Science.gov

Sample records for efficient visible light

  1. Hybrid bilayer plasmonic metasurface efficiently manipulates visible light.

    PubMed

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

    2016-01-01

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

  2. Hybrid bilayer plasmonic metasurface efficiently manipulates visible light

    PubMed Central

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

    2016-01-01

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

  3. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density. PMID:27334788

  4. Highly efficient and stable Si nanowires array embedded into transparent polymer for visible light photoelectrochemical cell

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Wang, Jian-Tao; Ou, Xue-Mei; Li, Fan; Zhang, Xiao-Hong

    2014-07-01

    Photoelectrochemical (PEC) cell supports a renewable method for solving current environmental and energy issues by combining solar energy collection and photocatalysis in a single semiconductor photoelectrode. However, it is still challenged by visible light photoelectrodes. The present work reports fabricating highly efficient and stable Si nanowires (SiNWs) array as visible light photoelectrodes. It involves embedding SiNWs arrays into a transparent polymer substrate to build an axial carrier collection geometry. We demonstrated that this strategy could significantly strengthen the chemical stability of SiNWs by largely reducing their surface area. Moreover, this device structure can also enhance visible light absorption efficiency through taking advantage of the highly crystalline structure of vapor-liquid-solid (VLS) grown SiNWs. Thus it can double the photodegradation ability of SiNWs.

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

    PubMed

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

    2014-08-13

    Herein, we report the development of a ZnO-based visible-light-driven photocatalyst by interfacial charge transfer process for the inactivation of pathogens under visible-light illumination. Surface modification by a cocatalyst on ZnO, prepared by flame spray pyrolysis process is carried out to induce the visible-light absorption in ZnO. Optical studies showed that surface modification of Cu(2+) induces the visible-light absorption in ZnO by interfacial charge transfer between ZnO and surface Cu(2+) ions upon light irradiation. The photocatalytic efficiency of pure and modified ZnO is evaluated for the inactivation of pathogens and the decomposition of methylene blue under visible-light illumination. The antibacterial activity of Cu(2+)-ZnO is several orders higher than pure ZnO and commercial Degussa-P25 and comparable with Cu(2+)-TiO2. Cu(2+)-ZnO nanorods show better photocatalytic activity than Cu(2+)-ZnO nanosphere, which is attributed to high surface area to volume ratio of former than later. The holes generated in the valence band and the Cu(1+) species generated during the interfacial charge transfer process may attribute for the inactivation of bacteria, whereas the strong oxidation power of hole is responsible for the decomposition of methylene blue. Besides the advantage of Cu(2+)-modified ZnO for visible-light-assisted photocatalytic applications, the method (FSP) used for the synthesis of ZnO in the present study is attractive for commercial application because the process has potential for the production of large quantities (2-3 kg/h) of semiconductors. PMID:25029041

  6. Polarization-independent and high-efficiency dielectric metasurfaces for visible light.

    PubMed

    Li, Qi-Tong; Dong, Fengliang; Wang, Bong; Gan, Fengyuan; Chen, Jianjun; Song, Zhiwei; Xu, Lixua; Chu, Weiguo; Xiao, Yun-Feng; Gong, Qihuang; Li, Yan

    2016-07-25

    Dielectric metasurfaces are capable of completely manipulating the phase, amplitude, and polarization of light with high spatial resolutions. The emerging design based on high-index and low-loss dielectrics has led to the realization of novel metasurfaces with high transmissions, but these devices usually operate at the limited bandwidth, and are sensitive to the incident polarization. Here, we report the realization of the polarization-independent and high-efficiency silicon metasurfaces spanning the visible wavelengths about 200 nm. The fabricated computer-generated meta-holograms exhibit a 90% diffraction efficiency, which are verified by gradient metasurfaces with measured efficiencies up to 93% at 670 nm, and exceeding 75% at the wavelengths from 600 to 800 nm for the two orthogonally polarized incidences. These dielectric metasurfaces effectively decouple the phase modulation from the polarization states and frequencies for visible light, which hold great potential for novel flat optical devices operating over a broad spectrum. PMID:27464084

  7. A low emittance and high efficiency visible light photocathode for high brightness accelerator-based X-ray light sources

    SciTech Connect

    Vecchione, T.; Ben-Zvi, I.; Dowell, D.H.; Feng, J.; Rao, T.; Smedley, J.; Wan, W.; Padmore, H.A.

    2011-07-21

    Free-electron lasers and energy recovery linacs represent a new generation of ultra-high brightness electron accelerator based x-ray sources. Photocathodes are a critical performance-limiting component of these systems. Here, we describe the development of photocathodes based on potassium-cesium-antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light, and low transverse emittance.

  8. A low emittance and high efficiency visible light photocathode for high brightness accelerator-based X-ray light sources

    SciTech Connect

    Vecchione, T.; Feng, J.; Wan, W.; Padmore, H. A.; Ben-Zvi, I.; Dowell, D. H.; Rao, T.; Smedley, J.

    2011-07-18

    Free-electron lasers and energy recovery linacs represent a new generation of ultra-high brightness electron accelerator based x-ray sources. Photocathodes are a critical performance-limiting component of these systems. Here, we describe the development of photocathodes based on potassium-cesium-antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light, and low transverse emittance.

  9. Efficient visible-light photocatalytic performance of cuprous oxide porous nanosheet arrays

    SciTech Connect

    Li, Xianghua; Wang, Jianqiang; Cao, Minhua

    2015-10-15

    Graphical Abstract: We demonstrated a facile and efficient process for fabricating Cu{sub 2}O porous nanosheet arrays on Cu mesh. Benefiting from the 1D array structure and porous structure, the as-prepared Cu{sub 2}O sample exhibited significantly improved photocatalytic activity for methyl orange degradation under visible light irradiation. - Highlights: • Cu{sub 2}O porous nanosheet arrays on Cu mesh were synthesized via the facile and efficient process. • The Cu{sub 2}O sample exhibited the 1D array structure and porous nanosheet morphology. • The as-prepared Cu{sub 2}O porous nanosheet arrays exhibited significantly improved photocatalytic activity. - Abstract: One-dimensional nanostructures are of great interest for a wide range of applications. In this work, we demonstrated the fabrication of visible-light-responsive Cu{sub 2}O porous nanosheet arrays. The synthesis involved the growth of Cu(OH){sub 2} nanosheet arrays on Cu mesh by solution-based corrosion and thermal transformation of Cu(OH){sub 2} nanosheet to Cu{sub 2}O porous nanosheets on Cu mesh. Benefiting from the one dimensional array structure and porous structure, the as-prepared Cu{sub 2}O porous nanosheet arrays exhibited significantly improved photocatalytic activity for methyl orange degradation under visible light irradiation.

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

    PubMed

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

    2014-02-21

    Visible-light-driven hydrogen evolution with high efficiency is important in the current photocatalysis research. Here we report for the first time the design and synthesis of a new graphene-semiconductor nanocomposite consisting of YInO3 nanoparticles and two-dimensional graphene sheets as efficient photocatalysts for hydrogen evolution under visible light irradiation. The graphene/YInO3 nanocomposites were synthesized using a facile solvothermal method in which the formation of graphene and the deposition of YInO3 nanoparticles on the graphene sheets can be achieved simultaneously. The addition of graphene as a cocatalyst can narrow the band gap of YInO3 to visible photon energy and prolong the separation and lifetime of electron-hole pairs by the chemical bonding between YInO3 and graphene. The photocatalytic reaction with this nanocomposite reaches a high H2 evolution rate of 400.4 μmol h(-1) g(-1) when the content of graphene is 0.5 wt%, over 127 and 3.7 times higher than that of pure YInO3 and Pt/YInO3, respectively. This work can provide an effective approach to the fabrication of graphene-based photocatalysts with high performance in the field of energy conversion. PMID:24413676

  11. Constraints on drivers for visible light communications emitters based on energy efficiency.

    PubMed

    Del Campo-Jimenez, Guillermo; Perez-Jimenez, Rafael; Lopez-Hernandez, Francisco Jose

    2016-05-01

    In this work we analyze the energy efficiency constraints on drivers for Visible light communication (VLC) emitters. This is the main reason why LED is becoming the main source of illumination. We study the effect of the waveform shape and the modulation techniques on the overall energy efficiency of an LED lamp. For a similar level of illumination, we calculate the emitter energy efficiency ratio η (PLED/PTOTAL) for different signals. We compare switched and sinusoidal signals and analyze the effect of both OOK and OFDM modulation techniques depending on the power supply adjustment, level of illumination and signal amplitude distortion. Switched and OOK signals present higher energy efficiency behaviors (0.86≤η≤0.95) than sinusoidal and OFDM signals (0.53≤η≤0.79). PMID:27137609

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  13. Fe ion-implanted TiO2 thin film for efficient visible-light photocatalysis

    NASA Astrophysics Data System (ADS)

    Impellizzeri, G.; Scuderi, V.; Romano, L.; Sberna, P. M.; Arcadipane, E.; Sanz, R.; Scuderi, M.; Nicotra, G.; Bayle, M.; Carles, R.; Simone, F.; Privitera, V.

    2014-11-01

    This work shows the application of metal ion-implantation to realize an efficient second-generation TiO2 photocatalyst. High fluence Fe+ ions were implanted into thin TiO2 films and subsequently annealed up to 550 °C. The ion-implantation process modified the TiO2 pure film, locally lowering its band-gap energy from 3.2 eV to 1.6-1.9 eV, making the material sensitive to visible light. The measured optical band-gap of 1.6-1.9 eV was associated with the presence of effective energy levels in the energy band structure of the titanium dioxide, due to implantation-induced defects. An accurate structural characterization was performed by Rutherford backscattering spectrometry, transmission electron microscopy, Raman spectroscopy, X-ray diffraction, and UV/VIS spectroscopy. The synthesized materials revealed a remarkable photocatalytic efficiency in the degradation of organic compounds in water under visible light irradiation, without the help of any thermal treatments. The photocatalytic activity has been correlated with the amount of defects induced by the ion-implantation process, clarifying the operative physical mechanism. These results can be fruitfully applied for environmental applications of TiO2.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  15. Highly efficient and ultrastable visible-light photocatalytic water splitting over ReS2.

    PubMed

    Liu, Huimei; Xu, Bo; Liu, J-M; Yin, Jiang; Miao, Feng; Duan, Chun-Gang; Wan, X G

    2016-06-01

    Two dimensional materials have many outstanding intrinsic advantages that can be utilized to enhance the photocatalytic efficiency of water splitting. Herein, based on ab initio calculations, we reveal that for monolayer and multilayer rhenium disulphide (ReS2), the band gap and band edge positions are an excellent match with the water splitting energy levels. Moreover, the effective masses of the carriers are relatively light, and the optical absorption coefficients are high under visible illumination. Due to the feature of weak interlayer coupling, these properties are independent of the layer thickness. Our results suggest that ReS2 is a stable and efficient photocatalyst with potential applications in the use of solar energy for water splitting. PMID:27167677

  16. Microcrystalline sodium tungsten bronze nanowire bundles as efficient visible light-responsive photocatalysts.

    PubMed

    Wang, Lei; Zhan, Jinhua; Fan, Weiliu; Cui, Guanwei; Sun, Honggang; Zhuo, Linhai; Zhao, Xian; Tang, Bo

    2010-12-14

    Microcrystalline sodium tungsten bronze nanowire bundles were obtained via a facile hydrothermal synthesis, and were applied in water purification as visible-light-driven photocatalysts for the first time. PMID:20953497

  17. Copper nanoparticles on graphene support: an efficient photocatalyst for coupling of nitroaromatics in visible light.

    PubMed

    Guo, Xiaoning; Hao, Caihong; Jin, Guoqiang; Zhu, Huai-Yong; Guo, Xiang-Yun

    2014-02-10

    Copper is a low-cost plasmonic metal. Efficient photocatalysts of copper nanoparticles on graphene support are successfully developed for controllably catalyzing the coupling reactions of aromatic nitro compounds to the corresponding azoxy or azo compounds under visible-light irradiation. The coupling of nitrobenzene produces azoxybenzene with a yield of 90 % at 60 °C, but azobenzene with a yield of 96 % at 90 °C. When irradiated with natural sunlight (mean light intensity of 0.044 W cm(-2) ) at about 35 °C, 70 % of the nitrobenzene is converted and 57 % of the product is azobenzene. The electrons of the copper nanoparticles gain the energy of the incident light through a localized surface plasmon resonance effect and photoexcitation of the bound electrons. The excited energetic electrons at the surface of the copper nanoparticles facilitate the cleavage of the NO bonds in the aromatic nitro compounds. Hence, the catalyzed coupling reaction can proceed under light irradiation and moderate conditions. This study provides a green photocatalytic route for the production of azo compounds and highlights a potential application for graphene. PMID:24505013

  18. Efficient Visible-Light Photocatalytic Properties in Low-Temperature Bi-Nb-O System Photocatalysts.

    PubMed

    Zhai, Haifa; Shang, Shuying; Zheng, Liuyang; Li, Panpan; Li, Haiqin; Luo, Hongying; Kong, Jizhou

    2016-12-01

    Low-temperature Bi-Nb-O system photocatalysts were prepared by a citrate method using homemade water-soluble niobium precursors. The structures, morphologies, and optical properties of Bi-Nb-O system photocatalysts with different compositions were investigated deeply. All the Bi-Nb-O powders exhibit appreciably much higher photocatalytic efficiency of photo-degradation of methyl violet (MV), especially for Bi-Nb-O photocatalysts sintered at 750 °C (BNO750), only 1.5 h to completely decompose MV, and the obtained first-order rate constant (k) is 1.94/h. A larger degradation rate of Bi-Nb-O photocatalysts sintered at 550 °C (BNO550) can be attributed to the synergistic effect between β-BiNbO4 and Bi5Nb3O15. Bi5Nb3O15 with small particle size on β-BiNbO4 surface can effectively short the diffuse length of electron. BNO750 exhibits the best photocatalytic properties under visible-light irradiation, which can be attributed to its better crystallinity and the synergistic effect between β-BiNbO4 and α-BiNbO4. The small amount of α-BiNbO4 loading on surface of β-BiNbO4 can effectively improve the electron and hole segregation and migration. Holes are the main active species of Bi-Nb-O system photocatalysts in aqueous solution under visible-light irradiation. PMID:27576523

  19. Multifunctional polyoxometalates encapsulated in MIL-100(Fe): highly efficient photocatalysts for selective transformation under visible light.

    PubMed

    Liang, Ruowen; Chen, Rui; Jing, Fenfen; Qin, Na; Wu, Ling

    2015-11-01

    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. PMID:26426950

  20. Hot-electron-transfer enhancement for the efficient energy conversion of visible light.

    PubMed

    Yu, Sungju; Kim, Yong Hwa; Lee, Su Young; Song, Hyeon Don; Yi, Jongheop

    2014-10-13

    Great strides have been made in enhancing solar energy conversion by utilizing plasmonic nanostructures in semiconductors. However, current generation with plasmonic nanostructures is still somewhat inefficient owing to the ultrafast decay of plasmon-induced hot electrons. It is now shown that the ultrafast decay of hot electrons across Au nanoparticles can be significantly reduced by strong coupling with CdS quantum dots and by a Schottky junction with perovskite SrTiO3 nanoparticles. The designed plasmonic nanostructure with three distinct components enables a hot-electron-assisted energy cascade for electron transfer, CdS→Au→SrTiO3, as demonstrated by steady-state and time-resolved photoluminescence spectroscopy. Consequently, hot-electron transfer enabled the efficient production of H2 from water as well as significant electron harvesting under irradiation with visible light of various wavelengths. These findings provide a new approach for overcoming the low efficiency that is typically associated with plasmonic nanostructures. PMID:25169852

  1. Water-plasma-assisted synthesis of black titania spheres with efficient visible-light photocatalytic activity.

    PubMed

    Panomsuwan, Gasidit; Watthanaphanit, Anyarat; Ishizaki, Takahiro; Saito, Nagahiro

    2015-06-01

    Black titania spheres (H-TiO2-x) were synthesized via a simple green method assisted by water plasma at a low temperature and atmospheric pressure. The in situ production of highly energetic hydroxyl and hydrogen species from water plasma are the prominent factors in the oxidation and hydrogenation reactions during the formation of H-TiO2-x, respectively. The visible-light photocatalytic activity toward the dye degradation of H-TiO2-x can be attributed to the synergistic effect of large-surface area, visible-light absorption and the existence of oxygen vacancies and Ti(3+) sites. PMID:25946395

  2. Carbon quantum dots with photo-generated proton property as efficient visible light controlled acid catalyst

    NASA Astrophysics Data System (ADS)

    Li, Haitao; Liu, Ruihua; Kong, Weiqian; Liu, Juan; Liu, Yang; Zhou, Lei; Zhang, Xing; Lee, Shuit-Tong; Kang, Zhenhui

    2013-12-01

    Developing light-driven acid catalyst will be very meaningful for the controlled-acid catalytic processes towards a green chemical industry. Here, based on scanning electrochemical microscopy (SECM) and ΔpH testing, we demonstrate that the 5-10 nm carbon quantum dots (CQDs) synthesized by electrochemical ablation of graphite have strong light-induced proton properties under visible light in solution, which can be used as an acid catalyst. The 5-10 nm CQDs' catalytic activity is strongly dependent on the illumination intensity and the temperature of the reaction system. As an effective visible light driven and controlled acid-catalyst, 5-10 nm CQDs can catalyze a series of organic reactions (esterification, Beckmann rearrangement and aldol condensation) with high conversion (34.7-46.2%, respectively) in water solution under visible light, while the 1-4 nm CQDs and 10-2000 nm graphite do not have such excellent catalytic activity. The use of 5-10 nm CQDs as a light responsive and controllable photocatalyst is truly a novel application of carbon-based nanomaterials, which may significantly push research in the current catalytic industry, environmental pollution and energy issues.Developing light-driven acid catalyst will be very meaningful for the controlled-acid catalytic processes towards a green chemical industry. Here, based on scanning electrochemical microscopy (SECM) and ΔpH testing, we demonstrate that the 5-10 nm carbon quantum dots (CQDs) synthesized by electrochemical ablation of graphite have strong light-induced proton properties under visible light in solution, which can be used as an acid catalyst. The 5-10 nm CQDs' catalytic activity is strongly dependent on the illumination intensity and the temperature of the reaction system. As an effective visible light driven and controlled acid-catalyst, 5-10 nm CQDs can catalyze a series of organic reactions (esterification, Beckmann rearrangement and aldol condensation) with high conversion (34

  3. Highly efficient photocatalytic hydrogen evolution from nickel quinolinethiolate complexes under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Rao, Heng; Yu, Wen-Qian; Zheng, Hui-Qin; Bonin, Julien; Fan, Yao-Ting; Hou, Hong-Wei

    2016-08-01

    Earth-abundant metal complexes have emerged as promising surrogates of platinum for catalyzing the hydrogen evolution reaction (HER). In this study, we report the design and synthesis of two novel nickel quinolinethiolate complexes, namely [Ni(Hqt)2(4, 4‧-Z-2, 2‧-bpy)] (Hqt = 8-quinolinethiol, Z = sbnd H [1] or sbnd CH3 [2], bpy = bipyridine). An efficient three-component photocatalytic homogeneous system for hydrogen generation working under visible light irradiation was constructed by using the target complexes as catalysts, triethylamine (TEA) as sacrificial electron donor and xanthene dyes as photosensitizer. We obtain turnover numbers (TON, vs. catalyst) for H2 evolution of 5923/7634 under the optimal conditions with 5.0 × 10-6 M complex 1/2 respectively, 1.0 × 10-3 M fluorescein and 5% (v/v) TEA at pH 12.3 in EtOH/H2O (1:1, v/v) mixture after 8 h irradiation (λ > 420 nm). We discuss the mechanism of H2 evolution in the homogeneous photocatalytic system based on fluorescence spectrum and cyclic voltammetry data.

  4. Highly efficient photocatalytic hydrogen evolution from nickel quinolinethiolate complexes under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Rao, Heng; Yu, Wen-Qian; Zheng, Hui-Qin; Bonin, Julien; Fan, Yao-Ting; Hou, Hong-Wei

    2016-08-01

    Earth-abundant metal complexes have emerged as promising surrogates of platinum for catalyzing the hydrogen evolution reaction (HER). In this study, we report the design and synthesis of two novel nickel quinolinethiolate complexes, namely [Ni(Hqt)2(4, 4‧-Z-2, 2‧-bpy)] (Hqt = 8-quinolinethiol, Z = sbnd H [1] or sbnd CH3 [2], bpy = bipyridine). An efficient three-component photocatalytic homogeneous system for hydrogen generation working under visible light irradiation was constructed by using the target complexes as catalysts, triethylamine (TEA) as sacrificial electron donor and xanthene dyes as photosensitizer. We obtain turnover numbers (TON, vs. catalyst) for H2 evolution of 5923/7634 under the optimal conditions with 5.0 × 10-6 M complex 1/2 respectively, 1.0 × 10-3 M fluorescein and 5% (v/v) TEA at pH 12.3 in EtOH/H2O (1:1, v/v) mixture after 8 h irradiation (λ > 420 nm). We discuss the mechanism of H2 evolution in the homogeneous photocatalytic system based on fluorescence spectrum and cyclic voltammetry data.

  5. Ultrafast and Efficient Transport of Hot Plasmonic Electrons by Graphene for Pt Free, Highly Efficient Visible-Light Responsive Photocatalyst.

    PubMed

    Kumar, Dinesh; Lee, Ahreum; Lee, Taegon; Lim, Manho; Lim, Dong-Kwon

    2016-03-01

    We report that reduced graphene-coated gold nanoparticles (r-GO-AuNPs) are excellent visible-light-responsive photocatalysts for the photoconversion of CO2 into formic acid (HCOOH). The wavelength-dependent quantum and chemical yields of HCOOH shows a significant contribution of plasmon-induced hot electrons for CO2 photoconversion. Furthermore, the presence and reduced state of the graphene layers are critical parameters for the efficient CO2 photoconversion because of the electron mobility of graphene. With an excellent selectivity toward HCOOH (>90%), the quantum yield of HCOOH using r-GO-AuNPs is 1.52%, superior to that of Pt-coated AuNPs (quantum yield: 1.14%). This indicates that r-GO is a viable alternative to platinum metal. The excellent colloidal stability and photocatalytic stability of r-GO-AuNPs enables CO2 photoconversion under more desirable reaction conditions. These results highlight the role of reduced graphene layers as highly efficient electron acceptors and transporters to facilitate the use of hot electrons for plasmonic photocatalysts. The femtosecond transient spectroscopic analysis also shows 8.7 times higher transport efficiency of hot plasmonic electrons in r-GO-AuNPs compared with AuNPs. PMID:26854830

  6. Towards visible light hydrogen generation: quantum dot-sensitization via efficient light harvesting of hybrid-TiO2.

    PubMed

    Kim, Kwanghyun; Kim, Myeong-Jong; Kim, Sun-I; Jang, Ji-Hyun

    2013-01-01

    We report pronounced enhancement of photoelectrochemical hydrogen generation of a quantum dot-sensitized hybrid-TiO2 (QD/H-TiO2) electrode that is composed of a mesoporous TiO2 layer sandwiched by a double sided energy harvesting layer consisting of a surface-textured TiO2 inverse opals layer on the bottom and a patterned mesoporous TiO2 layer on the top. CdSe/H-TiO2 exhibits a maximum photocurrent density of ~16.2 mA/cm(2), which is 35% higher than that of the optimized control sample (CdSe/P25), achieved by matching of the bandgap of quantum dot-sensitization with the wavelength where light harvesting of H-TiO2 is observed. Furthermore, CdSe/H-TiO2 under filtered exposure conditions recorded current density of ~14.2 mA/cm(2), the greatest value in the visible range. The excellent performance of the quantum dot-sensitized H-TiO2 suggests that alteration of the photoelectrodes to suitable nanostructures with excellent light absorption may offer optimal strategies for attaining maximum efficiency in a variety of photoconversion systems. PMID:24270426

  7. Towards Visible Light Hydrogen Generation: Quantum Dot-Sensitization via Efficient Light Harvesting of Hybrid-TiO2

    NASA Astrophysics Data System (ADS)

    Kim, Kwanghyun; Kim, Myeong-Jong; Kim, Sun-I.; Jang, Ji-Hyun

    2013-11-01

    We report pronounced enhancement of photoelectrochemical hydrogen generation of a quantum dot-sensitized hybrid-TiO2 (QD/H-TiO2) electrode that is composed of a mesoporous TiO2 layer sandwiched by a double sided energy harvesting layer consisting of a surface-textured TiO2 inverse opals layer on the bottom and a patterned mesoporous TiO2 layer on the top. CdSe/H-TiO2 exhibits a maximum photocurrent density of ~16.2 mA/cm2, which is 35% higher than that of the optimized control sample (CdSe/P25), achieved by matching of the bandgap of quantum dot-sensitization with the wavelength where light harvesting of H-TiO2 is observed. Furthermore, CdSe/H-TiO2 under filtered exposure conditions recorded current density of ~14.2 mA/cm2, the greatest value in the visible range. The excellent performance of the quantum dot-sensitized H-TiO2 suggests that alteration of the photoelectrodes to suitable nanostructures with excellent light absorption may offer optimal strategies for attaining maximum efficiency in a variety of photoconversion systems.

  8. Co3 O4 Hexagonal Platelets with Controllable Facets Enabling Highly Efficient Visible-Light Photocatalytic Reduction of CO2.

    PubMed

    Gao, Chao; Meng, Qiangqiang; Zhao, Kun; Yin, Huajie; Wang, Dawei; Guo, Jun; Zhao, Shenlong; Chang, Lin; He, Meng; Li, Qunxiang; Zhao, Huijun; Huang, Xingjiu; Gao, Yan; Tang, Zhiyong

    2016-08-01

    A heterogeneous catalyst made of well-defined Co3 O4 hexagonal platelets with varied exposed facets is coupled with [Ru(bpy)3 ]Cl2 photosensitizers to effectively and efficiently reduce CO2 under visible-light irradiation. Systematic investigation based on both experiment and theory discloses that the exposed {112} facets are crucial for activating CO2 molecules, giving rise to significant enhancement of photocatalytic CO2 reduction efficiency. PMID:27171564

  9. Efficient Mineralization of Toluene by W-Doped TiO2 Nanofibers Under Visible Light Irradiation.

    PubMed

    Zhang, Li; Li, Yaogang; Xie, Hongyong; Wang, Hongzhi; Zhang, Qinghong

    2015-04-01

    Toxic toluene gas caused enormous harm to human health, and the traditional method to deal with this puzzle is using physical adsorption, which just transfer the toluene from one medium to another. Photocatalysis has great potential to mineralize toluene into CO2 under visible light irradiation, but their applications have been limited by difficulties in preparing efficient photocatalysts with fine crystallite size, considerable visible light response, and large surface area to contact with toluene gas. To address this problem, we have developed a film composed of W-doped TiO2 nanofibers to mineralize toluene under visible light irradiation. The electrospinning preparation route allows incorporation of up to 50 wt% of W in substitutional positions of titanium atom in the anatase network. The W-doped TiO2 nanofibers behave finer crystallite size, stronger visible light absorbance, and larger surface area comparing with pure TiO2 nanofibers. The nanofiber structured morphology on the quartz tube promotes the reaction rates for the gas-phase photo-oxidation of toluene. The concentrations of the produced CO2 keep steady during the photodegradation process, indicating the practicality and operability for the whole experiment. This research is conducive to the development of novel photocatalytic materials to efficiently mineralize toxic gas pollutants including toluene for practical application. PMID:26353518

  10. Photocatalytic Ohmic layered nanocomposite for efficient utilization of visible light photons

    SciTech Connect

    Kim, Hyun Gyu; Jeong, Euh Duck; Borse, Pramod H.; Jeon, Seongho; Yong, Kijung; Lee, Jae Sung; Li Wei; Oh, Se H.

    2006-08-07

    The WO{sub 3}/W/PbBi{sub 2}Nb{sub 1.9}Ti{sub 0.1}O{sub 9} photocatalyst was fabricated by depositing the tungsten clusters over the p-type perovskite base material with the chemical vapor deposition method, and later partly oxidizing the surfaces of these clusters to obtain n-type WO{sub 3} overlayers and W metal layer as an Ohmic junction. This NCPC showed unprecedented high activity for the photocatalytic oxidation of water, photocurrent generation, and acetaldehyde decomposition under visible light irradiation ({lambda}{>=}420 nm)

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  12. Solvothermal synthesis of designed nonstoichiometric strontium titanate for efficient visible-light photocatalysis

    NASA Astrophysics Data System (ADS)

    Sulaeman, Uyi; Yin, Shu; Sato, Tsugio

    2010-09-01

    SrTiO3 powders with various Sr/Ti atomic ratios were synthesized by microwave-assisted solvothermal reactions of SrCl2 and Ti(OC3H7)4 in KOH aqueous solutions. The nanoparticles of perovskite type SrTiO3 structure with the particle size of 30-40 nm were synthesized. The photocatalytic activity was determined by deNOx ability using light emitting diode lamps of various wavelengths such as 627 nm (red), 530 nm (green), 445 nm (blue), and 390 nm (UV). The photocatalytic activity significantly changed depending on the Sr/Ti atomic ratio, i.e., the strontium rich sample (Sr/Ti atomic ratio>1) showed excellent visible light responsive photocatalytic activity for the oxidative destruction of NO.

  13. Solvothermal synthesis of designed nonstoichiometric strontium titanate for efficient visible-light photocatalysis

    SciTech Connect

    Sulaeman, Uyi; Yin, Shu; Sato, Tsugio

    2010-09-06

    SrTiO{sub 3} powders with various Sr/Ti atomic ratios were synthesized by microwave-assisted solvothermal reactions of SrCl{sub 2} and Ti(OC{sub 3}H{sub 7}){sub 4} in KOH aqueous solutions. The nanoparticles of perovskite type SrTiO{sub 3} structure with the particle size of 30-40 nm were synthesized. The photocatalytic activity was determined by deNO{sub x} ability using light emitting diode lamps of various wavelengths such as 627 nm (red), 530 nm (green), 445 nm (blue), and 390 nm (UV). The photocatalytic activity significantly changed depending on the Sr/Ti atomic ratio, i.e., the strontium rich sample (Sr/Ti atomic ratio>1) showed excellent visible light responsive photocatalytic activity for the oxidative destruction of NO.

  14. Hollow porous carbon nitride immobilized on carbonized nanofibers for highly efficient visible light photocatalytic removal of NO.

    PubMed

    Wu, Hongxin; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

    2016-06-01

    With the deterioration of air quality, great efforts were devoted to designing various photocatalysts for effective removal of NOx in air. However, the present photocatalysts have a fatal problem of low photocatalytic efficiency. In this work, a hollow porous carbon nitride nanosphere coupled with reduced graphene oxide (HCNS/rGO) was exploited as a visible-light photocatalyst to remove nitrogen monoxide in air at a low concentration (600 ppb level) under irradiation of an energy saving lamp. HCNS/rGO showed a NO removal ratio of 64%, which was superior to that of most other visible-light photocatalysts. The excellent photocatalytic ability of HCNS/rGO originates from the hollow porous morphology of HCNS and the grafted rGO on the surface. HCNS/rGO was immobilized on porous carbonized polymer nanofibers to obtain a photocatalytic membrane without affecting photocatalytic efficiency. Furthermore, the membrane showed excellent photochemical stability and recyclability. PMID:27245319

  15. Hollow porous carbon nitride immobilized on carbonized nanofibers for highly efficient visible light photocatalytic removal of NO

    NASA Astrophysics Data System (ADS)

    Wu, Hongxin; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

    2016-06-01

    With the deterioration of air quality, great efforts were devoted to designing various photocatalysts for effective removal of NOx in air. However, the present photocatalysts have a fatal problem of low photocatalytic efficiency. In this work, a hollow porous carbon nitride nanosphere coupled with reduced graphene oxide (HCNS/rGO) was exploited as a visible-light photocatalyst to remove nitrogen monoxide in air at a low concentration (600 ppb level) under irradiation of an energy saving lamp. HCNS/rGO showed a NO removal ratio of 64%, which was superior to that of most other visible-light photocatalysts. The excellent photocatalytic ability of HCNS/rGO originates from the hollow porous morphology of HCNS and the grafted rGO on the surface. HCNS/rGO was immobilized on porous carbonized polymer nanofibers to obtain a photocatalytic membrane without affecting photocatalytic efficiency. Furthermore, the membrane showed excellent photochemical stability and recyclability.With the deterioration of air quality, great efforts were devoted to designing various photocatalysts for effective removal of NOx in air. However, the present photocatalysts have a fatal problem of low photocatalytic efficiency. In this work, a hollow porous carbon nitride nanosphere coupled with reduced graphene oxide (HCNS/rGO) was exploited as a visible-light photocatalyst to remove nitrogen monoxide in air at a low concentration (600 ppb level) under irradiation of an energy saving lamp. HCNS/rGO showed a NO removal ratio of 64%, which was superior to that of most other visible-light photocatalysts. The excellent photocatalytic ability of HCNS/rGO originates from the hollow porous morphology of HCNS and the grafted rGO on the surface. HCNS/rGO was immobilized on porous carbonized polymer nanofibers to obtain a photocatalytic membrane without affecting photocatalytic efficiency. Furthermore, the membrane showed excellent photochemical stability and recyclability. Electronic supplementary information

  16. Visible light treatment of photoaging.

    PubMed

    Dierickx, Christine C; Anderson, R Rox

    2005-01-01

    Recently, a number of new devices have been developed specifically to improve the visible signs of aging in a noninvasive way. These include visible or near-infrared lasers, intense pulsed light sources (IPL), light-emitting diode (LED), and radiofrequency devices. This paper reviews the use of visible light sources and examines the attributes of specific systems for noninvasive skin rejuvenation. PMID:16229721

  17. Interlayer-I-doped BiOIO3 nanoplates with an optimized electronic structure for efficient visible light photocatalysis.

    PubMed

    Sun, Yanjuan; Xiong, Ting; Dong, Fan; Huang, Hongwei; Cen, Wanglai

    2016-07-01

    The success in the synthesis of Bi-based layered photocatalysts with high photocatalytic activities has triggered intensive studies. Herein, we prepared interlayer-I-doped BiOIO3 nanoplates by a facile method. Interestingly, it was found that I atoms were doped into the BiOIO3 interlayers instead of substituting for the lattice atoms based on theoretical and experimental results. The interbedded I atoms endowed BiOIO3 with an extended light response from the UV to the visible region by narrowing the bandgap and generating a middle level. The enhanced oxidation capability via positive-shifting the valence band position and improved carrier separation efficiency via forming charge delivery channels at the adjacent two layers can be achieved simultaneously. As expected, I-intercalated BiOIO3 with an optimized electronic structure demonstrated outstanding NO removal ability under visible light irradiation, much superior to pure BiOIO3. The present success in fabricating interlayer-I-doped BiOIO3 would open a promising route to prepare other Bi-based layered semiconductors with efficient visible-light photocatalysis. PMID:27284595

  18. CdS nanoparticles/CeO2 nanorods composite with high-efficiency visible-light-driven photocatalytic activity

    NASA Astrophysics Data System (ADS)

    You, Daotong; Pan, Bao; Jiang, Fan; Zhou, Yangen; Su, Wenyue

    2016-02-01

    Different mole ratios of CdS nanoparticles (NPs)/CeO2 nanorods (NRs) composites with effective contacts were synthesized through a two-step hydrothermal method. The crystal phase, microstructure, optical absorption properties, electrochemical properties and photocatalytic H2 production activity of these composites were investigated. It was concluded that the photogenerated charge carriers in the CdS NPs/CeO2 NRs composite with a proper mole ratio (1:1) exhibited the longest lifetime and highest separation efficiency, which was responsible for the highest H2-production rate of 8.4 mmol h-1 g-1 under visible-light irradiation (λ > 420 nm). The superior photocatalytic H2 evolution properties are attributed to the transfer of visible-excited electrons of CdS NPs to CeO2 NRs, which can effectively extend the light absorption range of wide-band gap CeO2 NRs. This work provides feasible routes to develop visible-light responsive CeO2-based nanomaterial for efficient solar utilization.

  19. Towards efficient visible-light active photocatalysts: CdS/Au sensitized TiO2 nanotube arrays.

    PubMed

    Nguyen, VanManh; Cai, Qingyun; Grimes, Craig A

    2016-12-01

    A visible-light active photocatalyst, CdS/Au/TiO2 nanotube array (NTA) photoelectrode, was prepared by electrodeposition of Au nanoparticles onto TiO2 NTA with subsequent deposition of visible-light absorbable 2.4eV band-gap CdS quantum dots using successive ion layer adsorption and reaction (SILAR). The Au nanoparticles here act as electron sinks facilitating charge carrier separation. Under AM1.5G illumination a photoconversion efficiency of 4.06% was achieved for the CdS/Au/TiO2 NTA photoelectrode, suggesting the promise of the material architecture for achieving high-performance cost-effective materials. PMID:27565960

  20. Efficient visible-light photocatalytic degradation of sulfadiazine sodium with hierarchical Bi₇O₉I₃under solar irradiation.

    PubMed

    Xu, MengMeng; Zhao, YaLei; Yan, QiShe

    2015-01-01

    Bi₇O₉I₃, a kind of visible-light-responsive photocatalyst, with hierarchical micro/nano-architecture was successfully synthesized by oil-bath heating method, with ethylene glycol as solvent, and applied to degrade sulfonamide antibiotics. The as-prepared product was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflection spectra and scanning electron microscopy (SEM). XRD and XPS tests confirmed that the product was indeed Bi₇O₉I₃. The result of SEM observation shows that the as-synthesized Bi₇O₉I₃ consists of a large number of micro-sheets with parallel rectangle structure. The optical test exhibited strong photoabsorption in visible light irradiation, with 617 nm of absorption edges. Moreover, the difference in the photocatalytic efficiency of as-prepared Bi₇O₉I₃ at different seasons of a whole year was investigated in this study. The chemical oxygen demand removal efficiency and concentration of NO(3)(-) and SO(4)(2-) of solution after reaction were also researched to confirm whether degradation of the pollutant was complete; the results indicated a high mineralization capacity of Bi₇O₉I₃. The as-synthesized Bi₇O₉I₃exhibits an excellent oxidizing capacity of sulfadiazine sodium and favorable stability during the photocatalytic reaction. PMID:26675999

  1. In Situ Fluorine Doping of TiO2 Superstructures for Efficient Visible-Light Driven Hydrogen Generation.

    PubMed

    Zhang, Peng; Tachikawa, Takashi; Fujitsuka, Mamoru; Majima, Tetsuro

    2016-03-21

    With the aid of breakthroughs in nanoscience and nanotechnology, it is imperative to develop metal oxide semiconductors through visible light-driven hydrogen generation. In this study, TiOF2 was incorporated as an n-type F-dopant source to TiO2 mesocrystals (TMCs) with visible-light absorption during the topotactic transformation. The crystal growth, structural change, and dynamic morphological evolution, from the initial intermediate NH4 TiOF3 to HTiOF3 , TiOF2 , and F-doped TMCs, were verified through in situ temperature-dependent techniques to elucidate the doping mechanism from intermediate TiOF2 . The visible-light efficiencies of photocatalytic hydrogen were dependent on the contents of the dopant as compared with the pure TMC and a controled reference. Using femtosecond time-resolved diffuse reflectance spectroscopy, the charge-transfer dynamics were monitored to confirm the improvement of charge separation after doping. PMID:26871554

  2. Iron Oxide Nanowires from Bacteria Biofilm as an Efficient Visible-Light Magnetic Photocatalyst.

    PubMed

    Wang, Luoshan; Kumeria, Tushar; Santos, Abel; Forward, Peter; Lambert, Martin F; Losic, Dusan

    2016-08-10

    Naturally produced iron oxide nanowires by Mariprofundus ferrooxydans bacteria as biofilm are evaluated for their structural, chemical, and photocatalytic performance under visible-light irradiation. The crystal phase structure of this unique natural material presents a 1-dimensional (1D) nanowire-like geometry, which is transformed from amorphous to crystalline (hematite) by thermal annealing at high temperature without changing their morphology. This study systematically assesses the effect of different annealing temperatures on the photocatalytic activity of iron oxide nanowires produced by Mariprofundus ferrooxydans bacteria. The nanowires processed at 800 °C were the most optimal for photocatalytic applications degrading a model dye (rhodamine B) in less than an hour. These nanowires displayed excellent reusability with no significant loss of activity even after 6 cycles. Kinetic studies by using hydrogen peroxide (radical generator) and isopropyl alcohol (radical scavenger) suggest that OH• is the dominant photooxidant. These nanowires are naturally produced, inexpensive, highly active, stable, and magnetic and have the potential to be used for broad applications including environmental remediation, water disinfection, and industrial catalysis. PMID:27420121

  3. Ag loaded WO3 nanoplates for efficient photocatalytic degradation of sulfanilamide and their bactericidal effect under visible light irradiation.

    PubMed

    Zhu, Wenyu; Liu, Jincheng; Yu, Shuyan; Zhou, Yan; Yan, Xiaoli

    2016-11-15

    Sulfonamides (SAs) are extensively used antibiotics and their residues in the water bodies propose potential threat to the public. In this study, degradation efficiency of sulfanilamide (SAM), which is the precursor of SAs, using WO3 nanoplates and their Ag heterogeneous as photocatalysts was investigated. WO3 nanoplates with uniform size were synthesized by a facile one step hydrothermal method. Different amount of Ag nanoparticles (Ag NPs) were loaded onto WO3 nanoplates using a photo-reduction method to generate WO3/Ag composites. The physio-chemical properties of synthesized nanomaterials were systematically characterized. Photodegradation of SAM by WO3 and WO3/Ag composites was conducted under visible light irradiation. The results show that WO3/Ag composites performed much better than pure WO3 where the highest removal rate was 96.2% in 5h. Ag as excellent antibacterial agent also endows certain antibacterial efficiency to WO3, and 100% removal efficiency against Escherichia Coli and Bacillus subtilis could be achieved in 2h under visible light irradiation for all three WO3/Ag composites synthesized. The improved performance in terms of SAM degradation and antibacterial activity of WO3/Ag can be attributed to the improved electron-hole pair separation rate where Ag NPs act as effective electron trapper during the photocatalytic process. PMID:27450332

  4. Mussel-inspired green synthesis of polydopamine-Ag-AgCl composites with efficient visible-light-driven photocatalytic activity.

    PubMed

    Cai, Aijun; Wang, Xiuping; Guo, Aiying; Chang, Yongfang

    2016-09-01

    Polydopamine-Ag-AgCl composites (PDA-Ag-AgCl) were synthesized using a mussel-inspired method at room temperature, where PDA acts as a reducing agent to obtain the noble Ag nanoparticles from a precursor. The morphologies and structures of the as-prepared PDA-Ag-AgCl were characterized by several techniques including field emission scanning electron microscopy (FESEM), transmission electron microscopy (SEM), Raman spectra, and X-Ray photoelectron spectrum (XPS). The morphological observation depicts formation of nanoparticles with various micrometer size diameters and surface XPS analysis shows presence of various elements including Ag, N, Cl, and O. The enhanced absorbance of the PDA-Ag-AgCl particles in the visible light region is confirmed through UV-Vis diffuse reflectance spectra (DRS), and the charge transfer is demonstrated by photoluminescence (PL) and photocurrent response. The synthesized PDA-Ag-AgCl composites could be used as visible-light-driven photocatalysts for the degradation of Rhodamine B. The elevated photocatalytic activity is ascribed to the effective charge transfer from plasmon-excited Ag to AgCl that can improve the efficiency of the charge separation during the photocatalytic reaction. Furthermore, differences in the photocatalytic performance among the different PDA-Ag-AgCl composites are noticed that could be attributed to the Brunauer-Emmett-Teller (BET) specific surface area, which benefits to capture the visible light efficiently. The PDA-Ag-AgCl exhibits excellent stability without a significant loss in activity after 5cycles. The proposed method is low-cost and environmentally friendly, hence a promising new way to fabricate plasmon photocatalysts. PMID:27450302

  5. Efficiency droop effects of GaN-based light-emitting diodes on the performance of code division multiple access visible-light communication system

    NASA Astrophysics Data System (ADS)

    Lu, Huimin; Yan, Chaowen; Gao, Wei; Yu, Tongjun; Wang, Jianping

    2016-02-01

    The physical mechanism in efficiency droop of GaN-based light-emitting diodes (LEDs) was investigated using a modified rate equation model considering inhomogeneous carrier distribution and was compared with the measured result. On this basis, the efficiency droop effect on the performance of a code division multiple access (CDMA) visible-light communication (VLC) system using GaN-based LEDs was also analyzed. The results reveal that the obvious transmitted signal error under the effect of LED efficiency droop leads to performance deterioration of multiuser CDMA VLC systems. Also, the performance of CDMA VLC systems is reduced with the user number increase due to LED efficiency droop. The bit error rate of a CDMA VLC system was further calculated for different branch signal levels and bias currents. It is demonstrated that the efficiency droop effect on the performance of CDMA VLC systems can be alleviated by adjusting the branch signal level and the bias current.

  6. Fe ion-implanted TiO{sub 2} thin film for efficient visible-light photocatalysis

    SciTech Connect

    Impellizzeri, G. Scuderi, V.; Sanz, R.; Privitera, V.; Romano, L.; Sberna, P. M.; Arcadipane, E.; Scuderi, M.; Nicotra, G.; Bayle, M.; Carles, R.; Simone, F.

    2014-11-07

    This work shows the application of metal ion-implantation to realize an efficient second-generation TiO{sub 2} photocatalyst. High fluence Fe{sup +} ions were implanted into thin TiO{sub 2} films and subsequently annealed up to 550 °C. The ion-implantation process modified the TiO{sub 2} pure film, locally lowering its band-gap energy from 3.2 eV to 1.6–1.9 eV, making the material sensitive to visible light. The measured optical band-gap of 1.6–1.9 eV was associated with the presence of effective energy levels in the energy band structure of the titanium dioxide, due to implantation-induced defects. An accurate structural characterization was performed by Rutherford backscattering spectrometry, transmission electron microscopy, Raman spectroscopy, X-ray diffraction, and UV/VIS spectroscopy. The synthesized materials revealed a remarkable photocatalytic efficiency in the degradation of organic compounds in water under visible light irradiation, without the help of any thermal treatments. The photocatalytic activity has been correlated with the amount of defects induced by the ion-implantation process, clarifying the operative physical mechanism. These results can be fruitfully applied for environmental applications of TiO{sub 2}.

  7. p-n junction CuO/BiVO₄ heterogeneous nanostructures: synthesis and highly efficient visible-light photocatalytic performance.

    PubMed

    Wang, Wenzhong; Wang, Jun; Wang, Zhizhen; Wei, Xuanzhen; Liu, Li; Ren, Qingshan; Gao, Wenliang; Liang, Yujie; Shi, Honglong

    2014-05-14

    A new strategy via coupling a polyol route with an oxidation process has been developed to successfully synthesize p-n junction CuO/BiVO4 heterogeneous nanostructures. The experimental results reveal that the as-prepared p-n junction CuO/BiVO4 heterogeneous nanostructures exhibit much higher visible-light-driven photocatalytic activity for the degradation of model dye rhodamine B (RhB) than the pure BiVO4 nanocrystals. The photocatalytic degradation rate (C/C0) of the RhB for p-n junction CuO/BiVO4 heterogeneous nanostructures is about two times higher than that of pure BiVO4 nanocrystals. The enhanced photocatalytic efficiency is attributed to a large number of p-n junctions in CuO/BiVO4 heterogeneous nanostructures, which effectively reduces the recombination of electrons and holes by charge transfer from n-type BiVO4 to the attached p-type CuO nanoparticles. This work not only provides an efficient route to enhance the visible-light-driven photocatalytic activity of BiVO4, but also offers a new strategy for fabricating p-n junction heterogeneous nanostructure photocatalysts, which are expected to show considerable potential application in solar-driven wastewater treatment and water splitting. PMID:24643776

  8. Synthesis and characterization of the efficient visible-light-induced photocatalyst AgBr and its photodegradation activity

    NASA Astrophysics Data System (ADS)

    Liu, Ling; Xu, Hui; Li, Huaming; Xu, Yuanguo; Xia, Jiexiang; Yin, Sheng

    2012-04-01

    AgBr photocatalysts were prepared with the 1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br) reactable ionic liquid at different temperatures by one-step hydrothermal method, in which the ionic liquid acted as a precursor and a template to control the size of AgBr crystal. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), the Brunauer-Emmett-Teller (BET) surface area and diffuse reflectance spectroscopy (DRS). Methyl orange (MO) dye was chosen as a model pollutant to investigate the photocatalytic activity and the stability of the samples under visible light irradiation. The results indicated that the AgBr photocatalysts showed high efficiency in the degradation of MO under visible light irradiation. The kinetic property of the reaction followed the first-order reaction model. During the photocatalytic degradation reaction, AgBr was transformed to the Ag0/AgBr composite. However, the photocatalytic efficiency was still high and the photocatalytic activity was stable. The possible photocatalytic mechanism of the photocatalysts was also eventually proposed.

  9. Selective Deposition of Silver Oxide on Single-Domain Ferroelectric Nanoplates and Their Efficient Visible-Light Photoactivity.

    PubMed

    Chen, Fang; Ren, Zhaohui; Gong, Siyu; Li, Xiang; Shen, Ge; Han, Gaorong

    2016-08-16

    In this work, single-crystal and single-domain PbTiO3 nanoplates are employed as substrates to prepare Ag2 O/PbTiO3 composite materials through a photodeposition method. It is revealed that silver oxide nanocrystals with an average size of 63 nm are selectively deposited on the positive polar surface of the ferroelectric substrate. The possible mechanism leading to the formation of silver oxide is that silver ions are first reduced to silver and then oxidized by oxygen generation. The composite shows an efficient photodegradation performance towards rhodamine B (RhB) and methyl orange (MO) under visible-light irradiation. Such highly efficient photoactivity can be attributed to the ferroelectric polarization effect of the substrate, which promotes the separation of photogenerated electrons and holes at the interface. PMID:27430192

  10. Removing organic contaminants with bifunctional iron modified rectorite as efficient adsorbent and visible light photo-Fenton catalyst.

    PubMed

    Zhao, Xiaorong; Zhu, Lihua; Zhang, Yingying; Yan, Jingchun; Lu, Xiaohua; Huang, Yingping; Tang, Heqing

    2012-05-15

    Iron-modified rectorite (FeR) was prepared as both adsorbent and catalyst. The iron modification increased layer-to-layer spacing and surface area of rectorite, leading to much increased adsorption of Rhodamine B (RhB) on rectorite. The maximum adsorption capacity of RhB on FeR reached 101mgg(-1) at pH 4.5, being 11 folds of that on the unmodified one. The iron modification also enabled rectorite to have efficient visible light photocatalytic ability. The apparent rate constant for the degradation of RhB (80μM) at 298K and pH 4.5 in the presence of H(2)O(2) (6.0mM) and FeR (0.4gL(-1)) was evaluated to be 0.0413min(-1) under visible light and 0.122min(-1) under sunlight, respectively. The analysis with electron spin resonance spin-trapping technique supported that the iron modified rectorite effectively catalyzed the decomposition of H(2)O(2) into hydroxyl radicals. On the basis of the characterization and analysis, the new bifunctional material was well clarified as both adsorbent and photocatalyst in the removing of organic pollutants. PMID:22410720

  11. Sonochemical Synthesis of CdS/C3N4 Composites with Efficient Photocatalytic Performance Under Visible Light Irradiation.

    PubMed

    Chai, Bo; Wang, Xing

    2016-02-01

    The CdS/C3N4 composites with efficient photocatalytic performance under visible light irradiation were synthesized by a facile sonochemical route. The as-prepared CdS/C3N4 composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution trans- mission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance absorption spectra (DRS), fourier transform infrared spectroscopy (FTIR) and photoluminescence spectra (PL). The photocatalytic degradation of rhodamine B (RhB) by the CdS/C3N4 composites was explored and optimized, suggesting the optimal amount of CdS in the composites was 50 wt%. The significantly enhanced photocatalytic activity of CdS/C3N4 composites could be attributed to the effectively interfacial transfer of photogenerated charge carriers between CdS and C3N4, which restrained the recombination of electron-hole pairs. PMID:27433724

  12. Efficient Gate-tunable light-emitting device made of defective boron nitride nanotubes: from ultraviolet to the visible

    PubMed Central

    Attaccalite, Claudio; Wirtz, Ludger; Marini, Andrea; Rubio, Angel

    2013-01-01

    Boron nitride is a promising material for nanotechnology applications due to its two-dimensional graphene-like, insulating, and highly-resistant structure. Recently it has received a lot of attention as a substrate to grow and isolate graphene as well as for its intrinsic UV lasing response. Similar to carbon, one-dimensional boron nitride nanotubes (BNNTs) have been theoretically predicted and later synthesised. Here we use first principles simulations to unambiguously demonstrate that i) BN nanotubes inherit the highly efficient UV luminescence of hexagonal BN; ii) the application of an external perpendicular field closes the electronic gap keeping the UV lasing with lower yield; iii) defects in BNNTS are responsible for tunable light emission from the UV to the visible controlled by a transverse electric field (TEF). Our present findings pave the road towards optoelectronic applications of BN-nanotube-based devices that are simple to implement because they do not require any special doping or complex growth. PMID:24060843

  13. Cobalt phosphide nanowires: efficient nanostructures for fluorescence sensing of biomolecules and photocatalytic evolution of dihydrogen from water under visible light.

    PubMed

    Tian, Jingqi; Cheng, Ningyan; Liu, Qian; Xing, Wei; Sun, Xuping

    2015-04-27

    The detection of specific DNA sequences plays an important role in the identification of disease-causing pathogens and genetic diseases, and photochemical water splitting offers a promising avenue to sustainable, environmentally friendly hydrogen production. Cobalt-phosphorus nanowires (CoP NWs) show a high fluorescence quenching ability and different affinity toward single- versus double-stranded DNA. Based on this result, the utilization of CoP NWs as fluorescent DNA nanosensors with a detection limit of 100 pM and a selectivity down to single-base mismatch was demonstrated. The use of a thrombin-specific DNA aptamer also enabled the selective detection of thrombin. The photoinduced electron transfer from the excited dye that labels the oligonucleotide probe to the CoP semiconductor led to efficient fluorescence quenching, and largely enhanced the photocatalytic evolution of hydrogen from water under visible light. PMID:25721096

  14. AgI/Ag{sub 3}PO{sub 4} hybrids with highly efficient visible-light driven photocatalytic activity

    SciTech Connect

    Katsumata, Hideyuki; Hayashi, Takahiro; Taniguchi, Masanao; Suzuki, Tohru; Kaneco, Satoshi

    2015-03-15

    Highlights: • AgI/Ag{sub 3}PO{sub 4} hybrid was prepared via an in situ anion-exchange method. • AgI/Ag{sub 3}PO{sub 4} displays the excellent photocatalytic activity under visible light. • AgI/Ag{sub 3}PO{sub 4} readily transforms to be Ag@AgI/Ag{sub 3}PO{sub 4} system. • h{sup +} and O{sub 2}{sup ·−} play the major role in the AO 7 decolorization over AgI/Ag{sub 3}PO{sub 4}. • The activity enhancement is ascribed to a Z-scheme system composed of Ag{sub 3}PO{sub 4}, Ag and AgI. - Abstract: Highly efficient visible-light-driven AgI/Ag{sub 3}PO{sub 4} hybrid photocatalysts with different mole ratios of AgI were prepared via an in situ anion-exchange method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) technique. Under visible light irradiation (>420 nm), the AgI/Ag{sub 3}PO{sub 4} photocatalysts displayed the higher photocatalytic activity than pure Ag{sub 3}PO{sub 4} and AgI for the decolorization of acid orange 7 (AO 7). Among the hybrid photocatalysts, AgI/Ag{sub 3}PO{sub 4} with 80% of AgI exhibited the highest photocatalytic activity for the decolorization of AO 7. X-ray photoelectron spectroscopy (XPS) results revealed that AgI/Ag{sub 3}PO{sub 4} readily transformed to be Ag@AgI/Ag{sub 3}PO{sub 4} system while the photocatalytic activity of AgI/Ag{sub 3}PO{sub 4} remained after 5 recycling runs. In addition, the quenching effects of different scavengers displayed that the reactive h{sup +} and O{sub 2}{sup ·−} play the major role in the AO 7 decolorization. The photocatalytic activity enhancement of AgI/Ag{sub 3}PO{sub 4} hybrids can be ascribed to the efficient separation of electron–hole pairs through a Z-scheme system composed of Ag{sub 3}PO{sub 4}, Ag and AgI, in which Ag nanoparticles act as the charge separation center.

  15. Silicon-Based Chemical Motors: An Efficient Pump for Triggering and Guiding Fluid Motion Using Visible Light

    PubMed Central

    2015-01-01

    We report a simple yet highly efficient chemical motor that can be controlled with visible light. The motor made from a noble metal and doped silicon acts as a pump, which is driven through a light-activated catalytic reaction process. We show that the actuation is based on electro-osmosis with the electric field generated by chemical reactions at the metal and silicon surfaces, whereas the contribution of diffusio-osmosis to the actuation is negligible. Surprisingly, the pump can be operated using water as fuel. This is possible because of the large ζ-potential of silicon, which makes the electro-osmotic fluid motion sizable even though the electric field generated by the reaction is weak. The electro-hydrodynamic process is greatly amplified with the addition of reactive species, such as hydrogen peroxide, which generates higher electric fields. Another remarkable finding is the tunability of silicon-based pumps. That is, it is possible to control the speed of the fluid with light. We take advantage of this property to manipulate the spatial distribution of colloidal microparticles in the liquid and to pattern colloidal microparticle structures at specific locations on a wafer surface. Silicon-based pumps hold great promise for controlled mass transport in fluids. PMID:26349036

  16. Silicon-Based Chemical Motors: An Efficient Pump for Triggering and Guiding Fluid Motion Using Visible Light.

    PubMed

    Esplandiu, Maria J; Farniya, Ali Afshar; Bachtold, Adrian

    2015-11-24

    We report a simple yet highly efficient chemical motor that can be controlled with visible light. The motor made from a noble metal and doped silicon acts as a pump, which is driven through a light-activated catalytic reaction process. We show that the actuation is based on electro-osmosis with the electric field generated by chemical reactions at the metal and silicon surfaces, whereas the contribution of diffusio-osmosis to the actuation is negligible. Surprisingly, the pump can be operated using water as fuel. This is possible because of the large ζ-potential of silicon, which makes the electro-osmotic fluid motion sizable even though the electric field generated by the reaction is weak. The electro-hydrodynamic process is greatly amplified with the addition of reactive species, such as hydrogen peroxide, which generates higher electric fields. Another remarkable finding is the tunability of silicon-based pumps. That is, it is possible to control the speed of the fluid with light. We take advantage of this property to manipulate the spatial distribution of colloidal microparticles in the liquid and to pattern colloidal microparticle structures at specific locations on a wafer surface. Silicon-based pumps hold great promise for controlled mass transport in fluids. PMID:26349036

  17. The High-efficiency LED Driver for Visible Light Communication Applications

    NASA Astrophysics Data System (ADS)

    Gong, Cihun-Siyong Alex; Lee, Yu-Chen; Lai, Jyun-Liang; Yu, Chueh-Hao; Huang, Li Ren; Yang, Chia-Yen

    2016-08-01

    This paper presents a LED driver for VLC. The main purpose is to solve the low data rate problem used to be in switching type LED driver. The GaN power device is proposed to replace the traditional silicon power device of switching LED driver for the purpose of increasing switching frequency of converter, thereby increasing the bandwidth of data transmission. To achieve high efficiency, the diode-connected GaN power transistor is utilized to replace the traditional ultrafast recovery diode used to be in switching type LED driver. This work has been experimentally evaluated on 350-mA output current. The results demonstrate that it supports the data of PWM dimming level encoded in the PPM scheme for VLC application. The experimental results also show that system’s efficiency of 80.8% can be achieved at 1-Mb/s data rate.

  18. The High-efficiency LED Driver for Visible Light Communication Applications

    PubMed Central

    Gong, Cihun-Siyong Alex; Lee, Yu-Chen; Lai, Jyun-Liang; Yu, Chueh-Hao; Huang, Li Ren; Yang, Chia-Yen

    2016-01-01

    This paper presents a LED driver for VLC. The main purpose is to solve the low data rate problem used to be in switching type LED driver. The GaN power device is proposed to replace the traditional silicon power device of switching LED driver for the purpose of increasing switching frequency of converter, thereby increasing the bandwidth of data transmission. To achieve high efficiency, the diode-connected GaN power transistor is utilized to replace the traditional ultrafast recovery diode used to be in switching type LED driver. This work has been experimentally evaluated on 350-mA output current. The results demonstrate that it supports the data of PWM dimming level encoded in the PPM scheme for VLC application. The experimental results also show that system’s efficiency of 80.8% can be achieved at 1-Mb/s data rate. PMID:27498921

  19. The High-efficiency LED Driver for Visible Light Communication Applications.

    PubMed

    Gong, Cihun-Siyong Alex; Lee, Yu-Chen; Lai, Jyun-Liang; Yu, Chueh-Hao; Huang, Li Ren; Yang, Chia-Yen

    2016-01-01

    This paper presents a LED driver for VLC. The main purpose is to solve the low data rate problem used to be in switching type LED driver. The GaN power device is proposed to replace the traditional silicon power device of switching LED driver for the purpose of increasing switching frequency of converter, thereby increasing the bandwidth of data transmission. To achieve high efficiency, the diode-connected GaN power transistor is utilized to replace the traditional ultrafast recovery diode used to be in switching type LED driver. This work has been experimentally evaluated on 350-mA output current. The results demonstrate that it supports the data of PWM dimming level encoded in the PPM scheme for VLC application. The experimental results also show that system's efficiency of 80.8% can be achieved at 1-Mb/s data rate. PMID:27498921

  20. Facile fabrication of an efficient BiVO4 thin film electrode for water splitting under visible light irradiation.

    PubMed

    Jia, Qingxin; Iwashina, Katsuya; Kudo, Akihiko

    2012-07-17

    An efficient BiVO(4) thin film electrode for overall water splitting was prepared by dipping an F-doped SnO(2) (FTO) substrate electrode in an aqueous nitric acid solution of Bi(NO(3))(3) and NH(4)VO(3), and subsequently calcining it. X-ray diffraction of the BiVO(4) thin film revealed that a photocatalytically active phase of scheelite-monoclinic BiVO(4) was obtained. Scanning electron microscopy images showed that the surface of an FTO substrate was uniformly coated with the BiVO(4) film with 300-400 nm of the thickness. The BiVO(4) thin film electrode gave an excellent anodic photocurrent with 73% of an IPCE at 420 nm at 1.0 V vs. Ag/AgCl. Modification with CoO on the BiVO(4) electrode improved the photoelectrochemical property. A photoelectrochemical cell consisting of the BiVO(4) thin film electrode with and without CoO, and a Pt counter electrode was constructed for water splitting under visible light irradiation and simulated sunlight irradiation. Photocurrent due to water splitting to form H(2) and O(2) was confirmed with applying an external bias smaller than 1.23 V that is a theoretical voltage for electrolysis of water. Water splitting without applying external bias under visible light irradiation was demonstrated using a SrTiO(3)Rh photocathode and the BiVO(4) photoanode. PMID:22699499

  1. Facile fabrication of an efficient BiVO4 thin film electrode for water splitting under visible light irradiation

    PubMed Central

    Jia, Qingxin; Iwashina, Katsuya; Kudo, Akihiko

    2012-01-01

    An efficient BiVO4 thin film electrode for overall water splitting was prepared by dipping an F-doped SnO2 (FTO) substrate electrode in an aqueous nitric acid solution of Bi(NO3)3 and NH4VO3, and subsequently calcining it. X-ray diffraction of the BiVO4 thin film revealed that a photocatalytically active phase of scheelite-monoclinic BiVO4 was obtained. Scanning electron microscopy images showed that the surface of an FTO substrate was uniformly coated with the BiVO4 film with 300–400 nm of the thickness. The BiVO4 thin film electrode gave an excellent anodic photocurrent with 73% of an IPCE at 420 nm at 1.0 V vs. Ag/AgCl. Modification with CoO on the BiVO4 electrode improved the photoelectrochemical property. A photoelectrochemical cell consisting of the BiVO4 thin film electrode with and without CoO, and a Pt counter electrode was constructed for water splitting under visible light irradiation and simulated sunlight irradiation. Photocurrent due to water splitting to form H2 and O2 was confirmed with applying an external bias smaller than 1.23 V that is a theoretical voltage for electrolysis of water. Water splitting without applying external bias under visible light irradiation was demonstrated using a SrTiO3∶Rh photocathode and the BiVO4 photoanode. PMID:22699499

  2. Self-assembled cabbage-like NaInS{sub 2} microstructures with efficient visible light photocatalytic performance

    SciTech Connect

    Gao, Yuanhao Zhai, Xuezhen; Zhang, Yange; Xu, Zhihong; Li, Pinjiang; Zheng, Zhi

    2013-07-15

    Cabbage-like NaInS{sub 2} microstructures have been synthesized by reacting In(NO{sub 3}){sub 3} with the alkaline sulfur aqueous solution of NaOH in a simple hydrothermal process without any shape-directing surfactants. The cabbage-like NaInS{sub 2} architectures are monodispersed in large quantities. The cabbage-like morphologies depend strongly on the different ratios of S powder to NaOH, the reaction temperature and reaction time. The possible growth mechanism for the formation of cabbage-like NaInS{sub 2} architectures is discussed. The cabbage-like NaInS{sub 2} architectures exhibit the superiority of photocatalytic performance for the photodegradation of RhB irradiation under visible light irradiation. It is believed that the photocatalytic superiority of the cabbage-like NaInS{sub 2} architectures is mainly due to their special surface areas and inner interconnected structural features. - Graphical abstract: Cabbage-like NaInS{sub 2} microstructures were facilely synthesized via simple hydrothermal reaction. The cabbage-like NaInS{sub 2} architectures exhibit the superiority of photocatalytic performance for the photodegradation of RhB irradiation under visible light irradiation. - Highlights: • Cabbage-like NaInS{sub 2} microstructures were facilely synthesized via a hydrothermal reaction. • Influencing parameters on the NaInS{sub 2} morphologies have been discussed in detail. • The cabbage-like NaInS{sub 2} architectures hold efficient photocatalytic performance. • The photocatalytic superiority is mainly due to their special structural features.

  3. Measuring scintillation light using Visible Light

    NASA Astrophysics Data System (ADS)

    Chavarria, Alvaro

    2006-11-01

    A new search for the neutron electric dipole moment (EDM) using ultra cold neutrons proposes an improvement on the neutron EDM by two orders of magnitude over the current limit (to 10-28 e*cm). Detection of scintillation light in superfluid ^4He is at the heart of this experiment. One possible scheme to detect this light is to use wavelength-shifting fibers in the superfluid ^4He to collect the scintillation light and transport it out of the measuring cell. The fiber terminates in a visible light photon counter (VLPC). VLPCs are doped, silicon based, solid state photomultipliers with high quantum efficiency (up to 80%) and high gain ( 40000 electrons per converted photon). Moreover, they are insensitive to magnetic fields and operate at temperatures of 6.5K. A test setup has been assembled at Duke University using acrylic cells wrapped in wavelength-shifting fibers that terminate on VLPCs. This setup is being used to evaluate the feasibility of this light detection scheme. The results obtained in multiple experiments done over the past summer (2006) and the current status of the project will be presented at the conference.Reference:A New Search for the Neutron Electric Dipole Moment, funding pre-proposal by the EDM collaboration; R. Golub and S. Lamoreaux, Phys. Rep. 237, 1 (1994).

  4. Reduced Graphene Oxide-Immobilized Tris(bipyridine)ruthenium(II) Complex for Efficient Visible-Light-Driven Reductive Dehalogenation Reaction.

    PubMed

    Li, Xiaoyan; Hao, Zhongkai; Zhang, Fang; Li, Hexing

    2016-05-18

    A sodium benzenesulfonate (PhSO3Na)-functionalized reduced graphene oxide was synthesized via a two-step aryl diazonium coupling and subsequent NaCl ion-exchange procedure, which was used as a support to immobilize tris(bipyridine)ruthenium(II) complex (Ru(bpy)3Cl2) by coordination reaction. This elaborated Ru(bpy)3-rGO catalyst exhibited excellent catalytic efficiency in visible-light-driven reductive dehalogenation reactions under mild conditions, even for ary chloride. Meanwhile, it showed the comparable reactivity with the corresponding homogeneous Ru(bpy)3Cl2 catalyst. This high catalytic performance could be attributed to the unique two-dimensional sheet-like structure of Ru(bpy)3-rGO, which efficiently diminished diffusion resistance of the reactants. Meanwhile, the nonconjugated PhSO3Na-linkage between Ru(II) complex and the support and the very low electrical conductivity of the catalyst inhibited energy/electron transfer from Ru(II) complex to rGO support, resulting in the decreased support-induced quenching effect. Furthermore, it could be easily recycled at least five times without significant loss of catalytic reactivity. PMID:27104739

  5. Vertically aligned InGaN nanowires with engineered axial In composition for highly efficient visible light emission

    PubMed Central

    Ebaid, Mohamed; Kang, Jin-Ho; Yoo, Yang-Seok; Lim, Seung-Hyuk; Cho, Yong-Hoon; Ryu, Sang-Wan

    2015-01-01

    We report on the fabrication of novel InGaN nanowires (NWs) with improved crystalline quality and high radiative efficiency for applications as nanoscale visible light emitters. Pristine InGaN NWs grown under a uniform In/Ga molar flow ratio (UIF) exhibited multi-peak white-like emission and a high density of dislocation-like defects. A phase separation and broad emission with non-uniform luminescent clusters were also observed for a single UIF NW investigated by spatially resolved cathodoluminescence. Hence, we proposed a simple approach based on engineering the axial In content by increasing the In/Ga molar flow ratio at the end of NW growth. This new approach yielded samples with a high luminescence intensity, a narrow emission spectrum, and enhanced crystalline quality. Using time-resolved photoluminescence spectroscopy, the UIF NWs exhibited a long radiative recombination time (τr) and low internal quantum efficiency (IQE) due to strong exciton localization and carrier trapping in defect states. In contrast, NWs with engineered In content demonstrated three times higher IQE and a much shorter τr due to mitigated In fluctuation and improved crystal quality. PMID:26585509

  6. Efficient Visible Light Nitrogen Fixation with BiOBr Nanosheets of Oxygen Vacancies on the Exposed {001} Facets.

    PubMed

    Li, Hao; Shang, Jian; Ai, Zhihui; Zhang, Lizhi

    2015-05-20

    Even though the well-established Haber-Bosch process has been the major artificial way to "fertilize" the earth, its energy-intensive nature has been motivating people to learn from nitrogenase, which can fix atmospheric N2 to NH3 in vivo under mild conditions with its precisely arranged proteins. Here we demonstrate that efficient fixation of N2 to NH3 can proceed under room temperature and atmospheric pressure in water using visible light illuminated BiOBr nanosheets of oxygen vacancies in the absence of any organic scavengers and precious-metal cocatalysts. The designed catalytic oxygen vacancies of BiOBr nanosheets on the exposed {001} facets, with the availability of localized electrons for π-back-donation, have the ability to activate the adsorbed N2, which can thus be efficiently reduced to NH3 by the interfacial electrons transferred from the excited BiOBr nanosheets. This study might open up a new vista to fix atmospheric N2 to NH3 through the less energy-demanding photochemical process. PMID:25874655

  7. Synthesis of black ultrathin BiOCl nanosheets for efficient photocatalytic H2 production under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Ye, Liqun; Jin, Xiaoli; Leng, Yumin; Su, Yurong; Xie, Haiquan; Liu, Chao

    2015-10-01

    The thickness of 2D BiOCl nanosheets along [001] direction control the internal electric fields intensity. In order to enhance the photocatalytic properties of BiOCl, decreasing the thickness is the best choice. In this paper, black ultrathin BiOCl nanosheet (BU-BiOCl) with expanded spacing of the (001) crystal plane and oxygen vacancy was synthesized in high viscosity and alcohol group concentration glycerol system. It was characterized by X-ray diffraction patterns (XRD), X-ray photoelectron spectroscopy (XPS), X-ray photoelectron scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM), electron spin resonance (ESR), UV-vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. The experimental characterization and theoretical calculation results also indicated that expanded facets spacing and oxygen vacancy of as-synthesized BU-BiOCl enhanced separation efficiency of photoinduced carriers and photon absorption efficiency. Therefore, BU-BiOCl showed higher activity than bulk BiOCl for H2 production under visible light irradiation.

  8. Effect of post-synthesis acid activation of TiO2 nanofilms on the photocatalytic efficiency under visible light

    NASA Astrophysics Data System (ADS)

    Stambolova, I.; Blaskov, V.; Shipochka, M.; Eliyas, A.; Vassilev, S.

    2014-12-01

    Nanosized TiO2 films were deposited by spray pyrolysis and thermally treated at 400oC. Then the films were dipped in 1M aqueous solution of HCl. The activated samples were divided into two parts - one part was dried (A) and another was annealed (AT) in air. The photocatalytic degradation of Reactive Black (RB5) textile dye under visible light was tested. The following instrumental methods: X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied for the phase and surface characterization of obtained samples. According to Raman and XRD analyses all films are anatase. The XRD showed that activated films are better crystallized than non activated TiO2 film. The presence of chlorine at 200.3 eV was registered for acid activated samples by X-Ray photoelectron spectroscopy. The acidic activated films exhibited higher rate of dye photodegradation than that of the reference TiO2 sample. The photocatalytic efficiency decreases in the order A > AT> non activated TiO2 films. The degradation rate constant for acid activated films is two times higher than those of the reference film. The hydroxyl content in TiO2 acidic activated films is greater than that of the non- activated films, which results in significant increase in the photocatalytic activity. In addition, the presence of chlorine may also lead to enhancement in efficiency.

  9. In-situ synthesis of highly efficient visible light driven stannic oxide/graphitic carbon nitride heterostructured photocatalysts.

    PubMed

    Tao, Binglin; Yan, Zifeng

    2016-10-15

    Novel and efficient visible-light-driven stannic oxide/graphitic carbon nitride heterostructured photocatalysts are prepared via a simple in-situ solvothermal method. Characterization results demonstrate that there exist strong interactions between SnO2 nanoparticles and g-C3N4 matrix, which indicates the formation of SnO2/g-C3N4 heterojunction. The as-synthesized SnO2/g-C3N4 composite exhibits improved efficiency for photodegradation of rhodamine B in aqueous solutions, with an apparent rate constant 6.5 times higher than that of commercial TiO2 (Degussa P25). The enhanced photocatalytic activity is attributed to synergistic effect between SnO2 and g-C3N4, resulting in effective interfacial charge transfer and prolonged charge-hole separation time. Moreover, SnO2/g-C3N4 composite photocatalysts possess excellent durability and stability after 6 recycling runs, and a possible photocatalytic mechanism is also proposed. This research highlights the promising applications of two dimensional g-C3N4 based composite photocatalysts in the field of waste water disposal and environmental remediation. PMID:27421114

  10. Energy-level matching of Fe(III) ions grafted at surface and doped in bulk for efficient visible-light photocatalysts.

    PubMed

    Liu, Min; Qiu, Xiaoqing; Miyauchi, Masahiro; Hashimoto, Kazuhito

    2013-07-10

    Photocatalytic reaction rate (R) is determined by the multiplication of light absorption capability (α) and quantum efficiency (QE); however, these two parameters generally have trade-off relations. Thus, increasing α without decreasing QE remains a challenging issue for developing efficient photocatalysts with high R. Herein, using Fe(III) ions grafted Fe(III) doped TiO2 as a model system, we present a novel method for developing visible-light photocatalysts with efficient R, utilizing the concept of energy level matching between surface-grafted Fe(III) ions as co-catalysts and bulk-doped Fe(III) ions as visible-light absorbers. Photogenerated electrons in the doped Fe(III) states under visible-light efficiently transfer to the surface grafted Fe(III) ions co-catalysts, as the doped Fe(III) ions in bulk produced energy levels below the conduction band of TiO2, which match well with the potential of Fe(3+)/Fe(2+) redox couple in the surface grafted Fe(III) ions. Electrons in the surface grafted Fe(III) ions efficiently cause multielectron reduction of adsorbed oxygen molecules to achieve high QE value. Consequently, the present Fe(III)-FexTi1-xO2 nanocomposites exhibited the highest visible-light R among the previously reported photocatalysts for decomposition of gaseous organic compounds. The high R can proceed even under commercial white-light emission diode irradiation and is very stable for long-term use, making it practically useful. Further, this efficient method could be applied in other wide-band gap semiconductors, including ZnO or SrTiO3, and may be potentially applicable for other photocatalysis systems, such as water splitting, CO2 reduction, NOx removal, and dye decomposition. Thus, this method represents a strategic approach to develop new visible-light active photocatalysts for practical uses. PMID:23768256

  11. Efficient visible light-driven water oxidation catalyzed by an all-inorganic copper-containing polyoxometalate.

    PubMed

    Yu, Li; Du, Xiaoqiang; Ding, Yong; Chen, Hongli; Zhou, Panpan

    2015-12-21

    [Cu5(OH)4(H2O)2(A-α-SiW9O33)2](10-) (1) was tested as the first copper-containing polyoxometalate catalyst for O2 production via visible light-driven water oxidation. Multiple experiments confirm that 1 is an active and dominant catalyst during water oxidation. PMID:26468511

  12. Facile fabrication of highly efficient g-C₃N₄/BiFeO₃ nanocomposites with enhanced visible light photocatalytic activities.

    PubMed

    Wang, Xingfu; Mao, Weiwei; Zhang, Jian; Han, Yumin; Quan, Chuye; Zhang, Qiaoxia; Yang, Tao; Yang, Jianping; Li, Xing'ao; Huang, Wei

    2015-06-15

    Graphitic carbon nitride/bismuth ferrite (g-C3N4/BiFeO3) nanocomposites with various g-C3N4 contents have been synthesized by a simple method. After the deposition-precipitation process, the novel BiFeO3 spindle-like nanoparticles with the size of ∼100 nm were homogeneously decorated on the surfaces of the C3N4 nanosheets. A possible deposition growth mechanism is proposed on the basis of experimental results. The as-prepared g-C3N4/BiFeO3 composites exhibit high efficiency for the degradation of methyl orange (MO) under visible light irradiation, which can be mainly attributed to the synergic effect between g-C3N4 and BiFeO3. The ability to tune surface and interfacial characteristics for the optimization of photophysical properties suggests that the deposition growth process may enable formation of hybrids suitable for a range of photocatalytic applications based on g-C3N4. PMID:25706200

  13. Highly efficient photocatalytic H₂ evolution from water using visible light and structure-controlled graphitic carbon nitride.

    PubMed

    Martin, David James; Qiu, Kaipei; Shevlin, Stephen Andrew; Handoko, Albertus Denny; Chen, Xiaowei; Guo, Zhengxiao; Tang, Junwang

    2014-08-25

    The major challenge of photocatalytic water splitting, the prototypical reaction for the direct production of hydrogen by using solar energy, is to develop low-cost yet highly efficient and stable semiconductor photocatalysts. Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g-C3N4) from a low-cost precursor, urea, is reported. The g-C3N4 exhibits an extraordinary hydrogen-evolution rate (ca. 20,000 μmol h(-1) g(-1) under full arc), which leads to a high turnover number (TON) of over 641 after 6 h. The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5% under visible light, which is nearly an order of magnitude higher than that observed for any other existing g-C3N4 photocatalysts. Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen-evolution rate is significantly enhanced. PMID:25045013

  14. Development of high efficient visible light-driven N, S-codoped TiO2 nanowires photocatalysts

    NASA Astrophysics Data System (ADS)

    Zhang, Yanlin; Liu, Peihong; Wu, Honghai

    2015-02-01

    One-dimensional (1D) nanowire material (especially nonmetal doped 1D nanowires) synthesized by a facile way is of great significance and greatly desired as it has higher charge carrier mobility and lower carrier recombination rate. N, S-codoped TiO2 nanowires were synthesized using titanium sulfate as a precursor and isopropanol as a protective capping agent by a hydrothermal route. The obtained doped nanowires were characterized by XRD, SEM, HRTEM, SAED, XPS, BET and UV-vis absorption spectrum. The incorporation of N and S into TiO2 NWs can lead to the expansion of its lattice and remarkably lower its electron-transfer resistance. Photocatalytic activity measurement showed that the N, S-codoped TiO2 nanowires with high quantum efficiency revealed the best photocatalytic performance for atrazine degradation under visible light irradiation compared to N, S-codoped TiO2 nanoparticles and S-doped TiO2 nanowires, which was attributed to (i) the synergistic effect of N and S doping in narrowing the band gap, separating electron-hole pairs and increasing the photoinduced electrons, and (ii) extending the anatase-to-rutile transformation temperature above 600 °C.

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

    PubMed

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

    2014-08-01

    A photosensitized BiOCl catalyst was found to be effective for photocatalytic water purification and air remediation under visible light irradiation (λ > 420 nm). Prepared by a solvothermal method, the BiOCl crystals possessed a 3D hierarchical spherical structure with the highly active facets exposed. When sensitized by Rhodamine B (RhB), the photocatalyst system was more active than N-doped TiO2 for breaking down 4-chlorophenol (4-CP, 200 ppm) and nitric monoxide (NO, 500 ppb). The high activity could be attributed to the hierarchical structure (supplying feasible reaction tunnels for adsorption and transition of reactants or products) and the efficient exposure of the {001} facets. The former provides an enriched oxygen atom density that promotes adsorption of cationic dye RhB, and creates an oxygen vacancy state. The HO˙ and ˙O2(-) radicals produced from the injected electrons from the excited dye molecule (RhB*) into the conduction band of BiOCl were responsible for the excellent photocatalytic performance of the RhB-BiOCl system. PMID:24934740

  16. Highly Efficient Photocatalytic H2 Evolution from Water using Visible Light and Structure-Controlled Graphitic Carbon Nitride**

    PubMed Central

    Martin, David James; Qiu, Kaipei; Shevlin, Stephen Andrew; Handoko, Albertus Denny; Chen, Xiaowei; Guo, Zhengxiao; Tang, Junwang

    2014-01-01

    The major challenge of photocatalytic water splitting, the prototypical reaction for the direct production of hydrogen by using solar energy, is to develop low-cost yet highly efficient and stable semiconductor photocatalysts. Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g-C3N4) from a low-cost precursor, urea, is reported. The g-C3N4 exhibits an extraordinary hydrogen-evolution rate (ca. 20 000 μmol h−1 g−1 under full arc), which leads to a high turnover number (TON) of over 641 after 6 h. The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5 % under visible light, which is nearly an order of magnitude higher than that observed for any other existing g-C3N4 photocatalysts. Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen-evolution rate is significantly enhanced. PMID:25045013

  17. Highly efficient visible light photocatalytic reduction of CO2 to hydrocarbon fuels by Cu-nanoparticle decorated graphene oxide.

    PubMed

    Shown, Indrajit; Hsu, Hsin-Cheng; Chang, Yu-Chung; Lin, Chang-Hui; Roy, Pradip Kumar; Ganguly, Abhijit; Wang, Chen-Hao; Chang, Jan-Kai; Wu, Chih-I; Chen, Li-Chyong; Chen, Kuei-Hsien

    2014-11-12

    The production of renewable solar fuel through CO2 photoreduction, namely artificial photosynthesis, has gained tremendous attention in recent times due to the limited availability of fossil-fuel resources and global climate change caused by rising anthropogenic CO2 in the atmosphere. In this study, graphene oxide (GO) decorated with copper nanoparticles (Cu-NPs), hereafter referred to as Cu/GO, has been used to enhance photocatalytic CO2 reduction under visible-light. A rapid one-pot microwave process was used to prepare the Cu/GO hybrids with various Cu contents. The attributes of metallic copper nanoparticles (∼4-5 nm in size) in the GO hybrid are shown to significantly enhance the photocatalytic activity of GO, primarily through the suppression of electron-hole pair recombination, further reduction of GO's bandgap, and modification of its work function. X-ray photoemission spectroscopy studies indicate a charge transfer from GO to Cu. A strong interaction is observed between the metal content of the Cu/GO hybrids and the rates of formation and selectivity of the products. A factor of greater than 60 times enhancement in CO2 to fuel catalytic efficiency has been demonstrated using Cu/GO-2 (10 wt % Cu) compared with that using pristine GO. PMID:25354234

  18. Visible light-induced intramolecular dearomative cyclization of α-bromo-N-benzyl-alkylamides: efficient construction of 2-azaspiro[4.5]decanes.

    PubMed

    Hu, Bei; Li, Yuyuan; Dong, Wuheng; Ren, Kai; Xie, Xiaomin; Wan, Jun; Zhang, Zhaoguo

    2016-03-01

    An efficient intramolecular dearomative cyclization via visible light-induced photoredox catalysis allows for a highly regioselective dearomative cyclization of α-bromo-N-benzyl-alkylamides to construct 2-azaspiro[4.5]decanes in the presence of an iridium catalyst. PMID:26865333

  19. Synthesis of Mn-intercalated layered titanate by exfoliation-flocculation approach and its efficient photocatalytic activity under visible-light

    SciTech Connect

    Fu, Jie; Tian, Yanlong; Chang, Binbin; Li, Gengnan; Xi, Fengna; Dong, Xiaoping

    2012-12-15

    A novel Mn-intercalated layered titanate as highly active photocatalyst in visible-light region has been synthesized via a convenient and efficient exfoliation-flocculation approach with divalent Mn ions and monolayer titanate nanosheets. The 0.91 nm interlayer spacing of obtained photocatalyst is in accordance with the sum of the thickness of titanate nanosheet and the diameter of Mn ions. The yellow photocatalyst shows a spectral response in visible-light region and the calculated band gap is 2.59 eV. The photocatalytic performance of this material was evaluated by degradation and mineralization of an aqueous dye methylene blue under visible-light irradiation, and an enhanced photocatalytic activity in comparison with protonated titanate as well as the P25 TiO{sub 2} and N-doped TiO{sub 2} was obtained. Additionally, the layered structure is retained, no dye ions intercalating occurs during the photocatalysis process, and a {approx}90% photocatalytic activity can be remained after reusing 3 cycles. - Graphical abstract: Mn-intercalated layered titanate as a novel and efficient visible-light harvesting photocatalyst was synthesized via a convenient and efficient exfoliation-flocculation approach in a mild condition. Highlights: Black-Right-Pointing-Pointer Mn-intercalated titanate has been prepared by exfoliation-flocculation approach. Black-Right-Pointing-Pointer The as-prepared catalyst shows spectral response in the visible-light region. Black-Right-Pointing-Pointer Heat treatment at certain temperature enables formation of Mn-doped TiO{sub 2}. Black-Right-Pointing-Pointer Dye can be degradated effectively by the catalyst under visible light irradiation.

  20. Energy efficiency for the removal of non-polar pollutants during ultraviolet irradiation, visible light photocatalysis and ozonation of a wastewater effluent.

    PubMed

    Santiago-Morales, Javier; Gómez, María José; Herrera-López, Sonia; Fernández-Alba, Amadeo R; García-Calvo, Eloy; Rosal, Roberto

    2013-10-01

    This study aims to assess the removal of a set of non-polar pollutants in biologically treated wastewater using ozonation, ultraviolet (UV 254 nm low pressure mercury lamp) and visible light (Xe-arc lamp) irradiation as well as visible light photocatalysis using Ce-doped TiO2. The compounds tracked include UV filters, synthetic musks, herbicides, insecticides, antiseptics and polyaromatic hydrocarbons. Raw wastewater and treated samples were analyzed using stir-bar sorptive extraction coupled with comprehensive two-dimensional gas chromatography (SBSE-CG × GC-TOF-MS). Ozone treatment could remove most pollutants with a global efficiency of over 95% for 209 μM ozone dosage. UV irradiation reduced the total concentration of the sixteen pollutants tested by an average of 63% with high removal of the sunscreen 2-ethylhexyl trans-4-methoxycinnamate (EHMC), the synthetic musk 7-acetyl-1,1,3,4,4,6-hexamethyltetrahydronaphthalene (tonalide, AHTN) and several herbicides. Visible light Ce-TiO2 photocatalysis reached ~70% overall removal with particularly high efficiency for synthetic musks. In terms of power usage efficiency expressed as nmol kJ(-1), the results showed that ozonation was by far the most efficient process, ten-fold over Xe/Ce-TiO2 visible light photocatalysis, the latter being in turn considerably more efficient than UV irradiation. In all cases the efficiency decreased along the treatments due to the lower reaction rate at lower pollutant concentration. The use of photocatalysis greatly improved the efficiency of visible light irradiation. The collector area per order decreased from 9.14 ± 5.11 m(2) m(-3) order(-1) for visible light irradiation to 0.16 ± 0.03 m(2) m(-3) order(-1) for Ce-TiO2 photocatalysis. The toxicity of treated wastewater was assessed using the green alga Pseudokirchneriella subcapitata. Ozonation reduced the toxicity of treated wastewater, while UV irradiation and visible light photocatalysis limited by 20-25% the algal growth due to

  1. Graphitic C3 N4 -Sensitized TiO2 Nanotube Layers: A Visible-Light Activated Efficient Metal-Free Antimicrobial Platform.

    PubMed

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

    2016-03-14

    Herein, we use a facile procedure to graft a thin graphitic C3N4 (g-C3N4) layer on aligned TiO2 nanotube arrays (TiNT) by a one-step chemical vapor deposition (CVD) approach. This provides a platform to enhance the visible-light response of TiO2 nanotubes for antimicrobial applications. The formed g-C3N4/TiNT binary nanocomposite exhibits excellent bactericidal efficiency against Escherichia coli (E. coli) as a visible-light activated antibacterial coating, without the use of additional bactericides. PMID:26789421

  2. Template synthesis of Ag/AgCl microrods and their efficient visible light-driven photocatalytic performance

    SciTech Connect

    Chen, Hua; Xiao, Liang; Huang, Jianhua

    2014-09-15

    Highlights: • Preparation ofAg/AgCl microrods by reaction of Ag{sub 2}WO{sub 4} microrods with NaCl solution. • Generation of metallic Ag is induced by the ambient light in the synthesis process. • Ag/AgCl shows excellent visible light-driven photodegradation of organic dyes. - Abstract: Ag/AgCl microrods, aggregated by nanoparticles with a diameter ranging from 100 nm to 2 μm, were prepared by an ion-exchange reaction at 80 °C between Ag{sub 2}WO{sub 4} template and NaCl solution. The existence of metallic Ag species was confirmed by XRD, DRS and XPS measurements. Ag/AgCl microrods showed excellent photocatalytic activity for the degradation of rhodamine B and methylene blue under visible light irradiation. The degradation rate constants of rhodamine B and methylene blue are 0.176 and 0.114 min{sup −1}, respectively. The cycling photodegradation experiments suggest that Ag/AgCl microds could be employed as stable plasmonic photocatalysts for the degradation of organic dyes under visible light irradiation.

  3. A compact and efficient hyper coherent light source of visible violet laser diode based on Pound-Drever-Hall technique

    NASA Astrophysics Data System (ADS)

    Sasaki, Wakao; Yashiro, Hideyuki; Miura, Yukio; Mizutani, Kouki; Nakajima, Jun

    2007-09-01

    In the present work, we have developed an efficient and well stablized hyper coherent diode laser light source as compact as even portable using commercially available visible 400 nm band laser diodes. The attained coherence of the present system can always be controlled at the best condition indifferent to changes in its settled environmental conditions by applying Pound-Drever-Hall technique in which the frequency of a 160mW type 405nm GaN violet laser diode is locked to a reference Fabry-Perot cavity by negative electrical feedback for the injection current of the laser diode based on FM sideband technique. In addition to this frequency stabilization system, we have also realized a stability evaluation system that can measure the Allan variance of the frequency fluctuations of our frequency stabilized laser source in real-time basis by using simple devices of a portable computer and a digital signal processing unit. As a result, we have accomplished a compact and efficient hyper coherent laser system which can always perform its optimum conditions even if the environmental conditions around the laser are to be dynamically changed when used in a field basis. The attained values of power spectral density (PSD) of FM noise calculated from the error signals of our system under controlled condition were better by about 1~2 orders than typical values of free-running conditions in the fourier frequency domain from 100Hz to 300kHz. The best achieved value of PSD was about 2.56×10 7 [Hz2/Hz] in the fourier frequency domain from 100Hz to 1kHz, while as for the Allan variance as another measure of frequency stability, the achieved value of the minimum square root of Allan variance was 3.46×10 -11 in a 400nm type violet laser diode at integration time of 10 ms, which has been well comparable to the hyper coherent condition for the laser diode light sources.

  4. Highly efficient visible light-induced O₂ generation by self-assembled nanohybrids of inorganic nanosheets and polyoxometalate nanoclusters.

    PubMed

    Gunjakar, Jayavant L; Kim, Tae Woo; Kim, In Young; Lee, Jang Mee; Hwang, Seong-Ju

    2013-01-01

    Unusually high photocatalytic activity of visible light-induced O₂ generation can be achieved by electrostatically-derived self-assembly between exfoliated Zn-Cr-LDH 2D nanosheets and POM 0D nanoclusters (W₇O₂₄⁶⁻ and V₁₀O₂₈⁶⁻) acting as an electron acceptor. This self-assembly can provide a high flexibility in the control of the chemical composition and pore structure of the resulting LDH-based nanohybrids. The hybridization with POM nanoclusters remarkably enhances the photocatalytic activity of the pristine Zn-Cr-LDH, which is attributable to the formation of porous structure and depression of charge recombination. Of prime interest is that the excellent photocatalytic activity of the as-prepared Zn-Cr-LDH-POM nanohybrid for visible light-induced O₂ generation can be further enhanced by calcination at 200 °C, leading to the very high apparent quantum yield of ∼75.2% at 420 nm. The present findings clearly demonstrate that the self-assembly of LDH-POM is fairly powerful in synthesizing novel LDH-based porous nanohybrid photocatalyst for visible light-induced O₂ generation. PMID:23801108

  5. Highly Efficient Visible Light-Induced O2 Generation by Self-Assembled Nanohybrids of Inorganic Nanosheets and Polyoxometalate Nanoclusters

    PubMed Central

    Gunjakar, Jayavant L.; Kim, Tae Woo; Kim, In Young; Lee, Jang Mee; Hwang, Seong-Ju

    2013-01-01

    Unusually high photocatalytic activity of visible light-induced O2 generation can be achieved by electrostatically-derived self-assembly between exfoliated Zn-Cr-LDH 2D nanosheets and POM 0D nanoclusters (W7O246− and V10O286−) acting as an electron acceptor. This self-assembly can provide a high flexibility in the control of the chemical composition and pore structure of the resulting LDH-based nanohybrids. The hybridization with POM nanoclusters remarkably enhances the photocatalytic activity of the pristine Zn-Cr-LDH, which is attributable to the formation of porous structure and depression of charge recombination. Of prime interest is that the excellent photocatalytic activity of the as-prepared Zn-Cr-LDH-POM nanohybrid for visible light-induced O2 generation can be further enhanced by calcination at 200 °C, leading to the very high apparent quantum yield of ∼75.2% at 420 nm. The present findings clearly demonstrate that the self-assembly of LDH–POM is fairly powerful in synthesizing novel LDH-based porous nanohybrid photocatalyst for visible light-induced O2 generation. PMID:23801108

  6. The efficient photocatalytic degradation of methyl tert-butyl ether under Pd/ZnO and visible light irradiation.

    PubMed

    Seddigi, Zaki S; Ahmed, Saleh A; Bumajdad, Ali; Danish, Ekram Y; Shawky, Ahmed M; Gondal, Mohammed A; Soylak, Mustafa

    2015-01-01

    Methyl tert-butyl ether is a commonly used fuel oxygenate that is present in gasoline. It was introduced to eliminate the use of leaded gasoline and to improve the octane quality because it aids in the complete combustion of fuel by supplying oxygen during the combustion process. Over the past decade, the use of MTBE has increased tremendously worldwide. For obvious reasons relating to accidental spillage, MTBE started to appear as an environmental and human health threat because of its nonbiodegradable nature and carcinogenic potential, respectively. In this work, MTBE was degraded with the help of an advanced oxidation process through the use of zinc oxide as a photocatalyst in the presence of visible light. A mixture of 200 mg of zinc oxide in 350 mL of 50 ppm MTBE aqueous solution was irradiated with visible light for a given time. The complete degradation of MTBE was recorded, and approximately 99% photocatalytic degradation of 100 ppm MTBE solution was observed. Additionally, the photoactivity of 1% Pd-doped ZnO was tested under similar conditions to understand the effect of Pd doping on ZnO. Our results obtained under visible light irradiation are very promising, and they could be further explored for the degradation of several nondegradable environmental pollutants. PMID:25400159

  7. Copper(II) imidazolate frameworks as highly efficient photocatalysts for reduction of CO2 into methanol under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Li, Jingtian; Luo, Deliang; Yang, Chengju; He, Shiman; Chen, Shangchao; Lin, Jiawei; Zhu, Li; Li, Xin

    2013-07-01

    Three copper(II) imidazolate frameworks were synthesized by a hydrothermal (or precipitation) reaction. The catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectra (FTIR), thermogravimetry (TG). Meanwhile, the photocatalytic activities of the samples for reduction of CO2 into methanol and degradation of methylene blue (MB) under visible light irradiation were also investigated. The results show that the as-prepared samples exhibit better photocatalytic activities for the reduction of carbon dioxide into methanol with water and degradation of MB under visible light irradiation. The orthorhombic copper(II) imidazolate frameworks with a band gap of 2.49 eV and green (G) color has the best photocatalytic activity for reduction of CO2 into methanol, 1712.7 μmol/g over 5 h, which is about three times as large as that of monoclinic copper(II) imidazolate frameworks with a band gap 2.70 eV and blue (J) color. The degradation kinetics of MB over three photocatalysts fitted well to the apparent first-order rate equation and the apparent rate constants for the degradation of MB over G, J and P (with pink color) are 0.0038, 0.0013 and 0.0016 min-1, respectively. The synergistic effects of smallest band gap and orthorhombic crystal phase structure are the critical factors for the better photocatalytic activities of G. Moreover, three frameworks can also be stable up to 250 °C. The investigation of Cu-based zeolitic imidazolate frameworks maybe provide a design strategy for a new class of photocatalysts applied in degradation of contaminations, reduction of CO2, and even water splitting into hydrogen and oxygen under visible light.

  8. Efficient photocatalytic reduction of aqueous Cr(VI) over flower-like SnIn4S8 microspheres under visible light illumination.

    PubMed

    Wang, Lin; Li, Xinyong; Teng, Wei; Zhao, Qidong; Shi, Yong; Yue, Renliang; Chen, Yunfa

    2013-01-15

    Photocatalytic reduction of aqueous Cr(VI) was successfully achieved on nanostructured SnIn(4)S(8). The SnIn(4)S(8) particles with flower-like nanostructure were synthesized via a facile solvothermal method. UV-vis diffuse reflectance spectra (DRS) indicated that the SnIn(4)S(8) particles had strong absorption in visible region and the band gap was estimated to be from 2.27 to 2.35 eV. The photocatalytic reduction of aqueous Cr(VI) by flower-like SnIn(4)S(8) was evaluated under visible light (λ>400 nm) irradiation. The polyvinyl pyrrolidone (PVP) assisted SnIn(4)S(8) sample exhibits excellent removal efficiency of Cr(VI) (~97%) and good photocatalytic stability. The predominant photocatalytic activity is due to its large surface area, strong absorption in visible-light region and excellent charge separation characteristics. PMID:23177248

  9. Dye-sensitized InGaN nanowire arrays for efficient hydrogen production under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Kibria, M. G.; Chowdhury, F. A.; Trudeau, M. L.; Guo, H.; Mi, Z.

    2015-07-01

    Solar water splitting is a key sustainable energy technology for clean, storable and renewable source of energy in the future. Here we report that Merocyanine-540 dye-sensitized and Rh nanoparticle-decorated molecular beam epitaxially grown In0.25Ga0.75N nanowire arrays have produced hydrogen from ethylenediaminetetraacetic acid (EDTA) and acetonitrile mixture solution under green, yellow and orange solar spectra (up to 610 nm) for the first time. An apparent quantum efficiency of 0.3% is demonstrated for wavelengths 525-600 nm, providing a viable approach to harness deep-visible and near-infrared solar energy for efficient and stable water splitting.

  10. High efficiency incandescent lighting

    SciTech Connect

    Bermel, Peter; Ilic, Ognjen; Chan, Walker R.; Musabeyoglu, Ahmet; Cukierman, Aviv Ruben; Harradon, Michael Robert; Celanovic, Ivan; Soljacic, Marin

    2014-09-02

    Incandescent lighting structure. The structure includes a thermal emitter that can, but does not have to, include a first photonic crystal on its surface to tailor thermal emission coupled to, in a high-view-factor geometry, a second photonic filter selected to reflect infrared radiation back to the emitter while passing visible light. This structure is highly efficient as compared to standard incandescent light bulbs.

  11. Efficiently Visible-Light Driven Photoelectrocatalytic Oxidation of As(III) at Low Positive Biasing Using Pt/TiO2 Nanotube Electrode.

    PubMed

    Qin, Yanyan; Li, Yilian; Tian, Zhen; Wu, Yangling; Cui, Yanping

    2016-12-01

    A constant current deposition method was selected to load highly dispersed Pt nanoparticles on TiO2 nanotubes in this paper, to extend the excited spectrum range of TiO2-based photocatalysts to visible light. The morphology, elemental composition, and light absorption capability of as-obtained Pt/TiO2 nanotubes electrodes were characterized by FE-SEM, energy dispersive spectrometer (EDS), X-ray photoelectron spectrometer (XPS), and UV-vis spectrometer. The photocatalytic and photoelectrocatalytic oxidation of As(III) using a Pt/TiO2 nanotube arrays electrode under visible light (λ > 420 nm) irradiation were investigated in a divided anode/cathode electrolytic tank. Compared with pure TiO2 which had no As(III) oxidation capacity under visible light, Pt/TiO2 nanotubes exhibited excellent visible-light photocatalytic performance toward As(III), even at dark condition. In anodic cell, As(III) could be oxidized with high efficiency by photoelectrochemical process with only 1.2 V positive biasing. Experimental results showed that photoelectrocatalytic oxidation process of As(III) could be well described by pseudo-first-order kinetic model. Rate constants depended on initial concentration of As(III), applied bias potential and solution pH. At the same time, it was interesting to find that in cathode cell, As(III) was also continuously oxidized to As(V). Furthermore, high-arsenic groundwater sample (25 m underground) with 0.32 mg/L As(III) and 0.35 mg/L As(V), which was collected from Daying Village, Datong basin, Northern China, could totally transform to As(V) after 200 min under visible light in this system. PMID:26787051

  12. Efficiently Visible-Light Driven Photoelectrocatalytic Oxidation of As(III) at Low Positive Biasing Using Pt/TiO2 Nanotube Electrode

    NASA Astrophysics Data System (ADS)

    Qin, Yanyan; Li, Yilian; Tian, Zhen; Wu, Yangling; Cui, Yanping

    2016-01-01

    A constant current deposition method was selected to load highly dispersed Pt nanoparticles on TiO2 nanotubes in this paper, to extend the excited spectrum range of TiO2-based photocatalysts to visible light. The morphology, elemental composition, and light absorption capability of as-obtained Pt/TiO2 nanotubes electrodes were characterized by FE-SEM, energy dispersive spectrometer (EDS), X-ray photoelectron spectrometer (XPS), and UV-vis spectrometer. The photocatalytic and photoelectrocatalytic oxidation of As(III) using a Pt/TiO2 nanotube arrays electrode under visible light ( λ > 420 nm) irradiation were investigated in a divided anode/cathode electrolytic tank. Compared with pure TiO2 which had no As(III) oxidation capacity under visible light, Pt/TiO2 nanotubes exhibited excellent visible-light photocatalytic performance toward As(III), even at dark condition. In anodic cell, As(III) could be oxidized with high efficiency by photoelectrochemical process with only 1.2 V positive biasing. Experimental results showed that photoelectrocatalytic oxidation process of As(III) could be well described by pseudo-first-order kinetic model. Rate constants depended on initial concentration of As(III), applied bias potential and solution pH. At the same time, it was interesting to find that in cathode cell, As(III) was also continuously oxidized to As(V). Furthermore, high-arsenic groundwater sample (25 m underground) with 0.32 mg/L As(III) and 0.35 mg/L As(V), which was collected from Daying Village, Datong basin, Northern China, could totally transform to As(V) after 200 min under visible light in this system.

  13. Achieving significantly enhanced visible-light photocatalytic efficiency using a polyelectrolyte: the composites of exfoliated titania nanosheets, graphene, and poly(diallyl-dimethyl-ammonium chloride)

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; An, Qi; Luan, Xinglong; Huang, Hongwei; Li, Xiaowei; Meng, Zilin; Tong, Wangshu; Chen, Xiaodong; Chu, Paul K.; Zhang, Yihe

    2015-08-01

    A high-performance visible-light-active photocatalyst is prepared using the polyelectrolyte/exfoliated titania nanosheet/graphene oxide (GO) precursor by flocculation followed by calcination. The polyelectrolyte poly(diallyl-dimethyl-ammonium chloride) serves not only as an effective binder to precipitate GO and titania nanosheets, but also boosts the overall performance of the catalyst significantly. Unlike most titania nanosheet-based catalysts reported in the literature, the composite absorbs light in the UV-Vis-NIR range. Its decomposition rate of methylene blue is 98% under visible light. This novel strategy of using a polymer to enhance the catalytic performance of titania nanosheet-based catalysts affords immense potential in designing and fabricating next-generation photocatalysts with high efficiency.A high-performance visible-light-active photocatalyst is prepared using the polyelectrolyte/exfoliated titania nanosheet/graphene oxide (GO) precursor by flocculation followed by calcination. The polyelectrolyte poly(diallyl-dimethyl-ammonium chloride) serves not only as an effective binder to precipitate GO and titania nanosheets, but also boosts the overall performance of the catalyst significantly. Unlike most titania nanosheet-based catalysts reported in the literature, the composite absorbs light in the UV-Vis-NIR range. Its decomposition rate of methylene blue is 98% under visible light. This novel strategy of using a polymer to enhance the catalytic performance of titania nanosheet-based catalysts affords immense potential in designing and fabricating next-generation photocatalysts with high efficiency. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03256c

  14. Highly efficient photocatalysis of p-type Cu{sub 2}ZnSnS{sub 4} under visible-light illumination

    SciTech Connect

    Hou, Xian; Li, Yan Yan, Jian-Jun; Wang, Cheng-Wei

    2014-12-15

    Highlights: • Kesterite CZTS nanocrystal powder was synthesized by one-pot method. • First successful use CZTS nanocrystal powder as photocatalyst. • CZTS shows an efficient photocatalysis under visible light irradiation. • CZTS photocatalyst having excellent stability. - Abstract: Cu{sub 2}ZnSnS{sub 4}, as a very promising p-type semiconductor material, has been extensively used in the study of solar cells owing to its suitable band gap (1.1–1.5 eV), large absorption coefficient of 10{sup 4} cm{sup −1} in the visible spectrum, good photo stability, nontoxicity and relative abundance of the component elements. In this paper, we have successfully synthesized p-type kesterite Cu{sub 2}ZnSnS{sub 4} nanocrystal powder by facile one-pot method, and made our first successful attempt to use Cu{sub 2}ZnSnS{sub 4} nanocrystal powder as a photocatalyst to degradation methyl orange under visible-light irradiation. The exciting results show that in the visible light region, Cu{sub 2}ZnSnS{sub 4} nanocrystal powder possesses an excellent photocatalytic performance of K = 0.0317 min{sup −1}, nearly about 6 times of well known commercial P25 titania powder performance under the same conditions, which suggests that the p-type kesterite Cu{sub 2}ZnSnS{sub 4} nanocrystal would be a promising candidate of photocatalyst.

  15. Efficient Banknote Recognition Based on Selection of Discriminative Regions with One-Dimensional Visible-Light Line Sensor

    PubMed Central

    Pham, Tuyen Danh; Park, Young Ho; Kwon, Seung Yong; Park, Kang Ryoung; Jeong, Dae Sik; Yoon, Sungsoo

    2016-01-01

    Banknote papers are automatically recognized and classified in various machines, such as vending machines, automatic teller machines (ATM), and banknote-counting machines. Previous studies on automatic classification of banknotes have been based on the optical characteristics of banknote papers. On each banknote image, there are regions more distinguishable than others in terms of banknote types, sides, and directions. However, there has been little previous research on banknote recognition that has addressed the selection of distinguishable areas. To overcome this problem, we propose a method for recognizing banknotes by selecting more discriminative regions based on similarity mapping, using images captured by a one-dimensional visible light line sensor. Experimental results with various types of banknote databases show that our proposed method outperforms previous methods. PMID:26959022

  16. Self-assembled cabbage-like NaInS2 microstructures with efficient visible light photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Gao, Yuanhao; Zhai, Xuezhen; Zhang, Yange; Xu, Zhihong; Li, Pinjiang; Zheng, Zhi

    2013-07-01

    Cabbage-like NaInS2 microstructures have been synthesized by reacting In(NO3)3 with the alkaline sulfur aqueous solution of NaOH in a simple hydrothermal process without any shape-directing surfactants. The cabbage-like NaInS2 architectures are monodispersed in large quantities. The cabbage-like morphologies depend strongly on the different ratios of S powder to NaOH, the reaction temperature and reaction time. The possible growth mechanism for the formation of cabbage-like NaInS2 architectures is discussed. The cabbage-like NaInS2 architectures exhibit the superiority of photocatalytic performance for the photodegradation of RhB irradiation under visible light irradiation. It is believed that the photocatalytic superiority of the cabbage-like NaInS2 architectures is mainly due to their special surface areas and inner interconnected structural features.

  17. Efficient photocatalytic degradation of ibuprofen in aqueous solution using novel visible-light responsive graphene quantum dot/AgVO3 nanoribbons.

    PubMed

    Lei, Zhen-Dong; Wang, Jia-Jun; Wang, Liang; Yang, Xiong-Yu; Xu, Gang; Tang, Liang

    2016-07-15

    Single crystalline, non-toxicity, and long-term stability graphene quantum dots (GQDs) were modified onto the AgVO3 nanoribbons by a facile hydrothermal and sintering technique which constructs a unique heterojunction photocatalyst. Characterization results indicate that GQDs are well dispersed on the surface of AgVO3 nanoribbons and GQD/AgVO3 heterojunctions are formed, which can greatly promote the separation efficiency of photogenerated electron-hole pairs under visible light irradiation. By taking advantage of this feature, the GQD/AgVO3 heterojunctions exhibit considerable improvement on the photocatalytic activities for the degradation of ibuprofen (IBP) under visible light irradiation as compared to pure AgVO3. The photocatalytic activity of GQD/AgVO3 heterojunctions is relevant with GQD ratio and the optimal activity is obtained at 3wt% with the highest separation efficiency of photogenerated electron-hole pairs. Integrating the physicochemical and photocatalytic properties, the factors controlling the photocatalytic activity of GQD/AgVO3 heterojunctions are discussed in detail. Moreover, potential photocatalytic degradation mechanisms of IBP via GQD/AgVO3 heterojunctions under visible light are proposed. PMID:27046507

  18. Plasmonic silver quantum dots coupled with hierarchical TiO2 nanotube arrays photoelectrodes for efficient visible-light photoelectrocatalytic hydrogen evolution

    PubMed Central

    Lian, Zichao; Wang, Wenchao; Xiao, Shuning; Li, Xin; Cui, Yingying; Zhang, Dieqing; Li, Guisheng; Li, Hexing

    2015-01-01

    A plasmonic Ag/TiO2 photocatalytic composite was designed by selecting Ag quantum dots (Ag QDs) to act as a surface plasmon resonance (SPR) photosensitizer for driving the visible-light driven photoelectrocatalytic hydrogen evolution. Vertically oriented hierarchical TiO2 nanotube arrays (H-TiO2-NTAs) with macroporous structure were prepared through a two-step method based on electrochemical anodization. Subsequently, Ag QDs, with tunable size (1.3-21.0 nm), could be uniformly deposited on the H-TiO2 NTAs by current pulsing approach. The unique structure of the as-obtained photoelectrodes greatly improved the photoelectric conversion efficiency. The as-obtained Ag/H-TiO2-NTAs exhibited strong visible-light absorption capability, high photocurrent density, and enhanced photoelectrocatalytic (PEC) activity toward photoelectrocatalytic hydrogen evolution under visible-light irradiation (λ > 420 nm). The enhancement in the photoelectric conversion efficiency and activity was ascribed to the synergistic effects of silver and the unique hierarchical structures of TiO2 nanotube arrays, strong SPR effect, and anti-shielding effect of ultrafine Ag QDs. PMID:26067850

  19. Plasmonic silver quantum dots coupled with hierarchical TiO2 nanotube arrays photoelectrodes for efficient visible-light photoelectrocatalytic hydrogen evolution.

    PubMed

    Lian, Zichao; Wang, Wenchao; Xiao, Shuning; Li, Xin; Cui, Yingying; Zhang, Dieqing; Li, Guisheng; Li, Hexing

    2015-01-01

    A plasmonic Ag/TiO2 photocatalytic composite was designed by selecting Ag quantum dots (Ag QDs) to act as a surface plasmon resonance (SPR) photosensitizer for driving the visible-light driven photoelectrocatalytic hydrogen evolution. Vertically oriented hierarchical TiO2 nanotube arrays (H-TiO2-NTAs) with macroporous structure were prepared through a two-step method based on electrochemical anodization. Subsequently, Ag QDs, with tunable size (1.3-21.0 nm), could be uniformly deposited on the H-TiO2 NTAs by current pulsing approach. The unique structure of the as-obtained photoelectrodes greatly improved the photoelectric conversion efficiency. The as-obtained Ag/H-TiO2-NTAs exhibited strong visible-light absorption capability, high photocurrent density, and enhanced photoelectrocatalytic (PEC) activity toward photoelectrocatalytic hydrogen evolution under visible-light irradiation (λ>420 nm). The enhancement in the photoelectric conversion efficiency and activity was ascribed to the synergistic effects of silver and the unique hierarchical structures of TiO2 nanotube arrays, strong SPR effect, and anti-shielding effect of ultrafine Ag QDs. PMID:26067850

  20. Preparation and efficient visible light-induced photocatalytic activity of m-BiVO4 with different morphologies

    NASA Astrophysics Data System (ADS)

    Lu, Yanjie; Shang, Huishan; Shi, Fengjuan; Chao, Cong; Zhang, Xiang; Zhang, Bing

    2015-10-01

    The monoclinic scheelite BiVO4 crystals with peanut-like, oval, twin-quadrangle and twin-four-pointed star morphologies were synthesized via a facile one step hydrothermal method by using sodium citrate as the chelating agent. The X-ray diffraction and scanning electron microscopy were employed to elucidate the structures and mophologies of the as-prepared BiVO4 samples. The results showed that the formation of m-BiVO4 with different morphologies relied on the pH value of the precursor solution. The band gaps values (Eg) of all the BiVO4 samples were around 2.37-2.45 eV according to the UV-vis diffuse reflectance spectrum, which indicated that samples could strongly absorb in the visible light region. The photocatalytic activities of BiVO4 crystals were evaluated by degradation of MB in aqueous solution under artificial solar-light. The BiVO4 samples obtained at different pH values showed different photocatalytic activities during the sunlight-driven photodegradation of methylene blue (MB). The sample with peanut-like-shape prepared at pH=1 exhibited the highest activity, and the photocatalytic conversion could reach above 90% after 3 h of irradiation. The result suggested that m-BiVO4 with peanut-like-shape could be used as an effective photocatalyst in practical application for organic pollutants degradation.

  1. Ultrasonic-assisted one-pot preparation of ZnO/Ag3VO4 nanocomposites for efficiently degradation of organic pollutants under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Kiantazh, Fariba; Habibi-Yangjeh, Aziz

    2015-11-01

    We report a facile ultrasonic-assisted one-pot method for preparation of ZnO/Ag3VO4 nanocomposites with different mole fractions of silver vanadate. The preparation method has considerable merits such as short preparation time, large-scale, and one-pot strategy. The resultant samples were fairly characterized by means of XRD, EDX, SEM, TEM, UV-vis DRS, FT-IR, and PL techniques. Visible-light activity of the resultant samples was investigated by degradation of rhodamine B (RhB), methylene blue (MB), and methyl orange (MO). Among the prepared nanocomposites, the ZnO/Ag3VO4 nanocomposite with 0.073 mole fraction of Ag3VO4 exhibited the best activity and excessive amount of Ag3VO4 resulted in decrease of the activity. Photocatalytic activity of this nanocomposite under visible-light irradiation is about 21, 56, and 2.8-fold higher than that of the ZnO sample in degradation of RhB, MB, and MO, respectively. The highly enhanced activity of the nanocomposite was attributed to greater generation of electron-hole pairs, due to photosensitizing role of Ag3VO4 under visible-light irradiation, and efficiently separation of the photogenerated electron-hole pairs, due to formation of n-n heterojunction between the counterparts. Furthermore, it was revealed that the photocatalytic activity largely depends on ultrasonic irradiation time, calcination temperature, and scavengers of the reactive species.

  2. Highly Efficient F, Cu doped TiO2 anti-bacterial visible light active photocatalytic coatings to combat hospital-acquired infections

    PubMed Central

    Leyland, Nigel S.; Podporska-Carroll, Joanna; Browne, John; Hinder, Steven J.; Quilty, Brid; Pillai, Suresh C.

    2016-01-01

    Bacterial infections are a major threat to the health of patients in healthcare facilities including hospitals. One of the major causes of patient morbidity is infection with Staphylococcus aureus. One of the the most dominant nosocomial bacteria, Methicillin Resistant Staphylococcus aureus (MRSA) have been reported to survive on hospital surfaces (e.g. privacy window glasses) for up to 5 months. None of the current anti-bacterial technology is efficient in eliminating Staphylococcus aureus. A novel transparent, immobilised and superhydrophilic coating of titanium dioxide, co-doped with fluorine and copper has been prepared on float glass substrates. Antibacterial activity has demonstrated (by using Staphylococcus aureus), resulting from a combination of visible light activated (VLA) photocatalysis and copper ion toxicity. Co-doping with copper and fluorine has been shown to improve the performance of the coating, relative to a purely fluorine-doped VLA photocatalyst. Reductions in bacterial population of log10 = 4.2 under visible light irradiation and log10 = 1.8 in darkness have been achieved, compared with log10 = 1.8 under visible light irradiation and no activity, for a purely fluorine-doped titania. Generation of reactive oxygen species from the photocatalytic coatings is the major factor that significantly reduces the bacterial growth on the glass surfaces. PMID:27098010

  3. Highly Efficient F, Cu doped TiO2 anti-bacterial visible light active photocatalytic coatings to combat hospital-acquired infections

    NASA Astrophysics Data System (ADS)

    Leyland, Nigel S.; Podporska-Carroll, Joanna; Browne, John; Hinder, Steven J.; Quilty, Brid; Pillai, Suresh C.

    2016-04-01

    Bacterial infections are a major threat to the health of patients in healthcare facilities including hospitals. One of the major causes of patient morbidity is infection with Staphylococcus aureus. One of the the most dominant nosocomial bacteria, Methicillin Resistant Staphylococcus aureus (MRSA) have been reported to survive on hospital surfaces (e.g. privacy window glasses) for up to 5 months. None of the current anti-bacterial technology is efficient in eliminating Staphylococcus aureus. A novel transparent, immobilised and superhydrophilic coating of titanium dioxide, co-doped with fluorine and copper has been prepared on float glass substrates. Antibacterial activity has demonstrated (by using Staphylococcus aureus), resulting from a combination of visible light activated (VLA) photocatalysis and copper ion toxicity. Co-doping with copper and fluorine has been shown to improve the performance of the coating, relative to a purely fluorine-doped VLA photocatalyst. Reductions in bacterial population of log10 = 4.2 under visible light irradiation and log10 = 1.8 in darkness have been achieved, compared with log10 = 1.8 under visible light irradiation and no activity, for a purely fluorine-doped titania. Generation of reactive oxygen species from the photocatalytic coatings is the major factor that significantly reduces the bacterial growth on the glass surfaces.

  4. Highly Efficient F, Cu doped TiO2 anti-bacterial visible light active photocatalytic coatings to combat hospital-acquired infections.

    PubMed

    Leyland, Nigel S; Podporska-Carroll, Joanna; Browne, John; Hinder, Steven J; Quilty, Brid; Pillai, Suresh C

    2016-01-01

    Bacterial infections are a major threat to the health of patients in healthcare facilities including hospitals. One of the major causes of patient morbidity is infection with Staphylococcus aureus. One of the the most dominant nosocomial bacteria, Methicillin Resistant Staphylococcus aureus (MRSA) have been reported to survive on hospital surfaces (e.g. privacy window glasses) for up to 5 months. None of the current anti-bacterial technology is efficient in eliminating Staphylococcus aureus. A novel transparent, immobilised and superhydrophilic coating of titanium dioxide, co-doped with fluorine and copper has been prepared on float glass substrates. Antibacterial activity has demonstrated (by using Staphylococcus aureus), resulting from a combination of visible light activated (VLA) photocatalysis and copper ion toxicity. Co-doping with copper and fluorine has been shown to improve the performance of the coating, relative to a purely fluorine-doped VLA photocatalyst. Reductions in bacterial population of log10 = 4.2 under visible light irradiation and log10 = 1.8 in darkness have been achieved, compared with log10 = 1.8 under visible light irradiation and no activity, for a purely fluorine-doped titania. Generation of reactive oxygen species from the photocatalytic coatings is the major factor that significantly reduces the bacterial growth on the glass surfaces. PMID:27098010

  5. Highly efficient hydroxyapatite/TiO2 composites covered by silver halides as E. coli disinfectant under visible light and dark media.

    PubMed

    Azimzadehirani, Maryam; Elahifard, MohammadReza; Haghighi, Saeed; Gholami, MohammadReza

    2013-10-01

    TiO2-based photocatalysts are seen as the most common agents for the photodegradation of bacteria. In this study, AgCl/TiO2, hydroxyapatite(Hp)/AgCl/TiO2, AgI/TiO2, and Hp/AgI/TiO2 were prepared by the deposition-precipitation method on P25 TiO2 nanoparticles and were characterized by XRD, SEM, FT-IR, EDX and BET methods. The prepared composites showed high efficiency for the inactivation of Escherichia coli (E. coli) bacteria under visible light and in dark media with different catalyst amounts of 12 and 24 mg, respectively. In less than 30 min, AgI/TiO2, prepared by the combination of cationic surfactant and PVPI2, disinfected 1 × 10(7) colony-forming units of E. coli completely. However, AgCl/TiO2 was not stable under the same conditions. Hp was added to AgCl/TiO2 and AgI/TiO2 to extend the antibacterial effect to dark media. Hp/AgCl/TiO2 showed desirable disinfection capabilities under visible light irradiations that function in less than 30 min. During the time interval when the inactivation was complete, the photocatalytic activity of Hp/AgCl/TiO2 under visible light was maintained effectively without the destruction of AgCl. Hp/AgCl/TiO2 and Hp/AgI/TiO2 were found to prevent bacteria from growing during 3 h in the dark. The antibacterial properties of Hp composites in dark environments are mainly due to the strong linkage between Hp and the cell wall which limits the nourishment of bacteria, while under visible light, in addition to the photocatalytic process, the sense-shoot phenomena and the adsorption effects can be accepted. PMID:23824359

  6. Visible light broadband perfect absorbers

    NASA Astrophysics Data System (ADS)

    Jia, X. L.; Meng, Q. X.; Yuan, C. X.; Zhou, Z. X.; Wang, X. O.

    2016-03-01

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

  7. Rapid sonochemical synthesis of irregular nanolaminar-like Bi2WO6 as efficient visible-light-active photocatalysts.

    PubMed

    Zhang, Feng-Jun; Xie, Fa-Zhi; Liu, Jin; Zhao, Wei; Zhang, Kan

    2013-01-01

    Irregular Bi(2)WO(6) nanolaminars have been successfully synthesized via a rapid sonochemical approach using bismuth nitrate and tungstic acid as precursors in an aqueous solution. The characteristics of them were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N(2) adsorption, pore value, PL spectroscopy and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). These irregular nanolaminars are of geometric shapes of orthorhombic Bi(2)WO(6) with their basal plane being (001). They possess high crystallinity, lager surface area and pore value, which means fewer traps and stronger photocatalytic activity. The growth mechanism of such special nanolaminar was related to the sonochemical synthesis route, which played a key role in the formation of Bi(2)WO(6) nanolaminar. Simultaneously, it was found that the formation of Bi(2)WO(6) nanolaminar is a time dependent process. The Bi(2)WO(6) nanolaminar has higher photocatalytic activity than bulk Bi(2)WO(6) nanoparticle obtained by refluxing method for rhodamine B (Rh.B) degradation under visible light irradiation (λ>400 nm). PMID:22925548

  8. Band Gap Tuning of h-MoO3 Nanocrystals for Efficient Visible Light Photocatalytic Activity Against Methylene Blue Dye.

    PubMed

    Chithambararaj, A; Winston, B; Sanjini, N S; Velmathi, S; Bose, A Chandra

    2015-07-01

    The photocatalytic degradation of methylene blue (MB) dye in aqueous solution was investigated using hexagonal molybdenum oxide (h-MoO3) nanocrystals under visible light irradiation. Chemical precipitation method was utilized to synthesize h-MoO3 and control over the crystal size, shape and distribution were characterized by using HNO3 and HCl as precipitating reagents. The photocatalysts were examined through X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDX) for structural, functional, surface morphology and elemental analysis, respectively. The XRD results revealed that the samples were in single phase hexagonal crystal structure. XRD peak broadening analysis was used for crystallite size and strain estimation. The particles were anisotropic in nature and showed one dimensional (1-D) rod structure with hexagonal cross section. Further, the crystal phase stability, optical absorption and emission properties were studied by thermo gravimetric analysis (TGA), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) measurements, respectively. The photocatalytic results demonstrated that the photocatalytic activity of h-MoO3 synthesized using HCl was improved, in comparison to that of HNO3 utilized h-MoO3 sample. PMID:26373056

  9. Syntheses of asymmetric zinc phthalocyanines as sensitizer of Pt-loaded graphitic carbon nitride for efficient visible/near-IR-light-driven H2 production.

    PubMed

    Yu, Lijuan; Zhang, Xiaohu; Zhuang, Chuansheng; Lin, Li; Li, Renjie; Peng, Tianyou

    2014-03-01

    Zinc phthalocyanine (ZnPc) derivatives with asymmetric (Zn-tri-PcNc-2) or symmetric (Zn-tetrad-Nc) structure, which possess wide spectral response in the visible/near-IR light region, are synthesized and utilized as a sensitizer of graphitic carbon nitride (g-C3N4) with 0.5 wt% Pt-loading for photocatalytic H2 production. The experimental results indicate that Zn-tri-PcNc-2 exhibits much better photosensitization on g-C3N4 than Zn-tetrad-Nc under visible/near-IR light although Zn-tetrad-Nc possesses wider and stronger optical absorption property than Zn-tri-PcNc-2. Zn-tri-PcNc-2-Pt/g-C3N4 exhibits an average H2 production rate of 132 μmol h(-1), which is much better than that (26.1 μmol h(-1)) of Zn-tetrad-Nc-Pt/g-C3N4 under visible-light (λ ≥ 500 nm) irradiation. Moreover, Zn-tri-PcNc-2-Pt/g-C3N4 also shows much higher apparent quantum yield (AQY) than Zn-tetrad-Nc-Pt/g-C3N4 under red/near-IR light irradiation. Especially, Zn-tri-PcNc-2-Pt/g-C3N4 exhibits impressively higher AQY (1.07%) than that (0.22%) of the Zn-tetrad-Nc-Pt/g-C3N4 under 700 nm monochromatic light irradiation. The much better photoactivity of Zn-tri-PcNc-2-Pt/g-C3N4 than Zn-tetrad-Nc-Pt/g-C3N4 is caused by the asymmetric structure of Zn-tri-PcNc-2, which can result in the electronic orbital directionality of its excited state, much faster photogenerated electron transfer to g-C3N4, and higher red/near-IR light utilization efficiency as compared to Zn-tetrad-Nc-Pt/g-C3N4. The present results provide an important insight into the effects of molecular structure and optical absorption property of phthalocyanine derivatives on the photoactivity of the dye-sensitized semiconductor, and also guide us to further improve the solar energy conversion efficiency by optimizing the molecular structure and effectively utilizing the visible/near-IR light of sunlight. PMID:24448755

  10. TiO2 Fibers Supported β-FeOOH Nanostructures as Efficient Visible Light Photocatalyst and Room Temperature Sensor

    PubMed Central

    Zhu, Ting; Li Ong, Wei; Zhu, Liangliang; Wei Ho, Ghim

    2015-01-01

    Hierarchical heterostructures of beta-iron oxyhydroxide (β-FeOOH) nanostructures on electrospun TiO2 nanofibers were synthesized by a facile hydrothermal method. This synthesis method proves to be versatile to tailoring of β-FeOOH structural design that cuts across zero-dimensional particles (TF-P), one-dimensional needles (TF-N) to two-dimensional flakes (TF-F). In addition, synthesizing such oxyhyroxide nanostructures presents the advantage of exhibiting similar functional performances to its oxides counterpart however, without the need to undergo any annealing step which leads to undesirable structural collapse or sintering. The as-prepared hierarchical heterostructures possess high surface area for dye adsorptivity, efficient charge separation and visible photocatalytic activity. Also, for the first time, hydrogen gas sensing has been demonstrated on β-FeOOH nanostructures at room temperature. The reported hierarchical heterostructures of β-FeOOH on TiO2 nanofibers afford multiple functions of photocatalysis and sensing which are highly promising for environment monitoring and clean up applications. PMID:26030002

  11. Cadmium sulfide/graphitic carbon nitride heterostructure nanowire loading with a nickel hydroxide cocatalyst for highly efficient photocatalytic hydrogen production in water under visible light.

    PubMed

    Yan, Zhiping; Sun, Zijun; Liu, Xiang; Jia, Hongxing; Du, Pingwu

    2016-02-28

    Photocatalytic hydrogen production from water in a noble-metal-free system has attracted much attention in recent years. Herein we report on the use of core/shell cadmium sulfide/graphitic carbon nitride (CdS/g-C3N4) heterojunction nanorods modified by nickel hydroxide (Ni(OH)2) as a highly efficient photocatalyst for visible light-driven hydrogen production from water. Due to efficient separation of the photoexcited charge carriers in the CdS/g-C3N4 core/shell nanorods and the synergistic effect of Ni(OH)2, the optimal hydrogen evolution rate over Ni(OH)2-CdS/g-C3N4 is 115.18 μmol h(-1) mg(-1) under visible light irradiation (λ > 420 nm), which is ∼26 times higher than the CdS/g-C3N4 nanorod composite without Ni(OH)2 and ∼7 times better than the 0.5 wt% Pt-CdS/g-C3N4 nanorod composite. The apparent quantum efficiency is ∼16.7% at an excitation of 450 nm. During photocatalysis, no degradation of Ni(OH)2 was observed based on the XPS data, indicating that it is a robust cocatalyst. Moreover, the present photocatalyst showed excellent photocatalytic stability for hydrogen production and the turnover number (TON) reached ∼24,600 over 90 hours. PMID:26862011

  12. Bright visible light emission from graphene

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  13. Bright visible light emission from graphene.

    PubMed

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

    2015-08-01

    Graphene and related two-dimensional materials are promising candidates for atomically thin, flexible and transparent optoelectronics. In particular, the strong light-matter interaction in graphene has allowed for the development of state-of-the-art photodetectors, optical modulators and plasmonic devices. In addition, electrically biased graphene on SiO2 substrates can be used as a low-efficiency emitter in the mid-infrared range. However, emission in the visible range has remained elusive. Here, we report the observation of bright visible light emission from electrically biased suspended graphene devices. In these devices, heat transport is greatly reduced. Hot electrons (∼2,800 K) therefore become spatially localized at the centre of the graphene layer, resulting in a 1,000-fold enhancement in thermal radiation efficiency. Moreover, strong optical interference between the suspended graphene and substrate can be used to tune the emission spectrum. We also demonstrate the scalability of this technique by realizing arrays of chemical-vapour-deposited graphene light emitters. These results pave the way towards the realization of commercially viable large-scale, atomically thin, flexible and transparent light emitters and displays with low operation voltage and graphene-based on-chip ultrafast optical communications. PMID:26076467

  14. A Crystalline Copper(II) Coordination Polymer for the Efficient Visible-Light-Driven Generation of Hydrogen.

    PubMed

    Dong, Xi-Yan; Zhang, Mei; Pei, Ru-Bo; Wang, Qian; Wei, Dong-Hui; Zang, Shuang-Quan; Fan, Yao-Ting; Mak, Thomas C W

    2016-02-01

    A crystalline coordination polymer (CP) photocatalyst (Cu-RSH) which combines redox-active copper centers with photoactive rhodamine-derived ligands remains stable in acid and basic solutions from pH 2 to 14, and efficiently catalyzes dihydrogen evolution at a maximum rate of 7.88 mmol g(-1)  h(-1) in the absence of a mediator and a co-catalyst. Cyclic voltammetry, control experiments, and DFT calculations established that copper nodes with open coordination sites and favorable redox potentials, aided by spatially ordered stacking of rhodamine-based linkers, account for the high catalytic performance of Cu-RSH. Emission quenching, time-resolved fluorescence decay, and transient photocurrent experiments disclosed the charge separation and transfer process in the catalytic system. The present study demonstrates the potential of crystalline copper CPs for the practical utilization of light. PMID:26709609

  15. Efficient photocatalytic degradation of organic pollutants by magnetically recoverable nitrogen-doped TiO2 nanocomposite photocatalysts under visible light irradiation.

    PubMed

    Hamzezadeh-Nakhjavani, Sahar; Tavakoli, Omid; Akhlaghi, Seyed Parham; Salehi, Zeinab; Esmailnejad-Ahranjani, Parvaneh; Arpanaei, Ayyoob

    2015-12-01

    Preparation of novel nanocomposite particles (NCPs) with high visible-light-driven photocatalytic activity and possessing recovery potential after advanced oxidation process (AOP) is much desired. In this study, pure anatase phase titania (TiO2) nanoparticles (NPs) as well as three types of NCPs including nitrogen-doped titania (TiO2-N), titania-coated magnetic silica (Fe3O4 cluster@SiO2@TiO2 (FST)), and a novel magnetically recoverable TiO2 nanocomposite photocatalyst containing nitrogen element (Fe3O4 cluster@SiO2@TiO2-N (FST-N)) were successfully synthesized via a sol-gel process. The photocatalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM) with an energy-dispersive X-ray (EDX) spectroscopy analysis, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and vibrating sample magnetometer (VSM). The photocatalytic activity of as-prepared samples was further investigated and compared with each other by degradation of phenol, as a model for the organic pollutants, in deionized (DI) water under visible light irradiation. The TiO2-N (55 ± 1.5%) and FST-N (46 ± 1.5%) samples exhibited efficient photocatalytic activity in terms of phenol degradation under visible light irradiation, while undoped samples were almost inactive under same operating conditions. Moreover, the effects of key operational parameters, the optimum sample calcination temperature, and reusability of FST-N NCPs were evaluated. Under optimum conditions (calcination temperature of 400 °C and near-neutral reaction medium), the obtained results revealed efficient degradation of phenol for FST-N NCPs under visible light irradiation (46 ± 1.5%), high yield magnetic separation and efficient reusability of FST-N NCPs (88.88% of its initial value) over 10 times reuse. PMID:26206125

  16. In-situ generated H₂O₂ induced efficient visible light photo-electrochemical catalytic oxidation of PCP-Na with TiO₂.

    PubMed

    Liu, Wei; Liu, Huichao; Ai, Zhihui

    2015-05-15

    In this study, we developed a novel photo-electrochemical catalytic oxidation wastewater treatment system by interacting the cathodic in-situ generated H₂O₂ with TiO₂ suspension to form interfacial ≡ Ti(IV)OOH species, which endowed the PEC system with superior efficiency for degrading sodium pentachlorophenate (PCP-Na) under visible light irradiation at neutral pH. The apparent PCP-Na degradation rate constant of the PEC system was more than 10 times that of the electrochemical oxidation counterpart. In the PEC system, the interfacial ≡ Ti(IV)OOH species injected electrons to the conduction band of TiO₂ to initiate the activation of O₂ and the in-situ generated H₂O₂ adsorbed on the surface of TiO₂, lead to producing reactive oxygen species of superoxide anions and hydroxyl radicals, which were responsible for the dechlorination and mineralization of PCP-Na during the PEC process, respectively. The dosage of TiO₂ catalyst and the current intensity applied on PCP-Na degradation were optimized. This study develops a high efficient PEC oxidation system for wastewater treatment and provides new insight into the role of cathodic in-situ generated H₂O₂ on PEC oxidation of PCP-Na with TiO₂ under visible light irradiation. PMID:25698570

  17. New class of photocatalytic materials and a novel principle for efficient water splitting under infrared and visible light: MgB2 as unexpected example.

    PubMed

    Kravets, V G; Grigorenko, A N

    2015-11-30

    Water splitting is unanimously recognized as environment friendly, potentially low cost and renewable energy solution based on the future hydrogen economy. Especially appealing is photocatalytic water splitting whereby a suitably chosen catalyst dramatically improves efficiency of the hydrogen production driven by direct sunlight and allows it to happen even at zero driving potential. Here, we suggest a new class of stable photocatalysts and the corresponding principle for catalytic water splitting in which infrared and visible light play the main role in producing the photocurrent and hydrogen. The new class of catalysts - ionic or covalent binary metals with layered graphite-like structures - effectively absorb visible and infrared light facilitating the reaction of water splitting, suppress the inverse reaction of ion recombination by separating ions due to internal electric fields existing near alternating layers, provide the sites for ion trapping of both polarities, and finally deliver the electrons and holes required to generate hydrogen and oxygen gases. As an example, we demonstrate conversion efficiency of ~27% at bias voltage Vbias = 0.5V for magnesium diboride working as a catalyst for photoinduced water splitting. We discuss its advantages over some existing materials and propose the underlying mechanism of photocatalytic water splitting by binary layered metals. PMID:26698811

  18. The loading of coordination complex modified polyoxometalate nanobelts on activated carbon fiber: a feasible strategy to obtain visible light active and highly efficient polyoxometalate based photocatalysts.

    PubMed

    Lu, Tingting; Xu, Xinxin; Li, Huili; Li, Zhenyu; Zhang, Xia; Ou, Jinzhao; Mei, Mingliang

    2015-02-01

    To enhance the photocatalytic properties of coordination complex modified polyoxometalates (CC/POMs) in the visible light region, its nanobelts (CC/POMNBs) were loaded on activated carbon fiber (ACF) through a simple colloidal blending process. The resulting coordination complex modified polyoxometalate nanobelts loaded activated carbon fiber composite materials (CC/POMNBs/ACF) exhibited dramatic photocatalytic activity for the degradation of rhodamine B (RhB) under visible light irradiation. Optical and electrochemical methods illustrated the enhanced photocatalytic activity of CC/POMNBs/ACF, which originates from the high separation efficiency of the photogenerated electrons and holes on the interface of the CC/POMNBs and ACF, which results from the synergistic effects between them. In the composite material, the role of ACF could be described as a photosensitizer and a good electron transporter. Furthermore, the influence of the mass ratio between the CC/POMNBs and ACF on the photocatalytic performance of the resulting composite material was discussed, and an ideal value to obtain highly efficient photocatalysts was obtained. The results suggested that the loading of CC/POMNBs on the surface of ACF would be a feasible strategy to enhance their photocatalytic activity. PMID:25529472

  19. Loading of a coordination polymer nanobelt on a functional carbon fiber: a feasible strategy for visible-light-active and highly efficient coordination-polymer-based photocatalysts.

    PubMed

    Xu, Xin-Xin; Yang, Hong-Yu; Li, Zhen-Yu; Liu, Xiao-Xia; Wang, Xiu-Li

    2015-02-23

    To improve the photocatalytic properties of coordination polymers under irradiation in the visible-light region, coordination polymer nanobelts (CPNB) were loaded on functional carbon fiber (FCF) through the use of a simple colloidal blending process. The resulting coordination polymer nanobelt loaded functional carbon fiber composite material (CPNB/FCF) exhibited dramatically improved photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation. Optical and electrochemical methods illustrated the enhanced photocatalytic activity of CPNB/FCF originated from high separation efficiency of photogenerated electrons and holes on the interface of CPNB and FCF, which was produced by the synergy effect between them. In the composite material, the role of FCF could be described as photosensitizer and good electron transporter. For FCF, the number of functional groups on its surface has a significant influence on the photocatalytic performance of the resulting CPNB/FCF composite material, and an ideal FCF carrier was obtained as a highly efficient CPNB/FCF photocatalyst. CPNB/FCF showed outstanding stability during the degradation of rhodamine B (RhB); thus, the material is suitable for use as a photocatalyst in the treatment of organic dyes in water. PMID:25641070

  20. Au/BiOCl heterojunction within mesoporous silica shell as stable plasmonic photocatalyst for efficient organic pollutants decomposition under visible light.

    PubMed

    Yan, Xiaoqing; Zhu, Xiaohui; Li, Renhong; Chen, Wenxing

    2016-02-13

    A new mesoporous silica protected plasmonic photocatalyst, Au/BiOCl@mSiO2, was prepared by a modified AcHE method and a subsequent UV light induced photodeposition process. The surfactant-free heterojunction allows the electrons spontaneously flow from Au to nearby BiOCl surface, leading to the accumulation of positive charges on Au surface, and negative charges on Bi species under visible light. Au/BiOCl@mSiO2 exhibits high visible light photocatalytic efficiency in complete oxidation of aqueous formaldehyde and Rhodamin B. We showed that a positive relationship exists between the LSPR effect and rate enhancements, and leads to a hypothesis that the metallic Au LSPR enhances the photocatalytic rates on nearby semiconductors by transferring energetic electrons to BiOCl and increasing the steady-state concentration of active OH species by a multi-electron reduction of molecular oxygen. The OH species is the main oxidant in photocatalytic transformations, whose intensity is greatly enhanced in the dye-involving systems due to the synergetic effect between LSPR and dye sensitization processes. In addition, the mesoporous SiO2 shell not only inhibits the over growth of BiOCl nanocrystals within the silica frameworks, but also protects the dissolution of chloride or Au species into aqueous solution, which ultimately makes the Au/BiOCl@mSiO2 catalysts rather stable during photocatalysis. PMID:26513558

  1. Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction as a highly efficient and stable visible light photocatalyst.

    PubMed

    Liu, Chengbin; Cao, Chenghao; Luo, Xubiao; Luo, Shenglian

    2015-03-21

    A unique Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction (Ag-Ag2O/TiO2 NT) was fabricated by simple electrochemical method. Ag nanoparticles were firstly electrochemically deposited onto the surface of TiO2 NT and then were partly oxidized to Ag2O nanowires while the rest of Ag mother nanoparticles were located at the junctions of Ag2O nanowire network. The Ag-Ag2O/TiO2 NT heterostructure exhibited strong visible-light response, effective separation of photogenerated carriers, and high adsorption capacity. The integration of Ag-Ag2O self-stability structure and p-n heterojunction permitted high and stable photocatalytic activity of Ag-Ag2O/TiO2 NT heterostructure photocatalyst. Under 140-min visible light irradiation, the photocatalytic removal efficiency of both dye acid orange 7 (AO7) and industrial chemical p-nitrophenol (PNP) over Ag-Ag2O/TiO2 NT reached nearly 100% much higher than 17% for AO7 or 13% for PNP over bare TiO2 NT. After 5 successive cycles under 600-min simulated solar light irradiation, Ag-Ag2O/TiO2 NT remained highly stable photocatalytic activity. PMID:25528230

  2. Effect of some operational parameters on the hydrogen generation efficiency of Ni-ZnO/PANI composite under visible-light irradiation

    SciTech Connect

    Nsib, Mohamed Faouzi; Naffati, Naima; Rayes, Ali; Moussa, Noomen; Houas, Ammar

    2015-10-15

    Graphical abstract: UV–vis spectra of PANI, ZnO, Ni{sub 0.01}Zn{sub 0.99}O, Ni{sub 0.01}Zn{sub 0.99}O/PANI3 and Ni{sub 0.1}Zn{sub 0.9}O/PANI{sub 10} nanocomposites. - Highlights: • Ni{sub x}Zn{sub 1−x}O/PANI{sub y} photocatalysts are synthesized by the impregnation method. • Ni{sup 2+} amount control the morphology of ZnO and enhances its photoactivity. • Both Ni{sup 2+} and PANI extend the light absorption of ZnO toward the visible region. • Both Ni{sup 2+} and PANI enhance the electron–hole separation. - Abstract: Ni{sub x}Zn{sub 1−x}O/Polyaniline hybrid photocatalysts are synthesized and used for the experiments of hydrogen production from water-splitting under visible irradiation. XRD, UV–vis DRS and SEM are used to characterize the prepared materials. It is shown that the Ni{sup 2+} amount doped into ZnO controls its morphology and enhances its photoactivity for H{sub 2} generation. Polyaniline (PANI) is shown to sensitize ZnO and to extend its light absorption toward the visible region. The hybrid photocatalyst with 10 mol% Ni{sup 2+} and 10 wt.% PANI shows the maximum photocatalytic H{sub 2} production for one hour of visible irradiation: ∼558 μmol while only ∼178 μmol in the presence of pure ZnO. Additives like sacrificial electron donors and carbonate salts are found to play a key role in the improvement of H{sub 2} evolution. Thus, the hydrogen photoproduction efficiency increases in the order: thiosulfate > sulfide > propanol and HCO{sub 3}{sup −} > CO{sub 3}{sup 2−}.

  3. Ag{sub 3}PO{sub 4}/ZnO: An efficient visible-light-sensitized composite with its application in photocatalytic degradation of Rhodamine B

    SciTech Connect

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

    2013-01-15

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

  4. Visible light communication applications in healthcare.

    PubMed

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

    2016-01-01

    With the development in science, methods of communication are also improved, replacing old ones with new advanced ways in an attempt to make data transfer more secure, safer for health, and time as well as cost efficient. One of such methods is Visible Light Communication, as the name implies data is transferred through a light equipment such as incandescent or florescent bulb having speed of 10 Kb/s or LEDs approaching speed of 500 Mb/s [1]. VLC uses visible light between 384 and 789 THz [2,3]. Though range is limitation of VLC, however data transfer up-to distance of 1 to 2 km although at lower transfer rate has been reached.The VLC system comprises of light source like LED and receiver equipment, however, with advancement, now LEDs are used for both sending and receiving data. LED remains on all the time, and there is no change in brightness level during the whole process, making it safe for eyes. Currently, VLC system is facing some serious technical challenges before it could be applied in daily life. PMID:26484883

  5. Photo and Chemical Reduction of Copper onto Anatase-Type TiO2 Nanoparticles with Enhanced Surface Hydroxyl Groups as Efficient Visible Light Photocatalysts.

    PubMed

    Eskandarloo, Hamed; Badiei, Alireza; Behnajady, Mohammad A; Mohammadi Ziarani, Ghodsi

    2015-01-01

    In this study, the photocatalytic efficiency of anatase-type TiO2 nanoparticles synthesized using the sol-gel low-temperature method, were enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement. UV-light-assisted photo and NaBH4 -assisted chemical reduction methods were used for deposition of copper onto TiO2. The surface hydroxyl groups of TiO2 were enhanced with the assistance of NaOH modification. The prepared catalysts were immobilized on glass plates and used as the fixed-bed systems for the removal of phenazopyridine as a model drug contaminant under visible light irradiation. NaOH-modified Cu/TiO2 nanoparticles demonstrated higher photocatalytic efficiency than that of pure TiO2 due to the extending of the charge carriers lifetime and enhancement of the adsorption capacity of TiO2 toward phenazopyridine. The relationship of structure and performance of prepared nanoparticles has been established by using various techniques, such as XRD, XPS, TEM, EDX, XRF, TGA, DRS and PL. The effects of preparation variables, including copper content, reducing agents rate (NaBH4 concentration and UV light intensity) and NaOH concentration were investigated on the photocatalytic efficiency of NaOH-modified Cu/TiO2 nanoparticles. PMID:25809844

  6. Improvement of III-nitride visible and ultraviolet light-emitting diode performance, including extraction efficiency, electrical efficiency, thermal management and efficiency maintenance at high current densities

    NASA Astrophysics Data System (ADS)

    Vampola, Kenneth

    In this work, highly efficient broad-area LEDs on bulk GaN substrates were developed and the fabrication process and device layout were optimized. This optimization relied in part on electrical, optical, thermal and recombination models. The peak external quantum efficiency of the 450 nm LEDs was over 68% when biased at 20 mA. The efficiency characteristic showed a typical droop curve, decreasing at high current densities. The cause of this droop is unknown. An exploratory experiment was conducted to characterize electron overflow and its role in efficiency droop. Novel device structures were developed, allowing direct measurement of overflow electrons in LED-like structures under electrical injection. In these test structures, electrons were observed in the p-type region of the LED only at current densities where efficiency droop was active. The onset of efficiency droop was preceded by the onset of electron overflow. However, the magnitude of the overflow current could not be measured and it is undetermined whether the dominant cause of efficiency droop is electron overflow or some other process such as Auger recombination. Calibration structures allowing measurement of the magnitude of the overflow are proposed. Work on deep-ultraviolet, 275 nm, LEDs is also presented. Demonstration of direct-wafer bonded LEDs to beta-Ga2O3 is presented. A SiC substrate removal process is discussed. LEDs fabricated by this flip-chip process exhibited up to 1.8 times greater power compared to LEDs fabricated by a standard process but suffered from increased forward voltage and premature failure. Further process development leading to electrically efficient operation is proposed.

  7. Highly efficient and stable Ag-AgBr/TiO2 composites for destruction of Escherichia coli under visible light irradiation.

    PubMed

    Wang, Xiaoping; Lim, Teik-Thye

    2013-08-01

    A series of Ag-AgBr/TiO2 composites were prepared by a sol-gel method followed by photoreduction. Effect of Ag-AgBr content on the physicochemical properties and antibacterial activities of the Ag-AgBr/TiO2 composites was investigated. These composites showed intrinsic antibacterial activities against Escherichia coli (E. coli) in the dark attributed to the Ag nanoparticles dispersed in the composites. Under visible light irradiation, inactivation of E. coli over these Ag-AgBr/TiO2 composites was attributed to both their photocatalytic disinfection activities and intrinsic antibacterial properties. The Ag-AgBr/TiO2 with an optimum Ti/Ag atomic ratio of 10 exhibited superior visible-light photocatalytic activities for ibuprofen degradation and mineralization as compared to the other Ag-AgBr/TiO2 composites and also Ag-AgBr/P25, Ag/TiO2 and TiO2. It is probably because of the coexistence of two visible-light active components (AgBr and Ag nanoparticles) and the most effective separation of photogenerated electrons and holes in this photocatalyst. Correspondingly, the photocatalyst achieved a much higher efficiency of E. coli destruction than Ag-AgBr/P25 and TiO2. E. coli was almost completely inactivated (7-log reduction) within 60 min by the photocatalyst with a rather low dosage of 0.05 g L(-1) under white LED irradiation. Furthermore, the Ag-AgBr/TiO2 showed high stability for photocatalytic destruction of E. coli and the dark repair and photoreactivation did not occur after the photocatalytic process. Finally, the action spectrum of this photocatalyst for E. coli inactivation and the influence of several inorganic ions present in surface water were also investigated. PMID:23562562

  8. Infrared spectroscopy with visible light

    NASA Astrophysics Data System (ADS)

    Kalashnikov, Dmitry A.; Paterova, Anna V.; Kulik, Sergei P.; Krivitsky, Leonid A.

    2016-02-01

    Spectral measurements in the infrared optical range provide unique fingerprints of materials, which are useful for material analysis, environmental sensing and health diagnostics. Current infrared spectroscopy techniques require the use of optical equipment suited for operation in the infrared range, components of which face challenges of inferior performance and high cost. Here, we develop a technique that allows spectral measurements in the infrared range using visible-spectral-range components. The technique is based on nonlinear interference of infrared and visible photons, produced via spontaneous parametric down conversion. The intensity interference pattern for a visible photon depends on the phase of an infrared photon travelling through a medium. This allows the absorption coefficient and refractive index of the medium in the infrared range to be determined from the measurements of visible photons. The technique can substitute and/or complement conventional infrared spectroscopy and refractometry techniques, as it uses well-developed components for the visible range.

  9. Hot-Electron-Induced Highly Efficient O2 Activation by Pt Nanoparticles Supported on Ta2O5 Driven by Visible Light.

    PubMed

    Sakamoto, Hirokatsu; Ohara, Tomoyuki; Yasumoto, Naoki; Shiraishi, Yasuhiro; Ichikawa, Satoshi; Tanaka, Shunsuke; Hirai, Takayuki

    2015-07-29

    Aerobic oxidation on a heterogeneous catalyst driven by visible light (λ >400 nm) at ambient temperature is a very important reaction for green organic synthesis. A metal particles/semiconductor system, driven by charge separation via an injection of "hot electrons (e(hot)(-))" from photoactivated metal particles to semiconductor, is one of the promising systems. These systems, however, suffer from low quantum yields for the reaction (<5% at 550 nm) because the Schottky barrier created at the metal/semiconductor interface suppresses the e(hot)(-) injection. Some metal particle systems promote aerobic oxidation via a non-e(hot)(-)-injection mechanism, but require high reaction temperatures (>373 K). Here we report that Pt nanoparticles (∼5 nm diameter), when supported on semiconductor Ta2O5, promote the reaction without e(hot)(-) injection at room temperature with significantly high quantum yields (∼25%). Strong Pt-Ta2O5 interaction increases the electron density of the Pt particles and enhances interband transition of Pt electrons by absorbing visible light. A large number of photogenerated e(hot)(-) directly activate O2 on the Pt surface and produce active oxygen species, thus promoting highly efficient aerobic oxidation at room temperature. PMID:26158296

  10. Design of a novel Cu₂O/TiO₂/carbon aerogel electrode and its efficient electrosorption-assisted visible light photocatalytic degradation of 2,4,6-trichlorophenol.

    PubMed

    Wang, Yabo; Zhang, Ya-Nan; Zhao, Guohua; Tian, Hongyi; Shi, Huijie; Zhou, Tianchen

    2012-08-01

    Cu(2)O/TiO(2) heterojunction photocatalyst is built on carbon aerogel (CA) substrate with good adsorption properties by sol impregnation and seed-mediated synthesis approach. The Cu(2)O/TiO(2)/CA electrode has excellent electrosorptive and high efficient photocatalytic properties. Its morphology and surface chemical composition are characterized with SEM, TEM, X-ray diffraction (XRD) and Raman spectra. The UV-vis diffuse reflectance spectra show that the optical absorption edge for Cu(2)O/TiO(2)/CA appears at 636 nm. Under visible-light (λ > 420 nm) irradiation, the photocurrent density increment on Cu(2)O/TiO(2)/CA is 60 times of that on Cu(2)O/TiO(2)/FTO. The electrochemical characteristic is investigated with electrochemical impedance spectrum (EIS). The Cu(2)O/TiO(2)/CA electrode is further applied in the electrosorptive photodegradation of the 2,4,6-trichlorophenol (2,4,6-TCP) wastewater. The result shows that the removal ratio of 2,4,6-TCP in 5.5 h on Cu(2)O/TiO(2)/CA is 96.3% and the TOC removal is 91.3%. The intermediates generated in the degradation process are analyzed by GC-MS and HPLC. The possible mechanism of visible light photocatalytic degradation of 2,4,6-TCP on Cu(2)O/TiO(2)/CA is also studied. PMID:22780307

  11. Facile one-step synthesis of N-doped ZnO micropolyhedrons for efficient photocatalytic degradation of formaldehyde under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Wu, Changle

    2014-11-01

    N-doped ZnO micropolyhedrons were fabricated by calcining the mixture of commercial ZnO (analytical grade) and NH4NO3 at 600 °C for 1.5 h, in which NH4NO3 was utilized as the nitrogen source. The structure, composition, BET specific surface area and optical properties of N-doped ZnO sample were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, wavelength dispersive X-ray fluorescence spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, N2 adsorption-desorption isotherms, and UV-vis diffuse reflectance spectroscopy. The photocatalytic results demonstrated that the as-synthesized N-doped ZnO microcrystals possessed much higher photocatalytic activity than N-doped TiO2 (which was synthesized by calcining the mixture of P25 TiO2 and NH4NO3 at 600 °C for 1.5 h) and commercial pure ZnO in the decomposition of formaldehyde under visible-light (λ > 420 nm) irradiation. The present work suggests that NH4NO3 is a promising nitrogen source for one-step calcination synthesis of microcrystalline N-doped ZnO, which can be applied as a visible-light-activated photocatalyst in efficient utilization of solar energy for treating formaldehyde wastewater.

  12. Efficient Visible Light-Driven Splitting of Alcohols into Hydrogen and Corresponding Carbonyl Compounds over a Ni-Modified CdS Photocatalyst.

    PubMed

    Chai, Zhigang; Zeng, Ting-Ting; Li, Qi; Lu, Liang-Qiu; Xiao, Wen-Jing; Xu, Dongsheng

    2016-08-17

    Splitting of alcohols into hydrogen and corresponding carbonyl compounds has potential applications in hydrogen production and chemical industry. Herein, we report that a heterogeneous photocatalyst (Ni-modified CdS nanoparticles) could efficiently split alcohols into hydrogen and corresponding aldehydes or ketones in a stoichiometric manner under visible light irradiation. Optimized apparent quantum yields of 38%, 46%, and 48% were obtained at 447 nm for dehydrogenation of methanol, ethanol, and 2-propanol, respectively. In the case of dehydrogenation of 2-propanol, a turnover number of greater than 44 000 was achieved. To our knowledge, these are unprecedented values for photocatalytic splitting of liquid alcohols under visible light to date. Besides, the current catalyst system functions well with other aliphatic and aromatic alcohols, affording the corresponding carbonyl compounds with good to excellent conversion and outstanding selectivity. Moreover, mechanistic investigations suggest that an interface between Ni nanocrystal and CdS plays a key role in the reaction mechanism of the photocatalytic splitting of alcohol. PMID:27477237

  13. Direct synthesis of novel vanadium oxide embedded porous carbon nanofiber decorated with iron nanoparticles as a low-cost and highly efficient visible-light-driven photocatalyst.

    PubMed

    Taha, Ahmed Aboueloyoun; Hriez, Amir A; Wu, Yi-nan; Wang, Hongtao; Li, Fengting

    2014-03-01

    Template-free porous carbon nanofibers embedded by vanadium oxide and decorated with iron nanoparticles (Fe@V-CNF) were prepared in a time and cost-saving manner by combining electrospinning and heat treatment processes. Cost-saving ammonium metavanadate was used as a semiconductor precursor of vanadium oxide (VOx) as well as porogen. The generated pores in the carbon nanofiber (CNFs) matrix formed pathways between the embedded VOx and the surface of CNFs and Fe NPs, thus, facilitate photo-generated electron transfer. The characterization results revealed that Fe@V-CNF comprised graphitic fibers with well-dispersed distribution of nanosized Fe NPs (~7 nm) along the surface of CNF. Thereby, it enhanced the visible-light harvesting. The prepared Fe@V-CNF had remarkable light absorption in the visible region. It demonstrated much higher photocatalytic efficiency of photodegradation of organic dyes compared with the pure CNF and vanadium oxide embedded CNF (V-CNF). Notably, Fe@V-CNF achieved 99.9% dye degradation within 15-20 min. And, it could be conveniently recycled due to its one-dimensional nanostructural property. PMID:24407677

  14. One-step synthesis of novel PANI-Fe3O4@ZnO core-shell microspheres: An efficient photocatalyst under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoyuan; Wu, Jianning; Meng, Guihua; Guo, Xuhong; Liu, Chang; Liu, Zhiyong

    2016-03-01

    For the first time, novel multifunctional superparamagnetic PANI-Fe3O4@ZnO core-shell composite photocatalysts with different PANI: ZnO ratios were synthesized by Pickering emulsion route in one step in the presence of ZnO nanoparticles. PANI-Fe3O4@ZnO core-shell microspheres consist of PANI core which embedded with Fe3O4-OA (oleic acid modified Fe3O4) nanoparticles and tunable ZnO shell thickness. The resulting samples were thoroughly studied by using X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The catalytic activity of the as-prepared PANI-Fe3O4@ZnO core-shell microspheres is investigated by the degradation of MB under visible light irradiation. As expected, the as prepared PANI-Fe3O4@ZnO photocatalysts exhibit highly enhanced photocatalytic activities in the degradation of MB under visible light irradiation owing to fast separation of photo-generated electron-hole pairs. Significantly, the PANI-Fe3O4@ZnO catalysts can be separated from the reaction media by applying an external magnet, and can be reused for seven cycles without change in stability and degradation efficiency.

  15. Preparation of MIL-53(Fe)-Reduced Graphene Oxide Nanocomposites by a Simple Self-Assembly Strategy for Increasing Interfacial Contact: Efficient Visible-Light Photocatalysts.

    PubMed

    Liang, Ruowen; Shen, Lijuan; Jing, Fenfen; Qin, Na; Wu, Ling

    2015-05-13

    In this work, MIL-53(Fe)-reduced graphene oxide (M53-RGO) nanocomposites have been successfully fabricated by a facile and efficient electrostatic self-assembly strategy for improving the interfacial contact between RGO and the MIL-53(Fe). Compared with D-M53-RGO (direct synthesis of MIL-53(Fe)-reduced graphene oxide nanocomposites via one-pot solvothermal approach), M53-RGO nanocomposites exhibit improved photocatalytic activity compared with the D-M53-RGO under identical experimental conditions. After 80 min of visible light illumination (λ ≥ 420 nm), the reduction ratio of Cr(VI) is rapidly increased to 100%, which is also higher than that of reference sample (N-doped TiO2). More significantly, the M53-RGO nanocomposites are proven to perform as bifunctional photocatalysts with considerable activity in the mixed systems (Cr(VI)/dyes) under visible light, which made it a potential candidate for industrial wastewater treatment. Combining with photoelectrochemical analyses, it could be revealed that the introduction of RGO would minimize the recombination of photogenerated electron-hole pairs. Additionally, the effective interfacial contact between MIL-53(Fe) and RGO surface would further accelerate the transfer of photogenerated electrons, leading to the enhancement of photocatalytic activity of M53-RGO toward photocatalytic reactions. Finally, a possible photocatalytic reaction mechanism is also investigated in detail. PMID:25894300

  16. Cadmium sulfide/graphitic carbon nitride heterostructure nanowire loading with a nickel hydroxide cocatalyst for highly efficient photocatalytic hydrogen production in water under visible light

    NASA Astrophysics Data System (ADS)

    Yan, Zhiping; Sun, Zijun; Liu, Xiang; Jia, Hongxing; Du, Pingwu

    2016-02-01

    Photocatalytic hydrogen production from water in a noble-metal-free system has attracted much attention in recent years. Herein we report on the use of core/shell cadmium sulfide/graphitic carbon nitride (CdS/g-C3N4) heterojunction nanorods modified by nickel hydroxide (Ni(OH)2) as a highly efficient photocatalyst for visible light-driven hydrogen production from water. Due to efficient separation of the photoexcited charge carriers in the CdS/g-C3N4 core/shell nanorods and the synergistic effect of Ni(OH)2, the optimal hydrogen evolution rate over Ni(OH)2-CdS/g-C3N4 is 115.18 μmol h-1 mg-1 under visible light irradiation (λ > 420 nm), which is ~26 times higher than the CdS/g-C3N4 nanorod composite without Ni(OH)2 and ~7 times better than the 0.5 wt% Pt-CdS/g-C3N4 nanorod composite. The apparent quantum efficiency is ~16.7% at an excitation of 450 nm. During photocatalysis, no degradation of Ni(OH)2 was observed based on the XPS data, indicating that it is a robust cocatalyst. Moreover, the present photocatalyst showed excellent photocatalytic stability for hydrogen production and the turnover number (TON) reached ~24 600 over 90 hours.Photocatalytic hydrogen production from water in a noble-metal-free system has attracted much attention in recent years. Herein we report on the use of core/shell cadmium sulfide/graphitic carbon nitride (CdS/g-C3N4) heterojunction nanorods modified by nickel hydroxide (Ni(OH)2) as a highly efficient photocatalyst for visible light-driven hydrogen production from water. Due to efficient separation of the photoexcited charge carriers in the CdS/g-C3N4 core/shell nanorods and the synergistic effect of Ni(OH)2, the optimal hydrogen evolution rate over Ni(OH)2-CdS/g-C3N4 is 115.18 μmol h-1 mg-1 under visible light irradiation (λ > 420 nm), which is ~26 times higher than the CdS/g-C3N4 nanorod composite without Ni(OH)2 and ~7 times better than the 0.5 wt% Pt-CdS/g-C3N4 nanorod composite. The apparent quantum efficiency is ~16.7% at an

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

    SciTech Connect

    Liu, Xin-Ling; Wang, Rong; Yuan, Yu-Peng E-mail: cxue@ntu.edu.sg; Zhang, Ming-Yi; Xue, Can E-mail: cxue@ntu.edu.sg

    2015-10-01

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

  18. Efficiently Enhancing Visible Light Photocatalytic Activity of Faceted TiO2 Nanocrystals by Synergistic Effects of Core-Shell Structured Au@CdS Nanoparticles and Their Selective Deposition.

    PubMed

    Tong, Ruifeng; Liu, Chang; Xu, Zhenkai; Kuang, Qin; Xie, Zhaoxiong; Zheng, Lansun

    2016-08-24

    Integrating wide bandgap semiconductor photocatalysts with visible-light-active inorganic nanoparticles (such as Au and CdS) as sensitizers is one of the most efficient methods to improve their photocatalytic activity in the visible light region. However, as for all such composite photocatalysts, a rational design and precise control over their architecture is often required to achieve optimal performance. Herein, a new TiO2-based ternary composite photocatalyst with superior visible light activity was designed and synthesized. In this composite photocatalyst, the location of the visible light sensitizers was engineered according to the intrinsic facet-induced effect of well-faceted TiO2 nanocrystals on the spatial separation of photogenerated carriers. Experimentally, core-shell structured Au@CdS nanoparticles acting as visible light sensitizers were selectively deposited onto photoreductive {101} facets of well-faceted anatase TiO2 nanocrystals through a two-step in situ photodeposition route. Because the combination of Au@CdS and specific {101} facets of TiO2 nanocrystals facilitates the transport of charges photogenerated under visible light irradiation, this well-designed ternary composite photocatalyst exhibited superior activity in visible-light-driven photocatalytic H2 evolution, as expected. PMID:27479634

  19. Broadband Visible Light Induced NO Formation

    NASA Astrophysics Data System (ADS)

    Lubart, Rachel; Eichler, Maor; Friedmann, Harry; Savion, N.; Breitbart, Haim; Ankri, Rinat

    2009-06-01

    Nitric oxide formation is a potential mechanism for photobiomodulation because it is synthesized in cells by nitric oxide synthase (NOS), which contains both flavin and heme, and thus absorbs visible light. The purpose of this work was to study broadband visible light induced NO formation in various cells. Cardiac, endothelial, sperm cells and RAW 264.7 macrophages were illuminated with broadband visible light, 40-130 mW/cm2, 2.4-39 J/cm2, and nitric oxide production was quantified by using the Griess reagent. The results showed that visible light illumination increased NO concentration both in sperm and endothelial cells, but not in cardiac cells. Activation of RAW 264.7 macrophages was very small. It thus appears that NO is involved in photobiomodulation, though different light parameters and illumination protocols are needed to induce NO in various cells.

  20. Broadband Visible Light Induced NO Formation

    SciTech Connect

    Lubart, Rachel; Eichler, Maor; Friedmann, Harry; Ankri, Rinat; Savion, N.; Breitbart, Haim

    2009-06-19

    Nitric oxide formation is a potential mechanism for photobiomodulation because it is synthesized in cells by nitric oxide synthase (NOS), which contains both flavin and heme, and thus absorbs visible light. The purpose of this work was to study broadband visible light induced NO formation in various cells. Cardiac, endothelial, sperm cells and RAW 264.7 macrophages were illuminated with broadband visible light, 40-130 mW/cm2, 2.4-39 J/cm2, and nitric oxide production was quantified by using the Griess reagent. The results showed that visible light illumination increased NO concentration both in sperm and endothelial cells, but not in cardiac cells. Activation of RAW 264.7 macrophages was very small. It thus appears that NO is involved in photobiomodulation, though different light parameters and illumination protocols are needed to induce NO in various cells.

  1. Hollow Au-Cu2O Core-Shell Nanoparticles with Geometry-Dependent Optical Properties as Efficient Plasmonic Photocatalysts under Visible Light.

    PubMed

    Lu, Biao; Liu, Aiping; Wu, Huaping; Shen, Qiuping; Zhao, Tingyu; Wang, Jianshan

    2016-03-29

    Hollow Au-Cu2O core-shell nanoparticles were synthesized by using hollow gold nanoparticles (HGNs) as the plasmon-tailorable cores to direct epitaxial growth of Cu2O nanoshells. The effective geometry control of hollow Au-Cu2O core-shell nanoparticles was achieved through adjusting the HGN core sizes, Cu2O shell thicknesses, and morphologies related to structure-directing agents. The morphology-dependent plasmonic band red-shifts across the visible and near-infrared spectral regions were observed from experimental extinction spectra and theoretical simulation based on the finite-difference time-domain method. Moreover, the hollow Au-Cu2O core-shell nanoparticles with synergistic optical properties exhibited higher photocatalytic performance in the photodegradation of methyl orange when compared to pristine Cu2O and solid Au-Cu2O core-shell nanoparticles under visible-light irradiation due to the efficient photoinduced charge separation, which could mainly be attributed to the Schottky barrier and plasmon-induced resonant energy transfer. Such optical tunability achieved through the hollow cores and structure-directed shells is of benefit to the performance optimization of metal-semiconductor nanoparticles for photonic, electronic, and photocatalytic applications. PMID:26954100

  2. Self-assembly of ultrathin Cu2MoS4 nanobelts for highly efficient visible light-driven degradation of methyl orange

    NASA Astrophysics Data System (ADS)

    Zhang, Ke; Chen, Wenxing; Lin, Yunxiang; Chen, Haiping; Haleem, Yasir A.; Wu, Chuanqiang; Ye, Fei; Wang, Tianxing; Song, Li

    2015-10-01

    We demonstrate ultrathin self-assembled Cu2MoS4 nanobelts synthesized by using Cu2O as the starting sacrificial template via a hydrothermal method. The nanobelts exhibit strong light absorption over a broad wavelength spectrum, suggesting their potential application as photocatalysts. The photocatalytic activity of nanobelts is evaluated by the degradation of Methyl Orange (MO) dye under visible light irradiation. Notably, the nanobelts can completely degrade 100 mL of 15 mg mL-1 MO in 20 minutes with excellent recycling and structural stability, suggesting their excellent photocatalytic performance. In comparison with a sheet-like sample, the high efficiency of the self-assembled Cu2MoS4 nanobelts is attributed to a high surface area and a unique band gap, agreeing with the nitrogen adsorption analysis and photoluminescence spectra. This study offers a self-assembled synthetic route to create new multifunctional nanoarchitectures composed of atomic layers, and thus may open a window for greatly extending potential applications in water pollution treatment, photocatalytic water-splitting, solar cells and other related fields.We demonstrate ultrathin self-assembled Cu2MoS4 nanobelts synthesized by using Cu2O as the starting sacrificial template via a hydrothermal method. The nanobelts exhibit strong light absorption over a broad wavelength spectrum, suggesting their potential application as photocatalysts. The photocatalytic activity of nanobelts is evaluated by the degradation of Methyl Orange (MO) dye under visible light irradiation. Notably, the nanobelts can completely degrade 100 mL of 15 mg mL-1 MO in 20 minutes with excellent recycling and structural stability, suggesting their excellent photocatalytic performance. In comparison with a sheet-like sample, the high efficiency of the self-assembled Cu2MoS4 nanobelts is attributed to a high surface area and a unique band gap, agreeing with the nitrogen adsorption analysis and photoluminescence spectra. This study

  3. Solar Synthesis: Prospects in Visible Light Photocatalysis

    PubMed Central

    Schultz, Danielle M.; Yoon, Tehshik P.

    2015-01-01

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

  4. Photocatalytic reforming of glucose under visible light over morphology controlled Cu2O: efficient charge separation by crystal facet engineering.

    PubMed

    Zhang, Longzhou; Shi, Jinwen; Liu, Maochang; Jing, Dengwei; Guo, Liejin

    2014-01-01

    Multifaceted Cu2O with controlled crystal facet exposure was synthesized via a facile one-step method. It was found that photogenerated electrons prefer to accumulate on high index planes, while holes tend to migrate to {100} facets of a Cu2O polyhedron, leading to efficient charge separation and enhanced photocatalytic reforming of glucose. PMID:24217641

  5. Ag/AgBr/g-C{sub 3}N{sub 4}: A highly efficient and stable composite photocatalyst for degradation of organic contaminants under visible light

    SciTech Connect

    Cao, Jing; Zhao, Yijie; Lin, Haili; Xu, Benyan; Chen, Shifu

    2013-10-15

    Graphical abstract: Ag/AgBr/g-C{sub 3}N{sub 4} composite photocatalysts displayed excellent photocatalytic activities on the degradation of methyl orange (MO) under visible light. The improved photocatalytic performance and stability of Ag/AgBr/g-C{sub 3}N{sub 4} originated from the synergetic effects of AgBr/g-C{sub 3}N{sub 4} interface and metallic Ag nanoparticles. ·O{sub 2}−, one of the reactive species, was responsible for the photodegradation of MO compared to H+ and ·OH. - Highlights: • Novel Ag/AgBr/g-C{sub 3}N{sub 4} composite photocatalyst was reported. • Ag/AgBr/g-C{sub 3}N{sub 4} had novel energy band combination between AgBr and g-C{sub 3}N{sub 4}. • Synergetic effects of AgBr/g-C{sub 3}N{sub 4} interface and metallic Ag nanoparticles. • Electron trapping role of metallic Ag dominated the stability of Ag/AgBr/g-C{sub 3}N{sub 4}. - Abstract: Novel Ag/AgBr/g-C{sub 3}N{sub 4} composite photocatalysts were constructed via deposition–precipitation method and extensively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and UV–vis diffuse reflectance spectroscopy (DRS). Under visible light (λ > 420 nm), Ag/AgBr/g-C{sub 3}N{sub 4} composite photocatalysts displayed much higher photocatalytic activities than those of Ag/AgBr and g-C{sub 3}N{sub 4} for degradation of methyl orange (MO). 50% Ag/AgBr/g-C{sub 3}N{sub 4} presented the best photocatalytic performance, which was mainly attributed to the synergistic effects of AgBr/g-C{sub 3}N{sub 4} interface and the in situ metallic Ag nanoparticles for efficiently separating electron–hole pairs. Furthermore, Ag/AgBr/g-C{sub 3}N{sub 4} remained good photocatalytic activity through 5 times of cycle experiments. Additionally, the radical scavengers experiment indicated that ·O{sub 2}{sup −} was the main reactive species for the MO degradation under visible light.

  6. Efficient visible light-driven H₂ production in water by CdS/CdSe core/shell nanocrystals and an ordinary nickel-sulfur complex.

    PubMed

    Wang, Ping; Zhang, Jie; He, Haili; Xu, Xiaolong; Jin, Yongdong

    2014-11-21

    Solar energy conversion to hydrogen has gained tremendous interest due to its great potential in solving the problem of energy crisis. Among different ways to achieve the goals of H2 photogeneration, the quantum dot (QD)-based multicomponent system has been proven to be one of the most prominent methods. Although significant advances have been made recently, the development of a practical visible light-driven hydrogen generation system with high efficiency and low-cost is still challenging. In this work, we report that a highly active catalyst could be simply obtained through the complexing of nickel ions with S(2-) or 3-mercaptopropionic acid, and after further combination with the carefully designed CdS/CdSe core/shell nanocrystals, the aqueous system exhibits a good stability and high efficiency for the H2 photogeneration. It is expected that our findings would provide new insights for the facile construction of a highly efficient and cost-effective solar H2 generation system for practical applications. PMID:25315042

  7. MoS2/CdS Nanosheets-on-Nanorod Heterostructure for Highly Efficient Photocatalytic H2 Generation under Visible Light Irradiation.

    PubMed

    Yin, Xing-Liang; Li, Lei-Lei; Jiang, Wen-Jie; Zhang, Yun; Zhang, Xiang; Wan, Li-Jun; Hu, Jin-Song

    2016-06-22

    Semiconductor-based photocatalytic H2 generation as a direct approach of converting solar energy to fuel is attractive for tackling the global energy and environmental issues but still suffers from low efficiency. Here, we report a MoS2/CdS nanohybrid as a noble-metal-free efficient visible-light driven photocatalyst, which has the unique nanosheets-on-nanorod heterostructure with partially crystalline MoS2 nanosheets intimately but discretely growing on single-crystalline CdS nanorod. This heterostructure not only facilitates the charge separation and transfer owing to the formed heterojunction, shorter radial transfer path, and fewer defects in single-crystalline nanorod, thus effectively reducing the charge recombination, but also provides plenty of active sites for hydrogen evolution reaction due to partially crystalline structure of MoS2 as well as enough room for hole extraction. As a result, the MoS2/CdS nanosheets-on-nanorod exhibits a state-of-the-art H2 evolution rate of 49.80 mmol g(-1) h(-1) and an apparent quantum yield of 41.37% at 420 nm, which is the advanced performance among all MoS2/CdS composites and CdS/noble metal photocatalysts. These findings will open opportunities for developing low-cost efficient photocatalysts for water splitting. PMID:27237623

  8. Biomolecule-mediated CdS-TiO2-reduced graphene oxide ternary nanocomposites for efficient visible light-driven photocatalysis.

    PubMed

    Dutta, Soumen; Sahoo, Ramakrishna; Ray, Chaiti; Sarkar, Sougata; Jana, Jayasmita; Negishi, Yuichi; Pal, Tarasankar

    2015-01-01

    We report an environmentally friendly synthetic strategy to fabricate reduced graphene oxide (rGO)-based ternary nanocomposites, in which glutathione (GSH) acts both as a reducing agent for graphene oxide and sulfur donor for CdS synthesis under modified hydrothermal (MHT) conditions. The report becomes interesting as pH variation evolves two distinctly different semiconducting nanocrystals of anatase/rutile TiO2 and hexagonal yellow/cubic red CdS, and their packaging makes them suitable photocatalysts for dye degradation. Herein, a titanium peroxo compound, obtained from commercial TiO2, is hydrolyzed to TiO2 nanostructures without any additives. The yellow colored CdS-TiO2-rGO (YCTG), one of the ternary photocatalysts, shows maximum efficiency compared to the corresponding red ternary CdS-TiO2-rGO or binary photocatalysts (CdS-rGO, TiO2-rGO and CdS-TiO2) for dye degradation under visible light irradiation. Systematic characterizations reveal that TiO2 presents at the interface of rGO and CdS in YCTG and thus makes a barrier that inhibits the direct interaction between rGO and CdS. This leads to a relatively higher bandgap value for CdS in YCTG (2.15 eV vs. 2.04 eV for CdS-rGO) but with better photocatalytic activity simply by diminishing the possibility of the charge-recombination process. In the present situation, rGO in the YCTG also supports faster dye degradation through higher dye adsorption and rapid internal electron transfer (CdS→TiO2→rGO) in the YCTG nanocomposite. Thus, a simple aqueous phase and a greener synthetic procedure results in a low-cost, highly effective visible light-responsive material for environmental application. PMID:25369862

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

    PubMed

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

    2015-09-01

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

  10. New organic donor-acceptor-π-acceptor sensitizers for efficient dye-sensitized solar cells and photocatalytic hydrogen evolution under visible-light irradiation.

    PubMed

    Li, Xing; Cui, Shicong; Wang, Dan; Zhou, Ying; Zhou, Hao; Hu, Yue; Liu, Jin-Gang; Long, Yitao; Wu, Wenjun; Hua, Jianli; Tian, He

    2014-10-01

    Two organic donor-acceptor-π-acceptor (D-A-π-A) sensitizers (AQ and AP), containing quinoxaline/pyrido[3,4-b]pyrazine as the auxiliary acceptor, have been. Through fine-tuning of the auxiliary acceptor, a higher designed and synthesized photoelectric conversion efficiency of 6.02% for the AQ-based dye-sensitized solar cells under standard global AM1.5 solar conditions was achieved. Also, it was found that AQ-Pt/TiO2 photocatalysts displayed a better rate of H2 evolution under visible-light irradiation (420 nm<λ<780 nm) because of the stability of the oxidized states and the lower rates of electron recombination. Importantly, sensitizers AQ and AP-Pt/TiO2 showed strong photocatalytic activity during continuous light soaking for 10 h with methanol as the sacrificial electron donor. Additionally, the processes of their intermolecular electron transfer were further investigated theoretically by using time-dependent DFT. The calculated results indicate that the auxiliary acceptor plays the role of an electron trap and results in broad spectral responses. PMID:25154958

  11. Visible light metasurfaces based on gallium nitride high contrast gratings

    NASA Astrophysics Data System (ADS)

    Wang, Zhenhai; He, Shumin; Liu, Qifa; Wang, Wei

    2016-05-01

    We propose visible-light metasurfaces (VLMs) capable of serving as lens and beam deflecting element based on gallium nitride (GaN) high contrast gratings (HCGs). By precisely manipulating the wavefront of the transmitted light, we theoretically demonstrate an HCG focusing lens with transmissivity of 86.3%, and a VLM with beam deflection angle of 6.09° and transmissivity as high as 91.4%. The proposed all-dielectric metasurfaces are promising for GaN-based visible light-emitting diodes (LEDs), which would be robust and versatile for controlling the output light propagation and polarization, as well as enhancing the extraction efficiency of the LEDs.

  12. Efficient Photocatalytic Disinfection of Escherichia coli O157:H7 using C70-TiO2 Hybrid under Visible Light Irradiation

    PubMed Central

    Ouyang, Kai; Dai, Ke; Walker, Sharon L.; Huang, Qiaoyun; Yin, Xixiang; Cai, Peng

    2016-01-01

    Efficient photocatalytic disinfection of Escherichia coli O157:H7 was achieved by using a C70 modified TiO2 (C70-TiO2) hybrid as a photocatalyst under visible light (λ > 420 nm) irradiation. Disinfection experiments showed that 73% of E. coli O157:H7 died within 2 h with a disinfection rate constant of k = 0.01 min−1, which is three times that measured for TiO2. The mechanism of cell death was investigated by using several scavengers combined with a partition system. The results revealed that diffusing hydroxyl radicals play an important role in the photocatalytically initiated bacterial death, and direct contact between C70-TiO2 hybrid and bacteria is not indispensable in the photocatalytic disinfection process. Extracellular polymeric substances (EPS) of bacteria have little effect on the disinfection efficiency. Analyses of the inhibitory effect of C70-TiO2 thin films on E. coli O157:H7 showed a decrease of the bacterial concentration from 3 × 108 to 38 cfu mL−1 in the solution with C70-TiO2 thin film in the first 2 h of irradiation and a complete inhibition of the growth of E. coli O157:H7 in the later 24 h irradiation. PMID:27161821

  13. Efficient Photocatalytic Disinfection of Escherichia coli O157:H7 using C70-TiO2 Hybrid under Visible Light Irradiation.

    PubMed

    Ouyang, Kai; Dai, Ke; Walker, Sharon L; Huang, Qiaoyun; Yin, Xixiang; Cai, Peng

    2016-01-01

    Efficient photocatalytic disinfection of Escherichia coli O157:H7 was achieved by using a C70 modified TiO2 (C70-TiO2) hybrid as a photocatalyst under visible light (λ > 420 nm) irradiation. Disinfection experiments showed that 73% of E. coli O157:H7 died within 2 h with a disinfection rate constant of k = 0.01 min(-1), which is three times that measured for TiO2. The mechanism of cell death was investigated by using several scavengers combined with a partition system. The results revealed that diffusing hydroxyl radicals play an important role in the photocatalytically initiated bacterial death, and direct contact between C70-TiO2 hybrid and bacteria is not indispensable in the photocatalytic disinfection process. Extracellular polymeric substances (EPS) of bacteria have little effect on the disinfection efficiency. Analyses of the inhibitory effect of C70-TiO2 thin films on E. coli O157:H7 showed a decrease of the bacterial concentration from 3 × 10(8) to 38 cfu mL(-1) in the solution with C70-TiO2 thin film in the first 2 h of irradiation and a complete inhibition of the growth of E. coli O157:H7 in the later 24 h irradiation. PMID:27161821

  14. Ultrathin g-C3 N4 Nanosheets Coupled with AgIO3 as Highly Efficient Heterostructured Photocatalysts for Enhanced Visible-Light Photocatalytic Activity.

    PubMed

    Li, Yunfeng; Li, Kai; Yang, Yang; Li, Leijiao; Xing, Yan; Song, Shuyan; Jin, Rongchao; Li, Mei

    2015-12-01

    The photocatalytic activity of graphite-like carbon nitride (g-C3 N4 ) could be enhanced by heterojunction strategies through increasing the charge-separation efficiency. As a surface-based process, the heterogeneous photocatalytic process would become more efficient if a larger contact region existed in the heterojunction interface. In this work, ultrathin g-C3 N4 nanosheets (g-C3 N4 -NS) with much larger specific surface areas are employed instead of bulk g-C3 N4 (g-C3 N4 -B) to prepare AgIO3 /g-C3 N4 -NS nanocomposite photocatalysts. By taking advantage of this feature, the as-prepared composites exhibit remarkable performances for photocatalytic wastewater treatment under visible-light irradiation. Notably, the optimum photocatalytic activity of AgIO3 /g-C3 N4 -NS composites is almost 80.59 and 55.09 times higher than that of pure g-C3 N4 -B towards the degradation of rhodamine B and methyl orange pollutants, respectively. Finally, the stability and possible photocatalytic mechanism of the AgIO3 /g-C3 N4 -NS system are also investigated. PMID:26490265

  15. Visible light communication based motion detection.

    PubMed

    Sewaiwar, Atul; Tiwari, Samrat Vikramaditya; Chung, Yeon-Ho

    2015-07-13

    In this paper, a unique and novel visible light communication based motion detection is presented. The proposed motion detection is performed based on white light LEDs and an array of photodetectors from existing visible light communication (VLC) links, thus providing VLC with three functionalities of illumination, communication and motion detection. The motion is detected by observing the pattern created by intentional obstruction of the VLC link. Experimental and simulation results demonstrate the validity of the proposed VLC based motion detection technique. The VLC based motion detection can benefit smart devices control in VLC based smart home environments. PMID:26191937

  16. Damaging effects of visible light

    NASA Astrophysics Data System (ADS)

    Williams, T. P.; Baker, B. N.

    1982-02-01

    The right eyes of anesthetized, ten week old albino rats are exposed to constant photon fluxes at 6 wavelengths for 6 hours. The left eye of each animal is patched during the exposure and is used as control. Histologic examination of retinal sections disclosed a region in the superior retina which is more damaged than are other areas. Attempting to ascertain an action spectrum by measuring outer nuclear layer (ONL) lost in this sensitive region fails. However, it is shown that when ONL thickness is integrated over the entire retinal sections, a rhodopsin action-spectrum emerges. It is concluded that retinal light damage in the albina rat under these conditions is rhodopsin mediated; and assessment of the extent of damage is best made by some method which integrates over the entire retinal section. The latter methodology is not routinely incorporated into studies of retinal light-damage but probably should be.

  17. Efficient visible-light photocatalytic activity by band alignment in mesoporous ternary polyoxometalate-Ag2S-CdS semiconductors

    NASA Astrophysics Data System (ADS)

    Kornarakis, I.; Lykakis, I. N.; Vordos, N.; Armatas, G. S.

    2014-07-01

    Porous multicomponent semiconductor materials show improved photocatalytic performance due to the large and accessible pore surface area and high charge separation efficiency. Here we report the synthesis of well-ordered porous polyoxometalate (POM)-Ag2S-CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process. Ag2S compounds and polyoxometalate cluster anions with different reduction potentials, such as PW12O403-, SiW12O404- and PMo12O403-, were employed as electron acceptors in these ternary heterojunction photocatalysts. Characterization by small-angle X-ray scattering, X-ray diffraction, transmission electron microscopy and N2 physisorption measurements showed hexagonal arrays of POM-Ag2S-CdS hybrid nanorods with large internal BET surface areas and uniform mesopores. The Keggin structure of the incorporated POM clusters was also verified by elemental X-ray spectroscopy microanalysis, infrared and diffuse-reflectance ultraviolet-visible spectroscopy. These new porous materials were implemented as visible-light-driven photocatalysts, displaying exceptional high activity in aerobic oxidation of various para-substituted benzyl alcohols to the corresponding carbonyl compounds. Our experiments show that the spatial separation of photogenerated electrons and holes at CdS through the potential gradient along the CdS-Ag2S-POM interfaces is responsible for the increased photocatalytic activity.Porous multicomponent semiconductor materials show improved photocatalytic performance due to the large and accessible pore surface area and high charge separation efficiency. Here we report the synthesis of well-ordered porous polyoxometalate (POM)-Ag2S-CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process. Ag2S compounds and polyoxometalate cluster

  18. Olympus Mons In Visible Light

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This is a VIS image of the same location on the flank of Olympus Mons as the IR images of the past two days. At the higher resolution of the visible imager it is easy to see individual lava flows. Note that many flows have a central channel with raised edges and are fairly narrow, this is due to the slope of the volcano that the flow is running down.

    Image information: VIS instrument. Latitude 17.1, Longitude 230.2 East (129.8 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  19. Arsia Mons by Visible Light

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Last week we looked at Arsia Mons lava flows in the nighttime IR. Today's image looks at the same flows at visible wavelengths. This image illustrates the very rough surface texture of young flows, the overlapping nature of lava flows, and how the margins of overlapping flows trap windblown sand and dust. Note the subdued texture of the flow at the top of the image; not only does this flow contain more dust than the younger flow, but it also contains more impact craters.

    Image information: VIS instrument. Latitude -2.4, Longitude 221.8 East (138.2 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  20. Relating productivity to visibility and lighting

    SciTech Connect

    Clear, R.; Berman, S.

    1982-01-01

    The problem of determining the appropriate light levels for visual tasks is a cost-benefit problem. Existing light level recommendations seriously underweight the importance of economic factors. Furthermore, the relative importance of the visibility factors in determining the optimal light levels appears inconsistent with the importance of these factors in determining visibility and visual performance. It is shown that calculations based on acuities give a lower limit of 100 to 200 lux for cost-effective light levels for office tasks. Upper limits are calculated from correlations of task performance to visibility levels. Visibility levels become progressively insensitive to luminance as luminance increases. Average power densities above 100 watts/m/sup 2/ are cost-effective only when visibility is very low. However, there is a 3-to-10 times larger increase in benefits from improving contrast or contrast sensitivity than from using more than 10 watts/m/sup 2/. Contrast or contrast sensitivity can be improved by using forms with larger print, using xerographic copy instead of carbon or mimeo, making sure office workers have the right eyeglasses, or even by transferring workers with visual problems to less visually demanding tasks. Once these changes are made it is no longer cost-effective to use more than 10 watts/m/sup 2/. This conclusion raises serious questions about recommendations that lead to greater than about 10 watts/m/sup 2/ of installed lighting for general office work.

  1. Solid-Phase Synthesis as a Platform for the Discovery of New Ruthenium Complexes for Efficient Release of Photocaged Ligands with Visible Light

    PubMed Central

    Sharma, Rajgopal; Knoll, Jessica D.; Ancona, Nicholas; Martin, Phillip D.; Turro, Claudia; Kodanko, Jeremy J.

    2015-01-01

    Ruthenium-based photocaging groups have important applications as biological tools and show great potential as therapeutics. A method was developed to rapidly synthesize, screen and identify ruthenium-based caging groups that release nitriles upon irradiation with visible light. A diverse library of tetra- and pentadentate ligands was synthesized on polystyrene resin. Ruthenium complexes of the general formula [Ru(L)(MeCN)n]m+ (n = 1–3, m = 1–2) were generated from these ligands on solid phase, then cleaved from resin for photochemical analysis. Data indicate a wide range of spectral tuning and reactivity with visible light. Three complexes that showed strong absorbance in the visible range were synthesized by solution phase for comparison. Photochemical behavior of solution- and solid-phase complexes was in good agreement, confirming that the library approach is useful in identifying candidates with desired photoreactivity in short order, avoiding time consuming chromatography and compound purification. PMID:25611351

  2. Measuring scintillation light using Visible Light Photon Counters (VLPC)

    NASA Astrophysics Data System (ADS)

    Chavarria, Alvaro

    2006-10-01

    A new search for the neutron electric dipole moment (EDM) using ultra cold neutrons proposes an improvement on the neutron EDM by two orders of magnitude over the current limit (to 10-28 e*cm). Detection of scintillation light in superfluid ^4He is at the heart of this experiment.One possible scheme to detect this light is to use wavelength-shifting fibers in the superfluid ^4He to collect the scintillation light and transport it out of the measuring cell. The fiber terminates in a visible light photon counter (VLPC). VLPCs are doped, silicon based, solid state photomultipliers with high quantum efficiency (up to 80%) and high gain ( 40000 electrons per converted photon). Moreover, they are insensitive to magnetic fields and operate at temperatures of 6.5K.A test setup has been assembled at Duke University using acrylic cells wrapped in wavelength-shifting fibers that terminate on VLPCs. This setup is being used to evaluate the feasibility of this light detection scheme. The results obtained in multiple experiments done over the past summer (2006) and the current status of the project will be presented at the conference.Reference:A New Search for the Neutron Electric Dipole Moment, funding pre-proposal by the EDM collaboration; R. Golub and S. Lamoreaux, Phys. Rep. 237, 1 (1994).

  3. Visible Light Wireless Communication for Audio Signals

    NASA Astrophysics Data System (ADS)

    Vibin, A. M.; Prince, Shanthi

    2011-10-01

    In the current century there is an increased demand for broad band wireless access for satisfying different customer needs. These applications requires large amount of frequency resources for its efficient implementation. Radio Frequency techniques, which dominate the current wireless technology, have the limitation of available frequency spectrum that can be used. Researchers identified Optical Wireless Communication as a potential candidate for solving this problem. Studies shows that white light can also be used as a carrier for wireless communication and this area is generally known as Visible Light Communication. The provision of voice data and visual communications to users by using optical wireless has become a key area of research and product development. This paper discusses a novel method for transmission of voice in real time so that the system can be used for both communication and illumination simultaneously. A prototype of the system is implemented successfully and performance analyses are carried out based on the experimental results. SNR and BER calculations for the designed system is done theoretically and simulated. The developed system is having the advantages of very high band width, no interference with adjacent rooms as walls are opaque, no license is required as it doesn't cause electromagnetic interference and communication simultaneously with illumination.

  4. Optical bidirectional beacon based visible light communications.

    PubMed

    Tiwari, Samrat Vikramaditya; Sewaiwar, Atul; Chung, Yeon Ho

    2015-10-01

    In an indoor bidirectional visible light communications (VLC), a line-of-sight (LOS) transmission plays a major role in obtaining adequate performance of a VLC system. Signals are often obstructed in the LOS transmission path, causing an effect called optical shadowing. In the absence of LOS, the performance of the VLC system degrades significantly and, in particular, at uplink transmission this degradation becomes severe due to design constraints and limited power at uplink devices. In this paper, a novel concept and design of an optical bidirectional beacon (OBB) is presented as an efficient model to counter the performance degradation in a non-line-of-sight (NLOS) VLC system. OBB is an independent operating bidirectional transceiver unit installed on walls, composed of red, green, and blue (RGB) light emitting diodes (LEDs), photodetectors (PDs) and color filters. OBB improves the coverage area in the form of providing additional or alternate paths for transmission and enhances the performance of the VLC system in terms of bit error rate (BER). To verify the effectiveness of the proposed system, simulations were carried out under optical shadowing conditions at various locations in an indoor environment. The simulation results and analysis show that the implementation of OBB improves the performance of the VLC system significantly, especially when the LOS bidirectional transmission paths are completely or partially obstructed. PMID:26480168

  5. TiO2/carboxylate-rich porous carbon: A highly efficient visible-light-driven photocatalyst based on the ligand-to-metal charge transfer (LMCT) process

    NASA Astrophysics Data System (ADS)

    Qu, Lingling; Huang, Dongliang; Shi, Hefei; Gu, Mengbin; Li, Jilei; Dong, Fei; Luo, Zhijun

    2015-10-01

    A novel visible-light-driven photocatalyst based on TiO2/carboxylate-rich porous carbon composite (TiO2/CRPC) was successfully synthesized by low temperature carbonization process in air. Sodium gluconate plays a crucial role in the formation of TiO2/CRPC. Different functional groups of sodium gluconate play synergetic roles in the formation of TiO2/CRPC. XRD and Raman spectra studies indicated that there are two different TiO2 crystalline phases existing in TiO2/CRPC, which are anatase and brookite, and the CRPC is amorphous. Via FT-IR and XPS spectra investigations, it was demonstrated that carboxylate group, the ligand-to-metal charge transfer (LMCT) forming functional group, was solidified into the CRPC and form the LMCT complex on TiO2 surface through the fabrication of TiO2/CRPC. Compared with the pure TiO2, TiO2/CRPC exhibit enhanced absorption in the UV and visible light region around 260-600 nm. The strong absorption in the visible light region gives TiO2/CRPC advantages over pure TiO2 for the degradation of organic pollutants. TiO2/CRPC can activate O2 in air under mild conditions and exhibit excellent visible-light-driven photocatalytic activities. However, TiO2/C composite obtained by using glucose instead of sodium gluconate exhibits poor photocatalytic activity, which demonstrated that carboxylate-TiO2 complexes are responsible for the prominent photocatalytic properties of TiO2/CRPC under visible light irradiation.

  6. Rhenium complexes with visible-light-induced anticancer activity.

    PubMed

    Kastl, Anja; Dieckmann, Sandra; Wähler, Kathrin; Völker, Timo; Kastl, Lena; Merkel, Anna Lena; Vultur, Adina; Shannan, Batool; Harms, Klaus; Ocker, Matthias; Parak, Wolfgang J; Herlyn, Meenhard; Meggers, Eric

    2013-06-01

    Shedding light on the matter: Rhenium(I) indolato complexes with highly potent visible-light-triggered antiproliferative activity (complex 1: EC50 light=0.1 μM vs EC50 dark=100 μM) in 2D- and 3D-organized cancer cells are reported and can be traced back to an efficient generation of singlet oxygen, causing rapid morphological changes and an induction of apoptosis. PMID:23568508

  7. A novel p-n heterostructured photocatalyst for the efficient photocatalytic degradation of different kinds of organic compounds under irradiation of both ultraviolet and visible light.

    PubMed

    Ao, Yanhui; Bao, Jiaqiu; Wang, Peifang; Wang, Chao; Hou, Jun

    2016-09-21

    In this study, BiOBr-titanium phosphate (BiOBr/TP) plate-on-plate composites with p-n heterojunctions were synthesized using a simple, feasible two-step method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and UV-vis diffuse reflectance spectrometry (DRS) were used to evaluate the structure, morphology and optical properties of the composites. Rhodamine B (RhB) and ciprofloxacin (CIP) were chosen as model pollutants to evaluate the photocatalytic activity of the synthesized samples under irradiation of both ultraviolet and visible light. The BiOBr/TP composites exhibited much higher photocatalytic activity for the degradation of both pollutants than pure TP. The enhanced photocatalytic performance can be ascribed to the formed p-n heterojunctions between p-type BiOBr and n-type TP, which efficiently reduced the recombination rate of photo-excited electrons and holes. Moreover, a possible photocatalytic mechanism of organic pollutant degradation by the obtained samples was presented in detail. PMID:27523034

  8. Efficient removal of radioactive iodide ions from water by three-dimensional Ag2O-Ag/TiO2 composites under visible light irradiation.

    PubMed

    Liu, Shuaishuai; Wang, Na; Zhang, Yuchang; Li, Yaru; Han, Zhuo; Na, Ping

    2015-03-01

    Three-dimensional Ag2O and Ag co-loaded TiO2 (3D Ag2O-Ag/TiO2) composites have been synthesized through a facile method, characterized using SEM, EDX, TEM, XRD, XPS, UV-vis DRS, BET techniques, and applied to remove radioactive iodide ions (I(-)). The photocatalytic adsorption capacity (207.6 mg/g) of the 3D Ag2O-Ag/TiO2 spheres under visible light is four times higher than that in the dark, which is barely affected by other ions, even in simulated salt lake water where the concentration of Cl(-) is up to 590 times that of I(-). The capability of the composites to remove even trace amounts of I(-) from different types of water, e.g., deionized or salt lake water, is demonstrated. The composites also feature good reusability, as they were separated after photocatalytic adsorption and still performed well after a simple regeneration. Furthermore, a mechanism explaining the highly efficient removal of radioactive I(-) has been proposed according to characterization analyses of the composites after adsorption and subsequently been verified by adsorption and desorption experiments. The proposed cooperative effects mechanism considers the interplay of three different phenomena, namely, the adsorption performance of Ag2O for I(-), the photocatalytic ability of Ag/TiO2 for oxidation of I(-), and the readsorption performance of AgI for I2. PMID:25463231

  9. Hierarchical Integration of Photosensitizing Metal-Organic Frameworks and Nickel-Containing Polyoxometalates for Efficient Visible-Light-Driven Hydrogen Evolution.

    PubMed

    Kong, Xiang-Jian; Lin, Zekai; Zhang, Zhi-Ming; Zhang, Teng; Lin, Wenbin

    2016-05-23

    Metal-organic frameworks (MOFs) provide a tunable platform for hierarchically integrating multiple components to effect synergistic functions that cannot be achieved in solution. Here we report the encapsulation of a Ni-containing polyoxometalate (POM) [Ni4 (H2 O)2 (PW9 O34 )2 ](10-) (Ni4 P2 ) into two highly stable and porous phosphorescent MOFs. The proximity of Ni4 P2 to multiple photosensitizers in Ni4 P2 @MOF allows for facile multi-electron transfer to enable efficient visible-light-driven hydrogen evolution reaction (HER) with turnover numbers as high as 1476. Photophysical and electrochemical studies established the oxidative quenching of the excited photosensitizer by Ni4 P2 as the initiating step of HER and explained the drastic catalytic activity difference of the two POM@MOFs. Our work shows that POM@MOF assemblies not only provide a tunable platform for designing highly effective photocatalytic HER catalysts but also facilitate detailed mechanistic understanding of HER processes. PMID:27094346

  10. Broadband polygonal invisibility cloak for visible light.

    PubMed

    Chen, Hongsheng; Zheng, Bin

    2012-01-01

    Invisibility cloaks have recently become a topic of considerable interest thanks to the theoretical works of transformation optics and conformal mapping. The design of the cloak involves extreme values of material properties and spatially dependent parameter tensors, which are very difficult to implement. The realization of an isolated invisibility cloak in the visible light, which is an important step towards achieving a fully movable invisibility cloak, has remained elusive. Here, we report the design and experimental demonstration of an isolated polygonal cloak for visible light. The cloak is made of several elements, whose electromagnetic parameters are designed by a linear homogeneous transformation method. Theoretical analysis shows the proposed cloak can be rendered invisible to the rays incident from all the directions. Using natural anisotropic materials, a simplified hexagonal cloak which works for six incident directions is fabricated for experimental demonstration. The performance is validated in a broadband visible spectrum. PMID:22355767

  11. Broadband polygonal invisibility cloak for visible light

    PubMed Central

    Chen, Hongsheng; Zheng, Bin

    2012-01-01

    Invisibility cloaks have recently become a topic of considerable interest thanks to the theoretical works of transformation optics and conformal mapping. The design of the cloak involves extreme values of material properties and spatially dependent parameter tensors, which are very difficult to implement. The realization of an isolated invisibility cloak in the visible light, which is an important step towards achieving a fully movable invisibility cloak, has remained elusive. Here, we report the design and experimental demonstration of an isolated polygonal cloak for visible light. The cloak is made of several elements, whose electromagnetic parameters are designed by a linear homogeneous transformation method. Theoretical analysis shows the proposed cloak can be rendered invisible to the rays incident from all the directions. Using natural anisotropic materials, a simplified hexagonal cloak which works for six incident directions is fabricated for experimental demonstration. The performance is validated in a broadband visible spectrum. PMID:22355767

  12. Why can we see visible light?

    NASA Astrophysics Data System (ADS)

    Bochnícek, Zdenek

    2007-01-01

    Visible light constitutes only a very narrow part of the wide electromagnetic spectrum. This article outlines several reasons why the human eye can see only within this limited range. Solar emissions and low absorption in the atmosphere are determining causes, but not the only ones. The energy of chemical bonds, the optical properties of matter, black body emissions and the wave character of light cause further limitations, all of which have a remarkable congruence.

  13. Solvothermal synthesis of stable nanoporous polymeric bases-crystalline TiO2 nanocomposites: visible light active and efficient photocatalysts for water treatment

    NASA Astrophysics Data System (ADS)

    Liu, Fujian; Kong, Weiping; Wang, Liang; Noshadi, Iman; Zhang, Zhonghua; Qi, Chenze

    2015-02-01

    Visible light active and stable nanoporous polymeric base-crystalline TiO2 nanocomposites were solvothermally synthesized from in situ copolymerization of divinylbenzene (DVB) with 1-vinylimidazolate (VI) or 4-vinylpyridine (Py) in the presence of tetrabutyl titanate without the use of any other additives (PDVB-VI-TiO2-x, PDVB-Py-TiO2-x, where x stands for the molar ratio of TiO2 to VI or Py), which showed excellent activity with respect to catalyzing the degradation of organic pollutants of p-nitrophenol (PNP) and rhodamine-B (RhB). TEM and SEM images show that PDVB-VI-TiO2-x and PDVB-Py-TiO2-x have abundant nanopores, and TiO2 nanocrystals with a high degree of crystallinity were homogeneously embedded in the PDVB-VI-TiO2-x and PDVB-Py-TiO2-x, forming a stable ‘brick-and-mortar’ nanostructure. PDVB-VI and PDVB-Py supports act as the glue linking TiO2 nanocrystals to form nanopores and constraining the agglomeration of TiO2 nanocrystals. XPS spectra show evidence of unique interactions between TiO2 and basic sites in these samples. UV diffuse reflectance shows that PDVB-VI-TiO2-x and PDVB-Py-TiO2-x exhibit a unique response to visible light. Catalytic tests show that the PDVB-VI-TiO2-x and PDVB-Py-TiO2-x were active in catalyzing the degradation of PNP and RhB organic pollutants under visible light irradiation. The enhanced activities of the PDVB-VI-TiO2-x and PDVB-Py-TiO2-x were ascribed to synergistic effects between abundant nanopores and the unique optical adsorption of visible light in the samples.

  14. Solvothermal synthesis of stable nanoporous polymeric bases-crystalline TiO2 nanocomposites: visible light active and efficient photocatalysts for water treatment.

    PubMed

    Liu, Fujian; Kong, Weiping; Wang, Liang; Noshadi, Iman; Zhang, Zhonghua; Qi, Chenze

    2015-02-27

    Visible light active and stable nanoporous polymeric base-crystalline TiO2 nanocomposites were solvothermally synthesized from in situ copolymerization of divinylbenzene (DVB) with 1-vinylimidazolate (VI) or 4-vinylpyridine (Py) in the presence of tetrabutyl titanate without the use of any other additives (PDVB-VI-TiO2-x, PDVB-Py-TiO2-x, where x stands for the molar ratio of TiO2 to VI or Py), which showed excellent activity with respect to catalyzing the degradation of organic pollutants of p-nitrophenol (PNP) and rhodamine-B (RhB). TEM and SEM images show that PDVB-VI-TiO2-x and PDVB-Py-TiO2-x have abundant nanopores, and TiO2 nanocrystals with a high degree of crystallinity were homogeneously embedded in the PDVB-VI-TiO2-x and PDVB-Py-TiO2-x, forming a stable 'brick-and-mortar' nanostructure. PDVB-VI and PDVB-Py supports act as the glue linking TiO2 nanocrystals to form nanopores and constraining the agglomeration of TiO2 nanocrystals. XPS spectra show evidence of unique interactions between TiO2 and basic sites in these samples. UV diffuse reflectance shows that PDVB-VI-TiO2-x and PDVB-Py-TiO2-x exhibit a unique response to visible light. Catalytic tests show that the PDVB-VI-TiO2-x and PDVB-Py-TiO2-x were active in catalyzing the degradation of PNP and RhB organic pollutants under visible light irradiation. The enhanced activities of the PDVB-VI-TiO2-x and PDVB-Py-TiO2-x were ascribed to synergistic effects between abundant nanopores and the unique optical adsorption of visible light in the samples. PMID:25656872

  15. Electrodeposition of hierarchical ZnO/Cu{sub 2}O nanorod films for highly efficient visible-light-driven photocatalytic applications

    SciTech Connect

    Ren, S. T.; Fan, G. H.; Liang, M. L.; Wang, Q.; Zhao, G. L.

    2014-02-14

    The development of high-performance visible-light-responsive photocatalytic materials has attracted widespread interest due to their potential applications in the environmental and energy industries. In this work, hierarchical ZnO nanorods films were successfully prepared on the stainless steel mesh substrates via a simple two-step seed-assisted electrodeposition route. Cu{sub 2}O nanoparticles were then electrodeposited on the surface of ZnO nanorods to form the core-shell heterostructure. The synthesized ZnO/Cu{sub 2}O nanocomposites were characterized by X-ray diffraction, field-emission scanning electron microscopy, and UV-visible spectrophotometer. Due to the branched hierarchical morphologies and core-shell structure, ZnO/Cu{sub 2}O nanomaterials show a prominent visible-light-driven photocatalytic performance under the low-intensity light irradiation (40 mW/cm{sup 2}). The influence of some experimental parameters, such as Cu{sub 2}O loading amount, ZnO morphologies, the substrate type, and the PH of the Cu{sub 2}O precursor solution on ZnO/Cu{sub 2}O photocatalytic performance was evaluated.

  16. High efficient photocatalytic selective oxidation of benzyl alcohol to benzaldehyde by solvothermal-synthesized ZnIn2S4 microspheres under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Chen, Zhixin; Xu, Jingjing; Ren, Zhuyun; He, Yunhui; Xiao, Guangcan

    2013-09-01

    Hexagonal ZnIn2S4 samples have been synthesized by a solvothermal method. Their properties have been determined by X-ray diffraction, ultraviolet-visible-light diffuse reflectance spectra, field emission scanning electron microscopy, nitrogen adsorption-desorption and X-ray photoelectron spectra. These results demonstrate that ethanol solvent has significant influence on the morphology, optical and electronic nature for such marigold-like ZnIn2S4 microspheres. The visible light photocatalytic activities of the ZnIn2S4 have been evaluated by selective oxidation of benzyl alcohol to benzaldehyde using molecular oxygen as oxidant. The results show that 100% conversion along with >99% selectivity are reached over ZnIn2S4 prepared in ethanol solvent under visible light irradiation (λ>420 nm) of 2 h, but only 58% conversion and 57% yield are reached over ZnIn2S4 prepared in aqueous solvent. A possible mechanism of the high photocatalytic activity for selective oxidation of benzyl alcohol over ZnIn2S4 is proposed and discussed.

  17. Visible-Light-Activated Molecular Switches.

    PubMed

    Bléger, David; Hecht, Stefan

    2015-09-21

    The ability to influence key properties of molecular systems by using light holds much promise for the fields of materials science and life sciences. The cornerstone of such systems is molecules that are able to reversibly photoisomerize between two states, commonly referred to as photoswitches. One serious restriction to the development of functional photodynamic systems is the necessity to trigger switching in at least one direction by UV light, which is often damaging and penetrates only partially through most media. This review provides a summary of the different conceptual strategies for addressing molecular switches in the visible and near-infrared regions of the optical spectrum. Such visible-light-activated molecular switches tremendously extend the scope of photoswitchable systems for future applications and technologies. PMID:26096635

  18. Highly efficient visible-light-induced photocatalytic activity of Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterojunction photocatalysts

    SciTech Connect

    Chaiwichian, Saranyoo; Inceesungvorn, Burapat; Wetchakun, Khatcharin; Phanichphant, Sukon; Kangwansupamonkon, Wiyong; Wetchakun, Natda

    2014-06-01

    Highlights: • Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterojunction photocatalysts were obtained using hydrothermal method. • Physicochemical properties played a significant role on photocatalytic efficiency. • Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterogeneous structures were greatly enhanced for degradation of MB. • A tentative mechanism of charge transfer process in MB degradation was proposed. - Abstract: The Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterojunction photocatalysts were synthesized by hydrothermal method. Physical properties of the heterojunction photocatalyst samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The XRD results indicated that BiVO{sub 4} retain monoclinic and tetragonal structures, while Bi{sub 2}WO{sub 6} presented as orthorhombic structure. The Brunauer, Emmett and Teller (BET) adsorption–desorption of nitrogen gas for specific surface area determination at the temperature of liquid nitrogen was performed on all samples. UV–vis diffuse reflectance spectra (UV–vis DRS) were used to identify the absorption range and band gap energy of the heterojunction photocatalysts. The photocatalytic performance of Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterojunction photocatalysts was studied via the photodegradation of methylene blue (MB) under visible light irradiation. The results indicated that the heterojunction photocatalyst at 0.5:0.5 mole ratio of Bi{sub 2}WO{sub 6}:BiVO{sub 4} shows the highest photocatalytic activity.

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

    PubMed

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

    2016-01-18

    A diarylethene photoswitch was covalently connected to two small triplet sensitizer moieties in a conjugated and nonconjugated fashion and the photochromic performance of the resulting compounds was investigated. In comparison with the parent diarylethene (without sensitizers) and one featuring saturated linkages, the conjugated photoswitch offers superior fatigue resistance upon visible-light excitation due to effective triplet energy transfer from the biacetyl termini to the diarylethene core. Our design makes it possible to switch diarylethenes with visible light in both directions in a highly efficient and robust fashion based on extending π-conjugation and by-product-free ring-closure via the triplet manifold. PMID:26662470

  20. High efficient photocatalytic selective oxidation of benzyl alcohol to benzaldehyde by solvothermal-synthesized ZnIn{sub 2}S{sub 4} microspheres under visible light irradiation

    SciTech Connect

    Chen, Zhixin; Xu, Jingjing; Ren, Zhuyun; He, Yunhui; Xiao, Guangcan

    2013-09-15

    Hexagonal ZnIn{sub 2}S{sub 4} samples have been synthesized by a solvothermal method. Their properties have been determined by X-ray diffraction, ultraviolet–visible-light diffuse reflectance spectra, field emission scanning electron microscopy, nitrogen adsorption–desorption and X-ray photoelectron spectra. These results demonstrate that ethanol solvent has significant influence on the morphology, optical and electronic nature for such marigold-like ZnIn{sub 2}S{sub 4} microspheres. The visible light photocatalytic activities of the ZnIn{sub 2}S{sub 4} have been evaluated by selective oxidation of benzyl alcohol to benzaldehyde using molecular oxygen as oxidant. The results show that 100% conversion along with >99% selectivity are reached over ZnIn{sub 2}S{sub 4} prepared in ethanol solvent under visible light irradiation (λ>420 nm) of 2 h, but only 58% conversion and 57% yield are reached over ZnIn{sub 2}S{sub 4} prepared in aqueous solvent. A possible mechanism of the high photocatalytic activity for selective oxidation of benzyl alcohol over ZnIn{sub 2}S{sub 4} is proposed and discussed. - Graphical abstract: Marigold-like ZnIn{sub 2}S{sub 4} microspheres were synthesized by a solvothermal method. The high visible photocatalytic activities of ZnIn{sub 2}S{sub 4} were evaluated by selective oxidation of benzyl alcohol to benzaldehyde under mild conditions. Display Omitted - Highlights: • Marigold-like ZnIn{sub 2}S{sub 4} microspheres were synthesized by a solvothermal method. • The solvents have a remarkably influence on the morphology and properties of samples. • It is the first time to apply ZnIn{sub 2}S{sub 4} for selective oxidation of benzyl alcohol. • ZnIn{sub 2}S{sub 4} shows high photocatalytic activity for selective oxidation of benzyl alcohol.

  1. Fabrication and photocatalytic activity of high-efficiency visible-light-responsive photocatalyst ZnTe/TiO{sub 2} nanotube arrays

    SciTech Connect

    Liu Yutang; Liu Chengbin

    2011-03-15

    A new ZnTe modified TiO{sub 2} nanotube (NT) array catalyst was prepared by pulse potential electrodeposition of ZnTe nanoparticles (NPs) onto TiO{sub 2} NT arrays, and its application for photocatalytic degradation of anthracene-9-carboxylic acid (9-AnCOOH) was investigated. The even distribution of ZnTe NPs was well-proportionately grown on the top surface of the TiO{sub 2} NT while without clogging the tube entrances. Compared with the unmodified TiO{sub 2} NT, the ZnTe modified TiO{sub 2} NT (ZnTe/TiO{sub 2} NT) showed significantly enhanced photocatalytic activity towards 9-AnCOOH under simulated solar light. After 70 min of irradiation, 9-AnCOOH was degraded with the removal ratio of 45% on the bare TiO{sub 2} NT, much lower than 80%, 90%, and 100% on the ZnTe/TiO{sub 2} NT with the ZnTe NPs prepared under the pulsed 'on' potentials of -0.8, -1.0, and -2.0 V, respectively. The increased photodegradation efficiency mainly results from the improved photocurrent density as results of enhanced visible-light absorption and decreased hole-electron recombination due to the presence of narrow-band-gap p-type semiconductor ZnTe. -- Graphical abstract: Surface-view SEM images of ZnTe/TiO{sub 2} NT prepared under -2.0 V, and the inset is the corresponding enlarged drawings. Display Omitted Research highlights: {yields} A new method to deposit chalcogenides of transition metals on the TiO{sub 2} nanotubes. {yields} The even distribution of ZnTe nanoparticles was well-proportionedly grown onto TiO{sub 2} NT arrays. {yields} ZnTe/TiO{sub 2} NT showed remarkably increased photocurrent density. {yields} ZnTe/TiO{sub 2} NT showed good photocatalytic performance. {yields} The prepared new catalyst has a promising application in practical systems.

  2. Green synthetic approach for Ti3+ self-doped TiO2-x nanoparticles with efficient visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Gao, Shanmin; Xu, Hui; Lou, Zaizhu; Wang, Wenjun; Huang, Baibiao; Dai, Ying

    2013-02-01

    Rice-shaped Ti3+ self-doped TiO2-x nanoparticles were synthesized by mild hydrothermal treatment of TiH2 in H2O2 aqueous solution. The structure, crystallinity, morphology, and other properties of the as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microcopy and X-ray photoelectron spectra. Electron paramagnetic resonance spectra confirm the presence of high concentration of paramagnetic Ti3+ in the bulk and surface of the as-prepared samples. The particles showed a strong absorption across the UV to the visible light region and retained their light-blue color upon storage in ambient atmosphere or water for one month at 40 °C. The formation mechanism of Ti3+ self-doped TiO2-x nanoparticles was discussed. Under visible light irradiation, the samples exhibit higher photocatalytic activity for hydrogen evolution and photooxidation of methylene blue than that of the commercial P25 TiO2 nanoparticles. The sample obtained at 160 °C for 27 h showed a 9-fold enhancement for the visible light decomposition of methylene blue and 12.5 times higher for H2 production in comparison to P25 TiO2. The samples also showed an excellent cycling stability of the photocatalytic activity.Rice-shaped Ti3+ self-doped TiO2-x nanoparticles were synthesized by mild hydrothermal treatment of TiH2 in H2O2 aqueous solution. The structure, crystallinity, morphology, and other properties of the as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microcopy and X-ray photoelectron spectra. Electron paramagnetic resonance spectra confirm the presence of high concentration of paramagnetic Ti3+ in the bulk and surface of the as-prepared samples. The particles showed a strong absorption across the UV to the visible light region and retained their light-blue color upon storage in ambient atmosphere or water for one month at 40 °C. The

  3. Copper(II) imidazolate frameworks as highly efficient photocatalysts for reduction of CO{sub 2} into methanol under visible light irradiation

    SciTech Connect

    Li, Jingtian; Luo, Deliang; Yang, Chengju; He, Shiman; Chen, Shangchao; Lin, Jiawei; Zhu, Li; Li, Xin

    2013-07-15

    Three copper(II) imidazolate frameworks were synthesized by a hydrothermal (or precipitation) reaction. The catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), Fourier transform infrared spectra (FTIR), thermogravimetry (TG). Meanwhile, the photocatalytic activities of the samples for reduction of CO{sub 2} into methanol and degradation of methylene blue (MB) under visible light irradiation were also investigated. The results show that the as-prepared samples exhibit better photocatalytic activities for the reduction of carbon dioxide into methanol with water and degradation of MB under visible light irradiation. The orthorhombic copper(II) imidazolate frameworks with a band gap of 2.49 eV and green (G) color has the best photocatalytic activity for reduction of CO{sub 2} into methanol, 1712.7 μmol/g over 5 h, which is about three times as large as that of monoclinic copper(II) imidazolate frameworks with a band gap 2.70 eV and blue (J) color. The degradation kinetics of MB over three photocatalysts fitted well to the apparent first-order rate equation and the apparent rate constants for the degradation of MB over G, J and P (with pink color) are 0.0038, 0.0013 and 0.0016 min{sup −1}, respectively. The synergistic effects of smallest band gap and orthorhombic crystal phase structure are the critical factors for the better photocatalytic activities of G. Moreover, three frameworks can also be stable up to 250 °C. The investigation of Cu-based zeolitic imidazolate frameworks maybe provide a design strategy for a new class of photocatalysts applied in degradation of contaminations, reduction of CO{sub 2}, and even water splitting into hydrogen and oxygen under visible light. - Graphical abstract: Carbon dioxide was reduced into methanol with water over copper(II) imidazolate frameworks under visible light irradiation. - Highlights: • Three copper

  4. Visible light communications with compound spectra

    NASA Astrophysics Data System (ADS)

    Vitasek, Jan; Vasinek, Vladimir; Latal, Jan; Hajek, Lukas

    2016-03-01

    At present the Visible Light Communications (VLC) attract attention of academia and industry thanks to rapid progress in the development of white light emitting diodes (LED). This article deals with the VLC and proposes their new solution, which may help remove some lacks of the current VLC. The substance of the new VLC solution is purposeful suppression of a part of the spectrum by a notch filter and by subsequent reconstruction of the original spectrum. Thus, only a part of the visible spectrum will transmit the information data. This is the main difference in comparison with the current VLC. This might be the way how the crucial parameters of the VLC may be improved.

  5. Synthesis and photocatalytic performance of an efficient Ag@AgBr/K{sub 2}Ti{sub 4}O{sub 9} composite photocatalyst under visible light

    SciTech Connect

    Liang, Yinghua; Lin, Shuanglong; Liu, Li; Hu, Jinshan; Cui, Wenquan

    2014-08-15

    Highlights: • The plasmatic Ag@AgBr sensitized K{sub 2}Ti{sub 4}O{sub 9} composite photocatalysts. • Ag@AgBr greatly increased visible light absorption for K{sub 2}Ti{sub 4}O{sub 9}. • The plamonic photocatalysts exhibited enhanced activity for the degradation of RhB. - Abstract: Ag@AgBr nanoparticle-sensitized K{sub 2}Ti{sub 4}O{sub 9} composite photocatalysts (Ag@AgBr/K{sub 2}Ti{sub 4}O{sub 9}) were prepared by a facile precipitation–photoreduction method. The photocatalytic activities of the Ag@AgBr/K{sub 2}Ti{sub 4}O{sub 9} nanocomposites were evaluated for photocatalytic degradation of (RhB) under visible light irradiation. The composites exhibited excellent visible light absorption, which was attributable to the surface plasmon effect of Ag nanoparticles. The Ag@AgBr was uniformly scattered on the surface of K{sub 2}Ti{sub 4}O{sub 9} and possessed sizes in the range of 20–50 nm. The loading amount of Ag@AgBr was also studied, and was found to influence the absorption spectra of the resulting composites. Approximately 95.9% of RhB was degraded by Ag@AgBr (20 wt.%)/K{sub 2}Ti{sub 4}O{sub 9} after irradiation for 1 h. The stability of the material was also investigated by performing consecutive runs. Additionally, studies performed using radical scavengers indicated that ·O{sub 2}{sup −} and Br{sup 0} acted as the main reactive species. Based on the experimental results, a photocatalytic mechanism for organics degradation over Ag@AgBr/K{sub 2}Ti{sub 4}O{sub 9} photocatalysts was proposed.

  6. Co doped ZnO nanowires as visible light photocatalysts

    NASA Astrophysics Data System (ADS)

    Šutka, Andris; Käämbre, Tanel; Pärna, Rainer; Juhnevica, Inna; Maiorov, Mihael; Joost, Urmas; Kisand, Vambola

    2016-06-01

    High aspect ratio cobalt doped ZnO nanowires showing strong photocatalytic activity and moderate ferromagnetic behaviour were successfully synthesized using a solvothermal method and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), vibrating sample magnetometry (VSM) and UV-visible absorption spectroscopy. The photocatalytic activities evaluated for visible light driven degradation of an aqueous methylene orange (MO) solution were higher than for Co doped ZnO nanoparticles at the same doping level and synthesized by the same synthesis route. The rate constant for MO visible light photocatalytic degradation was 1.9·10-3 min-1 in case of nanoparticles and 4.2·10-3 min-1 in case of nanowires. We observe strongly enhanced visible light photocatalytic activity for moderate Co doping levels, with an optimum at a composition of Zn0.95Co0.05O. The enhanced photocatalytic activities of Co doped ZnO nanowires were attributed to the combined effects of enhanced visible light absorption at the Co sites in ZnO nanowires, and improved separation efficiency of photogenerated charge carriers at optimal Co doping.

  7. Large-scale synthesis of ultrathin tungsten oxide nanowire networks: an efficient catalyst for aerobic oxidation of toluene to benzaldehyde under visible light.

    PubMed

    Bai, Hua; Yi, Wencai; Liu, Jingyao; Lv, Qing; Zhang, Qing; Ma, Qiang; Yang, Haifeng; Xi, Guangcheng

    2016-07-14

    As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%. PMID:27357748

  8. Hierarchical three-dimensional branched hematite nanorod arrays with enhanced mid-visible light absorption for high-efficiency photoelectrochemical water splitting.

    PubMed

    Wang, Degao; Chang, Guoliang; Zhang, Yuying; Chao, Jie; Yang, Jianzhong; Su, Shao; Wang, Lihua; Fan, Chunhai; Wang, Lianhui

    2016-07-01

    Herein, we presented hierarchical three-dimensional (3D) branched hematite nanorod arrays (NAs) on transparent fluorine-doped tin oxide (FTO) conductive glass substrates, which exhibited high PEC water splitting performance due to the enhancement of mid-visible light harvesting as well as charge separation and transfer. The introduction of a TiO2 underlayer made the as-prepared 3D branched hematite NAs achieve a photocurrent density of 0.61 mA cm(-2) at 1.23 V vs. reversible hydrogen electrode (RHE) without high-temperature activation. PMID:27283270

  9. Surface reconstruction of titania with g-C3N4 and Ag for promoting efficient electrons migration and enhanced visible light photocatalysis

    NASA Astrophysics Data System (ADS)

    Leong, Kah Hon; Liu, Sze Ling; Sim, Lan Ching; Saravanan, Pichiah; Jang, Min; Ibrahim, Shaliza

    2015-12-01

    The developments of heterogeneous photocatalysts are one among the competent reconstruction approach to enrich the visible light responsiveness of conventional TiO2. In the present work the TiO2 was reconstructed with graphitic carbon nitride (g-C3N4) and silver (Ag) to form a ternary (g-C3N4)-Ag/TiO2. The graphitic carbon nitride an intriguing material was prepared through a facile pyrolysis by using urea as a precursor. The silver (Ag) that plays a role as electron-conduction mobiliser in the ternary was synthesised through solar mediated photodeposition method. The synthesised ternary composite characteristics were thoroughly investigated through various physical and chemical analyses. The presence of g-C3N4 in the ternary photocatalysts promoted the formation of interface between the Ag/TiO2 and g-C3N4 and stimulated the electron transfer between them. These electrons migration acknowledged by the synergic effect prolonged the lifetime of charge carriers. The g-C3N4 also significantly tuned the energy band of conventional TiO2. The prepared ternary exhibited significantly high visible light photocatalytic performance by degrading Amoxicillin (AMX) a poor photosensitising pollutant at highest rate.

  10. Hierarchical three-dimensional branched hematite nanorod arrays with enhanced mid-visible light absorption for high-efficiency photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Wang, Degao; Chang, Guoliang; Zhang, Yuying; Chao, Jie; Yang, Jianzhong; Su, Shao; Wang, Lihua; Fan, Chunhai; Wang, Lianhui

    2016-06-01

    Herein, we presented hierarchical three-dimensional (3D) branched hematite nanorod arrays (NAs) on transparent fluorine-doped tin oxide (FTO) conductive glass substrates, which exhibited high PEC water splitting performance due to the enhancement of mid-visible light harvesting as well as charge separation and transfer. The introduction of a TiO2 underlayer made the as-prepared 3D branched hematite NAs achieve a photocurrent density of 0.61 mA cm-2 at 1.23 V vs. reversible hydrogen electrode (RHE) without high-temperature activation.Herein, we presented hierarchical three-dimensional (3D) branched hematite nanorod arrays (NAs) on transparent fluorine-doped tin oxide (FTO) conductive glass substrates, which exhibited high PEC water splitting performance due to the enhancement of mid-visible light harvesting as well as charge separation and transfer. The introduction of a TiO2 underlayer made the as-prepared 3D branched hematite NAs achieve a photocurrent density of 0.61 mA cm-2 at 1.23 V vs. reversible hydrogen electrode (RHE) without high-temperature activation. Electronic supplementary information (ESI) available: Experimental details. See DOI: 10.1039/c6nr03855g

  11. Single Atom (Pd/Pt) Supported on Graphitic Carbon Nitride as an Efficient Photocatalyst for Visible-Light Reduction of Carbon Dioxide.

    PubMed

    Gao, Guoping; Jiao, Yan; Waclawik, Eric R; Du, Aijun

    2016-05-18

    Reducing carbon dioxide to hydrocarbon fuel with solar energy is significant for high-density solar energy storage and carbon balance. In this work, single atoms of palladium and platinum supported on graphitic carbon nitride (g-C3N4), i.e., Pd/g-C3N4 and Pt/g-C3N4, respectively, acting as photocatalysts for CO2 reduction were investigated by density functional theory calculations for the first time. During CO2 reduction, the individual metal atoms function as the active sites, while g-C3N4 provides the source of hydrogen (H*) from the hydrogen evolution reaction. The complete, as-designed photocatalysts exhibit excellent activity in CO2 reduction. HCOOH is the preferred product of CO2 reduction on the Pd/g-C3N4 catalyst with a rate-determining barrier of 0.66 eV, while the Pt/g-C3N4 catalyst prefers to reduce CO2 to CH4 with a rate-determining barrier of 1.16 eV. In addition, deposition of atom catalysts on g-C3N4 significantly enhances the visible-light absorption, rendering them ideal for visible-light reduction of CO2. Our findings open a new avenue of CO2 reduction for renewable energy supply. PMID:27116595

  12. Simple and large scale one-pot method for preparation of AgBr-ZnO nanocomposites as highly efficient visible light photocatalyst

    NASA Astrophysics Data System (ADS)

    Pirhashemi, Mahsa; Habibi-Yangjeh, Aziz

    2013-10-01

    Nanocomposites of AgBr-ZnO were successfully prepared in water by refluxing about at 90 °C for 3 h. In this method, zinc nitrate, silver nitrate, sodium bromide and sodium hydroxide were used as starting materials without using any additive and post preparation treatment. The nanocomposites were investigated by XRD, SEM, EDX, UV-vis DRS, and FT-IR techniques. In the nanocomposites, the ZnO has wurtzite hexagonal crystalline phase and loading of AgBr does not change its structure. The SEM images show that with increasing mole fraction of AgBr, surface morphology of the samples is changing to nanorods with smaller diameter. Photocatalytic activity of the nanocomposites was evaluated by degradation of methylene blue (MB) under visible light irradiation. The nanocomposites exhibit higher activity relative to the pure ZnO and AgBr. Among the prepared nanocomposites, the sample with 0.2372 mole fraction of AgBr exhibits highest photocatalytic activity. Moreover, influence of various operational parameters on the degradation reaction was studied and a possible degradation mechanism proposed. Chemical oxygen demand (COD) measurements were applied to check mineralization of MB on the nanocomposite under visible light irradiation.

  13. Large-scale synthesis of ultrathin tungsten oxide nanowire networks: an efficient catalyst for aerobic oxidation of toluene to benzaldehyde under visible light

    NASA Astrophysics Data System (ADS)

    Bai, Hua; Yi, Wencai; Liu, Jingyao; Lv, Qing; Zhang, Qing; Ma, Qiang; Yang, Haifeng; Xi, Guangcheng

    2016-07-01

    As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%.As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%. Electronic supplementary information (ESI) available: Experimental procedure, XRD patterns, TEM and HRTEM images, energy-dispersive X-ray spectra, UV-vis spectra, X-ray photoelectron spectroscopy (XPS), and EDS. See DOI: 10.1039/c6nr02949c

  14. Traffic light to vehicle visible light communication channel characterization.

    PubMed

    Cui, Kaiyun; Chen, Gang; Xu, Zhengyuan; Roberts, Richard D

    2012-09-20

    Outdoor visible light communication (VLC) between an LED traffic light and an automobile has been proposed for intelligent transportation system development. An unobstructed line-of-sight (LOS) channel has to be guaranteed for this communication system. In this paper, an analytical LOS path loss model is proposed and validated by the measurement results. Commercial-off-the-shelf (COTS) LED traffic lights are characterized for use as transmitters and possible interference sources are studied, such as background solar radiation and artificial lighting. Accordingly, the performance of an outdoor VLC system is evaluated using different modulation schemes. PMID:23033030

  15. Advances and prospects in visible light communications

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    Visible light communication (VLC) is an emerging technology in optical wireless communication (OWC) that has attracted worldwide research in recent years. VLC can combine communication and illumination together, which could be applied in many application scenarios such as visible light communication local area networks (VLANs), indoor localization, and intelligent lighting. In recent years, pioneering and significant work have been made in the field of VLC. In this paper, an overview of the recent progress in VLC is presented. We also demonstrate our recent experiment results including bidirectional 100 Mbit/s VLAN or Li-Fi system based on OOK modulation without blue filter. The VLC systems that we proposed are good solutions for high-speed VLC application systems with low-cost and low-complexity. VLC technology shows a bright future due to its inherent advantages, shortage of RF spectra and ever increasing popularity of white LEDs. Project supported by the National High Technology Research and Development Program of China (Nos. 2015AA033303, 2013AA013602, 2013AA013603, 2013AA03A104), the National Natural Science Foundation of China (Nos. 61178051, 61321063, 61335010, 61178048, 61275169), and the National Basic Research Program of China (Nos. 2013CB329205, 2011CBA00608).

  16. Fabrication of hierarchically structured novel redox-mediator-free ZnIn2S4 marigold flower/Bi2WO6 flower-like direct Z-scheme nanocomposite photocatalysts with superior visible light photocatalytic efficiency.

    PubMed

    Jo, Wan-Kuen; Lee, Joon Yeob; Natarajan, Thillai Sivakumar

    2016-01-14

    Novel, hierarchically nanostructured, redox-mediator-free, direct Z-scheme nanocomposite photocatalysts were synthesized via a facile hydrothermal method followed by wet-impregnation. The photocatalysts had a ZnIn2S4 marigold flower/Bi2WO6 flower-like (ZIS/BW) composition, which led to superior visible-light photocatalytic efficiency with excellent stability and reusability. The hierarchical marigold flower and flower-like morphologies of ZIS and BW were confirmed by FE-SEM and TEM analyses and further revealed that formation of the hierarchical marigold flower-like ZIS structure followed the formation of nanoparticles, growth of the ZIS petals, and self-assembly of these species. Powder X-ray diffraction and UV-visible diffuse reflectance spectroscopy analyses as well as the enhancement in the surface area and pore volume of the composite provide evidence of strong coupling between hierarchical BW and the ZIS nanostructures. The efficiency of the hierarchical direct Z-scheme photocatalysts for photocatalytic decomposition of metronidazole (MTZ) under visible-light irradiation was evaluated. The hierarchically nanostructured ZIS/BW nanocomposites with 50% loading of ZIS exhibited superior visible-light photocatalytic decomposition efficiency (PDE) compared to the composites with other percentages of ZIS and pristine BW. A probable mechanism for the enhanced photocatalytic efficiency of the ZIS/BW composite in MTZ degradation under visible irradiation was proposed. Radical quenching studies demonstrated that h(+), ˙OH, and O2˙(-) are the primary reactive radicals involved, which confirms that the Z-scheme mechanism of transfer of charge carriers accounts for the higher photocatalytic activity. Kinetic analysis revealed that MTZ degradation follows pseudo-first-order kinetics and the reusability of the composite catalyst for up to four cycles confirms the excellent stability of the hierarchical structure. It is concluded that the hierarchical structure of the ZIS

  17. Soft chemical synthesis of Ag{sub 3}SbS{sub 3} with efficient and recyclable visible light photocatalytic properties

    SciTech Connect

    Gusain, Meenakshi; Rawat, Pooja; Nagarajan, Rajamani

    2014-12-15

    Highlights: • Highly crystalline Ag{sub 3}SbS{sub 3} synthesized using soft chemical approach. • First time report of photocatalytic activity of Ag{sub 3}SbS{sub 3}. • Ag{sub 3}SbS{sub 3} degraded the harmful organic dyes rapidly under visible radiation. • Pseudo first order kinetics have been followed in these sets of reactions. • Up to 90% of Methylene Blue degraded even after 4th cycle of catalyst reuse. • Structure of catalyst is intact after reuse. • As the catalyst is heavy, its separation after use is quite simple. - Abstract: Application of Ag{sub 3}SbS{sub 3}, obtained by soft chemical approach involving rapid reaction of air stable metal–thiourea complexes in ethylene glycol medium, as visible light photocatalyst for the degradation of dye solutions was investigated. Ag{sub 3}SbS{sub 3} was confirmed by high resolution powder X-ray diffraction pattern and its no defined morphology was present in SEM images. From UV–vis spectroscopy measurements, optical band gap of 1.77 eV was deduced for Ag{sub 3}SbS{sub 3}. Rapid degradation kinetics and recyclability was exhibited by Ag{sub 3}SbS{sub 3} towards Methylene Blue, Methyl Orange, Malachite Green, and Rhodamine 6G dye solutions under visible radiation. All these processes followed pseudo first order kinetics. High surface area (6.39 m{sup 2}/g), with mesopores (3.81 nm), arising from solvent mediated synthesis of Ag{sub 3}SbS{sub 3} has been correlated to its catalytic activity.

  18. Synthesis of CdS hollow spheres coupled with g-C3N4 as efficient visible-light-driven photocatalysts

    NASA Astrophysics Data System (ADS)

    Zhang, Chunyan; Lu, Yongfeng; Jiang, Qingqing; Hu, Juncheng

    2016-09-01

    CdS hollow spheres (CdS HS) coupled with graphitic carbon nitride (g-C3N4) photocatalysts are synthesized and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflection spectroscopy (DRS), x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence spectroscopy (PL). The effect of CdS content on CdS HS/g-C3N4 activity is investigated by the degradation of Rhodamine B (RhB). The sample of 20 wt% CdS content shows the best photocatalytic performance under visible-light irradiation, with the corresponding RhB degradation rate reaching 97.3%. The excellent photoactivity of CdS HS/g-C3N4 is attributed to the synergistic effect of g-C3N4 and CdS HS. A possible photocatalytic mechanism of the CdS HS/g-C3N4 composite is proposed and corroborated by PL.

  19. Synthesis of CdS hollow spheres coupled with g-C3N4 as efficient visible-light-driven photocatalysts.

    PubMed

    Zhang, Chunyan; Lu, Yongfeng; Jiang, Qingqing; Hu, Juncheng

    2016-09-01

    CdS hollow spheres (CdS HS) coupled with graphitic carbon nitride (g-C3N4) photocatalysts are synthesized and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflection spectroscopy (DRS), x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence spectroscopy (PL). The effect of CdS content on CdS HS/g-C3N4 activity is investigated by  the degradation of Rhodamine B (RhB). The sample of 20 wt% CdS content shows the best photocatalytic performance under visible-light irradiation, with the corresponding RhB degradation rate reaching 97.3%. The excellent photoactivity of CdS HS/g-C3N4 is attributed to the synergistic effect of g-C3N4 and CdS HS. A possible photocatalytic mechanism of the CdS HS/g-C3N4 composite is proposed and corroborated by PL. PMID:27455387

  20. Efficient Geometric Sound Propagation Using Visibility Culling

    NASA Astrophysics Data System (ADS)

    Chandak, Anish

    2011-07-01

    Simulating propagation of sound can improve the sense of realism in interactive applications such as video games and can lead to better designs in engineering applications such as architectural acoustics. In this thesis, we present geometric sound propagation techniques which are faster than prior methods and map well to upcoming parallel multi-core CPUs. We model specular reflections by using the image-source method and model finite-edge diffraction by using the well-known Biot-Tolstoy-Medwin (BTM) model. We accelerate the computation of specular reflections by applying novel visibility algorithms, FastV and AD-Frustum, which compute visibility from a point. We accelerate finite-edge diffraction modeling by applying a novel visibility algorithm which computes visibility from a region. Our visibility algorithms are based on frustum tracing and exploit recent advances in fast ray-hierarchy intersections, data-parallel computations, and scalable, multi-core algorithms. The AD-Frustum algorithm adapts its computation to the scene complexity and allows small errors in computing specular reflection paths for higher computational efficiency. FastV and our visibility algorithm from a region are general, object-space, conservative visibility algorithms that together significantly reduce the number of image sources compared to other techniques while preserving the same accuracy. Our geometric propagation algorithms are an order of magnitude faster than prior approaches for modeling specular reflections and two to ten times faster for modeling finite-edge diffraction. Our algorithms are interactive, scale almost linearly on multi-core CPUs, and can handle large, complex, and dynamic scenes. We also compare the accuracy of our sound propagation algorithms with other methods. Once sound propagation is performed, it is desirable to listen to the propagated sound in interactive and engineering applications. We can generate smooth, artifact-free output audio signals by applying

  1. High-efficient photo-electron transport channel in SiC constructed by depositing cocatalysts selectively on specific surface sites for visible-light H2 production

    NASA Astrophysics Data System (ADS)

    Wang, Da; Peng, Yuan; Wang, Qi; Pan, Nanyan; Guo, Zhongnan; Yuan, Wenxia

    2016-04-01

    Control cocatalyst location on a metal-free semiconductor to promote surface charge transfer for decreasing the electron-hole recombination is crucial for enhancing solar energy conversion. Based on the findings that some metals have an affinity for bonding with the specific atoms of polar semiconductors at a heterostructure interface, we herein control Pt deposition selectively on the Si sites of a micro-SiC photocatalyst surface via in-situ photo-depositing. The Pt-Si bond forming on the interface constructs an excellent channel, which is responsible for accelerating photo-electron transfer from SiC to Pt and then reducing water under visible-light. The hydrogen production is enhanced by two orders of magnitude higher than that of bare SiC, and 2.5 times higher than that of random-depositing nano-Pt with the same loading amount.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  3. 33 CFR 83.22 - Visibility of lights (Rule 22).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Visibility of lights (Rule 22). 83.22 Section 83.22 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY INLAND NAVIGATION RULES RULES Lights and Shapes § 83.22 Visibility of lights (Rule 22). The lights prescribed in these Rules shall have an intensity...

  4. Macroscopic invisibility cloak for visible light.

    PubMed

    Zhang, Baile; Luo, Yuan; Liu, Xiaogang; Barbastathis, George

    2011-01-21

    Invisibility cloaks, a subject that usually occurs in science fiction and myths, have attracted wide interest recently because of their possible realization. The biggest challenge to true invisibility is known to be the cloaking of a macroscopic object in the broad range of wavelengths visible to the human eye. Here we experimentally solve this problem by incorporating the principle of transformation optics into a conventional optical lens fabrication with low-cost materials and simple manufacturing techniques. A transparent cloak made of two pieces of calcite is created. This cloak is able to conceal a macroscopic object with a maximum height of 2 mm, larger than 3500 free-space-wavelength, inside a transparent liquid environment. Its working bandwidth encompassing red, green, and blue light is also demonstrated. PMID:21405275

  5. Macroscopic Invisibility Cloak for Visible Light

    NASA Astrophysics Data System (ADS)

    Zhang, Baile; Luo, Yuan; Liu, Xiaogang; Barbastathis, George

    2011-01-01

    Invisibility cloaks, a subject that usually occurs in science fiction and myths, have attracted wide interest recently because of their possible realization. The biggest challenge to true invisibility is known to be the cloaking of a macroscopic object in the broad range of wavelengths visible to the human eye. Here we experimentally solve this problem by incorporating the principle of transformation optics into a conventional optical lens fabrication with low-cost materials and simple manufacturing techniques. A transparent cloak made of two pieces of calcite is created. This cloak is able to conceal a macroscopic object with a maximum height of 2 mm, larger than 3500 free-space-wavelength, inside a transparent liquid environment. Its working bandwidth encompassing red, green, and blue light is also demonstrated.

  6. Coded source imaging simulation with visible light

    NASA Astrophysics Data System (ADS)

    Wang, Sheng; Zou, Yubin; Zhang, Xueshuang; Lu, Yuanrong; Guo, Zhiyu

    2011-09-01

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

  7. Macroscopic invisibility cloaking of visible light

    PubMed Central

    Chen, Xianzhong; Luo, Yu; Zhang, Jingjing; Jiang, Kyle; Pendry, John B.; Zhang, Shuang

    2011-01-01

    Invisibility cloaks, which used to be confined to the realm of fiction, have now been turned into a scientific reality thanks to the enabling theoretical tools of transformation optics and conformal mapping. Inspired by those theoretical works, the experimental realization of electromagnetic invisibility cloaks has been reported at various electromagnetic frequencies. All the invisibility cloaks demonstrated thus far, however, have relied on nano- or micro-fabricated artificial composite materials with spatially varying electromagnetic properties, which limit the size of the cloaked region to a few wavelengths. Here, we report the first realization of a macroscopic volumetric invisibility cloak constructed from natural birefringent crystals. The cloak operates at visible frequencies and is capable of hiding, for a specific light polarization, three-dimensional objects of the scale of centimetres and millimetres. Our work opens avenues for future applications with macroscopic cloaking devices. PMID:21285954

  8. Pupillary efficient lighting system

    DOEpatents

    Berman, Samuel M.; Jewett, Don L.

    1991-01-01

    A lighting system having at least two independent lighting subsystems each with a different ratio of scotopic illumination to photopic illumination. The radiant energy in the visible region of the spectrum of the lighting subsystems can be adjusted relative to each other so that the total scotopic illumination of the combined system and the total photopic illumination of the combined system can be varied independently. The dilation or contraction of the pupil of an eye is controlled by the level of scotopic illumination and because the scotopic and photopic illumination can be separately controlled, the system allows the pupil size to be varied independently of the level of photopic illumination. Hence, the vision process can be improved for a given level of photopic illumination.

  9. Fabrication of cation-doped BaTaO{sub 2}N photoanodes for efficient photoelectrochemical water splitting under visible light irradiation

    SciTech Connect

    Higashi, Masanobu; Yamanaka, Yuta; Tomita, Osamu; Abe, Ryu

    2015-10-01

    A series of cation-doped BaTaO{sub 2}N particle was synthesized to control the donor density in the bulk for improving the performance of photoelectrochemical water splitting on porous BaTaO{sub 2}N photoanodes under visible light. Among the dopants (Mo{sup 6+}, W{sup 6+}, Zr{sup 4+}, and Ti{sup 4+}) examined, Mo{sup 6+} cations can be introduced into the Ta{sup 5+} site up to 5 mol. % without producing any impurity phases; the donor density of BaTaO{sub 2}N was indeed increased significantly by introducing higher ratio of Mo{sup 6+} dopant. The porous photoanodes of Mo-doped BaTaO{sub 2}N showed much higher photocurrent than others including undoped one and also exhibited much improved performance in photoelectrochemical water splitting into H{sub 2} and O{sub 2} after loaded with cobalt oxide cocatalyst and coupled with Pt counter electrode.

  10. Ternary ZnO/Ag3VO4/Fe3O4 nanocomposites: Novel magnetically separable photocatalyst for efficiently degradation of dye pollutants under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Shekofteh-Gohari, Maryam; Habibi-Yangjeh, Aziz

    2015-10-01

    In this work, we successfully prepared a series of novel magnetically separable ZnO/Ag3VO4/Fe3O4 nanocomposites by a facile refluxing method using Fe3O4, zinc nitrate, silver nitrate, ammonium metavanadate, and sodium hydroxide as starting materials without using any post preparation treatments. The microstructure, purity, morphology, spectroscopic, and magnetic properties of the prepared samples were studied using XRD, EDX, SEM, TEM, UV-vis DRS, FT-IR, PL, and VSM techniques. The ZnO/Ag3VO4/Fe3O4 nanocomposite with 8:1 weight ratio of ZnO/Ag3VO4 to Fe3O4 has the superior activity in degradation of rhodamine B under visible-light irradiation. Photocatalytic activity of this nanocomposite is about 11.5-fold higher than that of the ZnO/Fe3O4 nanocomposite. The results showed that the preparation time and calcination temperature significantly affect on the photocatalytic activity. The trapping experiments revealed that superoxide ions and holes have major influence on the degradation reaction. Furthermore, the enhanced activity of the nanocomposite for degradation of two more dye pollutants was confirmed. Finally, the nanocomposite was magnetically separated from the treated solution after four successive cycles.

  11. Energy-efficient photodegradation of azo dyes with TiO(2) nanoparticles based on photoisomerization and alternate UV-visible light.

    PubMed

    Zhang, Hao; Chen, Da; Lv, Xiaojun; Wang, Ying; Chang, Haixin; Li, Jinghong

    2010-02-01

    Herein, we demonstrated a UV-vis light alternate photocatalysis (UVLAP) strategy in the photodegradation of azo dyes. The UVLAP of azo dyes over TiO(2) catalysts exhibited significantly higher energy efficiency than the conventional UV process by 40%, which was attributed to the photoisomerization of azo dyes and the resulting diversity of dyes' cis and trans states in interfacial properties, including conductance and spatial effects. This UVLAP strategy could contribute to the energy-saving photodegradation of azo dyes and other pollutants with photoisomerization properties and facilitate the practical application of TiO(2) in the environmental remediation. PMID:20039724

  12. Visible Light Mediated Photoredox Catalytic Arylation Reactions.

    PubMed

    Ghosh, Indrajit; Marzo, Leyre; Das, Amrita; Shaikh, Rizwan; König, Burkhard

    2016-08-16

    Introducing aryl- and heteroaryl moieties into molecular scaffolds are often key steps in the syntheses of natural products, drugs, or functional materials. A variety of cross-coupling methods have been well established, mainly using transition metal mediated reactions between prefunctionalized substrates and arenes or C-H arylations with functionalization in only one coupling partner. Although highly developed, one drawback of the established sp2-sp2 arylations is the required transition metal catalyst, often in combination with specific ligands and additives. Therefore, photoredox mediated arylation methods have been developed as alternative over the past decade. We begin our survey with visible light photo-Meerwein arylation reactions, which allow C-H arylation of heteroarenes, enones, alkenes, and alkynes with organic dyes, such as eosin Y, as the photocatalyst. A good number of examples from different groups illustrate the broad application of the reaction in synthetic transformations. While initially only photo-Meerwein arylation-elimination processes were reported, the reaction was later extended to photo-Meerwein arylation-addition reactions giving access to the photoinduced three component synthesis of amides and esters from alkenes, aryl diazonium salts, nitriles or formamides, respectively. Other substrates with redox-active leaving groups have been explored in photocatalyzed arylation reactions, such as diaryliodonium and triarylsulfonium salts, and arylsulfonyl chlorides. We discus some examples with their scope and limitations. The scope of arylation reagents for photoredox reactions was extended to aryl halides. The challenge here is the extremely negative reduction potential of aryl halides in the initial electron transfer step compared to, e.g., aryl diazonium or diaryliodonium salts. In order to reach reduction potentials over -2.0 V vs SCE two consecutive photoinduced electron transfer steps were used. The intermediary formed colored radical

  13. Visible Light Responsive Catalyst for Air Water Purification Project

    NASA Technical Reports Server (NTRS)

    Wheeler, Raymond M.

    2014-01-01

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

  14. Catadioptric lenses in Visible Light Communications

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  15. Transfer of ultraviolet photon energy into fluorescent light in the visible path represents a new and efficient protection mechanism of sunscreens.

    PubMed

    Vergou, Theognosia; Patzelt, Alexa; Richter, Heike; Schanzer, Sabine; Zastrow, Leonhard; Golz, Karin; Doucet, Olivier; Antoniou, Christina; Sterry, Wolfram; Lademann, Juergen

    2011-10-01

    The development of sunscreens with high sun protection factor (SPF) values but low filter concentrations is the ultimate goal. The purpose of the present study was to investigate why a sunscreen spray and cream with different concentrations of the same UV-filters provided the same SPF. Therefore, the homogeneity of the distribution of both sunscreens was investigated by laser scanning microscopy (LSM) and tape stripping (TS). Additionally, the energy transfer mechanisms of the sunscreens on the skin were analyzed. The TS and LSM showed a better homogeneity of the distribution of the spray. With Wood's light, a total absorption of the irradiation was detected in the spray area. In contrast, after cream treatment, an intensive fluorescent signal was observed. It was demonstrated that this fluorescent signal was caused by nonthermal energy transferred from the UV-filters to one compound of the cream releasing its excitation energy by fluorescence. This nonthermal energy transfer seemed to be the reason for the high efficiency of the cream, which is subjected to thermal relaxation. The transfer of UV photon energy into fluorescent light represents a new approach to increase the efficiency of sunscreens and could form the basis for a new generation of sunscreens. PMID:22029345

  16. Transfer of ultraviolet photon energy into fluorescent light in the visible path represents a new and efficient protection mechanism of sunscreens

    NASA Astrophysics Data System (ADS)

    Vergou, Theognosia; Patzelt, Alexa; Richter, Heike; Schanzer, Sabine; Zastrow, Leonhard; Golz, Karin; Doucet, Olivier; Antoniou, Christina; Sterry, Wolfram; Lademann, Juergen

    2011-10-01

    The development of sunscreens with high sun protection factor (SPF) values but low filter concentrations is the ultimate goal. The purpose of the present study was to investigate why a sunscreen spray and cream with different concentrations of the same UV-filters provided the same SPF. Therefore, the homogeneity of the distribution of both sunscreens was investigated by laser scanning microscopy (LSM) and tape stripping (TS). Additionally, the energy transfer mechanisms of the sunscreens on the skin were analyzed. The TS and LSM showed a better homogeneity of the distribution of the spray. With Wood's light, a total absorption of the irradiation was detected in the spray area. In contrast, after cream treatment, an intensive fluorescent signal was observed. It was demonstrated that this fluorescent signal was caused by nonthermal energy transferred from the UV-filters to one compound of the cream releasing its excitation energy by fluorescence. This nonthermal energy transfer seemed to be the reason for the high efficiency of the cream, which is subjected to thermal relaxation. The transfer of UV photon energy into fluorescent light represents a new approach to increase the efficiency of sunscreens and could form the basis for a new generation of sunscreens.

  17. Hexaarylbiimidazoles as Visible Light Thiol–Ene Photoinitiators

    PubMed Central

    Clarkson, Brian H.; Scott, Timothy F.

    2015-01-01

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

  18. Gigabit polarization division multiplexing in visible light communication.

    PubMed

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

    2014-04-01

    In this Letter, polarization division multiplexing is proposed and experimentally demonstrated for the first time that we know of, in visible light communication systems based on incoherent light emitting diodes and two orthogonal groups of linear polarizers. Spectrally efficient 16-ary quadrature amplitude modulation Nyquist single carrier frequency domain equalization is employed to obtain a maximum spectral efficiency. We achieve an aggregate data rate of 1  Gb/s, with bit error rate results for two polarization directions both below the 7% pre-forward-error-correction threshold of 3.8×10(-3) after 80 cm free-space transmission. Moreover, the cross talk between x and y polarization is also discussed and analyzed. PMID:24686614

  19. Novel mesoporous P-doped graphitic carbon nitride nanosheets coupled with ZnIn2S4 nanosheets as efficient visible light driven heterostructures with remarkably enhanced photo-reduction activity.

    PubMed

    Chen, Wei; Liu, Tian-Yu; Huang, Ting; Liu, Xiao-Heng; Yang, Xu-Jie

    2016-02-14

    In this report, we rationally designed and fabricated P-C3N4/ZnIn2S4 nanocomposites by in situ immobilizing ZnIn2S4 nanosheets onto the surface of mesoporous P-doped graphite carbon nitrogen (P-C3N4) nanosheets in a mixed solvothermal environment; their application to the photoreduction of 4-nitroaniline was used to estimate the photocatalytic performance. Different to the template route, here the mesoporous P-C3N4 nanosheets were prepared with a template-free strategy. The as-fabricated P-C3N4/ZnIn2S4 nanocomposites were systematically characterized by analyzing the phase structure, chemical components, electronic and optical properties and separation of charge carrier pairs. More importantly, these P-C3N4/ZnIn2S4 heterostructures have been proven to be highly efficient visible light responsive photocatalysts for photo-reduction, and meanwhile exhibit excellent photo-stability during recycling runs. The sufficient evidence reveals that the significantly improved photocatalytic performance is mainly attributed to the more efficient charge carrier separation based on the construction of a close heterogeneous interface. This work may provide new insights into the utilization of P-C3N4/ZnIn2S4 nanocomposites as visible light driven photocatalysts for comprehensive organic transformations in the field of fine chemical engineering. PMID:26815611

  20. Organocatalyzed atom transfer radical polymerization driven by visible light.

    PubMed

    Theriot, Jordan C; Lim, Chern-Hooi; Yang, Haishen; Ryan, Matthew D; Musgrave, Charles B; Miyake, Garret M

    2016-05-27

    Atom transfer radical polymerization (ATRP) has become one of the most implemented methods for polymer synthesis, owing to impressive control over polymer composition and associated properties. However, contamination of the polymer by the metal catalyst remains a major limitation. Organic ATRP photoredox catalysts have been sought to address this difficult challenge but have not achieved the precision performance of metal catalysts. Here, we introduce diaryl dihydrophenazines, identified through computationally directed discovery, as a class of strongly reducing photoredox catalysts. These catalysts achieve high initiator efficiencies through activation by visible light to synthesize polymers with tunable molecular weights and low dispersities. PMID:27033549

  1. TiO{sub 2}-coated carbon nanotubes: A redshift enhanced photocatalysis at visible light

    SciTech Connect

    Lu, S.-Y.; Tang, C.-W.; Lin, Y.-H.; Kuo, H.-F.; Lai, Y.-C.; Ouyang Hao; Hsu, W.-K.; Tsai, M.-Y.

    2010-06-07

    Annealing of carbon nanotubes coated with thin and uniform TiO{sub 2} results in carbon diffusion into oxygen lattices and doping induced redshift is evident by an efficient photocatalysis at visible light. The underlying mechanism is discussed.

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

    NASA Astrophysics Data System (ADS)

    Hranilovic, Steve

    2015-01-01

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

  3. Visible Light Communication Physical Layer Design for Jist Simulation

    NASA Astrophysics Data System (ADS)

    Tomaš, Boris

    2014-12-01

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

  4. Asymmetric photoredox transition-metal catalysis activated by visible light

    NASA Astrophysics Data System (ADS)

    Huo, Haohua; Shen, Xiaodong; Wang, Chuanyong; Zhang, Lilu; Röse, Philipp; Chen, Liang-An; Harms, Klaus; Marsch, Michael; Hilt, Gerhard; Meggers, Eric

    2014-11-01

    Asymmetric catalysis is seen as one of the most economical strategies to satisfy the growing demand for enantiomerically pure small molecules in the fine chemical and pharmaceutical industries. And visible light has been recognized as an environmentally friendly and sustainable form of energy for triggering chemical transformations and catalytic chemical processes. For these reasons, visible-light-driven catalytic asymmetric chemistry is a subject of enormous current interest. Photoredox catalysis provides the opportunity to generate highly reactive radical ion intermediates with often unusual or unconventional reactivities under surprisingly mild reaction conditions. In such systems, photoactivated sensitizers initiate a single electron transfer from (or to) a closed-shell organic molecule to produce radical cations or radical anions whose reactivities are then exploited for interesting or unusual chemical transformations. However, the high reactivity of photoexcited substrates, intermediate radical ions or radicals, and the low activation barriers for follow-up reactions provide significant hurdles for the development of efficient catalytic photochemical processes that work under stereochemical control and provide chiral molecules in an asymmetric fashion. Here we report a highly efficient asymmetric catalyst that uses visible light for the necessary molecular activation, thereby combining asymmetric catalysis and photocatalysis. We show that a chiral iridium complex can serve as a sensitizer for photoredox catalysis and at the same time provide very effective asymmetric induction for the enantioselective alkylation of 2-acyl imidazoles. This new asymmetric photoredox catalyst, in which the metal centre simultaneously serves as the exclusive source of chirality, the catalytically active Lewis acid centre, and the photoredox centre, offers new opportunities for the `green' synthesis of non-racemic chiral molecules.

  5. Enhancing the visibility of injuries with narrow-banded beams of light within the visible light spectrum.

    PubMed

    Limmen, Roxane M; Ceelen, Manon; Reijnders, Udo J L; Joris Stomp, S; de Keijzer, Koos C; Das, Kees

    2013-03-01

    The use of narrow-banded visible light sources in improving the visibility of injuries has been hardly investigated, and studies examining the extent of this improvement are lacking. In this study, narrow-banded beams of light within the visible light spectrum were used to explore their ability in improving the visibility of external injuries. The beams of light were induced by four crime-lites(®) providing narrow-banded beams of light between 400 and 550 nm. The visibility of the injuries was assessed through specific long-pass filters supplied with the set of crime-lites(®) . Forty-three percent of the examined injuries improved in visibility by using the narrow-banded visible light. In addition, injuries were visualized that were not visible or just barely visible to the naked eye. The improvements in visibility were particularly marked with the use of crime-lites(®) "violet" and "blue" covering the spectrum between 400-430 and 430-470 nm. The simple noninvasive method showed a great potential contribution in injury examination. PMID:23278497

  6. Efficient visible through SWIR focal plane MTF measurement

    NASA Astrophysics Data System (ADS)

    Malone, Neil; Fierro, Josh; Troup, Richard; Willberger, Gary; Wyles, Jessica; Boe, Raymond; Dixon, Andrew

    2015-09-01

    Raytheon Vision Systems (RVS) has developed an efficient method to measure MTF on Visible through MWIR small pixel FPAs. The measured data was obtained using an advanced but low cost test set with sub μm target projection on the FPA and real time display of the LSF as the slit is walked through focus. The test set is commercially procured, maintained and calibrated, provides target and filter holders and a light source. The analysis summary includes references from simplified MTF published analysis tools and a list of artifacts to be aware of when measuring MTF. The SWIR and MWIR detectors have a Mesa structure geometry for improved MTF performance and the Visible has state of the art crosstalk control to provide excellent MTF performance. The modeled data is compared to measured tilted slit MTF measured data and shows close agreement.

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

    NASA Astrophysics Data System (ADS)

    Straub, Jeremy

    2015-05-01

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

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

    PubMed Central

    Garlets, Zachary J.; Nguyen, John D.

    2014-01-01

    Visible-light photoredox catalysis has recently emerged as a viable alternative for radical reactions otherwise carried out with tin and boron reagents. It has been recognized that by merging photoredox catalysis with flow chemistry, slow reaction times, lower yields, and safety concerns may be obviated. While flow reactors have been successfully applied to reactions carried out with UV light, only recent developments have demonstrated the same potential of flow reactors for the improvement of visible-light-mediated reactions. This review examines the initial and continuing development of visible-light-mediated photoredox flow chemistry by exemplifying the benefits of flow chemistry compared with conventional batch techniques. PMID:25484447

  9. Modulation selection for visible light communications using lighting LEDs

    NASA Astrophysics Data System (ADS)

    Siuzdak, Jerzy

    2015-09-01

    The paper analyzes suitability of various spectrally efficient modulations (PAM, CAP, OFDM/DMT) in a VLC system using lighting LEDs as a transmitter. Although under ideal conditions all modulation have similar efficiency i.e. they produce similar throughputs with a given BER, their practical performances are different. For example, the level of nonlinear distortions generated by each modulation is the least for PAM and by far the greatest for OFDM/DMT locating CAP in the middle. The suitability of various OFDM/DMT variants in a VLC LED link was also analyzed proving that the asymmetrically clipped (ACO) OFDM has a worse performance as compared with DC biased (DCO) OFDM.

  10. Short-wavelength visible light emission from silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Pi, Xiaodong; Liptak, Rick; Campbell, Stephen; Kortshagen, Uwe

    2007-03-01

    Si is the material of choice for modern microelectronics but, as an indirect-bandgap semiconductor, it is not an efficient light emitter. An electrically pumped Si laser would present a breakthrough for optoelectronic integration that may enable optical interconnect to make computers faster. Si light emitting diodes may revolutionize solid-state lighting and displays because of the low cost and environmental friendliness of Si. One of the most challenging problems of Si-based lighting and displays is the lack of a reliable and efficient full visible spectrum emission. Si nanocrystals (Si-NCs) have so far been the most promising form of Si to emit light. Most of the synthesis approaches of Si-NCs, however, only lead to red light emission. Our recent work on Si-NCs synthesized by non-thermal plasmas has focused on extending their light emission into the short-wavelength range. Firstly, the process of oxidation-etching-oxidation of Si-NCs is investigated. This process causes the size of Si-NCs to decrease, leading to shorter wavelength light emission from Si-NCs. Yellow or green photoluminescence (PL) has been observed from initially oxidized red light emitting Si-NCs after HF vapour etching and atmospheric oxidation. The intensity of PL from Si-NCs, however, decreases by a factor up to 100. It is found that HF etching restructures the surface of Si-NCs. This leads to a decrease in the incorporation of O during subsequent oxidation, which finally results in silicon suboxide SiO1.9. Such an understoichiometry indicates a high density of defects such as Si dangling bonds at the Si-NC/oxide interface. Therefore, the PL efficiency is extremely low for short-wavelength light emitting Si-NCs obtained by the process of oxidation-etching-oxidation. Secondly, an integrated two-stage plasma system is employed to achieve the light emission from Si-NCs in the full visible spectrum range. Red-light-emitting Si-NCs are produced in the first stage by the plasma decomposition of SiH4

  11. Novel mesoporous P-doped graphitic carbon nitride nanosheets coupled with ZnIn2S4 nanosheets as efficient visible light driven heterostructures with remarkably enhanced photo-reduction activity

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Liu, Tian-Yu; Huang, Ting; Liu, Xiao-Heng; Yang, Xu-Jie

    2016-02-01

    In this report, we rationally designed and fabricated P-C3N4/ZnIn2S4 nanocomposites by in situ immobilizing ZnIn2S4 nanosheets onto the surface of mesoporous P-doped graphite carbon nitrogen (P-C3N4) nanosheets in a mixed solvothermal environment; their application to the photoreduction of 4-nitroaniline was used to estimate the photocatalytic performance. Different to the template route, here the mesoporous P-C3N4 nanosheets were prepared with a template-free strategy. The as-fabricated P-C3N4/ZnIn2S4 nanocomposites were systematically characterized by analyzing the phase structure, chemical components, electronic and optical properties and separation of charge carrier pairs. More importantly, these P-C3N4/ZnIn2S4 heterostructures have been proven to be highly efficient visible light responsive photocatalysts for photo-reduction, and meanwhile exhibit excellent photo-stability during recycling runs. The sufficient evidence reveals that the significantly improved photocatalytic performance is mainly attributed to the more efficient charge carrier separation based on the construction of a close heterogeneous interface. This work may provide new insights into the utilization of P-C3N4/ZnIn2S4 nanocomposites as visible light driven photocatalysts for comprehensive organic transformations in the field of fine chemical engineering.In this report, we rationally designed and fabricated P-C3N4/ZnIn2S4 nanocomposites by in situ immobilizing ZnIn2S4 nanosheets onto the surface of mesoporous P-doped graphite carbon nitrogen (P-C3N4) nanosheets in a mixed solvothermal environment; their application to the photoreduction of 4-nitroaniline was used to estimate the photocatalytic performance. Different to the template route, here the mesoporous P-C3N4 nanosheets were prepared with a template-free strategy. The as-fabricated P-C3N4/ZnIn2S4 nanocomposites were systematically characterized by analyzing the phase structure, chemical components, electronic and optical properties and

  12. Modulation based cells distribution for visible light communication.

    PubMed

    Wu, Yongsheng; Yang, Aiying; Feng, Lihui; Zuo, Lin; Sun, Yu-Nan

    2012-10-22

    Cells distribution for visible light communication can enhance the capacity of the data transmission by the reuse of optical spectrum. In this paper, we adopt three modulation formats as OOK, PPM and PWM for neighboring cells A, B and C respectively. The prototype experiment results demonstrate the error free transmission of 1.0 Mbit/s and 6.25 Mbit/s visible light communication system with our scheme. With the available LED, we can expect that the data rate of a visible light communication system with seamless connectivity can be up to 71.4 Mbit/s. PMID:23187182

  13. Coherence and visibility for vectorial light.

    PubMed

    Luis, Alfredo

    2010-08-01

    Two-path interference of transversal vectorial waves is embedded within a larger scheme: this is four-path interference between four scalar waves. This comprises previous approaches to coherence between vectorial waves and restores the equivalence between correlation-based coherence and visibility. PMID:20686580

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

    PubMed Central

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

    2016-01-01

    We developed new optic devices – singly-doped luminescence glasses and nanoparticle-coated lenses that convert UV light to visible light – for improvement of visual system functions. Tb3+ or Eu3+ singly-doped borate glasses or CdS-quantum dot (CdS-QD) coated lenses efficiently convert UV light to 542 nm or 613 nm wavelength narrow-band green or red light, or wide-spectrum white light, and thereby provide extra visible light to the eye. In zebrafish (wild-type larvae and adult control animals, retinal degeneration mutants, and light-induced photoreceptor cell degeneration models), the use of Tb3+ or Eu3+ doped luminescence glass or CdS-QD coated glass lenses provide additional visible light to the rod and cone photoreceptor cells, and thereby improve the visual system functions. The data provide proof-of-concept for the future development of optic devices for improvement of visual system functions in patients who suffer from photoreceptor cell degeneration or related retinal diseases. PMID:26860393

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

    PubMed

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

    2016-01-01

    We developed new optic devices - singly-doped luminescence glasses and nanoparticle-coated lenses that convert UV light to visible light - for improvement of visual system functions. Tb(3+) or Eu(3+) singly-doped borate glasses or CdS-quantum dot (CdS-QD) coated lenses efficiently convert UV light to 542 nm or 613 nm wavelength narrow-band green or red light, or wide-spectrum white light, and thereby provide extra visible light to the eye. In zebrafish (wild-type larvae and adult control animals, retinal degeneration mutants, and light-induced photoreceptor cell degeneration models), the use of Tb(3+) or Eu(3+) doped luminescence glass or CdS-QD coated glass lenses provide additional visible light to the rod and cone photoreceptor cells, and thereby improve the visual system functions. The data provide proof-of-concept for the future development of optic devices for improvement of visual system functions in patients who suffer from photoreceptor cell degeneration or related retinal diseases. PMID:26860393

  16. Melanin Photosensitization and the Effect of Visible Light on Epithelial Cells

    PubMed Central

    Chiarelli-Neto, Orlando; Ferreira, Alan Silva; Martins, Waleska Kerllen; Pavani, Christiane; Severino, Divinomar; Faião-Flores, Fernanda; Maria-Engler, Silvya Stuchi; Aliprandini, Eduardo; Martinez, Glaucia R.; Di Mascio, Paolo; Medeiros, Marisa H. G.; Baptista, Maurício S.

    2014-01-01

    Protecting human skin from sun exposure is a complex issue that involves unclear aspects of the interaction between light and tissue. A persistent misconception is that visible light is safe for the skin, although several lines of evidence suggest otherwise. Here, we show that visible light can damage melanocytes through melanin photosensitization and singlet oxygen (1O2) generation, thus decreasing cell viability, increasing membrane permeability, and causing both DNA photo-oxidation and necro-apoptotic cell death. UVA (355 nm) and visible (532 nm) light photosensitize 1O2 with similar yields, and pheomelanin is more efficient than eumelanin at generating 1O2 and resisting photobleaching. Although melanin can protect against the cellular damage induced by UVB, exposure to visible light leads to pre-mutagenic DNA lesions (i.e., Fpg- and Endo III-sensitive modifications); these DNA lesions may be mutagenic and may cause photoaging, as well as other health problems, such as skin cancer. PMID:25405352

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

    PubMed Central

    Chen, Hongjun

    2014-01-01

    Summary To better utilize the sunlight for efficient solar energy conversion, the research on visible-light active photocatalysts has recently attracted a lot of interest. The photosensitization of transition metal oxides is a promising approach for achieving effective visible-light photocatalysis. This review article primarily discusses the recent progress in the realm of a variety of nanostructured photosensitizers such as quantum dots, plasmonic metal nanostructures, and carbon nanostructures for coupling with wide-bandgap transition metal oxides to design better visible-light active photocatalysts. The underlying mechanisms of the composite photocatalysts, e.g., the light-induced charge separation and the subsequent visible-light photocatalytic reaction processes in environmental remediation and solar fuel generation fields, are also introduced. A brief outlook on the nanostructure photosensitization is also given. PMID:24991507

  18. A review on visible light active perovskite-based photocatalysts.

    PubMed

    Kanhere, Pushkar; Chen, Zhong

    2014-01-01

    Perovskite-based photocatalysts are of significant interest in the field of photocatalysis. To date, several perovskite material systems have been developed and their applications in visible light photocatalysis studied. This article provides a review of the visible light (λ > 400 nm) active perovskite-based photocatalyst systems. The materials systems are classified by the B site cations and their crystal structure, optical properties, electronic structure, and photocatalytic performance are reviewed in detail. Titanates, tantalates, niobates, vanadates, and ferrites form important photocatalysts which show promise in visible light-driven photoreactions. Along with simple perovskite (ABO3) structures, development of double/complex perovskites that are active under visible light is also reviewed. Various strategies employed for enhancing the photocatalytic performance have been discussed, emphasizing the specific advantages and challenges offered by perovskite-based photocatalysts. This review provides a broad overview of the perovskite photocatalysts, summarizing the current state of the work and offering useful insights for their future development. PMID:25532834

  19. Physical Layer Characteristics and Techniques for Visible Light Communications

    NASA Astrophysics Data System (ADS)

    Cui, Kaiyun

    With the rapid development of semiconductor lighting technologies, the light emitting diodes (LEDs) are promising to eventually replace traditional incandescent and fluorescent lamps for their high energy efficiency, environmental friendliness, and long lifetime. Visible light communication (VLC) utilizing lighting LEDs as transmitters has been an emerging research area since its first proposal. Ubiquitous communication coverage will become possible with wide deployment of lighting LEDs. This thesis studies physical layer characteristics of VLC systems based on either indoor LED lighting or outdoor LED traffic signaling infrastructure. Advanced communication techniques are proposed to cope with LED bandwidth limitations and grant multiple accesses. Their performance is comprehensively analyzed in typical lighting and signaling environments. Firstly, communication link issues are studied. A conversion method from photometric parameters for illumination to radiometric parameters for communication is developed. Two typical VLC links, the line-of-sight (LOS) link and non-line-of-sight (NLOS) diffuse link, are characterized both experimentally and numerically. Some optional reverse link provisions are evaluated for a full duplex system. Different noise sources and background interferences are analyzed, and dominant noises are identified under typical application scenarios. With identified signal propagation and noise characteristics, link performance is then evaluated. Secondly, transceiver design techniques to increase the data rate are proposed, including digital pre-equalization techniques and the optical orthogonal frequency division multiplexing (O-OFDM) whose peak to average power ratio (PAPR) issue is investigated. Thirdly, the capacity of the multiple-input multiple-output (MIMO) VLC system exploring inherent multiple LED transmitters and multiple photodetectors is evaluated. The effects of some system parameters involved in non-imaging and imaging transceivers

  20. Making Light Rays Visible in 3-D

    ERIC Educational Resources Information Center

    Logiurato, F.; Gratton, L. M.; Oss, S.

    2007-01-01

    Students become deeply involved in physics classes when spectacular demonstrations take over from abstract and formal presentations. In this paper we propose a simple experimental setup in which the wave behavior of light can be made spectacularly evident along the whole path of the light beam in a practically unlimited number of configurations.…

  1. Efficiency of Cu2O/BiVO4 particles prepared with a new soft procedure on the degradation of dyes under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Aguilera-Ruiz, Eduardo; García-Pérez, Ulises M.; de la Garza-Galván, María; Zambrano-Robledo, Patricia; Bermúdez-Reyes, Bárbara; Peral, José

    2015-02-01

    Cu2O/BiVO4 composites with different concentrations of Cu2O were synthesized by a simple impregnation method at 200 °C under N2 atmosphere for 4 h. The as-synthesized samples were characterized by X-ray powder diffraction, scanning electron microscopy, UV-vis diffuse reflection absorption and vis photoluminescence. The morphology of the as-synthesized composites with different weight ratios of Cu2O is composed by quasi-spherical and dendrite-like particles. The photocatalytic performance of the Cu2O/BiVO4 composites was evaluated by degradation of methyl orange solutions under visible-LED irradiation. The results obtained show that the photocatalytic behavior of the p-n heterojunction Cu2O/BiVO4 composites was better than pure Cu2O and BiVO4. The variation of the reaction parameters, such as solution pH and presence of O2, improved the photocatalytic performance of Cu2O/BiVO4 composite. Meanwhile, a possible mechanism for methyl orange photocatalytic degradation over Cu2O/BiVO4 photocatalysts was proposed. The chemical stability and reusability of Cu2O/BiVO4 powders were also investigated.

  2. A titanium and visible light-polymerized resin obturator.

    PubMed

    Rilo, Benito; da Silva, José Luis; Martinez-Insua, Arturo; Santana, Urbano

    2002-04-01

    Obturator prostheses are typically large, and their weight and size are often important design factors. This article describes the fabrication of an obturator prosthesis with a titanium framework and visible light-polymerized denture base resin. It is speculated that these low-density materials may produce prostheses lighter than similar ones made with conventional materials. An added advantage is that visible light-polymerizing resins facilitate relining. PMID:12011852

  3. Visible light-driven CdSe nanotube array photocatalyst

    PubMed Central

    2013-01-01

    Large-scale CdSe nanotube arrays on indium tin oxide (ITO) glass have been synthesized using ZnO nanorod template. The strong visible light absorption in CdSe, its excellent photoresponse, and the large surface area associated with the tubular morphology lead to good visible light-driven photocatalytic capability of these nanotube arrays. Compared to freestanding nanoparticles, such one-piece nanotube arrays on ITO make it very convenient for catalyst recycling after their usage PMID:23680487

  4. Visible light-driven CdSe nanotube array photocatalyst

    NASA Astrophysics Data System (ADS)

    Zhu, Haojun; Li, Quan

    2013-05-01

    Large-scale CdSe nanotube arrays on indium tin oxide (ITO) glass have been synthesized using ZnO nanorod template. The strong visible light absorption in CdSe, its excellent photoresponse, and the large surface area associated with the tubular morphology lead to good visible light-driven photocatalytic capability of these nanotube arrays. Compared to freestanding nanoparticles, such one-piece nanotube arrays on ITO make it very convenient for catalyst recycling after their usage

  5. Visible light-driven CdSe nanotube array photocatalyst.

    PubMed

    Zhu, Haojun; Li, Quan

    2013-01-01

    Large-scale CdSe nanotube arrays on indium tin oxide (ITO) glass have been synthesized using ZnO nanorod template. The strong visible light absorption in CdSe, its excellent photoresponse, and the large surface area associated with the tubular morphology lead to good visible light-driven photocatalytic capability of these nanotube arrays. Compared to freestanding nanoparticles, such one-piece nanotube arrays on ITO make it very convenient for catalyst recycling after their usage. PMID:23680487

  6. Imaging of Biological Tissues by Visible Light CDI

    NASA Astrophysics Data System (ADS)

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

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

  7. Robotic visible-light laser adaptive optics

    NASA Astrophysics Data System (ADS)

    Baranec, Christoph; Riddle, Reed; Law, Nicholas; Ramaprakash, A. N.; Tendulkar, Shriharsh; Bui, Khanh; Burse, Mahesh; Chordia, Pravin; Das, Hillol; Dekany, Richard; Kulkarni, Shrinivas; Punnadi, Sujit

    2013-12-01

    Robo-AO is the first autonomous laser adaptive optics system and science instrument operating on sky. With minimal human oversight, the system robotically executes large scale surveys, monitors long-term astrophysical dynamics and characterizes newly discovered transients, all at the visible diffraction limit. The adaptive optics setup time, from the end of the telescope slew to the beginning of an observation, is a mere ~50-60 s, enabling over 200 observations per night. The first of many envisioned systems has finished 58 nights of science observing at the Palomar Observatory 60-inch (1.5 m) telescope, with over 6,400 robotic observations executed thus far. The system will be augmented in late 2013 with a low-noise wide field infrared camera, which doubles as a tip-tilt sensor, to widen the spectral bandwidth of observations and increase available sky coverage while also enabling deeper visible imaging using adaptive-optics sharpened infrared tip-tilt guide sources. Techniques applicable to larger telescope systems will also be tested: the infrared camera will be used to demonstrate advanced multiple region-of-interest tip-tilt guiding methods, and a visitor instrument port will be used for evaluation of other instrumentation, e.g. single-mode and photonic fibers to feed compact spectrographs.

  8. Tailorable, Visible Light Emission From Silicon Nanocrystals

    SciTech Connect

    Samara, G.A.; Wilcoxon, J.P.

    1999-07-20

    J. P. Wilcoxon and G. A. Samara Crystalline, size-selected Si nanocrystals in the size range 1.8-10 nm grown in inverse micellar cages exhibit highly structured optical absorption and photoluminescence (PL) across the visible range of the spectrum. The most intense PL for the smallest nanocrystals produced This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. to induce a useful level of visible photoluminescence (PL) from silicon (Si). The approaches understood. Visible PL has been observed from Si nanocrystals, or quantum dots, produced by a variety of techniques including aerosols,2 colloids,3 and ion implantation.4 However, all of The optical absorption spectra of our nanocrystals are much richer in spectral features spectrum of bulk Si where the spectral features reflect the details of the band structure shown in nanocrystals estimated to have a Si core diameter of 1-2 nm. These measured quantum those in the spectrum of bulk Si in Fig. 1 are striking indicating that nanocrystals of this size 8-Room temperature PL results on an HPLC size-selected, purified 2 nm nanocrystals but blue shifted by -0.4 eV due to quantum confinement. Excitation at 245 nm yields

  9. Visible light surface emitting semiconductor laser

    DOEpatents

    Olbright, Gregory R.; Jewell, Jack L.

    1993-01-01

    A vertical-cavity surface-emitting laser is disclosed comprising a laser cavity sandwiched between two distributed Bragg reflectors. The laser cavity comprises a pair of spacer layers surrounding one or more active, optically emitting quantum-well layers having a bandgap in the visible which serve as the active optically emitting material of the device. The thickness of the laser cavity is m .lambda./2n.sub.eff where m is an integer, .lambda. is the free-space wavelength of the laser radiation and n.sub.eff is the effective index of refraction of the cavity. Electrical pumping of the laser is achieved by heavily doping the bottom mirror and substrate to one conductivity-type and heavily doping regions of the upper mirror with the opposite conductivity type to form a diode structure and applying a suitable voltage to the diode structure. Specific embodiments of the invention for generating red, green, and blue radiation are described.

  10. Ligand-assisted soft-chemical synthesis of self-assembled different shaped mesoporous Co3O4: efficient visible light photocatalysts.

    PubMed

    Roy, Mouni; Ghosh, Sourav; Naskar, Milan Kanti

    2015-04-21

    Mesoporous self-assembled cobalt oxide (Co3O4) of different shapes was synthesized by a facile soft-chemical process using cobalt nitrate, oxalic acid and phosphoric acid in the presence of cationic templates, cetyltrimethylammonium bromide, 1-butyl-3-methylimidazolium bromide, and pyridinium bromide at 75 °C/2 h followed by calcination at 300 °C. The effect of cationic templates of the samples on the physico-chemical properties, and the photocatalytic efficiency for the degradation of Chicago Sky Blue 6B was studied. Pyridinium bromide and 1-butyl-3-methylimidazolium bromide facilitated formation of particles with different shaped morphology compared to cetyltrimethylammonium bromide. The rod-like particles having higher surface area exhibited higher photocatalytic performance. PMID:25792483

  11. Kinetic study of acetaminophen degradation by visible light photocatalysis.

    PubMed

    Gotostos, Mary Jane N; Su, Chia-Chi; De Luna, Mark Daniel G; Lu, Ming-Chun

    2014-01-01

    In this work, a novel photocatalyst K3[Fe(CN)6]/TiO2 synthesized via a simple sol-gel method was utilized to degrade acetaminophen (ACT) under visible light with the use of blue and green LED lights. Parameters (medium pH, initial concentration of reactant, catalyst concentration, temperature, and number of blue LED lights) affecting photocatalytic degradation of ACT were also investigated. The experimental result showed that compared to commercially available Degussa P-25 (DP-25) photocatalyst, K3[Fe(CN)6]/TiO2 gave higher degradation efficiency and rate constant (kapp) of ACT. The degradation efficiency or kapp decreased with increasing initial ACT concentration and temperature, but increased with increased number of blue LED lamps. Additionally, kapp increased as initial pH was increased from 5.6 to 6.9, but decreased at a high alkaline condition (pH 8.3). Furthermore, the degradation efficiency and kapp of ACT increased as K3[Fe(CN)6]/TiO2 loading was increased to 1 g L(-1) but decreased and eventually leveled off at photocatalyst loading above this value. Photocatalytic degradation of ACT in K3[Fe(CN)6]/TiO2 catalyst system follows a pseudo-first-order kinetics. The Langmuir-Hinshelwood equation was also satisfactorily used to model the degradation of ACT in K3[Fe(CN)6]/TiO2 catalyst system indicated by a satisfactory linear correlation between 1/kapp and Co, with kini = 6.54 × 10(-4) mM/min and KACT = 17.27 mM(-1). PMID:24766590

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

    SciTech Connect

    Atac, M.

    1998-02-01

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

  13. Light-concentrating plasmonic Au superstructures with significantly visible-light-enhanced catalytic performance.

    PubMed

    Yang, Jinhu; Li, Ying; Zu, Lianhai; Tong, Lianming; Liu, Guanglei; Qin, Yao; Shi, Donglu

    2015-04-22

    Noble metals are well-known for their surface plasmon resonance effect that enables strong light absorption typically in the visible regions for gold and silver. However, unlike semiconductors, noble metals are commonly considered incapable of catalyzing reactions via photogenerated electron-hole pairs due to their continuous energy band structures. So far, photonically activated catalytic system based on pure noble metal nanostructures has seldom been reported. Here, we report the development of three different novel plasmonic Au superstructures comprised of Au nanoparticles, multiple-twinned nanoparticles and nanoworms assembling on the surfaces of SiO2 nanospheres respectively via a well-designed synthetic strategy. It is found that these novel Au superstructures show enhanced broadband visible-light absorption due to the plasmon resonance coupling within the superstructures, and thus can effectively focus the energy of photon fluxes to generate much more excited hot electrons and holes for promoting catalytic reactions. Accordingly, these Au superstructures exhibit significantly visible-light-enhanced catalytic efficiency (up to ∼264% enhancement) for the commercial reaction of p-nitrophenol reduction. PMID:25840556

  14. Efficient visible driven photocatalyst, silver phosphate: performance, understanding and perspective.

    PubMed

    Martin, David James; Liu, Guigao; Moniz, Savio J A; Bi, Yingpu; Beale, Andrew M; Ye, Jinhua; Tang, Junwang

    2015-11-01

    Photocatalysis is a promising technology that can contribute to renewable energy production from water and water purification. In order to further develop the field and meet industrial requirements, it is imperative to focus on advancing high efficiency visible light photocatalysts, such as silver phosphate (Ag3PO4). This review aims to highlight the recent progress made in the field, focusing on oxygen production from water, and organic contaminant decomposition using Ag3PO4. The most important advances are discussed and explained in detail, including semiconductor-semiconductor junctions, metal-semiconductor junctions, exposing facet control, and fundamental understanding using advanced spectroscopies and computational chemistry. The review then concludes by critically summarising both findings and current perspectives, and ultimately how the field might best advance in the near future. PMID:26204436

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

    PubMed

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

    2015-07-01

    Intimate coupling of photocatalysis and biodegradation (ICPB) technology is attractive for phenolic wastewater treatment, but has only been investigated using UV light (called UPCB). We examined the intimate coupling of visible-light-induced photocatalysis and biodegradation (VPCB) for the first time. Our catalyst was prepared doping both of Er(3+) and YAlO3 into TiO2 which were supported on macroporous carriers. The macroporous carriers was used to support for the biofilms as well. 99.8% removal efficiency of phenol was achieved in the VPCB, and this was 32.6% higher than that in the UPCB. Mineralization capability of UPCB was even worse, due to less adsorbable intermediates and cell lysis induced soluble microbial products release. The lower phenol degradation in the UPCB was due to the serious detachment of the biofilms, and then the microbes responsible for phenol degradation were insufficient due to disinfection by UV irradiation. In contrast, microbial communities in the carriers were well protected under visible light irradiation and extracellular polymeric substances secretion was enhanced. Thus, we found that the photocatalytic reaction and biodegradation were intimately coupled in the VPCB, resulting in 64.0% removal of dissolved organic carbon. Therefore, we found visible light has some advantages over UV light in the ICPB technology. PMID:26076382

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

    NASA Astrophysics Data System (ADS)

    Luo, Zhijie; Zhang, WeiNan; Zhou, GuoFu

    2016-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Luo, Zhijie; Zhang, WeiNan; Zhou, GuoFu

    2016-06-01

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

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

    PubMed

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

    2015-09-01

    Owing to the effect of energy band bending, p-type Co3O4 quantum dots sensitized by Eosin Y showed a high and stable photocatalytic activity (∼13,440 μmol h(-1) g(-1)(cat)) for water reduction and hydrogen production under visible-light irradiation without any cocatalyst. PMID:26234704

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    A well-organised reduced graphene oxide (RGO) and silver (Ag) wrapped TiO2 nano-hybrid was successfully achieved through a facile and easy route. The inherent characteristics of the synthesized RGO-Ag/TiO2 were revealed through crystalline phase, morphology, chemical composition, Raman scattering, UV-visible absorption, and photoluminescence analyses. The adopted synthesis route significantly controlled the uniform formation of silver nanoparticles and contributed for the absorption of light in the visible spectrum through localized surface plasmon resonance effects. The wrapped RGO nanosheets triggered the electron mobility and promoted visible light shift towards red spectrum. The accomplishment of synergised effect of RGO and Ag well degraded Bisphenol A under visible light irradiation with a removal efficiency of 61.9%.

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

    PubMed

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

    2015-09-01

    Highly transparent phototransistors that can detect visible light have been fabricated by combining indium-gallium-zinc oxide (IGZO) and quantum dots (QDs). A wide-band-gap IGZO film was used as a transparent semiconducting channel, while small-band-gap QDs were adopted to absorb and convert visible light to an electrical signal. Typical IGZO thin-film transistors (TFTs) did not show a photocurrent with illumination of visible light. However, IGZO TFTs decorated with QDs showed enhanced photocurrent upon exposure to visible light. The device showed a responsivity of 1.35×10(4) A/W and an external quantum efficiency of 2.59×10(4) under illumination by a 635 nm laser. The origin of the increased photocurrent in the visible light was the small band gap of the QDs combined with the transparent IGZO films. Therefore, transparent phototransistors based on IGZO and QDs were fabricated and characterized in detail. The result is relevant for the development of highly transparent photodetectors that can detect visible light. PMID:26293387

  1. Ganymede in Visible and Infrared Light

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This montage compares New Horizons' best views of Ganymede, Jupiter's largest moon, gathered with the spacecraft's Long Range Reconnaissance Imager (LORRI) and its infrared spectrometer, the Linear Etalon Imaging Spectral Array (LEISA).

    LEISA observes its targets in more than 200 separate wavelengths of infrared light, allowing detailed analysis of their surface composition. The LEISA image shown here combines just three of these wavelengths -- 1.3, 1.8 and 2.0 micrometers -- to highlight differences in composition across Ganymede's surface. Blue colors represent relatively clean water ice, while brown colors show regions contaminated by dark material.

    The right panel combines the high-resolution grayscale LORRI image with the color-coded compositional information from the LEISA image, producing a picture that combines the best of both data sets.

    The LEISA and LORRI images were taken at 9:48 and 10:01 Universal Time, respectively, on February 27, 2007, from a range of 3.5 million kilometers (2.2 million miles). The longitude of the disk center is 38 degrees west. With a diameter of 5,268 kilometers (3,273 miles), Ganymede is the largest satellite in the solar system.

  2. Towards a 100 Gb/s visible light wireless access network.

    PubMed

    Tsonev, Dobroslav; Videv, Stefan; Haas, Harald

    2015-01-26

    Potential visible light communication (VLC) data rates at over 10 Gb/s have been recently demonstrated using light emitting diodes (LEDs). The disadvantage is, LEDs have an inherent trade-off between optical efficiency and bandwidth. Consequently, laser diodes (LDs) can be considered as a very promising alternative for better utilization of the visible light spectrum for communication purposes. This work investigates the communication capabilities of off-the-shelf LDs in a number of scenarios with illumination constraints. The results indicate that optical wireless access data rates in the excess of 100 Gb/s are possible at standard indoor illumination levels. PMID:25835920

  3. Visible Light Driven Photocatalytic Reactor Based on Micro-structured Polymer Optical Fiber Preform

    NASA Astrophysics Data System (ADS)

    Li, Dong-Dong; She, Jiang-Bo; Wang, Chang-Shun; Peng, Bo

    2014-05-01

    A novel visible light driven photocatalytic reactor with 547 pieces of Ag/AgBr-film-modified capillaries is reported and it is derived from a microstructured polymer optical fiber (MPOF) preform. The MPOF preform not only plays the role of a light-transmitting media, but it is also a Ag/AgBr supporting and waste-water pipe to supply the photocatalytic degradation of dyes solute. The photocatalytic reactor has such a large surface area for Ag/AgBr loading, which is a visible light driven photocatalyst that photodegradation efficiency is enhanced.

  4. Is it effective to harvest visible light by decreasing the band gap of photocatalytic materials?

    NASA Astrophysics Data System (ADS)

    Fu, Ning; Tang, Xinhu; Li, Dongyang

    2012-02-01

    In situ variations in the electron work function and photo-current of TiO2 nanotubes demonstrate that long-wavelength illumination only has a minor effect on the excitation of electrons in the nanotubes after being exposed to short-wavelength light or when the short-wavelength light coexisted, indicating that the solar spectrum may not be utilized as efficiently as expected by extending the absorption spectrum of the photocatalytic material to visible light range with decreased band gaps.

  5. Water splitting on semiconductor catalysts under visible-light irradiation.

    PubMed

    Navarro Yerga, Rufino M; Alvarez Galván, M Consuelo; del Valle, F; Villoria de la Mano, José A; Fierro, José L G

    2009-01-01

    Sustainable hydrogen production is a key target for the development of alternative, future energy systems that will provide a clean and affordable energy supply. The Sun is a source of silent and precious energy that is distributed fairly all over the Earth daily. However, its tremendous potential as a clean, safe, and economical energy source cannot be exploited unless the energy is accumulated or converted into more useful forms. The conversion of solar energy into hydrogen via the water-splitting process, assisted by photo-semiconductor catalysts, is one of the most promising technologies for the future because large quantities of hydrogen can potentially be generated in a clean and sustainable manner. This Minireview provides an overview of the principles, approaches, and research progress on solar hydrogen production via the water-splitting reaction on photo-semiconductor catalysts. It presents a survey of the advances made over the last decades in the development of catalysts for photochemical water splitting under visible-light irradiation. The Minireview also analyzes the energy requirements and main factors that determine the activity of photocatalysts in the conversion of water into hydrogen and oxygen using sunlight. Remarkable progress has been made since the pioneering work by Fujishima and Honda in 1972, but he development of photocatalysts with improved efficiencies for hydrogen production from water using solar energy still faces major challenges. Research strategies and approaches adopted in the search for active and efficient photocatalysts, for example through new materials and synthesis methods, are presented and analyzed. PMID:19536754

  6. Effect of various visible light photoinitiators on the polymerization and color of light-activated resins.

    PubMed

    Arikawa, Hiroyuki; Takahashi, Hideo; Kanie, Takahito; Ban, Seiji

    2009-07-01

    The purpose of this study was to investigate effects of various visible light photoinitiators on the polymerization efficiency and color of the light-activated resins. Four photoinitiators, including camphorquinone, phenylpropanedione, monoacrylphosphine oxide (TPO), and bisacrylphosphine oxide (Ir819), were used. Each photoinitiator was dissolved in a Bis-GMA and TEGDMA monomer mixture. Materials were polymerized using dental quartz-tungsten halogen lamp (QTH), plasma-ark lamp and blue LED light-curing units, and a custom-made violet LED light unit. The degree of monomer conversion and CIE L*a*b* color values of the resins were measured using a FTIR and spectral transmittance meter. The degree of monomer conversions of TPO- and Ir819-containing resins polymerized with the violet-LED unit were higher than camphorquinone-containing resin polymerized with the QTH light-curing unit. The lowest color values were observed for the TPO-containing resin. Our results indicate that the TPO photoinitiator and the violet-LED light unit may provide a useful and improved photopolymerization system for dental light-activated resins. PMID:19721283

  7. Non-Noble-Metal Nanoparticle Supported on Metal-Organic Framework as an Efficient and Durable Catalyst for Promoting H2 Production from Ammonia Borane under Visible Light Irradiation.

    PubMed

    Wen, Meicheng; Cui, Yiwen; Kuwahara, Yasutaka; Mori, Kohsuke; Yamashita, Hiromi

    2016-08-24

    In this work, we propose a straightforward method to enhance the catalytic activity of AB dehydrogenation by using non-noble-metal nanoparticle supported on chromium-based metal-organic framework (MIL-101). It was demonstrated to be effective for hydrogen generation from ammonia borane under assistance of visible light irradiation as a noble-metal-free catalyst. The catalytic activity of metal nanoparticles supported on MIL-101 under visible light irradiation is remarkably higher than that without light irradiation. The TOFs of Cu/MIL-101, Co/MIL-101, and Ni/MIL-101 are 1693, 1571, and 3238 h(-1), respectively. The enhanced activity of catalysts can be primarily attributed to the cooperative promoting effects from both non-noble-metal nanoparticles and photoactive metal-organic framework in activating the ammonia borane molecule and strong ability in the photocatalytic production of hydroxyl radicals, superoxide anions, and electron-rich non-noble-metal nanoparticle. This work sheds light on the exploration of active non-noble metals supported on photoactive porous materials for achieving high catalytic activity of various redox reactions under visible light irradiation. PMID:27478964

  8. Development and Progress in Enabling the Photocatalyst Ti02 Visible-Light-Active

    NASA Technical Reports Server (NTRS)

    Levine, Lanfang H.; Coutts, Janelle L.; Clausen, Christian A.

    2011-01-01

    Photocatalytic oxidation (PCO) of organic contaminants is a promising air and water quality management approach which offers energy and cost savings compared to thermal catalytic oxidation (TCO). The most widely used photocatalyst, anatase TiO2, has a wide band gap (3.2 eV) and is activated by UV photons. Since solar radiation consists of less than 4% UV, but contains 45% visible light, catalysts capable of utilizing these visible photons need to be developed to make peo approaches more efficient, economical, and safe. Researchers have attempted various approaches to enable TiO2 to be visible-light-active with varied degrees of success'. Strategies attempted thus far fall into three categories based on their electrochemical' mechanisms: 1) narrowing the band gap of TiO2 by implantation of transition metal elements or nonmetal elements such as N, S, and C, 2) modifying electron-transfer processes during PCO by adsorbing sensitizing dyes, and 3) employing light-induced interfacial electron transfer in the heteronanojunction systems consisting of narrow band gap semiconductors represented by metal sulfides and TiO2. There are diverse technical approaches to implement each of these strategies. This paper presents a review of these approaches and results of the photocatalytic activity and photonic efficiency of the end .products under visible light. Although resulting visible-light-active (VLA) photocatalysts show promise, there is often no comparison with unmodified TiO2 under UV. In a limited number of studies where such comparison was provided, the UV-induced catalytic activity of bare TiO2 is much greater than the visible-light-induced catalytic activity of the VLA catalyst. Furthermore, VLA-catalysts have much lower quantum efficiency compared to the approx.50% quantum efficiency of UV-catalysts. This stresses the need for continuing research in this area.

  9. Three-visible-light wave combiner based on photonic crystal waveguides.

    PubMed

    Liu, Dingwen; Sun, Yiling; Ouyang, Zhengbiao

    2014-07-20

    We present a three-visible-light wave combiner based on two-dimensional photonic crystal waveguides whose widths are not integral multiples of the lattice period. The proposed device consists of two cascaded directional couplers. It combines three visible light waves with different wavelengths from three input ports into a single output port. As an example, a combiner for combining light waves of 635, 532, and 488 nm, which are commonly used as the three primary colors in laser display systems, is designed and demonstrated through the finite-difference time-domain method. The results show that the proposed device can perform efficient synthesis for three visible light waves with transmittance exceeding 89% for each wavelength and high ability in preventing the backward coupling of waves from different waveguides. The method for designing the combiner is useful for designing other waveguide couplers based on photonic crystals made of dispersion materials. PMID:25090219

  10. Using metallic photonic crystals as visible light sources

    NASA Astrophysics Data System (ADS)

    Belousov, Sergei; Bogdanova, Maria; Deinega, Alexei; Eyderman, Sergey; Valuev, Ilya; Lozovik, Yurii; Polischuk, Ilya; Potapkin, Boris; Ramamurthi, Badri; Deng, Tao; Midha, Vikas

    2012-11-01

    In this paper we study numerically and experimentally the possibility of using metallic photonic crystals (PC's) of different geometries (log-piles, direct and inverse opals) as visible light sources. It is found that by tuning geometrical parameters of a direct opal PC one can achieve substantial reduction of the emissivity in the infrared along with its increase in the visible. We take into account disorder of the PC elements in their sizes and positions, and we get quantitative agreement between the numerical and experimental results. We analyze the influence of known temperature-resistant refractory host materials necessary for fixing the PC elements, and we find that PC effects become completely destroyed at high temperatures due to the host absorption. Therefore, creating PC-based visible light sources requires that low-absorbing refractory materials for the embedding medium be found.

  11. Fluorescent Photochromic Diarylethene That Turns on with Visible Light.

    PubMed

    Sumi, Takaki; Kaburagi, Tomohiro; Morimoto, Masakazu; Une, Kanako; Sotome, Hikaru; Ito, Syoji; Miyasaka, Hiroshi; Irie, Masahiro

    2015-10-01

    A new fluorescent photochromic diarylethene that can be activated by irradiation with 405 nm light was synthesized. The turn-on mode switching of fluorescence with visible light is favorable for application to biological systems. The fluorescence quantum yield of the photogenerated closed-ring isomer was as high as 0.8 in less or medium polar solvents, and even in polar acetonitrile the yield was higher than 0.6. PMID:26376422

  12. Emission of Visible Light by Hot Dense Metals

    SciTech Connect

    More, R.M.; Goto, M.; Graziani, F.; Ni, P.A.; Yoneda, H.

    2009-12-01

    We consider the emission of visible light by hot metal surfaces having uniform and non-uniform temperature distributions and by small droplets of liquid metal. The calculations employ a nonlocal transport theory for light emission, using the Kubo formula to relate microscopic current fluctuations to the dielectric function of the material. We describe a related algorithm for calculating radiation emission in particle simulation of hot fusion plasmas.

  13. Photoacid-mediated ring opening polymerization driven by visible light.

    PubMed

    Fu, Changkui; Xu, Jiangtao; Boyer, Cyrille

    2016-06-01

    A novel methodology of visible light regulated ring opening polymerization in the presence of reversible merocyanine-based photoacid was reported for the first time. In combination with a photoinduced radical polymerization technique, a dual wavelength light controlled orthogonal polymerization system was investigated to switch the polymerization between two different monomers and for the preparation of block and graft copolymers in one pot. PMID:27167862

  14. Developing Tools for Undergraduate Spectroscopy: An Inexpensive Visible Light Spectrometer

    ERIC Educational Resources Information Center

    Vanderveen, Jesse R.; Martin, Brian; Ooms, Kristopher J.

    2013-01-01

    The design and implementation of an inexpensive, high-resolution Littrow-type visible light spectrometer is presented. The instrument is built from low-cost materials and interfaced with the program RSpec for real-time spectral analysis, making it useful for classroom and laboratory exercises. Using a diffraction grating ruled at 1200 lines/mm and…

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

    NASA Astrophysics Data System (ADS)

    Vyas, G. L.; Prakash, R.; Pal, U. N.; Manchanda, R.; Halder, N.

    2016-06-01

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

  16. Preparation of visible light-driven g-C₃N₄@ZnO hybrid photocatalyst via mechanochemistry.

    PubMed

    Zhou, Jianwei; Zhang, Mo; Zhu, Yongfa

    2014-09-01

    C3N4@ZnO hybrid materials with visible light photocatalytic performance have been prepared by facile mechanical milling. The dispersion of conjugated molecule g-C3N4 on the surface of ZnO improved during mechanical process, and the multilayer hybrid structure of g-C3N4@ZnO materials with remarkable visible light photocatalytic activity was formed by ball milling. The photocatalytic activity and photocurrent intensity of g-C3N4@ZnO under visible light irradiation was 3.0 and 2.0 times higher than those of pure C3N4, respectively. The great enhancement of visible light response originates from the increase of separation and immigration efficiency of photogenerated electron-hole pairs. Furthermore, a synergistic photocatalysis mechanism between ZnO and g-C3N4 was proposed. The enhanced visible light photocatalytic properties originate from the injection of excited electrons from the LUMO of C3N4 to the CB of ZnO. However, the photocatalytic activity of the photocatalyst is much lower than that of ZnO under UV light, which is caused by the lattice defect of ZnO formed during milling. PMID:25028311

  17. Scheduling for indoor visible light communication based on graph theory.

    PubMed

    Tao, Yuyang; Liang, Xiao; Wang, Jiaheng; Zhao, Chunming

    2015-02-01

    Visible light communication (VLC) has drawn much attention in the field of high-rate indoor wireless communication. While most existing works focused on point-to-point VLC technologies, few studies have concerned multiuser VLC, where multiple optical access points (APs) transmit data to multiple user receivers. In such scenarios, inter-user interference constitutes the major factor limiting the system performance. Therefore, a proper scheduling scheme has to be proposed to coordinate the interference and optimize the whole system performance. In this work, we aim to maximize the sum rate of the system while taking into account user fairness by appropriately assigning LED lamps to multiple users. The formulated scheduling problem turns out to be a maximum weighted independent set problem. We then propose a novel and efficient resource allocation method based on graph theory to achieve high sum rates. Moreover, we also introduce proportional fairness into our scheduling scheme to ensure the user fairness. Our proposed scheduling scheme can, with low complexity, achieve more multiplexing gains, higher sum rate, and better fairness than the existing works. PMID:25836136

  18. Visible light to electrical energy conversion using photoelectrochemical cells

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  19. 1-Dodecane-sulfonic-acid-sodium-salt(LAS) assisted hydrothermal synthesis of Cd{sub x}Zn{sub 1-x}S solid solution as efficient photocatalysts under visible light irradiation

    SciTech Connect

    Jia, B.; Guo, L. J.

    2010-03-01

    With anionic surfactant LAS assisted, series of zinc cadmium sulfide semiconductor photocatalysts were synthesized by hydrothermal method. These products were characterized by X-ray diffraction (XRD), UV-Vis absorption spectra (UV-Vis) and scanning electron microscopy (FESEM). The photocatalytic activities of as-prepared samples were evaluated by photocatalytic hydrogen production from water under visible-light irradiation. The best synthesis parameters are: Composition 0.9:0.1 (Cd:Zn molar ratio), Temperature 160 deg. C, Hydrothermal Time 48 Hour, LAS Concentration 1.7 mmol/L, the maximum visible-light-catalytic hydrogen production rate is 161.25 {mu}mol/h (lambda>430 nm) which is higher than those of by coprecipitation method. The experiment results indicate that surfactant assisted hydrothermal method is an effective way to get highly active CdZnS solid solution photocatalyst.

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

    EPA Science Inventory

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

  1. Visible-light-induced photocatalytic azotrifluoromethylation of alkenes with aryldiazonium salts and sodium triflinate.

    PubMed

    Yu, Xing-Long; Chen, Jia-Rong; Chen, Dong-Zhen; Xiao, Wen-Jing

    2016-07-01

    The efficient visible light photocatalytic azotrifluoromethylation of alkenes with aryldiazonium salts and sodium triflinate is described, which gave the corresponding trifluoromethylated azo compounds in generally good yields. The trifluoromethylated azo products can be easily transformed into useful heterocycles and nitrogen-containing building blocks. PMID:27292589

  2. Yttrium oxide based three dimensional metamaterials for visible light cloaking

    NASA Astrophysics Data System (ADS)

    Rai, Pratyush; Kumar, Prashanth S.; Varadan, Vijay K.; Ruffin, Paul; Brantley, Christina; Edwards, Eugene

    2014-04-01

    Metamaterial with negative refractive index is the key phenomenon behind the concept of a cloaking device to hide an object from light in visible spectrum. Metamaterials made of two and three dimensional lattices of periodically placed electromagnetic resonant cells can achieve absorption and propagation of incident electromagnetic radiation as confined electromagnetic fields confined to a waveguide as surface plasmon polaritons, which can be used for shielding an object from in-tune electromagnetic radiation. The periodicity and dimensions of resonant cavity determine the frequency, which are very small as compared to the wavelength of incident light. Till now the phenomena have been demonstrated only for lights in near infrared spectrum. Recent advancements in fabrication techniques have made it possible to fabricate array of three dimensional nanostructures with cross-sections as small as 25 nm that are required for negative refractive index for wavelengths in visible light spectrum of 400-700 nm and for wider view angle. Two types of metamaterial designs, three dimensional concentric split ring and fishnet, are considered. Three dimensional structures consisted of metal-dielectric-metal stacks. The metal is silver and dielectric is yttrium oxide, other than conventional materials such as FR4 and Duroid. High κ dielectric and high refractive index as well as large crystal symmetry of Yttrium oxide has been investigated as encapsulating medium. Dependence of refractive index on wavelength and bandwidth of negative refractive index region are analyzed for application towards cloaking from light in visible spectrum.

  3. A possible mechanism for visible-light-induced skin rejuvenation

    NASA Astrophysics Data System (ADS)

    Longo, Leonardo; Lubart, Rachel; Friedman, Harry; Lavie, R.

    2004-09-01

    In recent years there has been intensive research in the field of non-ablative skin rejuvenation. This comes as a response to the desire for a simple method of treating rhytids caused by aging, UV exposure and acne scars. In numerous studies intense visible light pulsed systems (20-30J/cm2) are used. The mechanism of action was supposed to be a selective heat induced denaturalization of dermal collagen that leads to subsequent reactive synthesis. In this study we suggest a different mechanism for photorejuvenation based on light induced Reactive Oxygen Species (ROS) formation. We irradiated collagen in-vitro with a broad band of visible light, 400-800 nm, 12-22J/cm2, and used the spin trapping coupled with electron paramagnetic resonance (EPR) spectroscopy to detect ROS. In vivo, we used dose 30 J in average (35 for acnis scars, 25 for wrinkles and redness). Irradiated collagen results in hydroxyl and methyl radicals formation. We propose, as a new concept, that visible light at the intensity used for skin rejuvenation, 20-30J/cm2, produces high amounts of ROS which destroy old collagen fibers encouraging the formation of new ones. On the other hand at inner depths of the skin, where the light intensity is much weaker, low amounts of ROS are formed which are well known to stimulate fibroblast proliferation.

  4. Molecular design strategy toward diarylethenes that photoswitch with visible light.

    PubMed

    Fukaminato, Tuyoshi; Hirose, Takashi; Doi, Takao; Hazama, Masaki; Matsuda, Kenji; Irie, Masahiro

    2014-12-10

    Photoactive molecules that reversibly switch upon visible light irradiation are one of the most attractive targets for biological as well as imaging applications. One possible approach to prepare such photoswitches is to extend π-conjugation length of molecules and shift the absorption bands to longer wavelengths. Although several attempts have been demonstrated based on this approach for diarylethene (DAE) photoswitches, photoreactivity of the DAE derivatives is dramatically suppressed when the conjugation length is extended by connecting aromatic dyes at the side positions of aryl groups in the DAE unit. In this study, we successfully prepared a visible-light reactive DAE derivative by introducing an aromatic dye at the reactive carbon atom of the DAE unit, optimizing orbital level of each component, and controlling the mutual orientation of the aromatic dye and the DAE unit. The DAE derivative (3) undergoes a photocyclization reaction upon irradiation with 560 nm light and the closed-isomer converts to the open-ring isomer upon irradiation with 405 nm light. The high photoconversion yields (>90%) were achieved for both photocyclization and photocycloreversion reactions. The photoreactivity induced by visible light irradiation and the molecular design strategy were discussed based on theoretical calculations. PMID:25390547

  5. Conducting polymer nanostructures for photocatalysis under visible light

    NASA Astrophysics Data System (ADS)

    Ghosh, Srabanti; Kouamé, Natalie A.; Ramos, Laurence; Remita, Samy; Dazzi, Alexandre; Deniset-Besseau, Ariane; Beaunier, Patricia; Goubard, Fabrice; Aubert, Pierre-Henri; Remita, Hynd

    2015-05-01

    Visible-light-responsive photocatalysts can directly harvest energy from solar light, offering a desirable way to solve energy and environment issues. Here, we show that one-dimensional poly(diphenylbutadiyne) nanostructures synthesized by photopolymerization using a soft templating approach have high photocatalytic activity under visible light without the assistance of sacrificial reagents or precious metal co-catalysts. These polymer nanostructures are very stable even after repeated cycling. Transmission electron microscopy and nanoscale infrared characterizations reveal that the morphology and structure of the polymer nanostructures remain unchanged after many photocatalytic cycles. These stable and cheap polymer nanofibres are easy to process and can be reused without appreciable loss of activity. Our findings may help the development of semiconducting-based polymers for applications in self-cleaning surfaces, hydrogen generation and photovoltaics.

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

    PubMed

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

    2016-05-01

    Carbon dots, generally defined as small carbon nanoparticles with various surface passivation schemes, have emerged as a new class of quantum-dot-like nanomaterials, with their optical properties and photocatalytic functions resembling those typically found in conventional nanoscale semiconductors. In this work, carbon dots were evaluated for their photoinduced bactericidal functions, with the results suggesting that the dots were highly effective in bacteria-killing with visible-light illumination. In fact, the inhibition effect could be observed even simply under ambient room lighting conditions. Mechanistic implications of the results are discussed and so are opportunities in the further development of carbon dots into a new class of effective visible/natural light-responsible bactericidal agents for a variety of bacteria control applications. PMID:27064729

  7. Controlled release of fragrant molecules with visible light.

    PubMed

    Wang, Zhuozhi; Johns, Valentine K; Liao, Yi

    2014-11-01

    Controlled release of odorous molecules is the key to digital scent technology which will add another dimension to electronics. Photorelease is a cold mechanism that promises better temporal and spatial control than thermal release. Herein we report a novel material composed of an acid-sensitive polymer carrying a fragrant aldehyde and a reversible metastable-state photoacid. It releases the fragrant molecule under visible light, and stops releasing it after the light is turned off. A metastable-state photoacid with a fast reverse-reaction rate was developed to quickly stop the release after irradiation. Both the carrier polymer and the photoacid can be reused after all the fragrant molecules have been released. The material combines the advantages of visible-light activity, fast on/off rate, easy preparation, and recyclability, and thus is promising for digital scent technology. PMID:25284277

  8. Resource allocation for multichannel broadcasting visible light communication

    NASA Astrophysics Data System (ADS)

    Le, Nam-Tuan; Jang, Yeong Min

    2015-11-01

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

  9. Superior preferential oxidation of carbon monoxide in hydrogen-rich stream under visible light irradiation over gold loaded hedgehog-shaped titanium dioxide nanospheres: Identification of copper oxide decoration as an efficient promoter

    NASA Astrophysics Data System (ADS)

    Yang, Kai; Huang, Kun; Lin, Liuliu; Chen, Xun; Dai, Wenxin; Fu, Xianzhi

    2015-06-01

    Gold nanoparticles loaded on the special three-dimensional urchin-like micro/nano hierarchical TiO2 microspheres, with CuO layer modification, are performed for the CO preferential oxidation in H2-rich stream at room temperature under visible light irradiation or not. It is found that the suitable outer decoration of CuO in TiO2 microspheres can obviously improve the catalytic activity of Au/TiO2, and adding visible light can further promote the performance. Based on the characterizations of catalysts, it is proposed that the CuO layer distributed on the shell of TiO2 urchin-like microspheres can enhance the electron transfer among Au, TiO2 and CuO sites to drive the increase in surface electron densities of Au and support sites induced by both the localized surface plasmon resonance of Au nanoparticles and the photo-excitation of CuO under visible light irradiation, resulting in the adsorptions and activations of CO and O2. Therefore, as a synactic result of its unique band gap relation, its unique electron property and its morphologic effect, the novel CuO modified TiO2 support not only enhances the microstrain itself on the stabilization of the size of Au nanoparticles, but more importantly also reinforces the electron interaction between support and Au sites.

  10. Visible-Light-Induced Decarboxylative Functionalization of Carboxylic Acids and Their Derivatives.

    PubMed

    Xuan, Jun; Zhang, Zhao-Guo; Xiao, Wen-Jing

    2015-12-21

    Visible-light-induced radical decarboxylative functionalization of carboxylic acids and their derivatives has recently received considerable attention as a novel and efficient method to create CC and CX bonds. Generally, this visible-light-promoted decarboxylation process can smoothly occur under mild reaction conditions with a broad range of substrates and an excellent functional-group tolerance. The radical species formed from the decarboxylation step can participate in not only single photocatalytic transformations, but also dual-catalytic cross-coupling reactions by combining photoredox catalysis with other catalytic processes. Recent advances in this research area are discussed herein. PMID:26509837

  11. Efficient visibility-driven medical image visualisation via adaptive binned visibility histogram.

    PubMed

    Jung, Younhyun; Kim, Jinman; Kumar, Ashnil; Feng, David Dagan; Fulham, Michael

    2016-07-01

    'Visibility' is a fundamental optical property that represents the observable, by users, proportion of the voxels in a volume during interactive volume rendering. The manipulation of this 'visibility' improves the volume rendering processes; for instance by ensuring the visibility of regions of interest (ROIs) or by guiding the identification of an optimal rendering view-point. The construction of visibility histograms (VHs), which represent the distribution of all the visibility of all voxels in the rendered volume, enables users to explore the volume with real-time feedback about occlusion patterns among spatially related structures during volume rendering manipulations. Volume rendered medical images have been a primary beneficiary of VH given the need to ensure that specific ROIs are visible relative to the surrounding structures, e.g. the visualisation of tumours that may otherwise be occluded by neighbouring structures. VH construction and its subsequent manipulations, however, are computationally expensive due to the histogram binning of the visibilities. This limits the real-time application of VH to medical images that have large intensity ranges and volume dimensions and require a large number of histogram bins. In this study, we introduce an efficient adaptive binned visibility histogram (AB-VH) in which a smaller number of histogram bins are used to represent the visibility distribution of the full VH. We adaptively bin medical images by using a cluster analysis algorithm that groups the voxels according to their intensity similarities into a smaller subset of bins while preserving the distribution of the intensity range of the original images. We increase efficiency by exploiting the parallel computation and multiple render targets (MRT) extension of the modern graphical processing units (GPUs) and this enables efficient computation of the histogram. We show the application of our method to single-modality computed tomography (CT), magnetic resonance

  12. Novel coupled structures of FeWO4/TiO2 and FeWO4/TiO2/CdS designed for highly efficient visible-light photocatalysis.

    PubMed

    Bera, Sandipan; Rawal, Sher Bahadur; Kim, Hark Jin; Lee, Wan In

    2014-06-25

    A quadrilateral disk-shaped FeWO4 nanocrystal (NC) with an average size of ∼35 nm was prepared via hydrothermal reaction. The obtained dark brown FeWO4 NC with a bandgap (Eg) of 1.98 eV was then coupled with TiO2 to form FeWO4/TiO2 composites. The valence band (VB) of FeWO4 (+2.8 eV vs NHE) was more positive than that of TiO2 (+2.7 eV); thus this system could be classified as a Type-B heterojunction. Under visible-light irradiation, 5/95 FeWO4/TiO2 (by wt %) exhibited remarkable photocatalytic activity: the amount of CO2 evolved from gaseous 2-propanol (IP) and the decomposition rate of aqueous salicylic acid (SA) were, respectively, 1.7 and 2.5 times greater than those of typical nitrogen-doped TiO2 (N-TiO2). This unique catalytic property was deduced to arise from the intersemiconductor hole transfer between the VBs of FeWO4 and TiO2. Herein, several experimental evidence were also provided to confirm the hole-transfer mechanism. To further enhance the catalytic efficiency, double-heterojunctioned FeWO4/TiO2/CdS composites were prepared by loading CdS quantum dots (QDs) onto the FeWO4/TiO2 surface. Surprisingly, the catalytic activity for evolving CO2 from IP was 2.6 times greater than that of bare FeWO4/TiO2 and 4.4 times greater than that of N-TiO2, suggesting that both holes and electrons were essential species in decomposing organic compounds. PMID:24847976

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

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

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

    PubMed

    Wu, Deyong; Long, Mingce

    2012-01-01

    For the sake of efficient utilization of sunlight, Ag nanoparticles loaded N-doped TiO₂ photocatalysts (Ag/N-TiO₂) were successfully fabricated via a two-step method to make the best use of the respective advantages of noble metal loading and nonmetal doping. Ag/N-TiO₂ was characterized using XRD, XPS and UV-Vis DRS. Compared to TiO₂, the dramatic enhancement of the visible-light-induced photocatalytic degradation efficiency of Ag/N-TiO₂ obtained for the degradation of methyl orange should be attributed to the synergistic effect of N-doping and Ag-loading, including the good visible light absorption and the effective electron-hole separations. This demonstrates Ag/N-TiO₂ is a promising photocatalytic material for organic pollutant degradation under visible light irradiation. PMID:22377998

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

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

    PubMed Central

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

    2015-01-01

    Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet–visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films. PMID:26156001

  17. Heterogeneous visible light photocatalysis for selective organic transformations.

    PubMed

    Lang, Xianjun; Chen, Xiaodong; Zhao, Jincai

    2014-01-01

    The future development of chemistry entails environmentally friendly and energy sustainable alternatives for organic transformations. Visible light photocatalysis can address these challenges, as reflected by recent intensive scientific endeavours to this end. This review covers state-of-the-art accomplishments in visible-light-induced selective organic transformations by heterogeneous photocatalysis. The discussion comprises three sections based on the photocatalyst type: metal oxides such as TiO2, Nb2O5 and ZnO; plasmonic photocatalysts like nanostructured Au, Ag or Cu supported on metal oxides; and polymeric graphitic carbon nitride. Finally, recent strides in bridging the gap between photocatalysis and other areas of catalysis will be highlighted with the aim of overcoming the existing limitations of photocatalysis by developing more creative synthetic methodologies. PMID:24162830

  18. Visible Light Photon Counters (VLPCs) for high rate tracking medical imaging and particle astrophysics

    SciTech Connect

    Atac, M. |

    1998-11-01

    This paper is on the operation principles of the Visible Light Photon Counters (VLPCs), application to high luminosity-high multiplicity tracking for High Energy Charged Particle Physics, and application to Medical Imaging and Particle Astrophysics. The VLPCs as Solid State Photomultipliers (SSPMs) with high quantum efficiency can detect down to single photons very efficiently with excellent time resolution and high avalanche gains. {copyright} {ital 1998 American Institute of Physics.}

  19. Trifluoromethylation of alkenes by visible light photoredox catalysis.

    PubMed

    Iqbal, Naeem; Choi, Sungkyu; Kim, Eunjin; Cho, Eun Jin

    2012-12-21

    A method for trifluoromethylation of alkenes has been developed employing visible light photoredox catalysis with CF(3)I, Ru(Phen)(3)Cl(2), and DBU. This process works especially well for terminal alkenes to give alkenyl-CF(3) products with only E-stereochemistry. The mild reaction conditions enable the trifluoromethylation of a range of alkenes that bear various functional groups. PMID:23167602

  20. Visible light photon counters optimization for quantum information applications

    SciTech Connect

    Molina, J.; Estrada, J.; Bross, A.; Ginther, G.; Buscher, V.; /Freiburg U.

    2006-10-01

    In this paper we describe the studies of the main parameters needed for optimal operation of Visible Light Photon Counters (VLPCs) when used in quantum information systems. The isolation of the single photon signal is analyzed through the definition of a contamination parameter. A compromise in the minimization of this parameter for temperature, bias voltage and dark count variation must be achieved and this depends on the experimental conditions.

  1. Lighting quality and energy efficiency

    SciTech Connect

    Benya, J.R.

    1996-01-01

    Ten design actions result in good lighting quality if applied intelligently. These actions are to: conceal the light source; provide enough light; relate to the architecture; relate to the human mood; utilize and manage the color of light; utilize and manage contrast; relate to the human being; solve technical problems created by other light sources; relate to the quality of the space; and realize the creative potential of the space. The starting characteristics for energy-efficient lighting include dimming capability, color capabilities, and optical capabilities. The most efficacious light source for the job should be used. This includes daylight, although it is not always reliable. Energy-efficient quality lighting is evident, but to make it persistent, to give it staying power, there must be some changes, such as: minor product improvements; two to a few major product breakthroughs; better education for the designers and specifiers; lower prices for key components and systems; higher value placed on environmental quality; ongoing applications research; doing it right; more industry awards and recoginition for energy-efficient designs; continuation of utility efforts in rebates, education programs, and technology centers; unification of the industry and avoidance of duplication; more positive governmental response and less arbitrary product-oriented legislation until this issue is better understood.

  2. Light Duty Efficient, Clean Combustion

    SciTech Connect

    Stanton, Donald W.

    2011-06-03

    Cummins has successfully completed the Light Duty Efficient Clean Combustion (LDECC) cooperative program with DoE. This program was established in 2007 in support of the Department of Energy’s Vehicles Technologies Advanced Combustion and Emissions Control initiative to remove critical barriers to the commercialization of advanced, high efficiency, emissions compliant internal combustion (IC) engines for light duty vehicles. Work in this area expanded the fundamental knowledge of engine combustion to new regimes and advanced the knowledge of fuel requirements for these diesel engines to realize their full potential. All of our objectives were met with fuel efficiency improvement targets exceeded.

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

    SciTech Connect

    Bataller, A. Koulakis, J.; Pree, S.; Putterman, S.

    2014-12-01

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

  4. Asynchronous indoor positioning system based on visible light communications

    NASA Astrophysics Data System (ADS)

    Zhang, Weizhi; Chowdhury, M. I. Sakib; Kavehrad, Mohsen

    2014-04-01

    Indoor positioning has become an attractive research topic within the past two decades. However, no satisfying solution has been found with consideration of both accuracy and system complexity. Recently, research on visible light communications (VLC) offer new opportunities in realizing accurate indoor positioning with relatively simple system configuration. An indoor positioning system based on VLC technology is introduced, with no synchronization requirement on the transmitters. Simulation results show that, with over 95% confidence, the target receiver can be located with an accuracy of 5.9 cm, assuming indirect sunlight exposure and proper installation of light-emitting diode bulbs.

  5. Visible-Light-Sensitive Photocatalysts: Nanocluster-Grafted Titanium Dioxide for Indoor Environmental Remediation.

    PubMed

    Miyauchi, Masahiro; Irie, Hiroshi; Liu, Min; Qiu, Xiaoqing; Yu, Huogen; Sunada, Kayano; Hashimoto, Kazuhito

    2016-01-01

    Photocatalytic degradation of organic compounds requires photoexcited holes with strong oxidative power in the valence band (VB) of semiconductors. Although numerous types of doped semiconductors, such as nitrogen-doped TiO2, have been studied as visible-light-sensitive photocatalysts, the quantum yields of these materials were very low because of the limited oxidation power of holes in the nitrogen level above the VB. Recently, we developed visible-light-sensitive Cu(II) and Fe(III) nanocluster-grafted TiO2 using a facile impregnation method and demonstrated that visible-light absorption occurs at the interface between the nanoclusters and TiO2, as electrons in the VB of TiO2 are excited to the nanoclusters under visible-light irradiation. In addition, photogenerated holes in the VB of TiO2 efficiently oxidize organic contaminants, and the excited electrons that accumulate in nanoclusters facilitate the multielectron reduction of oxygen. Notably, Cu(II) and Fe(III) nanocluster-grafted TiO2 photocatalyst has the highest quantum yield among reported photocatalysts and has antiviral, self-cleaning, and air purification properties under illumination by indoor light fixtures equipped with white fluorescent bulbs or white light-emitting diodes. PMID:26654353

  6. Atomic-layer molybdenum sulfide optical modulator for visible coherent light

    NASA Astrophysics Data System (ADS)

    Zhang, Yuxia; Wang, Shuxian; Yu, Haohai; Zhang, Huaijin; Chen, Yanxue; Mei, Liangmo; di Lieto, Alberto; Tonelli, Mauro; Wang, Jiyang

    2015-06-01

    Coherent light sources in the visible range are playing important roles in our daily life and modern technology, since about 50% of the capability of the our human brains is devoted to processing visual information. Visible lasers can be achieved by nonlinear optical process of infrared lasers and direct lasing of gain materials, and the latter has advantages in the aspects of compactness, efficiency, simplicity, etc. However, due to lack of visible optical modulators, the directly generated visible lasers with only a gain material are constrained in continuous-wave operation. Here, we demonstrated the fabrication of a visible optical modulator and pulsed visible lasers based on atomic-layer molybdenum sulfide (MoS2), a ultrathin two-dimensional material with about 9-10 layers. By employing the nonlinear absorption of the modulator, the pulsed orange, red and deep red lasers were directly generated. Besides, the present atomic-layer MoS2 optical modulator has broadband modulating properties and advantages in the simple preparation process. The present results experimentally verify the theoretical prediction for the low-dimensional optoelectronic modulating devices in the visible wavelength region and may open an attractive avenue for removing a stumbling block for the further development of pulsed visible lasers.

  7. Atomic-layer molybdenum sulfide optical modulator for visible coherent light

    PubMed Central

    Zhang, Yuxia; Wang, Shuxian; Yu, Haohai; Zhang, Huaijin; Chen, Yanxue; Mei, Liangmo; Di Lieto, Alberto; Tonelli, Mauro; Wang, Jiyang

    2015-01-01

    Coherent light sources in the visible range are playing important roles in our daily life and modern technology, since about 50% of the capability of the our human brains is devoted to processing visual information. Visible lasers can be achieved by nonlinear optical process of infrared lasers and direct lasing of gain materials, and the latter has advantages in the aspects of compactness, efficiency, simplicity, etc. However, due to lack of visible optical modulators, the directly generated visible lasers with only a gain material are constrained in continuous-wave operation. Here, we demonstrated the fabrication of a visible optical modulator and pulsed visible lasers based on atomic-layer molybdenum sulfide (MoS2), a ultrathin two-dimensional material with about 9–10 layers. By employing the nonlinear absorption of the modulator, the pulsed orange, red and deep red lasers were directly generated. Besides, the present atomic-layer MoS2 optical modulator has broadband modulating properties and advantages in the simple preparation process. The present results experimentally verify the theoretical prediction for the low-dimensional optoelectronic modulating devices in the visible wavelength region and may open an attractive avenue for removing a stumbling block for the further development of pulsed visible lasers. PMID:26067821

  8. Atomic-layer molybdenum sulfide optical modulator for visible coherent light.

    PubMed

    Zhang, Yuxia; Wang, Shuxian; Yu, Haohai; Zhang, Huaijin; Chen, Yanxue; Mei, Liangmo; Di Lieto, Alberto; Tonelli, Mauro; Wang, Jiyang

    2015-01-01

    Coherent light sources in the visible range are playing important roles in our daily life and modern technology, since about 50% of the capability of the our human brains is devoted to processing visual information. Visible lasers can be achieved by nonlinear optical process of infrared lasers and direct lasing of gain materials, and the latter has advantages in the aspects of compactness, efficiency, simplicity, etc. However, due to lack of visible optical modulators, the directly generated visible lasers with only a gain material are constrained in continuous-wave operation. Here, we demonstrated the fabrication of a visible optical modulator and pulsed visible lasers based on atomic-layer molybdenum sulfide (MoS2), a ultrathin two-dimensional material with about 9-10 layers. By employing the nonlinear absorption of the modulator, the pulsed orange, red and deep red lasers were directly generated. Besides, the present atomic-layer MoS2 optical modulator has broadband modulating properties and advantages in the simple preparation process. The present results experimentally verify the theoretical prediction for the low-dimensional optoelectronic modulating devices in the visible wavelength region and may open an attractive avenue for removing a stumbling block for the further development of pulsed visible lasers. PMID:26067821

  9. [Development of low-concentration hydrogen peroxide whitening agent using visible light-responsive titania photocatalyst].

    PubMed

    Arai, Hiroshi

    2010-06-01

    Although highly concentrated hydrogen peroxide (HP) has been used to bleach vital discolored teeth during office whitening, low-concentration HP was recognized to have insufficient whitening ability. We demonstrated that using a visible light-responsive titania photocatalyst (VLRTP) and a vis-Nd : YAG laser, 3 wt% HP-bleached oxytetracycline (OTC)-stained teeth models were more efficient than 30 wt% HP. The stained samples were prepared by soaking synthetic hydroxyapatite ceramic disks in OTC aqueous solutions. Color images of the OTC-stained models before and after whitening were taken with a conventional flatbed scanner and calibrated using a photocell colorimeter. By VLRTP treatment with vis-Nd : YAG laser irradiation, the lightness value (L*) significantly increased and the yellowness index (b*) significantly approached zero. This suggests that a diluted HP agent with VLRTP can more efficiently decolorize stained teeth by visible light irradiation. PMID:20662305

  10. Nitrogen-sensitized dual phase titanate/titania for visible-light driven phenol degradation

    SciTech Connect

    Cheng, Yu Hua; Subramaniam, Vishnu P.; Gong, Dangguo; Tang, Yuxin; Highfield, James; Pehkonen, Simo O.; Pichat, Pierre; Chen, Zhong

    2012-12-15

    A dual-phase material (DP-160) comprising hydrated titanate (H{sub 2}Ti{sub 3}O{sub 7}{center_dot}xH{sub 2}O) and anatase (TiO{sub 2}) was synthesized in a low-temperature one-pot process in the presence of triethylamine (TEA) as the N-source. The unique structure exhibits strong visible light absorption. The chromophore is linked to Ti-N bonds derived from both surface sensitization and sub-surface (bulk) doping. From transmission electron microscope (TEM) and textural studies by N{sub 2} physisorption, the composite exists as mesoporous particles with a grain size of {approx}20 nm and mean pore diameter of 3.5 nm, responsible for the high surface area ({approx}180 m{sup 2}/g). DP-160 demonstrated photocatalytic activity in the degradation of phenol under visible light ({lambda}>420 nm). The activity of the composite was further enhanced by a small addition (0.001 M) of H{sub 2}O{sub 2}, which also gave rise to some visible light activity in the control samples. This effect is believed to be associated with the surface peroxo-titanate complex. GC-MS analyses showed that the intermediate products of phenol degradation induced by visible light irradiation of DP-160 did not differ from those obtained by UV (band-gap) irradiation of TiO{sub 2}. The overall performance of the composite is attributed to efficient excitation via inter-band states (due to N-doping), surface sensitization, improved adsorptive properties of aromatic compounds due to the N-carbonaceous overlayer, and the presence of heterojunctions that are known to promote directional charge transfer in other mixed-phase titanias like Degussa P25. - graphical abstract: Nitrogen-sensitized dual phase titanate/titania photocatalyst showing extended visible light absorption and efficient photocatalytic degradation of phenol. Highlights: Black-Right-Pointing-Pointer Low temperature one-pot synthesis of visible light active dual phase photocatalyst. Black-Right-Pointing-Pointer The dual phase consists of

  11. Earth-abundant NiS co-catalyst modified metal-free mpg-C3N4/CNT nanocomposites for highly efficient visible-light photocatalytic H2 evolution.

    PubMed

    Zhong, Yongming; Yuan, Jielin; Wen, Jiuqing; Li, Xin; Xu, Yuehua; Liu, Wei; Zhang, Shengsen; Fang, Yueping

    2015-11-01

    In the present work, the earth-abundant NiS co-catalyst modified mesoporous graphite-like C3N4 (mpg-C3N4)/CNT nanocomposites were prepared via a two-step strategy: the sol-gel method and the direct precipitation process. The mpg-C3N4/CNT/NiS composite photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy, photoluminescence spectroscopy (PL), photoelectrochemical (PEC) and electrochemical impedance spectra (EIS) experiments. The photocatalytic H2-production activity over the composite catalysts was also evaluated by using an aqueous solution containing triethanolamine under visible light (λ≥ 420 nm). The results showed that the loading of earth-abundant NiS co-catalysts onto metal-free mpg-C3N4/CNT nanocomposites can remarkably enhance their photocatalytic H2-production activity. The optimal loading amount of NiS on metal-free mpg-C3N4/CNT nanocomposites was about 1 wt%. The as-obtained mpg-C3N4/CNT/1% NiS ternary composite photocatalyst exhibits the best H2-evolution activity with the highest rate of about 521 μmol g(-1) h(-1) under visible light (λ≥ 420 nm), which is almost 148 times that of a pure mpg-C3N4/CNT sample. The enhanced photocatalytic activity can be mainly attributed to the synergistic effect of effectively promoted separation of photo-generated electron-hole pairs and enhanced H2-evolution kinetics. The co-loading of nanocarbon materials and earth-abundant co-catalysts onto metal-free mpg-C3N4 photocatalysts offers great potential for practical applications in photocatalytic H2 evolution under visible light illumination. PMID:26426584

  12. Energy efficient lighting and communications

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Kavehrad, M.; Deng, P.

    2012-01-01

    As Light-Emitting Diode (LED)'s increasingly displace incandescent lighting over the next few years, general applications of Visible Light Communication (VLC) technology are expected to include wireless internet access, vehicle-to-vehicle communications, broadcast from LED signage, and machine-to-machine communications. An objective in this paper is to reveal the influence of system parameters on the power distribution and communication quality, in a general plural sources VLC system. It is demonstrated that sources' Half-Power Angles (HPA), receivers' Field-Of Views (FOV), sources layout and the power distribution among sources are significant impact factors. Based on our findings, we developed a method to adaptively change working status of each LED respectively according to users' locations. The program minimizes total power emitted while simultaneously ensuring sufficient light intensity and communication quality for each user. The paper also compares Orthogonal Frequency-Division Multiplexing (OFDM) and On-Off Keying (OOK) signals performance in indoor optical wireless communications. The simulation is carried out for different locations where different impulse response distortions are experienced. OFDM seems a better choice than prevalent OOK for indoor VLC due to its high resistance to multi-path effect and delay spread. However, the peak-to-average power limitations of the method must be investigated for lighting LEDs.

  13. Visible light assisted degradation of organic dye using Ag3PO4

    NASA Astrophysics Data System (ADS)

    Dhanabal, R.; Velmathi, S.; Bose, A. Chandra

    2015-06-01

    The study of visible light photodegradation of organic dye Methylene Blue (MB) have been investigated using silver phosphate (Ag3PO4) as a photocatalyst which is good efficient material for photocatalytic reaction. The simple ion-exchange method is used to prepare Ag3PO4. The structure of the material have been confirmed using X-ray diffraction which shows cubic structure of Ag3PO4. The functional group of the Ag3PO4 has been verified by Fourier transform infrared spectroscopy. The bandgap of Ag3PO4 is calculated using kubelka-munk function from the ultra violet-visible diffuse reflectance spectroscopy, the absorption of Ag3PO4 starts from 470 nm. Under simulated visible light irradiation, Ag3PO4 catalyst exhibits good catalytic ability for degrading MB dye.

  14. Visible-light active conducting polymer nanostructures with superior photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Ghosh, Srabanti; Kouame, Natalie Amoin; Remita, Samy; Ramos, Laurence; Goubard, Fabrice; Aubert, Pierre-Henri; Dazzi, Alexandre; Deniset-Besseau, Ariane; Remita, Hynd

    2015-12-01

    The development of visible-light responsive photocatalysts would permit more efficient use of solar energy, and thus would bring sustainable solutions to many environmental issues. Conductive polymers appear as a new class of very active photocatalysts under visible light. Among them poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most promising conjugated polymer with a wide range of applications. PEDOT nanostructures synthesized in soft templates via chemical oxidative polymerization demonstrate unprecedented photocatalytic activities for water treatment without the assistance of sacrificial reagents or noble metal co-catalysts and turn out to be better than TiO2 as benchmark catalyst. The PEDOT nanostructures exhibit a narrow band gap (E = 1.69 eV) and are characterized by excellent ability to absorb light in visible and near infrared region. The novel PEDOT-based photocatalysts are very stable with cycling and can be reused without appreciable loss of activity. Interestingly, hollow micrometric vesicular structures of PEDOT are not effective photocatalysts as compared to nanometric spindles suggesting size and shape dependent photocatalytic properties. The visible-light active photocatalytic properties of the polymer nanostructures present promising applications in solar light harvesting and broader fields.

  15. Visible-light active conducting polymer nanostructures with superior photocatalytic activity

    PubMed Central

    Ghosh, Srabanti; Kouame, Natalie Amoin; Remita, Samy; Ramos, Laurence; Goubard, Fabrice; Aubert, Pierre-Henri; Dazzi, Alexandre; Deniset-Besseau, Ariane; Remita, Hynd

    2015-01-01

    The development of visible-light responsive photocatalysts would permit more efficient use of solar energy, and thus would bring sustainable solutions to many environmental issues. Conductive polymers appear as a new class of very active photocatalysts under visible light. Among them poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most promising conjugated polymer with a wide range of applications. PEDOT nanostructures synthesized in soft templates via chemical oxidative polymerization demonstrate unprecedented photocatalytic activities for water treatment without the assistance of sacrificial reagents or noble metal co-catalysts and turn out to be better than TiO2 as benchmark catalyst. The PEDOT nanostructures exhibit a narrow band gap (E = 1.69 eV) and are characterized by excellent ability to absorb light in visible and near infrared region. The novel PEDOT-based photocatalysts are very stable with cycling and can be reused without appreciable loss of activity. Interestingly, hollow micrometric vesicular structures of PEDOT are not effective photocatalysts as compared to nanometric spindles suggesting size and shape dependent photocatalytic properties. The visible-light active photocatalytic properties of the polymer nanostructures present promising applications in solar light harvesting and broader fields. PMID:26657168

  16. Enhanced visible-light photoactivity of La-doped ZnS thin films

    NASA Astrophysics Data System (ADS)

    Chen, Yuan; Huang, Gui-Fang; Huang, Wei-Qing; Zou, B. S.; Pan, Anlian

    2012-09-01

    ZnS and La-doped ZnS thin films were successfully synthesized using chemical-bath deposition on conductive glass substrates. The effects of La-doping on the surface morphology, composition, structure and optical properties of the films were investigated. The photocatalytic performances of undoped and doped ZnS films were evaluated by photodegrading methyl orange aqueous solution under both ultraviolet-light and visible-light irradiation. The results show that the stoichiometry ratio and the properties of ZnS can be tailored by the La-doping concentration. An appropriate amount of La-doping effectively extends the absorption edge to visible-light region, which leads to the significant enhancement of the photocatalytic activity of ZnS thin films under visible-light irradiation. The mechanism of enhanced visible-light photoactivity by La-doping is briefly discussed. The present study provides a simple method for designing the highly efficient semiconductor photocatalysts that can effectively utilize sunlight.

  17. Redundant uplink optical channel for visible light communication systems

    NASA Astrophysics Data System (ADS)

    Vladescu, Marian; Vuza, Dan Tudor

    2015-02-01

    The increased interest in optical wireless (OW), as a complementary solution for radio frequency (RF) wireless technology, in conjunction with the significant deployments in LED lighting technology, led to the need to achieve lighting and wireless communication simultaneously in indoor environments. Visible light communication (VLC) technology provides an opportunity and infrastructure for the high-speed low-cost wireless communication. There are still open issues in VLC such as: uplink channel, LED modulation bandwidth, and LED nonlinearity. In this paper we addressed the uplink channel implementation, being a key issue in the OW communication system in order to allow full connectivity for a terminal (duplex transmission). VLC in full duplex mode requires the usage of a hybrid technology, such as infrared optical uplink, retro-reflecting transceivers, or even RF. The solution we proposed is to create a redundant optical uplink channel, using near ultraviolet (UV) and near infrared (IR) spectra.

  18. An Ag3PO4/nitridized Sr2Nb2O7 composite photocatalyst with adjustable band structures for efficient elimination of gaseous organic pollutants under visible light irradiation.

    PubMed

    Guo, Jianjun; Zhou, Han; Ouyang, Shuxin; Kako, Tetsuya; Ye, Jinhua

    2014-07-01

    A new Ag3PO4/nitridized Sr2Nb2O7 (N: 0-6.18 wt%) heterojunction was designed to eliminate gaseous pollutants under visible light irradiation. The phase compositions, optical properties, and morphologies of the heterojunction photocatalysts were systematically investigated via powder X-ray diffraction, UV-visible absorption spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Calculations of the electronic structure indicated that the top of the valance band of Sr2Nb2O7 could be raised by nitrogen doping. Therefore, the electronic structure of the Ag3PO4/nitridized Sr2Nb2O7 composite photocatalysts could be continually changed by controlling the amount of nitrogen in nitridized Sr2Nb2O7. Photocatalytic degradation of isopropyl alcohol (IPA) was carried out to test the photocatalytic activity of the heterojunction. The highest activity (CO2 evolution rate, 10.32 ppm h(-1)) was observed over the Ag3PO4/nitridized Sr2Nb2O7 heterojunction prepared by nitridation of Sr2Nb2O7 (SNO) at 1023 K. The CO2 evolution rate over the heterojunction was about 40 times higher than that over pure Ag3PO4 (CO2 evolution rate, 0.26 ppm h(-1)) under visible light irradiation. An investigation of the energy-band structure via valence band X-ray photoelectron spectroscopy indicated that the conduction band (CB) and valence band (VB) of Ag3PO4 are both more positive than those of nitridized Sr2Nb2O7, which facilitates the separation and transfer of photogenerated electrons and holes between the two photocatalysts. By continually adjusting the electronic structures, an optimal band gap for the nitridized Sr2Nb2O7 of 2.15 eV was obtained, and the potential of the valance band was +1.88 eV. PMID:24847986

  19. Qubit transfer between photons at telecom and visible wavelengths in a slow-light atomic medium

    SciTech Connect

    Gogyan, A.

    2010-02-15

    We propose a method that enables efficient conversion of the quantum information frequency between different regions of a spectrum of light based on recently demonstrated strong parametric coupling between two narrow-band single-photon pulses propagating in a slow-light atomic medium [N. Sisakyan and Yu. Malakyan, Phys. Rev. A, 75, 063831 (2007)]. We show that an input qubit at telecom wavelength is transformed into another at a visible domain in a lossless and shape-conserving manner while keeping the initial quantum coherence and entanglement. These transformations can be realized with a quantum efficiency close to its maximum value.

  20. Visible-Light-Mediated Synthesis of Amides from Aldehydes and Amines via in Situ Acid Chloride Formation.

    PubMed

    Iqbal, Naeem; Cho, Eun Jin

    2016-03-01

    An efficient visible-light photocatalysis-based one-pot amide synthesis method was developed; visible-light irradiation of a mixture of an aldehyde, tert-butyl hydrogen peroxide, and N-chlorosuccinimide using a Ru(bpy)3Cl2 photocatalyst afforded an acid chloride, which subsequently reacted with amine to yield the corresponding amide. The reaction was used to synthesize moclobemide and a D3 receptor intermediate. PMID:26836367

  1. Controlled drug release to cancer cells from modular one-photon visible light-responsive micellar system.

    PubMed

    Poelma, Saemi O; Oh, Seung Soo; Helmy, Sameh; Knight, Abigail S; Burnett, G Leslie; Soh, H Tom; Hawker, Craig J; Read de Alaniz, Javier

    2016-08-18

    We present a one-photon visible light-responsive micellar system for efficient, on-demand delivery of small molecules. Release is mediated by a novel class of photochromic material - donor-acceptor Stenhouse adducts (DASAs). We demonstrate controlled delivery of small molecules such as the chemotherapeutic agent (paclitaxel) to human breast cancer cells triggered by micellar switching with low intensity, visible light. PMID:27491357

  2. Studies on microleakage associated with visible light cured dental composites.

    PubMed

    Krishnan, V K; Bindhu, D B; Manjusha, K

    1996-04-01

    The objective of this investigation was twofold: 1) to determine the extent of microleakage associated with two visible light cured dental composites, one of which is an indigenously developed light cure composite (chitra light cure system) compared with a commercially available control material (Prisma APH light cure system), and 2) to study the effect of using bonding agents upon the above phenomena. The bonding agents used along with the above composites during restoration were chitra bonding agent system containing chitra primer/chitra resin and a control (Probond) which was purchased commercially. A comparison of microleakage in freshly restored human premolar teeth by silver nitrate staining technique was made during the above study. Cavities were restored with both composites with and without bonding agents, stored in 50 percent silver nitrate, and sections were cut after developing. The microtomed sections were observed under the optical light microscope and scanning electron microscope. Results indicate that bonding agents are mandatory for effective bonding at the tooth/resin interface and subsequent reduction in marginal leakage. Chitra bonding agent showed excellent adhesive bonding characteristics at the dentine/composite interface with minimal marginal leakage compared to the control bonding system. The chitra light cure composite material also showed lower shrinkage characteristics compared to Prisma APH composite. PMID:8859406

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

    PubMed

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

    2005-08-15

    Here we report the simultaneous Cr(VI) reduction and 4-chlorophenol (4-CP) oxidation in water under visible light (wavelength > 400 nm) using commercial Degussa P25 TiO2. This remarkable observation was attributed to a synergistic effect among TiO2, Cr(VI), and 4-CP. It is well known that TiO2 alone cannot remove either 4-CP or Cr(VI) efficiently under visible light. Moreover, the interaction between Cr(VI) and 4-CP is minimal if not negligible. However, we found that the combination of TiO2, Cr(VI), and 4-CP together can enable efficient Cr(VI) reduction and 4-CP oxidation under visible light. The specific roles of the three ingredients in the synergistic system were studied parametrically. It was found that optimal concentrations of Cr(VI) and TiO2 exist for the Cr(VI) reduction and 4-CP oxidation. Cr(VI) was compared experimentally with other metals such as Cu(ll), Fe(lll), Mn(IV), Ce(IV), and V(V). Among all these metal ions, only Cr(VI) promotes the photocatalytic oxidation of 4-CP. The amount of 4-CP removed was directly related to the initial concentration of Cr(VI). The system was also tested with four other chemicals (aniline, salicylic acid, formic acid, and diethyl phosphoramidate). We found that the same phenomenon occurred for organics containing acid and/or phenolic groups. Cr(VI) was reduced at the same time as the organic chemicals being oxidized during photoreaction under visible light. The synergistic effect was also found with pure anatase TiO2 and rutile TiO2. This study demonstrates a possible economical way for environmental cleanup under visible light. PMID:16173589

  4. Bright, Light and Energy Efficient.

    ERIC Educational Resources Information Center

    American School and University, 1981

    1981-01-01

    The new Sharon Elementary School in Newburgh (Indiana) has a three-fuel plan that will allow selection of the most economical energy source for each heating season with an energy-efficient lighting system that includes skylights. (Author/MLF)

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

    SciTech Connect

    Saoud, Khaled; Alsoubaihi, Rola; Bensalah, Nasr; Bora, Tanujjal; Bertino, Massimo; Dutta, Joydeep

    2015-03-15

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

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

    PubMed

    Do, Trong-Hop; Yoo, Myungsik

    2016-01-01

    This paper elucidates the fundamentals of visible light communication systems that use the rolling shutter mechanism of CMOS sensors. All related information involving different subjects, such as photometry, camera operation, photography and image processing, are studied in tandem to explain the system. Then, the system performance is analyzed with respect to signal quality and data rate. To this end, a measure of signal quality, the signal to interference plus noise ratio (SINR), is formulated. Finally, a simulation is conducted to verify the analysis. PMID:26938535

  7. Visible-light optical coherence tomography for retinal oximetry.

    PubMed

    Yi, Ji; Wei, Qing; Liu, Wenzhong; Backman, Vadim; Zhang, Hao F

    2013-06-01

    We applied a visible-light spectroscopic optical coherence tomography (vis-OCT) for in vivo retinal oximetry. To extract hemoglobin oxygen saturation (sO(2)) in individual retinal vessels, we established a comprehensive analytical model to describe optical absorption, optical scattering, and blood cell packing factor in the whole blood and fit the acquired vis-OCT signals from the bottom of each imaged vessel. We found that averaged sO(2) values in arterial and venous bloods were 95% and 72%, respectively. PMID:23722747

  8. Performance Analysis of Visible Light Communication Using CMOS Sensors

    PubMed Central

    Do, Trong-Hop; Yoo, Myungsik

    2016-01-01

    This paper elucidates the fundamentals of visible light communication systems that use the rolling shutter mechanism of CMOS sensors. All related information involving different subjects, such as photometry, camera operation, photography and image processing, are studied in tandem to explain the system. Then, the system performance is analyzed with respect to signal quality and data rate. To this end, a measure of signal quality, the signal to interference plus noise ratio (SINR), is formulated. Finally, a simulation is conducted to verify the analysis. PMID:26938535

  9. Visible Light Communication System Using an Organic Bulk Heterojunction Photodetector

    PubMed Central

    Arredondo, Belén; Romero, Beatriz; Pena, José Manuel Sánchez; Fernández-Pacheco, Agustín; Alonso, Eduardo; Vergaz, Ricardo; de Dios, Cristina

    2013-01-01

    A visible light communication (VLC) system using an organic bulk heterojunction photodetector (OPD) is presented. The system has been successfully proven indoors with an audio signal. The emitter consists of three commercial high-power white LEDs connected in parallel. The receiver is based on an organic photodetector having as active layer a blend of poly(3-hexylthiophene) (P3HT) and phenyl C61-butyric acid methyl ester (PCBM). The OPD is opto-electrically characterized, showing a responsivity of 0.18 A/W and a modulation response of 790 kHz at −6 V. PMID:24036584

  10. Application of microflow conditions to visible light photoredox catalysis.

    PubMed

    Neumann, Matthias; Zeitler, Kirsten

    2012-06-01

    Applications of microflow conditions for visible light photoredox catalysis have successfully been developed. Operationally simple microreactor and FEP (fluorinated ethylene propylene copolymer) tube reactor systems enable significant improvement of several photoredox reactions using different photocatalysts such as [Ru(bpy)(3)](2+) and Eosin Y. Apart from rate acceleration, this approach facilitates previously challenging transformations of nonstabilized intermediates. Additionally, the productivity of the synergistic, catalytic enantioselective photoredox α-alkylation of aldehydes was demonstrated to be increased by 2 orders of magnitude. PMID:22587670

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

    SciTech Connect

    Shen, Jianfeng; Li, Xianfu; Huang, Weishi; Li, Na; Ye, Mingxin

    2013-09-01

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

  12. Conversion of far ultraviolet to visible radiation: absolute measurements of the conversion efficiency of tetraphenyl butadiene

    NASA Astrophysics Data System (ADS)

    Vest, Robert E.; Coplan, Michael A.; Clark, Charles W.

    Far ultraviolet (FUV) scintillation of noble gases is used in dark matter and neutrino research and in neutron detection. Upon collisional excitation, noble gas atoms recombine into excimer molecules that decay by FUV emission. Direct detection of FUV is difficult. Another approach is to convert it to visible light using a wavelength-shifting medium. One such medium, tetraphenyl butadiene (TPB) can be vapor-deposited on substrates. Thus the quality of thin TPB films can be tightly controlled. We have measured the absolute efficiency of FUV-to-visible conversion by 1 μm-thick TPB films vs. FUV wavelengths between 130 and 300 nm, with 1 nm resolution. The energy efficiency of FUV to visible conversion varies between 1% and 5%. We make comparisons with other recent results. Work performed at the NIST SURF III Synchrotron Ultraviolet Radiation Facility,.

  13. Visible-light-accelerated oxygen vacancy migration in strontium titanate

    PubMed Central

    Li, Y.; Lei, Y.; Shen, B. G.; Sun, J. R.

    2015-01-01

    Strontium titanate is a model transition metal oxide that exhibits versatile properties of special interest for both fundamental and applied researches. There is evidence that most of the attractive properties of SrTiO3 are closely associated with oxygen vacancies. Tuning the kinetics of oxygen vacancies is then highly desired. Here we reported on a dramatic tuning of the electro-migration of oxygen vacancies by visible light illumination. It is found that, through depressing activation energy for vacancy diffusion, light illumination remarkably accelerates oxygen vacancies even at room temperature. This effect provides a feasible approach towards the modulation of the anionic processes. The principle proved here can be extended to other perovskite oxides, finding a wide application in oxide electronics. PMID:26420376

  14. Dual-polarity plasmonic metalens for visible light

    PubMed Central

    Chen, Xianzhong; Huang, Lingling; Mühlenbernd, Holger; Li, Guixin; Bai, Benfeng; Tan, Qiaofeng; Jin, Guofan; Qiu, Cheng-Wei; Zhang, Shuang; Zentgraf, Thomas

    2012-01-01

    Surface topography and refractive index profile dictate the deterministic functionality of a lens. The polarity of most lenses reported so far, that is, either positive (convex) or negative (concave), depends on the curvatures of the interfaces. Here we experimentally demonstrate a counter-intuitive dual-polarity flat lens based on helicity-dependent phase discontinuities for circularly polarized light. Specifically, by controlling the helicity of the input light, the positive and negative polarity are interchangeable in one identical flat lens. Helicity-controllable real and virtual focal planes, as well as magnified and demagnified imaging, are observed on the same plasmonic lens at visible and near-infrared wavelengths. The plasmonic metalens with dual polarity may empower advanced research and applications in helicity-dependent focusing and imaging devices, angular-momentum-based quantum information processing and integrated nano-optoelectronics. PMID:23149743

  15. Visible-Light-Promoted Oxidative [4 + 2] Cycloadditions of Aryl Silyl Enol Ethers.

    PubMed

    Yang, Bo; Lu, Zhan

    2016-08-19

    Visible-light-promoted oxidative [4 + 2] cycloadditions of ε,3-unsaturated silyl enol ethers have been developed to efficiently and diastereoselectively construct polycyclic skeletons under mild conditions. The diastereoselectivities were dependent on the stereoconfiguration of silyl enol ether, substitutions on the link, as well as electric properties of substitutions on aryl rings. The intermediates could be trapped by TEMPO, oxygen or methanol. Mechanistic studies indicated the reaction was initiated by one-electron oxidation of the silyl enol ether. PMID:27391768

  16. Visible-light-driven photocatalytic water oxidation catalysed by iron-based metal-organic frameworks.

    PubMed

    Horiuchi, Yu; Toyao, Takashi; Miyahara, Kenta; Zakary, Lionet; Van, Dang Do; Kamata, Yusuke; Kim, Tae-Ho; Lee, Soo Wohn; Matsuoka, Masaya

    2016-04-14

    An iron-based metal-organic framework, MIL-101(Fe), promotes photocatalytic water oxidation to produce oxygen from aqueous silver nitrate solution under visible-light irradiation. The finely dispersed iron-oxo clusters embedded as nodes of the porous framework would contribute importantly to the efficient promotion of the reaction as compared to bulk hematite (α-Fe2O3). PMID:26996996

  17. Visible-Light-Induced Specific Desulfurization of Cysteinyl Peptide and Glycopeptide in Aqueous Solution.

    PubMed

    Gao, Xiao-Fei; Du, Jing-Jing; Liu, Zheng; Guo, Jun

    2016-03-01

    Visible-light-induced specific desulfurization of cysteinyl peptides has been explored. The photocatalytic desulfurization catalyzed by Ru(bpy)3(2+) can proceed efficiently at room temperature in aqueous solution or in binary mixtures of aqueous/organic solvent and be compatible with the presence of residues of amino acids, carbohydrates, and various sulfur-containing functional groups. This approach was successfully applied to synthesize linear and cyclic peptides through the ligation-desulfurization protocol. PMID:26892036

  18. Zn3(OH)2V2O7·2H2O/g-C3N4: A novel composite for efficient photodegradation of methylene blue under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Wang, Qizhao; Zheng, Longhui; Bai, Yan; Zhao, Jianjun; Wang, Fangping; Zhang, Rong; Huang, Haohao; Su, Bitao

    2015-08-01

    In this work, we used a facile method to prepare a series of Zn3(OH)2V2O7·2H2O/g-C3N4 composites in a 70 °C water bath for 10 h and characterized them by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET), and photoluminescence (PL). Degradation of methylene blue (MB) and phenol were carried out to evaluate the photocatalytic activities of samples under visible light irradiation. Presence of Zn3(OH)2V2O7·2H2O increased surface areas and promoted the charge separation, exerted great influence on the photocatalytic activity and absorption capacity of g-C3N4. In addition, the synergic effect was explained and a possible photocatalytic mechanism was proposed.

  19. Visible light powered self-disinfecting coatings for influenza viruses

    NASA Astrophysics Data System (ADS)

    Weng, Ding; Qi, Hangfei; Wu, Ting-Ting; Yan, Ming; Sun, Ren; Lu, Yunfeng

    2012-04-01

    Influenza A viruses, the pathogens responsible for the recent swine flu outbreak and many historical pandemics, remain a threat to the public health. We report herein the fabrication of self-disinfecting surfaces from photoactive building nanocrystals, which can inactivate influenza viruses rapidly, spontaneously and continuously under visible light illumination.Influenza A viruses, the pathogens responsible for the recent swine flu outbreak and many historical pandemics, remain a threat to the public health. We report herein the fabrication of self-disinfecting surfaces from photoactive building nanocrystals, which can inactivate influenza viruses rapidly, spontaneously and continuously under visible light illumination. Electronic supplementary information (ESI) available: XRD, UV-Vis absorbance, TEM, AFM of as-prepared nanocrystals and as-fabricated self-disinfecting surfaces, disinfection of influenza A virus by TiO2 (P25) with UV irradiation as reference control, photoinactivation of influenza A virus envelope proteins and photoinactivation of trypsin. See DOI: 10.1039/c2nr30388d

  20. Invisibility Cloaking Based on Geometrical Optics for Visible Light

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  1. Realizing high visible-light-induced carriers mobility in TiO2-based photoanodes

    NASA Astrophysics Data System (ADS)

    He, Jingfu; Zhang, Shibao; Sun, Zhihu; Cheng, Weiren; Liu, Qinghua; Jiang, Yong; Hu, Fengchun; Pan, Zhiyun; He, Bo; Wu, Ziyu; Yan, Wensheng; Wei, Shiqiang

    2014-04-01

    Increasing the quantum conversion efficiency in visible-light region is a key issue for the efficient usage of solar energy in the process of photoelectrochemical (PEC) water splitting. Here, based on the N anion and S cation codoped TiO2 thin film photoanodes, we find experimentally and theoretically that the transport ability of visible-light-induced carriers can be notably enhanced by engineering the dopant electronic energy states. The hole transport resistivity is decreased from 6.8 × 104 to 1.3 × 104 Ω m via delocalizing the introduced bands, leading to an evident increase of the internal quantum efficiency from 5% to 20% at the visible-light region of 450-550 nm. Further DFT calculations exhibit that the split of the isolated band is induced by a strong N and S hybridization, which favors to decrease the hole effective mass and to improve the hole mobility by three times. The photocurrent of N - S codoped TiO2 thin film is thus twice that of monodoping cases, the best value for doping modified TiO2 thin film photoanodes. This work may provide not only a design principle but also a candidate for tailoring and optimizing TiO2 towards high PEC activity.

  2. Intensity estimation method of LED array for visible light communication

    NASA Astrophysics Data System (ADS)

    Ito, Takanori; Yendo, Tomohiro; Arai, Shintaro; Yamazato, Takaya; Okada, Hiraku; Fujii, Toshiaki

    2013-03-01

    This paper focuses on a road-to-vehicle visible light communication (VLC) system using LED traffic light as the transmitter and camera as the receiver. The traffic light is composed of a hundred of LEDs on two dimensional plain. In this system, data is sent as two dimensional brightness patterns by controlling each LED of the traffic light individually, and they are received as images by the camera. Here, there are problems that neighboring LEDs on the received image are merged due to less number of pixels in case that the receiver is distant from the transmitter, and/or due to blurring by defocus of the camera. Because of that, bit error rate (BER) increases due to recognition error of intensity of LEDs To solve the problem, we propose a method that estimates the intensity of LEDs by solving the inverse problem of communication channel characteristic from the transmitter to the receiver. The proposed method is evaluated by BER characteristics which are obtained by computer simulation and experiments. In the result, the proposed method can estimate with better accuracy than the conventional methods, especially in case that the received image is blurred a lot, and the number of pixels is small.

  3. Light Duty Efficient, Clean Combustion

    SciTech Connect

    Donald Stanton

    2010-12-31

    Cummins has successfully completed the Light Duty Efficient Clean Combustion (LDECC) cooperative program with DoE. This program was established in 2007 in support of the Department of Energy's Vehicles Technologies Advanced Combustion and Emissions Control initiative to remove critical barriers to the commercialization of advanced, high efficiency, emissions compliant internal combustion (IC) engines for light duty vehicles. Work in this area expanded the fundamental knowledge of engine combustion to new regimes and advanced the knowledge of fuel requirements for these diesel engines to realize their full potential. All of the following objectives were met with fuel efficiency improvement targets exceeded: (1) Improve light duty vehicle (5000 lb. test weight) fuel efficiency by 10.5% over today's state-of-the-art diesel engine on the FTP city drive cycle; (2) Develop and design an advanced combustion system plus aftertreatment system that synergistically meets Tier 2 Bin 5 NOx and PM emissions standards while demonstrating the efficiency improvements; (3) Maintain power density comparable to that of current conventional engines for the applicable vehicle class; and (4) Evaluate different fuel components and ensure combustion system compatibility with commercially available biofuels. Key accomplishments include: (1) A 25% improvement in fuel efficiency was achieved with the advanced LDECC engine equipped with a novel SCR aftertreatment system compared to the 10.5% target; (2) An 11% improvement in fuel efficiency was achieved with the advanced LDECC engine and no NOx aftertreamtent system; (3) Tier 2 Bin 5 and SFTP II emissions regulations were met with the advanced LDECC engine equipped with a novel SCR aftertreatment system; (4) Tier 2 Bin 5 emissions regulations were met with the advanced LDECC engine and no NOx aftertreatment, but SFTP II emissions regulations were not met for the US06 test cycle - Additional technical barriers exist for the no NOx

  4. Efficient estimation of orthophoto images using visibility restriction

    NASA Astrophysics Data System (ADS)

    Miura, Hiroyuki; Chikatsu, Hirofumi

    2015-05-01

    The orthophoto image which is generated using an aerial photo is used in river management, road design and the various fields since the orthophoto has ability to visualize land use with position information. However, the image distortion often occurs in the ortho rectification process. This image distortion is used to estimate manually by the evaluation person with great time. The image distortion should be automatically estimated from the view point of efficiency of the process. With this motive, formed angle V between view vector at exposure point and normal vector at center point of a patch area was focused in this paper. In order to evaluate the relation between image distortion and formed angle V, DMC image which were acquired 2000m height were used and formed angle V for 10m×10m patch was adopted for computing visibility restriction. It was confirmed that image distortion occurred for the patch which show rather than 69 degree of the formed angle V. Therefore, it is concluded that efficient orthophoto visibility restriction is able to perform using the formed angle V as visibility restriction in this paper.

  5. Efficient quantum memory for light.

    PubMed

    Hedges, Morgan P; Longdell, Jevon J; Li, Yongmin; Sellars, Matthew J

    2010-06-24

    Storing and retrieving a quantum state of light on demand, without corrupting the information it carries, is an important challenge in the field of quantum information processing. Classical measurement and reconstruction strategies for storing light must necessarily destroy quantum information as a consequence of the Heisenberg uncertainty principle. There has been significant effort directed towards the development of devices-so-called quantum memories-capable of avoiding this penalty. So far, successful demonstrations of non-classical storage and on-demand recall have used atomic vapours and have been limited to low efficiencies, of less than 17 per cent, using weak quantum states with an average photon number of around one. Here we report a low-noise, highly efficient (up to 69 per cent) quantum memory for light that uses a solid-state medium. The device allows the storage and recall of light more faithfully than is possible using a classical memory, for weak coherent states at the single-photon level through to bright states of up to 500 photons. For input coherent states containing on average 30 photons or fewer, the performance exceeded the no-cloning limit. This guaranteed that more information about the inputs was retrieved from the memory than was left behind or destroyed, a feature that will provide security in communications applications. PMID:20577210

  6. Photocatalytic activities of various pentavalent bismuthates under visible light irradiation

    SciTech Connect

    Takei, Takahiro; Haramoto, Rie; Dong, Qiang; Kumada, Nobuhiro; Yonesaki, Yoshinori; Kinomura, Nobukazu; Mano, Takayuki; Nishimoto, Shunsuke; Kameshima, Yoshikazu; Miyake, Michihiro

    2011-08-15

    LiBiO{sub 3}, NaBiO{sub 3}, MgBi{sub 2}O{sub 6}, KBiO{sub 3}, ZnBi{sub 2}O{sub 6}, SrBi{sub 2}O{sub 6}, AgBiO{sub 3}, BaBi{sub 2}O{sub 6} and PbBi{sub 2}O{sub 6} were synthesized by various processes such as hydrothermal treatment, heating and so on. These materials were examined for their photocatalytic activities in the decolorization of methylene blue and decomposition of phenol under visible light irradiation. For methylene blue decolorization, the presence of KBiO{sub 3} resulted in complete decoloration within 5 min. For phenol decomposition, NaBiO{sub 3} showed the highest activity, while LiBiO{sub 3}, SrBi{sub 2}O{sub 6} and BaBi{sub 2}O{sub 6} possessed almost comparable decomposition rates. Their decomposition rates were apparently higher than that by anatase (P25) under UV irradiation. - Graphical abstract: Nine pentavalent bismuthates were synthesized and were examined for their photocatalytic activities by decomposition of phenol under visible light irradiation. NaBiO{sub 3}, LiBiO{sub 3}, SrBi{sub 2}O{sub 6} and BaBi{sub 2}O{sub 6} indicated faster decomposition rate than that of anatase (P25) under UV-vis light irradiation. Highlights: > KBiO{sub 3} decolorize methylene blue aqueous solution immediately within 5 min. > NaBiO{sub 3}, LiBiO{sub 3}, SrBi{sub 2}O{sub 6} and BaBi{sub 2}O{sub 6} indicated high decomposition rate of phenol. > The d electron of Zn, Ag and Pb form broad conduction band. > The broad conduction band poses to diminish photocatalytic activity.

  7. Formation of visible single-mode light sources using quantum dots

    NASA Astrophysics Data System (ADS)

    Baig, Sarfaraz; Xu, Jianfeng; Wu, Pengfei; Chen, Bing; Wang, Michael

    2008-08-01

    The market demands for innovative, efficient, small package and single-mode light sources are always high because of their broad applications in scientific, medical, industrial, and commercial fields. The high photoluminescence quantum yield, photophysical and photochemical stability, and tunable emission wavelength make quantum dots ideal for a new generation of solid state light sources. We report on the realization of various single-mode light sources in the visible spectral band by using semiconductor quantum dots. The effective use of a waveguide structure can help achieve the divergence control of the output light beam. This technique may benefit the development for next generation light emitting diodes, optical communication, intelligent optical sensors, microprocessors, and nanoscale optical imaging systems.

  8. Fabrication and efficient visible light photocatalytic properties of novel zinc indium sulfide (ZnIn2S4) - graphitic carbon nitride (g-C3N4)/bismuth vanadate (BiVO4) nanorod-based ternary nanocomposites with enhanced charge separation via Z-scheme transfer.

    PubMed

    Jo, Wan-Kuen; Natarajan, Thillai Sivakumar

    2016-11-15

    Novel ZnIn2S4-g-C3N4/BiVO4 nanorod-based ternary nanocomposite photocatalysts with enhanced visible light absorption were synthesized and systematically characterized to confirm the formation of ZnIn2S4 marigold flowers, the layered structure of the g-C3N4, BiVO4 nanorods, and the formation of binary and ternary nanocomposites. The visible light absorption of BiVO4 was significantly improved after coupling with g-C3N4 and ZnIn2S4, which was confirmed by UV-visible diffuse reflectance spectroscopic analysis. Ternary ZnIn2S4-g-C3N4/BiVO4 nanocomposites exhibited excellent visible light photocatalytic decomposition efficiency (VL-PDE) when used for the degradation of congo red (CR) dye and metronidazole (MTZ) pharmaceutical, as well as excellent stability and reusability. The ternary 5%ZnIn2S4-50%-g-C3N4/BiVO4 nanocomposite showed higher VL-PDE for CR (81.5%) and MTZ (59%) degradation than the binary composites, g-C3N4 and BiVO4. Radical quenching experiments showed that h(+), OH, and O2(-) were the reactive radicals, validating that the Z-scheme charge carrier transfer mechanism was responsible for the enhanced VL-PDE of the ternary ZnIn2S4-g-C3N4/BiVO4 nanocomposites, which was further confirmed by photoluminescence analysis. Furthermore, kinetic studies showed that the degradation followed pseudo-first-order kinetics, and that the ternary photocatalysts could be reused up to three times with good stability. The enhanced visible light absorption, high surface area, high adsorption capacity, Z-scheme charge carrier transfer, and increased lifetime of photo-produced electron-hole pairs were responsible for the increased visible light photocatalytic decomposition efficiency. PMID:27491002

  9. A visible light-sensitive tungsten carbide/tungsten trioxde composite photocatalyst

    SciTech Connect

    Kim, Young-ho; Irie, Hiroshi; Hashimoto, Kazuhito

    2008-05-05

    A photocatalyst composed of tungsten carbide (WC) and tungsten oxide (WO{sub 3}) has been prepared by the mechanical mixing of each powder. Its photocatalytic activity was evaluated by the gaseous isopropyl alcohol decomposition process. The photocatalyst showed high visible light photocatalytic activity with a quantum efficiency of 3.2% for 400-530 nm light. The photocatalytic mechanism was explained by means of enhanced oxygen reduction reaction due to WC, which may serve as a multielectron reduction catalyst, as well as the photogeneration of holes in the valence band of WO{sub 3}.

  10. QPSK modulation for AC-power-signal-biased visible light communication system

    NASA Astrophysics Data System (ADS)

    Liu, Yu-Feng; Yeh, Chien-Hung; Chow, Chi-Wai; Liu, Yang

    2013-01-01

    With the integration of light emitting diode (LED), visible light communication (VLC) can provide wireless communication link using the lightning system. Due to the consideration of power efficiency, AC-LED has the design of reducing energy waste with alternating current from the power outlet. In this work, we propose an AC-power-signalbiased system that provides communication on both DC-LED and AC-LED. The bias circuit is designed to combine ACpower signal and the message signal with QPSK format. This driving scheme needs no AC-to-DC converters and it is suitable for driving AC LED. Synchronization is completed to avoid threshold effect of LED.

  11. Microfluidic reactors for visible-light photocatalytic water purification assisted with thermolysis.

    PubMed

    Wang, Ning; Tan, Furui; Wan, Li; Wu, Mengchun; Zhang, Xuming

    2014-09-01

    Photocatalytic water purification using visible light is under intense research in the hope to use sunlight efficiently, but the conventional bulk reactors are slow and complicated. This paper presents an integrated microfluidic planar reactor for visible-light photocatalysis with the merits of fine flow control, short reaction time, small sample volume, and long photocatalyst durability. One additional feature is that it enables one to use both the light and the heat energy of the light source simultaneously. The reactor consists of a BiVO4-coated glass as the substrate, a blank glass slide as the cover, and a UV-curable adhesive layer as the spacer and sealant. A blue light emitting diode panel (footprint 10 mm × 10 mm) is mounted on the microreactor to provide uniform irradiation over the whole reactor chamber, ensuring optimal utilization of the photons and easy adjustments of the light intensity and the reaction temperature. This microreactor may provide a versatile platform for studying the photocatalysis under combined conditions such as different temperatures, different light intensities, and different flow rates. Moreover, the microreactor demonstrates significant photodegradation with a reaction time of about 10 s, much shorter than typically a few hours using the bulk reactors, showing its potential as a rapid kit for characterization of photocatalyst performance. PMID:25584117

  12. Polymerization of a Photocleavable Monomer Using Visible Light.

    PubMed

    Bagheri, Ali; Yeow, Jonathan; Arandiyan, Hamidreza; Xu, Jiangtao; Boyer, Cyrille; Lim, May

    2016-06-01

    The polymerization of the photocleavable monomer, o-nitrobenzyl methacrylate (NBMA), is investigated using photoinduced electron/energy transfer reversible addition-fragmentation chain transfer polymerization. The polymerizations under visible red (λ max = 635 nm, 0.7 mW cm(-2) ) and yellow (λ max = 560 nm, 9.7 mW cm(-2) ) light are performed and demonstrate rational evidence of a controlled/living radical polymerization process. Well-defined poly(o-nitrobenzyl methacrylate) (PNBMA) homopolymers with good control over the molecular weight and polymer dispersity are successfully synthesized by varying the irradiation time and/or targeted degree of polymerization. Chain extension of a poly(oligo(ethylene glycol) methyl ether methacrylate) macro-chain transfer agent with NBMA is carried out to fabricate photocleavable amphiphilic block copolymers (BCP). Finally, these self-assembled BCP rapidly dissemble under UV light suggesting the photoresponsive character of NBMA is not altered during the polymerization under yellow or red light. Such photoresponsive polymers can be potentially used for the remote-controlled delivery of therapeutic compounds. PMID:27121222

  13. A visible light-responsive iodine-doped titanium dioxide nanosphere.

    PubMed

    He, Zhiqiao; Zhan, Liyong; Hong, Fangyue; Song, Shuang; Lin, Zhengying; Chen, Jianmeng; Jin, Mantong

    2011-01-01

    I-doped titanium dioxide nanospheres (I-TNSs) were synthesized via a two-step hydrothermal synthesis route, their potential for the efficient utilization of visible light was evaluated. The prepared anatase-phase I-TNSs had a bimodal porous size distribution with a Brunauer-Emmett-Teller surface area of 76 m2/g, a crystallite size of approximately 14 nm calculated from X-ray diffraction data, and a remarkable absorption in the visible light region at wavelengths > 400 nm. The photocatalytic activity of the samples was evaluated by decoloration of Methyl Orange in aqueous solution under visible light irradiation in comparison to the iodine-doped TiO2 (I-TiO2). The I-TNSs showed higher photocatalytic efficiency compared with I-TiO2 after irradiation for 180 min even though the latter had a much greater surface area (115 m2/g). It was concluded that the surface area was not the predominant factor determining photocatalytic activity, and that the good crystallization and bimodal porous nanosphere structure were favourable for photocatalysis. PMID:21476357

  14. Graphene oxide modified TiO2 nanotube arrays: enhanced visible light photoelectrochemical properties

    SciTech Connect

    Song, Peng; Zhang, Xiaoyan; Sun, Mingxuan; Cui, Xiaoli; Lin, Yuehe

    2012-01-01

    Novel nanocomposite films based on graphene oxide (GO) and TiO2 nanotube arrays were synthesized by assembling GO on the surface of self-organized TiO2 nanotube arrays through a simple assembling method. The composite films were characterized with field emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and UV-vis diffuse reflectance spectroscopy. Photoelectrochemical properties of the composite nanotube arrays were investigated under visible light illumination. Remarkably enhanced visible light photoelectrochemical response was observed for the GO decorated TiO2 nanotube composite electrode compared with pristine TiO2 nanotube arrays. Sensitizing effect of GO on the photoelectrochemical response of TiO2 nanotube arrays was demonstrated and about 15 times enhanced maximum photoconversion efficiency was obtained with the presence of GO. Enhanced photocatalytic activity of TiO2 nanotube arrays towards degradation of methyl blue was also demonstrated after modification of GO. The results presented here demonstrate GO to be efficient for the improvement of utilization of visible light for TiO2 nanotube arrays.

  15. 10m/500 Mbps WDM visible light communication systems.

    PubMed

    Lin, Wen-Yi; Chen, Chia-Yi; Lu, Hai-Han; Chang, Ching-Hung; Lin, Ying-Pyng; Lin, Huang-Chang; Wu, Hsiao-Wen

    2012-04-23

    A wavelength-division-multiplexing (WDM) visible light communiction (VLC) system employing red and green laser pointer lasers (LPLs) with directly modulating data signals is proposed and experimentally demonstrated. With the assistance of preamplifier and adaptive filter at the receiving sites, low bit error rate (BER) at 10 m/500 Mbps operation is obtained for each wavelength. The use of preamplifier and adaptive filter offer significant improvements for free-space transmission performance. Improved performance of BER of <10(-9), as well as better and clear eye diagram were achieved in our proposed WDM VLC systems. LPL features create a new category of good performance with high-speed data rate, long transmission length (>5m), as well as easy handling and installation. This proposed WDM VLC system reveals a prominent one to present its advancement in simplicity and convenience to be installed. PMID:22535084

  16. Visible light responsive systems based on metastable-state photoacids

    NASA Astrophysics Data System (ADS)

    Liao, Yi

    2015-09-01

    Proton transfer is one of the most fundamental processes in nature. Metastable-state photoacids can reversibly generate a large proton concentration under visible light with moderate intensity. which provides a general approach to control various proton transfer processes. Several applications of mPAHs have been demonstrated recently including control of acid-catalyzed reactions, volume-change of hydrogels, polymer conductivity, bacteria killing, odorant release, and color change of materials. They have also been utilized to control supramolecular assemblies, molecular switches, microbial fuel cells and cationic sensors. In this talk, the mechanism, structure design, and applications of metastable-state photoacids are introduced. Recent development of different types of metastable-state photoacids is presented. Challenges and future work are also discussed.

  17. Performance of indoor optical femtocell by visible light communication

    NASA Astrophysics Data System (ADS)

    Cui, Kaiyun; Quan, Jinguo; Xu, Zhengyuan

    2013-07-01

    Femotocell has been proposed and deployed to improve the indoor coverage and capacity of a cellular network. One big challenge in its deployment is the interference between the macrocell and femtocell cellular networks. In this paper we propose a new physical layer for the implementation of indoor femtocells - optical femtocells by LED-based visible light communication. A general system structure of the indoor optical femtocell network is first introduced. A combined wavelength division and code division multiple access scheme is proposed to differentiate cells and multiple users within a cell. This scheme coupled with directional beaming characteristics of the LEDs helps to mitigate intercell interference and intracell inference. The communication performance adopting the dimming compatible variable-PPM modulation suggested by the IEEE standard is analyzed. Monte-Carlo simulation is then carried out to reveal the system performance numerically under typical system settings and effects of various parameters.

  18. Ti-O-O coordination bond caused visible light photocatalytic property of layered titanium oxide

    PubMed Central

    Kong, Xingang; Zeng, Chaobin; Wang, Xing; Huang, Jianfeng; Li, Cuiyan; Fei, Jie; Li, Jiayin; Feng, Qi

    2016-01-01

    The layered titanium oxide is a useful and unique precursor for the facile and rapid preparation of the peroxide layered titanium oxide H1.07Ti1.73O4·nH2O (HTO) crystal with enhanced visible light photoactivity. The H2O2 molecules as peroxide chemicals rapidly enter into the interlayers of HTO crystal, and coordinate with Ti within TiO6 octahedron to form a mass of Ti-O-O coordination bond in the interlayers. The introduction of these Ti-O-O coordination bonds result in lowering the band gap of HTO, and promoting the separation efficiency of the photo induced electron–hole pairs. Meanwhile, the photocatalytic investigation indicates that such peroxide HTO crystal has the enhanced photocatalytic performance for RhB degradation and water splitting to generate oxygen under visible light irradiating. PMID:27350285

  19. Visible-light-driven hydrogen production in a dye sensitized polyoxometalate system without noble metals

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Li, Yuexiang; Peng, Shaoqin; Lai, Hua; Yi, Zhengji

    2016-05-01

    In this work, a noble-metal-free homogeneous system was constructed in one step with Keggin-type polyoxometalate (POM) SiW12O404- as a catalyst, Eosin Y as a photosensitizer, and triethanolamine (TEOA) as a sacrificial electron donor for water splitting to produce hydrogen under visible-light irradiation. A two-electron reduced heteropoly blue SiW12O406- is produced by photosensitization under visible-light irradiation. The effect of various component concentrations and POMs with different central atoms (PW12O403-, GeW12O404-, etc.) on hydrogen production was discussed. This simple system made of earth-abundant elements is expected to contribute toward the development of functional and efficient artificial photosynthetic system.

  20. Iron-Based Metal-Organic Frameworks as Catalysts for Visible Light-Driven Water Oxidation.

    PubMed

    Chi, Le; Xu, Qian; Liang, Xiaoyu; Wang, Jide; Su, Xintai

    2016-03-01

    The development of earth-abundant, active, and stable catalysts is important for solar energy conversion. Metal-organic frameworks (MOFs) have been viewed as a promising class of porous materials, which may have innovative application in photocatalysis. In this paper, three types of Fe-based MOFs and their aminofunctionalized derivatives have been fabricated and systematically studied as water oxidation catalysts (WOCs) for oxygen evolution under visible light irradiation. MIL-101(Fe) possesses a higher current density and earlier onset potential and exhibits excellent visible light-driven oxygen evolution activity than the other Fe-based catalysts. It speeds up the oxygen evolution reaction rate with the higher initial turnover frequencies value of 0.10 s(-1) . Our study demonstrates that Fe-based MOFs as efficient WOCs are promising candidates for photocatalytic water oxidation process. PMID:26756919

  1. Construction of carbon nanodots/tungsten trioxide and their visible-light sensitive photocatalytic activity.

    PubMed

    Yan, Fanyong; Kong, Depeng; Fu, Yang; Ye, Qianghua; Wang, Yinyin; Chen, Li

    2016-03-15

    Herein we designed a simple and effective method for synthesizing carbon nanodots/tungsten trioxide nanocomposite with high photocatalytic activity. The as-prepared carbon nanodots/ tungsten trioxide has strong photoabsorption under visible light irradiation. Then, carbon nanodots/tungsten trioxide was successfully applied to the degradation of methylene blue. The photodegradation efficiency of methylene blue can be reached as high as 100% after 0.5 h visible light illumination. In addition, carbon nanodots/tungsten trioxide could also be used to degrade rhodamine B and methyl orange. Most importantly, the photocatalytic activity of carbon nanodots/tungsten trioxide did not exhibit obvious changes after five cycles. The results indicate that carbon nanodots/tungsten trioxide has potential applications in the degradation of organic pollutants in industrial waste water. PMID:26745743

  2. Ti-O-O coordination bond caused visible light photocatalytic property of layered titanium oxide.

    PubMed

    Kong, Xingang; Zeng, Chaobin; Wang, Xing; Huang, Jianfeng; Li, Cuiyan; Fei, Jie; Li, Jiayin; Feng, Qi

    2016-01-01

    The layered titanium oxide is a useful and unique precursor for the facile and rapid preparation of the peroxide layered titanium oxide H1.07Ti1.73O4·nH2O (HTO) crystal with enhanced visible light photoactivity. The H2O2 molecules as peroxide chemicals rapidly enter into the interlayers of HTO crystal, and coordinate with Ti within TiO6 octahedron to form a mass of Ti-O-O coordination bond in the interlayers. The introduction of these Ti-O-O coordination bonds result in lowering the band gap of HTO, and promoting the separation efficiency of the photo induced electron-hole pairs. Meanwhile, the photocatalytic investigation indicates that such peroxide HTO crystal has the enhanced photocatalytic performance for RhB degradation and water splitting to generate oxygen under visible light irradiating. PMID:27350285

  3. Photocatalytic water splitting to hydrogen production of reduced graphene oxide/SiC under visible light

    NASA Astrophysics Data System (ADS)

    Yang, Jingjing; Zeng, Xiaopeng; Chen, Lijuan; Yuan, Wenxia

    2013-02-01

    We report a method to realize the H2 production and graphene-oxide (GO) reduction simultaneously over GO/SiC composite under visible light irradiation with KI as sacrifice reagent. The weight content of GO is regulated in the reaction system. The rate of H2 production reaches to 95 μL/h with 1% GO content in GO/SiC composite system, which is 1.3 times larger compared to the case in pure SiC NPs under visible light. The reduced-GO sheet can serve as an electron collector and transporter to efficiently separate the photo-generated electron-hole pairs, lengthening the lifetime of the charge carriers effectively.

  4. Accelerated gas-liquid visible light photoredox catalysis with continuous-flow photochemical microreactors.

    PubMed

    Straathof, Natan J W; Su, Yuanhai; Hessel, Volker; Noël, Timothy

    2016-01-01

    In this protocol, we describe the construction and use of an operationally simple photochemical microreactor for gas-liquid photoredox catalysis using visible light. The general procedure includes details on how to set up the microreactor appropriately with inlets for gaseous reagents and organic starting materials, and it includes examples of how to use it to achieve continuous-flow preparation of disulfides or trifluoromethylated heterocycles and thiols. The reported photomicroreactors are modular, inexpensive and can be prepared rapidly from commercially available parts within 1 h even by nonspecialists. Interestingly, typical reaction times of gas-liquid visible light photocatalytic reactions performed in microflow are lower (in the minute range) than comparable reactions performed as a batch process (in the hour range). This can be attributed to the improved irradiation efficiency of the reaction mixture and the enhanced gas-liquid mass transfer in the segmented gas-liquid flow regime. PMID:26633128

  5. Self-Sensitized Carbon Nitride Microspheres for Long-Lasting Visible-Light-Driven Hydrogen Generation.

    PubMed

    Gu, Quan; Gao, Ziwei; Xue, Can

    2016-07-01

    A new type of metal-free photocatalyst is reported having a microsphere core of oxygen-containing carbon nitride and self-sensitized surfaces by covalently linked polymeric triazine dyes. These self-sensitized carbon nitride microspheres exhibit high visible-light activities in photocatalytic H2 generation with excellent stability for more than 100 h reaction. Comparing to the traditional g-C3 N4 with activities terminated at 450 nm, the polymeric triazine dyes on the carbon nitride microsphere surface allow for effective wide-range visible-light harvesting and extend the H2 generation activities up to 600 nm. It is believed that this new type of highly stable self-sensitized metal-free structure opens a new direction of future development of low-cost photocatalysts for efficient and long-term solar fuels production. PMID:27225827

  6. Ti-O-O coordination bond caused visible light photocatalytic property of layered titanium oxide

    NASA Astrophysics Data System (ADS)

    Kong, Xingang; Zeng, Chaobin; Wang, Xing; Huang, Jianfeng; Li, Cuiyan; Fei, Jie; Li, Jiayin; Feng, Qi

    2016-06-01

    The layered titanium oxide is a useful and unique precursor for the facile and rapid preparation of the peroxide layered titanium oxide H1.07Ti1.73O4·nH2O (HTO) crystal with enhanced visible light photoactivity. The H2O2 molecules as peroxide chemicals rapidly enter into the interlayers of HTO crystal, and coordinate with Ti within TiO6 octahedron to form a mass of Ti-O-O coordination bond in the interlayers. The introduction of these Ti-O-O coordination bonds result in lowering the band gap of HTO, and promoting the separation efficiency of the photo induced electron–hole pairs. Meanwhile, the photocatalytic investigation indicates that such peroxide HTO crystal has the enhanced photocatalytic performance for RhB degradation and water splitting to generate oxygen under visible light irradiating.

  7. Bottom-up design of 2D organic photocatalysts for visible-light driven hydrogen evolution.

    PubMed

    Wang, Peng; Jiang, Xue; Zhao, Jijun

    2016-01-27

    To design two-dimensional (2D) organocatalysts, three series of covalent organic frameworks (COFs) are constructed using bottom-up strategies, i.e. molecular selection, tunable linkage, and functionalization. First-principles calculations are performed to confirm their photocatalytic activity under visible light. Two of our constructed 2D COF models (B1 and C3) are identified as a sufficiently efficient organocatalyst for visible light water splitting. The controllable construction of such COFs from suitable organic subunit, linkage, and functional groups paves the way for correlating band edge alignments and geometry parameters of 2D organic materials. Our theoretical prediction not only provides essential insights into designing 2D-COF photocatalysts for water splitting, but also sparks other technological applications for 2D organic materials. PMID:26704386

  8. Bottom-up design of 2D organic photocatalysts for visible-light driven hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Jiang, Xue; Zhao, Jijun

    2016-01-01

    To design two-dimensional (2D) organocatalysts, three series of covalent organic frameworks (COFs) are constructed using bottom-up strategies, i.e. molecular selection, tunable linkage, and functionalization. First-principles calculations are performed to confirm their photocatalytic activity under visible light. Two of our constructed 2D COF models (B1 and C3) are identified as a sufficiently efficient organocatalyst for visible light water splitting. The controllable construction of such COFs from suitable organic subunit, linkage, and functional groups paves the way for correlating band edge alignments and geometry parameters of 2D organic materials. Our theoretical prediction not only provides essential insights into designing 2D-COF photocatalysts for water splitting, but also sparks other technological applications for 2D organic materials.

  9. Functional inactivation of lymphocytes by methylene blue with visible light.

    PubMed

    Zhang, Bo; Cheng, Zhenzhen; Mo, Qin; Wang, Li; Wang, Xun; Wu, Xiaofei; Jia, Yao; Huang, Yuwen

    2015-10-01

    Transfusion of allogeneic white blood cells (WBCs) may cause adverse reactions in immunocompromised recipients, including transfusion-associated graft-versus-host disease (TA-GVHD), which is often fatal and incurable. In this study, the in vitro effect of methylene blue with visible light (MB + L) treatment on lymphocyte proliferation and cytokine production was measured to investigate whether MB + L can be used to prevent immune reactions that result from transfused lymphocytes. WBCs and 3 μM of MB were mixed and transferred into medical PVC bags, which were then exposed to visible light. Gamma irradiation was conducted as a parallel positive control. The cells without treatment were used as untreated group. All the groups were tested for the ability of cell proliferation and cytokine production upon stimulation. After incubation with mitogen phytohemagglutinin (PHA) or plate-bound anti-CD3 plus anti-CD28, the proliferation of MB + L/gamma-irradiation treated lymphocytes was significantly inhibited (P < 0.01) as compared to the untreated ones; the proliferation inhibitive rate of the MB + L group was even higher than that of gamma-irradiated cells (73.77% ± 28.75% vs. 44.72% ± 38.20%). MB + L treated cells incubated up to 7 days with PHA also showed no significant proliferation. The levels of TNF-α, IFN-γ, IL-6, IL-8, IL-10 and IL-1β present in the supernatant of MB + L treated lymphocytes upon stimulation were significantly lower than those of untreated lymphocytes. These results demonstrated that MB + L treatment functionally and irreversibly inactivated lymphocytes by inhibiting lymphocyte proliferation and the production of cytokines. MB + L treatment might be a promising method for the prevention of adverse immune responses caused by WBCs. PMID:26295729

  10. CO2 SEQUESTRATION AND RECYCLE BY PHOTOCATALYSIS WITH VISIBLE LIGHT

    SciTech Connect

    Steven S.C. Chuang

    2001-10-01

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

  11. Group III-nitride nanowire structures for photocatalytic hydrogen evolution under visible light irradiation

    SciTech Connect

    Chowdhury, Faqrul A.; Mi, Zetian Kibria, Md G.; Trudeau, Michel L.

    2015-10-01

    The performance of photochemical water splitting over the emerging nanostructured photocatalysts is often constrained by their surface electronic properties, which can lead to imbalance in redox reactions, reduced efficiency, and poor stability. We have investigated the impact of surface charge properties on the photocatalytic activity of InGaN nanowires. By optimizing the surface charge properties through controlled p-type dopant (Mg) incorporation, we have demonstrated an apparent quantum efficiency of ∼17.1% and ∼12.3% for InGaN nanowire arrays under visible light irradiation (400 nm–490 nm) in aqueous methanol and in the overall neutral-pH water splitting reaction, respectively.

  12. Group III-nitride nanowire structures for photocatalytic hydrogen evolution under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Chowdhury, Faqrul A.; Mi, Zetian; Kibria, Md G.; Trudeau, Michel L.

    2015-10-01

    The performance of photochemical water splitting over the emerging nanostructured photocatalysts is often constrained by their surface electronic properties, which can lead to imbalance in redox reactions, reduced efficiency, and poor stability. We have investigated the impact of surface charge properties on the photocatalytic activity of InGaN nanowires. By optimizing the surface charge properties through controlled p-type dopant (Mg) incorporation, we have demonstrated an apparent quantum efficiency of ˜17.1% and ˜12.3% for InGaN nanowire arrays under visible light irradiation (400 nm-490 nm) in aqueous methanol and in the overall neutral-pH water splitting reaction, respectively.

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

    SciTech Connect

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

    2011-08-15

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

  14. Surface Defects Enhanced Visible Light Photocatalytic H2 Production for Zn-Cd-S Solid Solution.

    PubMed

    Zhang, Xiaoyan; Zhao, Zhao; Zhang, Wanwan; Zhang, Guoqiang; Qu, Dan; Miao, Xiang; Sun, Shaorui; Sun, Zaicheng

    2016-02-10

    In order to investigate the defect effect on photocatalytic performance of the visible light photocatalyst, Zn-Cd-S solid solution with surface defects is prepared in the hydrazine hydrate. X-ray photoelectron spectra and photoluminescence results confirm the existence of defects, such as sulfur vacancies, interstitial metal, and Zn and Cd in the low valence state on the top surface of solid solutions. The surface defects can be effectively removed by treating with sulfur vapor. The solid solution with surface defect exhibits a narrower band gap, wider light absorption range, and better photocatalytic perfomance. The optimized solid solution with defects exhibits 571 μmol h(-1) for 50 mg photocatalyst without loading Pt as cocatalyst under visible light irradiation, which is fourfold better than that of sulfur vapor treated samples. The wavelength dependence of photocatalytic activity discloses that the enhancement happens at each wavelength within the whole absorption range. The theoretical calculation shows that the surface defects induce the conduction band minimum and valence band maximum shift downward and upward, respectively. This constructs a type I junction between bulk and surface of solid solution, which promotes the migration of photogenerated charges toward the surface of nanostructure and leads to enhanced photocatalytic activity. Thus a new method to construct highly efficient visible light photocatalysts is opened. PMID:26691211

  15. Mechanisms of interaction of monochromatic visible light with cells

    NASA Astrophysics Data System (ADS)

    Karu, Tiina I.

    1996-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Pennington, Ashley Marie

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

  17. Reduced graphene oxide and Ag wrapped TiO{sub 2} photocatalyst for enhanced visible light photocatalysis

    SciTech Connect

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

    2015-10-01

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

  18. Preparation of titania nanotube-Cd0.65Zn0.35S nanocomposite by a hydrothermal sulfuration method for efficient visible-light-driven photocatalytic hydrogen production

    NASA Astrophysics Data System (ADS)

    Li, Juan; Wu, Liangpeng; Long, Lizhen; Xi, Min; Li, Xinjun

    2014-12-01

    Titania nanotube-Cd0.65Zn0.35S nanocomposite (Cd0.65Zn0.35S-TiO2) was synthesized from titanate nanotubes for ion change of Cd2+ and Zn2+ followed by hydrothermal sulfuration treatment using thiourea as sulfur source. The Cd0.65Zn0.35S-TiO2 with enhanced crystallinity of TiO2 nanotube can be obtained by increasing hydrothermal temperature from 90 °C to 120 °C. And further increasing hydrothermal temperature to 150 °C, TiO2 nanotubes collapse and transform into irregular shaped particles. The photocatalytic activity for hydrogen production of the prepared Cd0.65Zn0.35S-TiO2 with different hydrothermal temperature was investigated under visible-light irradiation. The result shows that the Cd0.65Zn0.35S-TiO2 with hydrothermal temperature of 120 °C presents the highest hydrogen evolution rate and photostability, which can be attributed to a rapid charge transfer at the interface between Cd0.65Zn0.35S and TiO2 nanotube due to the increased crystallinity and unique 1-D nanotubular structure of TiO2.

  19. Conversion of visible light to electrical energy - Stable cadmium selenide photoelectrodes in aqueous electrolytes

    NASA Technical Reports Server (NTRS)

    Wrighton, M. S.; Ellis, A. B.; Kaiser, S. W.

    1977-01-01

    Stabilization of n-type CdSe to photoanodic dissolution is reported. The stabilization is accomplished by the competitive oxidation of S(--) or S(n)(--) at the CdSe photoanode in an electrochemical cell. Such stabilized cells are shown to sustain the conversion of low energy (not less than 1.7 eV) visible light to electricity with good efficiency and no deterioration of the CdSe photoelectrode or of the electrolyte. The electrolyte undergoes no net chemical change because the oxidation occurring at the photoelectrode is reversed at the cathode. Conversion of monochromatic light at 633 nm to electricity is shown to be up to approximately 9% efficient with output potentials of approximately 0.4 V. Conversion of solar energy to electricity is estimated to be approximately 2% efficient.

  20. Performance of dimming control scheme in visible light communication system.

    PubMed

    Wang, Zixiong; Zhong, Wen-De; Yu, Changyuan; Chen, Jian; Francois, Chin Po Shin; Chen, Wei

    2012-08-13

    We investigate the performance of visible light communication (VLC) system with a pulse width modulation (PWM) dimming control scheme. Under this scheme, the communication quality in terms of number of transmitted bits and bit error rate (BER) of less than 10(-3) should be guaranteed. However, for on-off-keying (OOK) signal, the required data rate becomes 10 times as high as the original data rate when the duty cycle of dimming control signal is 0.1. To make the dimming control scheme easy to be implemented in VLC system, we propose the variable M-QAM OFDM VLC system, where M is adjusted according to the brightness of LED light in terms of duty cycle. The results show that with different duty cycles the required data rates are not higher than the original value and less LED lamp power is required to guarantee the communication quality, which makes the dimming control system that satisfies both communication and illumination requirements easy to be implemented and power-saving. PMID:23038525

  1. Plasmonic interaction of visible light with gold nanoscale checkerboards

    NASA Astrophysics Data System (ADS)

    Ramakrishna, S. Anantha; Mandal, P.; Jeyadheepan, K.; Shukla, N.; Chakrabarti, S.; Kadic, M.; Enoch, S.; Guenneau, S.

    2011-12-01

    Intersecting corners and checkerboards of negative refractive index materials (NRIM) represent highly singular electromagnetic systems that involve very highly enhanced local fields and the local density of modes. It is well known that plasmonic metallic systems can mimic the behavior of NRIM in the near-field limit at optical frequencies. Opaque gold films have been structured by focused ion-beam technologies at submicrometer scales in a checkerboard fashion and their optical properties measured. Subwavelength square holes in thick gold films placed in checkerboard fashion show a broadband extraordinary transmission of light at visible wavelengths. We find that the smaller the square holes, the larger is the transmission over a band of wavelengths from 650 to 950 nm suggesting that such structured surfaces have very unusual effective medium properties, which is confirmed by the band-structure diagrams computed with finite elements. Theoretical results also confirm the experimental transmission measured to be well over 80% from 750 to 950 nm for a checkerboard with 150nm×150 nm square holes. This unusual broadband nature of checkerboard structured films is confirmed by the dark-field reflection spectra. Microscopic studies reveal that these structures have enhanced interaction of light at the edges and corners. These checkerboards are also found to give rise to an enhancement of fluorescence by imbedded dye molecules. There is a strong correspondence between the theoretical predictions and the experimental measurements.

  2. Distributed user-centric scheduling for visible light communication networks.

    PubMed

    Chen, Lingjiao; Wang, Jiaheng; Zhou, Jiantao; Ng, Derrick Wing Kwan; Schober, Robert; Zhao, Chunming

    2016-07-11

    Visible light communication (VLC) networks, consisting of multiple light-emitting diodes (LEDs) acting as optical access points (APs), can provide low-cost high-rate data transmission to multiple users simultaneously in indoor environments. However, the performance of VLC networks is severely limited by the interference between different users. In this paper, we establish a distributed user-centric scheduling framework based on stable marriage theory, and propose a novel decentralized scheduling method to manage interference by forming flexible amorphous cells for all users. The proposed scheduling method has provable low computational complexity and requires only the exchange of a few 1-bit messages between the APs and the users but not the feedback of the channel state information of the entire network. We further show that the proposed method can achieve both user-wise and system-wise optimality as well as a certain level of fairness. Simulation results indicate that our decentralized user-centric scheduling method outperforms existing centralized approaches in terms of throughput, fairness, and computational complexity. PMID:27410830

  3. Ellipse-based DCO-OFDM for visible light communications

    NASA Astrophysics Data System (ADS)

    Mao, Tianqi; Wang, Zhaocheng; Wang, Qi; Dai, Linglong

    2016-02-01

    Ellipse-based DC-biased optical orthogonal frequency division multiplexing (E-DCO-OFDM) is proposed for visible light communications (VLC), which achieves a significant peak-to-average power ratio (PAPR) reduction, thus enhancing the overall performance when light-emitting diode (LED) nonlinearity is considered. In E-DCO-OFDM, the real-valued output of OFDM is modulated onto an ellipse, whereby only the imaginary part of the complex point on the ellipse is transmitted. Although the PAPR of E-DCO-OFDM decreases as the ratio of major radius to minor radius becomes larger, it may be more vulnerable to the effect of noise, leading to the performance loss. Therefore, the relationship between the system performance and the critical parameters in E-DCO-OFDM, such as the ratio between the major and minor radius of the ellipse, is investigated. Meanwhile, simulations demonstrate that E-DCO-OFDM adopting the optimal parameters achieves a considerable signal-to-noise ratio (SNR) gain over the conventional DCO-OFDM.

  4. Indium oxide thin film as potential photoanodes for corrosion protection of stainless steel under visible light

    SciTech Connect

    Zhang, Yan; Yu, Jianqiang; Sun, Kai; Zhu, Yukun; Bu, Yuyu; Chen, Zhuoyuan

    2014-05-01

    Graphical abstract: If the conduction band potential of In{sub 2}O{sub 3} is more negative than the corrosion potential of stainless steel, photo-induced electrons will be transferred from In{sub 2}O{sub 3} to the steel, thus shifting the potential of the steel into a corrosion immunity region and preventing the steel from the corrosion. - Highlights: • Indium oxide performed novel application under visible light. • Indium oxide by sol–gel method behaved better photoelectrochemical properties. • Electrons were transferred to stainless steel from indium oxide once light on. - Abstract: This paper reports the photoelectrochemical cathodic protection of 304 stainless steel by In{sub 2}O{sub 3} thin-film under visible-light. The films were fabricated with In{sub 2}O{sub 3} powders, synthesized by both sol–gel (In{sub 2}O{sub 3}-sg) and solid-state (In{sub 2}O{sub 3}-ss) processes. The photo-induced open circuit potential and the photo-to-current efficiency measurements suggested that In{sub 2}O{sub 3} could be a promising candidate material for photoelectrochemical cathodic protection of metallic alloys under visible light. Moreover, the polarization curve experimental results indicated that In{sub 2}O{sub 3}-sg thin-film can mitigate the corrosion potential of 304 stainless steel to much more negative values with a higher photocurrent density than the In{sub 2}O{sub 3}-ss film under visible-light illumination. All the results demonstrated that the In{sub 2}O{sub 3}-sg thin-film provides a better photoelectrochemical cathodic protection for 304 stainless steel than In{sub 2}O{sub 3}-ss thin-film under visible-light illumination. The higher photoelectrochemical efficiency is possibly due to the uniform thin films produced with the smaller particle size of In{sub 2}O{sub 3}-sg, which facilitates the transfer of the photo-induced electrons from bulk to the surface and suppresses the charge recombination of the electrons and holes.

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

    PubMed

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

    2015-07-13

    With increasing interest in visible light communication, the laser diode (LD) provides an attractive alternative, with higher efficiency, shorter linewidth and larger bandwidth for high-speed visible light communication (VLC). Previously, more than 3 Gbps data rate was demonstrated using LED. By using LDs and spectral-efficient orthogonal frequency division multiplexing encoding scheme, significantly higher data rates has been achieved in this work. Using 16-QAM modulation scheme, in conjunction with red, blue and green LDs, data rates of 4.4 Gbps, 4 Gbps and 4 Gbps, with the corresponding BER/SNR/EVM of 3.3 × 10⁻³/15.3/17.9, 1.4 × 10⁻³/16.3/15.4 and 2.8 × 10⁻³/15.5/16.7were obtained over transmission distance of ~20 cm. We also simultaneously demonstrated white light emission using red, blue and green LDs, after passing through a commercially available diffuser element. Our work highlighted that a tradeoff exists in operating the blue LDs at optimum bias condition while maintaining good color temperature. The best results were obtained when encoding red LDs which gave both the strongest received signal amplitude and white light with CCT value of 5835K. PMID:26191934

  6. Efficient telecom to visible wavelength conversion in doubly resonant gallium phosphide microdisks

    NASA Astrophysics Data System (ADS)

    Lake, David P.; Mitchell, Matthew; Jayakumar, Harishankar; dos Santos, Laís Fujii; Curic, Davor; Barclay, Paul E.

    2016-01-01

    Resonant second harmonic generation between 1550 nm and 775 nm with normalized outside efficiency > 3.8 × 10 - 4 mW - 1 is demonstrated in a gallium phosphide microdisk supporting high-Q modes at visible ( Q ˜ 10 4 ) and infrared ( Q ˜ 10 5 ) wavelengths. The double resonance condition is satisfied for a specific pump power through intracavity photothermal temperature tuning using ˜ 360 μ W of 1550 nm light input to a fiber taper and coupled to a microdisk resonance. Power dependent efficiency consistent with a simple model for thermal tuning of the double resonance condition is observed.

  7. Plasmonic nanostructures to enhance catalytic performance of zeolites under visible light.

    PubMed

    Zhang, Xingguang; Ke, Xuebin; Du, Aijun; Zhu, Huaiyong

    2014-01-01

    Light absorption efficiency of heterogeneous catalysts has restricted their photocatalytic capability for commercially important organic synthesis. Here, we report a way of harvesting visible light efficiently to boost zeolite catalysis by means of plasmonic gold nanoparticles (Au-NPs) supported on zeolites. Zeolites possess strong Brønsted acids and polarized electric fields created by extra-framework cations. The polarized electric fields can be further intensified by the electric near-field enhancement of Au-NPs, which results from the localized surface plasmon resonance (LSPR) upon visible light irradiation. The acetalization reaction was selected as a showcase performed on MZSM-5 and Au/MZSM-5 (M = H(+), Na(+), Ca(2+), or La(3+)). The density functional theory (DFT) calculations confirmed that the intensified polarized electric fields played a critical role in stretching the C = O bond of the reactants of benzaldehyde to enlarge their molecular polarities, thus allowing reactants to be activated more efficiently by catalytic centers so as to boost the reaction rates. This discovery should evoke intensive research interest on plasmonic metals and diverse zeolites with an aim to take advantage of sunlight for plasmonic devices, molecular electronics, energy storage, and catalysis. PMID:24448225

  8. Plasmonic nanostructures to enhance catalytic performance of zeolites under visible light

    PubMed Central

    Zhang, Xingguang; Ke, Xuebin; Du, Aijun; Zhu, Huaiyong

    2014-01-01

    Light absorption efficiency of heterogeneous catalysts has restricted their photocatalytic capability for commercially important organic synthesis. Here, we report a way of harvesting visible light efficiently to boost zeolite catalysis by means of plasmonic gold nanoparticles (Au-NPs) supported on zeolites. Zeolites possess strong Brønsted acids and polarized electric fields created by extra-framework cations. The polarized electric fields can be further intensified by the electric near-field enhancement of Au-NPs, which results from the localized surface plasmon resonance (LSPR) upon visible light irradiation. The acetalization reaction was selected as a showcase performed on MZSM-5 and Au/MZSM-5 (M = H+, Na+, Ca2+, or La3+). The density functional theory (DFT) calculations confirmed that the intensified polarized electric fields played a critical role in stretching the C = O bond of the reactants of benzaldehyde to enlarge their molecular polarities, thus allowing reactants to be activated more efficiently by catalytic centers so as to boost the reaction rates. This discovery should evoke intensive research interest on plasmonic metals and diverse zeolites with an aim to take advantage of sunlight for plasmonic devices, molecular electronics, energy storage, and catalysis. PMID:24448225

  9. Plasmonic nanostructures to enhance catalytic performance of zeolites under visible light

    NASA Astrophysics Data System (ADS)

    Zhang, Xingguang; Ke, Xuebin; Du, Aijun; Zhu, Huaiyong

    2014-01-01

    Light absorption efficiency of heterogeneous catalysts has restricted their photocatalytic capability for commercially important organic synthesis. Here, we report a way of harvesting visible light efficiently to boost zeolite catalysis by means of plasmonic gold nanoparticles (Au-NPs) supported on zeolites. Zeolites possess strong Brønsted acids and polarized electric fields created by extra-framework cations. The polarized electric fields can be further intensified by the electric near-field enhancement of Au-NPs, which results from the localized surface plasmon resonance (LSPR) upon visible light irradiation. The acetalization reaction was selected as a showcase performed on MZSM-5 and Au/MZSM-5 (M = H+, Na+, Ca2+, or La3+). The density functional theory (DFT) calculations confirmed that the intensified polarized electric fields played a critical role in stretching the C = O bond of the reactants of benzaldehyde to enlarge their molecular polarities, thus allowing reactants to be activated more efficiently by catalytic centers so as to boost the reaction rates. This discovery should evoke intensive research interest on plasmonic metals and diverse zeolites with an aim to take advantage of sunlight for plasmonic devices, molecular electronics, energy storage, and catalysis.

  10. Visible Light Responsive Catalysts Using Quantum Dot-Modified Ti02 for Air and Water Purification

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Levine, Lanfang H.; Richards, Jeffrey T.; Hintze, paul; Clausen, Christian

    2012-01-01

    The method of photocatalysis utilizing titanium dioxide, TiO2, as the catalyst has been widely studied for trace contaminant control for both air and water applications because of its low energy consumption and use of a regenerable catalyst. Titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors and are a setback for the technology for space application due to the possibility of Hg contamination. The development of a visible light responsive (VLR) TiO2-based catalyst could lead to the use of solar energy in the visible region (approx.45% of the solar spectrum lies in the visible region; > 400 nm) or highly efficient LEDs (with wavelengths > 400 nm) to make PCO approaches more efficient, economical, and safe. Though VLR catalyst development has been an active area of research for the past two decades, there are few commercially available VLR catalysts; those that are available still have poor activity in the visible region compared to that in the UV region. Thus, this study was aimed at the further development of VLR catalysts by a new method - coupling of quantum dots (QD) of a narrow band gap semiconductor (e.g., CdS, CdSe, PbS, ZnSe, etc.) to the TiO2 by two preparation methods: 1) photodeposition and 2) mechanical alloying using a high-speed ball mill. A library of catalysts was developed and screened for gas and aqueous phase applications, using ethanol and 4-chlorophenol as the target contaminants, respectively. Both target compounds are well studied in photocatalytic systems serve as model contaminants for this research. Synthesized catalysts were compared in terms of preparation method, type of quantum dots, and dosage of quantum dots.

  11. A dye-sensitized visible light photocatalyst-Bi24O31Cl10

    PubMed Central

    Wang, Liang; Shang, Jun; Hao, Weichang; Jiang, Shiqi; Huang, Shiheng; Wang, Tianmin; Sun, Ziqi; Du, Yi; Dou, Shixue; Xie, Tengfeng; Wang, Dejun; Wang, Jiaou

    2014-01-01

    The p-block semiconductors are regarded as a new family of visible-light photocatalysts because of their dispersive and anisotropic band structures as well as high chemical stability. The bismuth oxide halides belong to this family and have band structures and dispersion relations that can be engineered by modulating the stoichiometry of the halogen elements. Herein, we have developed a new visible-light photocatalyst Bi24O31Cl10 by band engineering, which shows high dye-sensitized photocatalytic activity. Density functional theory calculations reveal that the p-block elements determine the nature of the dispersive electronic structures and narrow band gap in Bi24O31Cl10. Bi24O31Cl10 exhibits excellent visible-light photocatalytic activity towards the degradation of Rhodamine B, which is promoted by dye sensitization due to compatible energy levels and high electronic mobility. In addition, Bi24O31Cl10 is also a suitable photoanode material for dye-sensitized solar cells and shows power conversion efficiency of 1.5%. PMID:25488704

  12. Structural Effects in Visible-Light-Responsive Metal-Organic Frameworks Incorporating ortho-Fluoroazobenzenes.

    PubMed

    Castellanos, Sonia; Goulet-Hanssens, Alexis; Zhao, Fangli; Dikhtiarenko, Alla; Pustovarenko, Alexey; Hecht, Stefan; Gascon, Jorge; Kapteijn, Freek; Bléger, David

    2016-01-11

    The ability to control the interplay of materials with low-energy photons is important as visible light offers several appealing features compared to ultraviolet radiation (less damaging, more selective, predominant in the solar spectrum, possibility to increase the penetration depth). Two different metal-organic frameworks (MOFs) were synthesized from the same linker bearing all-visible ortho-fluoroazobenzene photoswitches as pendant groups. The MOFs exhibit different architectures that strongly influence the ability of the azobenzenes to isomerize inside the voids. The framework built with Al-based nodes has congested 1D channels that preclude efficient isomerization. As a result, local light-heat conversion can be used to alter the CO2 adsorption capacity of the material on exposure to green light. The second framework, built with Zr nodes, provides enough room for the photoswitches to isomerize, which leads to a unique bistable photochromic MOF that readily responds to blue and green light. The superiority of green over UV irradiation was additionally demonstrated by reflectance spectroscopy and analysis of digested samples. This material offers promising perspectives for liquid-phase applications such as light-controlled catalysis and adsorptive separation. PMID:26617393

  13. Zinc oxide nanorod mediated visible light photoinactivation of model microbes in water

    NASA Astrophysics Data System (ADS)

    Sapkota, Ajaya; Anceno, Alfredo J.; Baruah, Sunandan; Shipin, Oleg V.; Dutta, Joydeep

    2011-05-01

    The inactivation of model microbes in aqueous matrix by visible light photocatalysis as mediated by ZnO nanorods was investigated. ZnO nanorods were grown on glass substrate following a hydrothermal route and employed in the inactivation of gram-negative Escherichia coli and gram-positive Bacillus subtilis in MilliQ water. The concentration of Zn2 + ions in the aqueous matrix, bacterial cell membrane damage, and DNA degradation at post-exposure were also studied. The inactivation efficiencies for both organisms under light conditions were about two times higher than under dark conditions across the cell concentrations assayed. Anomalies in supernatant Zn2 + concentration were observed under both conditions as compared to control treatments, while cell membrane damage and DNA degradation were observed only under light conditions. Inactivation under dark conditions was hence attributed to the bactericidal effect of Zn2 + ions, while inactivation under light conditions was due to the combined effects of Zn2 + ions and photocatalytically mediated electron injection. The reduction of pathogenic bacterial densities by the photocatalytically active ZnO nanorods in the presence of visible light implies potential ex situ application in water decontamination at ambient conditions under sunlight.

  14. Fluorescence efficiency and visible re-emission spectrum of tetraphenyl butadiene films at extreme ultraviolet wavelengths

    NASA Astrophysics Data System (ADS)

    Gehman, V. M.; Seibert, S. R.; Rielage, K.; Hime, A.; Sun, Y.; Mei, D.-M.; Maassen, J.; Moore, D.

    2011-10-01

    A large number of current and future experiments in neutrino and dark matter detection use the scintillation light from noble elements as a mechanism for measuring energy deposition. The scintillation light from these elements is produced in the extreme ultraviolet (EUV) range, from 60 to 200 nm. Currently, the most practical technique for observing light at these wavelengths is to surround the scintillation volume with a thin film of tetraphenyl butadiene (TPB) to act as a fluor. The TPB film absorbs EUV photons and re-emits visible photons, detectable with a variety of commercial photosensors. Here we present a measurement of the re-emission spectrum of TPB films when illuminated with 128, 160, 175, and 250 nm light. We also measure the fluorescence efficiency as a function of incident wavelength from 120 to 250 nm.

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

    PubMed Central

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

    2015-01-01

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

  16. Energy Efficiency Through Lighting Upgrades

    SciTech Connect

    Berst, Kara; Howeth, Maria

    2013-02-26

    Lighting upgrades including neon to LED, incandescent to CFL's and T-12 to T-8 and T-5's were completed through this grant. A total of 16 Chickasaw nation facilities decreased their carbon footprint because of these grant funds. Calculations used were based on comparing the energy usage from the previous year's average and the current energy usage. For facilities without a full year's set of energy bills, the month after installation was compared to the same month from the previous year. Overall, the effect the lighting change-outs had for the gaming centers and casinos far exceeded expectations. For the Madill Gaming Center; both an interior and exterior upgrade was performed which resulted in a 31% decrease in energy consumption. This same reduction was seen in every facility that participated in the grant. Just by simply changing out light bulbs to newer energy efficient equivalents, a decrease in energy usage can be achieved and this was validated by the return on investment seen at Chickasaw Nation facilities. Along with the technical project tasks were awareness sessions presented at Chickasaw Head Starts. The positive message of environmental stewardship was passed down to head start students and passed along to Chickasaw employees. Excitement was created in those that learned what they could do to help reduce their energy bills and many followed through and took the idea home. For a fairy low cost, the general public can also use this technique to lower their energy consumption both at home and at work. Although the idea behind the project was somewhat simple, true benefits have been gained through environmental awareness and reductions of energy costs.

  17. Visible spatial frequency domain imaging with a digital light microprojector

    PubMed Central

    Lin, Alexander J.; Ponticorvo, Adrien; Konecky, Soren D.; Cui, Haotian; Rice, Tyler B.; Choi, Bernard; Durkin, Anthony J.

    2013-01-01

    Abstract. There is a need for cost effective, quantitative tissue spectroscopy and imaging systems in clinical diagnostics and pre-clinical biomedical research. A platform that utilizes a commercially available light-emitting diode (LED) based projector, cameras, and scaled Monte Carlo model for calculating tissue optical properties is presented. These components are put together to perform spatial frequency domain imaging (SFDI), a model-based reflectance technique that measures and maps absorption coefficients (μa) and reduced scattering coefficients (μs′) in thick tissue such as skin or brain. We validate the performance of the flexible LED and modulation element (FLaME) system at 460, 530, and 632 nm across a range of physiologically relevant μa values (0.07 to 1.5  mm−1) in tissue-simulating intralipid phantoms, showing an overall accuracy within 11% of spectrophotometer values for μa and 3% for μs′. Comparison of oxy- and total hemoglobin fits between the FLaME system and a spectrophotometer (450 to 1000 nm) is differed by 3%. Finally, we acquire optical property maps of a mouse brain in vivo with and without an overlying saline well. These results demonstrate the potential of FLaME to perform tissue optical property mapping in visible spectral regions and highlight how the optical clearing effect of saline is correlated to a decrease in μs′ of the skull. PMID:24005154

  18. Continuous zoom antenna for mobile visible light communication.

    PubMed

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

    2015-11-10

    In this paper, we design a continuous zoom antenna for mobile visible light communication (VLC). In the design, a right-angle reflecting prism was adopted to fold the space optical path, thus decreasing the antenna thickness. The surface of each lens in the antenna is spherical, and the system cost is relatively low. Simulation results indicated that the designed system achieved the following performance: zoom ratio of 2.44, field of view (FOV) range of 18°-48°, system gain of 16.8, and system size of 18 mm×6  mm. Finally, we established an indoor VLC system model in a room the size of 5  m ×5  m ×3  m and compared the detection results of the zoom antenna and fixed-focus antenna obtained in a multisource communication environment, a mobile VLC environment, and a multiple-input multiple-output communication environment. The simulation results indicated that the continuous zoom antenna could realize large FOV and high gain. Moreover, the system showed improved stability, mobility, and environmental applicability. PMID:26560793

  19. Toward user mobility for OFDM-based visible light communications.

    PubMed

    Hong, Yang; Chen, Lian-Kuan

    2016-08-15

    We propose and experimentally demonstrate a mobile visible light communications (mobi-VLC) transmission system. The impact of user mobility on the performance of the mobi-VLC system is characterized, and we propose the use of the channel-independent orthogonal circulant matrix transform (OCT) precoding to combat the packet loss performance degradation induced by mobility. A mobile user terminal is used to detect the signal from a blue laser placed at 1 m away from the moving track. Various moving speeds (20, 40, 60, and 80  cm/s) and lateral moving distances (30, 40, and 50 cm) of the user terminal are investigated. The effectiveness of the OCT precoding is evaluated by the comparison with the conventional orthogonal frequency division multiplexing (OFDM) scheme and the adaptive-loaded discrete multi-tone (DMT) scheme. Experimental results show that the system performance degrades with the increase in user mobility speed and in moving distance. Furthermore, the OCT precoding provides performance improvement that is superior over that of conventional OFDM schemes, and it exhibits lower packet loss rate than that of adaptive-loaded DMT. No packet loss for 300  Mb/s transmission is achieved with a 30 cm lateral moving distance at 20  cm/s. PMID:27519083

  20. Performance study for indoor visible light communication systems

    NASA Astrophysics Data System (ADS)

    Gao, Shuo

    The field of Optical Wireless Communications (OWC) has seen rapid development during the recent years. This growing popularity is due to several characteristics of considerable importance to consumer electronics products, such as large bandwidth that is also not having spectrum regulations imposed, low cost, and license free operation. As a branch of OWC, visible light communication (VLC) systems have their own unique advantages, with several new technologies, products and patents having been developed during since the end of last century. In this research, a VLC system for indoor application is proposed. In this work, we focus on reducing cost, and for that, we had to make appropriate selection of system's components, e.g. modulation, coding, filtering. Our objective was to achieve acceptable bit error rate (BER) performance for indoor use, with a low cost system. Through our research we met this objective. Our designs were evaluated through computer simulations. The acquired results proved the suitability of the proposed schemes and the performance's degree of dependency on several parameters such as distance, incidence angle and irradiance angle. A software tool was created allowing easy assessment of the communication system. It is using a user friendly GUI through which the user enters the system's parameters and the system outputs the corresponding BER value.

  1. Visible-light-initiated difluoromethylation of arene diazonium tetrafluoroborates.

    PubMed

    Wu, Ye-Bin; Lu, Guo-Ping; Zhou, Bao-Jing; Bu, Mei-Jie; Wan, Li; Cai, Chun

    2016-05-21

    A mild and efficient method for the radical addition of α-aryl-β,β-difluoroenol silyl with arene diazonium tetrafluoroborates at room temperature has been disclosed, which involves an innate radical long chain cycle, so only a small amount (0.05 mol%) of photocatalyst and a short light exposure time are required as radical initiators. A proposed mechanism for the transformation is also illustrated based on the results of control experiments and quantum calculations. A variety of α-aryl-α,α-difluoroketones were formed in moderate to high yields, and can be easily further transformed into various difluoromethylarenes under basic conditions. PMID:27055723

  2. Design of multicomponent photocatalysts for hydrogen production under visible light using water-soluble titanate nanodisks.

    PubMed

    Dinh, Cao-Thang; Pham, Minh-Hao; Seo, Yongbeom; Kleitz, Freddy; Do, Trong-On

    2014-05-01

    We report the design of efficient multicomponent photocatalysts (MPs) for H2 production under visible light by using water-soluble ultrathin titanate nanodisks (TNDs) stabilized by tetraethylammonium cations (TEA(+)) as building blocks. The photocatalysts are designed in such a way to significantly enhance simultaneously the efficiency of the three main steps in the photocatalytic process i.e., light absorption, charge separation and catalytic reaction. We show, as an example, the construction of water-soluble CdS-TND-Ni MPs. The designed CdS-TND-Ni MPs, in which CdS nanoparticles and TNDs are intimately assembled to enhance the charge transfer and surface area, are controlled in composition to optimize visible light absorption. The conception of the MPs allows them to be highly dispersed in water which markedly improves the photocatalytic H2 production process. Most importantly, a Ni co-catalyst is selectively located on the surface of TNDs, enabling vectorial electron transfer from CdS to TND and to Ni, which drastically improves the charge separation. Consequently, under visible light illumination (λ ≥ 420 nm), the optimally designed CdS-TND-Ni MPs could generate H2 from ethanol-water solution with rate as high as 15.326 mmol g(-1) h(-1) during a reaction course of 15 h and with an apparent quantum yield of 24% at 420 nm. Moreover, we also demonstrate that TNDs can be combined with other single or mixed metal sulfide to form water-soluble metal sulfide-TNDs composites which could also be of great interest for photocatalytic H2 production. PMID:24664235

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    We demonstrate visible-light electroluminescence (EL) due to d- d transitions in GaAs:Mn based LEDs. We design p+-n junctions with a p+ GaAs:Mn layer, in which at a reverse bias voltage (-3 to -6 V), an intense electric field builds up in the depletion layers of the p+-n junctions. Holes are injected to the depletion layer by Zener tunneling from the conduction band or by diffusion of minority holes from the valence band of the n-type layer. These holes are accelerated by the intense electric field in the depletion layer, and excite the d electrons of Mn in the p+ GaAs:Mn layer by impact excitations. We observe visible-light emission at E1 = 1.89 eV and E2 = 2.16 eV, which are exactly the same as the 4T1-->6A1 and 4A2-->4T1 transition energy of Mn. The threshold voltage for observation of visible-light EL is -4 V, corresponding to -(E1 +E2) / e. This indicates that the impact excitation is most effective for the one step excitation from the ground state 6A1 to the highest excited state 4A2 .

  4. Visible and Infra-red Light Emission in Boron-Doped Wurtzite Silicon Nanowires

    PubMed Central

    Fabbri, Filippo; Rotunno, Enzo; Lazzarini, Laura; Fukata, Naoki; Salviati, Giancarlo

    2014-01-01

    Silicon, the mainstay semiconductor in microelectronic circuitry, is considered unsuitable for optoelectronic applications owing to its indirect electronic band gap, which limits its efficiency as a light emitter. Here we show the light emission properties of boron-doped wurtzite silicon nanowires measured by cathodoluminescence spectroscopy at room temperature. A visible emission, peaked above 1.5 eV, and a near infra-red emission at 0.8 eV correlate respectively to the direct transition at the Γ point and to the indirect band-gap of wurtzite silicon. We find additional intense emissions due to boron intra-gap states in the short wavelength infra-red range. We present the evolution of the light emission properties as function of the boron doping concentration and the growth temperature. PMID:24398782

  5. AgI/TiO2 nanobelts monolithic catalyst with enhanced visible light photocatalytic activity.

    PubMed

    Yi, Junhui; Huang, Lingling; Wang, Hongjuan; Yu, Hao; Peng, Feng

    2015-03-01

    AgI nanoparticles (NPs) have been decorated on the TiO2 nanobelts (NBs) immobilized on a metal Ti substrate by a simple impregnating-precipitation method. The as-achieved AgI/TiO2 monolithic catalyst exhibits a high and stable visible photocatalytic activity toward acid orange II (AO-II) degradation, which is attributed to the suitable energy band match of AgI NPs and TiO2 NBs, leading to the efficient transfer of photo-generated electrons. In addition, it was found that ·O2(-) radicals and h(+) are the main reactive species for the degradation of AO-II under visible light irradiation. A reasonable photocatalytic mechanism of AgI/TiO2 photocatalyst toward AO-II degradation was discussed. This monolithic catalyst provides an advantage over the drawback encountered with powder suspension. PMID:25463235

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

    NASA Astrophysics Data System (ADS)

    Fan, Tao; Li, Yinle; Shen, Jianfeng; Ye, Mingxin

    2016-03-01

    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 (Eg = 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.

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

    PubMed Central

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

    2015-01-01

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

  8. BODIPY catalyzed amide synthesis promoted by BHT and air under visible light.

    PubMed

    Wang, Xiao-Fei; Yu, Shu-Sheng; Wang, Chao; Xue, Dong; Xiao, Jianliang

    2016-08-01

    A novel and efficient protocol for the synthesis of amides is reported which employs a BODIPY catalyzed oxidative amidation reaction between aromatic aldehydes and amines under visible light. Compared with the known Ru or Ir molecular catalysts and other organic dyes, the BODIPY catalyst showed higher reactivity toward this reaction. Mechanistic studies reveal that dioxygen could be activated through an ET and a SET pathway, forming active peroxides in situ, which are vital for the key step of the reaction, i.e. the oxidation of hemiaminal to amide. The broad substrate scope and mild reaction conditions make this reaction practically useful and environmentally friendly for the synthesis of amide compounds. PMID:27363514

  9. Synthesis of N-doped TiO2 Using Guanidine Nitrate: An Excellent Visible Light Photocatalyst

    EPA Science Inventory

    An excellent visible light active nitrogen-rich TiO2 photocatalyst have been synthesized by using guanidine nitrate as the doping material. The catalytic efficiency of the catalyst has been demonstrated by the decomposition of the dye, methyl orange (MO), and the pollutant, 2,4 d...

  10. Visible Light-Induced Radical Rearrangement to Construct C-C Bonds via an Intramolecular Aryl Migration/Desulfonylation Process.

    PubMed

    Li, Yuyuan; Hu, Bei; Dong, Wuheng; Xie, Xiaomin; Wan, Jun; Zhang, Zhaoguo

    2016-08-19

    A highly efficient intramolecular selective aryl migration/desulfonylation of 2-bromo-N-aryl-N-(arenesulfonyl)amide via visible light-induced photoredox catalysis has been accomplished. This approach allows for the construction of a variety of multisubstituted N,2-diarylacetamide under mild reaction conditions. PMID:27351977

  11. Difunctionalization of Alkenes via the Visible-Light-Induced Trifluoromethylarylation/1,4-Aryl Shift/Desulfonylation Cascade Reactions.

    PubMed

    Zheng, Lewei; Yang, Chao; Xu, ZhaoZhong; Gao, Fei; Xia, Wujiong

    2015-06-01

    A novel visible-light-induced trifluoromethylarylation/1,4-aryl shift/desulfonylation cascade reaction using CF3SO2Cl as CF3 source was described. The protocol provides an efficient approach for the synthesis of α-aryl-β-trifluoromethyl amides and/or CF3-containing oxindoles as well as the isoquinolinediones under benign conditions. PMID:25955879

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  13. TiO{sub 2}/carbon nanotube hybrid nanostructures: Solvothermal synthesis and their visible light photocatalytic activity

    SciTech Connect

    Tian Lihong; Ye Liqun; Deng Kejian; Zan Ling

    2011-06-15

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

  14. Visible-light-driven photodegradation of sulfamethoxazole and methylene blue by Cu2O/rGO photocatalysts.

    PubMed

    Liu, Shou-Heng; Wei, Yu-Shao; Lu, Jun-Sheng

    2016-07-01

    The cuprous oxide-reduced graphene oxide (Cu2O/rGO-x) composites were prepared via a simple wet-chemical method by using CuSO4·5H2O and graphene oxide as precursors and ascorbic acid as a reducing agent, respectively. These Cu2O/rGO-x were employed as photocatalysts for degrading emerging contaminants and organic dye pollutants (i.e., sulfamethoxazole (SMX) and methylene blue (MB)) under visible light. A variety of different spectroscopic and analytical techniques, such as X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman scattering spectroscopy and UV-Visible spectroscopy were used to characterize the physical properties of photocatalysts. In the photodegrading experiments, it can be found that the Cu2O/rGO-80 photocatalyst has the superior visible-light response of ca. 50% removal efficiency of SMX within 120 min and 100% removal efficiency of MB within 40 min. These observations may be attributed the well-dispersed and visible-light-responsive Cu2O nanoparticles are supported on the surface of rGO sheets that can enhance absorption of visible light during photocatalysis. PMID:27043377

  15. Visible light active TiO 2 films prepared by electron beam deposition of noble metals

    NASA Astrophysics Data System (ADS)

    Hou, Xing-Gang; Ma, Jun; Liu, An-Dong; Li, De-Jun; Huang, Mei-Dong; Deng, Xiang-Yun

    2010-03-01

    TiO 2 films prepared by sol-gel method were modified by electron beam deposition of noble metals (Pt, Pd, and Ag). Effects of noble metals on the chemical and surface characteristics of the films were studied using XPS, TEM and UV-Vis spectroscopy techniques. Photocatalytic activity of modified TiO 2 films was evaluated by studying the degradation of methyl orange dye solution under visible light UV irradiation. The result of TEM reveals that most of the surface area of TiO 2 is covered by tiny particles of noble metals with diameter less than 1 nm. Broad red shift of UV-Visible absorption band of modified photocatalysts was observed. The catalytic degradation of methyl orange in aqueous solutions under visible light illumination demonstrates a significant enhancement of photocatalytic activity of these films compared with the un-loaded films. The photocatalytic efficiency of modified TiO 2 films by this method is affected by the concentration of impregnating solution.

  16. Visible light assisted degradation of organic dye using Ag{sub 3}PO{sub 4}

    SciTech Connect

    Dhanabal, R.; Bose, A. Chandra; Velmathi, S.

    2015-06-24

    The study of visible light photodegradation of organic dye Methylene Blue (MB) have been investigated using silver phosphate (Ag{sub 3}PO{sub 4}) as a photocatalyst which is good efficient material for photocatalytic reaction. The simple ion-exchange method is used to prepare Ag{sub 3}PO{sub 4}. The structure of the material have been confirmed using X-ray diffraction which shows cubic structure of Ag{sub 3}PO{sub 4}. The functional group of the Ag{sub 3}PO{sub 4} has been verified by Fourier transform infrared spectroscopy. The bandgap of Ag{sub 3}PO{sub 4} is calculated using kubelka-munk function from the ultra violet-visible diffuse reflectance spectroscopy, the absorption of Ag{sub 3}PO{sub 4} starts from 470 nm. Under simulated visible light irradiation, Ag{sub 3}PO{sub 4} catalyst exhibits good catalytic ability for degrading MB dye.

  17. Microwave-assisted synthesis of bismuth oxybromochloride nanoflakes for visible light photodegradation of pollutants

    NASA Astrophysics Data System (ADS)

    Bijanzad, Keyvan; Tadjarodi, Azadeh; Moghaddasi Khiavi, Mohammad; Akhavan, Omid

    2015-10-01

    BiOBrxCl1-x (0visible diffuse reflectance and photoluminescence (PL) spectroscopies revealed the indirect band gap of ~2.82 eV for the bismuth oxybromochloride nanoflakes. Visible light-assisted photocatalytic studies showed that the degradation efficiency of the as-prepared BiOBrxCl1-x for (100 mL of 10 mg L-1) Rhodamine B (RhB), Natural Red 4 (N-Red) dye solutions was 98.14% and for the colorless organic pentachlorophenol (PCP) solution was 91.09% over 150 min. The possible mechanisms involved in the visible light photodegradation of the pollutants by BiOBrxCl1-x photocatalyst were also discussed.

  18. A Visible-Light-Induced α-H Chlorination of Alkylarenes with Inorganic Chloride under NanoAg@AgCl.

    PubMed

    Liu, Shouxin; Zhang, Qi; Li, Huiying; Yang, Yihua; Tian, Xia; Whiting, Andrew

    2015-06-26

    An efficient, photocatalytic chlorination of alkylarene α-H groups using NaCl/HCl as a chlorine source has been developed, which involves a radical mechanism under visible-light (including sunlight) conditions. A chlorine radical is proposed to be formed by an electron transfer from chloride ion to O2 in air through the bandgap hole of the semiconductor AgCl. The chlorination protocol is characterized by its use of natural sunlight or other visible light, mild conditions, cheap source of chlorine, green solvent, and high selectivity. The yield of benzylchloride is 95% with a toluene conversion as high as 40%, which rivals traditional chlorination methods. PMID:26061749

  19. Unprecedented photocatalytic activity of carbon coated/MoO3 core-shell nanoheterostructurs under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Ghaffar, Iqra; Warsi, Muhammad Farooq; Shahid, Muhammad; Shakir, Imran

    2016-05-01

    We reveal that nano-scale carbon layer deposited by hydrothermal process on molybdenum oxide (MoO3) nanowires surface significantly improve the light absorption range. Furthermore, the graphene-carbon coated MoO3 nanocopmosite (rGO/C-MoO3 nanocomposite) exhibits excellent chemical stability and enhanced photocatalytic activity for methylene blue in aqueous solution under visible light irradiation compared to the bare MoO3 nanowires and carbon coated MoO3 nanowires (C-MoO3 nanowires). The enhanced photocatalytic activity of rGO/C-MoO3 nanocomposite could be attributed to the extended light absorption range, better adsorptivity of dye molecules and efficient separation of photogenerated electrons and holes. Overall, this work provides new insights that the as synthesized rGO/C-MoO3 nanocomposite can be efficiently used as high performance photocatalysts to improve the environmental protection issues under visible light irradiation.

  20. Visible-light emission at room temperature in Mn-doped Si light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Hai, Pham Nam; Maruo, Daiki; Anh, Le Duc; Tanaka, Masaaki

    2016-03-01

    We demonstrate Si-based light-emitting diodes that continuously emit reddish-yellow visible light at room temperature by utilizing optical transitions between the p-d hybrid orbitals of Mn atoms doped in Si. Our light-emitting diodes show clear visible-light electroluminescence with two peaks at E1=1.75 and E2=2.30 eV , corresponding to optical transitions between p-d hybrid orbitals of Mn atoms. The electrons at the p-d hybrid orbitals of Mn in Si are excited by hot holes that are accelerated by an intensive electric field in the depletion layer of reverse biased Si p -n junctions containing a Mn-doped Si (Si:Mn) layer. The observed two peaks at E1=1.75 and E2=2.30 eV are redshifted and blueshifted by 0.14 eV, respectively, from those of GaAs:Mn or ZnS:Mn. Our observations are consistent with the p -d hybridized electronic structure of Mn atoms doped in Si as predicted by first-principles calculations.

  1. Fluorescence enhancement in visible light: dielectric or noble metal?

    PubMed

    Sun, S; Wu, L; Bai, P; Png, C E

    2016-07-28

    A high permittivity dielectric gives the impression of outperforming plasmonic noble metal in visible light fluorescence enhancement primarily because of its small loss. Nonetheless, the performances of these two platforms in various situations remain obscure due to the different optical confinement mechanisms as well as the complexity in the fluorescence enhancement process. This study presents a comprehensive comparison between these two platforms based on nanoparticles (NPs) to evaluate their capability and applicability in fluorescence enhancement by taking into account the fluorescence excitation rate, the quantum yield, the fluorophore wavelengths and Stokes shifts as well as the far field intensity. In a low permittivity sensing medium (e.g. air), the dielectric NP can achieve comparable or higher fluorescence enhancement than the metal NP due to its decent NP-enhanced excitation rate and larger quantum yield. In a relatively high permittivity sensing medium (e.g. water), however, there is a significant decrement of the excitation rate of the dielectric NP as the permittivity contrast decreases, leading to a smaller fluorescence enhancement compared to the metallic counterpart. Combining the fluorescence enhancement and the far field intensity studies, we further conclude that for both dielectric and plasmonic NPs, the optimal situation occurs when the fluorescence excitation wavelength, the fluorescence emission wavelength and the electric-dipole-mode of the dielectric NP (or the plasmonic resonance of the metal NP) are the same and all fall in the low conductivity region of the NP material. We also find that the electric-dipole-mode of the dielectric NP performs better than the magnetic-dipole-mode for fluorescence enhancement applications because only the electric-dipole-mode can be strongly excited by the routinely used fluorescent dyes and quantum dots, which behave as electric dipoles by nature. PMID:27374052

  2. Visible light degradation of Orange II using xCuyOz/TiO2 heterojunctions.

    PubMed

    Helaïli, N; Bessekhouad, Y; Bouguelia, A; Trari, M

    2009-08-30

    Cu(2)O/TiO(2), Cu/Cu(2)O/TiO(2) and Cu/Cu(2)O/CuO/TiO(2) heterojunctions were prepared and studied for their potential application as photocatalysts able to induce high performance under visible light. Orange II was used as a representative dye molecule. The effect of the amount and composition of the photosensitizers toward the activation of TiO(2) was studied. In each case, the global mechanism of Inter Particle Electrons Injection (IPEI) was discussed. The highest photocatalytic activity was observed for the system Cu/Cu(2)O/CuO (MB2 catalyst) under visible light (t(1/2)=24 min, k=159.7 x 10(-3)min(-1)) and for the heterojunction cascade Cu/Cu(2)O/CuO/TiO(2) (MB2 (50%)/TiO(2)) under UV-vis light (t(1/2)=4 min, k=1342 x 10(-3)min(-1)). In the last case, the high performance was attributed firstly to the electromotive forces developed under this configuration in which CuO energy bands mediate the electrons transfer from Cu(2)O to TiO(2). The formation of monobloc sensitizers also accounts for the decrease of the probability of the charges lost. It was demonstrated that "Cu(2)O/CuO" governs the capability of the heterojunction cascade and Cu does not play a significant role regardless of the heterojunction cascade efficiency. The electrical energy consumption per order of magnitude for photocatalytic degradation of Orange II was investigated for some representative catalytic systems. Visible/MB2 and UV/vis MB2 (50%)/TiO(2) exhibited respectively 0.340 and 0.05 kW hm(-3) demonstrating the high efficiency of the systems. PMID:19307056

  3. Visible light photocatalytic degradation of 4-chlorophenol using vanadium and nitrogen co-doped TiO2

    NASA Astrophysics Data System (ADS)

    Jaiswal, R.; Patel, N.; Kothari, D. C.; Miotello, A.

    2013-02-01

    Vanadium and Nitrogen were codoped in TiO2 photocatalyst by Sol-gel method to utilize visible light more efficiently for photocatalytic reactions. A noticeable shift of absorption edge to visible light region was obtained for the singly-doped namely V-TiO2, N-TiO2 and codoped V-N-TiO2 samples in comparison with undoped TiO2, with smallest band gap obtained with codoped-TiO2. The photocatalytic activities for all TiO2 photocatalysts were tested by 4-chlorophenol (organic pollutant) degradation under visible light irradiation. It was found that codoped TiO2 exhibits the best photocatalytic activity, which could be attributed to the synergistic effect produced by V and N dopants.

  4. Visible light photocatalytic degradation of 4-chlorophenol using vanadium and nitrogen co-doped TiO{sub 2}

    SciTech Connect

    Jaiswal, R.; Kothari, D. C.; Patel, N.; Miotello, A.

    2013-02-05

    Vanadium and Nitrogen were codoped in TiO{sub 2} photocatalyst by Sol-gel method to utilize visible light more efficiently for photocatalytic reactions. A noticeable shift of absorption edge to visible light region was obtained for the singly-doped namely V-TiO{sub 2}, N-TiO{sub 2} and codoped V-N-TiO{sub 2} samples in comparison with undoped TiO{sub 2}, with smallest band gap obtained with codoped-TiO{sub 2}. The photocatalytic activities for all TiO{sub 2} photocatalysts were tested by 4-chlorophenol (organic pollutant) degradation under visible light irradiation. It was found that codoped TiO{sub 2} exhibits the best photocatalytic activity, which could be attributed to the synergistic effect produced by V and N dopants.

  5. Broadband visible light source based on AllnGaN light emitting diodes

    DOEpatents

    Crawford, Mary H.; Nelson, Jeffrey S.

    2003-12-16

    A visible light source device is described based on a light emitting diode and a nanocluster-based film. The light emitting diode utilizes a semiconductor quantum well structure between n-type and p-type semiconductor materials on the top surface a substrate such as sapphire. The nanocluster-based film is deposited on the bottom surface of the substrate and can be derived from a solution of MoS.sub.2, MoSe.sub.2, WS.sub.2, and WSe.sub.2 particles of size greater than approximately 2 nm in diameter and less than approximately 15 nm in diameter, having an absorption wavelength greater than approximately 300 nm and less than approximately 650 nm.

  6. Photocatalytic Oxidation of Propylene on Pd-Loaded Anatase TiO2 Nanotubes Under Visible Light Irradiation

    NASA Astrophysics Data System (ADS)

    Li, Chen; Zong, Lanlan; Li, Qiuye; Zhang, Jiwei; Yang, Jianjun; Jin, Zhensheng

    2016-05-01

    TiO2 nanotubes attract much attention because of their high photoelectron-chemical and photocatalytic efficiency. But their large band gap leads to a low absorption of the solar light and limits the practical application. How to obtain TiO2 nanotubes without any dopant and possessing visible light response is a big challenge nowadays. Orthorhombic titanic acid nanotubes (TAN) are a special precursor of TiO2, which possess large Brunauer-Emmett-Teller (BET) surface areas and strong ion exchange and adsorption capacity. TAN can transform to a novel TiO2 with a large amount of single-electron-trapped oxygen vacancies (SETOV) during calcination, while their nanotubular structure would be destroyed, and a BET surface area would decrease remarkably. And interestingly, SETOV can lead to a visible light response for this kind of TiO2. Herein, glucose was penetrated into TAN by the vacuum inhalation method, and TAN would dehydrate to anatase TiO2, and glucose would undergo thermolysis completely in the calcination process. As a result, the pure TiO2 nanotubes with visible light response and large BET surface areas were obtained. For further improving the photocatalytic activity, Pd nanoparticles were loaded as the foreign electron traps on TiO2 nanotubes and the photocatalytic oxidation efficiency of propylene was as high as 71 % under visible light irradiation, and the photostability of the catalyst kept over 90 % after 4 cyclic tests.

  7. Photocatalytic Oxidation of Propylene on Pd-Loaded Anatase TiO2 Nanotubes Under Visible Light Irradiation.

    PubMed

    Li, Chen; Zong, Lanlan; Li, Qiuye; Zhang, Jiwei; Yang, Jianjun; Jin, Zhensheng

    2016-12-01

    TiO2 nanotubes attract much attention because of their high photoelectron-chemical and photocatalytic efficiency. But their large band gap leads to a low absorption of the solar light and limits the practical application. How to obtain TiO2 nanotubes without any dopant and possessing visible light response is a big challenge nowadays. Orthorhombic titanic acid nanotubes (TAN) are a special precursor of TiO2, which possess large Brunauer-Emmett-Teller (BET) surface areas and strong ion exchange and adsorption capacity. TAN can transform to a novel TiO2 with a large amount of single-electron-trapped oxygen vacancies (SETOV) during calcination, while their nanotubular structure would be destroyed, and a BET surface area would decrease remarkably. And interestingly, SETOV can lead to a visible light response for this kind of TiO2. Herein, glucose was penetrated into TAN by the vacuum inhalation method, and TAN would dehydrate to anatase TiO2, and glucose would undergo thermolysis completely in the calcination process. As a result, the pure TiO2 nanotubes with visible light response and large BET surface areas were obtained. For further improving the photocatalytic activity, Pd nanoparticles were loaded as the foreign electron traps on TiO2 nanotubes and the photocatalytic oxidation efficiency of propylene was as high as 71 % under visible light irradiation, and the photostability of the catalyst kept over 90 % after 4 cyclic tests. PMID:27229518

  8. An Efficient Composition for Bengal Lights.

    ERIC Educational Resources Information Center

    Comet, M.; Schreyeck, L.; Fuzellier, H.

    2002-01-01

    Reports the discovery of an efficient base composition for making bengal lights that is obtained with potassium chlorate and thiourea. Combining this mixture with appropriate flame coloring can produce several impressive bengal lights. (DDR)

  9. Adaptive scheme for maintaining the performance of the in-home white-LED visible light wireless communications using OFDM

    NASA Astrophysics Data System (ADS)

    Chow, C. W.; Yeh, C. H.; Liu, Y. F.; Huang, P. Y.; Liu, Y.

    2013-04-01

    Spectral-efficient orthogonal frequency division multiplexing (OFDM) is a promising modulation format for the light-emitting-diode (LED) optical wireless (OW) visible light communication (VLC). VLC is a directional and line-of-sight communication; hence the offset of the optical receiver (Rx) and the LED light source will result in a large drop of received optical power. In order to keep the same luminance of the LED light source, we propose and demonstrate an adaptive control of the OFDM modulation-order to maintain the VLC transmission performance. Experimental results confirm the feasibility of the proposed scheme.

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

    SciTech Connect

    Zanatta, A. R.

    2012-06-15

    Even though the great interest in studying the near-infrared light emission due to Er{sup 3+} ions for telecommunication purposes, efficient visible radiation can be achieved from many different rare-earth (RE) ions. In fact, visible and/or near-infrared light emission takes place in RE-doped wide bandgap semiconductors following either photon or electron excitation, suggesting their technological potential in devices such as light-emitting diodes (LED's) and flat-panel displays, for example. Taking into consideration these aspects, the present contribution reports on the investigation of AlN, BeN, GeN, and SiN thin films doped with samarium. The samples were prepared by sputtering and as a result of the deposition method and conditions they present an amorphous structure and Sm concentrations in the low 0.5 at. %. After deposition, the samples were submitted to thermal annealing treatments and investigated by different spectroscopic techniques. A detailed examination of the experimental data allowed to identify optical transitions due to Sm{sup 3+} and Sm{sup 2+} ions as well as differences in their mechanisms of photon excitation and recombination. Moreover, it is shown that the Sm-related spectral features and emission intensity are susceptible, respectively, to the atomic environment the Sm{sup 3+}/Sm{sup 2+} ions experience and to the presence of non-radiative recombination centers.

  11. Mesoporous TiN microspheres with hierarchical chambers and enhanced visible light-driven hydrogen evolution.

    PubMed

    Li, Guisheng; Zhang, Peng; Bian, Zhenfeng; Zhu, Jian; Wu, Ling; Li, Hexing

    2013-08-01

    Mesoporous titanium nitride (TiN) microspheres with tunable chamber structures were synthesized through NH3 nitridation of organotitania obtained via solvothermal alcoholysis. Owing to high content of organic species in organotitania, which stabilized the original structure and also promoted the nitridation at low temperature, TiN duplicated the solid, yolk-shell, and hollow chambers of organotitania in NH3 nitridation and also formed the mesoporous structure after removing organic species. During visible light-induced photocatalytic water splitting, the yolk-shell TiN demonstrated a higher H2 evolution efficiency than the solid, hollow, and crushed TiN; the yolk-shell TiN obtained through N2 nitridation; and other semiconductor photocatalysts reported so far without the aid of noble metals. This could be attributed mainly to the narrow energy band gap for absorbing visible light, high surface area, and excellent electrical conductivity, which facilitated light harvesting, reactant adsorption, and photoelectron-hole separation to suppress their recombination. Moreover, it could be easily recycled and thus used repetitively. PMID:23784852

  12. Visible light induced green transformation of primary amines to imines using a silicate supported anatase photocatalyst.

    PubMed

    Zavahir, Sifani; Zhu, Huaiyong

    2015-01-01

    Catalytic oxidation of amine to imine is of intense present interest since imines are important intermediates for the synthesis of fine chemicals, pharmaceuticals, and agricultural chemicals. However, considerable efforts have been made to develop efficient methods for the oxidation of secondary amines to imines, while little attention has until recently been given to the oxidation of primary amines, presumably owing to the high reactivity of generated imines of primary amines that are easily dehydrogenated to nitriles. Herein, we report the oxidative coupling of a series of primary benzylic amines into corresponding imines with dioxygen as the benign oxidant over composite catalysts of TiO2 (anatase)-silicate under visible light irradiation of λ > 460 nm. Visible light response of this system is believed to be as a result of high population of defects and contacts between silicate and anatase crystals in the composite and the strong interaction between benzylic amine and the catalyst. It is found that tuning the intensity and wavelength of the light irradiation and the reaction temperature can remarkably enhance the reaction activity. Water can also act as a green medium for the reaction with an excellent selectivity. This report contributes to the use of readily synthesized, environmentally benign, TiO2 based composite photocatalyst and solar energy to realize the transformation of primary amines to imine compounds. PMID:25629455

  13. Mediator-free direct Z-scheme photocatalytic system: BiVO4/g-C3N4 organic-inorganic hybrid photocatalyst with highly efficient visible-light-induced photocatalytic activity.

    PubMed

    Tian, Na; Huang, Hongwei; He, Ying; Guo, Yuxi; Zhang, Tierui; Zhang, Yihe

    2015-03-01

    We disclose the fabrication of a mediator-free direct Z-scheme photocatalyst system BiVO4/g-C3N4 using a mixed-calcination method based on the more reliable interfacial interaction. The facet coupling occurred between the g-C3N4 (002) and BiVO4 (121), and it was revealed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). The crystal structure and optical properties of the as-prepared samples have also been characterized by Fourier-transform infrared (FTIR), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectra (DRS) in details. The photocatalytic experiments indicated that the BiVO4/g-C3N4 composite photocatalysts display a significantly enhanced photocatalytic activity pertaining to RhB degradation and photocurrent generation (PC) compared to the pristine BiVO4 and g-C3N4. This remarkably improved photocatalytic performance should be attributed to the fabrication of a direct Z-scheme system of BiVO4/g-C3N4, which can result in a more efficient separation of photoinduced charge carriers than band-band transfer, thus endowing it with the much more powerful oxidation and reduction capability, as confirmed by the photoluminescence (PL) spectra and electrochemical impedance spectra (EIS). The Z-scheme mechanism of BiVO4/g-C3N4 heterostructure was verified by a series of combined techniques, including the active species trapping experiments, NBT transformation and terephthalic acid photoluminescence probing technique (TA-PL) over BiVO4/g-C3N4 composites and the pristine samples. The present work not only furthered the understanding of mediator-free Z-scheme photocatalysis, but also shed new light on the design of heterostructural photocatalysts with high-performance. PMID:25635354

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

    NASA Astrophysics Data System (ADS)

    Früchtl, Marion; Janssen, Christof; Röckmann, Thomas

    2014-05-01

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

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

    PubMed

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

    2015-11-01

    We used the synthesized dinaphthylmethane (Hdnm) ligand whose absorption extends to the visible-light wavelength, to prepare a family of ternary lanthanide complexes, named as [Ln(dnm)3 phen] (Ln = Sm, Nd, Yb, Er, Tm, Pr). The properties of these complexes were investigated by Fourier transform infrared (FT-IR) spectroscopy, diffuse reflectance (DR) spectroscopy, thermogravimetric analyses, and excitation and emission spectroscopy. Generally, excitation with visible light is much more advantageous than UV excitation. Importantly, upon excitation with visible light (401-460 nm), the complexes show characteristic visible (Sm(3+)) as well as near-infrared (Sm(3+), Nd(3+), Yb(3+), Er(3+), Tm(3+), Pr(3+)) luminescence of the corresponding lanthanide ions, attributed to the energy transfer from the ligands to the lanthanide ions, an antenna effect. Now, using these near-infrared luminescent lanthanide complexes, the luminescent spectral region from 800 to 1650 nm, can be covered completely, which is of particular interest for biomedical imaging applications, laser systems, and optical amplification applications. PMID:25691149

  16. 33 CFR 83.22 - Visibility of lights (Rule 22).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...; (4) A towing light, 3 miles; (5) A white, red, green or yellow all-round light, 3 miles; and (6) A... sidelight, 2 miles; (3) A sternlight, 2 miles; (4) A towing light, 2 miles; (5) A white, red, green or... sidelight, 1 mile; (3) A sternlight, 2 miles; (4) A towing light, 2 miles; (5) A white, red, green or...

  17. Damaging effects of visible light. Comprehensive progress report

    SciTech Connect

    1981-01-01

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

  18. Guide to Energy-Efficient Lighting

    SciTech Connect

    2010-10-01

    A fact sheet from the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy: Lighting accounts for about 15% of an average home’s electricity use, so it pays to make energy-efficient choices.

  19. Low temperature performance of photomultiplier tubes illuminated in pulsed mode by visible and vacuum ultraviolet light

    NASA Astrophysics Data System (ADS)

    Araújo, H. M.; Chepel, V. Yu.; Lopes, M. I.; Marques, R. Ferreira; Policarpo, A. J. P. L.

    1997-01-01

    Detecting the ultraviolet scintillation light of the liquefied rare gases, in particular liquid xenon, requires the use of photomultiplier tubes (PMTs) in a temperature range where their operation is not ensured by manufacturers. Simultaneously, monitoring of the PMTs should be done in the visible for technical reasons. Bialkali photocathodes, that present high quantum efficiency and low dark noise, exhibit a very strong increase of electrical resistivity upon cooling that, apart from other reasons, can lead to operation failure at low temperature. Photomultiplier tubes with bialkali photocathodes and quartz windows (two EMI 9750Q and one Philips XP 2020Q) and another with S11-type photocathode and glass window (FEU 85A) were tested down to -160 °C with a pulsed light source, both in the visible region and at the xenon scintillation wavelength in the vacuum ultraviolet. For the visible range, the results obtained with bialkali photomultipliers display a sharp drop of response at about -100 °C, depending on the count rate, regardless of the wavelength, and a shift of the spectral sensitivity curve towards shorter wavelengths. Concerning the vacuum ultraviolet region, a significant increase of the response was observed between room temperature and that of the efficiency drop. For some photomultiplier tubes, the response as a function of temperature was observed to depend on their past history, probably due to mechanical effects arising in the multiplier system upon cooling. It is concluded that photomultipliers with bialkali photocathode can, in principle, be used for the detection of liquid xenon scintillation, although they have to be carefully monitored while in operation.

  20. Facile synthesis of thermal- and photostable titania with paramagnetic oxygen vacancies for visible-light photocatalysis.

    PubMed

    Zou, Xiaoxin; Liu, Jikai; Su, Juan; Zuo, Fan; Chen, Jiesheng; Feng, Pingyun

    2013-02-18

    A novel dopant-free TiO(2) photocatalyst (V(o)(.)-TiO(2)), which is self-modified by a large number of paramagnetic (single-electron-trapped) oxygen vacancies, was prepared by calcining a mixture of a porous amorphous TiO(2) precursor, imidazole, and hydrochloric acid at elevated temperature (450 °C) in air. Control experiments demonstrate that the porous TiO(2) precursor, imidazole, and hydrochloric acid are all necessary for the formation of V(o)(.)-TiO(2). Although the synthesis of V(o)(.)-TiO(2) originates from such a multicomponent system, this synthetic approach is facile, controllable, and reproducible. X-ray diffraction, XPS, and EPR spectroscopy reveal that the V(o)(.)-TiO(2) material with a high crystallinity embodies a mass of paramagnetic oxygen vacancies, and is free of other dopant species such as nitrogen and carbon. UV/Vis diffuse-reflectance spectroscopy and photoelectrochemical measurement demonstrate that V(o)(.)-TiO(2) is a stable visible-light-responsive material with photogenerated charge separation efficiency higher than N-TiO(2) and P25 under visible-light irradiation. The V(o)(.)-TiO(2) material exhibits not only satisfactory thermal- and photostability, but also superior photocatalytic activity for H(2) evolution (115 μmol h(-1) g(-1)) from water with methanol as sacrificial reagent under visible light (λ>400 nm) irradiation. Furthermore, the effects of reaction temperature, ratio of starting materials (imidazole:TiO(2) precursor) and calcination time on the photocatalytic activity and the microstructure of V(o)(.)-TiO(2) were elucidated. PMID:23307339

  1. Visible-light-responsive ZnCuO nanoparticles: benign photodynamic killers of infectious protozoans.

    PubMed

    Nadhman, Akhtar; Nazir, Samina; Khan, Malik Ihsanullah; Ayub, Attiya; Muhammad, Bakhtiar; Khan, Momin; Shams, Dilawar Farhan; Yasinzai, Masoom

    2015-01-01

    Human beings suffer from several infectious agents such as viruses, bacteria, and protozoans. Recently, there has been a great interest in developing biocompatible nanostructures to deal with infectious agents. This study investigated benign ZnCuO nanostructures that were visible-light-responsive due to the resident copper in the lattice. The nanostructures were synthesized through a size-controlled hot-injection process, which was adaptable to the surface ligation processes. The nanostructures were then characterized through transmission electron microscopy, X-ray diffraction, diffused reflectance spectroscopy, Rutherford backscattering, and photoluminescence analysis to measure crystallite nature, size, luminescence, composition, and band-gap analyses. Antiprotozoal efficiency of the current nanoparticles revealed the photodynamic killing of Leishmania protozoan, thus acting as efficient metal-based photosensitizers. The crystalline nanoparticles showed good biocompatibility when tested for macrophage toxicity and in hemolysis assays. The study opens a wide avenue for using toxic material in resident nontoxic forms as an effective antiprotozoal treatment. PMID:26604755

  2. Visible-light-responsive ZnCuO nanoparticles: benign photodynamic killers of infectious protozoans

    PubMed Central

    Nadhman, Akhtar; Nazir, Samina; Khan, Malik Ihsanullah; Ayub, Attiya; Muhammad, Bakhtiar; Khan, Momin; Shams, Dilawar Farhan; Yasinzai, Masoom

    2015-01-01

    Human beings suffer from several infectious agents such as viruses, bacteria, and protozoans. Recently, there has been a great interest in developing biocompatible nanostructures to deal with infectious agents. This study investigated benign ZnCuO nanostructures that were visible-light-responsive due to the resident copper in the lattice. The nanostructures were synthesized through a size-controlled hot-injection process, which was adaptable to the surface ligation processes. The nanostructures were then characterized through transmission electron microscopy, X-ray diffraction, diffused reflectance spectroscopy, Rutherford backscattering, and photoluminescence analysis to measure crystallite nature, size, luminescence, composition, and band-gap analyses. Antiprotozoal efficiency of the current nanoparticles revealed the photodynamic killing of Leishmania protozoan, thus acting as efficient metal-based photosensitizers. The crystalline nanoparticles showed good biocompatibility when tested for macrophage toxicity and in hemolysis assays. The study opens a wide avenue for using toxic material in resident nontoxic forms as an effective antiprotozoal treatment. PMID:26604755

  3. Secure communication zone for white-light LED visible light communication

    NASA Astrophysics Data System (ADS)

    Chow, Chi-Wai; Liu, Yang; Yeh, Chien-Hung; Chen, Chung-Yen; Lin, Chao-Nan; Hsu, Dar-Zu

    2015-06-01

    As visible light communication (VLC) can be one of the promising wireless communication technologies in the future, improving the transmission security in VLC is highly desirable. We propose and demonstrate a secure VLC system using data superposition of different light emitting diodes (LEDs). The eavesdroppers can receive similar illumination but cannot obtain enough signal-to-noise ratio (SNR) for communication. The channel model and simulation parameters are presented. Analysis of the secure VLC zone forming using practical in-home scenarios is also discussed, showing the flexibly control the size and shift of secure VLC zone. A proof-of-concept experiment is performed, and there is a good match in trend between the experimental and simulation results.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    We observed visible-light electroluminescence (EL) due to d-d transitions in light-emitting diodes with Mn-doped GaAs layers (here, referred to as GaAs:Mn). Besides the band-gap emission of GaAs, the EL spectra show two peaks at 1.89 eV and 2.16 eV, which are exactly the same as 4A2(4F) → 4T1(4G) and 4T1(4G) → 6A1(6S) transitions of Mn atoms doped in ZnS. The temperature dependence and the current-density dependence are consistent with the characteristics of d-d transitions. We explain the observed EL spectra by the p-d hybridized orbitals of the Mn d electrons in GaAs.

  5. Quantum dots/silica/polymer nanocomposite films with high visible light transmission and UV shielding properties

    NASA Astrophysics Data System (ADS)

    Mumin, Md Abdul; Xu, William Z.; Charpentier, Paul A.

    2015-08-01

    The dispersion of light-absorbing inorganic nanomaterials in transparent plastics such as poly(ethylene-co-vinyl acetate) (PEVA) is of enormous current interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Nanocrystalline semiconductor or quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light, which can control plant growth in greenhouses or enhance PV panel efficiencies. This work provides a new and simple approach for loading mesoporous silica-encapsulated QDs into PEVA. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm size were synthesized using a modified facile approach based on pyrolysis of the single-molecule precursors and capping the CdS QDs with a thin layer of ZnS. To make both the bare and core-shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs through a reverse microemulsion technique based on hydrophobic interactions. By careful experimental tuning, this encapsulation technique enhanced the quantum yield (˜65%) and photostability compared to the bare QDs. Both the encapsulated bare and core-shell QDs were then melt-mixed with EVA pellets using a mini twin-screw extruder and pressed into thin films with controlled thickness. The results demonstrated for the first time that mesoporous silica not only enhanced the quantum yield and photostability of the QDs but also improved the compatibility and dispersibility of QDs throughout the PEVA films. The novel light selective films show high visible light transmission (˜90%) and decreased UV transmission (˜75%).

  6. Quantum dots/silica/polymer nanocomposite films with high visible light transmission and UV shielding properties.

    PubMed

    Mumin, Md Abdul; Xu, William Z; Charpentier, Paul A

    2015-08-01

    The dispersion of light-absorbing inorganic nanomaterials in transparent plastics such as poly(ethylene-co-vinyl acetate) (PEVA) is of enormous current interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Nanocrystalline semiconductor or quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light, which can control plant growth in greenhouses or enhance PV panel efficiencies. This work provides a new and simple approach for loading mesoporous silica-encapsulated QDs into PEVA. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm size were synthesized using a modified facile approach based on pyrolysis of the single-molecule precursors and capping the CdS QDs with a thin layer of ZnS. To make both the bare and core-shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs through a reverse microemulsion technique based on hydrophobic interactions. By careful experimental tuning, this encapsulation technique enhanced the quantum yield (∼65%) and photostability compared to the bare QDs. Both the encapsulated bare and core-shell QDs were then melt-mixed with EVA pellets using a mini twin-screw extruder and pressed into thin films with controlled thickness. The results demonstrated for the first time that mesoporous silica not only enhanced the quantum yield and photostability of the QDs but also improved the compatibility and dispersibility of QDs throughout the PEVA films. The novel light selective films show high visible light transmission (∼90%) and decreased UV transmission (∼75%). PMID:26177824

  7. Highly Visible Light Responsive, Narrow Band gap TiO2 Nanoparticles Modified by Elemental Red Phosphorus for Photocatalysis and Photoelectrochemical Applications.

    PubMed

    Ansari, Sajid Ali; Cho, Moo Hwan

    2016-01-01

    This paper reports that the introduction of elemental red phosphorus (RP) into TiO2 can shift the light absorption ability from the UV to the visible region, and confirmed that the optimal RP loading and milling time can effectively improve the visible light driven-photocatalytic activity of TiO2. The resulting RP-TiO2 nanohybrids were characterized systematically by a range of techniques and the photocatalytic ability of the RP-TiO2 photocatalysts was assessed further by the photodegradation of a model Rhodamine B pollutant under visible light irradiation. The results suggest that the RP-TiO2 has superior photodegradation ability for model contaminant decomposition compared to other well-known photocatalysts, such as TiO2 and other reference materials. Furthermore, as a photoelectrode, electrochemical impedance spectroscopy, differential pulse voltammetry, and linear scan voltammetry were also performed in the dark and under visible light irradiation. These photoelectrochemical performances of RP-TiO2 under visible light irradiation revealed more efficient photoexcited electron-hole separation and rapid charge transfer than under the dark condition, and thus improved photocatalytic activity. These findings show that the use of earth abundant and inexpensive red phosphorus instead of expensive plasmonic metals for inducing visible light responsive characteristics in TiO2 is an effective strategy for the efficient energy conversion of visible light. PMID:27146098

  8. Highly Visible Light Responsive, Narrow Band gap TiO2 Nanoparticles Modified by Elemental Red Phosphorus for Photocatalysis and Photoelectrochemical Applications

    NASA Astrophysics Data System (ADS)

    Ansari, Sajid Ali; Cho, Moo Hwan

    2016-05-01

    This paper reports that the introduction of elemental red phosphorus (RP) into TiO2 can shift the light absorption ability from the UV to the visible region, and confirmed that the optimal RP loading and milling time can effectively improve the visible light driven-photocatalytic activity of TiO2. The resulting RP-TiO2 nanohybrids were characterized systematically by a range of techniques and the photocatalytic ability of the RP-TiO2 photocatalysts was assessed further by the photodegradation of a model Rhodamine B pollutant under visible light irradiation. The results suggest that the RP-TiO2 has superior photodegradation ability for model contaminant decomposition compared to other well-known photocatalysts, such as TiO2 and other reference materials. Furthermore, as a photoelectrode, electrochemical impedance spectroscopy, differential pulse voltammetry, and linear scan voltammetry were also performed in the dark and under visible light irradiation. These photoelectrochemical performances of RP-TiO2 under visible light irradiation revealed more efficient photoexcited electron-hole separation and rapid charge transfer than under the dark condition, and thus improved photocatalytic activity. These findings show that the use of earth abundant and inexpensive red phosphorus instead of expensive plasmonic metals for inducing visible light responsive characteristics in TiO2 is an effective strategy for the efficient energy conversion of visible light.

  9. Highly Visible Light Responsive, Narrow Band gap TiO2 Nanoparticles Modified by Elemental Red Phosphorus for Photocatalysis and Photoelectrochemical Applications

    PubMed Central

    Ansari, Sajid Ali; Cho, Moo Hwan

    2016-01-01

    This paper reports that the introduction of elemental red phosphorus (RP) into TiO2 can shift the light absorption ability from the UV to the visible region, and confirmed that the optimal RP loading and milling time can effectively improve the visible light driven-photocatalytic activity of TiO2. The resulting RP-TiO2 nanohybrids were characterized systematically by a range of techniques and the photocatalytic ability of the RP-TiO2 photocatalysts was assessed further by the photodegradation of a model Rhodamine B pollutant under visible light irradiation. The results suggest that the RP-TiO2 has superior photodegradation ability for model contaminant decomposition compared to other well-known photocatalysts, such as TiO2 and other reference materials. Furthermore, as a photoelectrode, electrochemical impedance spectroscopy, differential pulse voltammetry, and linear scan voltammetry were also performed in the dark and under visible light irradiation. These photoelectrochemical performances of RP-TiO2 under visible light irradiation revealed more efficient photoexcited electron-hole separation and rapid charge transfer than under the dark condition, and thus improved photocatalytic activity. These findings show that the use of earth abundant and inexpensive red phosphorus instead of expensive plasmonic metals for inducing visible light responsive characteristics in TiO2 is an effective strategy for the efficient energy conversion of visible light. PMID:27146098

  10. Janus magneto-electric nanosphere dimers exhibiting unidirectional visible light scattering and strong electromagnetic field enhancement.

    PubMed

    Wang, Hao; Liu, Pu; Ke, Yanlin; Su, Yunkun; Zhang, Lei; Xu, Ningsheng; Deng, Shaozhi; Chen, Huanjun

    2015-01-27

    Steering incident light into specific directions at the nanoscale is very important for future nanophotonics applications of signal transmission and detection. A prerequisite for such a purpose is the development of nanostructures with high-efficiency unidirectional light scattering properties. Here, from both theoretical and experimental sides, we conceived and demonstrated the unidirectional visible light scattering behaviors of a heterostructure, Janus dimer composed of gold and silicon nanospheres. By carefully adjusting the sizes and spacings of the two nanospheres, the Janus dimer can support both electric and magnetic dipole modes with spectral overlaps and comparable strengths. The interference of these two modes gives rise to the narrow-band unidirectional scattering behaviors with enhanced forward scattering and suppressed backward scattering. The directionality can further be improved by arranging the dimers into one-dimensional chain structures. In addition, the dimers also show remarkable electromagnetic field enhancements. These results will be important not only for applications of light emitting devices, solar cells, optical filters, and various surface enhanced spectroscopies but also for furthering our understanding on the light-matter interactions at the nanoscale. PMID:25554917

  11. Synthesis and photocatalytic activity of mesoporous cerium doped TiO{sub 2} as visible light sensitive photocatalyst

    SciTech Connect

    Aman, Noor; Satapathy, P.K.; Mishra, T.; Mahato, M.; Das, N.N.

    2012-02-15

    Graphical abstract: Cerium doped titania having optimum 5 wt% of cerium can decompose methylene blue and reduce selenium (IV) efficiently under visible light. Highlights: Black-Right-Pointing-Pointer Effect of cerium doping on the surface properties and visible light mediated photocatalytic reaction is studied. Black-Right-Pointing-Pointer Cerium doping increases the anatase phase stability, surface area (up to 137 m{sup 2}/g) and visible light absorption. Black-Right-Pointing-Pointer Importance of Ce{sup 3+}/Ce{sup 4+}, oxygen vacancy, surface area and crystallinity is correlated with improved catalytic activity. Black-Right-Pointing-Pointer Material with 5 wt% Ce is found to be most active photocatalyst for methylene blue decomposition and Se (IV) reduction. -- Abstract: Cerium doped titania materials were synthesized varying the cerium concentration from 0 to 10 wt%. Materials are characterised by XRD, TEM, XPS and N{sub 2} adsorption desorption method. Surface area and visible light absorption substantially increases and crystallite size decreases with the increasing cerium content. Cerium doping stabilizes the anatase phase and surface area even at 600 Degree-Sign C calcination. Photocatalytic activity towards methylene blue decomposition and selenium (IV) reduction is found to increase with the cerium content up to 5 wt% and then decreases. Materials calcined at 600 Degree-Sign C shows better activity than that calcined at 400 Degree-Sign C, even though surface area decreases. Anatase crystallinity mostly decides the photocatalytic activity rather than only surface area. It can be concluded that the optimum visible light absorption and oxygen vacancy with 5% cerium doping enhances the photocatalytic activity. In addition photocatalytic performance is found to depend on the presence of Ce{sup 4+}/Ce{sup 3+} rather than only visible light absorption.

  12. Enhanced photocatalytic activity of ZnO/CuO nanocomposite for the degradation of textile dye on visible light illumination.

    PubMed

    Saravanan, R; Karthikeyan, S; Gupta, V K; Sekaran, G; Narayanan, V; Stephen, A

    2013-01-01

    The photocatalytic degradation of organic dyes such as methylene blue and methyl orange in the presence of various percentages of composite catalyst under visible light irradiation was carried out. The catalyst ZnO nanorods and ZnO/CuO nanocomposites of different weight ratios were prepared by new thermal decomposition method, which is simple and cost effective. The prepared catalysts were characterized by different techniques such as X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and UV-visible absorption spectroscopy. Further, the most photocatalytically active composite material was used for degradation of real textile waste water under visible light illumination. The irradiated samples were analysed by total organic carbon and chemical oxygen demand. The efficiency of the catalyst and their photocatalytic mechanism has been discussed in detail. PMID:25428048

  13. Role of Visible Light-Activated Photocatalyst on the Reduction of Anthrax Spore-Induced Mortality in Mice

    PubMed Central

    Huang, Hsin-Hsien; Wong, Ming-Show; Lin, Hung-Chi; Chang, Hsin-Hou

    2009-01-01

    Background Photocatalysis of titanium dioxide (TiO2) substrates is primarily induced by ultraviolet light irradiation. Anion-doped TiO2 substrates were shown to exhibit photocatalytic activities under visible-light illumination, relative environmentally-friendly materials. Their anti-spore activity against Bacillus anthracis, however, remains to be investigated. We evaluated these visible-light activated photocatalysts on the reduction of anthrax spore-induced pathogenesis. Methodology/Principal Findings Standard plating method was used to determine the inactivation of anthrax spore by visible light-induced photocatalysis. Mouse models were further employed to investigate the suppressive effects of the photocatalysis on anthrax toxin- and spore-mediated mortality. We found that anti-spore activities of visible light illuminated nitrogen- or carbon-doped titania thin films significantly reduced viability of anthrax spores. Even though the spore-killing efficiency is only approximately 25%, our data indicate that spores from photocatalyzed groups but not untreated groups have a less survival rate after macrophage clearance. In addition, the photocatalysis could directly inactivate lethal toxin, the major virulence factor of B. anthracis. In agreement with these results, we found that the photocatalyzed spores have tenfold less potency to induce mortality in mice. These data suggest that the photocatalysis might injury the spores through inactivating spore components. Conclusion/Significance Photocatalysis induced injuries of the spores might be more important than direct killing of spores to reduce pathogenicity in the host. PMID:19132100

  14. Superior visible light hydrogen evolution of Janus bilayer junctions via atomic-level charge flow steering.

    PubMed

    Li, Jie; Zhan, Guangming; Yu, Ying; Zhang, Lizhi

    2016-01-01

    Although photocatalytic hydrogen evolution (PHE) is ideal for solar-to-fuel conversion, it remains challenging to construct a highly efficient PHE system by steering the charge flow in a precise manner. Here we tackle this challenge by assembling 1T MoS2 monolayers selectively and chemically onto (Bi12O17) end-faces of Bi12O17Cl2 monolayers to craft two-dimensional (2D) Janus (Cl2)-(Bi12O17)-(MoS2) bilayer junctions, a new 2D motif different from van der Waals heterostructure. Electrons and holes from visible light-irradiated Bi12O17Cl2 are directionally separated by the internal electric field to (Bi12O17) and (Cl2) end-faces, respectively. The separated electrons can further migrate to MoS2 via Bi-S bonds formed between (Bi12O17) and MoS2 monolayers. This atomic-level directional charge separation endows the Janus bilayers with ultralong carrier lifetime of 3,446 ns and hence a superior visible-light PHE rate of 33 mmol h(-1) g(-1). Our delineated Janus bilayer junctions on the basis of the oriented assembly of monolayers presents a new design concept to effectively steer the charge flow for PHE. PMID:27157679

  15. Microwave hydrothermal synthesis of AgInS{sub 2} with visible light photocatalytic activity

    SciTech Connect

    Zhang, Wenjuan; Li, Danzhen; Chen, Zhixin; Sun, Meng; Li, Wenjuan; Lin, Qiang; Fu, Xianzhi

    2011-07-15

    Highlights: {yields} AgInS{sub 2} nanoparticles were synthesized by a microwave hydrothermal method. {yields} This method involves no organic solvents, catalysts, or surfactants. {yields} AgInS{sub 2} showed higher activity for photocatalytic degradation MO than TiO{sub 2-x}N{sub x}. {yields} Holes, O{sub 2}{center_dot}{sup -}, and H{sub 2}O{sub 2} played an important role in the photocatalytic process. -- Abstract: AgInS{sub 2} nanoparticles with superior visible light photocatalytic activity were successfully synthesized by a microwave hydrothermal method. This method is a highly efficient and rapid route that involves no organic solvents, catalysts, or surfactants. The photocatalytic activity of AgInS{sub 2} nanoparticles was investigated through the degradation of dyes under visible light irradiation. Compared with TiO{sub 2-x}N{sub x}, AgInS{sub 2} has exhibited a superior activity for photocatalytic degradation MO under the same condition. The experiment results showed that superoxide radicals (O{sub 2}{center_dot}{sup -}), hydrogen peroxides (H{sub 2}O{sub 2}) and holes (h{sup +}) were the mainly active species for the degradation of organic pollutants over AgInS{sub 2}. Through the determination of flat band potential, the energy band structure of the sample was obtained. A possible mechanism for the degradation of organic pollutant over AgInS{sub 2} was proposed.

  16. Activation of peroxymonosulfate by BiVO4 under visible light for degradation of Rhodamine B

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Guo, Hongguang; Zhang, Yongli; Tang, Weihong; Cheng, Xin; Liu, Hongwei

    2016-06-01

    A photocatalytic system involving visible light and BiVO4 (Vis/BiVO4) in the presence of peroxymonosulfate (PMS) has been developed to oxidize the target pollutant Rhodamine B (RhB) in aqueous solution. It was found that PMS could enhance the photocatalytic efficiency of BiVO4 and could be activated to promote the removal of RhB with sulfate radicals, hydroxyl radicals and superoxide radicals. Critical impacting factors in the Vis/BiVO4/PMS system were investigated concerning the influence of PMS concentration, solution pH, catalyst dosage, initial concentration of RhB and the presence of anions (Cl- and CO32-). In addition, by using isopropanol, tert-butanol, 1,4-benzoquinone and ethylenediamine tetraacetic acid disodium salt as probe compounds, the main active species were demonstrated including radSO4-, radOH and radO2- in the system, and a detail photocatalytic mechanism for the Vis/BiVO4/PMS system was proposed. Finally, up to 10 intermediate products of RhB were identified by GC/MS, included benzenoid organic compounds, organic acids and three nitrogenous organic compounds. This study provides a feasible way to degrade organic pollutants in wastewater using BiVO4 with PMS under visible light.

  17. [BiOBr promoted the photocatalytic degradation of beta-cypermethrin under visible light].

    PubMed

    Peng, Yi-Zhu; Zhao, Xiao-Rong; Jia, Man-Ke; Zhou, Wei; Huang, Ying-Ping

    2014-05-01

    As a visible light photocatalyst, bismuth oxide bromide (BiOBr) was used to catalyze the degradation of beta-cypermethrin (beta-CP). The photocatalytic degradation of beta-CP was studied with gas chromatography. The effects of pH and catalyst dose on the photocatalytic degradation efficiency were discussed. The oxidization and mineralization of beta-CP were detected by chemical oxygen demand (COD) analyzer. The results showed that beta-CP could be effectively degraded under visible light irradiation using BiOBr as the catalyst. At given experimental conditions, the degradation rate of beta-CP reached 94. 68% after 10 h and the COD removal rate reached 67. 99% after 36 h. With the increase of catalyst dose and pH value, the degradation rate was improved. The photocatalytic oxidation species was determined by peroxidase method and terephthalic acid fluorescence method. These results suggested that the photocatalytic degradation process mainly referred to hydroxyl radical ( OH) mechanism. PMID:25055669

  18. Superior visible light hydrogen evolution of Janus bilayer junctions via atomic-level charge flow steering

    PubMed Central

    Li, Jie; Zhan, Guangming; Yu, Ying; Zhang, Lizhi

    2016-01-01

    Although photocatalytic hydrogen evolution (PHE) is ideal for solar-to-fuel conversion, it remains challenging to construct a highly efficient PHE system by steering the charge flow in a precise manner. Here we tackle this challenge by assembling 1T MoS2 monolayers selectively and chemically onto (Bi12O17) end-faces of Bi12O17Cl2 monolayers to craft two-dimensional (2D) Janus (Cl2)-(Bi12O17)-(MoS2) bilayer junctions, a new 2D motif different from van der Waals heterostructure. Electrons and holes from visible light-irradiated Bi12O17Cl2 are directionally separated by the internal electric field to (Bi12O17) and (Cl2) end-faces, respectively. The separated electrons can further migrate to MoS2 via Bi–S bonds formed between (Bi12O17) and MoS2 monolayers. This atomic-level directional charge separation endows the Janus bilayers with ultralong carrier lifetime of 3,446 ns and hence a superior visible-light PHE rate of 33 mmol h−1 g−1. Our delineated Janus bilayer junctions on the basis of the oriented assembly of monolayers presents a new design concept to effectively steer the charge flow for PHE. PMID:27157679

  19. Visible light induced H2PO(4)(-) removal over CuAlO2 catalyst.

    PubMed

    Benreguia, N; Omeiri, S; Bellal, B; Trari, M

    2011-09-15

    The delafossite CuAlO(2) is successfully used for the visible light driven H(2)PO(4)(-) reduction. It is prepared from the nitrates decomposition in order to increase the ratio of reaction surface per given mass. CuAlO(2) is a narrow band gap semiconductor which exhibits a good chemical stability with a corrosion rate of 1.70 μmol year(-1) at neutral pH. The flat band potential (+0.25 V(SCE)) is determined from the Mott-Schottky characteristic. Hence, the conduction band, positioned at (-1.19 V(SCE)), lies below the H(2)PO(4)(-) level yielding a spontaneous reduction under visible illumination. The photocatalytic process is investigated under mild conditions and 30% conversion occurs in less than ~6h with a quantum efficiency of 0.04% under full light. The concentration decreases by a factor of 39% after a second cycle. The photoactivity follows a first order kinetic with a rate constant of 6.6 × 10(-2)h(-1). The possibility of identifying the reaction products via the intensity-potential characteristics is explored. The decrease of the conversion rate over illumination time is due to the competitive water reduction. PMID:21782331

  20. Superior visible light hydrogen evolution of Janus bilayer junctions via atomic-level charge flow steering

    NASA Astrophysics Data System (ADS)

    Li, Jie; Zhan, Guangming; Yu, Ying; Zhang, Lizhi

    2016-05-01

    Although photocatalytic hydrogen evolution (PHE) is ideal for solar-to-fuel conversion, it remains challenging to construct a highly efficient PHE system by steering the charge flow in a precise manner. Here we tackle this challenge by assembling 1T MoS2 monolayers selectively and chemically onto (Bi12O17) end-faces of Bi12O17Cl2 monolayers to craft two-dimensional (2D) Janus (Cl2)-(Bi12O17)-(MoS2) bilayer junctions, a new 2D motif different from van der Waals heterostructure. Electrons and holes from visible light-irradiated Bi12O17Cl2 are directionally separated by the internal electric field to (Bi12O17) and (Cl2) end-faces, respectively. The separated electrons can further migrate to MoS2 via Bi-S bonds formed between (Bi12O17) and MoS2 monolayers. This atomic-level directional charge separation endows the Janus bilayers with ultralong carrier lifetime of 3,446 ns and hence a superior visible-light PHE rate of 33 mmol h-1 g-1. Our delineated Janus bilayer junctions on the basis of the oriented assembly of monolayers presents a new design concept to effectively steer the charge flow for PHE.

  1. Photosensitized reduction of DDT using visible light: the intermediates and pathways of dechlorination.

    PubMed

    Lin, Chitsan; Chang, Tien-Chin

    2007-01-01

    A reaction mixture containing DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane), methylene green (as the photosensitizer), and triethylamine (as the electron donor) in acetonitrile:water (1:1) was irradiated by an ordinary 150-W GE-Miser spotlight to facilitate visible-light photosensitized DDT dehalogenation. The intermediates and reaction products were identified by GC/MS (gas chromatography/mass spectrometer) and NMR (nuclear magnetic resonance). The photosensitized dehalogenation method partially degraded DDT via an electron transfer relay mechanism. Results indicate that DDT lost about three chlorines after a total of 19 days of irradiation. Aliphatic chlorines were found to be removed easier than aromatic chlorines. Various types of reductants were compared for electron donation efficiency, and photosensitizer concentration was optimized for our reaction system. In most cases, clean and simple dechlorinated products were observed. The proposed photosensitized reduction was coexisted with a thermal elimination effect for the first chlorine removal of DDT, and the photosensitized electron transfer reduction was shown to be the dominating mechanism responsible for further dechlorination after the initial stage. A sequential dechlorination pathway was proposed, with each successive dehalogenation, the reaction proceeds more slowly. The results have shown the feasibility of utilizing visible light, nontoxic dyes and electron donors to render a toxic compound less toxic and to enhance the natural carbon regeneration rates. PMID:16949127

  2. Decoration of BiOI quantum size nanoparticles with reduced graphene oxide in enhanced visible-light-driven photocatalytic studies

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    Herein, a reverse microemulsion route was developed to synthesize bismuth oxyiodide (BiOI) nanocrystals and reduced graphene oxide (RGO) nanocomposites as a highly efficient photocatalyst, and both the formation of BiOI and the reduction of RGO were achieved in situ in microemulsions simultaneously at low temperature (60 °C). The uniform nanocrystal size and structure were indicated by XRD, TEM, and the reduction of GO by ascorbic acid was evidenced by FTIR, XPS, and Raman spectra techniques. The enhanced photoactivity of RGO/BiOI nanocomposites under visible light was attributed to improved light absorption and efficient charge separation and transportation.

  3. Reduction of Cr(VI) to Cr(III) using silicon nanowire arrays under visible light irradiation.

    PubMed

    Fellahi, Ouarda; Barras, Alexandre; Pan, Guo-Hui; Coffinier, Yannick; Hadjersi, Toufik; Maamache, Mustapha; Szunerits, Sabine; Boukherroub, Rabah

    2016-03-01

    We report an efficient visible light-induced reduction of hexavalent chromium Cr(VI) to trivalent Cr(III) by direct illumination of an aqueous solution of potassium dichromate (K2Cr2O7) in the presence of hydrogenated silicon nanowires (H-SiNWs) or silicon nanowires decorated with copper nanoparticles (Cu NPs-SiNWs) as photocatalyst. The SiNW arrays investigated in this study were prepared by chemical etching of crystalline silicon in HF/AgNO3 aqueous solution. The Cu NPs were deposited on SiNW arrays via electroless deposition technique. Visible light irradiation of an aqueous solution of K2Cr2O7 (10(-4)M) in presence of H-SiNWs showed that these substrates were not efficient for Cr(VI) reduction. The reduction efficiency achieved was less than 10% after 120 min irradiation at λ>420 nm. Addition of organic acids such as citric or adipic acid in the solution accelerated Cr(VI) reduction in a concentration-dependent manner. Interestingly, Cu NPs-SiNWs was found to be a very efficient interface for the reduction of Cr(VI) to Cr(III) in absence of organic acids. Almost a full reduction of Cr(VI) was achieved by direct visible light irradiation for 140 min using this photocatalyst. PMID:26610097

  4. Sustainable Strategy Utilizing Biomass: Visible-Light-Mediated Synthesis of γ-Valerolactone

    EPA Science Inventory

    A novel sustainable approach to valued γ-valerolactone is described that exploits visible light mediated conversion of biomass-derived levulinic acid using a bimetallic catalyst on graphitic carbon nitride, AgPd@g-C3N4.

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

    DOEpatents

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

    2015-03-24

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

  6. Phase-dependent photocatalytic H2 evolution of copper zinc tin sulfide under visible light.

    PubMed

    Chang, Zhi-Xian; Zhou, Wen-Hui; Kou, Dong-Xing; Zhou, Zheng-Ji; Wu, Si-Xin

    2014-10-28

    CZTS exhibited apparently phase-dependent photocatalytic H2 evolution under visible light. Possible factors for the phase-dependent photocatalytic activity of CZTS were discussed in detail. PMID:25205452

  7. Origin of photoactivity of oxygen-deficient TiO{sub 2} under visible light

    SciTech Connect

    Lo, H.-H.; Gopal, Neeruganti O.; Ke, S.-C.

    2009-08-24

    As it is now well established that oxygen vacancies are spontaneously introduced during nitrogen doping of anatase TiO{sub 2}, there is a lively debate on whether nitrogen dopant or oxygen vacancy contributes to the visible light photoactivity of the doped catalyst. We showed that the coordinately unsaturated Ti site is integral to the visible light photoactivity in anatase oxygen-deficient TiO{sub 2} catalyst. Accordingly, oxygen vacancies may contribute to the visible light photoactivities in N-doped TiO{sub 2} and other nonmetallic ion-doped TiO{sub 2} as well. A redox active visible light photocatalyst has been developed based on oxygen-deficient structure in anatase TiO{sub 2}.

  8. Fabrication of anion exchanger resin/nano-CdS composite photocatalyst for visible light RhB degradation

    NASA Astrophysics Data System (ADS)

    Xie, Yingmei; Lv, Lu; Zhang, Shujuan; Pan, Bingcai; Wang, Xiaoshu; Chen, Qun; Zhang, Weiming; Zhang, Quanxing

    2011-07-01

    A novel nanocomposite photocatalyst, D201-CdS beads (0.70-0.80 mm in diameter), was fabricated for visible light (λ > 420 nm) photodegradation of Rhodamine B (RhB). Sphalerite CdS nanoparticles (5-15 nm) were distributed within the outer layer of D201 for favorable visible light permeation. Ultraviolet-visible spectral changes of RhB solution indicated that efficient RhB photodegradation was achieved by D201-CdS under visible light irradiation. More attractively, negligible photocorrosion of the hybrid catalyst D201-CdS was demonstrated by the constant photodegradation efficiency and negligible CdS leaching during five-cycle batch runs. Besides the higher stability, D201-CdS is superior to CdS in terms of separation. The used nanocomposite can be readily separated from solutions by a simple filtration while a high speed centrifugation is needed for the separation of CdS. The above results suggested that the resultant D201-CdS nanocomposite catalyst is promising for practical application in environmental remediation.

  9. Enhancement of visible-light-driven photoresponse of Mn/ZnO system: photogenerated charge transfer properties and photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Lu, Yongchun; Lin, Yanhong; Xie, Tengfeng; Shi, Shoulei; Fan, Haimei; Wang, Dejun

    2012-09-01

    A visible-light-active ZnO photocatalyst system in the presence of manganese ions (Mn/ZnO) was prepared via a simple and rapid approach. XRD, XPS, Raman scattering and UV-Vis DRS confirmed the manganese exists in multivalent forms (Mn3+/Mn2+) in the ZnO lattice, furthermore, ZnO light absorption is extended to the visible region. The photocatalytic activities of the catalysts were evaluated by measuring the photodegrading efficiency of 2,4-dichlorophenol (DCP) under visible light irradiation. With an optimal molar ratio of 5% in Mn/ZnO the highest rate photodegradation was achieved under the experimental conditions. We have characterized the separation and transfer behavior of the photogenerated charges in the visible region by means of surface photovoltage (SPV), surface photocurrent (SPC) and transient photovoltage (TPV) techniques. Based on the comprehensive investigation of the photovoltaic properties of Mn/ZnO photocatalyst, we illustrate the behavior of photogenerated charges have distinct effects on the photocatalytic activity. It is demonstrated that the incorporation of multivalent Mn in ZnO promoted the separation of photogenerated charges, inhibited the recombination of photogenerated carriers, and thus prolonged the charges lifetime to participate in the photocatalytic reaction, resulting in highly efficient photocatalytic activity, which is attributed to the formation of a strong electronic interaction between the multivalent Mn and ZnO.

  10. Enhancement of visible-light-driven photoresponse of Mn/ZnO system: photogenerated charge transfer properties and photocatalytic activity.

    PubMed

    Lu, Yongchun; Lin, Yanhong; Xie, Tengfeng; Shi, Shoulei; Fan, Haimei; Wang, Dejun

    2012-10-21

    A visible-light-active ZnO photocatalyst system in the presence of manganese ions (Mn/ZnO) was prepared via a simple and rapid approach. XRD, XPS, Raman scattering and UV-Vis DRS confirmed the manganese exists in multivalent forms (Mn(3+)/Mn(2+)) in the ZnO lattice, furthermore, ZnO light absorption is extended to the visible region. The photocatalytic activities of the catalysts were evaluated by measuring the photodegrading efficiency of 2,4-dichlorophenol (DCP) under visible light irradiation. With an optimal molar ratio of 5% in Mn/ZnO the highest rate photodegradation was achieved under the experimental conditions. We have characterized the separation and transfer behavior of the photogenerated charges in the visible region by means of surface photovoltage (SPV), surface photocurrent (SPC) and transient photovoltage (TPV) techniques. Based on the comprehensive investigation of the photovoltaic properties of Mn/ZnO photocatalyst, we illustrate the behavior of photogenerated charges have distinct effects on the photocatalytic activity. It is demonstrated that the incorporation of multivalent Mn in ZnO promoted the separation of photogenerated charges, inhibited the recombination of photogenerated carriers, and thus prolonged the charges lifetime to participate in the photocatalytic reaction, resulting in highly efficient photocatalytic activity, which is attributed to the formation of a strong electronic interaction between the multivalent Mn and ZnO. PMID:22951578

  11. Photo-oxidation of polymer-like amorphous hydrogenated carbon under visible light illumination

    SciTech Connect

    Baxamusa, Salmaan; Laurence, Ted; Worthington, Matthew; Ehrmann, Paul

    2015-11-10

    Amorphous hydrogenated carbon (a-C:H), a polymer-like network typically synthesized by plasma chemical vapor deposition, has long been understood to exhibit optical absorption of visible light (λ > 400 nm). In this report we explain that this absorption is accompanied by rapid photo-oxidation (within minutes) that behaves in most respects like classic polymer photo-oxidation with the exception that it occurs under visible light illumination rather than ultraviolet illumination.

  12. Catalyst free visible light induced cycloaddition as an avenue for polymer ligation.

    PubMed

    Lederhose, Paul; Wüst, Kilian N R; Barner-Kowollik, Christopher; Blinco, James P

    2016-05-21

    The current study introduces a tetrazole species able to perform a rapid, visible light induced nitrile imine-mediated tetrazole-ene cycloaddition (NITEC). Full conversion of the tetrazole species under mild, catalyst free conditions is reported. Importantly, the visible light ligation technology is applied as a method for the modification and ligation of polymers featuring the rapid, clean and exclusive formation of the desired cycloadduct. PMID:27004740

  13. Scalable Synthesis of Piperazines Enabled by Visible-Light Irradiation and Aluminum Organometallics

    PubMed Central

    Suárez-Pantiga, Samuel; Colas, Kilian; Johansson, Magnus J; Mendoza, Abraham

    2015-01-01

    The development of more active C–H oxidation catalysts has inspired a rapid, scalable, and stereoselective assembly of multifunctional piperazines through a [3+3] coupling of azomethine ylides. A combination of visible-light irradiation and aluminum organometallics is essential to promote this transformation, which introduces visible-light photochemistry of main-group organometallics and sets the basis for new and promising catalysts. PMID:26337253

  14. Towards efficient photoinduced charge separation in carbon nanodots and TiO2 composites in the visible region.

    PubMed

    Sun, Mingye; Qu, Songnan; Ji, Wenyu; Jing, Pengtao; Li, Di; Qin, Li; Cao, Junsheng; Zhang, Hong; Zhao, Jialong; Shen, Dezhen

    2015-03-28

    In this work, photoinduced charge separation behaviors in non-long-chain-molecule-functionalized carbon nanodots (CDs) with visible intrinsic absorption (CDs-V) and TiO2 composites were investigated. Efficient photoinduced electron injection from CDs-V to TiO2 with a rate of 8.8 × 10(8) s(-1) and efficiency of 91% was achieved in the CDs-V/TiO2 composites. The CDs-V/TiO2 composites exhibited excellent photocatalytic activity under visible light irradiation, superior to pure TiO2 and the CDs with the main absorption band in the ultraviolet region and TiO2 composites, which indicated that visible photoinduced electrons and holes in such CDs-V/TiO2 composites could be effectively separated. The incident photon-to-current conversion efficiency (IPCE) results for the CD-sensitized TiO2 solar cells also agreed with efficient photoinduced charge separation between CDs-V and the TiO2 electrode in the visible range. These results demonstrate that non-long-chain-molecule-functionlized CDs with a visible intrinsic absorption band could be appropriate candidates for photosensitizers and offer a new possibility for the development of a well performing CD-based photovoltaic system. PMID:25721932

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

    NASA Astrophysics Data System (ADS)

    Kaewgun, Sujaree

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

  16. Enhanced visibility of ghost imaging and interference using squeezed thermal light

    NASA Astrophysics Data System (ADS)

    Liu, Ruifeng; Fang, Aiping; Zhou, Yu; Zhang, Pei; Gao, Shaoyan; Li, Hongrong; Gao, Hong; Li, Fuli

    2016-01-01

    Ghost imaging and interference using squeezed thermal light are investigated. We show that squeezed thermal light can have a very strong photon-bunching effect in the region of very weak squeezing and thermal excitation. As a result, the visibility of the image and interference pattern can be greatly enhanced and raised to be much higher than the limitation 1 /3 to thermal light. In the squeezed vacuum case, especially, the visibility can approach to the level of entangled photon pairs from spontaneous parametric down-conversion. The present investigation may open a new potential application of squeezed light.

  17. Particulates vs. fibers: dimension featured magnetic and visible light driven photocatalytic properties of Sc modified multiferroic bismuth ferrite nanostructures.

    PubMed

    Sakar, M; Balakumar, S; Saravanan, P; Bharathkumar, S

    2016-01-14

    We report the magnetic and visible light driven photocatalytic properties of scandium (Sc) substituted bismuth ferrite (BSFO) particulate and fiber nanostructures. An increasing concentration of Sc was found to reduce the crystallite size, particle size and band gap energy of the BSFO nanostructures, which was evident from X-ray diffraction, field emission scanning electron microscopy and UV-Visible diffuse reflectance spectroscopy analysis respectively. The temperature dependent magnetic studies carried out using a SQUID magnetometer suggested that the origin of the magnetic properties in the pure BFO system could be the emergence of an antiferromagnetic-core/ferromagnetic-shell like structure, in contrast to the modified spin canted structures in the case of the BSFO nanostructures. The observed photocatalytic efficiency was attributed to the enhanced band bending process and recombination resistance in the BSFO nanostructures. For a comparative study, the photocatalytic activities of some selected compositions were also investigated under simulated solar light along with natural solar light. PMID:26667276

  18. Low light comparison of target visibility with night vision goggles

    NASA Astrophysics Data System (ADS)

    Craig, Gregory; Brulotte, Michel; Carignan, Stephan; Macuda, Todd; Jennings, Sion

    2008-04-01

    Different night vision goggle image intensification technologies were tested to compare goggle performance in low light conditions. A total of four different night vision goggles were tested in a laboratory dark room. The laboratory tests consisted of viewing Landolt acuity stimuli of different contrast levels with each set of goggles and without the goggles in full light conditions (baseline performance). The results from the laboratory testing indicated that there were significant differences in acuity between the NVGs, particularly for low contrast targets. These data suggest that NVG standards developed using high contrast targets, even in low light conditions may not provide the full story of how the NVG will perform in flight.

  19. Space-based visible all-reflective stray light telescope

    NASA Astrophysics Data System (ADS)

    Wang, Dexter; Gardner, Leo R.; Wong, Wallace K.; Hadfield, Peter

    1991-08-01

    A 6-inch diameter aperture space-based visible telescope has been optimized to perform surveillance against the space background with earth albedo as a primary source of straylight. A three mirror off-axis anastigmat has been designed to cover a 1.4 degree(s) by 6.6 degree(s) field- of-view with 60 (mu) radian spatial resolution. The telescope body and optics are constructed of 6061-T6 aluminum to provide a thermally stable optical system. The optical elements are 'superfinished' to minimize scatter. Extensive baffles and stops are utilized to further reduce straylight. The telescope will be used on the Midcourse Space Experiment platform.

  20. Visible Light-Induced Photoredox Construction of Trifluoromethylated Quaternary Carbon Centers from Trifluoromethylated Tertiary Bromides.

    PubMed

    Huan, Feng; Chen, Qing-Yun; Guo, Yong

    2016-08-19

    A mild, operationally simple, visible light-induced photoredox method for constructing novel trifluoromethylated quaternary carbon centers from trifluoromethylated tertiary bromides has been developed. Using this method, a wide range of alkenes were successfully bifunctionalized to γ-butyrolactams. As for electron-rich alkenes, reactions catalyzed by Ir(dF(CF3)ppy)2(dtbbpy)(PF6) were kinetic processes with high yields and short times. For styrenes, reactions catalyzed by Ir(ppy)2(dtbbpy)(PF6) were thermodynamic processes with moderate yields and prolonged reaction times. For aliphatic alkenes, the reactions were neither thermodynamic nor kinetic and fac-Ir(ppy)3 was used as catalyst. Thus, reactions were not as efficient as electron-rich alkenes. The atom-transfer radical addition reactions of trifluoromethylated tertiary bromides with alkynes were also achieved. The configuration of products we separated was E type only. Some of the products exhibited bactericidal activity. PMID:27438228

  1. Metal Complexes Supported on Solid Matrices for Visible-Light-Driven Molecular Transformations.

    PubMed

    Mori, Kohsuke; Yamashita, Hiromi

    2016-08-01

    Hybridization of visible-light-responsive metal complexes with solid matrices offers an attractive route for practical catalyst design of nanostructured photocatalysts that are operationally simple and can attain unprecedented reactions owing to synergistic effects. This Minireview highlights the precise architectures of hybrid photocatalysts that enable efficient and selective photochemical molecular transformations, including selective oxidation by O2 and H2 evolution from water. Several techniques for the immobilization of metal complexes are discussed, including encapsulation within zeolite cavities, anchoring within mesoporous channels, incorporation within the macroreticular space of ion-exchange resins, intercalation within the interlayer spaces of layered materials, and anchoring onto the plasmonic colloidal Ag nanoparticles. The relationships between photoluminescence characteristics and photocatalytic activities of these hybrid materials are also discussed. PMID:27314619

  2. An ultrathin invisibility skin cloak for visible light.

    PubMed

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

    2015-09-18

    Metamaterial-based optical cloaks have thus far used volumetric distribution of the material properties to gradually bend light and thereby obscure the cloaked region. Hence, they are bulky and hard to scale up and, more critically, typical carpet cloaks introduce unnecessary phase shifts in the reflected light, making the cloaks detectable. Here, we demonstrate experimentally an ultrathin invisibility skin cloak wrapped over an object. This skin cloak conceals a three-dimensional arbitrarily shaped object by complete restoration of the phase of the reflected light at 730-nanometer wavelength. The skin cloak comprises a metasurface with distributed phase shifts rerouting light and rendering the object invisible. In contrast to bulky cloaks with volumetric index variation, our device is only 80 nanometer (about one-ninth of the wavelength) thick and potentially scalable for hiding macroscopic objects. PMID:26383946

  3. An ultrathin invisibility skin cloak for visible light

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  4. An ultrathin invisibility skin cloak for visible light

    NASA Astrophysics Data System (ADS)

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

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

  5. Consecutive visible-light photoredox decarboxylative couplings of adipic acid active esters with alkynyl sulfones leading to cyclic compounds.

    PubMed

    Li, Jingjing; Tian, Hua; Jiang, Min; Yang, Haijun; Zhao, Yufen; Fu, Hua

    2016-07-01

    Novel and efficient consecutive photoredox decarboxylative couplings of adipic acid active esters (bis(1,3-dioxoisoindolin-2-yl)-substituted hexanedioates) with substituted 1-(2-arylethynylsulfonyl)benzenes have been developed under visible-light photocatalysis. The successive photoredox decarboxylative C-C bond formation at room temperature afforded the corresponding cyclic compounds in good yields with tolerance of some functional groups. PMID:27345832

  6. Visible-light-promoted iminyl radical formation from vinyl azides: synthesis of 6-(fluoro)alkylated phenanthridines.

    PubMed

    Sun, Xiaoyang; Yu, Shouyun

    2016-09-18

    An efficient strategy assisted by visible-light-promoted iminyl radical formation has been developed for the synthesis of 6-(fluoro)alkylated phenanthridine derivatives. In the reactions, addition of alkyl and trifluoromethyl radicals onto vinyl azides gives iminyl radicals, which then undergo intramolecular homolytic aromatic substitution leading to phenanthridines. These reactions can be carried out under mild conditions with high chemical yields and broad substrate scope. PMID:27530901

  7. Heterogeneous Decomposition of Volatile Organic Compounds by Visible-Light Activated N, C, S-Embedded Titania.

    PubMed

    Chun, Ho-Hwan; Jo, Wan-Kuen

    2016-05-01

    In this study, a N-, C-, and S-doped titania (NCS-TiO2) composite was prepared by combining the titanium precursor with a single dopant source, and the photocatalytic activity of this system for the decomposition of volatile organic compounds (VOCs) at indoor-concentration levels, under exposure to visible light, was examined. The NCS-TiO2 composite and the pure TiO2 photocatalyst, used as a reference, were characterized via X-ray diffraction, scanning electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The average efficiencies of benzene, toluene, ethyl benzene, and o-xylene decomposition using NCS-TiO2 for were 70, 87, -100, and -100%, respectively, whereas the values obtained using the pure TiO2 powder were -0, 18, 49, and 51%, respectively. These results suggested that, for the photocatalytic decomposition of toxic VOCs under visible-light exposure conditions, NCS-TiO2 was superior to the reference photocatalyst. The decomposition efficiencies of the target VOCs were inversely related to the initial concentration and relative humidity as well as to the air-flow rate. The decomposition efficiencies of the target chemicals achieved with a conventional lamp/NCS-TiO2 system were higher than those achieved with a light emitting diode/NCS-TiO2 system. Overall, NCS-TiO2 can be used for the efficient decomposition of VOCs under visible-light exposure, if the operational conditions are optimized. PMID:27483788

  8. Particulates vs. fibers: dimension featured magnetic and visible light driven photocatalytic properties of Sc modified multiferroic bismuth ferrite nanostructures

    NASA Astrophysics Data System (ADS)

    Sakar, M.; Balakumar, S.; Saravanan, P.; Bharathkumar, S.

    2015-12-01

    We report the magnetic and visible light driven photocatalytic properties of scandium (Sc) substituted bismuth ferrite (BSFO) particulate and fiber nanostructures. An increasing concentration of Sc was found to reduce the crystallite size, particle size and band gap energy of the BSFO nanostructures, which was evident from X-ray diffraction, field emission scanning electron microscopy and UV-Visible diffuse reflectance spectroscopy analysis respectively. The temperature dependent magnetic studies carried out using a SQUID magnetometer suggested that the origin of the magnetic properties in the pure BFO system could be the emergence of an antiferromagnetic-core/ferromagnetic-shell like structure, in contrast to the modified spin canted structures in the case of the BSFO nanostructures. The observed photocatalytic efficiency was attributed to the enhanced band bending process and recombination resistance in the BSFO nanostructures. For a comparative study, the photocatalytic activities of some selected compositions were also investigated under simulated solar light along with natural solar light.We report the magnetic and visible light driven photocatalytic properties of scandium (Sc) substituted bismuth ferrite (BSFO) particulate and fiber nanostructures. An increasing concentration of Sc was found to reduce the crystallite size, particle size and band gap energy of the BSFO nanostructures, which was evident from X-ray diffraction, field emission scanning electron microscopy and UV-Visible diffuse reflectance spectroscopy analysis respectively. The temperature dependent magnetic studies carried out using a SQUID magnetometer suggested that the origin of the magnetic properties in the pure BFO system could be the emergence of an antiferromagnetic-core/ferromagnetic-shell like structure, in contrast to the modified spin canted structures in the case of the BSFO nanostructures. The observed photocatalytic efficiency was attributed to the enhanced band bending process

  9. Visible light emitting vertical cavity surface emitting lasers

    DOEpatents

    Bryan, R.P.; Olbright, G.R.; Lott, J.A.; Schneider, R.P. Jr.

    1995-06-27

    A vertical cavity surface emitting laser that emits visible radiation is built upon a substrate, then having mirrors, the first mirror on top of the substrate; both sets of mirrors being a distributed Bragg reflector of either dielectrics or other materials which affect the resistivity or of semiconductors, such that the structure within the mirror comprises a plurality of sets, each having a thickness of {lambda}/2n where n is the index of refraction of each of the sets; each of the mirrors adjacent to spacers which are on either side of an optically active bulk or quantum well layer; and the spacers and the optically active layer are from one of the following material systems: In{sub z}(Al{sub y}Ga{sub 1{minus}y}){sub 1{minus}z}P, InAlGaAs, AlGaAs, InGaAs, or AlGaP/GaP, wherein the optically active region having a length equal to m {lambda}/2n{sub eff} where m is an integer and n{sub eff} is the effective index of refraction of the laser cavity, and the spacer layer and one of the mirrors being transmissive to radiation having a wavelength of {lambda}/n, typically within the green to red portion of the visible spectrum. 10 figs.

  10. Visible light emitting vertical cavity surface emitting lasers

    DOEpatents

    Bryan, Robert P.; Olbright, Gregory R.; Lott, James A.; Schneider, Jr., Richard P.

    1995-01-01

    A vertical cavity surface emitting laser that emits visible radiation is built upon a substrate, then having mirrors, the first mirror on top of the substrate; both sets of mirrors being a distributed Bragg reflector of either dielectrics or other materials which affect the resistivity or of semiconductors, such that the structure within the mirror comprises a plurality of sets, each having a thickness of .lambda./2n where n is the index of refraction of each of the sets; each of the mirrors adjacent to spacers which are on either side of an optically active bulk or quantum well layer; and the spacers and the optically active layer are from one of the following material systems: In.sub.z (Al.sub.y Ga.sub.1-y).sub.1-z P, InAlGaAs, AlGaAs, InGaAs, or AlGaP/GaP, wherein the optically active region having a length equal to m .lambda./2n.sub.eff where m is an integer and n.sub.eff is the effective index of refraction of the laser cavity, and the spacer layer and one of the mirrors being transmissive to radiation having a wavelength of .lambda./n, typically within the green to red portion of the visible spectrum.

  11. Environmentally benign technology for efficient warm-white light emission.

    PubMed

    Shen, Pin-Chun; Lin, Ming-Shiun; Lin, Ching-Fuh

    2014-01-01

    Nowadays efficient down conversion for white light emission is mainly based on rare-earth doped phosphors or cadmium-containing quantum dots. Although they exhibit high luminescence efficiency, the rare-earth mining and cadmium pollution have so far led to extremely high environmental cost, which conflicts the original purpose of pursuing efficient lighting. Here, we explore a new strategy to achieve efficient luminescence conversion based on polymer-decorated nanoparticles. The ZnO and Mn(2+) doped ZnS nanoparticles are encapsulated by poly(9,9-di-n- hexylfluorenyl-2,7-diyl). The resultant core-shell nanocomposites then encompass three UV-to-visible luminescence conversion routes for photon emissions at blue, green, and orange colors, respectively. As a result, the color temperature is widely tunable (2100 K ~ 6000 K), so candle light or pure white light can be generated. The quantum yield up to 91% could also be achieved. Such rare-earth-element free nanocomposites give the bright perspectives for energy-saving, healthy, and environmentally benign lighting. PMID:24930640

  12. Environmentally Benign Technology for Efficient Warm-White Light Emission

    NASA Astrophysics Data System (ADS)

    Shen, Pin-Chun; Lin, Ming-Shiun; Lin, Ching-Fuh

    2014-06-01

    Nowadays efficient down conversion for white light emission is mainly based on rare-earth doped phosphors or cadmium-containing quantum dots. Although they exhibit high luminescence efficiency, the rare-earth mining and cadmium pollution have so far led to extremely high environmental cost, which conflicts the original purpose of pursuing efficient lighting. Here, we explore a new strategy to achieve efficient luminescence conversion based on polymer-decorated nanoparticles. The ZnO and Mn2+ doped ZnS nanoparticles are encapsulated by poly(9,9-di-n- hexylfluorenyl-2,7-diyl). The resultant core-shell nanocomposites then encompass three UV-to-visible luminescence conversion routes for photon emissions at blue, green, and orange colors, respectively. As a result, the color temperature is widely tunable (2100 K ~ 6000 K), so candle light or pure white light can be generated. The quantum yield up to 91% could also be achieved. Such rare-earth-element free nanocomposites give the bright perspectives for energy-saving, healthy, and environmentally benign lighting.

  13. Band engineering of ZnS by codoping for visible-light photocatalysis

    NASA Astrophysics Data System (ADS)

    Wan, Hui; Xu, Liang; Huang, Wei-Qing; Huang, Gui-Fang; He, Chao-Ni; Zhou, Jia-Hui; Peng, P.

    2014-08-01

    Codoping is demonstrated as an efficient approach to narrow the band gap of ZnS and enhance its photocatalytic activity. Herein, we perform the density-function theory calculations of ZnS by codoping of X (N, F) with transition metals (TM = V, Cu). The band gap is reduced in four different types of codoped ZnS. In particular, CuZnFS codoping, a charge-compensated donor-acceptor pair, leads to an about 32 % reduction of the energy gap, thus extending the absorption edge to visible-light region. The band gap reduction is due to the upshift of the top valence band comprised with the delocalized hybridizing levels of Cu 3d and S 3p states, and the downshift of the bottom conduction band consisting of F 2s states. Moreover, the larger value of m e*/ m h* in CuZnFS-ZnS would result in a lower recombination rate of the electron-hole pairs. Both band gap reduction and low recombination rate are critical elements for efficient light-to-current conversion in codoped ZnS. These findings raise the prospect of using codoped ZnS with specifically engineered electronic properties in a variety of photocatalytic applications.

  14. Efficient Visible-Light-Driven Z-Scheme Overall Water Splitting Using a MgTa2O(6-x)N(y)/TaON Heterostructure Photocatalyst for H2 Evolution.

    PubMed

    Chen, Shanshan; Qi, Yu; Hisatomi, Takashi; Ding, Qian; Asai, Tomohiro; Li, Zheng; Ma, Su Su Khine; Zhang, Fuxiang; Domen, Kazunari; Li, Can

    2015-07-13

    An (oxy)nitride-based heterostructure for powdered Z-scheme overall water splitting is presented. Compared with the single MgTa2O(6-x)N(y) or TaON photocatalyst, a MgTa2O(6-x)N(y)/TaON heterostructure fabricated by a simple one-pot nitridation route was demonstrated to effectively suppress the recombination of carriers by efficient spatial charge separation and decreased defect density. By employing Pt-loaded MgTa2O(6-x)N(y)/TaON as a H2-evolving photocatalyst, a Z-scheme overall water splitting system with an apparent quantum efficiency (AQE) of 6.8% at 420 nm was constructed (PtO(x)-WO3 and IO3(-)/I(-) pairs were used as an O2-evolving photocatalyst and a redox mediator, respectively), the activity of which is circa 7 or 360 times of that using Pt-TaON or Pt-MgTa2O(6-x)N)y) as a H2-evolving photocatalyst, respectively. To the best of our knowledge, this is the highest AQE among the powdered Z-scheme overall water splitting systems ever reported. PMID:26037473

  15. Mitigation technique for receiver performance variation of multi-color channels in visible light communication.

    PubMed

    Uddin, Muhammad Shahin; Cha, Jae Sang; Kim, Jin Young; Jang, Yeong Min

    2011-01-01

    "Green" and energy-efficient wireless communication schemes have recently experienced rapid development and garnered much interest. One such scheme is visible light communication (VLC) which is being touted as one of the next generation wireless communication systems. VLC allows communication using multi-color channels that provide high data rates and illumination simultaneously. Even though VLC has many advantageous features compared with RF technologies, including visibility, ubiquitousness, high speed, high security, harmlessness for the human body and freedom of RF interference, it suffers from some problems on the receiver side, one of them being photo sensitivity dissimilarity of the receiver. The photo sensitivity characteristics of a VLC receiver such as Si photo-detector depend on the wavelength variation. The performance of the VLC receiver is not uniform towards all channel colors, but it is desirable for receivers to have the same performance on each color channel. In this paper, we propose a mitigation technique for reducing the performance variation of the receiver on multi-color channels. We show received power, SNR, BER, output current, and outage probability in our simulation for different color channels. Simulation results show that, the proposed scheme can reduce the performance variation of the VLC receiver on multi-color channels. PMID:22163946

  16. 33 CFR 83.22 - Visibility of lights (Rule 22).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... at the following minimum ranges: (a) Vessel of 50 meters or more in length. In a vessel of 50 meters... special flashing light, 2 miles. (b) Vessels of 12 meters or more in length but less than 50 meters in length. In a vessel of 12 meters or more in length but less than 50 meters in length: (1) A...

  17. 33 CFR 83.22 - Visibility of lights (Rule 22).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... at the following minimum ranges: (a) Vessel of 50 meters or more in length. In a vessel of 50 meters... special flashing light, 2 miles. (b) Vessels of 12 meters or more in length but less than 50 meters in length. In a vessel of 12 meters or more in length but less than 50 meters in length: (1) A...

  18. 33 CFR 83.22 - Visibility of lights (Rule 22).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... at the following minimum ranges: (a) Vessel of 50 meters or more in length. In a vessel of 50 meters... special flashing light, 2 miles. (b) Vessels of 12 meters or more in length but less than 50 meters in length. In a vessel of 12 meters or more in length but less than 50 meters in length: (1) A...

  19. Optimized 2D array of thin silicon pillars for efficient antireflective coatings in the visible spectrum

    PubMed Central

    Proust, Julien; Fehrembach, Anne-Laure; Bedu, Frédéric; Ozerov, Igor; Bonod, Nicolas

    2016-01-01

    Light reflection occuring at the surface of silicon wafers is drastically diminished by etching square pillars of height 110 nm and width 140 nm separated by a 100 nm gap distance in a square lattice. The design of the nanostructure is optimized to widen the spectral tolerance of the antireflective coatings over the visible spectrum for both fundamental polarizations. Angle and polarized resolved optical measurements report a light reflection remaining under 5% when averaged in the visible spectrum for both polarizations in a wide angular range. Light reflection remains almost insensitive to the light polarization even in oblique incidence. PMID:27109643

  20. Optimized 2D array of thin silicon pillars for efficient antireflective coatings in the visible spectrum.

    PubMed

    Proust, Julien; Fehrembach, Anne-Laure; Bedu, Frédéric; Ozerov, Igor; Bonod, Nicolas

    2016-01-01

    Light reflection occuring at the surface of silicon wafers is drastically diminished by etching square pillars of height 110 nm and width 140 nm separated by a 100 nm gap distance in a square lattice. The design of the nanostructure is optimized to widen the spectral tolerance of the antireflective coatings over the visible spectrum for both fundamental polarizations. Angle and polarized resolved optical measurements report a light reflection remaining under 5% when averaged in the visible spectrum for both polarizations in a wide angular range. Light reflection remains almost insensitive to the light polarization even in oblique incidence. PMID:27109643