, Steven J; Pillai, Suresh C

    2016-04-14

    Graphitic carbon nitride ( g -C₃N₄) and titanium dioxide (TiO₂) were chosen as a model system to investigate photocatalytic abilities of heterojunction system under UV and visible light conditions. The use of g -C₃N₄ has been shown to be effective in the reduction in recombination through the interaction between the two interfaces of TiO₂ and g -C₃N₄. A simple method of preparing g -C₃N₄ through the pyrolysis of melamine was employed, which was then added to undoped TiO₂ material to form the g -C₃N₄-TiO₂ system. These materials were then fully characterized by X-ray diffraction (XRD), Brunauer Emmett Teller (BET), and various spectroscopic techniques including Raman, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), diffuse absorbance, and photoluminescence analysis. Photocatalysis studies were conducted using the model dye, rhodamine 6G utilizing visible and UV light irradiation. Raman spectroscopy confirmed that a composite of the materials was formed as opposed to a mixture of the two. Using XPS analysis, a shift in the nitrogen peak to that indicative of substitutional nitrogen was detected for all doped samples. This is then mirrored in the diffuse absorbance results, which show a clear decrease in band gap values for these samples, showing the effective band gap alteration achieved through this preparation process. When g -C₃N₄-TiO₂ samples were analyzed under visible light irradiation, no significant improvement was observed compared that of pure TiO₂. However, under UV light irradiation conditions, the photocatalytic ability of the doped samples exhibited an increased reactivity when compared to the undoped TiO₂ (0.130 min -1 ), with 4% g -C₃N₄-TiO₂ (0.187 min -1 ), showing a 43.9% increase in reactivity. Further doping to 8% g -C₃N₄-TiO₂ lead to a decrease in reactivity against rhodamine 6G. BET analysis determined that the surface area of the 4% and 8% g -C

  13. Light pollution in ultraviolet and visible spectrum: effect on different visual perceptions.

    Directory of Open Access Journals (Sweden)

    Héctor Antonio Solano Lamphar

    Full Text Available In general terms, lighting research has been focused in the development of artificial light with the purpose of saving energy and having more durable lamps. However, the consequences that artificial night lighting could bring to the human being and living organisms have become an important issue recently. Light pollution represents a significant problem to both the environment and human health causing a disruption of biological rhythms related not only to the visible spectrum, but also to other parts of the electromagnetic spectrum. Since the lamps emit across a wide range of the electromagnetic spectrum, all photobiological species may be exposed to another type of light pollution. By comparing five different lamps, the present study attempts to evaluate UV radiative fluxes relative to what humans and two species of insects perceive as sky glow level. We have analyzed three atmospheric situations: clear sky, overcast sky and evolving precipitable water content. One important finding suggests that when a constant illuminance of urban spaces has to be guaranteed the sky glow from the low pressure sodium lamps has the most significant effect to the visual perception of the insects tested. But having the fixed number of luminaires the situation changes and the low pressure sodium lamp would be the best choice for all three species. The sky glow effects can be interpreted correctly only if the lamp types and the required amount of scotopic luxes at the ground are taken into account simultaneously. If these two factors are combined properly, then the ecological consequences of sky glow can be partly reduced. The results of this research may be equally useful for lighting engineers, architects, biologists and researchers who are studying the effects of sky glow on humans and biodiversity.

  14. Light pollution in ultraviolet and visible spectrum: effect on different visual perceptions.

    Science.gov (United States)

    Solano Lamphar, Héctor Antonio; Kocifaj, Miroslav

    2013-01-01

    In general terms, lighting research has been focused in the development of artificial light with the purpose of saving energy and having more durable lamps. However, the consequences that artificial night lighting could bring to the human being and living organisms have become an important issue recently. Light pollution represents a significant problem to both the environment and human health causing a disruption of biological rhythms related not only to the visible spectrum, but also to other parts of the electromagnetic spectrum. Since the lamps emit across a wide range of the electromagnetic spectrum, all photobiological species may be exposed to another type of light pollution. By comparing five different lamps, the present study attempts to evaluate UV radiative fluxes relative to what humans and two species of insects perceive as sky glow level. We have analyzed three atmospheric situations: clear sky, overcast sky and evolving precipitable water content. One important finding suggests that when a constant illuminance of urban spaces has to be guaranteed the sky glow from the low pressure sodium lamps has the most significant effect to the visual perception of the insects tested. But having the fixed number of luminaires the situation changes and the low pressure sodium lamp would be the best choice for all three species. The sky glow effects can be interpreted correctly only if the lamp types and the required amount of scotopic luxes at the ground are taken into account simultaneously. If these two factors are combined properly, then the ecological consequences of sky glow can be partly reduced. The results of this research may be equally useful for lighting engineers, architects, biologists and researchers who are studying the effects of sky glow on humans and biodiversity.

  15. Rational design of 3D inverse opal heterogeneous composite microspheres as excellent visible-light-induced NO2 sensors at room temperature.

    Science.gov (United States)

    Wang, Tianshuang; Yu, Qi; Zhang, Sufang; Kou, Xueying; Sun, Peng; Lu, Geyu

    2018-03-08

    The lower gas sensitivity, humidity dependence of the gas sensing properties, and long recovery times of room-temperature gas sensors severely limit their applications. Herein, to address these issues, a series of 3D inverse opal (IO) In 2 O 3 -ZnO heterogeneous composite microspheres (HCMs) are fabricated by ultrasonic spray pyrolysis (USP) employing self-assembled sulfonated polystyrene (S-PS) spheres as a sacrificial template. The 3D IO In 2 O 3 -ZnO HCMs possess highly ordered 3D inverse opal structures and bimodal (meso-scale and macro-scale) pores, which can provide large accessible surface areas and rapid mass transfer, resulting in enhanced gas sensing characteristics. Furthermore, the 3D IO architecture and n-n heterojunctions can extend the photoabsorption range to the visible light area, effectively prolonging the lifetimes of photo-generated charge carriers, and can increase separation of visible light-generated charges. As a result, the as-prepared 3D IO In 2 O 3 -ZnO HCMs deliver excellent NO 2 sensing performance under visible light irradiation at room temperature, such as high sensitivity (R gas /R air = 54.3 to 5 ppm NO 2 ), low detection limit (250 ppb), fast recovery time (188 s), excellent selectivity and humidity independence. These enhanced photo-electronic gas sensing properties are attributed to the combination of highly ordered 3D IO microspheres and In 2 O 3 -ZnO heterogeneous composites.

  16. Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst.

    Science.gov (United States)

    Yeow, Jonathan; Xu, Jiangtao; Boyer, Cyrille

    2016-06-08

    Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (λ = 460 nm, 0.7 mW/cm(2)), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

  17. Down-conversion phosphors as noble-metal-free co-catalyst in ZnO for efficient visible light photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Haipeng [Institute of Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018 (China); Liu, Xinjuan, E-mail: lxj669635@126.com [Institute of Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018 (China); Liu, Jiaqing [Engineering Research Center for Nanophotonics & Advanced Instrument, Ministry of Education, Department of Physics, East China Normal University, Shanghai 200062 (China); Lei, Wenyan [Institute of Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018 (China); Li, Jinliang [Engineering Research Center for Nanophotonics & Advanced Instrument, Ministry of Education, Department of Physics, East China Normal University, Shanghai 200062 (China); Wu, Tianyang [Institute of Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018 (China); Li, Ping [Shanghai Nanotechnology Promotion Center, Shanghai 200237 (China); Li, Huili; Pan, Likun [Engineering Research Center for Nanophotonics & Advanced Instrument, Ministry of Education, Department of Physics, East China Normal University, Shanghai 200062 (China)

    2017-01-01

    Graphical abstract: ZnO-Lu{sub 3}(Al,Si){sub 5}(O,N){sub 12}:Ce{sup 3+} hybrid photocatalysts were synthesized via a fast microwave-assisted approach for visible light photocatalytic degradation of organic pollutions with a high degradation rate of 91%. - Highlights: • ZnO-Lu{sub 3}(Al,Si){sub 5}(O,N){sub 12}:Ce{sup 3+} were synthesized via a facile microwave-assisted method. • Lu{sub 3}(Al,Si){sub 5}(O,N){sub 12}:Ce{sup 3+} acts as co-catalyst to facilitates the self-sensitized degradation of MB. • ZnO-Lu{sub 3}(Al,Si){sub 5}(O,N){sub 12}:Ce{sup 3+} exhibited enhanced visible light photocatalytic activity. • A high MB degradation rate of 91% was achieved under visible light irradiation. - Abstract: Exploring novel visible light responsive photocatalysts is one of greatly significant issues from the viewpoint of using solar energy. Here we report the yellow-orange emitting α-Si{sub 3}N{sub 4}-doped Lu{sub 3}Al{sub 5}O{sub 12}:Ce{sup 3+} (Lu{sub 3}Al{sub 5-x}Si{sub x}O{sub 12-x}N{sub x}:Ce{sup 3+}) phosphors as a noble-metal-free co-catalyst for enhanced visible light photocatalytic activity of ZnO. The results show that ZnO-Lu{sub 3}Al{sub 5-x}Si{sub x}O{sub 12-x}N{sub x}:Ce{sup 3+} hybrid photocatalysts using a fast microwave-assisted approach exhibits a 91% methylene blue (MB) degradation under visible light irradiation at 240 min, which evidence the synergistic effect of ZnO and Lu{sub 3}Al{sub 5-x}Si{sub x}O{sub 12-x}N{sub x}:Ce{sup 3+} that suppress the rate of charge recombination and increase the self-sensitized degradation of MB. ZnO-down conversion phosphors can be envisaged as potential candidate in environmental engineering and solar energy applications.

  18. Blue Light Protects Against Temporal Frequency Sensitive Refractive Changes.

    Science.gov (United States)

    Rucker, Frances; Britton, Stephanie; Spatcher, Molly; Hanowsky, Stephan

    2015-09-01

    Time spent outdoors is protective against myopia. The outdoors allows exposure to short-wavelength (blue light) rich sunlight, while indoor illuminants can be deficient at short-wavelengths. In the current experiment, we investigate the role of blue light, and temporal sensitivity, in the emmetropization response. Five-day-old chicks were exposed to sinusoidal luminance modulation of white light (with blue; N = 82) or yellow light (without blue; N = 83) at 80% contrast, at one of six temporal frequencies: 0, 0.2, 1, 2, 5, 10 Hz daily for 3 days. Mean illumination was 680 lux. Changes in ocular components and corneal curvature were measured. Refraction, eye length, and choroidal changes were dependent on the presence of blue light (P light, refraction did not change across frequencies (mean change -0.24 [diopters] D), while in the absence of blue light, we observed a hyperopic shift (>1 D) at high frequencies, and a myopic shift (>-0.6 D) at low frequencies. With blue light there was little difference in eye growth across frequencies (77 μm), while in the absence of blue light, eyes grew more at low temporal frequencies and less at high temporal frequencies (10 vs. 0.2 Hz: 145 μm; P light. Illuminants rich in blue light can protect against myopic eye growth when the eye is exposed to slow changes in luminance contrast as might occur with near work.

  19. Radiation mutagenesis and modifying thereof by visible light in c3G male gamets of Drosophilla melanogaster

    International Nuclear Information System (INIS)

    Aleksandrov, I.D.

    1979-01-01

    A study was made of photoreactivation of γ-ray-induced genetic damages in postmeiotic male germ cells of c3G mutant of Drosophila melanogaster. Room light was found to decrease (DRF 1.5-2.2) the frequency of both the chromosomal mutations at five selected loci and large deletions of the X-chromosome. This effect of visible light is similar to that produced on the survival rate of γ-irradiated E. coli cells. On the other hand, exposure to light leads to a significant increase in the yield of both the point visible mutations and recessive sex-linked lethals as compared to that obtained in the dark

  20. The Effect of Nitrogen-Doped ATO Nanotubes on Radical Multiplication of Buffer Media by Visible Light Photocatalysis Rather UV

    Directory of Open Access Journals (Sweden)

    Kan-Hung Hu

    2012-01-01

    Full Text Available The use of TiO2 in photodynamic therapy for the treatment of cancer has generally been studied in cultured cancer cells in serum-containing RPMI 1640 medium under visible light application rather than ultraviolet (UV light. An ordered channel array of N-doped anodic titanium dioxide (ATO has been successfully made for visible light application. ATO nanotubes in the anatase form with a length of 10 μm are more effective than nanotubes of 1.8 μm in length as a photocatalyst for radical multiplication in buffer solution by generating hydroxyl radicals and superoxide radical anions under UV-A exposure. Only the N-doped ATO is applicable to visible light photocatalysis for radical multiplication in RPMI 1640+1% FBS and acrylamide, a free radical carrier.

  1. Reactive magnetron sputtering deposition of bismuth tungstate onto titania nanoparticles for enhancing visible light photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Ratova, Marina, E-mail: marina_ratova@hotmail.com [Surface Engineering Group, School of Engineering, Manchester Metropolitan University, Manchester, M1 5GD (United Kingdom); Kelly, Peter J.; West, Glen T. [Surface Engineering Group, School of Engineering, Manchester Metropolitan University, Manchester, M1 5GD (United Kingdom); Tosheva, Lubomira; Edge, Michele [School of Science and the Environment, Manchester Metropolitan University, Manchester M1 5GD (United Kingdom)

    2017-01-15

    Highlights: • Bismuth tungstate coatings were deposited by reactive magnetron sputtering. • Oscillating bowl was introduced to the system to enable coating of nanopartulates. • Deposition of Bi{sub 2}WO{sub 6} enhanced visible light activity of titania nanoparticles. • The best results were obtained for coating with Bi:W ratio of approximately 2:1. • Deposition of Bi{sub 2}WO{sub 6} onto TiO{sub 2} resulted in more efficient electron-hole separation. - Abstract: Titanium dioxide − bismuth tungstate composite materials were prepared by pulsed DC reactive magnetron sputtering of bismuth and tungsten metallic targets in argon/oxygen atmosphere onto anatase and rutile titania nanoparticles. The use of an oscillating bowl placed beneath the two magnetrons arranged in a co-planar closed field configuration enabled the deposition of bismuth tungstate onto loose powders, rather than a solid substrate. The atomic ratio of the bismuth/tungsten coatings was controlled by varying the power applied to each target. The effect of the bismuth tungstate coatings on the phase, optical and photocatalytic properties of titania was investigated by X-ray diffraction, energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) surface area measurements, transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy and an acetone degradation test. The latter involved measurements of the rate of CO{sub 2} evolution under visible light irradiation of the photocatalysts, which indicated that the deposition of bismuth tungstate resulted in a significant enhancement of visible light activity, for both anatase and rutile titania particles. The best results were achieved for coatings with a bismuth to tungsten atomic ratio of 2:1. In addition, the mechanism by which the photocatalytic activity of the TiO{sub 2} nanoparticles was enhanced by compounding it with bismuth tungstate was studied by microwave cavity perturbation. The results of these

  2. Investigation of L(+)-Ascorbic Acid with Raman Spectroscopy in Visible and UV Light

    DEFF Research Database (Denmark)

    Berg, Rolf W.

    2015-01-01

    Abstract: Raman spectroscopy investigations of l(+)-ascorbic acid and its mono- and di-deprotonated anions (AH(-) and A(2-)) are reviewed and new measurements reported with several wavelengths, 229, 244, 266, 488, and 532nm. Results are interpreted, assisted by new DFT/B3LYP quantum chemical calc......). Relatively weak preresonance enhancement was seen for A(2-) when excitation was done with 229nm UV light, allowing water bands to become observable as for normal visible light Raman spectra....... calculations with 6-311++G(d,p) basis sets for several conformations of ascorbic acid and the anions. Raman spectra were measured during titration with NaOH base in an oxygen-poor environment to avoid fluorescence when solutions were alkaline. The ultraviolet (UV) absorption band for ascorbic acid in aqueous......cm(-1). Finally, for the ascorbate di-anion, absorption was found at similar to 298.4nm with molar absorptivity of similar to 7,000 L mol(-1) cm(-1) and below similar to 220nm. With UV light (244 and 266nm), strongly basic solutions gave pronounced Raman resonance enhancement at similar to 1556cm(-1...

  3. Exchangeable cations-mediated photodegradation of polycyclic aromatic hydrocarbons (PAHs) on smectite surface under visible light.

    Science.gov (United States)

    Jia, Hanzhong; Li, Li; Chen, Hongxia; Zhao, Yue; Li, Xiyou; Wang, Chuanyi

    2015-04-28

    Clay minerals saturated with different exchangeable cations are expected to play various roles in photodegradation of polycyclic aromatic hydrocarbons (PAHs) via direct and/or indirect pathways on clay surfaces. In the present study, anthracene and phenanthrene were selected as molecule probes to investigate the roles of exchangeable cations on their photodegradation under visible light irradiation. For five types of cation-modified smectite clays, the photodegradation rate of anthracene and phenanthrene follows the order: Fe(3+)>Al(3+)>Cu(2+)>Ca(2+)>K(+)>Na(+), which is consistent with the binding energy of cation-π interactions between PAHs and exchangeable cations. The result suggests that PAHs photolysis rate depends on cation-π interactions on clay surfaces. Meanwhile, the deposition of anthracene at the Na(+)-smectite and K(+)-smectite surface favors solar light absorption, resulting in enhanced direct photodecomposition of PAHs. On the other hand, smectite clays saturated with Fe(3+), Al(3+), and Cu(2+) are highly photoreactive and can act as potential catalysts giving rise to oxidative radicals such as O2(-) , which initiate the transformation of PAHs. The present work provides valuable insights into understanding the transformation and fate of PAHs in the natural soil environment and sheds light on the development of technologies for contaminated land remediation. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Modeling and Analysis of DIPPM: A New Modulation Scheme for Visible Light Communications

    Directory of Open Access Journals (Sweden)

    Sana Ullah Jan

    2015-01-01

    Full Text Available Visible Light Communication (VLC uses an Intensity-Modulation and Direct-Detection (IM/DD scheme to transmit data. However, the light source used in VLC systems is continuously switched on and off quickly, resulting in flickering. In addition, recent illumination systems include dimming support to allow users to dim the light sources to the desired level. Therefore, the modulation scheme for data transmission in VLC system must include flicker mitigation and dimming control capabilities. In this paper, the authors propose a Double Inverse Pulse Position Modulation (DIPPM scheme that minimizes flickering and supports a high level of dimming for the illumination sources in VLC systems. To form DIPPM, some changes are made in the symbol structure of the IPPM scheme, and a detailed explanation and mathematical model of DIPPM are given in this paper. Furthermore, both analytical and simulation results for the error performance of 2-DIPPM are compared with the performance of VPPM. Also, the communication performance of DIPPM is analyzed in terms of the normalized required power.

  5. Performance enhancement technique of visible light communications using passive photovoltaic cell

    Science.gov (United States)

    Wu, Jhao-Ting; Chow, Chi-Wai; Liu, Yang; Hsu, Chin-Wei; Yeh, Chien-Hung

    2017-06-01

    The light emitting diode (LED) based visible light communication (VLC) system can provide lighting and communication simultaneously. It has attracted much attenuation recently. As the photovoltaic cell (also known as solar cell) is physically flexible, low cost, and easily available, it could be a good choice for the VLC receiver (Rx). Furthermore, besides acting as the VLC Rx, the solar cell can convert VLC signal into electricity for charging up the Rx devices. Hence, it could be a promising candidate for the future internet-of-thing (IoT) networks. However, using solar cell as VLC Rx is challenging, since the response of the solar cell is highly limited and it will limit the VLC data rate. In this work, we propose and demonstrate for the first time using pre-distortion Manchester coding (MC) signal to enhance the signal performance of solar cell Rx based VLC. The proposed scheme can significantly mitigate the slow response, as well as the direct-current (DC) wandering effect of the solar cell; hence 50 times increase in data rate can be experimentally achieved.

  6. Recognition of Banknote Fitness Based on a Fuzzy System Using Visible Light Reflection and Near-infrared Light Transmission Images.

    Science.gov (United States)

    Kwon, Seung Yong; Pham, Tuyen Danh; Park, Kang Ryoung; Jeong, Dae Sik; Yoon, Sungsoo

    2016-06-11

    Fitness classification is a technique to assess the quality of banknotes in order to determine whether they are usable. Banknote classification techniques are useful in preventing problems that arise from the circulation of substandard banknotes (such as recognition failures, or bill jams in automated teller machines (ATMs) or bank counting machines). By and large, fitness classification continues to be carried out by humans, and this can cause the problem of varying fitness classifications for the same bill by different evaluators, and requires a lot of time. To address these problems, this study proposes a fuzzy system-based method that can reduce the processing time needed for fitness classification, and can determine the fitness of banknotes through an objective, systematic method rather than subjective judgment. Our algorithm was an implementation to actual banknote counting machine. Based on the results of tests on 3856 banknotes in United States currency (USD), 3956 in Korean currency (KRW), and 2300 banknotes in Indian currency (INR) using visible light reflection (VR) and near-infrared light transmission (NIRT) imaging, the proposed method was found to yield higher accuracy than prevalent banknote fitness classification methods. Moreover, it was confirmed that the proposed algorithm can operate in real time, not only in a normal PC environment, but also in an embedded system environment of a banknote counting machine.

  7. Recognition of Banknote Fitness Based on a Fuzzy System Using Visible Light Reflection and Near-infrared Light Transmission Images

    Directory of Open Access Journals (Sweden)

    Seung Yong Kwon

    2016-06-01

    Full Text Available Fitness classification is a technique to assess the quality of banknotes in order to determine whether they are usable. Banknote classification techniques are useful in preventing problems that arise from the circulation of substandard banknotes (such as recognition failures, or bill jams in automated teller machines (ATMs or bank counting machines. By and large, fitness classification continues to be carried out by humans, and this can cause the problem of varying fitness classifications for the same bill by different evaluators, and requires a lot of time. To address these problems, this study proposes a fuzzy system-based method that can reduce the processing time needed for fitness classification, and can determine the fitness of banknotes through an objective, systematic method rather than subjective judgment. Our algorithm was an implementation to actual banknote counting machine. Based on the results of tests on 3856 banknotes in United States currency (USD, 3956 in Korean currency (KRW, and 2300 banknotes in Indian currency (INR using visible light reflection (VR and near-infrared light transmission (NIRT imaging, the proposed method was found to yield higher accuracy than prevalent banknote fitness classification methods. Moreover, it was confirmed that the proposed algorithm can operate in real time, not only in a normal PC environment, but also in an embedded system environment of a banknote counting machine.

  8. Understanding the superior photocatalytic activity of noble metals modified titania under UV and visible light irradiation.

    Science.gov (United States)

    Bumajdad, Ali; Madkour, Metwally

    2014-04-28

    Although TiO2 is one of the most efficient photocatalysts, with the highest stability and the lowest cost, there are drawbacks that hinder its practical applications like its wide band gap and high recombination rate of the charge carriers. Consequently, many efforts were directed toward enhancing the photocatalytic activity of TiO2 and extending its response to the visible region. To head off these attempts, modification of TiO2 with noble metal nanoparticles (NMNPs) received considerable attention due to their role in accelerating the transfer of photoexcited electrons from TiO2 and also due to the surface plasmon resonance which induces the photocatalytic activity of TiO2 under visible light irradiation. This insightful perspective is devoted to the vital role of TiO2 photocatalysis and its drawbacks that urged researchers to find solutions such as modification with NMNPs. In a coherent context, we discussed here the characteristics which qualify NMNPs to possess a great enhancement effect for TiO2 photocatalysis. Also we tried to understand the reasons behind this effect by means of photoluminescence (PL) and electron paramagnetic resonance (EPR) spectra, and Density Functional Theory (DFT) calculations. Then the mechanism of action of NMNPs upon deposition on TiO2 is presented. Finally we introduced a survey of the behaviour of these noble metal NPs on TiO2 based on the particle size and the loading amount.

  9. The Simplest Way to Iodine-Doped Anatase for Photocatalysts Activated by Visible Light

    Directory of Open Access Journals (Sweden)

    Václav Štengl

    2011-01-01

    Full Text Available Iodine-doped TiO2 was prepared by thermal hydrolysis of aqueous solutions of the titanium peroxo-complex, which includes no organic solvents or organometallic compounds. The synthesized samples were characterized by X-ray diffraction (XRD, Raman spectroscopy (RS, infrared spectroscopy (IR, specific surface area (BET, and porosity determination (BJH. The morphology and particle size was determined by high-resolution transmission electron microscopy (HRTEM and selected area electron diffraction (SAED. All prepared samples have a red-shifted band-gap transition, well crystalline anatase structure, and porous particles with a 100–200 m2 g−1 specific surface area. The photocatalytic activity of iodine-doped titania samples was determined by decomposition of Orange II dye during irradiation at 365 nm and 400 nm. Iodine doping promotes the titania photocatalytic activity very efficiently under visible light irradiation. The titania sample with 0.32 wt.% I has the highest catalytic activity during the photocatalyzed degradation of Orange II dye in an aqueous suspension in the UV and visible regions.

  10. Visible light assisted photoelectrocatalytic degradation of sugarcane factory wastewater by sprayed CZTS thin films

    Science.gov (United States)

    Hunge, Y. M.; Mahadik, M. A.; Patil, V. L.; Pawar, A. R.; Gadakh, S. R.; Moholkar, A. V.; Patil, P. S.; Bhosale, C. H.

    2017-12-01

    Highly crystalline Cu2ZnSnS4 (CZTS) thin films have been deposited onto glass and FTO coated glass substrates by simple chemical spray-pyrolysis technique. It is an important material for solar energy conversion through the both photovoltaics and photocatalysis. The effect of substrate temperatures on the physico-chemical properties of the CZTS films is studied. The XRD study shows the formation of single phase CZTS with kesterite structure. FE-SEM analysis reveals nano flakes architecture with pin-hole and crake free surface with more adherent. The film deposited at optimized substrate temperature exhibits optical band gap energy of 1.90 eV, which lies in the visible region of the solar spectrum and useful for photocatalysis application. The photoelectrocatalytic activities of the large surface area (10 × 10 cm2) deposited CZTS thin film photocatalysts were evaluated for the degradation of sugarcane factory wastewater under visible light irradiation. The results show that the CZTS thin film photocatalyst exhibited about 90% degradation of sugar cane factory wastewater. The mineralization of sugarcane factory wastewater is studied by measuring chemical oxygen demand (COD) values.

  11. Probing Photocatalytic Characteristics of Sb-Doped TiO2 under Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Lingjing Luo

    2014-01-01

    Full Text Available Sb-doped TiO2 nanoparticle with varied dopant concentrations was synthesized using titanium tetrachloride (TiCl4 and antimony chloride (SbCl3 as the precursors. The properties of Sb-doped TiO2 nanoparticles were characterized by X-ray diffraction (XRD, scanning electron microscope (SEM, fluorescence spectrophotometer, and Uv-vis spectrophotometer. The absorption edge of TiO2 nanoparticles could be extended to visible region after doping with antimony, in contrast to the UV absorption of pure TiO2. The results showed that the photocatalytic activity of Sb-doped TiO2 nanoparticles was much more active than pure TiO2. The 0.1% Sb-doped TiO2 nanoparticles demonstrated the best photocatalytic activity which was better than that of the Degussa P25 under visible light irradiation using terephthalic acid as fluorescent probe. The effects of Sb dopant on the photocatalytic activity and the involved mechanism were extensively investigated in this work as well.

  12. Layered-Double-Hydroxide Nanosheets as Efficient Visible-Light-Driven Photocatalysts for Dinitrogen Fixation.

    Science.gov (United States)

    Zhao, Yufei; Zhao, Yunxuan; Waterhouse, Geoffrey I N; Zheng, Lirong; Cao, Xingzong; Teng, Fei; Wu, Li-Zhu; Tung, Chen-Ho; O'Hare, Dermot; Zhang, Tierui

    2017-11-01

    Semiconductor photocatalysis attracts widespread interest in water splitting, CO 2 reduction, and N 2 fixation. N 2 reduction to NH 3 is essential to the chemical industry and to the Earth's nitrogen cycle. Industrially, NH 3 is synthesized by the Haber-Bosch process under extreme conditions (400-500 °C, 200-250 bar), stimulating research into the development of sustainable technologies for NH 3 production. Herein, this study demonstrates that ultrathin layered-double-hydroxide (LDH) photocatalysts, in particular CuCr-LDH nanosheets, possess remarkable photocatalytic activity for the photoreduction of N 2 to NH 3 in water at 25 °C under visible-light irradiation. The excellent activity can be attributed to the severely distorted structure and compressive strain in the LDH nanosheets, which significantly enhances N 2 chemisorption and thereby promotes NH 3 formation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Visible-light photocatalytic activity of graphene oxide-wrapped Bi2WO6 hierarchical microspheres

    Science.gov (United States)

    Zhai, Jiali; Yu, Hongwen; Li, Haiyan; Sun, Lei; Zhang, Kexin; Yang, Hongjun

    2015-07-01

    A facile approach of fabricating homogeneous graphene oxide (GO)-wrapped Bi2WO6 microspheres (GO/Bi2WO6) is developed. The transmission electron microscopy (TEM) results show that a heterojunction interface between GO and Bi2WO6. The UV-vis diffuse reflection spectra (DRS) reveal that the as-prepared GO/Bi2WO6 composites own more intensive absorption in the visible light range compared with pure Bi2WO6. These characteristic structural and optical properties endow GO/Bi2WO6 composites with enhanced photocatalytic activity. The enhanced photocatalytic activity of the GO/Bi2WO6 is attributed predominantly to the synergetic effect between GO and Bi2WO6, causing rapid generation and separation of photo-generated charge carriers.

  14. Multiple bio-monitoring system using visible light for electromagnetic-wave free indoor healthcare

    Science.gov (United States)

    An, Jinyoung; Pham, Ngoc Quan; Chung, Wan-Young

    2017-12-01

    In this paper, a multiple biomedical data transmission system with visible light communication (VLC) is proposed for an electromagnetic-wave-free indoor healthcare. VLC technology has emerged as an alternative solution to radio-frequency (RF) wireless systems, due to its various merits, e.g., ubiquity, power efficiency, no RF radiation, and security. With VLC, critical bio-medical signals, including electrocardiography (ECG), can be transmitted in places where RF radiation is restricted. This potential advantage of VLC could save more lives in emergency situations. A time hopping (TH) scheme is employed to transfer multiple medical-data streams in real time with a simple system design. Multiple data streams are transmitted using identical color LEDs and go into an optical detector. The received multiple data streams are demodulated and rearranged using a TH-based demodulator. The medical data is then monitored and managed to provide the necessary medical care for each patient.

  15. Visible-Light-Driven Hydrogen Evolution Using Planarized Conjugated Polymer Photocatalysts.

    Science.gov (United States)

    Sprick, Reiner Sebastian; Bonillo, Baltasar; Clowes, Rob; Guiglion, Pierre; Brownbill, Nick J; Slater, Benjamin J; Blanc, Frédéric; Zwijnenburg, Martijn A; Adams, Dave J; Cooper, Andrew I

    2016-01-26

    Linear poly(p-phenylene)s are modestly active UV photocatalysts for hydrogen production in the presence of a sacrificial electron donor. Introduction of planarized fluorene, carbazole, dibenzo[b,d]thiophene or dibenzo[b,d]thiophene sulfone units greatly enhances the H 2 evolution rate. The most active dibenzo[b,d]thiophene sulfone co-polymer has a UV photocatalytic activity that rivals TiO 2 , but is much more active under visible light. The dibenzo[b,d]thiophene sulfone co-polymer has an apparent quantum yield of 2.3 % at 420 nm, as compared to 0.1 % for platinized commercial pristine carbon nitride.

  16. Visible light communication using DC-biased optical filter bank multi-carrier modulation

    KAUST Repository

    Chen, Rui

    2018-03-19

    Filter bank multicarrier (FBMC) has become a promising candidate to replace conventional orthogonal frequency-division multiplexing (OFDM) scheme in 5G technology due to its better spectral confinement which results in a reduced inter-channel interference (ICI). However, the viability of using FBMC in visible light communication has not been verified. In this work we present the first experimental validation of the DC-biased optical filter bank multicarrier (DCO-FBMC) modulation scheme over a free-space optical channel. Under different receiving powers, up to three times bit error rate performance improvement has been achieved using DCO-FBMC with different overlapping factors compared to that of conventional DCO-OFDM.

  17. Visible-light-responsive ZnCuO nanoparticles: benign photodynamic killers of infectious protozoans.

    Science.gov (United States)

    Nadhman, Akhtar; Nazir, Samina; Khan, Malik Ihsanullah; Ayub, Attiya; Muhammad, Bakhtiar; Khan, Momin; Shams, Dilawar Farhan; Yasinzai, Masoom

    2015-01-01

    Human beings suffer from several infectious agents such as viruses, bacteria, and protozoans. Recently, there has been a great interest in developing biocompatible nanostructures to deal with infectious agents. This study investigated benign ZnCuO nanostructures that were visible-light-responsive due to the resident copper in the lattice. The nanostructures were synthesized through a size-controlled hot-injection process, which was adaptable to the surface ligation processes. The nanostructures were then characterized through transmission electron microscopy, X-ray diffraction, diffused reflectance spectroscopy, Rutherford backscattering, and photoluminescence analysis to measure crystallite nature, size, luminescence, composition, and band-gap analyses. Antiprotozoal efficiency of the current nanoparticles revealed the photodynamic killing of Leishmania protozoan, thus acting as efficient metal-based photosensitizers. The crystalline nanoparticles showed good biocompatibility when tested for macrophage toxicity and in hemolysis assays. The study opens a wide avenue for using toxic material in resident nontoxic forms as an effective antiprotozoal treatment.

  18. Material-Efficient Microfluidic Platform for Exploratory Studies of Visible-Light Photoredox Catalysis.

    Science.gov (United States)

    Coley, Connor W; Abolhasani, Milad; Lin, Hongkun; Jensen, Klavs F

    2017-08-07

    We present an automated microfluidic platform for in-flow studies of visible-light photoredox catalysis in liquid or gas-liquid reactions at the 15 μL scale. An oscillatory flow strategy enables a flexible residence time while preserving the mixing and heat transfer advantages of flow systems. The adjustable photon flux made possible with the platform is characterized using actinometry. Case studies of oxidative hydroxylation of phenylboronic acids and dimerization of thiophenol demonstrate the capabilities and advantages of the system. Reaction conditions identified through droplet screening translate directly to continuous synthesis with minor platform modifications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Engaging unactivated alkyl, alkenyl and aryl iodides in visible-light-mediated free radical reactions

    Science.gov (United States)

    Nguyen, John D.; D'Amato, Erica M.; Narayanam, Jagan M. R.; Stephenson, Corey R. J.

    2012-10-01

    Radical reactions are a powerful class of chemical transformations. However, the formation of radical species to initiate these reactions has often required the use of stoichiometric amounts of toxic reagents, such as tributyltin hydride. Recently, the use of visible-light-mediated photoredox catalysis to generate radical species has become popular, but the scope of these radical precursors has been limited. Here, we describe the identification of reaction conditions under which photocatalysts such as fac-Ir(ppy)3 can be utilized to form radicals from unactivated alkyl, alkenyl and aryl iodides. The generated radicals undergo reduction via hydrogen atom abstraction or reductive cyclization. The reaction protocol utilizes only inexpensive reagents, occurs under mild reaction conditions, and shows exceptional functional group tolerance. Reaction efficiency is maintained upon scale-up and decreased catalyst loading, and the reaction time can be significantly shortened when the reaction is performed in a flow reactor.

  20. Photocatalytic degradation of selected herbicides in aqueous suspensions of doped titania under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Sojic, Daniela V., E-mail: daniela.sojic@dh.uns.ac.rs [Department of Chemistry, Biochemistry and Environmental Protection, Faculty of Sciences, University of Novi Sad, Trg D. Obradovica 3, 21000 Novi Sad (Serbia); Despotovic, Vesna N., E-mail: vesna.despotovic@dh.uns.ac.rs [Department of Chemistry, Biochemistry and Environmental Protection, Faculty of Sciences, University of Novi Sad, Trg D. Obradovica 3, 21000 Novi Sad (Serbia); Abazovic, Nadica D., E-mail: kiki@vinca.rs [Vinca Institute of Nuclear Sciences, 11001 Beograd, PO Box 522 (Serbia); Comor, Mirjana I., E-mail: mirjanac@vinca.rs [Vinca Institute of Nuclear Sciences, 11001 Beograd, PO Box 522 (Serbia); Abramovic, Biljana F., E-mail: biljana.abramovic@dh.uns.ac.rs [Department of Chemistry, Biochemistry and Environmental Protection, Faculty of Sciences, University of Novi Sad, Trg D. Obradovica 3, 21000 Novi Sad (Serbia)

    2010-07-15

    The aim of this work was to study the efficiency of Fe- and N-doped titania suspensions in the photocatalytic degradation of the herbicides RS-2-(4-chloro-o-tolyloxy)propionic acid (mecoprop, MCPP), (4-chloro-2-methylphenoxy)acetic acid (MCPA), and 3,6-dichloropyridine-2-carboxylic acid (clopyralid, CP) under the visible light ({lambda} {>=} 400 nm) irradiation. The obtained results were compared with those of the corresponding undoped TiO{sub 2} (rutile/anatase) and of the most frequently used TiO{sub 2} Degussa P25. Computational modeling procedures were used to optimize geometry and molecular electrostatic potentials of MCPP, MCPA and CP and discuss the obtained results. The results indicate that the efficiency of photocatalytic degradation is greatly influenced by the molecular structure of the compound. Lowering of the band gap of titanium dioxide by doping is not always favorable for increasing photocatalytic efficiency of degradation.