ZnO四足和多足纳米结构的制备和光致发光性能研究

采用简单的热蒸发法,在没有使用载气和催化剂的情况下成功制备出ZnO四足和多足纳米结构。采用场发射扫描电镜、X射线衍射、高分辨透射电子显微镜和荧光分光光度计研究了ZnO纳米结构的形貌、结构和光致发光性能。结果表明所合成的ZnO是由具有六方纤锌矿结构的四足和多足纳米结构组成,足部呈棒状并沿[0001]方向生长。提出了四足和多足ZnO纳米结构的生长机制。在室温下的光致发光光谱中,494nm处出现一个较强的绿色发射峰,391nm处出现一个较弱的紫外发射峰。     

水溶性ZnSe纳米晶的微波制备与表征

本文利用微波辐射方法,在水相中直接快速制备,得到了谷胱甘肽修饰的水溶性ZnSe纳米晶,并详细讨论了制备条件(溶液中离子配比、PH值、反应温度和时间等)对结果的影响.在最佳条件下制备所得的ZnSe纳米晶,发射波长在360nm～410nm之间可调,荧光光谱半峰宽最小值可达到21nm.另外,进一步利用光辐射方法,对ZnSe纳米晶进行表面修饰,将其荧光量子效率提高到了55%.本文制备方法具有过程简单、经济的优点,此外,这种水溶性ZnSe纳米晶具有优良的光谱性能和良好的生物相溶性,可使其作为荧光探针进一步应用在生物领域.     

ZnSe晶体的气相法制备和性能研究

采用化学气相输运法,以单质Zn和Se为原料生长ZnSe晶体。比较了加碘(Zn-Se-I2)和未加碘(Zn-Se)两种情况下产物的特征,借助XRD和SEM检测仪器对所生长的ZnSe晶体的结构、形貌和成分进行了分析。结果表明,加入碘后生长的ZnSe晶体为橙黄色,具有较好的结晶性能,晶格常数为5.668nm,Zn与Se的化学成分比为1∶1,没有其它杂质峰;未加碘的产物为多孔状陶瓷,说明加碘可以明显提高ZnSe的结晶性能,解决了一致升华范围较窄的限制条件,避免了ZnSe生长动力学的限制,因此可以获得理想化学计量比的ZnSe晶体。     

立方相MgZnO纳米线的制备和表征

利用热蒸发方法,在硅衬底上制备出立方MgZnO纳米线。以Mg粉为源材料,所制备的为立方相MgO纳米线。以Mg粉和Zn粉混合物为源材料,可以制备出立方相MgZnO纳米线,Zn含量7%,直径200～300nm,具有单晶结构;同时产物中还包括六方相ZnO纳米线,直径30nm左右。MgZnO纳米线中Zn含量远低于源材料中的Zn含量,这可能是ZnO和Zn的蒸汽压远大于MgO和Mg的缘故。     

热压热变形纳米晶钕铁硼磁体微观结构研究(英文)

利用MQ-C快淬粉末并结合热压热变形技术制得致密的各向异性纳米晶Nd-Fe-B磁体,并研究了磁体磁性能及微观结构的变化。结果表明,热变形后磁体呈现较强的c轴取向,磁体磁性能大幅增大;快淬磁粉颗粒在热压过程中沿压力方向规则堆垛,而热变形后,粉末颗粒形状与晶粒变化趋势相同,呈现沿垂直于压力方向拉长;热变形后,磁体中仍有大量未取向的超大颗粒存在,能谱分析表明其Nd含量要高于周围取向晶粒。     

纳米碲粉体的制备及表征

利用惰性气体保护蒸发-冷凝法制备了碲（Te）纳米粉体颗粒。通过热力学计算得到碲的蒸汽压随温度的变化关系。利用X射线衍射（XRD）、透射电子显微镜（TEM）、激光粒度仪观测了碲纳米颗粒的晶体结构、形貌,并研究了粉末粒径、分布及形貌与蒸发冷凝过程中气氛压力的关系。结果表明,随着气氛压力的增加,粉末粒径分布范围变窄,粉末粒度...     

纳米NiZn铁氧体纳米晶的制备及表征

应用化学共沉淀法制备了NiZn铁氧体的前驱体粉末。对前驱体在900℃热处理后,得到尖晶石型NiZn铁氧体样品。用X射线衍射（XRD）和电子扫描显微镜（SEM）对其进行表征,结果表明：样品的晶体形貌为准六角形,粒径大小Dsem≈3.5μm,而Dxrd≈80nm,即Dsem≈44Dxrd这是NiZn铁氧体制备领域一个新颖的结果。采用该方法制备的样品可能具有一定的实用价值与经济价值。     

四氧化三铁纳米晶的热溶剂法制备研究

采用切片石蜡作为热溶剂法的高温溶剂来制备四氧化三铁纳米晶,在300~340℃的石蜡溶剂中,研究了油酸铁直接热解制备四氧化三铁纳米晶过程中溶剂的温度和反应物连续注入的方式对纳米晶的粒度和形貌的影响规律。结果表明,采用反应物连续注入的方式可制备出单相、形貌规则、平均粒径在24~60 nm,标准偏差在11%~13%的Fe3O4纳米晶。热溶剂温度在一定范围内对纳米晶尺寸影响不大,纳米晶的平均尺寸随着反应物注入速度的提高而减小。     

微纳米晶CuInSe_2溶剂热合成与表征

以硝酸铟、硝酸铜及硒粉为原料,以乙醇胺和无水乙醇作为溶剂,采用溶剂热法合成了铜铟硒(CuInSe2,简称为CIS)微纳米晶,通过单因素实验方法考察了原料的物质的量比、反应时间、反应温度等因素对产物的影响,得出了制备CuInSe2纳米晶粉末的适宜条件。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、紫外可见吸收(Uv-Vis)等方法对产物进行表征和测试。     

A voltammetric and nanogravimetric study of ZnSe electrodeposition from an acid bath containing Zn(II) and Se(IV)

The negative potential sweep of a polycrystalline Au electrode in a solution containing 5 × 10^− 4 mol L^− 1 SeO₂, 0.2 mol L^− 1 Zn(ClO₄)₂ and 0.5 mol L^− 1 HClO₄ was analyzed at 0.05 V s^− 1. The simultaneously collected voltammetric and nanogravimetric responses allowed to analyze the several electrochemical processes occurring in the studied range of potential, finishing with the formation of a thin film of ZnSe. The association of results obtained using both techniques was applied to identify the species involved in the AuO reduction as (AuO)₂H₂SeO₃, which was desorbed during the oxide reduction with a mass variation much larger than that one observed in the supporting electrolyte. Initially, the Se(IV) reduction results in Se_ads coverage, followed by a further reduction to H₂Se, which is a gas and desorbs from the electrode surface. Finally, the Zn(II) reduction inhibits the H₂Se formation and generates a thin film of ZnSe, as the final coating. The strong dependence of the nature of reacting compound and the mass as well as the charge variations allowed to postulate a reaction mechanism.     

水溶液法制备CdSe和ZnSe纳米棒

用水溶液法直接合成了水溶性、发荧光的ZnSe和CdSe纳米棒。ZnSe纳米棒的直径约20～30nm,长度可达60～70nm;CdSe纳米棒的直径约30～60nm,长度可达150～450nm。用X射线衍射仪(XRD)、透射电镜(TEM)、高分辨透射电镜(HR-TEM)、荧光仪等仪器对纳米棒进行了表征。XRD和HRTEM的结果显示纳米棒具有立方结构,结晶度较高。讨论了纳米棒的形成机理以及pH对纳米棒发光强度的影响。合成的纳米棒在水溶液中至少稳定半年,表面被氨基和羧基化,在生物分析中具有广泛的应用前景。     

控制O2流量生长结状 ZnO微纳米棒及其特性研究

采用热蒸发法以锌粉和二水醋酸锌作为源材料在Si（111）衬底上制备了高密度的ZnO微纳米棒，制得的每根ZnO棒明显分为直径不同的四段．利用X射线衍射、扫描电镜、透射电镜、拉曼光谱和光致发光谱等测试手段对制备的样品进行了形貌、结构和光学性能的分析，结果表明制备的ZnO棒晶体质量良好，仅存在很少量的缺陷.通过讨论该结构的生长机理，发现O2分压对制备的ZnO微纳米棒的形貌有显著的影响，调节O2流量可控制ZnO纳米结构的形貌．     

Synthesis and luminescence properties of water-dispersible ZnSe nanocrystals

Water-dispersible ZnSe nanocrystals were synthesized by a green and simple route. Growth of the nanocrystals was performed under water-bath temperature, using selenium powder and zinc acetate as precursors, upon addition of mercaptoacetic acid as a stabilizer. Products were characterized by X-ray photoelectron spectra (XPS), X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), absorption and fluorescence spectra. Photoluminescence (PL) properties of ZnSe nanocrystals in evolution are discussed. PL is the contribution of both excitonic and defect emission. The excitonic emission peak can be tuned by changing the refluxing time and pH value. Mercaptoacetic acid is available in controlling the ratio of excitonic emission to defect emission. All desired properties of nanocrystals prepared here imply the possibility of high quality ZnSe nanocrystals developed under a mild condition.     

Fabrication and Characterization of Modulation-Doped ZnSe/(Zn,Cd)Se (110) Quantum Wells: A New System for Spin Coherence Studies

We describe the growth of modulation-doped ZnSe/(Zn,Cd)Se quantum wells on (110) GaAs substrates. Unlike the well-known protocol for the epitaxy of ZnSe-based quantum structures on (001) GaAs, we find that the fabrication of quantum well structures on (110) GaAs requires significantly different growth conditions and sample architecture. We use magnetotransport measurements to confirm the formation of a two-dimensional electron gas in these samples, and then measure transverse electron spin relaxation times using time-resolved Faraday rotation. In contrast to expectations based upon known spin relaxation mechanisms, we find surprisingly little difference between the spin lifetimes in these (110)-oriented samples in comparison with (100)-oriented control samples.     

Preparation,spectroscopic characterization and energy transfer investigation of iron-chromium diffusion co-doped ZnSe for mid-IR laser applications

The spectroscopic characterization and energy transfer mechanism of iron-chromium co-doped ZnSe polycrystalline (Cr,Fe:ZnSe) were reported with dimension of 15 mm × 15 mm × 2 mm obtained by controlled post-growth thermal diffusion method. The infrared absorption is characterized by a strong broad-band centered at 1770 nm which can be attributed to the only spin-allowed transition ⁵T₂ → ⁵E within the 3d⁴ shell of Cr²⁺ ions. Photoluminescence spectrum shows a relatively strong broad emission band centered at 4.1 μm with a width of 0.8 μm (FWHM) under 1770 nm excitation at room temperature and reveals effective Cr²⁺ → Fe²⁺ energy transfer process. Room temperature photoluminescence decay about 8 μs was measured. All the results indicate that Cr,Fe:ZnSe could achieve laser operation at 3.7–4.5 μm via Cr²⁺ → Fe²⁺ energy transfer using a more convenient laser pump source in the near IR region.     

球形纳米银粒子制备新方法及其表征

采用水热法,不添加任何还原剂,在表面活性剂聚乙烯吡咯烷酮(polyvinyl pyrrolidone,PVP)的保护下,热分解碳酸银制得纳米银溶胶.将纳米银溶胶经过后续离心分离,干燥后得到纳米银粉.通过改变反应温度、反应时间、表面活性剂浓度、种类及反应物浓度等反应条件,分析了各反应条件对纳米银粒子形貌的影响.利用X射线衍射仪(X-ray diffraction,XRD)、扫描电子显微镜(scanning electron microscope,SEM)和电子能谱仪(energy dispersivespectroscopy,EDS)分析表明,在反应温度为180℃、反应时间为5 h、AgNO3浓度为0.1 mol/L、NaHCO3浓度为0.05mol/L、PVP为1.7 g的最佳制备工艺条件下,纳米银粒子为球形,粒径分布范围窄,单一分散,粒径40 nm左右.结果表明,表面分散剂PVP以及AgNO3与NaHCO3的浓度对球形纳米银的合成具有关键作用.