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Sample records for visible light sensitive

  1. Visible Light Dye-Sensitized Photosensititve Systems

    National Research Council Canada - National Science Library

    Fang Gao; Yong-yuan Yang

    2000-01-01

      The visible light dyes were employed to sensitized o-Cl-Hexaarylbiimidazole (o-Cl-HABI). The obtained results suggested that o-Cl-HABI displayed a efficient sensitized photocleavage when exposed to Xenon lamp...

  2. 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.

  3. 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.

  4. A fast, visible-light-sensitive azobenzene for bioorthogonal ligation.

    Science.gov (United States)

    Poloni, Claudia; Szymański, Wiktor; Hou, Lili; Browne, Wesley R; Feringa, Ben L

    2014-01-20

    Azobenzenes have been used as photoresponsive units for the control of numerous biological processes. Primary prerequisites for such applications are site-selective incorporation of photoswitchable units into biomolecules and the possibility of using non-destructive and deep-tissue-penetrating visible light for the photoisomerization. Here we report a push-pull azobenzene that readily undergoes a Staudinger-Bertozzi ligation with azide groups, that can be addressed with visible light (>440 nm) and exhibits the solvato- and acidochromism typical for push-pull systems. The thermal relaxation in aqueous environment proceeds on the low-millisecond timescale, thus enabling control over biological processes on similar timescales. The approach is demonstrated in the modification of a quartz surface and in the incorporation of an azobenzene unit into a functional peptide, the third zinc finger in the mammalian factor Sp1. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Visible Light Dye-Sensitized Photosensitive Systems: A Comprehensive Study on Photoimaging

    National Research Council Canada - National Science Library

    Gao, Fang; Yang, Yong-yuan

    2000-01-01

    The visible light dyes were employed to sensitized o-Cl-Hexaarylbiimidazole (o-Cl-HABI). The obtained results suggested that o-Cl-HABI displayed a efficient sensitized photocleavage when exposed to Xenon lamp...

  6. Visible-light sensitized luminescent europium(III)-β-diketonate complexes: bioprobes for cellular imaging.

    Science.gov (United States)

    Reddy, M L P; Divya, V; Pavithran, Rani

    2013-11-21

    Visible-light sensitized luminescent europium(III) molecular materials are of considerable importance because their outstanding photophysical properties make them well suited as labels in fluorescence-based bioassays and low-voltage driven pure red-emitters in optoelectronic technology. One challenge in this field is development of visible-light sensitizing ligands that can form highly emissive europium(III) complexes with sufficient stability and aqueous solubility for practical applications. Indeed, some of the recent reports have demonstrated that the excitation-window can be shifted to longer-wavelengths in europium(III)-β-diketonate complexes by appropriate molecular engineering and suitably expanded π-conjugation in the complex molecules. In this review, attention is focused on the latest innovations in the syntheses and photophysical properties of visible-light sensitized europium(III)-β-diketonate complexes and their application as bioprobes for cellular imaging. Furthermore, luminescent nanomaterials derived from long-wavelength sensitized europium(III)-β-diketonate complexes and their application in life sciences are also highlighted.

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

    Science.gov (United States)

    Chen, Hongjun

    2014-01-01

    Summary 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. PMID:24991507

  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. Visible light sensitive photocatalyst, delafossite structured alpha-AgGaO(2).

    Science.gov (United States)

    Maruyama, Yoshihiko; Irie, Hiroshi; Hashimoto, Kazuhito

    2006-11-23

    Delafossite structured alpha-AgGaO(2) powder was successfully synthesized through a cation exchange reaction. alpha-AgGaO(2) has a band gap of 2.4 eV, absorbs visible light up to 520 nm, and effectively decomposes 2-propanol to CO2 via acetone by irradiating with either UV light (300-400 nm) or visible light (420-530 nm). The values of the quantum efficiency are similar (ca. 0.6%) under light irradiations with wavelengths of 365, 390, 430, 470, and 510 +/- 10 nm, but steeply decrease with wavelengths longer than 530 +/- 10 nm, which support a 2.4 eV band gap. In contrast, the other polymorph, alpha-AgGaO(2) powder, which has a band gap of 2.1 eV, shows a negligible activity when irradiating with either UV light or visible light. The higher oxidation activity of alpha-AgGaO(2) is probably due to its larger band gap, which is formed at the top of its valence band in a lower energy region as compared to alpha-AgGaO(2). Moreover, the first-principle calculations of alpha-AgGaO(2) and alpha-AgGaO(2) clearly indicate that alpha-AgGaO(2) has a remarkably larger dispersed valence band as compared to alpha-AgGaO(2), which is advantageous to the photocatalytic activity due to the efficient hole conduction.

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

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    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.

  11. Investigation of curcumin as sensitizer for anatase TiO2 nanoparticles in photodegradation of of phenazopyridine with visible light

    Directory of Open Access Journals (Sweden)

    ZYOUD Ahed H.

    2014-11-01

    Full Text Available This work describes a photodegradation catalyst, for water organic contaminants in visible light, based on curcumin (a natural dye sensitized TiO2 (anatase nanoparticles. Phenazopyridine (a pharmaceutically active gradient was used as a contaminant. A 400 nm, and shorter, cut of filter was used to confirm only visible light was used in photodegradation process with no UV radiation. The catalyst system was characterized by electronic absorption spectroscopy and XRD. The particle size forthe catalyst nanaprticles was calculated using Scherrer equation and found to be ~45 nm in average. Different reaction parameters were studied, such as effect of contaminant concentration, amount of loaded catalyst, and pH value on the photodegradation rate. Turn number (T.N. and quantum yield (Q.Y. values were calculated for comparative assessment of the catalyst effeciency. The results show the ability of curcumin dyes to sensitize TiO2 anatase nanoparticles in photodegradation phenazopyridine under visible radiation.

  12. Novel polypyrrole-sensitized hollow TiO2/fly ash cenospheres: Synthesis, characterization, and photocatalytic ability under visible light

    Science.gov (United States)

    Wang, Bing; Li, Chuang; Pang, Jianfeng; Qing, Xutang; Zhai, Jianping; Li, Qin

    2012-10-01

    The polypyrrole-sensitized TiO2 layer on fly ash cenosphere (PPy-TiO2/FAC) was successfully prepared as a promising photocatalyst with visible light response. Photocatalytic activity and kinetics of PPy-TiO2/FAC under visible light were detected in details from aspects of different dopant concentration of HCl and different pyrrole (Py)/Ti molar ratio by detecting photodegradation of methylene blue (MB) and phenol, respectively. It was found that the decomposition rate increased with the increasing Py/Ti molar ratio up to an optimal value, beyond which the photocatalytic activity showed a decreasing tendency. The concentration of HCl in the preparation of PPy-TiO2/FAC also largely influenced the photodecomposition rate of target contamination. The results demonstrate that when the molar ratio of Py/Ti is 1% and the concentration of HCl is 1 mol L-1, the synthesized photocatalyst showed the best photocatalytic activity under visible light.

  13. 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.

  14. 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.

  15. Eosin Y-sensitized artificial photosynthesis by highly efficient visible-light-driven regeneration of nicotinamide cofactor.

    Science.gov (United States)

    Lee, Sahng Ha; Nam, Dong Heon; Kim, Jae Hong; Baeg, Jin-Ook; Park, Chan Beum

    2009-07-06

    Dye-sensitized photosynthesis: Eosin Y (EY), a dye photosensitizer, works efficiently as a molecular photoelectrode by catalyzing the visible-light-driven electron-transfer reaction for efficient regeneration of NADH through a photosensitizer-electron relay dyad. Injection of the photosensitized electron resulted in highly accelerated regeneration of NADH, which can be used by glutamate dehydrogenase for the photosynthesis of L-glutamate.

  16. Fluorescent Brighteners as Visible LED-Light Sensitive Photoinitiators for Free Radical Photopolymerizations.

    Science.gov (United States)

    Zuo, Xiaoling; Morlet-Savary, Fabrice; Graff, Bernadette; Blanchard, Nicolas; Goddard, Jean-Philippe; Lalevée, Jacques

    2016-05-01

    The photochemical and electrochemical investigations of commercially available, safe, and cheap fluorescent brighteners, namely, triazinylstilbene (commercial name: fluorescent brightener 28) and 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene, as well as their original use as photoinitiators of polymerization upon light emitting diode (LED) irradiation are reported. Remarkably, their excellent near-UV-visible absorption properties combined with outstanding fluorescent properties allow them to act as high-performance photoinitiators when used in combination with diaryliodonium salt. These two-component photoinitiating systems can be employed for free radical polymerizations of acrylate. In addition, this brightener-initiated photopolymerization is able to overcome oxygen inhibition even upon irradiation with low LED light intensity. The underlying photochemical mechanisms are investigated by electron-spin resonance-spin trapping, fluorescence, cyclic voltammetry, and steady-state photolysis techniques. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Visible light absorption and photo-sensitizing properties of spinach leaves and beetroot extracted natural dyes

    Science.gov (United States)

    Sengupta, D.; Mondal, B.; Mukherjee, K.

    2015-09-01

    Herein, chlorophyll and betalain dyes are extracted from fresh spinach leaves and beetroots. Fourier transform infrared spectra are used to identify the characteristic peaks of the extracted dyes. UV-vis light absorption characteristics of the dyes and their mixed counterpart are investigated by varying their pH and temperature. These dyes are used as photo sensitizer for fabrication of zinc oxide photo-anode based dye sensitized solar cells (DSSCs). The photo-voltaic characteristics of the developed DSSCs are measured under simulated solar light (power of incident light 100 mW cm-2 from Air Mass 1.5G). The solar to electric conversion efficiencies for the chlorophyll, betalain and mixed dye based solar cells are estimated as 0.148%, 0.197% and 0.294% respectively. The highest conversion efficiency for mixed dye based solar cell is attributed due to the absorption of wider range of solar spectrum.

  18. Visible light absorption and photo-sensitizing properties of spinach leaves and beetroot extracted natural dyes.

    Science.gov (United States)

    Sengupta, D; Mondal, B; Mukherjee, K

    2015-09-05

    Herein, chlorophyll and betalain dyes are extracted from fresh spinach leaves and beetroots. Fourier transform infrared spectra are used to identify the characteristic peaks of the extracted dyes. UV-vis light absorption characteristics of the dyes and their mixed counterpart are investigated by varying their pH and temperature. These dyes are used as photo sensitizer for fabrication of zinc oxide photo-anode based dye sensitized solar cells (DSSCs). The photo-voltaic characteristics of the developed DSSCs are measured under simulated solar light (power of incident light 100 mW cm(-2) from Air Mass 1.5G). The solar to electric conversion efficiencies for the chlorophyll, betalain and mixed dye based solar cells are estimated as 0.148%, 0.197% and 0.294% respectively. The highest conversion efficiency for mixed dye based solar cell is attributed due to the absorption of wider range of solar spectrum. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. A bifunctionalized dye-sensitized TiO(2) film for efficient degradation of methyl orange under visible light irradiation.

    Science.gov (United States)

    Wu, Quanping; Zhao, Jun; Qin, Guohui; Wang, Xuezheng; Tong, Xinli; Xue, Song

    2012-01-01

    A new bifunctionalized TiO(2) film containing a dye-sensitized region and a degradation region was described. A similar structure of dye-sensitized solar cell (DSSC) was fabricated in the dye-sensitized region to accomplish separation of electrons from positive charges, and separation of dye from pollutants to avoid dye decomposition. The bifunctionalized TiO(2) film electrode and anode electrode can degrade methyl orange (MO) in reactors A and B, respectively. The degradation efficiency was enhanced remarkably by an external electrical potential. The decolorization of MO reaches as high as 95% after 2 h visible light irradiation at an external potential of 0.5 V along with a loss of 41% total organic carbon (TOC). The possible reason for the improvement of degradation by external DC potential was discussed. Effects of pH and inorganic salts on the decolorization are present.

  20. Quantum dots in photocatalytic applications: efficiently enhancing visible light photocatalytic activity by integrating CdO quantum dots as sensitizers.

    Science.gov (United States)

    Reshak, A H

    2017-09-20

    The amalgamation of a wide optical band gap photocatalyst with visible-light-active CdO quantum dots (QDs) as sensitizers is one of the most efficient ways to improve photocatalytic performance under visible light irradiation. The photocatalytic performance of cadmium benzoate ((Cd(C 7 H 5 O 2 ) 2 ) 3 (CH 3 CN) 1 ) is comprehensively investigated. The estimated optical band gap of cadmium benzoate is 2.64 eV and the EPc and EPv are about -0.09 V (vs. NHE) and +2.55 V (vs. NHE), respectively, which implies that cadmium benzoate possesses a high negative reduction potential of excited electrons due to its higher conduction band position, and hence, the locations of the conduction band minimum and the valence band maximum meet the redox capacity. Thus, this composite photocatalyst exhibits superior activity in visible-light-driven photocatalytic H 2 evolution. We found that introducing the QDs enhance the photocatalytic performance towards the visible light region. The electronic band structure shows high k-dispersion bands around the Fermi level, which implies low effective masses, and hence, the high mobility carriers favor the enhancement of the charge transfer process. The mobility of the photogenerated carriers significantly influences the photocatalytic efficiency and the higher photogenerated carriers' mobility enhances the photocatalytic performance. Moreover, the result shows a great effective mass difference between electrons (e - ) and holes (h + ), which can facilitate the e - and h + migration and separation, and finally improve the photocatalytic performance. The large mobility difference is useful for the separation of e - and h + , the reduction of the e - and h + recombination rate, and the improvement of the photocatalytic activity. Thus, cadmium benzoate exhibits rapid generation of e - -h + pairs with photoexcitation and a high negative reduction potential of excited electrons due to its higher CB position. Based on these results one can conclude

  1. 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.

  2. 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)

  3. 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.

  4. Improving Visible Light-Absorptivity and Photoelectric Conversion Efficiency of a TiO2 Nanotube Anode Film by Sensitization with Bi2O3 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Menglei Chang

    2017-05-01

    Full Text Available This study presents a novel visible light-active TiO2 nanotube anode film by sensitization with Bi2O3 nanoparticles. The uniform incorporation of Bi2O3 contributes to largely enhancing the solar light absorption and photoelectric conversion efficiency of TiO2 nanotubes. Due to the energy level difference between Bi2O3 and TiO2, the built-in electric field is suggested to be formed in the Bi2O3 sensitized TiO2 hybrid, which effectively separates the photo-generated electron-hole pairs and hence improves the photocatalytic activity. It is also found that the photoelectric conversion efficiency of Bi2O3 sensitized TiO2 nanotubes is not in direct proportion with the content of the sensitizer, Bi2O3, which should be carefully controlled to realize excellent photoelectrical properties. With a narrower energy band gap relative to TiO2, the sensitizer Bi2O3 can efficiently harvest the solar energy to generate electrons and holes, while TiO2 collects and transports the charge carriers. The new-type visible light-sensitive photocatalyst presented in this paper will shed light on sensitizing many other wide-band-gap semiconductors for improving solar photocatalysis, and on understanding the visible light-driven photocatalysis through narrow-band-gap semiconductor coupling.

  5. Improving Visible Light-Absorptivity and Photoelectric Conversion Efficiency of a TiO2 Nanotube Anode Film by Sensitization with Bi2O3 Nanoparticles

    Science.gov (United States)

    Chang, Menglei; Hu, Huawen; Zhang, Yuyuan; Chen, Dongchu; Wu, Liangpeng; Li, Xinjun

    2017-01-01

    This study presents a novel visible light-active TiO2 nanotube anode film by sensitization with Bi2O3 nanoparticles. The uniform incorporation of Bi2O3 contributes to largely enhancing the solar light absorption and photoelectric conversion efficiency of TiO2 nanotubes. Due to the energy level difference between Bi2O3 and TiO2, the built-in electric field is suggested to be formed in the Bi2O3 sensitized TiO2 hybrid, which effectively separates the photo-generated electron-hole pairs and hence improves the photocatalytic activity. It is also found that the photoelectric conversion efficiency of Bi2O3 sensitized TiO2 nanotubes is not in direct proportion with the content of the sensitizer, Bi2O3, which should be carefully controlled to realize excellent photoelectrical properties. With a narrower energy band gap relative to TiO2, the sensitizer Bi2O3 can efficiently harvest the solar energy to generate electrons and holes, while TiO2 collects and transports the charge carriers. The new-type visible light-sensitive photocatalyst presented in this paper will shed light on sensitizing many other wide-band-gap semiconductors for improving solar photocatalysis, and on understanding the visible light-driven photocatalysis through narrow-band-gap semiconductor coupling. PMID:28486406

  6. A Novel Delafossite Structured Visible-Light Sensitive AgFeO2 Photocatalyst: Preparation, Photocatalytic Properties, and Reaction Mechanism

    Directory of Open Access Journals (Sweden)

    Lu Yin

    2016-05-01

    Full Text Available This work presents a systematic study of a novel efficient visible-light sensitive AgFeO2 photocatalyst. The photocatalysts were prepared via simple hydrothermal procedure at 160 °C with different reaction time. The structures, morphologies, specific surface areas, and optical properties of the photocatalysts were explored by X-ray diffraction (XRD, field emission scanning electron microscopy (FE-SEM, Brunauer-Emmett-Teller (BET model, and UV-vis diffuse reflectance spectra (DRS. Photoluminescence and photocurrent analysis were conducted for the understanding of photogenerated electron-hole pair separation. AgFeO2 with a six-hour hydrothermal procedure demonstrated the most efficient photocatalytic performance which resulted in 97% degradation of methyl orange (MO within 180 min. The enhanced photocatalytic activity was attributed to the combined effect of its relatively large surface area and high separation electron-hole pair efficiency. Holes and ·O2− were the dominant reactive species responsible for MO degradation and holes played the leading role according to the quenching effects analysis and detection of active species. The conduction and valence band position of AgFeO2 were calculated to be −0.5 V and 1.32 V, respectively. Based on active species detection, along with the band structure, the photocatalytic mechanism was proposed.

  7. Preparation and enhanced visible-light photocatalytic H2-production activity of CdS-sensitized Pt/TiO2 nanosheets with exposed (001) facets.

    Science.gov (United States)

    Qi, Lifang; Yu, Jiaguo; Jaroniec, Mietek

    2011-05-21

    CdS-sensitized Pt/TiO(2) nanosheets with exposed (001) facets were prepared by hydrothermal treatment of a Ti(OC(4)H(9))(4)-HF-H(2)O mixed solution followed by photochemical reduction deposition of Pt nanoparticles (NPs) on TiO(2) nanosheets (TiO(2) NSs) and chemical bath deposition of CdS NPs on Pt/TiO(2) NSs, successively. The UV and visible-light driven photocatalytic activity of the as-prepared samples was evaluated by photocatalytic H(2) production from lactic acid aqueous solution under UV and visible-light (λ ≥ 420 nm) irradiation. It was shown that no photocatalytic H(2)-production activity was observed on the pure TiO(2) NSs under UV and/or visible-light irradiation. Deposition of CdS NPs on Pt/TiO(2) NSs caused significant enhancement of the UV and visible-light photocatalytic H(2)-production rates. The morphology of TiO(2) particles had also significant influence on the visible-light H(2)-production activity. Among TiO(2) NSs, P25 and the NPs studied, the CdS-sensitized Pt/TiO(2) NSs show the highest photocatalytic activity (13.9% apparent quantum efficiency obtained at 420 nm), exceeding that of CdS-sensitized Pt/P25 by 10.3% and that of Pt/NPs by 1.21%, which can be attributed to the combined effect of several factors including the presence of exposed (001) facets, surface fluorination and high specific surface area. After many replication experiments of the photocatalytic hydrogen production in the presence of lactic acid, the CdS-sensitized Pt/TiO(2) NSs did not show great loss in the photocatalytic activity, confirming that the CdS/Pt/TiO(2) NSs system is stable and not photocorroded. © The Owner Societies 2011

  8. Inactivation of normal and mutant Neurospora crassa conidia by visible light and near-UV: role of /sup 1/O/sub 2/, carotenoid composition and sensitizer location

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, S.A.; Sargent, M.L.; Tuveson, R.W. (Illinois Univ., Urbana (USA))

    1981-03-01

    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, /sup 1/O/sub 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 /sup 1/O/sub 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.

  9. Graphitic C3N4 Sensitized TiO2 Nanotube Layers: A Visible Light Activated Efficient Antimicrobial Platform

    CERN Document Server

    Xu, Jingwen; Zhou, Xuemei; Li, Yuzhen; Gao, Zhi-Da; Song, Yan-Yan; Schmuki, Patrik

    2016-01-01

    In this work, we introduce a facile procedure to graft a thin graphitic C3N4 (g-C3N4) layer on aligned TiO2 nanotube arrays (TiNT) by one-step chemical vapor deposition (CVD) approach. This provides a platform to enhance the visible-light response of TiO2 nanotubes for antimicrobial applications. The formed g- C3N4/TiNT binary nanocomposite exhibits excellent bactericidal efficiency against E. coli as a visiblelight activated antibacterial coating.

  10. In situ plasmonic Au nanoparticle anchored nickel ferrite: An efficient plasmonic photocatalyst for fluorescein-sensitized hydrogen evolution under visible light irradiation

    Science.gov (United States)

    Zeng, Jian; Zeng, Wangdong; Zeng, Heping

    2017-09-01

    Photocatalytic hydrogen generation is a considerable promising technology to decrease climate change effect of CO2 and to solve the increasing global demand for clean energy. Hydrogen generation driven by visible light still faces many challenges although great efforts have been made. Efficient charge separation plays an important role in solar-energy conversion by heterojunction photocatalysts. Herein we report that nickel ferrites covered by gold plasmonics form well-defined plasmonic photocatalysts for fluorescein-sensitized hydrogen production under visible-light irradiation with largely enhanced photoactivity due to fast separation of photogenerated electron-hole pairs. The optimal Au/NiFe2O4 plasmonic photocatalysts with AuNP loading of 1.5 wt% shows the hydrogen production rate of 0.256 mmol g-1 h-1via localized surface plasmon resonance effect of AuNPs. Fluorescein was acted as photosensitizer to extend the visible-light absorption of Au/NiFe2O4 plasmonic photocatalysts and enhance photocatalytic hydrogen generation efficiency under visible-light irradiation. The optimum rate for hydrogen generation reached 3.162 mmol g-1 h-1 and the rate is about 60-fold and 12-fold higher than that of pure NiFe2O4 and 1.5 wt% Au/NiFe2O4 plasmonic photocatalysts, respectively.

  11. A new route for visible/near-infrared-light-driven H2 production over titania: Co-sensitization of surface charge transfer complex and zinc phthalocyanine

    Science.gov (United States)

    Zhang, Xiaohu; Peng, Bosi; Peng, Tianyou; Yu, Lijuan; Li, Renjie; Zhang, Jing

    2015-12-01

    This work introduces a new strategy for visible/near-infrared (NIR) light responsive H2 production over TiO2 nanoparticles co-sensitized with zinc phthalocyanine derivative (Zn-tri-PcNc) and surface ligand-to-metal charge transfer (LMCT) complex, which is in situ formed on the TiO2 nanoparticles' surfaces by using ascorbic acid (AA). The in situ formed surface LMCT complex (AA-TiO2) exhibits obvious visible-light-responsive photoactivity (126.2 μmol/h) for H2 production with a high apparent quantum yield (AQY) of 16.1% at 420 nm monochromatic light irradiation. Moreover, the co-sensitized TiO2 nanoparticles (Zn-tri-PcNc-TiO2-AA) shows a much higher photoactivity (162.2 μmol/h) for H2 production than the surface LMCT complex, and broader spectral responsive region (400-800 nm) with a relatively high AQY value (0.97%) at 700 nm monochromatic light irradiation. The present result reveals a possible substitute for the conventional Ru(II)-bipyridyl complexes or organic dyes as sensitizer of semiconductors in the field of solar fuel conversion.

  12. Recyclable and visible light sensitive Ag–AgBr/TiO{sub 2}: Surface adsorption and photodegradation of MO

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinxin [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Zhang, Dong [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Guo, Biao; Qu, Yue; Tian, Ge [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Yue, Huijuan, E-mail: huijuan@jlu.edu.cn [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Feng, Shouhua [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China)

    2015-10-30

    Graphical abstract: - Highlights: • Nanoheterojunction Ag–AgBr/TiO{sub 2} sphere are prepared by CTAB-assisted method. • Uncalcined samples exhibit predominantly surface adsorption on dye removal. • Calcined composites demonstrate excellent degradation activity for MO under visible light irradiation. • The loading of Ag–AgBr is optimized. • The catalyst possesses good photochemical stability and reusability. - Abstract: A range of highly efficient nanoheterojunction structured Ag–AgBr/TiO{sub 2} photocatalysts have been synthesized by CTAB-assisted method and characterized by X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL). The results demonstrated that Ag–AgBr nanoparticles were successfully deposited on the surface of anatase TiO{sub 2} hierarchical spheres. The remarkable adsorptive removal of methyl orange (MO) by the uncalcined samples was investigated before evaluating its photocatalytic ability. All the calcined three-component catalysts possessed excellent photocatalytic activities for degrading MO under visible light, in which, 162.4% Ag–AgBr/TiO{sub 2} exhibited highest efficiency. The greatly enhanced activity can be attributed to the well combination of surface plasmons photocatalyst Ag–AgBr and TiO{sub 2}, which can simultaneously inhibit the photo-generated electrons and holes recombination. The nanoheterojunctions architecture catalyst also showed high stability even after five consecutive cycles. Meanwhile, the possible mechanism and interpretation of the photocatalytic process were also proposed.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Visible light-sensitive APTES-bound ZnO nanowire toward a potent nanoinjector sensing biomolecules in a living cell.

    Science.gov (United States)

    Lee, Jooran; Choi, Sunyoung; Bae, Seon Joo; Yoon, Seok Min; Choi, Joon Sig; Yoon, Minjoong

    2013-11-07

    Nanoscale cell injection techniques combined with nanoscopic photoluminescence (PL) spectroscopy have been important issues in high-resolution optical biosensing, gene and drug delivery and single-cell endoscopy for medical diagnostics and therapeutics. However, the current nanoinjectors remain limited for optical biosensing and communication at the subwavelength level, requiring an optical probe such as semiconductor quantum dots, separately. Here, we show that waveguided red emission is observed at the tip of a single visible light-sensitive APTES-modified ZnO nanowire (APTES-ZnO NW) and it exhibits great enhancement upon interaction with a complementary sequence-based double stranded (ds) DNA, whereas it is not significantly affected by non-complementary ds DNA. Further, the tip of a single APTES-ZnO NW can be inserted into the subcellular region of living HEK 293 cells without significant toxicity, and it can also detect the enhancement of the tip emission from subcellular regions with high spatial resolution. These results indicate that the single APTES-ZnO NW would be useful as a potent nanoinjector which can guide visible light into intracellular compartments of mammalian cells, and can also detect nanoscopic optical signal changes induced by interaction with the subcellular specific target biomolecules without separate optical probes.

  18. 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

  19. 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.

  20. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hongbin; Yu, Xiang; Zhu, Yi, E-mail: tzhury@jnu.edu.cn; Fu, Xionghui; Zhang, Yuanming [Jinan University, Department of Chemistry (China)

    2016-08-15

    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{sup +}) 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.

  2. Mutagenesis by near-visible light.

    Science.gov (United States)

    Kubitschek, H E

    1967-03-24

    Mutants resistant to bacter iophage T5 were produced both in continuous and in stationary cultures of Escherichia coli by near-visible light, 320 to 400 millimicrons, at rates greatly exceeding spontaneous rates in the ab sence of light. Aerobic mutation rates were about twice anaerobic rates, which shows that mutations were induced in either of at least two different proces ses. Mutations induced by near-visible light involve different photochemical processes than those induced by ul traviolet light.

  3. Visible light-sensitive APTES-bound ZnO nanowire toward a potent nanoinjector sensing biomolecules in a living cell

    Science.gov (United States)

    Lee, Jooran; Choi, Sunyoung; Bae, Seon Joo; Yoon, Seok Min; Choi, Joon Sig; Yoon, Minjoong

    2013-10-01

    Nanoscale cell injection techniques combined with nanoscopic photoluminescence (PL) spectroscopy have been important issues in high-resolution optical biosensing, gene and drug delivery and single-cell endoscopy for medical diagnostics and therapeutics. However, the current nanoinjectors remain limited for optical biosensing and communication at the subwavelength level, requiring an optical probe such as semiconductor quantum dots, separately. Here, we show that waveguided red emission is observed at the tip of a single visible light-sensitive APTES-modified ZnO nanowire (APTES-ZnO NW) and it exhibits great enhancement upon interaction with a complementary sequence-based double stranded (ds) DNA, whereas it is not significantly affected by non-complementary ds DNA. Further, the tip of a single APTES-ZnO NW can be inserted into the subcellular region of living HEK 293 cells without significant toxicity, and it can also detect the enhancement of the tip emission from subcellular regions with high spatial resolution. These results indicate that the single APTES-ZnO NW would be useful as a potent nanoinjector which can guide visible light into intracellular compartments of mammalian cells, and can also detect nanoscopic optical signal changes induced by interaction with the subcellular specific target biomolecules without separate optical probes.Nanoscale cell injection techniques combined with nanoscopic photoluminescence (PL) spectroscopy have been important issues in high-resolution optical biosensing, gene and drug delivery and single-cell endoscopy for medical diagnostics and therapeutics. However, the current nanoinjectors remain limited for optical biosensing and communication at the subwavelength level, requiring an optical probe such as semiconductor quantum dots, separately. Here, we show that waveguided red emission is observed at the tip of a single visible light-sensitive APTES-modified ZnO nanowire (APTES-ZnO NW) and it exhibits great enhancement upon

  4. RhB-sensitized effect on the enhancement of photocatalytic activity of BiOCl toward bisphenol-A under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Xiaoming; Fan, Caimei, E-mail: fancm@163.com; Wang, Yawen; Wang, Yunfang; Zhang, Xiaochao

    2014-10-30

    Graphical abstract: - Highlights: • BiOCl with narrow band gap energy was synthesized successfully. • The addition of RhB could enhance the reaction rate of BPA prominently. • RhB exhibited photosensitized effect in BPA degradation with as-prepared BiOCl. • The main active species involved in BPA degradation was h{sup +} and O{sub 2}·{sup −}. • The double-electron-source reaction mechanism was proposed. - Abstract: A bismuth oxychloride (BiOCl) photocatalyst with visible light activity was successfully synthesized using NaBiO{sub 3} and HCl as raw materials. The crystal structure, morphology, and UV–vis diffuse reflectance spectra of the as-synthesized BiOCl were characterized. Rhodamine B (RhB), as a photosensitizer, can remarkably enhance light utilization and improve the photocatalytic activity of BiOCl toward bisphenol-A (BPA). The effects of BiOCl dosage, RhB dosage, BPA initial concentration and initial solution pH on the photocatalytic performance of BiOCl were studied. The photocatalytic oxidation of BPA followed pseudo first-order kinetics, and the highest photodegradation efficiency of BPA was observed using a BiOCl dosage of 1.5 g L{sup −1} and RhB dosage of 5 mg L{sup −1} in BPA solution (c{sub 0} = 20 mg L{sup −1}, pH = 6) under visible light irradiation for 30 min. Under these conditions, the reaction rate constant of the system was 11.3 times greater than that of BiOCl without RhB. The superior photocatalytic activity observed was attributed to the sensitization effect of RhB. Experimental scavenging results revealed that h{sup +} and O{sub 2}·{sup −} are the main active species involved in BPA degradation. The as-synthesized BiOCl exhibited good photocatalytic stability during photodegradation, which suggests promising prospects in the practical application of organic pollutant photodegradation.

  5. Role of oxygen active species in the photocatalytic degradation of phenol using polymer sensitized TiO{sub 2} under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Dongdong [School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Qiu Rongliang [School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275 (China)], E-mail: eesqrl@mail.sysu.edu.cn; Song Lin [School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Department of Environmental Engineering, Jinan University, Guangzhou 510630 (China); Eric, Brewer [Viridian Environmental LLC, VA 22207 (United States); Mo Yueqi [College of Material Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Huang Xiongfei [School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275 (China)

    2009-04-30

    The role of dissolved oxygen, and of active species generated by photo-induced reactions with oxygen, in the photocatalytic degradation of phenol was investigated using polymer [poly-(fluorene-co-thiophene) with thiophene content of 30%, so-called PFT30] sensitized TiO{sub 2} (PFT30/TiO{sub 2}) under visible light irradiation. The photoluminescent (PL) quantum yield of PFT30/TiO{sub 2} was about 30% of that of PFT30/Al{sub 2}O{sub 3}, proving that electron transfer took place between the polymer and TiO{sub 2}. The result that photocatalytic degradation of phenol was almost stopped when the solution was saturated with N{sub 2} proved the importance of O{sub 2}. Addition of NaN{sub 3}, an effective quencher of singlet oxygen ({sup 1}O{sub 2}), caused about a 40% decrease in the phenol degradation ratio. Addition of alcohols caused about a 60% decrease in the phenol photodegradation ratio, indicating that the hydroxyl radicals (OH{center_dot}), whose presence was confirmed by electron spin resonance (ESR) spectroscopy, was the predominant active species in aqueous solution. In anhydrous solution, singlet oxygen ({sup 1}O{sub 2}) was the predominant species. These results indicate that oxygen plays a very important role in the photocatalytic degradation of phenol.

  6. 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.

  7. Solar Synthesis: Prospects in Visible Light Photocatalysis

    Science.gov (United States)

    Schultz, Danielle M.; Yoon, Tehshik P.

    2015-01-01

    Chemists have long aspired to synthesize molecules the way that plants do — using sunlight to facilitate the construction of complex molecular architectures. Nevertheless, the use of visible light in photochemical synthesis is fundamentally challenging because organic molecules tend not to interact with the wavelengths of visible light that are most strongly emitted in the solar spectrum. Recent research has begun to leverage the ability of visible light absorbing transition metal complexes to catalyze a broad range of synthetically valuable reactions. In this review, we highlight how an understanding of the mechanisms of photocatalytic activation available to these transition metal complexes, and of the general reactivity patterns of the intermediates accessible via visible light photocatalysis, has accelerated the development of this diverse suite of reactions. PMID:24578578

  8. Wavelength-sensitive photocatalytic degradation of methyl orange in aqueous suspension over iron(III)-doped TiO2 nanopowders under UV and visible light irradiation.

    Science.gov (United States)

    Wang, X H; Li, J-G; Kamiyama, H; Moriyoshi, Y; Ishigaki, T

    2006-04-06

    Well-crystallized iron(III)-doped TiO2 nanopowders with controlled Fe3+ doping concentration and uniform dopant distribution, have been synthesized with plasma oxidative pyrolysis. The photocatalytic reactivity of the synthesized TiO2 nanopowders with a mean particle size of 50-70 nm was quantified in terms of the degradation rates of methyl orange (MO) in aqueous TiO2 suspension under UV (mainly 365 and 316 nm) and visible light irradiation (mainly 405 and 436 nm). The photodecomposition of MO over TiO2 nanopowders followed a distinct two-stage pseudo first order kinetics. Interestingly, the photocatalytic reactivity depends not only on the iron doping concentration but also on the wavelength of the irradiating light. Under UV irradiation, nominally undoped TiO2 had much higher reactivity than Fe3+ -doped TiO2, suggesting that Fe3+ doping (> 0.05 at. %) in TiO2 with a mean particle size of approximately 60 nm was detrimental to the photocatalytic decomposition of methyl orange. Whereas, under visible light irradiation, the Fe3+ -doped TiO2 with an intermediate iron doping concentration of approximately 1 at. % had the highest photocatalytic reactivity due to the narrowing of band gap so that it could effectively absorb the light with longer wavelength. A strategy for improving the photocatalytic reactivity of Fe3+ -doped TiO2 used in the visible light region is also proposed.

  9. Photo-reductive decolorization of an azo dye by natural sphalerite: Case study of a new type of visible light-sensitized photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Li Yan [Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Yiheyuan Road 5, Haidian District, Beijing 100871 (China); Lu Anhuai, E-mail: ahlu@pku.edu.cn [Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Yiheyuan Road 5, Haidian District, Beijing 100871 (China); Jin Song [Department of Civil and Architectural Engineering, University of Wyoming, Laramie, WY 82071 (United States); MWH Americas, 3665 JFK Parkway, Suite 206, Fort Collins, CO 80525 (United States); Wang Changqiu [Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Yiheyuan Road 5, Haidian District, Beijing 100871 (China)

    2009-10-15

    Natural sphalerite, which represents a new class of mineral-based catalyst, was characterized and investigated for photo-reduction of an azo dye methyl orange (MO) under visible light. After 2 h of visible light irradiation, a complete decolorization of the MO solution was achieved. The degradation rate was related to the pH conditions. Spectra from FT-IR analysis indicate an initial adsorption of MO to sphalerite via its sulfonate group. Further reduction of the adsorbed MO by sphalerite under light irradiation led to the destruction of the azo structure, as indicated by the results from UV-vis, FT-IR and ESI-MS analyses. The visible light-induced photocatalytic reductive activity of natural sphalerite was mainly attributed to the distribution of foreign metal atoms in its crystal lattice, which reduces the intrinsic bandgap of sphalerite and also broadens its spectra responding range. In addition, the high conduction band potential of natural sphalerite may also enhance the photo-reduction of MO.

  10. A visible-light-sensitive water splitting photocatalyst composed of Rh3+ in a 4d6 electronic configuration, Rh3+-doped ZnGa2O4.

    Science.gov (United States)

    Kumagai, Naoya; Ni, Lei; Irie, Hiroshi

    2011-02-14

    Using the Rh(3+) ion (Rh d(6)) in a regular octahedral coordination, which forms fully occupied t(2g)(6) and empty e(g)(0) as a result of ligand-field splitting, we demonstrated that Rh-doped ZnGa(2)O(4) had midgap states created by t(2g)(6) and e(g)(0) that had suitable potentials to produce either hydrogen or oxygen in the presence of sacrificial agents under visible-light irradiation.

  11. A Carpet Cloak Device for Visible Light

    CERN Document Server

    Gharghi, Majid; Zentgraf, Thomas; Liu, Yongmin; Yin, Xiaobo; Valentine, Jason; Zhang, Xiang

    2011-01-01

    We report an invisibility carpet cloak device, which is capable of making an object undetectable by visible light. The cloak is designed using quasi conformal mapping and is fabricated in a silicon nitride waveguide on a specially developed nano-porous silicon oxide substrate with a very low refractive index. The spatial index variation is realized by etching holes of various sizes in the nitride layer at deep subwavelength scale creating a local effective medium index. The fabricated device demonstrates wideband invisibility throughout the visible spectrum with low loss. This silicon nitride on low index substrate can also be a general scheme for implementation of transformation optical devices at visible frequency.

  12. 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

  13. Visible light guided manipulation of liquid wettability on photoresponsive surfaces

    Science.gov (United States)

    Kwon, Gibum; Panchanathan, Divya; Mahmoudi, Seyed Reza; Gondal, Mohammed A.; McKinley, Gareth H.; Varanasi, Kripa K.

    2017-04-01

    Photoresponsive titania surfaces are of great interest due to their unique wettability change upon ultraviolet light illumination. However, their applications are often limited either by the inability to respond to visible light or the need for special treatment to recover the original wettability. Sensitizing TiO2 surfaces with visible light-absorbing materials has been utilized in photovoltaic applications. Here we demonstrate that a dye-sensitized TiO2 surface can selectively change the wettability towards contacting liquids upon visible light illumination due to a photo-induced voltage across the liquid and the underlying surface. The photo-induced wettability change of our surfaces enables external manipulation of liquid droplet motion upon illumination. We show demulsification of surfactant-stabilized brine-in-oil emulsions via coalescence of brine droplets on our dye-sensitized TiO2 surface upon visible light illumination. We anticipate that our surfaces will have a wide range of applications including microfluidic devices with customizable wettability, solar-driven oil-water clean-up and demulsification technologies.

  14. Band gap engineering of ZnO using core/shell morphology with environmentally benign Ag₂S sensitizer for efficient light harvesting and enhanced visible-light photocatalysis.

    Science.gov (United States)

    Khanchandani, Sunita; Srivastava, Pawan Kumar; Kumar, Sandeep; Ghosh, Subhasis; Ganguli, Ashok K

    2014-09-02

    Band gap engineering offers tunable optical and electronic properties of semiconductors in the development of efficient photovoltaic cells and photocatalysts. Our study demonstrates the band gap engineering of ZnO nanorods to develop a highly efficient visible-light photocatalyst. We engineered the band gap of ZnO nanorods by introducing the core/shell geometry with Ag2S sensitizer as the shell. Introduction of the core/shell geometry evinces great promise for expanding the light-harvesting range and substantial suppression of charge carrier recombination, which are of supreme importance in the realm of photocatalysis. To unveil the superiority of Ag2S as a sensitizer in engineering the band gap of ZnO in comparison to the Cd-based sensitizers, we also designed ZnO/CdS core/shell nanostructures having the same shell thickness. The photocatalytic performance of the resultant core/shell nanostructures toward methylene blue (MB) dye degradation has been studied. The results imply that the ZnO/Ag2S core/shell nanostructures reveal 40- and 2-fold enhancement in degradation constant in comparison to the pure ZnO and ZnO/CdS core/shell nanostructures, respectively. This high efficiency is elucidated in terms of (i) efficient light harvesting owing to the incorporation of Ag2S and (ii) smaller conduction band offset between ZnO and Ag2S, promoting more efficient charge separation at the core/shell interface. A credible photodegradation mechanism for the MB dye deploying ZnO/Ag2S core/shell nanostructures is proposed from the analysis of involved active species such as hydroxyl radicals (OH(•)), electrons (e(-)(CB)), holes (h(+)(VB)), and superoxide radical anions (O2(•-)) in the photodegradation process utilizing various active species scavengers and EPR spectroscopy. The findings show that the MB oxidation is directed mainly by the assistance of hydroxyl radicals (OH(•)). The results presented here provide new insights for developing band gap engineered

  15. 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.

  16. 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.

  17. [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

  18. 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.

  19. Facile Synthesis of High {001} Facets Dominated BiOCl Nanosheets and Their Selective Dye-Sensitized Photocatalytic Activity Induced by Visible Light

    Directory of Open Access Journals (Sweden)

    Da Zhang

    2016-01-01

    Full Text Available Single-crystal BiOCl nanosheets, with high {001} facets exposed, were synthesized through a facile hydrolysis reaction under general atmospheric pressure, without adding any organic surfactant or agent. The thickness of the BiOCl nanosheets is about 20 nm, and the diameter is arranged from 200 to 400 nm. The structure of the BiOCl nanosheets was characterized by X-ray diffraction, energy disperse X-ray spectrum, transmission electron microscopy, and selective area electron diffraction. Moreover, three different dyes were used as model molecules to test the photocatalytic activity of BiOCl nanosheets under visible light. It was found that the BiOCl nanosheets possess selective photocatalytic behavior as their activity over RhB is much higher than that over MO or MB. Based on the analysis of the experimental results, the potential mechanism was discussed.

  20. 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.

  1. 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.

  2. 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.

  3. Bright visible light emission from graphene.

    Science.gov (United States)

    Kim, Young Duck; Kim, Hakseong; Cho, Yujin; Ryoo, Ji Hoon; Park, Cheol-Hwan; Kim, Pilkwang; Kim, Yong Seung; Lee, Sunwoo; Li, Yilei; Park, Seung-Nam; Yoo, Yong Shim; Yoon, Duhee; Dorgan, Vincent E; Pop, Eric; Heinz, Tony F; Hone, James; Chun, Seung-Hyun; Cheong, Hyeonsik; Lee, Sang Wook; Bae, Myung-Ho; Park, Yun Daniel

    2015-08-01

    Graphene and related two-dimensional materials are promising candidates for atomically thin, flexible and transparent optoelectronics. In particular, the strong light-matter interaction in graphene has allowed for the development of state-of-the-art photodetectors, optical modulators and plasmonic devices. In addition, electrically biased graphene on SiO2 substrates can be used as a low-efficiency emitter in the mid-infrared range. However, emission in the visible range has remained elusive. Here, we report the observation of bright visible light emission from electrically biased suspended graphene devices. In these devices, heat transport is greatly reduced. Hot electrons (∼2,800 K) therefore become spatially localized at the centre of the graphene layer, resulting in a 1,000-fold enhancement in thermal radiation efficiency. Moreover, strong optical interference between the suspended graphene and substrate can be used to tune the emission spectrum. We also demonstrate the scalability of this technique by realizing arrays of chemical-vapour-deposited graphene light emitters. These results pave the way towards the realization of commercially viable large-scale, atomically thin, flexible and transparent light emitters and displays with low operation voltage and graphene-based on-chip ultrafast optical communications.

  4. Lethal effects of short-wavelength visible light on insects

    OpenAIRE

    Hori, Masatoshi; Shibuya, Kazuki; Sato, Mitsunari; Saito, Yoshino

    2014-01-01

    We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiatio...

  5. Seeing elements by visible-light digital camera.

    Science.gov (United States)

    Zhao, Wenyang; Sakurai, Kenji

    2017-03-31

    A visible-light digital camera is used for taking ordinary photos, but with new operational procedures it can measure the photon energy in the X-ray wavelength region and therefore see chemical elements. This report describes how one can observe X-rays by means of such an ordinary camera - The front cover of the camera is replaced by an opaque X-ray window to block visible light and to allow X-rays to pass; the camera takes many snap shots (called single-photon-counting mode) to record every photon event individually; an integrated-filtering method is newly proposed to correctly retrieve the energy of photons from raw camera images. Finally, the retrieved X-ray energy-dispersive spectra show fine energy resolution and great accuracy in energy calibration, and therefore the visible-light digital camera can be applied to routine X-ray fluorescence measurement to analyze the element composition in unknown samples. In addition, the visible-light digital camera is promising in that it could serve as a position sensitive X-ray energy detector. It may become able to measure the element map or chemical diffusion in a multi-element system if it is fabricated with external X-ray optic devices. Owing to the camera's low expense and fine pixel size, the present method will be widely applied to the analysis of chemical elements as well as imaging.

  6. Seeing elements by visible-light digital camera

    Science.gov (United States)

    Zhao, Wenyang; Sakurai, Kenji

    2017-01-01

    A visible-light digital camera is used for taking ordinary photos, but with new operational procedures it can measure the photon energy in the X-ray wavelength region and therefore see chemical elements. This report describes how one can observe X-rays by means of such an ordinary camera - The front cover of the camera is replaced by an opaque X-ray window to block visible light and to allow X-rays to pass; the camera takes many snap shots (called single-photon-counting mode) to record every photon event individually; an integrated-filtering method is newly proposed to correctly retrieve the energy of photons from raw camera images. Finally, the retrieved X-ray energy-dispersive spectra show fine energy resolution and great accuracy in energy calibration, and therefore the visible-light digital camera can be applied to routine X-ray fluorescence measurement to analyze the element composition in unknown samples. In addition, the visible-light digital camera is promising in that it could serve as a position sensitive X-ray energy detector. It may become able to measure the element map or chemical diffusion in a multi-element system if it is fabricated with external X-ray optic devices. Owing to the camera’s low expense and fine pixel size, the present method will be widely applied to the analysis of chemical elements as well as imaging. PMID:28361916

  7. Advances and prospects in visible light communications

    Science.gov (United States)

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

    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. Project supported by the National High Technology Research and Development Program of China (Nos. 2015AA033303, 2013AA013602, 2013AA013603, 2013AA03A104), the National Natural Science Foundation of China (Nos. 61178051, 61321063, 61335010, 61178048, 61275169), and the National Basic Research Program of China (Nos. 2013CB329205, 2011CBA00608).

  8. 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

  9. Macroscopic invisibility cloaking of visible light

    DEFF Research Database (Denmark)

    Chen, Xianzhong; Luo, Y.; Zhang, Jingjing

    2011-01-01

    invisibility cloaks has been reported at various electromagnetic frequencies. All the invisibility cloaks demonstrated thus far, however, have relied on nano- or micro-fabricated artificial composite materials with spatially varying electromagnetic properties, which limit the size of the cloaked region...... to a few wavelengths. Here, we report the first realization of a macroscopic volumetric invisibility cloak constructed from natural birefringent crystals. The cloak operates at visible frequencies and is capable of hiding, for a specific light polarization, three-dimensional objects of the scale...

  10. Opsins in Limulus eyes: characterization of three visible light-sensitive opsins unique to and co-expressed in median eye photoreceptors and a peropsin/RGR that is expressed in all eyes

    OpenAIRE

    Battelle, Barbara-Anne; Kempler, Karen E.; Saraf, Spencer R.; Marten, Catherine E.; Dugger, Donald R.; Speiser, Daniel I.; Oakley, Todd H.

    2015-01-01

    The eyes of the horseshoe crab Limulus polyphemus have long been used for studies of basic mechanisms of vision, and the structure and physiology of Limulus photoreceptors have been examined in detail. Less is known about the opsins Limulus photoreceptors express. We previously characterized a UV opsin (LpUVOps1) that is expressed in all three types of Limulus eyes (lateral compound eyes, median ocelli and larval eyes) and three visible light-sensitive rhabdomeric opsins (LpOps1, -2 and -5) t...

  11. Lethal effects of short-wavelength visible light on insects

    Science.gov (United States)

    Hori, Masatoshi; Shibuya, Kazuki; Sato, Mitsunari; Saito, Yoshino

    2014-12-01

    We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiation with short-wavelength visible (blue) light killed eggs, larvae, pupae, and adults of Drosophila melanogaster. Blue light was also lethal to mosquitoes and flour beetles, but the effective wavelength at which mortality occurred differed among the insect species. Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic. For some animals, such as insects, blue light is more harmful than UV light.

  12. Photophysics and light-activated biocidal activity of visible-light-absorbing conjugated oligomers.

    Science.gov (United States)

    Parthasarathy, Anand; Goswami, Subhadip; Corbitt, Thomas S; Ji, Eunkyung; Dascier, Dimitri; Whitten, David G; Schanze, Kirk S

    2013-06-12

    The photophysical properties of three cationic π-conjugated oligomers were correlated with their visible light activated biocidal activity vs S. aureus. The oligomers contain three arylene units (terthiophene, 4a; thiophene-benzotriazole-thiophene, 4b; thiophene-benzothiadiazole-thiophene, 4c) capped on each end by cationic -(CH2)3NMe3(+) groups. The oligomers absorb in the visible region due to their donor-acceptor-donor electronic structure. Oligomers 4a and 4b have high intersystem crossing and singlet oxygen sensitization efficiency, but 4c has a very low intersystem crossing efficiency and it does not sensitize singlet oxygen. The biocidal activity of the oligomers under visible light varies in the order 4a > 4b ≈ 4c.

  13. 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.

  14. Coded source imaging simulation with visible light

    Energy Technology Data Exchange (ETDEWEB)

    Wang Sheng [State Key Laboratory of Nuclear Physics and Technology and School of Physics, IHIP, Peking University, Yiheyuan Lu 5, Beijing 100871 (China); Zou Yubin, E-mail: zouyubin@pku.edu.cn [State Key Laboratory of Nuclear Physics and Technology and School of Physics, IHIP, Peking University, Yiheyuan Lu 5, Beijing 100871 (China); Zhang Xueshuang; Lu Yuanrong; Guo Zhiyu [State Key Laboratory of Nuclear Physics and Technology and School of Physics, IHIP, Peking University, Yiheyuan Lu 5, Beijing 100871 (China)

    2011-09-21

    A coded source could increase the neutron flux with high L/D ratio. It may benefit a neutron imaging system with low yield neutron source. Visible light CSI experiments were carried out to test the physical design and reconstruction algorithm. We used a non-mosaic Modified Uniformly Redundant Array (MURA) mask to project the shadow of black/white samples on a screen. A cooled-CCD camera was used to record the image on the screen. Different mask sizes and amplification factors were tested. The correlation, Wiener filter deconvolution and Richardson-Lucy maximum likelihood iteration algorithm were employed to reconstruct the object imaging from the original projection. The results show that CSI can benefit the low flux neutron imaging with high background noise.

  15. 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.

  16. 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.

  17. Hexaarylbiimidazoles as Visible Light Thiol–Ene Photoinitiators

    Science.gov (United States)

    Clarkson, Brian H.; Scott, Timothy F.

    2015-01-01

    Objectives The aim of this study is to determine if hexaarylbiimidazoles (HABIs) are efficient, visible light-active photoinitiators for thiol–ene systems. We hypothesize that, owing to the reactivity of lophyl radicals with thiols and the necessarily high concentration of thiol in thiol–ene formulations, HABIs will effectively initiate thiol–ene polymerization upon visible light irradiation. Methods UV-vis absorption spectra of photoinitiator solutions were obtained using UV-vis spectroscopy, while EPR spectroscopy was used to confirm radical species generation upon HABI photolysis. Functional group conversions during photopolymerization were monitored using FTIR spectroscopy, and thermomechanical properties were determined using dynamic mechanical analysis. Results The HABI derivatives investigated exhibit less absorptivity than camphorquinone at 469 nm; however, they afford increased sensitivity at this wavelength when compared with bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide. Photolysis of the investigated HABIs affords lophyl radicals. Affixing hydroxyhexyl functional groups to the HABI core significantly improved solubility. Thiol–ene resins formulated with HABI photoinitiators polymerized rapidly upon irradiation with 469 nm. The glass transition temperatures of the thiol–ene resin formulated with a bis(hydroxyhexyl)-functionalized HABI and photopolymerized at room and body temperature were 49.5±0.5°C and 52.2±0.1°C, respectively. Significance Although thiol–enes show promise as continuous phases for composite dental restorative materials, they show poor reactivity with the conventional camphorquinone/tertiary amine photoinitiation system. Conversely, despite their relatively low visible light absorptivity, HABI photoinitiators afford rapid thiol–ene photopolymerization rates. Moreover, minor structural modifications suggest pathways for improved HABI solubility and visible light absorption. PMID:26119702

  18. A novel visible light responsive nanosystem for cancer treatment.

    Science.gov (United States)

    Martínez-Carmona, M; Lozano, D; Baeza, A; Colilla, M; Vallet-Regí, M

    2017-10-26

    A novel singlet-oxygen sensitive drug delivery nanocarrier able to release its cargo after exposure to visible (Vis) light from a common lamp is presented. This nanodevice is based on mesoporous silica nanoparticles (MSN) decorated with porphyrin-caps grafted via reactive oxygen species (ROS)-cleavable linkages. In the presence of Vis light porphyrin-nanocaps produce singlet oxygen molecules that break the sensitive-linker, which triggers pore uncapping and therefore allows the release of the entrapped cargo (topotecan, TOP). This new system takes advantage of the non-toxicity and greater penetration capacity of Vis radiation and a double antitumor effect due to the drug release and the ROS production. In vitro tests with HOS osteosarcoma cancer cells reveal that TOP is able to be released in a controlled fashion inside the tumor cells. This research work constitutes a proof of concept that opens up promising expectations in the search for new alternatives for the treatment of cancer.

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

    DEFF Research Database (Denmark)

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

    2014-01-01

    With the advent of high efficacy light emitting diode (LED) directional lamps as a key component in focal lighting, new possibilities emerge for re-designing the smart home scenario. A smart home scenario is characterized by enabled intelligent interworking of various wireless and wired...... (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...

  20. Visible Light Communication Physical Layer Design for Jist Simulation

    Directory of Open Access Journals (Sweden)

    Tomaš Boris

    2014-12-01

    Full Text Available Current advances in computer networking consider using visible light spectrum to encode and decode digital data. This approach is relatively non expensive. However, designing appropriate MAC or any other upper layer protocol for Visible Light Communication (VLC requires appropriate hardware. This paper proposes and implements such hardware simulation (physical layer that is compatible with existing network stack.

  1. Visible-light-induced water splitting based on two-step photoexcitation between dye-sensitized layered niobate and tungsten oxide photocatalysts in the presence of a triiodide/iodide shuttle redox mediator.

    Science.gov (United States)

    Abe, Ryu; Shinmei, Kenichi; Koumura, Nagatoshi; Hara, Kohjiro; Ohtani, Bunsho

    2013-11-13

    cocatalyst, instead of undesirable oxidation of I(-). Simultaneous evolution of H2 and O2 under visible light was then achieved by combining the Pt/H4Nb6O17 semiconductor sensitized with the dye molecules having an oligothiophene moiety, which can stably generate H2 and I3(-) from an aqueous KI solution, with the IrO2-Pt-loaded WO3 photocatalyst that can reduce the I3(-) back to I(-) and oxidize water to O2.

  2. 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.

  3. 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)

  4. 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...

  5. A Carpet Cloak for Visible Light

    Science.gov (United States)

    2011-01-01

    of transformation optical devices at visible frequencies. KEYWORDS:Optical metamaterials , invisibility cloak , transformation optics, nanofabrication...Berkeley, California 94720, United States Invisibility cloaks , a family of optical illusion devices that routeelectromagnetic (EM) waves around an object...EM properties, known as metamaterials ,1,2 have been used to control the propagation of EM waves. Metamaterials have been applied to cloaking using the

  6. Infrared-sensitive spatial light modulator

    Science.gov (United States)

    Warde, Cardinal

    1987-11-01

    This final report summarizes a preliminary investigation of an infrared-sensitive spatial light modulator that is designed to respond to white light in the 3 to 5 micrometers wavelength range. The device can be read out with visible light and, as such, is intended to function simultaneously as an image wavelength upconverter and light modulator. The device design employs a thin-film InSb photoconductor that addresses a DKDP crystal which is cooled near the Curie temperature (-51 degrees centigrade) of DKDP. Preliminary results are reported on: thin flash-evaporated films on InSb; the development of the cooled DKDP substrates; design and fabrication of the modulator vacuum cell; and theoretical modelling of the device performance.

  7. A Visible-Light-Sensitive Caged Serotonin

    OpenAIRE

    Cabrera, R.; Filevich, O; Garcia-Acosta, B; Athilingam, J; Bender, KJ; Poskanzer, KE; R. Etchenique

    2017-01-01

    Serotonin, or 5-hydroxytryptamine (5HT), is an important neurotransmitter in the nervous system of both vertebrates and invertebrates. Deficits in 5HT signaling are responsible for many disabling psychiatric conditions, and its molecular machinery is the target of many pharmaceuticals. We present a new 5HT phototrigger, the compound [Ru(bpy)2(PMe3)(5HT)]2+, where PMe3 is trimethylphosphine. As with other ruthenium-bipyridyl based caged compounds, [Ru(bpy)2(PMe3)(5HT)]2+ presents activity in t...

  8. Implementasi Visible Light Communication (VLC Pada Sistem Komunikasi

    Directory of Open Access Journals (Sweden)

    ARSYAD RAMADHAN DARLIS

    2017-06-01

    Full Text Available Abstrak Perkembangan teknologi telah menunjukkan peningkatan yang cukup signifikan, terutama untuk bidang komunikasi. Hal ini terbukti dengan banyaknya media komunikasi baik itu nirkabel dan kabel. Pada penelitian ini dimanfaatkan cahaya tampak sebagai media dalam sistem komunikasi, dimana selama ini cahaya hanya digunakan sebagai penerangan saja. Visible Light Communication (VLC adalah sebuah teknologi komunikasi yang memanfaatkan pancaran cahaya tampak dari lampu pada sistem komunikasi. Sistem komunikasi visible light ini terdiri dari pemancar dan penerima. Pemancar terdiri dari Light Emitting Dioda, audio transformator dan baterai, dan pada penerima terdiri dari solar cell dan photodioda, amplifier dan catu daya. Hal-hal yang dapat mempengaruhi hasil output sistem komunikasi adalah jarak, terang cahaya lampu pemancar dan cahaya luar. Pada penelitian ini, komunikasi menggunakan VLC dapat dilakukan pada jarak pengiriman data sebesar 2,5 m dan dengan range frekuensi 600 Hz sampai dengan 45 kHz dimana data dapat disalurkan dengan baik. Kata kunci: Visible light, Sistem komunikasi, Light Emitting Dioda, solar cell, photodioda. Abstract Technological developments have shown a significant increase, especially in the field of communication. This is proved by the many communications media using both wireless and wired. This study utilized the visible light as a medium of communication system, which has been used as an illumination light only. Visible Light Communication (VLC is a communication technology which utilize visible light emitted from the lamp in the communication system. The visible light communication system consists of a transmitter and receiver. The transmitter consists of a Light Emitting Diode, audio transformer and battery, and the receiver consists of a solar cell and a photodiode, amplifier and power supply. Things that can affect the output of the communication system is the distance, bright light and outdoor light. In the research

  9. 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.

  10. Direct effects of visible and UVA light on pigment migration in erythrophores of Nile tilapia.

    Science.gov (United States)

    Sato, Masako; Ishikura, Ryo; Oshima, Noriko

    2004-10-01

    Erythrophores derived from Nile tilapia (Oreochromis niloticus) are sensitive to visible light of defined wavelengths in primary culture in the same manner as erythrophores in the skin. Cultured erythrophores aggregate their pigment in response to light with peak wavelengths near 400 or 600 nm, while dispersion is caused by light near 500 nm. In this study, we report that ultraviolet A (UVA) with a peak wavelength near 365 nm also induces pigment aggregation in erythrophores in the skin and in primary culture. The responses of erythrophores in the skin or in culture depend on the light intensity, although the photo-sensitivity differs among individual cells. From the results, we conclude that the action of visible light and UVA light on tilapia erythrophores is direct, and that multiple types of visual pigments may coexist in individual erythrophores.

  11. VISIBLE LIGHT INDUCED PHOTOCATALYTIC DEGRADATION OF ...

    African Journals Online (AJOL)

    a

    Photocatalytic degradation of eosin and erythrosin-B (xanthene dyes) has been carried out using anthracene semiconductor ... KEY WORDS: Photocatalytic, Degradation, Xanthene dyes, Immobilized anthracene ... light intensity was measured with the help of a solarimeter (Surya Mapi Model CEL 201, India). The progress ...

  12. VISIBLE LIGHT INDUCED PHOTOCATALYTIC DEGRADATION OF ...

    African Journals Online (AJOL)

    a

    ABSTRACT. 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.

  13. Ultraviolet and visible light penetration of epidermis

    Energy Technology Data Exchange (ETDEWEB)

    Eggset, G.; Kavli, G.; Volden, G. (Tromsoe Univ. (Norway). Dept. of Dermatology); Krokan, H. (Tromsoe Univ. (Norway). Inst. of Medical Biology)

    1984-10-01

    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.

  14. 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.

  15. Visible and ultraviolet light sources based nonlinear interaction of lasers

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer; Tidemand-Lichtenberg, Peter; Jain, Mayank

    Different light sources can be used for optically stimulated luminescence measurements and usually a halogen lamp in combination with filters or light emitting diodes (LED’s) are used to provide the desired stimulation wavelength. However lasers can provide a much more well-defined beam, very...... for synthesizing any wavelength in the visible and ultraviolet light based sum frequency generation between two lasers is presented....

  16. 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.

  17. Aviation signal lighting : impacts of lighting characteristics on visibility.

    Science.gov (United States)

    2011-01-01

    This paper summarizes research on visual responses to colored light signals in the aviation and : roadway environment and on government requirements for lighting along airfields. The objective : is to identify gaps in the knowledge about how individu...

  18. Graphene quantum dot sensitized leaf-like InVO4/BiVO4 nanostructure: a novel ternary heterostructured QD-RGO/InVO4/BiVO4 composite with enhanced visible-light photocatalytic activity.

    Science.gov (United States)

    Lin, Xue; Wang, Yushuang; Zheng, Jia; Liu, Chang; Yang, Yang; Che, Guangbo

    2015-11-28

    Leaf-like InVO4/BiVO4 nanostructures with sizes of 2-5 μm were synthesized by a simple hydrothermal method. Graphene quantum dots (QD-RGO) were then deposited onto the surfaces of the leaf-like InVO4/BiVO4 crystals through a facile deposition-precipitation technique. Under visible light irradiation (λ > 420 nm), the QD-RGO/InVO4/BiVO4 photocatalyst degraded rhodamine B (Rh B) efficiently and displayed a much higher photocatalytic activity than pure BiVO4, InVO4, RGO/InVO4, RGO/BiVO4 or an InVO4/BiVO4 hybrid. The InVO4/BiVO4 photocatalyst with 3 wt% of QD-RGO exhibited the highest photocatalytic efficiency. The quenching effects of different scavengers demonstrated that O2˙(-) played a major role in Rh B degradation. It was elucidated that the excellent photocatalytic activity of QD-RGO/InVO4/BiVO4 for the degradation of Rh B under visible light (λ > 420 nm) can be ascribed to the extended absorption in the visible light region resulting from the QD-RGO loading, the high specific surface area, and the efficient separation of photogenerated electrons and holes through the QD-RGO/InVO4/BiVO4 heterostructure.

  19. High visibility two-photon interference with classical light.

    Science.gov (United States)

    Hong, Peilong; Xu, Lei; Zhai, Zhaohui; Zhang, Guoquan

    2013-06-17

    Two-photon interference with independent classical sources, in which superposition of two indistinguishable two-photon paths plays a key role, is of limited visibility with a maximum value of 50%. By using a random-phase grating to modulate the wavefront of a coherent light, we introduce superposition of multiple indistinguishable two-photon paths, which enhances the two-photon interference effect with a signature of visibility exceeding 50%. The result shows the importance of phase control in the control of high-order coherence of classical light.

  20. 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.

  1. 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.

  2. Enhancement of visible light irradiation photocatalytic activity of ...

    Indian Academy of Sciences (India)

    Mohamed Abdel Salam

    2017-09-25

    Sep 25, 2017 ... Yin D and Zhao F 2015 Visible-light-responsive sulfated vanadium-doped TS-1 with hollow structure: Enhanced photocatalytic activity in selective oxidation of cyclo- hexane J. Catal. 330 208. 11. Kim J, Ichikuni N, Hara T and Shimazu S 2016 Study on the selectivity of propane photo-oxidation reaction on.

  3. 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.

  4. Integrating TEMPO and Its Analogues with Visible-Light Photocatalysis.

    Science.gov (United States)

    Lang, Xianjun; Zhao, Jincai

    2018-01-16

    Visible light has risen to become a very important facilitator for selective radical reactions enabled by well-cognized photocatalysts. The renaissance of visible-light photocatalysis on this matter partly relies on integrating it with other fields of catalysis. In parallel, 2,2,6,6-tetramethylpiperidin N-oxide (TEMPO), a quintessential persistent radical, has a wide range of uses owing to its exceptional redox behavior, which gives rise to its latest prominence in catalysis. Therefore, integrating the catalysis of TEMPO with photocatalysis to perform visible-light-induced selective reactions becomes a very convenient marriage of merits. In this context, the integration of different types of photocatalysts, including metal complexes, metal-free organic dyes, and semiconductors, with TEMPO for outstanding organic transformations will be summarized. To expand further the catalytic repertoire, the integration of TEMPOH analogues such as NHPI (N-hydroxyphthalimide) and NHS (N-hydroxysuccinimide) with photocatalysis will also be discussed. Hopefully, these advances will pave the way for more breakthroughs by integrating TEMPO and its analogues with photocatalysis to lead to a valuable blueprint for visible-light-induced selective organic transformations. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Enhancement of visible light irradiation photocatalytic activity of ...

    Indian Academy of Sciences (India)

    SrTiO₃ and Pt/SrTiO₃ nanoparticles were characterized by XRD, XPS, TEM, BET surface area UV–Vis and PL techniques in order to explore their chemical and physical properties. The visible light irradiation photocatalyticperformances of SrTiO₃ nanoparticles and Pt/SrTiO₃ nanoparticles for photocatalytic oxidation of ...

  6. Visible light photocatalytic properties of novel molybdenum treated ...

    Indian Academy of Sciences (India)

    Visible light photocatalytic properties of novel molybdenum treated carbon nanotube/titania composites. FENG-JUN ZHANG† and WON-CHUN OH. ∗. School of Materials and Chemical Engineering, Anhui University of Architecture, Anhui Hefei 230022,. P. R. China. †Department of Advanced Materials & Engineering, ...

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

    OpenAIRE

    Dupuy, Charles G.; Allen, Thomas L.; Williams, George M.; David Schut

    2014-01-01

    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 ro...

  8. A possible mechanism for visible light-induced wound healing.

    Science.gov (United States)

    Lipovsky, Anat; Nitzan, Yeshayahu; Lubart, Rachel

    2008-09-01

    Chronic wounds resistant to conventional therapy have been treated successfully with low energy lasers and light emitting diodes (LEDs) in the visible and near IR region. It has been proposed that production of low level reactive oxygen species (ROS) following illumination is the first step of photobiomodulation. It was also shown that white light (400-800 nm) has similar stimulatory effects as lasers and LEDs. ROS at higher levels are toxic to cells and bacteria. In the present study, we examined the phototoxicity of broadband (400-800 nm, 120 J/cm(2)) visible light on the survival of several pathogenic bacteria: Staphylococcus aureus 195, Pseudomonas aeruginosa 1316, Escherichia coli 1313, and Serratia marcescens. These bacteria were chosen due to their high prevalence in infected wounds. The survival of bacterial cells following illumination was monitored by counting the number of colony forming units before and after exposure to light. Illumination with white light, 120 J/cm(2), caused a reduction of 62%, 83%, and 56% in the colony count of E. coli 1313, S. aureus 195 and S. marcescens, respectively, though no reduction in the viability of P. aeruginosa 1316 was demonstrated. The phototoxic effect was found to involve induction of ROS production by the bacteria. It was also found that illumination of S. aureus 195 and E. coli 1313 in the presence of pyocyanin, known to be secreted by P. aeruginosa, had a stronger bactericidal effect compared to illumination alone. Visible light at high intensity can kill bacteria in infected wounds. Thus, illumination of infected wounds with intense visible light, prior to low intensity illumination for stimulating wound closure, may reduce infection and promote healing.

  9. Visible-Light-Activated Bactericidal Functions of Carbon "Quantum" Dots.

    Science.gov (United States)

    Meziani, Mohammed J; Dong, Xiuli; Zhu, Lu; Jones, Les P; LeCroy, Gregory E; Yang, Fan; Wang, Shengyuan; Wang, Ping; Zhao, Yiping; Yang, Liju; Tripp, Ralph A; Sun, Ya-Ping

    2016-05-04

    Carbon dots, generally defined as small carbon nanoparticles with various surface passivation schemes, have emerged as a new class of quantum-dot-like nanomaterials, with their optical properties and photocatalytic functions resembling those typically found in conventional nanoscale semiconductors. In this work, carbon dots were evaluated for their photoinduced bactericidal functions, with the results suggesting that the dots were highly effective in bacteria-killing with visible-light illumination. In fact, the inhibition effect could be observed even simply under ambient room lighting conditions. Mechanistic implications of the results are discussed and so are opportunities in the further development of carbon dots into a new class of effective visible/natural light-responsible bactericidal agents for a variety of bacteria control applications.

  10. 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.

  11. Reflection beamshifts of visible light due to graphene

    Science.gov (United States)

    Hermosa, Nathaniel

    2016-02-01

    I present calculations of reflection beamshifts, Goos-Hänchen and Imbert-Fedorov shifts, due to the presence of a graphene monolayer on a dielectric medium when using a beam with wavelength in the visible range. Measuring the Goos-Hänchen and Imbert-Fedorov shifts is an alternative method to determine graphene’s conductivity. I look at beamshifts for different polarization states (p, s, 450, {σ }+) and I discuss other possible experimental routes to determine these beamshifts and consequently, the graphene’s optical conductivity. The Goos-Hänchen shifts for visible light I calculated are in good agreement with results of a recent experiment.

  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

    -order GSP resonance and thereby involve relatively large nanobricks, can successfully be used for efficient polarization-controlled steering of visible light. The reflection amplitude and phase maps for a 450 nm period array of 50 nm thick nanobricks placed atop a 40 nm thick silica layer supported...... 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...... (electric field perpendicular to the plane of diffraction) being significantly better (experimentally > 20 % and theoretically > 40 %) than for the TM polarization. This difference becomes even more pronounced for the light incidence deviating from normal. Finally, we discuss possible improvements...

  13. Visible light driven plasmonic photochemistry on nano-textured silver.

    Science.gov (United States)

    Walia, Jaspreet; Guay, Jean-Michel; Krupin, Oleksiy; Variola, Fabio; Berini, Pierre; Weck, Arnaud

    2017-12-20

    Plasmon assisted generation of silver sulfate from dodecanethiol is demonstrated on a nano-textured silver substrate with a strong surface plasmon resonance in the visible range. The observed photo-physical processes are attributed to hot charge carriers that are generated from the excitation of surface plasmon resonances using 532 nm laser light. Excited charge carriers are responsible for cleaving the alkane chain, and for generating reactive oxygen species which rapidly photooxidize the exposed sulfur atoms. The ability to drive photochemical reactions with photon energies in the visible range rather than in the UV, on nano-textured silver surfaces, will enable researchers to study photochemical transformations for a wide variety of applications. The strong optical absorbance across the visible range, combined with the fact that the substrates can be fabricated over large areas, naturally makes them candidates for solar driven photochemical applications, and for large scale plasmonic reactors.

  14. Enhanced photoresponse towards visible light in Ru doped titania nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Khan, M. Alam [School of Semiconductor and Chemical Engineering and Solar Energy Research Center, Chonbuk National University, 664-14 Dukjin dong, 1Ga, Jeonju 719-756 (Korea, Republic of); School of Display and Chemical Engineering, Yeungnam University, 214-1 Dae-Dong, Gyeongsan 712-749 (Korea, Republic of); Han, Do Hung [School of Display and Chemical Engineering, Yeungnam University, 214-1 Dae-Dong, Gyeongsan 712-749 (Korea, Republic of); Yang, O.-Bong [School of Semiconductor and Chemical Engineering and Solar Energy Research Center, Chonbuk National University, 664-14 Dukjin dong, 1Ga, Jeonju 719-756 (Korea, Republic of)], E-mail: obyang@chonbuk.ac.kr

    2009-01-01

    Doping of ruthenium by the ion exchange method to the hydrothermally synthesized titania nanotube (TiNT) was found to be an effective photocatalyst active under visible light for methylene blue dye decoloration. The well dispersed and well embedded ionized ruthenium particles of about {approx}2-4 nm significantly reduced the band gap energy of synthesized TiNTs from 3.1 eV to 2.56 eV in (Ru(IE)/TiNT). The loading method, size of ruthenium particles and metal dispersion pattern at the nanotube textures have great influence on its photocatalytic performances exhibiting higher photocatalytic activity (>80%) of methylene blue dye. However, large aggregated ruthenium particles (sizes {approx}12-60 nm) on Ru(IM)/TiNT prepared by impregnation method failed to respond in visible light. The prepared catalysts were analysed by TEM, FESEM, FE-SEMEDX, XRD, UV-vis DRS spectra, XPS and BET surface area techniques.

  15. Heterogeneous visible light photocatalysis for selective organic transformations.

    Science.gov (United States)

    Lang, Xianjun; Chen, Xiaodong; Zhao, Jincai

    2014-01-07

    The future development of chemistry entails environmentally friendly and energy sustainable alternatives for organic transformations. Visible light photocatalysis can address these challenges, as reflected by recent intensive scientific endeavours to this end. This review covers state-of-the-art accomplishments in visible-light-induced selective organic transformations by heterogeneous photocatalysis. The discussion comprises three sections based on the photocatalyst type: metal oxides such as TiO2, Nb2O5 and ZnO; plasmonic photocatalysts like nanostructured Au, Ag or Cu supported on metal oxides; and polymeric graphitic carbon nitride. Finally, recent strides in bridging the gap between photocatalysis and other areas of catalysis will be highlighted with the aim of overcoming the existing limitations of photocatalysis by developing more creative synthetic methodologies.

  16. Photocatalytic Degradation of Thiram (Fungicides under Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Sanjay R. Thakare

    2005-01-01

    Full Text Available Pesticides in the different form are toxic to the environment and removal of its form the various sources is a difficult task. The thiram undergoes photocatalytic degradation under visible light when prepared TiO2∼PVA polymer composite was used as a photocatalyst. The data represent that prepared TiO2∼PVA polymer composite is a more efficient photocatalyst than the neat TiO2. Photocatalytic efficiency of prepared TiO2∼PVA polymer composite was measured in term of no adsorption of pollutant, higher degradation rate and act as a photocatalyst under visible light irradiation. 150 minutes are required for the complete degradation of the thiram. The end products of photocatalytic degradation of thiram are CO2, nitrate and sulphate.

  17. Multipath Reflections Analysis on Indoor Visible Light Positioning System

    CERN Document Server

    Gu, Wenjun; Kavehrad, Mohsen

    2015-01-01

    Visible light communication (VLC) has become a promising research topic in recent years, and finds its wide applications in indoor environments. Particularly, for location based services (LBS), visible light also provides a practical solution for indoor positioning. Multipath-induced dispersion is one of the major concerns for complex indoor environments. It affects not only the communication performance but also the positioning accuracy. In this paper, we investigate the impact of multipath reflections on the positioning accuracy of indoor VLC positioning systems. Combined Deterministic and Modified Monte Carlo (CDMMC) approach is applied to estimate the channel impulse response considering multipath reflections. Since the received signal strength (RSS) information is used for the positioning algorithm, the power distribution from one transmitter in a typical room configuration is first calculated. Then, the positioning accuracy in terms of root mean square error is obtained and analyzed.

  18. Visible light laser voltage probing on thinned substrates

    Science.gov (United States)

    Beutler, Joshua; Clement, John Joseph; Miller, Mary A.; Stevens, Jeffrey; Cole, Jr., Edward I.

    2017-03-21

    The various technologies presented herein relate to utilizing visible light in conjunction with a thinned structure to enable characterization of operation of one or more features included in an integrated circuit (IC). Short wavelength illumination (e.g., visible light) is applied to thinned samples (e.g., ultra-thinned samples) to achieve a spatial resolution for laser voltage probing (LVP) analysis to be performed on smaller technology node silicon-on-insulator (SOI) and bulk devices. Thinning of a semiconductor material included in the IC (e.g., backside material) can be controlled such that the thinned semiconductor material has sufficient thickness to enable operation of one or more features comprising the IC during LVP investigation.

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

    DEFF Research Database (Denmark)

    Melentieva, Anastasiya; Kucheryavskiy, Sergey; Bogomolov, Andrey

    2012-01-01

    VISIBLE LIGHT SCATTER AS A QUANTITATIVE INFORMATION SOURCE ON MILK CONSTITUENTS A. Melenteva 1, S. Kucheryavski 2, A. Bogomolov 1,31Samara State Technical University, Molodogvardeyskaya Street 244, 443100 Samara, Russia. 2Aalborg University, campus Esbjerg, Niels Bohrs vej 8, 6700 Esbjerg, Denmar...... research area are presented and discussed. References: [1] A. Bogomolov, S. Dietrich, B. Boldrini, R.W. Kessler, Food Chemistry (2012), doi:10.1016/j.foodchem.2012.02.077....

  20. Performance Analysis of Visible Light Communication Using CMOS Sensors.

    Science.gov (United States)

    Do, Trong-Hop; Yoo, Myungsik

    2016-02-29

    This paper elucidates the fundamentals of visible light communication systems that use the rolling shutter mechanism of CMOS sensors. All related information involving different subjects, such as photometry, camera operation, photography and image processing, are studied in tandem to explain the system. Then, the system performance is analyzed with respect to signal quality and data rate. To this end, a measure of signal quality, the signal to interference plus noise ratio (SINR), is formulated. Finally, a simulation is conducted to verify the analysis.

  1. 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.

  2. 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.

  3. Investigation of electron transfer between hexaarylbiimidazole and visible sensitizer

    Science.gov (United States)

    Lin, Yi; Liu, Andong; Trifunac, Alexander D.; Krongauz, Vadim V.

    1992-10-01

    Photoinduced electron transfer between the hexaarylbiimidazole (HABI) and visible sensitizer, 2,5-bis [(2,3,6,7-tetrahydro- 1H,5H-benzo [i,j] quinolizin- l-yl ) methylene] cyclopentanone (JAW), in liquid solution was investigated experimentally. The relative fluorescence quantum yield of the sensitizer molecule was measured as a function of HABI concentration. An exponential dependence on HABI concentration was observed for the sensitizer fluorescence yield, from which the critical distance for the electron transfer interaction was determined to be approximately 12 A. The time-dependent fluorescence quenching was studied with the time-correlated single-photon counting technique. The dynamics of the electron transfer process was determined by comparing the experimental data to existing models of electron transfer in liquids, The inclusion of the relative diffusion between the electron donor and acceptor molecules is necessary to fit all the observations and to obtain accurate transfer parameters.

  4. 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.

  5. Indoor localization system utilizing two visible light emitting diodes

    Science.gov (United States)

    Mousa, Farag I. K.; Le-Minh, Hoa; Ghassemlooy, Zabih; Dai, Xuewu; Tran, Son T.; Boucouvalas, Anthony C.; Liaw, Shien-Kuei

    2016-11-01

    Indoor positioning or localization based on visible light communications (VLC) is an emerging technology with wide applications. In conventional localization schemes, the trilateration technique is widely used with at least three separate lighting sources to determine the user's location. An indoor VLC positioning scheme based on the optical power distributions of only two light emitting diodes (LEDs) is reported for different environments. We have used two received signal strength indications to determine the user's position based on the LEDs configuration offering less complexity. We propose comprehensive mathematical models for the VLC localization system considering the noise and its impact on the user's location, and numerically evaluated it over a range of signal-to-noise ratios (SNRs). In addition, it is compared to the results with the exiting trilateration technique. The performance of the proposed system is evaluated with a reported accuracy of 13 dB.

  6. 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.

  7. MIMO decorrelation for visible light communication based on angle optimization

    Science.gov (United States)

    Zhang, Haiyong; Zhu, Yijun

    2017-03-01

    Recently, many researchers have used the normal vector tilting to solve the problems about low rate of multiplexing and channel strong correlation in Visible Light Communication Multiple-Input Multiple-Output (VLC-MIMO) system, but they all lack of the theoretical support. In this paper, we establish a channel model about 2×2 VLC-MIMO, then translate the communication problem about vector tilting optimal angle in a certain range into a mathematical problem about seeking the minimum value of function. Finally, we deduced the mathematic expressions about the optimal tilting angles of corresponding LEDs and PDs, and these expressions will provide a theoretical basis for the further study.

  8. Performance Analysis of Visible Light Communication Using CMOS Sensors

    Directory of Open Access Journals (Sweden)

    Trong-Hop Do

    2016-02-01

    Full Text Available This paper elucidates the fundamentals of visible light communication systems that use the rolling shutter mechanism of CMOS sensors. All related information involving different subjects, such as photometry, camera operation, photography and image processing, are studied in tandem to explain the system. Then, the system performance is analyzed with respect to signal quality and data rate. To this end, a measure of signal quality, the signal to interference plus noise ratio (SINR, is formulated. Finally, a simulation is conducted to verify the analysis.

  9. 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.

  10. Secure positioning technique based on the encrypted visible light map

    Science.gov (United States)

    Lee, Y. U.; Jung, G.

    2017-01-01

    For overcoming the performance degradation problems of the conventional visible light (VL) positioning system, which are due to the co-channel interference by adjacent light and the irregularity of the VL reception position in the three dimensional (3-D) VL channel, the secure positioning technique based on the two dimensional (2-D) encrypted VL map is proposed, implemented as the prototype for the specific embedded positioning system, and verified by performance tests in this paper. It is shown from the test results that the proposed technique achieves the performance enhancement over 21.7% value better than the conventional one in the real positioning environment, and the well known PN code is the optimal stream encryption key for the good VL positioning.

  11. Spatial dimming scheme for optical OFDM based visible light communication.

    Science.gov (United States)

    Yang, Yang; Zeng, Zhimin; Cheng, Julian; Guo, Caili

    2016-12-26

    A new dimming control scheme termed spatial dimming orthogonal frequency division multiplexing (SD-OFDM) is proposed for multiple-input and multiple output OFDM based visible light communication. The basic idea of SD-OFDM is that the illumination can be represented by the number of glared light emitting diodes (LEDs) in an LED lamp. As the biasing level of LEDs does not adjust to represent the required illumination level, the proposed scheme can significantly mitigate the clipping noise compared to analogue dimming schemes. Furthermore, unlike digital dimming schemes that control illumination levels by setting different duty cycles of pulse width modulation, the proposed scheme is always in the "on-state" for varied illumination levels. Both analytical and simulation results indicate that the proposed scheme is an efficient and feasible dimmable scheme.

  12. 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.

  13. 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.

  14. EDTA-Reduction of Water to Molecular Hydrogen Catalyzed by Visible-Light-Response TiO2-Based Materials Sensitized by Dawson- and Keggin-Type Rhenium(V-Containing Polyoxotungstates

    Directory of Open Access Journals (Sweden)

    Yusuke Kataoka

    2010-02-01

    Full Text Available The synthesis and characterization of a Keggin-type mono-rhenium(V-substituted polyoxotungstate are described. The dimethylammonium salt [Me2NH2]4[PW11ReVO40] was obtained as analytically pure homogeneous black-purple crystals by reacting mono-lacunary Keggin polyoxotungstate with [ReIVCl6]2- in water, followed by crystallization from acetone at ca. 5 °C. Single-crystal X-ray structural analysis of [PW11ReVO40]4- revealed a monomeric structure with overall Td symmetry. Characterization of [Me2NH2]4[PW11ReVO40] was also accomplished by elemental analysis, magnetic susceptibility, TG/DTA, FTIR, UV-vis, diffuse reflectance (DR UV-vis, and solution 31P-NMR spectroscopy. Furthermore, [PW11ReVO40]4- and the Dawson-type dirhenium(V-oxido-bridged polyoxotungstate [O{ReV(OH(α2-P2W17O61}2]14- were supported onto anatase TiO2 surface by the precipitation methods using CsCl and Pt(NH34Cl2. With these materials, hydrogen evolution from water in the presence of EDTA⋅2Na (ethylenediamine tetraacetic acid disodium salt under visible light irradiation (≥400 nm was achieved.

  15. 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.

  16. A bisazobenzene crosslinker that isomerizes with visible light

    Directory of Open Access Journals (Sweden)

    Subhas Samanta

    2012-12-01

    Full Text Available Background: Large conformational and functional changes of azobenzene-modified biomolecules require longer azobenzene derivatives that undergo large end-to-end distance changes upon photoisomerization. In addition, isomerization that occurs with visible rather than UV irradiation is preferred for biological applications.Results: We report the synthesis and characterization of a new crosslinker in which a central piperazine unit links two azobenzene chromophores. Molecular modeling indicates that this crosslinker can undergo a large change in end-to-end distance upon trans,trans to cis,cis isomerization. Photochemical characterization indicates that it does isomerize with visible light (violet to blue wavelengths. However, the thermal relaxation rate of this crosslinker is rather high (τ½ ~ 1 s in aqueous buffer at neutral pH so that it is difficult to produce large fractions of the cis,cis-species without very bright light sources.Conclusion: While cis-lifetimes may be longer when the crosslinker is attached to a biomolecule, it appears the para-piperazine unit may be best suited for applications where rapid thermal relaxation is required.

  17. 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.

  18. 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.

  19. Innovative, energy-efficient lighting for New York state roadways : opportunities for incorporating mesopic visibility considerations into roadway lighting practice

    Science.gov (United States)

    2008-04-01

    The present report outlines activities undertaken to assess the potential for implementing research on visibility at mesopic light levels into lighting practices for roadways in New York State. Through measurements of light levels at several roadway ...

  20. Enhancement of Light via Surface Plasmon Coupling in the Visible

    Science.gov (United States)

    Ray, Emily A.

    The incidence of light with momentum components outside the light cone on the surface of a negative permittivity material results in the excitation of a surface plasmon polariton and the enhancement of the incident signal when there is momentum and energy conservation. This process has an impact across many fields including imaging, optical computing, signaling, and photovoltaic devices, among others. I examine the role and tunability of light-surface plasmon interactions in several applications. I demonstrate a tuned metamaterial grating system that allows the signal from evanescent waves to be detected in the far field in the visible regime. I fabricate a metamaterial that is tuned to support surface plasmons that couple to visible light across a wide range of wavelengths. I characterize the plasmonic response through a simple technique wherein a the reflection from a subwavelength grating on a metamaterial indicates surface plasmon coupling when its intensity dips. With this I demonstrate that the reflection trends match well with simulation, indicating that coupling of light to surface plasmons occurs at the expected crossing points. The strength of coupling (denoted by the drop in reflection) however, is less than expected. Transmission measurements reveal a depolarizing effect that accounts for the decrease in evanescent light enhancement by the surface plasmons and is due to the surface roughness at the interfaces between the metal and dielectric. I also use a tuned metamaterial perforated with a subwavelength array of circular apertures to exhibit extraordinary transmission in the visible. I compare the transmission of the metamaterial to that of a thin film of Ag with equivalent thickness that has fewer plasmon modes and a resonance position in the UV to find that for 400 nm, both thin films exhibit a transmission minimum at 650 nm. Both film spectra have plasmon-aided extraordinary transmission peaks where there is momentum and energy conservation between

  1. Refractive index sensitivity in etched FBG in the visible range

    Science.gov (United States)

    Kuhne, Jean F.; Nadas, Rafael B.; Inácio, Patricia L.; Chiamenti, Ismael; Kamicawachi, Ricardo C.; Kalinowski, Hypolito José

    2017-08-01

    A visible fiber Bragg grating (Vis-FBG) with wavelength peak centered at 673.07 nm was inscribed in a multimode fiber designed for infrared (IR) operation using a femtosecond (fs) laser emitting at 248 nm. The fiber cladding is removed by chemical etching in hydrofluoric acid solution (40%). The sensor refractive index response is determined by dipping the sensor into diluted glycerin solution at different concentrations with refractive index range from 1.3328 to 1.4607. The Vis-FBG performance is compared with an IR etched FBG (EFBG) with similar diameter. The sensitivity found for the Vis-FBG sensor is 15.71nm/RIU with a 6.34 x 10-3 RIU resolution for a refractive index of 1.4607.

  2. A comparative study of optical concentrators for visible light communications

    Science.gov (United States)

    Mulyawan, Rahmat; Gomez, Ariel; Chun, Hyunchae; Rajbhandari, Sujan; Manousiadis, Pavlos P.; Vithanage, Dimali A.; Faulkner, Grahame; Turnbull, Graham A.; Samuel, Ifor D. W.; Collins, Stephen; O'Brien, Dominic

    2017-01-01

    Given the imminent radio frequency spectrum crunch, Visible Light Communication (VLC) is being proposed as an alternative wireless technology allowing for scalable connectivity to potentially millions of mobile and Internet-of- Things (IoT) devices. A VLC system uses a photo-detector (PD) receiver that converts the optically modulated light from a light source into a modulated electrical signal. The corresponding receiver electrical bandwidth is typically inversely proportional to the PD active area. Consequently, to construct a high-speed VLC link, the PD active area is often substantially reduced and an optical concentrator is used to enhance the receiver collection area. However, to achieve high concentrating factor, the link field-of-view (FOV) needs to be narrow due to the étendue conservation in linear passive optical systems. This paper studies a Fluorescent Concentrator (FC) that breaks this étendue conservation. The FC is not only based on reflective and refractive principles but also makes use of fluorescence process. A comparison between the FC and conventional optical concentrators, namely Compound Parabolic Concentrator (CPC) is also investigated. The trade-off between received signal strength and incoming link angle is demonstrated over 60° coverage. Experimental results show that performance degradation as the link angle increases using FC-based receivers is significantly lower than for conventional CPC.

  3. 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.

  4. Generation of powerful tungsten reductants by visible light excitation.

    Science.gov (United States)

    Sattler, Wesley; Ener, Maraia E; Blakemore, James D; Rachford, Aaron A; LaBeaume, Paul J; Thackeray, James W; Cameron, James F; Winkler, Jay R; Gray, Harry B

    2013-07-24

    The homoleptic arylisocyanide tungsten complexes, W(CNXy)6 and W(CNIph)6 (Xy = 2,6-dimethylphenyl, Iph = 2,6-diisopropylphenyl), display intense metal to ligand charge transfer (MLCT) absorptions in the visible region (400-550 nm). MLCT emission (λ(max) ≈ 580 nm) in tetrahydrofuran (THF) solution at rt is observed for W(CNXy)6 and W(CNIph)6 with lifetimes of 17 and 73 ns, respectively. Diffusion-controlled energy transfer from electronically excited W(CNIph)6 (*W) to the lowest energy triplet excited state of anthracene (anth) is the dominant quenching pathway in THF solution. Introduction of tetrabutylammonium hexafluorophosphate, [Bu(n)4N][PF6], to the THF solution promotes formation of electron transfer (ET) quenching products, [W(CNIph)6](+) and [anth](•-). ET from *W to benzophenone and cobalticenium also is observed in [Bu(n)4N][PF6]/THF solutions. The estimated reduction potential for the [W(CNIph)6](+)/*W couple is -2.8 V vs Cp2Fe(+/0), establishing W(CNIph)6 as one of the most powerful photoreductants that has been generated with visible light.

  5. 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.

  6. Inverse design of LED arrangement for visible light communication systems

    Science.gov (United States)

    Zheng, Huanhuan; Chen, Jian; Yu, Changyuan; Gurusamy, Mohan

    2017-01-01

    In this paper, an optimal LED arrangement for indoor visible light communications (VLC) is proposed and numerically investigated. By using the concept of inverse design, the LED distribution can be formulated as a convex optimization problem and resolved accordingly. We show that sufficient brightness and uniform signal to noise ratio (SNR) can be achieved within the indoor coverage by using the proposed optimal LED arrangement, thus enabling the terminal mobility for indoor VLC. In addition, the analysis of delay spread distribution over the receiving plane shows that the design exhibits enhanced tolerance of inter-symbol interference (ISI). With the consideration of cabling cost for practical implementation, the suboptimal LED arrangement design is also investigated. Numerical results indicate that the suboptimal design can reduce the power consumption of the system with acceptable performance degradation.

  7. OCT angiography and visible-light OCT in diabetic retinopathy.

    Science.gov (United States)

    Nesper, Peter L; Soetikno, Brian T; Zhang, Hao F; Fawzi, Amani A

    2017-10-01

    In recent years, advances in optical coherence tomography (OCT) techniques have increased our understanding of diabetic retinopathy, an important microvascular complication of diabetes. OCT angiography is a non-invasive method that visualizes the retinal vasculature by detecting motion contrast from flowing blood. Visible-light OCT shows promise as a novel technique for quantifying retinal hypoxia by measuring the retinal oxygen delivery and metabolic rates. In this article, we discuss recent insights provided by these techniques into the vascular pathophysiology of diabetic retinopathy. The next milestones for these modalities are large multicenter studies to establish consensus on the most reliable and consistent outcome parameters to study diabetic retinopathy. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. 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.

  9. 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.

  10. CO2 SEQUESTRATION AND RECYCLE BY PHOTOCATALYSIS WITH VISIBLE LIGHT

    Energy Technology Data Exchange (ETDEWEB)

    Steven S.C. Chuang

    2001-10-01

    Visible light-photocatalysis could provide a cost-effective route to recycle CO{sub 2} to useful chemicals or fuels. Development of an effective catalyst for the photocatalytic synthesis requires (i) the knowledge of the surface band gap and its relation to the surface structure, (ii) the reactivity of adsorbates and their reaction pathways, and (iii) the ability to manipulate the actives site for adsorption, surface reaction, and electron transfer. The objective of this research is to study the photo-catalytic activity of TiO{sub 2}-base catalyst. A series of TiO{sub 2}-supported metal catalysts were prepared for determining the activity and selectivity for the synthesis of methane and methanol. 0.5 wt% Cu/SrTiO{sub 3} was found to be the most active and selective catalyst for methanol synthesis. The activity of the catalyst decreased in the order: Ti silsesquioxane > Cu/SrTiO{sub 3} > Pt/TiO{sub 2} > Cu/TiO{sub 2} > TiO{sub 2} > Rh/TiO{sub 2}. To further increase the number of site for the reaction, we propose to prepare monolayer and multiplayer TiOx on high surface area mesoporous oxides. These catalysts will be used for in situ IR study in the Phase II research project to determine the reactivity of adsorbates. Identification of active adsorbates and sites will allow incorporation of acid/basic sites to alter the nature of CO{sub 2} and H{sub 2}O adsorbates and with Pt/Cu sites to direct reaction pathways of surface intermediates, enhancing the overall activity and selectivity for methanol and hydrocarbon synthesis. The overall goal of this research is to provide a greater predictive capability for the design of visible light-photosynthesis catalysts by a deeper understanding of the reaction kinetics and mechanism as well as by better control of the coordination/chemical environment of active sites.

  11. 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.

  12. Visibility sweeps for joint-hierarchical importance sampling of direct lighting for stochastic volume rendering

    NARCIS (Netherlands)

    Kroes, T.; Eisemann, M.; Eisemann, E.

    2015-01-01

    Physically-based light transport in heterogeneous volumetric data is computationally expensive because the rendering integral (particularly visibility) has to be stochastically solved. We present a visibility estimation method in concert with an importance-sampling technique for efficient and

  13. The high frequency characteristics of laser reflection and visible light during solid state disk laser welding

    Science.gov (United States)

    Gao, Xiangdong; You, Deyong; Katayama, Seiji

    2015-07-01

    Optical properties are related to weld quality during laser welding. Visible light radiation generated from optical-induced plasma and laser reflection is considered a key element reflecting weld quality. An in-depth analysis of the high-frequency component of optical signals is conducted. A combination of a photoelectric sensor and an optical filter helped to obtain visible light reflection and laser reflection in the welding process. Two groups of optical signals were sampled at a high sampling rate (250 kHz) using an oscilloscope. Frequencies in the ranges 1-10 kHz and 10-125 kHz were investigated respectively. Experimental results showed that there was an obvious correlation between the high-frequency signal and the laser power, while the high-frequency signal was not sensitive to changes in welding speed. In particular, when the defocus position was changed, only a high frequency of the visible light signal was observed, while the high frequency of the laser reflection signal remained unchanged. The basic correlation between optical features and welding status during the laser welding process is specified, which helps to provide a new research focus for investigating the stability of welding status.

  14. 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.

  15. 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.

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

    DEFF Research Database (Denmark)

    Zhang, Zhongyang; Xu, Ruodan; Wang, Zegao

    2017-01-01

    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...

  17. Debris Disk Dust Characterization through Spectral Types: Deep Visible-Light Imaging of Nine Systems

    Science.gov (United States)

    Choquet, Elodie

    2017-08-01

    We propose STIS coronagraphy of 9 debris disks recently seen in the near-infrared from our re-analysis of archival NICMOS data. STIS coronagraphy will provide complementary visible-light images that will let us characterize the disk colors needed to place constraints on dust grain sizes, albedos, and anisotropy of scattering of these disks. With 3 times finer angular resolution and much better sensitivity, our STIS images will dramatically surpass the NICMOS discovery images, and will more clearly reveal disk local structures, cleared inner regions, and test for large-scale asymmetries in the dust distributions possibly triggered by associated planets in these systems. The exquisite sensitivity to visible-light scattering by submicron particles uniquely offered by STIS coronagraphy will let us detect and spatially characterize the diffuse halo of dust blown out of the systems by the host star radiative pressure. Our sample includes disks around 3 low-mass stars, 3 solar-type stars, and 3 massive A stars; together with our STIS+NICMOS imaging of 6 additional disks around F and G stars, our sample covers the full range of spectral types and will let us perform a comparative study of dust distribution properties as a function of stellar mass and luminosity. Our sample makes up more than 1/3 of all debris disks imaged in scattered light to date, and will offer the first homogeneous characterization of the visible-light to near-IR properties of debris disk systems over a large range of spectral types. Our program will let us analyze how the dynamical balance is affected by initial conditions and star properties, and how it may be perturbed by gas drag or planet perturbations.

  18. 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.

  19. Visible light Laue diffraction from woodpile photonic crystals.

    Science.gov (United States)

    Brüser, Björn; Staude, Isabelle; von Freymann, Georg; Wegener, Martin; Pietsch, Ullrich

    2012-10-01

    Bragg diffraction is often used as a tool to assess the structural quality of two-dimensional and three-dimensional (3D) photonic crystals. However, direct conclusions from the Laue diagrams to the underlying crystals structure cannot be drawn, as multiple scattering due to the high index contrast takes place. Here we systematically study the scattering of visible light by 3D woodpile photonic crystals with varying internal refractive index contrast Δn, to determine the limits of the single (kinematic) scattering approach. We aim to describe the intensity distribution of diffracting Bragg peaks with analytic expressions similarly to x-ray scattering at electronic crystals. Measured scattering curves of selected Bragg reflections are classified in terms of Δn. We find that the kinematic approach describes the shape and intensity distribution of experimental scattering curves in acceptable accuracy as long as Δn<0.15. The transition between single and multiple scattering is observed for Δn≈0.16-0.25 before multiple scattering dominates for larger Δn. The classification of the scattering regimes is confirmed by simulations in terms of numerical solution of Maxwell's equations.

  20. Immobilization of TiO2 Nanoparticles on Chlorella pyrenoidosa Cells for Enhanced Visible-Light-Driven Photocatalysis

    Directory of Open Access Journals (Sweden)

    Aijun Cai

    2017-05-01

    Full Text Available TiO2 nanoparticles are immobilized on chlorella cells using the hydrothermal method. The morphology, structure, and the visible-light-driven photocatalytic activity of the prepared chlorella/TiO2 composite are investigated by various methods. The chlorella/TiO2 composite is found to exhibit larger average sizes and higher visible-light intensities. The sensitization of the photosynthesis pigment originating from chlorella cells provides the anatase TiO2 with higher photocatalytic activities under the visible-light irradiation. The latter is linked to the highly efficient charge separation of the electron/hole pairs. The results also suggest that the photocatalytic activity of the composite remains substantial after four cycles, suggesting a good stability.

  1. 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

  2. Enhancing optical absorption of metal–organic frameworks for improved visible light photocatalysis

    NARCIS (Netherlands)

    Nasalevich, M.A.; Goesten, M.G.; Savenije, T.J.; Kapteijn, F.; Gascon, J.

    2013-01-01

    NH2-MIL-125(Ti) has been post-synthetically functionalized with dye-like molecular fragments. The new material (methyl red-MIL- 125(Ti)) exhibits improved light absorption over a wide range of the visible spectrum, and shows enhanced photocatalytic oxidation activity under visible light

  3. Efficient visible-light photocatalytic degradation system assisted by conventional Pd catalysis

    Science.gov (United States)

    Yu, Yanlong; He, Tao; Guo, Lingju; Yang, Yajun; Guo, Limei; Tang, Yue; Cao, Yaan

    2015-01-01

    Different approaches like doping and sensitization have been used to develop photocatalysts that can lead to high reactivity under visible-light illumination, which would allow efficient utilization of solar irradiation and even interior lighting. We demonstrated a conceptually different approach by changing reaction route via introducing the idea of conventional Pd catalysis used in cross-coupling reactions into photocatalysis. The –O–Pd–Cl surface species modified on Ni-doped TiO2 can play a role the same as that in chemical catalysis, resulting in remarkably enhanced photocatalytic activity under visible-light irradiation. For instance, Pd/Ni-TiO2 has much higher activity than N-TiO2 (about 3 ~ 9 times for all of the 4-XP systems) upon irradiation with wavelength of 420 nm. The catalytically active Pd(0) is achieved by reduction of photogenerated electrons from Ni-TiO2. Given high efficient, stable Pd catalysts or other suitable chemical catalysts, this concept may enable realization of the practical applications of photocatalysis. PMID:25825365

  4. Recent progress in oxynitride photocatalysts for visible-light-driven water splitting.

    Science.gov (United States)

    Takata, Tsuyoshi; Pan, Chengsi; Domen, Kazunari

    2015-06-01

    Photocatalytic water splitting into hydrogen and oxygen is a method to directly convert light energy into storable chemical energy, and has received considerable attention for use in large-scale solar energy utilization. Particulate semiconductors are generally used as photocatalysts, and semiconductor properties such as bandgap, band positions, and photocarrier mobility can heavily impact photocatalytic performance. The design of active photocatalysts has been performed with the consideration of such semiconductor properties. Photocatalysts have a catalytic aspect in addition to a semiconductor one. The ability to control surface redox reactions in order to efficiently produce targeted reactants is also important for photocatalysts. Over the past few decades, various photocatalysts for water splitting have been developed, and a recent main concern has been the development of visible-light sensitive photocatalysts for water splitting. This review introduces the study of water-splitting photocatalysts, with a focus on recent progress in visible-light induced overall water splitting on oxynitride photocatalysts. Various strategies for designing efficient photocatalysts for water splitting are also discussed herein.

  5. 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 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.

  6. Damaging effects of visible light. Comprehensive progress report

    Energy Technology Data Exchange (ETDEWEB)

    None

    1981-01-01

    Research progress is reported on studies of retinal light damage. A myriad of variables effect the production of light damage. These include age, prior light history, body temperature, vitamin A status, intensity, wavelength and duration of light. The intensity-duration function and the age function have been studied in detail in rats. Studies have been begun on the wavelength variable. (ACR)

  7. 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

  8. Highly efficient visible light mediated azo dye degradation through barium titanate decorated reduced graphene oxide sheets

    Science.gov (United States)

    Rastogi, Monisha; Kushwaha, H. S.; Vaish, Rahul

    2016-03-01

    This study investigates BaTiO3 decorated reduced graphene oxide sheets as a potential visible light active catalyst for dye degradation (Rhodamine B). The composites were prepared through conventional hydrothermal synthesis technique using hydrazine as a reducing agent. A number of techniques have been employed to affirm the morphology, composition and photocatalytic properties of the composites; these include UV-visible spectrophotoscopy that assisted in quantifying the concentration difference of Rhodamine B. The phase homogeneity of the composites was examined through x-ray powder diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) was employed to confirm the orientation of the BaTiO3 particles over the reduced graphene oxide sheets. Photoluminescence (PL) emission spectra assisted in determining the surface structure and excited state of the catalyst. Fourier transformed-infrared (FTIR) spectra investigated the vibrations and adsorption peak of the composites, thereby ascertaining the formation of reduced graphene oxide. In addition, diffuse reflectance spectroscopy (DRS) demonstrated an enhanced absorption in the visible region. The experimental investigations revealed that graphene oxide acted as charge collector and simultaneously facilitated surface adsorption and photo-sensitization. It could be deduced that BaTiO3-reduced graphene oxide composites are of significant interest the field of water purification through solar photocatalysis. [Figure not available: see fulltext.

  9. Enhanced visible light photocatalysis through fast crystallization of zinc oxide nanorods

    Directory of Open Access Journals (Sweden)

    Sunandan Baruah

    2010-11-01

    Full Text Available Hydrothermally grown ZnO nanorods have inherent crystalline defects primarily due to oxygen vacancies that enhance optical absorption in the visible spectrum, opening up possibilities for visible light photocatalysis. Comparison of photocatalytic activity of ZnO nanorods and nanoparticle films on a test contaminant methylene blue with visible light irradiation at 72 kilolux (klx showed that ZnO nanorods are 12–24% more active than ZnO nanoparticulate films. This can be directly attributed to the increased effective surface area for adsorption of target contaminant molecules. Defects, in the form of interstitials and vacancies, were intentionally created by faster growth of the nanorods by microwave activation. Visible light photocatalytic activity was observed to improve by ≈8% attributed to the availability of more electron deficient sites on the nanorod surfaces. Engineered defect creation in nanostructured photocatalysts could be an attractive solution for visible light photocatalysis.

  10. Visible-near-infrared luminescent lanthanide ternary complexes based on beta-diketonate using visible-light excitation.

    Science.gov (United States)

    Sun, Lining; Qiu, Yannan; Liu, Tao; Feng, Jing; Deng, Wei; Shi, Liyi

    2015-11-01

    We used the synthesized dinaphthylmethane (Hdnm) ligand whose absorption extends to the visible-light wavelength, to prepare a family of ternary lanthanide complexes, named as [Ln(dnm)3 phen] (Ln = Sm, Nd, Yb, Er, Tm, Pr). The properties of these complexes were investigated by Fourier transform infrared (FT-IR) spectroscopy, diffuse reflectance (DR) spectroscopy, thermogravimetric analyses, and excitation and emission spectroscopy. Generally, excitation with visible light is much more advantageous than UV excitation. Importantly, upon excitation with visible light (401-460 nm), the complexes show characteristic visible (Sm(3+)) as well as near-infrared (Sm(3+), Nd(3+), Yb(3+), Er(3+), Tm(3+), Pr(3+)) luminescence of the corresponding lanthanide ions, attributed to the energy transfer from the ligands to the lanthanide ions, an antenna effect. Now, using these near-infrared luminescent lanthanide complexes, the luminescent spectral region from 800 to 1650 nm, can be covered completely, which is of particular interest for biomedical imaging applications, laser systems, and optical amplification applications. Copyright © 2015 John Wiley & Sons, Ltd.

  11. SINGLE: single photon sensitive cryogenic light detectors

    Science.gov (United States)

    Biassoni, Matteo; SINGLE Collaboration

    2017-09-01

    Thermal detectors operated at few mK as calorimeters are a powerful tool for the study of rare particle physics processes. In order to implement particle identification, light detection can be effectively performed by means of other thermal detectors operated as light sensors. This configuration can be used also in large scale, thousand-channels setups, but the light sensors must be sensitive enough to detect few, possibly a single, photons. The SINGLE project described here aims at producing silicon based, large area devices that can be operated as thermal detectors with single-photon sensitivity, and demonstrate the reliability of the performance, scalability of the production process and integrability with present and next generation cryogenic experiments for the search for rare events.

  12. Highly luminescent S, N co-doped graphene quantum dots with broad visible absorption bands for visible light photocatalysts

    Science.gov (United States)

    Qu, Dan; Zheng, Min; Du, Peng; Zhou, Yue; Zhang, Ligong; Li, Di; Tan, Huaqiao; Zhao, Zhao; Xie, Zhigang; Sun, Zaicheng

    2013-11-01

    A facile hydrothermal synthesis route to N and S, N co-doped graphene quantum dots (GQDs) was developed by using citric acid as the C source and urea or thiourea as N and S sources. Both N and S, N doped GQDs showed high quantum yield (78% and 71%), excitation independent under excitation of 340-400 nm and single exponential decay under UV excitation. A broad absorption band in the visible region appeared in S, N co-doped GQDs due to doping with sulfur, which alters the surface state of GQDs. However, S, N co-doped GQDs show different color emission under excitation of 420-520 nm due to their absorption in the visible region. The excellent photocatalytic performance of the S, N co-doped GQD/TiO2 composites was demonstrated by degradation of rhodamine B under visible light. The apparent rate of S, N:GQD/TiO2 is 3 and 10 times higher than that of N:GQD/TiO2 and P25 TiO2 under visible light irradiation, respectively.A facile hydrothermal synthesis route to N and S, N co-doped graphene quantum dots (GQDs) was developed by using citric acid as the C source and urea or thiourea as N and S sources. Both N and S, N doped GQDs showed high quantum yield (78% and 71%), excitation independent under excitation of 340-400 nm and single exponential decay under UV excitation. A broad absorption band in the visible region appeared in S, N co-doped GQDs due to doping with sulfur, which alters the surface state of GQDs. However, S, N co-doped GQDs show different color emission under excitation of 420-520 nm due to their absorption in the visible region. The excellent photocatalytic performance of the S, N co-doped GQD/TiO2 composites was demonstrated by degradation of rhodamine B under visible light. The apparent rate of S, N:GQD/TiO2 is 3 and 10 times higher than that of N:GQD/TiO2 and P25 TiO2 under visible light irradiation, respectively. Electronic supplementary information (ESI) available: More XPS and UV-Vis spectra. See DOI: 10.1039/c3nr04402e

  13. 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.

  14. 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.

  15. Distinguishing Visual Information from Visible Background Light Sources

    OpenAIRE

    Theorell, Axel; Osika, Anton

    2013-01-01

    This thesis regards problems of the form: Two light sources are present. The two sources have dierent light spectra. One of the sources carries information and the other source can be regarded as background light. How can we maximize the contrast between the information and the background light using optical ltering techniques? A relevant question when working with this problem is the theoretical limit of how big dierence a lter can make. The dierence is calculated with regards to the optimal...

  16. 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.

  17. 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.

  18. Visible Light Activated Photocatalytic Water Polishing System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal targets development of a LED light activated photocatalytic water polishing system that enables reduction of organic impurities (TOC and...

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

    Directory of Open Access Journals (Sweden)

    Rongbo Wang

    2017-09-01

    Full Text Available 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.

  20. Photolyase activity induction by UVC irradiation and visible light in barley root

    Energy Technology Data Exchange (ETDEWEB)

    Zukas, K.; Ambrozaitis, K. [University of Vilnius, Departement of Botany and Genetics, (Lithuania)

    1997-03-01

    Using Micrococcus luteus UV-endonuclease sensitive sites (EES) photoreactivation test, photolyase (PHL) activity has been detected in barley seedlings but not in extracts from barley roots. This lack of activity was used create a model system for the investigation of PHL activity induction. It was detected that short wave ultraviolet (UVC,{lambda}{sub max} = 254 nm, dose 1 kJ/m{sup 2}) induced PHL activity in roots after 60 min. post-irradiation incubation in a dark. Extract from roots of barley seedlings illuminated with a visible light (10 kJ/m{sup 2}) and maintained in a dark up to 90 min. cause PR of 46.7 % ESS in UV-irradiated DNA from Bacillus subtilis. (authors)

  1. Optimization lighting layout based on gene density improved genetic algorithm for indoor visible light communications

    Science.gov (United States)

    Liu, Huanlin; Wang, Xin; Chen, Yong; Kong, Deqian; Xia, Peijie

    2017-05-01

    For indoor visible light communication system, the layout of LED lamps affects the uniformity of the received power on communication plane. In order to find an optimized lighting layout that meets both the lighting needs and communication needs, a gene density genetic algorithm (GDGA) is proposed. In GDGA, a gene indicates a pair of abscissa and ordinate of a LED, and an individual represents a LED layout in the room. The segmented crossover operation and gene mutation strategy based on gene density are put forward to make the received power on communication plane more uniform and increase the population's diversity. A weighted differences function between individuals is designed as the fitness function of GDGA for reserving the population having the useful LED layout genetic information and ensuring the global convergence of GDGA. Comparing square layout and circular layout, with the optimized layout achieved by the GDGA, the power uniformity increases by 83.3%, 83.1% and 55.4%, respectively. Furthermore, the convergence of GDGA is verified compared with evolutionary algorithm (EA). Experimental results show that GDGA can quickly find an approximation of optimal layout.

  2. 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.

  3. Visibility Enhancement and Power Saving by Pro-beam LED Tunnel Lighting Method

    National Research Council Canada - National Science Library

    Sato, Motohisa; Hagio, Tomokazu

    2014-01-01

    .... The pro-beam lighting system however has an advantage to enhance visibility with reversed silhouette and has being investigated for more safe and comfortable driving in the tunnel for several years...

  4. AIRFIELD RUNWAY LIGHTING EFFICIENCY ESTIMATING BASED ON SIMULATING LANDING PROCESS IN LOW VISIBILITY

    Directory of Open Access Journals (Sweden)

    Yu. T. Zyryanov

    2014-01-01

    Full Text Available The paper presents an approach to solving important scientific application at the evaluation of the effectiveness of airfields runway lighting in low visibility conditions using the integral index-based fashion.

  5. 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.

  6. 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...

  7. 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...

  8. The power conversion efficiency of visible light emitting devices in standard BiCMOS processes

    NARCIS (Netherlands)

    Kuindersma, P.; Hoang, T.; Schmitz, Jurriaan; Vijayaraghavan, M.N.; Dijkstra, Mindert; Dijkstra, M.; van Noort, W.A.; Vanhoucke, T.; Peters, W.C.M.; Kramer, M.C.J.C.M.

    2008-01-01

    We present experimental and theoretical proof for a single and unique relationship between the breakdown voltage and power efficiency of visible light emitting devices fabricated in standard BiCMOS processes.

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

    OpenAIRE

    Jamal Al-Sabahi; Tanujjal Bora; Mohammed Al-Abri; Joydeep Dutta

    2016-01-01

    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 we...

  10. Redox Mediators in Visible Light Photocatalysis: Photocatalytic Radical Thiol?Ene Additions

    OpenAIRE

    Tyson, Elizabeth L.; Niemeyer, Zachary L.; Yoon, Tehshik P.

    2014-01-01

    Synthetically useful radical thiol?ene reactions can be initiated by visible light irradiation in the presence of transition metal polypyridyl photocatalysts. The success of this method relies upon the use of p-toluidine as an essential additive. Using these conditions, high-yielding thiol?ene reactions of cysteine-containing biomolecules can be accomplished using biocompatibile wavelengths of visible light, under aqueous conditions, and with the thiol component as the limiting reagent. We pr...

  11. 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.

  12. X-ray intensifying screen visible light detection meter.

    Science.gov (United States)

    McLean, D; Eisenhuth, J; Knight, P; Bui, Q

    1997-06-01

    A light meter has been designed and built for the purpose of measuring the light emitted from an intensifying screen during x-ray irradiation. The meter uses a photodiode detector with a minimal drift amplification system. The meter repeatability was better than 0.5% and was found to be linear. A significant x-ray induced signal was recorded during measurement which needed to be subtracted from readings to deduce the intensification screen light output. The energy response of four screen types was subsequently measured.

  13. Light-Driven Preparation, Microstructure, and Visible-Light Photocatalytic Property of Porous Carbon-Doped TiO2

    Directory of Open Access Journals (Sweden)

    Xiao-Xin Zou

    2012-01-01

    Full Text Available Highly porous carbon-doped TiO2 (C-TiO2 has been prepared, for the first time, through a light-driven approach using crystalline titanium glycolate (TG as the single-source precursor. Although the nonthermally prepared porous C-TiO2 is amorphous, it shows a remarkable visible-light photocatalytic activity higher than that of nitrogen-doped TiO2 (N-TiO2 due to its significant surface area (530 m2/g and pore-rich structure. X-ray photoelectron, electron paramagnetic resonance, and UV-Vis diffuse reflectance spectroscopy reveal that the as-prepared porous C-TiO2 photocatalyst contains Ti–O–C bonds which result in visible-light absorption of the material at wavelengths less than 550 nm. Furthermore, it is discovered that the Ti–O–C bonds in the as-prepared C-TiO2 is easily transformed to coke-type species under mild thermal treatment (200°C. The resulting coke-containing porous TiO2 is an even better visible-light photocatalyst, almost twice as effective as N-TiO2, because of its stronger visible-light absorption. The Ti–O–C and the coke-containing porous TiO2 materials follow two different mechanisms in the visible-light photocatalysis process for degradation of methylene blue.

  14. An ultrathin invisibility skin cloak for visible light

    Science.gov (United States)

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

    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 to macroscopic sizes. In addition, 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 to hide macroscopic objects.

  15. Challenges and potentials for visible light communications: State of the art

    Science.gov (United States)

    Jha, Pranav Kumar; Mishra, Neha; Kumar, D. Sriram

    2017-06-01

    Visible Light Communication is the emerging field in the area of Indoor Optical Wireless Communication which uses white light LEDs for transmitting data and light simultaneously. LEDs can be modulated at very high speeds which increases its efficiency and enabling it for the dual purposes of data communication and illumination simultaneously. Radio Frequency have some limitations which is not at par with the current demand of bandwidth but using visible light, it is possible to achieve higher data rates per user. In this paper, we discuss some challenges, potentials and possible future applications for this new technology. Basically, visible light communication is for indoor application capable of multiuser access. We also design a very basic illumination pattern inside a room using uniform power distribution.

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

    DEFF Research Database (Denmark)

    Zhang, Zhongyang; Xu, Ruodan; Wang, Zegao

    2017-01-01

    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...... 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...... 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...

  17. Fabrication and characterization of brookite-rich, visible light-active TiO2 films for water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Hui [ORNL; Qiu, Xiaofeng [ORNL; Ivanov, Ilia N [ORNL; Meyer III, Harry M [ORNL; Wang, Wei [ORNL; Zhu, Wenguang [ORNL; Paranthaman, Mariappan Parans [ORNL; Zhang, Zhenyu [ORNL; Eres, Gyula [ORNL; Gu, Baohua [ORNL

    2009-01-01

    We report that mild oxidation of Ti foils in air results in brookite-rich titanium oxide (TiO2) films with similar spectral response to that of dye-sensitized TiO2. X-ray powder diffraction and Raman spectroscopy show that the onset of brookite formation occurs at 500 8C, and the material is characterized by a strong absorption band in the visible spectral range. The first-principle calculations show that enhanced visible light absorption correlates with the presence of Ti interstitials. Photocurrent density measurements of water splitting reveal that the brookite-rich TiO2 exhibits the highest photocatalytic performance among the different forms of TiO2 produced by oxidation of Ti foils. With increasing oxidation temperature transformation to the rutile phase accompanied by declining visible range photoactivity is observed.

  18. Deployment methods of visible light communication lights for energy efficient buildings

    Science.gov (United States)

    Niaz, Muhammad Tabish; Imdad, Fatima; Kim, Soomi; Kim, Hyung Seok

    2016-10-01

    Indoor visible light communication (VLC) uses light emitting diodes (LEDs) to provide both illumination and data communication. The deployment of LED plays an important role in maintaining a steady optical power distribution over the reference receiving plane. Typical ways of luminaire deployment in offices and homes are not optimized for VLC. This paper investigates various configurations of LEDs for deploying them on the ceilings of offices and homes. The existing square array deployment of LEDs does not provide a full coverage on the receiving plane leaving dead spaces, which in turn affects the performance of the whole system. An optimized circular deployment scheme is proposed that considers both the position of the LED transmitters on the ceiling and the first reflections at each wall to yield more accurate results. Rectangular deployment and circular deployment are analyzed through simulation of the received optical power distribution, average outage area rate, and energy consumption. An optimization technique is developed to analyze the LED deployment schemes. It is clear from the results that the circular LED deployment provides a better performance than the square array grid LED deployment.

  19. Visible light-based human visual system conceptual model

    OpenAIRE

    Prangnell, Lee

    2016-01-01

    There is a widely held belief in the digital image and video processing community, which is as follows: the Human Visual System (HVS) is more sensitive to luminance (often confused with brightness) than photon energies (often confused with chromaticity and chrominance). Passages similar to the following occur with high frequency in the peer reviewed literature and academic text books: “the HVS is much more sensitive to brightness than colour” or “the HVS is much more sensitive to luma than ch...

  20. Electrical properties of SiO2-based graphene under monochromatic visible light irradiation

    Science.gov (United States)

    Li, Xiangdi; Liu, Xianming; Cao, Xueying; Zhang, Peng; Lei, Xiaohua; Chen, Weimin

    2017-08-01

    The purpose of this study is to investigate the electrical properties of graphene transparent conductive film under visible light irradiation. Sample in the study is chemical vapor deposition (CVD) growth graphene on the surface of copper foils and then transferred to the SiO2 substrate. Three monochromatic visible lights with wavelength of 635nm, 520nm and 450nm representing red (R), green (G) and blue (B) lights are used as irradiation sources. Results show that the graphene resistances increase slowly under light irradiation with all the three different wavelengths, while decrease slowly after the light is switched off. Light irradiation with higher power density will induce larger relative resistance change. When graphene is irradiated at the same density, blue light irradiation may result in the largest resistance change.

  1. Light Sensitivity of Lactococcus lactis Thioredoxin Reductase

    DEFF Research Database (Denmark)

    Skjoldager, Nicklas

    system is an alternative thiol-based antioxidant system, but the glutathione biosynthesis system is not present in all organisms. This thesis focuses on the TrxR from the lactic acid bacteria (LAB) model organism Lactococcus lactis ssp. cremoris MG1363, a strain that is glutathione- and catalasenegative......,4-dihydroxyphenylalanine (DOPA). A novel FAD si-face open space was identified in all structures of LlTrxR and predicted to accommodate O2, thus acting as an oxygen pocket. This model explains how the protein-bound FAD can function as a de facto photosensitizer, generating reactive oxygen species (ROS) upon light exposure...... conditions. Cell extracts from the same 17 h in vivo irradiated cells showed ~14% remaining TrxR activity. The present investigation shows that TrxR light sensitivity might be a widespread phenomenon among bacteria, particular within the phylum of Firmicutes. This feature can potentially be exploited...

  2. Visible Light Photocatalysis for the Generation and Use of Reactive Azolyl and Polyfluoroaryl Intermediates.

    Science.gov (United States)

    Arora, Amandeep; Weaver, Jimmie D

    2016-10-18

    Photocatalysis offers several mechanistically unique pathways that are not rivaled by mainstream catalysis. Primarily, the ability to convert photochemical energy into single electron oxidation and reduction events provides a new dimension for chemists to consider when choosing how to activate a molecule or approach a complex synthesis. Since most organic molecules do not absorb light in the visible region, they are impervious to direct visible light photochemistry, which provides an opportunity for photocatalysis in which a visible light absorbing compound can serve as a mediator. In this Account, we discuss the consequences of catalyst mediated, photoinduced electron transfer to several classes of reducible arenes. While the bulk of the work discussed within this Account utilizes iridium-based photocatalysts, in principle the chemistry is not limited to this class of photocatalyst, and the principles should be more general. Instead, this Account focuses largely on the consequences of single electron transfer to poly- and perfluorinated arenes and 2-halo azoles. Electron transfer converts these stable molecules into reactive intermediates whose behavior often depends entirely on the identity of the halogen that undergoes substitution. The result is both diverse chemistry and an alternative way of thinking about the chemical reactivity of these motifs. Specifically, we discuss our efforts and those of others to develop strategies for the generation of radicals or radical anions from perfluoroarenes and azoles and the behavior of these intermediates as implied by reactions in which they participate. The divergent pathway is illustrated by 2-bromoazoles, which yield azolyl radicals and can be utilized for addition to π-bonds, while use of the 2-chloroazole substrate leads to an entirely different reaction profile. Under the appropriate reaction conditions, the reactive and transient intermediates are useful coupling partners and often provide unrivaled access to new

  3. 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 ...

  4. Environmental remediation and superhydrophilicity of ultrafine antibacterial tungsten oxide-based nanofibers under visible light source

    Energy Technology Data Exchange (ETDEWEB)

    Srisitthiratkul, Chutima; Yaipimai, Wittaya [Nano Functional Textile Laboratory, National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), 111 Thailand Science Park, Phahonyothin Rd., Klong 1, Klong Luang, Pathumthani 12120 (Thailand); Intasanta, Varol, E-mail: varol@nanotec.or.th [Nano Functional Textile Laboratory, National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), 111 Thailand Science Park, Phahonyothin Rd., Klong 1, Klong Luang, Pathumthani 12120 (Thailand)

    2012-10-15

    Graphical abstract: Nanosilver-decorated WO{sub 3} photocatalytic nanofibers are antibacterial and superhydrophilic under a visible light source. Highlights: Black-Right-Pointing-Pointer Deposition of nanosilver onto electrospun WO{sub 3} nanofibers' surface was done exploiting visible or UV light driven photoreduction of silver ion. Black-Right-Pointing-Pointer Nanofibers showed antibacterial characteristics. Black-Right-Pointing-Pointer Nanofibers degraded a model toxin effectively. Black-Right-Pointing-Pointer Nanofibers showed superhydrophilicity under a visible light source. - Abstract: Fabrication of nanosilver-decorated WO{sub 3} nanofibers was successfully performed. First, deposition of nanosilver onto electrospun WO{sub 3} nanofibers' surface was done via photoreduction of silver ion under visible or UV light. The resulting hybrid nanofibers not only revealed antibacterial characteristics but also maintained their photocatalytic performance towards methylene blue decomposition. Unexpectedly, the nanofibrous layers prepared from these nanofibers showed superhydrophilicity under a visible light source. The nanofibers might be advantageous in environmental and hygienic nanofiltration under natural light sources, where the self-cleaning characteristics could be valuable in maintenance processes.

  5. 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.

  6. [Enhanced visible-light absorbance of nanosized AgI/TiO2 by using calcination combined with light irradiation].

    Science.gov (United States)

    Liang, Zhu; Ni, Jin-Ren

    2009-07-15

    With the aim to enhance visible-light absorbance, calcination combined with light irradiation was used to modify nanosized AgI/TiO2. UV-Vis spectrum curves indicated that the modified sample exhibited an intense absorption in the whole visible light range and a spectrum shifted from 465 nm to 800 nm, and that absorbance at 500 nm was improved three times as much as that of the reported pertinent material. XRD analytic results demonstrated that calcined AgI/TiO2 possessed more rutile phase with reduced band gap from 2.89 eV to 2.81 eV, and that the following xenon-light irradiation further enhanced the relative contents of anatase TiO2, rutile TiO2 and AgI accompanied with produced AgCl phase, leading to the decrease in band gap to 1.55 eV. Formation of AgCl and increases in the relative contents of rutile TiO2 and AgI should take the main responsibilities for the decrease in the band gap and enlargement of visible-light absorbance. Additionally, it was confirmed that only the spectrum absorption of the calcined AgI/TiO2 could be improved by light irradiation, and that ultraviolet light played more role than visible part during the light irradiation. Moreover, it was proposed here that two or more silver halides supported on TiO2 could show more capabilities to stimulate visible-light activation of TiO2.

  7. Visible-Light Excitation of a Molecular Motor with an Extended Aromatic Core.

    Science.gov (United States)

    van Leeuwen, Thomas; Pol, Jasper; Roke, Diederik; Wezenberg, Sander J; Feringa, Ben L

    2017-03-17

    Exploring routes to visible-light-driven rotary motors, the possibility of red-shifting the excitation wavelength of molecular motors by extension of the aromatic core is studied. Introducing a dibenzofluorenyl moiety in a standard molecular motor resulted in red-shifting of the absorption spectrum. UV/vis and 1 H NMR spectroscopy showed that these motors could be isomerized with light of wavelengths up to 490 nm and that the structural modification did not impair the anticipated rotary behavior. Extension of the aromatic core is therefore a suitable strategy to apply in pursuit of visible-light-driven molecular motors.

  8. 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......ABSTRACT: BACKGROUND: The human lens is continuously exposed to high levels of light. Ultraviolet radiation is believed to play a causative role in the development of cataract. In vivo, however, the lens is mainly exposed to visible light and the ageing lens absorbs a great part of the short....... 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...

  9. 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......BACKGROUND: The human lens is continuously exposed to high levels of light. Ultraviolet radiation is believed to play a causative role in the development of cataract. In vivo, however, the lens is mainly exposed to visible light and the ageing lens absorbs a great part of the short wavelength......: 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...

  10. 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

  11. Visible light induces matrix metalloproteinase-9 expression in rat eye.

    Science.gov (United States)

    Papp, Andrea M; Nyilas, Rita; Szepesi, Zsuzsanna; Lorincz, Magor L; Takács, Eszter; Abrahám, István; Szilágyi, Nóra; Tóth, Júlia; Medveczky, Péter; Szilágyi, László; Juhász, Gábor; Juhász, Gábor

    2007-12-01

    Up-regulation of matrix metalloproteinase-9 (MMP-9, gelatinase B) in the nervous system has been demonstrated when excitotoxicity-induced tissue remodeling and neuronal death occurs. Induction of MMP-9 by a natural stimulus has not been observed yet. Using RT-PCR and gelatin-zymography we demonstrated MMP-9 induction at transcriptional and protein levels in different structures of the rat eye following over-stimulation with white light. MMP-9 elevation occurred in the retina without reduction in photoreceptor number or major anatomical reorganization. A transient decrease in electroretinogram b-wave indicated the functional recovery. Retrobulbar injection of a broad-spectrum MMP-inhibitor GM6001, slowed the recovery rate of b-wave amplitude. Even room-light applied to dark-adapted awake animals induced MMP-9 increase in the retina, which suggests a role for MMP-9 in physiological functional plasticity of the nervous system, such as light adaptation. This is the first demonstration of MMP-9 induction by a sensory stimulus.

  12. 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.

  13. 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

  14. Visible light spectral domain optical coherence microscopy system for ex vivo imaging

    Science.gov (United States)

    Lichtenegger, Antonia; Harper, Danielle J.; Augustin, Marco; Eugui, Pablo; Fialová, Stanislava; Woehrer, Adelheid; Hitzenberger, Christoph K.; Baumann, Bernhard

    2017-02-01

    A visible light spectral domain optical coherence microscopy system operating in the wavelength range of 450-680 nm was developed. The resulting large wavelength range of 230 nm enabled an ultrahigh axial resolution of 0.88μm in tissue. The setup consisted of a Michelson interferometer combined with a homemade spectrometer with a spectral resolution of 0.03 nm. Scanning of 1 x 1 mm2 and 0.5 x 0.5 mm2 areas was performed by an integrated microelectromechanical mirror. After scanning the light beam is focused onto the tissue by a commercial objective with a 10 x magnification, resulting in a transverse resolution of 2 μm . Specification measurements showed that a -89 dB sensitivity with a 24 dB/mm roll-off could be achieved with the system. First of all the capabilities of the system were tested by investigating millimeter paper, tape and the USAF (US Air Force) 1951 resolution test target. Finally cerebral tissues from non-pathological and Alzheimer's disease affected brains were investigated. The results showed that structures, such as white and gray matter, could be distinguished. Furthermore a first effort was made to differentiate Alzheimer's disease from healthy brain tissue.

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

    Science.gov (United States)

    Buda, Samaila; Shafie, Suhaidi; Rashid, Suraya Abdul; Jaafar, Haslina; Sharif, N. F. M.

    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.

  16. 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.

  17. 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.

  18. 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.

  19. Efficient ZnO-based visible-light-driven photocatalyst for antibacterial applications.

    Science.gov (United States)

    Kumar, Raju; Anandan, Srinivasan; Hembram, Kaliyan; Rao, Tata Narasinga

    2014-08-13

    Herein, we report the development of a ZnO-based visible-light-driven photocatalyst by interfacial charge transfer process for the inactivation of pathogens under visible-light illumination. Surface modification by a cocatalyst on ZnO, prepared by flame spray pyrolysis process is carried out to induce the visible-light absorption in ZnO. Optical studies showed that surface modification of Cu(2+) induces the visible-light absorption in ZnO by interfacial charge transfer between ZnO and surface Cu(2+) ions upon light irradiation. The photocatalytic efficiency of pure and modified ZnO is evaluated for the inactivation of pathogens and the decomposition of methylene blue under visible-light illumination. The antibacterial activity of Cu(2+)-ZnO is several orders higher than pure ZnO and commercial Degussa-P25 and comparable with Cu(2+)-TiO2. Cu(2+)-ZnO nanorods show better photocatalytic activity than Cu(2+)-ZnO nanosphere, which is attributed to high surface area to volume ratio of former than later. The holes generated in the valence band and the Cu(1+) species generated during the interfacial charge transfer process may attribute for the inactivation of bacteria, whereas the strong oxidation power of hole is responsible for the decomposition of methylene blue. Besides the advantage of Cu(2+)-modified ZnO for visible-light-assisted photocatalytic applications, the method (FSP) used for the synthesis of ZnO in the present study is attractive for commercial application because the process has potential for the production of large quantities (2-3 kg/h) of semiconductors.

  20. Visible-light-Mediated TiO2 photocatalysis of fluoroquinolone antibacterial agents.

    Science.gov (United States)

    Paul, Tias; Miller, Penney L; Strathmann, Timothy J

    2007-07-01

    This study reports on the photocatalytic transformation of fluoroquinolone antibacterial agents (ciprofloxacin, enrofloxacin, norfloxacin, and flumequine) in aqueous titanium dioxide (TiO2) suspensions irradiated with ultraviolet (UV; lambda > 324 nm) or visible light (lambda > 400, > 420, or > 450 nm). Visible-light-mediated fluoroquinolone degradation is unexpected from direct photolysis or established TiO2 band gap photoexcitation mechanisms, which both require UV light. Visible-light-mediated photocatalysis requires an appropriate conduction band electron acceptor (e.g., O2, BrO3-), but is not dependent upon hydroxyl radical, superoxide, or other reactive oxygen species generated upon TiO2 band gap excitation. The process slows considerably when fluoroquinolone adsorption is inhibited. Whereas fluoroquinolone decomposition in UV-irradiated TiO2 suspensions is accompanied by mineralization, no changes in dissolved organic carbon occur during visible-light-photocatalyzed degradation. Results are consistent with a proposed charge-transfer mechanism initiated by photoexcitation of surface-complexed fluoroquinolone molecules. Complexation to the TiO2 surface causes a red shift in the fluoroquinolone absorption spectrum (via ligand-to-metal charge transfer), enabling photoexcitation by visible light. Fluoroquinolone oxidation then occurs by electron transfer into the TiO2 conduction band, which delivers the electron to an adsorbed electron acceptor. The lack of organic carbon mineralization indicates formation of stable organic byproducts that are resistant to further degradation by visible light. In UV-irradiated TiO2 suspensions, the charge-transfer mechanism acts in parallel with the semiconductor band gap photoexcitation mechanism.

  1. Metal-dielectric superlenses for ultraviolet and visible light

    DEFF Research Database (Denmark)

    Nielsen, Rasmus Bundgaard

    This thesis describes a variety of experiments towards the goal of improved superlensing. This new type of lenses are based on materials with a negative refractive index, which opens up the possibility of resolving details that are significantly smaller than the wavelength of light. The results s......, due to their tunable optical properties. The results show, that when using such composites, it is indeed possible to selectively alter the real part of the permittivity, as predicted by effective medium theory, but the loss is much higher than expected....... the enhanced field local field intensity from a nanoantenna array, and the results indicate a successful transfer, which opens up a number of possibilities within the fields of biological, chemical and medical diagnostics. The use of multilayer lenses to improve imaging was also tested, for which a very low...

  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. 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.

  4. W ion implantation boosting visible-light photoelectrochemical water splitting over ZnO nanorod arrays

    Science.gov (United States)

    Cai, Li; Zhou, Wu; Ren, Feng; Chen, Jie; Cai, Guangxu; Liu, Yichao; Guan, Xiangjiu; Shen, Shaohua

    2017-01-01

    W ions were doped into ZnO nanorod arrays hydrothermally grown on the F-doped tin-oxide-coated glass substrates via an advanced ion implantation technique for photoelectrochemical (PEC) water splitting under visible light. It was found that W incorporation could narrow the bandgap of ZnO and shift the optical absorption into visible light regions obviously, with the one-dimensional nanorod structure maintained for superior charge transfer. As a result, the W-doped ZnO nanorod arrays exhibit considerable PEC performance relative to ZnO nanorod arrays under visible light illumination (λ>420 nm), with photocurrent density achieved up to 15.2 μA/cm2 at 1.0 V (versus Ag/AgCl). The obtained PEC properties indicate that ion implantation can be an alternative approach to develop unique materials for efficient solar energy conversion.

  5. Photoinduced reactions between Pb3O4 and organic dyes in aqueous solution under visible light.

    Science.gov (United States)

    Zhou, Yangen; Long, Jinlin; Gu, Quan; Lin, Huaxiang; Lin, Huan; Wang, Xuxu

    2012-12-03

    Pb(3)O(4) could react with organic dyes in aqueous solution under visible light irradiation, in which Pb(3)O(4) was transformed into Pb(3)(CO(3))(2)(OH)(2) along with oxidation of the organic dyes. Cu(2+) has considerable effect on the reaction. In the presence of Cu(2+), MO (20 ppm) and RhB (10(-5) mol L(-1)) were completely degraded under visible light within 6 and 20 min, respectively, while both Pb(3)O(4) and Cu(2+) keep almost stable during photodegradation. The mechanisms of the reactions with and without Cu(2+) ions were studied. The photochemical system of Pb(3)O(4) cooperating with Cu(2+) ions is probably used for the treatment of organic pollutants in water under visible light.

  6. Differences in visible and near-infrared light reflectance between orange fruit and leaves

    Science.gov (United States)

    Gausman, H. W.; Escobar, D. E.; Berumen, A.

    1975-01-01

    The objective was to find the best time during the season (April 26, 1972 to January 8, 1973) to distinguish orange fruit from leaves by spectrophotometrically determining at 10-day intervals when the difference in visible (550- and 650-nm wavelengths) and near-infrared (850-nm wavelength) light reflectance between fruit and nearby leaves was largest. December 5 to January 8 was the best time to distinguish fruit from leaves. During this period the fruit's color was rapidly changing from green to yellow, and the difference in visible light reflectance between fruit and leaves was largest. The difference in near-infrared reflectance between leaves and fruit remained essentially constant during ripening when the difference in visible light reflectance between leaves and fruit was largest.

  7. 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.

  8. 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.

  9. 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.

  10. Visible light assisted photocatalytic degradation of methyl orange using Ag/N-TiO₂ photocatalysts.

    Science.gov (United States)

    Wu, Deyong; Long, Mingce

    2012-01-01

    For the sake of efficient utilization of sunlight, Ag nanoparticles loaded N-doped TiO₂ photocatalysts (Ag/N-TiO₂) were successfully fabricated via a two-step method to make the best use of the respective advantages of noble metal loading and nonmetal doping. Ag/N-TiO₂ was characterized using XRD, XPS and UV-Vis DRS. Compared to TiO₂, the dramatic enhancement of the visible-light-induced photocatalytic degradation efficiency of Ag/N-TiO₂ obtained for the degradation of methyl orange should be attributed to the synergistic effect of N-doping and Ag-loading, including the good visible light absorption and the effective electron-hole separations. This demonstrates Ag/N-TiO₂ is a promising photocatalytic material for organic pollutant degradation under visible light irradiation.

  11. Visible-Light Active and Magnetically Recyclable Nanocomposites for the Degradation of Organic Dye

    Directory of Open Access Journals (Sweden)

    Helin Niu

    2014-05-01

    Full Text Available Recyclable visible-light photocatalyst Fe3O4@TiO2 with core-shell structure was prepared by a simple synthetic strategy using solvothermal crystallization of titanium precursor on preformed Fe3O4 nanopartiles. The photo-degradation reaction of neutral red aqueous solution was tested to evaluate the visible-light photocatalytic activity of the as prepared Fe3O4@TiO2 nanoparticles, which show excellent photocatalytic activity compared with commercial P25 catalyst. Moreover, the Fe3O4@TiO2 nanocomposites can be easily separated from the reaction mixture, and maintain favorable photocatalytic activity after five cycles. The high visible light absorption of the Fe3O4@TiO2 nanocomposites may originate from the absence of electronic heterojunction, excellently dispersity and the high specific surface area of the as-synthesized Fe3O4@TiO2 samples.

  12. Impact of different visible light spectra on oxygen absorption and surface discoloration of bologna sausage.

    Science.gov (United States)

    Böhner, Nadine; Rieblinger, Klaus

    2016-11-01

    The objective of this study was to evaluate the influence of several visible light spectra in various intensities on the oxygen absorption and surface color of sliced bologna. Sausage samples were stored in a gastight model packaging system and illuminated at 5°C with six single-colored LEDs covering the main part of the visible light spectrum. The initial oxygen level was set at 0.5% in order to simulate common residual oxygen amounts in conventional packaging. The oxygen absorption and the discoloration measured as changes in CIE a*-value were dependent from the applied light intensity. The color stability of bologna was differently affected by light of various wavelengths. The results show that the use of suitable LEDs with specific spectra for display illumination can help to reduce the light induced deterioration of cured sausages in retail markets. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    Tanabe, Ichiro; Kurawaki, Yuji

    2017-11-07

    Attenuated total reflectance spectra including the far-ultraviolet (FUV, ≤200nm) 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. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Some Effects of Visible Light on Escherichia coli1

    Science.gov (United States)

    D'Aoust, Jean Y.; Giroux, J.; Barran, L. R.; Schneider, Henry; Martin, W. G.

    1974-01-01

    Light above 400 nm had selective effects on Escherichia coli ML-308: several processes or enzymes were strongly inhibited, whereas others were relatively unaffected. There was a correlation between the inhibition of respiration and the inhibition of active uptake of glycine. However, phenylalanine uptake did not show such a correlation. The decrease in adenosine 5′-triphosphate level during the first few minutes of illumination resembled the inactivation kinetics of phenylalanine uptake. The results suggest that phenylalanine uptake may not depend greatly on oxidative energy and may depend on the adenosine 5′-triphosphate level. The results for glycine suggest either that its active uptake and respiration involve a common photosensitive component or alternately, that only the respiratory chain contains the photosensitive component, and that glycine uptake is coupled almost exclusively to respiration. The critical photochemical lesion does not involve d-lactate dehydrogenase, succinate dehydrogenase, or l-α-glycerophosphate dehydrogenase since their inactivation rate is markedly lower than that for respiration. Images PMID:4281776

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

    Science.gov (United States)

    A novel sustainable approach to valued g-valerolactone was investigated.This approach exploits the visible-light-mediated conversion of biomass-derived levulinic acid by using a bimetallic catalyst on a graphitic carbon nitride, AgPd@g-C3N4.This dataset is associated with the following publication:Verma, S., R.B.N. Baig, M. Nadagouda , and R. Varma. Sustainable Strategy Utilizing Biomass: Visible-Light-Mediated Synthesis of γ-Valerolactone. ChemCatChem. Wiley-VCH, WEINHEIM, GERMANY, 8(4): 872, (2016).

  16. Recent advancements in plasmon-enhanced visible light-driven water splitting

    Directory of Open Access Journals (Sweden)

    Qingzhe Zhang

    2017-03-01

    Full Text Available Recently, the combination of plasmonic noble metallic nanostructures with semiconductors for plasmon-enhanced visible light-driven water splitting (WS has attracted considerable attention. This review first presents three prime enhancement mechanisms for plasmon-enhanced photocatalytic WS, and then some state-of-the-art representative studies are introduced according to different enhancement mechanisms. Furthermore, the design parameters of plasmonic-metal/semiconductor photocatalysts are discussed in detail, focusing on the effect of shape, size and geometric position of metallic nanostructures on the photocatalytic activity of visible light-driven WS. Finally, the challenges and perspectives for plasmon-enhanced solar WS are proposed.

  17. 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...... spectrum, by appropriate choice of semiconductor material and single-pass laser wavelength....

  18. Atom-Transfer Radical Addition to Unactivated Alkenes by using Heterogeneous Visible-Light Photocatalysis.

    Science.gov (United States)

    Mao, Liang-Liang; Cong, Huan

    2017-11-23

    Heterogeneous visible-light photocatalysis represents an important route toward the development of sustainable organic synthesis. In this study visible light-induced, heavy metal-free atom-transfer radical addition to unactivated terminal olefins is carried out by using the combination of heterogeneous titanium dioxide as photocatalyst and a hypervalent iodine(III) reagent as co-initiator. The reaction can be applied to a range of substrates with good functional-group tolerance under very mild conditions. In addition to a number of commonly used atom-transfer reagents, the relatively challenging chloroform is also suitable. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. xBiOI-(1 - x)BiOCl as efficient visible-light-driven photocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Wang Wendeng [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Huang Fuqiang [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)], E-mail: huangfq@mail.sic.ac.cn; Lin Xinping [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2007-04-15

    A new class of oxyhalide photocatalysts, xBiOI-(1 - x)BiOCl, were prepared by a soft chemical method. The samples with x = 0.2-1.0 have intense absorptions in the visible light region and the optical band gaps are in the range 1.92-2.31 eV. They possess high photocatalytic activities under visible light irradiation for the degradation of methyl orange. This high photocatalytic activity is in close relation with the deep valance band edge position and the internal electric fields between [Bi{sub 2}O{sub 2}] slabs and halogen anionic slabs.

  20. Characterization of internal geometry / covered surface defects with a visible light sensing system

    Science.gov (United States)

    Straub, Jeremy

    2016-05-01

    Previous work has used visible light scanning to detect and characterize defects in 3D printed objects. This paper focuses on assessing the internal structures and external surfaces (that will be later hidden) of complex objects. These features make in-process defect detection far more important than it would be with an object that can be fully assessed with a post-completion scan, as it is required both for in-process correction and end-product quality assurance. This paper presents work on the use of a multi-camera visible light 3D scanning system to identify defects with printed objects' interior and covered / obscured exterior surfaces.

  1. 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.

  2. 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

  3. Oxygen deficient ZnO 1-x nanosheets with high visible light photocatalytic activity.

    Science.gov (United States)

    Guo, Hong-Li; Zhu, Qing; Wu, Xi-Lin; Jiang, Yi-Fan; Xie, Xiao; Xu, An-Wu

    2015-04-28

    Zinc oxide is one of the most important wide-band-gap (3.2 eV) materials with versatile properties, however, it can not be excited by visible light. In this work, we have developed an exquisite and simple way to prepare oxygen-deficient ZnO 1-x nanosheets with a gray-colored appearance and excellent visible light photocatalytic activity. Detailed analysis based on UV-Vis absorption spectra, X-band electron paramagnetic resonance (EPR) spectra, and photoluminescence (PL) spectra confirms the existence of oxygen vacancies in ZnO 1-x. The incorporation of oxygen defects could effectively extend the light absorption of ZnO 1-x into the visible-light region due to the fact that the energy of the localized state is located in the forbidden gap. Thus, our obtained ZnO 1-x shows a higher photodegradation of methyl orange (MO) compared to defect-free ZnO under visible light illumination. Additionally, the high content of ˙OH radicals with a strong photo-oxidation capability over the ZnO 1-x nanosheets significantly contributes to the improvement in the photocatalytic performance. Our oxygen deficient ZnO 1-x sample shows a very high photocatalytic activity for the degradation of MO even after 5 cycles without any obvious decline. The results demonstrate that defect engineering is a powerful tool to enhance the optoelectronic and photocatalytic performances of nanomaterials.

  4. 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.

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

    Science.gov (United States)

    Aubé, Martin; Roby, Johanne; Kocifaj, Miroslav

    2013-01-01

    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.

  7. 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

  8. 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.

  9. 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.

  10. Structural and functional human retinal imaging with a fiber-based visible light OCT ophthalmoscope (Conference Presentation)

    Science.gov (United States)

    Chong, Shau Poh; Bernucci, Marcel T.; Borycki, Dawid; Radhakrishnan, Harsha; Srinivasan, Vivek J.

    2017-02-01

    Visible light is absorbed by intrinsic chromophores such as photopigment, melanin, and hemoglobin, and scattered by subcellular structures, all of which are potential retinal disease biomarkers. Recently, high-resolution quantitative measurement and mapping of hemoglobin concentrations was demonstrated using visible light Optical Coherence Tomography (OCT). Yet, most high-resolution visible light OCT systems adopt free-space, or bulk, optical setups, which could limit clinical applications. Here, the construction of a multi-functional fiber-optic OCT system for human retinal imaging with high-resolution visible light OCT has potential for depth-resolved functional imaging of the eye.

  11. Mitochondrial reactive oxygen species generation and calcium increase induced by visible light in astrocytes.

    Science.gov (United States)

    Jou, Mei-Jie; Jou, Shuo-Bin; Guo, Mei-Jin; Wu, Hong-Yueh; Peng, Tsung-I

    2004-04-01

    Mitochondria contain photosensitive chromophores that can be activated or inhibited by light in the visible range. Rather than utilizing light energy, however, mitochondrial electron transport oxidation-reduction reaction and energy coupling could be stimulated or damaged by visible light. Our previous work demonstrated that reactive oxygen species (ROS) were generated in cultured astrocytes after visible laser irradiation. With confocal fluorescence microscopy, we found that ROS were generated mostly from mitochondria. This mitochondrial ROS (mROS) formation plays a critical role in photoirradiation-induced phototoxicity and apoptosis. In this study, we measured changes of mitochondrial calcium level ([Ca(2+)](m)) in cultured astrocytes (RBA-1 cell line) irradiated with blue light and examined the association between mROS formation and [Ca(2+)](m) level changes. Changes of intracellular ROS and [Ca(2+)](m) were visualized using fluorescent probes 2',7'-dichlorodihydrofluorescein (DCF), and rhod-2. After exposure to visible light irradiation, RBA-1 astrocytes showed a rapid increase in ROS accumulation particularly in the mitochondrial area. Increase in [Ca(2+)](m) was also induced by photoirradiation. The levels of increase in DCF fluorescence intensity varied among different astrocytes. Some of the cells generated much higher levels of ROS than others. For those cells that had high ROS levels, mitochondrial Ca(2+) levels were also high. In cells that had mild ROS levels, mitochondrial Ca(2+) levels were only slightly increased. The rate of increase in DCF fluorescence seemed to be close to the rate of rhod-2 fluorescence increase. There is a positive and close correlation between mitochondrial ROS levels and mitochondrial Ca(2+) levels in astrocytes irradiated by visible light.

  12. 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.

  13. 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...... a quasipoint source with a spatial extension similar to the size of a dangling bond. [S0031-9007(98)08376-8]....

  14. A photo-auxiliary approach - enabling excited state classical phototransformations with metal free visible light irradiation.

    Science.gov (United States)

    Iyer, Akila; Jockusch, Steffen; Sivaguru, Jayaraman

    2017-02-04

    Most traditional photoreactions require UV light to yield the desired product. To address this issue, photoreaction of hydrazide based chromophores was evaluated with visible light using a metal free photocatalyst to afford photoproducts in high yields. This hydrazide functionality itself may be removed/modified after the photoreaction, highlighting its role as a "photo-auxiliary". A preliminary mechanistic model based on photophysical experiments is provided to highlight the generality of the strategy.

  15. Synthesis and characterization of the hybrid Ni-TiO2/PANI for an efficient hydrogen photoproduction under visible light

    Directory of Open Access Journals (Sweden)

    Mohamed Faouzi Nsib

    2014-07-01

    Full Text Available NixZn1-xO/Polyaniline hybrid photocatalysts are synthesized by the impregnation method at ambient temperature and used for hydrogen photoproduction experiments. XRD, UV-Vis DRS, SEM and TGA are used to characterize the prepared materials. It is shown that the Ni2+ amount doped into ZnO controls its morphology and enhances its photoactivity for H2 generation. Polyaniline (PANI is shown to sensitize ZnO and to extend its light absorption toward the visible region. The hybrid photocatalyst with 10 mol. % Ni2+ and 10 wt. % PANI shows the maximum photocatalytic H2 production for one hour of visible irradiation: ~ 558 μmole while only ~ 178 μmole in the presence of pure ZnO. It is also observed that the hydrogen photoproduction efficiency depends strongly on the nature of the sacrificial electron donor and increases in the order: thiosulfate >sulfide> propanol.

  16. 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.

  17. Generation of pulsed light in the visible spectral region based on non-linear cavity dumping

    DEFF Research Database (Denmark)

    Johansson, Sandra; Andersen, Martin; Tidemand-Lichtenberg, Peter

    We propose a novel generic approach for generation of pulsed light in the visible spectrum based on sum-frequency generation between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser. For demonstration, we used a CW 1342 nm laser mixed with a pass...

  18. UV and visible light photodegradation effect on Fe–CNT/TiO2 ...

    Indian Academy of Sciences (India)

    ... the MB photodegradation increase with an increase of visible light intensity can be ascribed to the enhancement MB cationic radical. In addition, chemical oxygen demand (COD) of piggery waste and reduction efficiency of Cr (IV) was done at regular intervals, which gave a good idea about mineralization of wastewater.

  19. UV and visible light photodegradation effect on Fe–CNT/TiO2 ...

    Indian Academy of Sciences (India)

    intervals, which gave a good idea about mineralization of wastewater. Keywords. Fe–CNT/TiO2 composites; photocatalytic activity; ultraviolet; visible light. 1. Introduction. The photocatalytic activity of wide bandgap semiconductors has been the subject of numerous studies due to their abil- ity to simultaneously harvest solar ...

  20. Synthesis of novel photocatalytic RGO-InVO{sub 4} nanocomposites with visible light photoactivity

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Jianfeng; Li, Xianfu [Department of Materials Science, Fudan University, Shanghai, 200433 (China); Huang, Weishi; Li, Na [Center of Special Materials and Technology, Fudan University, Shanghai, 200433 (China); Ye, Mingxin, E-mail: mxye@fudan.edu.cn [Department of Materials Science, Fudan University, Shanghai, 200433 (China); Center of Special Materials and Technology, Fudan University, Shanghai, 200433 (China)

    2013-09-01

    Graphical abstract: A facile method for preparation of reduced graphene oxide (RGO) sheets supported indium vanadate (InVO{sub 4}) photocatalysts is reported. The visible light response and adsorption ability of RGO-InVO{sub 4} nanocomposites is greatly improved, which can effectively remove methyl orange and Cr (VI) from water. - Highlights: • Supramolecular photocatalyst of RGO-InVO{sub 4} was achieved. • Reduction of GO and preparation of RGO-InVO{sub 4} was simultaneous. • The prepared RGO-InVO{sub 4} shows high photocatalytic activity and adsorption capacity under visible light. • In situ growth of uniform InVO{sub 4} particles on RGO sheets is facile and efficient - Abstract: In this study, we report a facile method for preparation of reduced graphene oxide (RGO) sheets supported indium vanadate (InVO{sub 4}) photocatalysts. A wide range of characterization techniques, such as Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, Thermogravimetric analysis and Transmission electron microscopy were applied to characterize the obtained composites. The results indicated that the composites consist of uniformly dispersed InVO{sub 4} nanocrystals on RGO sheets. Visible light responses of RGO-InVO{sub 4} nanocomposites are greatly improved as compared with the bulk InVO{sub 4}. The as-prepared RGO-InVO{sub 4} nanocomposites can effectively remove methyl orange and Cr (VI) from water under visible light irradiation, which can be used as novel photocatalysts for environmental protection.

  1. Visible light induced fast synthesis of protein-polymer conjugates: controllable polymerization and protein activity.

    Science.gov (United States)

    Li, Xin; Wang, Lei; Chen, Gaojian; Haddleton, David M; Chen, Hong

    2014-06-21

    Herein visible light is used to induce RAFT polymerization from protein for preparing protein-polymer conjugates at ambient temperature. Polymerization is fast and can be conveniently controlled with irradiation time. By site-specific polymerization of NIPAm to protein, the protein activity is maintained and in certain cases it presents an efficient on-off-switchable property.

  2. 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.

  3. 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.

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

    Science.gov (United States)

    Al-Sabahi, Jamal; Bora, Tanujjal; Al-Abri, Mohammed; Dutta, Joydeep

    2016-01-01

    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. PMID:28773363

  5. Intraoperative assessment of microperfusion with visible light spectroscopy for prediction of anastomotic leakage in colorectal anastomoses

    NARCIS (Netherlands)

    Karliczek, A.; Benaron, D. A.; Baas, P. C.; Zeebregts, C. J.; Wiggers, T.; van Dam, G. M.

    2010-01-01

    Purpose Anastomotic leakage is associated with increased morbidity and mortality. However, there is no accurate tool to predict its occurrence. We evaluated the predictive value of visible light spectroscopy (VLS), a novel method to measure tissue oxygenation [saturated O(2) (StO(2))], for

  6. 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.

  7. Visible light induced photobleaching of methylene blue over melamine-doped TiO2 nanocatalyst

    Science.gov (United States)

    TiO2 doping with N-rich melamine produced a stable, active and visible light sentisized nanocatalyst that showed a remarkable efficiency towards the photobleaching of a model compound – methylene blue (MB) in aqueous solution. The photobleaching followed a mixed reaction order ki...

  8. 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.

  9. Symmetry-Breaking-Induced Enhancement of Visible Light Absorption in Delafossite Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Huda, M. N.; Yan, Y.; Walsh, A.; Wei, S. H.; Al-Jassim, M. M.

    2009-06-01

    Through density functional theory calculations, we demonstrate that enhancement of optical absorption and optimization of the fundamental band gap for Cu delafossites can be achieved through alloying group IIIA and IIIB delafossites. These alloys significantly improved the flexibility in designing delafossite-based photoelectrodes for application in photoelectrochemical decomposition of water by visible spectra of solar light.

  10. Photocatalytic generation of hydrogen under visible light on La2CuO4

    Indian Academy of Sciences (India)

    Bull. Mater. Sci., Vol. 38, No. 4, August 2015, pp. 1043–1048. c Indian Academy of Sciences. Photocatalytic generation of hydrogen under visible light on La2CuO4. H LAHMAR and M TRARI. ∗. Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry (USTHB),. B.P. 32, 16111 Algiers, Algeria.

  11. Visible-Light Photoredox-Catalyzed Coupling Reaction of Azoles with α-Carbamoyl Sulfides.

    Science.gov (United States)

    Jarrige, Lucie; Levitre, Guillaume; Masson, Géraldine

    2016-08-19

    A simple, straightforward strategy for the synthesis of N-substituted azoles is reported that involves a visible-light photoredox-catalyzed coupling reaction of azoles with α-carbamoyl sulfides. A variety of heterocyclic units, including pyrazoles, benzopyrazoles, benzoimidazoles, and purines, can be efficiently incorporated under mild reaction conditions in respectable yields.

  12. Role of particle size in visible light photocatalysis of Congo Red ...

    Indian Academy of Sciences (India)

    Their visible light photocatalytic activity was tested for the degradation of Congo Red dye. Maximum photodegradation was observed for the NC with = 0.1 synthesized by CPH (particle size, 71 nm). Similar composition prepared by SSR method (particle size, 6.19 m) showed lower photoactivity in comparison even with ...

  13. Visible light Cr(VI) reduction and organic chemical oxidation by TiO2 photocatalysis.

    Science.gov (United States)

    Sun, Bo; Reddy, Ettireddy P; Smirniotis, Panagiotis G

    2005-08-15

    Here we report the simultaneous Cr(VI) reduction and 4-chlorophenol (4-CP) oxidation in water under visible light (wavelength > 400 nm) using commercial Degussa P25 TiO2. This remarkable observation was attributed to a synergistic effect among TiO2, Cr(VI), and 4-CP. It is well known that TiO2 alone cannot remove either 4-CP or Cr(VI) efficiently under visible light. Moreover, the interaction between Cr(VI) and 4-CP is minimal if not negligible. However, we found that the combination of TiO2, Cr(VI), and 4-CP together can enable efficient Cr(VI) reduction and 4-CP oxidation under visible light. The specific roles of the three ingredients in the synergistic system were studied parametrically. It was found that optimal concentrations of Cr(VI) and TiO2 exist for the Cr(VI) reduction and 4-CP oxidation. Cr(VI) was compared experimentally with other metals such as Cu(ll), Fe(lll), Mn(IV), Ce(IV), and V(V). Among all these metal ions, only Cr(VI) promotes the photocatalytic oxidation of 4-CP. The amount of 4-CP removed was directly related to the initial concentration of Cr(VI). The system was also tested with four other chemicals (aniline, salicylic acid, formic acid, and diethyl phosphoramidate). We found that the same phenomenon occurred for organics containing acid and/or phenolic groups. Cr(VI) was reduced at the same time as the organic chemicals being oxidized during photoreaction under visible light. The synergistic effect was also found with pure anatase TiO2 and rutile TiO2. This study demonstrates a possible economical way for environmental cleanup under visible light.

  14. [TiO2-Induced Photodegradation of Levofloxacin by Visible Light and Its Mechanism].

    Science.gov (United States)

    Guo, Hong-sheng; Liu, Ya-nan; Qiao, Qi; Wei, Hong; Dong, Cheng-xing; Xue, Jie; Li, Ke-bin

    2015-05-01

    Levofloxacin is an emerging pollutant. Single levofloxacin and TiO2 have no visible-light activity. However, photodegradation of levofloxacin dramatically enhanced in the presence of TiO2 under visible light irradiation. Considering this finding, he photodegradation of levofloxacin over TiO2 was investigated under visible light irradiation. Effects of TiO2 dosage, levofloxacin concentration, and solution pH on levofloxacin photodegradation were examined by monitoring its concentration decay with time. The results showed that levofloxacin photodegradation fitted the Langmuir-Hinshelwood kinetic model. Solution pH, TiO2 dose, and levofloxacin concentration had significant effects on the photodegradation rates. In addition, batch adsorption experiments revealed that adsorption of levofloxacin on TiO2 conformed to the pseudo-second-order kinetics and the Langmuir isotherm. DRS spectrum of levofloxacin-adsorbed TiO2 suggested that a surface complex was formed between levofloxacin and TiO2. Addition of radical scavengers and N2-degassing affecting levofloxacin photodegradation indicated that the superoxide ion radical was mainly active species. UV-Vis spectra of a deaerated TiO2 and levofloxacin suspensions further confirmed that the electron injection into TiO2 conduction band took place under visible light irradiation. Based on these results, a charge-transfer mechanism initiated by photoexcitation of TiO2/ levofloxacin surface complex was proposed for levofloxacin photocatalytic degradation over TiO2 under visible light. This study indicates that the charge-transfer-complex-mediated photocatalytic technique has promising applications in the removal of colorless organic pollutants.

  15. Graphene oxide sheets involved in vertically aligned zinc oxide nanowires for visible light photoinactivation of bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Nourmohammadi, Amin; Rahighi, Reza [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Akhavan, Omid, 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); Moshfegh, Alireza [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)

    2014-11-05

    Highlights: • Involvement of GO into the vertically aligned ZnO nanowires using electrophoretic deposition. • UV assisted photocatalytic reduction of the GO sheets involved in the ZnO nanowires. • Visible light photoinactivation of bacteria by the reduced graphene oxide/ZnO nanocomposite. - Abstract: Vertically aligned ZnO nanowires (NWs) hybridized with reduced graphene oxide sheets (rGO) were applied in efficient visible light photoinactivation of bacteria. To incorporate graphene oxide (GO) sheets within the NWs two different methods of drop-casting and electrophoretic deposition (EPD) were utilized. The EPD method yielded effective penetration of the positively charged GO sheets into the NWs to form a spider net-like structure, whereas the drop-casting method resulted in only a surface coverage of the GO sheets on top of the NWs. The electrical connection between the EPD-incorporated sheets and the NWs was checked by monitoring the electron transfer from UV-assisted photoexcited ZnO NWs into the GO sheets, during photocatalytic reduction of the sheets. The obtained rGO/ZnO composites were applied in visible light photoinactivation of Escherichia coli bacteria. The ZnO NWs could inactivate only ∼58% of the bacteria, while both drop-casting and EPD-prepared GO/ZnO composites exhibited strong antibacterial activities (especially the EPD sample with ∼99.5% photoinactivation), under visible light irradiation for 1 h. In fact, the visible light photocatalytic activity of the EPD-prepared GO/ZnO NW composite was found ∼1.9 and 6.2 folds of the activity of the GO/ZnO composite prepared by drop-casting method and the bare ZnO NWs.

  16. Genetic and Physiological Effects of Noncoherent Visible Light Combined with Hydrogen Peroxide on Streptococcus mutans in Biofilm ▿

    Science.gov (United States)

    Steinberg, Doron; Moreinos, Daniel; Featherstone, John; Shemesh, Moshe; Feuerstein, Osnat

    2008-01-01

    Oral biofilms are associated with the most common infections of the oral cavity. Bacteria embedded in the biofilms are less sensitive to antibacterial agents than planktonic bacteria are. Recently, an antibacterial synergic effect of noncoherent blue light and hydrogen peroxide (H2O2) on planktonic Streptococcus mutans was demonstrated. In this study, we tested the effect of a combination of light and H2O2 on the vitality and gene expression of S. mutans embedded in biofilm. Biofilms of S. mutans were exposed to visible light (wavelengths, 400 to 500 nm) for 30 or 60 s (equivalent to 34 or 68 J/cm2) in the presence of 3 to 300 mM H2O2. The antibacterial effect was assessed by microbial counts of each treated sample compared with that of the control. The effect of light combined with H2O2 on the different layers of the biofilm was evaluated by confocal laser scanning microscopy. Gene expression was determined by real-time reverse transcription-PCR. Our results show that noncoherent light, in combination with H2O2, has a synergistic antibacterial effect through all of the layers of the biofilm. Furthermore, this treatment was more effective against bacteria in biofilm than against planktonic bacteria. The combined light and H2O2 treatment up-regulated the expression of several genes such as gtfB, brp, smu630, and comDE but did not affect relA and ftf. The ability of noncoherent visible light in combination with H2O2 to affect bacteria in deep layers of the biofilm suggests that this treatment may be applied in biofilm-related diseases as a minimally invasive antibacterial procedure. PMID:18316516

  17. Preparation and characterization of Cobalt Sulfophthalocyanine/TiO 2/fly-ash cenospheres photocatalyst and study on degradation activity under visible light

    Science.gov (United States)

    Huo, Pengwei; Yan, Yongsheng; Li, Songtian; Li, Huaming; Huang, Weihong

    2009-05-01

    Cobalt Sulfophthalocyanine (CoSPc) sensitized TiO 2 sol samples were prepared through a Sol-Gel method using Cobalt Sulfophthalocyanine as a sensitizer. Loading and modified floating photocatalyst was prepared by hydrothermal method using fly-ash cenospheres as a carrier. The properties of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and UV-vis diffuse reflectance spectrum (DRS). Photocatalytic activity was studied by degrading wastewater of methylene blue under visible light. The results indicate that the fly-ash cenospheres are covered by modified TiO 2 film which composed of the anatase, brookite and rutile misch crystal phase. CoSPc/TiO 2/fly-ash cenospheres samples have good catalytic activity under visible light, and have strong absorbency during 600-700 nm. The sensitization of CoSPc can enhance visible light catalytic activity of TiO 2/fly-ash cenospheres. The degradation rate of methylene blue reaches 73.36% in 180 min under the visible light illumination. But too much CoSPc can decrease its catalytic activity.

  18. Preparation and characterization of Cobalt Sulfophthalocyanine/TiO{sub 2}/fly-ash cenospheres photocatalyst and study on degradation activity under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Huo Pengwei [School of Chemistry and Chemical Engineering, Jiangsu University, Jiangsu, Xuefu Road 301, Zhenjiang 212013 (China); Yan Yongsheng, E-mail: henanhuo@yahoo.com [School of Chemistry and Chemical Engineering, Jiangsu University, Jiangsu, Xuefu Road 301, Zhenjiang 212013 (China); Li Songtian; Li Huaming; Huang Weihong [School of Chemistry and Chemical Engineering, Jiangsu University, Jiangsu, Xuefu Road 301, Zhenjiang 212013 (China)

    2009-05-15

    Cobalt Sulfophthalocyanine (CoSPc) sensitized TiO{sub 2} sol samples were prepared through a Sol-Gel method using Cobalt Sulfophthalocyanine as a sensitizer. Loading and modified floating photocatalyst was prepared by hydrothermal method using fly-ash cenospheres as a carrier. The properties of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and UV-vis diffuse reflectance spectrum (DRS). Photocatalytic activity was studied by degrading wastewater of methylene blue under visible light. The results indicate that the fly-ash cenospheres are covered by modified TiO{sub 2} film which composed of the anatase, brookite and rutile misch crystal phase. CoSPc/TiO{sub 2}/fly-ash cenospheres samples have good catalytic activity under visible light, and have strong absorbency during 600-700 nm. The sensitization of CoSPc can enhance visible light catalytic activity of TiO{sub 2}/fly-ash cenospheres. The degradation rate of methylene blue reaches 73.36% in 180 min under the visible light illumination. But too much CoSPc can decrease its catalytic activity.

  19. Visible Light Image-Based Method for Sugar Content Classification of Citrus

    Science.gov (United States)

    Wang, Xuefeng; Wu, Chunyan; Hirafuji, Masayuki

    2016-01-01

    Visible light imaging of citrus fruit from Mie Prefecture of Japan was performed to determine whether an algorithm could be developed to predict the sugar content. This nondestructive classification showed that the accurate segmentation of different images can be realized by a correlation analysis based on the threshold value of the coefficient of determination. There is an obvious correlation between the sugar content of citrus fruit and certain parameters of the color images. The selected image parameters were connected by addition algorithm. The sugar content of citrus fruit can be predicted by the dummy variable method. The results showed that the small but orange citrus fruits often have a high sugar content. The study shows that it is possible to predict the sugar content of citrus fruit and to perform a classification of the sugar content using light in the visible spectrum and without the need for an additional light source. PMID:26811935

  20. 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.

  1. Photocatalytic dye degradation with copper–titanium dioxide nanocomposites under sunlight and visible light irradiation

    Science.gov (United States)

    Qayyum Khan, Abdul; Yuan, Shuai; Niu, Sheng; Liu, Fengjiang; Feng, Guang; Jiang, Mengci; Zeng, Heping

    2018-01-01

    Photocatalytic methalyne blue dye degradation was carried out with copper (Cu)–titanium dioxide (TiO2) nanocomposites under sunlight and visible light irradiation. The Cu–TiO2 nanocomposites were fabricated via femtosecond laser ablation of pressed targets in water. The current method provides a facile route for Cu–TiO2 nanocomposites preparation, which is free from impurities on the catalysts surface. The Cu–TiO2 nanocomposites (with Cu content of 5 wt%) have shown 3 folds faster dye degradation kinetics compared with TiO2 nanoparticles under sunlight irradiation. While under visible light irradiation, the same nanocomposites exhibited 2.6 folds faster kinetics compared with TiO2 nanoparticles. The faster light harvesting efficiency of the catalysts is attributed to more hydroxyl radical generation.

  2. On-chip integration for in-plane video transmission using visible light

    Science.gov (United States)

    Yang, Yongchao; Yuan, Jialei; Li, Yuanhang; Gao, Xumin; Wang, Yongjin

    2016-10-01

    We demonstrate a wafer-level process for achieving monolithic photonic integration of a light-emitting diode (LED) with a waveguide and photodiode on a GaN-on-silicon platform. Both silicon removal and back-side thinning are conducted to achieve a suspended device architecture. A highly confined waveguide that utilizes the large index contrast between GaN and air is used for the connection between the LED and the photodiode. The suspended waveguide is considered as an in-plane escape cone of the LED, and the photodiode is located at the other end of the waveguide. The photons emitted from the LED are transported to the photodiode through the suspended waveguide parallel to the LED surface, leading to in-plane data transport using visible light. This proof-of-concept monolithic integration paves the way towards in-plane visible light communication as well as photonic computation on a single chip.

  3. Enhanced visible light photocatalytic hydrogen evolution over porphyrin hybridized graphitic carbon nitride.

    Science.gov (United States)

    Mei, Shunkang; Gao, Jianping; Zhang, Ye; Yang, Jiangbing; Wu, Yongli; Wang, Xiaoxue; Zhao, Ruiru; Zhai, Xiangang; Hao, Chaoyue; Li, Ruixia; Yan, Jing

    2017-11-15

    Tetra (4-carboxyphenyl) porphyrin (TCPP) was loaded on the surface of Pt/g-C3N4 via a simple adsorption process, and the microstructure and chemical structure of the composites were characterized by high resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV-visible diffused reflectance spectroscopy and photoluminescence spectroscopy. Loading TCPP onto Pt/g-C3N4 enhanced the visible-light-driven photocatalytic evolution of H2 from water. The TCPP/Pt/g-C3N4 composite with a TCPP loading of 1wt% had the highest photoactivity, which was 2.1 times higher than that of Pt/g-C3N4. This improvement is attributed to enhanced visible light utilization by the TCPP/Pt/g-C3N4 resulting from the strong visible light response of TCPP. In addition, the formed organic heterostructure between TCPP and g-C3N4 with overlapping bad gaps accelerates the electron transfer and inhibits the recombination of the photogenerated electrons and holes on g-C3N4. Copyright © 2017. Published by Elsevier Inc.

  4. Enhanced Photoactivity of Fe + N Codoped Anatase-Rutile Nanowire Film under Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Kewei Li

    2012-01-01

    Full Text Available Rutile-anatase phase mixed codoped TiO2 nanowires were designed and prepared by a two-step anodic oxidation method. The results of X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy confirm that the prepared codoped TiO2 nanowires exhibit intimately contacted anatase-rutile heterostructure with the rutile content of 21.89%. The X-ray photoelectron spectroscopy measurements show that nitrogen and iron atoms are incorporated into the titania oxide lattice, and the UV-visible absorption spectra show that the codoping of iron and nitrogen atoms could extend the absorption to visible light region. The photocatalytic activities of all the samples were evaluated by photocatalytic degradation of methylene blue under visible light irradiation. The codoped sample achieves the best response to visible light and the highest photocatalytic activities. The enhancement of photocatalytic activity for codoped sample should be ascribed to the synergistic effects of codoped nitrogen and iron ions and the anatase-rutile heterostructure.

  5. 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.

  6. Hydrothermal Preparation of Visible-Light-Driven N-Br-Codoped TiO2 Photocatalysts

    Directory of Open Access Journals (Sweden)

    Yonggang Sheng

    2008-01-01

    Full Text Available Using a facile hydrothermal method, N-Br-codoped TiO2 photocatalyst that had intense absorption in visible region was prepared at low temperature (100°C, through a direct reaction between nanocrystalline anatase TiO2 solution and cetyltrimethylammonium bromide (CTAB. The results of X-ray photoelectron spectroscopy (XPS showed the existence of N-Ti-N, O-Ti-N-R, Ti3+ (attribute to the doped Br atoms by charge compensation, and TiOxNy species, indicating the successful codoping of N and Br atoms, which were substituted for lattice oxygen without any influence on the crystalline phase of TiO2. In contrast to the N-doped sample, the N-Br-codoped TiO2 photocatalyst could more readily photodegrade methylene blue (MB under visible-light irradiation. The visible-light catalytic activity of thus-prepared photocatalyst resulted from the synergetic effect of the doped nitrogen and bromine, which not only gave high absorbance in the visible-light range, but also reduced electron-hole recombination rate.

  7. [Degrading anticancer drugs in the medical environment using a visible light-driven photocatalyst].

    Science.gov (United States)

    Sato, Junya; Kikuchi, Satomi; Kudo, Kenzo

    2014-01-01

      Occupational exposure to anticancer drugs is recognized as a risk for healthcare workers. Reducing anticancer drugs in the environment is important to prevent the exposure of individuals to anticancer drugs. However, there are currently no effective degrading agents for all anticancer drugs used in clinical settings. We previously reported the resolution of an anticancer drug with the use of a photocatalyst (TiO2), which acts by absorbing ultraviolet light to degrade organic compounds. In this study, we evaluated anticancer drug degradation using a visible light-driven photocatalyst (Cu/WO3). Anticancer drugs [cyclophosphamide (CPA), paclitaxel (PTX), methotrexate (MTX), irinotecan (CPT-11), cytarabine (Ara-C), and 5-fluorouracil (5-FU)], were experimentally deposited on a stainless steel plate. The visible light-driven photocatalytic agent (0.075% Cu/WO3 solution) was sprayed onto the plate, and the plate was then left under a fluorescent lamp for 12 h. The anticancer drugs remaining on the plate were assayed by high-performance liquid chromatography (HPLC). CPA, PTX, MTX, CPT-11, Ara-C, and 5-FU were found to be degraded by up to 37.7%, >99.0%, 57.1%, 54.6%, 69.5%, and 36.3%, respectively. The visible light-driven photocatalyst was therefore confirmed to degrade anticancer drugs under a fluorescent lamp. The ability of the visible light-driven photocatalyst to degrade multiple chemotherapeutic agents without the need for altering the light source could make it a useful tool for reducing anticancer drug pollution in clinical settings.

  8. Carbon dioxide photoconversion driven by visible-light excitation of small carbon nanoparticles in various configurations

    Science.gov (United States)

    Sahu, Sushant; Cao, Li; Meziani, Mohammed J.; Bunker, Christopher E.; Shiral Fernando, K. A.; Wang, Ping; Sun, Ya-Ping

    2015-08-01

    In the CO2 sequestration, a desirable yet challenging option is the photocatalytic conversion with solar irradiation. While nanoscale semiconductors have been at the center of attention in the development of suitable photocatalysts for the CO2 conversion, carbon nanoparticles have recently emerged as a new class of photoactive materials for harvesting visible photons to drive photocatalytic processes. Results from this study demonstrate that aqueous suspended bare carbon nanoparticles could be excited with visible light to photocatalytically convert CO2 into formic acid, with the performance competitive to that of widely used semiconductor nanoparticles.

  9. In-plane visible light communication made with InGaN turning mirror

    Science.gov (United States)

    Yuan, Jialei; Shi, Zheng; Li, Xin; Yang, Yongchao; Gao, Xumin; Jiang, Yuan; Du, Guanxiang; Wang, Yongjin

    2017-11-01

    The refractive index contrast between AlGaN and InGaN leads to the formation of an optically-confined InGaN waveguide structure. Therefore, we propose a simple fabrication procedure to achieve on-chip photonic integration including a light source, waveguide, beam splitter, turning mirror and photodiode on an III-nitride-on-silicon platform. By inserting InGaN/GaN multiple-quantum-well active layer inside the InGaN waveguide, the emitted light is confined and coupled to the light waveguide. The in-plane light propagation that is directly observed due to the visible light emission is manipulated by the beam splitter and turning mirror. The waveguide-splitter-mirror-integrated III-nitride photonic circuit experimentally demonstrates an in-plane data transmission at 50 Mbps using visible light, suggesting its great potential for diverse applications in on-chip power monitoring, high-resolution blue printing and in-plane light communication.

  10. Oxidative photodecarboxylation of α-hydroxycarboxylic acid derivatives with FSM-16 under visible light irradiation of fluorescent lamp.

    Science.gov (United States)

    Tada, Norihiro; Matsusaki, Yoko; Miura, Tsuyoshi; Itoh, Akichika

    2011-01-01

    Hydroxycarboxylic acids were converted to the corresponding carbonyl compounds under aerobic photo-oxidative conditions in the presence of FSM-16 under visible light irradiation by a fluorescent lamp. This synthetic protocol is the first example of FSM-16 functioning as a photocatalyst by visible light.

  11. 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.

  12. A versatile new method for synthesis and deposition of doped, visible light-activated TiO2 thin films

    DEFF Research Database (Denmark)

    In, Su-il; Kean, A.H.; Orlov, A.

    2009-01-01

    A flexible and widely applicable method allows the deposition of carbon-doped visible light-activated photocatalytic TiO2 thin films on a variety of substrates.......A flexible and widely applicable method allows the deposition of carbon-doped visible light-activated photocatalytic TiO2 thin films on a variety of substrates....

  13. Biogenic C-doped titania templated by cyanobacteria for visible-light photocatalytic degradation of Rhodamine B.

    Science.gov (United States)

    He, Jiao; Zi, Guoli; Yan, Zhiying; Li, Yongli; Xie, Jiao; Duan, Deliang; Chen, Yongjuan; Wang, Jiaqiang

    2014-05-01

    Cyanobacteria, which occurred in eutrophic water harvest solar light to carry out photosynthesis with high efficiency. In this work, cyanobacteria (Microcystis sp.) were used as biotemplate to synthesize titania structure. The synthesized titania sample had similar morphology to that of the original template in spite of the fragile unicellular structures and extremely high water content of cyanobacterial cells. Incorporation of biogenic C, as well as the morphology inherited from biotemplate improved visible-light absorbance of the titania structure. The sample exhibited higher visible-light photocatalytic activity than commercial titania photocatalyst Degussa P25 for Rhodamine B (RhB) degradation. Compared with those C-doped titania photocatalysts prepared by other methods, cyanobacteria templated titania photocatalyst offer some potential for competitive advantages. The reported strategy opened up a new use for the cyanobacteria. It could also be used for titania in applications such as treatment of polluted water, dye-sensitized solar cells, or other regions. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

  14. CdS-graphene Nanocomposite for Efficient Visible-light-driven Photocatalytic and Photoelectrochemical Applications.

    Science.gov (United States)

    Khan, Mohammad Ehtisham; Khan, Mohammad Mansoob; Cho, Moo Hwan

    2016-11-15

    This paper reports cadmium sulphide nanoparticles-(CdS NPs)-graphene nanocomposite (CdS-Graphene), prepared by a simple method, in which CdS NPs were anchored/decorated successfully onto graphene sheets. The as-synthesized nanocomposite was characterized using standard characterization techniques. A combination of CdS NPs with the optimal amount of two-dimensional graphene sheets had a profound influence on the properties of the resulting hybrid nanocomposite, such as enhanced optical, photocatalytic, and photo-electronic properties. The photocatalytic degradation ability of the CdS-Graphene nanocomposite was evaluated by degrading different types of dyes in the dark and under visible light irradiation. Furthermore, the photoelectrode performance of the nanocomposite was evaluated by different electrochemical techniques. The results showed that the CdS-Graphene nanocomposite can serve as an efficient visible-light-driven photocatalyst as well as photoelectrochemical performance for optoelectronic applications. The significantly enhanced photocatalytic and photoelectrochemical performance of the CdS-Graphene nanocomposite was attributed to the synergistic effects of the enhanced light absorption behaviour and high electron conductivity of the CdS NPs and graphene sheets, which facilitates charge separation and lengthens the lifetime of photogenerated electron-hole pairs by reducing the recombination rate. The as-synthesized narrow band gap CdS-Graphene nanocomposite can be used for wide range of visible light-induced photocatalytic and photoelectrochemical based applications. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Curcumin in combination with visible light inhibits tumor growth in a xenograft tumor model.

    Science.gov (United States)

    Dujic, Jadranka; Kippenberger, Stefan; Ramirez-Bosca, Ana; Diaz-Alperi, Joaquin; Bereiter-Hahn, Jürgen; Kaufmann, Roland; Bernd, August; Hofmann, Matthias

    2009-03-15

    It is known that curcumin, a dietary pigment from the plant Curcuma longa, inhibits cell proliferation and induces apoptosis in different cell lines; however, the therapeutic benefit is hampered by very low absorption after transdermal or oral application. Recent studies from our laboratory have demonstrated that curcumin at low concentrations (0.2-1 microg/ml) offered the described effects only when applied with UVA or visible light. Nevertheless, the in vivo efficacy of this combination is lacking. In the present study, we used a xenograft tumor model with human epithelial carcinoma A431 cells to test the effect of curcumin and visible light on tumor growth. It was found that tumor growth was significantly inhibited in mice that were i.p. injected with curcumin and consecutively irradiated with visible light. Furthermore, immunohistochemistry showed a reduction of Ki 67 expression, indicating a decrease of cycling cells and induction of apoptotic bodies. The effect on apoptosis was further confirmed by Western blot analysis showing enhanced activation of caspases-9. Vice versa inhibition of extracellular regulated kinases (ERK) 1/2 and epidermal growth factor receptor (EGF-R) was observed which may aid inhibition of proliferation and induction of apoptosis. In summary, the present findings suggest a combination of curcumin and light as a new therapeutic concept to increase the efficacy of curcumin in the treatment of cancer.

  16. Visible-Light Photodegradation of Dye on Co-Doped Titania Nanotubes Prepared by Hydrothermal Synthesis

    Directory of Open Access Journals (Sweden)

    Jung-Pin Wang

    2012-01-01

    Full Text Available Highly porous Co-doped TiO2 nanotubes synthesized from a hydrothermal treatment were used to photodecompose methylene blue (MB in liquid phase under visible light irradiation. The anatase-type titania nanotubes were found to have high specific surface areas of about 289–379 m2/g. These tubes were shown to be hollow scrolls with outer diameter of about 10–15 nm and length of several micrometers. UV absorption confirmed that Co doping makes the light absorption of nanotubes shift to visible light region. With increasing the dopant concentration, the optical band gap of nanotubes became narrower, ranging from 2.4 eV to 1.8 eV, determined by Kubelka-Munk plot. The Co-doped nanotubes exhibit not only liquid-phase adsorption ability, but also visible-light-derived photodegradation of MB in aqueous solution. The synergetic effect involves two key factors in affecting the photocatalytic activity of Co-doped titania nanotubes under fluorescent lamp, that is, high porosity and optical band gap. The merit of the present work is to provide an efficient route for preparing Co-doped TiO2 nanotubes and to clarifying their adsorption and photocatalytic activity under fluorescent lamp.

  17. 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.

  18. Chlorine-functionalized carbon dots for highly efficient photodegradation of pollutants under visible-light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Shengliang, E-mail: hsliang@yeah.net [School of Material Science and Engineering, North University of China, Taiyuan 030051 (China); Ding, Yanli [School of Material Science and Engineering, North University of China, Taiyuan 030051 (China); Chang, Qing, E-mail: changneu@gmail.com [School of Material Science and Engineering, North University of China, Taiyuan 030051 (China); Yang, Jinlong [State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084 (China); Lin, Kui, E-mail: linkui@tju.edu.cn [Analytical Instrumentation Center, Tianjin University, Tianjin 300072 (China)

    2015-11-15

    Graphical abstract: Chlorine-functionalized carbon dots (Cl-CDs) were synthesized through the substitution reaction. Cl-CDs show highly photocatalytic activity under visible-light irradiation, and can quickly degrade phthalocyanine with the thermal and chemical stability. This work suggests that surface engineering of carbon dots with heteroatoms can be used to enhance their photochemical properties. - Highlights: • Chlorine-functionalized carbon dots (Cl-CDs) were synthesized by substitution reaction. • Cl-CDs show highly photocatalytic activity under visible-light irradiation. • The thermally and chemically stable phthalocyanine is even photodegraded by Cl-CDs. - Abstract: Chlorine-functionalized carbon dots (Cl-CDs) were prepared by the substitution reaction between Cl radicals into thionyl chloride molecules and carbon dots with containing OH/COOH groups at their surface (O-CDs). The obtained Cl-CDs with a size of 2–5 nm contain 2–3% Cl atoms and emit blue light. Compared with amine-functionalzed carbon dots (N-CDs) and O-CDs, Cl-CDs exhibit much higher photocatalytic activity under visible-light irradiation. The thermally and chemically stable phthalocyanine can be even degraded quickly through Cl-CDs. This work suggests that surface engineering of carbon dots with heteroatoms can be used to enhance their photochemical properties.

  19. In vitro and in vivo analysis of visible light crosslinkable gelatin methacryloyl (GelMA) hydrogels.

    Science.gov (United States)

    Noshadi, Iman; Hong, Seonki; Sullivan, Kelly E; Shirzaei Sani, Ehsan; Portillo-Lara, Roberto; Tamayol, Ali; Shin, Su Ryon; Gao, Albert E; Stoppel, Whitney L; Black, Lauren D; Khademhosseini, Ali; Annabi, Nasim

    2017-09-26

    Photocrosslinkable materials have been frequently used for constructing soft and biomimetic hydrogels for tissue engineering. Although ultraviolet (UV) light is commonly used for photocrosslinking such materials, its use has been associated with several biosafety concerns such as DNA damage, accelerated aging of tissues, and cancer. Here we report an injectable visible light crosslinked gelatin-based hydrogel for myocardium regeneration. Mechanical characterization revealed that the compressive moduli of the engineered hydrogels could be tuned in the range of 5-56 kPa by changing the concentrations of the initiator, co-initiator and co-monomer in the precursor formulation. In addition, the average pore sizes (26-103 μm) and swelling ratios (7-13%) were also shown to be tunable by varying the hydrogel formulation. In vitro studies showed that visible light crosslinked GelMA hydrogels supported the growth and function of primary cardiomyocytes (CMs). In addition, the engineered materials were shown to be biocompatible in vivo, and could be successfully delivered to the heart after myocardial infarction in an animal model to promote tissue healing. The developed visible light crosslinked hydrogel could be used for the repair of various soft tissues such as the myocardium and for the treatment of cardiovascular diseases with enhanced therapeutic functionality.

  20. A fast fusion scheme for infrared and visible light images in NSCT domain

    Science.gov (United States)

    Zhao, Chunhui; Guo, Yunting; Wang, Yulei

    2015-09-01

    Fusion of infrared and visible light images is an effective way to obtain a simultaneous visualization of details of background provided by visible light image and hiding target information provided by infrared image, which is more suitable for browsing and further processing. Two crucial components for infrared and visual light image fusion are improving its fusion performance as well as reducing its computational burden. In this paper, a novel fusion algorithm named pixel information estimation is proposed, which determines the weights by evaluating the information of pixel and is well applied in visible light and infrared image fusion with better fusion quality and lower time-consumption. Besides, a fast realization of non-subsampled contourlet transform is also proposed in this paper to improve the computational efficiency. To verify the advantage of the proposed method, this paper compares it with several popular ones in six evaluation metrics over four different image groups. Experimental results show that the proposed algorithm gets a more effective result with much less time consuming and performs well in both subjective evaluation and objective indicators.

  1. 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.

  2. Visible Light Triggered Drug Release from TiO2 Nanotube Arrays: A Novel Controllable Antibacterial Platform

    CERN Document Server

    Xu, Jingwen; Gao, Zhida; Song, Yan-Yan; Schmuki, Patrik

    2016-01-01

    In this work, we use a double-layered stack of TiO2 nanotubes (TiNTs) to construct a visible-light triggered drug delivery system. Key for visible-light drug release is a hydrophobic cap on the nanotubes containing Au nanoparticles (AuNPs). The AuNPs allow for a photocatalytic scission of the hydrophobic chain under visible light. To demonstrate the principle, we loaded antibiotic (ampicillin sodium (AMP)) in the lower part of the TiO2 nanotube stack, triggered visible light induced release, and carried out antibacterial studies. The release from the platform becomes most controllable if the drug is silane-grafted in hydrophilic bottom layer for drug storage. Thus visible-light photocatalysis can also determine the release kinetics of the active drug from the nanotube wall.

  3. Analysis of polarimetric synthetic aperture radar and passive visible light polarimetric imaging data fusion for remote sensing applications

    Science.gov (United States)

    Maitra, Sanjit

    The recent launch of spaceborne (TerraSAR-X, RADARSAT-2, ALOS-PALSAR, RISAT) and airborne (SIRC, AIRSAR, UAVSAR, PISAR) polarimetric radar sensors, with capability of imaging through day and night in almost all weather conditions, has made polarimetric synthetic aperture radar (PolSAR) image interpretation and analysis an active area of research. PolSAR image classification is sensitive to object orientation and scattering properties. In recent years, significant work has been done in many areas including agriculture, forestry, oceanography, geology, terrain analysis. Visible light passive polarimetric imaging has also emerged as a powerful tool in remote sensing for enhanced information extraction. The intensity image provides information on materials in the scene while polarization measurements capture surface features, roughness, and shading, often uncorrelated with the intensity image. Advantages of visible light polarimetric imaging include high dynamic range of polarimetric signatures and being comparatively straightforward to build and calibrate. This research is about characterization and analysis of the basic scattering mechanisms for information fusion between PolSAR and passive visible light polarimetric imaging. Relationships between these two modes of imaging are established using laboratory measurements and image simulations using the Digital Image and Remote Sensing Image Generation (DIRSIG) tool. A novel low cost laboratory based S-band (2.4GHz) PolSAR instrument is developed that is capable of capturing 4 channel fully polarimetric SAR image data. Simple radar targets are formed and system calibration is performed in terms of radar cross-section. Experimental measurements are done using combination of the PolSAR instrument with visible light polarimetric imager for scenes capturing basic scattering mechanisms for phenomenology studies. The three major scattering mechanisms studied in this research include single, double and multiple bounce. Single

  4. Multilevel modulation scheme using the overlapping of two light sources for visible light communication with mobile phone camera.

    Science.gov (United States)

    Shi, Jin; He, Jing; He, Jing; Deng, Rui; Wei, Yiran; Long, Fengting; Cheng, Yun; Chen, Lin

    2017-07-10

    Visible light communication (VLC) with light emitting diodes (LEDs) is an emerging technology for 5G wireless communications. Recently, using complementary metal-oxide-semiconductor (CMOS) image sensor as VLC receiver is developed owing to its flexibility and low-cost. However, two illumination levels such as on-off keying (OOK) signal are used. To improve the system throughput and reduce complexity of the hardware design, in this paper, we propose and experimentally demonstrate a multilevel modulation scheme for VLC system utilizing the overlapping of two light sources for the first time, and the two light sources are modulated by an OOK and a Manchester signal respectively. At the receiver, a CMOS camera can demodulate the Manchester and the OOK signal simultaneously. Meanwhile, a low-pass filter (LPF) is used to enhance the system performance. The experimental results demonstrate that the proposed multilevel modulation scheme can achieve a net data rate of 4.32 kbit/s.

  5. Using Visible Infrared Imaging Radiometer Suite (VIIRS) Imagery to identify and analyze light pollution

    Science.gov (United States)

    Nurbandi, Wahyu; Ramadhani Yusuf, Febrina; Prasetya, Ruwanda; Dimas Afrizal, Mousafi

    2016-11-01

    Light pollution is any adverse effect of artificial lighting including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste. Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object. Remote sensing can be used for identification of light pollution. The purpose of this study is to identify and analyze the light pollution by using remote sensing imagery. This study uses VIIRS DNB Free Cloud Composites imagery to identify light pollution in Yogyakarta province and surrounding areas. VIIRS imagery which obtained is processed to get information of light pollution by classifying the information into several classes presented in a map. Selected few sample points as test sites to determine the actual condition. Field work conducted at theree location, they are Yogyakarta City, Depok Beach, and Gajah Mungkur reservoir. Night sky condition analysis conducted field tests as well as night time shooting the night sky conditions. Analysis of the night sky conditions are calculated qualitatively using Bortle Dark-Sky Scale with a value range of 1-9. Field test results show that Yogyakarta City has a value of 8, Depok has a value of 3, and Gajah Mungkur Reservoir has a value of 4. The conclusion of study is VIIRS imagery can be used for identification light pollution and calculation analysis of light pollution can use Bortle Dark-Sky Scale.

  6. 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..

  7. Unique visible-light-assisted field emission of tetrapod-shaped ZnO/reduced graphene-oxide core/coating nanocomposites

    Science.gov (United States)

    Wu, Chaoxing; Kim, Tae Whan; Guo, Tailiang; Li, Fushan

    2016-12-01

    The electronic and the optoelectronic properties of graphene-based nanocomposites are controllable, making them promising for applications in diverse electronic devices. In this work, tetrapod-shaped zinc oxide (T-ZnO)/reduced graphene oxide (rGO) core/coating nanocomposites were synthesized by using a hydrothermal-assisted self-assemble method, and their optical, photoelectric, and field-emission properties were investigated. The ZnO, an ideal ultraviolet-light-sensitive semiconductor, was observed to have high sensitivity to visible light due to the rGO coating, and the mechanism of that sensitivity was investigated. We demonstrated for the first time that the field-emission properties of the T-ZnO/rGO core/coating nanocomposites could be dramatically enhanced under visible light by decreasing the turn-on field from 1.54 to 1.41 V/μm and by increasing the current density from 5 to 12 mA/cm2 at an electric field of 3.5 V/μm. The visible-light excitation induces an electron jump from oxygen vacancies on the surface of ZnO to the rGO layer, resulting in a decrease in the work function of the rGO and an increase in the emission current. Furthermore, a field-emission light-emitting diode with a self-enhanced effect was fabricated making full use of the photo-assisted field-emission process.

  8. A visible light-induced photocatalytic silver enhancement reaction for gravimetric biosensors

    Science.gov (United States)

    Ko, Wooree; Yim, Changyong; Jung, Namchul; Joo, Jinmyoung; Jeon, Sangmin; Seo, Hyejung; Lee, Soo Suk; Park, Jae Chan

    2011-10-01

    We have developed a novel microgravimetric immunosensor using a WO3 nanoparticle-modified immunoassay and a silver enhancement reaction. When the nanoparticles in silver ion solution (i.e. AgNO3) are exposed to visible light, the silver ions are photocatalytically reduced and form a metallic silver coating on the nanoparticles. This silver coating consequently induces changes in the mass and light absorption spectrum. Although photocatalytic reduction reactions can be achieved using ultraviolet (UV) light and TiO2 nanoparticles as described in our previous publication (Seo et al 2010 Nanotechnology 21 505502), the use of UV light in biosensing applications has drawbacks in that UV light can damage proteins. In addition, conventional quartz crystal substrates must be passivated to prevent undesirable silver ion reduction on their gold-coated sensing surfaces. We addressed these problems by adopting a visible light-induced photocatalytic silver enhancement method using WO3 nanoparticles and lateral field excited (LFE) quartz crystals. As a proof-of-concept demonstration of the technique, streptavidin was adsorbed onto an LFE quartz crystal, and its mass was enhanced with biotinylated WO3 nanoparticles, this being followed by a photocatalytic silver enhancement reaction. The mass change due to the enhancement was found to be > 30 times greater than the mass change obtained with the streptavidin alone.

  9. A visible light-induced photocatalytic silver enhancement reaction for gravimetric biosensors

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Wooree; Yim, Changyong; Jung, Namchul; Joo, Jinmyoung; Jeon, Sangmin [Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang (Korea, Republic of); Seo, Hyejung; Lee, Soo Suk; Park, Jae Chan, E-mail: jeons@postech.ac.kr [Samsung Advanced Institute of Technology (SAIT), Suwon (Korea, Republic of)

    2011-10-07

    We have developed a novel microgravimetric immunosensor using a WO{sub 3} nanoparticle-modified immunoassay and a silver enhancement reaction. When the nanoparticles in silver ion solution (i.e. AgNO{sub 3}) are exposed to visible light, the silver ions are photocatalytically reduced and form a metallic silver coating on the nanoparticles. This silver coating consequently induces changes in the mass and light absorption spectrum. Although photocatalytic reduction reactions can be achieved using ultraviolet (UV) light and TiO{sub 2} nanoparticles as described in our previous publication (Seo et al 2010 Nanotechnology 21 505502), the use of UV light in biosensing applications has drawbacks in that UV light can damage proteins. In addition, conventional quartz crystal substrates must be passivated to prevent undesirable silver ion reduction on their gold-coated sensing surfaces. We addressed these problems by adopting a visible light-induced photocatalytic silver enhancement method using WO{sub 3} nanoparticles and lateral field excited (LFE) quartz crystals. As a proof-of-concept demonstration of the technique, streptavidin was adsorbed onto an LFE quartz crystal, and its mass was enhanced with biotinylated WO{sub 3} nanoparticles, this being followed by a photocatalytic silver enhancement reaction. The mass change due to the enhancement was found to be > 30 times greater than the mass change obtained with the streptavidin alone.

  10. 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.

  11. Increased visible-light photocatalytic activity of TiO2 via band gap manipulation

    Science.gov (United States)

    Pennington, Ashley Marie

    Hydrogen gas is a clean burning fuel that has potential applications in stationary and mobile power generation and energy storage, but is commercially produced from non-renewable fossil natural gas. Using renewable biomass as the hydrocarbon feed instead could provide sustainable and carbon-neutral hydrogen. We focus on photocatalytic oxidation and reforming of methanol over modified titanium dioxide (TiO2) nanoparticles to produce hydrogen gas. Methanol is used as a model for biomass sugars. By using a photocatalyst, we aim to circumvent the high energy cost of carrying out endothermic reactions at commercial scale. TiO2 is a semiconductor metal oxide of particular interest in photocatalysis due to its photoactivity under ultraviolet illumination and its stability under catalytic reaction conditions. However, TiO2 primarily absorbs ultraviolet light, with little absorption of visible light. While an effective band gap for absorbance of photons from visible light is 1.7 eV, TiO2 polymorphs rutile and anatase, have band gaps of 3.03 eV and 3.20 eV respectively, which indicate ultraviolet light. As most of incident solar radiation is visible light, we hypothesize that decreasing the band gap of TiO2 will increase the efficiency of TiO2 as a visible-light active photocatalyst. We propose to modify the band gap of TiO2 by manipulating the catalyst structure and composition via metal nanoparticle deposition and heteroatom doping in order to more efficiently utilize solar radiation. Of the metal-modified Degussa P25 TiO2 samples (P25), the copper and nickel modified samples, 1%Cu/P25 and 1%Ni/P25 yielded the lowest band gap of 3.05 eV each. A difference of 0.22 eV from the unmodified P25. Under visible light illumination 1%Ni/P25 and 1%Pt/P25 had the highest conversion of methanol of 9.9% and 9.6%, respectively.

  12. Study of Visible Light Reactive Photocatalyst TIO2 Prepared with Thiourea

    Science.gov (United States)

    Murai, Kei-Ichiro; Endo, Kazuki; Nakagawa, Taisuke; Yamahata, Akiko; Moriga, Toshihiro

    Visible light reactive N-doped TiO2 samples were prepared with thiourea in the sol-gel method. They had the single anatase-type crystal structure. N-doped TiO2 synthesized with thiourea (T-TiO2) had a higher catalytic activity than that synthesized with urea (U-TiO2). The S2p peak observed on the surface of T-TiO2 was assigned to S6+ by XPS measurement. It was estimated that sulfuric acid species exist on the surface of T-TiO2. However, it was concluded that sulfuric acid species do not have the catalytic activity directly, but depress the crystallinity, the decrease of specific surface area and the decrease of visible light absorption.

  13. Mesoporous cerium oxide nanospheres for the visible-light driven photocatalytic degradation of dyes

    Science.gov (United States)

    Chen, Shi; Ng, Chin Fan; Huan, Cheng Hon Alfred

    2014-01-01

    Summary 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. PMID:24991486

  14. Theoretical design of visible light driven azobenzene-based photo-switching molecules

    Science.gov (United States)

    Pang, Juan; Tian, Ziqi; Ma, Jing

    2014-10-01

    The preparation of switchable azobenzene derivatives driven by visible light is desirable for applications in biomolecular systems. o-R-substituted 4,4‧-diacetamidoazobenzene derivatives (Rdbnd H, CH3, OCH3 or OH) were investigated by using both density functional theory (DFT) and reactive molecular dynamics simulations. DFT calculations demonstrated that the nonplanar azo trans geometric structure, which caused by bulky groups tetra substituted in the ortho-position, is the key factor to enable the trans → cis transition with visible light. Furthermore, 100 independent reactive MD simulations demonstrated that 71% trans isomers of tetra o-OCH3-substituted 4,4‧-diacetamidoazobenzene translated to cis, in good agreement with the experimental data.

  15. Strongly Reducing, Visible-Light Organic Photoredox Catalysts as Sustainable Alternatives to Precious Metals.

    Science.gov (United States)

    Du, Ya; Pearson, Ryan M; Lim, Chern-Hooi; Sartor, Steven M; Ryan, Matthew D; Yang, Haishen; Damrauer, Niels H; Miyake, Garret M

    2017-08-16

    Photoredox catalysis is a versatile approach for the construction of challenging covalent bonds under mild reaction conditions, commonly using photoredox catalysts (PCs) derived from precious metals. As such, there is need to develop organic analogues as sustainable replacements. Although several organic PCs have been introduced, there remains a lack of strongly reducing, visible-light organic PCs. Herein, we establish the critical photophysical and electrochemical characteristics of both a dihydrophenazine and a phenoxazine system that enables their success as strongly reducing, visible-light PCs for trifluoromethylation reactions and dual photoredox/nickel-catalyzed C-N and C-S cross-coupling reactions, both of which have been historically exclusive to precious metal PCs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Formation of nitric oxide under action of UV and visible light on S-nitrosocompounds

    Science.gov (United States)

    Stepuro, Ivan I.; Adamchuk, Raisa I.; Anufrik, Slavomir S.; Stepuro, Vitali I.; Maskevich, Sergei A.

    2000-06-01

    It has been shown that NO is released under the exposure of the aqueous solutions of S-nitrosocompounds as well as blood plasma proteins and whole blood of healthy donors to UV and visible light. The NO release from degrading S- nitrosocompounds was monitored both spectrophotometrically (by nitrosohemoglobin formation) and using the quenching of pyrene fluorescence by nitric oxide. In addition to NO, thyil radicals which dismutate to disulfides, were formed under anaerobic conditions. In the presence of oxygen, peroxide compounds, cysteine acid derivatives and S-nitrocompounds are formed apart from disulfides, and NO is mainly converted to NO2-. It is suggested that NO releasing under the actin of UV and visible light from physiological depots induces vascular relaxation, which enhances the blood flow.

  17. Mineralization of Azo Dye Using Combined Photo-Fenton and Photocatalytic Processes under Visible Light

    Directory of Open Access Journals (Sweden)

    Selma K. Kuriechen

    2013-01-01

    Full Text Available Visible-light-assisted photodegradation of an azo dye, Reactive Red 180 (RR180, in the presence of nitrogen-doped TiO2 (N-TiO2 has been studied. The photodegradation of RR180 is evaluated through decolorization studies and total organic carbon analysis. The efficacy of hydrogen peroxide (H2O2, potassium peroxomonosulfate (oxone or PMS, and potassium peroxodisulfate (PDS in improving the photodegradation of the dye in the N-TiO2-RR180 system is also examined. The effect of combining photo-Fenton-like reaction with N-TiO2-mediated photodegradation of RR180 under visible light has been investigated. The photoactivity of N-TiO2-RR180-Fe3+/Cu2+-oxidant systems is compared with the individual techniques of photocatalysis and photo-Fenton-like reactions. The coupled system possesses superior photomineralization ability towards the abatement of RR180.

  18. A review of gallium nitride LEDs for multi-gigabit-per-second visible light data communications

    Science.gov (United States)

    Rajbhandari, Sujan; McKendry, Jonathan J. D.; Herrnsdorf, Johannes; Chun, Hyunchae; Faulkner, Grahame; Haas, Harald; Watson, Ian M.; O'Brien, Dominic; Dawson, Martin D.

    2017-02-01

    The field of visible light communications (VLC) has gained significant interest over the last decade, in both fibre and free-space embodiments. In fibre systems, the availability of low cost polymer optical fibre (POF) that is compatible with visible data communications has been a key enabler. In free-space applications, the availability of hundreds of THz of the unregulated spectrum makes VLC attractive for wireless communications. This paper provides an overview of the recent developments in VLC systems based on gallium nitride (GaN) light-emitting diodes (LEDs), covering aspects from sources to systems. The state-of-the-art technology enabling bandwidth of GaN LEDs in the range of >400 MHz is explored. Furthermore, advances in key technologies, including advanced modulation, equalisation, and multiplexing that have enabled free-space VLC data rates beyond 10 Gb s-1 are also outlined.

  19. 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.

  20. 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.

  1. Spiky TiO2/Au nanorod plasmonic photocatalysts with enhanced visible-light photocatalytic activity.

    Science.gov (United States)

    Sun, Hang; Zeng, Shan; He, Qinrong; She, Ping; Xu, Kongliang; Liu, Zhenning

    2017-03-21

    A facile approach for the preparation of spiky TiO2/Au nanorod (NR) plasmonic photocatalysts has been demonstrated, which is through in situ nucleation and growth of spiky TiO2 onto AuNRs. Different aspect ratios of AuNRs in 2.5, 2.7, 4.1 and 4.5 have been applied to prepare spiky TiO2/AuNR nanohybrids to achieve tunable and broad localized surface plasmon resonance (LSPR) bands. All spiky TiO2/AuNR nanohybrids exhibit enhanced light harvesting by extending visible light absorption range by both transverse and longitudinal LSPR bands and decreasing light reflectance by their unique spiky structures. Compared to the bare AuNRs, commercial TiO2 (P25) and spiky TiO2/Au nanosphere photocatalysts, the spiky TiO2/AuNR photocatalysts exhibit significantly enhanced visible light photocatalytic activity in Rhodamine B (RhB) degradation due to their simultaneous enhancement in the light harvesting, charge utilization efficiency, and substrate accessibility. In particular, the spiky TiO2/AuNR-685 photocatalysts show the best photocatalytic activity with ∼98.9% of the RhB degraded within 90 min under the irradiation of 420-780 nm, which could be ascribed to the most extended visible light absorption range and sufficient photon energy of TiO2/AuNR-685 photocatalysts within this irradiation region. The bio-inspired nanostructure, as well as the facile and scalable fabrication approach, will open a new avenue for the rational design and preparation of high-performance photocatalysts for pollutant removal and water splitting.

  2. A novel sandwich-type polyoxometalate compound with visible-light photocatalytic H2 evolution activity.

    Science.gov (United States)

    Zhang, Zhenyu; Lin, Qipu; Zheng, Shou-Tian; Bu, Xianhui; Feng, Pingyun

    2011-04-07

    A tin(II) tungstosilicate derivative K(11)H[Sn(4)(SiW(9)O(34))(2)]·25H(2)O with four sandwiched Sn(2+) cations was prepared by reaction of SnCl(2), KCl and Na(10)[α-SiW(9)O(34)]·xH(2)O. Visible-light photocatalytic H(2) evolution activity was observed with Pt nanoparticles as co-catalyst and methanol as sacrificial agent.

  3. Simulation of impulse response for indoor visible light communications using 3D CAD models

    OpenAIRE

    Pérez Rodríguez, Silvestre; Pérez Jiménez, Rafael; Rodríguez Mendoza, Beatriz; López Hernández, Francisco José; Ayala Alfonso, Alejandro José

    2013-01-01

    n this article, a tool for simulating the channel impulse response for indoor visible light communications using 3D computer-aided design (CAD) models is presented. The simulation tool is based on a previous Monte Carlo ray-tracing algorithm for indoor infrared channel estimation, but including wavelength response evaluation. The 3D scene, or the simulation environment, can be defined using any CAD software in which the user specifies, in addition to the setting geometry, the reflect...

  4. Two-Step, One-Pot Synthesis of Visible-Light-Responsive 6-Azopurines.

    Science.gov (United States)

    Kolarski, Dušan; Szymanski, Wiktor; Feringa, Ben L

    2017-10-06

    The first general two-step, one-pot synthetic route to 6-azopurines is presented. Microwave-assisted nucleophilic aromatic substitution of protected 6-chloropurines with hydrazines or hydrazides, followed by metal-free oxidation with oxygen, gives 6-azopurines in high to excellent yields. Photophysical studies revealed intensive n-π* absorption band that makes trans-to-cis photoswitching possible using visible light (λ = 530 nm).

  5. Mechanical Properties and Failure Analysis of Visible Light Crosslinked Alginate-Based Tissue Sealants

    OpenAIRE

    Charron, Patrick; Fenn, Spencer L.; Poniz, Alex; Oldinski, Rachael A.

    2016-01-01

    Moderate to weak mechanical properties limit the use of naturally-derived tissue sealants for dynamic medical applications, e.g., sealing a lung leak. To overcome these limitations, we developed visible-light crosslinked alginate-based hydrogels, as either non-adhesive methacrylated alginate (Alg-MA) hydrogel controls, or oxidized Alg-MA (Alg-MA-Ox) tissue adhesive tissue sealants, which form covalent bonds with extracellular matrix (ECM) proteins. Our study investigated the potential for vis...

  6. 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.

  7. 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.

  8. Experimental demonstration of block interleaved frequency division multiple access for bidirectional visible light communications

    Science.gov (United States)

    Lin, Bangjiang; Yang, Hui; Ye, Weiping; Tang, Xuan; Ghassemlooy, Zabih

    2017-01-01

    We propose a power efficient multiple access scheme for visible light communications (VLC) based on the block interleaved frequency division multiple access (B-IFDMA) which provides large frequency-diversity, flexible bandwidth allocation, low complexity of channel equalization, and user separation. Bidirectional B-IFDMA VLC transmission is experimentally demonstrated to verify its feasibility. The impact of the number of subcarriers per block on the transmission performance under wireless optical channel is investigated.

  9. Self-Strengthening Hybrid Dental Adhesive via Visible-light Irradiation Triple Polymerization

    OpenAIRE

    Song, Linyong; Ye, Qiang.; Ge, Xueping; Misra, Anil; Tamerler, Candan; Spencer, Paulette

    2016-01-01

    A self-strengthening methacrylate-based dental adhesive system was developed by introducing an epoxy cyclohexyl trimethoxysilane (TS) which contains both epoxy and methoxysilyl functional groups. The experimental formulation, HEMA/BisGMA/TS (22.5/27.5/50, wt%), was polymerized by visible-light. Real-time Fourier transform infrared spectroscopy (FTIR) was used to investigate in situ the free radical polymerization of methacrylate, ring-opening cationic polymerization of epoxy, and photoacid-in...

  10. A General Strategy for Visible-Light Decaging Based on the Quinone Trimethyl Lock.

    Science.gov (United States)

    Walton, David P; Dougherty, Dennis A

    2017-04-05

    Visible-light triggered quinone trimethyl locks are reported as a general design for long-wavelength photoremovable protecting groups for alcohols and amines. Intramolecular photoreduction unmasks a reactive phenol that undergoes fast lactonization to release alcohols and amines. Model substrates are released in quantitative yield along with well-defined, colorless hydroquinone byproducts. Substituent modifications of the quinone core allow absorption from 400 to 600 nm.

  11. Visible light communications in heterogeneous networks: pave the way for user-centric design

    OpenAIRE

    Zhang, Rong; Wang, Jiaheng; Wang, Zhaocheng; Xu, Zhengyuan; Zhao, Chunming; Hanzo, Lajos

    2015-01-01

    At the time of writing, there is substantial research interest in the subject of Visible Light Communications (VLC) owing to its capability of offering significant traffic offloading potential in highly crowded Radio Frequency (RF) scenarios. We introduce the user-centric design of VLC for Heterogeneous Networks (HetNet), where three key aspects are identified and elaborated on, namely 1) signal coverage quality, 2) system control and 3) service provision aspects. More explicitly, the concept...

  12. 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.

  13. Photoelectrocatalytic degradation of methylene blue using F doped TiO2photoelectrode under visible light irradiation.

    Science.gov (United States)

    Liu, Dong; Tian, Renwen; Wang, Jianqiao; Nie, Er; Piao, Xianqing; Li, Xin; Sun, Zhuo

    2017-10-01

    Photoelectrocatalysis (PEC) has attracted great interest due to cost effectiveness and high efficiency in water treatment. In this study, F doped TiO 2 (F-TiO 2 ) photoelectrodes with honeycomb like morphology were prepared, and the PEC performance was investigated. F-TiO 2 particles that showed enhanced absorption of visible light were synthesized via a sol-gel method. F-TiO 2 particles were anchored onto the surface of F-doped SnO 2 glass by a screen-printing method to prepare the F-TiO 2 photoelectrodes. The PEC performance of the F-TiO 2 photoelectrodes was investigated via the degradation of methylene blue (MB) under visible light irradiation. The results show that the F-TiO 2 photoelectrodes exhibited an excellent PEC performance that was affected by the F doping content, applied bias and solution pH. A maximum decolorization percentage of 97.8% was achieved by the FT-15 photoelectrode, with a 1.4 V bias at pH 9.94 after 4.0 h of visible light irradiation. The high PEC performance of the F-TiO 2 photoelectrodes is mainly ascribed to the efficient separation of electron-hole (e - -h + ) pairs and the creation of active radicals such as hydroxyl radicals (OH). The PEC decolorization kinetic data were analyzed using the first-order kinetic model and the Langmuir-Hinshelwood (L-H) model. The data indicates that the PEC degradation of MB molecules mainly occurred on the surface of the F-TiO 2 photoelectrodes, and the MB molecules were discolored mainly by h + (41.5%) and OH (46.5%). In addition, 8.2% of the MB molecules were discolored by other oxidative species, and 3.8% of the MB molecules were discolored by self-sensitized oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Demonstration of high-speed multi-user multi-carrier CDMA visible light communication

    Science.gov (United States)

    Yang, Chao; Wang, Yuanquan; Wang, Yiguang; Huang, Xingxing; Chi, Nan

    2015-02-01

    We experimentally demonstrated a high-speed multi-user multi-carrier code-division multiple access (MC-CDMA) visible light communication (VLC) system. By employing a commercially available red light emitting diode (LED) and an avalanche photo diode (APD), we achieved a 16-user VLC system enabled by MC-CDMA, pre- and post-equalization, with an overall bit rate of 750 Mb/s over 1.5 m free-space transmission. The measured bit error ratio (BER) of each user is below the 7% pre-forward-error-correction (pre-FEC) threshold of 3.8×10-3.

  15. Visible Red Light Emitting Diode Photobiomodulation for Skin Fibrosis: Key Molecular Pathways.

    Science.gov (United States)

    Mamalis, Andrew; Siegel, Daniel; Jagdeo, Jared

    Skin fibrosis, also known as skin scarring, is an important global health problem that affects an estimated 100 million persons per year worldwide. Current therapies are associated with significant side effects and even with combination therapy, progression, and recurrence is common. Our goal is to review the available published data available on light-emitting diode-generated (LED) red light phototherapy for treatment of skin fibrosis. A search of the published literature from 1 January 2000 to present on the effects of visible red light on skin fibrosis, and related pathways was performed in January 2016. A search of PubMed and EMBASE was completed using specific keywords and MeSH terms. "Fibrosis" OR "skin fibrosis" OR "collagen" was combined with ("light emitting diode," "LED," "laser," or "red light"). The articles that were original research studies investigating the use of visible red light to treat skin fibrosis or related pathways were selected for inclusion. Our systematic search returned a total of 1376 articles. Duplicate articles were removed resulting in 1189 unique articles, and 133 non-English articles were excluded. From these articles, we identified six articles related to LED effects on skin fibrosis and dermal fibroblasts. We augmented our discussion with additional in vitro data on related pathways. LED phototherapy is an emerging therapeutic modality for treatment of skin fibrosis. There is a growing body of evidence demonstrating that visible LED light, especially in the red spectrum, is capable of modulating key cellular characteristic associated with skin fibrosis. We anticipate that as the understanding of LED-RL's biochemical mechanisms and clinical effects continue to advance, additional therapeutic targets in related pathways may emerge. We believe that the use of LED-RL, in combination with existing and new therapies, has the potential to alter the current treatment paradigm of skin fibrosis. There is a current lack of clinical trials

  16. Bias-polarity dependent ultraviolet/visible switchable light-emitting devices.

    Science.gov (United States)

    Ni, Pei-Nan; Shan, Chong-Xin; Li, Bing-Hui; Wang, Shuang-Peng; Shen, De-Zhen

    2014-06-11

    By taking semiconductors with different band-gap energies as the active layers and controlling the electron-hole recombination region through the electric field, bias-polarity dependent ultraviolet/visible switchable light-emitting devices have been realized in Au/MgO/Mg0.49Zn0.51O/MgxZn1-xO/n-ZnO structures, of which the emission bands can be switched from the ultraviolet region to the orange region by changing the polarity of the applied bias. The results reported here may provide a feasible idea to multicolor-switchable light-emitting devices.

  17. A visible light-activated direct-bonding material: An in vivo comparative study

    OpenAIRE

    O'Brien, K. D.; Read, M. J F; Sandison, R. J.; Roberts, C. T.

    1989-01-01

    A clinical trial was carried out to evaluate and compare the clinical performance of a visible light-cured material with a chemically cured adhesive. This was used in combination with two types of bracket base. Fifty-two patients entered the trial and 542 bracket bases were placed. The incidence and site of bond failure were recorded. The overall failure rate for the light-cured material in combination with both types of bracket was 4.7% and 6% for the chemical-cured adhesive. There were no s...

  18. Person Recognition System Based on a Combination of Body Images from Visible Light and Thermal Cameras.

    Science.gov (United States)

    Nguyen, Dat Tien; Hong, Hyung Gil; Kim, Ki Wan; Park, Kang Ryoung

    2017-03-16

    The human body contains identity information that can be used for the person recognition (verification/recognition) problem. In this paper, we propose a person recognition method using the information extracted from body images. Our research is novel in the following three ways compared to previous studies. First, we use the images of human body for recognizing individuals. To overcome the limitations of previous studies on body-based person recognition that use only visible light images for recognition, we use human body images captured by two different kinds of camera, including a visible light camera and a thermal camera. The use of two different kinds of body image helps us to reduce the effects of noise, background, and variation in the appearance of a human body. Second, we apply a state-of-the art method, called convolutional neural network (CNN) among various available methods, for image features extraction in order to overcome the limitations of traditional hand-designed image feature extraction methods. Finally, with the extracted image features from body images, the recognition task is performed by measuring the distance between the input and enrolled samples. The experimental results show that the proposed method is efficient for enhancing recognition accuracy compared to systems that use only visible light or thermal images of the human body.

  19. Real time biomedical signal transmission of mixed ECG signal and patient information using visible light communication.

    Science.gov (United States)

    Tan, Yee Yong; Jung, Sang-Joong; Chung, Wan-Young

    2013-01-01

    The utilization of radio-frequency (RF) communication technology in healthcare application, especially in the transmission of health-related data such as biomedical signal and patient information is often perturbed by electromagnetic interference (EMI). This will not only significantly reduce the accuracy and reliability of the data transmitted, but could also compromise the safety of the patients due to radio frequency (RF) radiation. In this paper, we propose a method which utilizes visible light communication technology as a platform for transmission and to provide real-time monitoring of heart rate and patient information. White LED beam is used as the illuminating source to simultaneously transmit biomedical signal as well as patient record. On-off Keying (OOK) modulation technique is used to modulate all the data onto the visible light beam. Both types of data will be transmitted using a single data packet. At the receiving end, a receiver circuit consisting of a high-speed PIN photodetector and a demodulation circuit is employed to demodulate the data from the visible light beam. The demodulated data is then serially transmitted to a personal computer where the biomedical signal, patient information and heart rate can be monitored in real-time.

  20. 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.

  1. Facile synthesis and visible-light photocatalytic activity of bismuth titanate nanorods

    Science.gov (United States)

    Hou, Jungang; Jiao, Shuqiang; Zhu, Hongmin; Kumar, R. V.

    2011-10-01

    Highly crystalline bismuth titanate (Bi12TiO20, BiT) nanorods, as visible-light photocatalysts were prepared by a template-free hydrothermal process. The as-prepared BiT nanorods fabricated in high yields by simply manipulating pH values in the absence of any capping agent, were characterized by a number of techniques, such as XRD, SEM, TEM, HRTEM, BET, and UV-Vis spectrum. In this case, hydroxide ions seem to play a pivotal role in controlling the formation of seeds and the growth of the BiT nanorods. Based on the structural analysis of nanocrystals obtained at different pH values, we proposed a plausible mechanism to account for the formation of the tunable morphologies. Most importantly, the BiT nanorods with good stability exhibited higher photocatalytic activities in the degradation of Rhodamine B under visible light irradiation (λ ≥ 420 nm) than the commercial P25 TiO2 and bulk BiT powders, demonstrating that Bi12TiO20 is a promising candidate as a visible-light photocatalyst.

  2. A versatile, fast, and efficient method of visible-light-induced surface grafting polymerization.

    Science.gov (United States)

    Xiong, Xinhong; Liu, Wei; Luan, Yafei; Du, Jun; Wu, Zhaoqiang; Chen, Hong

    2014-05-20

    To overcome the problem caused by the lability of the Au-S bond, we demonstrate the first use of Mn2(CO)10 for visible-light-induced surface grafting polymerization on Au surfaces in this paper. The visible-light-induced surface grafting of poly(N-isopropylacrylamide) (PNIPAAm) has the features of a "controlled" polymerization, which is characterized by a linear relationship between the thickness of the grafting layer and the monomer concentration. Ellipsometry indicated the formation of PNIPAAm films of up to ∼200 nm in thickness after only 10 min of polymerization at room temperature, demonstrating that this is a very fast process in comparison with traditional grafting polymerization techniques. Moreover, to demonstrate the potential applications of our approach, different substrates grafted by PNIPAAm and the covalent immobilization of a range of polymers on Au surfaces were also demonstrated. Considering the advantages of simplicity, efficiency, and mild reaction conditions as well as the ability of catecholic derivatives to bind to a large variety of substrates, this visible-light-induced grafting method is expected to be useful in designing functional interfaces.

  3. Visible-Light Photocatalysis: Does it make a difference in Organic Synthesis?

    Science.gov (United States)

    Marzo, Leyre; Pagire, Santhosh K; Reiser, Oliver; König, Burkhard

    2018-02-19

    Visible light photocatalysis has evolved over the last decade into a widely used method in organic synthesis. For many important transformations, such as cross-coupling reactions, alpha-amino functionalizations, cycloadditions, ATRA reactions, or fluorinations, photocatalytic variants have been reported. In this review, we try to compare classical and photocatalytic procedures for selected classes of reactions and highlight their advantages and limitations. In many cases, the photocatalytic reactions proceed at milder reaction conditions, typically at room temperature, and stoichiometric reagents are replaced by simple oxidants or reductants, like air oxygen or amines. This way, besides providing alternative protocols for established transformations that allow a broadening of the substrate scope, also new transformations become possible, especially by merging photocatalysis with organo- or metal catalysis. Does visible light photocatalysis make a difference in organic synthesis? The prospect to shuttle electrons back and forth to substrates and intermediates or to selectively transfer energy through a visible light absorbing photocatalyst holds the promise to improve current protocols in radical chemistry and to open up new avenues by accessing reactive species hitherto unknown. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Visible-Light-Driven Photocatalytic Degradation of Organic Water Pollutants Promoted by Sulfite Addition.

    Science.gov (United States)

    Deng, Wei; Zhao, Huilei; Pan, Fuping; Feng, Xuhui; Jung, Bahngmi; Abdel-Wahab, Ahmed; Batchelor, Bill; Li, Ying

    2017-11-21

    Solar-driven heterogeneous photocatalysis has been widely studied as a promising technique for degradation of organic pollutants in wastewater. Herein, we have developed a sulfite-enhanced visible-light-driven photodegradation process using BiOBr/methyl orange (MO) as the model photocatalyst/pollutant system. We found that the degradation rate of MO was greatly enhanced by sulfite, and the enhancement increased with the concentration of sulfite. The degradation rate constant was improved by 29 times in the presence of 20 mM sulfite. Studies using hole scavengers suggest that sulfite radicals generated by the reactions of sulfite (sulfite anions or bisulfite anions) with holes or hydroxyl radicals are the active species for MO photodegradation using BiOBr under visible light. In addition to the BiOBr/MO system, the sulfite-assisted photocatalysis approach has been successfully demonstrated in BiOBr/rhodamine B (RhB), BiOBr/phenol, BiOI/MO, and Bi 2 O 3 /MO systems under visible light irradiation, as well as in TiO 2 /MO system under simulated sunlight irradiation. The developed method implies the potential of introducing external active species to improve photodegradation of organic pollutants and the beneficial use of air pollutants for the removal of water pollutants since sulfite is a waste from flue gas desulfurization process.

  5. 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.

  6. 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.

  7. Preparation and visible-light photocatalytic performances of cyclized polyacrylonitrile/TiO2 nanocomposites

    Directory of Open Access Journals (Sweden)

    Xiaojing WANG

    2015-10-01

    Full Text Available TiO2 nanomaterials were prepared by a conventional sol-gel method with tetrabutyl titanate as Ti source. The polyacrylonitrile solution with dimethyl sulfoxide as solvent was added into TiO2 sols to form TiO2 gels containing polyacrylonitrile, then the as-prepared TiO2 gels were heat-treated to prepare cyclized polyacrylonitrile/TiO2 (CPAN/TiO2 nanocomposites. The CPAN/TiO2 nanocomposites were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, UV-vis diffuse reflection spectroscopy (DRS and photoluminescence spectroscopy (PL. The visible-light photocatalytic performances of CPAN/TiO2 nanocomposites were investigated by evaluating the decomposition of methyl orange. The results reveal CPAN/TiO2 nanocomposites exhibit excellent visible-light photocatalytic acitivity and stability, and show the highest visible-light photocatalytic activity when the mass ratio of CPAN to TiO2, heat-treatment temperature and time are 1∶300, 270 ℃ and 1 h, respectively.

  8. Conjugated Microporous Polymer Nanosheets for Overall Water Splitting Using Visible Light.

    Science.gov (United States)

    Wang, Lei; Wan, Yangyang; Ding, Yanjun; Wu, Sikai; Zhang, Ying; Zhang, Xinlei; Zhang, Guoqing; Xiong, Yujie; Wu, Xiaojun; Yang, Jinlong; Xu, Hangxun

    2017-10-01

    Direct water splitting into H2 and O2 using photocatalysts by harnessing sunlight is very appealing to produce storable chemical fuels. Conjugated polymers, which have tunable molecular structures and optoelectronic properties, are promising alternatives to inorganic semiconductors for water splitting. Unfortunately, conjugated polymers that are able to efficiently split pure water under visible light (400 nm) via a four-electron pathway have not been previously reported. This study demonstrates that 1,3-diyne-linked conjugated microporous polymer nanosheets (CMPNs) prepared by oxidative coupling of terminal alkynes such as 1,3,5-tris-(4-ethynylphenyl)-benzene (TEPB) and 1,3,5-triethynylbenzene (TEB) can act as highly efficient photocatalysts for splitting pure water (pH ≈ 7) into stoichiometric amounts of H2 and O2 under visible light. The apparent quantum efficiencies at 420 nm are 10.3% and 7.6% for CMPNs synthesized from TEPB and TEB, respectively; the measured solar-to-hydrogen conversion efficiency using the full solar spectrum can reach 0.6%, surpassing photosynthetic plants in converting solar energy to biomass (globally average ≈0.10%). First-principles calculations reveal that photocatalytic H2 and O2 evolution reactions are energetically feasible for CMPNs under visible light irradiation. The findings suggest that organic polymers hold great potential for stable and scalable solar-fuel generation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. 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.

  10. Person Recognition System Based on a Combination of Body Images from Visible Light and Thermal Cameras

    Science.gov (United States)

    Nguyen, Dat Tien; Hong, Hyung Gil; Kim, Ki Wan; Park, Kang Ryoung

    2017-01-01

    The human body contains identity information that can be used for the person recognition (verification/recognition) problem. In this paper, we propose a person recognition method using the information extracted from body images. Our research is novel in the following three ways compared to previous studies. First, we use the images of human body for recognizing individuals. To overcome the limitations of previous studies on body-based person recognition that use only visible light images for recognition, we use human body images captured by two different kinds of camera, including a visible light camera and a thermal camera. The use of two different kinds of body image helps us to reduce the effects of noise, background, and variation in the appearance of a human body. Second, we apply a state-of-the art method, called convolutional neural network (CNN) among various available methods, for image features extraction in order to overcome the limitations of traditional hand-designed image feature extraction methods. Finally, with the extracted image features from body images, the recognition task is performed by measuring the distance between the input and enrolled samples. The experimental results show that the proposed method is efficient for enhancing recognition accuracy compared to systems that use only visible light or thermal images of the human body. PMID:28300783

  11. Mechanical properties and failure analysis of visible light crosslinked alginate-based tissue sealants.

    Science.gov (United States)

    Charron, Patrick N; Fenn, Spencer L; Poniz, Alex; Oldinski, Rachael A

    2016-06-01

    Moderate to weak mechanical properties limit the use of naturally-derived tissue sealants for dynamic medical applications, e.g., sealing a lung leak. To overcome these limitations, we developed visible-light crosslinked alginate-based hydrogels, as either non-adhesive methacrylated alginate (Alg-MA) hydrogel controls, or oxidized Alg-MA (Alg-MA-Ox) tissue adhesive tissue sealants, which form covalent bonds with extracellular matrix (ECM) proteins. Our study investigated the potential for visible-light crosslinked Alg-MA-Ox hydrogels to serve as effective surgical tissue sealants for dynamic in vivo systems. The Alg-MA-Ox hydrogels were designed to be an injectable system, curable in situ. Burst pressure experiments were conducted on a custom-fabricated burst pressure device using constant air flow; burst pressure properties and adhesion characteristics correlated with the degrees of methacrylation and oxidation. In summary, visible light crosslinked Alg-MA-Ox hydrogel tissue sealants form effective seals over critically-sized defects, and maintain pressures up to 50mm Hg. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. 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.

  13. 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.

  14. 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.

  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. 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.

  17. 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.

  18. The Influence of Visible Light on the Sulfhydryl Content of Yeast Cells After Ionizing and Ultraviolet Irradiation

    Science.gov (United States)

    1951-12-15

    u„ Report No. 72 AMRt Project No. 6 -59-08-013 -S-4 MEDEA 15 December 1951 ABSTRACT // THE INFLUENCE OF VISIBLE LIGHT ON THE SULFHYDRYL...effect of visible light on ultraviolet irradiated cells) has shed new light on the complexities of the irradiation phenomena, but the under- lying...136, 1943. Vi 4. Lea, D. E. Actions of radiations onliving cells * New York, ’ Macmillan, 1947. 5. Keiner, A. Photore activation of

  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. 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.

  1. Graphene–Ag/ZnO nanocomposites as high performance photocatalysts under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, M., E-mail: mzkhm73@gmail.com [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Ahmed, E. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Hong, Z.L., E-mail: hong_zhanglian@zju.edu.cn [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Khalid, N.R. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Ahmed, W.; Elhissi, A. [Institute of Nanotechnology and Bioengineering, University of Central Lancashire, School of Medicine and Dentistry, Preston PR1 2HE (United Kingdom)

    2013-11-15

    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

  2. Visible light-harvesting photoanodes for solar energy conversion: A comparison of anchoring groups to titanium dioxide

    Science.gov (United States)

    Martini, Lauren A.

    Environmental concerns related to climate change and geopolitical issues related to energy security have led to a widespread pursuit of alternative, non-fossil fuel energy sources capable of meeting our increasing global energy demands. Solar energy, which strikes the earth's surface at a rate vastly exceeding our current worldwide power demand, presents itself as a promising source of clean, abundant and renewable energy. The capture and conversion of solar energy into electricity as well as storable, transportable chemical fuels has therefore become major area of chemical research. Inspired by photosynthesis in nature, in which plants and algae convert sunlight, water, and carbon dioxide into oxygen and stored chemical fuel in the form of sugars, recent work has focused on visible light-driven water-splitting technologies for the production of solar fuels. Honda and Fujishima reported the first example of photoelectrochemical water oxidation in 1972. In their system, an inexpensive titanium dioxide semiconductor irradiated with ultraviolet light produced oxygen at the photoanode surface and hydrogen at the surface of a platinum counter electrode. In attempt to harness visible light instead, titanium dioxide and other inexpensive wide band gap photoanodes have been functionalized with visible light-absorbing molecular dyes. These dye-sensitized photoanodes have been used successfully to convert solar energy into electrical current, as in dye-sensitized solar cells, and to drive chemical processes like water oxidation, as in photocatalytic cells. In both systems, a long-lived charge separation is established upon illumination of the photoanode surface when a photoexcited molecular chromophore transfers an electron to the semiconductor conduction band. Following this electron injection process, a nearby redox-active species is oxidized and refills the hole left behind on the molecular chromophore. While the steps of this scheme are relatively straightforward, the

  3. Facile fabrication of visible light induced Bi2O3 nanorod using conventional heat treatment method

    Science.gov (United States)

    Raza, Waseem; Khan, Azam; Alam, Umair; Muneer, M.; Bahnemann, D.

    2016-03-01

    In this paper, a new Bi2O3 based photocatalyst doped with varying concentration of Nb and Mn metal ion was fabricated by conventional heat treatment method and their photocatalytic activity was investigated. The prepared material was characterized by X-ray diffraction (XRD), UV-Visible Spectroscopy, Fourier transform infrared (FTIR) and Scanning Electron Microscopic (SEM) techniques. The XRD analysis of synthesized photocatalyst was found to exhibit characteristic peaks of well crystallized monoclinic α-Bi2O3. The XRD pattern of pure and metal doped Bi2O3 were found to more or less similar. The crystallite size of doped materials were smaller than pure Bi2O3 and size decreases with increasing dopant concentration from 0.5 to 2.0% for Nb & 1.0-3.0% for Mn and remains almost constant at higher dopant concentration. The SEM analysis clearly indicate the formation of nanorod like morphologies. The UV-Vis absorption spectra of synthesized nanorods revealed that the absorption edge shift towards longer wavelength on doping with Nb and Mn metal ions which is beneficial for absorbing more visible light in the solar spectrum. The prepared doped Bi2O3 nanorod showed the excellent photocatalytic activity for degradation of selected organic pollutants, such as Methylene Blue (MB) and Rodaamime B (RhB) under visible light source. The higher activity of doped Bi2O3 nanorod may be attributed to absorption of more visible light leading to generation of higher photogenerated electron hole pairs and efficient separation of photoinduced charge carrier to inhibit the recombination rate.

  4. 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.

  5. Visible-light photoredox-catalyzed desulfurization of thiol- and disulfide-containing amino acids and small peptides.

    Science.gov (United States)

    Lee, Myungmo; Neukirchen, Saskia; Cabrele, Chiara; Reiser, Oliver

    2017-07-01

    A scalable protocol for the desulfurization of cysteine by using visible light, the photocatalyst Ir(dF(CF3 )ppy)2 (dtb-bpy)PF6 and triethylphosphite under biphasic reaction conditions has been developed. The loading of the catalyst can be as low as 0.01 mol%, which can be efficiently removed during the workup (≤0.3 ppm), giving rise to the corresponding desulfurized product in high yields. This method has been applied also to cystine, penicillamine, and reduced and oxidized glutathione. The desulfurization has been found to be pH sensitive, with an optimal pH value of 6.5 and 7.0 for the cysteine derivatives and glutathione, respectively. In addition, during the desulfurization of a decapeptide containing cysteine and methionine, concurrent oxidation of the two sulfur-containing residues to disulfide and sulfoxide has been observed. Therefore, whereas the presented protocol allows a straightforward visible light-mediated desulfurization of simple thiols by using very low catalyst loading and a cost-effective trialkylphosphite as thiyl radical trapping agent, its application to complex substrates needs to be carefully validated. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

  6. 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.

  7. Photocatalytic activity of polymer-modified ZnO under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Qiu Rongliang [School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)], E-mail: eesqrl@mail.sysu.edu.cn; Zhang Dongdong [School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Mo Yueqi [College of Material Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Song Lin [School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Department of Environmental Engineering, Jinan University, Guangzhou 510630 (China); Brewer, Eric [Viridian Environmental, LLC, Arlington, VA 22207 (United States); Huang Xiongfei; Xiong Ya [School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2008-08-15

    Photocatalytic removal of phenol, rhodamine B, and methyl orange was studied using the photocatalyst ZnO/poly-(fluorene-co-thiophene) (PFT) under visible light. After 2 h irradiation with three 1 W LED (light-emitting diode) lights, about 40% removal of both phenol and methyl orange was achieved; rhodamine B was completely degraded to rhodamine. Diffuse reflectance spectra showed that the absorbance range of PFT/ZnO was expanded from 387 nm (ZnO) to about 500 nm. Photoluminescent spectra and photoluminescent quantum efficiency indicated that electrons were transferred from PFT to the conduction band of ZnO. Electron spin resonance (ESR) signals of spin-trapped paramagnetic species with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) evidenced that the OH{center_dot} radicals were indeed formed in the PFT/ZnO system under visible light irradiation. A working mechanism involving excitation of PFT, followed by charge injection into the ZnO conduction band is proposed.

  8. 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.

  9. 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.

  10. Going beyond 4 Gbps data rate by employing RGB laser diodes for visible light communication.

    Science.gov (United States)

    Janjua, Bilal; Oubei, Hassan M; Durán Retamal, Jose R; Ng, Tien Khee; Tsai, Cheng-Ting; Wang, Huai-Yung; Chi, Yu-Chieh; Kuo, Hao-Chung; Lin, Gong-Ru; He, Jr-Hau; Ooi, Boon S

    2015-07-13

    With increasing interest in visible light communication, the laser diode (LD) provides an attractive alternative, with higher efficiency, shorter linewidth and larger bandwidth for high-speed visible light communication (VLC). Previously, more than 3 Gbps data rate was demonstrated using LED. By using LDs and spectral-efficient orthogonal frequency division multiplexing encoding scheme, significantly higher data rates has been achieved in this work. Using 16-QAM modulation scheme, in conjunction with red, blue and green LDs, data rates of 4.4 Gbps, 4 Gbps and 4 Gbps, with the corresponding BER/SNR/EVM of 3.3 × 10⁻³/15.3/17.9, 1.4 × 10⁻³/16.3/15.4 and 2.8 × 10⁻³/15.5/16.7were obtained over transmission distance of ~20 cm. We also simultaneously demonstrated white light emission using red, blue and green LDs, after passing through a commercially available diffuser element. Our work highlighted that a tradeoff exists in operating the blue LDs at optimum bias condition while maintaining good color temperature. The best results were obtained when encoding red LDs which gave both the strongest received signal amplitude and white light with CCT value of 5835K.

  11. Visible emission from bismuth-doped yttrium oxide thin films for lighting and display applications.

    Science.gov (United States)

    Scarangella, Adriana; Fabbri, Filippo; Reitano, Riccardo; Rossi, Francesca; Priolo, Francesco; Miritello, Maria

    2017-12-11

    Due to the great development of light sources for several applications from displays to lighting, great efforts are devoted to find stable and efficient visible emitting materials. Moreover, the requirement of Si compatibility could enlarge the range of applications inside microelectronic chips. In this scenario, we have studied the emission properties of bismuth doped yttrium oxide thin films grown on crystalline silicon. Under optical pumping at room temperature a stable and strong visible luminescence has been observed. In particular, by the involvement of Bi ions in the two available lattice sites, the emission can be tuned from violet to green by changing the excitation wavelength. Moreover, under electron beam at low accelerating voltages (3 keV) a blue emission with high efficiency and excellent stability has been recorded. The color is generated by the involvement of Bi ions in both the lattice sites. These peculiarities make this material interesting as a luminescent medium for applications in light emitting devices and field emission displays by opening new perspectives for the realization of silicon-technology compatible light sources operating at room temperature.

  12. Switching Thin Films of Azobenzene-Containing Metal-Organic Frameworks with Visible Light.

    Science.gov (United States)

    Müller, Kai; Knebel, Alexander; Zhao, Fangli; Bléger, David; Caro, Jürgen; Heinke, Lars

    2017-04-24

    Stimuli-responsive molecules change their properties when exposed to external signals, such as light, and enable the preparation of smart materials. UV light, which often destroys organic materials, is typically required for activating the desired response of photoswitchable compounds, significantly limiting the potential applications of light-operated smart materials. Herein, we present the first metal-organic framework (MOF), which enables reversible modulation of key properties upon irradiation with visible light only. The fluorinated azobenzene side groups in the MOF structure can be reversibly switched between the trans and cis state by green and violet light, avoiding UV light. It was demonstrated that the uptake of guest molecules by these MOF films can be switched in a fully remote-controlled way. The membrane separation of hydrogen/hydrocarbon mixtures was investigated. The light-induced changes of the MOF pore size result in the switching of the permeation and of the selection factor. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. 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.

  14. Novel GQD-PVP-CdS composite with enhanced visible-light-driven photocatalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Tao; Li, Yinle; Shen, Jianfeng, E-mail: jfshen@fudan.edu.cn; Ye, Mingxin, E-mail: mxye@fudan.edu.cn

    2016-03-30

    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{sub 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.

  15. Highly efficient photocatalytic hydrogen evolution of graphene/YInO3 nanocomposites under visible light irradiation.

    Science.gov (United States)

    Ding, Jianjun; Yan, Wenhao; Xie, Wei; Sun, Song; Bao, Jun; Gao, Chen

    2014-02-21

    Visible-light-driven hydrogen evolution with high efficiency is important in the current photocatalysis research. Here we report for the first time the design and synthesis of a new graphene-semiconductor nanocomposite consisting of YInO3 nanoparticles and two-dimensional graphene sheets as efficient photocatalysts for hydrogen evolution under visible light irradiation. The graphene/YInO3 nanocomposites were synthesized using a facile solvothermal method in which the formation of graphene and the deposition of YInO3 nanoparticles on the graphene sheets can be achieved simultaneously. The addition of graphene as a cocatalyst can narrow the band gap of YInO3 to visible photon energy and prolong the separation and lifetime of electron-hole pairs by the chemical bonding between YInO3 and graphene. The photocatalytic reaction with this nanocomposite reaches a high H2 evolution rate of 400.4 μmol h(-1) g(-1) when the content of graphene is 0.5 wt%, over 127 and 3.7 times higher than that of pure YInO3 and Pt/YInO3, respectively. This work can provide an effective approach to the fabrication of graphene-based photocatalysts with high performance in the field of energy conversion.

  16. Sulfur/Gadolinium-Codoped TiO2 Nanoparticles for Enhanced Visible-Light Photocatalytic Performance

    Directory of Open Access Journals (Sweden)

    Eric S. Agorku

    2014-01-01

    Full Text Available A series of S/Gd3+-codoped TiO2 photocatalysts were synthesized by a modified sol-gel method. The materials were characterized by X-ray diffraction (XRD, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR, UV-visible diffuse reflectance spectroscopy, scanning electron microscopy (SEM/energy-dispersive X-ray spectroscopy (EDX, and transmission electron microscopy (TEM/energy-dispersive spectroscopy (EDS. Laboratory experiments with Indigo Carmine chosen as a model for organic pollutants were used to evaluate the photocatalytic performance of S/Gd3+-codoped TiO2 under visible-light with varying concentrations of Gd3+ ions in the host material. XRD and Raman results confirmed the existence of anatase phase TiO2 with particle size ranging from 5 to 12 nm. Codoping has exerted a great influence on the optical responses along with red shift in the absorption edge. S/Gd3+-codoped TiO2 showed significant visible-light induced photocatalytic activity towards Indigo Carmine dye compared with S-TiO2 or commercial TiO2. TiO2-S/Gd3+ (0.6% Gd3+ degraded the dye (ka = 5.6 × 10−2 min−1 completely in 50 min.

  17. Gold-plasmon enhanced photocatalytic performance of anatase titania nanotubes under visible-light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Bingyang [Key Laboratory of Luminescence and Optical Information, Beijing Jiaotong University, Beijing, 100044 (China); He, Dawei, E-mail: dwhe@bjtu.edu.cn [Key Laboratory of Luminescence and Optical Information, Beijing Jiaotong University, Beijing, 100044 (China); Wang, Wenshuo [Institute of Particle Technology, Friedrich-Alexander University Erlangen-Nuremberg, Cauerstrasse 4, D-91058 Erlangen (Germany); Zhuo, Zuliang; Wang, Yongsheng [Key Laboratory of Luminescence and Optical Information, Beijing Jiaotong University, Beijing, 100044 (China)

    2016-02-15

    Highlights: • APTMS/(TNTs-Au) was synthesized using a deposition-precipitation process. • APTMS/(TNTs-Au) showed superior visible light activity for the degradation of methylene blue. • The electromagnetic field distribution at the interface between TNTs and Au NPs were estimated by the 3D finite-difference time domain simulation. • The working mechanism of the photocatalytic activity of APTMS/(TNTs-Au) was illustrated. - Abstract: [3-Aminopropyl]trimethoxysilane-modified titania nanotubes decorated with Au nanoparticles (APTMS/(TNTs-Au)) nanocomposites were synthesized using a deposition-precipitation process. The results showed that Au nanoparticles (NPs) in the metallic state were firmly adhered to the surface of the anatase TNTs. APTMS/(TNTs-Au) exhibited great photocatalytic activities which were evaluated from the degradation rate of methylene blue aqueous solution under visible light irradiation. 3D finite-difference time domain simulation was performed to estimate the electromagnetic field distribution at the interface between TNTs and Au NPs. The visible photocatalytic activity of APTMS/(TNTs-Au) was largely attributed to the surface plasmon absorption of metallic Au NPs, which generated and transferred hot electrons to the CB of TNTs. In addition, the hot electrons on the surface of TNTs also suppressed the radiative electron–hole recombination and consequently enhanced the photocatalytic activity.

  18. Facile synthesis of CuS nanostructured flowers and their visible light photocatalytic properties

    Science.gov (United States)

    Wu, Huijie; Li, Yuan; Li, Qing

    2017-03-01

    Uniform CuS nanostructured flowers have been generated conveniently in aqueous solution without using any surfactant. The products were characterized by XRD, XPS, EDX, FESEM, TEM, UV-Vis, PL, and BET techniques. The as-prepared CuS nanostructured flowers have a diameter of about 800-1200 nm and are in high yield. The flowers were formed by the assembly of numerous nanosheets. A tentative explanation for the growth mechanism of CuS nanostructured flowers was proposed. UV-Vis absorption spectrum and PL spectrum were used to investigate the optical properties of CuS nanostructured flowers. UV-Vis absorption spectrum shows a broad absorption band in the visible range and PL spectrum shows a strong ultraviolet emission peak. The BET surface area of the as-prepared product was determined to be 61.55 m2/g with a dominant pore diameter of 26 nm. The photocatalytic activity was evaluated by measuring the decomposition rate of methylene blue aqueous solution under visible light irradiation and results indicated that the as-prepared CuS nanostructured flowers exhibit enhanced visible light photocatalytic activity with the assistence of H2O2.

  19. Electrochemical deposition of copper decorated titania nanotubes and its visible light photocatalytic performance

    Science.gov (United States)

    Lim, Y. C.; Siti, A. S.; Nur Amiera, P.; Devagi, K.; Lim, Y. P.

    2017-09-01

    Coupling of titania with narrow band gap materials has been a promising strategy in preparing visible light responsive photocatalyst. In this work, self-organized copper decorated TiO2 nanotube (Cu/TNT) was prepared via electrodeposition of Cu onto highly ordered titania nanotube arrays (TNT). The catalysts were characterized by X-ray diffraction, diffuse reflectance spectroscopy (DRS), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). The DRS studies clearly show the extended absorption of Cu/TNT into the visible region and present a red shift of band gap to 2.1 eV. FESEM analysis has shown the dispersion of cubic-like Cu particles upon electrodeposition and EDX analysis supports the presence of copper species on the nanotubes surface. The photocatalytic ability of Cu/TNT was evaluated by the degradation of methyl orange from aqueous solution under low power visible light illumination. Compared to TNT, an appreciable improvement in methyl orange removal was observed for Cu/TNT and the highest removal efficiency of 80% was achieved. The effects of catalyst loading and samples repeatability were investigated and under optimum conditions, the removal efficiency of methyl orange over Cu/TNT had further increased to 93.4%. This work has demonstrated a feasible and simple way to introduce narrow band gap transition metal into nanotube arrays, which could create novel properties for functionalized nanotube arrays as well as promise a wide range of applications.

  20. 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.

  1. Wide-angle and high-efficiency achromatic metasurfaces for visible light

    CERN Document Server

    Deng, Zi-Lan; Wang, Guo Ping

    2016-01-01

    Recently, an achromatic metasurface was successfully demonstrated to deflect light of multiple wavelengths in the same direction and it was further applied to the design of planar lenses without chromatic aberrations [Science, 347, 1342(2015)]. However, such metasurface can only work for normal incidence and exhibit low conversion efficiency. Here, we present an ultrawide-angle and high-efficiency metasurface without chromatic aberration for wavefront shaping in visible range. The metasurface is constructed by multiple metallic nano-groove gratings, which support enhanced diffractions for an ultrawide incident angle range from 10o to 80o due to the excitations of localized gap plasmon modes at different resonance wavelengths. Incident light at these resonance wavelengths can be efficiently diffracted into the same direction with complete suppression of the specular reflection. This approach is applied to the design of an achromatic flat lens for focusing light of different wavelengths into the same position. ...

  2. Design of optical transmitting antenna with enhance performance in visible light communication

    Science.gov (United States)

    Kuang, Dang; Wang, Jianping; Lu, Huimin

    2016-10-01

    An optical transmitting antenna for visible light communication(VLC) is designed in this work, in which the antenna is positioned before the light-emitting diodes (LED) source to change the lighting distribution, in order to achieve uniform received power effect. The method to design antenna is introduced into physical optical lens principle. According to the energy conservation law and Snell law, the antenna is designed via establishing energy mapping between the luminous flux emitted by a LED source with Lambertian distribution and the target plane. The coordinates of the antenna model are obtained under matrix laboratory (MATLAB). The antenna model entity is generated through three dimensional (3D) composition software AutoCAD with the coordinates of antenna. Ray-tracing software Tracepro is used to trace the ray which through antenna, and validate the irradiance maps. The uniformity of illumination and received power of the designed VLC is improved from approximately 35% to over 83%.

  3. 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.

  4. Switchable sensitizers stepwise lighting up lanthanide emissions

    Science.gov (United States)

    Zhang, Yan; Jiao, Peng-Chong; Xu, Hai-Bing; Tang, Ming-Jing; Yang, Xiao-Ping; Huang, Shaoming; Deng, Jian-Guo

    2015-01-01

    Analagous to a long-ranged rocket equipped with multi-stage engines, a luminescent compound with consistent emission signals across a large range of concentrations from two stages of sensitizers can be designed. In this approach, ACQ, aggregation-caused quenching effect of sensitizers, would stimulate lanthanide emission below 10−4 M, and then at concentrations higher than 10−3 M, the “aggregation-induced emission” (AIE) effect of luminophores would be activated with the next set of sensitizers for lanthanide emission. Simultaneously, the concentration of the molecules could be monitored digitally by the maximal excitation wavelengths, due to the good linear relationship between the maximal excitation wavelengths and the concentrations {lg(M)}. This model, wherein molecules are assembled with two stages (both AIE and ACQ effect) of sensitizers, may provide a practicable strategy for design and construction of smart lanthanide bioprobes, which are suitable in complicated bioassay systems in which concentration is variable. PMID:25791467

  5. Visible light crosslinking of methacrylated hyaluronan hydrogels for injectable tissue repair.

    Science.gov (United States)

    Fenn, Spencer L; Oldinski, Rachael A

    2016-08-01

    Tissue engineering hydrogels are primarily cured in situ using ultraviolet (UV) radiation which limits the use of hydrogels as drug or cell carriers. Visible green light activated crosslinking systems are presented as a safe alternative to UV photocrosslinked hydrogels, without compromising material properties such as viscosity and stiffness. The objective of this study was to fabricate and characterize photocrosslinked hydrogels with well-regulated gelation kinetics and mechanical properties for the repair or replacement of soft tissue. An anhydrous methacrylation of hyaluronan (HA) was performed to control the degree of modification (DOM) of HA, verified by (1) H-NMR spectroscopy. UV-activated crosslinking was compared to visible green light activated crosslinking. While the different photocrosslinking techniques resulted in varied crosslinking times, comparable mechanical properties of UV and green light activated crosslinked hydrogels were achieved using each photocrosslinking method by adjusting time of light exposure. Methacrylated HA (HA-MA) hydrogels of varying molecular weight, DOM, and concentration exhibited compressive moduli ranging from 1 kPa to 116 kPa, for UV crosslinking, and 3 kPa to 146 kPa, for green light crosslinking. HA-MA molecular weight and concentration were found to significantly influence moduli values. HA-MA hydrogels did not exhibit any significant cytotoxic effects toward human mesenchymal stem cells. Green light activated crosslinking systems are presented as a viable method to form natural-based hydrogels in situ. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1229-1236, 2016. © 2015 Wiley Periodicals, Inc.

  6. Charge-coupled device /CCD/ visible light sensor for the Teal Ruby Experiment

    Science.gov (United States)

    Roberts, A.

    The Teal Ruby Experiment (TRE), employing a Space-Shuttle-launched infrared telescope, will mark a major milestone in the application of mosaic infrared detectors in space. However, it is generally recognized that supplemental overview imagery acquired in the visible portion of the spectrum is necessary to assist in accurately interpreting the data generated by the infrared focal plane. For this purpose, the TRE will be equipped with a Charge Coupled Device (CCD) Visible Light Sensor (VLS) that will yield the cloud and ground truth data needed to assist in pointing and scene verification. The optical format of the VLS is designed to overlay the TRE footprint on the earth from a distance of 1000 nautical miles. The VLS is designed, built and will be qualified to meet the environmental and reliability requirements for an on-orbit mission in excess of one year. The TRE/VLS is tentatively scheduled for launch in mid 1983.

  7. Visible light photoactivity of Polypropylene coated Nano-TiO2 for dyes degradation in water

    Science.gov (United States)

    Giovannetti, R.; Amato, C. A. D’; Zannotti, M.; Rommozzi, E.; Gunnella, R.; Minicucci, M.; Di Cicco, A.

    2015-01-01

    The use of Polypropylene as support material for nano-TiO2 photocatalyst in the photodegradation of Alizarin Red S in water solutions under the action of visible light was investigated. The optimization of TiO2 pastes preparation using two commercial TiO2, Aeroxide P-25 and Anatase, was performed and a green low-cost dip-coating procedure was developed. Scanning electron microscopy, Atomic Force Microscopy and X-Ray Diffraction analysis were used in order to obtain morphological and structural information of as-prepared TiO2 on support material. Equilibrium and kinetics aspects in the adsorption and successive photodegradation of Alizarin Red S, as reference dye, are described using polypropylene-TiO2 films in the Visible/TiO2/water reactor showing efficient dyes degradation. PMID:26627118

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

    Science.gov (United States)

    2017-11-01

    sent from light-emitting diodes (LEDs) of 5 colors (green, red, white , amber, and blue). Experiment 1 involved controlled laboratory measurements of...for operation at 12 VDC. Specifications for colored and white LEDs are in Table 1. * A picture of...520 nm Blue 15 mA 1000 mcd 465 nm White LED specifications Color Current draw Output Effective color temperature Cool white 20 mA 4100 mcd 6000 K

  9. 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

  10. 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.

  11. 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

    2012-01-01

    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. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. 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

    2018-01-18

    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 TiO2 (PDs-TiO2) nanohybrids with TiOC bonds were prepared by a facile in-situ hydrothermal treatment of PDs and Ti (SO4)2. Under visible light irradiation, the PDs-TiO2 demonstrate excellent photocatalytic activity for methyl orange degradation, and the photocatalytic rate constant of PDs-TiO2 is 3.6 and 9.5 times higher than that of pure TiO2 and commercial P25, respectively. In addition, the PDs-TiO2 exhibit good recycle stability under UV-Vis light irradiation. The interfacial TiOC bonds and the π-conjugated structures in PDs-TiO2 can act as the pathways to quickly transfer the excited electrons between PDs and TiO2, therefore contribute to the excellent photocatalytic activity. Copyright © 2018 Elsevier Ltd. All rights reserved.

  13. Degradation of gaseous formaldehyde via visible light photocatalysis using multi-element doped titania nanoparticles.

    Science.gov (United States)

    Laciste, Maricris T; de Luna, Mark Daniel G; Tolosa, Nolan C; Lu, Ming-Chun

    2017-09-01

    This study developed a modified titanium dioxide photocatalyst doped with multi-element synthesized via sol-gel process to productize a novel photocatalyst. The study includes degradation of gaseous formaldehyde under visible light using the synthesized novel titanium dioxide photocatalyst. Varying molar ratios from 0 to 2 percent (% mole in titanium dioxide) of ammonium fluoride, silver nitrate and sodium tungstate as dopant precursors for nitrogen, fluorine, silver and tungsten were used. Photodegradation of gaseous formaldehyde was examined on glass tubular reactors illuminated with blue light emitting diodes (LEDs) using immobilized photocatalyst. The photocatalytic yield is analyzed based on the photocatalyst surface chemical properties via X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) Spectrophotometry, Brunauer-Emmett-Teller (BET) and X-ray Diffraction (XRD) characterization results. The applied modifications enhanced the visible light capability of the catalyst in comparison to the undoped catalyst and commercially available Degussa P-25, such that it photocatalytically degrades 88.1% of formaldehyde in 120 min. Synthesized titanium dioxide photocatalyst exhibits a unique spin orbital at 532.07 eV and 533.27 eV that came from the hybridization of unoccupied Ti d(t 2g ) levels. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Effect of visible laser light on ATP level of anaemic red blood cell.

    Science.gov (United States)

    Suardi, Nursakinah; Sodipo, Bashiru Kayode; Mustafa, Mohd Zulkifli; Ali, Zalila

    2016-09-01

    In this work we present influence of visible laser light on ATP level and viability of anaemic red blood cell (RBC). The visible laser lights used in this work are 460nm and 532nm. The responses of ATP level in anaemic and normal RBC before and after laser irradiation at different exposure time (30, 40, 50 and 60s) were observed. Three aliquots were prepared from the ethylenediaminetetraacetic acid (EDTA) blood sample. One served as a control (untreated) and another two were irradiated with 460nm and 560nm lasers. Packed RBC was prepared to study ATP level in the RBC using CellTiter-GloLuminescent cell Viability Assay kit. The assay generates a glow type signal produced by luciferase reaction, which is proportional to the amount of ATP present in RBCs. Paired t-test were done to analyse ATP level before and after laser irradiation. The results revealed laser irradiation improve level of ATP in anaemic RBC. Effect of laser light on anaemic RBCs were significant over different exposure time for both 460nm (p=0.000) and 532nm (p=0.003). The result of ATP level is further used as marker for RBC viability. The influence of ATP level and viability were studied. Optical densities obtained from the data were used to determine cell viability of the samples. Results showed that laser irradiation increased viability of anaemic RBC compared to normal RBC. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Antibacterial Properties of Visible-Light-Responsive Carbon-Containing Titanium Dioxide Photocatalytic Nanoparticles against Anthrax

    Directory of Open Access Journals (Sweden)

    Der-Shan Sun

    2016-12-01

    Full Text Available The bactericidal activity of conventional titanium dioxide (TiO2 photocatalyst is effective only on irradiation by ultraviolet light, which restricts the applications of TiO2 for use in living environments. Recently, carbon-containing TiO2 nanoparticles [TiO2(C NP] were found to be a visible-light-responsive photocatalyst (VLRP, which displayed significantly enhanced antibacterial properties under visible light illumination. However, whether TiO2(C NPs exert antibacterial properties against Bacillus anthracis remains elusive. Here, we evaluated these VLRP NPs in the reduction of anthrax-induced pathogenesis. Bacteria-killing experiments indicated that a significantly higher proportion (40%–60% of all tested Bacillus species, including B. subtilis, B. cereus, B. thuringiensis, and B. anthracis, were considerably eliminated by TiO2(C NPs. Toxin inactivation analysis further suggested that the TiO2(C NPs efficiently detoxify approximately 90% of tested anthrax lethal toxin, a major virulence factor of anthrax. Notably, macrophage clearance experiments further suggested that, even under suboptimal conditions without considerable bacterial killing, the TiO2(C NP-mediated photocatalysis still exhibited antibacterial properties through the reduction of bacterial resistance against macrophage killing. Our results collectively suggested that TiO2(C NP is a conceptually feasible anti-anthrax material, and the relevant technologies described herein may be useful in the development of new strategies against anthrax.

  16. 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.

  17. Synthesis and Characterization of Cerium Doped Titanium Catalyst for the Degradation of Nitrobenzene Using Visible Light

    Directory of Open Access Journals (Sweden)

    Padmini Ellappan

    2014-01-01

    Full Text Available Cerium doped catalyst was synthesized using Titanium isopropoxide as the Titanium source. The metal doped nanoparticles semiconductor catalyst was prepared by sol-sol method with the sol of Cerium. The synthesized catalyst samples were characterized by powder X-ray diffraction, BET surface area, thermogravimetric analysis (TGA, scanning electron microscopy (SEM, and UV-vis diffuse reflectance measurements (DRS and compared with undoped TiO2 catalyst. The photocatalytic activity of the sample was investigated for the decomposition of nitrobenzene (NB using visible light as the artificial light source. Cerium doped catalyst was found to have better degradation of nitrobenzene owing to its shift in the band gap from UV to visible region as compared to undoped TiO2 catalyst. The operational parameters were optimized with catalyst dosage of 0.1 g L−1, pH of 9, and light intensity of 500 W. The degradation mechanism followed the Langmuir Hinshelwood kinetic model with the rate constant depending nonlinearly on the operational parameters as given by the relationship Kapp (theoretical = 2.29 * 10−4 * Intensity0.584 * Concentration−0.230 * Dosage0.425 * pH0.336.

  18. Visible light emission and energy transfer processes in Sm-doped nitride films

    Science.gov (United States)

    Zanatta, A. R.

    2012-06-01

    Even though the great interest in studying the near-infrared light emission due to Er3+ ions for telecommunication purposes, efficient visible radiation can be achieved from many different rare-earth (RE) ions. In fact, visible and/or near-infrared light emission takes place in RE-doped wide bandgap semiconductors following either photon or electron excitation, suggesting their technological potential in devices such as light-emitting diodes (LED's) and flat-panel displays, for example. Taking into consideration these aspects, the present contribution reports on the investigation of AlN, BeN, GeN, and SiN thin films doped with samarium. The samples were prepared by sputtering and as a result of the deposition method and conditions they present an amorphous structure and Sm concentrations in the low 0.5 at. %. After deposition, the samples were submitted to thermal annealing treatments and investigated by different spectroscopic techniques. A detailed examination of the experimental data allowed to identify optical transitions due to Sm3+ and Sm2+ ions as well as differences in their mechanisms of photon excitation and recombination. Moreover, it is shown that the Sm-related spectral features and emission intensity are susceptible, respectively, to the atomic environment the Sm3+/Sm2+ ions experience and to the presence of non-radiative recombination centers.

  19. 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

  20. 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....

  1. 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.

  2. Antimicrobial materials for water disinfection based on visible-light photocatalysts

    Science.gov (United States)

    Wu, Pinggui

    Since the discovery of photocatalytic water-splitting on TiO2 in 1972, enormous effort has been devoted to the study of TiO2. Since the optical properties of TiO2 and e--h + recombination are essential to the photon-driven applications, these two areas have drawn tremendous research attention in the past few years. But there is no single optimal system to date that has visible-light activity, high photo-efficiency and easy recovery. In this study, chemical co-doping approach was adopted to achieve desirable properties of TiO2-based photocatalyst. Nitrogen and metal ions selected from the transition metal or the rare earth element group were incorporated into TiO2 to induce a red-shift to the visible-light absorption regime and to enhance photocatalytic activity. The anion and cation co-doped TiO2 was made into various forms, including thin film, fiber, and foam that circumvent the problems associated with catalyst recovery. Chemical composition, structure, microstructure, optical, and photocatalytic properties were investigated to characterize each type of the materials. Electronic structure calculation and electron paramagnetic resonance spectroscopy were conducted to understand the role of nitrogen and metal ions. The photocatalytic property of these visible-light-active photocatalysts were studied in the inactivation of bacteria and bacterial spores in water. Fast killing rate was obtained for the inactivation of E. coli, P. aeruginosa, S. aureus and B. subtilis endospores. The results of mechanistic study provided evidence of oxidative damages, and indicated that hydroxyl radicals are one of the key killing species. Atomic force microscopy and electron microscopy showed that the cell walls were attacked by photocatalytic inactivation. The potential application of the photocatalyst in water disinfection was demonstrated by flow-through tests.

  3. 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.

    2015-08-01

    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%).

  4. 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.

  5. 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.

  6. 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.

  7. Visible-Light-Driven Photocatalytic Activation of Inert Sulfur Ylides for 3-Acyl Oxindole Synthesis.

    Science.gov (United States)

    Xia, Xu-Dong; Lu, Liang-Qiu; Liu, Wen-Qiang; Chen, Dong-Zhen; Zheng, Yu-Han; Wu, Li-Zhu; Xiao, Wen-Jing

    2016-06-13

    Bicarbonyl-substituted sulfur ylide is a useful, but inert reagent in organic synthesis. Usually, harsh reaction conditions are required for its transformation. For the first time, it was demonstrated that a new, visible-light photoredox catalytic annulation of sulfur ylides under extremely mild conditions, permits the synthesis of oxindole derivatives in high selectivities and efficiencies. The key to its success is the photocatalytic single-electron-transfer (SET) oxidation of the inert amide and acyl-stabilized sulfur ylides to reactive radical cations, which easily proceeds with intramolecular C-H functionalization to give the final products. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. 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.

  9. Photocatalytic Degradation of Isopropanol Over PbSnO3Nanostructures Under Visible Light Irradiation

    Science.gov (United States)

    2009-01-01

    Nanostructured PbSnO3photocatalysts with particulate and tubular morphologies have been synthesized from a simple hydrothermal process. As-prepared samples were characterized by X-ray diffraction, Brunauer–Emmet–Teller surface area, transmission electron microscopy, and diffraction spectroscopy. The photoactivities of the PbSnO3nanostructures for isopropanol (IPA) degradation under visible light irradiation were investigated systematically, and the results revealed that these nanostructures show much higher photocatalytic properties than bulk PbSnO3material. The possible growth mechanism of tubular PbSnO3catalyst was also investigated briefly. PMID:20596379

  10. 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.

  11. Oxygen vacancies and intense luminescence in manganese loaded Zno microflowers for visible light water splitting

    Science.gov (United States)

    Sambandam, Balaji; Michael, Robin Jude Vimal; Manoharan, Periakaruppan T.

    2015-08-01

    ZnO nanorods and Mn/ZnO microflowers with nano-sized petals exhibit singly ionized oxygen vacancies, V+O. This is strongly supported by a green photoluminescence emission at 2.22 eV and an EPR g value of 1.953, both of which are suppressed greatly after annealing in an oxygen atmosphere. A strong red emission observed during exposure to X-rays reveals the presence of F+ centres as a consequence of the V+O. Mn/ZnO displayed enhanced H2 generation with visible light exposure, when compared to pure ZnO and annealed Mn/ZnO in the visible region, which directly correlated with the oxygen vacancy concentration. There is an interesting correlation between the intensities of the EPR lines at the g-value of 1.953 due to the oxygen vacancies, the intensity of light emitted from the exposure to X-rays, the intensity of the photoluminescence due to oxygen vacancies and the quantity of H2 produced by the photocatalytic effect when comparing the three different nanomaterials, viz. pure ZnO, Mn/ZnO before and after annealing, all having been made exactly by the same methodologies.ZnO nanorods and Mn/ZnO microflowers with nano-sized petals exhibit singly ionized oxygen vacancies, V+O. This is strongly supported by a green photoluminescence emission at 2.22 eV and an EPR g value of 1.953, both of which are suppressed greatly after annealing in an oxygen atmosphere. A strong red emission observed during exposure to X-rays reveals the presence of F+ centres as a consequence of the V+O. Mn/ZnO displayed enhanced H2 generation with visible light exposure, when compared to pure ZnO and annealed Mn/ZnO in the visible region, which directly correlated with the oxygen vacancy concentration. There is an interesting correlation between the intensities of the EPR lines at the g-value of 1.953 due to the oxygen vacancies, the intensity of light emitted from the exposure to X-rays, the intensity of the photoluminescence due to oxygen vacancies and the quantity of H2 produced by the

  12. Detection of tumor markers based on extinction spectra of visible light passing through gold nanoholes

    Science.gov (United States)

    Gao, Di; Chen, Wilfred; Mulchandani, Ashok; Schultz, Jerome S.

    2007-02-01

    The authors demonstrate that nanometric holes in optically thin gold films on glass slides can be used as biochemical sensors based on extinction spectra of visible light passing through these holes. Binding and adsorption of biomolecules to the surfaces of gold and glass result in a redshift of the localized surface plasmon resonance peak in the extinction spectrum of the gold holes. Selective sensing of antigens such as cancer antigen 19-9 (of less than 1pg on an ˜0.1mm2 probing area) can be realized using this type of devices after functionalizing the gold and glass surfaces with bioreceptors.

  13. Session 4: Solid solution sulfide photo-catalysts for hydrogen evolution under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Tsuji, I.; Kato, H. [Tokyo Univ., Faculty of Science, Dept. of Applied Chemistry (Japan); Kudo, A.; Kobayashi, H. [Kurashiki Univ. of Science and the Arts, (Japan); Kudo, A. [Japan Science and Technology Agency, Core Research for Evolutional Science and Technology (Japan)

    2004-07-01

    In the present study, we tried to make a new visible-light driven photo-catalyst for H{sub 2} evolution by making solid solutions between ZnS photo-catalyst with a wide band gap, and AgInS{sub 2} and CuInS{sub 2} with narrow band gaps. The photophysical and photo-catalytic properties of (MIn){sub x}Zn{sub 2(1-x)}S{sub 2} (M=Cu, Ag) solid solutions were investigated. (authors)

  14. 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

  15. 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.

  16. 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.

  17. The synergistic effect of visible light and gentamycin on Pseudomona aeruginosa microorganisms.

    Science.gov (United States)

    Reznick, Yana; Banin, Ehud; Lipovsky, Anat; Lubart, Rachel; Polak, Pazit; Zalevsky, Zeev

    2013-07-02

    Recently there were several publications on the bactericidal effect of visible light, most of them claiming that blue part of the spectrum (400 nm-500 nm) is responsible for killing various pathogens(1-5). The phototoxic effect of blue light was suggested to be a result of light-induced reactive oxygen species (ROS) formation by endogenous bacterial photosensitizers which mostly absorb light in the blue region(4,6,7). There are also reports of biocidal effect of red and near infra red(8) as well as green light(9). In the present study, we developed a method that allowed us to characterize the effect of high power green (wavelength of 532 nm) continuous (CW) and pulsed Q-switched (Q-S) light on Pseudomonas aeruginosa. Using this method we also studied the effect of green light combined with antibiotic treatment (gentamycin) on the bacteria viability. P. aeruginosa is a common noscomial opportunistic pathogen causing various diseases. The strain is fairly resistant to various antibiotics and contains many predicted AcrB/Mex-type RND multidrug efflux systems(10). The method utilized free-living stationary phase Gram-negative bacteria (P. aeruginosa strain PAO1), grown in Luria Broth (LB) medium exposed to Q-switched and/or CW lasers with and without the addition of the antibiotic gentamycin. Cell viability was determined at different time points. The obtained results showed that laser treatment alone did not reduce cell viability compared to untreated control and that gentamycin treatment alone only resulted in a 0.5 log reduction in the viable count for P. aeruginosa. The combined laser and gentamycin treatment, however, resulted in a synergistic effect and the viability of P. aeruginosa was reduced by 8 log's. The proposed method can further be implemented via the development of catheter like device capable of injecting an antibiotic solution into the infected organ while simultaneously illuminating the area with light.

  18. Intelligent rear light for compensation of environmental effects on car visibility

    Science.gov (United States)

    Gruner, Roman; Schubert, Jorg

    2004-01-01

    LIDAR remote sensing technology has not only applications in geographical, atmospheric or biological sciences but it can also play an important role in the everyday life. Within the last 10 years statistics of European car traffic has shown that about one third of all accidents go back to darkness and poor road conditions. A system collecting information about visibility and distance to following vehicles and setting appropriate rear light intensities could provide a much safer road travel under various environmental conditions. The system that is being developed co-operates with a dirt and brightness sensor to take into account these various external influences on an automobile and applies them to the operation of the rear light. The developed sensors are integrated in an advanced micro-system and capable of providing external environmental data for automatic brightness control within a requested range of light output for constant perceptibility of light signals to the following traffic. This conference gives further information about: (1) construction, optical and laser parameters, (2) application in rear light systems, (3) measurement characteristics, (4) test equipment (LIDAR_Probe), (5) measurement results, test rides, raw data.

  19. Synthesis of nanocomposite based on Semnan natural zeolite for photocatalytic degradation of tetracycline under visible light

    Directory of Open Access Journals (Sweden)

    Farzaneh Saadati

    2016-04-01

    Full Text Available This study investigated the photocatalytic behaviors for the nanocomposite of TiO2 P25 and Semnan natural zeolite in the decomposition of tetracycline under visible light in an aqueous solution. The structural features of the composite were investigated by a series of complementary techniques that included X-ray diffractometer (XRD, Fourier transform infrared spectroscopy (FTIR, scanning electron microscopy (SEM, surface area (BET measurement, and ultraviolet-visible diffuse reflectance spectroscopy (DRS. The surface area measurement disclosed an enhancement of surface area by ~2 times for the synthesized TiO2/Semnan natural zeolite than that of commercial TiO2 P25. The as-prepared photocatalyst (TiO2/Semnan natural zeolite showed pH dependence and more than 87% of the tetracycline could be degraded from the solution under visible irradiation within 90 min at a pH of 6. This excellent catalytic ability was mainly attributed to the hybrid effect of the photocatalyst and adsorbent. The results provided new insight into the performance of active photocatalysts on the treatment of pharmaceutical wastewater. In addition, the immobilization of TiO2 onto Semnan natural zeolite permitted easier separation of the adsorbent from the treated water.

  20. Structure, optical properties and visible-light-induced photochemical activity of nanocrystalline ZnO films deposited by atomic layer deposition onto Si(100)

    Energy Technology Data Exchange (ETDEWEB)

    Drozd, V.E.; Titov, V.V.; Kasatkin, I.A.; Basov, L.L. [Fock Institute of Physics, Department of Physics, Saint-Petersburg State University, Ul' yanovskaya st., 1, Saint-Petersburg, 198504 (Russian Federation); Lisachenko, A.A., E-mail: a.lisachenko@spbu.ru [Fock Institute of Physics, Department of Physics, Saint-Petersburg State University, Ul' yanovskaya st., 1, Saint-Petersburg, 198504 (Russian Federation); Stroyuk, O.L., E-mail: alstroyuk@ukr.net [L.V. Pysarzhevsky Institute of Physical Chemistry of National Academy of Sciences of Ukraine, 31 Nauky av., Kyiv 03028 (Ukraine); Kuchmiy, S.Y. [L.V. Pysarzhevsky Institute of Physical Chemistry of National Academy of Sciences of Ukraine, 31 Nauky av., Kyiv 03028 (Ukraine)

    2014-12-31

    Nano-layers of ZnO (thickness 2–300 nm) were deposited on the surface of p-Si(100), SiO{sub x}/p-Si(100), and n-Si(111) using the atomic layer deposition technique. Morphology, microstructure, and electronic structure of the ZnO/Si(100), ZnO/SiO{sub x}/Si(100), and n- Si(111) films were characterized using scanning electron microscopy, X-ray diffraction and reflectometry, and X-ray photoelectron spectroscopy. The layers have good adhesion to the substrate, polycrystalline structure, and uniform thickness. Starting from the thickness of 4 nm, the hexagonal crystal structure of zincite (wurtzite-type) could be detected with a weak texture changing from [100] to [001] with increasing thickness of the layer. Desorption of H{sub 2}O and CO{sub 2} at ∼ 10{sup −4} Pa from the surface under irradiation with visible light (λ > 500 nm)—the interval of ZnO transparency—was measured by mass-spectrometry. This proves a sensitization of the photocatalytically active ZnO films to the visible light by silicon substrate and opens possibilities of using the composite Si/ZnO materials. - Highlights: • ZnO films (2–300-nm thick) were deposited on Si(100) by atomic layer deposition. • Si substrate sensitizes ZnO nano-layer to the visible light (λ > 500 nm). • Si/ZnO heterojunction can act as a visible-light-sensitive photocatalyst.

  1. (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.

  2. Total absorption of visible light in ultra-thin weakly-absorbing semiconductor gratings

    CERN Document Server

    Sturmberg, Björn C P; Choi, Duk-Yong; White, Thomas P; Botten, Lindsay C; Dossou, Kokou B; Poulton, Christopher G; Catchpole, Kylie R; McPhedran, Ross C; de Sterke, C Martijn

    2016-01-01

    The perfect absorption of light in subwavelength thickness layers generally relies on exotic materials, metamaterials or thick metallic gratings. Here we demonstrate that total light absorption can be achieved in ultra-thin gratings composed of conventional materials, including relatively weakly-absorbing semiconductors, which are compatible with optoelectronic applications such as photodetectors and optical modulators. We fabricate a 41 nm thick antimony sulphide grating structure that has a measured absorptance of A = 99.3% at a visible wavelength of 591 nm, in excellent agreement with theory. We infer that the absorption within the grating is A = 98.7%, with only A = 0.6% within the silver mirror. A planar reference sample absorbs A = 7.7% at this wavelength.

  3. Visible light induced ocular delayed bioluminescence as a possible origin of negative afterimage

    CERN Document Server

    Bokkon, I; Wang, C; Dai, J; Salari, V; Grass, F; Antal, I

    2011-01-01

    The delayed luminescence of biological tissues is an ultraweak reemission of absorbed photons after exposure to external monochromatic or white light illumination. Recently, Wang, B\\'okkon, Dai and Antal (Brain Res. 2011) presented the first experimental proof of the existence of spontaneous ultraweak biophoton emission and visible light induced delayed ultraweak photon emission from in vitro freshly isolated rat's whole eye, lens, vitreous humor and retina. Here, we suggest that the photobiophysical source of negative afterimage can also occur within the eye by delayed bioluminescent photons. In other words, when we stare at a colored (or white) image for few seconds, external photons can induce excited electronic states within different parts of the eye that is followed by a delayed reemission of absorbed photons for several seconds. Finally, these reemitted photons can be absorbed by nonbleached photoreceptors that produce a negative afterimage. Although this suggests the photobiophysical source of negativ...

  4. 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.

  5. 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.

  6. 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.

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

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer

    -doped GdCOB crystals. The crystals are optimized for noncritical phasematching in the blue-UV spectral region through co-doping with Lu and Sc, a nonlinear coefficient for these crystals of 0.78, 0.81 and 0.89 pm/V are measured, which is comparable to LBO. The ability to adjust the noncritical......The main goal of this project is to develop a generic approach to synthesise any wavelength in the visible and UV spectral region based on sum frequency generation. The approach is based on a hybrid system combining solid state and semiconductor technology. The generation of light in the UV...... phasematching by co-doping of these crystals makes them promising candidates for generation of light in the blue-UV region. A novel method for cavity dumping based on nonlinear frequency conversion is investigated. A high finesse laser is constructed with an intracavity nonlinear material inserted in a beam...

  8. 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.

  9. 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.

  10. Low Efficiency Upconversion Nanoparticles for High-Resolution Coalignment of Near-Infrared and Visible Light Paths on a Light Microscope.

    Science.gov (United States)

    Sundaramoorthy, Sriramkumar; Garcia Badaracco, Adrian; Hirsch, Sophia M; Park, Jun Hong; Davies, Tim; Dumont, Julien; Shirasu-Hiza, Mimi; Kummel, Andrew C; Canman, Julie C

    2017-03-08

    The combination of near-infrared (NIR) and visible wavelengths in light microscopy for biological studies is increasingly common. For example, many fields of biology are developing the use of NIR for optogenetics, in which an NIR laser induces a change in gene expression and/or protein function. One major technical barrier in working with both NIR and visible light on an optical microscope is obtaining their precise coalignment at the imaging plane position. Photon upconverting particles (UCPs) can bridge this gap as they are excited by NIR light but emit in the visible range via an anti-Stokes luminescence mechanism. Here, two different UCPs have been identified, high-efficiency micro540-UCPs and lower efficiency nano545-UCPs, that respond to NIR light and emit visible light with high photostability even at very high NIR power densities (>25 000 Suns). Both of these UCPs can be rapidly and reversibly excited by visible and NIR light and emit light at visible wavelengths detectable with standard emission settings used for Green Fluorescent Protein (GFP), a commonly used genetically encoded fluorophore. However, the high efficiency micro540-UCPs were suboptimal for NIR and visible light coalignment, due to their larger size and spatial broadening from particle-to-particle energy transfer consistent with a long-lived excited state and saturated power dependence. In contrast, the lower efficiency nano-UCPs were superior for precise coalignment of the NIR beam with the visible light path (∼2 μm versus ∼8 μm beam broadening, respectively) consistent with limited particle-to-particle energy transfer, superlinear power dependence for emission, and much smaller particle size. Furthermore, the nano-UCPs were superior to a traditional two-camera method for NIR and visible light path alignment in an in vivo Infrared-Laser-Evoked Gene Operator (IR-LEGO) optogenetics assay in the budding yeast Saccharomyces cerevisiae. In summary, nano-UCPs are powerful new tools for

  11. Synthetic gene involving azobenzene-tethered T7 promoter for the photocontrol of gene expression by visible light.

    Science.gov (United States)

    Kamiya, Yukiko; Takagi, Toshiki; Ooi, Hideaki; Ito, Hiroshi; Liang, Xingguo; Asanuma, Hiroyuki

    2015-04-17

    In the present study, we demonstrate photoregulation of gene expression in a cell-free translation system from a T7 promoter containing two azobenzene derivatives at specific positions. As photoswitches, we prepared azobenzene-4'-carboxlyic acid (Azo) and 2,6-dimethylazobenzene-4'-carboxylic acid (DM-Azo), which were isomerized from trans to cis upon irradiation with UV light (λ azobenzene-4'-carobxylic acid (S-DM-Azo), which were cis-isomerized by irradiation with 400 nm visible light. Expression of green fluorescent protein from a promoter modified with S-Azo or S-DM-Azo could be induced by harmless visible light whereas that from a promoter modified with Azo or DM-Azo was induced only by UV light (340-360 nm). Thus, efficient photoregulation of green fluorescent protein production was achieved in a cell-free translation system with visible light without photodamage.

  12. Adsorption and Photocatalytic Kinetics of Visible-Light Response N-Doped TiO2 Nanocatalyst for Indoor Acetaldehyde Removal under Dark and Light Conditions

    OpenAIRE

    Yu-Hao Lin; Chih-Huang Weng; Jing-Hua Tzeng; Yao-Tung Lin

    2016-01-01

    Understanding the removal nature of the indoor volatile organic compounds under realistic environment conditions would give clear guidance for the development of air purification devices. The study investigated the removal of indoor acetaldehyde using visible-light-responsive N-doped TiO2 (N-TiO2) photocatalyst under visible-light irradiation (light) and in the absence of light (dark). The adsorption kinetics of acetaldehyde onto N-TiO2 followed a pseudo-second-order model. The magnitude of a...

  13. Self-biasing photoelectrochemical cell for spontaneous overall water splitting under visible-light illumination.

    Science.gov (United States)

    Chen, Quanpeng; Li, Jinhua; Li, Xuejin; Huang, Ke; Zhou, Baoxue; Shangguan, Wenfeng

    2013-07-01

    A self-biasing photoelectrochemical (PEC) cell that could work for spontaneous overall water splitting in a neutral solution was established based on the mismatched Fermi levels between the photoelectrodes. A Pt-catalyst-decorated crystalline silicon photovoltaic cell (Pt/PVC) was prepared and employed as an effective photocathode. This was coupled with a poly(ethylene glycol)-directed WO3/W photoanode prepared by a hydrothermal process. Both of the photoelectrodes showed a response to visible light. The WO3/W photoanode had a positively located valence band edge, the energy level of which was enough for water oxidation, and the Pt/PVC photocathode possessed a negatively located conduction band edge, which was capable of water reduction. More importantly, the Fermi level of the WO3/W photoanode was more positive than that of the Pt/PVC photocathode because of the p-n junction of the PVC that decoupled the band bending and enlarged the photovoltage. Under visible-light irradiation, the WO3/W photoanode provided a negative bias for the Pt/PVC photocathode, and the Pt/PVC photocathode provided a positive bias for the WO3/W photoanode. An interior bias was generated that could relax the strict criteria of overall water splitting by cooperatively separating the hole-electron pairs at both photoelectrodes. In this system, the short-circuit current and the open-circuit voltage increased with increasing light intensity (AM 1.5 illumination) to reach 121 μA cm(-2) and 0.541 V, respectively, at a light intensity of 100 mW cm(-2). Such a combination provides a promising method for the fabrication of self-driven devices for solar-energy storage. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Heterostructures of Ag₃PO₄/TiO₂ mesoporous spheres with highly efficient visible light photocatalytic activity.

    Science.gov (United States)

    Li, Yanjuan; Yu, Liangmin; Li, Nan; Yan, Wenfu; Li, Xiaotian

    2015-07-15

    Heterostructured Ag3PO4/m-TiO2 (mesoporous sphere) visible-light photocatalyst has been synthesized via a facile method. The resultant composite consists of numerous Ag3PO4 nanoparticles with diameter less than 10nm, and these nanoparticles deposit onto the TiO2 nanoparticles surface forming a heterostructure. N2 adsorption-desorption measurements have suggested that the composite was porous with relative high surface area. Studies of the photocatalytic activity and stability of heterostructured Ag3PO4/m-TiO2 for the degradation of methylene blue (MB) have indicated that its visible light photocatalytic performance was improved compared with pure Ag3PO4 and Ag3PO4/m-TiO2, and exhibited excellent photocatalytic stability. The performance was improved attributing to three aspects: (1) the large specific surface area enhanced the adsorption of MB; (2) numerous pores enlarged the contact area between photocatalyst and MB; (3) the most importantly, depositing Ag3PO4 onto the surface of TiO2 facilitated the separation of electron and hole pairs, which also elevates the photocatalytic performance. Furthermore, the photocatalytic mechanism also has been discussed. Compare with Ag3PO4, the Ag weight percent of Ag3PO4/m-TiO2 decreases from 77% to 20.8%, significantly reducing the cost of photocatalyst. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Highly efficient visible light photocatalysis of novel CuS/ZnO heterostructure nanowire arrays.

    Science.gov (United States)

    Lee, Mikyung; Yong, Kijung

    2012-05-17

    Here, a facile approach for the fabrication of CuS nanoparticle (NP)/ZnO nanowire (NW) heterostructures on a mesh substrate through a simple two-step solution method is demonstrated. Successive ionic layer adsorption and reaction (SILAR) was employed to uniformly deposit CuS NPs on the hydrothermally grown ZnO NW array. The synthesized CuS/ZnO heterostructure NWs exhibited superior photocatalytic activity under visible light compared to bare ZnO NWs. This strong photocatalytic activity under visible light is due to the interfacial charge transfer (IFCT) from the valence band of the ZnO NW to the CuS NP, which reduces CuS to Cu(2)S. After repeated cycles of photodecolorization of Acid Orange 7 (AO7), the photocatalytic behavior of CuS/ZnO heterostructure NWs exhibited no significant loss of activity. Furthermore, our CuS/ZnO NWs/mesh photocatalyst floats in solution via partial superhydrophobic modification of the NWs.

  16. Flower-like BiVO4 Microspheres and Their Visible Light-Driven Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Arini Nuran Zulkifili

    2018-01-01

    Full Text Available A flower-like BiVO4 microsphere photocatalyst was synthesized with a simple template-free homogeneous precipitation method at 60 °C for 24 h. The purpose of this study is to explore a low-cost, simple method of synthesizing the self-assembled 3D structure in order to enhance photocatalytic performance under visible light irradiation (λ > 420 nm. In this study, the morphology, structure, and photo-absorption of flower-like BiVO4 microspheres were characterized, and the effects of photocatalysis were analyzed. The results indicate that the size of the flower-like microspheres was about 2 μm to 4 μm and they were composed of several nanosheets. The mechanism of hierarchical microsphere formation has been proposed as the Ostwald ripening process and the self-assembled process. The obtained samples were calcined under different temperatures (300 °C, 400 °C, 500 °C and 600 °C to study the effects of calcination on the structure and on photocatalysis. The photocatalytic process was then evaluated by decolorization of methylene blue dye under visible-light irradiation.

  17. Visible light photooxidative performance of a high-nuclearity molecular bismuth vanadium oxide cluster

    Directory of Open Access Journals (Sweden)

    Johannes Tucher

    2014-05-01

    Full Text Available The visible light photooxidative performance of a new high-nuclearity molecular bismuth vanadium oxide cluster, H3[{Bi(dmso3}4V13O40], is reported. Photocatalytic activity studies show faster reaction kinetics under anaerobic conditions, suggesting an oxygen-dependent quenching of the photoexcited cluster species. Further mechanistic analysis shows that the reaction proceeds via the intermediate formation of hydroxyl radicals which act as oxidant. Trapping experiments using ethanol as a hydroxyl radical scavenger show significantly decreased photocatalytic substrate oxidation in the presence of EtOH. Photocatalytic performance analyses using monochromatic visible light irradiation show that the quantum efficiency Φ for indigo photooxidation is strongly dependent on the irradiation wavelength, with higher quantum efficiencies being observed at shorter wavelengths (Φ395nm ca. 15%. Recycling tests show that the compound can be employed as homogeneous photooxidation catalyst multiple times without loss of catalytic activity. High turnover numbers (TON ca. 1200 and turnover frequencies up to TOF ca. 3.44 min−1 are observed, illustrating the practical applicability of the cluster species.

  18. Visible light-dependent degradation of lipidic phytoplanktonic components during senescence: a review.

    Science.gov (United States)

    Rontani, J F

    2001-09-01

    Though most of the organic components of phytoplankton are susceptible to being photodegraded during senescence, until recent years there has been very little research in this area. Recently, however, there have been a renewal of interest, and the heterogeneous visible light-induced degradative reactions of lipidic compounds associated with phytodetritus have been studied. The present paper reviews the results obtained in the course of these studies. In the first part, the production and quenching of excited states of chlorophyll and toxic oxygen species (singlet oxygen, superoxide ion, hydroxyl radical and hydrogen peroxide) in healthy and senescent phytoplanktonic cells are discussed. Then, the photo-oxidation of the main lipidic cell components (chlorophyll, chlorophyll phytyl chain, carotenoids, sterols, unsaturated fatty acids, alkenones and unsaturated alkenes) in senescent phytoplanktonic cells is examined. Emphasis is given to the degradation rates and the mechanisms of visible light-induced degradation of the main lipidic components of phytoplankton and to the structure of the photoproducts formed. In each case, the selectivity of these compounds is discussed in order to select a "pool" of photoproducts able to act as tracers of photo-oxidative alterations in the marine medium. This "pool" of photoproducts could provide very useful information concerning the physiological state of phytoplanktonic communities and current environmental problems related to ozone depletion.

  19. A novel three-dimensional indoor positioning algorithm design based on visible light communication

    Science.gov (United States)

    Guan, Weipeng; Wu, Yuxiang; Wen, Shangsheng; Chen, Hao; Yang, Chen; Chen, Yingcong; Zhang, Zhaoze

    2017-06-01

    In this paper, a visible light communication based three dimensional indoor positioning system employing a dedicated algorithm and using the code division multiple access technique is proposed to solve the mutual interference among the reference source points. The light signal emitted from a CDMA modulated white LED, carrying LED's position information, is received by positioning terminal through intensity modulation and direct detection, and then the position of the terminal can be estimated based on the RSS-three dimensional localization algorithm. By using the orthogonality of the spreading codes, the separation of the overlap among visible identification code in time domain and frequency domain can be realized. According to the identification information, the position can be located in the associated area. And the precise location is calculated with a novel three dimensional positioning algorithm, based on the signal attenuation. The simulation results show that the proposed location algorithm has a high accuracy of under 7.06 cm and with an average positioning error of about 3.18 cm when the SNR is 30 dB. A real-time small positioning system was also demonstrate to test the performance of the system, which has a very good positioning accuracy. The proposed positioning algorithm is simple and does not require synchronization processing any more. These features outperform other existing indoor wireless localization approaches.

  20. Visible light photocatalytic synthesis of aniline with an Au/LaTiO{sub 3} nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Mkhalid, I.A., E-mail: imkhalid2@gmail.com

    2015-05-15

    Highlights: • Au/LaTiO{sub 3} nanoparticles were used for photocatalytic reduction of nitrobenzene. • Photocatalytic reduction of nitrobenzene was dependent on wt.% of Au. • Catalyst re-use revealed the present photocatalyst remain effective and active after five cycles. - Abstract: An ultrasonic method was used to prepare LaTiO{sub 3} nanoparticles and a photo-assisted deposition method was used to loading gold into surface of LaTiO{sub 3}. The samples obtained were characterized using a photoluminescence emission spectra, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet and visible light spectroscopy, surface area measurements and X-ray diffraction. In addition, photocatalytic activity of LaTiO{sub 3} and Au/LaTiO{sub 3} samples has been tested under visible light irradiation for reduction of nitrobenzene into aniline. XPS results reveal that gold was present as metallic gold by the presence of two peaks at 87.7 eV and 84.0 eV. The UV–Vis results reveal that loading of Au into LaTiO{sub 3} surfaces lead to a red shift. The maximum photocatalytic reduction efficiency (100%) was obtained using 0.3 wt.% Au/LaTiO{sub 3} nanocomposites after 90 min a reaction time. The Au/LaTiO{sub 3} nanocomposites can be recycled for the first five cycles without loss of photocatalytic activity.

  1. Hydrothermal Synthesis of BiFeO3 Nanoparticles for Visible Light Photocatalytic Applications.

    Science.gov (United States)

    Niu, Feng; Gao, Tong; Zhang, Ning; Chen, Zhi; Huang, Qiaoli; Qin, Laishun; Sun, Xingguo; Huang, Yuexiang

    2015-12-01

    Bismuth ferrite is a promising material for visible light response photocatalytic applications due to its narrow band gap. In this work, single crystalline BiFeO3 nanoparticles were prepared by a modified hydrothermal process. The effects of hydrothermal temperature, reaction time and precursor xerogel amoumt on the as-prepared BiFeO3 particle size and morphology were investigated by XRD, TEM and HRTEM. The XRD analysis reveals that single crystalline BiFeO3 particles can be obtained when the hydrothermal temperature is kept below 220 degrees C. TEM observation showed that the as-formed BFO particles are in a square or rectangle-like shape and that the particle size is increased with increasing hydrothermal temperature. The hydrothermal reaction time and the amount of xerogel could also influence the as-formed BFO particle morphology and size. The band gap of the as-prepared BFO nanoparticles was identified by UV-vis diffuse reflectance spectrum. The measurement of photodegradation of methyl orange dye in an aqueous solution revealed that the as-prepared BFO nanoparticles exhibit photocatalytic activity under visible light irradiation.

  2. Microemulsion synthesis, characterization of highly visible light responsive rare earth-doped Bi2O3.

    Science.gov (United States)

    Wu, Shuxing; Fang, Jianzhang; Xu, Xiaoxin; Liu, Zhang; Zhu, Ximiao; Xu, Weicheng

    2012-01-01

    In this paper, Bi(2)O(3) and rare earth (La, Ce)-doped Bi(2)O(3) visible-light-driven photocatalysts were prepared in a Triton X-100/n-hexanol/cyclohexane/water reverse microemulsion. The resulting materials were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area, photoluminescence spectra (PLS) and UV-Vis diffuse reflectance spectroscopy. The XRD patterns of the as-prepared catalysts calcined at 500 °C exhibited only the characteristic peaks of monoclinic α-Bi(2)O(3). PLS analysis implied that the separation efficiency for electron-hole has been enhanced when Bi(2)O(3) was doped with rare earth. UV-Vis diffuse reflectance spectroscopy measurements presented an extension of light absorption into the visible region. The photocatalytic activity of the samples was evaluated by degradation of methyl orange (MO) and 2,4-dichlorophenol (2,4-DCP). The results displayed that the photocatalytic activity of rare earth-doped Bi(2)O(3) was higher than that of dopant-free Bi(2)O(3). The optimal dopant amount of La or Ce was 1.0 mol%. And the mechanisms of influence on the photocatalytic activity of the catalysts were discussed. © 2012 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2012 The American Society of Photobiology.

  3. Oxygen vacancies and intense luminescence in manganese loaded Zno microflowers for visible light water splitting.

    Science.gov (United States)

    Sambandam, Balaji; Michael, Robin Jude Vimal; Manoharan, Periakaruppan T

    2015-09-07

    ZnO nanorods and Mn/ZnO microflowers with nano-sized petals exhibit singly ionized oxygen vacancies, V. This is strongly supported by a green photoluminescence emission at 2.22 eV and an EPR g value of 1.953, both of which are suppressed greatly after annealing in an oxygen atmosphere. A strong red emission observed during exposure to X-rays reveals the presence of F(+) centres as a consequence of the V. Mn/ZnO displayed enhanced H2 generation with visible light exposure, when compared to pure ZnO and annealed Mn/ZnO in the visible region, which directly correlated with the oxygen vacancy concentration. There is an interesting correlation between the intensities of the EPR lines at the g-value of 1.953 due to the oxygen vacancies, the intensity of light emitted from the exposure to X-rays, the intensity of the photoluminescence due to oxygen vacancies and the quantity of H2 produced by the photocatalytic effect when comparing the three different nanomaterials, viz. pure ZnO, Mn/ZnO before and after annealing, all having been made exactly by the same methodologies.

  4. 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.

  5. 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.

  6. Photodegradation of toluene over TiO(2-x)N(x) under visible light irradiation.

    Science.gov (United States)

    Irokawa, Yoshihiro; Morikawa, Takeshi; Aoki, Koyu; Kosaka, Satoru; Ohwaki, Takeshi; Taga, Yasunori

    2006-03-07

    We report the photooxidation of toluene over nitrogen doped TiO(2) (TiO(2-x)N(x)) under visible light irradiation. The photocatalytic oxidation of toluene in air over TiO(2-x)N(x) powders was studied using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), gas chromatography (GC), ion chromatography (IC), and gas chromatography mass spectrometry (GC-MS), focusing on the photocatalytic decomposition processes of toluene. Results obtained indicate that toluene, weakly adsorbed on the catalyst surface, is initially photooxidized to benzaldehyde which adsorbs onto the TiO(2-x)N(x) surface more strongly, leading to the formation of ring-opening products such as carboxylic acids and aldehydes. No gaseous intermediates were detected during the photooxidation. Major intermediates adsorbed at the catalyst surface were oxalic acid, (COOH)(2), acetic acid, CH(3)COOH, formic acid, HCOOH, and pyruvic acid, CH(3)COCOOH, whereas more complicated carboxylic species, including propionic acid, CH(3)CH(2)COOH, isovaleric acid, (CH(3))(2)CHCH(2)COOH, and succinic acid, (CH(2)COOH)(2), were also found in the early stage of the photooxidation. These intermediate products were gradually photodegraded to CO(2) and H(2)O under visible light irradiation.

  7. Nano-ferrites for water splitting: Unprecedented high photocatalytic hydrogen production under visible light

    KAUST Repository

    Mangrulkar, Priti A.

    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.

  8. 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.

  9. Intrinsic nature of visible-light absorption in amorphous semiconducting oxides

    Directory of Open Access Journals (Sweden)

    Youngho Kang

    2014-03-01

    Full Text Available To enlighten microscopic origin of visible-light absorption in transparent amorphous semiconducting oxides, the intrinsic optical property of amorphous InGaZnO4 is investigated by considering dipole transitions within the quasiparticle band structure. In comparison with the crystalline InGaZnO4 with the optical gap of 3.6 eV, the amorphous InGaZnO4 has two distinct features developed in the band structure that contribute to significant visible-light absorption. First, the conduction bands are down-shifted by 0.55 eV mainly due to the undercoordinated In atoms, reducing the optical gap between extended states to 2.8 eV. Second, tail states formed by localized oxygen p orbitals are distributed over ∼0.5 eV near the valence edge, which give rise to substantial subgap absorption. The fundamental understanding on the optical property of amorphous semiconducting oxides based on underlying electronic structure will pave the way for resolving instability issues in recent display devices incorporating the semiconducting oxides.

  10. Photoelectrochemical properties of polypyrrole/TiO2 nanotube arrays nanocomposite under visible light

    Science.gov (United States)

    Jia, Yichao; Xiao, Peng; He, Huichao; Yao, Jianyu; Liu, Feila; Wang, Zhifeng; Li, Yanhong

    2012-06-01

    In this study, different amount of polypyrrole (PPy) were electropolymerized on highly ordered TiO2 nanotube arrays (TiO2NTs) anodized by Ti foil in aqueous solution containing fluoride. In order to improve the conductivity of PPy, an anionic surfactant sodium dodecyl benzene sulfonate (SDBS) was used as doping during electropolymerization. The PPy modified TiO2NTs was confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR) and UV-vis spectroscopy (UV-vis). The results indicated that there might exist a strong interaction between TiO2NTs and PPy. Photoelectrochemical response showed that PPy/TiO2NTs electropolymerized for 30 s presented the maximum IPCE 1.81% under 550 nm visible light. The results were ascribed to the presence of narrow band gap p-type conducting polymer semiconductor PPy enhancing visible-light absorption and decreasing the recombination of photo electron-hole result in enhanced photocurrent. These results have implications for the use of PPy/TiO2NTs as a photoswitch or solar cell.

  11. Photoelectrochemical properties of polypyrrole/TiO{sub 2} nanotube arrays nanocomposite under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Jia Yichao [College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China); Xiao Peng, E-mail: xiaopeng@cqu.edu.cn [College of Physics, Chongqing University, Chongqing 400030 (China); College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China); He Huichao; Yao Jianyu; Liu Feila; Wang Zhifeng [College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China); Li Yanhong [College of Physics, Chongqing University, Chongqing 400030 (China)

    2012-06-15

    In this study, different amount of polypyrrole (PPy) were electropolymerized on highly ordered TiO{sub 2} nanotube arrays (TiO{sub 2}NTs) anodized by Ti foil in aqueous solution containing fluoride. In order to improve the conductivity of PPy, an anionic surfactant sodium dodecyl benzene sulfonate (SDBS) was used as doping during electropolymerization. The PPy modified TiO{sub 2}NTs was confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR) and UV-vis spectroscopy (UV-vis). The results indicated that there might exist a strong interaction between TiO{sub 2}NTs and PPy. Photoelectrochemical response showed that PPy/TiO{sub 2}NTs electropolymerized for 30 s presented the maximum IPCE 1.81% under 550 nm visible light. The results were ascribed to the presence of narrow band gap p-type conducting polymer semiconductor PPy enhancing visible-light absorption and decreasing the recombination of photo electron-hole result in enhanced photocurrent. These results have implications for the use of PPy/TiO{sub 2}NTs as a photoswitch or solar cell.

  12. 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.

  13. 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.

  14. Visible-light photocatalytic activity of nitrided TiO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Camps, Enrique, E-mail: enrique.camps@inin.gob.mx [Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027, Mexico DF 11801 (Mexico); Escobar-Alarcon, L. [Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027, Mexico DF 11801 (Mexico); Camacho-Lopez, Marco Antonio [Laboratorio de Investigacion y Desarrollo de Materiales Avanzados, Facultad de Quimica, UAEM, km 14.5 Carretera Toluca-Atlacomulco (Mexico); Casados, Dora A. Solis [Centro de Investigacion en Quimica Sustentable, Facultad de Quimica, UAEM, km 14.5 Carretera Toluca-Atlacomulco (Mexico)

    2010-10-25

    TiO{sub 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{sub 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{sub 2} and nitrided TiO{sub 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{sub 2} films had photocatalytic activity, while the unnitrided films did not.

  15. Visible light photocatalytic water disinfection and its kinetics using Ag-doped titania nanoparticles.

    Science.gov (United States)

    Younas, Hassan; Qazi, Ishtiaq A; Hashmi, Imran; Awan, M Ali; Mahmood, Asif; Qayyum, Hafiz Adil

    2014-01-01

    The UN estimated about five million deaths every year due to water-borne diseases, accounting from four billion patients. Keeping in view, the ever increasing health issues and to undermine this statistics, a reliable and sustainable water-treatment method has been developed using visible light for water treatment. titania nanoparticles (NPs) have been synthesized successfully by a more applicable method Viz: liquid impregnation (LI) method. The bacterial death rate by photocatalysis under visible light was studied by employing a typical fluorescent source and was found to follow pseudo first-order reaction kinetics. The nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy, and energy-dispersive X-ray spectroscopy to deduce their size range, surface morphology, and elemental compositions, respectively. Among all the prepared grades, 1% Ag-TiO2 was found to be a very effective photocatalytic agent against Escherichia coli. The resulted photoinactivated data were also evaluated by different empirical kinetic models for bacterial inactivation. Hom, Hom-power, Rational, and Selleck models were not able to explain the disinfection kinetics but modified-Hom model fitted best with the experimentally obtained data by producing a shoulder, log-linear, and a tail region.

  16. 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%.

  17. Sahlgren's Saturation Test for acquired dyschromatopsia: increased lightness enhances sensitivity.

    Science.gov (United States)

    Lindblom, B; Wikholm, M; Frisén, L

    1988-01-01

    Sahlgren's Saturation Test (SST) is a simple sorting test designed for the detection and grading of acquired color vision defects. Like other pigment-based color vision tests, the SST color samples have medium lightness, i.e., they belong to the intermediate part of the gray scale. We tested normal controls and subjects with congenital or acquired dyschromatopsia with five SST versions that differed only in the amount of lightness. The sensitivity of the test increased considerably with increasing lightness. Therefore, the lightness level of SST has now been changed from 30 to 10 Natural Color System units.

  18. Dilute-P GaNP Semiconductor Alloy for Visible Light Emitter

    Science.gov (United States)

    Tan, Chee-Keong; Tansu, Nelson

    2015-03-01

    Group III-Nitride semiconductor alloy in particular InGaN alloy is widely employed as the active media for the solid state lighting applications. In addition to the InGaN alloy, dilute-As GaNAs alloy has recently been suggested as the potential material for high efficiency solid state lighting devices. In conjunction with dilute-As GaNAs alloy, dilute-P GaNP alloy has the potential for its use in light emitting applications. The literature on dilute-P GaNP alloy is severely limited, thus the understanding of electronic properties of the material is of great importance in establishing the first step towards the device implementation. In this work we present the analysis of the electronic properties of dilute-P GaNP alloys through First-Principle Density Functional Theory (DFT). Our analysis shows that the replacement of N atoms with Phosphorus (P) atoms in the GaN alloy leads to significant changes in the band structure including the band gap and effective mass. In addition, our finding indicates minimal interband Auger recombination in the dilute-P GaNP alloys as compared to InGaN alloy, suggesting the potential of GaNP alloys as high efficiency visible light emitter. The electronic properties of the dilute-P GaNP alloys will be discussed in depth.

  19. Carbon nitride-TiO2 hybrid modified with hydrogenase for visible light driven hydrogen production.

    Science.gov (United States)

    Caputo, Christine A; Wang, Lidong; Beranek, Radim; Reisner, Erwin

    2015-10-01

    A system consisting of a [NiFeSe]-hydrogenase (H2ase) grafted on the surface of a TiO2 nanoparticle modified with polyheptazine carbon nitride polymer, melon (CN x ) is reported. This semi-biological assembly shows a turnover number (TON) of more than 5.8 × 105 mol H2 (mol H2ase)-1 after 72 h in a sacrificial electron donor solution at pH 6 during solar AM 1.5 G irradiation. An external quantum efficiency up to 4.8% for photon-to-hydrogen conversion was achieved under irradiation with monochromatic light. The CN x -TiO2-H2ase construct was also active under UV-free solar light irradiation (λ > 420 nm), where it showed a substantially higher activity than TiO2-H2ase and CN x -H2ase due, in part, to the formation of a CN x -TiO2 charge transfer complex and highly productive electron transfer to the H2ase. The CN x -TiO2-H2ase system sets a new benchmark for photocatalytic H2 production with a H2ase immobilised on a noble- and toxic-metal free light absorber in terms of visible light utilisation and stability.

  20. Improving the visible light photocatalytic activity of TiO{sub 2} nanotubes upon decoration with Sb{sub 2}S{sub 3} microcrystalline

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, J.S. [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Wang, Q.Y., E-mail: wangqingyao0532@163.com [School of Chemistry and Materials Science, Ludong University, Yantai 264025 (China); Liang, H. [Aladdin Chemical Reagent Co., Ltd., Shanghai 201206 (China); Chen, D.Q., E-mail: dqchen@hdu.edu.cn [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Ji, Z.G. [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China)

    2015-11-15

    TiO{sub 2} nanotube arrays sensitized with Sb{sub 2}S{sub 3} microcrystalline were successfully fabricated by a two-step process of photodeposition method followed by annealing treatment. The structural investigation by X-ray diffraction, scanning electron microscopy and transmission electron microscopy indicated that the Sb{sub 2}S{sub 3} microparticles grew uniformly on the walls of TiO{sub 2} nanotubes. The amorphous Sb{sub 2}S{sub 3} microspheres could be transformed into octahedral microcrystals after annealing treatment. The Sb{sub 2}S{sub 3} modification of the TiO{sub 2} nanotube arrays resulted in an increase in visible light adsorption and photocatalytic activities toward degradation of methyl orange (MO) and rhodamine B (RhB) dyes under visible light irradiation. - Highlights: • TiO{sub 2} nanotube arrays sensitized with Sb{sub 2}S{sub 3} microcrystalline were prepared. • The amorphous Sb{sub 2}S{sub 3} microspheres transformed into octahedral microcrystals after the annealing treatment. • The TiO{sub 2} NTs/Sb{sub 2}S{sub 3} exhibits excellent visible light photocatalytic activities.

  1. 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.

  2. 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.

  3. Visible Light Induced Organic Transformations Using Metal-Organic-Frameworks (MOFs).

    Science.gov (United States)

    Deng, Xiaoyu; Li, Zhaohui; García, Hermenegildo

    2017-08-22

    With the aim of developing renewable energy based processes, researchers are paying increasing interest to light induced organic transformations. Metal-organic frameworks (MOFs), a class of micro-/mesoporous hybrid materials, are recently emerging as a new type of photoactive materials for organic syntheses due to their unique structural characteristics. In this Review, we summarized the recent applications of MOFs as photocatalysts for light induced organic transformations, including (1) oxidation of alcohols, amines, alkene, alkanes and sulfides; (2) hydroxylation of aromatic compounds like benzene; (3) activation of the C-H bonds to construct new C-C or C-X bonds; (4) atom-transfer radical polymerization (ATRP). This Review starts with general background information of using MOFs in photocatalysis, followed by a description of light induced organic transformations promoted by photoactive inorganic nodes and photocatalytic active ligands in MOFs, respectively. Thereafter, the use of MOFs as multifunctional catalysts for light induced organic transformations via an efficient merge of the metal/ligand/guest based catalysis where the photocatalytic activity of MOFs plays a key role are discussed. Finally, the limitations, challenges and the future perspective of the application of MOFs for light induced organic transformations were addressed. The objective of this Review is to serve as a starting point for other researchers to get into this largely unexplored field. It is also our goal to stimulate intensive research in this field for rational designing of MOF materials to overcome their current limitations in photocatalysis, which can lead to more creative visible-light-induced organic transformations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. 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.

  5. An efficient visible-light photocatalyst prepared by modifying AgBr particles with a small amount of activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Desong, E-mail: dswang06@126.com; Zhao, Mangmang; Luo, Qingzhi; Yin, Rong; An, Jing; Li, Xueyan

    2016-04-15

    Highlights: • An efficient visible-light photocatalyst was prepared by modifying AgBr particles. • A small amount of activated carbon was used to modify AgBr particles. • The modified AgBr exhibited improved visible-light photocatalytic performances. - Abstract: An efficient visible-light photocatalyst was successfully prepared by modifying AgBr particles with a small amount of activated carbon (AC) via a simple chemical precipitation approach. The AC/AgBr composite was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, UV–vis diffuse reflection spectroscopy, photoluminescence spectroscopy, electrochemical impedance spectroscopy. The photocatalytic performances of the AC/AgBr composite were investigated by evaluating photodegradation of methyl orange (MO) and phenol under visible light irradiation, and the effects of the AC content in the composite, concentrations of AC/AgBr composite and MO, carrier scavengers on MO photodegradation rate were systematically investigated. The results indicated that the modification of AC can hardly change the crystalline and crystal size of AgBr particles, while significantly improve their specific surface areas, visible-light absorption and separation efficiency of photogenerated electron–hole pairs. Compared with pure AgBr, the AC/AgBr composite exhibited drastically enhanced visible-light photocatalytic activity and stability. The photogenerated electrons and holes, hydroxyl radicals are responsible to the photodegradation of organic pollutants, and the photogenerated holes are the main active species. On the basis of the results and the properties of AC and AgBr, the visible-light photocatalytic mechanism of the AC/AgBr composite was discussed.

  6. Unique visible-light-assisted field emission of tetrapod-shaped ZnO/reduced graphene-oxide core/coating nanocomposites

    Science.gov (United States)

    Wu, Chaoxing; Kim, Tae Whan; Guo, Tailiang; Li, Fushan

    2016-01-01

    The electronic and the optoelectronic properties of graphene-based nanocomposites are controllable, making them promising for applications in diverse electronic devices. In this work, tetrapod-shaped zinc oxide (T-ZnO)/reduced graphene oxide (rGO) core/coating nanocomposites were synthesized by using a hydrothermal-assisted self-assemble method, and their optical, photoelectric, and field-emission properties were investigated. The ZnO, an ideal ultraviolet-light-sensitive semiconductor, was observed to have high sensitivity to visible light due to the rGO coating, and the mechanism of that sensitivity was investigated. We demonstrated for the first time that the field-emission properties of the T-ZnO/rGO core/coating nanocomposites could be dramatically enhanced under visible light by decreasing the turn-on field from 1.54 to 1.41 V/μm and by increasing the current density from 5 to 12 mA/cm2 at an electric field of 3.5 V/μm. The visible-light excitation induces an electron jump from oxygen vacancies on the surface of ZnO to the rGO layer, resulting in a decrease in the work function of the rGO and an increase in the emission current. Furthermore, a field-emission light-emitting diode with a self-enhanced effect was fabricated making full use of the photo-assisted field-emission process. PMID:27941822

  7. Photocatalytic comparison of Cu- and Ag-doped TiO{sub 2}/GF for bioaerosol disinfection under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Pham, Thanh-Dong; Lee, Byeong-Kyu, E-mail: bklee@ulsan.ac.kr

    2015-12-15

    Photocatalysts, TiO{sub 2}/glass fiber (TiO{sub 2}/GF), Cu-doped TiO{sub 2}/glass fiber (Cu–TiO{sub 2}/GF) and Ag-doped TiO{sub 2}/glass fiber (Ag–TiO{sub 2}/GF), were synthesized by a sol–gel method. They were then used to disinfect Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in bioaerosols under visible light irradiation. TiO{sub 2}/GF did not show any significant disinfection effect. Both Cu and Ag acted as intermediate agents to enhance separation efficiency of electron–hole pairs of TiO{sub 2}, leading to improved photocatalytic activity of Cu–TiO{sub 2}/GF and Ag–TiO{sub 2}/GF under visible light. Cu in Cu–TiO{sub 2}/GF acted as a defective agent, increasing the internal quantum efficiency of TiO{sub 2}, while Ag in Ag–TiO{sub 2}/GF acted as a sensitive agent, enhancing the transfer efficiency of the electrons generated. The highest disinfection efficiencies of E. coli and S. aureus by Cu–TiO{sub 2}/GF were 84.85% and 65.21%, respectively. The highest disinfection efficiencies of E. coli and S. aureus by Ag–TiO{sub 2}/GF were 94.46% and 73.12%, respectively. Among three humidity conditions – 40±5% (dry), 60±5% (moderate), and 80±5% (humid) – the moderate humidity condition showed the highest disinfection efficiency for both E. coli and S. aureus. This study also showed that a Gram-negative bacterium (E. coli) were more readily disinfected by the photocatalysts than a Gram-positive bacterium (S. aureus). - Graphical abstract: Electron–hole pair separation mechanism of a metal-doped TiO{sub 2} system.

  8. Extraocular sensitivity to polarized light in an echinoderm.

    Science.gov (United States)

    Johnsen, S

    1994-10-01

    This study tests the hypotheses that the birefringent calcite and stereom structure of the brittlestar (Ophiuroidea, Echinodermata) endoskeleton polarizes light and that certain brittlestars respond to polarized light. The first hypothesis was tested in Ophioderma brevispinum by examining ossicles from freshly killed specimens under polarized light. This analysis revealed that the lateral arm shields, oral arm shields, arm spines and aboral disk ossicles are dichroic and thus polarize light. The second hypothesis was tested in two orientation experiments under polarized light. The results from the first orientation experiment showed (1) that, under polarized light, animals oriented significantly and unimodally, (2) that, under polarized light with the e-vector perpendicular to that in 1, animals oriented significantly and unimodally to within 18 degrees of the bearing of the animals in 1, and (3) that, under unpolarized light, animals did not orient significantly. The results from the second orientation experiment showed that, under polarized light, animals oriented significantly and unimodally to within 17 degrees of an individual preference previously established under polarized light; but under unpolarized light, animals did not orient significantly to an individual preference established under polarized light. Thus, O. brevispinum orients under polarized, but not unpolarized, light. The unimodal orientation and lack of consistent alignment with the e-vector suggest that polarized light is not used as a directional cue but instead as a signal to sustain oriented behavior. The dichroism of the ossicles of O. brevispinum and the animal's capacity (though eyeless) to discriminate between polarized and unpolarized light suggest that the mechanism of polarization sensitivity may rely on polarizing filters built from the animal's skeleton.

  9. An enhancing effect of visible light and UV radiation on phenolic compounds and various antioxidants in broad bean seedlings

    Science.gov (United States)

    Hasaneen, Mohammed Naguib Abdel-Ghany; Abdel-Aziz, Heba Mahmoud Mohammed

    2010-01-01

    Exposure of dark- or ambient visible light-grown broad bean seedlings to low (LL) and high (HL) visible light intensities, UV-A or UV-C, either alone or in combination, induced significant increases in total phenolic compounds as well as in anthocyanins content, throughout the germination period, as compared with the respective levels in control seedlings. In general, as compared with control levels, exposure of both dark- or light-grown broad bean seedlings to LL, HL, UV-A or UV-C, induced significant increases in the contents of non-enzymatic antioxidants (total ascorbate; ASA-DASA and total glutathione; GSSG-GSH) and enzymatic antioxidant activities (superoxide dismutase; SOD, catalase; CAT, ascorbate peroxidase; APO and glutathione reductase; GR). The obtained results are discussed in relation to induced mechanisms of protection and repair from the inevitable exposure to damaging visible light and UV radiation. PMID:20505357

  10. Exploration of Visible-Light Photocatalysis in Heterocycle Synthesis and Functionalization: Reaction Design and Beyond.

    Science.gov (United States)

    Chen, Jia-Rong; Hu, Xiao-Qiang; Lu, Liang-Qiu; Xiao, Wen-Jing

    2016-09-20

    Visible-light photocatalysis has recently received increasing attention from chemists because of its wide application in organic synthesis and its significance for sustainable chemistry. This catalytic strategy enables the generation of various reactive species, frequently without stoichiometric activation reagents under mild reaction conditions. Manipulation of these reactive intermediates can result in numerous synthetically useful bond formations in a controllable manner. In this Account, we describe our recent advances in the rational design and strategic application of photocatalysis in the synthesis of various synthetically and biologically important heterocycles. Our main research efforts toward this goal can be classified into four categories: formal cycloaddition and cyclization reactions, radical-mediated olefin functionalization/cyclization cascades, photocatalytic generation and cyclization of N-centered radicals, and photocatalytic functionalization of heterocycles by visible-light-induced dual catalysis. Inspired by the wide application of tertiary amines as reductive additives in photoredox catalysis, we exploited a series of readily accessible or rationally designed tertiary amines with reactive sites in a range of photocatalytic formal cycloaddition and cyclization reactions, providing efficient access to diverse nitrogen heterocycles. Employing various photogenerated radical species, we further developed a series of radical-mediated olefin functionalization/cyclization cascade reactions to successfully assemble various five- and six-membered heterocycles. We have also achieved for the first time the direct catalytic conversion of recalcitrant N-H bonds into neutral N-centered radicals through a visible-light-photocatalytic oxidative deprotonation electron transfer. Using this generic strategy, we have devised several types of radical cyclizations of unsaturated hydrazones, leading to the construction of diversely functionalized pyrazoline and

  11. 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

  12. Local changes in arterial oxygen saturation induced by visible and near-infrared light radiation.

    Science.gov (United States)

    Yesman, S S; Mamilov, S O; Veligotsky, D V; Gisbrecht, A I

    2016-01-01

    In this study, we investigate the efficiency of laser radiation on oxyhemoglobin (HbO2) rate in blood vessels and its wavelength dependence. The results of in vivo experimental measurements of the laser-induced photodissociation of HbO2 in cutaneous blood vessels in the visible and near-infrared (IR) spectral range are presented. Arterial oxygen saturation (SpO2) was measured by a method of fingertip pulse oximetry, which is based on the measurement of the modulated pulse wave of the blood. The light irradiating the finger was provided by corresponding light-emitting diodes (LED) at 15 wavelengths in the 400-940 nm spectrum range. Statistical results with a value of p oxyhemoglobin in deeper layers of tissue blood vessels. The obtained data correlate with the processes of light propagation in biological tissue. The observed reduction in SpO2 indicates the process of photodissociation of HbO2 in vivo and may result in local increase in O2 in the tissue. Such laser-induced enrichment of tissue oxygenation can be used in phototherapy of pathologies, where the elimination of local tissue hypoxia is critical.

  13. 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.

  14. WO3/W Nanopores Sensor for Chemical Oxygen Demand (COD Determination under Visible Light

    Directory of Open Access Journals (Sweden)

    Xuejin Li

    2014-06-01

    Full Text Available A sensor of a WO3 nanopores electrode combined with a thin layer reactor was proposed to develop a Chemical Oxygen Demand (COD determination method and solve the problem that the COD values are inaccurately determined by the standard method. The visible spectrum, e.g., 420 nm, could be used as light source in the sensor we developed, which represents a breakthrough by limiting of UV light source in the photoelectrocatalysis process. The operation conditions were optimized in this work, and the results showed that taking NaNO3 solution at the concentration of 2.5 mol·L−1 as electrolyte under the light intensity of 214 μW·cm−2 and applied bias of 2.5 V, the proposed method is accurate and well reproducible, even in a wide range of pH values. Furthermore, the COD values obtained by the WO3 sensor were fitted well with the theoretical COD value in the range of 3–60 mg·L−1 with a limit value of 1 mg·L−1, which reveals that the proposed sensor may be a practical device for monitoring and controlling surface water quality as well as slightly polluted water.

  15. WO₃/W nanopores sensor for chemical oxygen demand (COD) determination under visible light.

    Science.gov (United States)

    Li, Xuejin; Bai, Jing; Liu, Qiang; Li, Jianyong; Zhou, Baoxue

    2014-06-17

    A sensor of a WO3 nanopores electrode combined with a thin layer reactor was proposed to develop a Chemical Oxygen Demand (COD) determination method and solve the problem that the COD values are inaccurately determined by the standard method. The visible spectrum, e.g., 420 nm, could be used as light source in the sensor we developed, which represents a breakthrough by limiting of UV light source in the photoelectrocatalysis process. The operation conditions were optimized in this work, and the results showed that taking NaNO3 solution at the concentration of 2.5 mol·L(-1) as electrolyte under the light intensity of 214 μW·cm(-2) and applied bias of 2.5 V, the proposed method is accurate and well reproducible, even in a wide range of pH values. Furthermore, the COD values obtained by the WO3 sensor were fitted well with the theoretical COD value in the range of 3-60 mg·L(-1) with a limit value of 1 mg·L(-1), which reveals that the proposed sensor may be a practical device for monitoring and controlling surface water quality as well as slightly polluted water.

  16. WO3/W Nanopores Sensor for Chemical Oxygen Demand (COD) Determination under Visible Light

    Science.gov (United States)

    Li, Xuejin; Bai, Jing; Liu, Qiang; Li, Jianyong; Zhou, Baoxue

    2014-01-01

    A sensor of a WO3 nanopores electrode combined with a thin layer reactor was proposed to develop a Chemical Oxygen Demand (COD) determination method and solve the problem that the COD values are inaccurately determined by the standard method. The visible spectrum, e.g., 420 nm, could be used as light source in the sensor we developed, which represents a breakthrough by limiting of UV light source in the photoelectrocatalysis process. The operation conditions were optimized in this work, and the results showed that taking NaNO3 solution at the concentration of 2.5 mol·L−1 as electrolyte under the light intensity of 214 μW·cm−2 and applied bias of 2.5 V, the proposed method is accurate and well reproducible, even in a wide range of pH values. Furthermore, the COD values obtained by the WO3 sensor were fitted well with the theoretical COD value in the range of 3–60 mg·L−1 with a limit value of 1 mg·L−1, which reveals that the proposed sensor may be a practical device for monitoring and controlling surface water quality as well as slightly polluted water. PMID:24940868

  17. Designing large, high-efficiency, high-numerical-aperture, transmissive meta-lenses for visible light

    CERN Document Server

    Byrnes, Steven J; Aieta, Francesco; Capasso, Federico

    2015-01-01

    A metasurface lens (meta-lens) is a lens that bends light with an array of nanostructures on a flat surface, rather than by refraction. Macroscopic meta-lenses (mm- to cm-scale diameter) have been quite difficult to simulate and optimize, due to the large area, the lack of periodicity, and the billions of adjustable parameters. We describe a method for designing a large-area meta-lens that allows not only prediction of the efficiency and far-field, but also optimization of the shape and position of each individual nanostructure, with a computational cost that is almost independent of the lens size. Loosely speaking, the technique consists of designing a series of metasurface beam deflectors (blazed gratings), and then gluing them together. As a test of this framework, we design some high-numerical-aperture (NA=0.94) meta-lenses for visible light, based on TiO2 nano-pillars on a glass substrate. One of our designs is predicted to focus unpolarized 580nm light with 79% predicted efficiency; another focuses 580n...

  18. Reversed Three-Dimensional Visible Light Indoor Positioning Utilizing Annular Receivers with Multi-Photodiodes.

    Science.gov (United States)

    Xu, Yinfan; Zhao, Jiaqi; Shi, Jianyang; Chi, Nan

    2016-08-08

    Exploiting the increasingly wide use of light emitting diodes (LEDs) lighting, in this paper we propose a reversed indoor positioning system (IPS) based on LED visible light communication (VLC) in order to improve indoor positioning accuracy. Unlike other VLC positioning systems, we employ two annular receivers with multi-photodiodes installed on the ceiling to locate the persons who carry LEDs. The basic idea is using multi-photodiodes to calculate the angle while using the received signal strength (RSS) method to calculate the distance. The experiment results show that the effective positioning range of the proposed system is 1.8 m when the distance between two receivers is 1.2 m. Moreover, a positioning error less than 0.2 m can be achieved under the condition that the radius of the PIN circle is between 0.16 m and 0.2 m, and the distance of the transmitter-receiver plane is less than 1.8 m, which will be effective in practice.

  19. Design of visible light communication system for maintaining uniform data rate

    Science.gov (United States)

    Sung, Jiun-Yu; Lin, Wan-Feng; Wu, Yu-Fu; Chow, Chi-Wai; Yeh, Chien-Hung

    2014-09-01

    Light-emitting diode (LED) is gradually replacing the fluorescent lamp for lighting. Higher modulation bandwidth of LEDs makes the additional application of visible light communication (VLC) possible. Every location of a VLC system should be provided by equal data rate for smooth communication. However, locations away from the LED lamp have less power. These low-power locations have lower signal-to-noise ratio (SNR); and hence lower data rate can be achieved. For achieving high capacity VLC, strategies should be adequately provided to mitigate this problem. Moreover, for some real-time continuous applications, such as video and voice, latency reduction plan should also be considered. In this paper, an orthogonal frequency-division multiplexing access (OFDMA) based system was proposed to solve the above problem. Because we do not use time-division multiplexing access (TDMA) based system, the latency issue can be reduced. The OFDMA based system is also beneficial for large scale operation because the user bandwidth is not reduced by TDM mechanism. Signal-to-noise-plus-interference ratio (SNIR) distribution of the VLC system is designed to ensure uniform and optimal system capacity. Discrete multi-tone (DMT) is used for this VLC system. The DMT subcarriers are bit-loaded depending on the LED frequency response. More subcarriers are allocated for communication at low SNIR locations. Hence, nearly equal data rate can be provided everywhere. Demonstration of 17 Mb/s/LED data rate was provided.

  20. Enhanced Visible Light Photocatalytic Activity for TiO2 Nanotube Array Films by Codoping with Tungsten and Nitrogen

    Directory of Open Access Journals (Sweden)

    Min Zhang

    2013-01-01

    Full Text Available A series of W, N codoped TiO2 nanotube arrays with different dopant contents were fabricated by anodizing in association with hydrothermal treatment. The samples were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet-visible light diffuse reflection spectroscopy. Moreover, the photocatalytic activity of W and N codoped TiO2 nanotube arrays was evaluated by degradation of methylene blue under visible light irradiation. It was found that N in codoped TNAs exists in the forms of Ti-N-O, while W exists as W6+ by substituting Ti in the lattice of TiO2. In the meantime, W and N codoping successfully extends the absorption of TNAs into the whole visible light region and results in remarkably enhanced photocatalytic activity under visible light irradiation. The mechanism of the enhanced photocatalytic activity could be attributed to (i increasing number of hydroxyl groups on the surface of TNAs after the hydrothermal treatment, (ii a strong W-N synergistic interaction leads to produce new states, narrow the band gap which decrease the recombination effectively, and then greatly increase the visible light absorption and photocatalytic activity; (iii W ions with changing valences in all codoped samples which are considered to act as trapping sites, effectively decrease the recombination rate of electrons and holes, and improve the photocatalytic activity.

  1. Visible light photocatalytic activity induced by Rh(III) modification on the surface of BiOCl

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jinli; Wu, Xin; Huang, Caijin, E-mail: cjhuang@fzu.edu.cn; Fan, Wenjie; Qiu, Xiaoqing, E-mail: qiuxq@fzu.edu.cn

    2016-11-30

    Highlights: • Rh(III) clusters were deposited on the BiOCl microflowers as an efficient modifier. • The Rh(III)-BiOCl samples show an enhanced visible-light photocatalytic activity. • The Rh(III) clusters server as the redox reaction centers for the multi-electron reduction of O{sub 2}. - Abstract: Using impregnation technique, a small amount of Rh(III) clusters has been grafted on the BiOCl microflowers. The samples are characterized by X-ray diffraction, scanning electron microscopy coupled with high energy distribution X-ray, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activities are investigated by the decomposition of gaseous acetaldehyde under irradiation of visible light. The bare BiOCl microflowers exhibit the limited visible light photocatalytic activity because of its wide band gap. After surface modification of Rh(III) clusters, the Rh(III)-BiOCl samples show an enhanced photocatalytic activity for the decomposition gaseous acetaldehyde under visible light irradiation. It is found that the Rh(III) clusters play an important role for the visible light absorption, probably through the electron transfer between Rh(III) clusters and the BiOCl, as well as the redox reaction centers for the multi-electron reduction of O{sub 2}.

  2. 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.

  3. A Fine-Grained Visible Light Communication Position Detection System Embedded in One-Colored Light Using DMD Projector

    Directory of Open Access Journals (Sweden)

    Motoi Kodama

    2017-01-01

    Full Text Available When we consider the Internet of Things (IoT society that all of the people and things are connected by the Internet and with each other and they can use the variety of services and applications, the development of sensing and communication technology is very important. As one of its key technologies, the visible light communication (VLC has attracted attention in the point of ubiquity. In this paper, we propose a fine-grained VLC position detection system embedded in one-colored light using Digital Micromirror Device (DMD projector for new location services in millimeters and report its concept and fundamental experiment using our prototype of the receiver module with Linux single-board computer, Raspberry Pi. In addition, we mention the future application using our system in a clothes shop. Our experimental results show that our system has high accuracy in millimeters and the potential to be more convenient in the future’s location services using the VLC with the DMD projector. There was no trial to use a DMD projector as the illumination until now, but our study shows that the DMD projector has an availability of special modulated VLC illumination type beacon in the IoT age.

  4. 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.

  5. Bismuth titanate microspheres: Directed synthesis and their visible light photocatalytic activity

    Science.gov (United States)

    Lin, Xue; Lv, Peng; Guan, Qingfeng; Li, Haibo; Zhai, Hongjv; Liu, Chunbo

    2012-07-01

    Bismuth titanate, Bi4Ti3O12 (BIT), with a well-defined spherical structure, was synthesized by a facile hydrothermal process without using any surfactant or template. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) showed that BIT spheres could be fabricated in high yields by simply manipulating the concentrations of hydroxide ions. In this case, hydroxide ions seem to play a key role in controlling the formation of seeds and growth rates of BIT particles. Ultraviolet-visible (UV-vis) absorption spectra demonstrated that the band gap of BIT samples was about 2.79 eV. In addition, based on the structural analysis of samples obtained at different conditions, a possible mechanism for the formation of these distinctive morphologies was proposed. The as-prepared BIT microspheres exhibited higher photocatalytic activities in the degradation of methyl orange (MO) under visible light irradiation than that of N-TiO2. Furthermore, BIT microspheres which prepared at OH- concentration of 3 mol L-1 showed the highest photocatalytic activity.

  6. Origin of the visible light induced persistent luminescence of Cr3+-doped zinc gallate

    Science.gov (United States)

    Gourier, Didier; Bessière, Aurélie; Sharma, Suchinder. K.; Binet, Laurent; Viana, Bruno; Basavaraju, Neelima; Priolkar, Kaustubh R.

    2014-07-01

    ZnGa2O4:Cr3+ (ZGO:Cr) is a very bright persistent phosphor able to emit a near infrared light for hours following a UV (band to band excitation) or visible (Cr3 excitation) illumination. As such it serves as an outstanding biomarker for in vivo imaging. Persistent luminescence, due to trapping of electrons/holes at point defects, is studied here on a series of ZGO:Cr spinel compounds where the introduction of defects is controlled by varying the Zn/(Ga+Cr) nominal ratio during synthesis. Simulation of Electron Paramagnetic Resonance spectra revealed up to six types of Cr3+ ions with different neighboring defects and correlated to four emission lines in low temperature photoluminescence spectroscopy. Of particular importance, three EPR signals were attributed to Cr3+ with a pair of neighboring ZnGa' and GaZn0° antisite defects. They were identified to the emission line N2 that plays a key role in the persistent luminescence mechanism for both storage of visible excitation and persistent luminescence emission. A model is proposed whereby the local electric field at Cr3+ created by the two neighboring antisite defects triggers the electron-hole separation and trapping upon excitation of Cr3+. The process is equivalent to a photoinduced electron transfer from a donor (here ZnGa') to an acceptor (here GaZn0°) observed in some molecular systems.

  7. 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.

  8. 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.

  9. Visible-light photolytic synthesis of multinuclear and dendritic iron-nitrile cationic complexes.

    Science.gov (United States)

    Ornelas, Cátia; Ruiz, Jaime; Rodrigues, João; Astruc, Didier

    2008-05-19

    Multinuclear and dendritic iron-nitrile piano-stool cationic complexes were synthesized in quantitative yield by a single-step synthesis involving visible-light photolysis of the complex [CpFe(eta(6)-toluene)][PF6]. This synthetic strategy was applied to mono-, bis- and tris-nitrile ligands and to new nitrile-terminated dendrimers containing 9, 27, and 81 tethers. All the synthesized products are deep red solids or red waxy products, highly stable to air and moisture. They were characterized by (1)H, (13)C, and (31)P NMR, elemental analysis, UV-vis spectroscopy, and cyclic voltammetry (single reversible oxidation wave to Fe(III)). Only the para-disubstituted arene dinitrile diiron complex shows two separated reversible waves indicating some electronic communication between the iron centers through the nitrile ligands.

  10. Wet Chemical Controllable Synthesis of Hematite Ellipsoids with Structurally Enhanced Visible Light Property

    Directory of Open Access Journals (Sweden)

    Chengliang Han

    2013-01-01

    Full Text Available A facile and economic route has been presented for mass production of micro/nanostructured hematite microcrystals based on the wet chemical controllable method. The as-prepared samples were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-Vis absorption spectroscopy. The results showed that the product was mesoporous α-Fe2O3 and nearly elliptical in shape. Each hematite ellipsoid was packed by many α-Fe2O3 nanoparticles. The values of vapor pressure in reaction systems played vital roles in the formation of porous hematite ellipsoids. Optical tests demonstrated that the micro/nanostructured elliptical hematite exhibited enhanced visible light property at room temperature. The formation of these porous hematite ellipsoids could be attributed to the vapor pressure induced oriented assembling of lots of α-Fe2O3 nanoparticles.

  11. BICM-ID scheme for clipped DCO-OFDM in visible light communications.

    Science.gov (United States)

    Tan, Jiandong; Wang, Zhaocheng; Wang, Qi; Dai, Linglong

    2016-03-07

    Visible light communication (VLC) is recommended for indoor transmissions in 5G network, whereby DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) is adopted to eliminate the inter-symbol interference (ISI) but suffers from considerable performance loss induced by clipping distortion. In this paper, bit-interleaved coded modulation with iterative demapping and decoding (BICM-ID) scheme for clipped DCO-OFDM is investigated to enhance the performance of VLC systems. In order to further mitigate the clipping distortions, a novel soft demapping criterion is proposed, and a simplified demapping algorithm is developed to reduce the complexity of the proposed criterion. Simulation results illustrate that the enhanced demapping algorithm achieves a significant performance gain.

  12. Synthesis of highly functionalized polycyclic quinoxaline derivatives using visible-light photoredox catalysis.

    Science.gov (United States)

    He, Zhi; Bae, Minwoo; Wu, Jie; Jamison, Timothy F

    2014-12-22

    A mild and facile method for preparing highly functionalized pyrrolo[1,2-a]quinoxalines and other nitrogen-rich heterocycles, each containing a quinoxaline core or an analogue thereof, has been developed. The novel method features a visible-light-induced decarboxylative radical coupling of ortho-substituted arylisocyanides and radicals generated from phenyliodine(III) dicarboxylate reagents and exhibits excellent functional group compatibility. A wide range of quinoxaline heterocycles have been prepared. Finally, a telescoped preparation of these polycyclic compounds by integration of the in-line isocyanide formation and photochemical cyclization has been established in a three-step continuous-flow system. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Wet chemical controllable synthesis of hematite ellipsoids with structurally enhanced visible light property.

    Science.gov (United States)

    Han, Chengliang; Han, Jie; Li, Qiankun; Xie, Jingsong

    2013-01-01

    A facile and economic route has been presented for mass production of micro/nanostructured hematite microcrystals based on the wet chemical controllable method. The as-prepared samples were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-Vis absorption spectroscopy. The results showed that the product was mesoporous α -Fe2O3 and nearly elliptical in shape. Each hematite ellipsoid was packed by many α -Fe2O3 nanoparticles. The values of vapor pressure in reaction systems played vital roles in the formation of porous hematite ellipsoids. Optical tests demonstrated that the micro/nanostructured elliptical hematite exhibited enhanced visible light property at room temperature. The formation of these porous hematite ellipsoids could be attributed to the vapor pressure induced oriented assembling of lots of α -Fe2O3 nanoparticles.

  14. Ferrocene-modified carbon nitride for direct oxidation of benzene to phenol with visible light.

    Science.gov (United States)

    Ye, Xiangju; Cui, Yanjuan; Wang, Xinchen

    2014-03-01

    Ferrocene moieties were heterogenized onto carbon nitride polymers by a covalent -C=N- linkage bridging the two conjugation systems, enabling the merging of the redox function of ferrocene with carbon nitride photocatalysis to construct a heterogeneous Photo-Fenton system for green organocatalysis at neutral conditions. The synergistic donor-acceptor interaction between the carbon nitride matrix and ferrocene group, improved exciton splitting, and coupled photocatalytic performance allowed the direct synthesis of phenol from benzene in the presence of H2 O2 under visible light irradiation. This innovative modification method will offer an avenue to construct functionalized two-dimensional polymers useful also for other green synthesis processes using solar irradiation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Carrier dynamics of a visible-light-responsive Ta3N5 photoanode for water oxidation

    KAUST Repository

    Ziani, Ahmed

    2015-01-01

    The physicochemical properties of a tantalum nitride (Ta3N5) photoanode were investigated in detail to understand the fundamental aspects associated with the photoelectrochemical (PEC) water oxidation. The Ta3N5 thin films were synthesized using DC magnetron sputtering followed by annealing in air and nitridation under ammonia (NH3). A polycrystalline structure with a dense morphology of the monoclinic Ta3N5 films was obtained. A relatively low absorption coefficient (104 to 105 cm-1) in the visible light range was measured for Ta3N5, consistent with the nature of the indirect band-gap. Ultra-fast spectroscopic measurements revealed that the Ta3N5 with different thicknesses films possess low transport properties and fast carrier recombination (<10 ps). These critical kinetic properties of Ta3N5 as a photoanode may necessitate high overpotentials to achieve appreciable photocurrents for water oxidation (onset ∼0.6 V vs. RHE). This journal is

  16. Achievable information rate enhancement of visible light communication using probabilistically shaped OFDM modulation.

    Science.gov (United States)

    Xie, Chenhui; Chen, Zexin; Fu, Songnian; Liu, Wu; He, Zhixue; Deng, Lei; Tang, Ming; Liu, Deming

    2018-01-08

    We present the first experimental demonstration of orthogonal frequency division multiplexed (OFDM) modulation using the probabilistic shaping (PS) technique in visible light communication (VLC) systems, in order to increase the achievable information rate (AIR) according to the pre-estimated signal to noise ratio (SNR) of VLC channel. We numerically investigate the performance of PS technique and make a fair comparison with bit-loading technique under different scenarios. By using a phosphor-LED based VLC system with available bandwidth of ~45-MHz, OFDM with PS technique can experimentally realize an AIR of 204.1-Mb/s over 1-m free space transmission, leading to a 26.8% increment in comparison with OFDM using bit-loading technique at the expense of 16% overall forward error correction (FEC) overhead (OH).

  17. Characterization of a broadband interferometric autocorrelator for visible light with ultrashort blue laser pulses

    Science.gov (United States)

    Zürch, M.; Hoffmann, A.; Gräfe, M.; Landgraf, B.; Riediger, M.; Spielmann, Ch.

    2014-06-01

    We present a compact interferometric autocorrelator that allows the characterization of ultrashort laser pulses in the visible light domain (370-740 nm). The presented device uses a GaN photodiode with corresponding two-photon absorption. Different GaN and AlGaN photodiodes were characterized for this purpose. Despite AlGaN diodes have a better matched bandgap for this application, we have found that only the GaN diodes show sufficient nonlinear behavior. Using the autocorrelator we were able to characterize ultrashort frequency doubled Ti:Sapphire laser pulses with a pulse duration down to 18 fs in the second harmonic having just a few hundred nanojoules of pulse energy. The broadband behavior and extension towards the UV along with the need for only low energetic pulses are the novelties of this device.

  18. Visible light communication using mobile-phone camera with data rate higher than frame rate.

    Science.gov (United States)

    Chow, Chi-Wai; Chen, Chung-Yen; Chen, Shih-Hao

    2015-10-05

    Complementary Metal-Oxide-Semiconductor (CMOS) image sensors are widely used in mobile-phone and cameras. Hence, it is attractive if these image sensors can be used as the visible light communication (VLC) receivers (Rxs). However, using these CMOS image sensors are challenging. In this work, we propose and demonstrate a VLC link using mobile-phone camera with data rate higher than frame rate of the CMOS image sensor. We first discuss and analyze the features of using CMOS image sensor as VLC Rx, including the rolling shutter effect, overlapping of exposure time of each row of pixels, frame-to-frame processing time gap, and also the image sensor "blooming" effect. Then, we describe the procedure of synchronization and demodulation. This includes file format conversion, grayscale conversion, column matrix selection avoiding blooming, polynomial fitting for threshold location. Finally, the evaluation of bit-error-rate (BER) is performed satisfying the forward error correction (FEC) limit.

  19. 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.

  20. Photodegradation of methyl orange with PANI-modified BiOCl photocatalyst under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qizhao, E-mail: qizhaosjtu@gmail.com [College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education of China, Key Laboratory of Gansu Polymer Materials, Lanzhou 730070 (China); Hui, Juan; Li, Jiajia; Cai, Yuxia; Yin, Shuqun [College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Wang, Fangping, E-mail: wangfplz@163.com [College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Su, Bitao [College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China)

    2013-10-15

    Photocatalyst BiOCl modified by polyaniline (PANI/BiOCl) was synthesized via a facile chemisorptions method. X-ray diffraction (XRD), Scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy (DRS) were employed to study the phase structure, morphology and optical properties of the samples. The results showed that the PANI increased absorption intensity and absorption bands of the pure BiOCl. Photodegradation of methyl orange (MO) on the samples were investigated under visible light irradiation and 7 wt.% PANI/BiOCl composite showed the highest photocatalytic activity. The enhanced photocatalytic performance could be attributed to PANI/BiOCl composites and the synergistic effect between PANI and BiOCl. According to experimental results, the possible photocatalytic mechanism of the PANI/BiOCl photocatalysts was proposed.