Ag2S/Ag2WO4微米棒的声化学合成、表征及其高光催化性能

TiO2作为一种光催化剂广泛应用于各种污染物的降解.但是它较大的宽禁带(~3.2 eV)导致其很难吸收可见光,因此寻找窄禁带的具有可见光响应的半导体光催化剂成为近年来光催化研究的热点.在众多窄禁带光催化剂中,纯 Ag2S在降解污染物方面并不出色,但是作为一种窄禁带的直接带隙半导体,它在加快电子迁移和提高光量子效率方面表现出色.目前有许多高催化活性的 Ag2S异质结复合半导体光催化剂的报道,如 Ag2Mo3O10-Ag2S, TiO2-Ag2S, ZnS-Ag2S和NiO-Ag2S等. Ag2WO4是一种具有新颖物理化学性质的半导体材料,在催化、传感器、抗菌和光致发光等方面有着广泛应用.但是, Ag2WO4的理论带隙较宽,约为3.5 eV,而且光照下Ag2WO4很容易产生光化学腐蚀而分解出单质银,作为光催化剂存在太阳光利用率低和稳定性较差等缺点.声化学是一种特殊纳米材料的合成方法.它主要是利用超声空化产生特殊的物理化学环境来强化化学键的生成,同时实现半导体从无定形态到固定晶型转变.本文采用超声辅助共沉淀法制备了长为0.2?1μm、直径为20?30 nm的 Ag2S/Ag2WO4微米棒复合光催化剂.利用 X射线衍射(XRD)、N2物理吸附、扫描电镜、透射电镜、光电子能谱、光致发光谱(PL)和紫外-可见漫反射吸收光谱(UV-vis DRS)和光电流等手段对所制 Ag2S, Ag2WO4和 Ag2S/Ag2WO4进行了表征.结果表明,合成的样品比表面积较小(2.7?3.6 m2/g). UV-vis DRS测试表明,声化学处理能有效拓宽 Ag2S/Ag2WO4在可见光区的吸收范围,提高其可见光响应性能.另外, PL和光电流测试结果证实,在声化学制备的 Ag2S/Ag2WO4体系中,光生电子(e?)-空穴(h+)的复合过程被极大地限制,具有较高的 e?-h+分离效率.以金卤灯为光源进行了光催化降解染料亚甲基蓝的性能测试.结果表明,声化学合成的 Ag2S/Ag2WO4的反应速率常数(0.150 min?1)分别为单纯 Ag2WO4(0.031 min?1)和 Ag2S (0.004 min?1)的4.7和29.8倍.自由基捕获实验表明,在 Ag2S/Ag2WO4光催化降解甲基橙过程中主要的活性物种为超氧自由基(?O2?)和光生空穴(h+).此外,声化学合成的 Ag2S/Ag2WO4表现出很好的光催化稳定性.循环使用3次后,该样品对亚甲基蓝的光催化活性仍高达80.4%,而纯 Ag2WO4几乎完全失活. Ag2S/Ag2WO4具有很高的光催化活性的原因,一方面是声化学处理提高了催化剂的结晶度,同时生成了独特的棒状结构;另一方面是在超声作用下, Ag2S和 Ag2WO4两相紧密接触形成异质结,促进了可见光的吸收和光生 e?与 h+的分离.     

半胱氨酸在Ag2S/Cu2S纳米晶修饰玻碳电极上的电化学行为

制备了Ag2S/Cu2S纳米混晶修饰玻碳电极,研究了半胱氨酸在Ag2S/Cu2S纳米混晶修饰电极上的电化学行为.结果表明:Ag2S/Cu2S混晶修饰电极对半胱氨酸的电化学氧化过程具有非常明显的电催化作用,其氧化电位减小为0.23V,氧化峰电流为25.98 μA,与空白电极相比增加了8倍.在1.0×10-5～1.0×10-3 mol/L浓度范围内,稳态电流信号与半胱氨酸浓度呈现良好的线性变化关系.该修饰电极具有良好的稳定性和重现性.     

银/金纳米线阵列表面增强拉曼基底的制备及对孔雀石绿的高灵敏度检测

利用种子介导的软模板生长方法制备了金纳米线(Au NWs)阵列, 通过调节生长温度控制Au NWs阵列的形貌, 最后在经硼氢化钠(NaBH₄)清洗过的Au NWs阵列上化学沉积银纳米颗粒(Ag NPs), 制得银/金纳米线(Ag/Au NWs)阵列作为表面增强拉曼散射(SERS)基底. 选用罗丹明6G(R6G)作为拉曼探针分子测定了Ag/Au NWs阵列的SERS性能. 结果表明, Ag/Au NWs阵列作为SERS基底具有高灵敏度、 优异的信号均匀性和良好的稳定性. 使用Ag/Au NWs阵列对孔雀石绿(MG)检测的检出限可低至1×10^-8 mol/L, 线性范围为 1×10^-8~1×10^-4 mol/L. NaBH₄可以在不影响SERS性能的情况下去除Ag/Au NWs阵列上吸附的分子, 使得 SERS基底可以重复使用. 使用Ag/Au NWs阵列对湖水中的MG进行检测, 得到了可靠的回收率, 证明Ag/Au NWs 阵列在检测环境水体中的孔雀石绿上具有应用潜力.     

Preparation and femtosecond non-linear optical properties of Ag/SiO2 composite thin films

Ag nanoparticles embedded in SiO₂ thin films (Ag/SiO₂ films) were prepared by a multitarget sputtering method. In the optical absorption spectra of the Ag/SiO₂ films, the absorption peak due to the surface plasmon resonance (SPR) of Ag particle was clearly observed at the wavelength of 394–413 nm. The imaginary part of the third-order non-linear susceptibility, Im [χ⁽³⁾], of the Ag/SiO₂ film was estimated to be ?1.1×10^?8 esu measured by the femtosecond Z-scan technique near the SPR peak. The response time of the film measured from the decay of the differential transmission of the pump-probe experiment was 1.3 ps at the SPR peak.     

Study on the visible-light photocatalytic performance of Ag3PO4/Cu2O composite

Research on Chemical Intermediates - Ag3PO4/Cu2O composites were prepared by a facile wet chemical method. The specimens were examined by X-ray diffraction, scanning electron microscopy,...     

Photochemical Synthesis of Cu2O and Cu2O/Ag Nanoparticles in Polyols

Russian Journal of General Chemistry - Cu2O nanoparticles were synthesized by photoreduction of copper(II) complex compounds with ethylene glycol and glycerin in the photolite volume. Their optical...     

Fabrication of PZT/CuO composite films and their photovoltaic properties

In this paper, we reported the design and preparation of a double-layer antireflective (AR) coating, which possessed relatively high transmittance at 351, 527, and 1053?nm. The refractive indices and film thicknesses of the under layer and upper layer of the simulated AR coating were determined as 1.27, 95?nm and 1.18, 106?nm, respectively. The under layer of the double-layer coating dip-coated from a mixture of base-catalyzed and acid-catalyzed silica sols had a refractive index of 1.27. The upper layer fabricated by the deposition of methylated silica nanoparticles by simply adding methyltriethoxysilane into the base-catalyzed silica sols possessed a refractive index of 1.18. The hydrophobicity of coatings could be dramatically improved with the water contact angle increasing from 23.4° to 150.0°, and the refractive indices of the pure base-catalyzed silica coatings were easily decreased from 1.20 to 1.12 through the surface treatment of silica nanoparticles. Thus, we have successfully prepared a double-layer AR coating, which had a high transmittance of 99.8%, 96.1%, and 99.7% at 351, 527, and 1053?nm, respectively.

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ZnFe2O4/Ag/TiO2复合材料的制备及其光催化性能

以硝酸银、钛酸四丁酯、无水氯化锌、六水氯化铁为原料,采用溶胶-凝胶法与溶剂热相结合的方法制备了ZnFe₂O₄/Ag/TiO₂复合材料,通过扫描电子显微镜、能谱分析仪、X射线粉末衍射仪、X射线光电子能谱仪、振动样品磁强计、紫外可见分光光度计对样品进行表征及测试。结果表明： ZnFe₂O₄/Ag/TiO₂-10具有最佳的光催化效果,在紫外和可见光下对染料的降解率都能达到90%以上,具有优异的紫外可见光光催化活性。ZnFe₂O₄/Ag/TiO₂具有独特的磁性,能在外部磁场作用下进行回收利用,这使其在实际应用中成为可能。通过磁分离技术重复回收利用5次后仍然保持优良的光催化性能,说明ZnFe₂O₄/Ag/TiO₂-10具有优异的磁性及较高的光催化循环稳定性。     

ZnFe2O4/Ag/TiO2复合材料的制备及其光催化性能

以硝酸银、钛酸四丁酯、无水氯化锌、六水氯化铁为原料,采用溶胶-凝胶法与溶剂热相结合的方法制备了ZnFe₂O₄/Ag/TiO₂复合材料,通过扫描电子显微镜、能谱分析仪、X射线粉末衍射仪、X射线光电子能谱仪、振动样品磁强计、紫外可见分光光度计对样品进行表征及测试。结果表明：ZnFe₂O₄/Ag/TiO₂-10具有最佳的光催化效果,在紫外和可见光下对染料的降解率都能达到90%以上,具有优异的紫外可见光光催化活性。ZnFe₂O₄/Ag/TiO₂具有独特的磁性,能在外部磁场作用下进行回收利用,这使其在实际应用中成为可能。通过磁分离技术重复回收利用5次后仍然保持优良的光催化性能,说明ZnFe₂O₄/Ag/TiO₂-10具有优异的磁性及较高的光催化循环稳定性。     

Antibacterial and photocatalytic properties of Cu2O/ZnO composite film synthesized by electrodeposition

Research on Chemical Intermediates - The high antibacterial and photocatalytic activities of Cu2O/ZnO composite films were synthesized through the electrodeposition method. The crystalline phase...     

Benzyl alcohol oxidation and hydrogen generation over MoS2/ZnIn2S4 composite photocatalyst

Research on Chemical Intermediates - Owing to the simultaneous utilization of photogenerated electrons and holes, coupling light-driven hydrogen (H2) evolution reaction (HER) and biomass-derived...     

W/Cu(Ag)/S complexes containing bridging diphosphine ligands: Synthesis,structures and optical properties

The substitution reactions of [Et₄N]₂[WOS₃MCN] (M = Cu, Ag) with dppe (dppe = 1,2-bis(diphenylphosphino) ethane) in DMF afforded a tetranuclear cluster [Et₄N]₂[WOS₃Cu(dppe)]₂ · H₂O (1) and a polymer [WEE′S₂Ag(dppe)]₂ · CH₃CN (3) (E = 0.636S + 0.364O, E′ = 0.581O + 0.419S), respectively. Treatment of 1 with AgI at elevated temperature yielded polymeric complex [WS₄Cu₂(dppe)₂]_n (2). X-ray single crystal structural analyses revealed that in both 1 and 2, the W/Cu/S cluster units are linked by two dppe ligands to form a 10-membered [–Cu–P–C–C–P–]₂ ring. In the polymeric structure of 2, the W and Cu atoms form a helical chain whereas in 3 the cluster units (WEE′S₂Ag) are bridged by dppe ligands affording a zig-zag chain structure. The optical absorption spectra and the solid-state photoluminescent properties of the title complexes are also studied.     

Fabrication and photocatalytic activity of TiO2/SiO2 composite nanotubes

TiO₂/SiO₂ composite nanotube photocatalysts supported on Al substrates were prepared by the anodic aluminum oxide (AAO) liquid-phase deposition method for degradation of 100 mg/L methyl blue (MB). AAO templates were prepared in H₃PO₄ acidic electrolytes through the two-step anodic oxidation method. The photocatalysts were characterized by field-emission scanning electron microscopy, thermal analysis (TG-DTA), and Fourier-transform infrared, x-ray photoelectron, and UV?CVis diffuse spectroscopies. The results showed that the presence of SiO₂ in TiO₂ inhibited the crystal phase transformation temperature effectively, with a greater wall thickness of 80?C100 nm. It was found that Ti?CO?CSi bonds were formed on the surface and the surface hydroxyl concentration was increased, resulting in enhanced photocatalytic activity, being about 20% higher than for pure TiO₂ films. The calculated band structure for TiO₂/SiO₂ was investigated using first-principle calculations. The TiO₂/SiO₂ composite exhibited a wider conduction band which would effectively prohibit recombination of photogenerated electrons and holes.     

Impact of PS/SiO2 morphologies on the SERS activity of PS/SiO2/Ag nanocomposite particles

To understand the relationship between the morphology of carboxyl-functionalized polystyrene/silica (PS/SiO₂) nanocomposite microspheres and the surface-enhanced Raman scattering (SERS) performance of PS/SiO₂/Ag nanocomposite particles, core-shell and raspberry-like PS/SiO₂ composite microspheres were used as templates to prepare PS/SiO₂/Ag nanocomposite particles. The core-shell and raspberry-like structured PS/SiO₂ templates were prepared via in situ sol-gel reaction by hydrolysis tetraethyl orthosilicate (TEOS) in alkali solution. Silver nanoparticles (10–50 nm) were loaded on the PS/SiO₂ templates’ surface by chemical reduction. The morphology and structure of the PS/SiO₂/Ag particles were characterized by TEM, SEM, X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. Rhodamine 6G (R6G) was selected as a model chemical to study the enhancement performance of substrate constructed by PS/SiO₂/Ag nanocomposite. Results indicated that the PS/SiO₂/Ag nanocomposite prepared based on the core-shell templates showed higher SERS activity. The beneficial effect was associated with a lower specific area of core-shell structure and the larger average diameter of nanosilvers than that of the raspberry-like templates.     

Fabrication and Formation Mechanism of Ag Nanoplate‐Decorated Nanofiber Mats and Their Application in SERS

We report a new simple method to fabricate a highly active SERS substrate consisting of poly‐m‐phenylenediamine/polyacrylonitrile (PmPD/PAN) decorated with Ag nanoplates. The formation mechanism of Ag nanoplates is investigated. The synthetic process of the Ag nanoplate‐decorated PmPD/PAN (Ag nanoplates@PmPD/PAN) nanofiber mats consists of the assembly of Ag nanoparticles on the surface of PmPD/PAN nanofibers as crystal nuclei followed by in situ growth of Ag nanoparticles exclusively into nanoplates. Both the reducibility of the polymer and the concentration of AgNO₃ are found to play important roles in the formation and the density of Ag nanoplates. The optimized Ag nanoplates@PmPD/PAN nanofiber mats exhibit excellent activity and reproducibility in surface‐enhanced Raman scattering (SERS) detection of 4‐mercaptobenzoic acid (4‐MBA) with a detection limit of 10^?10 m , making the Ag nanoplates@PmPD/PAN nanofiber mats a promising substrate for SERS detection of chemical molecules. In addition, this work also provides a design and fabrication process for a 3D SERS substrate made of a reducible polymer with noble metals.     

微芯片上Ag2S电化学纳米开关的构筑及电学测量的初步研究

初步探索了利用电化学方法“自下而上”地构筑了Au/Ag/Ag2S-Au固体电化学纳米开关, 并确定了较适宜的开关工作条件. 小于1 nm的Ag2S-Au间隔是Ag2S开关器件的关键结构, 以保证电子的量子遂穿和间隔中Ag凸起的生长与收缩. 测量结果表明, Ag2S开关转换具有较好的可逆性和稳定性, 开关转换电流相差3个数量级以上.     

First principles calculations of electronic and optical properties of Ag2S

A theoretical study of structural, electronic and optical properties of Ag₂S is presented using the full potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). In this approach, the modified Becke Johnson (MBJ) potential coupled with Local Density Approximation (LDA) was used for the exchange-correlation potential calculation. Ground state properties are determined for the bulk material in monoclinic phase. Band structure reveals that this compound is a direct energy band gap semiconductor. MBJLDA results for the band gap of this compound are much better than those obtained using LDA, Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) and Engel–Vosko's GGA (EV-GGA). A very good agreement is observed between MBJLDA band gap and corresponding experimental values as compared to other calculations. Optical constants including the dielectric function, refractive index, extinction coefficient, electron energy loss function, reflectivity and absorption coefficient are obtained and discussed.     

理论研究Ag/MPH/TiO2体系的SERS光谱化学增强机理

采用密度泛函理论研究了Ag/对巯基苯酚(MPH)/TiO₂体系的表面增强拉曼散射(SERS)光谱化学增强机理. 分别研究了Ag₁₃/MPH和Ag₁₃/MPH/TiO₂复合物在514.5 nm激发波长下的拉曼光谱, 发现由于TiO₂的引入, 发生了非完全对称振动模式峰选择性增强的现象. 通过对电荷转移复合物基态和激发态的指认, 发现当激发波长大于MPH-TiO₂电荷转移复合物的光学吸收阈值(635 nm)时, 该体系内将发生从Ag到MPH-TiO₂部分的光诱导电荷转移现象. SERS光谱中b₂模式的选择性增强, 来源于相应振动模式与电荷转移跃迁的耦合(Herzberg-Teller机制). 我们的理论结果不仅支持了实验现象, 并且明确界定了电荷转移复合物, 对于该体系存在的光依赖SERS现象提供了一个清晰的理论阐述.