Sol-gel synthesis and photoluminescence of LaPO_4:Eu~(3+) nanorods

Monoclinic LaPO4 nanostructures with uniform rod shape have been successfully synthesized by a simple sol-gel method.The procedure involves formation of homogeneous,transparent,metal-citrate-EDTA gel precursors,followed by calcination to promote thermal decomposition of the gel precursors to yield the LaPO4 nanoparticles.Their morphologies and structures were characterized by XRD,TEM,TG-DSC and HRTEM.The results indicate that single monoclinic phase LaPO4 nanorods are readily obtained at 800 ℃ within 3 h.Furthermore,photoluminescence(PL) characterization of the Eu3+-doped LaPO4 nanocrystals was carried out.The effects of calcination temperatures and Eu3+ doping content on the PL properties were elaborated in detail.Room-temperature photoluminescence(PL) characterization reveals that the optical brightness as well as the intensity ratio of 5D0-7F1 to 5D0-7F2 is highly dependent on the calcination temperature,and the Eu0.05La0.95PO4 nanophosphor shows the relatively promising PL performance with the most intense emission.     

ZnO纳米棒的制备及光催化性能研究

采用水热法制备ZnO纳米棒。利用X射线粉末衍射(XRD)仪和透射电镜(TEM)对其结构和形貌分别进行表征,并通过紫外-可见分光光度计分析ZnO纳米棒光降解甲基紫来研究其光催化活性。结果表明,以氢氧化钠和醋酸锌为原料,聚丙烯酰胺为表面活性剂制备得到直径约26nm,长度达400nm的单晶纤锌矿结构的ZnO纳米棒。添加ZnO纳米棒光催化剂时的光降解率为70%,未加ZnO纳米棒的光降解率为30%,表明ZnO纳米棒具有很好的光催化活性。     

电化学沉积制备纳米晶Bi-Te薄膜及其表征

本文采用恒电流电化学沉积工艺制备Bi-Te二元薄膜。随着沉积时间的变化,在同一个电极上依次出现了单相的Bi₂Te₃和Bi₄Te₃薄膜。其中,Bi₂Te₃薄膜是由规则的长度为100 nm左右,平均宽度为10 nm的纳米棒组成。其具有非常大的比表面积,非常有利于其作为热电材料的应用。而Bi₄Te₃薄膜是由纳米颗粒团聚而成的不规则多面体组成的。本文的研究证明通过改变沉积参数,有可能在Bi-Te二元系统的沉积过程中对生成物的相组成和形貌进行调控。     

Fabrication of Worm-Like Nanorods and Ultrafine Nanospheres of Silver Via Solid-State Photochemical Decomposition

Worm-like nanorods and nanospheres of silver have been synthesized by photochemical decomposition of silver oxalate in water by UV irradiation in the presence of CTAB and PVP, respectively. No external seeds have been employed for the synthesis of Ag nanorods. The synthesized Ag colloids have been characterized by UV-visible spectra, powder XRD, HRTEM, and selected area electron diffraction (SAED). Ag nanospheres of average size around 2 nm have been obtained in the presence of PVP. XRD and TEM analyses revealed that top and basal planes of nanorods are bound with {111} facets. Williamson–Hall plot has revealed the presence of defects in the Ag nanospheres and nanorods. Formation of defective Ag nanocrystals is attributed to the heating effect of UV-visible irradiation.     

Trioctylphosphine as Both Solvent and Stabilizer to Synthesize CdS Nanorods

High quality CdS nanorods are synthesized reproducibly with cadmium acetate and sulfur as precursors in trioctylphosphine solution. The morphology, crystalline form and phase composition of CdS nanorods are characterized by transmission electron microscopy (TEM), high-resolution TEM and X-ray diffraction (XRD). CdS nanorods obtained are uniform with an aspect ratio of about 5:1 and in a wurtzite structure. The influence of reaction conditions on the growth of CdS nanorods demonstrates that low precursor concentration and high reaction temperature (260 °C) are favorable for the formation of uniform CdS nanorods with 85.3% of product yield.     

水热法合成CdWO_4纳米棒及其光致发光性能

以硝酸镉、钨酸钠为原料,十二烷基苯磺酸钠(sodium dodecyl benzenesulfonate,SDBS)为表面活性剂,采用水热法制备了钨酸镉(CdWO4)纳米棒。利用X射线衍射、场发射透射电镜和荧光光谱测试对样品进行表征。初步分析了SDBS浓度对CdWO4纳米粉末的微观形貌及其性能的影响,并探讨了其可能的形成机理。结果表明:当SDBS的浓度为0.002mol/L时,得到短柱状CdWO4纳米粉末,随着SDBS浓度增大,制得的CdWO4纳米棒长径比增大;当SDBS浓度为0.2mol/L时,得到长柱状CdWO4纳米棒,其长径比为20～25。在300nm波长激发下,短柱状和长柱状CdWO4纳米棒均有490nm的宽发射峰,且随着长径比的增大CdWO4纳米棒的光致发光性能增强。     

退火处理对氧化锌纳米棒形貌及气敏性能的影响（英文）

研究水热合成氧化锌纳米棒的高温热稳定性。采用X射线衍射和扫描电镜对氧化锌纳米棒的结构与形貌进行表征。采用热重分析研究氧化锌纳米棒在热处理过程中的失重情况。结果表明:在退火温度低于400°C时,氧化锌纳米棒具有较好的热稳定性。当退火温度超过600°C时,氧化锌纳米棒的长径比明显降低并且纳米棒的团聚趋势加剧。退火处理对氧化锌纳米棒的气敏性能具有显著影响。与未经退火处理的氧化锌纳米棒相比,经历400°C退火处理的氧化锌纳米棒对浓度为25×10-6的H2灵敏度可以从2.22提高至3.56。经历400°C热退火处理的氧化锌纳米棒对H2表现出最优的气敏性能。     

氧化镁纳米棒的晶格畸变及反常红外特性

以六水氯化镁和轻质氧化镁为原料,制备出碱式氯化镁纳米棒;再以碱式氯化镁纳米棒为前驱物,氢氧化钠为沉淀转化剂,合成出氢氧化镁纳米棒;采用煅烧前驱物氢氧化镁纳米棒分解得到氧化镁单晶纳米棒。通过X射线衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、区域电子衍射（SAED）和红外吸收光谱（FT-IR）等手段对所得产物的表征分析结果表明,氧化镁纳米棒的微结构中存在晶格畸变,表现为晶格膨胀,其红外吸收峰出现了红移和蓝移同时并存现象;随煅烧温度的升高,氧化镁纳米棒的平均晶粒尺寸增加,晶格常数减小,晶格畸变量减小。     

Time-dependent nanoscale plasticity of ZnO nanorods

External stresses are applied during operation or storage in flexible electronics, which makes understanding time-dependent plastic deformation of nanobuilding blocks more crucial for ensuring the reliability of the devices. Here, we systematically explored the time-dependent nanoscale plasticity of single-crystal ZnO nanorods and its size effects. A series of compression creep tests under different low stresses (in elastic regime) were performed on vertically oriented rods having equivalent diameters in the range of ～200 to ～2000 nm. It was revealed that creep indeed occurs in the rods even at ambient temperature, and is more pronounced in smaller nanorods. Analyzing the stress exponent and the activation volume suggests that the enhanced plasticity may be controlled by the diffusion creep (through the “space-charge layer” near the surface and/or along the interface between the punch and the top surface of the rod), which is supported by the results from in situ creep tests under electron-beam irradiation and in situ electric measurements.     

Polystyrene sphere monolayer assisted electrochemical deposition of ZnO nanorods with controlable surface density

In this paper we report the zinc oxide nanorods (ZnO NRs) growth by electrochemical deposition onto polycrystalline gold electrodes modified with assemblies of polystyrene sphere monolayers (PSSMs). Growth occurs through the interstitial spaces between the hexagonally close packed spheres. ZnO NRs nucleate in the region where three adjacent spheres leave a space, being able to grow and projected over the PSSMs. The nanorod surface density (N_NR) shows a linear dependence with respect to a PS sphere diameter selected. XRD analysis shows these ZnO NRs are highly oriented along the (0 0 2) plane (c-axis). This open the possibility to have electronic devices with mechanically supported nanometric materials.