Recent progress in photoactive organic field-effect transistors.

Science.gov (United States)

Wakayama, Yutaka; Hayakawa, Ryoma; Seo, Hoon-Seok

2014-04-01

Recent progress in photoactive organic field-effect transistors (OFETs) is reviewed. Photoactive OFETs are divided into light-emitting (LE) and light-receiving (LR) OFETs. In the first part, LE-OFETs are reviewed from the viewpoint of the evolution of device structures. Device performances have improved in the last decade with the evolution of device structures from single-layer unipolar to multi-layer ambipolar transistors. In the second part, various kinds of LR-OFETs are featured. These are categorized according to their functionalities: phototransistors, non-volatile optical memories, and photochromism-based transistors. For both, various device configurations are introduced: thin-film based transistors for practical applications, single-crystalline transistors to investigate fundamental physics, nanowires, multi-layers, and vertical transistors based on new concepts.

Recent progress in photoactive organic field-effect transistors

International Nuclear Information System (INIS)

Wakayama, Yutaka; Hayakawa, Ryoma; Seo, Hoon-Seok

2014-01-01

Recent progress in photoactive organic field-effect transistors (OFETs) is reviewed. Photoactive OFETs are divided into light-emitting (LE) and light-receiving (LR) OFETs. In the first part, LE-OFETs are reviewed from the viewpoint of the evolution of device structures. Device performances have improved in the last decade with the evolution of device structures from single-layer unipolar to multi-layer ambipolar transistors. In the second part, various kinds of LR-OFETs are featured. These are categorized according to their functionalities: phototransistors, non-volatile optical memories, and photochromism-based transistors. For both, various device configurations are introduced: thin-film based transistors for practical applications, single-crystalline transistors to investigate fundamental physics, nanowires, multi-layers, and vertical transistors based on new concepts. (review)

Incoherent manipulation of the photoactive yellow protein photocycle with dispersed pump-dump-probe spectroscopy

NARCIS (Netherlands)

Larsen, D.S.; van Stokkum, I.H.M.; Vengris, M.; Horst, M.A.; de Weerd, F.L.; Hellingwerf, K.J.; van Grondelle, R.

2004-01-01

Photoactive yellow protein is the protein responsible for initiating the "blue-light vision" of Halorhodospira halophila. The dynamical processes responsible for triggering the photoactive yellow protein photocycle have been disentangled with the use of a novel application of dispersed ultrafast

Incoherent manipulation of the photoactive yellow protein photocycle with dispersed pump-dump-probe spectroscopy.

NARCIS (Netherlands)

Larsen, D.S.; van Stokkum, I.H.M.; Vengris, M.; van der Horst, M.A.; de Weerd, F.; Hellingwerf, K.J.; van Grondelle, R.

2004-01-01

Photoactive yellow protein is the protein responsible for initiating the ``blue-light vision¿¿ of Halorhodospira halophila. The dynamical processes responsible for triggering the photoactive yellow protein photocycle have been disentangled with the use of a novel application of dispersed ultrafast

Green proteorhodopsin reconstituted into nanoscale phospholipid bilayers (nanodiscs) as photoactive monomers.

Science.gov (United States)

Ranaghan, Matthew J; Schwall, Christine T; Alder, Nathan N; Birge, Robert R

2011-11-16

Over 4000 putative proteorhodopsins (PRs) have been identified throughout the oceans and seas of the Earth. The first of these eubacterial rhodopsins was discovered in 2000 and has expanded the family of microbial proton pumps to all three domains of life. With photophysical properties similar to those of bacteriorhodopsin, an archaeal proton pump, PRs are also generating interest for their potential use in various photonic applications. We perform here the first reconstitution of the minimal photoactive PR structure into nanoscale phospholipid bilayers (nanodiscs) to better understand how protein-protein and protein-lipid interactions influence the photophysical properties of PR. Spectral (steady-state and time-resolved UV-visible spectroscopy) and physical (size-exclusion chromatography and electron microscopy) characterization of these complexes confirms the preparation of a photoactive PR monomer within nanodiscs. Specifically, when embedded within a nanodisc, monomeric PR exhibits a titratable pK(a) (6.5-7.1) and photocycle lifetime (∼100-200 ms) that are comparable to the detergent-solubilized protein. These ndPRs also produce a photoactive blue-shifted absorbance, centered at 377 or 416 nm, that indicates that protein-protein interactions from a PR oligomer are required for a fast photocycle. Moreover, we demonstrate how these model membrane systems allow modulation of the PR photocycle by variation of the discoidal diameter (i.e., 10 or 12 nm), bilayer thickness (i.e., 23 or 26.5 Å), and degree of saturation of the lipid acyl chain. Nanodiscs also offer a highly stable environment of relevance to potential device applications.

Initial photoinduced dynamics of the photoactive yellow protein

NARCIS (Netherlands)

Larsen, D.S.; van Grondelle, R.

2005-01-01

The photoactive yellow protein (PYP) is the photoreceptor protein responsible for initiating the blue-light repellent response of the Halorhodospira halophila bacterium. Optical excitation of the intrinsic chromophore in PYP, p-coumaric acid, leads to the initiation of a photocycle that comprises

Photoactive dye enhanced tissue ablation for endoscopic laser prostatectomy

Science.gov (United States)

Ahn, Minwoo; Nguyen, Trung Hau; Nguyen, Van Phuc; Oh, Junghwan; Kang, Hyun Wook

2015-02-01

Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia with high laser power. The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption and eventually to facilitate tissue ablation with low laser power. The experiment was implemented on chicken breast due to minimal optical absorption Amaranth (AR), black dye (BD), hemoglobin powder (HP), and endoscopic marker (EM), were selected and tested in vitro with a customized 532-nm laser system with radiant exposure ranging from 0.9 to 3.9 J/cm2. Light absorbance and ablation threshold were measured with UV-VIS spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes. Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and number of injection. Higher light absorption by injected dyes led to lower ablation threshold as well as more efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation efficiency principally increased with input parameter. Among the dyes, AR created the highest ablation rate of 44.2+/-0.2 μm/pulse due to higher absorbance and lower ablation threshold. Preliminary tests on canine prostate with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation efficiency to 120 W with no injection, indicating 33 % reduced laser power with almost equivalent performance. In-depth comprehension on photoactive dye-enhanced tissue ablation can help accomplish efficient and safe laser treatment for BPH with low power application.

Incoherent Manipulation of the Photoactive Yellow Protein Photocycle with Dispersed Pump-Dump-Probe Spectroscopy

OpenAIRE

Larsen, Delmar S.; van Stokkum, Ivo H. M.; Vengris, Mikas; van der Horst, Michael A.; de Weerd, Frank L.; Hellingwerf, Klaas J.; van Grondelle, Rienk

2004-01-01

Photoactive yellow protein is the protein responsible for initiating the ``blue-light vision¿¿ of Halorhodospira halophila. The dynamical processes responsible for triggering the photoactive yellow protein photocycle have been disentangled with the use of a novel application of dispersed ultrafast pump-dump-probe spectroscopy, where the photocycle can be started and interrupted with appropriately tuned and timed laser pulses. This ``incoherent¿¿ manipulation of the photocycle allows for the d...

Proline 68 enhances photoisomerization yield in photoactive yellow protein

NARCIS (Netherlands)

Rupenyan, A.B.; Vreede, J.; van Stokkum, I.H.M.; Hospes, M.; Kennis, J.T.M.; Hellingwerf, K.J.; Groot, M.L.

2011-01-01

In proteins and enzymes, the local environment of an active cofactor plays an important role in controlling the outcome of a functional reaction. In photoactive yellow protein (PYP), it ensures photoisomerization of the chromophore, a prerequisite for formation of a signaling state. PYP is the

Proline 68 Enhances Photoisomerization Yield in Photoactive Yellow Protein

NARCIS (Netherlands)

Rupenyan, A.B.; Vreede, J.; van Stokkum, I.H.M.; Hospes, M.; Kennis, J.T.M.; Hellingwerf, K.J.; Groot, M.L.

2011-01-01

In proteins and enzymes, the local environment of an active cofactor plays an important role in controlling the outcome of a functional reaction. In photoactive yellow protein (PYP), it ensures photoisomerization of the chromophore, a prerequisite for formation of a signaling state. PYP is the

Making waves in a photoactive polymer film

Science.gov (United States)

Gelebart, Anne Helene; Jan Mulder, Dirk; Varga, Michael; Konya, Andrew; Vantomme, Ghislaine; Meijer, E. W.; Selinger, Robin L. B.; Broer, Dirk J.

2017-06-01

Oscillating materials that adapt their shapes in response to external stimuli are of interest for emerging applications in medicine and robotics. For example, liquid-crystal networks can be programmed to undergo stimulus-induced deformations in various geometries, including in response to light. Azobenzene molecules are often incorporated into liquid-crystal polymer films to make them photoresponsive; however, in most cases only the bending responses of these films have been studied, and relaxation after photo-isomerization is rather slow. Modifying the core or adding substituents to the azobenzene moiety can lead to marked changes in photophysical and photochemical properties, providing an opportunity to circumvent the use of a complex set-up that involves multiple light sources, lenses or mirrors. Here, by incorporating azobenzene derivatives with fast cis-to-trans thermal relaxation into liquid-crystal networks, we generate photoactive polymer films that exhibit continuous, directional, macroscopic mechanical waves under constant light illumination, with a feedback loop that is driven by self-shadowing. We explain the mechanism of wave generation using a theoretical model and numerical simulations, which show good qualitative agreement with our experiments. We also demonstrate the potential application of our photoactive films in light-driven locomotion and self-cleaning surfaces, and anticipate further applications in fields such as photomechanical energy harvesting and miniaturized transport.

A general strategy for synthesis of cyclophane-braced peptide macrocycles via palladium-catalysed intramolecular sp3 C-H arylation

Science.gov (United States)

Zhang, Xuekai; Lu, Gang; Sun, Meng; Mahankali, Madhu; Ma, Yanfei; Zhang, Mingming; Hua, Wangde; Hu, Yuting; Wang, Qingbing; Chen, Jinghuo; He, Gang; Qi, Xiangbing; Shen, Weijun; Liu, Peng; Chen, Gong

2018-05-01

New methods capable of effecting cyclization, and forming novel three-dimensional structures while maintaining favourable physicochemical properties are needed to facilitate the development of cyclic peptide-based drugs that can engage challenging biological targets, such as protein-protein interactions. Here, we report a highly efficient and generally applicable strategy for constructing new types of peptide macrocycles using palladium-catalysed intramolecular C(sp3)-H arylation reactions. Easily accessible linear peptide precursors of simple and versatile design can be selectively cyclized at the side chains of either aromatic or modified non-aromatic amino acid units to form various cyclophane-braced peptide cycles. This strategy provides a powerful tool to address the long-standing challenge of size- and composition-dependence in peptide macrocyclization, and generates novel peptide macrocycles with uniquely buttressed backbones and distinct loop-type three-dimensional structures. Preliminary cell proliferation screening of the pilot library revealed a potent lead compound with selective cytotoxicity toward proliferative Myc-dependent cancer cell lines.

Morphological Control of the Photoactive Layer in Bulk Heterojunction Organic Solar Cells

KAUST Repository

Su, Yisong

2011-07-23

For its inherent advantages, such as lightweight, low cost, flexibility, and opportunity to cover large surface areas, organic solar cells have attracted more and more attention in both academia and industry. However, the efficiency of organic solar cell is still much lower than silicon solar cells, but steadily rising as it now stands above 8%. The architecture of bulk heterojunction solar cells can improve the performance of organic solar cell a lot, but these improvements are highly dependent on the morphology of photoactive layer. Therefore, by controlling the morphology of photoactive layer, most commonly composed of a P3HT donor polymer and PCBM small molecule, the performance of organic solar cells could be optimized. The use of solvent additives in the solution formulation is particularly interesting, because it is a low cost method of controlling the phase separation of the photoactive layer and possibly removing the need for subsequent thermal and solvent vapor annealing. However, the role of the solvent additive remains not well understood and much debate remains on the mechanisms by which it impacts phase separation. In the first part of this thesis, we investigate the role of the solvent additive on the individual components (solvent, donor and acceptor) of the solution and the photoactive layer both in the bulk solution, during solution-processing and in the post-processing solid state of the film. In the second part of this thesis, we investigate the role of the additive on the blended solution state and resulting thin film phase separation. Finally, we propose a new method of controlling phase separation based on the insight into the role of the solvent additive. In the first part, we used an additive [octandiethiol (OT)] in the solvent to help the aggregation of P3HT in the solution. From the UV-vis experiments, the crystallinity of P3HT in the solutions increased while it decreased in thin films with steady increase of additive concentration. This

Is the photoactive yellow protein a UV-B/blue light photoreceptor?

NARCIS (Netherlands)

Carroll, E. C.; Hospes, M.; Valladares, C.; Hellingwerf, K.J.; Larsen, D.S.

2011-01-01

UV light below 300 nm is shown to generate the first photocycle intermediate in the blue light photoreceptor Photoactive Yellow Protein. Fluorescence and ultrafast transient absorption measurements indicate two excitation pathways: UV-B absorption by the chromophore and Fluorescence Resonant Energy

Selective Oxidation of Alcohols Using Photoactive VO@g‑C3N4

Data.gov (United States)

U.S. Environmental Protection Agency — A photoactive VO@g-C3N4 catalyst has been developed for the selective oxidation of alcohols to the corresponding aldehydes and ketones. The visible light mediated...

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.

Inkjet printable-photoactive all inorganic perovskite films with long effective photocarrier lifetimes

Science.gov (United States)

Ilie, C. C.; Guzman, F.; Swanson, B. L.; Evans, I. R.; Costa, P. S.; Teeter, J. D.; Shekhirev, M.; Benker, N.; Sikich, S.; Enders, A.; Dowben, P. A.; Sinitskii, A.; Yost, A. J.

2018-05-01

Photoactive perovskite quantum dot films, deposited via an inkjet printer, have been characterized by x-ray diffraction and x-ray photoelectron spectroscopy. The crystal structure and bonding environment are consistent with CsPbBr3 perovskite quantum dots. The current–voltage (I–V) and capacitance–voltage (C–V) transport measurements indicate that the photo-carrier drift lifetime can exceed 1 ms for some printed perovskite films. This far exceeds the dark drift carrier lifetime, which is below 50 ns. The printed films show a photocarrier density 109 greater than the dark carrier density, making these printed films ideal candidates for application in photodetectors. The successful printing of photoactive-perovskite quantum dot films of CsPbBr3, indicates that the rapid prototyping of various perovskite inks and multilayers is realizable.

(2R,3aR,4S,7R,7aS,9R,10aR,11S,14R,14aS-rel-3a,4,7,7a,10a,11,14,14a-Octahydro-4,14:7,11-diepoxy-2,9-propanonaphtho[1,2-f:5,6-f′]diisoindole-1,3,8,10-tetrone (9CI: a cyclophane derived from naphtho[1,2-c:5,6-c]difuran

Directory of Open Access Journals (Sweden)

Peter W. Dibble

2008-09-01

Full Text Available The title compound, C25H18N2O6, is a naphthalenophane styled in the manner of Warrener's alicyclic cyclophanes or molecular racks wherein a trimethylene tether is perfectly staggered between the two N atoms such that the central methylene H atoms point toward the naphthalene π-system. The dihedral angle between the mean planes of the two benzene rings is 7.61 (7°.

Structural Evolution in Photoactive Yellow Protein Studied by Femtosecond Stimulated Raman Spectroscopy

Directory of Open Access Journals (Sweden)

Yoshizawa M.

2013-03-01

Full Text Available Ultrafast structural evolution in photoactive yellow protein (PYP is studied by femtosecond stimulated Raman spectroscopy. A comparison between wild-type PYP and E46Q mutant reveals that the hydrogen-bonding network surrounding the chromophore of PYP is immediately rearranged in the electronic excited state.

The enhanced photoactivity of nanosized Bi2WO6 catalyst for the degradation of 4-chlorophenol

International Nuclear Information System (INIS)

Fu Hongbo; Yao Wenqing; Zhang Liwu; Zhu Yongfa

2008-01-01

Nanosized Bi 2 WO 6 catalyst exhibited the enhanced photoactivity for the degradation of 4-chlorophenol (4-CP) under visible irradiation compared to the sample prepared by high-temperature solid reaction. The photoactivity of the catalyst was sensitive to pH variation of the suspension. Nanosized Bi 2 WO 6 catalyst showed the highest activity at pH 7.2. The photodegradation of 4-CP by nanosized Bi 2 WO 6 catalyst followed a pseudo-first-order reaction. After three recycling runs for the photodegradation of 4-CP, the activity of the catalyst did not show any significant loss, suggesting that the catalyst was stable under visible irradiation

Application of photoactive electrospun nanofiber materials with immobilized meso-tetraphenylporphyrin for parabens photodegradation

Czech Academy of Sciences Publication Activity Database

Gmurek, M.; Bizukojc, M.; Mosinger, Jiří; Ledakowicz, S.

2015-01-01

Roč. 240, FEB (2015), s. 160-167 ISSN 0920-5861 Institutional support: RVO:61388980 Keywords : Esters of p-hydroxybenzoic acid * Langmuir-Hinshelwood model * Heterogeneous photosensitized oxidation * Molecular singlet oxygen * Photoactive materials Subject RIV: CA - Inorganic Chemistry Impact factor: 4.312, year: 2015

Photoactive devices including porphyrinoids with coordinating additives

Science.gov (United States)

Forrest, Stephen R; Zimmerman, Jeramy; Yu, Eric K; Thompson, Mark E; Trinh, Cong; Whited, Matthew; Diev, Vlacheslav

2015-05-12

Coordinating additives are included in porphyrinoid-based materials to promote intermolecular organization and improve one or more photoelectric characteristics of the materials. The coordinating additives are selected from fullerene compounds and organic compounds having free electron pairs. Combinations of different coordinating additives can be used to tailor the characteristic properties of such porphyrinoid-based materials, including porphyrin oligomers. Bidentate ligands are one type of coordinating additive that can form coordination bonds with a central metal ion of two different porphyrinoid compounds to promote porphyrinoid alignment and/or pi-stacking. The coordinating additives can shift the absorption spectrum of a photoactive material toward higher wavelengths, increase the external quantum efficiency of the material, or both.

One-pot Synthesis of Soluble Nanoscale CIGS Photoactive Functional Materials

Directory of Open Access Journals (Sweden)

Yan Aixia

2007-01-01

Full Text Available Abstract Promising alternatives for solar energy utilization are thin film technologies involving various new materials. This contribution describes an easy and inexpensive synthetic method that can be used to prepare soluble nanoscale triphenyl phosphine-coordinated CIGS (TPP-CIGS photoactive functional materials. This complex is stable in the solid state under the irradiation of the ambient light, but its solution becomes a little bit unstable under the illumination of the low intensity laser.

Understanding the adsorptive and photoactivity properties of Ag-graphene oxide nanocomposites.

Science.gov (United States)

Martínez-Orozco, R D; Rosu, H C; Lee, Soo-Wohn; Rodríguez-González, V

2013-12-15

Nanocomposites of graphene oxide (GO) and silver nanoparticles (AgNPs) were synthetized using a practical photochemical silver functionalization. Their photocatalytic activities were evaluated with two dyes, Rhodamine B and Indigo Carmine, under visible-light irradiation. The prepared nanocomposites were characterized by HRTEM, FESEM, XRD, Raman, FTIR and UV-vis absorption spectroscopy. These nanocomposites present new defect domains of sp(3) type in combination with several graphitic functional groups that act as nucleation sites for anchoring AgNPs, while the sp(2)-sp(3) edge defects domains of GO generate the photoactivity. Furthermore, their photocatalytic performances are governed by their large adsorption capacity, and strong interaction with dye chromophores. A comprehensive photocatalytic way underlying the importance of adsorption is suggested to explain the low visible-light responsive photoactivity of the AgNPs-GO nanocomposites and the possible binding-site saturation. Then, the usage of H2SO4 allows the production of ionic species and helps to confirm the strong adsorption of both dyes. The ability to synthesize AgNPs-GO nanocomposites with extensive adsorptive capacity is certainly of interest for the efficient removal of hazardous materials. Copyright © 2013 Elsevier B.V. All rights reserved.

Detection of Singlet Oxygen Formation inside Photoactive Biohybrid Composite Material

Directory of Open Access Journals (Sweden)

Kata Hajdu

2017-12-01

Full Text Available Photosynthetic reaction center proteins (RCs are the most efficient light energy converter systems in nature. The first steps of the primary charge separation in photosynthesis take place in these proteins. Due to their unique properties, combining RCs with nano-structures promising applications can be predicted in optoelectronic systems. In the present work RCs purified from Rhodobacter sphaeroides purple bacteria were immobilized on multiwalled carbon nanotubes (CNTs. Carboxyl—and amine-functionalised CNTs were used, so different binding procedures, physical sorption and chemical sorption as well, could be applied as immobilization techniques. Light-induced singlet oxygen production was measured in the prepared photoactive biocomposites in water-based suspension by histidine mediated chemical trapping. Carbon nanotubes were applied under different conditions in order to understand their role in the equilibration of singlet oxygen concentration in the suspension. CNTs acted as effective quenchers of 1O2 either by physical (resonance energy transfer or by chemical (oxidation reaction and their efficiency showed dependence on the diffusion distance of 1O2.

Size-controlled soft-template synthesis of carbon nanodots toward versatile photoactive materials.

Science.gov (United States)

Kwon, Woosung; Lee, Gyeongjin; Do, Sungan; Joo, Taiha; Rhee, Shi-Woo

2014-02-12

Size-controlled soft-template synthesis of carbon nanodots (CNDs) as novel photoactive materials is reported. The size of the CNDs can be controlled by regulating the amount of an emulsifier. As the size increases, the CNDs exhibit blue-shifted photoluminescence (PL) or so-called an inverse PL shift. Using time-correlated single photon counting, ultraviolet photoelectron spectroscopy, and low-temperature PL measurements, it is revealed that the CNDs are composed of sp² clusters with certain energy gaps and their oleylamine ligands act as auxochromes to reduce the energy gaps. This insight can provide a plausible explanation on the origin of the inverse PL shift which has been debatable over a past decade. To explore the potential of the CNDs as photoactive materials, several prototypes of CND-based optoelectronic devices, including multicolored light-emitting diodes and air-stable organic solar cells, are demonstrated. This study could shed light on future applications of the CNDs and further expedite the development of other related fields. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoactive Nitric Oxide Delivery Systems based on Metal Nitrosyl-Biomaterial Composites

Science.gov (United States)

Heilman, Brandon James

Gaseous NO has been recognized as a potent antibiotic even against highly drug-resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) in both animal and human studies. However, difficulties in the delivery of the toxic (and reactive) gas demands innovative techniques to deliver NO in a controlled manner to malignant sites throughout the body. Metal nitrosyls reported by our group have demonstrated rapid NO release under the complete control of visible and NIR light. Careful incorporation of these photoactive nitrosyls into polymer matrices has afforded a set of nitrosyl-polymer composites in order to localize the NO-donors at a targeted site, ensure reliable NO release kinetics in vivo, and prevent potentially cytotoxic interactions of the metal nitrosyl or its reaction-products with the treatment site. The work presented in this thesis was pursued to derive clinically relevant NO-delivery systems and demonstrate their utility for the treatment of infection. In chapter 2, an NO-releasing polyurethane film (PUX-NO) is described with dispersed xerogel particles containing up to 3 mol% of [Mn(PaPy 3)(NO)](ClO4) entrapped in a silica matrix and swelled with excess moisture. The polyurethane based xerogel-nitrosyl (PUX-NO) films demonstrated rapid NO photorelease upon illumination with low-power visible light which was sufficient to eradicate clinically relevant loads (105 CFU mL-1 ) of several gram-positive and gram-negative pathogenic bacteria, including a strain of methicillin-resistant of S. aureus. The results of this study suggest that PUX-NO films are suitable for use as a NO-releasing occlusive film for the treatment of skin and soft-tissue infections or chronic, non-healing wounds. Since the NO-release rate from the films can be modulated by simple adjustment of the intensity of the light source, the films could be used to first clear the microbial burden from the wound site using high fluxes of NO, and then, provide a moderate

Magnetic Fe@g??C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

Science.gov (United States)

A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically separable Fe@g-C3N4 eliminates the use of high pressure hydrogenation, and the reaction can be accomplished using visible light without the need for external sources of energy.This dataset is associated with the following publication:Baig, N., S. Verma, R. Varma , and M. Nadagouda. Magnetic Fe@g-C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes. ACS Sustainable Chemistry & Engineering. American Chemical Society, Washington, DC, USA, 4(3): 1661-1664, (2016).

A novel photoactive and three-dimensional stainless steel anode dramatically enhances the current density of bioelectrochemical systems.

Science.gov (United States)

Feng, Huajun; Tang, Chenyi; Wang, Qing; Liang, Yuxiang; Shen, Dongsheng; Guo, Kun; He, Qiaoqiao; Jayaprada, Thilini; Zhou, Yuyang; Chen, Ting; Ying, Xianbin; Wang, Meizhen

2018-04-01

This study reports a high-performance 3D stainless-steel photoanode (3D SS photoanode) for bioelectrochemical systems (BESs). The 3D SS photoanode consists of 3D carbon-coated SS felt bioactive side and a flat α-Fe 2 O 3 -coated SS plate photoactive side. Without light illumination, the electrode reached a current density of 26.2 ± 1.9 A m -2 , which was already one of the highest current densities reported thus far. Under illumination, the current density of the electrode was further increased to 46.5 ± 2.9 A m -2 . The mechanism of the photo-enhanced current production can be attributed to the reduced charge-transfer resistance between electrode surface and the biofilm with illumination. It was also found that long-term light illumination can enhance the biofilm formation on the 3D SS photoanode. These findings demonstrate that using the synergistic effect of photocatalysis and microbial electrocatalysis is an efficient way to boost the current production of the existing high-performance 3D anodes for BESs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Centimetre-scale electron diffusion in photoactive organic heterostructures

Science.gov (United States)

Burlingame, Quinn; Coburn, Caleb; Che, Xiaozhou; Panda, Anurag; Qu, Yue; Forrest, Stephen R.

2018-02-01

The unique properties of organic semiconductors, such as flexibility and lightness, are increasingly important for information displays, lighting and energy generation. But organics suffer from both static and dynamic disorder, and this can lead to variable-range carrier hopping, which results in notoriously poor electrical properties, with low electron and hole mobilities and correspondingly short charge-diffusion lengths of less than a micrometre. Here we demonstrate a photoactive (light-responsive) organic heterostructure comprising a thin fullerene channel sandwiched between an electron-blocking layer and a blended donor:C70 fullerene heterojunction that generates charges by dissociating excitons. Centimetre-scale diffusion of electrons is observed in the fullerene channel, and this can be fitted with a simple electron diffusion model. Our experiments enable the direct measurement of charge diffusivity in organic semiconductors, which is as high as 0.83 ± 0.07 square centimetres per second in a C60 channel at room temperature. The high diffusivity of the fullerene combined with the extraordinarily long charge-recombination time yields diffusion lengths of more than 3.5 centimetres, orders of magnitude larger than expected for an organic system.

The Effect of Donor and Nonfullerene Acceptor Inhomogeneous Distribution within the Photoactive Layer on the Performance of Polymer Solar Cells with Different Device Structures

Directory of Open Access Journals (Sweden)

Yaping Wang

2017-11-01

Full Text Available Due to the inhomogeneous distribution of donor and acceptor materials within the photoactive layer of bulk heterojunction organic solar cells (OSCs, proper selection of a conventional or an inverted device structure is crucial for effective exciton dissociation and charge transportation. Herein, we investigate the donor and acceptor distribution within the non-fullerene photoactive layer based on PBDTTT-ET:IEICO by time-of-flight secondary-ion mass spectroscopy (TOF-SIMS and scanning Kelvin probe microscopy (SKPM, indicating that more IEICO enriches on the surface of the photoactive layer while PBDTTT-ET distributes homogeneously within the photoactive layer. To further understand the effect of the inhomogeneous component distribution on the photovoltaic performance, both conventional and inverted OSCs were fabricated. As a result, the conventional device shows a power conversion efficiency (PCE of 8.83% which is 41% higher than that of inverted one (6.26%. Eventually, we employed nickel oxide (NiOx instead of PEDOT:PSS as anode buffer layer to further enhance the stability and PCE of OSCs with conventional structure, and a promising PCE of 9.12% is achieved.

Incoherent manipulation of the photoactive yellow protein photocycle with dispersed pump-dump-probe spectroscopy.

Science.gov (United States)

Larsen, Delmar S; van Stokkum, Ivo H M; Vengris, Mikas; van Der Horst, Michael A; de Weerd, Frank L; Hellingwerf, Klaas J; van Grondelle, Rienk

2004-09-01

Photoactive yellow protein is the protein responsible for initiating the "blue-light vision" of Halorhodospira halophila. The dynamical processes responsible for triggering the photoactive yellow protein photocycle have been disentangled with the use of a novel application of dispersed ultrafast pump-dump-probe spectroscopy, where the photocycle can be started and interrupted with appropriately tuned and timed laser pulses. This "incoherent" manipulation of the photocycle allows for the detailed spectroscopic investigation of the underlying photocycle dynamics and the construction of a fully self-consistent dynamical model. This model requires three kinetically distinct excited-state intermediates, two (ground-state) photocycle intermediates, I(0) and pR, and a ground-state intermediate through which the protein, after unsuccessful attempts at initiating the photocycle, returns to the equilibrium ground state. Also observed is a previously unknown two-photon ionization channel that generates a radical and an ejected electron into the protein environment. This second excitation pathway evolves simultaneously with the pathway containing the one-photon photocycle intermediates.

Thermal Annealing Effect on Poly(3-hexylthiophene: Fullerene:Copper-Phthalocyanine Ternary Photoactive Layer

Directory of Open Access Journals (Sweden)

H. Derouiche

2013-01-01

Full Text Available We have fabricated poly(3-hexylthiophene (P3HT/copper phthalocyanine (CuPc/fullerene (C60 ternary blend films. This photoactive layer is sandwiched between an indium tin oxide (ITO/poly(3,4-ethylenedioxythiophene:poly(styrene sulfonate (PEDOT/PSS photoanode and a bathocuproine (BCP/aluminium photocathode. The thin films have been characterized by atomic force microscope (AFM and ultraviolet/visible spectroscopy in order to study the influence of P3HT doping on the morphological and optical properties of the photoactive layer. We have also compared the characteristics of three different organic solar cells: ITO/PEDOT:PSS/CuPc0.5:C600.5/BCP/Al and ITO/PEDOT:PSS/P3HT0.3:CuPc0.3:C600.4/BCP/Al with and without annealing. Both structures show good photovoltaic behaviour. Indeed, the incorporation of P3HT into CuPc:C60 thin film improves all the photovoltaic characteristics. We have also seen that thermal annealing significantly improves the optical absorption ability and stabilizes the organic solar cells making it more robust to chemical degradation.

Initial steps of signal generation in photoactive yellow protein revealed with femtosecond mid-infrared spectroscopy

NARCIS (Netherlands)

Groot, M.L.; van Wilderen, L.; Larsen, D.S.; Horst, M.A.; van Stokkum, I.H.M.; Hellingwerf, K.J.; van Grondelle, R.

2003-01-01

Photoactive yellow protein (PYP) is a bacterial blue light sensor that induces Halorhodospira halophila to swim away from intense blue light. Light absorption by PYP's intrinsic chromophore, p-coumaric acid, leads to the initiation of a photocycle that comprises several distinct intermediates. Here

Ultrafast dynamics of isolated model photoactive yellow protein chromophores: "Chemical perturbation theory" in the laboratory

NARCIS (Netherlands)

Vengris, M.; Larsen, D.S.; van der Horst, M.A.; Larsen, O.F.A.; Hellingwerf, K.J.; van Grondelle, R.

2005-01-01

Pump-probe and pump-dump probe experiments have been performed on several isolated model chromophores of the photoactive yellow protein (PYP). The observed transient absorption spectra are discussed in terms of the spectral signatures ascribed to solvation, excited-state twisting, and vibrational

Contrasting the excited-state dynamics of the photoactive yellow protein chromophore: Protein versus solvent environments

NARCIS (Netherlands)

Vengris, M.; Horst, M.A.; Zgrablic, G.; van Stokkum, I.H.M.; Haacke, S.; Chergui, M.; Hellingwerf, K.J.; van Grondelle, R.; Larsen, D.S.

2004-01-01

Wavelength- and time-resolved fluorescence experiments have been performed on the photoactive yellow protein, the E46Q mutant, the hybrids of these proteins containing a nonisomerizing "locked" chromophore, and the native and locked chromophores in aqueous solution. The ultrafast dynamics of these

[Ti8Zr2O12(COO16] Cluster: An Ideal Inorganic Building Unit for Photoactive Metal–Organic Frameworks

Directory of Open Access Journals (Sweden)

Shuai Yuan

2017-11-01

Full Text Available Metal–organic frameworks (MOFs based on Ti-oxo clusters (Ti-MOFs represent a naturally self-assembled superlattice of TiO2 nanoparticles separated by designable organic linkers as antenna chromophores, epitomizing a promising platform for solar energy conversion. However, despite the vast, diverse, and well-developed Ti-cluster chemistry, only a scarce number of Ti-MOFs have been documented. The synthetic conditions of most Ti-based clusters are incompatible with those required for MOF crystallization, which has severely limited the development of Ti-MOFs. This challenge has been met herein by the discovery of the [Ti8Zr2O12­(COO16] cluster as a nearly ideal building unit for photoactive MOFs. A family of isoreticular photoactive MOFs were assembled, and their orbital alignments were fine-tuned by rational functionalization of organic linkers under computational guidance. These MOFs demonstrate high porosity, excellent chemical stability, tunable photoresponse, and good activity toward photocatalytic hydrogen evolution reactions. The discovery of the [Ti8Zr2O12­(COO16] cluster and the facile construction of photoactive MOFs from this cluster shall pave the way for the development of future Ti-MOF-based photocatalysts.

[Ti8Zr2O12(COO)16] Cluster: An Ideal Inorganic Building Unit for Photoactive Metal-Organic Frameworks.

Science.gov (United States)

Yuan, Shuai; Qin, Jun-Sheng; Xu, Hai-Qun; Su, Jie; Rossi, Daniel; Chen, Yuanping; Zhang, Liangliang; Lollar, Christina; Wang, Qi; Jiang, Hai-Long; Son, Dong Hee; Xu, Hongyi; Huang, Zhehao; Zou, Xiaodong; Zhou, Hong-Cai

2018-01-24

Metal-organic frameworks (MOFs) based on Ti-oxo clusters (Ti-MOFs) represent a naturally self-assembled superlattice of TiO 2 nanoparticles separated by designable organic linkers as antenna chromophores, epitomizing a promising platform for solar energy conversion. However, despite the vast, diverse, and well-developed Ti-cluster chemistry, only a scarce number of Ti-MOFs have been documented. The synthetic conditions of most Ti-based clusters are incompatible with those required for MOF crystallization, which has severely limited the development of Ti-MOFs. This challenge has been met herein by the discovery of the [Ti 8 Zr 2 O 12 (COO) 16 ] cluster as a nearly ideal building unit for photoactive MOFs. A family of isoreticular photoactive MOFs were assembled, and their orbital alignments were fine-tuned by rational functionalization of organic linkers under computational guidance. These MOFs demonstrate high porosity, excellent chemical stability, tunable photoresponse, and good activity toward photocatalytic hydrogen evolution reactions. The discovery of the [Ti 8 Zr 2 O 12 (COO) 16 ] cluster and the facile construction of photoactive MOFs from this cluster shall pave the way for the development of future Ti-MOF-based photocatalysts.

A short history of structure based research on the photocycle of photoactive yellow protein.

Science.gov (United States)

Schmidt, Marius

2017-05-01

The goals of time-resolved macromolecular crystallography are to extract the molecular structures of the reaction intermediates and the reaction dynamics from time-resolved X-ray data alone. To develop the techniques of time-resolved crystallography, biomolecules with special properties are required. The Photoactive Yellow Protein is the most sparkling of these.

Photoactive layered nanocomposites obtained by direct transferring of anodic TiO{sub 2} nanotubes to commodity thermoplastics

Energy Technology Data Exchange (ETDEWEB)

Sanz, Ruy, E-mail: ruy.sanzgonzalez@cnr.it [CNR-IMM, Via Santa Sofia 64, I-95123 Catania (Italy); Buccheri, Maria Antonietta; Zimbone, Massimo; Scuderi, Viviana; Amiard, Guillaume; Impellizzeri, Giuliana [CNR-IMM, Via Santa Sofia 64, I-95123 Catania (Italy); Romano, Lucia [CNR-IMM, Via Santa Sofia 64, I-95123 Catania (Italy); Department of Physics, University of Catania, Via Santa Sofia 64, I-95123 Catania (Italy); Privitera, Vittorio [CNR-IMM, Via Santa Sofia 64, I-95123 Catania (Italy)

2017-03-31

Highlights: • Rapid and scalable synthesis of flexible photoactive layered nanocomposites is presented. • The nanocomposites show similar photonic efficiencies to TiO{sub 2} nanotubes and commercial products. • The nanocomposites exhibit antibacterial properties under 1 mW cm{sup −2} UVA. • The synthesis process is solvent-free and reduces the amount of raw materials. - Abstract: TiO{sub 2} nanotubes demonstrated to be a versatile nanostructure for biomaterials, clean energy and water remediation applications. However, the cost of titanium and the poor mechanical properties of the nanotubes hinder their adoption at large scale. This work presents a straightforward and scalable method for transferring photoactive anodic TiO{sub 2} nanotubes from titanium foils to commodity thermoplastic polymers, polypropylene, polyethylene terephthalate, polycarbonate, and polymethylmetacrylate, allowing the reusing of the remaining titanium. The obtained flexible nanocomposites reach a maximum photonic efficiencies of 0.038% (ISO-10678:2010) representing the 93% of photonic efficiency of TiO{sub 2} nanotubes on titanium. In addition, the nanocomposites and TiO{sub 2} nanotubes on titanium present similar antibacterial properties under 1 mW cm{sup −2} UV-A, 60% of Escherichia coli survival after 1 h of exposition. The final objective of this work is to point out main concepts and key parameters for a low-cost fabrication of a photoactive nanocomposite material.

On the involvement of single-bond rotation in the primary photochemistry of photoactive yellow protein

NARCIS (Netherlands)

Stahl, A.D.; Hospes, M.; Singhal, K.; van Stokkum, I.; van Grondelle, R.; Groot, M.L.; Hellingwerf, K.J.

2011-01-01

Prior experimental observations, as well as theoretical considerations, have led to the proposal that C4-C7 single-bond rotation may play an important role in the primary photochemistry of photoactive yellow protein (PYP). We therefore synthesized an analog of this protein's 4-hydroxy-cinnamic acid

A short history of structure based research on the photocycle of photoactive yellow protein

Directory of Open Access Journals (Sweden)

Marius Schmidt

2017-05-01

Full Text Available The goals of time-resolved macromolecular crystallography are to extract the molecular structures of the reaction intermediates and the reaction dynamics from time-resolved X-ray data alone. To develop the techniques of time-resolved crystallography, biomolecules with special properties are required. The Photoactive Yellow Protein is the most sparkling of these.

Magnetic Fe@g‑C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

Data.gov (United States)

U.S. Environmental Protection Agency — A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically...

Particle emission rates during electrostatic spray deposition of TiO2 nanoparticle-based photoactive coating

DEFF Research Database (Denmark)

Koivisto, Antti J.; Jensen, Alexander C. Ø.; Kling, Kirsten I.

2017-01-01

Here, we studied the particle release rate during Electrostatic spray deposition of anatase-(TiO2)-based photoactive coating onto tiles and wallpaper using a commercially available electrostatic spray device. Spraying was performed in a 20.3m3 test chamber while measuring concentrations of 5.6nm ...

Bonding of human meniscal and articular cartilage with photoactive 1,8-naphthalimide dyes

Science.gov (United States)

Judy, Millard M.; Nosir, Hany R.; Jackson, Robert W.; Matthews, James Lester; Lewis, David E.; Utecht, Ronald E.; Yuan, Dongwu

1996-05-01

This study focused on meniscal cartilage repair by using the laser-activated photoactive 1,8- naphthalimide dye N,N'-bis-{6-[2-(2-(2- aminoethoxy)ethoxy)ethoxyethyl]amino-1H-benz (de)isoquinolin-1,3(2H)-dion-2- yl}-1,11-diamino-3,6,9-trioxaundecane. Harvested cadaveric human menisci were debrided and carved into strips 1 mm thick, 10 mm long, and 3 mm wide. Each strip was divided into two flaps, the surface painted with photoactive dye, the painted surfaces overlapped, the sample wrapped in Saran film, and the composite sandwiched between two glass slides at a pressure of approximately 3 kg/cm2. The sample then was transilluminated by argon ion laser light of 457.9-nm wavelength at a power density of 200 mW/cm2 with exposure times up to 5 h (3902 J/cm2 energy density). Essentially, the same procedures were performed for human femoral articular cartilage samples. Control experiments were conducted with laser irradiation alone and with dye alone. All the specimens were stored in isotonic saline solution for 2 h after irradiation to ensure hydration. The bond shear-strength was then tested and samples prepared for optical and electron transmission microscopy. Shear strength values of up to 1.8 kg/cm2 for meniscal tissues and 1.2 kg/cm2 for articular cartilaginous tissues were obtained for exposures of 3902 J/cm2. Shear strength values of approximately 0.9 kg/cm2 and 0.4 kg/cm2, respectively, for meniscus and cartilage were obtained with 459 J/cm2 exposure. Dye- and light-only controls exhibited 0 kg/cm2 shear strength values. Microscopy revealed close contact at the bonded surface in the laser-activated, dye-treated-specimens. This study shows that the laser-activated photoactive dyes have the capability of athermally bonding the meniscal and articular cartilage surfaces.

Visible light photoactivity of TiO{sub 2} loaded with monometallic (Au or Pt) and bimetallic (Au/Pt) nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Gołąbiewska, Anna, E-mail: annagolabiewska@o2.pl [Department of Chemical Technology, Gdansk University of Technology, 80-233 Gdańsk (Poland); Lisowski, Wojciech [Mazovia Center for Surface Analysis, Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw (Poland); Jarek, Marcin; Nowaczyk, Grzegorz [NanoBioMedical Center, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Zielińska-Jurek, Anna; Zaleska, Adriana [Department of Chemical Technology, Gdansk University of Technology, 80-233 Gdańsk (Poland)

2014-10-30

Graphical abstract: - Highlights: • Au/Pt nanoparticles enhanced TiO{sub 2} photocatalytic activity under visible irradiation. • Higher photoactivity of Au/Pt-TiO{sub 2} resulted from smaller Au/Pt particles. • Intermetallic state of AuPt favors charge transfer between the metals. • TiO{sub 2} obtained by TIP hydrolysis seems to be best matrix for Au/Pt-TiO{sub 2}. - Abstract: TiO{sub 2} modified with monometallic (Au or Pt) and bimetallic (Au/Pt) nanoparticles have been prepared using a water-in-oil microemulsion system (water/AOT/cyclohexane) followed by calcination step. The effect of metal ratio, reducing agent type (NaBH{sub 4} or N{sub 2}H{sub 4}), TiO{sub 2} matrix type (P-25, ST-01, TiO-5, TiO{sub 2} nanotubes or TiO{sub 2} obtained by TIP hydrolysis) as well as calcination temperature (from 350 to 650 °C) were systematically investigated. Obtained photocatalysts were characterized by UV–vis diffuse-reflectance spectroscopy (DRS), BET surface area measurements, scanning transmission microscopy (STEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity under visible light (λ > 420 nm) has been estimated in phenol degradation reaction in aqueous phase. The results showed that phenol degradation rate under visible light in the presence of TiO{sub 2} loaded with Au/Pt nanoparticles differed from 0.7 to 2.2 μmol dm{sup −3} min{sup −1} for samples prepared using different reducing agent. Sodium borohydride (NaBH{sub 4}) favors formation of smaller Au/Pt nanoparticles and higher amount gold in Au/Pt is in the form of electronegative species (Au{sup δ−}) resulted in higher photoactivity. TiO{sub 2} obtained by TIP hydrolysis in microemulsion system seems to be the best support for Au/Pt nanoparticles from all among investigated matrix. It was also observed that enhancement of calcination temperature from 450 to 650 °C resulted in rapid drop of Au/Pt-TiO{sub 2} photoactivity under visible light

Photoactive glazed polymer-cement composite

Science.gov (United States)

Baltes, Liana; Patachia, Silvia; Tierean, Mircea; Ekincioglu, Ozgur; Ozkul, Hulusi M.

2018-04-01

Macro defect free cements (MDF), a kind of polymer-cement composites, are characterized by remarkably high mechanical properties. Their flexural strengths are 20-30 times higher than those of conventional cement pastes, nearly equal to that of an ordinary steel. The main drawback of MDF cements is their sensitivity to water. This paper presents a method to both diminish the negative impact of water on MDF cements mechanical properties and to enlarge their application by conferring photoactivity. These tasks were solved by glazing MDF cement with an ecological glaze containing nano-particles of TiO2. Efficiency of photocatalytic activity of this material was tested against methylene blue aqueous solution (4.4 mg/L). Influence of the photocatalyst concentration in the glaze paste and of the contact time on the photocatalysis process (efficiency and kinetic) was studied. The best obtained photocatalysis yield was of 97.35%, after 8 h of exposure to 254 nm UV radiation when used an MDF glazed with 10% TiO2 in the enamel paste. Surface of glazed material was characterized by optic microscopy, scratch test, SEM, XRD, and EDS. All these properties were correlated with the aesthetic aspect of the glazed surface aiming to propose using of this material for sustainable construction development.

Photoactive TiO2 Films Formation by Drain Coating for Endosulfan Degradation

Directory of Open Access Journals (Sweden)

Natalia Tapia-Orozco

2013-01-01

Full Text Available Heterogeneous photocatalysis is an advanced oxidation process in which a photoactive catalyst, such as TiO2, is attached to a support to produce free radical species known as reactive oxygen species (ROS that can be used to break down toxic organic compounds. In this study, the draining time, annealing temperature, and draining/annealing cycles for TiO2 films grown by the drain coating method were evaluated using a 23 factorial experimental design to determine the photoactivity of the films via endosulfan degradation. The TiO2 films prepared with a large number of draining/annealing cycles at high temperatures enhanced (P>0.05 endosulfan degradation and superoxide radical generation after 30 minutes of illumination with UV light. We demonstrated a negative correlation (R2=0.69; P>0.01 between endosulfan degradation and superoxide radical generation. The endosulfan degradation rates were the highest at 30 minutes with the F6 film. In addition, films prepared using conditions F1, F4, and F8 underwent an adsorption/desorption process. The kinetic reaction constants, Kapp (min−1, were 0.0101, 0.0080, 0.0055, 0.0048, and 0.0035 for F6, F2, F5, F3, and F1, respectively. The endosulfan metabolites alcohol, ether, and lactone were detected and quantified at varying levels in all photocatalytic assays.

Non-destructive lateral mapping of the thickness of the photoactive layer in polymer-based solar cells

DEFF Research Database (Denmark)

Sylvester-Hvid, Kristian O.; Tromholt, Thomas; Jørgensen, Mikkel

2013-01-01

Non-destructive lateral mapping of the thickness of the photoactive layer in poly(3-hexyl-thiophene) : 1-(3-methoxy-carbonyl)propyl-1-phenyl-(6,6)C61 (P3HT : PCBM) solar cells is demonstrated. The method employs a spatially resolved (XY) recording of ultraviolet-visible spectra in reflection...... geometry at normal incidence, using a dense raster defined by a circular probe spot of 800-µm diameter. The evaluation of the thickness of the photoactive layer at each raster point employs an algorithm-driven comparison of the measured absorption spectrum with spectral features, as compiled from......-coated float glass substrates. After this, two application examples for solar cells processed either by spin coating or slot die coating of the P3HT : PCBM layer follow. The spin-coated solar cells have glass as the substrate with the P3HT : PCBM spun at different spinning speeds. The slot die-coated solar...

Boosting the Visible-Light Photoactivity of BiOCl/BiVO4/N-GQD Ternary Heterojunctions Based on Internal Z-Scheme Charge Transfer of N-GQDs: Simultaneous Band Gap Narrowing and Carrier Lifetime Prolonging.

Science.gov (United States)

Zhu, Mingyue; Liu, Qian; Chen, Wei; Yin, Yuanyuan; Ge, Lan; Li, Henan; Wang, Kun

2017-11-08

The efficient separation of photogenerated electron-hole pairs in photoactive materials is highly desired, allowing their transfer to specific sites for undergoing redox reaction in various applications. The construction of ternary heterojunctions is a practical strategy to enhance the migration of photogenerated electron that realizes the synergistic effect of multicomponents rather than the simple overlay of single component. Here, we demonstrate an available way to fabricate new BiOCl/BiVO 4 /nitrogen-doped graphene quantum dot (N-GQD) ternary heterojunctions that exhibit higher efficiency in charge separation than any binary heterojunction or pure material under visible-light irradiation. UV-vis diffuse reflectance spectroscopy demonstrated that the proposed BiOCl/BiVO 4 /N-GQD ternary heterojunctions possess the narrower band gap energy. More importantly, the ternary heterojunctions reveal the prolonged lifetime of photogenerated charges and enhanced the separation efficiency of photogenerated electron-hole pairs, which may be ascribed to sensitization based on an internal Z-scheme charge transfer at the interface of N-GQDs with oxygen functional groups. Furthermore, we examine the photoactive performance of proposed ternary heterojunctions in aqueous solution by using the photodegradation of bisphenol A as a model system and BiOCl/BiVO 4 /N-GQD ternary heterojunctions also display a dramatically enhanced photodegradation rate. The proposed charge separation and transfer process of BiOCl/BiVO 4 /N-GQD ternary heterojunctions for the enhanced photoactivity were deduced by electrochemical measurements, photoluminescence, and electron spin resonance. The results demonstrate that a Z-scheme charge process was formed between BiOCl/BiVO 4 binary heterojunctions and N-GQDs, leading to an efficient charge carrier separation and strong photocatalytic ability. Notably, this work may assist in a better understanding of the role of N-GQDs in kinds of heterojunctions

Rational Design of Zirconium-doped Titania Photocatalysts with Synergistic Brønsted Acidity and Photoactivity.

Science.gov (United States)

Ma, Runyuan; Wang, Liang; Zhang, Bingsen; Yi, Xianfeng; Zheng, Anmin; Deng, Feng; Yan, Xuhua; Pan, Shuxiang; Wei, Xiao; Wang, Kai-Xue; Su, Dang Sheng; Xiao, Feng-Shou

2016-10-06

The preparation of photocatalysts with high activities under visible-light illumination is challenging. We report the rational design and construction of a zirconium-doped anatase catalyst (S-Zr-TiO 2 ) with Brønsted acidity and photoactivity as an efficient catalyst for the degradation of phenol under visible light. Electron microscopy images demonstrate that the zirconium sites are uniformly distributed on the sub-10 nm anatase crystals. UV-visible spectrometry indicates that the S-Zr-TiO 2 is a visible-light-responsive catalyst with narrower band gap than conventional anatase. Pyridine-adsorption infrared and acetone-adsorption 13 C NMR spectra confirm the presence of Brønsted acidic sites on the S-Zr-TiO 2 sample. Interestingly, the S-Zr-TiO 2 catalyst exhibits high catalytic activity in the degradation of phenol under visible-light illumination, owing to a synergistic effect of the Brønsted acidity and photoactivity. Importantly, the S-Zr-TiO 2 shows good recyclability. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoactive Blends of Poly(para-phenylenevinylene) (PPV) with Methanofullerenes from a Novel Precursor : Photophysics and Device Performance

NARCIS (Netherlands)

Brabec, C.J.; Cravino, A.; Zerza, G.; Sariciftci, N.S.; Kiebooms, R.; Vanderzande, D.; Hummelen, J.C.

2001-01-01

Homogeneous blends of a processable methanofullerene, [6,6]-phenyl C61-butyric acid methyl ester (PCBM), with poly(para-phenylenevinylene) (PPV) synthesized using a novel nonionic precursor route were produced. These photoactive blends have been investigated by excited-state spectroscopy and by

Synthesis of new, UV-photoactive dansyl derivatives for flow cytometric studies on bile acid uptake.

Science.gov (United States)

Rohacova, Jana; Marin, M Luisa; Martínez-Romero, Alicia; O'Connor, José-Enrique; Gomez-Lechon, M Jose; Donato, M Teresa; Castell, Jose V; Miranda, Miguel A

2009-12-07

Four new fluorescent derivatives of cholic acid have been synthesized; they incorporate a dansyl moiety at 3alpha-, 3beta-, 7alpha- or 7beta- positions. These cholic acid analogs are UV photoactive and also exhibit green fluorescence. In addition, they have been demonstrated to be suitable for studying the kinetics of bile acid transport by flow cytometry.

Realization of Intrinsically Stretchable Organic Solar Cells Enabled by Charge-Extraction Layer and Photoactive Material Engineering.

Science.gov (United States)

Hsieh, Yun-Ting; Chen, Jung-Yao; Fukuta, Seijiro; Lin, Po-Chen; Higashihara, Tomoya; Chueh, Chu-Chen; Chen, Wen-Chang

2018-06-12

The rapid development of wearable electronic devices has prompted a strong demand to develop stretchable organic solar cells (OSCs) to serve as the advanced powering systems. However, to realize an intrinsically stretchable OSC is challenging because it requires all the constituent layers to possess certain elastic properties. It thus necessitates a combined engineering of charge-transporting layers and photoactive materials. Herein, we first describe a stretchable electron-extraction layer using a blend of poly[(9,9-bis(3'-( N, N-dimethylamino)propyl)-2,7-fluorene)- alt-2,7-(9,9-dioctylfluorene)] (PFN) and nitrile butadiene rubber (NBR, Nipol 1072). This hybrid PFN/NBR layer exhibits a much lower Derjaguin-Muller-Toporov modulus (0.45 GPa) than the value (1.25 GPa) of the pristine PFN and could withstand a high strain (60% strain) without showing any cracks. Moreover, besides enriching the stretchability of PFN, the terminal carboxyl groups of NBR can ionize PFN to promote its solution-processability in polar solvents and to ensure the interfacial dipole formation at the corresponding interface in the device, as evidenced by the Fourier transform infrared and ultraviolet photoelectron spectroscopy analyses. By further coupling the replacement of [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) with nonfullerene acceptors owing to better mechanical stretchability in the photoactive layer, OSCs with improved intrinsically stretchability and performance were demonstrated. An all-polymer OSC can exhibit a power conversion efficiency of 2.82% after 10% stretching, surpassing the PCBM-based device that can only withstand 5% strain.

A novel photo-active Cd:1,4-benzene dicarboxylate metal organic framework templated using [Ru(ii)(2,2'-bipyridine)3]2+: synthesis and photophysics of RWLC-5.

Science.gov (United States)

Larsen, Randy W; Mayers, Jacob M; Wojtas, Lukasz

2017-09-26

The development of photoactive porous materials is of significant importance for applications ranging from sustainable energy to pharmaceutical development and catalysis. A particularly attractive class of photo-active materials is the metal-organic framework (MOF)-based platform in which the photo-active elements are components of the framework itself or photo-active guests encapsulated within the MOF cavities. It has now been demonstrated that the photo-active [Ru(2,2'-bipyridine) 3 ] 2+ (RuBpy) complex can template the formation of MOFs with varying three dimensional structures. Here we report the synthesis and structural and photo-physical characterization of a new RuBpy-templated MOF composed of Cd 2+ ions with 1,4-benzenedicarboxylate ligands (RWLC-5) that contains crystallographically resolved RuBpy complexes. The new material displays a biphasic emission decay (130 ns and 1180 ns, T = 20 °C) and a bathochromically shifted emission maximum, relative to RuBpy in solution (603 nm for RuBpy in ethanol vs. 630 nm for RWLC-5). The emission lifetimes also do not display temperature-dependent decays which are characteristic of RuBpy type complexes as well as other RuBpy templated MOFs. The lack of temperature dependence is consistent with the complete deactivation of the 3 LF state of the encapsulated RuBpy complex due to a constrained environment. The fast phase decay is attributed to a water molecule hydrogen bonded to a bipyridine ligand associated with ∼38% of the encapsulated RuBpy complexes resulting in the nonradiative deactivation of the 3 MLCT state.

Gas phase absorption studies of photoactive yellow protein chromophore derivatives.

Science.gov (United States)

Rocha-Rinza, Toms; Christiansen, Ove; Rajput, Jyoti; Gopalan, Aravind; Rahbek, Dennis B; Andersen, Lars H; Bochenkova, Anastasia V; Granovsky, Alexander A; Bravaya, Ksenia B; Nemukhin, Alexander V; Christiansen, Kasper Lincke; Nielsen, Mogens Brøndsted

2009-08-27

Photoabsorption spectra of deprotonated trans p-coumaric acid and two of its methyl substituted derivatives have been studied in gas phase both experimentally and theoretically. We have focused on the spectroscopic effect of the location of the two possible deprotonation sites on the trans p-coumaric acid which originate to either a phenoxide or a carboxylate. Surprisingly, the three chromophores were found to have the same absorption maximum at 430 nm, in spite of having different deprotonation positions. However, the absorption of the chromophore in polar solution is substantially different for the distinct deprotonation locations. We also report on the time scales and pathways of relaxation after photoexcitation for the three photoactive yellow protein chromophore derivatives. As a result of these experiments, we could detect the phenoxide isomer within the deprotonated trans p-coumaric acid in gas phase; however, the occurrence of the carboxylate is uncertain. Several computational methods were used simultaneously to provide insights and assistance in the interpretation of our experimental results. The calculated excitation energies S(0)-S(1) are in good agreement with experiment for those systems having a negative charge on a phenoxide moiety. Although our augmented multiconfigurational quasidegenerate perturbation theory calculations agree with experiment in the description of the absorption spectrum of anions with a carboxylate functional group, there are some puzzling disagreements between experiment and some calculational methods in the description of these systems.

TiO_2/WO_3 photoactive bilayers in the UV-Vis light region

International Nuclear Information System (INIS)

Vasilaki, E.; Vernardou, D.; Kenanakis, G.; Katsarakis, N.; Vamvakaki, M.

2017-01-01

In this work, photoactive bilayered films consisting of anatase TiO_2 and monoclinic WO_3 were synthesized by a sol-gel route. Titanium isopropoxide and tungsten hexachloride were used as metal precursors and deposition was achieved by spin-coating on Corning glass substrates. The samples were characterized by X-ray diffraction, photoluminescence, UV-Vis, and Raman spectroscopy, as well as field emission scanning electron microscopy. The prepared immobilized catalysts were tested for their photocatalytic performance by the decolorization of methylene blue in aqueous matrices, under UV-Vis light irradiation. The annealing process influenced the crystallinity of the bilayered films, while the concentration of the tungsten precursor solution and the position of the tungsten trioxide layer further affected their photocatalytic performance. In particular, the photocatalytic performance of the bilayered films was optimized at a concentration of 0.1 M of the WO_3 precursor solution, when deposited as an overlying layer on TiO_2 by two annealing steps (∝76% methylene blue decolorization in 300 min of irradiation versus ∝59% in the case of a bare TiO_2 film). In general, the coupled layer catalysts exhibited superior photoactivity compared to that of bare TiO_2 films with WO_3 acting as an electron trap, resulting, therefore, in a more efficient electron-hole separation and inhibiting their recombination. (orig.)

Incorporating an Electrode Modification Layer with a Vertical Phase Separated Photoactive Layer for Efficient and Stable Inverted Nonfullerene Polymer Solar Cells.

Science.gov (United States)

Shi, Zhenzhen; Liu, Hao; Wang, Yaping; Li, Jinyan; Bai, Yiming; Wang, Fuzhi; Bian, Xingming; Hayat, Tasawar; Alsaedi, Ahmed; Tan, Zhan'ao

2017-12-20

For bulk heterojunction polymer solar cells (PSCs), the donors and acceptors featuring specific phase separation and concentration distribution within the electron donor/acceptor blends crucially affect the exciton dissociation and charge transportation. Herein, efficient and stable nonfullerene inverted PSCs incorporating a phase separated photoactive layer and a titanium chelate electrode modification layer are demonstrated. Water contact angle (WCA), scanning kelvin probe microscopy (SKPM), and atomic force microscopy (AFM) techniques are implemented to characterize the morphology of photoactive layers. Compared with the control conventional device, the short-circuit current density (J sc ) is enhanced from 14.74 to 17.45 mAcm -2 . The power conversion efficiency (PCE) for the inverted PSCs with a titanium (diisopropoxide)-bis-(2,4-pentanedionate) (TIPD) layer increases from 9.67% to 11.69% benefiting from the declined exciton recombination and fairly enhanced charge transportation. Furthermore, the nonencapsulated inverted device with a TIPD layer demonstrates the best long-term stability, 85% of initial PCE remaining and an almost undecayed open-circuit voltage (V oc ) after 1440 h. Our results reveal that the titanium chelate is an excellent electrode modification layer to incorporate with a vertical phase separated photoactive layer for producing high-efficiency and high-stability inverted nonfullerene PSCs.

Photoactive curcumin-derived dyes with surface anchoring moieties used in ZnO nanoparticle-based dye-sensitized solar cells

International Nuclear Information System (INIS)

Ganesh, T.; Kim, Jong Hoon; Yoon, Seog Joon; Kil, Byung-Ho; Maldar, N.N.; Han, Jin Wook; Han, Sung-Hwan

2010-01-01

Photoactive, eco-friendly and high molar extinction coefficient, curcumin-derived dyes (BCMoxo and BCtCM) have been explored in ZnO nanoparticles (NPs)-based dye-sensitized solar cells (DSSCs). The boron complex curcumin dyes modified with di-carboxylic anchor groups (BCtCM) provided surface attachment with a strong UV-vis region absorption than the dye molecule without anchor groups (BCMoxo). Photoanodes primed with poly-dispersive ZnO NPs (∼80-50 nm) specifically devised for these dyes and optimized for the critical thickness, sensitization time and concentration using a solvent-free ionic electrolyte so as to get current density as high as 1.66 mA/cm 2 under 80 mW/cm 2 irradiation. Therefore, a successful conversion of visible light into electricity by using these curcumin-derived dyes (natural derived photoactive molecules) as photosensitizer in DSSCs would be a great interest in future studies for enhancing further conversion efficiencies.

Magnetic Fe@g-C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

Science.gov (United States)

A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically separable Fe@g-C3N4 eliminates the use of high pressure hydrogenation and the reaction can be accomplished using vi...

Locked chromophore analogs reveal that photoactive yellow protein regulates biofilm formation in the deep sea bacterium Idiomarina loihiensis

NARCIS (Netherlands)

van der Horst, M.A.; Stalcup, T.P.; Kaledhonkar, S.; Kumauchi, M.; Hara, M.; Xie, A.; Hellingwerf, K.J.; Hoff, W.D.

2009-01-01

Idiomarina loihiensis is a heterotrophic deep sea bacterium with no known photobiology. We show that light suppresses biofilm formation in this organism. The genome of I. loihiensis encodes a single photoreceptor protein: a homologue of photoactive yellow protein (PYP), a blue light receptor with

Synthesis and biological properties of 5-azido-2'-deoxyuridine 5'-triphosphate, a photoactive nucleotide suitable for making light-sensitive DNA

International Nuclear Information System (INIS)

Evans, R.K.; Haley, B.E.

1987-01-01

A photoactive nucleotide analogue of dUTP, 5-azido-2'-deoxyuridine 5'-triphosphate (5-N 3 dUTP), was synthesized from dUMP in five steps. The key reaction in the synthesis of 5-N 3 dUTP is the nitration of dUMP in 98% yield in 5 min at 25 0 C using an excess of nitrosonium tetrafluoroborate in anhydrous dimethylformamide. Reduction of the resulting 5-nitro compound with zinc and 20 mM HCl gave 5-aminodeoxyuridine monophosphate (5-NH 2 dUMP). Diazotization of 5-NH 2 dUMP with HNO 2 followed by the addition NaN 3 to the acidic diazonium salt solution gave a photoactive nucleotide derivative in 80-90% yield. The monophosphate product was identified as 5-N 3 dUMP by proton NMR, UV, IR, and chromatographic analysis as well as by the mode of synthesis and its photosensitivity. After formation of 5-N 3 dUTP through a chemical coupling of pyrophosphate to 5-N 3 dUMP, the triphosphate form of the nucleotide was found to support DNA synthesis by Escherichia coli DNA polymerase I at a rate indistinguishable from that supported by dTTP. When UMP was used as the starting compound, 5-N 3 UTP was formed in an analogous fashion with similar yields and produced a photoactive nucleotide which is a substrate for E. coli RNA polymerase. To prepare [γ- 32 P]-5-N 3 dUTP for use as an active-site-directed photoaffinity labeling reagent, a simple method of preparing γ- 32 P-labeled pyrimidine nucleotides was developed. [γ- 32 P]-5-N 3 dUTP is an effective photoaffinity labeling reagent for DNA polymerase I and was found to bind to the active site with a 2-fold higher affinity than dTTP. The photoactivity of 5-N 3 dUMP is stable to extremes of pH, and [γ- 32 P]-5-N 3 dUTP was an effective photolabeling reagent even in the presence of 10 mM dithiothreitol

Photoactive curcumin-derived dyes with surface anchoring moieties used in ZnO nanoparticle-based dye-sensitized solar cells

Energy Technology Data Exchange (ETDEWEB)

Ganesh, T.; Kim, Jong Hoon; Yoon, Seog Joon; Kil, Byung-Ho; Maldar, N.N. [Inorganic Nano-Materials Laboratory, Department of Chemistry, Hanyang University, Sung-Dong-Ku, Haengdang-dong 17, Seoul (Korea, Republic of); Han, Jin Wook, E-mail: jwhan@hanyang.ac.kr [Inorganic Nano-Materials Laboratory, Department of Chemistry, Hanyang University, Sung-Dong-Ku, Haengdang-dong 17, Seoul (Korea, Republic of); Han, Sung-Hwan, E-mail: shhan@hanyang.ac.kr [Inorganic Nano-Materials Laboratory, Department of Chemistry, Hanyang University, Sung-Dong-Ku, Haengdang-dong 17, Seoul (Korea, Republic of)

2010-09-01

Photoactive, eco-friendly and high molar extinction coefficient, curcumin-derived dyes (BCMoxo and BCtCM) have been explored in ZnO nanoparticles (NPs)-based dye-sensitized solar cells (DSSCs). The boron complex curcumin dyes modified with di-carboxylic anchor groups (BCtCM) provided surface attachment with a strong UV-vis region absorption than the dye molecule without anchor groups (BCMoxo). Photoanodes primed with poly-dispersive ZnO NPs ({approx}80-50 nm) specifically devised for these dyes and optimized for the critical thickness, sensitization time and concentration using a solvent-free ionic electrolyte so as to get current density as high as 1.66 mA/cm{sup 2} under 80 mW/cm{sup 2} irradiation. Therefore, a successful conversion of visible light into electricity by using these curcumin-derived dyes (natural derived photoactive molecules) as photosensitizer in DSSCs would be a great interest in future studies for enhancing further conversion efficiencies.

Virus Capsids as Targeted Nanoscale Delivery Vessels of Photoactive Compounds for Site-Specific Photodynamic Therapy

Science.gov (United States)

Cohen, Brian A.

The research presented in this work details the use of a viral capsid as an addressable delivery vessel of photoactive compounds for use in photodynamic therapy. Photodynamic therapy is a treatment that involves the interaction of light with a photosensitizing molecule to create singlet oxygen, a reactive oxygen species. Overproduction of singlet oxygen in cells can cause oxidative damage leading to cytotoxicity and eventually cell death. Challenges with the current generation of FDA-approved photosensitizers for photodynamic therapy primarily stem from their lack of tissue specificity. This work describes the packaging of photoactive cationic porphyrins inside the MS2 bacteriophage capsid, followed by external modification of the capsid with cancer cell-targeting G-quadruplex DNA aptamers to generate a tumor-specific photosensitizing agent. First, a cationic porphyrin is loaded into the capsids via nucleotide-driven packaging, a process that involves charge interaction between the porphyrin and the RNA inside the capsid. Results show that over 250 porphyrin molecules associate with the RNA within each MS2 capsid. Removal of RNA from the capsid severely inhibits the packaging of the cationic porphyrins. Porphyrin-virus constructs were then shown to photogenerate singlet oxygen, and cytotoxicity in non-targeted photodynamic treatment experiments. Next, each porphyrin-loaded capsid is externally modified with approximately 60 targeting DNA aptamers by employing a heterobifunctional crosslinking agent. The targeting aptamer is known to bind the protein nucleolin, a ubiquitous protein that is overexpressed on the cell surface by many cancer cell types. MCF-7 human breast carcinoma cells and MCF-10A human mammary epithelial cells were selected as an in vitro model for breast cancer and normal tissue, respectively. Fluorescently tagged virus-aptamer constructs are shown to selectively target MCF-7 cells versus MCF-10A cells. Finally, results are shown in which porphyrin

The Influence of Cr3+ on TiO2 Crystal Growth and Photoactivity Properties

Science.gov (United States)

Wahyuningsih, S.; Hidayatika, W. N.; Sari, P. L.; Sari, P. P.; Hidayat, R.; Munawaroh, H.; Ramelan, A. H.

2018-03-01

The photocatalyst technology is an integrated combination of photochemical processes and catalysis in order to carry out a chemical transformation reaction. One of the semiconductor materials that have good photocatalytic activity is TiO2 anatase. This study aim to determine the effect of the Cr3+ addition on the growth of TiO2 rutile crystal and the increasing of TiO2 photoactivity. Diffractogram X-Ray of the samples showed that the synthesized TiO2 at 400 °C has been produced 100% TiO2 anatase. Synthesis of TiO2 doped Cr3+ composite was using wet impregnation method. The TiO2 doped Cr3+ composites have beed grown by annealed at a temperature of 300, 400, 500, 600 and 700 °C, respectively Annealing process have capabled to gain to the TiO2 doped Cr3+ nanocomposite. The result product annealed at 500 °C only appear anatase phase due to the Cr3+ addition influence that was able to suppress the growth of rutile. Identification of TiO2 doped Cr3+ composite using Fourier Transform Infra-Red (FT-IR) showed O-Cr vibration at 2283.72 cm-1. The TiO2 doped Cr3+ photoactivity was studied to degrade Rhodamin B. The best result on photodegradation of Rhodamin B was performed by using TiO2 doped Cr3+ composite which was annealed at 700 °C i.e. 74.71%.

TiO{sub 2}/WO{sub 3} photoactive bilayers in the UV-Vis light region

Energy Technology Data Exchange (ETDEWEB)

Vasilaki, E. [University of Crete, Department of Chemistry, Heraklion, Crete (Greece); Technological Educational Institute of Crete, Center of Materials Technology and Photonics, School of Engineering, Heraklion, Crete (Greece); Vernardou, D. [Technological Educational Institute of Crete, Center of Materials Technology and Photonics, School of Engineering, Heraklion, Crete (Greece); Kenanakis, G.; Katsarakis, N. [Technological Educational Institute of Crete, Center of Materials Technology and Photonics, School of Engineering, Heraklion, Crete (Greece); Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Laser, Vassilika Vouton, P.O. Box 1385, Heraklion, Crete (Greece); Vamvakaki, M. [Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Laser, Vassilika Vouton, P.O. Box 1385, Heraklion, Crete (Greece); University of Crete, Department of Materials Science and Technology, Heraklion, Crete (Greece)

2017-04-15

In this work, photoactive bilayered films consisting of anatase TiO{sub 2} and monoclinic WO{sub 3} were synthesized by a sol-gel route. Titanium isopropoxide and tungsten hexachloride were used as metal precursors and deposition was achieved by spin-coating on Corning glass substrates. The samples were characterized by X-ray diffraction, photoluminescence, UV-Vis, and Raman spectroscopy, as well as field emission scanning electron microscopy. The prepared immobilized catalysts were tested for their photocatalytic performance by the decolorization of methylene blue in aqueous matrices, under UV-Vis light irradiation. The annealing process influenced the crystallinity of the bilayered films, while the concentration of the tungsten precursor solution and the position of the tungsten trioxide layer further affected their photocatalytic performance. In particular, the photocatalytic performance of the bilayered films was optimized at a concentration of 0.1 M of the WO{sub 3} precursor solution, when deposited as an overlying layer on TiO{sub 2} by two annealing steps (∝76% methylene blue decolorization in 300 min of irradiation versus ∝59% in the case of a bare TiO{sub 2} film). In general, the coupled layer catalysts exhibited superior photoactivity compared to that of bare TiO{sub 2} films with WO{sub 3} acting as an electron trap, resulting, therefore, in a more efficient electron-hole separation and inhibiting their recombination. (orig.)

Graphene nanoplatelet doping of P3HT:PCBM photoactive layer of bulk heterojunction organic solar cells for enhancing performance

Science.gov (United States)

Aïssa, Brahim; Nedil, Mourad; Kroeger, Jens; Ali, Adnan; Isaifan, Rima J.; Essehli, Rachid; Mahmoud, Khaled A.

2018-03-01

Hybrid organic photovoltaic (OPV) cells based on conjugated polymer photoactive materials are promising candidates for flexible, high-performance and low-cost energy sources owing to their inexpensive materials, cost-effective processing and ease of fabrication by simple solution processes. However, the modest PV performance obtained to date—in particular the low power conversion efficiency (PCE)—has impeded the large scale deployment of OPV cells. The low PCE in OPV solar cells is mainly attributed to the low carrier mobility, which is closely correlated to the transport diffusion length of the charge carriers within the photoactive layers. The 2D graphene material could be an excellent candidate for assisting charge transport improvement in the active layer of OPV cells, due to its huge carrier mobility, thermal and chemical stability, and its compatibility with the solution process. In this work, we report on the improvement of the optoelectronic properties and photovoltaic performance of graphene nanoplatelet (GNP)-doped P3HT:PCBM photoactive blended layers, integrated into a bulk heterojunction (BHJ) organic-photovoltaic-based device, using PEDOT:PSS on an ITO/glass substrate. First, the light absorption capacity was observed to increase with respect to the GNP content, while the photoluminescence showed clear quenching, indicating electron transfer between the graphene sheets and the polymeric matrix. Then, the incorporation of GNP into the BHJ active layer resulted in enhanced PV performance with respect to the reference cell, and the best PV performance was obtained with 3 wt.% of GNP loading, with an open-circuit voltage of 1.24 V, a short-circuit current density value of 6.18 mA cm-2, a fill factor of 47.12%, and a power conversion efficiency of about 3.61%. We believe that the obtained results contribute to the development of organic photovoltaic devices and to the understanding of the impact of sp2-bonded carbon therein.

The Diatom Staurosirella pinnata for Photoactive Material Production.

Directory of Open Access Journals (Sweden)

Roberta De Angelis

Full Text Available A native isolate of the colonial benthic diatom Staurosirella pinnata was cultivated for biosilica production. The silicified cell walls (frustules were used as a source of homogeneous and structurally predictable porous biosilica for dye trapping and random laser applications. This was coupled with the extraction of lipids from biomass showing potential to fabricate photoactive composite materials sustainably. The strain was selected for its ease of growth in culture and harvesting. Biosilica and lipids were obtained at the end of growth in indoor photobioreactors. Frustules were structurally characterized microscopically and their chemistry analyzed with Fourier Transform Infrared Spectroscopy. Frustule capacity of binding laser dyes was evaluated on a set of frustules/Rhodamine B (Rho B solutions and with respect to silicon dioxide and diatomite by Fluorescence Spectroscopy demonstrating a high affinity for the organic dye. The effect of dye trapping property in conveying Rho B emission to frustules, with enhancement of scattering events, was analyzed on Rho B doped polyacrylamide gels filled or not with frustules. Amplified spontaneous emission was recorded at increasing pump power indicating the onset of a random laser effect in frustule filled gels at lower power threshold compared to unfilled matrices.

The Diatom Staurosirella pinnata for Photoactive Material Production

Science.gov (United States)

Prosposito, Paolo; Casalboni, Mauro; Lamastra, Francesca Romana; Nanni, Francesca; Congestri, Roberta

2016-01-01

A native isolate of the colonial benthic diatom Staurosirella pinnata was cultivated for biosilica production. The silicified cell walls (frustules) were used as a source of homogeneous and structurally predictable porous biosilica for dye trapping and random laser applications. This was coupled with the extraction of lipids from biomass showing potential to fabricate photoactive composite materials sustainably. The strain was selected for its ease of growth in culture and harvesting. Biosilica and lipids were obtained at the end of growth in indoor photobioreactors. Frustules were structurally characterized microscopically and their chemistry analyzed with Fourier Transform Infrared Spectroscopy. Frustule capacity of binding laser dyes was evaluated on a set of frustules/Rhodamine B (Rho B) solutions and with respect to silicon dioxide and diatomite by Fluorescence Spectroscopy demonstrating a high affinity for the organic dye. The effect of dye trapping property in conveying Rho B emission to frustules, with enhancement of scattering events, was analyzed on Rho B doped polyacrylamide gels filled or not with frustules. Amplified spontaneous emission was recorded at increasing pump power indicating the onset of a random laser effect in frustule filled gels at lower power threshold compared to unfilled matrices. PMID:27828985

Ultrathin TiO2 layer coated-CdS spheres core-shell nanocomposite with enhanced visible-light photoactivity.

Science.gov (United States)

Chen, Zhang; Xu, Yi-Jun

2013-12-26

Development of various strategies for controllable fabrication of core-shell nanocomposites (CSNs) with highly active photocatalytic performance has been attracting ever-increasing research attention. In particular, control of the ultrathin layer TiO2 shell in constructing CSNs in an aqueous phase is a significant but technologically challenging issue. Here, this paper demonstrates the interface assembly synthesis of CdS nanospheres@TiO2 core-shell photocatalyst via the electrostatic interaction of negatively charged water-stable titania precursor with positively charged CdS nanospheres (CdS NSPs), followed by the formation of the ultrathin-layer TiO2 shell through a facile refluxing process in aqueous phase. The as-formed CdS NSPs@TiO2 core-shell nanohybrid exhibits a high visible-light-driven photoactivity for selective transformation and reduction of heavy metal ions. The ultrathin TiO2 layer coated on CdS NSPs results in excellent light transmission property, enhanced adsorption capacity, and improved transfer of charge carriers and lifespan of photoinduced electron-hole pairs, which would prominently contribute to the significant photoactivity enhancement. It is anticipated that this facile aqueous-phase synthesis strategy could be extended to design a variety of more efficient CSN photocatalysts with controllable morphology toward target applications in diverse photoredox processes.

Interactions of photoactive DNAs with terminal deoxynucleotidyl transferase: Identification of peptides in the DNA binding domain

International Nuclear Information System (INIS)

Farrar, Y.J.K.; Evans, R.K.; Beach, C.M.; Coleman, M.S.

1991-01-01

Terminal deoxynucleotidyl transferase (terminal transferase) was specifically modified in the DNA binding site by a photoactive DNA substrate (hetero-40-mer duplex containing eight 5-azido-dUMP residues at one 3' end). Under optimal photolabeling conditions, 27-40% of the DNA was covalently cross-linked to terminal transferase. The specificity of the DNA and protein interaction was demonstrated by protection of photolabeling at the DNA binding domain with natural DNA substrates. In order to recover high yields of modified peptides from limited amounts of starting material, protein modified with 32 P-labeled photoactive DNA and digested with trypsin was extracted 4 times with phenol followed by gel filtration chromatography. All peptides not cross-linked to DNA were extracted into the phenol phase while the photolyzed DNA and the covalently cross-linked peptides remained in the aqueous phase. The 32 P-containing peptide-DNA fraction was subjected to amino acid sequence analysis. Two sequences, Asp 221 -Lys 231 (peptide B8) and Cys 234 -Lys 249 (peptide B10), present in similar yield, were identified. Structure predictions placed the two peptides in an α-helical array of 39 angstrom which would accommodate a DNA helix span of 11 nucleotides. These peptides share sequence similarity with a region in DNA polymerase β that has been implicated in the binding of DNA template

Potential Impacts from Using Photoactive Roads as AN Air Quality Mitigation Strategy

Science.gov (United States)

Toro, C.; Jobson, B. T.; Shen, S.; Chung, S. H.; Haselbach, L.

2013-12-01

Mobile sources are major contributors to photochemical air pollution in urban areas. It has been proposed that the use of TiO2 coated roadways ('photoactive roads') could be an effective approach to reduce mobile source emissions by oxidizing NOx and VOC emissions at the roadway surface. However, studies have shown that formation of HONO and aldehydes can occur from some TiO2 treated surfaces during the photocatalytic oxidation of NOx and VOC, respectively. By changing the NOx-to-VOC ratio and generating photolabile HOx radical precursors, photoactive roads may enhance ozone formation rates in urban areas. In this work we present results that quantify NOx and VOC loss rates onto TiO2 treated asphalt and concrete samples, as well as HONO and aldehydes yields that result from the photocatalytic process. The treatment used a commercially available product. These objectives are relevant considering that the quantification of pollutant loss rates and yields of byproducts have not been determined for asphalt and that in the US more than 90% of the roadway surface is made of this material. Surface reaction probabilities (γ) and byproduct yields were determined using a CSTR photochemical chamber under varying conditions of water vapor and UV-A light intensity. Our results indicate that asphalt surfaces have a significantly higher molar yield of HONO compared to concrete surfaces with similar TiO2 loading. Concrete surfaces have reaction probabilities with NO one order of magnitude higher than asphalt samples. Fresh asphalt samples showed negligible photocatalytic activity, presumably due to absorption of TiO2 into the bitumen substrate. Laboratory-prepared asphalt samples with a higher degree of exposed aggregates showed increased HONO molar yields when compared to real-road asphalt samples, whose HONO molar yield was ~1%. Preliminary results for aldehydes formation showed similar molar yields between aged asphalt and concrete, even though aged asphalt samples had twice

Chemical Engineering of Photoactivity in Heterometallic Titanium-Organic Frameworks by Metal Doping.

Science.gov (United States)

Castells-Gil, Javier; Padial, Natalia M; Almora-Barrios, Neyvis; Albero, Josep; Ruiz-Salvador, A Rabdel; González-Platas, Javier; García, Hermenegildo; Martí-Gastaldo, Carlos

2018-06-06

We report a new family of titanium-organic frameworks that enlarges the limited number of crystalline, porous materials available for this metal. They are chemically robust and can be prepared as single crystals at multi-gram scale from multiple precursors. Their heterometallic structure enables engineering of their photoactivity by metal doping rather than by linker functionalization. Compared to other methodologies based on the post-synthetic metallation of MOFs, our approach is well-fitted for controlling the positioning of dopants at an atomic level to gain more precise control over the band-gap and electronic properties of the porous solid. Changes in the band-gap are also rationalized with computational modelling and experimentally confirmed by photocatalytic H 2 production. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature dependences of photoconductivity of CdHgTe crystals with photoactive inclusions

International Nuclear Information System (INIS)

Vlasenko, A.I.; Vlasenko, Z.K.

1999-01-01

Temperature dependences of life time τ and spectral characteristics of photoconductivity for Cd x Hg 1-x Te crystals (x = 0.2) with photoactive inclusions are investigated. It is shown that the N-type character of effective lifetime temperature dependences in nonhomogeneous crystals, in particular, its sharp temperature activation in the region of transition from the impurity to the intrinsic conductivity is determined by not the Shockley-Read mechanism, but by the interband impact mechanism with changing effective geometrical sizes of recombination active regions under temperature increase. Within the frames of this model the smoothing of the non-monotone character of the photoconductivity spectral characteristics in the region of fundamental absorption under the heating is explained. The calculation results that are in qualitative agreement with the experimental data are presented [ru

Multiphoton manipulations of enzymatic photoactivity in aspartate aminotransferase.

Science.gov (United States)

Hill, Melissa P; Freer, Lucy H; Vang, Mai C; Carroll, Elizabeth C; Larsen, Delmar S

2011-04-21

The aspartate aminotransferase (AAT) enzyme utilizes the chromophoric pyridoxal 5'-phosphate (PLP) cofactor to facilitate the transamination of amino acids. Recently, we demonstrated that, upon exposure to blue light, PLP forms a reactive triplet state that rapidly (in microseconds) generates the high-energy quinonoid intermediate when bound to PLP-dependent enzymes [J. Am. Chem. Soc.2010, 132 (47), 16953-16961]. This increases the net catalytic activity (k(cat)) of AAT, since formation of the quinonoid is partially rate limiting via the thermally activated enzymatic pathway. The magnitude of observed photoenhancement initially scales linearly with pump fluence; however when a critical threshold is exceeded, the photoactivity saturates and is even suppressed at greater excitation fluences. The photodynamic mechanisms associated with this suppression behavior are characterized with the use of ultrafast multipulse pump-dump-probe and pump-repump-probe transient absorption techniques in combination with complementary two-color, steady-state excitation assays. Via multistate kinetic modeling of the transient ultrafast data and the steady-state assay data, the nonmonotonic incident power dependence of the photoactivty in AAT is decomposed into contributions from high-intensity dumping of the excited singlet state and repumping of the excited triplet state with induces the repopulation of the ground state via rapid intersystem crossing in the higher-lying triplet electronic manifold.

Enhanced the hydrophobic surface and the photo-activity of TiO2-SiO2 composites

Science.gov (United States)

Wahyuni, S.; Prasetya, A. T.

2017-02-01

The aim of this research is to develop nanomaterials for coating applications. This research studied the effect of various TiO2-SiO2 composites in acrylic paint to enhance the hydrophobic properties of the substrate. Titanium dioxide containing silica in the range 20-35 mol% has been synthesized using sol-gel route. The XRD’s spectra show that increasing SiO2 content in the composite, decreasing its crystalline properties but increasing the surface area. TiO2-SiO2 composite was dispersed in acrylic paint in 2% composition by weight. The largest contact angle was 70, which produced by the substrate coated with TS-35-modified acrylic paint. This study also investigated the enhanced photo-activity of TiO2-SiO2 modified with poly-aniline. The XRD spectra show that the treatment does not change the crystal structure of TiO2. The photo-activity of the composite was evaluated by degradation of Rhodamine-B with visible light. The best performance of the degradation process was handled by the composite treated with 0.1mL anilines per gram of TiO2-SiO2 composite (TSP-A). On the other side, the contact angle 70 has not shown an excellent hydrophobic activity. However, the AFM spectra showed that nanoroughness has started to form on the surface of acrylic paint modified with TiO2-SiO2 than acrylic alone.

Controlled Deposition and Performance Optimization of Perovskite Solar Cells Using Ultrasonic Spray-Coating of Photoactive Layers.

Science.gov (United States)

Chang, Wei-Chieh; Lan, Ding-Hung; Lee, Kun-Mu; Wang, Xiao-Feng; Liu, Cheng-Liang

2017-04-10

This study investigated a new film-deposition technique, ultrasonic spray-coating, for use in the production of a photoactive layer of perovskite solar cells. Stable atomization and facile fabrication of perovskite thin films by ultrasonic spray-coating were achieved in a one-step method through manipulating the ink formulation (e.g., solution concentration, precursor composition, and mixing solvent ratio) and the drying kinetics (e.g., post-annealing temperature). The performance of the perovskite solar cells was mainly influenced by the intrinsic film morphology and crystalline orientation of the deposited perovskite layer. By suitable optimization of the spreading and drying conditions of the ink, ultrasonic spray-coated perovskite photovoltaic devices were obtained with a maximum power conversion efficiency of 11.30 %, a fill factor of 73.6 %, a short-circuit current of 19.7 mA cm -1 , and an open-circuit voltage of 0.78 V, respectively. Notably, the average power efficiency reached above 10 %, attributed to the large flower-like perovskite crystal with orientation along the (1 1 2)/(2 0 0) and (2 2 4)/(4 0 0) directions. Thus, the ultrasonic spray-coating method for perovskite photoactive layers, combining advantages of good photovoltaic performance results and benefits from cost and processing, has the potential for large-scale commercial production. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Small Molecule-Photoactive Yellow Protein Labeling Technology in Live Cell Imaging

Directory of Open Access Journals (Sweden)

Feng Gao

2016-08-01

Full Text Available Characterization of the chemical environment, movement, trafficking and interactions of proteins in live cells is essential to understanding their functions. Labeling protein with functional molecules is a widely used approach in protein research to elucidate the protein location and functions both in vitro and in live cells or in vivo. A peptide or a protein tag fused to the protein of interest and provides the opportunities for an attachment of small molecule probes or other fluorophore to image the dynamics of protein localization. Here we reviewed the recent development of no-wash small molecular probes for photoactive yellow protein (PYP-tag, by the means of utilizing a quenching mechanism based on the intramolecular interactions, or an environmental-sensitive fluorophore. Several fluorogenic probes have been developed, with fast labeling kinetics and cell permeability. This technology allows quick live-cell imaging of cell-surface and intracellular proteins without a wash-out procedure.

Lack of negative charge in the E46Q mutant of photoactive yellow protein prevents partial unfolding of the blue shifted intermediate

NARCIS (Netherlands)

Derix, N.M.; Wechselberger, R.W.|info:eu-repo/dai/nl/304829005; van der Horst, M.A.; Hellingwerf, K.J.; Boelens, R.|info:eu-repo/dai/nl/070151407; Kaptein, R.|info:eu-repo/dai/nl/074334603; van Nuland, N.A.J.

2003-01-01

The long-lived light-induced intermediate (pB) of the E46Q mutant (glutamic acid is replaced by glutamine at position 46) of photoactive yellow protein (PYP) has been investigated by NMR spectroscopy. The ground state of this mutant is very similar to that of wild-type PYP (WT), whereas the pB

Structural Determinats Underlying Photoprotection in the Photoactive Orange Carotenoid Protein of Cyanobacteria

Energy Technology Data Exchange (ETDEWEB)

Wilson, Adjele; Kinney, James N.; Zwart, Petrus H.; Punginelli, Claire; D' Haene, Sandrine; Perreau, Francois; Klein, Michael G.; Kirilovsky, Diana; Kerfeld, Cheryl

2010-04-01

The photoprotective processes of photosynthetic organisms involve the dissipation of excess absorbed light energy as heat. Photoprotection in cyanobacteria is mechanistically distinct from that in plants; it involves the Orange Carotenoid Protein (OCP), a water-soluble protein containing a single carotenoid. The OCP is a new member of the family of blue light photoactive proteins; blue-green light triggers the OCP-mediated photoprotective response. Here we report structural and functional characterization of the wildtype and two mutant forms of the OCP, from the model organism Synechocystis PCC6803. The structural analysis provides highresolution detail of the carotenoidprotein interactions that underlie the optical properties of the OCP, unique among carotenoid-proteins in binding a single pigment per polypeptide chain. Collectively, these data implicate several key amino acids in the function of the OCP and reveal that the photoconversion and photoprotective responses of the OCP to blue-green light can be decoupled.

ITO electrode/photoactive layer interface engineering for efficient inverted polymer solar cells based on P3HT and PCBM using a solution-processed titanium chelate

International Nuclear Information System (INIS)

Zhang Wenqing; Zheng Hua; Tan Zhan'ao; Qian Deping; Li Liangjie; Xu Qi; Li Shusheng; Li Yongfang

2012-01-01

We report efficient inverted polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) using alcohol-soluble titanium (diisopropoxide) bis (2,4-pentanedionate) (TIPD) as an electron selective layer between the indium tin oxide (ITO) electrode and the photoactive layer. The thermally annealed TIPD layer is highly transparent in the visible range and shows effective electron collection ability. By optimizing the electron-collecting layer, the photoactive layer and the hole-collecting layer, the power conversion efficiency (PCE) of the inverted device with the structure ITO/TIPD/P3HT : PCBM/MoO 3 /Ag reaches 4.10% under the illumination of AM1.5G, 100 mW cm -2 , which is among the highest values for inverted PSCs based on P3HT : PCBM. The PCE of the inverted device is improved in comparison with the conventional device (3.77%) under the same experimental conditions. (paper)

Direct in situ activation of Ag0 nanoparticles in synthesis of Ag/TiO2 and its photoactivity

International Nuclear Information System (INIS)

Jaafar, N.F.; Jalil, A.A.; Triwahyono, S.; Efendi, J.; Mukti, R.R.; Jusoh, R.; Jusoh, N.W.C.; Karim, A.H.; Salleh, N.F.M.; Suendo, V.

2015-01-01

Graphical abstract: - Highlights: • Ag 0 loaded on TiO 2 was prepared by a direct in situ electrochemical method. • 5 wt% Ag–TiO 2 demonstrated the best photocatalytic degradation of 2-CP. • Isomorphous substitution of Ag with Ti occurred to form Ti−O−Ag bonds. • Ag 0 and oxygen vacancies trapped electrons to enhance e–H + separation. • Substitution of Ag in the TiO 2 structure decreased the number of oxygen vacancies. - Abstract: Metallic Ag nanoparticles (Ag 0 ) were successfully activated using a direct in situ electrochemical method before being supported on TiO 2 . Catalytic testing showed that 5 wt% Ag–TiO 2 gave the highest photodegradation (94%) of 50 mg L −1 2-chlorophenol (2-CP) at pH 5 using 0.375 g L −1 catalyst within 6 h, while under similar conditions, 1 wt% and 10 wt% Ag–TiO 2 only gave 75% and 78% degradation, respectively. Characterization results illustrated that the photoactivity was affected by the amount of Ag 0 and oxygen vacancies which act as an electrons trap to enhance the electron–hole separation. While, the Ag−O−Ti bonds formation reduced the photoactivity. The degradation followed a pseudo-first order Langmuir–Hinshelwood model where adsorption was the controlling step. Study on the effect of scavengers showed that the hole (H + ) and hydroxyl radical (OH·) play important roles in the photodegradation. The regenerated photocatalyst was still stable after five cycling runs

Simple approach to detection and estimation of photoactivity of silver particles on graphene oxide in aqueous-organic dispersion

Science.gov (United States)

Vlasov, D. V.; Vlasova, T. D.; Apresyan, L. A.; Krasovskiy, V. I.; Feofanov, I. N.; Kazaryan, M. A.

2015-12-01

The effect of sediment flotation was observed in dispersion of graphene oxide flakes with Ag-particles deposited thereon in the aqueous-organic (containing dimethylformamide) under the visible light action, with subsequent stabilization of the dispersion, which does not occur in the absence of Ag-particles. The main reason for this laser light induced movement of sediment graphene oxide flakes may be associated with the appearance of small bubbles. The further development of this approach seem to be able to estimate the of graphene flakes photoactivity with different activating particles.

Photoactive layer-by-layer films of cellulose phosphate and titanium dioxide containing phosphotungstic acid

Energy Technology Data Exchange (ETDEWEB)

Ullah, Sajjad [Instituto de Química de São Carlos, Universidade de São Paulo, PO Box 780, São Carlos, São Paulo 13564-970 (Brazil); Acuña, José Javier Sáez [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo Andre, Sao Paulo, 09210-170 (Brazil); Pasa, André Avelino [Surface and Thin Film Laboratory, Physics Department, Federal University of Santa Catarina, PO Box 476, Florianópolis, SC 88040-900 (Brazil); Bilmes, Sara A. [Universidad de Buenos Aires, Facultad Ciencias Exactas y Naturales, Instituto de Química Física de los Materiales, Medio Ambiente y Energía – INQUIMAE, Ciudad Universitaria, Pab. 2, Buenos Aires C1428EHA (Argentina); Vela, Maria Elena; Benitez, Guillermo [Laboratorio de Nanoscopías y Fisicoquímica de Superficies, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata – CONICET, diagonal 113 esquina 64. C.C.16.Suc.4, 1900 La Plata (Argentina); Rodrigues-Filho, Ubirajara Pereira, E-mail: uprf@iqsc.usp.br [Instituto de Química de São Carlos, Universidade de São Paulo, PO Box 780, São Carlos, São Paulo 13564-970 (Brazil)

2013-07-15

A versatile layer-by-layer (LbL) procedure for the preparation of highly dispersed, adherent and porous multilayer films of TiO{sub 2} nanoparticles (NPs) and phosphotungstic acid (HPW) on a variety of substrates at room temperature was developed based on the use of cellulose phosphate (CP) as an efficient and non-conventional polyelectrolyte. UV/vis absorption spectroscopy confirmed the linear and regular growth of the films with the number of immersion cycles and a strong adsorption ability of CP towards TiO{sub 2} NPs. FTIR spectroscopy showed that HPW binds to the surface of TiO{sub 2} through the oxygen atom at the corner of the Keggin structure. XPS results showed that the interaction between TiO{sub 2} and CP is through Ti–O–P linkage. A model is proposed for the TiO{sub 2}–HPW interaction based on XPS and FTIR results. FEG/SEM study of the surface morphology revealed a porous film structure with a homogenous distribution of the TiO{sub 2} NPs induced by CP. HRTEM studies showed that the resulting composite films consist of crystalline anatase and rutile phases and poly-nano-crystalline HPW with a semi-crystalline TiO{sub 2}–HPW interface. These CP/TiO{sub 2} and CP/TiO{sub 2}/HPW LbL films showed good photoactivity against both saturated and unsaturated species, for instance, stearic acid (SA), crystal violet (CV) and methylene blue (MB) under UV irradiation. The CP/HPW films formed on bacterial cellulose (BC) showed good photochromic response which is enhanced in presence of TiO{sub 2} due to an interfacial electron transfer from TiO{sub 2} to HPW. This simple and environmentally safe method can be used to form coatings on a variety of surfaces with photoactive TiO{sub 2} and TiO{sub 2}/HPW films.

P3HT:PCBM Incorporated with Silicon Nanoparticles as Photoactive Layer in Efficient Organic Photovoltaic Devices

Directory of Open Access Journals (Sweden)

Shang-Chou Chang

2013-01-01

Full Text Available Silicon nanoparticles doped poly(3-hexylthiophene and [6,6]-phenyl C61-butyric acid methyl ester blends (P3HT:PCBM: Si NP have been produced as the photoactive layer of organic photovoltaic devices (OPVs. The silicon nanoparticles’ size is between 80 and 100 nm checked by transmission electron microscope (TEM. The 0.35 wt% Si NP doping OPVs exhibit higher power conversion efficiency (PCE than other OPVs. The PCE of the OPVs increases from 3.01% to 3.38% mainly due to increasing short-circuit current density from 8.38 to 9.48 mA/cm2, while the open-circuit voltage remains the same. The Si NP can provide extra exciton separation and electron pathways in hybrid solar cells.

The influence of alizarin and fluorescein on the photoactivity of Ni, Pt and Ru-doped TiO2 layers

International Nuclear Information System (INIS)

Rosu, Marcela-Corina; Suciu, Ramona-Crina; Lazar, Mihaela D.; Bratu, I.

2013-01-01

Highlights: ► The Ni, Pt, Ru-doped TiO 2 materials and sensitized with alizarin and fluorescein dyes were prepared by wet chemical route. ► The samples were characterized by: UV–vis spectroscopy, spectrofluorimetry, FT/IR spectroscopy and microscopy, X-ray diffraction and N 2 physisorption measurements. ► A combined influence of the dopants and dyes was observed, leading to a beneficial effect to TiO 2 photoactivity. -- Abstract: The doping with different metal ions and sensitization with organic compounds are two well known methods used to improve the photoactivity of TiO 2 . In this respect, the metallic ions-doped TiO 2 samples were prepared by embedding Ni, Pt and Ru ions into TiO 2 crystalline network and then, each sample was sensitized with alizarin and fluorescein dyes. The qualitative evaluation of prepared TiO 2 -based materials was made by: UV–vis spectroscopy, spectrofluorimetry, FT/IR spectroscopy and microscopy, X-ray diffraction and N 2 physisorption measurements. The optoelectronic properties investigated by UV–vis spectroscopy show that the optical response of Ni-doped TiO 2 layer shifts to visible. The X-ray spectra do not show peaks of nickel, platinum and ruthenium oxide crystals or pure metals. The FT/IR spectra proved the presence of dye molecules adsorbed on titania nanoparticles surface. These results demonstrated that the studied dopants and dyes have potential to promote modified TiO 2 -based materials as good candidates to be used in photolectrocatalytic processes

Inhibitor mechanisms in the S1 binding site of the dopamine transporter defined by multi-site molecular tethering of photoactive cocaine analogs.

Science.gov (United States)

Krout, Danielle; Pramod, Akula Bala; Dahal, Rejwi Acharya; Tomlinson, Michael J; Sharma, Babita; Foster, James D; Zou, Mu-Fa; Boatang, Comfort; Newman, Amy Hauck; Lever, John R; Vaughan, Roxanne A; Henry, L Keith

2017-10-15

Dopamine transporter (DAT) blockers like cocaine and many other abused and therapeutic drugs bind and stabilize an inactive form of the transporter inhibiting reuptake of extracellular dopamine (DA). The resulting increases in DA lead to the ability of these drugs to induce psychomotor alterations and addiction, but paradoxical findings in animal models indicate that not all DAT antagonists induce cocaine-like behavioral outcomes. How this occurs is not known, but one possibility is that uptake inhibitors may bind at multiple locations or in different poses to stabilize distinct conformational transporter states associated with differential neurochemical endpoints. Understanding the molecular mechanisms governing the pharmacological inhibition of DAT is therefore key for understanding the requisite interactions for behavioral modulation and addiction. Previously, we leveraged complementary computational docking, mutagenesis, peptide mapping, and substituted cysteine accessibility strategies to identify the specific adduction site and binding pose for the crosslinkable, photoactive cocaine analog, RTI 82, which contains a photoactive azide attached at the 2β position of the tropane pharmacophore. Here, we utilize similar methodology with a different cocaine analog N-[4-(4-azido-3-I-iodophenyl)-butyl]-2-carbomethoxy-3-(4-chlorophenyl)tropane, MFZ 2-24, where the photoactive azide is attached to the tropane nitrogen. In contrast to RTI 82, which crosslinked into residue Phe319 of transmembrane domain (TM) 6, our findings show that MFZ 2-24 adducts to Leu80 in TM1 with modeling and biochemical data indicating that MFZ 2-24, like RTI 82, occupies the central S1 binding pocket with the (+)-charged tropane ring nitrogen coordinating with the (-)-charged carboxyl side chain of Asp79. The superimposition of the tropane ring in the three-dimensional binding poses of these two distinct ligands provides strong experimental evidence for cocaine binding to DAT in the S1 site

Highly porous ZnS microspheres for superior photoactivity after Au and Pt deposition and thermal treatment

Energy Technology Data Exchange (ETDEWEB)

Singla, Shilpa; Pal, Bonamali, E-mail: bpal@thapar.edu

2013-11-15

Graphical abstract: Highly porous ZnS microsphere of size 2–5 μm having large surface area ca. 173.14 m{sup 2} g{sup −1} exhibits superior photocatalytic activity for the oxidation of 4-nitrophenol under UV light irradiation. The rate of photooxidation has been significantly improved by Au and Pt deposition and after sintering, respectively, due to rapid electron acceptance by metal from photoexcited ZnS and growth of crystalline ZnS phase. - Highlights: • Photoactive ZnS microsphere of size 2–5 μm was prepared by hydrothermal route. • Highly porous cubic spherical ZnS crystals possess a large surface area, 173 m{sup 2} g{sup −1}. • 1 wt% Au and Pt photodeposition highly quenched the photoluminescence at 437 nm. • Sintering and metal loading notably improve the photooxidation rate of 4-nitrophenol. • Pt co-catalyst always exhibits superior photoactivity of ZnS microsphere than Au. - Abstract: This work highlights the enhanced photocatalytic activity of porous ZnS microspheres after Au and Pt deposition and heat treatment at 500 °C for 2 h. Microporous ZnS particles of size 2–5 μm with large surface area 173.14 m{sup 2} g{sup −1} and pore volume 0.0212 cm{sup 3} g{sup −1} were prepared by refluxing under an alkaline medium. Photoluminescence of ZnS at 437 nm attributed to sulfur or zinc vacancies were quenched to 30% and 49%, respectively, after 1 wt% Au and Pt loading. SEM images revealed that each ZnS microparticle consist of several smaller ZnS spheres of size 2.13 nm as calculated by Scherrer's equation. The rate of photooxidation of 4-nitrophenol (10 μM) under UV (125 W Hg arc–10.4 mW/cm{sup 2}) irradiation has been significantly improved by Au and Pt deposition followed by sintering due to better electron capturing capacity of deposited metals and growth of crystalline ZnS phase with less surface defects.

Direct in situ activation of Ag{sup 0} nanoparticles in synthesis of Ag/TiO{sub 2} and its photoactivity

Energy Technology Data Exchange (ETDEWEB)

Jaafar, N.F. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Jalil, A.A., E-mail: aishah@cheme.utm.my [Institute of Hydrogen Economy, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Triwahyono, S. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Efendi, J. [Department of Chemistry, Universitas Negeri Padang, Jl. Prof. Hamka, Air Tawar, Padang, West Sumatera (Indonesia); Mukti, R.R. [Division of Inorganic and Physical Chemistry, Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, Jl Ganesha No. 10, Bandung 40132 (Indonesia); Jusoh, R.; Jusoh, N.W.C. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Karim, A.H. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Salleh, N.F.M. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Suendo, V. [Division of Inorganic and Physical Chemistry, Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, Jl Ganesha No. 10, Bandung 40132 (Indonesia)

2015-05-30

Graphical abstract: - Highlights: • Ag{sup 0} loaded on TiO{sub 2} was prepared by a direct in situ electrochemical method. • 5 wt% Ag–TiO{sub 2} demonstrated the best photocatalytic degradation of 2-CP. • Isomorphous substitution of Ag with Ti occurred to form Ti−O−Ag bonds. • Ag{sup 0} and oxygen vacancies trapped electrons to enhance e–H{sup +} separation. • Substitution of Ag in the TiO{sub 2} structure decreased the number of oxygen vacancies. - Abstract: Metallic Ag nanoparticles (Ag{sup 0}) were successfully activated using a direct in situ electrochemical method before being supported on TiO{sub 2}. Catalytic testing showed that 5 wt% Ag–TiO{sub 2} gave the highest photodegradation (94%) of 50 mg L{sup −1} 2-chlorophenol (2-CP) at pH 5 using 0.375 g L{sup −1} catalyst within 6 h, while under similar conditions, 1 wt% and 10 wt% Ag–TiO{sub 2} only gave 75% and 78% degradation, respectively. Characterization results illustrated that the photoactivity was affected by the amount of Ag{sup 0} and oxygen vacancies which act as an electrons trap to enhance the electron–hole separation. While, the Ag−O−Ti bonds formation reduced the photoactivity. The degradation followed a pseudo-first order Langmuir–Hinshelwood model where adsorption was the controlling step. Study on the effect of scavengers showed that the hole (H{sup +}) and hydroxyl radical (OH·) play important roles in the photodegradation. The regenerated photocatalyst was still stable after five cycling runs.

The influence of alizarin and fluorescein on the photoactivity of Ni, Pt and Ru-doped TiO{sub 2} layers

Energy Technology Data Exchange (ETDEWEB)

Rosu, Marcela-Corina, E-mail: marcela.rosu@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath Street, 400293, Cluj-Napoca (Romania); Suciu, Ramona-Crina; Lazar, Mihaela D.; Bratu, I. [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath Street, 400293, Cluj-Napoca (Romania)

2013-04-20

Highlights: ► The Ni, Pt, Ru-doped TiO{sub 2} materials and sensitized with alizarin and fluorescein dyes were prepared by wet chemical route. ► The samples were characterized by: UV–vis spectroscopy, spectrofluorimetry, FT/IR spectroscopy and microscopy, X-ray diffraction and N{sub 2} physisorption measurements. ► A combined influence of the dopants and dyes was observed, leading to a beneficial effect to TiO{sub 2} photoactivity. -- Abstract: The doping with different metal ions and sensitization with organic compounds are two well known methods used to improve the photoactivity of TiO{sub 2}. In this respect, the metallic ions-doped TiO{sub 2} samples were prepared by embedding Ni, Pt and Ru ions into TiO{sub 2} crystalline network and then, each sample was sensitized with alizarin and fluorescein dyes. The qualitative evaluation of prepared TiO{sub 2}-based materials was made by: UV–vis spectroscopy, spectrofluorimetry, FT/IR spectroscopy and microscopy, X-ray diffraction and N{sub 2} physisorption measurements. The optoelectronic properties investigated by UV–vis spectroscopy show that the optical response of Ni-doped TiO{sub 2} layer shifts to visible. The X-ray spectra do not show peaks of nickel, platinum and ruthenium oxide crystals or pure metals. The FT/IR spectra proved the presence of dye molecules adsorbed on titania nanoparticles surface. These results demonstrated that the studied dopants and dyes have potential to promote modified TiO{sub 2}-based materials as good candidates to be used in photolectrocatalytic processes.

Enhancement of Power Efficiency and Stability of P3HT-Based Organic Solar Cells under Elevated Operating-Temperatures by Using a Nanocomposite Photoactive Layer

Directory of Open Access Journals (Sweden)

Tran Thi Thao

2015-01-01

Full Text Available With the aim to find out an enhanced operating-temperature range for photovoltaic device parameters, two types of the photoactive layer were prepared: poly(3-hexylthiophene (P3HT and P3HT+nc-TiO2 (PTC thin films. The enhancement obtained for the photoelectrical conversion efficiency of the composite based OSCs is attributed to the presence of nanoheterojunctions of TiO2/P3HT. For the temperature range of 30–70°C, the decrease of the open-circuit potential was compensated by an increase of the fill factor; and the increase in the short-circuit current resulted in an overall increase of the energy conversion efficiency. At elevated temperatures of 60–80°C the efficiency of the P3HT- and PTC-based cells reached a maximum value of 1.6% and 2.1%, respectively. Over this temperature range the efficiency of P3HT-based OSC decreased strongly to zero, whereas for the PTC cells it maintained a value as large as 1.2% at the temperature range of 110–140°C. The improved thermal stability of the composite-based device was attributed to the lowered thermal expansion coefficient of the nanocomposite photoactive layer.

Electrochemical synthesis of photoactive In/sub 2/Se/sub 3/ thin films

Energy Technology Data Exchange (ETDEWEB)

Herrero, J; Ortega, J

1987-12-01

In/sub 2/Se/sub 3/ thin films were grown by alternate electrodeposition of selenium and indium from separate baths onto titanium substrates with subsequent thermal annealing. The influence of annealing temperature on the properties of the obtained films was examined. The results of X-ray diffraction patterns led to the conclusion that films were ..beta..-phase when the temperature ranged between 300 and 500/sup 0/C. At 600/sup 0/C the thin film loses Se and the ratio Se/In decreases. Only photoanodic response, n-type thin films, was observed when the samples were tested in a photoelectrochemical cell with a sulfite/sulfate redox couple. Values of the photocurrent on the spectra response were increased when the annealing temperature was also increased, showing the best photocurrent values at 500/sup 0/C, and the films that were annealed at 600/sup 0/C showed no photoactivity. Spectral responses after chemical etching of the samples showed a significant increase of the photocurrent. Application of Gaertner-Butler's model to the interface semiconductor-electrolyte makes it possible to obtain the semiconductor energy gap, on samples heated at 500/sup 0/C, corresponding to a direct allowed band transition.

Photoactivity of N-doped ZnO nanoparticles in oxidative and reductive reactions

Science.gov (United States)

Oliveira, Jéssica A.; Nogueira, André E.; Gonçalves, Maria C. P.; Paris, Elaine C.; Ribeiro, Caue; Poirier, Gael Y.; Giraldi, Tania R.

2018-03-01

N-doped ZnO is a prospective material for photocatalytic reactions. However, only oxidative paths are well investigated in the literature. This paper describes a comparative study about ZnO and ZnO:N potential for oxidative and reductive reactions, probed by rhodamine B dye photodegradation and CO2 photoreduction. The materials were prepared by the polymeric precursor method, using urea as a nitrogen source, and different heat treatments were used to observe their effects on surface decontamination, crystallinity, particle sizes and shapes, and photocatalytic performance. ZnO and ZnO:N presented a wurtzite crystalline structure and nanometric-scale particles. Samples submitted to higher temperatures showed lower specific surface areas, but higher crystallinity and lower contents of species adsorbed on their surfaces. On the other hand, the photocatalysts annealed in shorter times presented smaller crystallite sizes and lower crystallinity. These factors influenced the photoactivity in both conditions, i.e., oxidation and reduction reactions, under the ultraviolet and visible light, indicating that structural factors influenced the adequate charge separation and consequent photocatalytic activity since the as-synthesized samples were versatile photocatalysts in both redox reactions.

The preparation of new functionalized [2.2]paracyclophane derivatives with N-containing functional groups

Directory of Open Access Journals (Sweden)

Henning Hopf

2015-04-01

Full Text Available The two isomeric bis(isocyanates 4,12- and 4,16-di-isocyanato[2.2]paracyclophane, 16 and 28, have been prepared from their corresponding diacids by simple routes. The two isomers are versatile intermediates for the preparation of various cyclophanes bearing substituents with nitrogen-containing functional groups, e.g., the pseudo-ortho diamine 8, the bis secondary amine 23, and the crownophanes 18 and 19. Several of these new cyclophane derivatives (18, 19, 22, 26, 28 have been characterized by X-ray structural analysis.

Effect of doping (C or N) and co-doping (C+N) on the photoactive properties of magnetron sputtered titania coatings for the application of solar water-splitting.

Science.gov (United States)

Rahman, M; Dang, B H Q; McDonnell, K; MacElroy, J M D; Dowling, D P

2012-06-01

The photocatalytic splitting of water into hydrogen and oxygen using a photoelectrochemical (PEC) cell containing titanium dioxide (TiO2) photoanode is a potentially renewable source of chemical fuels. However, the size of the band gap (-3.2 eV) of the TiO2 photocatalyst leads to its relatively low photoactivity toward visible light in a PEC cell. The development of materials with smaller band gaps of approximately 2.4 eV is therefore necessary to operate PEC cells efficiently. This study investigates the effect of dopant (C or N) and co-dopant (C+N) on the physical, structural and photoactivity of TiO2 nano thick coating. TiO2 nano-thick coatings were deposited using a closed field DC reactive magnetron sputtering technique, from titanium target in argon plasma with trace addition of oxygen. In order to study the influence of doping such as C, N and C+N inclusions in the TiO2 coatings, trace levels of CO2 or N2 or CO2+N2 gas were introduced into the deposition chamber respectively. The properties of the deposited nano-coatings were determined using Spectroscopic Ellipsometry, SEM, AFM, Optical profilometry, XPS, Raman, X-ray diffraction UV-Vis spectroscopy and tri-electrode potentiostat measurements. Coating growth rate, structure, surface morphology and roughness were found to be significantly influenced by the types and amount of doping. Substitutional type of doping in all doped sample were confirmed by XPS. UV-vis measurement confirmed that doping (especially for C doped sample) facilitate photoactivity of sputtered deposited titania coating toward visible light by reducing bandgap. The photocurrent density (indirect indication of water splitting performance) of the C-doped photoanode was approximately 26% higher in comparison with un-doped photoanode. However, coating doped with nitrogen (N or N+C) does not exhibit good performance in the photoelectrochemical cell due to their higher charge recombination properties.

Nitridation of one-dimensional tungsten oxide nanostructures: Changes in structure and photoactivity

KAUST Repository

Varga, Tamás

2017-10-12

In the search for stable, visible light active photoelectrodes, hydrothermally synthesized tungsten oxide nanowires were modified via nitrogen incorporation into their structure. To this end, nanowires were heat-treated in ammonia/nitrogen atmosphere at different temperatures. This procedure caused transitions in their structure that were investigated along with the photoelectrochemical properties of the samples. Results were subsequently compared to the reference samples treated in inert nitrogen atmosphere. Morphological changes and structural transitions were followed by transmission and scanning electron microscopy and X-ray diffraction. Bandgap energies were determined from the UV–vis spectra of the materials, while photoelectrochemical properties were tested by linear sweep photovoltammetry and electrochemical impedance spectroscopy. Pristine tungsten oxide nanowires were first transformed into tungsten oxynitride and then tungsten nitride during high-temperature calcination in ammonia atmosphere. Electron microscopic investigation revealed that, along with phase transition, the initial fibrous morphology gradually converted into nanosheets. Simultaneously, bandgap energies significantly decreased in the calcination process, too. Photoelectrochemical measurements demonstrated that photoactivity in the treated samples was not improved by the decrease of the bandgap. This behavior might be explained with the deterioration of charge carrier transport properties of the materials due to the increased number of structural defects (acting as trap states), and current ongoing work aims to verify this notion.

Highly efficient polymer solar cells with printed photoactive layer: rational process transfer from spin-coating

KAUST Repository

Zhao, Kui

2016-09-05

Scalable and continuous roll-to-roll manufacturing is at the heart of the promise of low-cost and high throughput manufacturing of solution-processed photovoltaics. Yet, to date the vast majority of champion organic solar cells reported in the literature rely on spin-coating of the photoactive bulk heterojunction (BHJ) layer, with the performance of printed solar cells lagging behind in most instances. Here, we investigate the performance gap between polymer solar cells prepared by spin-coating and blade-coating the BHJ layer for the important class of modern polymers exhibiting no long range crystalline order. We find that thickness parity does not always yield performance parity even when using identical formulations. Significant differences in the drying kinetics between the processes are found to be responsible for BHJ nanomorphology differences. We propose an approach which benchmarks the film drying kinetics and associated BHJ nanomorphology development against those of the champion laboratory devices prepared by spin-coating the BHJ layer by adjusting the process temperature. If the optimization requires the solution concentration to be changed, then it is crucial to maintain the additive-to-solute volume ratio. Emulating the drying kinetics of spin-coating is also shown to help achieve morphological and performance parities. We put this approach to the test and demonstrate printed PTB7:PC71BM polymer solar cells with efficiency of 9% and 6.5% PCEs on glass and flexible PET substrates, respectively. We further demonstrate performance parity for two other popular donor polymer systems exhibiting rigid backbones and absence of a long range crystalline order, achieving a PCE of 9.7%, the highest efficiency reported to date for a blade coated organic solar cell. The rational process transfer illustrated in this study should help the broader and successful adoption of scalable printing methods for these material systems.

Building complex carbon skeletons with ethynyl[2.2]paracyclophanes

Directory of Open Access Journals (Sweden)

Ina Dix

2014-08-01

Full Text Available Ethynyl[2.2]paracyclophanes are shown to be useful substrates for the preparation of complex, highly unsaturated carbon frameworks. Thus both the pseudo-geminal- 2 and the pseudo-ortho-diethynylcyclophane 4 can be dimerized by Glaser coupling to the respective dimers 9/10 and 11/12. Whereas the former isomer pair could not be separated so far, the latter provided the pure diastereomers after extensive column chromatography/recrystallization. Isomer 11 is chiral and could be separated on a column impregnated with cellulose tris(3,5-dimethylphenylcarbamate. The bridge-extended cyclophane precursor 18 furnished the ring-enlarged cyclophanes 19 and 20 on Glaser–Hay coupling. Cross-coupling of 4 and the planar building block 1,2-diethynylbenzene (1 yielded the chiral hetero dimer 22 as the main product. An attempt to prepare the biphenylenophane 27 from the triacetylene 24 by CpCo(CO2-catalyzed cycloisomerization resulted in the formation of the cyclobutadiene Co-complex 26. Besides by their usual spectroscopic and analytical data, the new cyclophanes 11, 12, 19, 20, 22, and 26 were characterized by X-ray structural analysis.

Fabrication and photoactivity of ionic liquid-TiO2 structures for efficient visible-light-induced photocatalytic decomposition of organic pollutants in aqueous phase.

Science.gov (United States)

Gołąbiewska, Anna; Paszkiewicz-Gawron, Marta; Sadzińska, Aleksandra; Lisowski, Wojciech; Grabowska, Ewelina; Zaleska-Medynska, Adriana; Łuczak, Justyna

2018-01-01

To investigate the effect of the ionic liquid (IL) chain length on the surface properties and photoactivity of TiO 2 , a series of TiO 2 microspheres have been synthesized via a solvothermal method assisted by 1-methyl-3-octadecylimidazolium chloride ([ODMIM][Cl]) and 1-methyl-3-tetradecylimidazolium chloride ([TDMIM][Cl]). All as-prepared samples were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), scanning transmission microscopy (STEM) and the Brunauer-Emmett-Teller (BET) surface area method, whereas the photocatalytic activity was evaluated by the degradation of phenol in aqueous solution under visible light irradiation (λ > 420 nm). The highest photoefficiency (four times higher than pristine TiO 2 ) was observed for the TiO 2 sample obtained in the presence of [TDMIM][Cl] for a IL to TiO 2 precursor molar ratio of 1:3. It was revealed that interactions between the ions of the ionic liquid and the surface of the growing titanium dioxide spheres results in a red-shift of absorption edge for the IL-TiO 2 semiconductors. In this regard, the direct increase of the photoactivity of IL-TiO 2 in comparison to pristine TiO 2 was observed. The active species trapping experiments indicated that O 2 •- is the main active species, created at the surface of the IL-TiO 2 material under visible-light illumination, and is responsible for the effective phenol degradation.

Enhancement in light harvesting ability of photoactive layer P3HT: PCBM using CuO nanoparticles

Science.gov (United States)

Tiwari, D. C.; Dwivedi, Shailendra Kumar; Dipak, Pukhrambam; Chandel, Tarun

2018-05-01

In this paper, we have synthesized CuO nanoparticles via precipitation method and incorporated CuO nanoparticles in the P3HT-poly (3-hexyl) thiophene: PCBM-[6, 6]-phenyl-C61-butyric acid methyl ester heterogeneous blend. The ratio of P3HT to CuO in the blend was varied, while maintaining the fixed ratio of PCBM. The UV-visible absorption spectra of P3HT: PCBM photoactive layer containing different weight percentages of CuO nanoparticles showed a clear enhancement in the photo absorption of the active layer. The absorption band starts from 310 nm to 750 nm for P3HT: CuO (NPs):PCBM (0.5:0.5:1). This shows that incorporation of CuO nanoparticles leads to larger absorption band. In addition, the X-ray diffraction (XRD) shows improvement in P3HT crystallinity and the better formation of CuO nanostructures.

Synthesis of positron labeled photoactive compounds: 18F labeled aryl azides for positron labeling of biochemical molecules

International Nuclear Information System (INIS)

Hashizume, Kazunari; Hashimoto, Naota; Miyake, Yoshihiro

1995-01-01

The authors have prepared various [ 18 F] fluorine labeled aryl azides as a novel photoactive compounds suitable for positron labeling of biochemical molecules. The introduction of fluorine substituents to aryl azides can be expected to have dramatic effects on their nature and reactivity toward photolysis. Positron labeled reagents for labeling proteins or peptides have recently attracted considerable attention due to their wide applicability in biochemistry and positron emission tomography (PET). Various labeled azide compounds are often used in biochemistry for radiolabeling biological molecules by photolysis, but there have been no reports on the preparation or use of fluorine-18 labeled azides. The authors now report a novel synthesis of 18 F-labeled aryl azides which will have wide application in the biochemistry and nuclear medicine as a means for 18 F-fluorine labeling for proteins, peptides, and nucleic acids. 2 tabs

Enhanced photoactivity from single-crystalline SrTaO2N nanoplates synthesized by topotactic nitridation

International Nuclear Information System (INIS)

Fu, Jie; Skrabalak, Sara E.

2017-01-01

There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often give enhanced photoactivity. Herein, single-crystalline SrTaO 2 N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, in which single-crystalline SrTaO 2 N nanoplates form by topotactic nitridation of aerosol-prepared Sr 2 Ta 2 O 7 nanoplates and SrTaO 2 N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO 2 N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1 % for OER compared to the polyhedra (AQE: 1.6 %) and SrTaO 2 N polycrystals (AQE: 0.6 %). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Enhanced Photoactivity from Single-Crystalline SrTaO2 N Nanoplates Synthesized by Topotactic Nitridation.

Science.gov (United States)

Fu, Jie; Skrabalak, Sara E

2017-11-06

There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often give enhanced photoactivity. Herein, single-crystalline SrTaO 2 N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, in which single-crystalline SrTaO 2 N nanoplates form by topotactic nitridation of aerosol-prepared Sr 2 Ta 2 O 7 nanoplates and SrTaO 2 N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO 2 N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1 % for OER compared to the polyhedra (AQE: 1.6 %) and SrTaO 2 N polycrystals (AQE: 0.6 %). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surfactant-free synthesis of hierarchical niobic acid microflowers assembled from ultrathin nanosheets with efficient photoactivities

Energy Technology Data Exchange (ETDEWEB)

Dong, Wenhao [Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543 (Singapore); Singapore-Peking University Research Centre, Centre for Research Excellence & Technological Enterprise (CREATE), Singapore, 138602 (Singapore); Pan, Feng, E-mail: phypf2012@163.com [Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543 (Singapore); Singapore-Peking University Research Centre, Centre for Research Excellence & Technological Enterprise (CREATE), Singapore, 138602 (Singapore); Wang, Yanyan [Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543 (Singapore); Singapore-Peking University Research Centre, Centre for Research Excellence & Technological Enterprise (CREATE), Singapore, 138602 (Singapore); Xiao, Shuning [Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543 (Singapore); International Joint Lab on Resource Chemistry SHNU-NUS-PU, Department of Chemistry, Shanghai Normal University, Shanghai 200234 (China); Wu, Kai [Singapore-Peking University Research Centre, Centre for Research Excellence & Technological Enterprise (CREATE), Singapore, 138602 (Singapore); BNLMS, SKLSCUSS, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871 (China); Xu, Guo Qin [Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543 (Singapore); Singapore-Peking University Research Centre, Centre for Research Excellence & Technological Enterprise (CREATE), Singapore, 138602 (Singapore); National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Jiangsu Prov., 215123 (China); and others

2017-01-15

Highlights: • 3D hierarchical niobic acid microflower was synthesized by a surfactant-free method. • The microflower was composed of ultrathin nanosheets with ∼5 nm thickness. • The microflower showed high photoactivity owing to the 3D structural features. • This microflower was converted to Nb{sub 2}O{sub 5} without significant structural alteration. • Nb{sub 2}O{sub 5} nanoneedles can also be obtained by adjusting the pH value during synthesis. - Abstract: Hierarchical niobic acid (Nb{sub 2}O{sub 5}·nH{sub 2}O) microflowers are synthesized by a surfactant-free hydrothermal approach. The three-dimensional microflowers are assembled from two-dimensional ultrathin nanosheets with thickness of ∼5 nm. Using rhodamine B as a probe, the Nb{sub 2}O{sub 5}·nH{sub 2}O microflowers exhibit high photocatalytic activity under UV light irradiation. Furthermore, the Nb{sub 2}O{sub 5}·nH{sub 2}O microflowers are easily converted to niobium pentoxide without significant structural alteration.

Conversion of light-energy into molecular strain in the photocycle of the photoactive yellow protein.

Science.gov (United States)

Gamiz-Hernandez, Ana P; Kaila, Ville R I

2016-01-28

The Photoactive Yellow Protein (PYP) is a light-driven photoreceptor, responsible for the phototaxis of halophilic bacteria. Recently, a new short-lived intermediate (pR0) was characterized in the PYP photocycle using combined time-resolved X-ray crystallography and density functional theory calculations. The pR0 species was identified as a highly contorted cis-intermediate, which is stabilized by hydrogen bonds with protein residues. Here we show by hybrid quantum mechanics/classical mechanics (QM/MM) molecular dynamics simulations, and first-principles calculations of optical properties, that the optical shifts in the early steps of the PYP photocycle originate from the conversion of light energy into molecular strain, stored in the pR0 state, and its relaxation in subsequent reaction steps. Our calculations quantitatively reproduce experimental data, which enables us to identify molecular origins of the optical shifts. Our combined approach suggests that the short-lived pR0 intermediate stores ∼1/3 of the photon energy as molecular strain, thus providing the thermodynamic driving force for later conformational changes in the protein.

Probing the structural dependency of photoinduced properties of colloidal quantum dots using metal-oxide photo-active substrates

International Nuclear Information System (INIS)

Patty, Kira; Campbell, Quinn; Hamilton, Nathan; West, Robert G.; Sadeghi, Seyed M.; Mao, Chuanbin

2014-01-01

We used photoactive substrates consisting of about 1 nm coating of a metal oxide on glass substrates to investigate the impact of the structures of colloidal quantum dots on their photophysical and photochemical properties. We showed during irradiation these substrates can interact uniquely with such quantum dots, inducing distinct forms of photo-induced processes when they have different cores, shells, or ligands. In particular, our results showed that for certain types of core-shell quantum dot structures an ultrathin layer of a metal oxide can reduce suppression of quantum efficiency of the quantum dots happening when they undergo extensive photo-oxidation. This suggests the possibility of shrinking the sizes of quantum dots without significant enhancement of their non-radiative decay rates. We show that such quantum dots are not influenced significantly by Coulomb blockade or photoionization, while those without a shell can undergo a large amount of photo-induced fluorescence enhancement via such blockade when they are in touch with the metal oxide.

Cation Exchange Strategy for the Encapsulation of a Photoactive CO-Releasing Organometallic Molecule into Anionic Porous Frameworks.

Science.gov (United States)

Carmona, Francisco J; Rojas, Sara; Sánchez, Purificación; Jeremias, Hélia; Marques, Ana R; Romão, Carlos C; Choquesillo-Lazarte, Duane; Navarro, Jorge A R; Maldonado, Carmen R; Barea, Elisa

2016-07-05

The encapsulation of the photoactive, nontoxic, water-soluble, and air-stable cationic CORM [Mn(tacn)(CO)3]Br (tacn = 1,4,7-triazacyclononane) in different inorganic porous matrixes, namely, the metalorganic framework bio-MOF-1, (NH2(CH3)2)2[Zn8(adeninate)4(BPDC)6]·8DMF·11H2O (BPDC = 4,4'-biphenyldicarboxylate), and the functionalized mesoporous silicas MCM-41-SO3H and SBA-15-SO3H, is achieved by a cation exchange strategy. The CO release from these loaded materials, under simulated physiological conditions, is triggered by visible light. The results show that the silica matrixes, which are unaltered under physiological conditions, slow the kinetics of CO release, allowing a more controlled CO supply. In contrast, bio-MOF-1 instability leads to the complete leaching of the CORM. Nevertheless, the degradation of the MOF matrix gives rise to an enhanced CO release rate, which is related to the presence of free adenine in the solution.

The Influence of NiO Addition in TiO2 Structure and Its Photoactivity

Science.gov (United States)

Wahyuningsih, S.; Ramelan, A. H.; Purwanti, P. D.; Munawaroh, H.; Ichsan, S.; Kristiawan, Y. R.

2018-03-01

The synthesis of TiO2 together with the TiO2-NiO composite using various annealing temperatures has been studied. The synthesis of TiO2 was performed by sol gel method using Titanium Tetra Isopropoxide (TTIP) precursor, whereas the synthesis of TiO2-NiO composite was done by wet impregnation method using NiNO3.6H2O precursor. This study aims to determine the influence of NiO addition in its structure and photoactivity. The diffraction of synthesized TiO2 at 400 °C temperature shows anatase TiO2 peak at 2θ = 25.35 °. The addition of NiO dopant to the synthesis of TiO2 process is carried out by annealing at 300 °C, 400 °C, 500 °C, 600 °C, and 700 °C, respectively. The TiO2-NiO composite has been prepared and shows the diffraction peak of NiO at 2θ=43° about 33.08 to 36.68%. The optimum result of Rhodamine B photodegradation with TiO2 was 43.15%, while the optimum result of Rhodamine B degradation with TiO2-NiO composite was 92.85%.

Effect of nitrogen doping on wetting and photoactive properties of laser processed zinc oxide-graphene oxide nanocomposite layers

Energy Technology Data Exchange (ETDEWEB)

György, E., E-mail: egyorgy@icmab.es [Consejo Superior de Investigaciones Cientificas, Instituto de Ciencia de Materiales de Barcelona (CSIC-ICMAB), Campus UAB, 08193 Bellaterra (Spain); National Institute for Lasers, Plasma and Radiation Physics, P. O. Box MG 36, 76900 Bucharest V (Romania); Pérez del Pino, A. [Consejo Superior de Investigaciones Cientificas, Instituto de Ciencia de Materiales de Barcelona (CSIC-ICMAB), Campus UAB, 08193 Bellaterra (Spain); Logofatu, C. [National Institute for Materials Physics, P. O. Box MG. 7, 77125 Bucharest (Romania); Duta, A.; Isac, L. [Transilvania University of Brasov, Research Centre for Renewable Energy Systems and Recycling, Eroilor 29, 500036, Brasov (Romania)

2014-07-14

Zinc oxide-graphene oxide nanocomposite layers were submitted to laser irradiation in air or controlled nitrogen atmosphere using a frequency quadrupled Nd:YAG (λ = 266 nm, τ{sub FWHM} ≅ 3 ns, ν = 10 Hz) laser source. The experiments were performed in air at atmospheric pressure or in nitrogen at a pressure of 2 × 10{sup 4} Pa. The effect of the irradiation conditions, incident laser fluence value, and number of subsequent laser pulses on the surface morphology of the composite material was systematically investigated. The obtained results reveal that nitrogen incorporation improves significantly the wetting and photoactive properties of the laser processed layers. The kinetics of water contact angle variation when the samples are submitted to laser irradiation in nitrogen are faster than that of the samples irradiated in air, the surfaces becoming super-hydrophilic under UV light irradiation.

Charge carrier transport and collection enhancement of copper indium diselenide photoactive nanoparticle-ink by laser crystallization

Energy Technology Data Exchange (ETDEWEB)

Nian, Qiong; Cheng, Gary J., E-mail: gjcheng@purdue.edu [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47906 (United States); School of Industrial Engineering, Purdue University, West Lafayette, Indiana 47906 (United States); Zhang, Martin Y. [School of Industrial Engineering, Purdue University, West Lafayette, Indiana 47906 (United States); Wang, Yuefeng [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47906 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47906 (United States); Das, Suprem R.; Bhat, Venkataprasad S. [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47906 (United States); Huang, Fuqiang [Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 200050 (China)

2014-09-15

There has been increasing needs for cost-effective and high performance thin film deposition techniques for photovoltaics. Among all deposition techniques, roll-to-roll printing of nanomaterials has been a promising method. However, the printed thin film contains many internal imperfections, which reduce the charge-collection performance. Here, direct pulse laser crystallization (DPLC) of photoactive nanoparticles-inks is studied to meet this challenge. In this study, copper indium selenite (CIS) nanoparticle-inks is applied as an example. Enhanced crystallinity, densified structure in the thin film is resulted after DLPC under optimal conditions. It is found that the decreased film internal imperfections after DPLC results in reducing scattering and multi-trapping effects. Both of them contribute to better charge-collection performance of CIS absorber material by increasing extended state mobility and carrier lifetime, when carrier transport and kinetics are coupled. Charge carrier transport was characterized after DPLC, showing mobility increased by 2 orders of magnitude. Photocurrent under AM1.5 illumination was measured and shown 10 times enhancement of integrated power density after DPLC, which may lead to higher efficiency in photo-electric energy conversion.

Enhanced photoactivity from single-crystalline SrTaO{sub 2}N nanoplates synthesized by topotactic nitridation

Energy Technology Data Exchange (ETDEWEB)

Fu, Jie; Skrabalak, Sara E. [Department of Chemistry, Indiana University, Bloomington, IN (United States)

2017-11-06

There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often give enhanced photoactivity. Herein, single-crystalline SrTaO{sub 2}N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, in which single-crystalline SrTaO{sub 2}N nanoplates form by topotactic nitridation of aerosol-prepared Sr{sub 2}Ta{sub 2}O{sub 7} nanoplates and SrTaO{sub 2}N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO{sub 2}N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1 % for OER compared to the polyhedra (AQE: 1.6 %) and SrTaO{sub 2}N polycrystals (AQE: 0.6 %). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Fabrication of Ce/N co-doped TiO2/diatomite granule catalyst and its improved visible-light-driven photoactivity.

Science.gov (United States)

Chen, Yan; Liu, Kuiren

2017-02-15

Eliminating antibiotic remnants in aquatic environment has become one of the hottest topics among current research works. Thus, we prepared Ce, N co-doped TiO 2 /diatomite granule (CNTD-G) catalyst to provide a new method. As one typical antibiotics, oxytetracycline (OTC) was selected as the target pollutant to be degradated under visible light irradiation. The carrier diatomite helped the spread of TiO 2 nanoparticles onto its surface, and inhibited their agglomeration. The synergy of Ce and N dopants highly improved the visible-light-driven photoactivity of TiO 2 . The optimal doping amount and degradation conditions were determined. Besides, the effects of impurity ions were also investigated, including cations: Ca 2+ , Mg 2+ ; or anions: NO 3 - , SO 4 2- and PO 4 3- . The intermediates generated during degradation process were studied, and the mechanism of the photodegradation process was proposed. CNTD-G could be easily collected from the reactor, and showed excellent recyclability. Copyright © 2016 Elsevier B.V. All rights reserved.

A comparative study on the performance of hybrid solar cells containing ZnSTe QDs in hole transporting layer and photoactive layer

Energy Technology Data Exchange (ETDEWEB)

Najeeb, Mansoor Ani [Qatar University, Center for Advanced Materials (CAM) (Qatar); Abdullah, Shahino Mah; Aziz, Fakhra [University of Malaya, Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science (Malaysia); Ahmad, Zubair, E-mail: zubairtarar@qu.edu.qa; Shakoor, R. A. [Qatar University, Center for Advanced Materials (CAM) (Qatar); Mohamed, A. M. A. [Suez University, Department of Metallurgical and Materials Engineering, Faculty of Petroleum and Mining Engineering (Egypt); Khalil, Uzma [University of Peshawar, Department of Electronics, Jinnah College for Women (Pakistan); Swelm, Wageh; Al-Ghamdi, Ahmed A. [King Abdulaziz University, Department of Physics, Faculty of Science (Saudi Arabia); Sulaiman, Khaulah [University of Malaya, Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science (Malaysia)

2016-12-15

In this paper, ZnSTe quantum dots-based hybrid solar cells (HSC) with two different device architectures have been investigated. The improved performance of the poly(3-hexylthiophene) (P3HT) and [6,6]phenyl C{sub 71} butyric acid methyl ester (PC{sub 71}BM)-based bulk heterojunction (BHJ) solar cells by the incorporation of ZnSTe quantum dots (QDs) with an average size of 2.96 nm in PEDOT:PSS layer and active layer that have been demonstrated. Although the efficiency of both types of devices is almost the same, a close comparison reveals different reasons behind their improved performance. The device prepared with QDs in the HTL has shown reduced series resistance, increased shunt resistance, and improved mobility. On the other hand, QDs in the photoactive layer demonstrates increased photo-generation leading to improved efficiency.

Photoactive protochlorophyllide-enzyme complexes reconstituted with PORA, PORB and PORC proteins of A. thaliana: fluorescence and catalytic properties.

Directory of Open Access Journals (Sweden)

Michał Gabruk

Full Text Available Photoactive Pchlide-POR-NADPH complexes were reconstituted using protochlorophyllide (Pchlide and recombinant light-dependent protochlorophyllide oxidoreductase (POR proteins, His₆-PORA, His₆-PORB and His₆-PORC, from Arabidopsis thaliana. We did not observe any differences in the kinetics of the protochlorophyllide photoreduction at room temperature among the PORA, PORB and PORC proteins. In contrast, the PORC protein showed lower yield of Chlide formation than PORA and PORB when preincubated in the dark for 30 min and then illuminated for a short time. The most significant observation was that reconstituted Pchlide-POR-NADPH complexes showed fluorescence maxima at 77 K similar to those observed for highly aggregated Pchlide-POR-NADPH complexes in prolamellar bodies (PLBs in vivo. Homology models of PORA, PORB and PORC of Arabidopsis thaliana were developed to compare predicted structures of POR isoforms. There were only slight structural differences, mainly in the organisation of helices and loops, but not in the shape of whole molecules. This is the first comparative analysis of all POR isoforms functioning at different stages of A. thaliana development.

Dendronized macromonomers for three-dimensional data storage

DEFF Research Database (Denmark)

Khan, A.; Daugaard, Anders Egede; Bayles, A.

2009-01-01

A series of dendritic macromonomers have been synthesized and utilized as the photoactive component in holographic storage systems leading to high performance, low shrinkage materials.......A series of dendritic macromonomers have been synthesized and utilized as the photoactive component in holographic storage systems leading to high performance, low shrinkage materials....

Effect of urea on the photoactivity of titania powder prepared by sol-gel method

International Nuclear Information System (INIS)

Cheng Ping; Deng Changsheng; Gu Mingyuan; Dai Xiaming

2008-01-01

The synthesis of nanocrystalline titania powders from the hydrolysis of Ti(OBu n ) 4 in the presence of urea was investigated. DRS results showed that a redshift occurred in the absorption edge of titania with increasing the content of urea. XRD results indicated that urea showed a retarding effect on the transformation of titania from anatase to rutile. Moreover, the addition of urea resulted in a higher Brunauer-Emmett-Teller (BET) surface area as well as a larger average pore size of TiO 2 nanoparticles. The average pore size of urea/TiO 2 gels calcined at 500 deg. C increased with the increase of urea content, while the specific surface area increased with the amount of urea to reach a maximum at 10% and then decreased with further increase of the amount of urea. The maximal specific surface area of 64.4 m 2 g -1 was obtained for 10% urea/TiO 2 gels calcined at 500 deg. C, which showed an average particle size of 15 nm and pore size distribution in the range of mesopores centered at 5.8 nm. The photocatalytic experiments exhibited that titania nanoparticles prepared in the presence of urea could effectively photodegrade methyl orange under visible light irradiation due to the redshift of the absorption edge. The maximum photoactivity was achieved when the content of urea was 10%, which was attributed to the higher specific surface area

Particle emission rates during electrostatic spray deposition of TiO2 nanoparticle-based photoactive coating.

Science.gov (United States)

Koivisto, Antti J; Jensen, Alexander C Ø; Kling, Kirsten I; Kling, Jens; Budtz, Hans Christian; Koponen, Ismo K; Tuinman, Ilse; Hussein, Tareq; Jensen, Keld A; Nørgaard, Asger; Levin, Marcus

2018-01-05

Here, we studied the particle release rate during Electrostatic spray deposition of anatase-(TiO 2 )-based photoactive coating onto tiles and wallpaper using a commercially available electrostatic spray device. Spraying was performed in a 20.3m 3 test chamber while measuring concentrations of 5.6nm to 31μm-size particles and volatile organic compounds (VOC), as well as particle deposition onto room surfaces and on the spray gun user hand. The particle emission and deposition rates were quantified using aerosol mass balance modelling. The geometric mean particle number emission rate was 1.9×10 10 s -1 and the mean mass emission rate was 381μgs -1 . The respirable mass emission-rate was 65% lower than observed for the entire measured size-range. The mass emission rates were linearly scalable (±ca. 20%) to the process duration. The particle deposition rates were up to 15h -1 for deposited particles consisted of mainly TiO 2 , TiO 2 mixed with Cl and/or Ag, TiO 2 particles coated with carbon, and Ag particles with size ranging from 60nm to ca. 5μm. As expected, no significant VOC emissions were observed as a result of spraying. Finally, we provide recommendations for exposure model parameterization. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

Photophysical and antibacterial properties of complex systems based on smectite, a cationic surfactant and methylene blue.

Science.gov (United States)

Donauerová, Alena; Bujdák, Juraj; Smolinská, Miroslava; Bujdáková, Helena

2015-10-01

Solid or colloidal materials with embedded photosensitizers are promising agents from the medical or environmental perspective, where the direct use of photoactive solutions appears to be problematic. Colloids based on layered silicates of the saponite (Sap) and montmorillonite (Mon) type, including those modified with dodecylammonium cations (C12) and photosensitizer--methylene blue (MB) were studied. Two representatives of bacteria, namely Enterobacter cloacae and Escherichia coli, were selected for this work. A spectral study showed that MB solutions and also colloids with Sap including C12 exhibited the highest photoactivities. The antimicrobial properties of the smectite colloids were not directly linked to the photoactivity of the adsorbed MB cations. They were also influenced by other parameters, such as light vs. dark conditions, the spectrum, power and duration of the light used for the irradiation; growth phases, and the pre-treatment of microorganisms. Both the photoactivity and antimicrobial properties of the colloids were improved upon pre-modification with C12. Significantly higher antimicrobial properties were observed for the colloids based on Mon with MB in the form of molecular aggregates without significant photoactivities. The MB/Mon colloids, both modified and non-modified with C12 cations, exhibited higher antimicrobial effects than pure MB solution. Besides the direct effect of photosensitization, the surface properties of the silicate particles likely played a crucial role in the interactions with microorganisms. Copyright © 2015 Elsevier B.V. All rights reserved.

Gram-Scale Synthesis and Highly Regioselective Bromination of 1,1,9,9-Tetramethyl[9](2,11)teropyrenophane

Czech Academy of Sciences Publication Activity Database

Unikela, K. S.; Roemmele, T. L.; Houska, Václav; McGrath, K. E.; Tobin, D. M.; Dawe, L. N.; Boeré, R. T.; Bodwell, G. J.

2018-01-01

Roč. 57, č. 6 (2018), s. 1707-1711 ISSN 1433-7851 Institutional support: RVO:61388963 Keywords : aromaticity * bromination * cyclophanes * EPR spectroscopy * structure elucidation Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 11.994, year: 2016

Spectroscopic studies of model photo-receptors: validation of a nanosecond time-resolved micro-spectrophotometer design using photoactive yellow protein and α-phycoerythrocyanin.

Science.gov (United States)

Purwar, Namrta; Tenboer, Jason; Tripathi, Shailesh; Schmidt, Marius

2013-09-13

Time-resolved spectroscopic experiments have been performed with protein in solution and in crystalline form using a newly designed microspectrophotometer. The time-resolution of these experiments can be as good as two nanoseconds (ns), which is the minimal response time of the image intensifier used. With the current setup, the effective time-resolution is about seven ns, determined mainly by the pulse duration of the nanosecond laser. The amount of protein required is small, on the order of 100 nanograms. Bleaching, which is an undesirable effect common to photoreceptor proteins, is minimized by using a millisecond shutter to avoid extensive exposure to the probing light. We investigate two model photoreceptors, photoactive yellow protein (PYP), and α-phycoerythrocyanin (α-PEC), on different time scales and at different temperatures. Relaxation times obtained from kinetic time-series of difference absorption spectra collected from PYP are consistent with previous results. The comparison with these results validates the capability of this spectrophotometer to deliver high quality time-resolved absorption spectra.

Photoactive assemblies of organic compounds and biomolecules: drug-protein supramolecular systems

OpenAIRE

Vayá Pérez, Ignacio; Lhiaubet-Vallet, Virginie Lyria; Jiménez Molero, María Consuelo; Miranda Alonso, Miguel Ángel

2014-01-01

[EN] The properties of singlet and triplet excited states are strongly medium-dependent. Hence, these species constitute valuable tools as reporters to probe compartmentalised microenvironments, including drug@protein supramolecular systems. In the present review, the attention is focused on the photophysical properties of the probe drugs (rather than those of the protein chromophores) using transport proteins (serum albumins and 1-acid glycoproteins) as hosts. Specifically, f...

Photoactivity enhancement of the Cd{sub x}Zn{sub 1−x}S nanoparticles by immobilizing on the graphene under visible light irradiation

Energy Technology Data Exchange (ETDEWEB)

Wang, Jian, E-mail: wangjian@sxicc.ac.cn [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taoyuan South Road 27, Taiyuan 030001, Shanxi (China); University of Chinese Academy of Sciences, Beijing 100039 (China); Yang, Pengju [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taoyuan South Road 27, Taiyuan 030001, Shanxi (China); University of Chinese Academy of Sciences, Beijing 100039 (China); Zhao, Jianghong [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taoyuan South Road 27, Taiyuan 030001, Shanxi (China); Zhu, Zhenping, E-mail: zpzhu@sxicc.ac.cn [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taoyuan South Road 27, Taiyuan 030001, Shanxi (China)

2013-10-01

The photocatalytic activity of semiconductor is strongly dependent on the efficient separation of photogenerated electron–hole pairs. In the present work, the graphene-immobilized Cd{sub x}Zn{sub 1−x}S nanoparticles with a uniform and small diameter have been prepared by one-step solvothermal route. After dispersing Cd{sub x}Zn{sub 1−x}S on the graphene surface well, the composites of Cd{sub x}Zn{sub 1−x}S and graphenes show better photocatalytic activity than pure Cd{sub x}Zn{sub 1−x}S nanoparticles. And the issue of photocorrosion, a disadvantage of Cd{sub x}Zn{sub 1−x}S photocatalysts, has also been solved partly. The mechanisms on enhancement of photocatalytic activity were further investigated. Under visible light irradiation, photogenerated electrons of Cd{sub x}Zn{sub 1−x}S can be transferred into the graphene, and the electron and hole was effectively separated, leading to the photoactivity enhancement.

Characteristics of the excited states of Nitrofurantoin, an anti-inflammatory and photoactive nitrofuran derivative

Energy Technology Data Exchange (ETDEWEB)

Parra, Gustavo G., E-mail: gugparra@gmail.com [Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP (Brazil); Ferreira, Lucimara P.; Codognato, Débora C.K. [Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP (Brazil); Cavalheiro, Carla C.S. [Departamento de Físico-Química, Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São-Carlense 400, São Carlos, SP (Brazil); Borissevitch, Iouri [Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP (Brazil); Instituto de Física, Universidade Federal de Goiás, 74001-970 Goiânia, GO (Brazil)

2017-05-15

Spectral characteristics of bio and photoactive nitrofuran derivative drug [N-(5-nitro-2-furfurylidene)−1-aminohydantoin], (Nitrofurantoin, NFT) were investigated using optical absorption and fluorescence spectroscopies, both in “steady-state” and time resolved forms. The irradiation of the NFT in the UV region in aqueous solution induces the fluorescence with quantum yield Φ{sub fl}≈0.03% and lifetime τ{sub fl}≈1 ns with these values being practically independent of the NFT protonation state. The NFT transient absorption spectrum and lifetime (τ{sub T}) depend on the NFT protonation state with τ{sub T} being 0.04 μs for mono-protonated NFT state, 0.22 μs for its non-protonated one, and with quantum yield, Φ{sub T} ≈ 0.0001% which is practically independent of its protonation state. The quenching of this transient by molecular oxygen accompanied by simultaneous singlet oxygen formation ({sup 1}O{sub 2}) allows associate this specie with the NFT molecules in the triplet state being the efficiency of this process dependent of NFT protonation state, η{sub pH10}≈0.53 and η{sub pH2.5}≈0.07. The extremely low quantum yields, Φ{sub fl} and Φ{sub T}, and short τ{sub fl} and τ{sub T} are, probably, associated with alternative ways of the dissipation of the NFT excited state energy: the NFT photoisomerization and NO{sup •} photorelease. The synergic action of two highly reactive species such as {sup 1}O{sub 2} and NO{sup •} in biological medium is extremely valuable for applications in photochemotherapy, thus making NFT a potential candidate for further studies in vitro and in vivo.

Theoretical analysis of geometry and NMR isotope shift in hydrogen-bonding center of photoactive yellow protein by combination of multicomponent quantum mechanics and ONIOM scheme

Energy Technology Data Exchange (ETDEWEB)

Kanematsu, Yusuke; Tachikawa, Masanori [Quantum Chemistry Division, Yokohama City University, Seto 22-2, Kanazawa-ku, Yokohama 236-0027 (Japan)

2014-11-14

Multicomponent quantum mechanical (MC-QM) calculation has been extended with ONIOM (our own N-layered integrated molecular orbital + molecular mechanics) scheme [ONIOM(MC-QM:MM)] to take account of both the nuclear quantum effect and the surrounding environment effect. The authors have demonstrated the first implementation and application of ONIOM(MC-QM:MM) method for the analysis of the geometry and the isotope shift in hydrogen-bonding center of photoactive yellow protein. ONIOM(MC-QM:MM) calculation for a model with deprotonated Arg52 reproduced the elongation of O–H bond of Glu46 observed by neutron diffraction crystallography. Among the unique isotope shifts in different conditions, the model with protonated Arg52 with solvent effect reasonably provided the best agreement with the corresponding experimental values from liquid NMR measurement. Our results implied the availability of ONIOM(MC-QM:MM) to distinguish the local environment around hydrogen bonds in a biomolecule.

BORIC-ACID MEDIATED PREPARATION OF MESOCYCLIC THIOCROWN ETHERS CONTAINING XYLYLENE UNITS - MOLECULAR-STRUCTURES OF 3,8-DIBENZO-1,6-DITHIACYCLODECANE AND 2,5,8-TRITHIA-(9)-P-BENZENOPHANE

NARCIS (Netherlands)

EDEMA, JJH; STOCK, HT; KELLOGG, RM; SMEETS, WJJ; SPEK, AL

1993-01-01

Reaction of a dithiol with B(OH)3 and base in MeOH followed by reaction with xylylene dibromides proceeds selectively to give the corresponding ortho, meta or para-cyclophanes in good yield (70-86 %). The syntheses of examples of all three types of benzenophanes are discussed. The molecular

One-pot, facile fabrication of a Ag3PO4-based ternary Z-scheme photocatalyst with excellent visible-light photoactivity and anti-photocorrosion performance

Science.gov (United States)

Xie, Mingyuan; Zhang, Tailiang

2018-04-01

Ag3PO4 can-not be widely used as an efficient photocatalyst in practical applications because of its susceptibility to photocorrosion. In this study, a novel, ternary Z-scheme photocatalytic system containing graphene oxide (GO), Ag3PO4 and SnS2 was fabricated by a one-pot, mild, in-situ precipitation method successfully. Using Rhodamine B (RhB) as the target of elimination, GO/Ag3PO4/SnS2 exhibited outstanding photocatalytic and anti-photocorrosion properties compared with those of Ag3PO4, Ag3PO4/SnS2 and GO/Ag3PO4. RhB was thoroughly degraded over the optimized GO/Ag3PO4/SnS2 nanocomposite after only 15 min under visible-light irradiation; this result is approximately 2.14, 3.33 and 5.83 times faster than that of GO/Ag3PO4, Ag3PO4/SnS2 and Ag3PO4, respectively. After three reuses, the photocatalytic activity of the ternary composite slightly decreased but remained 2.36, 4.08 and 12.70 times higher than those of the reused GO/Ag3PO4, Ag3PO4/SnS2 and Ag3PO4, respectively. In this system, the efficient separation and migration of the photoinduced current carriers in Ag3PO4 was realized through a double Z-scheme electron-transfer mechanism in which the GO nanosheets acted as the photocatalyst and electron mediator, thereby enhancing the photoactivity and stability of Ag3PO4. The present study provides a new perspective for enhancing photocatalytic and anti-photocorrosion performances in perishable photocatalysts for organic sewage and other environmental contamination treatments.

FT-Raman and FTIR spectra of photoactive aminobenzazole derivatives in the solid state: A combined experimental and theoretical study

Energy Technology Data Exchange (ETDEWEB)

Alves, Rodrigo Martins [Universidade Federal do Pampa, Campus Bagé, Grupo de Pesquisa em Espectroscopia de Materiais Fotônicos, 96400-970 Bagé, RS (Brazil); Rodembusch, Fabiano Severo [Universidade Federal do Rio Grande do Sul, Grupo de Pesquisa em Fotoquímica Orgânica Aplicada, Av. Bento Gonçalves 9500, CEP 91501-970 Porto Alegre, RS (Brazil); Habis, Charles [Northern Virginia Community College, Manassas, VA (United States); Moreira, Eduardo Ceretta, E-mail: eduardomoreira@unipampa.edu.br [Universidade Federal do Pampa, Campus Bagé, Grupo de Pesquisa em Espectroscopia de Materiais Fotônicos, 96400-970 Bagé, RS (Brazil)

2014-12-15

This study reports the experimental investigation of two photoactive aminobenzazole derivatives in the solid state by FT-Raman and Infrared Spectroscopies (FTIR) and its comparison with theoretical models. The optimized molecular structure, vibrational frequencies, and corresponding vibrational assignments of these compounds have been investigated experimentally and theoretically using Spanish Initiative for Electronic Simulations with Thousands of Atoms (SIESTA) and Gaussian03 Software Package. The FT-Raman and FTIR spectra were acquired with high resolution and emission frequencies identified by simulating the vibrational modes. The most intense peak observed in the FT-Raman spectra is the in-plane deformation vibrational of O–H bond that could be related to the vibrational region responsible for the stabilization of the enol conformer in the ground state which undergoes ESIPT to form a keto tautomer in the excited state. Additionally, the position of the amino group played an important role on the vibrational characteristics of the studied compounds. Also, the simulations proved to be a good approach in undertaking the FTIR and FT-Raman experiments. The use of graphic correlations helps us to determine the method and basis that best fit the experimental results. - Highlights: • Structural and vibrational properties of two aminobenzazoles were reported. • Comparison between experimental techniques and theoretical models. • The position of the amino group played an important role on the vibrational characteristics of the studied compounds.

Fabrication of Ce/N co-doped TiO_2/diatomite granule catalyst and its improved visible-light-driven photoactivity

International Nuclear Information System (INIS)

Chen, Yan; Liu, Kuiren

2017-01-01

Highlights: • Ce/N co-doped TiO_2/diatomite granule (CNTD-G) was prepared via sol-gel method. • The optimal doping amount of Ce was determined. • The effects of impurity ions on photodegradation process were studied. • The intermediates generated during photodegradation process were deduced. • The mechanism of photodegradation process was proposed. - Abstract: Eliminating antibiotic remnants in aquatic environment has become one of the hottest topics among current research works. Thus, we prepared Ce, N co-doped TiO_2/diatomite granule (CNTD-G) catalyst to provide a new method. As one typical antibiotics, oxytetracycline (OTC) was selected as the target pollutant to be degradated under visible light irradiation. The carrier diatomite helped the spread of TiO_2 nanoparticles onto its surface, and inhibited their agglomeration. The synergy of Ce and N dopants highly improved the visible-light-driven photoactivity of TiO_2. The optimal doping amount and degradation conditions were determined. Besides, the effects of impurity ions were also investigated, including cations: Ca"2"+, Mg"2"+; or anions: NO_3"−, SO_4"2"− and PO_4"3"−. The intermediates generated during degradation process were studied, and the mechanism of the photodegradation process was proposed. CNTD-G could be easily collected from the reactor, and showed excellent recyclability.

Visible-light photoactivity of plasmonic silver supported on mesoporous TiO2 nanoparticles (Ag-MTN) for enhanced degradation of 2-chlorophenol: Limitation of Ag-Ti interaction

Science.gov (United States)

Jaafar, N. F.; Jalil, A. A.; Triwahyono, S.

2017-01-01

Various weight loadings of Ag (1-10 wt.%) were introduced to mesoporous titania nanoparticles (MTN) via a direct in-situ electrochemical method. The catalysts were characterized by XRD, surface area analysis, FTIR, ESR, FESEM-EDX and TEM. Characterization results indicated that the introduction of Ag onto MTN decreased the particles size and band gap of the MTN while increasing the number of oxygen vacancies (OV) and Ti3+ site defects (TSD). The activity performance of Ag-MTN on photodegradation of 2-chlorophenol (2-CP) under visible light irradiation was in the following order: 5 wt% Ag-MTN> 1 wt% Ag-MTN > MTN > 10 wt% Ag-MTN, with degradation percentages of 97, 88, 80 and 63%, respectively. The synergistic effect between Ag0 and MTN seemed to play an important role in the system. The Ag0 acted as both an electron trap and a plasmonic sensitizer which suppressed the electron-hole recombination, while OV and TSD in the MTN accelerated the production of hydroxyl radicals for enhanced degradation of 2-CP. However, the formation of Ti-O-Ag in 10 wt% Ag-MTN was found to decrease the photoactivity due to the decrease in the formation of Ag0, TSD and OV as well as the increase in band gap energy. The photodegradation of 5 wt% Ag-MTN followed a pseudo-first-order Langmuir- Hinshelwood model and the catalyst was still stable after five cycles.

Photocatalytic deposition of Ag nanoparticles on TiO2: Metal precursor effect on the structural and photoactivity properties

Directory of Open Access Journals (Sweden)

E. Albiter

2015-09-01

Full Text Available A series of 1 wt.% Ag–TiO2 photocatalysts were obtained by photodeposition using different organic (acetylacetonate, Ag-A and inorganic (nitrate, Ag-N, and perchlorate, Ag-C silver precursors in order to determinate the influence of the silver precursor on final properties of the photocatalysts. The resulting photocatalytic materials were characterized by different techniques (UV–Vis DRS, TEM/HRTEM and XPS and their photocatalytic activity was evaluated in the degradation of rhodamine B (used as model pollutant in aqueous solution under simulated solar light. The photocatalytic reduction of Ag species to Ag0 on TiO2 was higher with silver nitrate as precursor compared to acetylacetonate or perchlorate. All the Ag-modified TiO2 photocatalysts exhibited a surface plasmon resonance effect in the visible region (400–530 nm indicating different metal particle sizes depending on the Ag precursor used in their synthesis. A higher photocatalytic activity was obtained with all the Ag/TiO2 samples compared with non-modified TiO2. The descending order of photocatalytic activity was as follows: Ag-A/TiO2 ≈ Ag-N/TiO2 > Ag-C/TiO2 > TiO2-P25. The enhanced photoactivity was attributed to the presence of different amounts Ag0 nanoparticles homogeneously distributed on Ag2O and TiO2, trapping the photogenerated electrons and avoiding charge recombination.

Fabrication of Ce/N co-doped TiO{sub 2}/diatomite granule catalyst and its improved visible-light-driven photoactivity

Energy Technology Data Exchange (ETDEWEB)

Chen, Yan; Liu, Kuiren, E-mail: liukr@smm.neu.edu.cn

2017-02-15

Highlights: • Ce/N co-doped TiO{sub 2}/diatomite granule (CNTD-G) was prepared via sol-gel method. • The optimal doping amount of Ce was determined. • The effects of impurity ions on photodegradation process were studied. • The intermediates generated during photodegradation process were deduced. • The mechanism of photodegradation process was proposed. - Abstract: Eliminating antibiotic remnants in aquatic environment has become one of the hottest topics among current research works. Thus, we prepared Ce, N co-doped TiO{sub 2}/diatomite granule (CNTD-G) catalyst to provide a new method. As one typical antibiotics, oxytetracycline (OTC) was selected as the target pollutant to be degradated under visible light irradiation. The carrier diatomite helped the spread of TiO{sub 2} nanoparticles onto its surface, and inhibited their agglomeration. The synergy of Ce and N dopants highly improved the visible-light-driven photoactivity of TiO{sub 2}. The optimal doping amount and degradation conditions were determined. Besides, the effects of impurity ions were also investigated, including cations: Ca{sup 2+}, Mg{sup 2+}; or anions: NO{sub 3}{sup −}, SO{sub 4}{sup 2−} and PO{sub 4}{sup 3−}. The intermediates generated during degradation process were studied, and the mechanism of the photodegradation process was proposed. CNTD-G could be easily collected from the reactor, and showed excellent recyclability.

Theoretical modelling of photoactive molecular systems: insights using the Density Functional Theory

Energy Technology Data Exchange (ETDEWEB)

Ciofini, I.; Adamo, C. [Ecole Nationale Superieure de Chimie de Paris, Lab. d' Electrochimie et Chimie Analytique, CNRS UMR 7575, 75 - Paris (France); Laine, Ph.P. [Universite Rene-Descartes, Lab. de Chimie et Biochimie Pharmacologiques et Toxicologiques, CNRS UMR 8601, 75 - Paris (France); Bedioui, F. [Ecole Nationale Superieure de Chimie de Paris, Lab. de Pharmacologie Chimique et Genetique, CNRS FRE 2463 and INSERM U 640, 75 - Paris (France); Daul, C.A. [Fribourg Univ., Dept. de Chimie (Switzerland)

2006-02-15

An account of the performance of a modern and efficient approach to Density Functional Theory (DFT) for the prediction of the photophysical behavior of a series of Ru(II) and Os(II) complexes is given. The time-dependent-DFT method was used to interpret their electronic spectra. Two different types of compounds have been analyzed: (1) a complex undergoing a light induced isomerization of one of its coordination bonds; (2) an inorganic dyads expected to undergo intramolecular photoinduced electron transfer to form a charge separated (CS) sate. Besides the noticeable quantitative agreement between computed and experimental absorption spectra, our results allow to clarify, by first principles, both the nature of the excited states and the photochemical behavior of these complex systems, thus underlying the predictive character of the theoretical approach. (authors)

Theoretical optical spectroscopy of complex systems

Energy Technology Data Exchange (ETDEWEB)

Conte, A. Mosca, E-mail: adriano.mosca.conte@roma2.infn.it [MIFP, NAST, ETSF,CNR INFM-SMC, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma (Italy); Violante, C., E-mail: claudia.violante@roma2.infn.it [MIFP, NAST, ETSF,CNR INFM-SMC, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma (Italy); Missori, M., E-mail: mauro.missori@isc.cnr.it [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Via Salaria Km 29.300, 00016 Monterotondo Scalo (Rome) (Italy); Bechstedt, F., E-mail: bech@ifto.physik.uni-jena.de [Institut fur Festkorpertheorie und -optik, Friedrich-Schiller-Universitat, Max-Wien-Platz 1, 07743 Jena (Germany); Teodonio, L. [MIFP, NAST, ETSF,CNR INFM-SMC, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma (Italy); Istituto centrale per il restauro e la conservazione del patrimonio archivistico e librario (IC-RCPAL), Italian Minister for Cultural Heritage, Via Milano 76, 00184 Rome (Italy); Ippoliti, E.; Carloni, P. [German Research School for Simulation Sciences, Julich (Germany); Guidoni, L., E-mail: leonardo.guidoni@univaq.it [Università degli Studi di L’Aquila, Dipartimento di Chimica e Materiali, Via Campo di Pile, 67100 L’Aquila (Italy); Pulci, O., E-mail: olivia.pulci@roma2.infn.it [MIFP, NAST, ETSF,CNR INFM-SMC, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma (Italy)

2013-08-15

Highlights: ► We review some theoretical condensed matter ab initio spectroscopic computational techniques. ► We show several applications ranging from 0 to 3 dimensional systems. ► For each system studied, we show which kind of information it is possible to obtain by performing these calculations. -- Abstract: We review here some of the most reliable and efficient computational theoretical ab initio techniques for the prediction of optical and electronic spectroscopic properties and show some important applications to molecules, surfaces, and solids. We investigate the role of the solvent in the optical absorption spectrum of indole molecule. We study the excited-state properties of a photo-active minimal model molecule for the retinal of rhodopsin, responsible for vision mechanism in animals. We then show a study about spectroscopic properties of Si(1 1 1) surface. Finally we simulate a bulk system: paper, that is mainly made of cellulose, a pseudo-crystalline material representing 40% of annual biomass production in the Earth.

Theoretical optical spectroscopy of complex systems

International Nuclear Information System (INIS)

Conte, A. Mosca; Violante, C.; Missori, M.; Bechstedt, F.; Teodonio, L.; Ippoliti, E.; Carloni, P.; Guidoni, L.; Pulci, O.

2013-01-01

Highlights: ► We review some theoretical condensed matter ab initio spectroscopic computational techniques. ► We show several applications ranging from 0 to 3 dimensional systems. ► For each system studied, we show which kind of information it is possible to obtain by performing these calculations. -- Abstract: We review here some of the most reliable and efficient computational theoretical ab initio techniques for the prediction of optical and electronic spectroscopic properties and show some important applications to molecules, surfaces, and solids. We investigate the role of the solvent in the optical absorption spectrum of indole molecule. We study the excited-state properties of a photo-active minimal model molecule for the retinal of rhodopsin, responsible for vision mechanism in animals. We then show a study about spectroscopic properties of Si(1 1 1) surface. Finally we simulate a bulk system: paper, that is mainly made of cellulose, a pseudo-crystalline material representing 40% of annual biomass production in the Earth

Carbon Domains on MoS2/TiO2 System via Catalytic Acetylene Oligomerization: Synthesis, Structure, and Surface Properties

Directory of Open Access Journals (Sweden)

Sara Cravanzola

2017-11-01

Full Text Available Carbon domains have been obtained at the surface of a MoS2/TiO2 (Evonik, P25 system via oligomerization and cyclotrimerization reactions involved in the interaction of the photoactive material with acetylene. Firstly, MoS2 nanosheets have been synthesized at the surface of TiO2, via sulfidation of a molybdenum oxide precursor with H2S (bottom-up method. Secondly, the morphology and the structure, the optical and the vibrational properties of the obtained materials, for each step of the synthesis procedure, have been investigated by microscopy and spectroscopy methods. In particular, transmission electron microscopy images provide a simple tool to highlight the effectiveness of the sulfidation process, thus showing 1L, 2L, and stacked MoS2 nanosheets anchored to the surface of TiO2 nanoparticles. Lastly, in-situ FTIR spectroscopy investigation gives insights into the nature of the oligomerized species, showing that the formation of both polyenic and aromatic systems can be taken into account, being their formation promoted by both Ti and Mo catalytic sites. This finding gives an opportunity for the assembly of extended polyenic, polyaromatic, or mixed domains firmly attached at the surface of photoactive materials. The presented approach, somehow different from the carbon adding or doping processes of TiO2, is of potential interest for the advanced green chemistry and energy conversion/transport applications.

A new photoactive Ru(II)tris(2,2'-bipyridine) templated Zn(II) benzene-1,4-dicarboxylate metal organic framework: structure and photophysical properties.

Science.gov (United States)

Whittington, Christi L; Wojtas, Lukasz; Gao, Wen-Yang; Ma, Shengqian; Larsen, Randy W

2015-03-28

It has now been demonstrated that Ru(ii)tris(2,2'-bipyridine) (RuBpy) can be utilized to template the formation of new metal organic framework (MOF) materials containing crystallographically resolved RuBpy clusters with unique photophysical properties. Two such materials, RWLC-1 and RWLC-2, have now been reported from our laboratory and are composed of RuBpy encapsulated in MOFs composed of Zn(ii) ions and 1,3,5-tris(4-carboxyphenyl)benzene ligands (C. L. Whittington, L. Wojtas and R. W. Larsen, Inorg. Chem., 2014, 53, 160-166). Here, a third RuBpy templated photoactive MOF is described (RWLC-3) that is derived from the reaction between Zn(ii) ions and 1,4-dicarboxybenzene in the presence of RuBpy. Single Crystal X-ray diffraction studies determined the position of RuBpy cations within the crystal lattice. The RWLC-3 structure is described as a 2-fold interpenetrated pillared honeycomb network (bnb) containing crystallographically resolved RuBpy clusters. The two bnb networks are weakly interconnected. The encapsulated RuBpy exhibits two emission decay lifetimes (τ-fast = 120 ns, τ-slow = 453 ns) and a bathochromic shift in the steady state emission spectrum relative to RuBpy in ethanol.

Structural rearrangement of mesostructured silica nanoparticles incorporated with ZnO catalyst and its photoactivity: Effect of alkaline aqueous electrolyte concentration

International Nuclear Information System (INIS)

Jusoh, N.W.C.; Jalil, A.A.; Triwahyono, S.; Karim, A.H.; Salleh, N.F.; Annuar, N.H.R.; Jaafar, N.F.; Firmansyah, M.L.; Mukti, R.R.; Ali, M.W.

2015-01-01

Graphical abstract: - Highlights: • Hierarchical-like structure of MSN was formed in alkaline aqueous electrolyte. • Desilication generated abundant silanol groups and oxygen vacancies. • Zn 2+ inserted to external –OH groups of the MSN to form Si–O–Zn bonds. • Oxygen vacancies trapped electrons to enhance electron–hole pair separation. • Hydroxyl radical generated from three main sources greatly influenced photoactivity. - Abstract: ZnO-incorporated mesostructured silica nanoparticles (MSN) catalysts (ZM) were prepared by the introduction of Zn ions into the framework of MSN via a simple electrochemical system in the presence of various concentrations of NH 4 OH aqueous solution. The physicochemical properties of the catalysts were studied by XRD, 29 Si MAS NMR, nitrogen adsorption–desorption, FE-SEM, TEM, FTIR, and photoluminescence spectroscopy. Characterization results demonstrated that the alkaline aqueous electrolyte simply generated abundant silanol groups on the surface of the catalysts as a consequence of desilication to form the hierarchical-like structure of the MSN. Subsequent restructuring of the silica network by the creation of oxygen vacancies and formation of Si–O–Zn during the electrolysis, as well as formation of new Si–O–Si bonds during calcination seemed to be the main factors that enhanced the catalytic performance of photodecolorization of methyl orange. A ZM prepared in the presence of 1.0 M NH 4 OH (ZM-1.0) was determined to be the most effective catalyst. The catalyst displays a higher first-order kinetics rate of 3.87 × 10 −1 h −1 than unsupported ZnO (1.13 × 10 −1 h −1 ) that prepared under the same conditions in the absence of MSN. The experiment on effect of scavengers showed that hydroxyl radicals generated from the three main sources; reduced O 2 at the conduction band, decomposed water at the valence band and irradiated H 2 O 2 in the solution, are key factors that influenced the reaction. It is

Structural rearrangement of mesostructured silica nanoparticles incorporated with ZnO catalyst and its photoactivity: Effect of alkaline aqueous electrolyte concentration

Energy Technology Data Exchange (ETDEWEB)

Jusoh, N.W.C. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Jalil, A.A., E-mail: aishah@cheme.utm.my [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Institute of Hydrogen Economy, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Triwahyono, S.; Karim, A.H. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Salleh, N.F. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Annuar, N.H.R.; Jaafar, N.F.; Firmansyah, M.L. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Mukti, R.R. [Division of Inorganic and Physical Chemistry, Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, Jl Ganesha No 10, Bandung 40132 (Indonesia); Ali, M.W. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Institute of Hydrogen Economy, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia)

2015-03-01

Graphical abstract: - Highlights: • Hierarchical-like structure of MSN was formed in alkaline aqueous electrolyte. • Desilication generated abundant silanol groups and oxygen vacancies. • Zn{sup 2+} inserted to external –OH groups of the MSN to form Si–O–Zn bonds. • Oxygen vacancies trapped electrons to enhance electron–hole pair separation. • Hydroxyl radical generated from three main sources greatly influenced photoactivity. - Abstract: ZnO-incorporated mesostructured silica nanoparticles (MSN) catalysts (ZM) were prepared by the introduction of Zn ions into the framework of MSN via a simple electrochemical system in the presence of various concentrations of NH{sub 4}OH aqueous solution. The physicochemical properties of the catalysts were studied by XRD, {sup 29}Si MAS NMR, nitrogen adsorption–desorption, FE-SEM, TEM, FTIR, and photoluminescence spectroscopy. Characterization results demonstrated that the alkaline aqueous electrolyte simply generated abundant silanol groups on the surface of the catalysts as a consequence of desilication to form the hierarchical-like structure of the MSN. Subsequent restructuring of the silica network by the creation of oxygen vacancies and formation of Si–O–Zn during the electrolysis, as well as formation of new Si–O–Si bonds during calcination seemed to be the main factors that enhanced the catalytic performance of photodecolorization of methyl orange. A ZM prepared in the presence of 1.0 M NH{sub 4}OH (ZM-1.0) was determined to be the most effective catalyst. The catalyst displays a higher first-order kinetics rate of 3.87 × 10{sup −1} h{sup −1} than unsupported ZnO (1.13 × 10{sup −1} h{sup −1}) that prepared under the same conditions in the absence of MSN. The experiment on effect of scavengers showed that hydroxyl radicals generated from the three main sources; reduced O{sub 2} at the conduction band, decomposed water at the valence band and irradiated H{sub 2}O{sub 2} in the solution

Synthesis, characterization, and photoactivity of InTaO4 and In0.9Ni0.1TaO4 thin films prepared by electron evaporation

International Nuclear Information System (INIS)

Rico, V. J.; Frutos, F.; Yubero, F.; Espinos, J. P.; Gonzales-Elipe, A. R.

2010-01-01

InTaO 4 and In 0.9 Ni 0.1 TaO 4 thin films have been prepared by electron evaporation of successive layers of the single oxide components and posterior annealing at T>800 deg. C. The annealed thin films presented the monoclinic crystallographic structure typical of these mixed oxides. The electrical and optical behaviors of the films, assessed by C-V measurements, surface conductivity as a function of temperature, and UV-vis absorption spectroscopy, indicate that these oxides are wide band gap semiconductors with a variable dielectric constant depending on the annealing conditions. By reflection electron energy loss spectroscopy some electronic states have been found in the gap at an energy that is compatible with the activation energy deduced from the conductivity versus 1/T plots for these oxides. The photoactivity of these materials has been assessed by looking to the evolution of the wetting contact angle as a function of the irradiation time. All the films became superhydrophilic when irradiated with UV light, while the In 0.9 Ni 0.1 TaO 4 thin films also presented a small partial decrease in wetting angle when irradiated with visible photons.

Photoactive assemblies of organic compounds and biomolecules: drug-protein supramolecular systems.

Science.gov (United States)

Vayá, Ignacio; Lhiaubet-Vallet, Virginie; Jiménez, M Consuelo; Miranda, Miguel A

2014-06-21

The properties of singlet and triplet excited states are strongly medium-dependent. Hence, these species constitute valuable tools as reporters to probe compartmentalised microenvironments, including drug@protein supramolecular systems. In the present review, the attention is focused on the photophysical properties of the probe drugs (rather than those of the protein chromophores) using transport proteins (serum albumins and α1-acid glycoproteins) as hosts. Specifically, fluorescence measurements allow investigation of the structural and dynamic properties of biomolecules or their complexes. Thus, the emission quantum yields and the decay kinetics of the drug singlet excited states provide key information to determine important parameters such as the stoichiometry of the complex, the binding constant, the relative degrees of occupancy of the different compartments, etc. Application of the FRET concept allows determination of donor-acceptor interchromophoric distances. In addition, anisotropy measurements can be related to the orientation of the drug within the binding sites, where the degrees of freedom for conformational relaxation are restricted. Transient absorption spectroscopy is also a potentially powerful tool to investigate the binding of drugs to proteins, where formation of encapsulated triplet excited states is favoured over other possible processes leading to ionic species (i.e. radical ions), and their photophysical properties are markedly sensitive to the microenvironment experienced within the protein binding sites. Even under aerobic conditions, the triplet lifetimes of protein-complexed drugs are remarkably long, which provides a broad dynamic range for identification of distinct triplet populations or for chiral discrimination. Specific applications of the laser flash photolysis technique include the determination of drug distribution among the bulk solution and the protein binding sites, competition of two types of proteins to bind a drug

Regenerable Photovoltaic Devices with a Hydrogel-Embedded Microvascular Network

Science.gov (United States)

Koo, Hyung-Jun; Velev, Orlin D.

2013-01-01

Light-driven degradation of photoactive molecules could be one of the major obstacles to stable long term operation of organic dye-based solar light harvesting devices. One solution to this problem may be mimicking the regeneration functionality of a plant leaf. We report an organic dye photovoltaic system that has been endowed with such microfluidic regeneration functionality. A hydrogel medium with embedded channels allows rapid and uniform supply of photoactive reagents by a convection-diffusion mechanism. A washing-activation cycle enables reliable replacement of the organic component in a dye-sensitized photovoltaic system. Repetitive restoration of photovoltaic performance after intensive device degradation is demonstrated. PMID:23912814

Recyclable organic solar cells on substrates comprising cellulose nanocrystals (CNC)

Science.gov (United States)

Kippelen, Bernard; Fuentes-Hernandez, Canek; Zhou, Yinhua; Moon, Robert; Youngblood, Jeffrey P

2015-12-01

Recyclable organic solar cells are disclosed herein. Systems and methods are further disclosed for producing, improving performance, and for recycling the solar cells. In certain example embodiments, the recyclable organic solar cells disclosed herein include: a first electrode; a second electrode; a photoactive layer disposed between the first electrode and the second electrode; an interlayer comprising a Lewis basic oligomer or polymer disposed between the photoactive layer and at least a portion of the first electrode or the second electrode; and a substrate disposed adjacent to the first electrode or the second electrode. The interlayer reduces the work function associated with the first or second electrode. In certain example embodiments, the substrate comprises cellulose nanocrystals that can be recycled. In certain example embodiments, one or more of the first electrode, the photoactive layer, and the second electrode may be applied by a film transfer lamination method.

Organic photovoltaic cells utilizing ultrathin sensitizing layer

Science.gov (United States)

Rand, Barry P [Princeton, NJ; Forrest, Stephen R [Princeton, NJ

2011-05-24

A photosensitive device includes a series of organic photoactive layers disposed between two electrodes. Each layer in the series is in direct contact with a next layer in the series. The series is arranged to form at least one donor-acceptor heterojunction, and includes a first organic photoactive layer comprising a first host material serving as a donor, a thin second organic photoactive layer comprising a second host material disposed between the first and a third organic photoactive layer, and the third organic photoactive layer comprising a third host material serving as an acceptor. The first, second, and third host materials are different. The thin second layer serves as an acceptor relative to the first layer or as a donor relative to the third layer.

The Synthesis and Photophysical Characterization of Porphyrin Photoactive Materials for Use as Sensitizers in Organic Photovoltaics and Photodynamic Therapy

Science.gov (United States)

Marin, Dawn Marie

Solar energy conversion and photodynamic therapy (PDT) are very different applications. However, both utilize very similar photoactive molecules called porphyrins. Porphyrins are structural analogs of chlorophyll and also function as prosthetic groups in some biological enzymes. Understanding the structure/function relationship of these molecules is crucial for enhancing the energy generation efficiency of molecular solar cells and improving chemotherapeutic activity in PDT. In this dissertation, two approaches were applied with the goal of increasing the efficiency of molecular semiconductors for these applications: the heavy atom effect and donor-acceptor molecules. We enhanced the efficiency of triplet excited state formation and singlet oxygen generation for porphyrin sensitizers using the heavy atom effect. The heavy atom effect induces spin-orbit coupling to promote intersystem crossing into the triplet state. In this study, a carbomethoxyphenyl substituent was replaced with either a bromophenyl or an iodophenyl substituent on 5,10,15,20-tetrakis(4-carbomethoxyphenyl)porphyrin. The longer lifetimes obtained from the increase in the triplet excited state allow for longer exciton diffusion lengths and lower recombination rates in photovoltaics. Also, the enhanced intersystem crossing is beneficial for photodynamic therapy because it increases singlet oxygen generation, which destroys tumor cells. Optimizing photovoltaic performance and PDT efficacy can also be accomplished with donor-acceptor molecules because they have extended electronic pi bond delocalization across the molecule, which causes the molecule to absorb longer wavelengths of light. Donor-acceptor molecules should produce photovoltaic devices that absorb more of the solar spectrum and produce sensitizers that absorb wavelengths of light that can penetrate through tissues. Donor-acceptor molecules were synthesized using 5,15-bis(4-carbomethoxyphenyl)porphyrin as the acceptor and thiazolo[5,4-d

Morphology control for highly efficient organic–inorganic bulk heterojunction solar cell based on Ti-alkoxide

International Nuclear Information System (INIS)

Kato, Takehito; Hagiwara, Naoki; Suzuki, Eiji; Nasu, Yuki; Izawa, Satoru; Tanaka, Kouichi; Kato, Ariyuki

2016-01-01

The number of publications concerned with typical bulk-heterojunction solar cells that use fullerene derivatives and inorganic materials as electron acceptors has grown very rapidly. In this work, we focus on Ti-alkoxides as electron acceptors in the photoactive layers of fullerene-free bulk-heterojunction solar cells. We show that it is possible to control the morphology by adjusting the molecular structure and size of the Ti-alkoxides. The short-circuit current density (J_s_c) increased to 191 μA/cm"2 from 25 μA/cm"2 with a maximum, when the phase-separation structure was continuously formed to within about 20 nm below the exciton diffusion length by using either titanium(IV) ethoxide or isopropoxide as an electron acceptor. Within a thickness of 30 nm, the photoactive layer is not influenced by the electron transfer ability; thus, we demonstrate that the charge-separation efficiency is equivalent to that of a fullerene system. - Highlights: • An organic–inorganic bulk-heterojunction photoactive layer was used. • Electron donor was a semiconducting polymer and electron acceptor was Ti-alkoxide. • Demonstration of morphology control by Ti-alkoxide molecules. • Determination of Jsc value by the phase-separation structure in an ultra-thin film. • Charge-separation efficiency of Ti-alkoxide system equivalent to fullerene system.

Development of a versatile experimental setup for the evaluation of the photocatalytic properties of construction materials under realistic outdoor conditions.

Science.gov (United States)

Suárez, S; Portela, R; Hernández-Alonso, M D; Sánchez, B

2014-10-01

The interest on outdoor photocatalytic materials is growing in the last years. Nevertheless, most of the experimental devices designed for the assessment of their performance operate at controlled laboratory conditions, i.e., pollutant concentration, temperature, UV irradiation, and water vapor contents, far from those of real outdoor environments. The aim of the present study was the design and development of an experimental device for the continuous test of photocatalytic outdoor materials under sun irradiation using real outdoor air as feed, with the concomitant fluctuation of pollutant concentration, temperature, and water vapor content. A three-port measurement system based on two UV-transparent chambers was designed and built. A test chamber contained the photoactive element and a reference chamber to place the substrate without the photoactive element were employed. The third sampling point, placed outdoors, allowed the characterization of the surrounding air, which feeds the test chambers. Temperature, relative humidity (RH), and UV-A irradiance were monitored at each sampling point with specific sensors. NO x concentration was measured by a chemiluminescence NO x analyzer. Three automatic valves allowed the consecutive analysis of the concentration at the three points at fixed time intervals. The reliability of the analytical system was demonstrated by comparing the NO x concentration data with those obtained at the nearest weather station to the experimental device location. The use of a chamber-based reaction system leads to an attenuation of NO x and atmospheric parameter profiles, but maintaining the general trends. The air characterization results showed the wide operating window under which the photoactive materials should work outdoors, depending on the traffic intensity and the season, which are reproduced inside the test chambers. The designed system allows the measurement of the photoactivity of outdoor materials or the comparison of several

Visible-light photoactivity of plasmonic silver supported on mesoporous TiO2 nanoparticles (Ag-MTN) for enhanced degradation of 2-chlorophenol: Limitation of Ag-Ti interaction

International Nuclear Information System (INIS)

Jaafar, N.F.; Jalil, A.A.; Triwahyono, S.

2017-01-01

Highlights: • Ag 0 loaded on MTN was prepared by a direct in-situ electrochemical method. • The introduction of Ag 0 lowers the band gap and increases the number of OV and TSD. • Ag 0 acted as an electrons trapper and also a plasmonic sensitizer. • The formation of Ti-O-Ag in 10 wt% Ag-MTN decreased the amount of Ag 0 , TSD and OV. • 5 wt% Ag-MTN gave the highest percentage of photodegradation of 2-CP. - Abstract: Various weight loadings of Ag (1–10 wt.%) were introduced to mesoporous titania nanoparticles (MTN) via a direct in-situ electrochemical method. The catalysts were characterized by XRD, surface area analysis, FTIR, ESR, FESEM-EDX and TEM. Characterization results indicated that the introduction of Ag onto MTN decreased the particles size and band gap of the MTN while increasing the number of oxygen vacancies (OV) and Ti 3+ site defects (TSD). The activity performance of Ag-MTN on photodegradation of 2-chlorophenol (2-CP) under visible light irradiation was in the following order: 5 wt% Ag-MTN> 1 wt% Ag-MTN > MTN > 10 wt% Ag-MTN, with degradation percentages of 97, 88, 80 and 63%, respectively. The synergistic effect between Ag 0 and MTN seemed to play an important role in the system. The Ag0 acted as both an electron trap and a plasmonic sensitizer which suppressed the electron-hole recombination, while OV and TSD in the MTN accelerated the production of hydroxyl radicals for enhanced degradation of 2-CP. However, the formation of Ti-O-Ag in 10 wt% Ag-MTN was found to decrease the photoactivity due to the decrease in the formation of Ag 0 , TSD and OV as well as the increase in band gap energy. The photodegradation of 5 wt% Ag-MTN followed a pseudo-first-order Langmuir- Hinshelwood model and the catalyst was still stable after five cycles.

Direct formation of new, phase-stable, and photoactive anatase-type Ti1-2XNbXScXO2 solid solution nanoparticles by hydrothermal method

International Nuclear Information System (INIS)

Hirano, Masanori; Ito, Takaharu

2008-01-01

A new anatase phase of photoactive Ti 1-2X Nb X Sc X O 2 (X = 0-0.2) solid solutions was directly formed as nanoparticles from precursor solutions of TiOSO 4 , NbCl 5 , and Sc(NO 3 ) 3 under mild hydrothermal conditions at 180 deg. C for 5 h using the hydrolysis of urea. With the increase of the content of niobium and scandium from X = 0 to 0.2, the lattice parameters a 0 and c 0 , the crystallite size, and the optical band gap of anatase gradually increased. Their photocatalytic activity and adsorptivity were evaluated separately by the measurement of the concentration of methylene blue (MB) remained in the solution in the dark or under UV-light irradiation. The anatase-type Ti 1-2X Nb X Sc X O 2 (X = 0.05) showed approximately two times and three times as high photocatalytic activity as those of the hydrothermal anatase-type pure TiO 2 and commercially available reference pure TiO 2 (ST-01), respectively. The anatase phase of Ti 1-2X Nb X Sc X O 2 (X = 0-0.2) existed stably up to 900 deg. C during heat treatment in air. New rutile-type Ti 1-2X Nb X Sc X O 2 solid solutions are formed through the phase transformation. The starting temperature of anatase-to-rutile phase transformation for Ti 1-2X Nb X Sc X O 2 (X = 0-0.2) solid solutions was delayed but its completing temperature was accelerated

Anti-MRSA-acting carbamidocyclophanes H-L from the Vietnamese cyanobacterium Nostoc sp. CAVN2.

Science.gov (United States)

Preisitsch, Michael; Harmrolfs, Kirsten; Pham, Hang T L; Heiden, Stefan E; Füssel, Anna; Wiesner, Christoph; Pretsch, Alexander; Swiatecka-Hagenbruch, Monika; Niedermeyer, Timo H J; Müller, Rolf; Mundt, Sabine

2015-03-01

The methanol extract of the Vietnamese freshwater cyanobacterium Nostoc sp. CAVN2 exhibited cytotoxic effects against MCF-7 and 5637 cancer cell lines as well as against nontumorigenic FL and HaCaT cells and was active against methicillin-resistant Staphylococcus aureus (MRSA) and Streptococcus pneumoniae. High-resolution mass spectrometric analysis indicated the presence of over 60 putative cyclophane-like compounds in an antimicrobially active methanol extract fraction. A paracyclophanes-focusing extraction and separation methodology led to the isolation of 5 new carbamidocyclophanes (1-5) and 11 known paracyclophanes (6-16). The structures and their stereochemical configurations were elucidated by a combination of spectrometric and spectroscopic methods including HRMS, 1D and 2D NMR analyses and detailed comparative CD analysis. The newly described monocarbamoylated [7.7]paracyclophanes (1, 2, 4 and 5) differ by a varying degree of chlorination in the side chains. Carbamidocyclophane J (3) is the very first reported carbamidocyclophane bearing a single halogenation in both butyl residues. Based on previous studies a detailed phylogenetic examination of cyclophane-producing cyanobacteria was carried out. The biological evaluation of 1-16 against various clinical pathogens highlighted a remarkable antimicrobial activity against MRSA with MICs of 0.1-1.0 μM, and indicated that the level of antibacterial activity is related to the presence of carbamoyl moieties.

Amorphous oxide alloys as interfacial layers with broadly tunable electronic structures for organic photovoltaic cells.

Science.gov (United States)

Zhou, Nanjia; Kim, Myung-Gil; Loser, Stephen; Smith, Jeremy; Yoshida, Hiroyuki; Guo, Xugang; Song, Charles; Jin, Hosub; Chen, Zhihua; Yoon, Seok Min; Freeman, Arthur J; Chang, Robert P H; Facchetti, Antonio; Marks, Tobin J

2015-06-30

In diverse classes of organic optoelectronic devices, controlling charge injection, extraction, and blocking across organic semiconductor-inorganic electrode interfaces is crucial for enhancing quantum efficiency and output voltage. To this end, the strategy of inserting engineered interfacial layers (IFLs) between electrical contacts and organic semiconductors has significantly advanced organic light-emitting diode and organic thin film transistor performance. For organic photovoltaic (OPV) devices, an electronically flexible IFL design strategy to incrementally tune energy level matching between the inorganic electrode system and the organic photoactive components without varying the surface chemistry would permit OPV cells to adapt to ever-changing generations of photoactive materials. Here we report the implementation of chemically/environmentally robust, low-temperature solution-processed amorphous transparent semiconducting oxide alloys, In-Ga-O and Ga-Zn-Sn-O, as IFLs for inverted OPVs. Continuous variation of the IFL compositions tunes the conduction band minima over a broad range, affording optimized OPV power conversion efficiencies for multiple classes of organic active layer materials and establishing clear correlations between IFL/photoactive layer energetics and device performance.

Organic structures design applications in optical and electronic devices

CERN Document Server

Chow, Tahsin J

2014-01-01

""Presenting an overview of the syntheses and properties of organic molecules and their applications in optical and electronic devices, this book covers aspects concerning theoretical modeling for electron transfer, solution-processed micro- and nanomaterials, donor-acceptor cyclophanes, molecular motors, organogels, polyazaacenes, fluorogenic sensors based on calix[4]arenes, and organic light-emitting diodes. The publication of this book is timely because these topics have become very popular nowadays. The book is definitely an excellent reference for scientists working in these a

Dual Selectivity Expressed in [2+2+1] Dynamic Clipping of Unsymmetrical [2]Catenanes

Energy Technology Data Exchange (ETDEWEB)

Liu, Yi

2010-06-11

A {pi}-templated dynamic [2+2+1] clipping protocol is established for the synthesis of [2]catenanes from two parts dialdehyde, two parts diamine and one part tetracationic cyclophane. It is further diversified for the selective formation of an unsymmetrical [2]catenane showing great translational selectivity by employing two different dialdehydes in a one-pot reaction. The dual selectivity and the dynamic nature are verified by {sup 1}H NMR spectroscopy, X-ray single crystal structural studies and exchange experiments.

Nanocrystal solar cells processed from solution

Science.gov (United States)

Alivisatos, A. Paul; Gur, Ilan; Milliron, Delia

2013-05-14

A photovoltaic device having a first electrode layer, a high resistivity transparent film disposed on the first electrode, a second electrode layer, and an inorganic photoactive layer disposed between the first and second electrode layers, wherein the inorganic photoactive layer is disposed in at least partial electrical contact with the high resistivity transparent film, and in at least partial electrical contact with the second electrode. The photoactive layer has a first inorganic material and a second inorganic material different from the first inorganic material, wherein the first and second inorganic materials exhibit a type II band offset energy profile, and wherein the photoactive layer has a first population of nanostructures of a first inorganic material and a second population of nanostructures of a second inorganic material.

Visible-light photoactivity of plasmonic silver supported on mesoporous TiO{sub 2} nanoparticles (Ag-MTN) for enhanced degradation of 2-chlorophenol: Limitation of Ag-Ti interaction

Energy Technology Data Exchange (ETDEWEB)

Jaafar, N.F. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, UTM, 81310 Johor Bahru, Johor (Malaysia); Jalil, A.A., E-mail: aishahaj@utm.my [Centre of Hydrogen Energy, Institute of Future Energy, Universiti Teknologi Malaysia, UTM, 81310 Johor Bahru, Johor (Malaysia); Department of Chemical Engineering, Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia, UTM, 81310 Johor Bahru, Johor (Malaysia); Triwahyono, S. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, UTM, 81310 Johor Bahru, Johor (Malaysia); Centre for Sustainable Nanomaterials, Ibnu Sina Institute for Scientific and Industrial Research, Universiti Teknologi Malaysia, UTM, 81310 Johor Bahru, Johor (Malaysia)

2017-01-15

Highlights: • Ag{sup 0} loaded on MTN was prepared by a direct in-situ electrochemical method. • The introduction of Ag{sup 0} lowers the band gap and increases the number of OV and TSD. • Ag{sup 0} acted as an electrons trapper and also a plasmonic sensitizer. • The formation of Ti-O-Ag in 10 wt% Ag-MTN decreased the amount of Ag{sup 0}, TSD and OV. • 5 wt% Ag-MTN gave the highest percentage of photodegradation of 2-CP. - Abstract: Various weight loadings of Ag (1–10 wt.%) were introduced to mesoporous titania nanoparticles (MTN) via a direct in-situ electrochemical method. The catalysts were characterized by XRD, surface area analysis, FTIR, ESR, FESEM-EDX and TEM. Characterization results indicated that the introduction of Ag onto MTN decreased the particles size and band gap of the MTN while increasing the number of oxygen vacancies (OV) and Ti{sup 3+} site defects (TSD). The activity performance of Ag-MTN on photodegradation of 2-chlorophenol (2-CP) under visible light irradiation was in the following order: 5 wt% Ag-MTN> 1 wt% Ag-MTN > MTN > 10 wt% Ag-MTN, with degradation percentages of 97, 88, 80 and 63%, respectively. The synergistic effect between Ag{sup 0} and MTN seemed to play an important role in the system. The Ag0 acted as both an electron trap and a plasmonic sensitizer which suppressed the electron-hole recombination, while OV and TSD in the MTN accelerated the production of hydroxyl radicals for enhanced degradation of 2-CP. However, the formation of Ti-O-Ag in 10 wt% Ag-MTN was found to decrease the photoactivity due to the decrease in the formation of Ag{sup 0}, TSD and OV as well as the increase in band gap energy. The photodegradation of 5 wt% Ag-MTN followed a pseudo-first-order Langmuir- Hinshelwood model and the catalyst was still stable after five cycles.

Synthesis, structural characterization and evaluation of floating B-N codoped TiO{sub 2}/expanded perlite composites with enhanced visible light photoactivity

Energy Technology Data Exchange (ETDEWEB)

Wang, Xin; Wang, Wei; Wang, Xuejiang, E-mail: wangxj@tongji.edu.cn; Zhang, Jing; Zhao, Jianfu; Gu, Zaoli; Zhou, Lijie

2015-09-15

Graphical abstract: - Highlights: • We added expanded perlite as a floating carrier to immobilize B-N codoped TiO{sub 2}. • The photo-reaction occurred on the surface of water and easily utilized the solar energy and O{sub 2} to make photodegradation efficiently. • The composites combined the adsorptivity of expanded perlite and photoactivity of B-N-TiO{sub 2}. • The floating photocatalysts give a simple way to recycle, which is important to the application of photocatalysis technology. - Abstract: Floating photocatalysts of boron-nitrogen codoped TiO{sub 2} grafted on expanded perlite (B-N-TiO{sub 2}/EP) were prepared by a facile sol–gel method. The catalysts were characterized by N{sub 2} adsorption–desorption (BET), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (UV–vis–DRS). The results revealed that the physicochemical properties of the photocatalysts, such as BET surface area, porosity and pore size could be controlled by adjusting the calcination temperature and EP dosage. XRD patterns were mainly influenced by calcination temperature and the transformation of anatase to rutile occurred at 650 °C. Uniform TiO{sub 2} loading, higher surface area and absorption in visible light region were obtained for B-N-TiO{sub 2}/EP calcined at 550 °C with 3.0 g EP addition. Moreover, photocatalytic activity for RhB destruction under visible light irradiation was slightly influenced by TiO{sub 2} loading in the range of 1–3 g EP dosage. BNTEP550 showed the highest photocatalytic activity indicating to be a promising photocatalyst employed to remediate contaminated waters using solar irradiation.

A triphenylamine-based push-pull – σ – C60 dyad as photoactive molecular material for single-component organic solar cells: synthesis, characterizations and photophysical properties

KAUST Repository

Labrunie, Antoine; Gorenflot, Julien; Babics, Maxime; Aleveque, Olivier; Dabos-Seignon, Sylvie; Balawi, Ahmed H.; Kan, Zhipeng; Wohlfahrt, Markus; Levillain, Eric; Hudhomme, Pietrick; Beaujuge, Pierre; Laquai, Fré dé ric; Cabanetos, Clé ment; Blanchard, Philippe

2018-01-01

A push-pull – σ – C60 molecular dyad was synthesized via Huisgen-type click-chemistry and used as photoactive material for single-component organic solar cells. Steady-state photoluminescence (PL) experiments of the dyad in solution show a significant quenching of the emission of the push-pull moiety. Spin-casting of a solution of the dyad results in homogenous and smooth thin-films, which exhibit complete PL quenching in line with ultrafast photo-induced electron-transfer in the solid-state. Spectro-electrochemistry reveals the optical signatures of radical cations and radical anions. Evaluation of the charge carrier mobility by space-charge limited current measurements gives an electron-mobility of μe = 4.3 × 10-4 cm2 V-1 s-1, ca. 50 times higher than the hole-mobility. Single-component organic solar cells yield an open-circuit voltage Voc of 0.73 V and a short-circuit current density of 2.1 mA cm-2 however, a poor fill-factor FF (29%) is obtained, resulting in low power conversion efficiency of only 0.4%. Combined TA and time-delayed collection field (TDCF) experiments show mostly ultrafast photon-to-charge conversion and a small component of diffusion-limited exciton dissociation, revealing the presence of pure fullerene domains. Furthermore, a strong field dependence of charge generation is observed, governing the device fill factor, which is further reduced by a competition between extraction and fast recombination of separated charges.

A triphenylamine-based push-pull – σ – C60 dyad as photoactive molecular material for single-component organic solar cells: synthesis, characterizations and photophysical properties

KAUST Repository

Labrunie, Antoine

2018-04-23

A push-pull – σ – C60 molecular dyad was synthesized via Huisgen-type click-chemistry and used as photoactive material for single-component organic solar cells. Steady-state photoluminescence (PL) experiments of the dyad in solution show a significant quenching of the emission of the push-pull moiety. Spin-casting of a solution of the dyad results in homogenous and smooth thin-films, which exhibit complete PL quenching in line with ultrafast photo-induced electron-transfer in the solid-state. Spectro-electrochemistry reveals the optical signatures of radical cations and radical anions. Evaluation of the charge carrier mobility by space-charge limited current measurements gives an electron-mobility of μe = 4.3 × 10-4 cm2 V-1 s-1, ca. 50 times higher than the hole-mobility. Single-component organic solar cells yield an open-circuit voltage Voc of 0.73 V and a short-circuit current density of 2.1 mA cm-2 however, a poor fill-factor FF (29%) is obtained, resulting in low power conversion efficiency of only 0.4%. Combined TA and time-delayed collection field (TDCF) experiments show mostly ultrafast photon-to-charge conversion and a small component of diffusion-limited exciton dissociation, revealing the presence of pure fullerene domains. Furthermore, a strong field dependence of charge generation is observed, governing the device fill factor, which is further reduced by a competition between extraction and fast recombination of separated charges.

Hypericin-loaded nanoparticles for the photodynamic treatment of ovarian cancer.

Science.gov (United States)

Zeisser-Labouèbe, Magali; Lange, Norbert; Gurny, Robert; Delie, Florence

2006-12-01

A photodynamic approach has been suggested to improve diagnosis and therapy of ovarian cancer. As Hypericin (Hy), a natural photosensitizer (PS) extracted from Hypericum perforatum, has been shown to be efficient in vitro and in vivo for the detection or treatment of other cancers, Hy could also be a potent tool for the treatment and detection of ovarian cancer. Due to its hydrophobicity, systemic administration of Hy is problematic. Thus, polymeric nanoparticles (NPs) of polylactic acid (PLA) or polylactic-co-glycolic acid (PLGA) were used as a drug delivery system. Hy-loaded NPs were produced with the following characteristics: (i) size in the 200-300 nm range, (ii) negative zeta potential, (iii) low residual PVAL and (iv) drug loading from 0.03 to 0.15% (w/w). Their in vitro photoactivity was investigated on the NuTu-19 ovarian cancer cell model derived from Fischer 344 rats and compared to free drug. Hy-loaded PLA NPs exhibited a higher photoactivity than free drug. Increasing light dose or incubation time with cells induced an enhanced activity of Hy-loaded PLA NPs. Increased NP drug loading had a negative effect on their photoactivity on NuTu-19 cells: at the same Hy concentration, the higher was the drug loading, the lower was the phototoxic effect. The influence of NP drug loading on the Hy release from NPs was also investigated.

Organometallic Reactions Development, Mechanistic Studies and Synthetic Applications

DEFF Research Database (Denmark)

Dam, Johan Hygum

of the successful total synthesis of the cyclophane cavicularin, which contains a bent aromatic moiety. The pivotal step in the synthesis embodied a pyrone-alkyne Diels-Alder cycloaddition with CO2-extrusion to deliver the bent aromatic residue. The fourth project involved further development of the conditions...... previously discovered in the Madsen group for the direct coupling of alcohols and amines to amides under dihydrogen liberation. The goal was to synthesize isolatable ruthenium catalysts and two 18-electron complexes capable of performing the reaction in excellent yields were prepared and characterized...

A practical pathway for the preparation of Fe_2O_3 decorated TiO_2 photocatalyst with enhanced visible-light photoactivity

International Nuclear Information System (INIS)

Cheng, Li; Qiu, Shoufei; Chen, Juanrong; Shao, Jian; Cao, Shunsheng

2017-01-01

Shifting the ultra-violet of titania to visible light driven photocatalysis can be realized by coupling with metallic or non-metallic elements. However, time-consuming multi-step process and significant loss of UV photocatalytic activity of such TiO_2-based photocatalysts severely hinder their practical applications. In this work, we explore the idea of creating a practical method for the preparation of Fe_2O_3 decorated TiO_2 (TiO_2/Fe_2O_3) photocatalyst with controlled visible-light photoactivity. This method only involves the calcination of the mixture (commercial P25 powders and magnetic Fe_3O_4 nanoparticles) prepared by a mechanical process. The morphology and properties of TiO_2/Fe_2O_3 composites were characterized by Transmission electron microscope, X-ray diffraction, UV–vis spectroscopy, and X-ray photoelectron spectroscopy. Results confirm the fusion of TiO_2 and Fe_2O_3, which promotes photo-generated electrons/holes migration and separation. Because of the strong synergistic effect, the as-synthesized TiO_2/Fe_2O_3 composites manifest an enhanced visible-light photocatalytic activity. Especially, the TiO_2/Fe_2O_3 photocatalyst is very easy to be constructed via an one-step protocol that efficiently overcomes the time-consuming multi-step processes used in existed strategies for the preparation of Fe_2O_3/TiO_2 photocatalysts, providing a new insight into the practical application of TiO_2/Fe_2O_3 visible light photocatalyst. - Highlights: • We introduced a practical preparation of Fe_2O_3 decorated TiO_2 photocatalyst. • TiO_2/Fe_2O_3 was developed using commercial precursors in a high efficient manner. • Visible-light activity of TiO_2/Fe_2O_3 could be tuned by changing amount of Fe_3O_4 precursor. • TiO_2/Fe_2O_3 exhibited a higher visible-light photocatalytic activity than P25.

Nature-Inspired Design of Artificial Solar-to-Fuel Conversion Systems based on Copper Phosphate Microflowers.

Science.gov (United States)

Wang, Jing; Zhu, Ting; Ho, Ghim Wei

2016-07-07

Phosphates play significant roles in plant photosynthesis by mediating electron transportation and furnishing energy for CO2 reduction. Motivated by this, we demonstrate herein an artificial solar-to-fuel conversion system, involving versatile copper phosphate microflowers as template and titanium dioxide nanoparticles as host photocatalyst. The elaborate flowerlike architectures, coupled with a unique proton-reduction cycle from interchangeability of different species of orthophosphate ions, not only offer a 2D nanosheet platform for an optimal heterostructure interface but also effectively augment charge-carrier transfer, thereby contributing to enhanced photoactivity and hydrogen generation. These nature-inspired, phosphate-derived nanocomposites advance the synthesis of a large variety of functional materials, which holds great potential for photochemical, photoelectric and catalytic applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Method for improved selectivity in photo-activation of molecular agents

Science.gov (United States)

Fisher, Walter G.; Wachter, Eric A.; Dees, H. Craig

1998-01-01

A method for the treatment of a particular volume of plant or animal tissue comprising the steps of treating the plant or animal tissue with at least one photo-active molecular agent, wherein the particular volume of the plant or animal tissue retains at least a portion of the at least one photo-active molecular agent, and then treating the particular volume of the plant or animal tissue with light sufficient to promote a simultaneous two-photon excitation of at least one of the at least one photo-active molecular agent retained in the particular volume of the plant or animal tissue, wherein the at least one photo-active molecular agent becomes active in the particular volume of the plant or animal tissue. There is also disclosed a method for the treatment of cancer in plant or animal tissue and a method for producing at least one photo-activated molecular agent in a particular volume of a material.

Organic Semiconductor Photovoltaics

Science.gov (United States)

Sariciftci, Niyazi Serdar

2005-03-01

Recent developments on organic photovoltaic elements are reviewed. Semiconducting conjugated polymers and molecules as well as nanocrystalline inorganic semiconductors are used in composite thin films. The photophysics of such photoactive devices is based on the photoinduced charge transfer from donor type semiconducting molecules onto acceptor type molecules such as Buckminsterfullerene, C60 and/or nanoparticles. Similar to the first steps in natural photosynthesis, this photoinduced electron transfer leads to a number of potentially interesting applications which include sensitization of the photoconductivity and photovoltaic phenomena. Examples of photovoltaic architectures are discussed with their potential in terrestrial solar energy conversion. Several materials are introduced and discussed for their photovoltaic activities. Furthermore, nanomorphology has been investigated with AFM, SEM and TEM. The morphology/property relationship for a given photoactive system is found to be a major effect.

Measurement of the ground-state distributions in bistable mechanically interlocked molecules using slow scan rate cyclic voltammetry.

Science.gov (United States)

Fahrenbach, Albert C; Barnes, Jonathan C; Li, Hao; Benítez, Diego; Basuray, Ashish N; Fang, Lei; Sue, Chi-Hau; Barin, Gokhan; Dey, Sanjeev K; Goddard, William A; Stoddart, J Fraser

2011-12-20

In donor-acceptor mechanically interlocked molecules that exhibit bistability, the relative populations of the translational isomers--present, for example, in a bistable [2]rotaxane, as well as in a couple of bistable [2]catenanes of the donor-acceptor vintage--can be elucidated by slow scan rate cyclic voltammetry. The practice of transitioning from a fast scan rate regime to a slow one permits the measurement of an intermediate redox couple that is a function of the equilibrium that exists between the two translational isomers in the case of all three mechanically interlocked molecules investigated. These intermediate redox potentials can be used to calculate the ground-state distribution constants, K. Whereas, (i) in the case of the bistable [2]rotaxane, composed of a dumbbell component containing π-electron-rich tetrathiafulvalene and dioxynaphthalene recognition sites for the ring component (namely, a tetracationic cyclophane, containing two π-electron-deficient bipyridinium units), a value for K of 10 ± 2 is calculated, (ii) in the case of the two bistable [2]catenanes--one containing a crown ether with tetrathiafulvalene and dioxynaphthalene recognition sites for the tetracationic cyclophane, and the other, tetrathiafulvalene and butadiyne recognition sites--the values for K are orders (one and three, respectively) of magnitude greater. This observation, which has also been probed by theoretical calculations, supports the hypothesis that the extra stability of one translational isomer over the other is because of the influence of the enforced side-on donor-acceptor interactions brought about by both π-electron-rich recognition sites being part of a macrocyclic polyether.

Technology development for roll-to-roll production of organic photovoltaics

NARCIS (Netherlands)

Galagan, Y.O.; Vries, I.G. de; Langen, A.P.; Andriessen, H.A.J.M.; Verhees, W.J.H.; Veenstra, S.C.; Kroon, J.M.

2011-01-01

In order to reach the objective of low-cost, large area organic photovoltaic systems, we build up a knowledge base concerning the influence of process conditions on the performance of polymer solar cells. A large area solar cell module, with roll-to-roll coated PEDOT:PSS and photoactive layers

Protein Nanocage-Based Photo-Controlled Nitric Oxide Releasing Platform.

Science.gov (United States)

Li, Xiao; Zhang, Yajie; Sun, Jian; Chen, Weijian; Wang, Xuewei; Shao, Fenli; Zhu, Yuyu; Feng, Fude; Sun, Yang

2017-06-14

A photoactive NO releasing system was constructed by incorporation of NO-bound Fe-S clusters into horse spleen apoferritin cavities with high loading efficacy. The composites retained intact core-shell structure and indicated advantages such as enhanced stability, reduced cytotoxicity, efficient cellular uptake, and photocontrolled NO releasing property.

Fotoaktivita vodných suspenzí oxidů titanu a wolframu

Czech Academy of Sciences Publication Activity Database

Mastný, L.; Šaněk, F.; Brožek, Vlastimil

2010-01-01

Roč. 20, č. 5 (2010), s. 22-24 ISSN 1210-7409 R&D Projects: GA ČR GA202/08/1084 Institutional research plan: CEZ:AV0Z20430508 Keywords : Water stabilized plasma * plasma generator * photoactivity * photoactivity * photocatalysis * titanium oxide * tungsten oxide * sodium picramate Subject RIV: CA - Inorganic Chemistry

Tailoring intra- and intermolecular properties : from cyclophanes to daisy chains

OpenAIRE

Rotzler, Jürgen Stefan

2012-01-01

Todays high-tech society is striving for faster, cheaper and higher performing devices in all circumstances. Traditional materials have long since reached their limits making the search for new materials with altered properties inevitable. Easy processable, long-term stable polymeric materials with improved handling or switchable properties for use in plastics, conducting single molecular wires, switches, rectifiers in computer industry, nonlinear optic materials for data transmission at the ...

Optimizing the photocatalytic properties and the synergistic effects of graphene and nano titanium dioxide immobilized on cotton fabric

International Nuclear Information System (INIS)

Karimi, Loghman; Yazdanshenas, Mohammad Esmail; Khajavi, Ramin; Rashidi, Abosaeed; Mirjalili, Mohammad

2015-01-01

Graphical abstract: - Highlights: • Producing superior photo-active cotton fabric using graphene/titanium dioxide nanocomposite. • Optimizing processing conditions using response surface methodology. • Obtaining significant photo-activity properties on cotton fabric by this method under sun irradiation. • Possessing excellent antimicrobial activity with low cytotoxicity on human fibroblasts. - Abstract: A new facile route based on cotton fabric coated with graphene/titanium dioxide nanocomposite is reported to produce photo-active cellulose textiles. A thin layer of graphene oxide has been produced on cotton fabrics by a dip-dry process. The graphene oxide-coated cotton fabrics were then immersed in titanium trichloride aqueous solution to yield a fabric coated with graphene/titanium dioxide nanocomposite. The photo-activity efficiency of the coated fabrics was tested by degradation of methylene blue in aqueous solution under UV and sunlight irradiations. To obtain the optimum condition, the response surface methodology (RSM) through the central composite design was applied and the role of both graphene oxide and titanium trichloride concentrations on photo-activity efficiency was investigated. The physicochemical properties of the prepared samples has been characterized by a series of techniques, including Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The effect of the application of graphene/titanium dioxide nanocomposite on the physical properties of the cotton fabric, such as tensile strength, bending rigidity and crease recovery angle has been analyzed. Other characteristics of treated fabrics such as antibacterial, antifungal and cytotoxicity were also investigated. Cotton fabric coated with optimum concentrations of graphene oxide and titanium trichloride obtained significant photo-activity efficiency under UV and sunlight irradiations. Moreover, the graphene

Rational design of carbon and TiO2 assembly materials: covered or strewn, which is better for photocatalysis?

Science.gov (United States)

Cui, Guan-wei; Wang, Wei-liang; Ma, Ming-yue; Zhang, Ming; Xia, Xin-yuan; Han, Feng-yun; Shi, Xi-feng; Zhao, Ying-qiang; Dong, Yu-bin; Tang, Bo

2013-07-21

The rational design of carbonaceous hybrid nanostructures is very important for obtaining high photoactivity. TiO2 particles strewn with an optimal quantity of carbon nanodots have a much higher photoactivity than that of TiO2 covered with a carbon layer, showing the importance of carbon morphology in the photocatalysis of carbonaceous hybrid nanostructures.

Method for improved selectivity in photo-activation and detection of molecular diagnostic agents

Science.gov (United States)

Wachter, Eric A.; Fisher, Walter G.; Dees, H. Craig

1998-01-01

A method for the imaging of a particular volume of plant or animal tissue, wherein the plant or animal tissue contains at least one photo-active molecular agent. The method includes the steps of treating the particular volume of the plant or animal tissue with light sufficient to promote a simultaneous two-photon excitation of the photo-active molecular agent contained in the particular volume of the plant or animal tissue, photo-activating at least one of the at least one photo-active molecular agent in the particular volume of the plant or animal tissue, thereby producing at least one photo-activated molecular agent, wherein the at least one photo-activated molecular agent emits energy, detecting the energy emitted by the at least one photo-activated molecular agent, and producing a detected energy signal which is characteristic of the particular volume of plant or animal tissue. The present invention is also a method for the imaging of a particular volume of material, wherein the material contains at least one photo-active molecular agent.

Methods for improved selectivity in photo-activation and detection of molecular diagnostic agents

Science.gov (United States)

Wachter, Eric A [Oak Ridge, TN; Fisher, Walter G [Knoxville, TN; Dees, H Craig [Knoxville, TN

2008-03-18

A method for the imaging of a particular volume of plant or animal tissue, wherein the plant or animal tissue contains at least one photo-active molecular agent. The method comprises the steps of treating the particular volume of the plant or animal tissue with light sufficient to promote a simultaneous two-photon excitation of the photo-active molecular agent contained in the particular volume of the plant or animal tissue, photo-activating at least one of the at least one photo-active molecular agent in the particular volume of the plant or animal tissue, thereby producing at least one photo-activated molecular agent, wherein the at least one photo-activated molecular agent emits energy, detecting the energy emitted by the at least one photo-activated molecular agent, and producing a detected energy signal which is characteristic of the particular volume of plant or animal tissue. The present invention also provides a method for the imaging of a particular volume of material, wherein the material contains at least one photo-active molecular agent.

The effect of ZnO or TiO{sub 2} loaded nanoparticles on the adsorption and photocatalytic performance of Cu-BTC and ZIF-8 MOFs

Energy Technology Data Exchange (ETDEWEB)

Ökte, A.N., E-mail: okteayse@boun.edu.tr [Department of Chemistry, Boğaziçi University, Bebek, 34342, Istanbul (Turkey); Karamanis, D.; Chalkia, E. [Department of Environmental & Natural Resources Management, University of Patras, 30100, Agrinio (Greece); Tuncel, D. [Department of Chemistry, Boğaziçi University, Bebek, 34342, Istanbul (Turkey)

2017-02-01

Binary composites of ZnO or TiO{sub 2} nanocatalysts on Cu-BTC and ZIF-8 were characterized and tested for the decolorization of methylene blue (MB) and methyl orange (MO). X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) images evidenced the creation of catalyst nanoparticles. Composites with higher dark adsorption capacities facilitated the decolorization rates of the dye molecules. MB decolorization percentages increased in the presence of Cu-BTC supported composites. ZnO addition increased the photoactivities of ZIF-8 composites for both MB and MO. - Highlights: • Dark adsorption capacities affect the photoactivities of the composites. • Cu-BTC based composites show higher degradation efficiencies toward MB. • ZnO addition enhance the photoactivity of 0.25 M ZnO-ZIF-8 for both MB and MO.

Characterization of metal-bound water in bioactive Fe(III)-cyclophane complexes

Science.gov (United States)

Salazar-Medina, A. J.; Gámez-Corrales, R.; Ramírez, J. Z.; González-Aguilar, G. A.; Velázquez-Contreras, E. F.

2018-02-01

Binuclear Fe(III) complexes, Fe2PO and Fe2PC, have functions of antioxidants as well as superoxide dismutase and peroxidase mimickers. The role of water molecules in the non-cytotoxic properties of these complexes have been studied by thermogravimetric and IR/Raman-spectroscopic methods. The thermogravimetric analysis of Fe2PO shows the presence of nine water molecules (Fe2PO·9H2O), three of which are directly coordinated to the metallic ion; the remaining six molecules occupy the secondary coordination sphere. For Fe2PC, eight water molecules were detected (Fe2PC·8H2O), and only one of them directly coordinates to the metallic ion. IR/Raman spectrum analyses corroborate the presence of water molecules in both metallic complexes and the mode of coordination to the ligand, on the basis of bands characteristic of hydration water at ∼3300 cm-1 and bands of adsorbed water between 430 and 490 cm-1. A pentacoordinate geometry is proposed for Fe2PO and a hexacoordinated geometry for Fe2PC. Those results are consistent with theoretical calculations performed through a semiempirical PM7 method. The presence of coordinated water molecules is closely related to the reactivity of Fe2PO and Fe2PC in solution.

Unravelling the pH-dependence of a molecular photocatalytic system for hydrogen production.

Science.gov (United States)

Reynal, Anna; Pastor, Ernest; Gross, Manuela A; Selim, Shababa; Reisner, Erwin; Durrant, James R

2015-08-01

Photocatalytic systems for the reduction of aqueous protons are strongly pH-dependent, but the origin of this dependency is still not fully understood. We have studied the effect of different degrees of acidity on the electron transfer dynamics and catalysis taking place in a homogeneous photocatalytic system composed of a phosphonated ruthenium tris(bipyridine) dye ( RuP ) and a nickel bis(diphosphine) electrocatalyst ( NiP ) in an aqueous ascorbic acid solution. Our approach is based on transient absorption spectroscopy studies of the efficiency of photo-reduction of RuP and NiP correlated with pH-dependent photocatalytic H 2 production and the degree of catalyst protonation. The influence of these factors results in an observed optimum photoactivity at pH 4.5 for the RuP - NiP system. The electron transfer from photo-reduced RuP to NiP is efficient and independent of the pH value of the medium. At pH RuP photo-reduction by the sacrificial electron donor, ascorbic acid. At pH >4.5, the efficiency of the system is limited by the poor protonation of NiP , which inhibits its ability to reduce protons to hydrogen. We have therefore developed a rational strategy utilising transient absorption spectroscopy combined with bulk pH titration, electrocatalytic and photocatalytic experiments to disentangle the complex pH-dependent activity of the homogenous RuP - NiP photocatalytic system, which can be widely applied to other photocatalytic systems.

The structure and the photocatalytic activity of titania based nanotube and nanofiber coatings

Energy Technology Data Exchange (ETDEWEB)

Radtke, A., E-mail: aradtke@umk.pl [Faculty of Chemistry, Nicolaus Copernicus University, ul. Gagarina 7, 87-100 Toruń (Poland); Piszczek, P.; Topolski, A.; Lewandowska, Ż. [Faculty of Chemistry, Nicolaus Copernicus University, ul. Gagarina 7, 87-100 Toruń (Poland); Talik, E. [A. Chełkowski Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Andersen, I. Hald; Nielsen, L. Pleth [Tribology Centre, Danish Technological Institute, Kongsvang Allé 29, 8000 Aarhus C (Denmark); Heikkilä, M.; Leskelä, M. [Centre of Excellence, Laboratory of Inorganic Chemistry, Chemistry Department, Faculty of Science, University of Helsinki, A.I. Virtasen aukio 1, FI-00014 (Finland)

2016-04-15

Graphical abstract: - Highlights: • The photoactivity of TNT and TNF has been quantified by two different methods. • The influence of the TNT and TNF structure on their photoactivity was studied. • The photoactivity comparison of TNT and TNF was carried out. • TNF coatings show higher photoactivity in comparison to TNT. - Abstract: The photocatalytic activity of TiO{sub 2} based nanotube (TNT) and nanofiber (TNF) coatings has been investigated, in correlation to their structure, morphology, specific surface area, acidity and the amount of surface H{sub 2}O molecules and −OH groups. Characterization of these materials was carried out using grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). The photocatalytic activity has been quantified by two different methods, based on the photodegradation of methylene blue (the pattern of water-soluble organic pollutant) and acetone (the pattern of volatile organic pollutant), respectively. Results of our investigations revealed that TNF coatings were significantly more active in case of both photodegradation processes in air and water, as compared to TNT, even if the specific surface area of TNF films was smaller than the adequate surface area of TNT. The microstructure of produced materials, the amount of adsorbed −OH groups and H{sub 2}O molecules located on the surface of materials, and the acidity of the surface, were the main factors which affect their photoactivity. Photocatalytic properties of tubular and porous TiO{sub 2}-based materials are the resultant of the compilation of individual factors impact and any of them cannot be neglected.

The structure and the photocatalytic activity of titania based nanotube and nanofiber coatings

International Nuclear Information System (INIS)

Radtke, A.; Piszczek, P.; Topolski, A.; Lewandowska, Ż.; Talik, E.; Andersen, I. Hald; Nielsen, L. Pleth; Heikkilä, M.; Leskelä, M.

2016-01-01

Graphical abstract: - Highlights: • The photoactivity of TNT and TNF has been quantified by two different methods. • The influence of the TNT and TNF structure on their photoactivity was studied. • The photoactivity comparison of TNT and TNF was carried out. • TNF coatings show higher photoactivity in comparison to TNT. - Abstract: The photocatalytic activity of TiO_2 based nanotube (TNT) and nanofiber (TNF) coatings has been investigated, in correlation to their structure, morphology, specific surface area, acidity and the amount of surface H_2O molecules and −OH groups. Characterization of these materials was carried out using grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). The photocatalytic activity has been quantified by two different methods, based on the photodegradation of methylene blue (the pattern of water-soluble organic pollutant) and acetone (the pattern of volatile organic pollutant), respectively. Results of our investigations revealed that TNF coatings were significantly more active in case of both photodegradation processes in air and water, as compared to TNT, even if the specific surface area of TNF films was smaller than the adequate surface area of TNT. The microstructure of produced materials, the amount of adsorbed −OH groups and H_2O molecules located on the surface of materials, and the acidity of the surface, were the main factors which affect their photoactivity. Photocatalytic properties of tubular and porous TiO_2-based materials are the resultant of the compilation of individual factors impact and any of them cannot be neglected.

High efficient plastic solar cells fabricated with a high-throughput gravure printing method

Energy Technology Data Exchange (ETDEWEB)

Kopola, P.; Jin, H.; Tuomikoski, M.; Maaninen, A.; Hast, J. [VTT, Kaitovaeylae 1, FIN-90571 Oulu (Finland); Aernouts, T. [IMEC, Organic PhotoVoltaics, Polymer and Molecular Electronics, Kapeldreef 75, B-3001 Leuven (Belgium); Guillerez, S. [CEA-INES RDI, 50 Avenue Du Lac Leman, 73370 Le Bourget Du Lac (France)

2010-10-15

We report on polymer-based solar cells prepared by the high-throughput roll-to-roll gravure printing method. The engravings of the printing plate, along with process parameters like printing speed and ink properties, are studied to optimise the printability of the photoactive as well as the hole transport layer. For the hole transport layer, the focus is on testing different formulations to produce thorough wetting of the indium-tin-oxide (ITO) substrate. The challenge for the photoactive layer is to form a uniform layer with optimal nanomorphology in the poly-3-hexylthiophene (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend. This results in a power conversion efficiency of 2.8% under simulated AM1.5G solar illumination for a solar cell device with gravure-printed hole transport and a photoactive layer. (author)

A practical pathway for the preparation of Fe{sub 2}O{sub 3} decorated TiO{sub 2} photocatalyst with enhanced visible-light photoactivity

Energy Technology Data Exchange (ETDEWEB)

Cheng, Li; Qiu, Shoufei [Institute of Polymer Materials, School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Chen, Juanrong, E-mail: Juanrongchen@ujs.edu.cn [School of Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013 (China); Shao, Jian [Institute of Polymer Materials, School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Cao, Shunsheng, E-mail: sscaochem@hotmail.com [Institute of Polymer Materials, School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China)

2017-04-01

Shifting the ultra-violet of titania to visible light driven photocatalysis can be realized by coupling with metallic or non-metallic elements. However, time-consuming multi-step process and significant loss of UV photocatalytic activity of such TiO{sub 2}-based photocatalysts severely hinder their practical applications. In this work, we explore the idea of creating a practical method for the preparation of Fe{sub 2}O{sub 3} decorated TiO{sub 2} (TiO{sub 2}/Fe{sub 2}O{sub 3}) photocatalyst with controlled visible-light photoactivity. This method only involves the calcination of the mixture (commercial P25 powders and magnetic Fe{sub 3}O{sub 4} nanoparticles) prepared by a mechanical process. The morphology and properties of TiO{sub 2}/Fe{sub 2}O{sub 3} composites were characterized by Transmission electron microscope, X-ray diffraction, UV–vis spectroscopy, and X-ray photoelectron spectroscopy. Results confirm the fusion of TiO{sub 2} and Fe{sub 2}O{sub 3}, which promotes photo-generated electrons/holes migration and separation. Because of the strong synergistic effect, the as-synthesized TiO{sub 2}/Fe{sub 2}O{sub 3} composites manifest an enhanced visible-light photocatalytic activity. Especially, the TiO{sub 2}/Fe{sub 2}O{sub 3} photocatalyst is very easy to be constructed via an one-step protocol that efficiently overcomes the time-consuming multi-step processes used in existed strategies for the preparation of Fe{sub 2}O{sub 3}/TiO{sub 2} photocatalysts, providing a new insight into the practical application of TiO{sub 2}/Fe{sub 2}O{sub 3} visible light photocatalyst. - Highlights: • We introduced a practical preparation of Fe{sub 2}O{sub 3} decorated TiO{sub 2} photocatalyst. • TiO{sub 2}/Fe{sub 2}O{sub 3} was developed using commercial precursors in a high efficient manner. • Visible-light activity of TiO{sub 2}/Fe{sub 2}O{sub 3} could be tuned by changing amount of Fe{sub 3}O{sub 4} precursor. • TiO{sub 2}/Fe{sub 2}O{sub 3} exhibited a higher

Five-membered ring annelation in [2.2]paracyclophanes by aldol condensation

Directory of Open Access Journals (Sweden)

Henning Hopf

2014-08-01

Full Text Available Under basic conditions 4,5,12,13-tetraacetyl[2.2]paracyclophane (9 cyclizes by a double aldol condensation to provide the two aldols 12 and 15 in a 3:7 ratio. The structures of these compounds were obtained from X-ray structural analysis, spectroscopic data, and mechanistic considerations. On acid treatment 12 is dehydrated to a mixture of the condensed five-membered [2.2]paracyclophane derivatives 18–20, whereas 15 yields a mixture of the isomeric cyclopentadienones 21–23. The structures of these elimination products are also deduced from X-ray and spectroscopic data. The sequence presented here constitutes the simplest route so far to cyclophanes carrying an annelated five-membered ring.

Band Gap Engineering of Titania Systems Purposed for Photocatalytic Activity

Science.gov (United States)

Thurston, Cameron

Ab initio computer aided design drastically increases candidate population for highly specified material discovery and selection. These simulations, carried out through a first-principles computational approach, accurately extrapolate material properties and behavior. Titanium Dioxide (TiO2 ) is one such material that stands to gain a great deal from the use of these simulations. In its anatase form, titania (TiO2 ) has been found to exhibit a band gap nearing 3.2 eV. If titania is to become a viable alternative to other contemporary photoactive materials exhibiting band gaps better suited for the solar spectrum, then the band gap must be subsequently reduced. To lower the energy needed for electronic excitation, both transition metals and non-metals have been extensively researched and are currently viable candidates for the continued reduction of titania's band gap. The introduction of multicomponent atomic doping introduces new energy bands which tend to both reduce the band gap and recombination loss. Ta-N, Nb-N, V-N, Cr-N, Mo-N, and W-N substitutions were studied in titania and subsequent energy and band gap calculations show a favorable band gap reduction in the case of passivated systems.

Multifunctional reduced graphene oxide trigged chemiluminescence resonance energy transfer: Novel signal amplification strategy for photoelectrochemical immunoassay of squamous cell carcinoma antigen.

Science.gov (United States)

Zhang, Yan; Sun, Guoqiang; Yang, Hongmei; Yu, Jinghua; Yan, Mei; Song, Xianrang

2016-05-15

Herein, a photoelectrochemical (PEC) immunoassay is constructed for squamous cell carcinoma antigen (SCCA) detection using zinc oxide nanoflower-bismuth sulfide (Bi2S3) composites as photoactive materials and reduced graphene oxide (rGO) as signal labels. Horseradish peroxidase is used to block sites against nonspecific binding, and then participated in luminol-based chemiluminescence (CL) system. The induced CL emission is acted as an inner light source to excite photoactive materials, simplifying the instrument. A novel signal amplification strategy is stem from rGO because of the rGO acts as an energy acceptor, while luminol serves as a donor to rGO, triggering the CL resonance energy transfer phenomenon between luminol and rGO. Thus, the efficient CL emission to photoactive materials decreases. Furthermore, the signal amplification caused by rGO labeled signal antibodies is related to photogenerated electron-hole pairs: perfect matching of energy levels between rGO and Bi2S3 makes rGO a sink to capture photogenerated electrons from Bi2S3; the increased steric hindrance hinders the electron donor to the surface of Bi2S3 for reaction with the photogenerated holes. On the basis of the novel signal amplification strategy, the proposed immunosensor exhibits excellent analytical performance for PEC detection of SCCA, ranging from 0.8 pg mL(-1) to 80 ng mL(-1) with a low detection limit of 0.21 pg mL(-1). Meanwhile, the designed signal amplification strategy provides a general format for future development of PEC assays. Copyright © 2015 Elsevier B.V. All rights reserved.

Achievement report for fiscal 1997 on development of technologies for practical photovoltaic system under New Sunshine Program. Manufacture of thin-film solar cell and of low-cost/large-area module (Formation of low-temperature film); 1997 nendo taiyoko hatsuden system jitsuyoka gijutsu kaihatsu seika hokokusho. Usukau taiyo denchi no seizo gijutsu kaihatsu, tei cost daimenseki module seizo gijutsu kaihatsu (teion maku keisei gijutsu kaihatsu)

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-03-01

A polycrystalline Si thin film formation technology is developed, which uses the flux process in which a reaction occurs between the target crystal and a flux component which is eutectic. Using this process, a crystal grain relatively large in diameter is obtained at a relatively low temperature. This method is now attracting attention as one of the technologies for producing crystalline Si film for use in thin-film polycrystalline Si solar cells. Especially when Al is used for flux, since Al is automatically doped into the target crystalline Si film, it is expected that the resulting film will serve as the ground for a photoactive layer provided with the BSF (back surface field) function which is important for the improvement of solar cell efficiency. A polycrystalline Si thin film is formed on a 2cm times 2cm-large glass substrate at a temperature not higher than 600 degrees C. It is recognized that films selectively oriented towards the (111) or (100) plane are acquired when other processes are employed. It is expected that the said Al-doped film provides a ground on which a BSF function-provided photoactive layer will be formed. (NEDO)

Enthalpy/entropy contributions to conformational KIEs: theoretical predictions and comparison with experiment.

Science.gov (United States)

Fong, Aaron; Meyer, Matthew P; O'Leary, Daniel J

2013-02-18

Previous theoretical studies of Mislow's doubly-bridged biphenyl ketone 1 and dihydrodimethylphenanthrene 2 have determined significant entropic contributions to their normal (1) and inverse (2) conformational kinetic isotope effects (CKIEs). To broaden our investigation, we have used density functional methods to characterize the potential energy surfaces and vibrational frequencies for ground and transition structures of additional systems with measured CKIEs, including [2.2]-metaparacyclophane-d (3), 1,1'-binaphthyl (4), 2,2'-dibromo-[1,1'-biphenyl]-4,4'-dicarboxylic acid (5), and the 2-(N,N,N-trimethyl)-2'-(N,N-dimethyl)-diaminobiphenyl cation (6). We have also computed CKIEs in a number of systems whose experimental CKIEs are unknown. These include analogs of 1 in which the C=O groups have been replaced with CH₂ (7), O (8), and S (9) atoms and ring-expanded variants of 2 containing CH₂ (10), O (11), S (12), or C=O (13) groups. Vibrational entropy contributes to the CKIEs in all of these systems with the exception of cyclophane 3, whose isotope effect is predicted to be purely enthalpic in origin and whose Bigeleisen-Mayer ZPE term is equivalent to DDH‡. There is variable correspondence between these terms in the other molecules studied, thus identifying additional examples of systems in which the Bigeleisen-Mayer formalism does not correlate with DH/DS dissections.

Enthalpy/Entropy Contributions to Conformational KIEs: Theoretical Predictions and Comparison with Experiment

Directory of Open Access Journals (Sweden)

Aaron Fong

2013-02-01

Full Text Available Previous theoretical studies of Mislow’s doubly-bridged biphenyl ketone 1 and dihydrodimethylphenanthrene 2 have determined significant entropic contributions to their normal (1 and inverse (2 conformational kinetic isotope effects (CKIEs. To broaden our investigation, we have used density functional methods to characterize the potential energy surfaces and vibrational frequencies for ground and transition structures of additional systems with measured CKIEs, including [2.2]-metaparacyclophane-d (3, 1,1'-binaphthyl (4, 2,2'-dibromo-[1,1'-biphenyl]-4,4'-dicarboxylic acid (5, and the 2-(N,N,N-trimethyl-2'-(N,N-dimethyl-diaminobiphenyl cation (6. We have also computed CKIEs in a number of systems whose experimental CKIEs are unknown. These include analogs of 1 in which the C=O groups have been replaced with CH2 (7, O (8, and S (9 atoms and ring-expanded variants of 2 containing CH2 (10, O (11, S (12, or C=O (13 groups. Vibrational entropy contributes to the CKIEs in all of these systems with the exception of cyclophane 3, whose isotope effect is predicted to be purely enthalpic in origin and whose Bigeleisen-Mayer ZPE term is equivalent to ΔΔ H‡. There is variable correspondence between these terms in the other molecules studied, thus identifying additional examples of systems in which the Bigeleisen-Mayer formalism does not correlate with ΔH/ΔS dissections.

Photoisomerization and Photoionization of the photoactive yellow protein chromophore in solution.

NARCIS (Netherlands)

Larsen, D.S.; Vengris, M.; van Stokkum, I.H.M.; van der Horst, M.A.; de Weerd, F.; Hellingwerf, K.J.; van Grondelle, R.

2004-01-01

Dispersed pump-dump-probe spectroscopy has the ability to characterize and identify the underlying ultrafast dynamical processes in complicated chemical and biological systems. This technique builds on traditional pump-probe techniques by exploring both ground- and excited-state dynamics and

Photochemically Powered AgCl Janus Micromotors as a Model System to Understand Ionic Self-Diffusiophoresis.

Science.gov (United States)

Zhou, Chao; Zhang, H P; Tang, Jinyao; Wang, Wei

2018-03-13

Micromotors are an emerging class of micromachines that could find potential applications in biomedicine, environmental remediation, and microscale self-assembly. Understanding their propulsion mechanisms holds the key to their future development. This is especially true for a popular category of micromotors that are driven by asymmetric surface photochemical reactions. Many of these micromotors release ionic species and are propelled via a mechanism termed "ionic self-diffusiophoresis". However, exactly how it operates remains vague. To address this fundamental yet important issue, we have developed a dielectric-AgCl Janus micromotor that clearly moves away from the AgCl side when exposed to UV or strong visible light. Taking advantage of numerical simulations and acoustic levitation techniques, we have provided tentative explanations for its speed decay over time as well as its directionality. In addition, photoactive AgCl micromotors demonstrate interesting gravitactic behaviors that hint at three-dimensional transport or sensing applications. The current work presents a well-controlled and easily fabricated model system to understand chemically powered micromotors, highlighting the usefulness of acoustic levitation for studying active matter free from the effect of boundaries.

Density functional theory study of the conformation and optical properties of hybrid Au(n)-dithienylethene systems (n = 3, 19, 25).

Science.gov (United States)

Fihey, Arnaud; Kloss, Benedikt; Perrier, Aurélie; Maurel, François

2014-07-03

We present a theoretical study of Aun-dithienylethene hybrid systems (n = 3, 19, 25), where the organic molecule is covalently linked to a nanometer-scaled gold nanoparticle (NP). We aim at gaining insights on the optical properties of such photochromic devices and proposing a size-limited gold aggregate model able to recover the optical properties of the experimental system. We thus present a DFT-based calculation scheme to model the ground-state (conformation, energetic parameters) and excited-state properties (UV-visible absorption spectra) of this type of hybrid systems. Within this framework, the structural parameters (adsorption site, orientation, and internal structure of the photochrome) are found to be slightly dependent on the size/shape of the gold aggregate. The influence of the gold fragment on the optical properties of the resulting hybrid system is then discussed with the help of TD-DFT combined with an analysis of the virtual orbitals involved in the photochromic transitions. We show that, for the open hybrid isomer, the number of gold atoms is the key parameter to recover the photoactive properties that are experimentally observed. On the contrary, for hybrid closed systems, the three-dimensional structure of the metallic aggregate is of high impact. We thus conclude that Au25 corresponds to the most appropriate fragment to model nanometer-sized NP-DTE hybrid device.

“One Ring to Bind Them All”—Part I: The Efficiency of the Macrocyclic Scaffold for G-Quadruplex DNA Recognition

Directory of Open Access Journals (Sweden)

David Monchaud

2010-01-01

Full Text Available Macrocyclic scaffolds are particularly attractive for designing selective G-quadruplex ligands essentially because, on one hand, they show a poor affinity for the “standard” B-DNA conformation and, on the other hand, they fit nicely with the external G-quartets of quadruplexes. Stimulated by the pioneering studies on the cationic porphyrin TMPyP4 and the natural product telomestatin, follow-up studies have developed, rapidly leading to a large diversity of macrocyclic structures with remarkable-quadruplex binding properties and biological activities. In this review we summarize the current state of the art in detailing the three main categories of quadruplex-binding macrocycles described so far (telomestatin-like polyheteroarenes, porphyrins and derivatives, polyammonium cyclophanes, and in addressing both synthetic issues and biological aspects.

Photoactive composite on the base of zeolite in process of wastes reducing

International Nuclear Information System (INIS)

Takacova, A.; Matus, P.; Semera, M.; Smolinska, M.

2015-01-01

In this study we used the immobilized heterogeneous system Algae - Fe-ZSM-Pt, for capture and chemical transformation of CO 2 to energy recoverable compounds. The addition of algae culture in a heterogeneous system we specifically added with respect to the content of relatively active natural photosensitizer of chlorophyll a. The results obtained by the technique of SPME-GC-MS in the case of algae culture were identified as products of photodegradation effect on cell membranes. It is ethanol, higher alcohols (C18-C10), fatty acids (linoleic acid, palmitic acid).

The optoelectronic properties of a photosystem I-carbon nanotube hybrid system

International Nuclear Information System (INIS)

Kaniber, Simone M; Holleitner, Alexander W; Simmel, Friedrich C; Carmeli, Itai

2009-01-01

The photoconductance properties of photosystem I (PSI) covalently bound to carbon nanotubes (CNTs) are measured. We demonstrate that the PSI forms active electronic junctions with the CNTs, enabling control of the CNTs' photoconductance by the PSI. In order to electrically contact the photoactive proteins, a cysteine mutant is generated at one end of the PSI by genetic engineering. The CNTs are covalently bound to this reactive group using carbodiimide chemistry. We detect an enhanced photoconductance signal of the hybrid material at photon wavelengths resonant to the absorption maxima of the PSI compared to non-resonant wavelengths. The measurements prove that it is feasible to integrate photosynthetic proteins into optoelectronic circuits at the nanoscale.

The optoelectronic properties of a photosystem I-carbon nanotube hybrid system

Energy Technology Data Exchange (ETDEWEB)

Kaniber, Simone M; Holleitner, Alexander W [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, D-85748 Garching (Germany); Simmel, Friedrich C [LMU Munich, Geschwister-Scholl-Platz 1, D-80539 Muenchen (Germany); Carmeli, Itai, E-mail: holleitner@wsi.tum.d, E-mail: itai@post.tau.ac.i [Chemistry Department and NIBN, Ben Gurion University, 84105 Be' er Sheva (Israel)

2009-08-26

The photoconductance properties of photosystem I (PSI) covalently bound to carbon nanotubes (CNTs) are measured. We demonstrate that the PSI forms active electronic junctions with the CNTs, enabling control of the CNTs' photoconductance by the PSI. In order to electrically contact the photoactive proteins, a cysteine mutant is generated at one end of the PSI by genetic engineering. The CNTs are covalently bound to this reactive group using carbodiimide chemistry. We detect an enhanced photoconductance signal of the hybrid material at photon wavelengths resonant to the absorption maxima of the PSI compared to non-resonant wavelengths. The measurements prove that it is feasible to integrate photosynthetic proteins into optoelectronic circuits at the nanoscale.

Development of a miRNA surface-enhanced Raman scattering assay using benchtop and handheld Raman systems

Science.gov (United States)

Schechinger, Monika; Marks, Haley; Locke, Andrea; Choudhury, Mahua; Cote, Gerard

2018-01-01

DNA-functionalized nanoparticles, when paired with surface-enhanced Raman spectroscopy (SERS), can rapidly detect microRNA. However, widespread use of this approach is hindered by drawbacks associated with large and expensive benchtop Raman microscopes. MicroRNA-17 (miRNA-17) has emerged as a potential epigenetic indicator of preeclampsia, a condition that occurs during pregnancy. Biomarker detection using an SERS point-of-care device could enable prompt diagnosis and prevention as early as the first trimester. Recently, strides have been made in developing portable Raman systems for field applications. An SERS assay for miRNA-17 was assessed and translated from traditional benchtop Raman microscopes to a handheld system. Three different photoactive molecules were compared as potential Raman reporter molecules: a chromophore, malachite green isothiocyanate (MGITC), a fluorophore, tetramethylrhodamine isothiocyanate, and a polarizable small molecule 5,5-dithio-bis-(2-nitrobenzoic acid) (DTNB). For the benchtop Raman microscope, the DTNB-labeled assay yielded the greatest sensitivity under 532-nm laser excitation, but the MGITC-labeled assay prevailed at 785 nm. Conversely, DTNB was preferable for the miniaturized 785-nm Raman system. This comparison showed significant SERS enhancement variation in response to 1-nM miRNA-17, implying that the sensitivity of the assay may be more heavily dependent on the excitation wavelength, instrumentation, and Raman reporter chosen than on the plasmonic coupling from DNA/miRNA-mediated nanoparticle assemblies.

Fabrication of flower-like direct Z-scheme β-Bi2O3/g-C3N4 photocatalyst with enhanced visible light photoactivity for Rhodamine B degradation

Science.gov (United States)

Zhang, Liping; Wang, Guohong; Xiong, Zhenzhong; Tang, Hua; Jiang, Chuanjia

2018-04-01

A combined hydrothermal-calcination approach is developed to synthesize hierarchical β-Bi2O3/g-C3N4 direct Z-scheme photocatalyst with enhanced visible light photoactivity for Rhodamine B (RhB) degradation. First, Bi2O2CO3 microflowers were hydrothermally prepared using Bi(NO3)3·5H2O as feedstocks, and then a series of β-Bi2O3/g-C3N4 direct Z-scheme photocatalysts were synthesized via a facile calcination method using Bi2O2CO3 and g-C3N4 as precursors. The samples were systematically characterized by various characterization technologies including X-ray diffraction, scanning and transmission electron microscopes, Fourier transform infrared spectroscopy and N2 absorption-desorption equipment. It was found that the g-C3N4 content in the precursors played a key role in affecting the photocatalytic activity of the final products. The β-Bi2O3/g-C3N4 heterojunction exhibited higher photocatalytic activity than single active components (β-Bi2O3 and g-C3N4), indicating the presence of a synergistic effect between two active components in β-Bi2O3/g-C3N4 heterojunction. Among all as-prepared catalysts, the 70 wt.% g-C3N4/Bi2O2CO3 exhibits the highest activity for RhB degradation, and the apparent reaction rate constant k (42.2 × 10-3 min-1) is 3.1 and 1.7 times as high as that of pure β-Bi2O3 (13.5 × 10-3 min-1) and g-C3N4 (25.2 × 10-3 min-1), respectively. The enhanced photocatalytic performance of β-Bi2O3/g-C3N4 heterostructure photocatalysts is mainly due to the high surface area, closely contacted interfaces between the β-Bi2O3 and g-C3N4 component, and the formation of direct Z-scheme structure in the β-Bi2O3/g-C3N4 composites.

Photo-induced isomerization of ethylene-bridged azobenzene explored by ab initio based non-adiabatic dynamics simulation: A comparative investigation of the isomerization in the gas and solution phases

Energy Technology Data Exchange (ETDEWEB)

Cao Jun; Liu Lihong; Fang Weihai [Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875 (China); Xie Zhizhong [Department of Chemistry, School of Science, Wuhan University of Technology, Wuhan 430070 (China); Zhang Yong [Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030 (United States)

2013-04-07

Azobenzene is one of the most widely used photoactive units and recently an ethylene-bridged azobenzene (BAB) was reported to have greatly enhanced conversion efficiency, quantum yield, and other favorable properties. As the first step towards exploring its photo-switchable character in real systems, we report here a systematic study on the photoisomerization dynamics between trans (E) and cis (Z) isomers in the gas phase and the CH{sub 3}OH solution, using ab initio based surface hopping and molecular dynamics, which is the first report of dynamics simulation to reveal the environmental effects on BAB photoreactions. Results show that while the relatively faster S{sub 1} relaxation of the photo-induced E{yields}Z process is only mildly affected by the solvent effect, the relatively slower S{sub 1} relaxation of the reverse reaction becomes even slower in the solution compared to the gas phase. The subsequent S{sub 0} dynamics from the conical intersection between S{sub 1} and S{sub 0} (CI{sub E}) to Z is accelerated in solution compared to the gas phase because of avoided re-crossing to the S{sub 1} state, while the S{sub 0} dynamics from the conical intersection between S{sub 1} and S{sub 0} (CI{sub Z}) to E are basically the same in both phases. Overall, the solvent effect was found to enhance the back-and-forth photo-switch efficiency between the Z and E isomers compared to the gas phase, while the quantum yields are reduced. But the solution yields of both the forward and backward photoreactions are still around 0.4. Therefore, BAB may have good photo-responsive properties if used as a photoactive unit in real systems. These results will facilitate future experimental and theoretical studies in this area to help design new azobenzene derivatives as photoactive units in biological processes, nanoscale devices, and photo-responsive materials.

TiO2-SiO2 Coatings with a Low Content of AuNPs for Producing Self-Cleaning Building Materials

Directory of Open Access Journals (Sweden)

Manuel Luna

2018-03-01

Full Text Available The high pollution levels in our cities are producing a significant increase of dust on buildings. An application of photoactive coatings on building materials can produce buildings with self-cleaning surfaces. In this study, we have developed a simple sol-gel route for producing Au-TiO2/SiO2 photocatalysts with application on buildings. The gold nanoparticles (AuNPs improved the TiO2 photoactivity under solar radiation because they promoted absorption in the visible range. We varied the content of AuNPs in the sols under study, in order to investigate their effect on self-cleaning properties. The sols obtained were sprayed on a common building stone, producing coatings which adhere firmly to the stone and preserve their aesthetic qualities. We studied the decolourization efficiency of the photocatalysts under study against methylene blue and against soot (a real staining agent for buildings. Finally, we established that the coating with an intermediate Au content presented the best self-cleaning performance, due to the role played by its structure and texture on its photoactivity.

One-step synthesis of highly active Ti-containing Cr-modified MCM-48 mesoporous material and the photocatalytic performance for decomposition of H{sub 2}S under visible light

Energy Technology Data Exchange (ETDEWEB)

Wang Zhen; Ci Xinbo; Dai Hongjun; Yin Lu [Department of Environmental Engineering, Zhejiang University, Hangzhou 310027 (China); Shi Huixiang, E-mail: lanyueheyu@163.com [Department of Environmental Engineering, Zhejiang University, Hangzhou 310027 (China)

2012-08-01

A highly photoactive Ti-containing Cr-modified MCM-48 photocatalyst (Si/Ti = 3.4, Si/Cr = 50) was prepared by a facile one-step method at room temperature. A combination of various physicochemical techniques such as X-ray diffraction (XRD), N{sub 2} physisorption, diffuse reflectance UV-vis spectra (DRS) and X-ray photoelectron spectra (XPS) were used to characterize the properties of the synthetic catalysts. The characterization and experimental results indicated that tetrahedral Ti oxide moieties as dominant Ti oxide were loaded into the mesoporous structure and there was a synergistic interaction between the Ti species anchored on the walls and the Cr ions presented in the MCM-48 framework, which was considered to be directly correlated to the photoactivity. The Ti-Cr-MCM-48 sample can remove H{sub 2}S with the efficiency of 92% under visible light, being the Cr{sup 6+} species primarily responsible for this photoactivity. A deactivation was observed as a consequence of sulfate accumulation on the surface of the catalyst and reduction of Cr{sup 6+}.

Reliable Screening of Dye Phototoxicity by Using a Caenorhabditis elegans Fast Bioassay.

Directory of Open Access Journals (Sweden)

Javier Ignacio Bianchi

Full Text Available Phototoxicity consists in the capability of certain innocuous molecules to become toxic when subjected to suitable illumination. In order to discover new photoactive drugs or characterize phototoxic pollutants, it would be advantageous to use simple biological tests of phototoxicy. In this work, we present a pilot screening of 37 dyes to test for phototoxic effects in the roundworm Caenorhabditis elegans. Populations of this nematode were treated with different dyes, and subsequently exposed to 30 min of white light. Behavioral outcomes were quantified by recording the global motility using an infrared tracking device (WMicrotracker. Of the tested compounds, 17 dyes were classified as photoactive, being phloxine B, primuline, eosin Y, acridine orange and rose Bengal the most phototoxic. To assess photoactivity after uptake, compounds were retested after washing them out of the medium before light irradiation. Dye uptake into the worms was also analyzed by staining or fluorescence. All the positive drugs were incorporated by animals and produced phototoxic effects after washing. We also tested the stress response being triggered by the treatments through reporter strains. Endoplasmic reticulum stress response (hsp-4::GFP strain was activated by 22% of phototoxic dyes, and mitochondrial stress response (hsp-6::GFP strain was induced by 16% of phototoxic dyes. These results point to a phototoxic perturbation of the protein functionality and an oxidative stress similar to that reported in cell cultures. Our work shows for the first time the feasibility of C. elegans for running phototoxic screenings and underscores its application on photoactive drugs and environmental pollutants assessment.

FEEDSTOCK-FLEXIBLE REFORMER SYSTEM (FFRS) FOR SOLID OXIDE FUEL CELL (SOFC)- QUALITY SYNGAS

Energy Technology Data Exchange (ETDEWEB)

Jezierski, Kelly; Tadd, Andrew; Schwank, Johannes; Kibler, Roland; McLean, David; Samineni, Mahesh; Smith, Ryan; Parvathikar, Sameer; Mayne, Joe; Westrich, Tom; Mader, Jerry; Faubert, F. Michael

2010-07-30

The U.S. Department of Energy National Energy Technology Laboratory funded this research collaboration effort between NextEnergy and the University of Michigan, who successfully designed, built, and tested a reformer system, which produced highquality syngas for use in SOFC and other applications, and a novel reactor system, which allowed for facile illumination of photocatalysts. Carbon and raw biomass gasification, sulfur tolerance of non-Platinum Group Metals (PGM) based (Ni/CeZrO2) reforming catalysts, photocatalysis reactions based on TiO2, and mild pyrolysis of biomass in ionic liquids (ILs) were investigated at low and medium temperatures (primarily 450 to 850 C) in an attempt to retain some structural value of the starting biomass. Despite a wide range of processes and feedstock composition, a literature survey showed that, gasifier products had narrow variation in composition, a restriction used to develop operating schemes for syngas cleanup. Three distinct reaction conditions were investigated: equilibrium, autothermal reforming of hydrocarbons, and the addition of O2 and steam to match the final (C/H/O) composition. Initial results showed rapid and significant deactivation of Ni/CeZrO2 catalysts upon introduction of thiophene, but both stable and unstable performance in the presence of sulfur were obtained. The key linkage appeared to be the hydrodesulfurization activity of the Ni reforming catalysts. For feed stoichiometries where high H2 production was thermodynamically favored, stable, albeit lower, H2 and CO production were obtained; but lower thermodynamic H2 concentrations resulted in continued catalyst deactivation and eventual poisoning. High H2 levels resulted in thiophene converting to H2S and S surface desorption, leading to stable performance; low H2 levels resulted in unconverted S and loss in H2 and CO production, as well as loss in thiophene conversion. Bimetallic catalysts did not outperform Ni-only catalysts, and small Ni particles were

Photoactive Zn(II)Porphyrin–multi-walled carbon nanotubes nanohybrids through covalent β-linkages

Energy Technology Data Exchange (ETDEWEB)

Lipińska, Monika E., E-mail: m.e.lipinska@gmail.com [REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal); Rebelo, Susana L.H., E-mail: susana.rebelo@fc.up.pt [REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal); Pereira, M. Fernando R., E-mail: fpereira@fe.up.pt [Laboratório de Catálise e Materiais (LCM), Laboratório Associado LSRE/LCM, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto (Portugal); Figueiredo, José L., E-mail: jlfig@fe.up.pt [Laboratório de Catálise e Materiais (LCM), Laboratório Associado LSRE/LCM, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto (Portugal); Freire, Cristina, E-mail: acfreire@fc.up.pt [REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal)

2013-12-16

Donor–acceptor nanohybrids by a covalent linkage between the β-position of a Zn(II)Porphyrin and multi-walled carbon nanotubes are reported for the first time, in a closer analogy to the natural light harvesting systems, which are based on β-substituted porphyrinoid structures, the chlorophylls. An unique and direct connection was established through the immobilization of the Zn(II)(β-NH{sub 2}-tetraphenylporphyrin), using diazonium chemistry, in order to afford i) a short and conjugated linkage between the two aromatic systems and ii) an amide bond resulting from a three-step functionalization synthesis. Electronic and steady-state fluorescence spectroscopies confirmed high photoinduced electron communication through the β-linkage when compared to analogous meso-phenyl linkers, stating its positive effect. The procedure involving the amide linkage allowed higher chromophore loadings; however, the direct conjugated bond showed improved photoinduced activity and a different emission pattern that can be associated with intense communication within the expanded π-system MWCNT–metalloporphyrin. - Graphical abstract: Preparation and photo-induced activity of two donor–acceptor nanohybrids is reported based on different linkages through β-position of porphyrin core to MWCNT, direct conjugation and amide bond. - Highlights: • β-linked Zn(II)Porphyrin–MWCNT nanohybrids were prepared through direct or amide bond. • Efficient and mild functionalizations were achieved using diazonium chemistry. • Good nanohybrid dispersibility was obtained in low boiling point solvent. • Nanohybrids showed strong photoinduced electronic transfer. • The emission quenching was higher for the π-expanded system.

Photoactive Zn(II)Porphyrin–multi-walled carbon nanotubes nanohybrids through covalent β-linkages

International Nuclear Information System (INIS)

Lipińska, Monika E.; Rebelo, Susana L.H.; Pereira, M. Fernando R.; Figueiredo, José L.; Freire, Cristina

2013-01-01

Donor–acceptor nanohybrids by a covalent linkage between the β-position of a Zn(II)Porphyrin and multi-walled carbon nanotubes are reported for the first time, in a closer analogy to the natural light harvesting systems, which are based on β-substituted porphyrinoid structures, the chlorophylls. An unique and direct connection was established through the immobilization of the Zn(II)(β-NH 2 -tetraphenylporphyrin), using diazonium chemistry, in order to afford i) a short and conjugated linkage between the two aromatic systems and ii) an amide bond resulting from a three-step functionalization synthesis. Electronic and steady-state fluorescence spectroscopies confirmed high photoinduced electron communication through the β-linkage when compared to analogous meso-phenyl linkers, stating its positive effect. The procedure involving the amide linkage allowed higher chromophore loadings; however, the direct conjugated bond showed improved photoinduced activity and a different emission pattern that can be associated with intense communication within the expanded π-system MWCNT–metalloporphyrin. - Graphical abstract: Preparation and photo-induced activity of two donor–acceptor nanohybrids is reported based on different linkages through β-position of porphyrin core to MWCNT, direct conjugation and amide bond. - Highlights: • β-linked Zn(II)Porphyrin–MWCNT nanohybrids were prepared through direct or amide bond. • Efficient and mild functionalizations were achieved using diazonium chemistry. • Good nanohybrid dispersibility was obtained in low boiling point solvent. • Nanohybrids showed strong photoinduced electronic transfer. • The emission quenching was higher for the π-expanded system

Reduction of V{sub 2}O{sub 5} thin films deposited by aqueous sol–gel method to VO{sub 2}(B) and investigation of its photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Monfort, Olivier [Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, 842 15 Bratislava (Slovakia); Roch, Tomas; Satrapinskyy, Leonid; Gregor, Maros; Plecenik, Tomas; Plecenik, Andrej [Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University, 842 48 Bratislava (Slovakia); Plesch, Gustav, E-mail: plesch@fns.uniba.sk [Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, 842 15 Bratislava (Slovakia)

2014-12-15

Graphical abstract: - Highlights: • Preparation of VO{sub 2}(B) films by aqueous sol–gel method and their characterization. • Influence of annealing conditions on the mechanism of V{sub 2}O{sub 5} film reduction. • The VO{sub 2}(B) films with energy gap of 2.8 eV show photocatalytic activity. • The films with higher roughness exhibit increased photoactivity. - Abstract: A way of preparation of VO{sub 2}(B) thin films by reduction of V{sub 2}O{sub 5} films synthesized from an aqueous sol–gel system has been developed and photocatalytic properties of the obtained films were studied. The reduction was performed by annealing of the V{sub 2}O{sub 5} film in vacuum as well as in H{sub 2}/Ar atmosphere, which was followed by temperature dependent XRD. It has been shown that the reduction is influenced by the layered-structure of the vanadium oxides. It is a two-step process, where the mixed-valence vanadium oxide V{sub 4}O{sub 9} is first formed before reaching the VO{sub 2}(B) phase. The film microstructure was characterized by SEM and AFM and the valence states of vanadium in VO{sub 2}(B) films were evaluated by XPS. The VO{sub 2}(B) polymorph shows an energy band-gap around 2.8 eV and it exhibits photocatalytic properties. It was measured by following the degradation of rhodamine B under UVA as well as metalhalogenide lamp irradiation, which has similar spectral distribution as natural sunlight. The VO{sub 2}(B) films show distinct photoactivities under both lamps, although they were found to be more active under the UVA irradiation. The film annealed under reducing hydrogen atmosphere, which exhibits higher granularity and surface roughness, shows higher photoactivity than the vacuum-annealed film.

Sol-gel synthesis of TiO2-SiO2 photocatalyst for β-naphthol photodegradation

International Nuclear Information System (INIS)

Qourzal, S.; Barka, N.; Tamimi, M.; Assabbane, A.; Nounah, A.; Ihlal, A.; Ait-Ichou, Y.

2009-01-01

Silica gel supported titanium dioxide particles (TiO 2 -SiO 2 ) prepared by sol-gel method was as photocatalyst in the degradation of β-naphthol in water under UV-illumination. The prepared sample has been characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The supported catalyst had large surface area and good sedimentation ability. The photodegradation rate of β-naphthol under UV-irradiation depended strongly on adsorption capacity of the catalyst, and the photoactivity of the supported catalyst was much higher than that of the pure titanium dioxides. The experiments were measured by high performance liquid chromatography (HPLC). The photodegradation rate of β-naphthol using 60% TiO 2 -SiO 2 particles was faster than that using TiO 2 'Degussa P-25', TiO 2 'PC-50' and TiO 2 'Aldrich' as photocatalyst by 2.7, 4 and 7.8 times, respectively. The kinetics of photocatalytic β-naphthol degradation was found to follow a pseudo-first-order rate law. The effect of the TiO 2 loading on the photoactivity of TiO 2 -SiO 2 particles was also discussed. With good photocatalytic activity under UV-irradiation and the ability to be readily separated from the reaction system, this novel kind of catalyst exhibited the potential effective in the treatment of organic pollutants in aqueous systems.

Constructing Solid-Gas-Interfacial Fenton Reaction over Alkalinized-C3N4 Photocatalyst To Achieve Apparent Quantum Yield of 49% at 420 nm.

Science.gov (United States)

Li, Yunxiang; Ouyang, Shuxin; Xu, Hua; Wang, Xin; Bi, Yingpu; Zhang, Yuanfang; Ye, Jinhua

2016-10-03

Efficient generation of active oxygen-related radicals plays an essential role in boosting advanced oxidation process. To promote photocatalytic oxidation for gaseous pollutant over g-C 3 N 4 , a solid-gas interfacial Fenton reaction is coupled into alkalinized g-C 3 N 4 -based photocatalyst to effectively convert photocatalytic generation of H 2 O 2 into oxygen-related radicals. This system includes light energy as power, alkalinized g-C 3 N 4 -based photocatalyst as an in situ and robust H 2 O 2 generator, and surface-decorated Fe 3+ as a trigger of H 2 O 2 conversion, which attains highly efficient and universal activity for photodegradation of volatile organic compounds (VOCs). Taking the photooxidation of isopropanol as model reaction, this system achieves a photoactivity of 2-3 orders of magnitude higher than that of pristine g-C 3 N 4 , which corresponds to a high apparent quantum yield of 49% at around 420 nm. In-situ electron spin resonance (ESR) spectroscopy and sacrificial-reagent incorporated photocatalytic characterizations indicate that the notable photoactivity promotion could be ascribed to the collaboration between photocarriers (electrons and holes) and Fenton process to produce abundant and reactive oxygen-related radicals. The strategy of coupling solid-gas interfacial Fenton process into semiconductor-based photocatalysis provides a facile and promising solution to the remediation of air pollution via solar energy.

Finding the lost open-circuit voltage in polymer solar cells by UV-ozone treatment of the nickel acetate anode buffer layer.

Science.gov (United States)

Wang, Fuzhi; Sun, Gang; Li, Cong; Liu, Jiyan; Hu, Siqian; Zheng, Hua; Tan, Zhan'ao; Li, Yongfang

2014-06-25

Efficient polymer solar cells (PSCs) with enhanced open-circuit voltage (Voc) are fabricated by introducing solution-processed and UV-ozone (UVO)-treated nickel acetate (O-NiAc) as an anode buffer layer. According to X-ray photoelectron spectroscopy data, NiAc partially decomposed to NiOOH during the UVO treatment. NiOOH is a dipole species, which leads to an increase in the work function (as confirmed by ultraviolet photoemission spectroscopy), thus benefitting the formation of ohmic contact between the anode and photoactive layer and leading to increased Voc. In addition, the UVO treatment improves the wettability between the substrate and solvent of the active layer, which facilitates the formation of an upper photoactive layer with better morphology. Further, the O-NiAc layer can decrease the series resistance (Rs) and increase the parallel resistance (Rp) of the devices, inducing enhanced Voc in comparison with the as-prepared NiAc-buffered control devices without UVO treatment. For PSCs based on the P3HT:PCBM system, Voc increases from 0.50 to 0.60 V after the NiAc buffer layer undergoes UVO treatment. Similarly, in the P3HT:ICBA system, the Voc value of the device with a UVO-treated NiAc buffer layer increases from 0.78 to 0.88 V, showing an enhanced power conversion efficiency of 6.64%.

Transparent Low Molecular Weight Poly(Ethylene Glycol Diacrylate-Based Hydrogels as Film Media for Photoswitchable Drugs

Directory of Open Access Journals (Sweden)

Théophile Pelras

2017-11-01

Full Text Available Hydrogels have shown a great potential as materials for drug delivery systems thanks to their usually excellent bio-compatibility and their ability to trap water-soluble organic molecules in a porous network. In this study, poly(ethylene glycol-based hydrogels containing a model dye were synthesized by ultraviolet (UV-A photopolymerization of low-molecular weight macro-monomers and the material properties (dye release ability, transparency, morphology, and polymerization kinetics were studied. Real-time infrared measurements revealed that the photopolymerization of the materials was strongly limited when the dye was added to the uncured formulation. Consequently, the procedure was adapted to allow for the formation of sufficiently cured gels that are able to capture and later on to release dye molecules in phosphate-buffered saline solution within a few hours. Due to the transparency of the materials in the 400–800 nm range, the hydrogels are suitable for the loading and excitation of photoactive molecules. These can be uptaken by and released from the polymer matrix. Therefore, such materials may find applications as cheap and tailored materials in photodynamic therapy (i.e., light-induced treatment of skin infections by bacteria, fungi, and viruses using photoactive drugs.

Development of a miRNA surface-enhanced Raman scattering assay using benchtop and handheld Raman systems.

Science.gov (United States)

Schechinger, Monika; Marks, Haley; Locke, Andrea; Choudhury, Mahua; Cote, Gerard

2018-01-01

DNA-functionalized nanoparticles, when paired with surface-enhanced Raman spectroscopy (SERS), can rapidly detect microRNA. However, widespread use of this approach is hindered by drawbacks associated with large and expensive benchtop Raman microscopes. MicroRNA-17 (miRNA-17) has emerged as a potential epigenetic indicator of preeclampsia, a condition that occurs during pregnancy. Biomarker detection using an SERS point-of-care device could enable prompt diagnosis and prevention as early as the first trimester. Recently, strides have been made in developing portable Raman systems for field applications. An SERS assay for miRNA-17 was assessed and translated from traditional benchtop Raman microscopes to a handheld system. Three different photoactive molecules were compared as potential Raman reporter molecules: a chromophore, malachite green isothiocyanate (MGITC), a fluorophore, tetramethylrhodamine isothiocyanate, and a polarizable small molecule 5,5-dithio-bis-(2-nitrobenzoic acid) (DTNB). For the benchtop Raman microscope, the DTNB-labeled assay yielded the greatest sensitivity under 532-nm laser excitation, but the MGITC-labeled assay prevailed at 785 nm. Conversely, DTNB was preferable for the miniaturized 785-nm Raman system. This comparison showed significant SERS enhancement variation in response to 1-nM miRNA-17, implying that the sensitivity of the assay may be more heavily dependent on the excitation wavelength, instrumentation, and Raman reporter chosen than on the plasmonic coupling from DNA/miRNA-mediated nanoparticle assemblies. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Photochemical reactions in biological systems: probing the effect of the environment by means of hybrid quantum chemistry/molecular mechanics simulations.

Science.gov (United States)

Boggio-Pasqua, Martial; Burmeister, Carl F; Robb, Michael A; Groenhof, Gerrit

2012-06-14

Organisms have evolved a wide variety of mechanisms to utilize and respond to light. In many cases, the biological response is mediated by structural changes that follow photon absorption in a protein complex. The initial step in such cases is normally the photoisomerization of a highly conjugated prosthetic group. To understand better the factors controlling the isomerization, we perform atomistic molecular dynamics simulations. In this perspective article we briefly review the key theoretical concepts of photochemical reactions and present a practical simulation scheme for simulating photochemical reactions in biomolecular systems. In our scheme, a multi-configurational quantum mechanical description is used to model the electronic rearrangement for those parts of the system that are involved in the photon absorption. For the remainder, typically consisting of the apo-protein and the solvent, a simple force field model is used. The interactions in the systems are thus computed within a hybrid quantum/classical framework. Forces are calculated on-the-fly, and a diabatic surface hopping procedure is used to model the excited-state decay. To demonstrate how this method is used we review our studies on photoactivation of the photoactive yellow protein, a bacterial photoreceptor. We will show what information can be obtained from the simulations, and, by comparing to recent experimental findings, what the limitations of our simulations are.

Enhancing the photocatalytic properties of TiO2 by coupling with carbon nanotubes and supporting gold

International Nuclear Information System (INIS)

Wang, Huihu; Dong, Shijie; Chang, Ying; Faria, Joaquim L.

2012-01-01

Highlights: ► Au–CNT–TiO 2 composites were synthesized by coupling CNT and Au to TiO 2 . ► The activity of Au–CNT–TiO 2 materials is higher than that of CNT–TiO 2 and Au–TiO 2 . ► The Au–CNT–TiO 2 composites possess both advantages of CNTs and Au. ► The Au–CNT–TiO 2 composites also overcome the disadvantages of surplus CNTs addition. - Abstract: The photodegradation of methylene blue in aqueous solutions is studied using various photocatalysts, including neat TiO 2 , CNT–TiO 2 , Au–TiO 2 , and Au–CNT–TiO 2 composites MB. Materials were synthesized and extensively characterized by XRD, TEM, DRFIT spectroscopy, N 2 adsorption–desorption isotherms, as well as diffuse reflectance UV–vis spectroscopy. By using CNT–TiO 2 composite as catalysts, it was found that CNT act as adsorbent and photosensitizer to improve the photoactivity of neat TiO 2 . Among the CNT–TiO 2 composites with different CNT weight ratio (0.2–20%), the 2%CNT–TiO 2 shows the best photoactivity. When CNT content is larger than 2%, the surplus CNT may absorb and scatter light photons. Combined with the decrease of TiO 2 amount in composite, the photoactivity is reduced. To further improve the photoactivity of 2%CNT–TiO 2 , different Au loads varying from 0.25% to 1% were introduced by the deposition–precipitation method. The 0.25%Au–2%CNT–TiO 2 composite had the highest photoactivity. The increase in activity was explained by the surface plasmon resonance of Au that makes the composite to absorb more photons than the 2%CNT–TiO 2 , thus overcoming the disadvantages of surplus CNT addition. On the other hand, 0.25%Au–2%CNT–TiO 2 composite also presents higher activity than 0.25%Au–TiO 2 due to higher adsorption capacity provided by CNT introduction. The addition of CNT and Au simultaneously has a much stronger synergic role than when each of them is introduced individually.

Synthesis of Poly(3,4,5-trihydroxybenzoate) dendrimers from Polyphenols and Their Chemiluminescence

International Nuclear Information System (INIS)

Jung, Dai Il; Song, Ju Hyun; Shin, Eun Hye; Kim, Yun Young; Lee, Do Hun; Choi, Soon Kyu; Hahn, Jung Tai

2010-01-01

Polyphenol dendrimers were synthesized to obtain a strong CL compound, and their CL intensities were found to be considerably stronger than the CL intensity of GA. The esterification of the hydroxyl groups of GA in the dendrimer was very effective in developing a strong CL. Further, the relationship between the CL intensity and structure of polyphenol dendrimers must be clarified to understand the reason behind the strong light emission of high-per-branch compounds such as poly(3,4,5-trihydroxybenzoate ester) dendrimers. Polyphenol CL dendrimers can be used for a wide variety of CL assays by utilizing the hydroxyl groups of the polyphenol for forming a hydrogen bond with oxygen in the analyte structure. Dendrimer chemistry is rapidly expanding both for fundamental reasons as well as due to requirements in technological applications. A recent interesting development in dendrimer chemistry concerns the coordination of metal ions by interior branches or exterior units. Dendrimers containing photoactive units are particularly interesting for two reasons: (1) cooperation among the photoactive components can allow the dendrimer to perform specific functions, and (2) changes in the properties of photoactive components can be exploited to monitor the participation of dendrimers in chemical processes

Implementation of a submicrometer patterning technique in azopolymer films towards optimization of photovoltaic solar cells efficiency

International Nuclear Information System (INIS)

Cocoyer, C.; Rocha, L.; Fiorini-Debuisschert, C.; Sicot, L.; Vaufrey, D.; Sentein, C.; Geffroy, B.; Raimond, P.

2006-01-01

The weak absorption of the photoactive layer appears as a one of the main factors limiting organic photovoltaic solar cells performances. In order to increase the interaction of the incident light with the photoactive materials, we investigate the effect of a periodic patterning of the solar cells surface with microstructures in the optical wavelength scale. In this aim, we present an original all optical patterning technique of polymer films. The method is based on a laser controlled mass transport in azopolymer films leading to efficient deformation of the film surface in conjunction with the incoming light interference pattern. The technique is used to pattern one-dimensional gratings on the surface of solar cells. In the work presented here, the cell photoactive material is based on the interpenetrated network of a conjugated donor polymer and a fullerene derivative. The cells investigated are illuminated in a reverse configuration through a semi-transparent top cathode. The effect of the periodic structures onto the incident light propagation has been investigated through optical characterizations. We demonstrate that a part of the incident light can be trapped inside the solar cell layers due to diffraction onto the periodic structures

DNA-templated photonic arrays and assemblies: design principles and future opportunities.

Science.gov (United States)

Su, Wu; Bonnard, Vanessa; Burley, Glenn A

2011-07-11

Molecular photonics is a rapidly developing and multi-disciplinary field of research involving the construction of molecular assemblies comprising photoactive building blocks that are responsive to a light stimulus. A salient challenge in this field is the controlled assembly of these building blocks with nanoscale precision. DNA exhibits considerable promise as an architecture for the templated assembly of photoactive materials. In this Concept Article we describe the progress that has been made in the area of DNA photonics, in which DNA acts as a platform for the construction of optoelectronic assemblies, thin films and devices. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Three-dimensional aromatic networks.

Science.gov (United States)

Toyota, Shinji; Iwanaga, Tetsuo

2014-01-01

Three-dimensional (3D) networks consisting of aromatic units and linkers are reviewed from various aspects. To understand principles for the construction of such compounds, we generalize the roles of building units, the synthetic approaches, and the classification of networks. As fundamental compounds, cyclophanes with large aromatic units and aromatic macrocycles with linear acetylene linkers are highlighted in terms of transannular interactions between aromatic units, conformational preference, and resolution of chiral derivatives. Polycyclic cage compounds are constructed from building units by linkages via covalent bonds, metal-coordination bonds, or hydrogen bonds. Large cage networks often include a wide range of guest species in their cavity to afford novel inclusion compounds. Topological isomers consisting of two or more macrocycles are formed by cyclization of preorganized species. Some complicated topological networks are constructed by self-assembly of simple building units.

Few-Layer MoS2 Nanodomains Decorating TiO2 Nanoparticles: A Case Study for the Photodegradation of Carbamazepine

Directory of Open Access Journals (Sweden)

Sara Cravanzola

2018-03-01

Full Text Available S-doped TiO2 and hybrid MoS2/TiO2 systems have been synthesized, via the sulfidation with H2S of the bare TiO2 and of MoOx supported on TiO2 systems, with the aim of enhancing the photocatalytic properties of TiO2 for the degradation of carbamazepine, an anticonvulsant drug, whose residues and metabolites are usually inefficiently removed in wastewater treatment plants. The focus of this study is to find a relationship between the morphology/structure/surface properties and photoactivity. The full characterization of samples reveals the strong effects of the H2S action on the properties of TiO2, with the formation of defects at the surface, as shown by transmission electron microscopy (TEM and infrared spectroscopy (IR, while also the optical properties are strongly affected by the sulfidation treatment, with changes in the electronic states of TiO2. Meanwhile, the formation of small and thin few-layer MoS2 domains, decorating the TiO2 surface, is evidenced by both high-resolution transmission electron microscopy (HRTEM and UV-Vis/Raman spectroscopies, while Fourier-transform infrared (FTIR spectra give insights into the nature of Ti and Mo surface sites. The most interesting findings of our research are the enhanced photoactivity of the MoS2/TiO2 hybrid photocatalyst toward the carbamazepine mineralization. Surprisingly, the formation of hazardous compounds (i.e., acridine derivatives, usually obtained from carbamazepine, is precluded when treated with MoS2/TiO2 systems.

Ionizing radiation and 5-brom-2'-deoxyuridine as tools for analysis of fundamental mechanism of aging in animals

International Nuclear Information System (INIS)

Akif'ev, A.P.; Potapenbko, A.I.; Rudakovskaya, E.G.

1997-01-01

The influence of gamma-irradiation and 5-brom-2'-deoxyuridine (BUDR) on the life span and behaviour (in photoactivity test) of D.melanogaster was studied. It was found that gamma-irradiation resulted in decrease of life span. However the form of surveys changed only under exposure to doses higher than 500 Gy. Treatment with BUDR distorted the form of survival curves and caused death of insects immediately after exclusion. It also caused abrupt decrease in photoactivity of insects, while irradiation even with very high doses did not affect this feature. It is proposed that initiating substrate in drosophila aging is DNA of nerve cells. The possible relationship between aging regularities and evolutional extinction of eukaryotic species in discussed

Sol-gel synthesis of TiO{sub 2}-SiO{sub 2} photocatalyst for {beta}-naphthol photodegradation

Energy Technology Data Exchange (ETDEWEB)

Qourzal, S., E-mail: samir_qourzal@yahoo.fr [Equipe de Materiaux Photocatalyse et Environnement, Departement de Chimie, Faculte des Sciences, Universite Ibn Zohr, B. P. 8106 Cite Dakhla, Agadir (Morocco); Barka, N.; Tamimi, M.; Assabbane, A. [Equipe de Materiaux Photocatalyse et Environnement, Departement de Chimie, Faculte des Sciences, Universite Ibn Zohr, B. P. 8106 Cite Dakhla, Agadir (Morocco); Nounah, A. [Ecole Superieure de Technologie, Avenue Prince Heritier Sidi Mohamed, B. P. 227, Sale-Medina (Morocco); Ihlal, A. [Laboratoire de Physique des Semi-conducteurs et Energie Solaire, Departement de Physique, Faculte, des Sciences, Universite Ibn Zohr, B. P. 8106 Cite Dakhla, Agadir (Morocco); Ait-Ichou, Y. [Equipe de Materiaux Photocatalyse et Environnement, Departement de Chimie, Faculte des Sciences, Universite Ibn Zohr, B. P. 8106 Cite Dakhla, Agadir (Morocco)

2009-06-01

Silica gel supported titanium dioxide particles (TiO{sub 2}-SiO{sub 2}) prepared by sol-gel method was as photocatalyst in the degradation of {beta}-naphthol in water under UV-illumination. The prepared sample has been characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The supported catalyst had large surface area and good sedimentation ability. The photodegradation rate of {beta}-naphthol under UV-irradiation depended strongly on adsorption capacity of the catalyst, and the photoactivity of the supported catalyst was much higher than that of the pure titanium dioxides. The experiments were measured by high performance liquid chromatography (HPLC). The photodegradation rate of {beta}-naphthol using 60% TiO{sub 2}-SiO{sub 2} particles was faster than that using TiO{sub 2} 'Degussa P-25', TiO{sub 2} 'PC-50' and TiO{sub 2} 'Aldrich' as photocatalyst by 2.7, 4 and 7.8 times, respectively. The kinetics of photocatalytic {beta}-naphthol degradation was found to follow a pseudo-first-order rate law. The effect of the TiO{sub 2} loading on the photoactivity of TiO{sub 2}-SiO{sub 2} particles was also discussed. With good photocatalytic activity under UV-irradiation and the ability to be readily separated from the reaction system, this novel kind of catalyst exhibited the potential effective in the treatment of organic pollutants in aqueous systems.

Photocatalytic effects of titanium dioxide nanoparticles on aquatic organisms—Current knowledge and suggestions for future research

Energy Technology Data Exchange (ETDEWEB)

Haynes, Vena N., E-mail: vena.haynes@uconn.edu [University of Connecticut, Department of Marine Sciences, 1080 Shennecossett Road, Groton, CT 06340 (United States); Ward, J. Evan, E-mail: evan.ward@uconn.edu [University of Connecticut, Department of Marine Sciences, 1080 Shennecossett Road, Groton, CT 06340 (United States); Russell, Brandon J., E-mail: brandon.russell@uconn.edu [University of Connecticut, Department of Marine Sciences, 1080 Shennecossett Road, Groton, CT 06340 (United States); Agrios, Alexander G., E-mail: agrios@engr.uconn.edu [University of Connecticut, Department of Civil & Environmental Engineering, 261 Glenbrook Road Unit 3037, Storrs, CT 06269 (United States)

2017-04-15

Highlights: • Ecotoxicological approaches are needed to predict effects of photoactive nanomaterials. • Research on effects of photoactive nanomaterials must include defined light fields. • Light fields must be appropriate for depth, latitude, season and water properties. • Physicochemical properties of water can alter light fields and photoreactivity. - Abstract: Nanoparticles are entering natural systems through product usage, industrial waste and post-consumer material degradation. As the production of nanoparticles is expected to increase in the next decade, so too are predicted environmental loads. Engineered metal-oxide nanomaterials, such as titanium dioxide, are known for their photocatalytic capabilities. When these nanoparticles are exposed to ultraviolet radiation in the environment, however, they can produce radicals that are harmful to aquatic organisms. There have been a number of studies that have reported the toxicity of titanium dioxide nanoparticles in the absence of light. An increasing number of studies are assessing the interactive effects of nanoparticles and ultraviolet light. However, most of these studies neglect environmentally-relevant experimental conditions. For example, researchers are using nanoparticle concentrations and light intensities that are too high for natural systems, and are ignoring water constituents that can alter the light field. The purpose of this review is to summarize the current knowledge of the photocatalytic effects of TiO{sub 2} nanoparticles on aquatic organisms, discuss the limitations of these studies, and outline environmentally-relevant factors that need to be considered in future experiments.

Enzyme-semiconductor interactions: Routes from fundamental aspects to photoactive devices

Energy Technology Data Exchange (ETDEWEB)

Lewerenz, H.J. [Division of Solar Energy, Hahn-Meitner-Institut GmbH, Berlin (Germany)

2008-09-15

Scanning tunnelling microscopy (STM) experiments at protein-semiconductor systems are analyzed using concepts from applied semiconductor physics such as Fermi level pinning and MIS (metal-insulator-semiconductor) junction electronics. Routes for immobilization of enzymes (proteins) on nanostructured surfaces of MoTe{sub 2} and Si are outlined using so-called DLVO and non-DLVO interaction forces. An overview of the catalytic activity of the imaged enzymes, reverse transcriptases of the retroviruses HIV 1 and AMV (avian myeloblastosis virus), is given including their tertiary structural properties which is revealed also in the STM and tapping mode AFM images. For the interpretation of STM images, a resonant charge transfer mechanism is invoked, based on the potential dependence of the image contrast and the energy band structure of MoTe{sub 2} near the valence band maximum. First analyses of the charge transport from the semiconductor to the STM tip at negative bias of MoTe{sub 2} suggest that the observed uninhibited conductivity in the constant current experiments results from solvation-assisted release of electrons from traps that exist along the polypeptide chains and that charge transport occurs at the circumference of the enzymes where biological water is present. Therefore, charge injection into catalytically active enzymes such as hydrogenase or water oxidase of photosystem I and II with subsequent charge transport to the active sites appears difficult to realize. Possibilities of radiation-less long-distance energy transfer based on the Foerster mechanism, its multichromic extension and on Dexter exciton hopping are considered for catalytically active hybrid inorganic/organic absorber-enzyme structures. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Large-scale photochemical reactions of nanocrystalline suspensions: a promising green chemistry method.

Science.gov (United States)

Veerman, Marcel; Resendiz, Marino J E; Garcia-Garibay, Miguel A

2006-06-08

Photochemical reactions in the solid state can be scaled up from a few milligrams to 10 grams by using colloidal suspensions of a photoactive molecular crystal prepared by the solvent shift method. Pure products are recovered by filtration, and the use of H(2)O as a suspension medium makes this method a very attractive one from a green chemistry perspective. Using the photodecarbonylation of dicumyl ketone (DCK) as a test system, we show that reaction efficiencies in colloidal suspensions rival those observed in solution. [reaction: see text

Solar-Driven Reduction of Aqueous Protons Coupled to Selective Alcohol Oxidation with a Carbon Nitride-Molecular Ni Catalyst System.

Science.gov (United States)

Kasap, Hatice; Caputo, Christine A; Martindale, Benjamin C M; Godin, Robert; Lau, Vincent Wing-Hei; Lotsch, Bettina V; Durrant, James R; Reisner, Erwin

2016-07-27

Solar water-splitting represents an important strategy toward production of the storable and renewable fuel hydrogen. The water oxidation half-reaction typically proceeds with poor efficiency and produces the unprofitable and often damaging product, O2. Herein, we demonstrate an alternative approach and couple solar H2 generation with value-added organic substrate oxidation. Solar irradiation of a cyanamide surface-functionalized melon-type carbon nitride ((NCN)CNx) and a molecular nickel(II) bis(diphosphine) H2-evolution catalyst (NiP) enabled the production of H2 with concomitant selective oxidation of benzylic alcohols to aldehydes in high yield under purely aqueous conditions, at room temperature and ambient pressure. This one-pot system maintained its activity over 24 h, generating products in 1:1 stoichiometry, separated in the gas and solution phases. The (NCN)CNx-NiP system showed an activity of 763 μmol (g CNx)(-1) h(-1) toward H2 and aldehyde production, a Ni-based turnover frequency of 76 h(-1), and an external quantum efficiency of 15% (λ = 360 ± 10 nm). This precious metal-free and nontoxic photocatalytic system displays better performance than an analogous system containing platinum instead of NiP. Transient absorption spectroscopy revealed that the photoactivity of (NCN)CNx is due to efficient substrate oxidation of the material, which outweighs possible charge recombination compared to the nonfunctionalized melon-type carbon nitride. Photoexcited (NCN)CNx in the presence of an organic substrate can accumulate ultralong-lived "trapped electrons", which allow for fuel generation in the dark. The artificial photosynthetic system thereby catalyzes a closed redox cycle showing 100% atom economy and generates two value-added products, a solar chemical, and solar fuel.

Organic photovoltaics: Crosslinking for optimal morphology and stability

KAUST Repository

Rumer, Joseph W.; McCulloch, Iain

2015-01-01

Organic solar cells now exceed 10% efficiency igniting interest not only in the fundamental molecular design of the photoactive semiconducting materials, but also in overlapping fields such as green chemistry, large-scale processing and thin film stability. For these devices to be commercially useful, they must have lifetimes in excess of 10 years. One source of potential instability, is that the two bicontinuous phases of electron donor and acceptor materials in the photoactive thin film bulk heterojunction, change in dimensions over time. Photocrosslinking of the π-conjugated semiconducting donor polymers allows the thin film morphology to be ‘locked’ affording patterned and stable blends with suppressed fullerene acceptor crystallization. This article reviews the performance of crosslinkable polymers, fullerenes and additives used to-date, identifying the most promising.

Organic photovoltaics: Crosslinking for optimal morphology and stability

KAUST Repository

Rumer, Joseph W.

2015-04-25

Organic solar cells now exceed 10% efficiency igniting interest not only in the fundamental molecular design of the photoactive semiconducting materials, but also in overlapping fields such as green chemistry, large-scale processing and thin film stability. For these devices to be commercially useful, they must have lifetimes in excess of 10 years. One source of potential instability, is that the two bicontinuous phases of electron donor and acceptor materials in the photoactive thin film bulk heterojunction, change in dimensions over time. Photocrosslinking of the π-conjugated semiconducting donor polymers allows the thin film morphology to be ‘locked’ affording patterned and stable blends with suppressed fullerene acceptor crystallization. This article reviews the performance of crosslinkable polymers, fullerenes and additives used to-date, identifying the most promising.

A versatile strategy towards non-covalent functionalization of graphene by surface-confined supramolecular self-assembly of Janus tectons

Directory of Open Access Journals (Sweden)

Ping Du

2015-03-01

Full Text Available Two-dimensional (2D, supramolecular self-assembly at surfaces is now well-mastered with several existing examples. However, one remaining challenge to enable future applications in nanoscience is to provide potential functionalities to the physisorbed adlayer. This work reviews a recently developed strategy that addresses this key issue by taking advantage of a new concept, Janus tecton materials. This is a versatile, molecular platform based on the design of three-dimensional (3D building blocks consisting of two faces linked by a cyclophane-type pillar. One face is designed to steer 2D self-assembly onto C(sp2-carbon-based flat surfaces, the other allowing for the desired functionality above the substrate with a well-controlled lateral order. In this way, it is possible to simultaneously obtain a regular, non-covalent paving as well as supramolecular functionalization of graphene, thus opening interesting perspectives for nanoscience applications.

Optical enhancement effects of plasmonic nanostructures on organic photovoltaic cells

KAUST Repository

Park, Hui Joon; Guo, L. Jay

2015-01-01

.g. hundreds of nanometers). Especially, the performances of OPVs with plasmonic nanoparticles in photoactive and buffer layers and with periodic nanostructures were investigated. Furthermore, nanoimprint lithography-based nanofabrication processes that can

High resolution laser beam induced current images under trichromatic laser radiation: approximation to the solar irradiation.

Science.gov (United States)

Navas, F J; Alcántara, R; Fernández-Lorenzo, C; Martín-Calleja, J

2010-03-01

A laser beam induced current (LBIC) map of a photoactive surface is a very useful tool when it is necessary to study the spatial variability of properties such as photoconverter efficiency or factors connected with the recombination of carriers. Obtaining high spatial resolution LBIC maps involves irradiating the photoactive surface with a photonic beam with Gaussian power distribution and with a low dispersion coefficient. Laser emission fulfils these characteristics, but against it is the fact that it is highly monochromatic and therefore has a spectral distribution different to solar emissions. This work presents an instrumental system and procedure to obtain high spatial resolution LBIC maps in conditions approximating solar irradiation. The methodology developed consists of a trichromatic irradiation system based on three sources of laser excitation with emission in the red, green, and blue zones of the electromagnetic spectrum. The relative irradiation powers are determined by either solar spectrum distribution or Planck's emission formula which provides information approximate to the behavior of the system if it were under solar irradiation. In turn, an algorithm and a procedure have been developed to be able to form images based on the scans performed by the three lasers, providing information about the photoconverter efficiency of photovoltaic devices under the irradiation conditions used. This system has been checked with three photosensitive devices based on three different technologies: a commercial silicon photodiode, a commercial photoresistor, and a dye-sensitized solar cell. These devices make it possible to check how the superficial quantum efficiency has areas dependent upon the excitation wavelength while it has been possible to measure global incident photon-to-current efficiency values approximating those that would be obtained under irradiation conditions with sunlight.

Unravelling the pH-dependence of a molecular photocatalytic system for hydrogen production† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5sc01349f Click here for additional data file.

Science.gov (United States)

Pastor, Ernest; Gross, Manuela A.; Selim, Shababa

2015-01-01

Photocatalytic systems for the reduction of aqueous protons are strongly pH-dependent, but the origin of this dependency is still not fully understood. We have studied the effect of different degrees of acidity on the electron transfer dynamics and catalysis taking place in a homogeneous photocatalytic system composed of a phosphonated ruthenium tris(bipyridine) dye (RuP) and a nickel bis(diphosphine) electrocatalyst (NiP) in an aqueous ascorbic acid solution. Our approach is based on transient absorption spectroscopy studies of the efficiency of photo-reduction of RuP and NiP correlated with pH-dependent photocatalytic H2 production and the degree of catalyst protonation. The influence of these factors results in an observed optimum photoactivity at pH 4.5 for the RuP–NiP system. The electron transfer from photo-reduced RuP to NiP is efficient and independent of the pH value of the medium. At pH RuP photo-reduction by the sacrificial electron donor, ascorbic acid. At pH >4.5, the efficiency of the system is limited by the poor protonation of NiP, which inhibits its ability to reduce protons to hydrogen. We have therefore developed a rational strategy utilising transient absorption spectroscopy combined with bulk pH titration, electrocatalytic and photocatalytic experiments to disentangle the complex pH-dependent activity of the homogenous RuP–NiP photocatalytic system, which can be widely applied to other photocatalytic systems. PMID:28717491

Development of a Vsible-Light-Active Film for Direct Solar Energy Storage

Science.gov (United States)

Salazar, Audrey

We conceived of a two-compartment photocatalytic assembly for direct storage of solar energy as chemical potential. Our approach was to maintain reductant and oxidant in separate compartments and develop a visible light (wavelength >400nm) photo-active film to effect an uphill photoreaction between compartments. A proton exchange membrane was included in the assembly to complete the electrical circuit. Towards obtaining a working prototype of the assembly, we developed a freeze-drying method to adhere visible-light photoactive nanoparticles to a self- standing, non-porous and conductive indium tin oxide-polyvinylidene difluoride (ITO-PVDF) support film, developed in-house. We explored the possibility of employing an iron-rich metal oxide as the photocatalytic component of the film and several were explored utilizing the sodium tartrate-assisted photoreduction of Cr(VI) to Cr(III). Although the Fe2O3-coated TiO2 nanoparticles were active for photoreduction, the initial reaction rate was modest and was slowed by substantial deactivation, making it unsuitable as a photo-active material for the composite film. A complete, two-compartment assembly was prepared using cadmium sulfide (CdS) and preliminarily examined for the Cr(VI) probe reaction, however, no catalytic activity was observed. To identify the reason(s) for this observation, further testing of the apparatus and the composite film is required.

MEH-PPV and PCBM Solution Concentration Dependence of Inverted-Type Organic Solar Cells Based on Eosin-Y-Coated ZnO Nanorod Arrays

Directory of Open Access Journals (Sweden)

Riski Titian Ginting

2013-01-01

Full Text Available The influence of polymer solution concentration on the performance of chlorobenzene- (CB- and chloroform- (CF- based inverted-type organic solar cells has been investigated. The organic photoactive layers consisted of poly(2-methoxy-5-(2-ethyl hexyloxy-1,4-phenylenevinylene (MEH-PPV and (6,6-phenyl C61 butyric acid methyl ester (PCBM were spin coated from CF with concentrations of 4, 6, and 8 mg/mL and from CB with concentrations of 6, 8, and 10 mg/mL onto Eosin-Y-coated ZnO nanorod arrays (NRAs. Fluorine doped tin oxide (FTO and silver (Ag were used as electron collecting electrode and hole collecting electrode, respectively. Experimental results showed that the short circuit current density and power conversion efficiency increased with decrease of solution concentration for both CB and CF devices, which could be attributed to reducing charge recombination in thinner photoactive layer and larger contact area between the rougher photoactive layer and Ag contact. However, the open circuit voltage decreased with decreasing solution concentration due to increase of leakage current from ZnO NRAs to Ag as the ZnO NRAs were not fully covered by the polymer blend. The highest power conversion efficiencies of 0.54 ± 0.10% and 0.87 ± 0.15% were achieved at the respective lowest solution concentrations of CB and CF.

Dominance of Plasmonic Resonant Energy Transfer over Direct Electron Transfer in Substantially Enhanced Water Oxidation Activity of BiVO4 by Shape-Controlled Au Nanoparticles.

Science.gov (United States)

Lee, Mi Gyoung; Moon, Cheon Woo; Park, Hoonkee; Sohn, Woonbae; Kang, Sung Bum; Lee, Sanghan; Choi, Kyoung Jin; Jang, Ho Won

2017-10-01

The performance of plasmonic Au nanostructure/metal oxide heterointerface shows great promise in enhancing photoactivity, due to its ability to confine light to the small volume inside the semiconductor and modify the interfacial electronic band structure. While the shape control of Au nanoparticles (NPs) is crucial for moderate bandgap semiconductors, because plasmonic resonance by interband excitations overlaps above the absorption edge of semiconductors, its critical role in water splitting is still not fully understood. Here, first, the plasmonic effects of shape-controlled Au NPs on bismuth vanadate (BiVO 4 ) are studied, and a largely enhanced photoactivity of BiVO 4 is reported by introducing the octahedral Au NPs. The octahedral Au NP/BiVO 4 achieves 2.4 mA cm -2 at the 1.23 V versus reversible hydrogen electrode, which is the threefold enhancement compared to BiVO 4 . It is the highest value among the previously reported plasmonic Au NPs/BiVO 4 . Improved photoactivity is attributed to the localized surface plasmon resonance; direct electron transfer (DET), plasmonic resonant energy transfer (PRET). The PRET can be stressed over DET when considering the moderate bandgap semiconductor. Enhanced water oxidation induced by the shape-controlled Au NPs is applicable to moderate semiconductors, and shows a systematic study to explore new efficient plasmonic solar water splitting cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis, Characterization and Applications of Photoactive Nanomaterials

Science.gov (United States)

2013-08-01

levitated in different media. He was able to make a 3-Dimensional optical trap using counter propagating laser beams, which lead to the development...collection of signal. The resulting emission was guided to a 1/4 m spectrometer (Acton Instruments) and liquid nitrogen cooled CCD camera (Princeton...fabrication techniques used in the semiconductor industry. Even though these techniques are common, they are high cost and not compatible with many

Organic Photovoltaic Structures as Photo-active Electrodes

International Nuclear Information System (INIS)

Gustafson, Matthew P.; Clark, Noel; Winther-Jensen, Bjorn; MacFarlane, Douglas R.

2014-01-01

This study demonstrated the novel use of a bulk heterojunction (BHJ), as present in modern organic solar cells, as a light-assisted electrocatalyst for water electrolysis reactions. Two separate organic photo-voltaic electrode structures were designed for targeting both the reduction, (ITO-PET/PEDOT:PSS/P3HT:PCBM)* and oxidation, (ITO-PET/ZnO/P3HT:PCBM)* reactions of water, denoted as OPE-R and OPE-O respectively. The OPE-R electrode supported both the proton reduction reaction (PRR) and oxygen reduction reaction (ORR) achieving photocurrents of -0.04 mAcm −2 (ORR) and -0.03 mAcm −2 (PRR) and a photovoltage of 0.50 V (ORR) and onset photovoltage at -0.59 V (PRR). By comparison, the OPE-O electrode achieved photocurrents of 0.15 mAcm −2 and photovoltages of 0.35 V for the water oxidation reaction (WOR). Both BHJ designs confirmed evidence of photo-enhanced Bulk Heterojunction Electrode (BHE) activity. The stability and sources of electrode degradation were also studied, with the OPE-O electrode proving to be more stable than the OPE-R electrode, most likely due to the PEDOT:PSS layer and PSS migration in the presence of water. *Indium Tin Oxide (ITO), Polyethylene Terephthalate (PET), Poly(3,4-ethylenedioxythiophene) (PEDOT), Polystyrenesulfonate acid (PSS), Poly(3-hexylthiophene) (P3HT), Phenyl-C 61 -Butyric acid Methyl ester (PCBM), Zinc Oxide (ZnO)

Photoactive oriented films of layered double hydroxides

Czech Academy of Sciences Publication Activity Database

Lang, Kamil; Kubát, Pavel; Mosinger, Jiří; Bujdák, J.; Hof, Martin; Janda, Pavel; Sýkora, Jan; Iyi, N.

2008-01-01

Roč. 10, č. 30 (2008), s. 4429-4434 ISSN 1463-9076 R&D Projects: GA ČR(CZ) GA203/06/1244 Grant - others:VEGA(SK) 2/6180/27; APVV(SK) 027405 Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z40400503 Keywords : singlet oxygen * AFM Subject RIV: CA - Inorganic Chemistry Impact factor: 4.064, year: 2008

The Surface of Hybrid Perovskite Crystals: A Boon or Bane

KAUST Repository

Banavoth, Murali; Yengel, Emre; Yang, Chen; Peng, Wei; Alarousu, Erkki; Bakr, Osman; Mohammed, Omar F.

2017-01-01

Hybrid perovskite single crystals have garnered tremendous research attention and are expected to be next-generation materials for high-efficiency photoactive devices. Therefore, it is fundamentally important to understand the 8 relationship between

Direct femtosecond observation of charge carrier recombination in ternary semiconductor nanocrystals: The effect of composition and shelling

KAUST Repository

Bose, Riya; Ahmed, Ghada H.; Alarousu, Erkki; Parida, Manas R.; Abdelhady, Ahmed L.; Bakr, Osman; Mohammed, Omar F.

2015-01-01

Heavy-metal free ternary semiconductor nanocrystals are emerging as key materials in photoactive applications. However, the relative abundance of intra-bandgap defect states and lack of understanding of their origins within this class

Organic solvent wetting properties of UV and plasma treated ZnO nanorods: printed electronics approach

KAUST Repository

Sliz, Rafal; Suzuki, Yuji; Nathan, Arokia; Myllyla, Risto; Jabbour, Ghassan E.

2012-01-01

Due to low manufacturing costs, printed organic solar cells are on the short-list of renewable and environmentally- friendly energy production technologies of the future. However, electrode materials and each photoactive layer require different

Synthesis, characterizations and photocatalytic studies of mesoporous titania prepared by using four plant skins as templates

Energy Technology Data Exchange (ETDEWEB)

Miao Yingchun [Department of Applied Chemistry, Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, Yunnan University, Kunming 650091 (China); Faculty of Chemical and Life Sciences, Qujing Normal University, Qujing 655000 (China); Zhai Zhongbiao [Department of Applied Chemistry, Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, Yunnan University, Kunming 650091 (China); Kunming Metallurgy Research Institute, Kunming 650031 (China); He Jiao; Li Bin; Li Junjie [Department of Applied Chemistry, Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, Yunnan University, Kunming 650091 (China); Wang Jiaqiang, E-mail: jqwang@ynu.edu.cn [Department of Applied Chemistry, Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, Yunnan University, Kunming 650091 (China)

2010-07-20

Anatase mesoporous titania with novel morphologies were synthesized by using the skins of tomatoes, bulb onions, grapes, and garlic bulbs, respectively, as templates and used for the photodegradation of Gentian violet, methyl violet, xylenol orange, and Rhodamine B under UV light. The samples were characterized by a combination of various physicochemical techniques, such as X-ray diffraction, SEM, HRTEM, N{sub 2} adsorption/desorption, diffuse reflectance UV-Vis, and FT-IR. It was found that all of the synthesized mesoporous titania samples exhibited similar morphologies to those of the original templates. The photoactivity of P25 TiO{sub 2} for the four dyes is nearly the same while the mesoporous titania samples synthesized by using the four skins as templates exhibited varied photoactivities for the four dyes.

Surface Interrogation Scanning Electrochemical Microscopy for a Photoelectrochemical Reaction: Water Oxidation on a Hematite Surface.

Science.gov (United States)

Kim, Jae Young; Ahn, Hyun S; Bard, Allen J

2018-03-06

To understand the pathway of a photoelectrochemical (PEC) reaction, quantitative knowledge of reaction intermediates is important. We describe here surface interrogation scanning electrochemical microscopy for this purpose (PEC SI-SECM), where a light pulse to a photoactive semiconductor film at a given potential generates intermediates that are then analyzed by a tip generated titrant at known times after the light pulse. The improvements were demonstrated for photoelectrochemical water oxidation (oxygen evolution) reaction on a hematite surface. The density of photoactive sites, proposed to be Fe 4+ species, on a hematite surface was successfully quantified, and the photoelectrochemical water oxidation reaction dynamics were elucidated by time-dependent redox titration experiments. The new configuration of PEC SI-SECM should find expanded usage to understand and investigate more complicated PEC reactions with other materials.

Photoreconfigurable polymers for biomedical applications: chemistry and macromolecular engineering.

Science.gov (United States)

Zhu, Congcong; Ninh, Chi; Bettinger, Christopher J

2014-10-13

Stimuli-responsive polymers play an important role in many biomedical technologies. Light responsive polymers are particularly desirable because the parameters of irradiated light and diverse photoactive chemistries produce a large number of combinations between functional materials and associated stimuli. This Review summarizes recent advances in utilizing photoactive chemistries in macromolecules for prospective use in biomedical applications. Special focus is granted to selection criterion when choosing photofunctional groups. Synthetic strategies to incorporate these functionalities into polymers and networks with different topologies are also highlighted herein. Prospective applications of these materials are discussed including programmable matrices for controlled release, dynamic scaffolds for tissue engineering, and functional coatings for medical devices. The article concludes by summarizing the state of the art in photoresponsive polymers for biomedical applications including current challenges and future opportunities.

Automatic generation of active coordinates for quantum dynamics calculations: Application to the dynamics of benzene photochemistry

International Nuclear Information System (INIS)

Lasorne, Benjamin; Sicilia, Fabrizio; Bearpark, Michael J.; Robb, Michael A.; Worth, Graham A.; Blancafort, Lluis

2008-01-01

A new practical method to generate a subspace of active coordinates for quantum dynamics calculations is presented. These reduced coordinates are obtained as the normal modes of an analytical quadratic representation of the energy difference between excited and ground states within the complete active space self-consistent field method. At the Franck-Condon point, the largest negative eigenvalues of this Hessian correspond to the photoactive modes: those that reduce the energy difference and lead to the conical intersection; eigenvalues close to 0 correspond to bath modes, while modes with large positive eigenvalues are photoinactive vibrations, which increase the energy difference. The efficacy of quantum dynamics run in the subspace of the photoactive modes is illustrated with the photochemistry of benzene, where theoretical simulations are designed to assist optimal control experiments

Enhanced photoactivity of graphene/titanium dioxide nanotubes for removal of Acetaminophen

International Nuclear Information System (INIS)

Tao, Hong; Liang, Xiao; Zhang, Qian; Chang, Chang-Tang

2015-01-01

Highlights: • TiO 2 and graphite oxide were used as precursors of titanium dioxide nanotubes and graphene respectively. Titanium dioxide nanotube and graphene (GR-TNT) nanocomposites were synthesized through a simple hydrothermal method. • And its application to removal acetaminophen, degradation efficiency is more than 96%. • The photocatalytic degradation results indicated that the sample with 5% GO in GR-TNT nanocomposites for 3 h had the highest degradation rate. • The degradation intermediates of acetaminophen by the composites were invested by GC-MS and the possible pathways were invested. - Abstract: Acetaminophen is commonly used as an antipyretic or analgesics agent and poses threat to human health. In this research, TiO 2 and graphite oxide were used as precursors of titanium dioxide nanotubes and graphene respectively. Titanium dioxide nanotube and graphene (GR-TNT) nanocomposites were synthesized through a hydrothermal method. FT-IR, UV-Vis, XRD, and TGA were used to characterize the catalysts. The acetaminophen degradation rate can reach up to 96% under UV light irradiation for 3 h and with the 5% GR-TNT dosage of 0.1 g L −1 . Further experiments were done to probe the mechanism of the photocatalytic reaction catalyzed by the GR-TNT composite. EDTA (hole scavengers) and t-BuOH (radical scavengers) were used to detect the main active oxidative species in the system. The results showed that the holes are the main oxidation species in the photocatalytic process. This study provides a new prospect for acetaminophen degradation by using high efficiency catalysts

Doctor Blade-Coated Polymer Solar Cells

KAUST Repository

Cho, Nam Chul

2016-10-25

In this work, we report polymer solar cells based on blade-coated P3HT:PC71BM and PBDTTT-EFT:PC71BM bulk heterojunction photoactive layers. Enhanced power conversion efficiency of 2.75 (conventional structure) and 3.03% (inverted structure) with improved reproducibility was obtained from blade-coated P3HT:PC71BM solar cells, compared to spin-coated ones. Furthermore, by demonstrating 3.10% efficiency flexible solar cells using blade-coated PBDTTT-EFT:PC71BM films on the plastic substrates, we suggest the potential applicability of blade coating technique to the high throughput roll-to-roll fabrication systems.

Journal of Chemical Sciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

-anthraquinone conjugate with an azomethine group separating the two photoactive subunits have been synthesized and characterized by mass (FAB), IR, UV-visible, 1H NMR and ESR spectroscopic techniques and also by cyclic and ...

Temperature-Induced Lattice Relaxation of Perovskite Crystal Enhances Optoelectronic Properties and Solar Cell Performance

KAUST Repository

Banavoth, Murali; Yengel, Emre; Peng, Wei; Chen, Zhijie; Alias, Mohd Sharizal; Alarousu, Erkki; Ooi, Boon S.; Burlakov, Victor; Goriely, Alain; Eddaoudi, Mohamed; Bakr, Osman; Mohammed, Omar F.

2016-01-01

Hybrid organic-inorganic perovskite crystals have recently become one of the most important classes of photoactive materials in the solar cell and optoelectronic communities. Albeit improvements have focused on state-of-the-art technology including

Semiconductor Quantum Dots for Applications to Advanced Concepts for Solar Photon Conversion to Electricity and Solar Fuels

Energy Technology Data Exchange (ETDEWEB)

Nozik, Arthur J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Beard, Matthew C [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2017-11-06

The challenge of photoconversion research is to produce photovoltaic electricity at costs much less than those based on fossil fuels. Novel photoactive semiconductors and molecules of various types and structures are discussed for this purpose.

INFLUENCE OF DOPED-CHARGE TRANSPORT LAYERS ON THE ...

African Journals Online (AJOL)

a

Baehr Str. 1, ... internal quantum efficiency where only the photoactive region absorbs visible light and recombination losses at ... considerable activity has been spurred by their lightweight, potential low-cost, tuneability of the electronic band gap ...

Application of Photosynthesis to Artificial Sight

National Research Council Canada - National Science Library

Greenbaum, B

2001-01-01

.... The goal of this project is insertion of purified Photosystem I (PSI) reaction centers or other photoactive agents into retinal cells where they will restore photoreceptor function to people who suffer from age-related macular degeneration (AMD...

Effect of surface plasmon resonance on the photocatalytic activity of Au/TiO2 under UV/visible illumination.

Science.gov (United States)

Tseng, Yao-Hsuan; Chang, I-Guo; Tai, Yian; Wu, Kung-Wei

2012-01-01

In this study, gold-loaded titanium dioxide was prepared by an impregnation method to investigate the effect of surface plasmon resonance (SPR) on photoactivity. The deposited gold nanoparticles (NPs) absorb visible light because of SPR. The effects of both the gold content and the TiO2 size of Au/TiO2 on SPR and the photocatalytic efficiency were investigated. The morphology, crystal structure, light absorption, emission from the recombination of a photoexcited electron and hole, and the degree of aggregation were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-visible-diffuse reflectance spectra (UV-VIS-DRS), photoluminescence (PL) spectroscopy, and turbidimetry, respectively. Photocatalytic activity was evaluated by the decolorization of methyl orange solution over modified titania under UV and UV/GLED (green light emitting diode) illumination. Au/TiO2 NPs exhibited an absorption peak (530-570 nm) because of SPR. The results of our photocatalytic experiments indicated that the UV-inducedly photocatalytic reaction rate was improved by simultaneously using UV and green light illumination; this corresponds to the adsorption region of SPR. Au/TiO2 could use the enhanced electric field amplitude on the surface of the Au particle in the spectral vicinity of its plasmon resonance and thus improve the photoactivity. Experimental results show that the synergistic effect between UV and green light for the improvement of photoactivity increases with increasing the SPR absorption, which in turn is affected by the Au content and TiO2 size.

Overcoming the efficiency limitations of SnS2 nanoparticle-based bulk heterojunction solar cells

Science.gov (United States)

Tam Nguyen Truong, Nguyen; Kieu Trinh, Thanh; Thanh Hau Pham, Viet; Smith, Ryan P.; Park, Chinho

2018-04-01

This study examined the effects of heat treatment, the electron transport layer, and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) incorporation on the performance of hybrid bulk heterojunction (BHJ) solar cells composed of tin disulfide (SnS2) nanoparticles (NPs) and low band gap energy polymers poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b3,4-b‧]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) or poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b‧]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PBT7). Inserting an electron transport layer (ETL) (i.e., ZnO) on the top of the photoactive layer improved the surface morphology of the photoactive layer, which led to an improvement in charge transport. Moreover, adding a suitable amount of PCBM to the SnS2/polymer active layer enhanced the device performance, such as short circuit current density (J sc) and power conversion efficiency (PCE). In particular, adding 0.5 mg of PCBM to the composite solution led to a 25% and 1.5% improvement in the J sc value and PCE, respectively. The enhanced performance was due mainly to the improvements in the surface morphology of the photoactive layer, charge carrier mobility within the donor-acceptor interface, and carrier collection efficiency at the cathode.

Comparative assessment of the efficiency of Fe-doped TiO2 prepared by two doping methods and photocatalytic degradation of phenol in domestic water suspensions

Directory of Open Access Journals (Sweden)

Mst. Shamsun Nahar, Kiyoshi Hasegawa, Shigehiro Kagaya and Shigeyasu Kuroda

2007-01-01

Full Text Available Fe-doped TiO2 particles responding to visible light were synthesized by impregnation and calcination method using TiO2 particle and Ti element, respectively. The optical and the chemical properties were characterized by measuring the X-ray diffraction (XRD and UV–visible spectroscopy. The onset of absorption shifted to longer wavelengths on doping TiO2 by the calcination process, which showed a better response as compared to the impregnation method. The photocatalytic reactivity was evaluated by the degradation of phenol with impregnated Fe-doped (0.5% w/w in Fe and calcined Fe-doped (FexTi1−xO2, x=0.005 (Fe/Ti molar ratio TiO2 separately in distilled and tap water. The characterization results have confirmed the advanced possibility of correlation between photoactivity and the special property of sulfur-containing calcined Fe-doped TiO2. In case of the coagulation of the undoped A-I and the Fe-doped B-I, the photoactivity showed a decrease due to the presence of natural electrolytes and due to the high pH of tap water, whereas in the case of the coagulation of calcined Fe-doped TiO2 prepared from sulfides (FexTiS2, the photoactivity showed an increase. In this study, highest catalytic activity was found to be strongly dependent both on catalyst structure and on the type of water used.

Fulltext PDF

Indian Academy of Sciences (India)

position of organic impurities in air and water, due to its high photoactivity ..... an additional thermal treatment in air was carried out pro- ducing aggregates with .... and grey solid lines display individual Lorentzian components. varied within a ...

Encapsulation with structured triglycerides

Science.gov (United States)

Lipids provide excellent materials to encapsulate bioactive compounds for food and pharmaceutical applications. Lipids are renewable, biodegradable, and easily modified to provide additional chemical functionality. The use of structured lipids that have been modified with photoactive properties are ...

Effect of PdS on Photocatalytic Hydrogen Evolution of Nanostructured CdS under Visible Light Irradiation

Directory of Open Access Journals (Sweden)

Qingyun Chen

2013-01-01

Full Text Available To investigate the effect of PdS as a cocatalyst for photocatalytic hydrogen evolution, nanostructured PdS/CdS were prepared by an in situ coprecipitation and hydrothermal method, respectively. The as-prepared photocatalysts were characterized by transmission electron microscopy (TEM, X-ray diffraction (XRD, UV-visible absorption spectra, and photoluminescence spectra (PL. With PdS highly dispersed in the CdS nanostructures, the photoactivity was evaluated by hydrogen evolution from aqueous solution containing Na2S/Na2SO3 as sacrificial reagents under visible light irradiation. When the concentration of PdS was 1% by weight, PdS/CdS, prepared by the in situ coprecipitation, showed the highest photocatalytic activity, while that prepared by hydrothermal method showed the most stability for hydrogen evolution. The effect of highly dispersed PdS on the photoactivity was discussed.

Synthesis of a ternary Ag/RGO/ZnO nanocomposite via microwave irradiation and its application for the degradation of Rhodamine B under visible light.

Science.gov (United States)

Surendran, Divya Kollikkara; Xavier, Marilyn Mary; Viswanathan, Vandana Parakkal; Mathew, Suresh

2017-06-01

Reduced graphene oxide supporting plasmonic photocatalyst (Ag) on ZnO has been synthesized via a facile two-step microwave synthesis using RGO/ZnO and AgNO 3 . First step involves fabrication of RGO/ZnO via microwave irradiation. The nanocomposites were characterized by X-ray diffraction analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. Ag/RGO/ZnO shows enhanced photoactivity under visible light for the degradation of Rhodamine B. Enhanced charge separation and migration have been assigned using UV-vis diffuse reflectance spectra, photoluminescence spectra, electrochemical impedance spectra, and TCSPC analysis. The improved photoactivity of Ag/RGO/ZnO can be ascribed to the prolonged lifetime of photogenerated electron-hole pairs and effective interfacial hybridization between RGO and Ag with ZnO nanoparticles. Ag nanoparticles can absorb visible light via surface plasmon resonance to enhance photocatalytic activity.

Theoretical and Experimental Study of Plasmonic Polymer Solar Cells

DEFF Research Database (Denmark)

Mirsafaei, Mina; Adam, Jost; Madsen, Morten

The organic bulk hetero-junction solar cell has remarkable advantages such as low cost, mechanical flexibility and simple process techniques. Recently, low-band gap photoactive materials have obtained a significant attention due to their potential to absorb a wider range of the solar spectrum...... to attain higher power conversion efficiencies. Many low-band gap photoactive materials, however, still show a relatively low external quantum efficiency of less than 60% [1]. One possible approach to improve the device performance is to increase the light absorption in the active layer. This may, amongst...... other approaches, be achieved by using nano- or micro-structures that trap light at specific wavelengths [2], or by using the localized surface plasmon resonance effect of metal nanoparticles in the devices. In this work, we theoretically studied planar polymer solar cell based on finite-difference time...

Nanoparticles and nanoimaging for organic solar cells

DEFF Research Database (Denmark)

Pedersen, Emil Bøje Lind

Solar energy is one of the few energy sources with the potential to power humanity in a future scenario where fossil fuels are not attractive due to their effect on the global climate or fossil fuels have been depleted all together. Organic photovoltaics is a promising technology for solar...... is devoted to studying organic photovolatics on the micro to nanometer scale, in particular photoactive Landfester particles. The ultimate goal is to increase the performance of Landfester particle layers so they can become a viable alternative to photoactive layers cast from organic solvent. Transition...... to a water based ink would provide a production environment without toxic fumes from organic solvents and the nanoparticle structure would provide additional morphological control. The first part of the dissertation maps photodegradation in active layers cast from organic solvents. Reduction in degradation...

Preparation of n- and p-InP films by PH{sub 3} treatment of electrodeposited In layers

Energy Technology Data Exchange (ETDEWEB)

Cattarin, S.; Musiani, M. [C.N.R., Padova (Italy). Istituto di Polarografia ed Elettrochimica Preparativa; Casellato, U.; Rossetto, G. [C.N.R., Padova (Italy). Istituto di Chimica e Tecnologie Inorganische e dei Materiali Avanzati; Razzini, G. [Politecnico di Milano (Italy). Dipt. di Chimica Fisica Applicata; Decker, F.; Scrosati, B. [Univ. La Sapienza, Roma (Italy). Dipt. di Chimica

1995-04-01

InP is among the few semiconducting materials with the potential for excellence in several applications, including solar energy conversion. Thin InP layers have been prepared by electrodeposition of In films on Ti substrates (ca. 2 mg/cm{sup 2} of In) and their annealing in PH{sub 3} flow. The obtained material, characterized by scanning electron microscopy-energy dispersive X-ray analysis and X-ray diffraction techniques, shows uneven substrate coverage but good crystallinity. Photoelectrochemical investigations in acidic polyiodide medium show significant n-type photoactivity for the samples prepared from a nominally pure In layer. A p-type photoactivity is obtained depositing a small amount of Zn on top of the In layer prior to annealing. Results are compared with those obtained preparing InP layers on Ti by a conventional metallorganic chemical vapor deposition technique.

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

KAUST Repository

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

2013-01-01

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

Hybrid Lead Halide Perovskites for Ultrasensitive Photoactive Switching in Terahertz Metamaterial Devices.

Science.gov (United States)

Manjappa, Manukumara; Srivastava, Yogesh Kumar; Solanki, Ankur; Kumar, Abhishek; Sum, Tze Chien; Singh, Ranjan

2017-08-01

The recent meteoric rise in the field of photovoltaics with the discovery of highly efficient solar-cell devices is inspired by solution-processed organic-inorganic lead halide perovskites that exhibit unprecedented light-to-electricity conversion efficiencies. The stunning performance of perovskites is attributed to their strong photoresponsive properties that are thoroughly utilized in designing excellent perovskite solar cells, light-emitting diodes, infrared lasers, and ultrafast photodetectors. However, optoelectronic application of halide perovskites in realizing highly efficient subwavelength photonic devices has remained a challenge. Here, the remarkable photoconductivity of organic-inorganic lead halide perovskites is exploited to demonstrate a hybrid perovskite-metamaterial device that shows extremely low power photoswitching of the metamaterial resonances in the terahertz part of the electromagnetic spectrum. Furthermore, a signature of a coupled phonon-metamaterial resonance is observed at higher pump powers, where the Fano resonance amplitude is extremely weak. In addition, a low threshold, dynamic control of the highly confined electric field intensity is also observed in the system, which could tremendously benefit the new generation of subwavelength photonic devices as active sensors, low threshold optically controlled lasers, and active nonlinear devices with enhanced functionalities in the infrared, optical, and the terahertz parts of the electromagnetic spectrum. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photocytotoxic lanthanide complexes

Indian Academy of Sciences (India)

Among many applications of lanthanides, gadolinium complexes are used as magnetic resonance imaging (MRI) contrast agents in clinical radiology and luminescent lanthanides for bioanalysis, imaging and sensing. The chemistry of photoactive lanthanide complexes showing biological applications is of recent origin.

Solution-Processing of Organic Solar Cells: From In Situ Investigation to Scalable Manufacturing

KAUST Repository

Abdelsamie, Maged

2016-01-01

-cost manufacturing of sufficiently efficient devices at high throughput on large-area rigid or flexible substrates with potentially low energy and carbon footprints. In OPVs, the photoactive layer is made of a bulk heterojunction (BHJ) layer and is typically composed

Trap-Free Hot Carrier Relaxation in Lead–Halide Perovskite Films

KAUST Repository

Bretschneider, Simon A.; Laquai, Fré dé ric; Bonn, Mischa

2017-01-01

Photovoltaic devices that employ lead-halide perovskites as photoactive materials exhibit power conversion efficiencies of 22%. One of the potential routes to go beyond the current efficiencies is to extract charge carriers that carry excess energy, that is, nonrelaxed or

Degradation mechanisms in organic photovoltaic devices

NARCIS (Netherlands)

Grossiord, Nadia; Kroon, Jan M.; Andriessen, Ronn; Blom, Paul W. M.

In the present review, the main degradation mechanisms occurring in the different layer stacking (i.e. photoactive layer, electrode, encapsulation film, interconnection) of polymeric organic solar cells and modules are discussed. Bulk and interfacial, as well as chemical and physical degradation

PHOTOELECTROCHEMICAL SOLAR ENERGY CONVERSION ...

African Journals Online (AJOL)

Preferred Customer

on indium-doped tin oxide (ITO) used as a photoactive electrode; amorphous ... The polymer electrolyte was prepared by dissolving 309 mg of POMOE in 25 mL .... The VOC of Bulk heterojunction (BHJ) based solar cells is strongly correlated ...

The effect of LED illumination on endodontic biofilms

DEFF Research Database (Denmark)

Markvart, Merete

Within endodontics photodynamic therapy (PDT) has been suggested as a disinfectant procedure during root canal treatment. A photoactive dye (photosensitizer), methylene blue or toluidine blue, are activated by a light source, usually lasers or light emitting diodes (LEDs), thereby forming free...

Trap-Free Hot Carrier Relaxation in Lead–Halide Perovskite Films

KAUST Repository

Bretschneider, Simon A.

2017-05-08

Photovoltaic devices that employ lead-halide perovskites as photoactive materials exhibit power conversion efficiencies of 22%. One of the potential routes to go beyond the current efficiencies is to extract charge carriers that carry excess energy, that is, nonrelaxed or

Transparent conductive electrodes of mixed TiO2−x–indium tin oxide for organic photovoltaics

KAUST Repository

Lee, Kyu-Sung; Lim, Jong-Wook; Kim, Han-Ki; Alford, T. L.; Jabbour, Ghassan E.

2012-01-01

A transparent conductive electrode of mixed titanium dioxide (TiO2−x)–indium tin oxide (ITO) with an overall reduction in the use of indium metal is demonstrated. When used in organic photovoltaicdevices based on bulk heterojunction photoactive

Solar Fuel Generator

Science.gov (United States)

Lewis, Nathan S. (Inventor); West, William C. (Inventor)

2017-01-01

The disclosure provides conductive membranes for water splitting and solar fuel generation. The membranes comprise an embedded semiconductive/photoactive material and an oxygen or hydrogen evolution catalyst. Also provided are chassis and cassettes containing the membranes for use in fuel generation.

Identification of a required for recovery of full antenna capacity in OCP-related photoprotective mechanism in cyanobacteria

NARCIS (Netherlands)

Boulay, C.; Wilson, A.; D'Haene, S.; Kirilovsky, D.

2010-01-01

High light can be lethal for photosynthetic organisms. Similar to plants, most cyanobacteria protect themselves from high irradiance by increasing thermal dissipation of excess absorbed energy. The photoactive soluble orange carotenoid protein (OCP) is essential for the triggering of this

Molecular Engineering for Enhanced Charge Transfer in Thin-Film Photoanode.

Science.gov (United States)

Kim, Jeong Soo; Kim, Byung-Man; Kim, Un-Young; Shin, HyeonOh; Nam, Jung Seung; Roh, Deok-Ho; Park, Jun-Hyeok; Kwon, Tae-Hyuk

2017-10-11

We developed three types of dithieno[3,2-b;2',3'-d]thiophene (DTT)-based organic sensitizers for high-performance thin photoactive TiO 2 films and investigated the simple but powerful molecular engineering of different types of bonding between the triarylamine electron donor and the conjugated DTT π-bridge by the introduction of single, double, and triple bonds. As a result, with only 1.3 μm transparent and 2.5-μm TiO 2 scattering layers, the triple-bond sensitizer (T-DAHTDTT) shows the highest power conversion efficiency (η = 8.4%; V OC = 0.73 V, J SC = 15.4 mA·cm -2 , and FF = 0.75) in an iodine electrolyte system under one solar illumination (AM 1.5, 1000 W·m -2 ), followed by the single-bond sensitizer (S-DAHTDTT) (η = 7.6%) and the double-bond sensitizer (D-DAHTDTT) (η = 6.4%). We suggest that the superior performance of T-DAHTDTT comes from enhanced intramolecular charge transfer (ICT) induced by the triple bond. Consequently, T-DAHTDTT exhibits the most active photoelectron injection and charge transport on a TiO 2 film during operation, which leads to the highest photocurrent density among the systems studied. We analyzed these correlations mainly in terms of charge injection efficiency, level of photocharge storage, and charge-transport kinetics. This study suggests that the molecular engineering of a triple bond between the electron donor and the π-bridge of a sensitizer increases the performance of dye-sensitized solar cell (DSC) with a thin photoactive film by enhancing not only J SC through improved ICT but also V OC through the evenly distributed sensitizer surface coverage.

Co-catalysis effect of different morphological facets of as prepared Ag nanostructures for the photocatalytic oxidation reaction by Ag–TiO{sub 2} aqueous slurry

Energy Technology Data Exchange (ETDEWEB)

Kaur, Rupinder; Pal, Bonamali, E-mail: bpal@thapar.edu

2013-12-16

This paper highlights the comparative co-catalytic efficiency of different shapes of prepared Ag nanoparticles of size much larger as well as smaller than titania for the Ag–TiO{sub 2} photocatalysis. Quantum sized Ag nanospheres (4{sup {sub 8}} nm), nanorod (length 70–75 nm and width 30–38 nm), polygonal nanosphere (80–120 nm) and truncated triangles (side length 70–140 nm) are prepared by solvothermal process. The co-catalytic activities of these Ag nanostructures were investigated by mixing them with TiO{sub 2} for the photocatalytic degradation of aqueous salicylic (0.5 mM) and benzoic acid (0.5 mM) under UV light (125 W-Hg arc, 10.4 mW cm{sup −2}) irradiation. The Ag co-catalysis effect imparted to TiO{sub 2} follows as polygonal nanosphere > nanorod > truncated triangle > small nanosphere due to the formation of many Ag–TiO{sub 2} interfaces by a single large-sized Ag nanoparticle than smaller one. As the surface coverage of Ag particles by TiO{sub 2} decreases, the Ag–TiO{sub 2} photoactivity is decreased accordingly. The efficient adsorption of salicylic acid to TiO{sub 2} surface through –COOH and –OH groups render its higher photodegradation rate (1.8–2.7 × 10{sup −2} μmol min{sup −1}) than benzoic acid (1.5–2.5 × 10{sup −2} μmol min{sup −1}) having one chelating –COOH group. Zeta potential and conductance measurement of photoreaction mixture were carried out to investigate the ionic interaction-adsorption of reactant substrates over Ag–TiO{sub 2} surface. - Graphical abstract: This study demonstrated the co-catalysis effect of relatively larger Ag nanostructures of different shapes than TiO{sub 2} for its improved photocatalytic activity during salicylic acid and benzoic acid degradation under UV light (125 W Hg-arc lamp, 10.4 mW cm{sup −2}) irradiation. The co-catalytic ability of Ag is found to exhibit as polygonal nanosphere > nanorod > truncated triangle > small nanosphere relative to bare TiO{sub 2

Tuning optical properties of opal photonic crystals by structural defects engineering

Science.gov (United States)

di Stasio, F.; Cucini, M.; Berti, L.; Comoretto, D.; Abbotto, A.; Bellotto, L.; Manfredi, N.; Marinzi, C.

2009-06-01

We report on the preparation and optical characterization of three dimensional colloidal photonic crystal (PhC) containing an engineered planar defect embedding photoactive push-pull dyes. Free standing polystyrene films having thickness between 0.6 and 3 mm doped with different dipolar chromophores were prepared. These films were sandwiched between two artificial opals creating a PhC structure with planar defect. The system was characterized by reflectance at normal incidence angle (R), variable angle transmittance (T) and photoluminescence spectroscopy (PL) Evidence of defect states were observed in T and R spectra which allow the light to propagate for selected frequencies within the pseudogap (stop band).

New Components for Dye-Sensitized Solar Cells

Directory of Open Access Journals (Sweden)

Stefano Caramori

2010-01-01

Full Text Available Dye-Sensitized Solar Cells (DSSCs are among the most promising solar energy conversion devices of new generation, since coupling ease of fabrication and low cost offer the possibility of building integration in photovoltaic windows and facades. Although in their earliest configuration these systems are close to commercialization, fundamental studies are still required for developing new molecules and materials with more desirable properties as well as improving our understanding of the fundamental processes at the basis of the functioning of photoactive heterogeneous interfaces. In this contribution, some recent advances, made in the effort of improving DSSC devices by finding alternative materials and configurations, are reviewed.

Vapor phase epitaxial growth of FeS sub 2 pyrite and evaluation of the carrier collection in liquid-junction solar cell

Energy Technology Data Exchange (ETDEWEB)

Ennaoui, A.; Schlichthoerl, G.; Fiechter, S.; Tributsch, H. (Hahn-Meitner-Inst., Abt. Solare Energetik und Materialforschung, Berlin (Germany))

1992-01-01

Photoactive epitaxial layers of FeS{sub 2} were grown using bromine as a transport agent and a simple closed ampoule technique. The substrates used were (100)-oriented slices of natural pyrite 1 mm thick. A vapor-liquid-solid (VLS) growth mechanism was elucidated by means of optical microscopy. Macrosteps, terrace surfaces and protuberances are often accompanied with the presence of liquid FeBr{sub 3} droplets. In the absence of a liquid phase growth hillocks are found. Localized photovoltaic response for the evaluation of carrier collection using a scanning laser spot system has been used to effectively locate and characterize non-uniformities present in the epitaxial thin films. (orig.).

Photochemistry and photopolymerisation activity of novel thioxanthone derivatives

International Nuclear Information System (INIS)

Nik Ghazali Salleh; Allen, N.S.; Edge, M.; Shah, M.; Green, A.

1999-01-01

In this paper, we aim to examine the influence of a range of 4-oxy substituted groups on the photochemical and photopolymerization of 1-chloro- and 1-phenylthio-thioxanhone. Here we have examined the effect of a number of acyloxy groups attached to the ring 4-position. The study includes a spectroscopic and photoinitiated polymerization evaluation using real time infrared and photocalorimetry. The photoactivities of the initiators are compared with those of the standard industrial system such as the 4-n-propoxy derivative and the basic compound like the 1-chloro-4-hydroxyl derivative which was used to synthesise all the derivatives examined here

Interim Proposal for Molecular Beam Studies of Surfactants in Sulfuric Acid Aerosols: Comparisons Between Hydrocarbon and Fluorocarbon Alcohols

National Research Council Canada - National Science Library

Nathanson, Gilbert

2003-01-01

.... These processes include the acid-catalyzed reactions of HCI and HBr with CIONO2 (BrONO2) and HOCI (HOBr) to generate photoactive halogen molecules, particularly in colder regions of the stratosphere where they are more soluble in the water-rich aerosols...

Doctor Blade-Coated Polymer Solar Cells

KAUST Repository

Cho, Nam Chul; Kim, Jong H.

2016-01-01

In this work, we report polymer solar cells based on blade-coated P3HT:PC71BM and PBDTTT-EFT:PC71BM bulk heterojunction photoactive layers. Enhanced power conversion efficiency of 2.75 (conventional structure) and 3.03% (inverted structure

Ultraviolet-resonance femtosecond stimulated Raman study of the initial events in photoreceptor chromophore

Directory of Open Access Journals (Sweden)

Tahara T.

2013-03-01

Full Text Available Newly-developed ultraviolet-resonance femtosecond stimulated-Raman spectroscopy was utilized to study the initial structural evolution of photoactive yellow protein chromophore in solution. The obtained spectra changed drastically within 1 ps, demonstrating rapid in-plane deformations of the chromophore.

Plasma-assisted cleaning of extreme UV optics

NARCIS (Netherlands)

Dolgov, Alexandr Alexeevich

2018-01-01

Plasma-assisted cleaning of extreme UV optics EUV-induced surface plasma chemistry of photo-active agents The next generation of photolithography, extreme ultraviolet (EUV) lithography, makes use of 13.5 nm radiation. The ionizing photon flux, and vacuum requirements create a challenging operating

Assembly of individual TiO2-C60/porphyrin hybrid nanoparticles for enhancement of photoconversion efficiency

International Nuclear Information System (INIS)

Jang, Jae Kwon; Park, Se Ho; Song, Hyunjoon; Park, Joon T; Kim, Chulwoo; Ko, Jaejung; Seo, Won Seok

2011-01-01

Rational organization of porphyrin and C 60 on the electrode surface in photovoltaic structures is essential to yield high quantum efficiency. In the present work, individual TiO 2 nanoparticles were modified by introducing C 60 and porphyrin units on the surface, and then electrophoretically deposited on an ITO/SnO 2 electrode. The morphology of the photoactive layer on the electrode was significantly different from that of the layer produced as a result of separate deposition of C 60 and porphyrin. The maximum incident photon to current efficiency of the resulting electrode approached 88% at 410 nm, which is the highest value among molecule-based photovoltaic cells reported to date. This indicates that molecular assembly of the C 60 and porphyrin units on the individual nanoparticles through strong chemical attachment is a key factor in improving effective electron transfer between the photoactive units and the electrodes.

Changes in UV absorption of sunscreens after UV irradiation

Science.gov (United States)

Tarras-Wahlberg, N.; Stenhagen, G.; Larkö, O.; Rosén, A.; Wennberg, A.-M.; Wennerström, O.

2000-03-01

In the present investigation we have studied the change in the absorption spectrum of some photoactive organic species in sunscreens after UVA and UVB irradiation in a dose normally encountered during a full day in the sun. The absorbance of 2-ethylhexyl 4-methoxycinnamate was reduced significantly, while 3-(4-methylbenzyliden)camphor seemed to be rather stable. The benzophenones studied seemed to be relatively stable. In the case of 4-tert.butyl-4´-methoxy-dibenzoylmethane there was a rapid decrease in the UVA absorption leading to unsatisfactory protection in the UVA region. 4-Isopropyl-dibenzoylmethane also lost most of its UV protective capacity after irradiation with UVA. UVB seemed to have a minor effect on all the samples. The present study including gas chromatography and mass spectrometry analysis indicates that some of the photoactive organic species commonly used today in sunscreens are unstable following UV irradiation.

An inter-laboratory stability study of roll-to-roll coated flexible polymer solar modules

DEFF Research Database (Denmark)

Gevorgyan, Suren; Medford, Andrew James; Bundgaard, Eva

2011-01-01

A large number of flexible polymer solar modules comprising 16 serially connected individual cells was prepared at the experimental workshop at Risø DTU. The photoactive layer was prepared from several varieties of P3HT (Merck, Plextronics, BASF and Risø DTU) and two varieties of ZnO (nanoparticu......A large number of flexible polymer solar modules comprising 16 serially connected individual cells was prepared at the experimental workshop at Risø DTU. The photoactive layer was prepared from several varieties of P3HT (Merck, Plextronics, BASF and Risø DTU) and two varieties of Zn......O (nanoparticulate, thin film) were employed as electron transport layers. The devices were all tested at Risø DTU and the functional devices were subjected to an inter-laboratory study involving the performance and the stability of modules over time in the dark, under light soaking and outdoor conditions. 24...

Photoelectrochemical cells based on emeraldine base form of polyaniline

International Nuclear Information System (INIS)

Sergawie, Assefa; Guenes, Serap; Neugebauer, Helmut; Sariciftci, Niyazi S.; Yohannes, Teketel

2007-01-01

Photoelectrochemical cells (PECs) have been fabricated using the emeraldine base form of polyaniline (EB) as a photoactive material and Eu 2+ /Eu 3+ redox couple in methanol as an electrolyte. A PEC with a structure: Glass/ITO/EB/electrolyte/Pt produces an open-circuit voltage (V OC ) of -0.132 V and a short-circuit current (I SC ) of 0.64 μA cm -2 under 50 mW cm -2 white light illumination from Xe lamp. In an effort to increase the photoresponse, a PEC with a structure: Glass/ITO/EB:Nc-TiO 2 /Electrolyte/Pt has been devised in which a composite film of EB and nanocrystalline TiO 2 (Nc-TiO 2 ) is used as a photoactive material. The cell shows a V OC of -0.205 V and an I SC of 105 μA cm -2 when illuminated under the same conditions. (author)

On the short circuit resilience of organic solar cells: prediction and validation.

Science.gov (United States)

Oostra, A Jolt; Smits, Edsger C P; de Leeuw, Dago M; Blom, Paul W M; Michels, Jasper J

2015-09-07

The operational characteristics of organic solar cells manufactured with large area processing methods suffers from the occurrence of short-circuits due to defects in the photoactive thin film stack. In this work we study the effect of a shunt resistance on an organic solar cell and demonstrate that device performance is not affected negatively as long as the shunt resistance is higher than approximately 1000 Ohm. By studying charge transport across PSS-lithium fluoride/aluminum (LiF/Al) shunting junctions we show that this prerequisite is already met by applying a sufficiently thick (>1.5 nm) LiF layer. We demonstrate that this remarkable shunt-resilience stems from the formation of a significant charge transport barrier at the PSS-LiF/Al interface. We validate our predictions by fabricating devices with deliberately severed photoactive layers and find an excellent agreement between the calculated and experimental current-voltage characteristics.

Improved solar light stimulated charge separation of g-C3N4 through self-altering acidic treatment

Science.gov (United States)

Leong, Kah Hon; Lim, Ping Feng; Sim, Lan Ching; Punia, Varun; Pichiah, Saravanan

2018-02-01

Herein, we report the use of acid treatment to treat g-C3N4 nanostructured by a direct and facile synthesis route. The adopted treatment enhanced photoactivity of g-C3N4 and reflected in the removal of recalcitrant organic pollutant, Bisphenol A under direct sunlight. A complete removal of Bisphenol A was attained in a short duration (225 min) as compared to pure g-C3N4. The analysis clearly substantiated the robustness of acid exfoliation that promoted a blue shift, extended the conjugated length of its respective conduction and valance band. It also drastically prolonged the recombination rate of charge carriers, by producing excess of unpaired electrons in the conduction band for active radicals' generation. Thus, this new findings could offer a new sight of self-alteration in improving the photoactivity of complex organic pollutants for sustainable environmental remediation.

Photocatalytic production of 1O2 and ·OH mediated by silver oxidation during the photoinactivation of Escherichia coli with TiO2

International Nuclear Information System (INIS)

Castro, Camilo A.; Osorio, Paula; Sienkiewicz, Andrzej; Pulgarin, Cesar; Centeno, Aristóbulo; Giraldo, Sonia A.

2012-01-01

Highlights: ► Metallic silver enhances the Ag–TiO 2 photoinactivation of Escherichia coli under Vis irradiation. ► 1 O 2 and ·OH were identified in Vis irradiated Ag–TiO 2 suspensions. ► UV oxidized the Ag metallic species in the material decreasing photoactivity. ► Dark contact of the UV oxidized material with E. coli regenerates the photocatalyst. - Abstract: Ag loaded TiO 2 was applied in the photocatalytic inactivation of Escherichia coli under ultraviolet (UV) and visible (Vis) light irradiations. Ag enhanced the TiO 2 photodisinfecting effect under Vis irradiation promoting the formation of singlet oxygen and hydroxyl radicals as identified by EPR analyses. Ag nanoparticles, determined on TEM analyses, undergo an oxidation process on the TiO 2 's surface under UV or Vis irradiation as observed by XPS. In particular, UV pre-irradiation of the material totally diminished its photodisinfection activity under a subsequent Vis irradiation test. Under UV, photodegradation of dichloroacetic acid (DCA), attributed to photoproduced holes in TiO 2 , was inhibited by the presence of Ag suggesting that oxidation of Ag 0 to Ag + and Ag 2+ is faster than the oxidative path of the TiO 2 's holes on DCA molecules. Furthermore, photoassisted increased of Ag + concentration on TiO 2 's surface enhances the bacteriostatic activity of the material in dark periods. Indeed, this latter dark contact of Ag + –TiO 2 and E. coli seems to induce recovering of the Vis light photoactivity promoted by the surface Ag photoactive species.

New composites of nanoparticle Cu (I) oxide and titania in a novel inorganic polymer (geopolymer) matrix for destruction of dyes and hazardous organic pollutants

Energy Technology Data Exchange (ETDEWEB)

Falah, Mahroo [MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington (New Zealand); MacKenzie, Kenneth J.D., E-mail: Kenneth.mackenzie@vuw.ac.nz [MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington (New Zealand); Knibbe, Ruth [Robinson Research Institute, Victoria University of Wellington (New Zealand); Page, Samuel J.; Hanna, John V. [Department of Physics, Warwick University, Coventry CV4 7AL (United Kingdom)

2016-11-15

Highlights: • Synthesis reported of new photoactive nano-oxide composites in a geopolymer matrix. • The novel aluminosilicate matrix is expanded with cetyltrimethylammonium bromide. • The photoactive component consists of a Cu(I) oxide and titania heterostructure. • Composites remove the model pollutant by both adsorption and photodegradation. • These new photocatalysts are extremely efficient and ecologically friendly. - Abstract: New photoactive composites to efficiently remove organic dyes from water are reported. These consist of Cu{sub 2}O/TiO{sub 2} nanoparticles in a novel inorganic geopolymer matrix modified by a large tertiary ammonium species (cetyltrimethylammonium bromide, CTAB) whose presence in the matrix is demonstrated by FTIR spectroscopy. The CTAB does not disrupt the tetrahedral geopolymer structural silica and alumina units as demonstrated by {sup 29}Si and {sup 27}Al MAS NMR spectroscopy. SEM/EDS, TEM and BET measurements suggest that the Cu{sub 2}O/TiO{sub 2} nanoparticles are homogenously distributed on the surface and within the geopolymer pores. The mechanism of removal of methylene blue (MB) dye from solution consists of a combination of adsorption (under dark conditions) and photodegradation (under UV radiation). MB adsorption in the dark follows pseudo second-order kinetics and is described by Freundlich-Langmuir type isotherms. The performance of the CTAB-modified geopolymer based composites is superior to composites based on unmodified geopolymer hosts, the most effective composite containing 5 wt% Cu{sub 2}O/TiO{sub 2} in a CTAB-modified geopolymer host. These composites constitute a new class of materials with excellent potential in environmental protection applications.

Theoretical description of protein field effects on electronic excitations of biological chromophores

International Nuclear Information System (INIS)

Varsano, Daniele; Caprasecca, Stefano; Coccia, Emanuele

2017-01-01

Photoinitiated phenomena play a crucial role in many living organisms. Plants, algae, and bacteria absorb sunlight to perform photosynthesis, and convert water and carbon dioxide into molecular oxygen and carbohydrates, thus forming the basis for life on Earth. The vision of vertebrates is accomplished in the eye by a protein called rhodopsin, which upon photon absorption performs an ultrafast isomerisation of the retinal chromophore, triggering the signal cascade. Many other biological functions start with the photoexcitation of a protein-embedded pigment, followed by complex processes comprising, for example, electron or excitation energy transfer in photosynthetic complexes. The optical properties of chromophores in living systems are strongly dependent on the interaction with the surrounding environment (nearby protein residues, membrane, water), and the complexity of such interplay is, in most cases, at the origin of the functional diversity of the photoactive proteins. The specific interactions with the environment often lead to a significant shift of the chromophore excitation energies, compared with their absorption in solution or gas phase. The investigation of the optical response of chromophores is generally not straightforward, from both experimental and theoretical standpoints; this is due to the difficulty in understanding diverse behaviours and effects, occurring at different scales, with a single technique. In particular, the role played by ab initio calculations in assisting and guiding experiments, as well as in understanding the physics of photoactive proteins, is fundamental. At the same time, owing to the large size of the systems, more approximate strategies which take into account the environmental effects on the absorption spectra are also of paramount importance. Here we review the recent advances in the first-principle description of electronic and optical properties of biological chromophores embedded in a protein environment. We show

Theoretical description of protein field effects on electronic excitations of biological chromophores

Science.gov (United States)

Varsano, Daniele; Caprasecca, Stefano; Coccia, Emanuele

2017-01-01

Photoinitiated phenomena play a crucial role in many living organisms. Plants, algae, and bacteria absorb sunlight to perform photosynthesis, and convert water and carbon dioxide into molecular oxygen and carbohydrates, thus forming the basis for life on Earth. The vision of vertebrates is accomplished in the eye by a protein called rhodopsin, which upon photon absorption performs an ultrafast isomerisation of the retinal chromophore, triggering the signal cascade. Many other biological functions start with the photoexcitation of a protein-embedded pigment, followed by complex processes comprising, for example, electron or excitation energy transfer in photosynthetic complexes. The optical properties of chromophores in living systems are strongly dependent on the interaction with the surrounding environment (nearby protein residues, membrane, water), and the complexity of such interplay is, in most cases, at the origin of the functional diversity of the photoactive proteins. The specific interactions with the environment often lead to a significant shift of the chromophore excitation energies, compared with their absorption in solution or gas phase. The investigation of the optical response of chromophores is generally not straightforward, from both experimental and theoretical standpoints; this is due to the difficulty in understanding diverse behaviours and effects, occurring at different scales, with a single technique. In particular, the role played by ab initio calculations in assisting and guiding experiments, as well as in understanding the physics of photoactive proteins, is fundamental. At the same time, owing to the large size of the systems, more approximate strategies which take into account the environmental effects on the absorption spectra are also of paramount importance. Here we review the recent advances in the first-principle description of electronic and optical properties of biological chromophores embedded in a protein environment. We show

Isolation and characterisation of photoactive haemolytic toxin from ...

African Journals Online (AJOL)

We found that cell-free methanol extract from H. circularisquama caused haemolysis of rabbit erythrocytes and showed cytotoxic effects on HeLa cells and on the rotifer Brachionus plicatilis in a dose- and time-dependent manner. Interestingly, the haemolytic activity and cytotoxic effects of the extract were completely ...

Applications of hydroxy acids: classification, mechanisms, and photoactivity

Directory of Open Access Journals (Sweden)

Andrija Kornhauser

2010-11-01

Full Text Available Andrija Kornhauser1, Sergio G Coelho2, Vincent J Hearing21US Food and Drug Administration [retired], Annandale, VA, USA; 2Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USAAbstract: Hydroxy acids (HAs represent a class of compounds which have been widely used in a number of cosmetic and therapeutic formulations in order to achieve a variety of beneficial effects for the skin. We review and discuss the most frequently used classes of these compounds, such as a-hydroxy acids, β-hydroxy acids, polyhydroxy acids, and bionic acids, and describe their applications as cosmetic and therapeutic agents. Special emphasis is devoted to the safety evaluation of these formulations, in particular on the effects of their prolonged use on sun-exposed skin. Furthermore, we summarize the very limited number of studies dealing with the modifications evoked by topical application of products containing HAs on photocarcinogenesis. In spite of the large number of reports on the cosmetic and clinical effects of HAs, their biological mechanism(s of action still require more clarification. Some of these mechanisms are discussed in this article along with important findings on the effect of HAs on melanogenesis and on tanning. We also emphasize the important contribution of cosmetic vehicles in these types of studies. Thus, HAs play an important role in cosmetic formulations, as well as in many dermatologic applications, such as in treating photoaging, acne, ichthyosis, rosacea, pigmentation disorders, and psoriasis.Keywords: hydroxy acids, glycolic acid, salicylic acid, UV, erythema, cosmetics

Spectral properties of porphyrins in the systems with layered silicates

International Nuclear Information System (INIS)

Ceklovsky, A.

2009-03-01

This work is focused on investigation of hybrid materials based on layered silicates, representing host inorganic component, and porphyrin dyes as organic guest. Aqueous colloidal dispersions, as well as thin solid films of layered silicate/porphyrin systems were studied. Modification of photophysical properties, such as absorption and fluorescence of molecules, adsorbed or incorporated in layered silicate hosts, were studied mainly to spread the knowledge about the environments suitable for incorporating aromatic compounds, providing photoactive properties of potential technological interest. TMPyP cations interact with the surfaces of layered silicates via electrostatic interactions. The extent of dye adsorption on colloidal particles of the silicates is influenced by the CEC values and swelling ability of silicates. Interaction of porphyrins with layered silicate hosts leads to significant changes of dye spectral properties. One of the key parameters that has a crucial impact on this interaction is the layer charge of silicate template. Other factors influence the resulting spectral properties of hybrid systems, such as the method of hybrid material preparation, the material's type (colloid, film), and the modification of the silicate host. Molecular orientation studies using linearly-polarized spectroscopies in VIS and IR regions revealed that TMPyP molecules were oriented in almost parallel fashion with respect to the silicate surface plane. Slightly higher values of the orientation angle of TMPyP transition moment were observed for the TMPyP/FHT system. Thus, flattening of the guest TMPyP molecules is the next important factor (mainly in the systems with lower layer charge), influencing its spectral properties upon the interaction with layered silicates. Fluorescence was effectively quenched in the systems based on solid films prepared from the high concentration of the dye (10-3 mol.dm-3). The quenching is most probably related to the structure of the

Azomethine-based Donor Materials for Organic Solar Cells

NARCIS (Netherlands)

Petrus, M.L.

2014-01-01

Solution processable organic photovoltaics (OPVs) are attracting much attention because of their anticipated advantages such as low cost, flexibility, lightweight, and the potential to be produced on a large scale. The photoactive layer of OPVs consists of a blend of an electron donating and an

Roll-to-Roll Slot–Die Coated Organic Photovoltaic (OPV) Modules with High Geometrical Fill Factors

NARCIS (Netherlands)

Galagan, Y.; Fledderus, H.; Gorter, H.; Mannetje, H.H. 't; Shanmugam, S.; Mandamparambil, R.; Bosman, J.; Rubingh, J.M.; Teunissen, J.P.; Salem, A.; Vries, I.G. de; Andriessen, R.; Groen, W.A.

2015-01-01

Flexible semi-transparent organic photovoltaic (OPV) modules were manufactured by roll-to-roll slot–die coating of three functional layers [ZnO, photoactive layer, and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)] and either the screen printing or inkjet printing of the top

The effect of branching in a semiconducting polymer on the efficiency of organic photovoltaic cells

NARCIS (Netherlands)

Heintges, G.H.L.; van Franeker, J.J.; Wienk, M.M.; Janssen, R.A.J.

2016-01-01

The impact of branching in a diketopyrrolopyrrole polymer on the performance of polymer–fullerene photovoltaic cells is investigated. Compared to the linear polymer, the branched polymer affords a more finely dispersed fibrillar network in the photoactive layer and as a result a large enhancement of

3 D Co3 (PO4 )2 -Reduced Graphene Oxide Flowers for Photocatalytic Water Splitting: A Type II Staggered Heterojunction System.

Science.gov (United States)

Samal, Alaka; Swain, Smrutirekha; Satpati, Biswarup; Das, Dipti Prakasini; Mishra, Barada Kanta

2016-11-23

The design, synthesis, and photoelectrochemical characterization of Co 3 (PO 4 ) 2 , a hydrogen evolving catalyst modified with reduced graphene oxide (RGO), is reported. The 3 D flowerlike Co 3 (PO 4 ) 2 heterojunction system, consisting of 3 D flowerlike Co 3 (PO 4 ) 2 and RGO sheets, was synthesized by a one-pot in situ photoassisted method under visible-light irradiation, which was achieved without the addition of surfactant or a structure-directing reagent. For the first time, Co 3 (PO 4 ) 2 is demonstrated to act as a hydrogen evolving catalyst rather than being used as an oxygen evolving photoanode. In particular, 3 D flowerlike Co 3 (PO 4 ) 2 anchored to RGO nanosheets is shown to possess dramatically improved photocatalytic activity. This enhanced photoactivity is mainly due to the staggered type II heterojunction system, in which photoinduced electrons from 3 D flowerlike Co 3 (PO 4 ) 2 transfer to the RGO sheets and result in decreased charge recombination, as evidenced by photoluminescence spectroscopy. The band gap of Co 3 (PO 4 ) 2 was calculated to be 2.35 eV by the Kubelka-Munk method. Again, the Co 3 (PO 4 ) 2 semiconductor displays n-type behavior, as observed from Mott-Schottky measurements. These RGO-Co 3 (PO 4 ) 2 conjugates are active in the visible range of solar light for water splitting and textile dye degradation, and can be used towards the development of greener and cheaper photocatalysts by exploiting solar light. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatial modeling of the 3D morphology of hybrid polymer-ZnO solar cells, based on electron tomography data

NARCIS (Netherlands)

Stenzel, O.; Hassfeld, H.; Thiedmann, R.; Koster, L. J. A.; Oosterhout, S. D.; van Bavel, S. S.; Wienk, M. M.; Loos, J.; Janssen, R. A. J.; Schmidt, V.

A spatial stochastic model is developed which describes the 3D nanomorphology of composite materials, being blends of two different (organic and inorganic) solid phases. Such materials are used, for example, in photoactive layers of hybrid polymer zinc oxide solar cells. The model is based on ideas

The xanthopsins : a new family of eubacterial blue-light photoreceptors

NARCIS (Netherlands)

Kort, R; Hoff, W.D.; West, M.E.; Kroon, A R; Hoffer, S.M.; Vlieg, K H; Crielaand, W; van Beeumen, J.; Hellingwerf, K J

1996-01-01

Photoactive yellow protein (PYP) is a photoreceptor that has been isolated from three halophilic phototrophic purple bacteria. The PYP from Ectothiorhodospira halophila BN9626 is the only member for which the sequence has been reported at the DNA level. Here we describe the cloning and sequencing of

The Xanthopsins: a new family of eubacterial blue-light photoreceptors

NARCIS (Netherlands)

Kort, R.; Hoff, W.D.; van West, W.S.; Kroon, A.R.; Hoffer, S.M.; Vlieg, K.H.; Crielaard, W.; van Beeumen, J.J.; Hellingwerf, K.J.

1996-01-01

Photoactive yellow protein (PYP) is a photoreceptor that has been isolated from three halophilic phototrophic purple bacteria. The PYP from Ectothiorhodospira halophila BN9626 is the only member for which the sequence has been reported at the DNA level. Here we describe the cloning and sequencing of

Solution-processed organic tandem solar cells with embedded optical spacers

NARCIS (Netherlands)

Hadipour, Afshin; de Boer, Bert; Blom, Paul W. M.

2007-01-01

We demonstrate a solution-processed polymer tandem solar cell in which the two photoactive single cells are separated by an optical spacer. The use of an optical spacer allows for an independent optimization of both the electronic and optical properties of the tandem cell. The optical transmission

Method of making metal-chalcogenide photosensitive devices

International Nuclear Information System (INIS)

Kazacos, M.S.; Miller, B.

1981-01-01

We have found that a photoactive metal selenide film, such as cdse, may be formed by cathodic eletrodeposition from a selenosulfite (Seso32-) solution without the need for a subsequent heat treating step which, it is hypothesized, was required by the simultaneous deposition of elemental selenium

Functionalized carbon nanotube doping of P3HT:PCBM photovoltaic devices for enhancing short circuit current and efficiency

Directory of Open Access Journals (Sweden)

Rohit Bhatia

2017-03-01

Full Text Available We have successfully functionalized multiwalled carbon nanotubes (MWCNTs using nitrene approach employing the two aryl azides as a precursor for nitrene generation. The dispersion of functionalized MWCNTs has been enhanced in various organic solvents. These functionalized MWCNTs have been successfully doped in various concentrations in the bulk heterojunction (BHJ organic photovoltaic (OPV cells with a poly (3-hexyl thiophene (P3HT and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM photoactive blended layer. The incorporation of MWCNTs with aryl functional groups, in active the layer, results in enhanced performance with respect to a reference cell. The maximum power conversion efficiency of 1.86% is achieved with adduct I while in the case of adduct II it gets double to 2.0% in comparison with a reference cell. This improvement in the device performance is attributed to enhanced exciton dissociation and improved charge transport properties due to the formation of a nanotube percolation network in the photoactive composite layer.

A nanoscale study of charge extraction in organic solar cells: the impact of interfacial molecular configurations.

Science.gov (United States)

Tang, Fu-Ching; Wu, Fu-Chiao; Yen, Chia-Te; Chang, Jay; Chou, Wei-Yang; Gilbert Chang, Shih-Hui; Cheng, Horng-Long

2015-01-07

In the optimization of organic solar cells (OSCs), a key problem lies in the maximization of charge carriers from the active layer to the electrodes. Hence, this study focused on the interfacial molecular configurations in efficient OSC charge extraction by theoretical investigations and experiments, including small molecule-based bilayer-heterojunction (sm-BLHJ) and polymer-based bulk-heterojunction (p-BHJ) OSCs. We first examined a well-defined sm-BLHJ model system of OSC composed of p-type pentacene, an n-type perylene derivative, and a nanogroove-structured poly(3,4-ethylenedioxythiophene) (NS-PEDOT) hole extraction layer. The OSC with NS-PEDOT shows a 230% increment in the short circuit current density compared with that of the conventional planar PEDOT layer. Our theoretical calculations indicated that small variations in the microscopic intermolecular interaction among these interfacial configurations could induce significant differences in charge extraction efficiency. Experimentally, different interfacial configurations were generated between the photo-active layer and the nanostructured charge extraction layer with periodic nanogroove structures. In addition to pentacene, poly(3-hexylthiophene), the most commonly used electron-donor material system in p-BHJ OSCs was also explored in terms of its possible use as a photo-active layer. Local conductive atomic force microscopy was used to measure the nanoscale charge extraction efficiency at different locations within the nanogroove, thus highlighting the importance of interfacial molecular configurations in efficient charge extraction. This study enriches understanding regarding the optimization of the photovoltaic properties of several types of OSCs by conducting appropriate interfacial engineering based on organic/polymer molecular orientations. The ultimate power conversion efficiency beyond at least 15% is highly expected when the best state-of-the-art p-BHJ OSCs are combined with present arguments.

BODIPY-Au(I): A Photosensitizer for Singlet Oxygen Generation and Photodynamic Therapy.

Science.gov (United States)

Üçüncü, Muhammed; Karakuş, Erman; Kurulgan Demirci, Eylem; Sayar, Melike; Dartar, Suay; Emrullahoğlu, Mustafa

2017-05-19

Upon complexation with Au(I), a photoinactive BODIPY derivative was transformed into a highly photoactive triplet sensitizer. Along with high efficiency in singlet oxygen generation (Φ Δ = 0.84), the new BODIPY-Au(I) skeleton showed excellent photocytotoxic activity against cancer cell lines (EC 50 = 2.5 nM).

Stability and photodegradation mechanisms of conjugated polymer/fullerene plastic solar cells

NARCIS (Netherlands)

Neugebauer, H.; Brabec, C.; Hummelen, J.C.; Sariciftci, N.S.

2000-01-01

Degradation studies of poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene-vinylene) (MDMO-PPV), fullerenes ((6,6)-phenyl C-61-butyric acid methyl ester (PCBM) and C-60), and mixtures, which are the photoactive components in plastic solar cells, are shown. The degradation processes of the

Up-scalable sheet-to-sheet production of high efficiency perovskite module and solar cells on 6-in. substrate using slot die coating

NARCIS (Netherlands)

Di Giacomo, Francesco; Shanmugam, Santhosh; Fledderus, Henri; Bruijnaers, Bardo J.; Verhees, Wiljan J.H.; Dorenkamper, Maarten S.; Veenstra, Sjoerd C.; Qiu, Weiming; Gehlhaar, Robert; Merckx, Tamara; Aernouts, Tom; Andriessen, Ronn; Galagan, Yulia

2018-01-01

Scalable sheet-to-sheet slot die coating processes have been demonstrated for perovskite solar cells and modules. The processes have been developed on 6 in. × 6 in. glass/ITO substrates for two functional layers: the perovskite photo-active layer and the Spiro-OMeTAD hole transport layer. Perovskite

Synthesis, spectral characterization and redox properties of iron (II ...

Indian Academy of Sciences (India)

Unknown

Arylazoheterocycles and their chemistry of transition and non-transition metals have been explored for more than two decades.1 Owing to their pH-response, photoactivity, light electron communication, stabilization of low valent metal oxidation state, exhibition of serial redox states of complexes, isolation of anion radicals, ...

To Enhance Performance of Light Soaking Process on ZnS/CuIn1-xGaxSe2 Solar Cell

Directory of Open Access Journals (Sweden)

Yu-Jen Hsiao

2013-01-01

Full Text Available The ZnS/CuInGaSe2 heterojunction solar cell fabricated on Mo coated glass is studied. The crystallinity of the CIGS absorber layer is prepared by coevaporated method and the ZnS buffer layer with a band gap of 3.21 eV. The MoS2 phase was also found in the CuInGaSe2/Mo system form HRTEM. The light soaking effect of photoactive film for 10 min results in an increase in F.F. from 55.8 to 64%, but series resistivity from 7.4 to 3.8 Ω. The efficiency of the devices improved from 8.12 to 9.50%.

Cold field emission dominated photoconductivity in ordered three-dimensional assemblies of octapod-shaped CdSe/CdS nanocrystals

KAUST Repository

Zhang, Yang

2013-01-01

Semiconductor nanocrystals, especially their ordered assemblies, are promising materials for various applications. In this paper, we investigate the photoconductive behavior of sub-micron size, ordered three-dimensional (3D) assemblies of octapod-shaped CdSe/CdS nanocrystals that are contacted by overlay electron-beam lithography. The regular structure of the assemblies leads to photocurrent-voltage curves that can be described by the cold field electron emission model. Mapping of the photoconductivity versus excitation wavelength and bias voltage allows the extraction of the band gap and identification of the photoactive region in the voltage and spectral domain. These results have important implications for the understanding of photoconductive transport in similar systems. © 2013 The Royal Society of Chemistry.

Electron transfer reactions in microporous solids

Energy Technology Data Exchange (ETDEWEB)

Mallouk, T.E.

1993-01-01

Basic thrust the research program involves use of microporous solids (zeolites, clays, layered and tunnel structure oxide semiconductors) as organizing media for artificial photosynthetic systems. Purpose of the microporous solid is twofold. First, it induces spatial organization of photoactive and electroactive components (sensitizers, semiconductor particles, electron relays, and catalysts) at the solid-solution interface, enhancing the quantum efficiency of charge separation and separating physically the ultimate electron donor and acceptor in the electron transport chain. Second, since the microcrystalline solid admits only molecules of a certain charge and size, it is possible to achieve permanent charge separation by sieving chemical photoproducts (e.g., H[sub 2] and I[sub 3][sup [minus

Wastewater remediation by TiO2-impregnated chitosan nano-grafts exhibited dual functionality: High adsorptivity and solar-assisted self-cleaning.

Science.gov (United States)

Essawy, Amr A; Sayyah, S M; El-Nggar, A M

2017-08-01

This work provides a very infrequent and unique avenue of a novel bio-based nanografted polymeric composites achieving encouraging results in green management of dye contaminants in wastewater. A chitosan-grafted-polyN-Methylaniline (Ch-g-PNMANI) and chitosan-grafted-polyN-Methylaniline imprinted TiO 2 nanocomposites (Ch-g-PNMANI/TiO 2 ) were prepared and efficiently applied in wastewater remediation. The nanocomposites were characterized by FT-IR spectroscopy, X-ray diffraction, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy and Brunauer-Emmett-Teller surface area (BET) measurements. The prepared composites exhibit higher adsorptivity in removing remazol red RB-133 (RR RB-133) dye compared to other adsorbents reported in literature. The effects of TiO 2 loadings, initial dye concentration, contact time, and pH on dye adsorption were investigated. The maximum adsorption of dye was found at low pH values. Furthermore, Ch-g-PNMANI/TiO 2 of the optimum TiO 2 loading has higher adsorption capacity (116.3mg/g) than the pristine Ch-g-PNMANI (108.7mg/g). Moreover, the prepared adsorbents are photoactive under sunlight-irradiation. The study addresses a nanocomposite of considerable adsorption and in the same time has the fastest self-cleaning photoactivity (t 1/2 =31.5min.) under sunlight irradiation where a plausible photodegradation mechanism was proposed. Interestingly, the presented photoactive adsorbents are still effective in removing dye after five adsorption/sunlight-assisted self-cleaning photoregeneration cycles and therefore, they can be potentially applied to the rapid, "green" and low-cost remediation of RR RB-133 enriched industrial printing and dyeing wastewater. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis and luminescent properties of novel Cu (II), Zn (II ...

Indian Academy of Sciences (India)

Administrator

solid state respectively, and the maximum wavelengths of the polymeric complexes 2 and 3 are red ... properties of inorganic and organic small molecule ... good electro- and photo-active properties. ... solution was poured over 600 mL of ice water and ... Extraction with ..... atom and carbon atom in the phenanthroline and.

Dip coating of air purifier ceramic honeycombs with photocatalytic TiO₂ nanoparticles: A case study for occupational exposure

DEFF Research Database (Denmark)

Koivisto, Antti Joonas; Kling, Kirsten Inga; Fonseca, Ana Sofia

2018-01-01

Nanoscale TiO2 (nTiO2) is manufactured in high volumes and is of potential concern in occupational health. Here, we measured workers exposure levels while ceramic honeycombs were dip coated with liquid photoactive nanoparticle suspension and dried with an air blade. The measured nTiO2 concentrati...

SYNTHESIS AND CHARACTERIZATION OF POLY[3-(2\\',5 ...

African Journals Online (AJOL)

PDHOPT sensitizes nanocrystalline titanium dioxide (nc-TiO2) in liquid-state photoelectrochemical cells. Devices where the photoactive electrode consists of nc-TiO2/PDHOPT composite film show improved performance over those that consist of only PDHOPT. Devices made of TiO2/PDHOPT composite film produced an ...

Chemical Sensors Based on Cyclodextrin Derivatives.

Science.gov (United States)

Ogoshi, Tomoki; Harada, Akira

2008-08-25

This review focuses on chemical sensors based on cyclodextrin (CD) derivatives. This has been a field of classical interest, and is now of current interest for numerous scientists. First, typical chemical sensors using chromophore appended CDs are mentioned. Various "turn-off" and "turn-on" fluorescent chemical sensors, in which fluorescence intensity was decreased or increased by complexation with guest molecules, respectively, were synthesized. Dye modified CDs and photoactive metal ion-ligand complex appended CDs, metallocyclodextrins, were also applied for chemical sensors. Furthermore, recent novel approaches to chemical sensing systems using supramolecular structures such as CD dimers, trimers and cooperative binding systems of CDs with the other macrocycle [2]rotaxane and supramolecular polymers consisting of CD units are mentioned. New chemical sensors using hybrids of CDs with p-conjugated polymers, peptides, DNA, nanocarbons and nanoparticles are also described in this review.

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

Science.gov (United States)

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

2015-11-01

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

3-D modelling of a bilayer heterojunction organic solar cell based on ...

African Journals Online (AJOL)

The thin film multilayer stacking theory is applied to the bilayer heterojunction organic solar cell, with the optical matrix of the Abeles theory leading to new expression of generation rate and density of exciton photogenerated in the organic photoactive layer of CuPc/C60. The excitons density is investigated considering the ...

CO2 photoreduction using NiO/InTaO4 in optical-fiber reactor for renewable energy

NARCIS (Netherlands)

Wang, Zhen-Yi; Chou, Hung-Chi; Wu, Jeffrey C.S.; Tsai, Din Ping; Mul, Guido

2010-01-01

The photocatalytic reduction of CO2 into fuels provides a direct route to produce renewable energy from sunlight. NiO loaded InTaO4 photocatalyst was prepared by a sol–gel method. Aqueous-phase CO2 photoreduction was performed in a quartz reactor to search for the highest photoactivity in a series

Proceedings from the Annual Army Environmental R&D Symposium (16th) Held 23-25 June 1992 at Fort Magruder Inn and Conference Center, Williamsburg, Virginia

Science.gov (United States)

1992-06-01

photoactivity. The second prong was to evaluate the perovskite materials to utilize the lattice oxygen for the oxidation step and was found unsuccessful...Loalized 0 Distributed (*24) WowK damage to ACM. Q Yes 0 NO 0 Lca -Hzed 0 Distributed (25) Proximity (P) of ACM to repaWrromzine mainm uin A. Friable

Photocatalytic production of {sup 1}O{sub 2} and {center_dot}OH mediated by silver oxidation during the photoinactivation of Escherichia coli with TiO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Castro, Camilo A. [Centro de Investigaciones en Catalisis, Escuela de Ingenieria Quimica, Universidad Industrial de Santander (UIS), A.A. 678, Bucaramanga (Colombia); Institute of Chemical Sciences and Engineering, GGEC, Swiss Federal Institute of Technology (EPFL), Station 6, CH-1015, Lausanne (Switzerland); Osorio, Paula [Institute of Chemical Sciences and Engineering, GGEC, Swiss Federal Institute of Technology (EPFL), Station 6, CH-1015, Lausanne (Switzerland); Sienkiewicz, Andrzej [Laboratory of Complex Matter Physics, Institute of Physics of Condensed Matter, EPFL, Station 3, CH-1015, Lausanne (Switzerland); Pulgarin, Cesar, E-mail: cesar.pulgarin@epfl.ch [Institute of Chemical Sciences and Engineering, GGEC, Swiss Federal Institute of Technology (EPFL), Station 6, CH-1015, Lausanne (Switzerland); Centeno, Aristobulo [Centro de Investigaciones en Catalisis, Escuela de Ingenieria Quimica, Universidad Industrial de Santander (UIS), A.A. 678, Bucaramanga (Colombia); Giraldo, Sonia A., E-mail: sgiraldo@uis.edu.co [Centro de Investigaciones en Catalisis, Escuela de Ingenieria Quimica, Universidad Industrial de Santander (UIS), A.A. 678, Bucaramanga (Colombia)

2012-04-15

Highlights: Black-Right-Pointing-Pointer Metallic silver enhances the Ag-TiO{sub 2} photoinactivation of Escherichia coli under Vis irradiation. Black-Right-Pointing-Pointer {sup 1}O{sub 2} and {center_dot}OH were identified in Vis irradiated Ag-TiO{sub 2} suspensions. Black-Right-Pointing-Pointer UV oxidized the Ag metallic species in the material decreasing photoactivity. Black-Right-Pointing-Pointer Dark contact of the UV oxidized material with E. coli regenerates the photocatalyst. - Abstract: Ag loaded TiO{sub 2} was applied in the photocatalytic inactivation of Escherichia coli under ultraviolet (UV) and visible (Vis) light irradiations. Ag enhanced the TiO{sub 2} photodisinfecting effect under Vis irradiation promoting the formation of singlet oxygen and hydroxyl radicals as identified by EPR analyses. Ag nanoparticles, determined on TEM analyses, undergo an oxidation process on the TiO{sub 2}'s surface under UV or Vis irradiation as observed by XPS. In particular, UV pre-irradiation of the material totally diminished its photodisinfection activity under a subsequent Vis irradiation test. Under UV, photodegradation of dichloroacetic acid (DCA), attributed to photoproduced holes in TiO{sub 2}, was inhibited by the presence of Ag suggesting that oxidation of Ag{sup 0} to Ag{sup +} and Ag{sup 2+} is faster than the oxidative path of the TiO{sub 2}'s holes on DCA molecules. Furthermore, photoassisted increased of Ag{sup +} concentration on TiO{sub 2}'s surface enhances the bacteriostatic activity of the material in dark periods. Indeed, this latter dark contact of Ag{sup +}-TiO{sub 2} and E. coli seems to induce recovering of the Vis light photoactivity promoted by the surface Ag photoactive species.

Photocatalytic activity of tin-doped TiO{sub 2} film deposited via aerosol assisted chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Chua, Chin Sheng, E-mail: cschua@simtech.a-star.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore); Tan, Ooi Kiang; Tse, Man Siu [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Ding, Xingzhao [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore)

2013-10-01

Tin-doped TiO{sub 2} films are deposited via aerosol assisted chemical vapor deposition using a precursor mixture composing of titanium tetraisopropoxide and tetrabutyl tin. The amount of tin doping in the deposited films is controlled by the volume % concentration ratio of tetrabutyl tin over titanium tetraisopropoxide in the mixed precursor solution. X-ray diffraction analysis results reveal that the as-deposited films are composed of pure anatase TiO{sub 2} phase. Red-shift in the absorbance spectra is observed attributed to the introduction of Sn{sup 4+} band states below the conduction band of TiO{sub 2}. The effect of tin doping on the photocatalytic property of TiO{sub 2} films is studied through the degradation of stearic acid under UV light illumination. It is found that there is a 10% enhancement on the degradation rate of stearic acid for the film with 3.8% tin doping in comparison with pure TiO{sub 2} film. This improvement of photocatalytic performance with tin incorporation could be ascribed to the reduction of electron-hole recombination rate through charge separation and an increased amount of OH radicals which are crucial for the degradation of stearic acid. Further increase in tin doping results in the formation of recombination site and large anatase grains, which leads to a decrease in the degradation rate. - Highlights: ► Deposition of tin-doped TiO{sub 2} film via aerosol assisted chemical vapor deposition ► Deposited anatase films show red-shifted in UV–vis spectrum with tin-dopants. ► Photoactivity improves at low tin concentration but reduces at higher concentration. ► Improvement in photoactivity due to bandgap narrowing from Sn{sup 4+} band states ► Maximum photoactivity achieved occurs for films with 3.8% tin doping.

Construction of photoelectrochemical thrombin aptasensor via assembling multilayer of graphene-CdS nanocomposites.

Science.gov (United States)

Shangguan, Li; Zhu, Wei; Xue, Yanchun; Liu, Songqin

2015-02-15

A photoelectrochemical (PEC) aptasensor for highly sensitive and specific detection of thrombin was developed by using graphene–CdS nanocomposites multilayer as photoactive species and electroactive mediator hexaammineruthenium(III) chloride (Ru(NH(3))(6)(3+)) as signal enhancer. Graphene–CdS nanocomposites (G–CdS) were synthesized by one-pot reduction of oxide graphene and CdCl2 with thioacetamide. The photoactive multilayer was prepared by alternative assembly of the negatively charged 3-mercaptopropionic acid modified graphene–CdS nanocomposites (MPA-G–CdS) and the positively charged polyethylenimine (PEI) on ITO electrode. This layer-by-layer assembly method enhanced the stability and homogeneity of the photocurrent readout of G–CdS. Thrombin aptamer was covalently bound to the multilayer by using glutaraldehyde as cross-linking. Electroactive mediator (Ru(NH(3))(6)(3+)) could interact with the DNA phosphate backbone and thus facilitated the electron transfer between G–CdS multilayer and electrode and enhanced the photocurrent. Hybridizing of a long complementary DNA with thrombin aptamer could increase the adsorption amount of (Ru(NH(3))(6)(3+)), which in turn boosted the signal readout. In the presence of target thrombin, the affinity interaction between thrombin and its aptamer resulted in the long complementary DNA releasing from the G–CdS multilayer and decreasing of photocurrent signal. On the basis of G–CdS multilayer as the photoactive species, (Ru (NH(3))(6)(3+)) as an electroactive mediator, and aptamer as a recognition module, a high sensitive PEC aptasensor for thrombin detection was proposed. The thrombin aptasensor displayed a linear range from 2.0 pM to 600.0 pM and a detection limit of 1.0 pM. The present strategy provided a promising ideology for the future development of PEC biosensor. Copyright © 2014 Elsevier B.V. All rights reserved.

Liposome-coated mesoporous silica nanoparticles loaded with L-cysteine for photoelectrochemical immunoassay of aflatoxin B1.

Science.gov (United States)

Lin, Youxiu; Zhou, Qian; Zeng, Yongyi; Tang, Dianping

2018-06-02

The authors describe a photoelectrochemical (PEC) immunoassay for determination of aflatoxin B 1 (AFB 1 ) in foodstuff. The competitive immunoreaction is carried out on a microplate coated with a capture antibody against AFB 1 using AFB 1 -bovine serum albumin (BSA)-liposome-coated mesoporous silica nanoparticles (MSN) loaded with L-cysteine as a support. The photocurrent is produced by a photoactive material consisting of cerium-doped Bi 2 MoO 6 . Initially, L-cysteine acting as the electron donor is gated in the pores by interaction between mesoporous silica and liposome. Thereafter, AFB 1 -BSA conjugates are covalently bound to the liposomes. Upon introduction of the analyte (AFB 1 ), the labeled AFB 1 -BSA complex competes with the analyte for the antibody deposited on the microplate. Accompanying with the immunocomplex, the liposomes on the MSNs are lysed upon addition of Triton X-100. This results in the opening of the pores and in a release of L-cysteine. Free cysteine then induces the electron-hole scavenger of the photoactive nanosheets to increase the photocurrent. The photocurrent (relative to background signal) increases with increasing AFB 1 concentration. Under optimum conditions, the photoactive nanosheets display good photoelectrochemical responses, and allow the detection of AFB 1 at a concentration as low as 0.1 pg·mL -1 within a linear response in the 0.3 pg·mL -1 to 10 ng·mL -1 concentration range. Accuracy was evaluated by analyzing naturally contaminated and spiked peanut samples by using a commercial AFB 1 ELISA kit as the reference, and well-matching results were obtained. Graphical abstract Schematic presentation of a photoelectrochemical immunoassay for AFB 1 . It is based on the use of Ce-doped Bi 2 MoO 6 nanosheets and of liposome-coated mesoporous silica nanoparticles loaded with L-cysteine.

Flexible organic/inorganic hybrid solar cells based on conjugated polymer and ZnO nanorod array

International Nuclear Information System (INIS)

Tong, Fei; Kim, Kyusang; Martinez, Daniel; Thapa, Resham; Ahyi, Ayayi; Williams, John; Park, Minseo; Kim, Dong-Joo; Lee, Sungkoo; Lim, Eunhee; Lee, Kyeong K

2012-01-01

We report on the photovoltaic characteristics of organic/inorganic hybrid solar cells fabricated on ‘flexible’ transparent substrates. The solar cell device is composed of ZnO nanorod array and the bulk heterojunction structured organic layer which is the blend of poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM). The ZnO nanorod array was grown on indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrates via a low-temperature (85 °C) aqueous solution process. The blend solution consisting of conjugated polymer P3HT and fullerene PCBM was spin coated at a low spinning rate of 400 rpm on top of the ZnO nanorod array structure and then the photoactive layer was slow dried at room temperature in air to promote its infiltration into the nanorod network. As a top electrode, silver was sputtered on top of the photoactive layer. The flexible solar cell with the structure of PET/ITO/ZnO thin film/ZnO nanorods/P3HT:PCBM/Ag exhibited a photovoltaic performance with an open circuit voltage (V OC ) of 0.52 V, a short circuit current density (J SC ) of 9.82 mA cm −2 , a fill factor (FF) of 35% and a power conversion efficiency (η) of 1.78%. All the measurements were performed under 100 mW cm −2 of illumination with an air mass 1.5 G filter. To the best of our knowledge, this is the first presentation of investigation into the fabrication and characterization of organic/inorganic hybrid solar cells based on bulk heterojunction structured conjugated polymer/fullerene photoactive layer and ZnO nanorod array constructed on flexible transparent substrates. (paper)

Změny fotokatalytické aktivity oxidu titaničitého vyvolané vysokými dávkami záření gama

Czech Academy of Sciences Publication Activity Database

Prášil, Z.; Vacek, K.; Šrank, Z.; Mastný, L.; Brožek, Vlastimil

2004-01-01

Roč. 98, č. 8 (2004), s. 572 ISSN 0009-2770. [Congress Chemical Societies/56th./. Ostrava, 06.09.2004-09.09.2004] Institutional research plan: CEZ:AV0Z2043910 Keywords : photoactivity, ionizing radiation, TiO2 irradiation Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.348, year: 2004

Synthesis of Ag2Se–graphene–TiO2 nanocomposite and analysis of ...

Indian Academy of Sciences (India)

2017-11-16

Nov 16, 2017 ... Synthesis of Ag2Se–graphene–TiO2 nanocomposite and analysis of photocatalytic ... photoactivity, obtaining a total CH3OH yield of 3.52μmol g. −1 h. −1 after 48h. .... a = b = 3.78 Å and c = 9.51 Å (JCPDS PDF#00-021-1279).

A photoactive bimetallic framework for direct aminoformylation of nitroarenes

Data.gov (United States)

U.S. Environmental Protection Agency — A bimetallic catalyst, AgPd@g-C3N4, synthesized by reducing silver and palladium salts over graphitic carbon nitride (g-C3N4), enables the concerted reductive...

Competitive light absorbers in photoactive dental resin-based materials.

Science.gov (United States)

Hadis, Mohammed A; Shortall, Adrian C; Palin, William M

2012-08-01

The absorbance profile of photoinitiators prior to, during and following polymerization of light curable resin-based materials will have a significant effect on the cure and color properties of the final material. So-called "colorless" photoinitiators are used in some light-activated resin-based composite restorative materials to lessen the yellowing effect of camphoroquinone (CQ) in order to improve the esthetic quality of dental restorations. This work characterizes absorption properties of commonly used photoinitiators, an acylphosphine oxide (TPO) and CQ, and assesses their influence on material discoloration. Dimethacrylate resin formulations contained low (0.0134 mol/dm(3)), intermediate (0.0405 mol/dm(3)) or high (0.0678 mol/dm(3)) concentrations of the photoinitiators and the inhibitor, butylated hydroxytoluene (BHT) at 0, 0.1 or 0.2% by mass. Disc shaped specimens (n = 3) of each resin were polymerized for 60s using a halogen light curing unit. Dynamic measurements of photoinitiator absorption, polymer conversion and reaction temperature were performed. A spectrophotometer was used to measure the color change before and after cure. GLM three-way analysis of variance revealed significant differences (pphotoinitiator type (df = 1; F = 176.12)>% BHT (df = 2, F = 13.17). BHT concentration affected the rate of polymerization and produced lower conversion in some of the CQ-based resins. Significant differences between photoinitiator type and concentrations were seen in color (where TPO resins became yellower and camphoroquinone resins became less yellow upon irradiation). Reaction temperature, kinetics and conversion also differed significantly for both initiators (presins producing a visually perceptible color change upon polymerization, the color change was significantly less than that produced with CQ-based resins. Although some photoinitiators such as TPO may be a more esthetic alternative to CQ, they may actually cause significant color contamination when used in high concentrations and therefore manufacturers should limit its concentration in order to improve its esthetic quality. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Light-activated phenalen-1-one bactericides: efficacy, toxicity and mechanism compared with benzalkonium chloride.

Science.gov (United States)

Muehler, Denise; Sommer, Kerstin; Wennige, Sara; Hiller, Karl-Anton; Cieplik, Fabian; Maisch, Tim; Späth, Andreas

2017-11-01

Five photoactive compounds with variable elongated alkyl-substituents in a phenalen-1-one structure were examined in view of structural similarity to the antimicrobial agent benzalkonium chloride (BAC). All phenalen-1-ones and BAC were evaluated for their antimicrobial properties against Staphylococcus aureus, methicillin-resistant S. aureus, Escherichia coli, Pseudomonas aeruginosa and for their eukaryotic toxicity against normal human epidermal keratinocyte (NHEK) cells to narrow down the BAC-like effect and the photodynamic effect depending on the chemical structure. All compounds were investigated for effective concentration ranges, where a bacterial reduction of 5 log 10 is achieved, while an NHEK survival of 80% is ensured. Effective concentration ranges were found for four out of five photoactive compounds, but not for BAC and the compound with BAC-like alkyl chain length. Chain length size and polar area of the respective head-groups of phenalen-1-one compounds or BAC showed an influence on the incorporation inside lipid membranes and thus, head-groups may have an impact on the toxicity of antimicrobials.

Characterization of the photocurrents generated by the laser of atomic force microscopes

Energy Technology Data Exchange (ETDEWEB)

Ji, Yanfeng; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano and Soft Materials (FUNSOM), Collaborative Innovation Center of Suzhou Nanoscience and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Iglesias, Vanessa [International Iberian Nanotechnology Laboratory, 4715-330 Braga (Portugal); Lewis, David [Nanonics Imaging, Har Hotzvim, Jerusalem 91487 (Israel); Niu, Jiebin; Long, Shibing; Liu, Ming [Laboratory of Nanofabrication and Novel Device Integration, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Hofer, Alexander; Frammelsberger, Werner; Benstetter, Guenther [Deggendorf Institute of Technology, Edlmairstr. 6+8, 94469 Deggendorf (Germany); Scheuermann, Andrew; McIntyre, Paul C. [Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States)

2016-08-15

The conductive atomic force microscope (CAFM) has become an essential tool for the nanoscale electronic characterization of many materials and devices. When studying photoactive samples, the laser used by the CAFM to detect the deflection of the cantilever can generate photocurrents that perturb the current signals collected, leading to unreliable characterization. In metal-coated semiconductor samples, this problem is further aggravated, and large currents above the nanometer range can be observed even without the application of any bias. Here we present the first characterization of the photocurrents introduced by the laser of the CAFM, and we quantify the amount of light arriving to the surface of the sample. The mechanisms for current collection when placing the CAFM tip on metal-coated photoactive samples are also analyzed in-depth. Finally, we successfully avoided the laser-induced perturbations using a two pass technique: the first scan collects the topography (laser ON) and the second collects the current (laser OFF). We also demonstrate that CAFMs without a laser (using a tuning fork for detecting the deflection of the tip) do not have this problem.

High efficiency organic photovoltaic cells employing hybridized mixed-planar heterojunctions

Science.gov (United States)

Xue, Jiangeng; Uchida, Soichi; Rand, Barry P; Forrest, Stephen

2013-11-19

A device is provided, having a first electrode, a second electrode, and a photoactive region disposed between the first electrode and the second electrode. The photoactive region includes a first organic layer comprising a mixture of an organic acceptor material and an organic donor material, wherein the first organic layer has a thickness not greater than 0.8 characteristic charge transport lengths, and a second organic layer in direct contact with the first organic layer, wherein: the second organic layer comprises an unmixed layer of the organic acceptor material or the organic donor material of the first organic layer, and the second organic layer has a thickness not less than about 0.1 optical absorption lengths. Preferably, the first organic layer has a thickness not greater than 0.3 characteristic charge transport lengths. Preferably, the second organic layer has a thickness of not less than about 0.2 optical absorption lengths. Embodiments of the invention can be capable of power efficiencies of 2% or greater, and preferably 5% or greater.

Doped titanium dioxide nanocrystalline powders with high photocatalytic activity

International Nuclear Information System (INIS)

Castro, A.L.; Nunes, M.R.; Carvalho, M.D.; Ferreira, L.P.; Jumas, J.-C.; Costa, F.M.; Florencio, M.H.

2009-01-01

Doped titanium dioxide nanopowders (M:TiO 2 ; M=Fe, Co, Nb, Sb) with anatase structure were successfully synthesized through an hydrothermal route preceded by a precipitation doping step. Structural and morphological characterizations were performed by powder XRD and TEM. Thermodynamic stability studies allowed to conclude that the anatase structure is highly stable for all doped TiO 2 prepared compounds. The photocatalytic efficiency of the synthesized nanopowders was tested and the results showed an appreciable enhancement in the photoactivity of the Sb:TiO 2 and Nb:TiO 2 , whereas no photocatalytic activity was detected for the Fe:TiO 2 and Co:TiO 2 nanopowders. These results were correlated to the doping ions oxidation states, determined by Moessbauer spectroscopy and magnetization data. - Graphical abstract: Doped titanium dioxide nanopowders (M:TiO 2 ; M=Fe, Co, Nb, Sb) with highly stable anatase structure were successfully synthesized through an hydrothermal route. The photocatalytic efficiencies of the synthesized nanopowders were tested and the results show an appreciable enhancement in the photoactivity of the Sb:TiO 2 and Nb:TiO 2 .

Capturing the photo-signaling state of a photoreceptor in a steady-state fashion by binding a transition metal complex.

Science.gov (United States)

Yu, Pengyun; Song, Lei; Qin, Jun; Wang, Jianping

2017-11-01

Binding a small molecule to proteins causes conformational changes, but often to a limited extent. Here, we demonstrate that the interaction of a CO-releasing molecule (CORM3) with a photoreceptor photoactive yellow protein (PYP) drives large structural changes in the latter. The interaction of CORM3 and a mutant of PYP, Met100Ala, not only trigger the isomerization of its chromophore, p-coumaric acid, from its anionic trans configuration to a protonated cis configuration, but also increases the content of β-sheet at the cost of α-helix and random coil in the secondary structure of the protein. The CORM3 derived Met100Ala is found to highly resemble the signaling state, which is one of the key photo-intermediates of this photoactive protein, in both protein local conformation and chromophore configuration. The organometallic reagents hold promise as protein engineering tools. This work highlights a novel approach to structurally accessing short lived intermediates of proteins in a steady-state fashion. © 2017 The Protein Society.

Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer

Science.gov (United States)

Duan, Hong-Guang; Prokhorenko, Valentyn I.; Cogdell, Richard J.; Ashraf, Khuram; Stevens, Amy L.; Thorwart, Michael; Miller, R. J. Dwayne

2017-08-01

During the first steps of photosynthesis, the energy of impinging solar photons is transformed into electronic excitation energy of the light-harvesting biomolecular complexes. The subsequent energy transfer to the reaction center is commonly rationalized in terms of excitons moving on a grid of biomolecular chromophores on typical timescales Olson protein, in which interference oscillatory signals up to 1.5 ps were reported and interpreted as direct evidence of exceptionally long-lived electronic quantum coherence. Here, we show that the optical 2D photon echo spectra of this complex at ambient temperature in aqueous solution do not provide evidence of any long-lived electronic quantum coherence, but confirm the orthodox view of rapidly decaying electronic quantum coherence on a timescale of 60 fs. Our results can be considered as generic and give no hint that electronic quantum coherence plays any biofunctional role in real photoactive biomolecular complexes. Because in this structurally well-defined protein the distances between bacteriochlorophylls are comparable to those of other light-harvesting complexes, we anticipate that this finding is general and directly applies to even larger photoactive biomolecular complexes.

Photo-assisted electrochemical oxidation of the urea onto TiO2-nanotubes modified by hematite

Directory of Open Access Journals (Sweden)

Waleed M. Omymen

2017-12-01

Full Text Available The electrochemical oxidation of the urea in near neutral pH is investigated on platinum electrode. It is shown that oxidation reaction is practically inhibited up to the potentials of ∼0.9 V. The same reaction is investigated onto electrochemically obtained titanium dioxide nanotubes modified by hematite using facile, low-cost successive ion layer adsorption and reaction (SILAR method. It is shown that such system possesses electrocatalytic activity at very low potentials, and activity can be further improved by the illumination of the electrode in the photo-assisted reaction. The possible application of the photoactive anode is considered in the application of urea based water electrolysis and urea based fuel cell. Keywords: Photoelectrochemical cell, Water electrolysis, Fuel cell, SILAR

Exploring the Effects of the Pb2+ Substitution in MAPbI3 on the Photovoltaic Performance of the Hybrid Perovskite Solar Cells.

Science.gov (United States)

Frolova, Lyubov A; Anokhin, Denis V; Gerasimov, Kirill L; Dremova, Nadezhda N; Troshin, Pavel A

2016-11-03

Here we report a systematic study of the Pb 2+ substitution in the hybrid iodoplumbate MAPbI 3 with a series of elements affecting optoelectronic, structural, and morphological properties of the system. It has been shown that even partial replacement of lead with Cd 2+ , Zn 2+ , Fe 2+ , Ni 2+ , Co 2+ , In 3+ , Bi 3+ , Sn 4+ , and Ti 4+ results in a significant deterioration of the photovoltaic characteristics. On the contrary, Hg-containing hybrid MAPb 1-x Hg x I 3 salts demonstrated a considerably improved solar cell performance at optimal mercury loading. This result opens up additional dimension in the compositional engineering of the complex lead halides for designing novel photoactive materials with advanced optoelectronic and photovoltaic properties.

Comparing the photophysics of the two forms of the Orange Carotenoid Protein using 2D electronic spectroscopy

Directory of Open Access Journals (Sweden)

Mathies R.A.

2013-03-01

Full Text Available Broadband two-dimensional electronic spectroscopy is applied to investigate the photophysics of the photoactive orange carotenoid protein, which is involved in nonphotochemical quenching in cyanobacteria. Differences in dynamics between the light and dark forms arise from the different structure of the carotenoid in the protein pocket, with consequences for the biological role of the two forms.

Improved Efficiency in Inverted Perovskite Solar Cells Employing a Novel Diarylamino-Substituted Molecule as PEDOT:PSS Replacement

KAUST Repository

El Labban, Abdulrahman

2016-03-15

An approach to fabricate high-efficiency inverted planar perovskites solar cells using solution-processed organic small molecules hole transporting layer is reported. Devices using CH3NH3PbI3 as photoactive layer and PC60BM as electron transport layer show power conversion efficiencies exceeding 12% and open-circuit voltages (VOC) higher than 1 V.

Efficiency Enhancement in Bulk Heterojunction Polymer Photovoltaic Cells Using ZrTiO4/Bi2O3 Metal-Oxide Nanocomposites

DEFF Research Database (Denmark)

Abdul Jabbar, Mohammed Hussain; Neppolian, B.; Shim, Hee-Sang

2010-01-01

We report the effect of metal-oxide nanocomposites on the performance of bulk heterojunction polymer solar cells. A photoactive layer composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was blended with a newly developed ZrTiO4/Bi2O3 (BITZ) metal-oxide...

Co-catalyst free Titanate Nanorods for improved Hydrogen ...

Indian Academy of Sciences (India)

Herein, we report a simplified method for the preparation of photo-active titanate nanorods catalyst .... The TEM images were taken with Philips Technai G2 FEI F12 trans- mission electron microscope operating at 80-100 kV. Optical properties were measured in DRS ..... Chen X, Shen S, Guo L and Mao S S 2010 Chem. Rev ...

Antibacterial nanofiber materials activated by light

Czech Academy of Sciences Publication Activity Database

Jesenská, S.; Plištil, L.; Kubát, Pavel; Lang, Kamil; Brožová, Libuše; Popelka, Štěpán; Szatmáry, Lórant; Mosinger, Jiří

99A, č. 4 (2011), s. 676-683 ISSN 1549-3296 R&D Projects: GA ČR GAP208/10/1678 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40320502; CEZ:AV0Z40500505 Keywords : antibacterial nanofiber materials * photoactive * singlet oxygen Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.625, year: 2011

Enhanced bulk heterojunction devices prepared by thermal and solvent vapor annealing processes

Science.gov (United States)

Forrest, Stephen R.; Thompson, Mark E.; Wei, Guodan; Wang, Siyi

2017-09-19

A method of preparing a bulk heterojunction organic photovoltaic cell through combinations of thermal and solvent vapor annealing are described. Bulk heterojunction films may prepared by known methods such as spin coating, and then exposed to one or more vaporized solvents and thermally annealed in an effort to enhance the crystalline nature of the photoactive materials.

Improved Efficiency in Inverted Perovskite Solar Cells Employing a Novel Diarylamino-Substituted Molecule as PEDOT:PSS Replacement

KAUST Repository

El Labban, Abdulrahman; Chen, Hu; Kirkus, Mindaugas; Barbe, Jeremy; Del Gobbo, Silvano; Neophytou, Marios; McCulloch, Iain; Eid, Jessica

2016-01-01

An approach to fabricate high-efficiency inverted planar perovskites solar cells using solution-processed organic small molecules hole transporting layer is reported. Devices using CH3NH3PbI3 as photoactive layer and PC60BM as electron transport layer show power conversion efficiencies exceeding 12% and open-circuit voltages (VOC) higher than 1 V.

Comparison of Interfacial Electron Transfer Efficiency in [Fe(ctpy)2]2+-TiO2 and [Fe(cCNC)2]2+-TiO2 Assemblies: Importance of Conformational Sampling.

Science.gov (United States)

Mukherjee, Sriparna; Liu, Chang; Jakubikova, Elena

2018-02-22

Fe(II)-polypyridines have limited applications as chromophores in dye-sensitized solar cells due to the short lifetimes (∼100 fs) of their photoactive metal-to-ligand charge transfer (MLCT) states formed upon photoexcitation. Recently, a 100-fold increase in the MLCT lifetime was observed in a [Fe(CNC) 2 ] 2+ complex (CNC = 2,6-bis(3-methylimidazole-1-ylidine)pyridine) which has strong σ-donating N-heterocyclic carbene ligand in comparison to the weaker field parent [Fe(tpy) 2 ] 2+ complex (tpy = 2,2':6',2″-terpyridine). This study utilizes density functional theory (DFT), time-dependent DFT, and quantum dynamics simulations to investigate the interfacial electron transfer (IET) in [Fe(cCNC) 2 ] 2+ (cCNC = 4'-carboxy-2,6-bis(3-methylimidazole-1-ylidine)pyridine) and [Fe(ctpy) 2 ] 2+ (ctpy = 4'-carboxy-2,2':6',2″-terpyridine) sensitized TiO 2 . Our results suggest that the replacement of tpy by CNC ligand does not significantly speed up the IET kinetics in the [Fe(cCNC) 2 ] 2+ -TiO 2 assembly in comparison to the [Fe(ctpy) 2 ] 2+ -TiO 2 analogue. The high IET efficiency in the [Fe(cCNC) 2 ] 2+ -TiO 2 assemblies is therefore due to longer lifetime of [Fe(cCNC) 2 ] 2+ photoactive 3 MLCT states rather than faster electron injection kinetics. It was also found that the inclusion of conformational sampling in the computational model is important for proper description of the IET processes in these systems, as the models relying on the use of only fully optimized structures may yield misleading results. The simulations presented in this work also illustrate various pitfalls of utilizing properties such as electronic coupling, number of available acceptor states, and driving force, as well as calculations based on Fermi's golden rule framework, to reach conclusions on the IET efficiency in dye-semiconductor systems.

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

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Hypericin-mediated selective photomodification of connective tissues

Science.gov (United States)

Hovhannisyan, V.; Hovhannisyan, A.; Ghukasyan, V.; Guo, H. W.; Lin, Hung-Ming; Chen, S. J.; Chen, Yang-Fang; Dong, Chen-Yuan

2017-02-01

Hypericin (Hyp) has received attention due to its high phototoxicity against viruses and anti-tumor photoactivity. Using two-photon imaging, we demonstrated that Hyp induced photosensitized modification of collagen fibers in native tissues. Dynamics of photo-processes was monitored by time-lapse multiphoton imaging. We showed that Hyp-mediated processes in collagen tissues may be used for the selective modification of collagen fibers.

Preparation of layered double hydroxides intercalated with organic anions and their application in LDH/poly(butyl methacrylate) nanocomposites

Czech Academy of Sciences Publication Activity Database

Kovanda, F.; Jindrová, E.; Lang, Kamil; Kubát, Pavel; Sedláková, Zdeňka

2010-01-01

Roč. 48, 1-2 (2010), s. 260-270 ISSN 0169-1317 R&D Projects: GA AV ČR KAN100500651 Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z40400503; CEZ:AV0Z40500505 Keywords : Layered double hydroxides * intercalation * poly(butyl methacrylate) nanocomposite * photoactive materials Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.303, year: 2010

Photocatalytic decouloration of malachite green dye by application of TiO2 nanotubes

International Nuclear Information System (INIS)

Prado, Alexandre G.S.; Costa, Leonardo L.

2009-01-01

The nanotubes of titania were synthesized in a hydrothermal system and characterized by scanning electronic microscopy (SEM), FT-IR, FT-Raman, and surface charge density by surface area analyzer. These nanomaterials were applied to photocatalyse malachite green dye degradation. Photodegradation capacity of TiO 2 nanotubes was compared to TiO 2 anatase photoactivity. Malachite dye was completely degraded in 75 and 105 min of reaction photocatalysed by TiO 2 nanotubes and TiO 2 anatase, respectively. Catalysts displayed high photodegradation activity at pH 4. TiO 2 nanotubes were easily recycled whereas the reuse of TiO 2 anatase was not effective. Nanotubes maintained 80% of their activity after 10 catalytic cycles and TiO 2 anatase presented only 8% of its activity after 10 cycles.

Computerized implementation of higher-order electron-correlation methods and their linear-scaling divide-and-conquer extensions.

Science.gov (United States)

Nakano, Masahiko; Yoshikawa, Takeshi; Hirata, So; Seino, Junji; Nakai, Hiromi

2017-11-05

We have implemented a linear-scaling divide-and-conquer (DC)-based higher-order coupled-cluster (CC) and Møller-Plesset perturbation theories (MPPT) as well as their combinations automatically by means of the tensor contraction engine, which is a computerized symbolic algebra system. The DC-based energy expressions of the standard CC and MPPT methods and the CC methods augmented with a perturbation correction were proposed for up to high excitation orders [e.g., CCSDTQ, MP4, and CCSD(2) TQ ]. The numerical assessment for hydrogen halide chains, polyene chains, and first coordination sphere (C1) model of photoactive yellow protein has revealed that the DC-based correlation methods provide reliable correlation energies with significantly less computational cost than that of the conventional implementations. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Enhancement of zinc oxide-mediated solar light decoloration of Acid Yellow 99 dye by addition of β-CD

Science.gov (United States)

Pitchaimuthu, Sakthivel; Rajalakshmi, Subramanian; Kannan, Nagarathinam; Velusamy, Ponnusamy

2015-06-01

In the current work, the commercially available ZnO photocatalyst was used to investigate the photodecoloration of Acid yellow 99 (AY99) dye under solar light radiation. Promising enhancement of photodecoloration of AY99 dye was also achieved by the addition of β-cyclodextrin (β-CD) with the ZnO (ZnO-β-CD). The effects of process parameters such as initial concentration, pH, catalyst loading, and illumination time on the extent of decoloration were investigated. The optimum catalyst loading was observed at 2.0 g/L. The higher photoactivity of ZnO-β-CD/solar light system than ZnO/solar light system can be ascribed due to the ligand to metal charge transfer (LMCT) from β-CD to ZnII. The complexation patterns have been confirmed with UV-visible and FT-IR spectroscopy and the interaction between ZnO and β-CD has been characterized by FE-SEM, powder XRD analysis, and UV-visible diffuse reflectance spectroscopy.

Synergistic effects of hollow structure and surface fluorination on the photocatalytic activity of titania

International Nuclear Information System (INIS)

Lv Kangle; Yu Jiaguo; Deng Kejian; Sun Jie; Zhao Yanxi; Du Dongyun; Li Mei

2010-01-01

To study the synergistic effects of hollow structure and surface fluorination on the photoactivity of TiO 2 , TiO 2 hollow microspheres were synthesized by a hydrolysis-precipitate method using sulfonated polystyrene (PS) as templates and tetrabutylorthotitanate (TBOT) as precursor, and then calcined at 500 o C for 2 h. The calcined samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N 2 sorption. Photocatalytic activity was evaluated using reactive brilliant red X3B, an anionic organic dye, as a model pollutant in water. The results show that the photocatalytic activity of TiO 2 hollow microspheres is significantly higher than that of TiO 2 nanoparticles prepared in the same experimental conditions. At pH 7 and 3, the apparent rate constants of the former exceed that of the latter by a factor of 3.38 and 3.15, respectively. After surface fluorination at pH 3, the photoactivity of hollow microspheres and nanoparticles further increases for another 1.61 and 2.19 times, respectively. The synergistic effect of surface fluorination and hollow structure can also be used to prepare other highly efficient photocatalyst.

Synthesis and characterization of CdS/CuAl2O4 core-shell: application to photocatalytic eosin degradation

Science.gov (United States)

Bellal, B.; Trari, M.; Afalfiz, A.

2015-08-01

The advantages of the hetero-junction CdS/CuAl2O4 for the photocatalytic eosin degradation are reported. Composite semiconductors are elaborated by co-precipitation of CdS on the spinel CuAl2O4 giving a core-shell structure with a uniform dispersion and intimate contact of the spinel nanoparticles inside the hexagonal CdS. The Mott-Schottky plots ( C -2- V) of both materials show linear behaviors from which flat band potentials are determined. The photoactivity increases with increasing the mass of the sensitizer CdS and the best performance is achieved on CdS/CuAl2O4 (85 %/15 %). The pH has a strong influence on the degradation and the photoactivity peaks at pH 7.78. The dark adsorption eosin is weak (~4 %), hence the change in the eosin concentration is attributed to the photocatalytic process. The degradation follows a zero-order kinetic with a rate constant of 5.2 × 10-8 mol L-1 mn-1 while that of the photolysis is seven times lower (0.75 × 10-8 mol L-1 mn-1).

Suppressing Structural Colors of Photocatalytic Optical Coatings on Glass: The Critical Role of SiO2.

Science.gov (United States)

Li, Ronghua; Boudot, Mickael; Boissière, Cédric; Grosso, David; Faustini, Marco

2017-04-26

The appearance of structural colors on coated-glass is a critical esthetical drawback toward industrialization of photocatalytic coatings on windows for architecture or automobile. Herein we describe a rational approach to suppress the structural color of mesoporous TiO 2 -based coatings preserving photoactivity and mechanical stiffness. Addition of SiO 2 as third component is discussed. Ti x Si (1-x) O 2 mesoporous coatings were fabricated by one-step liquid deposition process through the evaporation induced self-assembling and characterized by GI-SAXS, GI-WAXS, electron microscopies, and in situ Environmental Ellipsometry Porosimetry. Guided by optical simulation, we investigated the critical role of SiO 2 on the optical responses of the films but also on the structural, mechanical, and photocatalytic properties, important requirements to go toward real applications. We demonstrate that adding SiO 2 to porous TiO 2 allows tuning and suppression of structural colors through refractive index matching and up to 160% increase in mechanical stiffening of the films. This study leads us to demonstrate an example of "invisible" coating, in which the light reflection is angle- and thickness-independent, and exhibiting high porosity, mechanical stiffness, and photoactivity.

Colloidal nanocrystal ZnO- and TiO2-modified electrodes sensitized with chlorophyll a and carotenoids: a photoelectrochemical study

International Nuclear Information System (INIS)

Petrella, Andrea; Cosma, Pinalysa; Lucia Curri, M.; Rochira, Sergio; Agostiano, Angela

2011-01-01

Heterostructures formed of films of organic-capped ZnO and TiO 2 nanocrystals (both with the size of ca. 6 nm) and photosynthetic pigments were prepared and characterized. The surface of optically transparent electrodes (Indium Tin Oxide) was modified with nanocrystals and prepared by colloidal synthetic routes. The nanostructured electrodes were sensitized by a mixture of chlorophyll a and carotenoids. The characterization of the hybrid structures, carried out by means of steady-state optical measurements, demonstrated such class of dyes able to extend the photoresponse of the large band-gap semiconductors. The charge-transfer processes between the components of the heterojunction were investigated, and photoelectrochemical measurements taken on the sensitized ZnO and TiO 2 nanocrystals electrodes elucidated the photoactivity of the heterojunctions as a function of the dyes and of the red–ox mediator used in solution. The effect of methyl viologen as different red–ox mediator was also evaluated in order to show its effect on the heterojunction photoactivity. The overall results contributed to describe the photoelectrochemical potential of the investigated heterojunctions, highlighting a higher response of the dye-sensitized ZnO nanocrystals, and then provided the TiO 2 -modified counterparts.

Efficient Polymer Solar Cells with Alcohol-Soluble Zirconium(IV Isopropoxide Cathode Buffer Layer

Directory of Open Access Journals (Sweden)

Zhen Luo

2018-02-01

Full Text Available Interfacial materials are essential to the performance and stability of polymer solar cells (PSCs. Herein, solution-processed zirconium(IV isopropoxide (Zr[OCH(CH32]4, ZrIPO has been employed as an efficient cathode buffer layer between the Al cathode and photoactive layer. The ZrIPO buffer layer is prepared simply via spin-coating its isopropanol solution on the photoactive layer at room temperature without any post-treatment. When using ZrIPO/Al instead of the traditionally used Ca/Al cathode in PSCs, the short-circuit current density (Jsc is significantly improved and the series resistance of the device is decreased. The power conversion efficiency (PCE of the P3HT:PCBM-based device with ZrIPO buffer layer reaches 4.47% under the illumination of AM1.5G, 100 mW/cm2. A better performance with PCE of 8.07% is achieved when a low bandgap polymer PBDTBDD is selected as donor material. The results indicate that ZrIPO is a promising electron collection material as a substitute of the traditional low-work-function cathode for high performance PSCs.

Double Walled Carbon Nanotube/TiO2 Nanocomposites for Photocatalytic Dye Degradation

Directory of Open Access Journals (Sweden)

Alex T. Kuvarega

2016-01-01

Full Text Available Double walled carbon nanotube (DWCNT/N,Pd codoped TiO2 nanocomposites were prepared by a modified sol-gel method and characterised using FTIR, Raman spectroscopy, TGA, DRUV-Vis, XRD, SEM, and TEM analyses. TEM images showed unique pearl-bead-necklace structured morphologies at higher DWCNT ratios. The nanocomposite materials showed characteristic anatase TiO2 Raman bands in addition to the carbon nanotube D and G bands. Red shifts in the UV-Vis absorption edge were observed at low DWCNT percentages. The photocatalytic activity of DWCNT/N,Pd TiO2 nanocomposite was evaluated by the photocatalytic degradation of eosin yellow under simulated solar light irradiation and the 2% DWCNT/N,Pd TiO2 nanocomposite showed the highest photoactivity while the 20% DWCNT/N,Pd TiO2 hybrid was the least efficient. The photocatalytic enhancement was attributed to the synergistic effects of the supporting and electron channeling role of the DWCNTs as well as the electron trapping effects of the platinum group metal. These phenomena favour the separation of the photogenerated electron-hole pairs, reducing their recombination rate, which consequently lead to significantly enhanced photoactivity.

Synthesis of two-dimensional nanowall of Cu-Doped TiO2 and its application as photoanode in DSSCs

Science.gov (United States)

Dahlan, Dahyunir; Md Saad, Siti Khatijah; Berli, Ade Usra; Bajili, Abdil; Umar, Akrajas Ali

2017-07-01

Two-dimensional nanowall of Cu-doped TiO2 (CuTNW) has been prepared in this work to study the role of Cu doping on its photoactivity properties and its photovoltaic performance as photoanode in a dye-sensitized solar cell (DSSC). TiO2 nanowall with five Cu ion doping, i.e. 6.25, 12.5, 25.0, 50.0 and 100.0 mM, were prepared via a liquid-phase deposition method using ammoniumhexafluorotitanate and hexamethylenetetramine as the reagents with a growth temperature of 90 °C. The X-Ray Diffraction (XRD), X-ray energy dispersion (EDX) and diffuse optical reflectance spectroscopy analysis results confirmed the successfulness of the Cu doping process in the TiO2 nanowall and effective modification on the photoactivity of the TiO2 nanowall. We found that the power conversion efficiency of the DSSC utilizing TiO2 nanowall as photoanode can be enhanced up to 2 times, i.e. from 0.2% to 0.44%, when the TiO2 nanowall doped with Cu ion. The nanostructure preparation, device fabrication and the mechanism for the device performance enhancement will be discussed.

Energy-cascade organic photovoltaic devices incorporating a host-guest architecture.

Science.gov (United States)

Menke, S Matthew; Holmes, Russell J

2015-02-04

In planar heterojunction organic photovoltaic devices (OPVs), broad spectral coverage can be realized by incorporating multiple molecular absorbers in an energy-cascade architecture. Here, this approach is combined with a host-guest donor layer architecture previously shown to optimize exciton transport for the fluorescent organic semiconductor boron subphthalocyanine chloride (SubPc) when diluted in an optically transparent host. In order to maximize the absorption efficiency, energy-cascade OPVs that utilize both photoactive host and guest donor materials are examined using the pairing of SubPc and boron subnaphthalocyanine chloride (SubNc), respectively. In a planar heterojunction architecture, excitons generated on the SubPc host rapidly energy transfer to the SubNc guest, where they may migrate toward the dissociating, donor-acceptor interface. Overall, the incorporation of a photoactive host leads to a 13% enhancement in the short-circuit current density and a 20% enhancement in the power conversion efficiency relative to an optimized host-guest OPV combining SubNc with a nonabsorbing host. This work underscores the potential for further design refinements in planar heterojunction OPVs and demonstrates progress toward the effective separation of functionality between constituent OPV materials.

Two-channel dansyl/tryptophan emitters with a cholic acid bridge as reporters for local hydrophobicity within supramolecular systems based on bile salts.

Science.gov (United States)

Gomez-Mendoza, M; Marin, M Luisa; Miranda, Miguel A

2014-11-14

The aim of the present work is to develop two-channel emitters to probe local hydrophobicity by means of fluorescence quenching within different biomimetic supramolecular environments. To achieve this goal, the dansyl (Dns) and tryptophan (Trp) fluorophores have been covalently attached to cholic acid (CA) in order to ensure simultaneous incorporation of the two emitting units into the same compartment. In principle, the two fluorophores of the synthesized Dns-CA-Trp probes could either exhibit an orthogonal behavior or display excited state interactions. The fluorescence spectra of 3β-Dns-CA-Trp showed a residual Trp emission band at ca. 350 nm and an enhanced Dns maximum in the 500-550 nm region. This reveals a partial intramolecular energy transfer, which is consistent with the Dns and Trp singlet energies. Thus, the two photoactive units are not orthogonal; nevertheless, 3β-Dns-CA-Trp seems appropriate as a two-channel reporter for the supramolecular systems of interest. Fluorescence quenching of 3β-Dns-CA-Trp by iodide (which remains essentially in bulk water) was examined within sodium cholate, sodium taurocholate, sodium deoxycholate and mixed micelles. Interestingly, a decrease in the emission intensity of the two bands was observed with increasing iodide concentrations. The most remarkable effect was observed for mixed micelles, where the quenching rate constants were one order of magnitude lower than in solution. As anticipated, the quenching efficiency by iodide decreased with increasing hydrophobicity of the microenvironment, a trend that can be correlated with the relative accessibility of the probe to the ionic quencher.

A Thieno[3,2-b][1]benzothiophene Isoindigo Building Block for Additive- and Annealing-Free High-Performance Polymer Solar Cells

KAUST Repository

Yue, Wan; Ashraf, Raja Shahid; Nielsen, Christian B.; Collado-Fregoso, Elisa; Niazi, Muhammad Rizwan; Yousaf, Syeda Amber; Kirkus, Mindaugas; Chen, Hung-Yang; Amassian, Aram; Durrant, James R.; McCulloch, Iain

2015-01-01

A novel photoactive polymer with two different molecular weights is reported, based on a new building block: thieno[3,2-b][1]benzothiophene isoindigo. Due to the improved crystallinity, optimal blend morphology, and higher charge mobility, solar-cell devices of the high-molecular-weight polymer exhibit a superior performance, affording efficiencies of 9.1% without the need for additives, annealing, or additional extraction layers during device fabrication.

A Thieno[3,2-b][1]benzothiophene Isoindigo Building Block for Additive- and Annealing-Free High-Performance Polymer Solar Cells

KAUST Repository

Yue, Wan

2015-08-20

A novel photoactive polymer with two different molecular weights is reported, based on a new building block: thieno[3,2-b][1]benzothiophene isoindigo. Due to the improved crystallinity, optimal blend morphology, and higher charge mobility, solar-cell devices of the high-molecular-weight polymer exhibit a superior performance, affording efficiencies of 9.1% without the need for additives, annealing, or additional extraction layers during device fabrication.

New organic FET-like photoactive device, experiments and DFT modeling

Czech Academy of Sciences Publication Activity Database

Kratochvílová, Irena; Nešpůrek, Stanislav; Šebera, Jakub; Záliš, Stanislav; Pavelka, Matěj; Wang, G.; Sworakowski, J.

2008-01-01

Roč. 25, - (2008), s. 299-307 ISSN 1292-8941 R&D Projects: GA AV ČR KAN401770651; GA MŠk OC 137; GA MŠk(CZ) LC06063; GA AV ČR 1ET400400413; GA AV ČR IAA400400501; GA AV ČR KAN400720701 Grant - others:Ministery of Science and Higher Education (PL) 3 T08E 084 30; Programme Marie-Curie RTN BIMORE(XE) MRTN-CT-2006-035859 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z40400503; CEZ:AV0Z40500505 Source of funding: R - rámcový projekt EK Keywords : nanoelectronic devices * electronic transport * computational techniques - electronic structure atoms and molecules Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.943, year: 2008

3D morphology of photoactive layers of polymer solar cells

NARCIS (Netherlands)

Bavel, van S.S.

2009-01-01

Nanostructured polymer solar cells (PSCs) have emerged as a promising low-cost alternative to conventional silicon-based photovoltaic devices. Since PSCs can be fabricated by processing polymers, eventually together with other organic materials, from solution and depositing them onto different types

Preparation and characterization of photoactive composite kaolinite/TiO2

International Nuclear Information System (INIS)

Mamulova Kutlakova, K.; Tokarsky, J.; Kovar, P.; Vojteskova, S.; Kovarova, A.; Smetana, B.; Kukutschova, J.; Capkova, P.; Matejka, V.

2011-01-01

Preparation of nanocomposite kaolinite/TiO 2 , using hydrolysis of titanyl sulfate in the presence of kaolin was addressed. A variable (kaolin)/(titanyl sulfate) ratio has been used in order to achieve the desired TiO 2 content in prepared nanocomposites. Calcination of the composites at 600 deg, C led to the transformation of the kaolinite to metakaolinite and to origination of metakaolinite/TiO 2 composites. The prepared samples were investigated using X-ray fluorescence spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry and diffuse reflectance spectroscopy in the UV-VIS region. Structural ordering of TiO 2 on the kaolinite particle surface was modeled using empirical force field atomistic simulations in the Material Studio modeling environment. Photodegradation activity of the composites prepared was evaluated by the discoloration of Acid Orange 7 aqueous solution.

Non thermal preparation of photoactive titanium (IV) oxide thin layers

Czech Academy of Sciences Publication Activity Database

Klusoň, P.; Lusková, H.; Cajthaml, Tomáš; Šolcová, Olga

2006-01-01

Roč. 495, - (2006), s. 18-23 ISSN 0040-6090 R&D Projects: GA ČR GA104/04/0963; GA ČR GD203/03/H140; GA MPO FT-TA/023 Institutional research plan: CEZ:AV0Z50200510; CEZ:AV0Z40720504 Keywords : titanium dioxide * nanostructures * photocatalysis Subject RIV: EE - Microbiology, Virology Impact factor: 1.666, year: 2006

Photocatalytically active titanium dioxide nanopowders: Synthesis, photoactivity and magnetic separation

International Nuclear Information System (INIS)

Nikkanen, J-P; Heinonen, S; Saarivirta, E Huttunen; Honkanen, M; Levänen, E

2013-01-01

Two approaches were used to obtain nanocrystalline titanium dioxide (TiO 2 ) photocatalyst powders. Firstly, low-temperature synthesis method and secondly liquid flame spraying. The structural properties of the produced powders were determined with X-ray diffraction, transmission electron microscopy and nitrogen adsorption tests. The photocatalytic properties of the powders were studied with methylene blue (MB) discoloration tests. After discolorations tests, TiO 2 was coagulated with magnetite particles using FeCl 3 ·6 H 2 O at a fixed pH value. Magnetic separation of coagulated TiO 2 and magnetite was carried out by a permanent magnet. The obtained results showed that the particle size of the powders synthesized at low-temperature was very small and the specific surface area high. The phase content of the powder was also shown to depend greatly on the acidity of the synthesis solution. Powder synthesized by liquid flame spraying was mixture of anatase and rutile phases with essentially larger particle size and lower specific surface area than those of low-temperature synthesized powders. The MB discoloration test showed that photocatalytic activity depends on the phase structure as well as the specific surface area of the synthesized TiO 2 powder. The magnetic separation of TiO 2 –magnetite coagulate from solution proved to be efficient around pH:8

Correlating oxygen vacancies and phase ratio/interface with efficient photocatalytic activity in mixed phase TiO2

International Nuclear Information System (INIS)

Verma, Ranjana; Samdarshi, S.K.

2015-01-01

Graphical abstract: The correlation of interfacial behavior and oxygen vacancies in mixed phase titania nanoparticles on their performance as photocatalyst has been investigated to explain the impact of photoactivity under UV and visible irradiation compared to pristine counterparts. The defects at the junction effectively reduce the band gap as well decrease the carrier recombination to enhance the photocatalytic activity. - Highlights: • Pristine and mixed phases (A/R ratio) TiO 2 synthesized by sol gel route. • Photoactivity variation has been correlated with the changes in the phase ratio. • Enhanced UV and visible activity attributable to oxygen vacancy present at the interface. • Role of A/R ratio and oxygen vacancy in the photoactivity of mixed TiO 2 depicted through a model. - Abstract: The photocatalytic activity is a result of the synergy of a succession of phenomena-photogeneration, separation, and participation of the charge carriers in redox reaction at the catalyst surface. While the extent of photogeneration is assessable in terms of absorption spectrum (band gap), the redox reaction can be correlated to specific surface area. However the respective change in the photocatalytic activity has not been rationally and consistently correlated with the above mentioned parameters. A satisfactory explanation of suppression of recombination based on separation of carriers due to differential mobility/diffusivity in the material phase(s) and/or intrinsic potential barrier exists but its correlation with common identifiable parameter/characteristics is still elusive. This paper attempts to address this issue by correlating the carrier separation with the phase ratio (phase interface) in mixed phase titania and generalizing it with the presence of oxygen vacancy at the phase interface. It essentially appears to complete the quest for identifiable parameters in the sequence of phenomena, which endow a photocatalyst with an efficient activity level. It has

Photocatalytic reduction of Cr(VI) on the novel hetero-system CuFe{sub 2}O{sub 4}/CdS

Energy Technology Data Exchange (ETDEWEB)

Nasrallah, N.; Kebir, M. [Laboratory of Engineering Reaction, Faculty of Engineering Mechanic and Engineering Processus (USTHB), BP 32, Algiers (Algeria); Koudri, Z. [Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry (USTHB), BP 32, Algiers (Algeria); Trari, M., E-mail: solarchemistry@gmail.com [Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry (USTHB), BP 32, Algiers (Algeria)

2011-01-30

The photocatalytic HCrO{sub 4}{sup -} reduction was investigated in air equilibrated solution using the spinel CuFe{sub 2}O{sub 4} nanoparticles as sensitizers. The oxide is p-type semi conductor, prepared from nitrates decomposition. The catalytic performance increases with decreasing pH and the concomitant oxidation of salicylic acid contributes significantly to the photoactivity through the charges separation of electron/hole pairs (C{sub 7}H{sub 6}O{sub 3} + 6 O{sub 2} + 4 h{sup +} + 3 H{sub 2}O {yields} 7 CO{sub 2} + 4 H{sub 3}O{sup +}). Evidence has been given to show the advantages of the hetero-system CuFe{sub 2}O{sub 4}/CdS in the chromate reduction. CuFe{sub 2}O{sub 4} acts as electrons pump and the electron transfer to chromate is mediated via CdS hexagonal variety (greenockite). A reduction of 60% occurs and the process is well described by a pseudo first order kinetic with a half life of {approx}2.8 h and a quantum yield of {approx}0.12% for an initial HCrO{sub 4}{sup -} concentration of 3 x 10{sup -4} M. An improvement up to 72% is obtained when the reaction occurs in a stirred reactor and no cadmium was detected after 6 h illumination. The results indicate a competitive effect with the water reduction. The hydrogen evolutions are found to be 0.236 and 0.960 cm{sup 3} mn{sup -1} g{sup -1} in presence and in absence of HCrO{sub 4}{sup -}, respectively.

Supramolecular photochemistry of drugs in biomolecular environments.

Science.gov (United States)

Monti, Sandra; Manet, Ilse

2014-06-21

In this tutorial review we illustrate how the interaction of photoactive drugs/potential drugs with proteins or DNA in supramolecular complexes can determine the course of the reactions initiated by the drug absorbed photons, evidencing the mechanistic differences with respect to the solution conditions. We focus on photoprocesses, independent of oxygen, that lead to chemical modification of the biomolecules, with formation of new covalent bonds or cleavage of existing bonds. Representative systems are mainly selected from the literature of the last decade. The photoreactivity of some aryl propionic acids, (fluoro)quinolones, furocoumarins, metal coordination complexes, quinine-like compounds, naphthaleneimides and pyrenyl-peptides with proteins or DNA is discussed. The use of light for biomolecule photomodification, historically relevant to biological photosensitization processes and some forms of photochemotherapy, is nowadays becoming more and more important in the development of innovative methods in nanomedicine and biotechnology.

10.6% Certified Colloidal Quantum Dot Solar Cells via Solvent-Polarity-Engineered Halide Passivation.

Science.gov (United States)

Lan, Xinzheng; Voznyy, Oleksandr; García de Arquer, F Pelayo; Liu, Mengxia; Xu, Jixian; Proppe, Andrew H; Walters, Grant; Fan, Fengjia; Tan, Hairen; Liu, Min; Yang, Zhenyu; Hoogland, Sjoerd; Sargent, Edward H

2016-07-13

Colloidal quantum dot (CQD) solar cells are solution-processed photovoltaics with broad spectral absorption tunability. Major advances in their efficiency have been made via improved CQD surface passivation and device architectures with enhanced charge carrier collection. Herein, we demonstrate a new strategy to improve further the passivation of CQDs starting from the solution phase. A cosolvent system is employed to tune the solvent polarity in order to achieve the solvation of methylammonium iodide (MAI) and the dispersion of hydrophobic PbS CQDs simultaneously in a homogeneous phase, otherwise not achieved in a single solvent. This process enables MAI to access the CQDs to confer improved passivation. This, in turn, allows for efficient charge extraction from a thicker photoactive layer device, leading to a certified solar cell power conversion efficiency of 10.6%, a new certified record in CQD photovoltaics.

Activation of neuron generator of luciola mingrelica luminescence flashes under the effect of pulse X-radiation

International Nuclear Information System (INIS)

Bol'shakov, V.Yu.; Drobchenko, E.A.; Landa, S.B.; Pejmer, S.I.

1990-01-01

The effect of low-level pulse X-radiation on spontaneous photoactivity and luminous communicative behaviour of Luciola mingrelica has been investigated. It was shown that X-radiation doses of as low as 5x10 -5 Gy increased endogenous flashing activity and disinhibited the reaction of insects to light flashes imitating signals of mating partners. Powerful radiation pulses may influence significantly an instinctive behaviour and its neuronal organization

High-performance broadband photodetector using solution-processible PbSe-TiO(2)-graphene hybrids.

Science.gov (United States)

Manga, Kiran Kumar; Wang, Junzhong; Lin, Ming; Zhang, Jie; Nesladek, Milos; Nalla, Venkatram; Ji, Wei; Loh, Kian Ping

2012-04-03

Highly sensitive, multicomponent broadband photodetector devices are made from PbSe/graphene/TiO(2). TiO(2) and PbSe nanoparticles act as light harvesting photoactive materials from the UV to IR regions of the electromagnetic spectrum, while the graphene acts as a charge collector for both photogenerated holes and electrons under an applied electric field. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photodynamics of BLUF domain proteins: a new class of the biological blue-light photoreceptors

OpenAIRE

Zirak Yousefabadi, Peyman

2008-01-01

BLUF domains are light sensors of many microorganisms. They are present in the multi-domain proteins e.g. AppA from the phototrophic proteobacterium Rhodobacter sphaeroides, YcgF from Escherichia coli, PAC (photoactive adenylyl cyclase) from the unicellular flagellate Euglena gracilis and single domain proteins e.g. BlrB from Rhodobacter sphaeroides, Slr1694 from cyanobacterium Synechocystis sp.PCC6803, and Tll0078 of the thermophilic unicellular cyanobacterium Thermosynechococcus elongates B...

Simultaneous cross-linking and p-doping of a polymeric semiconductor film by immersion into a phosphomolybdic acid solution for use in organic solar cells.

Science.gov (United States)

Aizawa, Naoya; Fuentes-Hernandez, Canek; Kolesov, Vladimir A; Khan, Talha M; Kido, Junji; Kippelen, Bernard

2016-03-07

Poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) is shown to be simultaneously cross-linked and p-doped when immersed into a phosphomolybdic acid solution, yielding conductive films with low solubility that can withstand the solution processing of subsequent photoactive layers. Such a modified PCDTBT film serves to improve hole collection and limit carrier recombination in organic solar cells.

Nanoplasmonic Catalysis for Synthetic Fuel Production

Science.gov (United States)

2010-02-22

processes using mass spectrometry, gas chromatography, and potentiostatic electrochemistry while irradiating these plasmonic/catalytic nanostructures at...is of great interest for the removal of pollutants from water and air. Semiconductor photocatalysts (e.g., TiO2, ZnO , SnO, In2O3) have been shown to...34Photocatalytic Degradation of Methyl Orange over Single Crystalline ZnO : Orientation Dependence of Photoactivity and Photostability of ZnO ." Langmuir

Study of the intensification of solar photo-Fenton degradation of carbamazepine with ferrioxalate complexes and ultrasound.

Science.gov (United States)

Expósito, A J; Monteagudo, J M; Durán, A; San Martín, I; González, L

2018-01-15

The intensification of the solar photo-Fenton system with ferrioxalate photoactive complexes and ultrasound applied to the mineralization of 15mg/L carbamazepine aqueous solution (CBZ) was evaluated. The experiments were carried out in a solar compound parabolic collector (CPC) pilot plant reactor coupled to an ultrasonic processor. The dynamic behavior of hydroxyl radicals generated under the different studied reaction systems was discussed. The initial concentrations of hydrogen peroxide and ferrous/oxalic acid and pH were found to be the most significant variables (32.79%, 25.98% and 26.04%, respectively). Under the selected optimal conditions ([H 2 O 2 ] 0 =150mg/L; [Fe 2+ ] 0 =2.5mg/L/[(COOH) 2 ] 0 =12.1mg/L; pH=5) CBZ was fully degraded after 5min and 80% of TOC was removed using a solar photo-Fenton system intensified with ferrioxalate (SPFF). However, no improvement in the mineralization using SPFF process combined with ultrasound was observed. More mild pH conditions could be used in the SPFF system if compared to the traditional photo-Fenton (pH 3) acidic systems. Finally, a possible reaction pathway for the mineralization of CBZ by the SPFF system was proposed and therein discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Photocatalytic Oxidation of a Volatile Organic Component of Acetaldehyde Using Titanium Oxide Nanotubes

Directory of Open Access Journals (Sweden)

Yifeng Wang

2007-01-01

Full Text Available Titanium oxide nanotubes are prepared and treated with Au (Au/nanotube sample and Pt (Pt/nanotube sample, and the photoactivity of these catalysts compared to a standard Degussa P25 photocatalyst is investigated. The samples were analyzed using X-ray diffraction, field emission gun scanning transmission electron microscopy (STEM. Both high-resolution TEM images and high-angle annular dark-field (HAAD images were recorded for the specimens. Oxidation of acetaldehyde was used to test the efficiency of the catalysts. Nanotube samples showed better photoactivity than the standard P25, because the P25 titania deactivates quickly. Enhanced reactivity of the nanotube is related to surface charge polarity developed on outer and inner surfaces due to the difference in overlap of oxygen anions that resulted from curving of octahedral sheets. A tentative and qualitative surface polarity model is proposed for enhancing electron-hole pair separation. The inner surface benefits reduction; whereas, the outer surface benefits oxidation reactions. Both the metal identity and the size of the metal particles in the nanotubes affected the photocatalytic activity. Specifically, the addition of platinum increased the activity significantly, and increased the total yield. The addition of gold had lesser impact compared to the platinum. Formation of Pt large nanoparticles on the nanotube surfaces reduces the oxidation reactivity.

Immobilisation of bifenthrin for termite control.

Science.gov (United States)

Guan, Yan-Qing; Chen, Jia Mei; Li, Zhi Bin; Feng, Qi Li; Liu, Jun-Ming

2011-02-01

Termites are worldwide pests causing considerable damage to agriculture, forestry and buildings. While various approaches have been tried to eliminate termite populations, the relevant toxicants are associated with certain risks to the environment and human health. In this study, to combine the merits of effective chemical control by bifenthrin and a drug photoimmobilisation technique, silk fibroin was used as a carrier to embed bifenthrin, which was then photoactively immobilised by ultraviolet treatment on the surface of wood (cellulose). The immobilised bifenthrin embedded in the photoactive silk fibroin was characterised by Fourier transform infrared spectroscopy (FTIR), ultraviolet absorption spectroscopy (UV), fluorescence measurement and CHN analysis. The surface structures and biological activity were examined by scanning electron microscopy (SEM), atomic force microscopy (AFM), electron spectroscopy for chemical analysis (ESCA) and bioassays respectively. The results indicate that the embedded and immobilised bifenthrin has been very well protected from free release and has a long-term stability allowing slow release with a high efficiency against termites at a low dose of 1.25 µg cm(-2). This study provides a novel and environmentally benign technique for termite control by photoimmobilising silk-fibroin-embedded bifenthrin on the surface of materials that are otherwise easily attacked by termites. Copyright © 2010 Society of Chemical Industry.

Facile synthesis of well-dispersed Bi_2S_3 nanoparticles on reduced graphene oxide and enhanced photocatalytic activity

International Nuclear Information System (INIS)

Chen, Yajie; Tian, Guohui; Mao, Guijie; Li, Rong; Xiao, Yuting; Han, Taoran

2016-01-01

Highlights: • Well-dispersed Bi_2S_3 nanoparticles on reduced graphene oxide were prepared. • Poly(sodium-p-styrenesul-fonate) can maintain Bi_2S_3 small particle size. • The prepared composites inhibit the recombination of photogenerated charges. • The prepared composites exhibited better visible light photoactivity. - Abstract: Here we present a facile method for the synthesis of highly dispersed Bi_2S_3 nanoparticles (Bi_2S_3 NPs) with an average diameter of ca. 25 ± 3 nm on the surface of reduced graphene oxide (RGO) via a poly(sodium-p-styrenesul-fonate) (PSS) asisted hydrothermal process. Such synthetic strategy can avoid excess aggregates of Bi_2S_3 nanoparticles, meanwhile from effective interfacial contact between Bi_2S_3 nanoparticles and RGO nanosheets, and inhibit the recombination of photogenerated charges. The enhanced charge transfer properties were proved by photoluminescence (PL) measurement. The obtained Bi_2S_3 NPs/RGO composites showed more significant visible light photoactivity for the degradation of 2,4-dichlorophenol and Rhodamine B than that pure Bi_2S_3 and the control sample prepared in the absence of PSS. The enhanced photocatalytic performance could be attributed to the synergistic effect of efficient separation of photogenerated electron-hole pairs, increased catalytic active sites and visible light utilization.

New insight for enhancing photocatalytic activity of MWCNT/TiO{sub 2} by decorating palladium nanoparticles as charge-transfer channel

Energy Technology Data Exchange (ETDEWEB)

Zhang, Feng-Jun, E-mail: zhang-fengjun@hotmail.com [School of Materials and Chemical Engineering, Anhui University of Architecture, Anhui Hefei 230022 (China); Department of Advanced Materials and Science Engineering, Hanseo University, Seosan-si, Chungnam-do 356-706 (Korea, Republic of); Oh, Won-Chun, E-mail: wc_oh@hanseo.ac.kr [Department of Advanced Materials and Science Engineering, Hanseo University, Seosan-si, Chungnam-do 356-706 (Korea, Republic of); Zhang, Kan [Department of Advanced Materials and Science Engineering, Hanseo University, Seosan-si, Chungnam-do 356-706 (Korea, Republic of); Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, Hyojadong, Namgu, Pohang 790-784 (Korea, Republic of)

2012-03-15

Highlights: Black-Right-Pointing-Pointer A new insight for further improving photoactivity of MWCNT/TiO{sub 2} was reported. Black-Right-Pointing-Pointer The Pd as charge transfer channel trap electrons from MWCNT to TiO{sub 2} surface. Black-Right-Pointing-Pointer The Pd content can also influence photoactivity of MWCNT/TiO{sub 2} photocatalyst. Black-Right-Pointing-Pointer The approach is practically usable for other nanocarbon/semiconductor materials. -- Abstract: A surface bond-grafted multi-walled carbon nanotube (MWCNT)/TiO{sub 2} as supporter, palladium nanoparticles, approximately 3 nm in diameter, are uniformly deposited on the functional MWCNT surface in first, constructing a novel Pd-MWCNT/TiO{sub 2} photocatalyst for photocatalytic solar conversion. The characterization of photocatalysts by a series of joint techniques, including BET surface area, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), Raman spectroscopy and ultraviolet/visible (UV/vis) diffuse reflectance spectra, discloses that palladium nanoparticles has a crucial role in enhancement of photocatalytic activity of MWCNT/TiO{sub 2}, that is to act as a charge transfer channel, which helps to trap electrons from MWCNT to TiO{sub 2}.

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

International Nuclear Information System (INIS)

Fan, Tao; Li, Yinle; Shen, Jianfeng; Ye, Mingxin

2016-01-01

Graphical abstract: - Highlights: • GQD-PVP-CdS composite was prepared for the first time through a facile hydrothermal route. • GQD-PVP-CdS demonstrated outstanding photoactivity under visible light illumination. • GQDs and polymeric material are compounded with CdS nanoparticles simultaneously for the first time. • The addition of GQDs plays pivotal roles in the enhancement of the photoactivity. - Abstract: A facile one-step hydrothermal method to synthesize graphene quantum dots (GQDs)-polyvinyl pyrrolidone (PVP)-CdS nanocomposite was reported. The nanocomposite was thoroughly characterized with X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and ultraviolet–visible spectroscopy. The results confirmed the formation of GQD-PVP-CdS composite with a uniform size (5–10 nm) and a relatively low band gap (E_g = 2.23 eV). Moreover, the as-prepared composite exhibited enhanced photocatalytic activity toward the degradation of organic contaminants, with 92.3% of methyl orange (10 mg/L) removed after 3 hours of visible light illumination. This enhancement in photocatalytic activity was postulated to be attributed to the upconversion property of GQDs and a more efficient charge distribution between GQDs and CdS particles.

Superhydrophobic titania nanoparticles for fabrication of paper-based analytical devices: An example of heavy metals assays.

Science.gov (United States)

Xu, Wenjian; Chen, Xi; Cai, Songcai; Chen, Jin; Xu, Zhen; Jia, Hongpeng; Chen, Jing

2018-05-01

A new strategy has been introduced to successfully fabricate the hydrophobic barriers of PADs by using organofluorine-modified superhydrophobic TiO 2 NPs. Superhydrophobic TiO 2 -140 NPs with high-photoactivity can be converted to hydrophilicity by self-degradation of surface organic moieties under full spectrum light irradiation. Superhydrophobic TiO 2 -RT NPs with low-photoactivity exhibits good hydrophobic stability under light irradiation. Thus, combining these features, the PADs have been designed and constructed by photo-induced fabrication of hydrophobic barriers on the surface of the paper. To demonstrate the effectiveness of the constructed PADs, colorimetric detections have been displayed for Fe 3+ and Ni 2+ ions. The synchronous multi-component detections based on the "multi-channel" PADs and the intuitive detections based on the "chemical-symbol-style" PADs are rapid and feasible. A detection range of Fe 3+ and Ni 2+ ions based on the "circle-array" PAD is applicable and reliable in 0.2-6.0 mM and 0.4-4.0 mM, respectively. Thus, these results make it to be believed that this new strategy provides an alternative way to effectively construct the PADs. Copyright © 2018 Elsevier B.V. All rights reserved.

Charge conduction process and photovoltaic effects in thiazole yellow (TY) thin film based Schottky devices

Energy Technology Data Exchange (ETDEWEB)

Roy, M.S. [Defence Lab., Jodhpur (India). Camouflage Div.; Sharma, G.D.; Gupta, S.K. [Department of Physics, J.N.V. University, Jodhpur (Raj.) (India)

1997-11-21

The charge generation and photovoltaic effects observed with thin films of TY in the form of sandwich structures, were analysed by J-V, C-V and photoaction spectra. These measurements were explained in terms of n-type semiconductivity of TY thin film and by the formation of a Schottky barrier with ITO while Ohmic contact with an Al or In electrode. The existence of thermionic emission over the ITO-TY barrier has been observed in low voltage region, whereas at high voltages, the process is dominant by the series resistance of TY layer. Various electrical parameters were calculated from the analysis of J-V and C-V characteristics of the devices and discussed in details. The diode quality factor is higher for Al/TY/ITO than In/TY/ITO device which can be attributed to the formation of thin layer of Al{sub 2}O{sub 3} between Al and TY. The photoaction spectra of the devices reveal that the fraction of light which is absorbed near the ITO-TY interface, to the depth of 180 A, is responsible for producing the charge carriers. The photovoltaic parameters were also calculated from the J-V characteristics of the devices, under illumination and described in detail. (orig.) 21 refs.

Hydrogen peroxide route to Sn-doped titania photocatalysts

Directory of Open Access Journals (Sweden)

Štengl Václav

2012-10-01

Full Text Available Abstract Background The work aims at improving photocatalytic activity of titania under Vis light irradiation using modification by Sn ions and an original, simple synthesis method. Tin-doped titania catalysts were prepared by thermal hydrolysis of aqueous solutions of titanium peroxo-complexes in the presence of SnCl4 or SnCl2 using an original, proprietary "one pot" synthesis not employing organic solvents, metallo-organic precursors, autoclave aging nor post-synthesis calcination. The products were characterized in details by powder diffraction, XPS, UV–vis, IR, and Raman spectroscopies, electron microscopy and surface area and porosity measurements Results The presence of tin in synthesis mixtures favors the formation of rutile and brookite at the expense of anatase, decreases the particle size of all formed titania polymorphs, and extends light absorption of titania to visible light region >400 nm by both red shift of the absorption edge and introduction of new chromophores. The photocatalytic activity of titania under UV irradiation and >400 nm light was tested by decomposition kinetics of Orange II dye in aqueous solution Conclusions Doping by Sn improves titania photoactivity under UV light and affords considerable photoactivity under >400 nm light due to increased specific surface area and a phase heterogeneity of the Sn-doped titania powders.

Implementation of anion-receptor macrocycles in supramolecular tandem assays for enzymes involving nucleotides as substrates, products, and cofactors.

Science.gov (United States)

Florea, Mara; Nau, Werner M

2010-03-07

A supramolecular tandem assay for direct continuous monitoring of nucleotide triphosphate-dependent enzymes such as potato apyrase is described. The underlying principle of the assay relies on the use of anion-receptor macrocycles in combination with fluorescent dyes as reporter pairs. A combinatorial approach was used to identify two complementary reporter pairs, i.e. an amino-gamma-cyclodextrin with 2-anilinonaphtalene-6-sulfonate (ANS) as dye (fluorescence enhancement factor of 17 upon complexation) and a polycationic cyclophane with 8-hydroxy-1,3,6-pyrene trisulfonate (HPTS) as dye (fluorescence decrease by a factor of more than 2000), which allow the kinetic monitoring of potato apyrase activity at different ATP concentration ranges (microM and mM) with different types of photophysical responses (switch-ON and switch-OFF). Competitive fluorescence titrations revealed a differential binding of ATP (strongest competitor) versus ADP and AMP, which constitutes the prerequisite for monitoring enzymatic conversions (dephosphorylation or phosphorylation) involving nucleotides. The assay was tested for different enzyme and substrate concentrations and exploited for the screening of activating additives, namely divalent transition metal ions (Ni(2+), Mg(2+), Mn(2+), and Ca(2+)). The transferability of the assay could be demonstrated by monitoring the dephosphorylation of other nucleotide triphosphates (GTP, TTP, and CTP).

Conformation-Induced Remote meta-C–H Activation of Amines

Science.gov (United States)

Tang, Ri-Yuan; Li, Gang; Yu, Jin-Quan

2014-01-01

Achieving site selectivity in C–H functionalization is a long-standing challenge in organic synthesis. The small differences in intrinsic reactivity of C–H bonds in a given organic molecule often lead to poor discrimination by a catalyst. One solution to this problem is to distinguish C–H bonds based on their location with respect to a particular functional group. In this context, the activation of C–H bonds 5 or 6 bonds away from a functional group via cyclometalation has been extensively studied.1-13 However, directed activation of C–H bonds that are distal (>6 bonds away) from functional groups has remained difficult, especially when the target C–H bonds are geometrically inaccessible through directed metalation due to the ring strain encountered in cyclometalation.14,15 Herein we report a recyclable template that directs the olefination and acetoxyation of distal meta-C–H bonds (as far as 11 bonds away) of anilines and benzylic amines. Remarkably, this template is able to direct the meta-selective C–H functionalization of bicyclic heterocycles via highly strained tricyclic cyclophane-like palladated intermediates. X-ray and NMR studies reveal that the conformational biases induced by a single fluorine substitution in the template can be enhanced by a ligand to switch from ortho- to meta-selectivity. PMID:24622200

Insight into the mechanism revealing the peroxidase mimetic catalytic activity of quaternary CuZnFeS nanocrystals: colorimetric biosensing of hydrogen peroxide and glucose

Science.gov (United States)

Dalui, Amit; Pradhan, Bapi; Thupakula, Umamahesh; Khan, Ali Hossain; Kumar, Gundam Sandeep; Ghosh, Tanmay; Satpati, Biswarup; Acharya, Somobrata

2015-05-01

Artificial enzyme mimetics have attracted immense interest recently because natural enzymes undergo easy denaturation under environmental conditions restricting practical usefulness. We report for the first time chalcopyrite CuZnFeS (CZIS) alloyed nanocrystals (NCs) as novel biomimetic catalysts with efficient intrinsic peroxidase-like activity. Novel peroxidase activities of CZIS NCs have been evaluated by catalytic oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). CZIS NCs demonstrate the synergistic effect of elemental composition and photoactivity towards peroxidase-like activity. The quaternary CZIS NCs show enhanced intrinsic peroxidase-like activity compared to the binary NCs with the same constituent elements. Intrinsic peroxidase-like activity has been correlated with the energy band position of CZIS NCs extracted using scanning tunneling spectroscopy and ultraviolet photoelectron spectroscopy. Kinetic analyses indicate Michaelis-Menten enzyme kinetic model catalytic behavior describing the rate of the enzymatic reaction by correlating the reaction rate with substrate concentration. Typical color reactions arising from the catalytic oxidation of TMB over CZIS NCs with H2O2 have been utilized to establish a simple and sensitive colorimetric assay for detection of H2O2 and glucose. CZIS NCs are recyclable catalysts showing high efficiency in multiple uses. Our study may open up the possibility of designing new photoactive multi-component alloyed NCs as enzyme mimetics in biotechnology applications.Artificial enzyme mimetics have attracted immense interest recently because natural enzymes undergo easy denaturation under environmental conditions restricting practical usefulness. We report for the first time chalcopyrite CuZnFeS (CZIS) alloyed nanocrystals (NCs) as novel biomimetic catalysts with efficient intrinsic peroxidase-like activity. Novel peroxidase activities of CZIS NCs have been

Electron transfer reactions in microporous solids. Progress report, September 1990--January 1993

Energy Technology Data Exchange (ETDEWEB)

Mallouk, T.E.

1993-01-01

Basic thrust the research program involves use of microporous solids (zeolites, clays, layered and tunnel structure oxide semiconductors) as organizing media for artificial photosynthetic systems. Purpose of the microporous solid is twofold. First, it induces spatial organization of photoactive and electroactive components (sensitizers, semiconductor particles, electron relays, and catalysts) at the solid-solution interface, enhancing the quantum efficiency of charge separation and separating physically the ultimate electron donor and acceptor in the electron transport chain. Second, since the microcrystalline solid admits only molecules of a certain charge and size, it is possible to achieve permanent charge separation by sieving chemical photoproducts (e.g., H{sub 2} and I{sub 3}{sup {minus}}, or H{sub 2} and O{sub 2)} from each other. Spectroscopic and electrochemical methods are used to study the kinetics of electron transfer reactions in these hybrid molecular/solid state assemblies.

Energetic characterization of the photoactive FeS/sub 2/ (pyrite) interface

Energy Technology Data Exchange (ETDEWEB)

Ennaoui, A.; Tributsch, H.

1986-12-01

The electronic properties of synthetic single crystalline pyrite (100) orientation are investigated. The spectral response of the photoconductivity was determined by the four point probe technique. The carrier concentration and the flat band potential are calculated from capacitance measurements, the minority carrier diffusion length is determined by photocurrent and capacitance vs voltage measurements. The results allow the construction of an energy band diagram for the FeS/sub 2//electrolyte contact. The parameters determined explain the high quantum efficiency (approx. 90%) obtained with FeS/sub 2//I/sup -/, I/sub 3//sup -/, photoelectrochemical cells (PECs). The reasons for the main deficiency (photopotentials not exceeding 200 mV at AM0) are elaborated: photogenerated charges in the interface shift the flatband potential and trap-assisted electron transfer through the barrier short-circuits it. 32 refs.

Photoaffinity labeling of opiate receptors using intrinsically photoactive 3H-opiates

International Nuclear Information System (INIS)

Kooper, G.N.; Levinson, N.R.; Copeland, C.F.; Bowen, W.D.

1988-01-01

Opiate receptors in rat and cow brain membranes have been labeled irreversibly using the intrinsic photolability of 3H-opiates. Membranes were incubated with 3H-ligand and then irradiated with UV light of 254 nm. Nonspecific binding was determined in the presence of 10 microM unlabeled levallorphan. Irreversible binding was defined as binding which survived heat or acid denaturation of membranes. Specific incorporation of label into denatured samples was observed only when unbound or loosely bound 3H-ligand was washed free from the membranes prior to irradiation. There was a general correlation between photosensitivity of the 3H-ligand and its ability to photolabel receptors. Hence, photolabeling presumably results by covalent attachment of highly reactive species generated during photochemical decomposition of ligand. With 3H-etorphine, optimal irradiation time was 5 min. In addition to 3H-etorphine, receptors could be labeled irreversibly with 3H-oxymorphone, 3H-dihydromorphine, and 3H-ethylketocyclazocine. Of the specific binding present in irradiated, nondenatured samples, 45-60% remained attached to receptors upon denaturation. 3H-Ethylketocyclazocine exhibited an 86% yield of incorporation. Signal-to-noise levels of 50-80% could be achieved in denatured samples. Therefore, this method provides a means of covalently labeling opiate receptors in high yield and with high signal-to-noise ratios. The opioid peptides, 3H-D-Ala2,D-Leu5-enkephalin, 3H-D-Ser2,Leu5,Thr6-enkephalin, 3H-D-Ala2,Met5-enkephalin amide, and 3H-D-Ala2,N-MePhe4,Gly-ol5-enkephalin, as well as the benzomorphan, 3H-bremazocine, apparently lack the structural characteristics which allow photolabeling

Searching for new TiO2 crystal phases with better photoactivity

International Nuclear Information System (INIS)

Shang, Cheng; Zhao, Wei-Na; Liu, Zhi-Pan

2015-01-01

Using the recently developed stochastic surface walking global optimization method, this work explores the potential energy surface of TiO 2 crystals aiming to search for likely phases with higher photocatalytic activity. Five new phases of TiO 2 are identified and the lowest energy phase transition pathways connecting to the most abundant phases (rutile and anatase) are determined. Theory shows that a high-pressure phase, α-PbO 2 -like form (TiO 2 II) acts as the key intermediate in between rutile and anatase. The phase transition of anatase to rutile belongs to the diffusionless Martensitic phase transition, occurring through a set of habit planes, rutile(101)//TiO 2 II(001), and TiO 2 II(100)//anatase(112). With regard to the photocatalytic activity, three pure phases (#110, pyrite and fluorite) are found to possess the band gap narrower than rutile, but they are unstable at the low-pressure condition. Instead, a mixed anatase-TiO 2 II phase is found to have good stability and narrower band gap than both parent phases. Because of the phase separation, the mixed phase is also expected to improve the photocatalytic performance by reducing the probability of the electron-hole pair recombination. (paper)

New functional ligands for the preparation of photoactive nanoparticle‐based materials

OpenAIRE

Amorín Ferré, Laura

2014-01-01

La nanociència i la nanotecnologia han esdevingut les noves disciplines del nou mil·leni. Els processos desenvolupats per molts científics arreu del món, com per exemple el disseny, la fabricació i la manipulació a escala nanomètrica, han revolucionat la física, la química, la biologia i la tecnologia. La present tesi doctoral s'emmarca dins aquests camps. Més concretament, s'han dissenyat, sintetitzat i caracteritzat diferents lligands orgànics per (i) introduir-los en nanopartícul·les de po...

Facet-controlled synthesis of polyhedral hematite/carbon composites with enhanced photoactivity

Science.gov (United States)

Hu, Xiaoyi; Han, Sancan; Zhu, Yufang

2018-06-01

Much effort has been made to develop the semiconductor photocatalysis, but it is still challenging to fabricate low-cost and high-activity photocatalysts. In this study, Hematite (α-Fe2O3) with three kinds of morphologies including dodecahedron, tetrakaidecahedron and hexagonal nanoplates have been synthesized without any organic reagents. The photocatalytic performance reveals that the dodecahedron with exposed {1 0 1} facets is superior to the hexagonal nanoplates with predominant exposure of {0 0 1} facets in the case of similar BET surface area. For further enhancement of photocatalytic activity, carbon layer was coated on dodecahedral α-Fe2O3 through the self-polymerization of dopamine and following pyrolysis at 400 °C under Ar flow. Compared with the pristine dodecahedral α-Fe2O3, the α-Fe2O3/C composites exhibit stronger visible absorption, lower photoexcited electron-hole pairs recombination rate and better photodegradation activity. The photocatalytic performance showed the degradation rate of α-Fe2O3-D/4.5C is nearly 6 times higher than pristine α-Fe2O3, which have great potential for photocatalysis applications.

Porphyrin-layered double hydroxide/polymer composites as novel ecological photoactive surfaces

Czech Academy of Sciences Publication Activity Database

Káfuňková, Eva; Lang, Kamil; Kubát, Pavel; Klementová, Mariana; Mosinger, Jiří; Šlouf, Miroslav; Troutier-Thuilliez, A. L.; Leroux, F.; Verney, V.; Taviot-Guého, Ch.

2010-01-01

Roč. 20, č. 42 (2010), s. 9423-9432 ISSN 0959-9428 R&D Projects: GA ČR GAP207/10/1447 Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z40400503; CEZ:AV0Z40500505 Keywords : porphyrins * nanoparticles * hydroxide/polymer composites Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.101, year: 2010

The design, fabrication, and photocatalytic utility of nanostructured semiconductors: focus on TiO2-based nanostructures

Directory of Open Access Journals (Sweden)

Arghya Narayan Banerjee

2011-02-01

Full Text Available Arghya Narayan BanerjeeSchool of Mechanical Engineering, Yeungnam University, Gyeongsan, South KoreaAbstract: Recent advances in basic fabrication techniques of TiO2-based nanomaterials such as nanoparticles, nanowires, nanoplatelets, and both physical- and solution-based techniques have been adopted by various research groups around the world. Our research focus has been mainly on various deposition parameters used for fabricating nanostructured materials, including TiO2-organic/inorganic nanocomposite materials. Technically, TiO2 shows relatively high reactivity under ultraviolet light, the energy of which exceeds the band gap of TiO2. The development of photocatalysts exhibiting high reactivity under visible light allows the main part of the solar spectrum to be used. Visible light-activated TiO2 could be prepared by doping or sensitizing. As far as doping of TiO2 is concerned, in obtaining tailored material with improved properties, metal and nonmetal doping has been performed in the context of improved photoactivity. Nonmetal doping seems to be more promising than metal doping. TiO2 represents an effective photocatalyst for water and air purification and for self-cleaning surfaces. Additionally, it can be used as an antibacterial agent because of its strong oxidation activity and superhydrophilicity. Therefore, applications of TiO2 in terms of photocatalytic activities are discussed here. The basic mechanisms of the photoactivities of TiO2 and nanostructures are considered alongside band structure engineering and surface modification in nanostructured TiO2 in the context of doping. The article reviews the basic structural, optical, and electrical properties of TiO2, followed by detailed fabrication techniques of 0-, 1-, and quasi-2-dimensional TiO2 nanomaterials. Applications and future directions of nanostructured TiO2 are considered in the context of various photoinduced phenomena such as hydrogen production, electricity generation via

Spin-cast bulk heterojunction solar cells: A dynamical investigation

KAUST Repository

Chou, Kang Wei

2013-02-22

Spin-coating is extensively used in the lab-based manufacture of organic solar cells, including most of the record-setting solution-processed cells. We report the first direct observation of photoactive layer formation as it occurs during spin-coating. The study provides new insight into mechanisms and kinetics of bulk heterojunction formation, which may be crucial for its successful transfer to scalable printing processes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organic bulk heterojunction photovoltaic structures: design, morphology and properties

International Nuclear Information System (INIS)

Bulavko, G V; Ishchenko, A A

2014-01-01

Main approaches to the design of organic bulk heterojunction photovoltaic structures are generalized and systematized. Novel photovoltaic materials based on fullerenes, organic dyes and related compounds, graphene, conjugated polymers and dendrimers are considered. The emphasis is placed on correlations between the chemical structure and properties of materials. The effect of morphology of the photoactive layer on the photovoltaic properties of devices is analyzed. Main methods of optimization of the photovoltaic properties are outlined. The bibliography includes 338 references

Use of semiconductors in hydrogen production from water with solar energy as fuel

International Nuclear Information System (INIS)

Candea, M.R.

1980-01-01

Photoelectrolysis is a new and potentially low cost energy conversion scheme in which optical energy is converted into the chemical energy of H 2 and O 2 molecules using photoactive semiconducting electrodes in a photoelectrochemical cell. The aim of this paper is to acquaint the reader with the basic principles, the current problems and the advantages associated with photoelectrochemical cells as energy conversion devices. The present state of research in this area is also briefly reviewed. (author)

Spin-cast bulk heterojunction solar cells: A dynamical investigation

KAUST Repository

Chou, Kang Wei; Yan, Buyi; Li, Ruipeng; Li, Erqiang; Zhao, Kui; Anjum, Dalaver H.; Alvarez, Steven; Gassaway, Robert; Biocca, Alan K.; Thoroddsen, Sigurdur T; Hexemer, Alexander; Amassian, Aram

2013-01-01

Spin-coating is extensively used in the lab-based manufacture of organic solar cells, including most of the record-setting solution-processed cells. We report the first direct observation of photoactive layer formation as it occurs during spin-coating. The study provides new insight into mechanisms and kinetics of bulk heterojunction formation, which may be crucial for its successful transfer to scalable printing processes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Oriented Surface Dipole on Photoconversion Efficiency in an Alkane/Lipid-Hybrid-Bilayer-Based Photovoltaic Model System

KAUST Repository

Liu, Lixia

2013-06-21

When a phospholipid monolayer containing a zinc-coordinated porphyrin species formed atop a self-assembled monolayer of heptadecafluoro-1-decanethiol (CF3(CF2)7(CH2)2SH) is subjected to photoelectrochemical current generation, a significant modulation effect is observed. Compared with devices that contain similar photoactive lipid monolayers but formed on 1-dodecanethiol SAMs, these fluorinated hybrid bilayers produce a >60 % increase in cathodic currents and a similar decrease in anodic currents. Photovoltages recorded from these hybrid bilayers are found to vary in the same fashion. The modulation of photovoltaic responses in these hybrid-bilayer-based devices is explained by the opposite surface dipoles associated with the thiols employed in this study, which in one case (fluorothiol) increase and in another (alkanethiol) decrease the work function of the underlying gold substrates. A similar trend of photovoltage/photocurrent modulation is also observed if fullerene is used as the photoagent in these devices. Our results reveal the intricacy of orientated surface dipole in influencing the photovoltaic processes, and its subtle interplay with other factors related to the photoagents, such as their location and orientation within the organic matrix. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Oriented Surface Dipole on Photoconversion Efficiency in an Alkane/Lipid-Hybrid-Bilayer-Based Photovoltaic Model System

KAUST Repository

Liu, Lixia; Xie, Hong; Bostic, Heidi E.; Jin, Limei; Best, Michael D.; Zhang, X. Peter; Zhan, Wei

2013-01-01

When a phospholipid monolayer containing a zinc-coordinated porphyrin species formed atop a self-assembled monolayer of heptadecafluoro-1-decanethiol (CF3(CF2)7(CH2)2SH) is subjected to photoelectrochemical current generation, a significant modulation effect is observed. Compared with devices that contain similar photoactive lipid monolayers but formed on 1-dodecanethiol SAMs, these fluorinated hybrid bilayers produce a >60 % increase in cathodic currents and a similar decrease in anodic currents. Photovoltages recorded from these hybrid bilayers are found to vary in the same fashion. The modulation of photovoltaic responses in these hybrid-bilayer-based devices is explained by the opposite surface dipoles associated with the thiols employed in this study, which in one case (fluorothiol) increase and in another (alkanethiol) decrease the work function of the underlying gold substrates. A similar trend of photovoltage/photocurrent modulation is also observed if fullerene is used as the photoagent in these devices. Our results reveal the intricacy of orientated surface dipole in influencing the photovoltaic processes, and its subtle interplay with other factors related to the photoagents, such as their location and orientation within the organic matrix. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Graphitic-C(3)N(4)-hybridized TiO(2) nanosheets with reactive {001} facets to enhance the UV- and visible-light photocatalytic activity.

Science.gov (United States)

Gu, Liuan; Wang, Jingyu; Zou, Zhijuan; Han, Xijiang

2014-03-15

AnataseTiO(2)nanosheets with dominant {001} facets were hybridized with graphitic carbon nitride (g-C(3)N(4)) using a facile solvent evaporation method. On top of the superior photocatalytic performance of highly reactive {001} facets, the hybridization with g-C(3)N(4) is confirmed to further improve the reactivity through degrading a series of organic molecules under both UV- and visible-light irradiation. It is proposed that an effective charge separation between g-C(3)N(4) and TiO2 exists in the photocatalytic process, i.e., the transferring of photogenerated holes from the valence band (VB) of TiO(2) to the highest occupied molecular orbital (HOMO) of g-C(3)N(4), and the injecting of electrons from the lowest unoccupied molecular orbital (LUMO) of g-C(3)N(4) to the conduction band (CB) of TiO(2). Due to this synergistic effect, the enhancement of UV- and visible-light photoactivity over the hybrid is achieved. Furthermore, it has been revealed that holes were the main factor for the improved photoactivity under UV-light, while the OH radicals gained the predominance for degrading organic molecules under visible-light. Overall, this work would be significant for fabricating efficient UV-/visible-photocatalysts and providing deeper insight into the enhanced mechanisms of π-conjugated molecules hybridized semiconductors. Copyright © 2014 Elsevier B.V. All rights reserved.

High-performance PbS quantum dot vertical field-effect phototransistor using graphene as a transparent electrode

Science.gov (United States)

Che, Yongli; Zhang, Yating; Cao, Xiaolong; Song, Xiaoxian; Zhang, Haiting; Cao, Mingxuan; Dai, Haitao; Yang, Junbo; Zhang, Guizhong; Yao, Jianquan

2016-12-01

Solution processed photoactive PbS quantum dots (QDs) were used as channel in high-performance near-infrared vertical field-effect phototransistor (VFEpT) where monolayer graphene embedded as transparent electrode. In this vertical architecture, the PbS QD channel was sandwiched and naturally protected between the drain and source electrodes, which made the device ultrashort channel length (110 nm) simply the thickness of the channel layer. The VFEpT exhibited ambipolar operation with high mobilities of μe = 3.5 cm2/V s in n-channel operation and μh = 3.3 cm2/V s in p-channel operation at low operation voltages. By using the photoactive PbS QDs as channel material, the VFEpT exhibited good photoresponse properties with a responsivity of 4.2 × 102 A/W, an external quantum efficiency of 6.4 × 104% and a photodetectivity of 2.1 × 109 Jones at the light irradiance of 36 mW/cm2. Additionally, the VFEpT showed excellent on/off switching with good stability and reproducibility and fast response speed with a short rise time of 12 ms in n-channel operation and 10.6 ms in p-channel operation. These high mobilities, good photoresponse properties and simplistic fabrication of our VFEpTs provided a facile route to the high-performance inorganic photodetectors.

BM Solar Cells

KAUST Repository

Firdaus, Yuliar

2018-05-02

Fullerene‐based materials are widely used as electron acceptors in organic bulk‐heterojunction solar cells; yet, they have rarely been used as the only photoactive component due to their low absorbance and limited charge generation efficiency. However, blending the wide‐bandgap p‐type material copper (I) thiocyanate (CuSCN) with [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC70BM) leads to the formation of a unique mesostructured p‐n like heterointerface between CuSCN and PC70BM and solar cells with a power conversion efficiency (PCE) of up to 5.4%. Here, we examine in detail the reasons for the surprisingly good device performance and elucidate the charge photogeneration and recombination mechanisms in CuSCN‐based devices with PC70BM as the exclusive light‐absorbing material. Our studies clearly demonstrate that a substantial fraction of the photocurrent in the CuSCN‐based devices results from improved dissociation of fullerene excitons and efficient charge transfer at the CuSCN:PC70BM interface combined with reduced geminate and nongeminate charge recombination losses. Our results have implications beyond the fullerene‐based devices studied here, as they demonstrate that careful selection of a mesostructured p‐type transparent semiconductor paves the path to a new type of efficient single photoactive material solar cells.

Facile Synthesis and Characterization of N-Doped TiO2 Photocatalyst and Its Visible-Light Activity for Photo-Oxidation of Ethylene

Directory of Open Access Journals (Sweden)

Yu-Hao Lin

2015-01-01

Full Text Available A facile wet chemical method was adopted for preparing highly photoactive nitrogen doped TiO2 (N-TiO2 powders with visible responsive capability, which could be achieved by the hydrolysis of titanium isopropoxide (TTIP in the ammonium hydroxide precursor solution in various concentrations and then calcined at different temperatures. The N-TiO2 powders were characterized, and the photocatalytic activity was evaluated for the photocatalytic oxidation of ethylene gas under visible light irradiation to optimize the synthesizing conditions of N-TiO2 catalyst. The N-TiO2 photocatalytic powders were calcined in a range of temperatures from 300 to 600°C and obviously found to have greater photocatalytic activities than commercial TiO2 P25. The strong absorption in the visible light region could be ascribed to good crystallization and adapted sinter temperature of as prepared sample. XPS test demonstrated that the N was doped into TiO2 lattice and made an interstitial formation (Ti-O-N, and N doping also retarded the phase transformation from anatase to rutile as well. The N-TiO2 catalyst prepared with 150 mL ammonium hydroxide added and calcined at 500°C showed the best photocatalytic activity. The experimental results also proved the enhanced photoactivity of N-TiO2 material depends on the synthesizing conditions.

Single-Walled Carbon Nanotubes in Solar Cells.

Science.gov (United States)

Jeon, Il; Matsuo, Yutaka; Maruyama, Shigeo

2018-01-22

Photovoltaics, more generally known as solar cells, are made from semiconducting materials that convert light into electricity. Solar cells have received much attention in recent years due to their promise as clean and efficient light-harvesting devices. Single-walled carbon nanotubes (SWNTs) could play a crucial role in these devices and have been the subject of much research, which continues to this day. SWNTs are known to outperform multi-walled carbon nanotubes (MWNTs) at low densities, because of the difference in their optical transmittance for the same current density, which is the most important parameter in comparing SWNTs and MWNTs. SWNT films show semiconducting features, which make SWNTs function as active or charge-transporting materials. This chapter, consisting of two sections, focuses on the use of SWNTs in solar cells. In the first section, we discuss SWNTs as a light harvester and charge transporter in the photoactive layer, which are reviewed chronologically to show the history of the research progress. In the second section, we discuss SWNTs as a transparent conductive layer outside of the photoactive layer, which is relatively more actively researched. This section introduces SWNT applications in silicon solar cells, organic solar cells, and perovskite solar cells each, from their prototypes to recent results. As we go along, the science and prospects of the application of solar cells will be discussed.

Improving the photocatalytic performance of graphene-TiO2 nanocomposites via a combined strategy of decreasing defects of graphene and increasing interfacial contact.

Science.gov (United States)

Zhang, Yanhui; Zhang, Nan; Tang, Zi-Rong; Xu, Yi-Jun

2012-07-07

Incessant interest has been shown in the synthesis of graphene (GR)-semiconductor nanocomposites as photocatalysts aiming to utilize the excellent electron conductivity of GR to lengthen the lifetime of photoexcited charge carriers in the semiconductor and, hence, improve the photoactivity. However, research works focused on investigating how to make sufficient use of the unique electron conductivity of GR to design a more efficient GR-semiconductor photocatalyst have been quite lacking. Here, we show a proof-of-concept study on improving the photocatalytic performance of GR-TiO(2) nanocomposites via a combined strategy of decreasing defects of GR and improving the interfacial contact between GR and the semiconductor TiO(2). The GR-TiO(2) nanocomposite fabricated by this approach is able to make more sufficient use of the electron conductivity of GR, by which the lifetime and transfer of photoexcited charge carriers of GR-TiO(2) upon visible light irradiation will be improved more efficiently. This in turn leads to the enhancement of visible-light-driven photoactivity of GR-TiO(2) toward selective transformation of alcohols to corresponding aldehydes using molecular oxygen as a benign oxidant under ambient conditions. It is anticipated that our current work would inform ongoing efforts to exploit the rational design of smart, more efficient GR-semiconductor photocatalysts for conversion of solar to chemical energy by heterogeneous photocatalysis.

Preparation of Silver Immobilised TiO2-Hectorite for Phenol Removal and Eschericia coli Desinfection

Directory of Open Access Journals (Sweden)

Is Fatimah

2013-03-01

Full Text Available Preparation of silver immobilized TiO2-Hectorite and its application in phenol photooxidation and Eschericia coli bacteria desinfection has been conducted. Material was obtained by two steps of synthesis: preparation of TiO2-Hectorite and silver immobilization into TiO2-Hectorite. Physico-chemical characterization to the prepared material compared to raw hectorite was conducted by X-ray Diffraction, gas sorption analyzer, scanning electron microscope and DRUV-Visible spectrophotometry and for photoactivity study, phenol photooxidation and Eschericia coli desinfection were investigated. The results indicated that the modification to hectorite material improve the physico-chemical character related to its role as photo-catalyst. Kinetic study of phenol photooxidation revealed the role of TiO2 pillarization and silver immobilization in enhancing rate of reaction as well as increased photoactivity of the materials in E. coli desinfection. © 2013 BCREC UNDIP. All rights reservedReceived: 28th September 2012; Revised: 7th December 2012; Accepted: 20th Decemberber 2012[How to Cite: I. Fatimah (2013. Preparation of Silver Immobilised TiO2-Hectorite for Phenol Removal and Eschericia coli Desinfection. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (3: 191-197. (doi:10.9767/bcrec.7.3.4047.191-197][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.7.3.4047.191-197 ] View in  |

Efficacy of the Reactive Oxygen Species Generated by Immobilized TiO2 in the Photocatalytic Degradation of Diclofenac

Directory of Open Access Journals (Sweden)

B. Di Credico

2015-01-01

Full Text Available We report on the photodegradation of diclofenac (DCF by hydrothermal anatase nanocrystals either free or immobilized in porous silica matrix (TS in connection to the type and amount of reactive oxygen species (ROS, in order to have deeper insight into their role in the photocatalysis and to provide an effective tool to implement the DCF mineralization. TiO2 and TS exhibit a remarkable efficiency in the DCF abatement, supporting that the utilization of anatase nanoparticles with the highly reactive {001}, {010}, and {101} exposed surfaces can be an effective way for enhancing the photooxidation even of the persistent pollutants. Furthermore, the hydrothermal TiO2, when immobilized in silica matrix, preserves its functional properties, combining high photoactivity with an easy technical use and recovery of the catalyst. The catalysts performances have been related to the presence of OH•, O21, and O2-• species by electron paramagnetic resonance spin-trap technique. The results demonstrated that the ROS concentration increases with the increase of photoactivity and indicated a significant involvement of O21 in the DCF degradation. The efficacy of TiO2 when immobilized on a silica matrix was associated with the high ROS life time and with the presence of singlet oxygen, which contributes to the complete photomineralization of DCF.

BM Solar Cells

KAUST Repository

Firdaus, Yuliar; Seitkhan, Akmaral; Eisner, Flurin; Sit, Wai-Yu; Kan, Zhipeng; Wehbe, Nimer; Balawi, Ahmed H.; Yengel, Emre; Karuthedath, Safakath; Laquai, Fré dé ric; Anthopoulos, Thomas D.

2018-01-01

Fullerene‐based materials are widely used as electron acceptors in organic bulk‐heterojunction solar cells; yet, they have rarely been used as the only photoactive component due to their low absorbance and limited charge generation efficiency. However, blending the wide‐bandgap p‐type material copper (I) thiocyanate (CuSCN) with [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC70BM) leads to the formation of a unique mesostructured p‐n like heterointerface between CuSCN and PC70BM and solar cells with a power conversion efficiency (PCE) of up to 5.4%. Here, we examine in detail the reasons for the surprisingly good device performance and elucidate the charge photogeneration and recombination mechanisms in CuSCN‐based devices with PC70BM as the exclusive light‐absorbing material. Our studies clearly demonstrate that a substantial fraction of the photocurrent in the CuSCN‐based devices results from improved dissociation of fullerene excitons and efficient charge transfer at the CuSCN:PC70BM interface combined with reduced geminate and nongeminate charge recombination losses. Our results have implications beyond the fullerene‐based devices studied here, as they demonstrate that careful selection of a mesostructured p‐type transparent semiconductor paves the path to a new type of efficient single photoactive material solar cells.

Multifunctional polyoxometalates encapsulated in MIL-100(Fe): highly efficient photocatalysts for selective transformation under visible light.

Science.gov (United States)

Liang, Ruowen; Chen, Rui; Jing, Fenfen; Qin, Na; Wu, Ling

2015-11-07

H3PMo12O40 molecules have been successfully encapsulated in the cavities of MIL-100(Fe) via a facile hydrothermal method (denoted as HPMo@MIL-100(Fe)). A series of characterization has corroborated the insertion of H3PMo12O40 within the cavities of MIL-100(Fe). The resulting HPMo@MIL-100(Fe) nanocomposites have exhibited much higher photoactivity than the original-MIL-100(Fe) toward the photocatalytic selective oxidation of benzylic alcohols and the reduction of Cr(vi) under visible light irradiation (λ≥ 420 nm). The higher photoactivity of HPMo@MIL-100(Fe) can be attributed to the integrative effect of enhanced light absorption intensity and more efficient separation of photogenerated electron-hole pairs. The host porous structure of MIL-100(Fe) can achieve a uniform composition with H3PMo12O40, which is significantly important for producing highly reactive dispersed H3PMo12O40 molecules and enhancing the photocatalytic activity of HPMo@MIL-100(Fe) nanocomposites. And the immobilized H3PMo12O40 molecules are more convenient for recycling. Importantly, almost no Fe and Mo ions leach from the MIL-100(Fe) during the reaction, which verifies the photostability of the HPMo@MIL-100(Fe). In addition, possible photocatalytic redox reaction mechanisms have been investigated.

Photoelectrochemical properties of ZnO nanocrystals/MEH-PPV composite: The effects of nanocrystals synthetic route, film deposition and electrolyte composition

Energy Technology Data Exchange (ETDEWEB)

Petrella, A. [Dipartimento di Ingegneria Civile, Ambientale, del Territorio, Edile e Chimica, Politecnico di Bari, Via Orabona 4, 70125 Bari (Italy); Curri, M.L.; Striccoli, M. [CNR IPCF Sez. Bari c/o Dip. Chimica, Università di Bari, Via Orabona 4, 70126 Bari (Italy); Agostiano, A. [Dipartimento di Chimica, Università di Bari, via Orabona 4, 70126 Bari (Italy); CNR IPCF Sez. Bari c/o Dip. Chimica, Università di Bari, Via Orabona 4, 70126 Bari (Italy); Cosma, P., E-mail: pinalysa.cosma@uniba.it [Dipartimento di Chimica, Università di Bari, via Orabona 4, 70126 Bari (Italy); CNR IPCF Sez. Bari c/o Dip. Chimica, Università di Bari, Via Orabona 4, 70126 Bari (Italy)

2015-11-30

This paper reports a study on the photoelectrochemical processes occurring at the interface of ZnO nanocrystals/MEH-PPV composites. Colloidal chemical routes were used to obtain size controlled non-hydrolytic ZnO nanocrystals (NCs) dispersible in organic solvents, while a low molecular weight poly[2-methoxy-5-(2′-ethyl-hexyloxy)phenylene vinylene] (MEH-PPV), characterized by high degree of structural order, was synthesized via an organometallic method. The optical properties of the nanocomposite material were comprehensively investigated on solution and on films deposited by spin coating. Remarkably, a significant fluorescence quenching of the polymer at the MEH-PPV/ZnO junction was observed. Photoelectrochemical measurements demonstrated that the photoactivity of the composite material was significantly improved in the case of non-hydrolytic NCs with respect to hydrolytic route prepared ZnO. Moreover, the effective role of the organic/inorganic blend to improve the charge transfer with respect to the double layer hetero-junction was confirmed, thanks to the extended interfaces which enable an effective electron transfer between the hetero-junction components. The system was also studied at different film thicknesses and electrolyte compositions. The results indicated that film photoactivity increased with film thickness up to 300 nm due to the presence of a large number of interfaces, while the change of cation size influenced the ionic conductivity through the nanocomposite film. It was shown that efficient photoconductivity requires not only efficient charge separation, but also efficient transport of the carriers to the electrodes without recombination. - Highlights: • The photoelectrochemical processes at ZnO nanocrystals/MEH-PPV hetero-junction were studied. • Fluorescence quenching of the polymer at the MEH-PPV/ZnO interface was observed. • Non-hydrolytic ZnO junction showed higher photocurrents than hydrolytic equivalent. • The blends showed

Photoelectrochemical properties of ZnO nanocrystals/MEH-PPV composite: The effects of nanocrystals synthetic route, film deposition and electrolyte composition

International Nuclear Information System (INIS)

Petrella, A.; Curri, M.L.; Striccoli, M.; Agostiano, A.; Cosma, P.

2015-01-01

This paper reports a study on the photoelectrochemical processes occurring at the interface of ZnO nanocrystals/MEH-PPV composites. Colloidal chemical routes were used to obtain size controlled non-hydrolytic ZnO nanocrystals (NCs) dispersible in organic solvents, while a low molecular weight poly[2-methoxy-5-(2′-ethyl-hexyloxy)phenylene vinylene] (MEH-PPV), characterized by high degree of structural order, was synthesized via an organometallic method. The optical properties of the nanocomposite material were comprehensively investigated on solution and on films deposited by spin coating. Remarkably, a significant fluorescence quenching of the polymer at the MEH-PPV/ZnO junction was observed. Photoelectrochemical measurements demonstrated that the photoactivity of the composite material was significantly improved in the case of non-hydrolytic NCs with respect to hydrolytic route prepared ZnO. Moreover, the effective role of the organic/inorganic blend to improve the charge transfer with respect to the double layer hetero-junction was confirmed, thanks to the extended interfaces which enable an effective electron transfer between the hetero-junction components. The system was also studied at different film thicknesses and electrolyte compositions. The results indicated that film photoactivity increased with film thickness up to 300 nm due to the presence of a large number of interfaces, while the change of cation size influenced the ionic conductivity through the nanocomposite film. It was shown that efficient photoconductivity requires not only efficient charge separation, but also efficient transport of the carriers to the electrodes without recombination. - Highlights: • The photoelectrochemical processes at ZnO nanocrystals/MEH-PPV hetero-junction were studied. • Fluorescence quenching of the polymer at the MEH-PPV/ZnO interface was observed. • Non-hydrolytic ZnO junction showed higher photocurrents than hydrolytic equivalent. • The blends showed

Phototoxicity of TiO2 nanoparticles to a freshwater benthic amphipod: Are benthic systems at risk?

International Nuclear Information System (INIS)

Li, Shibin; Wallis, Lindsay K.; Ma, Hongbo; Diamond, Stephen A.

2014-01-01

This study investigated phototoxicity of TiO 2 nanoparticles (nano-TiO 2 ) to a freshwater benthic amphipod (Hyalella azteca) using 48-h and 96-h bioassays. Thorough monitoring of particle interactions with exposure media (Lake Superior water, LSW) and the surface of organisms was performed using dynamic light scattering, UV/Vis spectroscopy, and Scanning Electron Microscopy. Large agglomeration and sedimentation (> 77%) in LSW was observed after 0.5 h. A simulated solar radiation (SSR)-favored surface attachment of nanoparticles was observed, indicating enhanced phototoxicity with the increased attachment. A 96-h median lethal concentration (LC50) of 29.9 mg/L in H. azteca was calculated, with a daily 4-h UV exposure of 2.2 W/m 2 . Phototoxicity of nano-TiO 2 under SSR had a 21-fold increase as compared to that under ambient laboratory light. This phototoxicity was also dependent on UV dose, with calculated LC50s around 22.9 (95% CI, 20.5–23.3) Wh/m 2 when exposed to 20 mg/L nano-TiO 2 . Also, H. azteca exhibited negative phototaxis in the presence of shelters, indicating that other factors might play a role in environmental systems. Finally, the environmental implications of nano-TiO 2 to benthic organisms were illustrated, emphasizing the importance of various environmental factors in the ultimate phototoxicity. This increased phototoxicity and its complex interactions with various environmental factors suggest further investigations are needed for future risk assessment of photoactive nanomaterials to benthic organisms. - Graphical abstract: Display Omitted - Highlights: •Large aggregation of TiO 2 nanoparticles in Lake Superior water was observed. •Phototoxicity was dependent on the dose of both solar radiation and nanoparticle. •A solar radiation favored surface attachment of nanoparticles was observed. •Hyalella azteca exhibited negative phototaxis in the presence of shelters. •Factors influencing phototoxicity in the real environment were

Psoriasis, Psoralen and Sunlight

Directory of Open Access Journals (Sweden)

R.P.C Naik

1979-01-01

Full Text Available Topical or oral administration of photoactive furocumarins followed by exposure to ultra violet light from artificial sources has been shown previously to clear psoriatic lesions. Sunlight has been chosen as the source of UVL m two separate paired comparison studies using topical and, oral 4,5, 8 trimethylpsoralen. Two out of 21 on topical therapy and none out of 6 patients on oral paired-comparison study showed faster clearance of the drug treated lesions compared to control sites.

Solar detoxification of fuel-contaminated groundwater using fixed-bed photocatalysts

Energy Technology Data Exchange (ETDEWEB)

Crittenden, J. C. [Michigan Technological University, Houghton, Michigan (United States); Zhang, Y.; Hand, D. W.; Perram, D. L.; Marchand, E. G.

1996-05-15

A field test of a solar photocatalytic process for detoxification of water was conducted at Tyndall Air Force Base, Florida, where benzene, toluene, ethylbenzene, and xylene (BTEX) compounds were found in the fuel-contaminated groundwater. Platinized titanium dioxide supported on silica gel is packed in tubular photoreactors and used for single-pass operations. Catalyst fouling, destruction inhibition, and water pretreatment are investigated in addition to BTEX destruction. Ionic species were found to be primarily responsible for photocatalyst fouling and destruction inhibition. A simple pretreatment unit was developed for removing turbidity, adding oxidant, and ionic species. By using pretreatment, the reactor system operated efficiently, and no loss in catalyst photoactivity was found during the month-long test. On a rainy day, BTEX compounds of a total influent concentration of more than 2 mg/L were destroyed within 6.5 minutes of empty-bed contact time. Test results with various flow rates, reactor diameters, influent concentrations, solar irradiances, and weather conditions confirm the application potential of the process.

Solar detoxification of fuel-contaminated groundwater using fixed-bed photocatalysts

International Nuclear Information System (INIS)

Crittenden, J.C.; Zhang, Y.; Hand, D.W.; Perram, D.L.; Marchand, E.G.

1996-01-01

A field test of a solar photocatalytic process for detoxification of water was conducted at Tyndall Air Force Base, Florida, where benzene, toluene, ethylbenzene, and xylene (BTEX) compounds were found in the fuel-contaminated groundwater. Platinized titanium dioxide supported on silica gel is packed in tubular photoreactors and used for single-pass operations. Catalyst fouling, destruction inhibition, and water pretreatment are investigated in addition to BTEX destruction. Ionic species were found to be primarily responsible for photocatalyst fouling and destruction inhibition. A simple pretreatment unit was developed for removing turbidity, adding oxidant, and ionic species. By using pretreatment, the reactor system operated efficiently, and no loss in catalyst photoactivity was found during the month-long test. On a rainy day, BTEX compounds of a total influent concentration of more than 2 mg/L were destroyed within 6.5 minutes of empty-bed contact time. Test results with various flow rates, reactor diameters, influent concentrations, solar irradiances, and weather conditions confirm the application potential of the process

One-dimensional organic lead halide perovskites with efficient bluish white-light emission

Science.gov (United States)

Yuan, Zhao; Zhou, Chenkun; Tian, Yu; Shu, Yu; Messier, Joshua; Wang, Jamie C.; van de Burgt, Lambertus J.; Kountouriotis, Konstantinos; Xin, Yan; Holt, Ethan; Schanze, Kirk; Clark, Ronald; Siegrist, Theo; Ma, Biwu

2017-01-01

Organic-inorganic hybrid metal halide perovskites, an emerging class of solution processable photoactive materials, welcome a new member with a one-dimensional structure. Herein we report the synthesis, crystal structure and photophysical properties of one-dimensional organic lead bromide perovskites, C4N2H14PbBr4, in which the edge sharing octahedral lead bromide chains [PbBr4 2-]∞ are surrounded by the organic cations C4N2H14 2+ to form the bulk assembly of core-shell quantum wires. This unique one-dimensional structure enables strong quantum confinement with the formation of self-trapped excited states that give efficient bluish white-light emissions with photoluminescence quantum efficiencies of approximately 20% for the bulk single crystals and 12% for the microscale crystals. This work verifies once again that one-dimensional systems are favourable for exciton self-trapping to produce highly efficient below-gap broadband luminescence, and opens up a new route towards superior light emitters based on bulk quantum materials.

Nanoporous of W/WO{sub 3} thin film electrode grown by electrochemical anodization applied in the photoelectrocatalytic oxidation of the basic red 51 used in hair dye

Energy Technology Data Exchange (ETDEWEB)

Fraga, Luciano E.; Zanoni, Maria Valnice B., E-mail: fraga@iq.unesp.b [Universidade Estadual Paulista (IQ/UNESP), Araraquara, SP (Brazil). Inst. de Quimica. Dept. de Quimica Analitica

2011-07-01

Self-organized W/WO{sub 3} nanoporous electrodes can be obtained by simple electrochemical anodization of W foil in 0.15 mol L{sup -1} NaF solution as the supporting electrolyte, applying a ramp potential of 0.2 V s{sup -1} until it reached 60 V, which was maintained for 2 h. The monoclinic form is majority in the highly ordered WO{sub 3} annealed at 450 deg C, obtaining a higher photoactivity when irradiated by visible light than by UV light. The electrode promotes complete discoloration of the investigated basic red 51 dye after 60 min of photoelectrocatalytic oxidation, on current density of 1.25 mA cm{sup -2} and irradiation on wavelength of 420-630 nm. In this condition it was obtained 63% of mineralization. Lower efficiency is obtained for the system irradiated by wavelength (280- 400 nm) when only 40% of total organic carbon removal is obtained and 120 min is required for complete discoloration. (author)

Superhydrophobic ceramic coatings enabled by phase-separated nanostructured composite TiO2–Cu2O thin films

International Nuclear Information System (INIS)

Aytug, Tolga; Paranthaman, Parans M; Simpson, John T; Christen, David K; Bogorin, Daniela F; Mathis, John E

2014-01-01

By exploiting phase-separation in oxide materials, we present a simple and potentially low-cost approach to create exceptional superhydrophobicity in thin-film based coatings. By selecting the TiO 2 –Cu 2 O system and depositing through magnetron sputtering onto single crystal and metal templates, we demonstrate growth of nanostructured, chemically phase-segregated composite films. These coatings, after appropriate chemical surface modification, demonstrate a robust, non-wetting Cassie–Baxter state and yield an exceptional superhydrophobic performance, with water droplet contact angles reaching to ∼172° and sliding angles <1°. As an added benefit, despite the photo-active nature of TiO 2 , the chemically coated composite film surfaces display UV stability and retain superhydrophobic attributes even after exposure to UV (275 nm) radiation for an extended period of time. The present approach could benefit a variety of outdoor applications of superhydrophobic coatings, especially for those where exposure to extreme atmospheric conditions is required. (papers)

Influence of doped-charge transport layers on the photovoltaic performance of donor-acceptor blend p-i-n type organic solar cells

Directory of Open Access Journals (Sweden)

D. Gebeyehu

2004-06-01

Full Text Available This report demonstrates external power conversion efficiencies of 2% under 100 mW/cm2 simulated AM1.5 illumination for organic thin-film photovoltaic cells using a phthalocyanine-fullerene (ZnPc/C60 bulk heterojunction as an active layer, embedded into a p-i-n type architecture with doped wide-gap charge transport layers. For an optically optimized device, we found internal quantum efficiency (IQE of above 80% under short circuit conditions. Such optically thin cells with high internal quantum efficiency are an important step towards high efficiency tandem cells. The p-i-n architecture allows for the design of solar cells with high internal quantum efficiency where only the photoactive region absorbs visible light and recombination losses at contacts are avoided. The I-V characteristics, power conversion efficiencies, the dependence of short circuit current on incident white light intensity, incident photon to collected electron efficiency (IPCE and absorption spectra of the active layer system are discussed.

Extracting Information about the Electronic Quality of Organic Solar-Cell Absorbers from Fill Factor and Thickness

Science.gov (United States)

Kaienburg, Pascal; Rau, Uwe; Kirchartz, Thomas

2016-08-01

Understanding the fill factor in organic solar cells remains challenging due to its complex dependence on a multitude of parameters. By means of drift-diffusion simulations, we thoroughly analyze the fill factor of such low-mobility systems and demonstrate its dependence on a collection coefficient defined in this work. We systematically discuss the effect of different recombination mechanisms, space-charge regions, and contact properties. Based on these findings, we are able to interpret the thickness dependence of the fill factor for different experimental studies from the literature. The presented model provides a facile method to extract the photoactive layer's electronic quality which is of particular importance for the fill factor. We illustrate that over the past 15 years, the electronic quality has not been continuously improved, although organic solar-cell efficiencies increased steadily over the same period of time. Only recent reports show the synthesis of polymers for semiconducting films of high electronic quality that are able to produce new efficiency records.

Preparation of ZnO Nanoparticles and Photocatalytic H2 Production Activity from Different Sacrificial Reagent Solutions

Science.gov (United States)

Peng, Tian-you; Lv, Hong-jin; Zeng, Peng; Zhang, Xiao-hu

2011-08-01

ZnO nanoparticles were synthesized via a direct precipitation method followed by a heterogeneous azeotropic distillation and calcination processes, and then characterized by X-ray power diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption measurement. The effects of Pt-loading amount, calcination temperature, and sacrificial reagents on the photocatalytic H2 evolution efficiency from the present ZnO suspension were investigated. The experimental results indicate that ZnO nanoparticles calcined at 400 °C exhibit the best photoactivity for the H2 production in comparison with the samples calcined at 300 and 500 °C, and the photocatalytic H2 production efficiency from a methanol solution is much higher than that from a triethanolamine solution. It can be ascribed to the oxidization of methanol also contributes to the H2 production during the photochemical reaction process. Moreover, the photocatalytic mechanism for the H2 production from the present ZnO suspension system containing methanol solution is also discussed in detail.

Conformation-induced remote meta-C-H activation of amines

Science.gov (United States)

Tang, Ri-Yuan; Li, Gang; Yu, Jin-Quan

2014-03-01

Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a long-standing challenge in organic chemistry. The small differences in intrinsic reactivity of C-H bonds in any given organic molecule can lead to the activation of undesired C-H bonds by a non-selective catalyst. One solution to this problem is to distinguish C-H bonds on the basis of their location in the molecule relative to a specific functional group. In this context, the activation of C-H bonds five or six bonds away from a functional group by cyclometallation has been extensively studied. However, the directed activation of C-H bonds that are distal to (more than six bonds away) functional groups has remained challenging, especially when the target C-H bond is geometrically inaccessible to directed metallation owing to the ring strain encountered in cyclometallation. Here we report a recyclable template that directs the olefination and acetoxylation of distal meta-C-H bonds--as far as 11 bonds away--of anilines and benzylic amines. This template is able to direct the meta-selective C-H functionalization of bicyclic heterocycles via a highly strained, tricyclic-cyclophane-like palladated intermediate. X-ray and nuclear magnetic resonance studies reveal that the conformational biases induced by a single fluorine substitution in the template can be enhanced by using a ligand to switch from ortho- to meta-selectivity.

2,1,3-benzothiadiazole-5,6-dicarboxylic imide - A versatile building block for additive- and annealing-free processing of organic solar cells with effi ciencies exceeding 8%

KAUST Repository

Nielsen, Christian Bergenstof

2014-12-15

A new photoactive polymer comprising benzo[1,2-b:3,4-b′:5,6-d′]trithiophene and 2,1,3-benzothiadiazole-5,6-dicarboxylic imide is reported. The synthetic design allows for alkyl chains to be introduced on both electron-rich and electron-deficient components, which in turn allows for rapid optimization of the alkyl chain substitution pattern. Consequently, the optimized polymer shows a maximum efficiency of 8.3% in organic photovoltaic devices processed in commercially viable fashion without solvent additives, annealing, or device engineering.

Synthesis and spectroscopic characterization of a fluorescent pyrrole derivative containing electron acceptor and donor groups

Science.gov (United States)

Almeida, A. K. A.; Monteiro, M. P.; Dias, J. M. M.; Omena, L.; da Silva, A. J. C.; Tonholo, J.; Mortimer, R. J.; Navarro, M.; Jacinto, C.; Ribeiro, A. S.; de Oliveira, I. N.

2014-07-01

The synthesis and fluorescence characterization of a new pyrrole derivative (PyPDG) containing the electron donor-acceptor dansyl substituent is reported. The effects of temperature and solvent polarity on the steady-state fluorescence of this compound are investigated. Our results show that PyPDG exhibits desirable fluorescent properties which makes it a promising candidate to be used as the photoactive material in optical thermometry and thermography applications. Further, the electrochemical and emission properties of polymeric films obtained from the oxidation polymerization of PyPDG are also analyzed.

Inverted bulk-heterojunction organic solar cell using chemical bath deposited titanium oxide as electron collection layer

OpenAIRE

Kuwabara, Takayuki; Sugiyama, Hirokazu; Kuzuba, Mitsuhiro　　; Yamaguchi, Takahiro; Takahashi, Kohshin

2010-01-01

Chemical bath deposited titanium oxide (TiOx ) as an electron collection layer is introduced between the organic layer and the indium tin oxide (ITO) electrode for improving the performance of inverted bulk-heterojunction organic thin film solar cells with 1 cm2 active area, where regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) were mainly used as the photo-active layer. The uniform and thin TiOx film was easily prepared onto the ITO electrode ...

Interplay of Interfacial Layers and Blend Composition To Reduce Thermal Degradation of Polymer Solar Cells at High Temperature.

Science.gov (United States)

Ben Dkhil, Sadok; Pfannmöller, Martin; Schröder, Rasmus R; Alkarsifi, Riva; Gaceur, Meriem; Köntges, Wolfgang; Heidari, Hamed; Bals, Sara; Margeat, Olivier; Ackermann, Jörg; Videlot-Ackermann, Christine

2018-01-31

The thermal stability of printed polymer solar cells at elevated temperatures needs to be improved to achieve high-throughput fabrication including annealing steps as well as long-term stability. During device processing, thermal annealing impacts both the organic photoactive layer, and the two interfacial layers make detailed studies of degradation mechanism delicate. A recently identified thermally stable poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl

Photocatalysis application of zinc oxide fibers obtained by electrospinning

International Nuclear Information System (INIS)

Gerchman, D.; Alves, A.K.; Berutti, F.A.; Bergmann, C.P.

2010-01-01

Using the electrospinning technique, composite fibers of polyvinylbutyral and zinc nitrate were obtained. After a heat treatment at 600 deg C, nanostructured zinc oxide fibers were obtained. The fibers were characterized using X ray diffraction. The photocatalytic activity of the nanostructured fibers was determined using the photodegradation of a methyl orange solution. The increase in the heat treatment temperature decreases the photoactivity of the zinc oxide. The heat treatment, the phases and the surface area, affect the physical, chemical and photocatalytic activity of the zinc oxide. (author)

p-doped multiwall carbon nanotube/perylene diimide derivative photoelectrochemical cells for photocurrent generation

Energy Technology Data Exchange (ETDEWEB)

Troeger, Anna; Ledendecker, Marc; Margraf, Johannes T.; Sgobba, Vito; Guldi, Dirk M. [Department of Chemistry and Pharmacy and Interdisciplinary Center for Molecular Materials, Friedrich Alexander University Erlangen-Nuremberg, Erlangen (Germany); Vieweg, Benito F.; Spiecker, Erdmann [Center for Nanoanalysis and Electron Microscopy (CENEM) and Department Werkstoffwissenschaften/VII, Friedrich Alexander University Erlangen-Nuremberg, Erlangen (Germany); Suraru, Sabin-Lucian; Wuerthner, Frank [Institut fuer Organische Chemie and Roentgen Research Center for Complex Material Systems, Universitaet Wuerzburg, Wuerzburg (Germany)

2012-05-15

A perylene diimide (PDI) derivative bearing four chlorine substituents in the bay area is deposited together with pristine multiwall carbon nanotubes (MWNTs) and/or Nafion p-doped MWNTs (p-MWNTs) onto indium tin oxide (ITO) solid substrates by means of air-brushing. The resulting photoanodes are studied in photoelectrochemical cells and reveal highest photocurrent efficiencies when PDI and p-MWNT are combined as photoactive materials, indicating the beneficial effect of Nafion. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

2,1,3-benzothiadiazole-5,6-dicarboxylic imide - A versatile building block for additive- and annealing-free processing of organic solar cells with effi ciencies exceeding 8%

KAUST Repository

Nielsen, Christian Bergenstof; Ashraf, Raja Shahid; Treat, Neil D.; Schroeder, Bob C.; Donaghey, Jenny E.; White, Andrew J P; Stingelin, Natalie; McCulloch, Iain

2014-01-01

A new photoactive polymer comprising benzo[1,2-b:3,4-b′:5,6-d′]trithiophene and 2,1,3-benzothiadiazole-5,6-dicarboxylic imide is reported. The synthetic design allows for alkyl chains to be introduced on both electron-rich and electron-deficient components, which in turn allows for rapid optimization of the alkyl chain substitution pattern. Consequently, the optimized polymer shows a maximum efficiency of 8.3% in organic photovoltaic devices processed in commercially viable fashion without solvent additives, annealing, or device engineering.

Fulereno[C60]: química e aplicações Fullerene C60: chemistry and applications

Directory of Open Access Journals (Sweden)

Leandro José dos Santos

2010-01-01

Full Text Available Fullerene chemistry has become a very active research field in the two last decades, largely because of the exceptional properties of the C60 molecule and the variety of fullerene derivatives that appear to be possible. In this review, a general analysis of fullerene C60 reactivity is performed. The principal methods for the covalent modification of this fascinating carbon cage are presented. The prospects of using fullerene derivatives as medicinal drugs and photoactive materials in light converting devices are demonstrated.

Photocatalysis application of zinc oxide fibers obtained by electrospinning; Fribras de oxido de zinco obtidas por electrospinning aplicadas a fotocatalise

Energy Technology Data Exchange (ETDEWEB)

Gerchman, D.; Alves, A.K.; Berutti, F.A.; Bergmann, C.P. [Universidade Federal do Rio Grande do Sul (DEM/UFRGS), Porto Alegre, RS (Brazil). Dept. de Materiais

2010-07-01

Using the electrospinning technique, composite fibers of polyvinylbutyral and zinc nitrate were obtained. After a heat treatment at 600 deg C, nanostructured zinc oxide fibers were obtained. The fibers were characterized using X ray diffraction. The photocatalytic activity of the nanostructured fibers was determined using the photodegradation of a methyl orange solution. The increase in the heat treatment temperature decreases the photoactivity of the zinc oxide. The heat treatment, the phases and the surface area, affect the physical, chemical and photocatalytic activity of the zinc oxide. (author)

High throughput in situ scattering of roll-to-roll coated functional polymer films

DEFF Research Database (Denmark)

Andreasen, Jens Wenzel

2017-01-01

The development of conjugated polymers for organic electronics and photovoltaics has relied heavily on advanced X-ray scattering techniques almost since the earliest studies in the field. Almost from the beginning, structural studies focused on how the polymers self-organize in thin films......, and the relation between chemical configuration of the polymer, structure and performance. This chapter presents the latest developments where structural analysis is applied as in situ characterization of structure formation during roll-to-roll coating of photoactive layers for solar cells....

A comparison between a tristimulus colorimeter (Minolta ChromaMeter CR-200) and two spectrophotometers (Minolta Spectrophotometer CM-508i and CM-2002). Quantification of UV-B induced erythema in a hairless guinea pig model.

Science.gov (United States)

Fullerton, A; Keiding, J

1997-11-01

A comparison was made between a tristimulus colorimeter (Minolta ChromaMeter CR 200) and two spectrophotometers (Minolta CM-508i and CM-2002). The object was to compare skin colour data in the CIE 1976 L*a*d*colour space system obtained with the different instruments after UV-B exposure. Guinea pigs were exposed on their dorsal trunk with UV-B light for different time periods. Skin colour in the L*a*b* system was measured 6 and 24 h after exposure. Reproducible and objective measurements expressed in the CIE system were obtained with all three instruments. A strong correlation was found between the Minolta Chromameter CR200 and each of the two spectrophotometers. However, absolute values found with the Minolta ChromaMeter CR 200, especially for b*, differed from values obtained with the two spectrophotometers. The instruments were, despite minor inter-instrumental variation, suited for objective evaluation of erythema. The spectrophotometers were somewhat cumbersome to use due to their heavy weight and difficulties in positioning within the test sites; the Minolta CromaMeter CR200 (or later versions) is thus preferable for simple routine measurements. Use of the spectophotometers appears only indicated where specific information about skin pigments or photoactive substances relative to wavelength is needed.

Effect of surface ethoxy groups on photoactivity of TiO2 nanocrystals

International Nuclear Information System (INIS)

Tian Lihong; Deng Kejian; Ye Liqun; Zan Lin

2011-01-01

TiO 2 nanocrystals modified by ethoxy groups were prepared by a facile nonhydrolytic solvothermal method and characterized by XRD, TEM, TG-DTA and XPS, which showed an enhanced visible-light photocatalytic activity on the degradation of Rhodamine B compared with TiO 2 modified by benzyloxy groups and the 'naked' TiO 2 . The adsorption and degradation pathway of Rhodamine B on TiO 2 modified by ethoxy groups were also investigated. The zeta-potential (ζ) results showed that the TiO 2 modified by ethoxy groups had high negative surface charge, which incited the positive -N(Et) 2 group of RhB absorbing on the TiO 2 surface and preferably led the N-dealkylation pathway under visible light irradiation.

Photoactive nanocomplex formed from chlorophyll assembly on TMA-coated iron oxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Barbaros, Sibel; Meray, Zeynep; Tecim, Tuğba; Genç, Rükan, E-mail: rukangnc@gmail.com [Mersin University, Functional Nanomaterials Laboratory, Chemical Engineering Department, Engineering Faculty (Turkey)

2016-07-15

In this study, hierarchical self-assembly of photocatalytic nanodisks through non-covalent interactions between spinach-extracted chlorophyll molecules and trimethylammonium hydroxide-coated magnetic iron oxide nanoparticles was discussed. Combination of chlorophyll molecules with iron oxide nanoparticles generated an alteration in light absorption at both visible and near-IR region with accompanying enhancement in fluorescence emission. Further, photocatalytic role of resulting molecular assembly was studied by means of the photoinduced degradation of methylene blue dye under UV light and direct sun irradiation at neutral pH. In order to enhance the long-term stability of the hybrid nanocatalyst, commercially available cellulose membrane was used as a support and magnetic recovery and reusability was achieved where the nanocatalyst retained more than 90 % of its efficiency even after four cycles. This simple strategy could initiate the development of new materials for wastewater treatment including membrane-based technologies. On the other hand, their sunlight-induced photocatalytic activity could easily be conducted to dye-synthesized solar cells or their enhanced photoluminescence can provide a strong basis for future bioimaging tools.Graphical Abstract.

Nitridation of one-dimensional tungsten oxide nanostructures: Changes in structure and photoactivity

KAUST Repository

Varga, Tamá s; Haspel, Henrik; Kormá nyos, Attila; Janá ky, Csaba; Kukovecz, Á kos; Kó nya, Zoltá n

2017-01-01

nitrogen atmosphere. Morphological changes and structural transitions were followed by transmission and scanning electron microscopy and X-ray diffraction. Bandgap energies were determined from the UV–vis spectra of the materials, while photoelectrochemical

Toxicity of laser irradiated photoactive fluoride PrF3 nanoparticles toward bacteria

International Nuclear Information System (INIS)

Pudovkin, M S; Korableva, S L; Krasheninnicova, A O; Nizamutdinov, A S; Semashko, V V; Zelenihin, P V; Alakshin, E M; Nevzorova, T A

2014-01-01

The article is devoted to exploration of biological effects of crystalline PrF 3 nanoparticles toward Salmonella typhimurium TA 98 bacteria under the laser irradiation. Obtained results show bactericidal activity of PrF 3 nanoparticles and optimal parameters of laser irradiation (power of laser irradiation, wavelength, diameter of the laser spoil, and exposure time) have been found under which the effects of bactericidal activity become the most significant. Survival of bacterial cells under laser irradiation with wavelength 532 nm in colloidal solution of PrF 3 nanoparticles was 39%, 34%, 20% for exposure times 5 minutes, 15 minutes and 30 minutes, correspondingly

Synthesis variables effect on TiO2/polyester fabrics photoactivity and stability

Directory of Open Access Journals (Sweden)

Camilo Castro

2016-12-01

Full Text Available TiO2-SiO2 coatings on fabric samples were obtained by immersion of 9cm2 of commercial polyester in a TiO2-SiO2 suspension. This suspension was prepared by adding TiO2 P25 to a silica matrix obtained from the hydrolysis of tetraethyl orthosilicate (TEOS. The aim of this work was to study the relationship between the immersion time of the fabric on the photocatalytic activity and stability of the coating against several cycles of use and washing. Obtained samples were characterized by scanning electron microscopy (SEM, energy dispersive spectroscopy (EDS and infrared spectroscopy (FTIR-ATR. Evaluation of modified fabrics was performed by self-disinfection tests under 250W/m2 of simulated sunlight using E. coli as model bacteria. In general, all modified fabrics (except that obtained at 2h immersion time inactivated bacteria in less than 120min and its regrowth was prevented for at least 24h after the disinfection tests. It was determined that low immersion time (3-4h lead to active and stable fabrics to 3 cycles of use and washing, whereas higher immersion times (12h lead to more active but unstable fabrics.

Structure and crystallinity of water dispersible photoactive nanoparticles for organic solar cells

DEFF Research Database (Denmark)

Pedersen, Emil Bøje Lind; Pedersen, M.C.; Simonsen, Søren Bredmose

2015-01-01

Water based inks would be a strong advantage for large scale production of organic photovoltaic devices. Formation of water dispersible nanoparticles produced by the Landfester method is a promising route to achieve such inks. We provide new insights into the key ink properties of poly(3-hexylthi......Water based inks would be a strong advantage for large scale production of organic photovoltaic devices. Formation of water dispersible nanoparticles produced by the Landfester method is a promising route to achieve such inks. We provide new insights into the key ink properties of poly(3......-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) nanoparticles such as the internal structure and crystallinity of the dispersed nanoparticles and the previously unreported drastic changes that occur when the inks are cast into a film. We observe through transmission electron...

A Highly Luminescent Hexanuclear Molybdenum Cluster - A Promising Candidate toward Photoactive Materials

Czech Academy of Sciences Publication Activity Database

Kirakci, Kaplan; Kubát, Pavel; Dušek, Michal; Fejfarová, Karla; Šícha, Václav; Mosinger, Jiří; Lang, Kamil

2012-01-01

Roč. 2012, č. 19 (2012), s. 3107-3111 ISSN 1434-1948 R&D Projects: GA ČR(CZ) GAP204/11/0809; GA ČR GAP208/10/1678 Institutional support: RVO:61388980 ; RVO:61388955 ; RVO:68378271 Keywords : cluster compounds * luminescence * molybdenum * organic-inorganic hybrid composites * singlet oxygen Subject RIV: CA - Inorganic Chemistry Impact factor: 3.120, year: 2012

One pot synthesis of pure micro/nano photoactive α-PbO crystals

Science.gov (United States)

Bhagat, Dharini; Waldiya, Manmohansingh; Vanpariya, Anjali; Mukhopadhyay, Indrajit

2018-05-01

The present study reports a simple, fast and cost effective precipitation technique for synthesis of pure α-PbO powder. Lead monoxide powder with tetragonal structure was synthesized chemically at an elevated temperature using lead acetate and sodium hydroxide solution bath. XRD powder diffraction was used to find the structural properties as well as phase transition from alpha to beta. Study revealed that synthesized PbO powder was crystalline with tetragonal symmetry, having an average crystallite size of 70 nm and lattice constants; a=3.97Å, b=3.97Å, and c=5.02Å. Phase transition from tetragonal to orthorhombic structure was studied by comparing the XRD data of the annealed samples in the temperature range from 200 °C to 600 °C. UV-Visible spectroscopy was used to find out the optical properties of prepared PbO powder. Diffuse reflectance and absorbance spectra confirmed the formation of α-PbO with obtained direct band gap of 1.9 eV. Synthesized lead monoxide (α-PbO) powder has promising application in energy conversion as well as energy storage applications.

Photocatalytic efficiency of reusable ZnO thin films deposited by sputtering technique

International Nuclear Information System (INIS)

Ahumada-Lazo, R.; Torres-Martínez, L.M.; Ruíz-Gómez, M.A.; Vega-Becerra, O.E.

2014-01-01

Graphical abstract: - Highlights: • Decolorization of Orange G dye using highly c-axis-oriented ZnO thin films. • The flake-shaped film shows superior and stable photoactivity at a wide range of pH. • The highest photodecolorization was achieved at pH of 7. • The exposure of (101) and (100) facets enhanced the photoactivity. • ZnO thin films exhibit a promising performance as recyclable photocatalysts. - Abstract: The photocatalytic activity of ZnO thin films with different physicochemical characteristics deposited by RF magnetron sputtering on glass substrate was tested for the decolorization of orange G dye aqueous solution (OG). The crystalline phase, surface morphology, surface roughness and the optical properties of these ZnO films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV–visible spectroscopy (UV–Vis), respectively. The dye photodecolorization process was studied at acid, neutral and basic pH media under UV irradiation of 365 nm. Results showed that ZnO films grow with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a (002) preferential crystalline orientation. A clear relationship between surface morphology and photocatalytic activity was observed for ZnO films. Additionally, the recycling photocatalytic abilities of the films were also evaluated. A promising photocatalytic performance has been found with a very low variation of the decolorization degree after five consecutive cycles at a wide range of pH media

Fabrication of AgX-loaded Ag2CO3 (X = Cl, I) composites and their efficient visible-light-driven photocatalytic activity

International Nuclear Information System (INIS)

Xu, Hui; Zhu, Jiaxiang; Song, Yongxiu; Zhu, Tingting; Zhao, Wenkai; Song, Yanhua; Da, Zulin; Liu, Chengbao; Li, Huaming

2015-01-01

Highlights: • The novel AgX/Ag 2 CO 3 composites have been synthesized by ion exchange reaction. • AgX/Ag 2 CO 3 exhibit higher photoactivity and stability than that of Ag 2 CO 3 . • The band structure of AgX/Ag 2 CO 3 is beneficial to improve the photoactivity. - Abstract: The novel visible-light-driven AgX/Ag 2 CO 3 (X = Cl, I) hybrid materials were synthesized by ion exchange reaction. The physical and chemical properties of the catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM), diffuse-reflection spectra (DRS) and photocurrent techniques. The as-prepared AgX/Ag 2 CO 3 (X = Cl, I) composites showed higher photocatalytic activity than that of the pure Ag 2 CO 3 photocatalyst under visible light irradiation (λ ⩾ 400 nm) in the process of methylene blue (MB) degradation. The optimal mass percentage of AgCl and AgI in the AgX/Ag 2 CO 3 (X = Cl, I) composite was 20.54 wt% and 40 wt%, respectively. The enhancement of photocatalytic activity was attributed to the suitable band potential between AgX and Ag 2 CO 3 , which was beneficial to increase the separation efficiency of electrons and holes. Besides, the photocatalytic mechanism of AgX/Ag 2 CO 3 (X = Cl, I) composites was also proposed

Photo-electret effects in homogenous semiconductors

International Nuclear Information System (INIS)

Nabiev, G.A.

2004-01-01

In the given work is shown the opportunity and created the theory of photo-electret condition in semiconductors with Dember mechanism of photo-voltage generation. Photo-electret of such type can be created, instead of traditional and without an external field as a result of only one illumination. Polar factor, in this case, is the distinction of electrons and holes mobility. Considered the multilayered structure with homogeneous photoactive micro areas shared by the layers, which are interfering to alignment of carriers concentration. We consider, that the homogeneous photoactive areas contain deep levels of stick. Because of addition of elementary photo voltage in separate micro photo cells it is formed the abnormal-large photo voltage (APV-effect). Let's notice, that Dember photo-voltage in a separate micro photo-cell ≤kT/q. From the received expressions, in practically important, special case, when quasi- balance between valent zone and stick levels established in much more smaller time, than free hole lifetime, and we received, that photo-voltage is relaxing. Comparing of the received expressions with the laws of photo voltage attenuation in p-n- junction structures shows their identity; the difference is only in absolute meanings of photo voltage. During the illumination in the semiconductor are created the superfluous concentration of charge carriers and part from them stays at deep levels. At de-energizing light there is a gradual generation of carriers located at these levels

Graphitic carbon nitride/graphene oxide/reduced graphene oxide nanocomposites for photoluminescence and photocatalysis

Energy Technology Data Exchange (ETDEWEB)

Aleksandrzak, Malgorzata, E-mail: malgorzata.aleksandrzak@o2.pl; Kukulka, Wojciech; Mijowska, Ewa

2017-03-15

Highlights: • Graphitic carbon nitride modified with graphene nanostructures. • Influence of graphene nanostructures size in photocatalytic properties of g-C{sub 3}N{sub 4}. • Improved photocatalysis resulted from up-converted photoluminescence. - Abstract: The study presents a modification of graphitic carbon nitride (g-C{sub 3}N{sub 4}) with graphene oxide (GO) and reduced graphene oxide (rGO) and investigation of photoluminescent and photocatalytic properties. The influence of GO and rGO lateral sizes used for the modification was investigated. The nanomaterials were characterized with atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance UV–vis spectroscopy (DR-UV-vis) and photoluminescence spectroscopy (PL). PL revealed that pristine graphitic carbon nitride and its nanocomposites with GO and rGO emitted up-converted photoluminescence (UCPL) which could contribute to the improvement of photocatalytic activity of the materials. The photoactivity was evaluated in a process of phenol decomposition under visible light. A hybrid composed of rGO nanoparticles (rGONPs, 4–135 nm) exhibited the highest photoactivity compared to rGO with size of 150 nm–7.2 μm and graphene oxide with the corresponding sizes. The possible reason of the superior photocatalytic activity is the most enhanced UCPL of rGONPs, contributing to the emission of light with higher energy than the incident light, resulting in improved photogeneration of electron-hole pairs.

Surface properties and photocatalytic activity of KTaO3, CdS, MoS2 semiconductors and their binary and ternary semiconductor composites.

Science.gov (United States)

Bajorowicz, Beata; Cybula, Anna; Winiarski, Michał J; Klimczuk, Tomasz; Zaleska, Adriana

2014-09-24

Single semiconductors such as KTaO3, CdS MoS2 or their precursor solutions were combined to form novel binary and ternary semiconductor nanocomposites by the calcination or by the hydro/solvothermal mixed solutions methods, respectively. The aim of this work was to study the influence of preparation method as well as type and amount of the composite components on the surface properties and photocatalytic activity of the new semiconducting photoactive materials. We presented different binary and ternary combinations of the above semiconductors for phenol and toluene photocatalytic degradation and characterized by X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area and porosity. The results showed that loading MoS2 onto CdS as well as loading CdS onto KTaO3 significantly enhanced absorption properties as compared with single semiconductors. The highest photocatalytic activity in phenol degradation reaction under both UV-Vis and visible light irradiation and very good stability in toluene removal was observed for ternary hybrid obtained by calcination of KTaO3, CdS, MoS2 powders at the 10:5:1 molar ratio. Enhanced photoactivity could be related to the two-photon excitation in KTaO3-CdS-MoS2 composite under UV-Vis and/or to additional presence of CdMoO4 working as co-catalyst.

Surface Properties and Photocatalytic Activity of KTaO3, CdS, MoS2 Semiconductors and Their Binary and Ternary Semiconductor Composites

Directory of Open Access Journals (Sweden)

Beata Bajorowicz

2014-09-01

Full Text Available Single semiconductors such as KTaO3, CdS MoS2 or their precursor solutions were combined to form novel binary and ternary semiconductor nanocomposites by the calcination or by the hydro/solvothermal mixed solutions methods, respectively. The aim of this work was to study the influence of preparation method as well as type and amount of the composite components on the surface properties and photocatalytic activity of the new semiconducting photoactive materials. We presented different binary and ternary combinations of the above semiconductors for phenol and toluene photocatalytic degradation and characterized by X-ray powder diffraction (XRD, UV-Vis diffuse reflectance spectroscopy (DRS, scanning electron microscopy (SEM, Brunauer–Emmett–Teller (BET specific surface area and porosity. The results showed that loading MoS2 onto CdS as well as loading CdS onto KTaO3 significantly enhanced absorption properties as compared with single semiconductors. The highest photocatalytic activity in phenol degradation reaction under both UV-Vis and visible light irradiation and very good stability in toluene removal was observed for ternary hybrid obtained by calcination of KTaO3, CdS, MoS2 powders at the 10:5:1 molar ratio. Enhanced photoactivity could be related to the two-photon excitation in KTaO3-CdS-MoS2 composite under UV-Vis and/or to additional presence of CdMoO4 working as co-catalyst.

Photocatalytic efficiency of reusable ZnO thin films deposited by sputtering technique

Energy Technology Data Exchange (ETDEWEB)

Ahumada-Lazo, R.; Torres-Martínez, L.M. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Civil, Departamento de Ecomateriales y Energía, Av. Universidad S/N Ciudad Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66450, México (Mexico); Ruíz-Gómez, M.A. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Civil, Departamento de Ecomateriales y Energía, Av. Universidad S/N Ciudad Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66450, México (Mexico); Departmento de Física Aplicada, CINVESTAV-IPN, Antigua Carretera a Progreso km 6, Mérida, Yucatán 97310, México (Mexico); Vega-Becerra, O.E. [Centro de Investigación en Materiales Avanzados S.C, Alianza norte 202, Parque de Investigación e Innovación Tecnológica, C.P. 66600 Apodaca Nuevo León, México (Mexico); and others

2014-12-15

Graphical abstract: - Highlights: • Decolorization of Orange G dye using highly c-axis-oriented ZnO thin films. • The flake-shaped film shows superior and stable photoactivity at a wide range of pH. • The highest photodecolorization was achieved at pH of 7. • The exposure of (101) and (100) facets enhanced the photoactivity. • ZnO thin films exhibit a promising performance as recyclable photocatalysts. - Abstract: The photocatalytic activity of ZnO thin films with different physicochemical characteristics deposited by RF magnetron sputtering on glass substrate was tested for the decolorization of orange G dye aqueous solution (OG). The crystalline phase, surface morphology, surface roughness and the optical properties of these ZnO films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV–visible spectroscopy (UV–Vis), respectively. The dye photodecolorization process was studied at acid, neutral and basic pH media under UV irradiation of 365 nm. Results showed that ZnO films grow with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a (002) preferential crystalline orientation. A clear relationship between surface morphology and photocatalytic activity was observed for ZnO films. Additionally, the recycling photocatalytic abilities of the films were also evaluated. A promising photocatalytic performance has been found with a very low variation of the decolorization degree after five consecutive cycles at a wide range of pH media.

Some new methyl-8-methoxypsoralens: synthesis, photobinding to DNA, photobiological properties and molecular modelling.

Science.gov (United States)

Gia, O; Anselmo, A; Pozzan, A; Antonello, C; Magno, S M; Uriarte, E

1997-01-01

The tricyclic structure of known natural photochemotherapeutic drugs such as 8-methoxypsoralen and 5-methoxypsoralen is often taken as a model in the search of new photosensitizer agents with less phototoxic and mutagenic effects. This paper describes the synthesis, characterization, photobinding to DNA, photobiological properties and computational chemistry of some 8-methoxypsoralen derivatives bearing two or three methyl groups at the key positions of the two photoactive double bonds. Results showed that photoreactivity and photobiological behaviour depend on the pattern of methyl substitutions. Antiproliferative activity in cell lines shows good correlation with DNA interaction data.

Bulk Heterojunction Solar Cell Devices Prepared with Composites of Conjugated Polymer and Zinc Oxide Nanorods

Directory of Open Access Journals (Sweden)

Nguyen Tam Nguyen Truong

2017-01-01

Full Text Available ZnO nanorods (Nrods with ~20–50 nm lengths were synthesized using an aqueous solution of zinc acetate and glacial acetic acid. Bulk heterojunction solar cells were fabricated with the structure of indium tin oxide (ITO/polyethylenedioxythiophene doped with polystyrene-sulfonic acid (PEDOT:PSS/ZnO-Nrods + polymer/electron transport layer (ETL/Al. Current density-voltage characterization of the resulting cells showed that, by adding an ETL and using polymers with a low band gap energy, the photoactive layer surface morphology and the device performance can be dramatically improved.

Iron sulphide solar cells

Science.gov (United States)

Ennaoui, A.; Tributsch, H.

1984-12-01

The abundant, naturally occurring natural compound pyrite (FeS2) can be used as a semiconducting material for photoelectrochemical and photovoltaic solar cells. Unlike most of the intensively studied photoactive materials, pyrite solar cell production would never be limited by the availability of the elements or by their compatibility with the environment. An energy gap of 0.95 eV has been determined for pyrite, and it is noted that the theoretical efficiency limit for solar energy conversion in this material is of the order of 15-20 percent.

Series interconnected photovoltaic cells and method for making same

Science.gov (United States)

Albright, Scot P.; Chamberlin, Rhodes R.; Thompson, Roger A.

1995-01-01

A novel photovoltaic module (10) and method for constructing the same are disclosed. The module (10) includes a plurality of photovoltaic cells (12) formed on a substrate (14) and laterally separated by interconnection regions (15). Each cell (12) includes a bottom electrode (16), a photoactive layer (18) and a top electrode layer (20). Adjacent cells (12) are connected in electrical series by way of a conductive-buffer line (22). The buffer line (22) is also useful in protecting the bottom electrode (16) against severing during downstream layer cutting processes.

Photosensitive Ox/GaAs heterojunctions: Creation and properties

Energy Technology Data Exchange (ETDEWEB)

Rud' , V. Yu. [St. Petersburg State Polytechnical University (Russian Federation); Rud' , Yu. V., E-mail: yuryrud@mail.ioffe.ru; Terukov, E. I.; Ushakova, T. N. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2012-06-15

A method for the thermal oxidation of GaAs crystals in air is suggested and the first photosensitive Ox/n-GaAs heterojunctions, where Ox is a native oxide, are fabricated. The steady current-voltage characteristics and spectra of relative quantum efficiency of the new structures are studied. The features of the spectra of photoactive absorption of the obtained heterojunctions are discussed. The potential of using vacuumfree thermal oxidation of the GaAs crystals in air to fabricate broadband heterophotoconverters of optical radiation on their basis is established.

Photoresponsive Block Copolymers Containing Azobenzenes and Other Chromophores

Directory of Open Access Journals (Sweden)

Takaomi Kobayashi

2010-01-01

Full Text Available Photoresponsive block copolymers (PRBCs containing azobenzenes and other chromophores can be easily prepared by controlled polymerization. Their photoresponsive behaviors are generally based on photoisomerization, photocrosslinking, photoalignment and photoinduced cooperative motions. When the photoactive block forms mesogenic phases upon microphase separation of PRBCs, supramolecular cooperative motion in liquid-crystalline PRBCs enables them to self-organize into hierarchical structures with photoresponsive features. This offers novel opportunities to photocontrol microphase-separated nanostructures of well-defined PRBCs and extends their diverse applications in holograms, nanotemplates, photodeformed devices and microporous films.

Ultra high open circuit voltage (>1 V) of poly-3-hexylthiophene based organic solar cells with concentrated light

DEFF Research Database (Denmark)

Tromholt, Thomas; Madsen, Morten Vesterager; Krebs, Frederik C

2013-01-01

to 2000 solar intensities of these photoactive blends. Comparison of solar cells based on five different fullerene derivatives shows that at both short circuit and open circuit conditions, recombination remains unchanged up to 50 suns. Determination of Voc at 2000 suns demonstrated that the same......One approach to increasing polymer solar cell efficiency is to blend poly-(3-hexyl-thiophene) with poorly electron accepting fullerene derivatives to obtain higher open circuit voltage (Voc). In this letter concentrated light is used to study the electrical properties of cell operation at up...

Enhanced performance of hybrid solar cells using longer arms of quantum cadmium selenide tetrapods

KAUST Repository

Lee, Kyu-Sung

2011-12-01

We demonstrate that enhanced device performance of hybrid solar cells based on tetrapod (TP)-shaped cadmium selenide (CdSe) nanoparticles and conjugated polymer of poly (3-hexylthiophene) (P3HT) can be obtained by using longer armed tetrapods which aids in better spatial connectivity, thus decreasing charge hopping events which lead to better charge transport. Longer tetrapods with 10 nm arm length lead to improved power conversion efficiency of 1.12% compared to 0.80% of device having 5 nm short-armed tetrapods:P3HT photoactive blends.

Coherent Protein Dynamics Explored at FELIX

CERN Document Server

Austin, Robert

2004-01-01

We have discovered that there exists a very narrow (less than 0.02 microns) wide resonance in the amide I band of myoglobin and photoactive yellow protein that can be driven to greater than 30% saturation using very narrow linewidth pump-probe spectroscopy at FELIX. The extraordinary narrowness of this transition and the extraordinary ease of saturation inplies that this band is highly anharmonic and decoupled from the other oscillators in the amide I band. We will present detailed measurments on this discovery and implications for energy flow in proteins.

Enhanced performance of hybrid solar cells using longer arms of quantum cadmium selenide tetrapods

KAUST Repository

Lee, Kyu-Sung; Kim, Inho; Gullapalli, Sravani; Wong, Michael S.; Jabbour, Ghassan E.

2011-01-01

We demonstrate that enhanced device performance of hybrid solar cells based on tetrapod (TP)-shaped cadmium selenide (CdSe) nanoparticles and conjugated polymer of poly (3-hexylthiophene) (P3HT) can be obtained by using longer armed tetrapods which aids in better spatial connectivity, thus decreasing charge hopping events which lead to better charge transport. Longer tetrapods with 10 nm arm length lead to improved power conversion efficiency of 1.12% compared to 0.80% of device having 5 nm short-armed tetrapods:P3HT photoactive blends.

Probing hydrogen bonding interactions and proton transfer in proteins

Science.gov (United States)

Nie, Beining

Scope and method of study. Hydrogen bonding is a fundamental element in protein structure and function. Breaking a single hydrogen bond may impair the stability of a protein. It is therefore important to probe dynamic changes in hydrogen bonding interactions during protein folding and function. Time-resolved Fourier transform infrared spectroscopy is highly sensitive to hydrogen bonding interactions. However, it lacks quantitative correlation between the vibrational frequencies and the number, type, and strength of hydrogen bonding interactions of ionizable and polar residues. We employ quantum physics theory based ab initio calculations to study the effects of hydrogen bonding interactions on vibrational frequencies of Asp, Glu, and Tyr residues and to develop vibrational spectral markers for probing hydrogen bonding interactions using infrared spectroscopy. In addition, proton transfer process plays a crucial role in a wide range of energy transduction, signal transduction, and enzymatic reactions. We study the structural basis for proton transfer using photoactive yellow protein as an excellent model system. Molecular dynamics simulation is employed to investigate the structures of early intermediate states. Quantum theory based ab initio calculations are used to study the impact of hydrogen bond interactions on proton affinity and proton transfer. Findings and conclusions. Our extensive density function theory based calculations provide rich structural, spectral, and energetic information on hydrogen bonding properties of protonated side chain groups of Asp/Glu and Tyr. We developed vibrational spectral markers and 2D FTIR spectroscopy for structural characterization on the number and the type of hydrogen bonding interactions of the COOH group of Asp/Glu and neutral phenolic group of Tyr. These developments greatly enhance the power of time-resolved FTIR spectroscopy as a major experimental tool for structural characterization of functionally important

Ternary reduced-graphene-oxide/Bi2MoO6/Au nanocomposites with enhanced photocatalytic activity under visible light

International Nuclear Information System (INIS)

Bi, Jinhong; Fang, Wei; Li, Li; Li, Xiaofen; Liu, Minghua; Liang, Shijing; Zhang, Zizhong; He, Yunhui; Lin, Huaxiang; Wu, Ling; Liu, Shengwei; Wong, Po Keung

2015-01-01

A novel ternary nanocomposite photocatalyst consisted of reduced-graphene-oxide (RGO), Bi 2 MoO 6 and plasmonic Au nanoparticles were successfully fabricated by multiple steps including a simple solvothermal process and photochemical reduction process. RGO/Bi 2 MoO 6 /Au was characterized by X-ray powder diffraction patterns, transmission electron microscopy, UV–vis diffuse reflectance spectra, Raman spectroscopy and X-ray photoelectron spectroscopy. In comparison with Bi 2 MoO 6 , RGO/Bi 2 MoO 6 and Au/Bi 2 MoO 6 , RGO/Bi 2 MoO 6 /Au exhibits an enhanced photocatalytic activity for decomposition of Rhodamine B under visible light. The separation efficiency of the photogenerated holes and electrons on Bi 2 MoO 6 is promoted by the combined effect of both RGO and Au in the ternary composite, and thus enhances photocatalytic activity. The scavenger study revealed that both hole and superoxide are the major reactive species for the photocatalytic degradation of Rhodamine B using RGO/Bi 2 MoO 6 /Au photocatalyst. - Graphical abstract: A novel ternary nanocomposite photocatalyst consisted of reduced-graphene-oxide (RGO), Bi 2 MoO 6 and plasmonic Au nanoparticles were successfully fabricated by multiple steps including a simple solvothermal process and photochemical reduction process. The resulted ternary nanocomposites greatly enhanced the visible light photocatalytic properties compared to Bi 2 MoO 6 , RGO/Bi 2 MoO 6 or Au/Bi 2 MoO 6 binary systems. The improved photocatalytic activity was mainly attributed to the synergistic effect of Au and RGO with better separation of the photogenerated holes and electrons, resulting from the surface plasmonic resonance and extra strong electron magnetic field of Au nanoparticles and the high electron conductivity of RGO. - Highlights: • The ternary nanocomposites RGO/Bi 2 MoO 6 /Au were constructed for the first time. • RGO/Bi 2 MoO 6 /Au showed much higher visible photoactivity than RGO (Au)/Bi 2 MoO 6 . • The improved

Molecular modeling study of agglomeration of [6,6]-phenyl-C61-butyric acid methyl ester in solvents.

Science.gov (United States)

Mortuza, S M; Banerjee, Soumik

2012-12-28

The molecular interactions between solvent and nanoparticles during photoactive layer formation in organic photovoltaic (OPV) cells influence the morphology of the photoactive layer and hence determine the power conversion efficiency. Prediction of optimal synthesis parameters in OPVs, such as choice of solvent, processing temperature, and nanoparticle concentration, requires fundamental understanding of the mechanisms that govern the agglomeration of nanoparticles in solvents. In this study, we used molecular dynamics simulations to simulate a commonly used organic nanoparticle, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), in various solvents to correlate solvent-nanoparticle interactions with the size of the agglomerate structure of PCBM. We analyzed the effects of concentration of PCBM and operating temperature on the molecular rearrangement and agglomeration of PCBM in three solvents: (i) toluene, (ii) indane, and (iii) toluene-indane mixture. We evaluated the agglomeration behavior of PCBM by determining sizes of the largest clusters of PCBM and the corresponding size distributions. To obtain further insight into the agglomerate structure of PCBMs, we evaluated radial distribution functions (RDFs) and coordination numbers of the various moieties of PCBMs with respect to solvent atoms as well as with respect to that of other PCBMs. Our simulations demonstrate that PCBMs form larger clusters in toluene while they are relatively dispersed in indane, which indicates the greater solubility of PCBM in indane than in toluene. In toluene-indane mixture, PCBMs are clustered to a greater extent than in indane and less than that in toluene. To correlate agglomerate size to nanoparticle-solvent interactions, we also evaluated the potential of mean force (PMF) of the fullerene moiety of PCBM in toluene and indane. Our results also show that the cluster size of PCBM molecules increases with the increase of concentration of PCBM and the processing temperature. To

Molecular concepts of water splitting. Nature's approach

Energy Technology Data Exchange (ETDEWEB)

Cox, Nicholas; Lubitz, Wolfgang [Max-Planck-Institut fuer Chemische Energiekonversion, Muelheim an der Ruhr (Germany)

2013-07-01

Based on studies of natural systems, much has also been learned concerning the design principles required for biomimetic catalysis of water splitting and hydrogen evolution. In summary, these include use of abundant and inexpensive metals, the effective protection of the active sites in functional environments, repair/replacement of active components in case of damage, and the optimization of reaction rates. Biomimetic chemistry aims to mimic all these features; many labs are working toward this goal by developing new approaches in the design and synthesis of such systems, encompassing not only the catalytic center, but also smart matrices and assembly via self-organization. More stable catalysts that do not require self-repair may be obtained from fully artificial (inorganic) catalytic systems that are totally different from the biological ones and only apply some basic principles learned from nature. Metals other than Mn/Ca, Fe, and Ni could be used (e.g. Co) in new ligand spheres and other matrices. For light harvesting, charge separation/stabilization, and the effective coupling of the oxidizing/reducing equivalents to the redox catalysts, different methods have been proposed - for example, covalently linked molecular donor-acceptor systems, photo-voltaic devices, semiconductor-based systems, and photoactive metal complexes. The aim of all these approaches is to develop catalytic systems that split water with sunlight into hydrogen and oxygen while displaying high efficiency and long-term stability. Such a system - either biological, biomimetic, or bioinspired - has the potential to be used on a large scale to produce 'solar fuels' (e.g. hydrogen or secondary products thereof). (orig.)

Molecular concepts of water splitting. Nature's approach

International Nuclear Information System (INIS)

Cox, Nicholas; Lubitz, Wolfgang

2013-01-01

Based on studies of natural systems, much has also been learned concerning the design principles required for biomimetic catalysis of water splitting and hydrogen evolution. In summary, these include use of abundant and inexpensive metals, the effective protection of the active sites in functional environments, repair/replacement of active components in case of damage, and the optimization of reaction rates. Biomimetic chemistry aims to mimic all these features; many labs are working toward this goal by developing new approaches in the design and synthesis of such systems, encompassing not only the catalytic center, but also smart matrices and assembly via self-organization. More stable catalysts that do not require self-repair may be obtained from fully artificial (inorganic) catalytic systems that are totally different from the biological ones and only apply some basic principles learned from nature. Metals other than Mn/Ca, Fe, and Ni could be used (e.g. Co) in new ligand spheres and other matrices. For light harvesting, charge separation/stabilization, and the effective coupling of the oxidizing/reducing equivalents to the redox catalysts, different methods have been proposed - for example, covalently linked molecular donor-acceptor systems, photo-voltaic devices, semiconductor-based systems, and photoactive metal complexes. The aim of all these approaches is to develop catalytic systems that split water with sunlight into hydrogen and oxygen while displaying high efficiency and long-term stability. Such a system - either biological, biomimetic, or bioinspired - has the potential to be used on a large scale to produce 'solar fuels' (e.g. hydrogen or secondary products thereof). (orig.)

Spatiotemporal Observation of Electron-Impact Dynamics in Photovoltaic Materials Using 4D Electron Microscopy

KAUST Repository

Shaheen, Basamat

2017-05-17

Understanding light-triggered charge carrier dynamics near photovoltaic-material surfaces and at interfaces has been a key element and one of the major challenges for the development of real-world energy devices. Visualization of such dynamics information can be obtained using the one-of-a-kind methodology of scanning ultrafast electron microscopy (S-UEM). Here, we address the fundamental issue of how the thickness of the absorber layer may significantly affect the charge carrier dynamics on material surfaces. Time-resolved snapshots indicate that the dynamics of charge carriers generated by electron impact in the electron-photon dynamical probing regime is highly sensitive to the thickness of the absorber layer, as demonstrated using CdSe films of different thicknesses as a model system. This finding not only provides the foundation for potential applications of S-UEM to a wide range of devices in the fields of chemical and materials research, but also has impact on the use and interpretation of electron beam-induced current for optimization of photoactive materials in these devices.

III-V semiconductors for photoelectrochemical applications: surface preparation and characterization

Energy Technology Data Exchange (ETDEWEB)

Fertig, Dominic; Schaechner, Birgit; Calvet, Wofram; Kaiser, Bernhard; Jaegermann, Wolfram [TU Darmstadt, Fachbereich Materialwissenschaft, Fachgebiet Oberflaechenforschung (Germany)

2011-07-01

III-V semiconductors are promising reference systems for photoelectrochemical energy conversion. Therefore we have studied the influence of different acids and acidic solutions on the etching of p-doped gallium-arsenide and gallium-phosphide single crystal surfaces. From our experiments we conclude, that etching with HCl and subsequent annealing up to 450 C gives the best results for the removal of the carbonates and the oxides without affecting the quality of the sample. By treating the surfaces with ''piranha''-solution (H{sub 2}SO{sub 4}:H{sub 2}O{sub 2}:H{sub 2}O/7:2:1), the creation of an oxide layer with well defined thickness can be achieved. For the creation of an efficient photoelectrochemical cell, Pt nanoparticles have been deposited from solution. These surfaces are then characterized by photoelectron spectroscopy and AFM. Further electrochemical measurements try to correlate the effect of the surface cleaning and the Pt deposition on the photoactivity of the GaAs- and GaP-semiconductors.

Final Report: Photo-Directed Molecular Assembly of Multifunctional Inorganic Materials

Energy Technology Data Exchange (ETDEWEB)

B.G. Potter, Jr.

2010-10-15

This final report details results, conclusions, and opportunities for future effort derived from the study. The work involved combining the molecular engineering of photoactive Ti-alkoxide systems and the optical excitation of hydrolysis and condensation reactions to influence the development of the metal-oxygen-metal network at the onset of material formation. Selective excitation of the heteroleptic alkoxides, coupled with control of alkoxide local chemical environment, enabled network connectivity to be influenced and formed the basis for direct deposition and patterning of Ti-oxide-based materials. The research provided new insights into the intrinsic photoresponse and assembly of these complex, alkoxide molecules. Using a suite of electronic, vibrational, and nuclear spectroscopic probes, coupled with quantum chemical computation, the excitation wavelength and fluence dependence of molecular photoresponse and the nature of subsequent hydrolysis and condensation processes were probed in pyridine-carbinol-based Ti-alkoxides with varied counter ligand groups. Several methods for the patterning of oxide material formation were demonstrated, including the integration of this photoprocessing approach with conventional, dip-coating methodologies.

Transparent conductive oxides and alternative transparent electrodes for organic photovoltaics and OLEDs; Transparente leitfaehige Elektroden. Oxide und alternative Materialien fuer die organische Photovoltaik und OLEDs

Energy Technology Data Exchange (ETDEWEB)

Mueller-Meskamp, Lars; Sachse, Christoph; Kim, Yong Hyun; Furno, Mauro [Technische Univ. Dresden (DE). Inst. fuer Angewandte Photophysik (IAPP); May, Christian [Fraunhofer Institut fuer Photonische Mikrosysteme (IPMS), Dresden (Germany); Leo, Karl [Technische Univ. Dresden (DE). Inst. fuer Angewandte Photophysik (IAPP); Fraunhofer Institut fuer Photonische Mikrosysteme (IPMS), Dresden (Germany)

2012-08-15

Organic, photoactive devices, such as OLEDs or organic solar cells, currently use indium tin oxide (ITO) as transparent electrode. Whereas ITO is industry-proven for many years and shows very good electrical and optical properties, its application for low-cost and flexible devices might not be optimal. For such applications innovative technologies such as network-based metal nanowire or carbon nanotube electrodes, graphene, conductive polymers, metal thin-films and alternative transparent conductive oxides emerge. Although some of these technologies are rather experimental and far from application, some of them have the potential to replace ITO in selected applications. (orig.)

CdS loaded on coal based activated carbon nanofibers with enhanced photocatalytic property

Science.gov (United States)

Guo, Jixi; Guo, Mingxi; Jia, Dianzeng; Song, Xianli; Tong, Fenglian

2016-08-01

The coal based activated carbon nanofibers (CBACFs) were prepared by electrospinning a mixture of polyacrylonitrile (PAN) and acid treated coal. Cadmium sulfide (CdS) nanoparticles loaded on CBACFs were fabricated by solvothermal method. The obtained samples were characterized by FESEM, TEM, and XRD. The results reveal that the CdS nanoparticles are homogeneously dispersed on the surfaces of CBACFs. The CdS/CBACFs nanocomposites exhibited higher photoactivity for photodegradation of methyl blue (MB) under visible light irradiation than pure CdS nanoparticles. CBACFs can be used as low cost support materials for the preparation of nanocomposites with high photocatalytic activity.

Electrosynthesis of cadmium selenide films from sodium citrate-selenosulphite bath

International Nuclear Information System (INIS)

Lokhande, C.D.; Lee, Eun-Ho; Jung, Kwang-Deog; Joo, Oh-Shim

2005-01-01

Electrosynthesis of cadmium selenide (CdSe) film has been carried out from deposition bath containing sodium selenosulphite, along with cadmium complexed with sodium citrate under potentiostatic deposition condition on titanium substrates. The pH of deposition bath was weakly basic (< 9.0). The CdSe films up to 3.0 μm were deposited. The X-ray diffraction (XRD) studies revealed that the CdSe films are microcrystalline with increased grain size after annealing. The scanning electron microscopy showed that the films are porous with cauliflower-like morphology. The photelectrochemical characterization showed that the CdSe films are photoactive

Muons tomography applied to geosciences and volcanology

Energy Technology Data Exchange (ETDEWEB)

Marteau, J., E-mail: marteau@ipnl.in2p3.fr [Institut de Physique Nucleaire de Lyon (UMR CNRS-IN2P3 5822), Universite Lyon 1, Lyon (France); Gibert, D.; Lesparre, N. [Institut de Physique du Globe de Paris (UMR CNRS 7154), Sorbonne Paris Cite, Paris (France); Nicollin, F. [Geosciences Rennes (CNRS UMR 6118), Universite Rennes 1, Bat. 15 Campus de Beaulieu, 35042 Rennes cedex (France); Noli, P. [Universita degli studi di Napoli Federico II and INFN sez. Napoli (Italy); Giacoppo, F. [Laboratory for High Energy Physics, University of Bern, SidlerStrasse 5, CH-3012 Bern (Switzerland)

2012-12-11

Imaging the inner part of large geological targets is an important issue in geosciences with various applications. Different approaches already exist (e.g. gravimetry, electrical tomography) that give access to a wide range of information but with identified limitations or drawbacks (e.g. intrinsic ambiguity of the inverse problem, time consuming deployment of sensors over large distances). Here we present an alternative and complementary tomography method based on the measurement of the cosmic muons flux attenuation through the geological structures. We detail the basics of this muon tomography with a special emphasis on the photo-active detectors.

Optimized organic photovoltaics with surface plasmons

Science.gov (United States)

Omrane, B.; Landrock, C.; Aristizabal, J.; Patel, J. N.; Chuo, Y.; Kaminska, B.

2010-06-01

In this work, a new approach for optimizing organic photovoltaics using nanostructure arrays exhibiting surface plasmons is presented. Periodic nanohole arrays were fabricated on gold- and silver-coated flexible substrates, and were thereafter used as light transmitting anodes for solar cells. Transmission measurements on the plasmonic thin film made of gold and silver revealed enhanced transmission at specific wavelengths matching those of the photoactive polymer layer. Compared to the indium tin oxide-based photovoltaic cells, the plasmonic solar cells showed overall improvements in efficiency up to 4.8-fold for gold and 5.1-fold for the silver, respectively.

Effect of W doping level on TiO2 on the photocatalytic degradation of Diuron.

Science.gov (United States)

Foura, Ghania; Soualah, Ahcène; Robert, Didier

2017-01-01

In the present study, three compositions of W-doped titania nano-photocatalyst are synthesized via the sol-gel method. The powders obtained were characterized by X-ray diffraction, Raman spectroscopy and UV-visible diffuse reflectance spectroscopy. The photocatalytic performances of the different photocatalysts are tested with respect to the degradation of Diuron in water solutions under simulated solar light and visible light irradiation. The W 0.03 Ti 0.97 O 2 catalyst exhibits better photoactivity than the pure TiO 2 even under simulated solar light and visible light. This improvement in activity was attributed to photoelectron/hole separation efficiency.

Functionalized SU-8 patterned with X-ray Lithography

DEFF Research Database (Denmark)

Balslev, Søren; Romanato, F.

2005-01-01

spontaneous emission light source that couples out light normal to the chip plane. In addition we examine the influence of the x-ray irradiation on the fluorescence of thin films of dye doped SU-8. The dye embedded in the SU-8 is optically excited during, characterization by an external light source tuned......In this work we demonstrate the feasibility of x-ray lithography on SU-8 photoresist doped with the laser dye Rhodamine 6G, while retaining the photoactive properties of the embedded dye. Two kinds of structures are fabricated via soft x-ray lithography and characterized: a laser and in amplified...

Electrical and Photo-Induced Degradation of ZnO Layers in Organic Photovoltaics

DEFF Research Database (Denmark)

Manor, Assaf; Katz, Eugene A.; Tromholt, Thomas

2011-01-01

minutes) does not affect the short-circuit current of the device. However, a significant degradation of V-OC and FF has been recorded by measurements of the cell current-voltage curves with a variation of light intensity, for the devices before and after the treatment. The same degradation was found......We present the case of degradation of organic solar cells by sunlight concentrated to a moderate level (similar to 4 suns). This concentration level is not enough for sufficient acceleration of the photobleaching or trap-generation in the photoactive layer and therefore such short treatment (100...

Soft-Template Synthesis of Mesoporous Anatase TiO₂ Nanospheres and Its Enhanced Photoactivity.

Science.gov (United States)

Li, Xiaojia; Zou, Mingming; Wang, Yang

2017-11-10

Highly crystalline mesoporous anatase TiO₂ nanospheres with high surface area (higher than P25 and anatase TiO₂) are prepared by a soft-template method. Despite the high specific surface area, these samples have three times lower equilibrium adsorption (<2%) than Degussa P25. The rate constant of the mesoporous anatase TiO₂ (0.024 min -1 ) reported here is 364% higher than that of P25 (0.0066 min -1 ), for the same catalytic loading. The results of oxidation-extraction photometry using several reactive oxygen species (ROS) scavengers indicated that mesoporous anatase TiO₂ generates more ROS than P25 under UV-light irradiation. This significant improvement in the photocatalytic performance of mesoporous spherical TiO₂ arises from the following synergistic effects in the reported sample: (i) high surface area; (ii) improved crystallinity; (iii) narrow pore wall thicknesses (ensuring the rapid migration of photogenerated carriers to the surface of the material); and (iv) greater ROS generation under UV-light.

PHOTOACTIVE POLYACRYLONITRILE FIBERS COATED BY NANO-SIZED TITANIUM DIOXIDE: SYNTHESIS, CHARACTERIZATION, THERMAL INVESTIGATION

OpenAIRE

MOAFI, HADI FALLAH; FALLAH SHOJAIE, ABDOLLAH; ALI ZANJANCHI, MOHAMMAD

2011-01-01

Anatase nanocrystals were successfully synthesized and deposited onto polyacrylonitrile fibers with photocatalytic self-cleaning activity using the sol-gel process at low temperature. The original and treated samples have been characterized by several techniques such as scanning electron microscopy, fourier transform infrared spectroscopy, x-ray diffraction, diffuse reflectance spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The TiO2 nanoparticles, have been fo...

Multifunctional theranostic Pluronic mixed micelles improve targeted photoactivity of Verteporfin in cancer cells

Energy Technology Data Exchange (ETDEWEB)

Silva Pellosi, Diogo [Laboratory of Phobiology and photomdicine, Department of Chemistry (FFCLRP), University of São Paulo, Av. dos Bandeirantes 3900, 14040-901, Vila Monte Alegre, Ribeirão Preto (Brazil); Calori, Italo Rodrigo [Research Nucleus of Photodynamic Therapy, Department of Chemistry, State University of Maringá, Av. Colombo 5790, 97020-900 Maringá (Brazil); Barcelos de Paula, Leonardo [Laboratory of Phobiology and photomdicine, Department of Chemistry (FFCLRP), University of São Paulo, Av. dos Bandeirantes 3900, 14040-901, Vila Monte Alegre, Ribeirão Preto (Brazil); Hioka, Noboru [Research Nucleus of Photodynamic Therapy, Department of Chemistry, State University of Maringá, Av. Colombo 5790, 97020-900 Maringá (Brazil); Quaglia, Fabiana [Laboratory of Drug Delivery, Department of Pharmacy, University of Napoli Federico II, Via Domenico Montesanto 49, 80131 Napoli (Italy); Tedesco, Antonio Claudio, E-mail: atedesco@usp.br [Laboratory of Phobiology and photomdicine, Department of Chemistry (FFCLRP), University of São Paulo, Av. dos Bandeirantes 3900, 14040-901, Vila Monte Alegre, Ribeirão Preto (Brazil)

2017-02-01

Nanotechnology development provides new strategies to treat cancer by integration of different treatment modalities in a single multifunctional nanoparticle. In this scenario, we applied the multifunctional Pluronic P123/F127 mixed micelles for Verteporfin-mediated photodynamic therapy in PC3 and MCF-7 cancer cells. Micelles functionalization aimed the targeted delivery by the insertion of biotin moiety on micelle surface and fluorescence image-based through rhodamine-B dye conjugation in the polymer chains. Multifunctional Pluronics formed spherical nanoparticulated micelles that efficiently encapsulated the photosensitizer Verteporfin maintaining its favorable photophysical properties. Lyophilized formulations were stable at least for 6 months and readily reconstituted in aqueous media. The multifunctional micelles were stable in protein-rich media due to the dual Pluronic mixed micelles characteristic: high drug loading capacity provided by its micellar core and high kinetic stability due its biocompatible shell. Biotin surface functionalized micelles showed higher internalization rates due biotin-mediated endocytosis, as demonstrated by competitive cellular uptake studies. Rhodamine B-tagged micelles allowed monitoring cellular uptake and intracellular distribution of the formulations. Confocal microscopy studies demonstrated a larger intracellular distribution of the formulation and photosensitizer, which could drive Verteporfin to act on multiple cell sites. Formulations were not toxic in the dark condition, but showed high Verteporfin-induced phototoxicity against both cancer cell lines at low drug and light doses. These results point Verteporfin-loaded multifunctional micelles as a promising tool to further developments in photodynamic therapy of cancer. - Highlights: • We optimized the theranostic mixed micelles – verteporfin formulations. • Multifunctional Pluronic micelles formed nano-sized spherical nanoparticles. • Biotin surface conjugation allowed higher intracellular uptake in cancer cells. • Rhodamine-B inclusion provided a powerful tool for imaging purposes. • Functionalized nanoparticles showed marked phototoxicity after laser irradiation.

Photoactive Self-Standing Films Made of Layered Double Hydroxides with Arranged Porphyrin Molecules

Czech Academy of Sciences Publication Activity Database

Jiřičková, M.; Demel, Jan; Kubát, Pavel; Hostomský, Jiří; Kovanda, F.; Lang, Kamil

2011-01-01

Roč. 115, č. 44 (2011), s. 21700-21706 ISSN 1932-7447 R&D Projects: GA ČR GAP207/10/1447 Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z40400503 Keywords : singlet oxygen lifetime * hybrid materials * fluorescence * nanocomposites * transparent * sensitizers Subject RIV: CA - Inorganic Chemistry; CF - Physical ; Theoretical Chemistry (UFCH-W) Impact factor: 4.805, year: 2011