- Photocatalysis through Excitation of Adsorbates. 3. Effect of Electron Acceptors on the Efficiency of Interfacial Charge Separation
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Charge separation in photoexcited rhodamine B-CdS-electron acceptor systems was investigated photochemically and photoelectrochemically, by using acceptors with different standard reduction potentials (E0red.).The formal quantum efficiency (FQE) of N-deethylation of the dye after photoinduced electron injection into CdS (in photochemical suspension systems) and sensitized photocurrents flowing through a single-crystal CdS membrane separating the dye from an acceptor (in photoelectrochemical systems) were measured as a function of concentration of acceptors.Both FQE and sensitized photocurrents reflect the efficiency of charge separation between the dye and acceptors.Results indicate that charge separation occurs only in the presence of CdS and its efficiency rises as E0red. of the acceptor is more positive.The effectiveness of the present systems for photoinduced charge separation is discussed.
- Takizawa, Takuo,Watanabe, Tadashi,Honda, Kenichi
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- A comparative study on the efficacy of different probes to predict the photo-activity of nano-titanium dioxide toward biomolecules
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TiO2 is a reactive material able to cause the degradation of organic molecules following activation by UV light. This reactivity may be useful, e.g. in environmental or medical applications, but undesired when TiO2 is used as a UV filter in cosmetics and composites since it reduces the photo-stability of the material, and represents a possible pathway of injury. Conventional methods to measure the photo-activity of TiO2 include the degradation of small molecules or dyes. However the suitability of these methods to predict the photo-activity of TiO2 in biological systems is uncertain. This is the first product of a study, conducted within the FP7 EU project SETNanoMetro, that has as a main goal the standardizations of protocols to assess the oxidative potential of TiO2 nanopowders in biofluids. Here, the ability of a series of nano-TiO2 powders exhibiting different crystalline phases to degrade rhodamine B, a dye commonly used in photo-catalysis, and two model biomolecules (linoleic acid and 2-deoxyribose) under simulated sunlight was compared. Electron paramagnetic resonance (EPR) spectroscopy associated to different spin-probes or spin-traps was used to elucidate the reactive species involved in the processes. The results show how the photo-efficiency of TiO2 is affected by the kind of probe and by the presence of species that adsorb at the surface of the nanoparticles underlining the need of appropriate standard operating procedures (SOP) to evaluate the oxidative damage potential of semiconducting nanomaterials.
- Marucco,Carella,Fenoglio
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- The upconversion and enhanced visible light photocatalytic activity of Er3+-doped tetragonal BiVO4
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Er3+-doped BiVO4 with tetragonal structure is prepared by the microwave hydrothermal method. X-ray diffraction and Rietveld refinement demonstrate that the structure is transformed from the monoclinic (C2/c:c3) phase to the tetragonal (I41/amd:2) phase by doping with Er3+ ions. Er3+ doping also influences the morphology change of BiVO4 from irregular flake-like crystal to rod-like crystal, which leads to the increase of the surface areas from 3.25 to 11.96 m2 g-1. Compared with the monoclinic BiVO4, the upconversion of the Er3+-doped tetragonal BiVO4 occurs through the transitions from the 4I15/2 ground state to 4F7/2, 2H11/2, and 4F9/2 states, respectively. The photocatalytic experiment indicates that the tetragonal BiVO4 (8 at.%) with a larger specific surface area (9.88 m2 g-1) shows the best photocatalytic activity under visible light irradiation, which can efficiently improve the degradation rate of RhB up to 97.2% at 150 min. This journal is
- Yang, Wei,Tan, Guoqiang,Ren, Huijun,Zhang, Lili,Zhao, Chengcheng,Xia, Ao
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- Hierarchical BiOI nanostructures supported on a metal organic framework as efficient photocatalysts for degradation of organic pollutants in water
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Semiconductor-based photocatalysis is a green method for the removal of toxic organic pollutants by decomposition into harmless products. However, traditional single-component semiconductors are unable to reach high degradation efficiencies due to excessive photo charge carrier recombination. The use of hybrid nanocomposite photocatalysts is a promising strategy for overcoming this problem by reducing recombination as well as ensuring that large amounts of solar energy are harvested. Herein, a novel visible-light-active hybrid nanocomposite, BiOI/MIL-88B(Fe), was successfully synthesized through a simple precipitation method. In the BiOI/MIL-88B(Fe) composite, both BiOI and MIL-88B(Fe) have improved charge carrier separation and reduced recombination via a simple Z-scheme mechanism. Photocatalytic degradation of the pollutant RhB was carried out during irradiation of the as-synthesized composites with simulated solar light, and the BiOI/MIL-88B(Fe) (2 wt%) composite was found to exhibit the highest photocatalytic activity among the composites. In addition, colorless phenol and ciprofloxacin (CIP) degradation experiments were also performed to confirm the visible light photocatalytic performance of the BiOI/MIL-88B(Fe) hybrid nanocomposite. Scavenger experiments, PL analysis, NBT transformations, and TA-PL experiments all supported the proposed Z-scheme mechanism of the BiOI/MIL-88B(Fe) composite photocatalyst. Moreover, simple separation from solution provides this 3D composite with good reusability and long-term stability.
- Jahurul Islam,Kim, Hyun Kook,Amaranatha Reddy,Kim, Yujin,Ma, Rory,Baek, Heehyun,Kim, Joonghan,Kim, Tae Kyu
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- Visible light photodegradation of rhodamine B over VDF/CTFE copolymer-templated crystalline mesoporous titania
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Mesoporous TiO2 with anatase crystalline structure (MTiO 2/F2319) has been synthesized by using vinylidene fluoride/chlorotrifluoroethylene copolymer (1:9 in mole, F2319) as template. The synthesized mesoporous titania samples were characterized by a combination of various physicochemical techniques, such as X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and N2 adsorption/desorption. It was found that without any external doping, MTiO2/F2319 exhibited significantly higher photocatalytic activities for the degradation of rhodamine B (RhB) dye than P25 TiO2 under visible light irradiation. Furthermore, the UV-Vis absorption maximum of the dye solution exhibited a gradual hypsochromic shift due to de-ethylation and degradation of RhB dye. Springer Science+Business Media B.V. 2012.
- Zi, Guoli,Wang, Yi,Zheng, Kai,Zhao, Huan,Wang, Fuzhi,Zhang, Wenjun,Yan, Zhiying,He, Jiao,Wang, Jiaqiang
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- Self assembled flower like CdS-ZnO nanocomposite and its photo catalytic activity
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Self assembled flower like CdS-ZnO nanocomposite has been synthesized by a facile chemical route and the prepared materials have been investigated as catalyst in the photodegradation of rhodamine B (RhB) in aqueous solution facilitated by the effective charge transfer mechanism in this coupled semiconductor system. CdS has been grown first and then petal-like ZnO has been produced to assemble into a flower like nanostructure. XRD, SEM, TEM, EDX have been employed to study the structural, morphological and compositional details of this unique nanostructure. It is observed that a strong quenching of band-edge emission of CdS following the growth of ZnO petal on it which is evidence for the occurrence of charge transfer between CdS and ZnO. The strong photocatalytic activity of this novel nanostructure on RhB has been investigated in details.
- Jana,Pal,Chatterjee
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- New latent fluorophore for DT diaphorase
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This study describes the design and synthesis of a novel latent fluorophore 3 for DT diaphorase based on the trimethyl lock effect and characterization of its enzymatic kinetics. Fluorophore 3 is also a sensitive fluorimetric reagent for detecting glucose when coupled with DTD and glucose dehydrogenase.
- Huang, Sheng-Tung,Lin, Yuh-Ling
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- Fluorescence-Lifetime-Sensitive Probes for Monitoring ATP Cleavage
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Adenosine triphosphate (ATP) probes modified with fluorescence dyes that change their fluorescence properties upon cleavage are an interesting tool for monitoring enzymatic ATP turnover. As a readout parameter, fluorescence lifetime is attractive because it is nearly independent of concentration. In our study, we synthesised and investigated fifteen different ATP analogues, in which the fluorophores were attached to the γ-phosphate of ATP. All analogues showed distinctly different fluorescence lifetimes compared to the corresponding values of the free fluorophores. Both increases and decreases in fluorescence lifetime were observed upon attachment to ATP. To shed light on the photophysical processes governing the lifetime changes, we performed photoelectron spectroscopy in air (PESA) to determine HOMO energy levels and time-resolved fluorescence spectroscopy to obtain rate constants. We present evidence that fluorescence quenching in the compounds tested is dynamic and attributed to photoinduced electron transfer (PET), whereas fluorescence lifetime increases are caused by stacking interactions between chromophore and the nucleobase reducing non-radiative relaxation. Finally, we demonstrate that enzymatic cleavage of the ATP analogues presented can be followed by continuous monitoring of fluorescence lifetime changes.
- Hammler, Daniel,Marx, Andreas,Zumbusch, Andreas
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- A novel synthetic route for magnetically retrievable Bi2WO 6 hierarchical microspheres with enhanced visible photocatalytic performance
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We report a reliable and effective strategy to synthesize magnetically recyclable Bi2WO6 microspheres using Fe3O 4 nanoparticles as supports. The as-prepared hierarchical photocatalyst displays excellent photocatalytic activity and reusability under visible light irradiation. The Royal Society of Chemistry 2013.
- Liu, Zhi,Chen, Feitai,Gao, Yuanpeng,Liu, Yang,Fang, Pengfei,Wang, Shaojie
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- Photocatalytic application of nanosized CdS immobilized onto functionalized MWCNTs
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Nanosized semiconductor CdS immobilized onto modified multi-walled carbon nanotubes (MWCNTs) carrying poly(amidoamine) dendron units were visualized by HR-TEM. Evidently, spherical CdS nanoparticles 3-5 nm in diameter were identified. Moreover, EDX spectr
- Chronopoulos,Karousis,Zhao,Wang,Shinohara,Tagmatarchis
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- Tandem photocatalytic oxidation of Rhodamine B over surface fluorinated bismuth vanadate crystals
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BiVO4 crystals with monoclinic-phase and controllable morphologies were synthesized by NaF-mediated hydrothermal processes using Bi(NO3)3 and V2O5 as precursors. The NaF added as a structural controller not only affected the crystal evolution processes of BiVO4 crystals, but also enabled the in situ surface fluorination of the as-synthesized BiVO4 crystals. Interestingly, the photocatalytic oxidation reactions of RhB occurred in a stepwise manner over fluorinated BiVO4 photocatalyst, that is, a faster de-ethylation process (conversion of RhB into rhodamine) followed by a relatively slower mineralization process, involving the destruction of the conjugated structure in rhodamine. Surface fluorination favored the RhB adsorption and hole transfer between RhB molecules and BiVO4 photocatalyst, thus progressively enhancing the initial direct hole transfer mediated de-ethylation process. In contrast, surface fluorination exerts compromised effects on the ·O 2- mediated mineralization process, enhancing surface RhB adsorption versus retarding electron transfer from BiVO4 photocatalyst to O2 giving rise to ·O2-, and consequently, moderate surface fluorine coverage is required to balance the aforementioned conflicting effects and achieve the higher mineralization rate. The present study not only demonstrates that the photocatalytic efficiency can be modified by tuning photogenerated active species and photocatalytic reaction processes, but also provides new insights into the fluorination effects on the semiconductor photocatalysis.
- Liu, Shengwei,Yin, Kai,Ren, Wanshu,Cheng, Bei,Yu, Jiaguo
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- UV-visible and near-infrared active NaGdF4:Yb:Er/Ag/TiO2 nanocomposite for enhanced photocatalytic applications
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A near infra-red (NIR) active NaGdF4:Yb:Er/Ag/TiO2 nanocomposite photocatalyst was successfully synthesized by a one-pot thermal decomposition method. The composite structure, morphology and elemental mapping of the synthesized NaGdF4:Yb:Er/Ag/TiO2 nanocomposite were characterized by X-ray diffraction and transmission electron microscopy analysis. The energy transfer among NaGdF4:Yb:Er, Ag, and TiO2 was revealed by upconversion photoluminescence measurements at 980 nm. The Ag and NaGdF4 nanoparticles enhanced the visible and NIR light absorption property of the NaGdF4:Yb:Er/Ag/TiO2 nanocomposite. The NIR and UV-visible light induced photocatalytic study of the NaGdF4:Yb:Er/Ag/TiO2 composite was examined by rhodamine B degradation. The energy transfer among NaGdF4:Yb:Er, Ag, and TiO2 significantly influenced the photocatalytic activity under NIR irradiation. The catalysts produced oxidative species during NIR irradiation, which are responsible for the photocatalytic degradation of rhodamine B. NaGdF4:Yb:Er/Ag/TiO2 showed photocatalytic activity under NIR and UV-visible radiation (full solar irradiation), which is superior to a UV or visible light active photocatalyst. The study provided a UV-visible and NIR-responsive photocatalyst and its energy transfer mechanism.
- Prakash, Natarajan,Thangaraju, Dheivasigamani,Karthikeyan, Rajan,Arivanandhan, Mukannan,Shimura, Yosuke,Hayakawa, Yasuhiro
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- Piezocatalytic performance of Na0.5Bi0.5TiO3 nanoparticles for degradation of organic pollutants
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Piezocatalysis has been considered as a promising technology in water pollution treatment. In this work, a series of piezoelectric Na0.5Bi0.5TiO3 (NBT) nanoparticles were prepared by hydrothermal method using different titanium sources as titanium precursors. The piezocatalytic performances of the NBT nanoparticles were investigated by the degradation of Rhodamine B (RhB) with the concentration of 10 mg/L under ultrasonic vibration. It is found that the NBT nanoparticles prepared by using anatase titanium oxide as titanium precursor show optimum piezocatalytic activity and the rate constant of 0.022 min?1 is achieved for RhB. The initial RhB concentration, ultrasonic power, particles size and specific surface area of NBT materials play an important role in optimizing the piezocatalytic performance. Moreover, the NBT nanoparticles show a satisfactory stability and reusability for the piezocatalytic degradation. The piezocatalytic mechanism of NBT nanoparticles was elucidated by the identification of free radicals and intermediates in the degradation process. The work provides a guidance to design and develop new high-performance piezocatalysts.
- Chen, Lirong,Hao, Xihong,Li, Yong,Lu, Chunxiao,Shi, Lu,Zhang, Qiwei,Zhang, Tiejun
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- A visible light driven 3D hierarchical CoTiO3/BiOBr direct Z-scheme heterostructure with enhanced photocatalytic degradation performance
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A series of novel three-dimensional (3D) CoTiO3/BiOBr (CTBB) hierarchical heterostructures were preparedviaa simple hydrothermal method. In comparison with pure CoTiO3and BiOBr, all the CTBB nanocomposites display enhanced photocatalytic performance toward dye decomposition. Particularly, CTBB-5 reveals the best photocatalytic efficiency for RhB removal with aKof 0.2030 min?1, which is about 50.75 and 3.02-fold higher than that of pure CoTiO3and BiOBr, respectively. The outstanding activity is further demonstrated by MO photodegradation. The dramatically enhanced activity can be attributed to the increased surface area and reduced recombination probability of charge carriers. Furthermore, CTBB-5 exhibits excellent stability after repetitively running four times. The h+and ˙O2?are identified as the dominating reactive species contributing to the oxidation reaction. Finally, a possible Z-scheme charge transfer mechanism is presented and analyzed in detail.
- He, Shiwu,Li, Qiang,Lu, Xiaoxiao,Tian, Zhenfei,Wang, Lijie,Zhang, Jinfeng
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p. 124 - 135
(2021/12/30)
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- INTRACELLULAR ORGANELLE PEPTIDE TARGETED ENZYME SUBSTRATES
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This invention relates to substrates and methods for the visualization of intracellular organelles, such as the lysosome, peroxiosome, nucleus, Endoplasmic Reticulum and Golgi Apparatus, based upon organelle enzyme activity. Such compounds represent a novel combination of chemically distinct enzyme substrates with targeting and detection substrates which are activated by enzyme activity inside target organelles to produce a detectable signal. The organelle targeted enzyme substrates of this invention are designed to provide high fluorescence at lower pH values found in some organelles and can be used for monitoring enzyme activity inside cells at very low concentrations.
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- Reagents and methods for direct labeling of nucleotides
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The present invention provides systems and methods for production of activatable diazo-derivatives for use in labeling nucleotides. Labeling nucleotides is accomplished by contacting a stable hydrazide derivative of a detectable moiety with an activating polymer reagent which is used to directly label the nucleotide sample. Labeling occurs on the phosphate backbone of the nucleotide which does not perturb hybridization of the labeled nucleotide with its anti-sense strand. Since the method involves direct labeling, all types of nucleotides can be labeled without prior amplification or alteration.
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(2013/06/27)
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- Catalytic Azide Reduction in Biological Environments
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In the quest for the identification of catalytic transformations to be used in chemical biology and medicinal chemistry, we identified iron(III) meso-tetraarylporphines as efficient catalysts for the reduction of aromatic azides to their amines. The reaction uses thiols as reducing agents and tolerates water, air, and other biological components. A caged fluorophore was employed to demonstrate that the reduction can be performed even in living mammalian cells. However, in vivo experiments in nematodes (Caenorhabditis elegans) and zebrafish (Danio rerio) revealed a limitation to this method: the metabolic reduction of aromatic azides.
- Sasmal, Pijus K.,Carregal-Romero, Susana,Han, Alice A.,Streu, Craig N.,Lin, Zhijie,Namikawa, Kazuhiko,Elliott, Samantha L.,Koester, Reinhard W.,Parak, Wolfgang J.,Meggers, Eric
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experimental part
p. 1116 - 1120
(2012/08/13)
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