Role of chelating agent in chemical and fluorescent properties of SnO2 nanoparticles

A modified polyacrylamide gel route is applied to synthesize SnO2 nanoparticles. High-quality SnO2 nanoparticles with a uniform size are prepared using different chelating agents. The average particle size of the samples is found to depend on the choice of the chelating agent. The photoluminescence spectrum detected at λex = 230 nm shows a new peak located at 740 nm due to the surface defect level distributed at the nanoparticle boundaries.     

Optical spectroscopy studies on FeTelxSex and AxFe2uSe2 （A = K, Rb, Cs）： A brief overview

In this short overview, we summarize the optical spectroscopy FeTezxSex and AxFe2-ySe2. We elaborate that optical spectroscopy band structure evolution across the AFM phase transition temperature, studies on iron selenide superconducting systems measurements yield fruitful information about the the electronic correlation effect, the superconduct- ing pairing energy gap, the condensed carrier density or penetration depth, the inhomogeneity and the nanoscale phase separation between superconductivity and antiferromagnetism in those systems.     

强上转换发光的LiLu_(1-x)Yb_xF_4∶Tm@LiGdF_4核壳纳米晶的制备

利用高温热分解法制备了LiLuF_4∶Yb,Tm@LiGdF_4核壳纳米晶。在980nm激光激发下,与未包覆的样品相比,LiLuF_4∶Yb,Tm@LiGdF_4核壳纳米晶的发光增强了15倍左右,这主要是因为通过惰性壳层的包覆可以有效抑制表面猝灭效应。另外,随着核中Yb~(3+)离子的摩尔分数从20%增加到100%,上转换发光强度逐渐增大,最大增加了12.4倍左右。这主要是由于增加Yb~(3+)离子的浓度可以增加纳米粒子对激发光的吸收和提高Yb~(3+)到Tm~(3+)的能量传递速率。所制备的LiYbF_4∶2%Tm@LiGdF_4核壳纳米晶的发光效率高达4%。     

表面增强拉曼光谱研究正己硫醇分子在银基底表面自组装过程的时间和浓度因素影响

表面增强拉曼光谱(SERS)是一种具有超灵敏检测能力的谱学技术,可以在单分子水平上检测分子结构的动态变化过程。烷基硫醇的自组装膜是一类典型的类晶态有序结构薄膜,在仿生、材料、电子和化学等领域有着重要的应用,越来越受到人们的关注。本文利用SERS对正己硫醇(hexanethiol,HT)分子在银基底上的吸附和组装过程进行研究,对HT的拉曼和自组装膜SERS光谱进行了指认。根据C-S,C-C和CH₃键结构的反式和旁式的特征光谱信息,研究HT吸附在银纳米粒子表面的构象,以及自组装膜结构的有序性。研究了吸附时间和浓度两个因素对成膜规律产生的影响。实验结果表明,当HT溶液浓度较高时,HT单层膜成膜速率较快,且有序性较好;当HT溶液浓度较低时,HT单层膜成膜速率较慢,且有序性较差。这一研究结果对成膜动力学以及烷基硫醇的有序单层膜的制备具有重要的指导意义,为基于烷基硫醇的自组装单层膜在防腐、器件和生物方面的应用奠定了基础。     

C自掺杂TiO2纳米棒的制备与光催化性能研究

本文以TiC为前驱体和掺杂源,采用一步水热法合成了具有可见光吸收的C自掺杂金红石相TiO_2纳米棒.样品的结构、形貌、化学态和光学性质等可通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)、X射线光电子能谱仪(XPS)以及紫外可见分光光度计(UV-vis)来表征.所合成的样品具有较强的光催化活性,可通过在可见光照射下降解有机染料罗丹明B(RhB)来验证.C自掺杂TiO_2所呈现的较强光催化活性是由于其具有小的能带间隙(2.74 eV)、大的比表面积和高的电子-空穴对分离率.     

Determination of the Potential Barrier at the Metal／Oxide Interface in a Specular Spin Valve Structure with Nano—oxide Layers Using Electron Holography

The local potential distribution in a specular spin valve structure with nano-oxide layers has been mapped by using off-axis electron holography in a field emission gun transmission electron microscope.A potential jump of 3-4 V across the metal/oxide interface was detected for the first time.The presence of the potential barrier confirms the formation of the metal/insulator/metal structure,which contributes to the increasing mean free path of spin-polarized elecrons via the specular reflection of spin-polarized electrons at the metal/oxide interface.It leads to nearly double enhancement of the magnetoresistance ratio from 8% to 15%.     

Luminescent Properties of Eu^3＋—Doped Yttrium Oxide Chloride Embedded in Nanoporous Glass

The photoluminescence of Eu^3 -doped yttrium oxide chloride embedded in nanoporous glass has been observed.In comparison with those in the powder phosphor,the emission lines of Eu^3 ions becom much broader and lueshift was observed in the lines due to ^5D0→^7F2 transitions and the Eu-O charge transfer excitation band.The ratio intensities of the ^5D0→^7F1 transitions to the ^5D0→^7F2 transitions of Eu^3 ion become higher and change at different excitation excitation wavelengths,such as 393nm and 254nm.The two excitation wavelengths belong to the 4f→4f transition of the Eu^3 ion and the Eu-O charge transfer,respectively,This material may be developed into a new luminescent glass.     

Formation of Nanosuized Inclusions in Cubic Boron Nitride Single Crystals

Cubic boron nitride(c-BN) crystals with dimensions of 0.3-0.4mm,which have been synthesized using lithium nitride(Li3N) as a catalyst with a high-temperature method,were examined by transmission electron microscopy(TEM).The TEM result shows that there are some nanostructured areas containing several types of nanosized foreign particles within the as -grown c-BN crystals.We find that the nanometre inclusions are hexagonal BN with the lattice constants of α=2.05A and c=6.66A,tetragonal B25N with α=8.79A and c=5.08A,tetragonal B53N with α=8.79A and c=5.08A,and hexagonal Li3N with α=3.648A and c=3.875A.     

石墨炉原子吸收法测定高纯镍中痕量铋

本文利用石墨炉原子吸收法，在等温平台条件下直接测定了高纯镍中的痕量铋，并对石墨炉加热程序中的干燥时间，灰化温度及原子化温度进行了优化，同时也考察了介质酸度的影响，试验表明：基体镍对铋的测定有显著的影响，为此对标准系列进行了基体匹配，本方法的特征质量为6．1pg，相对标准偏差为3．6％，加标回收率为99．3％－104％。