Photocatalytic activity of silicon nanowires under UV and visible light irradiation

The communication reports on the high performance of hydrogen-terminated silicon nanowires and silicon nanowires coated with metal (Ag, Cu) nanostructures for the photodegradation of rhodamine B under UV and visible light irradiation.     

Photocatalytic water oxidation with nonsensitized IrO2 nanocrystals under visible and UV light

Rutile IrO(2) is known as being among the best electrocatalysts for water oxidation. Here we report on the unexpected photocatalytic water oxidation activity of 1.98 nm ± 0.11 nm succinic acid-stabilized IrO(2) nanocrystals. From aqueous persulfate and silver nitrate solution the nonsensitized particles evolve oxygen with initial rates up to 0.96 μmol min(-1), and with a quantum efficiency of at least 0.19% (measured at 530 nm). The catalytic process is driven by visible excitations from the Ir-d(t(2g)) to the Ir-d(e(g)) band (1.5-2.75 eV) and by ultraviolet excitations from the O-p band to the Ir-d(e(g)) (>3.0 eV) band. The formation of the photogenerated charge carriers can be directly observed with surface photovoltage spectroscopy. The results shed new light on the role of IrO(2) in dye- and semiconductor-sensitized water splitting systems.     

Monitoring of paintings under exposure to UV light by ATR-FT-IR spectroscopy and multivariate control charts

This paper concerns the improvement of a method, already applied for the conservation state monitoring of wooden and painted surfaces, to a system closely simulating a real artwork, namely a canvas painted with mixtures of three organic pigments (Alizarin, Permanent Red, Phtalocyanine Green). Ten mixtures of these pigments, according to an augmented simplex-centroid design, were prepared, mixed with linseed oil and spread on 10 cotton canvas strips. Drying ended, all the samples were analysed by ATR-FT-IR spectroscopy to describe the superficial variability in normal conditions of conservation, i.e. when no degradation is present. Successively, the samples were exposed to artificial UV light simulating the action of an aggressive portion of sunlight. The IR spectra of the surfaces were regularly acquired to monitor the superficial changes due to the UV aggression. Treatment ended, a chemometric study based on the Principal Component Analysis of the spectroscopic data collected both in normal conditions of conservation and during the artificial accelerated ageing, was performed and the multivariate Shewhart and Cusum control charts were built with the scores of the significant PCs (principal components). PCA based control charts showed to be able to identify the presence of significant changes of the painted surfaces, to identify the starting of the degradations and to provide insights about the chemical alterations induced by the UV exposure.     

Redox transformations and antiradical activity of triarylantimony(V) 3,6-di-tert-butyl-4,5-dimethoxycatecholates

Triarylantimony(V) catecholate complexes were synthesized by the oxidative addition of 3,6-di-tert-butyl-4,5-dimethoxy-o-benzoquinone to triarylstibines. The electrochemical properties and antiradical activity of the synthesized compounds were studied. According to cyclic viltammetry data, the complexes are oxidized via two consecutive quasi-reversible stages. Introduction of halogen atoms in para-position of phenyl groups at Sb(V) causes anodic shifts of the oxidation potentials and enhances stability of the mono- and dicationic forms of the compounds, which form in the course of electrochemical transformations. Triarylantimony(V) catecholate complexes exhibit appreciable antiradical activity in the auto-oxidation of oleic acid. In was found that the inhibitory activity of the complexes depends on their redox potential.     

Surface-active properties of humic and sulfochlorohumic acids

The surface tension of alkaline solutions of humic acids and their sulfochloroderivatives, which are synthesized by sulfonation of chlorohumic acids isolated from coal chlorinated by the electrochemical method, is investigated. It is established that humic compounds possess weak surface activity. Basic adsorption parameters are calculated.     

Photophysical properties and photocatalytic activities of bismuth molybdates under visible light irradiation

Aurivillius structure Bi(2)MoO(6) (BG: 2.70 eV) that is a low-temperature phase showed an intense absorption band in the visible light region and photocatalytic activity for O(2) evolution from an aqueous silver nitrate solution under visible light irradiation, among various bismuth molybdates (Bi(2)MoO(6), Bi(2)Mo(2)O(9), and Bi(2)Mo(3)O(12)) synthesized by solid-state and reflux reactions. Bi(2)Mo(3)O(12) (BG: 2.88 eV) also showed photocatalytic activity for O(2) evolution under full-arc irradiation of a Xe lamp (lambda > 300 nm). The photocatalytic activity of the Aurivillius structure Bi(2)MoO(6) prepared by the reflux method was dependent on the annealing temperature after the preparation. The crystallinity was the important factor for the activity. Calculation by the density functional method indicated that the conduction band of Aurivillius structure Bi(2)MoO(6) was made up of Mo 4d orbitals. It turned out that the visible-light absorption of this photocatalyst was due to the transition from the valence band consisting of O 2p orbitals to the conduction band. The corner-sharing structure of the MoO(6) octahedra contributed to the visible light response and the photocatalytic performance because excitation energy and/or photogenerated electron and hole pairs began to migrate easily in the Aurivillius structure.     

Membrane-active properties and antiradical activity of gossypol and its derivatives

A novel asymmetric gossypol derivative was synthesized. The antioxidant activity of gossypol and certain of its derivatives at the aldehyde groups and the interaction of these compounds with model membranes were studied. It was shown that the antiradical and membrane activities of the gossypol derivatives were determined by the structure of the substituent and that gossypol and its derivatives were partially localized in the lipid bilayer and possibly induced formation of a new interdigitating phase. Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 265–266, May–June, 2008.     

Photocatalytic activity of Fe and Cu co-doped TiO2 nanoparticles under visible light

Journal of Sol-Gel Science and Technology - The photocatalytic activity of single transition metal-doped TiO2 nanoparticles is well established. This article reports the synthesis of Fe and Cu...     

CQDs/TNS复合光催化剂的制备及其可见光催化活性

以明胶为原料用水热法一步合成了碳量子点(CQDs),经过聚乙二醇表面修饰后,在乙醇溶液中与二氧化钛纳米片(TNS)复合形成了碳量子点高分散负载的CQDs/TNS复合光催化剂.对复合光催化剂进行了XRD、FT-IR、HRTEM和XPS表征,结果表明合成的碳量子点的平均粒径为4nm且具有较好的荧光性能.与纯TNS相比,CQDs/TNS复合光催化剂在可见光下对罗丹明B表现出很好的光催化降解活性.当CQDs/TNS复合光催化剂中CQDs含量为7.5%时光催化活性最好,并且在3次循环降解后活性仍保持不变.其优异的光催化活性来自于碳量子点的独特上转换荧光性能和二氧化钛纳米片高活性{001}晶面的共同作用.     

First demonstration of CdSe as a photocatalyst for hydrogen evolution from water under UV and visible light

CdSe nanoribbons show catalytic activity for photochemical hydrogen evolution from aqueous Na2S/Na2SO3 solution under irradiation with ultraviolet and visible light.     

紫外和可见光照射下Fe-TiO2复合材料催化低浓度芳香族有机污染物降解（英文）

Fe‐TiO2 photocatalysts with different ratios of Fe to Ti were prepared by a sol‐gel process using tetra‐n‐butyl titanium and iron(III) nitrate as Ti and Fe sources, respectively. The photocatalytic function of the prepared composites was examined for the decomposition of low‐concentration(0.1 ppm) airborne benzene, toluene, ethyl benzene, and o‐xylene(BTEX). The Fe‐TiO2 composites were characterized by energy dispersive X‐ray spectroscopy, X‐ray diffraction, UV‐visible spectroscopy, and Fourier transform infrared spectroscopy. The time‐series ratios of outlet to inlet concentrations of toluene, ethyl benzene, and o‐xylene target chemicals, as determined by the Fe‐TiO2 composites under visible light exposure, were lower than or similar to those of the reference TiO2 photocatalyst. Moreover, the time‐series ratios of outlet to inlet concentrations of the three compounds, as determined for the Fe‐TiO2 composites, increased as the ratio of Fe to Ti increased from 0.001 to 0.010. In contrast, under UV exposure, the time‐series ratios of outlet to inlet concentrations of BTEX, determined for the Fe‐TiO2 composites, were similar to or higher than those obtained from the reference TiO2 photocatalyst. Fe‐TiO2 composites with an optimal Fe to Ti ratio could effectively be applied for the purification of low‐concentration aromatic organic pollutants.     

Photocatalytic activity of SrTiO3 codoped with nitrogen and lanthanum under visible light illumination

Yellow SrTiO3 powders codoped with nitrogen and lanthanum (STO:N,La) were studied as visible light photocatalysts. The crystal phase of STO:N,La exhibited a pure perovskite phase, and O and Sr sites atoms were substitutionally doped with N and La atoms, respectively. The first principle calculation of STO:N,La indicated that the edge of the N(2p) band is situated above the valence band, which consisted of O(2p) orbitals, and the La orbitals did not exist in the band gap of SrTiO3. STO:N,La exhibited a higher oxidation activity of gaseous 2-propanol under vis illumination than SrTiO3 doped only with nitrogen (STO:N). The high activity of STO:N,La was due to the decrease in the oxygen vacancies, which acted as electron-hole recombination centers, because codoping with La3+ and N3- ions maintained the charge balance. The optimum doping density of N and La for visible light activity was 0.5%, and STO:N,La(0.5%) had an activity under UV illumination similar to pure SrTiO3.     

The acidobasic and complexation properties of humic acids Study of complexation of Czech humic acids with metal ions

The acid-base and complexation properties of humic acids (HAs) extracted from bohemian brown coals were studied. The acid-base behavior corresponds with the model of HA as a mixture of mono- and diprotic acids. This model was also verified on commercial HA substances (Aldrich and Fluka). HA binds strongly with heavy metal ions and the highest stability constant of HA-metal ion complexes was observed for copper(II). Stability constant values were found to decrease in the order: Cu(2+)>Ba(2+)>Pb(2+)>Cd(2+)>Ca(2+). Both acidobasic models for HA alone and those for HA-metal ion interactions were proposed and the computational methodology for polyelectrolyte equilibria studies demonstrated.     

Study on anti-fungal activity of nitrogen-doped TiO2 nanophotocatalyst under visible light irradiation

<正>Nitrogen-doped TiO_2 nanophotocatalysts were prepared,and characterized by XRD patterns and UV-vis spectroscopy.The results indicated that nitrogen was doped effectively and the shift of the absorption edge to a lower energy and a stronger absorption in the visible light region were observed.The calcinations temperature is a key factor to narrow the band gap of titania,and consequently affects the response to visible light of nitrogen-doped TiO_2 nanocrystals.This photocatalyst can effectively inhibit the growth of Helminthosporium maydis,whereas undoped TiO_2 nanocrystals cannot inhibit the growth of H.maydis under the same experimental conditions.     

Significantly enhanced photocatalytic activity of TiO2/TiC coatings under visible light

Journal of Solid State Electrochemistry - Rutile TiO2 forms on TiC coatings (TiO2/TiC coatings) during carbon-embedding heat treatment (cHT) for TiC coatings. The photocatalytic activity of...     

溴化银/二氧化钛复合材料的可见光催化性能

将硝酸银的乙醇溶液与溶胶凝胶TiO2混合得到前驱体,随后经共沉淀-煅烧制备得到AgBr/TiO2复合材料;采用扫描电镜、X射线衍射仪、X射线光电子能谱仪分析了复合材料的形貌、晶体结构、Ag元素的价态,采用紫外-可见漫反射光谱仪测定了其光吸收性能;进而以甲基橙(MO)的可见光降解为探针反应测定了AgBr/TiO2复合材料的可见光催化性能.结果表明,当前驱体在不同温度下煅烧后,无定形TiO2颗粒逐渐增大,并逐渐转变为锐钛矿结构;担载的AgBr可明显拓展TiO2的可见光吸收范围;Ag物种主要以Ag+形式存在.当煅烧温度为300℃时,复合材料的光催化活性最高,MO的降解率在60min内达到90%以上;随着煅烧温度的增加,催化活性逐渐降低.     

Enhanced photocatalytic activity of SiC modified by BiVO4 under visible light irradiation

SiC-BiVO₄-P and SiC-BiVO₄-H composites have been prepared by precipitation method and hydrothermal method, respectively. Rod-like BiVO₄ particles dispersed on the surface of micro-sized SiC particles homogeneously in SiC-BiVO₄-H. Due to the formed heterostructure between BiVO₄ and SiC, photo-generated electrons and holes were effectively separated. Under visible light irradiation, SiC-BiVO₄-H exhibited the best performance for photocatalytic oxidation of Rhodamine B, achieved about 7.5 times improvement in photocatalytic degradation rate constants compared with that of the pristine SiC powder. The possible photocatalysis mechanism of SiC/BiVO₄ related to the band positions of the semiconductors under visible light irradiation was also discussed in detail. In addition, the radicals trapping experiments revealed that all three radicals (holes, OH, and O₂^?) play an important role in the Rhodamine B degradation.     

Photocatalytic activity of titanium dioxide modified with thiourea under the action of visible light

Photocatalyst powders were synthesized from nanosized titanium dioxide crystals modified by sintering with thiourea (TU). The powders contained anatase crystals of various sizes. TU-TiO₂ powders absorbed visible light to produce an oxidizer (oxidizing iodide) and a reducing agent (reducing tetranitromethane). The activity of TU-TiO₂ correlated with the size of nanocrystals. The photocatalytic activity of TU-TiO₂ was suggested to be related to impurity states appearing during modification in the forbidden band of TiO₂.     

Synthesis and properties of synthetic analogs of natural humic acids

A new procedure was suggested for preparing analogs of natural humic acids using as precursor a nitrogen-containing amphoteric polyelectrolyte prepared by condensation of pyrocatechol with hexamethylenetetramine. The physicochemical and spectral properties of the product were examined.