共查询到20条相似文献,搜索用时 23 毫秒
1.
Qi Wang Dr. Chuncheng Chen Prof. Wanhong Ma Prof. Huaiyong Zhu Prof. Jincai Zhao Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(19):4765-4769
Synergistic interactions between N and F can be used to tune the band structures of N‐doped TiO2 (see scheme). Reduction potential of conduction band electron is positively shifted to weaken unwanted O2 reduction, but enhances the target reduction reaction in air. The tuning also enhances the oxidation ability of the valence band to oxidize water to O2, which makes photocatalytic reduction proceed without any organic sacrificial reagents.
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Dr. Zhanfeng Zheng Jian Zhao Dr. Yong Yuan Dr. Hongwei Liu Dr. Dongjiang Yang Sarina Sarina Prof. Hongjie Zhang Dr. Eric R. Waclawika Prof. Huaiyong Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(18):5731-5741
Nitrogen‐doped TiO2 nanofibres of anatase and TiO2(B) phases were synthesised by a reaction between titanate nanofibres of a layered structure and gaseous NH3 at 400–700 °C, following a different mechanism than that for the direct nitrogen doping from TiO2. The surface of the N‐doped TiO2 nanofibres can be tuned by facial calcination in air to remove the surface‐bonded N species, whereas the core remains N doped. N‐Doped TiO2 nanofibres, only after calcination in air, became effective photocatalysts for the decomposition of sulforhodamine B under visible‐light irradiation. The surface‐oxidised surface layer was proven to be very effective for organic molecule adsorption, and the activation of oxygen molecules, whereas the remaining N‐doped interior of the fibres strongly absorbed visible light, resulting in the generation of electrons and holes. The N‐doped nanofibres were also used as supports of gold nanoparticle (Au NP) photocatalysts for visible‐light‐driven hydroamination of phenylacetylene with aniline. Phenylacetylene was activated on the N‐doped surface of the nanofibres and aniline on the Au NPs. The Au NPs adsorbed on N‐doped TiO2(B) nanofibres exhibited much better conversion (80 % of phenylacetylene) than when adsorbed on undoped fibres (46 %) at 40 °C and 95 % of the product is the desired imine. The surface N species can prevent the adsorption of O2 that is unfavourable for the hydroamination reaction, and thus, improve the photocatalytic activity. Removal of the surface N species resulted in a sharp decrease of the photocatalytic activity. These photocatalysts are feasible for practical applications, because they can be easily dispersed into solution and separated from a liquid by filtration, sedimentation or centrifugation due to their fibril morphology. 相似文献
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Dr. Leticia F. Velasco Dr. Joao C. Lima Dr. Conchi Ania 《Angewandte Chemie (International ed. in English)》2014,53(16):4146-4148
By using monochromatic light the ability of semiconductor‐free nanoporous carbons to convert the low‐energy photons from the visible spectrum into chemical reactions (i.e. phenol photooxidation) is demonstrated. Data shows that the onset wavelength of the photochemical activity can be tuned by surface functionalization, with enhanced visible‐light conversion upon introducing N‐containing groups. 相似文献
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FengHui Tian ChengBu Liu Dongju Zhang Aiping Fu Yunbo Duan Shuping Yuan Jimmy C. Yu 《Chemphyschem》2010,11(15):3269-3272
Plane‐wave‐based pseudopotential density functional theory (DFT) calculations are used to elucidate the origin of the high photocatalytic efficiency of carbonate‐doped TiO2. Two geometrically possible doping positions are considered, including interstitial and substitutional carbon atoms on Ti sites. From the optical absorption properties calculations, we believe that the formation of carbonates after doping with interstitial carbon atoms is crucial, whereas the contribution from the cationic doping on Ti sites is negligible. The carbonate species doped TiO2 exhibits excellent absorption in the visible‐light region of 400–800 nm, in good agreement with experimental observations. Electronic structure analysis shows that the carbonate species introduce an impurity state from Ti 3d below the conduction band. Excitations from the impurity state to the conduction band may be responsible for the high visible‐light activity of the carbon doped TiO2 materials. 相似文献
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通过在真空条件下将氯铂酸的乙醇溶液引入到钛酸纳米管内,再经过热处理制备了镶嵌铂的纳米管钛酸(简写为PNTA).X射线光电子能谱(XPS)表明氯铂酸大部分转变成Pt0和PtO,顺磁共振谱(ESR)表明在PNTA中生成了束缚单电子的氧空位,在紫外-可见扩散漫散射谱(DRS)谱上表现出对可见光有吸收能力.丙烯的可见光光催化氧化实验结果表明:在可见光激发下(λ>420nm),PNTA对丙烯的光催化去除反应具有活性. 相似文献
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Fabrication of Predominantly Mn4+‐Doped TiO2 Nanoparticles under Equilibrium Conditions and Their Application as Visible‐Light Photocatalyts 下载免费PDF全文
Lijie Wang Jiajie Fan Zetan Cao Dr. Yichao Zheng Zhiqiang Yao Prof. Guosheng Shao Prof. Junhua Hu 《化学:亚洲杂志》2014,9(7):1904-1912
The chemical state of a transition‐metal dopant in TiO2 can intrinsically determine the performance of the doped material in applications such as photocatalysis and photovoltaics. In this study, manganese‐doped TiO2 is fabricated by a near‐equilibrium process, in which the TiO2 precursor powder precipitates from a hydrothermally obtained transparent mother solution. The doping level and subsequent thermal treatment influence the morphology and crystallization of the TiO2 samples. FTIR spectroscopy and X‐ray photoelectron spectroscopy analyses indicate that the manganese dopant is substitutionally incorporated by replacing Ti4+ cations. The absorption band edge can be gradually shifted to 1.8 eV by increasing the nominal manganese content to 10 at %. Manganese atoms doped into the titanium lattice are associated with the dominant 4+ valence oxidation state, which introduces two curved, intermediate bands within the band gap and results in a significant enhancement in photoabsorption and the quantity of photogenerated hydroxyl radicals. Additionally, the high photocatalytic performance of manganese‐doped TiO2 is also attributed to the low oxygen content, owing to the equilibrium fabrication conditions. This work provides an important strategy to control the chemical and defect states of dopants by using an equilibrium fabrication process. 相似文献
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Sulfur doped ZnO/TiO2 nanocomposite photocatalysts were synthesized by a facile sol‐gel method. The structure and properties of catalysts were characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), UV‐vis diffusive reflectance spectroscopy (DRS) and N2 desorption‐adsorption isotherm. The XRD study showed that TiO2 was anatase phase and there was no obvious difference in crystal composition of various S‐ZnO/TiO2. The XPS study showed that the Zn element exists as ZnO and S atoms form SO2?4. The prepared samples had mesoporosity revealed by N2 desorption‐adsorption isotherm result. The degradation of Rhodamine B dye under visible light irradiation was chosen as probe reaction to evaluate the photocatalytic activity of the ZnO/TiO2 nanocomposite. The commercial TiO2 photocatalyst (Degussa P25) was taken as standard photocatalyst to contrast the prepared different photocatalyst in current work. The improvement of the photocatalytic activity of S‐ZnO/TiO2 composite photocatalyst can be attributed to the suitable energetic positions between ZnO and TiO2, the acidity site caused by sulfur doping and the enlargement of the specific area. S‐3.0ZnO/TiO2 exhibited the highest photocatalytic activity under visible light irradiation after Zn amount was optimized, which was 2.6 times higher than P25. 相似文献
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Dr. Dharmendra Kumar Tiwari Dr. Ram Awatar Maurya Dr. Jagadeesh Babu Nanubolu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):526-530
Structurally diverse imidazole derivatives were synthesized by a visible‐light/[Ru(bpy)3][(PF6)2]‐mediated coupling of vinyl azides and secondary amines in flow microreactors. This operationally simple and atom‐economical protocol allows the formation of three new C?N bonds through the functionalization of sp3 C?H bonds adjacent to the secondary nitrogen atom. In order to get mechanistic insight of the coupling reaction, several control experiments were carried out and discussed. 相似文献
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Multifunctional Nitrogen‐Doped Carbon Nanodots for Photoluminescence,Sensor, and Visible‐Light‐Induced H2 Production 下载免费PDF全文
Dr. Pengju Yang Dr. Jianghong Zhao Dr. Jian Wang Dr. Huijuan Cui Li Li Prof. Dr. Zhenping Zhu 《Chemphyschem》2015,16(14):3058-3063
Herein, multifunctional N‐doped carbon nanodots (NCNDs) were prepared through the one‐step hydrothermal treatment of yeast. Results show that the NCNDs can be used as a new photocatalyst to drive the water‐splitting reaction under UV light. Moreover, the NCNDs can efficiently catalyze the hydrogen evolution reaction. Under visible‐light irradiation, Eosin Y‐sensitized NCNDs exhibit excellent activity for hydrogen evolution. The hydrogen evolution rate of NCNDs (without any modification and co‐catalyst) reaches 107.1 μmol h?1 (2142 μmol g?1 h?1). When Pt is loaded on the NCNDs, the hydrogen evolution rate reaches 491.2 μmol h?1 (9824 μmol g?1 h?1) under visible‐light irradiation. In addition, the NCNDs show excellent fluorescent properties and can be applied as a fluorescent probe for the sensitive and selective detection of Fe3+. 相似文献
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Hybrid Density Functional Study on Mono‐ and Codoped NaNbO3 for Visible‐Light Photocatalysis 下载免费PDF全文
Dr. Guang‐Zhao Wang Prof. Hong Chen Gang Wu Prof. An‐Long Kuang Prof. Hong‐Kuang Yuan 《Chemphyschem》2016,17(4):489-499
Monodoping with Mo, Cr, and N atoms, and codoping with Mo?N and Cr?N atom pairs, are utilized to adjust the band structure of NaNbO3, so that NaNbO3 can effectively make use of visible light for the photocatalytic decomposition of water into hydrogen and oxygen, as determined by using the hybrid density functional. Codoping is energetically favorable compared with the corresponding monodoping, due to strong Coulombic interactions between the dopants and other atoms, and the effective band gap and stability for codoped systems increase with decreasing dopant concentration and the distance between dopants. The molybdenum, chromium, and nitrogen monodoped systems, as well as chromium–nitrogen codoped systems, are unsuitable for the photocatalytic decomposition of water by using visible light, because defects introduced by monodoping or the presence of unoccupied states above the Fermi level, which promotes electron–hole recombination processes, suppress their photocatalytic performance. The Mo?N codoped NaNbO3 sample is a promising photocatalyst for the decomposition of water by using visible light because Mo?N codoping can reduce the band gap to a suitable value with respect to the water redox level without introducing unoccupied states. 相似文献
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Jiaguo Yu Qin Li Shengwei Liu Mietek Jaroniec 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(7):2433-2441
Exploiting advanced photocatalysts under visible light is of primary significance for the development of environmentally relevant photocatalytic decontamination processes. In this study, the ionic liquid (IL), 1‐butyl‐3‐methylimidazolium tetrafluoroborate, was employed for the first time as both a structure‐directing agent and a dopant for the synthesis of novel fluorinated B/C‐codoped anatase TiO2 nanocrystals (TIL) through hydrothermal hydrolysis of tetrabutyl titanate. These TIL nanocrystals feature uniform crystallite and pore sizes and are stable with respect to phase transitions, crystal ripening, and pore collapse upon calcination treatment. More significantly, these nanocrystals possess abundant localized states and strong visible‐light absorption in a wide range of wavelengths. Because of synergic interactions between titania and codopants, the calcined TIL samples exhibited high visible‐light photocatalytic activity in the presence of oxidizing Rhodamine B (RhB). In particular, 300 °C‐calcined TIL was most photocatalytically active; its activity was much higher than that of TiO1.98N0.02 and reference samples (TW) obtained under identical conditions in the absence of ionic liquid. Furthermore, the possible photocatalytic oxidation mechanism and the active species involved in the RhB degradation photocatalyzed by the TIL samples were primarily investigated experimentally by using different scavengers. It was found that both holes and electrons, as well as their derived active species, such as .OH, contributed to the RhB degradation occurring on the fluorinated B/C‐codoped TiO2 photocatalyst, in terms of both the photocatalytic reaction dynamics and the reaction pathway. The synthesis of the aforementioned novel photocatalyst and the identification of specific active species involved in the photodegradation of dyes could shed new light on the design and synthesis of semiconductor materials with enhanced photocatalytic activity towards organic pollutants. 相似文献
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Scalable Synthesis of Piperazines Enabled by Visible‐Light Irradiation and Aluminum Organometallics 下载免费PDF全文
Dr. Samuel Suárez‐Pantiga Kilian Colas Dr. Magnus J. Johansson Dr. Abraham Mendoza 《Angewandte Chemie (International ed. in English)》2015,54(47):14094-14098
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. 相似文献
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Cover Picture: Fabrication of Predominantly Mn4+‐Doped TiO2 Nanoparticles under Equilibrium Conditions and Their Application as Visible‐Light Photocatalyts (Chem. Asian J. 7/2014) 下载免费PDF全文
Lijie Wang Jiajie Fan Zetan Cao Dr. Yichao Zheng Zhiqiang Yao Prof. Guosheng Shao Prof. Junhua Hu 《化学:亚洲杂志》2014,9(7):1685-1685
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Visible‐Light‐Mediated Generation of Nitrogen‐Centered Radicals: Metal‐Free Hydroimination and Iminohydroxylation Cyclization Reactions 下载免费PDF全文
Jacob Davies Samuel G. Booth Dr. Stephanie Essafi Prof. Robert A. W. Dryfe Dr. Daniele Leonori 《Angewandte Chemie (International ed. in English)》2015,54(47):14017-14021
The formation and use of iminyl radicals in novel and divergent hydroimination and iminohydroxylation cyclization reactions has been accomplished through the design of a new class of reactive O‐aryl oximes. Owing to their low reduction potentials, the inexpensive organic dye eosin Y could be used as the photocatalyst of the organocatalytic hydroimination reaction. Furthermore, reaction conditions for a unique iminohydroxylation were identified; visible‐light‐mediated electron transfer from novel electron donor–acceptor complexes of the oximes and Et3N was proposed as a key step of this process. 相似文献
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Lu Song Dr. Long Zhang Prof. Sanzhong Luo Prof.Dr. Jin‐Pei Cheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(44):14231-14234
We described herein a catalyst‐free visible‐light photolytic protocol for the imidation of arenes and heteroarenes. N‐Bromosaccharin was identified as a viable and chemoselective nitrogen radical precursor that undergoes controllable homolytic cleavage under ambient light irradiation. The reaction can be applied to a number of arenes and heteroarenes with good chemo‐ and regioselectivity. Mechanistic studies revealed that radical chain termination by electron transfer‐proton transfer (ET‐PT) is the leading productive pathway for the reaction. 相似文献
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Honghong Gong Yu Gu Yucheng Zhao Qinzhi Quan Shantao Han Mao Chen 《Angewandte Chemie (International ed. in English)》2020,59(2):919-927
Ultra‐high‐molecular‐weight (UHMW) polymers display outstanding properties and hold potential for wide applications. However, their precise synthesis remains challenging. Herein, we developed a novel reversible‐deactivation radical polymerization based on the strong and selective fluorine–fluorine interaction, allowing chain‐transfer agents to spontaneously differentiate into two groups that take charge of the chain growth and reversible deactivation of the growing chains, respectively. This method enables dramatically improved livingness of propagation, providing UHMW polymers with a surprisingly narrow molecular weight distribution (?≈1.1) from a variety of fluorinated (meth)acrylates and acrylamide at quantitative conversions under visible‐light irradiation. In situ chain‐end extensions from UHMW polymers facilitated the synthesis of well‐defined block copolymers, revealing the excellent chain‐end fidelity achieved by this method. 相似文献