Microwave assisted hydrothermal synthesis of well-dispersed and thermally stable Ag@SnO2 core–shell nanocomposites for propane sensing applications

A simple microwave assisted hydrothermal precipitation (M–H) technique for the synthesis of Ag@SnO₂ core–shell structure nanoparticles (NPs) is reported. Ag NPs were synthesized via chemical reduction of metal salt followed by M–H deposition of tin dioxide shell for fabrication of monodispersed core–shell particles. The phase and morphology has been investigated by X-ray diffraction technique (XRD) and transmission electron microscopy (TEM) respectively. Ag@SnO₂ core–shell nanocomposites have shown distinct surface Plasmon spectrum in the range of 407–440 nm. The core–shell morphology is confirmed from the TEM images. XRD patterns have suggested the formation of silver and tin dioxide in the face-centered cubic and Cassiterite form respectively. Our investigations suggested that the formation of core–shell structure results in the enhanced thermal stability of the system. Synthesized material is used for the detection of propane gas. To understand the multi gas sensing ability and selectivity for detection of propane gas by Ag@SnO₂ core–shell materials based devices, Sinha–Tripathy soft-sensor model has been proposed.     

Synthesis, characterization and photoluminescence studies of ZnOrod@SnO2 nanocomposites

The synthesis of II-VI semiconductor (ZnO_rod@SnO₂) nanocomposite materials with core-shell morphology has been reported. ZnO nanorods were grown by hydrothermal technique using zinc acetate as the reactant. SnO₂ was coated on the nanorods by a simple technique of colloid chemistry. The formation of tin dioxide shell on the ZnO nanorods was confirmed by the TEM images of the resultant materials. The formation of the nanocomposite was also supported by XRD pattern. The effect of tin dioxide shell on the optical properties of ZnO was investigated by photoluminescence spectroscopy and Raman spectroscopy.     

Studies on the photo-catalytic activity of semiconductor nanostructures and their gold core-shell on the photodegradation of malathion

This work is devoted to the synthesis of different semiconductor nanoparticles and their metal core-shell nanocomposites such as TiO2, Au/TiO2, ZnO, and Au/ZnO. The morphology and crystal structures of the developed nanomaterials were characterized by transmission electron microscopy (TEM) and x-ray diffraction (XRD). These materials were used as catalysts for the photodegradation of malathion, which is one of the most commonly used pesticides in developing countries. The degradation of 10 ppm malathion under ultraviolet (UV) and visible light in the presence of different synthesized nanocomposites was analyzed using high performance liquid chromatography (HPLC) and UV-visible spectra. A comprehensive study was carried out for the catalytic efficiency of the prepared nanoparticles. Moreover, the effects of different factors that could influence catalytic photodegradation, such as different light sources, surface coverage and the nature of the organic contaminants, were investigated. The results indicate that the core-shell nanocomposite of semiconductor-gold serves as a better catalytic system than the semiconductor nanoparticles themselves.     

Chemical fluid deposition of monometallic and bimetallic nanoparticles on ordered mesoporous silica as hydrogenation catalysts

A simple and green method of depositing monometallic (Ru, Rh, Pd) and bimetallic nanoparticles (Ru-Rh, Ru-Pd and Rh-Pd) on an ordered mesoporous silica support (MCM-41) in supercritical carbon dioxide (scCO2) is described. Metal acetylacetonates were used in the experiments as CO2-soluble metal precursors. Suitable temperature and pressure conditions for synthesizing each kind of nanoparticles were applied in this study. The characterizations of these nanocomposites were performed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The nanoparticles had average sizes varying from 2 nm to 8 nm. The Ru nanoparticles were clearly shown to be inside the mesopores of MCM-41 from the TEM image. These nanocomposites used as catalysts for hydrogenation was demonstrated. The efficiency of the scCO2 prepared Ru/MCM-41 catalyst was nearly 8 times than that of a Ru/MCM-41 catalyst prepared by conventional impregnation method.     

ZnS在TiO2纳米管上的分散对其光催化降解染料废水的影响

水热法制备了TiO2纳米管,并采用简单加热回流的方法制备了ZnS/TiO2纳米复合材料。采用TEM、XRD分析手段对产物进行表征,并对其光催化降解酸性玫瑰红B(AR)染料废水进行了研究。考察了反应物供给速率、硫化锌复合量、催化剂稳定性、光照对光催化降解效果的影响。研究表明控制反应物供给速率和硫化锌的负载量可使硫化锌在二氧化钛纳米管表面均匀分散。当染料废水初始浓度为10mg/L,ZnS:TiO2=8:1时,ZnS/TiO2复合材料光催化活性最高。且催化剂稳定性较好。     

CeO2/聚苯胺纳米复合材料的合成与表征

合成了具有核-壳结构的CeO2/聚苯胺纳米复合材料,并用傅立叶变换红外光谱仪(FTIR)、X射线衍射仪(XRD)、透射电子显微镜(TEM)和热分析仪(TG)等对样品的成分、结构、粒度和稳定性进行了表征.结果表明:该纳米复合材料具有核-壳结构,其核平均粒径为17nm,且热稳定性高.     

掺杂ZnO对SnO_2电极烧结性能的影响

通过共沉淀法制备了掺氧化锌的二氧化锡超细粉体,平均粒径为20nm,并制得氧化锡电极样品.主要研究了在氧化锡电极中添加不同含量的ZnO对电极烧结性能的影响情况,分析电极的力学性能、电学性能以及微观结构,结果表明,一定量ZnO掺杂有利于提高SnO2电极的烧结致密化,同时也提高了SnO2电极的导电性.     

磁性分子筛催化剂的制备及其性能

以改性Fe3O4颗粒为核,采用溶胶-凝胶法在Fe3O4核表面包覆SiO2壳层,并在SiO2孔道内负载纳米TiO2颗粒,得到易于固-液分离、平均直径为90~150 nm的具有核壳结构的Fe3O4-TiO2-MCM-41光催化剂复合颗粒,采用透射电镜、X射线衍射、X射线光电子能谱等手段对样品进行表征,并对该催化剂的光催化性能进行测试。结果表明:所制备的磁性分子筛催化剂在紫外光下对苯酚的降解率达94.12%,对重金属离子Cr6+的吸附能达到95.05%。     

Nanoparticulate SnS as an efficient photocatalyst under visible-light irradiation

SnS nanoparticles were synthesized using cheap and less toxic SnCl₂·2H₂O as the tin (II) precursor. The prepared nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-Vis diffuse reflectance spectra (DRS). XRD and TEM results indicate that the prepared product is SnS nanosphere and has a grain size of 5 nm in diameter. DRS show that SnS possesses the absorption profile across the whole visible-light region. Furthermore, SnS has a high photocatalytic activity for the decomposition of Rhodamine B under visible-light. It is proposed that both the strong visible-light absorption and the multiple exciton excitation contribute to the high visible-light photocatalytic activity.     

Sol-gel synthesis of silver/titanium dioxide (Ag/TiO2) core-shell nanowires for photocatalytic applications

Silver/titanium dioxide (Ag/TiO₂) core-shell nanowires were synthesized by direct coating of TiO₂ shells on the surface of silver nanowires (AgNWs) through a simple sol-gel process. TEM image and EDX elemental analysis had confirmed the presence of TiO₂ coating on the surface of AgNWs. The thickness of titanium dioxide coating was about 10 nm. These Ag/TiO₂ core-shell nanowires showed good photocatalytic activities in the decomposition of methylene blue as a model organic dye in aqueous solution under UV light irradiation. Ag/TiO₂ core-shell nanowires are potentially useful in photocatalytic applications.     

TiO2/Co3O4复合纳米颗粒的制备及其光催化制氢性能

通过碳辅助法和溶胶-凝胶法制备了具有可见光下光催化制氢性能的TiO₂/Co₃O₄复合纳米颗粒。采用X射线衍射仪(XRD)、透射电子显微镜(TEM)和高分辨率透射电子显微镜(HRTEM), 以及紫外可见分光光度计表征了复合纳米颗粒的晶体结构、微观形貌和紫外-可见光谱吸收能力。结果表明, 制备的复合纳米颗粒具有良好的晶型、结构以及紫外可见光吸收能力。实验测试了TiO₂/Co₃O₄复合纳米颗粒在模拟太阳光下的光催化制氢性能, 并研究了其光催化制氢的可重复利用性。结果表明, 在模拟太阳光照射下, 该复合纳米颗粒催化纯水产生氢气的速率约为8.25 μmol/(g·h), 且该复合纳米颗粒具有良好的可重复利用性。     

P(S-SS)/CdS核壳粒子的制备与表征

采用超声辐照乳液聚合得到聚(苯乙烯-苯乙烯磺酸钠)(P(S-SS))乳胶粒,用直接沉淀法在乳胶粒表面原位生成硫化镉(CdS)纳米粒子,得到P(S-SS)/CdS核壳粒子。用元素分析和XPS研究了共聚物的组成及磺酸基(-SO3-)的分布,结果表明,-SO3-主要分布在乳胶粒表面,有利于CdS纳米粒子在乳胶粒表面的沉积。用XRD、TEM及UV-v is表征了共聚物乳胶粒及P(S-SS)/CdS核壳粒子的结构及CdS的量子效应。结果表明,所制备的CdS纳米粒子为六方晶型,平均粒径为6 nm,在P(S-SS)乳胶粒外层形成多层包覆,P(S-SS)/CdS核壳粒子平均粒径为70 nm,CdS纳米粒子表现出明显的量子尺寸效应。     

聚苯胺/氧化铜纳米复合材料的制备及抗菌性能

通过水热法制得长2μm,直径100 nm~200 nm的氧化铜纳米棒,然后以此纳米棒采用原位聚合法得到了聚苯胺/氧化铜纳米复合材料。并用傅立叶红外光谱（FT-IR）、扫描电镜（SEM）、热重分析（TG）等测试方法对所得复合材料进行了表征。结果表明,聚苯胺对纳米氧化铜表面包覆,得到了棒状核壳结构的复合材料,当氧化铜添加质...     

稀土Ce掺杂对SnO2电极电学性能的影响

通过共沉淀法制备了铈掺杂二氧化锡超细粉体，平均粒径为20nm，并制得氧化锡电极样品。主要研究了在氧化锡电极中添加不同含量的Ce对电极导电性能的影响情况，通过XRD、SEM和电阻率表征样品性能。实验结果表明，Ce掺杂有利于提高SnO2电极的导电性能，并随Ce含量增加，导电性也提高。共沉淀制得的原料粉体具有纯度高、掺杂均匀等特点，有利于充分发挥添加剂在SnO2电极中起到的提高导电性能的作用，且共沉淀法操作较简便，易实现从实验室制备到实际生产的转化。     

Fabrication of ordered flower-like ZnO nanostructures by a microwave and ultrasonic combined technique and their enhanced photocatalytic activity

Ordered flower-like zinc oxide (ZnO) nanostructures were fabricated via a facile microwave and ultrasonic combined technique. The product was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction pattern (SAED). The flower-like ZnO nanostructures were assembled by a central petal and six symmetrical petals which grew radially from the center. The flower-like ZnO sample showed an enhanced photocatalytic performance compared with the ZnO microrods for the methylene blue (MB) degradation, which could be attributed to its special structure feature. Au/ZnO and Ag/ZnO nanocomposites were also synthesized and exhibited enhanced photocatalytic efficiency after decorating noble metal nanoparticles on the surface of flower-like ZnO nanostructures.     

Synthesis,characterisation and antimicrobial activity of manganese- and iron-doped zinc oxide nanoparticles

The present work reports study on antimicrobial activity of pure and doped ZnO nanocomposites. Polyvinyl pyrrolidone capped Mn- and Fe-doped ZnO nanocomposites were synthesised using simple chemical co-precipitation technique. The synthesised materials were characterised using transmission electron microscope (TEM), X-ray powder diffraction (XRD), energy dispersive X-ray fluorescence (EDXRF), Fourier transform infrared (FTIR) spectroscopy and ultraviolet (UV) visible spectroscopy. The XRD and TEM studies reveal that the synthesised ZnO nanocrystals have a hexagonal wurtzite structure with average crystalline size ～7–14 nm. EDXRF and FTIR study confirmed the doping and the incorporation of impurity in ZnO nanostructure. The antimicrobial activities of nanoparticles (NPs) were studied against fungi, gram-positive and gram-negative bacteria using the standard disc diffusion method. The photocatalytic activities of prepared NPs were evaluated by degradation of methylene blue dye in aqueous solution under UV light irradiation. Experimental results demonstrated that ZnO NPs doped with 10% of Mn and Fe ions showed maximum antimicrobial and photodegradation efficiency in contrast with that of the 1% loading. The enhancement in antimicrobial effect and photocatalytic degradation is attributed to the generation of reactive oxygen species due to the synergistic effects of Mn and Fe loading.     

Ti02光催化核壳材料的研究进展

TiO<,2>核壳材料作为光催化剂具有活性高、稳定性强、普适性广、应用前景广阔等优点而引起了人们广泛的兴趣.综述了近年来TiO<,2>核壳材料用作光催化剂的最新研究成果,主要包括TiO<,2>与金属、半导体、磁性材料等复合所得核壳材料及TiO<,2>自身组成核壳材料在光催化领域的应用,指出TiO<,2>与金属、半导体复合或离子掺杂等所得核壳材料都不同程度地提高了其催化性能;与磁性材料复合时虽然易于分离但是活性不理想;当以TiO<,2>为核时,通过控制合成条件可以制备出孔径不同的TiO<,2>壳层,该类核壳材料可以选择性地降解有机物.最后指出深入探讨TiO<,2>核壳材料光催化机理、开发易回收高效TiO<,2>催化剂及寻找简易制备TiO<,2>核壳材料的方法是未来TiO<,2>核壳材料研究的重要方向.     

碳包覆氧化亚钴纳米颗粒的制备与性能研究

采用直流电弧放电等离子体技术成功制备了碳包覆氧化亚钴纳米颗粒,并对样品的形貌、晶体结构、粒度、比表面积和孔结构采用高分辨透射电子显微镜(HRTEM)、X射线衍射(XRD)、X射线能量色散光谱(XEDS)、拉曼散射光谱(Raman)和N_2吸-脱附等测试手段进行了分析。HRTEM表明该方法制备的碳包覆氧化亚钴纳米颗粒具有典型的核壳结构,颗粒形貌主要为球形或椭球结构,粒度均匀,分散性良好,粒径分布在20~60nm,平均粒径为40nm,外壳碳层的厚度为5nm。XRD证明样品的内核为面心立方结构的氧化亚钴纳米颗粒,外壳为碳层。XEDS图谱表明样品中主要存在Co、O和C元素的特征峰。Raman光谱说明样品中碳外包覆层的石墨化程度较低,发生了红移现象。样品的N_2吸附-脱附等温曲线属Ⅳ型,BET比表面积为33m~2/g,BJH脱附累积总孔孔容和脱附平均孔径分别为0.078cm~3/g和11nm。当量粒径为43nm,与TEM和XRD测得的结果基本一致。     

Band gap narrowing and photocatalytic studies of Nd<Superscript>3+</Superscript> ion-doped SnO<Subscript>2</Subscript> nanoparticles using solar energy

Pure and Nd³⁺-doped tin oxide (SnO₂) nanoparticles have been prepared by the sol–gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive spectroscopy and UV–visible spectroscopy. The XRD patterns of all the samples are identified as tetragonal rutile-type SnO₂ phase which is further confirmed by TEM analysis. Neodymium doping introduces band gap narrowing in the prepared samples and enhances their absorption towards the visible-light region. The photocatalytic activity of all the samples was evaluated by monitoring the degradation of methylene blue solution under day light illumination and it was found that the photocatalytic activity significantly increases for the samples calcined at 600 than 400°C, which is due to the effective charge separation of photogenerated electron–hole pairs. The efficiency of photocatalysts was found to be related to neodymium doping percentage and calcination temperature.     

Electrical and optical studies in polyaniline nanofibre–SnO2 nanocomposites

Polyaniline nanofibre–tin oxide (PAni-SnO₂) nanocomposites are synthesized and mixed with polyvinyl alcohol (PVA) as stabilizer to cast free-standing films. Composite films are characterized by X-ray diffraction studies (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL) and UV-visible spectroscopy. XRD confirms the formation of PAni nanofibre–SnO₂ nanocomposite. From TEM images, diameter of the polyaniline nanofibre and SnO₂ nanoparticles in the PAni-SnO₂ nanocomposite are found to be 20–60 nm. SEM results show fibrous morphology of the PAni nanofibre and spherical morphology of polyaniline-SnO₂ composites. The nanocomposites exhibit high relative photoluminescence intensity in violet as well as green–yellow region of visible spectrum. From electrical conductivity measurement, it is confirmed that PAni nanofibre–SnO₂ nanocomposite follows Mott’s one-dimensional variable range hopping (VRH) model.