Improvement of the performance of dye sensitized solar cell using ZnO nanorods array deposited with Ag nanoparticles as photoanode

Well-aligned zinc oxide (ZnO) nanorods (NRs) arrays deposited with Ag nanoparticles (NPs) are prepared by a liquid phase epitaxial growth process followed by a reduction of Ag on the surface of the ZnO NRs. Transmission electron microscopy images show that most Ag NPs are deposited on the upper part of the ZnO NRs, and the overall optical absorption in the range of visible light can be enhanced due to the surface plasmon resonance of the Ag NPs. ZnO NRs with and without Ag NPs are used to assemble dye sensitized solar cells. Devices fabricated from the Ag NPs/ZnO NRs composite arrays exhibit a higher open voltage, short circuit current and fill factor than that fabricated from the bare ZnO NRs array, thus, the overall efficiency of the as-fabricated cell is increased from less than 0.5?% to 0.8?%. The main reason for the enhancement of the device performance may be ascribed to that the electron transfer back from ZnO to the dye and electrolyte is blocked by the Schottky barrier at the Ag/ZnO interface, resulting in a great increase of the electron density at the ZnO conduction band.     

Plasmon-enhanced photocatalytic properties of cu(2)o nanowire-au nanoparticle assemblies

Cu(2)O-Au nanocomposites (NCs) with tunable coverage of Au were prepared by a facile method of mixing gold nanoparticles (Au NPs) with copper(I) oxide nanowires (Cu(2)O NWs) in various ratios. These Cu(2)O-Au NCs display tunable optical properties, and their photocatalytic properties were dependent on the coverage density of Au NPs. The photocatalytic activity of Cu(2)O-Au NCs was examined by photodegradation of methylene blue. The presence of Au NPs enhanced the photodegradation efficiency of Cu(2)O NCs. The photocatalytic efficiency of Cu(2)O-Au NCs initially increased with the increasing coverage density of Au NPs and then decreased as the surface of Cu(2)O became densely covered by Au NPs. The enhanced photocatalytic efficiency was ascribed to enhanced light absorption (by the surface plasmon resonance) and the electron sink effect of the Au NPs.     

Template-free Polyoxometalate-assisted Synthesis of Au/ZnO Hollow Sphere Hererostructures for Photocatalytic Water Purification

The controlled synthesis of ZnO hollow spheres is successfully achieved through a facile solvothermal method using a Keggin-type silicotungstic acid(H_4 Si(W_3 O_(10))_4:HSW) as structure directing agent. The formation process of these hollow spheres is proposed based on a variety of controlled experiments. In addition, Au nanoparticles are loaded onto the surface of ZnO hollow spheres. It is found that the Au-loaded ZnO(Au/ZnO) composites exhibit greatly enhanced activity on oxidizing Rhodamine B(Rh B) under simulated UV or visible light irradiation, compared to the pristine ZnO hollow spheres. The improved performance of Au/ZnO heterostructures is mainly attributed to the enhanced optical absorption and the accelerated separation and migration of photogenerated charge carriers. Moreover, the photocatalytic reaction mechanisms are proposed based on the results of electron spin resonance(ESR) analysis, photoelectrochemical measurements, and photocatalytic evaluation. The results and findings are expected to provide significance to the synthesis of noble metal-semiconductor hybrids towards water purification.     

A facile method for gold decoration of Te@CdTe nanorods in aqueous solution

Colloidal synthesis of metal-semiconductor hybrid nanostructures is mainly achieved in organic solution. In some applications of hybrid nanoparticles relevant in aqueous media, phase transfer of hydrophobic metal-semiconductor hybrid nanostructures is essential. In this work, we present a simple method for direct synthesis of water-soluble gold (Au) decorated Te@CdTe hybrid nanorods (NRs) at room temperature by using aqueous Te@CdTe NRs as templates, which were preformed by using CdTe nanocrystals (NCs) as precursor in the presence of hydrazine hydrate (N(2)H(4)). Our results showed that NRs were decorated with Au islands both on tips and along the surface of the NRs. The size and density of Au islands can be controlled by varying the amount of Au precursor (mixture of HAuCl(4) and thioglycolic acid (TGA)) and TGA/HAuCl(4) ratio. A possible growth mechanism for the Au decoration of Te@CdTe NRs is concluded as three steps: (1) the formation of AuTe(1.7) via the substitution reaction of Cd(2+) by Au(3+), (2) adsorption of Au-TGA complex onto the preformed AuTe(1.7) anchors and following reduction by CdTe and N(2)H(4), leading to the formation of small Au NCs, (3) Au NCs grow to bigger ones, followed by reduction of more Au precursor by N(2)H(4).     

负载金纳米粒子的聚苯乙烯/聚丙烯酸微球的合成及pH响应性能

以两步聚合法合成的聚苯乙烯(PS)/聚丙烯酸(PAA)核-壳结构复合微凝胶为载体, 硼氢化钠为还原剂, 柠檬酸钠为稳定剂, 通过原位控制性还原获得pH敏感性微凝胶负载纳米金粒子的PS/PAA-Au复合材料. 研究发现, 不同酸碱条件时, 复合微凝胶壳层高分子链的溶胀/收缩变化, 不仅可以调节纳米金粒子的表面等离子吸收, 还可以调节反应底物的扩散传质, 即借助载体微环境的变化来调控纳米金光学性能和催化性能, 从而实现复合纳米金材料的pH调控性.     

BSA mediated Ag@Bi2S3 composites: synthesis,characterization, photodegradation of mixed dyes via metal-semiconductor interface,antimicrobial and antioxidant activities

Nowadays, the development of metal-metal sulfide interface semiconductors using green approach is best material for the photocatalytic and biological applications. Here, we provided for the first time, an environmentally friendly route to fabricate bovine serum albumin (BSA) assisted Ag@Bi₂S₃ composites through a metal-metal sulphide interface via a simple hydrothermal method for the evaluation of photochemical and biological applications. The synthesized composites were characterized by UV–vis DRS, PL, XRD, TEM, and N₂ adsorption-desorption isotherms. The UV–vis DRS and PL spectra show that the obtained nano-sized Ag@Bi₂S₃ composite displays enhanced visible-light absorption and a decreased fluorescence emission compared to that of Bi₂S₃ nanorods (NRs). The photocatalytic performances of the synthesized composites were evaluated by the degradation of the single (RhB and MB) and mixed dye (RhB+MB) under sunlight irradiation. The results indicated that the Ag@Bi₂S₃ composite exhibits superior photocatalytic activity (98.38%) than that of individual Ag NPs and Bi₂S₃ NRs due to the synergistic effect of Ag and Bi₂S₃ nanophases in the Ag@Bi₂S₃ composite, which results in an effective charge separation, fast electron transfer from Ag to Bi₂S₃, and a low recombination of photo-induced electron-hole pairs. The Ag@Bi₂S₃ composite also has good recycling stability up to 5 cycles and its mechanism also investigated. The evaluation of reactive species during the photocatalytic reaction was also carried out. Further, the effects of Bi₂S₃ and Ag NPs on the antimicrobial and antioxidant activity of the resultant Ag@Bi₂S₃ composite were also systematically investigated.     

Experimental and Theoretical Study of Enhanced Photocatalytic Activity of Mg‐Doped ZnO NPs and ZnO/rGO Nanocomposites

A systematic experimental and theoretical study of the origin of the enhanced photocatalytic performance of Mg‐doped ZnO nanoparticles (NPs) and Mg‐doped ZnO/reduced graphene oxide (rGO) nanocomposites has been performed. In addition to Mg, Cd was chosen as a doping material for the bandgap engineering of ZnO NPs, and its effects were compared with that of Mg in the photocatalytic performance of ZnO nanostructures. The experimental results revealed that Mg, as a doping material, recognizably ameliorates the photocatalytic performance of ZnO NPs and ZnO/graphene nanocomposites. Transmission electron microscopy (TEM) images showed that the Mg‐doped and Cd‐doped ZnO NPs had the same size. The optical properties of the samples indicated that Cd narrowed the bandgap, whereas Mg widened the bandgap of the ZnO NPs and the oxygen vacancy concentration was similar for both samples. Based on the experimental results, the narrowing of the bandgap, the particle size, and the oxygen vacancy did not enhance the photocatalytic performance. However, Brunauer–Emmett–Teller (BET) and Barret–Joyner–Halenda (BJH) models showed that Mg caused increased textural properties of the samples, whereas rGO played an opposite role. A theoretical study, conducted by using DFT methods, showed that the improvement in the photocatalytic performance of Mg‐doped ZnO NPs was due to a higher electron transfer from the Mg‐doped ZnO NPs to the dye molecules compared with pristine ZnO and Cd‐doped ZnO NPs. Moreover, according to the experimental results, along with Mg, graphene also played an important role in the photocatalytic performance of ZnO.     

One pot synthesis of Ag nanoparticle modified ZnO microspheres in ethylene glycol medium and their enhanced photocatalytic performance

Ag nanoparticles (NPs) modified ZnO microspheres (Ag/ZnO microspheres) were prepared by a facile one pot strategy in ethylene glycol (EG) medium. The EG played two important roles in the synthesis: it could act as a reaction media for the formation of ZnO and reduce Ag⁺ to Ag⁰. A series of the characterizations indicated the successful combination of Ag NPs with ZnO microspheres. It was shown that Ag modification could greatly enhance the photocatalytic efficiency of ZnO microspheres by taking the photodegradation of Rhodamine B as a model reaction. With appropriate ratio of Ag and ZnO, Ag/ZnO microspheres showed the better photocatalytic performance than commercial Degussa P-25 TiO₂. Photoluminescence and surface photovoltage spectra demonstrated that Ag modification could effectively inhibit the recombination of the photoinduced electron and holes of ZnO. This is responsible for the higher photocatalytic activity of Ag/ZnO composites.     

Microwave-Assisted Synthesis of ZnO–rGO Core–Shell Nanorod Hybrids with Photo- and Electro-Catalytic Activity

The unique two-dimensional structure and surface chemistry of reduced graphene oxide (rGO) along with its high electrical conductivity can be exploited to modify the electrochemical properties of ZnO nanoparticles (NPs). ZnO–rGO nanohybrids can be engineered in a simple new two-step synthesis, which is both fast and energy-efficient. The resulting hybrid materials show excellent electrocatalytic and photocatalytic activity. The structure and composition of the as-prepared bare ZnO nanorods (NRs) and the ZnO–rGO hybrids have been extensively characterised and the optical properties subsequently studied by UV/Vis spectroscopy and photoluminescence (PL) spectroscopy (including decay lifetime measurements). The photocatalytic degradation of Rhodamine B (RhB) dye is enhanced using the ZnO–rGO hybrids as compared to bare ZnO NRs. Furthermore, potentiometry comparing ZnO and ZnO–rGO electrodes reveals a featureless capacitive background for an Ar-saturated solution whereas for an O₂-saturated solution a well-defined redox peak was observed using both electrodes. The change in reduction potential and significant increase in current density demonstrates that the hybrid core–shell NRs possess remarkable electrocatalytic activity for the oxygen reduction reaction (ORR) as compared to NRs of ZnO alone.     

金/氧化亚铜异质球的制备及其可见光催化性能

使用L-半胱氨酸作为连接剂, 利用硼氢化钠原位还原预先吸附在介孔氧化亚铜表面的氯金酸根离子,得到了Au/Cu₂O异质结构. 应用X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱和N₂物理吸附等手段对催化剂进行表征, 并以λ>400 nm的可见光作为光源, 评价了该催化剂光催化降解亚甲基蓝(MB)的活性. 实验结果表明, 直径为4 nm的金颗粒完好地负载在介孔氧化亚铜的表面, 并且介孔氧化亚铜的细微结构与孔径均未发生变化. 研究表明, 以乙醇作为反应溶剂有效抑制了AuCl₄^-与Cu₂O之间的氧化还原反应, 从而有利于氧化亚铜介孔结构的保持及金颗粒的原位还原. 光催化降解亚甲基蓝的结果表明, Au/Cu₂O异质结构的光催化活性比纯氧化亚铜光催化活性有明显提高. 推测其光催化性能提高的主要原因如下: 一方面, 金颗粒良好的导电性有利于氧化亚铜表面电子的快速转移, 实现电子-空穴分离; 另一方面, 金颗粒可能存在的表面等离子共振现象加速了光生电子的产生.     

In situ synthesis and characterization of multiwalled carbon nanotube/Au nanoparticle composite materials

An effective and facile in situ reduction approach for the fabrication of carbon nanotube-supported Au nanoparticle (CNT/Au NP) composite nanomaterials is demonstrated in this article. Linear polyethyleneimine (PEI) is ingeniously used as both a functionalizing agent for the multiwalled carbon nanotubes (MWNTs) and a reducing agent for the formation of Au NPs. This method involves a simple mixing process followed by a mild heating process. This approach does not need the exhaustive surface oxidation process of CNTs. The coverage of Au NPs on CNTs is tunable by varying the experimental parameters, such as the initial molar ratio of PEI to HAuCl4, the relative concentration of PEI and HAuCl4 to MWNTs, and the temperature and duration of the heat treatment. More importantly, even the heterogeneous CNT/Au composite nanowires are obtainable through this method. TEM, XPS, and XRD are all used to characterize the CNT/Au composite materials. In addition, the optical and electrocatalytic properties are investigated.     

Enhanced Photocatalytic Performance of ZnO Nanorods Coupled by Two‐Dimensional α‐MoO3 Nanoflakes under UV and Visible Light Irradiation

We exploit the utilization of two‐dimensional (2D) molybdenum oxide nanoflakes as a co‐catalyst for ZnO nanorods (NRs) to enhance their photocatalytic performance. The 2D nanoflakes of orthorhombic α‐MoO₃ were synthesized through a sonication‐aided exfoliation technique. The 2D MoO₃ nanoflakes can be further converted to substoichiometric quasi‐metallic MoO_3?x by using UV irradiation. Subsequently, 1D–2D MoO₃/ZnO NR and MoO_3?x/ZnO NR composite photocatalysts have been successfully synthesized. The photocatalytic performances of the novel nanosystems in the decomposition of methylene blue are studied by using UV‐ and visible‐illumination setup. The incorporated 2D nanoflakes show a positive influence on the photocatalytic activity of the ZnO. The obtained rate constant values follow the order of pristine ZnO NR<MoO₃/ZnO NR<MoO_3?x/ZnO NR composites. The enhancement of the photocatalytic efficiency can be ascribed to a fast charge carrier separation and transport within the heterojunctions of the MoO₃/ZnO NRs. In particular, the best photocatalytic performance of the MoO_3?x/ZnO NR composite can be additionally attributed to a quasi‐metallic conductivity and substoichiometry‐induced mid‐gap states, which extend the light absorption range. A tentative photocatalytic degradation mechanism was proposed. The strategy presented in this work not only demonstrates that coupling with nanoscale molybdenum oxide nanoflakes is a promising approach to significantly enhance the photocatalytic activity of ZnO but also hints at new type of composite catalyst with extended applications in energy conversion and environmental purification.     

Organosulfur-functionalized Au, Pd, and Au-Pd nanoparticles on 1D silicon nanowire substrates: preparation and XAFS studies

A hybrid preparative method was developed to prepare organosulfur-functionalized Au nanoparticles (NPs) on silicon nanowires (SiNWs) by reacting HAuCl(4) with SiNW in the presence of thiol. A number of organosulfur molecules-dodecanethiol, hexanethiol, 1,6-hexanedithiol, and tiopronin-were used to functionalize the Au surface. Size-selected NPs ranging from 1.6 to 7.5 nm were obtained by varying the S/Au ratio and the concentration of HAuCl(4). This method was further extended to the preparation Pd and Pd-Au bimetallic NPs on SiNWs. The morphology of the metal nanostructures was examined by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The local structure and bonding of the SiNW-supported metal nanostructures were studied using X-ray absorption fine structures (XAFS) [including both X-ray near-edge structures (XANES) and extended X-ray absorption fine structures (EXAFS)] at the Au L(3)-, Pd K-, S K-, and Si K-edges. It was also found that the annealing of the thiol-capped Au NPs up to 500 degrees C transforms the surface of the thiol-capped NPs to gold sulfide, as identified using Au L(3)- and S K-edge XANES. We also illustrate that this preparative approach can be used to form size-controllable Au NPs on carbon nanotubes.     

球磨法制备异质结型光催化剂ZnO/Bi_4Ti_3O_(12)及催化性能

本文用水作为分散介质,掺杂一定量的ZnO于Bi_4Ti_3O_(12)中,采用高能球磨法制备了异质结型光催化剂ZnO/Bi_4Ti_3O_(12).利用UV-Vis、XRD、SEM和PL等仪器对样品进行了分析与表征.以375 W中压汞灯为光源,通过对亚甲基蓝的氧化来研究其光催化活性.结果表明,对于光氧化亚甲基蓝(MB),异质结型光催化剂ZnO/Bi_4Ti_3O_(12)光催化活性高于钛酸铋的光催化活性.当ZnO的掺杂量分别是0.0和0.5wt.%,异质结型光催化剂ZnO/Bi_4Ti_3O_(12)对亚甲基蓝光氧化率分别达到50.2和80.3 %.     

Preparation,characterization and photocatalytic properties of BiOBr/ZnO composites

BiOBr/ZnO composite photocatalysts were prepared by a simple hydrothermal method. The as-prepared samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), high-resolution transmission electron microscopy(HRTEM), UV–Vis diffusion reflectance spectroscopy(DRS) and photoluminescence(PL) spectroscopy, respectively. The photocatalytic activities were evaluated by the degradation of methyl blue(MB) under the simulated sunlight irradiation. Among all the samples, the BiOBr/ZnO composite with a mole ratio of 3:1(Bi:Zn) exhibited the best photocatalytic activity. The improvement of photocatalytic activity was mainly attributed to the low recombination ratio of photo-induced electron-hole pairs. The possible photocatalytic mechanism was discussed on the basis of the band structures of BiOBr and ZnO.     

Au/BiOBr/石墨烯复合物的制备及其苯酚降解光催化性能

采用水热法和多巴胺还原法制备了Bi OBr、Bi OBr/石墨烯和Au/Bi OBr/石墨烯光催化剂,并利用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、光致发光光谱(PL)和紫外-可见漫反射光谱(UV-vis DRS)等方法表征其形貌、相结构、光谱吸收性质以及组成结构。在可见光照射下,通过对水相中苯酚的降解,考察了Au/Bi OBr/石墨烯复合光催化剂活性。结果表明,由于量子效率的提高、带隙能的降低(2.25 e V)以及Au表面等离子体共振,复合光催化剂表现出比纯Bi OBr更高的光催化活性,Au/Bi OBr/石墨烯复合物在180 min内对苯酚降解率可达到64%。     

Size-dependence of Fermi energy of gold nanoparticles loaded on titanium(iv) dioxide at photostationary state

TiO(2) particle-supported Au nanoparticles (NPs) with varying sizes and good contact (Au/TiO(2)) were prepared under a constant loading amount by the deposition-precipitation method. The Fermi energy of Au NPs loaded on TiO(2) at the photostationary state (E(F)') was determined in water by the use of S/S(2-) having specific interaction with Au as a redox probe. The E(F)' value goes up as the mean size of Au NPs (d) increases at 3.0 相似文献   

超声驱动制备Au/CdS催化剂及其高效光催化产氢北大核心CSCD

以HAuCl_(4)为前驱体,采用一种简单、快速的超声驱动法,在甲醇溶液中形成Au纳米粒子并沉积在CdS基底上合成Au/CdS,用于光催化分解水产氢.结果表明:当沉积Au的含量达到1.0%(质量分数)时,Au/CdS的产氢活性显著增强,可达到6.7 mmol·g^(-1) ·h^(-1) ,是纯CdS的21.6倍.超声驱动可在甲醇溶液中有效将前驱体(HAuCl_(4))中的Au3+还原为Au纳米粒子,并与CdS表面紧密作用,提高了光生电荷的分离效率,实现了高效光催化产氢.有关结果为快速、有效制备光催化产氢性能较好的金属/半导体催化剂提供了新的方法.     

Surface-plasmon-enhanced band emission of ZnO nanoflowers decorated with Au nanoparticles

A simple strategy was used to enhance band emission through the transfer of defect emission from ZnO to Au by using the energy match between the defect emission of ZnO and the surface plasmon absorbance of Au NPs through decorating the surface of ZnO nanoflowers with Au nanoparticles (Au NPs). The ZnO nanostructure, which was comprised of six nanorods that were attached on one side in a flower-like fashion, was synthesized by using a hydrothermal method. The temperature-dependent morphology and detailed growth mechanism were studied. The influence of the density of the Au NPs that were deposited onto the surface of ZnO on photoluminescence was investigated to optimize the configuration of the ZnO/Au system in terms of the maximum band emission. The sequential transfer of defect energy from ZnO to Au and electron transfer from excited Au to ZnO was proposed as a possible mechanism for the enhanced band emission.