Structural, optical, and electronic properties of colloidal CuO nanoparticles formed by using a colloid-thermal synthesis process

Colloidal cupric oxide (CuO) nanoparticles were formed by using a colloid-thermal synthesis process. X-ray diffraction patterns, transmission electron microscopy (TEM) images, high-resolution TEM images, and X-ray energy dispersive spectrometry profiles showed that the colloidal CuO nanoparticles were formed. The optical band-gap energy of CuO nanoparticles at 300 K, as determined from the absorbance spectrum, was 3.63 eV. A photoluminescence spectrum at 300 K showed that a dominant emission peak appeared at the blue region. X-ray photoelectron spectroscopy profiles showed that the O 1s and the Cu 2p peaks corresponding to the CuO nanoparticles were observed.     

Ultrashort pulse generation using fiber FM laser

Ultrashort optical pulse generation using a fiber FM laser is presented and analyzed in detail. Fiber FM laser operation is realized using a fiber ring with an internal phase modulator and an erbium-doped fiber amplifier. To compress FM laser pulses, an external dispersive single-mode fiber is employed. Furthermore, by external intensity modulation, the pulse background is removed. The background ratio of the generated ultrashort pulse is calculated and compared with the experimental results. The experimental results show an output optical pulse width of 1.77 ps and a spectral bandwidth of 0.5 THz.     

Eu掺杂SiO2纳米基质的发光特性

采用溶胶-凝胶(sol-gel)法制备了Eu掺杂的SiO₂干凝胶,分别用光致发光(PL)光谱、透射电镜(TEM)、扫描电镜(SEM)、红外吸收(IR)谱等分析手段对样品进行了表征,研究了SiO₂的基质中Eu³⁺、Eu²⁺的发光特性以及退火温度对发射光谱的影响,并对其发光机理进行了分析。结果表明,样品掺杂均匀,颗粒尺寸大约在50~80 nm,硼(B)离子进入SiO₂网格,成为了基质的一部分,改变了基质的网络结构。当采用258 nm激发样品时,随着退火温度的升高,红光发射强度先增强后减弱。对于经800 ℃退火处理的样品红光发射最强,出现了576 nm(⁵D₀ →⁷F₀),620 nm(⁵D₀ →⁷F₂),658 nm(⁵D₀ →⁷F₃)3条谱线,其中主峰位于 620 nm红光发射,对应于Eu³⁺离子的⁵D₀ →⁷F₂超灵敏跃迁,进一步说明B离子参与到基质中,形成了Si—O—B键,导致Eu³⁺离子所处配位环境的对称性降低,从而有利于Eu³⁺离子的特征发射;当采用271 nm激发样品时,随着退火温度的升高,蓝光发射强度先增强后减弱,经850 ℃退火的样品400~500 nm蓝光发射最强,归属于Eu²⁺的5d→4f的跃迁发射,证明在铝离子(Al³⁺)存在的情形下,在高温退火过程中Al³⁺部分取代Si⁴⁺形成AlO^-₄基团,掺杂Eu³⁺填补AlO^-₄基团附近的空位,增加了Eu³⁺周围的AlO^-₄四面体中氧原子的电子给予能力,使得Eu³⁺还原成Eu²⁺,从而得到了较强的蓝光发射。但是,当退火温度达到900 ℃时,由于稀土离子发生位置的迁移形成团簇红光和蓝光都明显地降低。     

Optically gated resonant emission of single quantum dots

We report on the resonant emission in coherently driven single semiconductor quantum dots. We demonstrate that an ultraweak nonresonant laser acts as an optical gate for the quantum dot resonant response. We show that the gate laser suppresses Coulomb blockade at the origin of a resonant emission quenching, and that the optically gated quantum dots systematically behave as ideal two-level systems in both regimes of coherent and incoherent resonant emission.     

以最大原子密度定义合金相中的第一近邻团簇

本文提出利用不同壳层所包含的径向原子密度, 即单位体积内的原子个数随着径向的分布, 来方便而精确地定义团簇, 即具有最大径向原子密度的且表面呈现三角密堆结构的完整壳层为第一近邻团簇. 最后以Al-Ni-Zr合金相为例说明了该方法的合理性与适用性, 及此方法所定义的团簇与非晶形成的关系.     

Sequential over-barrier ionization of multi-electron atoms in the tens-to-hundreds keV/u energy range

Our previous work on the classical over-barrier ionization model for helium double ionization is extended to the complex multi-electron system of Ne.The total and q-fold ionization cross sections are calculated at energies ranging from a few tens to several hundred keV/u.The calculation results are in good agreement with the experimental data,and the energy dependence of the cross sections suggests that the multi-ionization of a strong perturbated complex atom is probably the sequential over-barrier ionization process.     

窗口可变滑动相关分析方法在激光诱导击穿光谱谱线自动识别中的应用

激光诱导击穿光谱(LIBS)谱线具有很窄的展宽,且光谱仪因外界温度条件的变化存在波长漂移,光谱数据为离散数字信号,受噪声、谱线重叠及连续背景的影响,信号存在失真和变形。而目前光谱仪自带谱线识别分析软件主要以"就近原则"为主,错误率较高,必须依赖于人眼的观察对比。针对这个问题,在研究LIBS光谱特性的基础上,提出了一种窗口可变滑动相关分析方法(CAASW),用于激光诱导击穿光谱谱线自动识别。以土壤标准物质为样品,对该方法进行了实验分析和评价,与光谱仪自带分析识别软件相比,CAASW明显提高了识别准确率和识别速度,最终实现了谱线的自动识别。     

板条增益介质波前畸变诊断方法

对波前重构算法中的区域法进行了改进,使其能够应用于板条增益介质的波前畸变诊断。利用该方法对47块Nd: YAG板条增益介质沿厚度方向波前畸变进行测量,指出镀膜和加工等环节对增益介质的波前畸变可能造成的影响。按照波前畸变峰谷（PV）值对测量结果进行了统计,结果表明:增益介质造成的静态波前畸变参差不齐,测量样本中静态畸变PV值最多可达5 m以上,且仅有4.1%的增益介质静态畸变PV值小于1 m。通过选取某些增益介质使之级联,测量其组合波前畸变,发现在系统中使用两块波面互补的增益介质有助于减小系统的静态波前畸变。     

原子核的有限体积效应对高离化态离子能级和波函数的影响

在相对论理论框架下,分别在点电荷和两参数Fermi核模型近似下计算了高离化态类氢离子（Z=80—112）n=1—3壳层的波函数和能级. 分析了核有限体积效应对它们的影响. 在此基础上,给出了核有限体积效应对原子能级的修正公式. 同时,还进一步讨论了相对论效应和核有限体积效应之间的相互影响,发现对高Z元素相对论效应与核有限体积效应之间有很强的耦合. 关键词： 原子核有限体积效应 高离化态离子 相对论效应     

Adsorption of surface functionalized silica nanoparticles onto mineral surfaces and decane/water interface

The adsorption of silica nanoparticles onto representative mineral surfaces and at the decane/water interface was studied. The effects of particle size (the mean diameters from 5 to 75?nm), concentration and surface type on the adsorption were studied in detail. Silica nanoparticles with four different surfaces [unmodified, surface modified with anionic (sulfonate), cationic (quaternary ammonium (quat)) or nonionic (polyethylene glycol (PEG)) surfactant] were used. The zeta potential of these silica nanoparticles ranges from ?79.8 to 15.3?mV. The shape of silica particles examined by a Hitachi-S5500 scanning transmission electron microscope (STEM) is quite spherical. The adsorption of all the nanoparticles (unmodified or surface modified) on quartz and calcite surfaces was found to be insignificant. We used interfacial tension (IFT) measurements to investigate the adsorption of silica nanoparticles at the decane/water interface. Unmodified nanoparticles or surface modified ones with sulfonate or quat do not significantly affect the IFT of the decane/water interface. It also does not appear that the particle size or concentration influences the IFT. However, the presence of PEG as a surface modifying material significantly reduces the IFT. The PEG surface modifier alone in an aqueous solution, without the nanoparticles, yields the same IFT reduction for an equivalent PEG concentration as that used for modifying the surface of nanoparticles. Contact angle measurements of a decane droplet on quartz or calcite plate immersed in water (or aqueous nanoparticle dispersion) showed a slight change in the contact angle in the presence of the studied nanoparticles. The results of contact angle measurements are in good agreement with experiments of adsorption of nanoparticles on mineral surfaces or decane/water interface. This study brings new insights into the understanding and modeling of the adsorption of surface-modified silica nanoparticles onto mineral surfaces and water/decane interface.