硫化镉纳米结构的制备与光学性质研究

采用直接热蒸发CdS粉末的方法,在不同的生长条件下制备出CdS纳米线和纳米带材料并对其形貌、结构和光学性质进行了研究.CdS纳米线具有单晶结构,且生长方向具有择优取向,而其纳米带不具有上述结构特征.光致发光光谱研究发现,室温下纳米线只在508 nm出现了CdS的本征发射带.然而,纳米带存在2个明显的发光峰,中心峰位分别位于513 nm和756 nm.这2个发射峰可分别指认为CdS的本征发射和V_s~+空位引起的发射.     

第一性原理方法研究CdS能带结构

使用基于局域密度近似的密度泛函方法,对立方相和六方相CdS的结构进行了模拟计算.结果表明:2种晶相的CdS不仅禁带宽度非常相近,两者相差8.51%,而且导带边都是由Cd5s轨道贡献,价带边都是由S3p轨道贡献.这种相似的能带结构导致立方相和六方相CdS在可见光波段具有相近的光学性能,从而解释了实验获得的两相混合CdS仍然能够具有较好光学性能的现象.     

溶剂对溶剂热合成CdS纳米晶体的形貌控制

以溶剂热法在不同溶剂里的160℃下反应12 h制备不同形貌的CdS纳米晶粒,分别选用水(H2O)、二甲基甲酰胺(DMF)、乙醇胺(an)和乙二胺(en)为溶剂来控制纳米CdS的形貌和尺寸.对样品的结构和性能进行表征,重点分析了溶剂的物理性质和结构特征对CdS纳米粒子晶体结构、形貌和尺寸的影响,不同溶剂的作用机制不同,可通过选择合适的反应溶剂来控制纳米粒子的形貌和尺寸,以制备满足不同应用需要的纳米结构,尤其是性能独特的一维纳米结构.     

银纳米线的改进溶剂热法合成与表征

采用溶剂热法和晶种法相结合的改进方法,以硝酸银为银源,乙二醇为还原剂,聚乙烯吡咯烷酮为稳定剂和分散剂,制备银纳米颗粒晶种,进而在溶剂热环境中合成了高均匀性的银纳米线。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、和紫外-可见光分光光度计(UV-Vis)对产物的尺寸形貌、晶体结构以及光学性能进行了表征。结果表明,利用改进的溶剂热法制备的银纳米线具有较高的长径比,尺寸分布均匀,分散性良好,具有优异的等离激元共振吸收特性。     

湿化学法合成高矫顽力FeCo纳米线及其磁性能

FeCo纳米材料具有高的饱和磁化强度和较大的磁导率，具有广阔的应用前景。但如何制备出高磁晶各向异性能的FeCo纳米材料，一直是该领域的难点。研究表明，各向异性的一维纳米线可以提高材料的磁性能。因此提出一种简便的湿化学法，通过溶剂十六胺以及表面活性剂油胺和油酸的配合、诱导，直接合成一维的FeCo纳米线。借助形状各向异性增强了FeCo相的磁晶各向异性，成功制备出具有较高矫顽力的FeCo纳米线。调节反应温度可对FeCo纳米材料的形貌和磁性能进行调控，在反应温度为280℃时，获得了分散均匀的一维FeCo纳米线。该纳米线的矫顽力H_c高达1 092 Oe,饱和磁化强度M_s为113 emu/g。为可控制备具有高矫顽力的一维FeCo纳米材料提供了新的路线和实验依据。     

大面积SiC纳米线网的合成及形成机理

利用气相化学反应法,在相对低的温度下,于自制石墨反应室中合成出二维半导体β-SiC纳米线网.该方法使用球磨及研磨混合后的Si和SiO2混合粉体及C3H6气体为原材料,通过调整基片与原料混合粉在石墨反应室的摆放位置、C3H6通入流量和时间、保温时间及其它工艺参数,可获得二维半导体β-SiC纳米线网.场发射扫描电镜、能量损失谱、X-Ray衍射、高分辨透射电镜结果表明纳米线彼此相连形成二维纳米线网,并且纳米线的直径大约在20 nm～70nm左右.值得注意的是绝大多数纳米线网的连接点是由3根纳米线交汇而成.纳米线是具有立方结构的β-SiC,其生长方向是〈111〉,并且存在大量面缺陷.最后对这种新型二维SiC纳米线网的形成机理进行了探讨.     

Bi2Te3纳米颗粒和纳米线的溶剂热合成及组织特征

分别以吡啶、无水乙醇为反应介质,以NaBH4为还原剂,采用溶剂热合成方法,在150℃下反应24 h制备了平均晶粒尺寸为15～20 nm的Bi2Te3纳米粒子.采用相同的合成方法,以去离子水为反应介质,合成了直径为30～80 nm,长径比大于100的Bi2Te3纳米线.XRD和TEM分析表明,随着溶剂介电常数和极性增加,所生成产物的物相纯度、结晶度增高,晶粒尺寸增大.     

溶剂热处理对ZnS和CdS超细粉末结构形貌的影响

采用均相沉淀法制备单分散的ZnS和CdS纳米微粒，考察了溶剂热处理对CdS和ZnS粉末结构形貌的影响。结果表明：采用溶剂热处理，粉末形状呈现负离子配位多面体生长特征，闪锌矿型ZnS粉末由球形变为双锥状或四面体状，颗粒上有明显的电子衍射花纹；闪锌矿型CdS晶体粉末主要呈四面体形状，而纤锌矿型CdS晶体粉末则以锥状为主，并且粉末的晶型随溶剂热处理温度的升高和时间的延长更趋于完整。该工艺能同时进行脱水、除杂和晶化，具有防止氧化、有机试剂易于回收和能工业化等优点。     

InN纳米线的制备与表征

采用静电纺丝法制备出了高长径比的立方相In2O3纳米线。将In2O3纳米线置于NH3气流中进行原位氮化反应,合成得到了高质量的InN纳米线,转化率高达100%。通过调节氮化反应的温度及时间,系统研究了制备InN纳米线的最佳合成工艺参数。利用这种方法得到的氮化铟纳米线具有长径比高、直径分布单一、纯度高以及产量大的特点,为今后InN纳米器件的大规模制备和应用提供了一个有效的途径。     

微波水热法制备分等级空心球状CdS纳米结构(英文)

以氯化镉和硫代硫酸钠为原料,以乙二胺四乙酸(EDTA)为模板剂,采用微波水热(M-H)法成功制备了空心球状 CdS 纳米结构。采用 X 射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、能量弥散X射线谱(EDS)和高分辨透射电子显微镜(HRTEM)对所制备的CdS 纳米结构进行表征。采用紫外-可见吸收光谱研究所制备的分等级空心球状 CdS 纳米结构的光学性能。结果表明:得到的CdS是具有纤锌矿结构的直径为 400～600nm的分等级空心球状纳米结构,这种结构由30nm左右的纳米颗粒自组装构成。EDTA和微波辐射在分等级空心球状 CdS纳米结构的形成过程中起了重要作用,讨论了这种作用并提出可能的生长机理。所制备的分等级空心球状CdS纳米结构具有较好的蓝光发射性能。     

Diphenylthiocarbazone (dithizone)-assisted solvothermal synthesis and optical properties of one-dimensional CdS nanostructures

One-dimensional (1D) cadmium sulfide (CdS) nanostructures with various aspect ratios were successfully synthesized by a diphenylthiocarbazone (dithizone)-assisted solvothermal method. The results showed that the dithizone-assisted synthesized samples had larger aspect ratio than that prepared in the absence of dithizone, and CdS nanowires with the highest aspect ratio were obtained with an appropriate dithizone amount (0.03 g/50 ml ethylenediamine in the present system). All the 1D CdS nanostructures were in hexagonal wurtzite phase. The as-synthesized large-scale CdS nanowires were in diameters ranging from 70 to 80 nm, length up to 20 μm, and aspect ratios of 250-285. Further characterization indicated that the CdS nanowires were single crystalline with a preferential growth orientation of [0 0 2], c-axis. Two optical absorption peaks were observed at about 488 nm and 502 nm for the CdS nanowire sample with high aspect ratio in the optical absorption spectroscopy, which could be attributed to the nanometer effect of nanowires. It was found that the additive dithizone was a crucial factor in controlling the morphology and optical properties of the 1D CdS nanostructures. The growth mechanism of 1D CdS nanostructure and the effects of dithizone in the present system were discussed.     

Growth of CdS thin films and nanowires for flexible photoelectrochemical cells

In this study, cadmium sulfide (CdS) nanocrystal thin films and nanowires have been deposited onto mechanically flexible substrates via dc-electrodeposition, which is a very suitable technique for large area manufacturing. For the first time with this study, flexible CdS nanocrystal thin films were integrated into photoelectrochemical (PEC) cells and their performances were compared with CdS nanowires. It has been demonstrated that PEC performance of both nanocrystal thin films and nanowires were a strong function of production conditions such as deposition time and voltage. The maximum power conversion efficiency of the CdS nanocrystal thin films obtained in this study was 0.3%. On the other hand, higher efficiencies (about 1.4%) were observed for the CdS nanowires. UV-vis analysis confirmed that both transmittance and band gap energies of the CdS nanowires were lower than that of CdS nanocrystal thin films. X-ray diffraction analysis revealed that both nanocrystal thin films and nanowires have a preferred orientation at 26° (2θ), which can be attributed to the CdS (0 0 2) structure.     

Solution-based synthesis of ZnO nanoparticle/CdS nanowire heterostructure

The heterostructure of ZnO nanoparticle (NP)/CdS nanowire (NW) was successfully fabricated by a two-step chemical solution method. The first, CdS nanowires were synthesized by a simple solvothermal route. The second, ZnO nanoparticles were grown on the surface of CdS nanowires in a chemical solution of Zn(CH₃COO)₂·2H₂O and anhydrous ethanol at 200 °C. The heterostructure of synthesized ZnO NP/CdS NW was characterized by transmission electron microscopy (TEM). The effects of reaction conditions, such as different reaction time of CdS nanowires synthesized and deposition reaction time were investigated. Moreover, the formation mechanism of the ZnO NP/CdS NW heterostructure has been phenomenologically discussed.     

Formation of Ag2S nanowires and Ag2S/CdS heterostructures via simple solvothermal route

In our present work, Ag₂S nanowires and Ag₂S/CdS heterostructures have been successfully prepared in anhydrous ethanol through a simple solvothermal route. From the transmission electron microscopy (TEM) analysis, it is found that the factors influenced the final product are the concentration of Ag⁺, reaction temperature, reaction time, and solvent. Ag₂S nanowires are formed by complete Ag⁺ cation exchange. Because of the selectivity for partial cation exchange, the reaction starts preferentially at the ends of the CdS nanowires to produce novel Ag₂S/CdS heterostructures. In addition, as the two end facets of wurtzite CdS nanowires are crystallographically nonequivalent, the produced Ag₂S/CdS heterostructures are asymmetric.     

不同维度的银微纳米材料研究进展

微纳米材料的性能受到其形貌的影响,以维度为分类原则,综述了不同类型银微纳米的制备和应用进展。零维的银纳米材料包括银原子和粒径小于15 nm的银纳米粉,主要提高催化性能、抗菌及光性能;一维的银纳米线由化学还原法制备,主要用于透明纳米银线薄膜制备的柔性电子器件;二维的银微纳米片可用球磨法、光诱导法、模板法等方法制备,其在导电浆料及电子元器件等方面有广泛的应用;三维的银微纳米材料包括球形和异形银粉,球形银粉主要用于导电浆料填充物,异形银粉主要应用催化、光学等方面。改善制备方法,实现微纳米材料的形貌控制,提升产物稳定性,是银纳米材料研究的发展方向。     

Influence of different solvents on the structural, optical and morphological properties of CdS nanoparticles

CdS is one of the most important II-VI semiconductors, with applications in solar cells, optoelectronics and electronic devices. CdS nanoparticles were synthesized via microwave-assisted solvothermal technique. Structural and morphological characterization revealed the presence of crystalline structures presenting single phase with different morphologies such as “nanoflowers” and nanoplates depending on the solvent used. Optical characterization was made by diffuse reflectance and photoluminescence spectroscopy, revealing the influence of the different solvents on the optical properties due to structural defects generated during synthesis. It is proposed that these defects are related to sulfur vacancies, with higher concentration of defects for the sample synthesized in ethylene glycol in comparison with the one synthesized in ethylene diamine.     

水热法制备ZnS/Ag复合纳米线及其光催化性能研究

采用水热法制备了负载Ag的ZnS纳米线,通过XRD, TEM以及UV-Vis对所合成的纳米线的相结构、形貌以及光学性能进行了表征。并以甲基橙为目标降解物,评价了所制备的复合纳米线在紫外光下的光催化性能。研究结果表明,水热法制备的ZnS纳米线对甲基橙溶液的光催化活性比商业ZnS粉体更高,并且银的负载对ZnS纳米线的光催化活性有显著的提高作用。这是由于银粒子复合ZnS纳米线能促进光生电子空穴对分离,增多ZnS纳米线的反应活性点,从而提高其光催化活性     

核壳结构CdS/TiO2的制备与表征

通过水热法合成分散性良好的CdS纳米颗粒,并采用声化学法在颗粒外包覆TiO2壳层,获得的复合材料具有更好的光催化特性.讨论了水热反应温度保温时间与晶粒尺寸、结晶性之间的关系以及声化学制备过程中反应条件与陈化时间对壳层生长的影响.采用X射线衍射、透射电镜、漫反射光谱、光催化性能测试等手段表征CdS颗粒的尺寸、形貌及CdS/TiO2的结构与光催化特性.结果表明水热过程中,提高反应温度、保温时间有利于提高产物的结晶性.声化学合成CdS/TiO2复合材料过程中,超声作用能促进核壳结构的形成.提高前驱溶液的浓度,在获得CdS/TiO2核壳结构的同时会析出TiO2纳米粒子.在降解甲基橙的实验中,CdS/TiO2材料表现出比单组分材料更好的催化性能.     

Photoconductivity of novel poly（N-vinyl）-3 - [p-nitrophenylazo] carbazole/ CdS-nanoparticle polymer composite

The photoconductive characteristic of the inorganic/organic hybridized polymer system is reported, in which a novel bi-functional photorefractive （PR） poly（N-vinyl）-3-[p-nitrophenylazo]carbazole （PVNPAK） serves as a polymeric charge-transporting and second-order nonliner optical matrix and quantum dots composed of surface passivated cadmium sulfide serve as a charge-generation sensitizer. The hybrid PVNPAK/CdS-nanoparticles polymer composites with different mass ratio of CdS to PVNPAK were prepared. The generation of photocurrent on illumination and photoconductive properties of the PVNPAK/CdS-nanoparticles polymer composites were studied. The results show that the addition of CdS nanoparticle as a photosensitizer can enhance the photoconductivity of the PVNPAK significantly because of the properties of the high quantum efficiency of photosensitization and high charge transport to conducting polymer.