低强度飞秒激光激发下CdTe和CdTe/CdS核壳量子点的荧光上转换研究

利用400 nm和800 nm不同波长的低强度飞秒激光,对CdTe和CdTe/CdS核壳量子点溶胶进行激发,研究其稳态和时间分辨荧光性质.800 nm飞秒激光激发下,CdTe和CdTe/CdS核壳量子点产生上转换发光现象,上转换荧光峰与400 nm激发下的荧光峰相比蓝移最多达15 nm,而且蓝移值与荧光量子产率有关.变功率激发确认激发光功率与上转换荧光强度间满足二次方关系,时间分辨荧光的研究表明荧光动力学曲线服从双e指数衰减.提出表面态辅助的双光子吸收模型是低激发强度上转换发光的主要机理.CdTe和CdT 关键词： CdTe量子点 CdTe/CdS核壳量子点 时间分辨荧光 上转换荧光     

石墨炉原子吸收光谱法测定催化有机残液中的微量铑

硝酸于聚四氟乙烯闷罐中消解样品 ,石墨炉原子吸收光谱法测定催化有机残液中的微量铑 ,相对标准偏差为 6 .2 %,回收率为 96 .5 %— 1 0 5 .4 %。方法简便、快速 ,分析结果令人满意。     

Study on the interaction between CdSe quantum dots and chitosan by scattering spectra

Two different stabilizing agents thioglycolic acid (TGA) and l-cysteine (l-Cys) capped CdSe QDs with the diameter of 2 nm were synthesized, large amounts of stabilizing agents connected to CdSe QDs surface through Cd–S bond. The interaction between chitosan and QDs had been investigated, respectively. The interaction lead to the remarkable enhancement of RRS, RNLS and the enchantments were in proportional to the concentration of chitosan in a certain range. Under the optimal conditions, compared with TGA–CdSe QDs, the interaction between l-Cys–CdSe QDs with chitosan owned more broad linear range 0.042–3.0 μg mL⁻¹ and lower detect limits 1.2 ng mL⁻¹. The influences of factors on the interaction between chitosan with QDs and some foreign substances were all examined, which showed that the methods had a good sensitivity and selectivity. Based on this, it is hoped to build a method for the determination of chitosan using CdSe QDs as probes. Through Fourier transform infrared spectroscopy (FTIR) transmission electron microscopy (TEM), it was speculated that CdSe QDs interacted with chitosan to form a network structure aggregates through electrostatic attraction and hydrophobic forces. The reasons for the enhancement of RRS intensity were assumed as follows: resonance enhanced Rayleigh scattering effect, increase of the molecular volume, and hydrophobic effect.     

Surface phase diagram and temperature induced phase transitions of Sn/Cu(1 0 0)

Room temperature deposition of Sn on Cu(1 0 0) gives rise to a rich variety of surface reconstructions in the submonolayer coverage range. In this work, we report a detailed investigation on the phases appearing and their temperature stability range by using low-energy electron diffraction and surface X-ray diffraction. Previously reported reconstructions in the submonolayer range are p(2 × 2) (for 0.2 ML), p(2 × 6) (for 0.33 ML), ()R45° (for 0.5 ML), and c(4 × 4) (for 0.65 ML). We find a new phase with a structure for a coverage of 0.45 ML. Furthermore, we analyze the temperature stability of all phases. We find that two phases exhibit a temperature induced reversible phase transition: the ()R45° phase becomes ()R45° phase above 360 K, and the new phase becomes p(2 × 2) also above 360 K. The origin of these two-phase transitions is discussed.     

高灵敏CdTe量子点探针的构建及与金属离子的作用

采用变性的牛血清白蛋白(dBSA)对水相合成的CdTe量子点进行修饰, 构建了高灵敏金属离子探针, 研究了其对重金属离子的检测性能并对机理进行了探讨. 通过优化反应条件, 合成了具有高量子产率的以巯基乙酸为稳定剂的水溶性CdTe量子点, 并采用变性的牛血清白蛋白分别对不同粒径的CdTe量子点进行修饰, 确定变性的牛血清白蛋白与不同粒径量子点之间的最佳比例. 在纯化变性的牛血清白蛋白修饰的量子点(dBSA-QDs)的基础上, 研究了该量子点与不同金属离子的作用. 结果表明, 量子点经修饰后, 其量子产率、 抗光漂白性及稳定性得到显著提高; 而且dBSA-QDs的荧光可被重金属离子有效猝灭, 与巯基乙酸稳定的量子点(TGA-QDs)相比, 检测灵敏度显著提高.     

铱催化甲醇羰基化制乙酸循环反应的理论探究

采用密度泛函理论DFT-B3LYP方法, 对铱、碘元素采用相对论校正赝势基组SDD, 对C、O、H采用6-311+G(2d, p)基组, 优化了各反应物、中间体和过渡态的构型特征, 通过能量和振动分析证实了过渡态的真实性. 理论研究了阴离子循环中铱催化甲醇羰基化制乙酸的循环反应机理. 运用能量跨度模型获得了反应的动力学信息, 确定了各反应的决速中间体和决速过渡态和各催化剂的能量跨度和转化频率. 通过对cis-[Ir(CO)2I2]- 和 trans-[Ir(CO)2I2]-催化剂电荷密度的分析比较, 得到中心金属的富电子性提高了其催化能力, 以上计算结论与文献假设相符.     

顺式羰基铑碘络合物催化甲醇制乙酸反应的动力学研究

本文运用密度泛函理论DFT-B3LYP方法,对铑、碘元素采用相对论校正赝势基组SDD,对C、O、H采用6-311+G(2d,p)基组,计算研究了顺式羰基铑碘络合物催化甲醇羰基化制乙酸反应的微观机理,优化了各反应物、中间体和过渡态的构型特征,用频率分析方法和内禀反应坐标方法对过渡态进行了验证,运用Kozuch撰写的能量跨度模型获得循环反应的动力学信息,确定了决定循环反应速率的决速过渡态和决速中间体,并利用转化频率评估了催化性能与温度的变化关系.     

新型Rh_2(esp)_2配体手性类似物的合成

以(R)-叔丁基亚磺酰胺为手性助剂,与1,3-苯二甲醛经缩合反应制得关键中间体——(Rs,Rs)-双叔丁基亚磺酰亚胺(7);锂化的羧酸酯与7经不对称加成反应合成了两个新型的Rh_2(esp)_2配体类似物——(Rs,Rs',R,R')-β-胺基羧酸酯和(Rs,Rs',R,R',R,R')-α,β-氮杂环丙烷羧酸酯,产率分别为96%和65%,非对映选择性均大于20∶1。化合物的结构经1H NMR和13C NMR表征。     

Flying qubits and entangled photons

Efficient generation of polarized single photons or entangled photon pairs is crucial for the implementation of quantum key distribution (QKD) systems. Self organized semiconductor quantum dots (QDs) are capable of emitting on demand one polarized photon or an entangled photon pair upon current injection. Highly efficient single‐photon sources consist of a pin structure inserted into a microcavity where single electrons and holes are funneled into an InAs QD via a submicron AlOx aperture, leading to emission of single polarized photons with record purity of the spectrum and non‐classicality of the photons. A new QD site‐control technique is based on using the surface strain field of an AlO_x current aperture below the QD. GaN/AlN QD based devices are promising to operate at room temperature and reveal a fine‐structure splitting (FSS) depending inversely on the QD size. Large GaN/AlN QDs show disappearance of the FSS. Theory also suggests QDs grown on (111)‐oriented GaAs substrates as source of entangled photon pairs.     

光谱法研究核壳量子点CdTe/CdS与牛血清白蛋白的相互作用

应用荧光光谱、圆二色光谱和紫外吸收光谱等技术研究核壳量子点CdTe/CdS与牛血清白蛋白(BSA)相互作用的结果表明,CdTe/CdS对BSA的荧光猝灭机理为静态猝灭。根据不同温度下量子点对BSA的荧光猝灭作用计算了结合常数、热力学参数,证明了量子点与BSA相互作用力主要是范德华力或氢键作用力。探讨了量子点对BSA构象的影响。