CdSe量子棒的线偏振光学性质

用有效质量包络函数理论研究了CdSe量子棒的线偏振光学性质,考虑了形状和磁场的影响.发现CdSe量子球具有负的线偏振因子(xy-平面内的线偏振发射),而小半径长量子棒具有正的线偏振因子(z-方向的线偏振发射).z-方向就是晶格c-轴方向.因六角晶格对称性和晶格场劈裂能的影响,大半径长量子棒具有负的线偏振因子.线偏振因子随着z-方向磁场的增加而减小,可能由正变负,即z-方向的线偏振发射相对xy-平面内的线偏振发射减小了.     

反应条件对水溶性CdSe量子点光学性能的影响

以巯基乙酸(TGA)为配位剂合成了水溶性CdSe量子点,研究了反应时间、溶液pH值及前驱体溶液中镉元素与硒元素的摩尔比对量子点光学性能的影响。以L-半胱氨酸(L-cys)、巯基乙酸和巯基乙胺(CA)为配位剂在优化的pH值条件下合成了系列水溶性量子点,研究了配位剂的种类对量子点光学性能的影响。结果表明:当以TGA为配位剂时,反应条件对量子点的粒径分布及光学性能有重要的影响;为获得粒径分布窄的量子点溶液,宜采用的最佳反应条件为pH值为10～12,Se与Cd的摩尔配比为2∶3,量子点的粒径随时间延长而增大;此外,利用不同的配位剂可有效改变水溶性量子点的表面物理化学特性,且量子点的尺寸大小因所用配位剂不同依以下顺序递减:巯基乙酸L-半胱氨酸巯基乙胺。     

Electronic Structure and optical Properties of Wurtzite CdSe Ouantum Ellipsoid

In the framework of the effective mass envelop function theory, we got the amiltonian of the quantum ellipsoidafter a coordinate transition. The energies wave functions are calculated as functions of the aspect ratio. With an overallconsideration of the transition matrix element and the Boltzmann distribution, we explained why the polarization factorincreases with increasing e and approaches a saturation value which tallies quite well with the experiment reported. The effects of the crystal field splitting energy temperature and transverse radius to the polarization are also considered. We discussed the band gap variation with the size and shape of the quantum ellipsoid at last.     

单分散闪锌矿型CdSe量子点的合成及表征

采用TOPO辅助油相合成的化学方法制备出单分散的CdSe量子点。通过透射电子显微镜、X射线粉末衍射、粒径分布、紫外-可见吸收光谱和光致发光谱等多种测试手段对产物进行了表征,结果表明,CdSe量子点具有闪锌矿型(立方)晶体结构、粒径均匀、尺寸分布窄、发光性能良好的特点。此外,对闪锌矿型CdSe量子点的形成进行了初步分析。     

Ligand Shell Engineering to Achieve Optimal Photoalignment of Semiconductor Quantum Rods for Liquid Crystal Displays

The photoalignment process to align semiconductor quantum rods (QRs) in the liquid crystal monomer (LCM) matrix is a flexible technology; however, the optical quality of the resulting enhancement films drops at high concentrations of the QRs. The compatibility between the ligand shell on the QRs and the LCM plays an important role in avoiding this issue. Herein, several kinds of ligand shells on the rod‐in‐rod CdSe/CdS QRs are designed, without affecting the optical properties of QRs, and their compatibility with LCM molecules is studied. Promesogenic dendritic ligands in combination with relatively short alkylphosphonic acids are found to provide the highest optical quality, without QR aggregation, and so the high brightness of the resulting enhancement films, even at higher concentrations of QRs in LCM, which is perfectly suitable for the application in liquid crystal displays.     

光纤量子密钥分发系统的几种偏振补偿技术

偏振补偿是偏振编码量子密钥分发(QKD)系统的一项关键技术。介绍了利用偏振控制器和双向光路进行偏振补偿的基本原理,简述了偏振编码的QKD系统中常用的光纤信道偏振补偿方案,包括双向光路偏振补偿方案,中断式偏振补偿方案,时分复用(TDM)偏振补偿方案和波分复用(WDM)偏振补偿方案。     

Highly Bright and Compact Alloyed Quantum Rods with Near Infrared Emitting: a Potential Multifunctional Nanoplatform for Multimodal Imaging In Vivo

Controlling synthesis of near‐infrared emitting quantum rods (QRs) for in vivo imaging is a major challenge in the fabrication of multifunctional nanoprobes. Here, a reliable synthetic approach for CdTe _x Se_1–x /ZnS alloy nanocrystals to achieve highly bright (quantum yields up to 80%) with controllable rod‐shape and near‐infrared (650–870 nm) emission is developed. Aspect ratio and emission of QRs are correlated with composition, which can be easily tuned by changing Te and Se mole ratio. It illustrates that the content of Se plays an important role in maintaining the rod‐shape, while Te has a significant impact on emitting of the nanorods. Besides exhibiting great stability over a broad range of pH (4–10) and ion strength (up to 2 mol L^‐1 NaCl solution), these hydrophilic QRs display good photo stability and storage stability. In particular, the specially absorbing of paramagnetic gadolinium ions on the QRs lead to a versatile method to engineer multimodal imaging nanoprobes, which are applied for in vivo lymph node dual‐modal imaging (fluorescence and magnetic resonance imaging). These results suggest a promising strategy for engineering multifunctional imaging nanoprobes with the stable near‐infrared QRs.     

CdSe量子点的制备与荧光特性研究

主要讨论了CdSe量子点的制备及荧光特性。CdSe量子点由化学方法制备，通过选择不同的反应时间得到不同尺度的量子点样品。用荧光方法研究了量子点样品在石英衬底和有机溶剂中的荧光特性。实验表明，这些量子点都有良好的荧光特性。还用无限深球方势阱模型分析了量子点样品的电子态，并根据荧光参数估算了量子点的尺度．各样品荧光峰具有一致的半峰宽，表明CdSe量子点的成核过程在反应开始时同时完成。     

量子棒中弱耦合杂质束缚极化子的性质

给出了具有椭球边界量子棒经过坐标变换成球形边界的哈密顿量。采用线性组合算符和幺正变换的方法,研究了在非均匀抛物限制势下量子棒中弱耦合杂质束缚极化子的振动频率、基态能量和基态结合能随库仑束缚势、电子-声子耦合强度和椭球的纵横比的变化关系。数值计算结果表明:振动频率、基态能量和基态结合能随库仑束缚势的增加而增大,基态能量和基态结合能随电子-声子耦合强度的增加而增加。当e′>1时,振动频率、基态能量和基态结合能随椭球的纵横比的增加而增加;e′<1时,随纵横比的减少,振动频率、基态能量和基态结合能都增大;当e′=1时,振动频率取极小值,基态能量和基态结合能也取较小的稳定值。     

Exciton spectroscopy on single CdSe/ZnSe quantum dot photodiodes

We have investigated the properties of neutral and charged excitons in single CdSe/ZnSe QD photodiodes by μ-photoluminescence spectroscopy. By applying a bias voltage, we have been able to control the number of electrons in a single QD by shifting the energy levels of the QD with respect to the Fermi level in the back contact. Also the quantum-confined Stark effect was observed as a function of the applied electric field.