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Huiming Cheng - One of the best experts on this subject based on the ideXlab platform.
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on the true Photoreactivity order of 001 010 and 101 facets of anatase tio2 crystals
Angewandte Chemie, 2011Co-Authors: Jian Pan, Gang Liu, Huiming ChengAbstract:Contrary to conventional understanding, clean anatase {001} facets exhibit lower Photoreactivity than {101} facets. Furthermore, the {010} facets showed the highest photocatalytic reactivity in generating OH radicals and hydrogen evolution. This behavior was revealed by studies on crystals grown hydrothermally to have a predominance of {001}, {101}, or {010} facets (left to right in picture(a) and (b)-(d), respectively).
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unique electronic structure induced high Photoreactivity of sulfur doped graphitic c3n4
Journal of the American Chemical Society, 2010Co-Authors: Gang Liu, Ping Niu, Chenghua Sun, Sean C Smith, Zhigang Chen, Huiming ChengAbstract:Electronic structure intrinsically controls the light absorbance, redox potential, charge-carrier mobility, and consequently, Photoreactivity of semiconductor photocatalysts. The conventional approach of modifying the electronic structure of a semiconductor photocatalyst for a wider absorption range by anion doping operates at the cost of reduced redox potentials and/or charge-carrier mobility, so that its Photoreactivity is usually limited and some important reactions may not occur at all. Here, we report sulfur-doped graphitic C(3)N(4) (C(3)N(4-x)S(x)) with a unique electronic structure that displays an increased valence bandwidth in combination with an elevated conduction band minimum and a slightly reduced absorbance. The C(3)N(4-x)S(x) shows a Photoreactivity of H(2) evolution 7.2 and 8.0 times higher than C(3)N(4) under lambda > 300 and 420 nm, respectively. More strikingly, the complete oxidation process of phenol under lambda > 400 nm can occur for sulfur-doped C(3)N(4), which is impossible for C(3)N(4) even under lambda > 300 nm. The homogeneous substitution of sulfur for lattice nitrogen and a concomitant quantum confinement effect are identified as the cause of this unique electronic structure and, consequently, the excellent Photoreactivity of C(3)N(4-x)S(x). The results acquired may shed light on general doping strategies for designing potentially efficient photocatalysts.
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unique electronic structure induced high Photoreactivity of sulfur doped graphitic c3n4
Journal of the American Chemical Society, 2010Co-Authors: Sean C Smith, Zhigang Chen, G Q Lu, Huiming ChengAbstract:Electronic structure intrinsically controls the light absorbance, redox potential, charge-carrier mobility, and consequently, Photoreactivity of semiconductor photocatalysts. The conventional approach of modifying the electronic structure of a semiconductor photocatalyst for a wider absorption range by anion doping operates at the cost of reduced redox potentials and/or charge-carrier mobility, so that its Photoreactivity is usually limited and some important reactions may not occur at all. Here, we report sulfur-doped graphitic C3N4 (C3N4−xSx) with a unique electronic structure that displays an increased valence bandwidth in combination with an elevated conduction band minimum and a slightly reduced absorbance. The C3N4−xSx shows a Photoreactivity of H2 evolution 7.2 and 8.0 times higher than C3N4 under λ > 300 and 420 nm, respectively. More strikingly, the complete oxidation process of phenol under λ > 400 nm can occur for sulfur-doped C3N4, which is impossible for C3N4 even under λ > 300 nm. The homoge...
Jean-pierre Lepoittevin - One of the best experts on this subject based on the ideXlab platform.
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chronic actinic dermatitis to sesquiterpene lactones 2 2 photoreaction toward thymidine of and α methylene hexahydrobenzofuranone with a cis ring junction
Photochemistry and Photobiology, 2010Co-Authors: Sébastien Fuchs, Valérie Berl, Jean-pierre LepoittevinAbstract:(+) and (-) alpha-methylene-hexahydrobenzofuranone derivatives with a stereochemically pure cis ring junction were used as models of sesquiterpene lactones to study their Photoreactivity toward thymidine. After 313 nm irradiation of a deoxygenated acetone solution of lactone models and thymidine, six [2+2] photoadducts were isolated for each enantiomer and fully characterized by a combination of NMR experiments. A common syn regioselectivity and exo stereoselectivity were observed for photoadducts. This high Photoreactivity of alpha-methylene-gamma-butyrolactone ring toward thymidine could be an explanation of the progressive evolution of allergic contact dermatitis toward chronic actinic dermatitis.
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evidence for 2 2 photoreaction of α methylene γ butyrolactones with thymine an explanation for chronic actinic dermatitis to sesquiterpene lactones
Photochemistry and Photobiology, 1999Co-Authors: Valérie Berl, Jean-pierre LepoittevinAbstract:The Photoreactivity of isoalantolactone, a natural sesquiterpene lactone, toward thymine was studied. After 313 nm irradiation of a deoxygenated acetone solution of isoalantolactone (2 x 10(-3) M) and thymine (4 x 10(-3) M), two intermolecular [2 + 2] photoadducts, 3 and 4, were isolated with respective yields of 30% and 18%. The structures of these two photoadducts were determined by a combination of NMR experiments. Compound 3 was identified as a cis-syn-exo intermolecular [2 + 2] photoadduct involving the 5,6 double bond of thymine and the exomethylenic double bond of the lactone, while compound 4 was identified as an intermolecular [2 + 2] photoadduct involving the same bonds but with the cis-syn-endo conformation. This high Photoreactivity of sesquiterpene lactones toward thymine could be an explanation of the progressive evolution of allergic contact dermatitis toward chronic actinic dermatitis.
Hong Jiang - One of the best experts on this subject based on the ideXlab platform.
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comparative investigation on Photoreactivity and mechanism of biogenic and chemosythetic ag c3n4 composites under visible light irradiation
ACS Sustainable Chemistry & Engineering, 2015Co-Authors: Ke Tian, Wujun Liu, Hong JiangAbstract:A Ag/C3N4 nanocomposite with optimum Ag content is an efficient and green photocatalyst for pollutant degradation under visible light irradiation. In this study, we synthesized Ag NPs using NaBH4 and the squeezed out liquid (SOL) of plant biomass. The Ag NPs thus obtained have been loaded to C3N4 to form Ag/C3N4 nanocomposites that show superior photocatalytic performance toward Rhodamine B (RhB) under visible light irradiation. The photocatalytic activity of both biogenic and chemogenic Ag/C3N4 nanocomposites with different Ag contents is compared. Results show that the biogenically synthesized Ag/C3N4 exhibits better photocatalytic performance than the chemosynthetic composite. Of all the different nanocomposites prepared in this study, Ag48/C3N4 (0.048% of Ag content) exhibits excellent Photoreactivity, with a reaction rate constant (k) 7-fold higher that the chemosynthetic Ag/C3N4. The observed improvement in the Photoreactivity is mainly attributed to the high dispersion of Ag NPs on C3N4, facilitate...
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facile modification of a graphitic carbon nitride catalyst to improve its Photoreactivity under visible light irradiation
Chemical Engineering Journal, 2014Co-Authors: Xuesong Zhang, Hong JiangAbstract:Abstract Graphitic carbon nitride (g-C 3 N 4 ) has attracted much attention worldwide ever since the recent discovery of its photocatalytic activity and metal-free property. In the current study, one-step acidification of melamine , by an easy to operate and low-cost approach, is proposed to improve the photocatalytic activity of prepared ag-C 3 N 4 . Rhodamine B (rhB), a typical organic dye, was chosen as a model pollutant to verify improvement in the photocatalytic performance of acidified g-C 3 N 4 (ag-C 3 N 4 ). The results reveal that the apparent reactive rate constant ( k app ) of ag-C 3 N 4 increases approximately three-fold under visible light at pH 7.0 compared to that of g-C 3 N 4 . Based on a systematic analysis of properties of ag-C 3 N 4 and g-C 3 N 4 , this substantial improvement in Photoreactivity is mainly attributed to changes in the growth orientation of self-polycondensed sheets and surface properties by acidification treatment, which endows ag-C 3 N 4 with a high Photoreactivity.
Gang Liu - One of the best experts on this subject based on the ideXlab platform.
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organic pollutant photodecomposition by ag knbo3 nanocomposites a combined experimental and theoretical study
Journal of Physical Chemistry C, 2016Co-Authors: Tingting Zhang, Wanying Lei, Ping Liu, Jose Rodriguez, Gang Liu, Minghua LiuAbstract:Ag nanoparticles supported on well-defined perovskite orthorhombic KNbO3 nanowires are synthesized via facile photoreduction and systematically characterized by XRD, Raman, DRUV–vis, XPS, PL, TEM, HRTEM, and HAADF-STEM. The Photoreactivity of Ag/KNbO3 nanocomposites as a function of Ag contents (0.4–2.8 wt %) is assessed toward aqueous rhodamine B degradation under UV- and visible-light, respectively. It is found that the UV-induced Photoreactivity initially increases and then decreases with increasing Ag contents. At an optimal Ag content (ca. 1.7 wt %), the greatest Photoreactivity is achieved under UV light, with the photocatalytic reaction rate of 1.7 wt % Ag/KNbO3 exceeding that of pristine KNbO3 by a factor of ca. 13. In contrast, visible light-induced Photoreactivity monotonically increases with increasing Ag contents in the range of 0.4–2.8 wt %. On the basis of the detected active species and intermediate products in the photocatalytic processes, conjugated structure cleavage and N-deethylation a...
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insights into the structure Photoreactivity relationships in well defined perovskite ferroelectric knbo3 nanowires
Chemical Science, 2015Co-Authors: Tingting Zhang, Wanying Lei, Ping Liu, Gang Liu, Jose A Rodriguez, Minghua LiuAbstract:Structure–function correlations are a central theme in heterogeneous (photo)catalysis. In this study, the geometric and electronic structure of perovskite ferroelectric KNbO3 nanowires with respective orthorhombic and monoclinic polymorphs have been systematically addressed. By virtue of aberration-corrected scanning transmission electron microscopy, we directly visualize surface photocatalytic active sites, measure local atomic displacements at an accuracy of several picometers, and quantify ferroelectric polarization combined with first-principles calculations. The Photoreactivity of the as-prepared KNbO3 nanowires is assessed toward aqueous rhodamine B degradation under UV light. A synergy between the ferroelectric polarization and electronic structure in Photoreactivity enhancement is uncovered, which accounts for the prominent reactivity order: orthorhombic > monoclinic. Additionally, by identifying new photocatalytic products, rhodamine B degradation pathways involving N-deethylation and conjugated structure cleavage are proposed. Our findings not only provide new insights into the structure–Photoreactivity relationships in perovskite ferroelectric photocatalysts, but also have broad implications in perovskite-based water splitting and photovoltaics, among others.
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on the true Photoreactivity order of 001 010 and 101 facets of anatase tio2 crystals
Angewandte Chemie, 2011Co-Authors: Jian Pan, Gang Liu, Huiming ChengAbstract:Contrary to conventional understanding, clean anatase {001} facets exhibit lower Photoreactivity than {101} facets. Furthermore, the {010} facets showed the highest photocatalytic reactivity in generating OH radicals and hydrogen evolution. This behavior was revealed by studies on crystals grown hydrothermally to have a predominance of {001}, {101}, or {010} facets (left to right in picture(a) and (b)-(d), respectively).
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unique electronic structure induced high Photoreactivity of sulfur doped graphitic c3n4
Journal of the American Chemical Society, 2010Co-Authors: Gang Liu, Ping Niu, Chenghua Sun, Sean C Smith, Zhigang Chen, Huiming ChengAbstract:Electronic structure intrinsically controls the light absorbance, redox potential, charge-carrier mobility, and consequently, Photoreactivity of semiconductor photocatalysts. The conventional approach of modifying the electronic structure of a semiconductor photocatalyst for a wider absorption range by anion doping operates at the cost of reduced redox potentials and/or charge-carrier mobility, so that its Photoreactivity is usually limited and some important reactions may not occur at all. Here, we report sulfur-doped graphitic C(3)N(4) (C(3)N(4-x)S(x)) with a unique electronic structure that displays an increased valence bandwidth in combination with an elevated conduction band minimum and a slightly reduced absorbance. The C(3)N(4-x)S(x) shows a Photoreactivity of H(2) evolution 7.2 and 8.0 times higher than C(3)N(4) under lambda > 300 and 420 nm, respectively. More strikingly, the complete oxidation process of phenol under lambda > 400 nm can occur for sulfur-doped C(3)N(4), which is impossible for C(3)N(4) even under lambda > 300 nm. The homogeneous substitution of sulfur for lattice nitrogen and a concomitant quantum confinement effect are identified as the cause of this unique electronic structure and, consequently, the excellent Photoreactivity of C(3)N(4-x)S(x). The results acquired may shed light on general doping strategies for designing potentially efficient photocatalysts.
Alison Butler - One of the best experts on this subject based on the ideXlab platform.
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iron iii siderophore coordination chemistry reactivity of marine siderophores
Coordination Chemistry Reviews, 2010Co-Authors: Alison Butler, Roslyn M TheisenAbstract:Two remarkable features of many siderophores produced by oceanic bacteria are the prevalence of an α-hydroxy-carboxylic acid functionality either in the form of the amino acid β-hydroxy aspartic acid or in the form of citric acid, as well as the predominance of amphiphilic siderophores. This review will provide an overview of the Photoreactivity that takes place when siderophores containing β-hydroxy aspartic acid and citric acid are coordinated to iron(III). This Photoreactivity raises questions about the role of this photochemistry in microbial iron acquisition as well as upper-ocean iron cycling. The self-assembly of amphiphilic siderophores and the coordination-induced phase-change of the micelle-to-vesicle transformation will also be reviewed. The distinctive photosensitive and self-assembly properties of marine siderophores hint at possibly new microbial iron acquisition mechanisms.
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photochemical reactivity of siderophores produced by marine heterotrophic bacteria and cyanobacteria based on characteristic fe iii binding groups
Limnology and Oceanography, 2003Co-Authors: Katherine A Barbeau, Eden L Rue, Charles G Trick, Kenneth W Bruland, Alison ButlerAbstract:Siderophores, high-affinity Fe(III) ligands produced by microorganisms to facilitate iron acquisition, might contribute significantly to dissolved Fe(III) complexation in ocean surface waters. In previous work, we demonstrated the Photoreactivity of the ferric ion complexes of several a-hydroxy carboxylic acid‐containing siderophores produced by heterotrophic marine bacteria. Here, we expand on our earlier studies and detail the Photoreactivity of additional siderophores produced by both heterotrophic marine bacteria and marine cyanobacteria, making comparisons to synthetic and terrestrial siderophores that lack the a-hydroxy carboxylate group. Our results suggest that, in addition to secondary photochemical reaction pathways involving reactive oxygen species, direct photolysis of Fe(III)-siderophore complexes might be a significant source of Fe(II) and reactive Fe(III) in ocean surface waters. Our findings further indicate that the Photoreactivity of siderophores is primarily determined by the chemical structure of the Fe(III) binding groups that they possess—hydroxamate, catecholate, or a-hydroxy carboxylate moieties. Hydroxamate groups are photochemically resistant regardless of Fe(III) complexation. Catecholates, in contrast, are susceptible to photooxidation in the uncomplexed form but stabilized against photooxidation when ferrated. a-Hydroxy carboxylate groups are stable as the uncomplexed acid, but when coordinated to Fe(III), these moieties undergo light-induced ligand oxidation and reduction of Fe(III) to Fe(II). These photochemical properties appear to determine the reactivity and fate of Fe(III)-binding siderophores in ocean surface waters, which in turn might significantly influence the biogeochemical cycling of iron.
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petrobactin a photoreactive siderophore produced by the oil degrading marine bacterium marinobacter hydrocarbonoclasticus
Journal of the American Chemical Society, 2002Co-Authors: Katherine A Barbeau, Guangping Zhang, David H Live, Alison ButlerAbstract:Petrobactin is a bis-catecholate, α-hydroxy acid siderophore produced by the oil-degrading marine bacterium Marinobacter hydrocarbonoclasticus. The Fe(III)-complexed form of petrobactin is photoreactive in natural sunlight, mediated by the Fe(III)-citrate moiety. The reaction results in decarboxylation of the petrobactin ligand and reduction of Fe(III) to Fe(II). This report is one of the first to show the Photoreactivity of Fe(III)-siderophores mediated by the ferric ion-α-hydroxy acid group. The demonstration of light-mediated decarboxylation of an Fe(III)-siderophore complex raises questions about a possible functional role for Photoreactivity in siderophore-mediated iron uptake.