激光诱导击穿光谱增强机制及技术研究进展

激光诱导击穿光谱技术是一种新的材料识别及定量分析技术。但是光谱的重复性低限制其由定性分析向定量分析的发展。因此提高激光诱导等离子光谱信号信噪比及等离子体的空间稳定性对于提高光谱信号的可重复性、降低基体效应等不利因素影响有着积极的作用。同时光谱信号信噪比的增强可降低对激光器输出能量的要求,有效降低了激光诱导击穿光谱集成系统的成本,有利于此技术向更多领域拓展。本文对实验中采用的双脉冲或多脉冲增强,放电脉冲再激发,空间限域,磁场束缚和微波辅助增强四大类方法加以总结及概括。在此基础上深入探讨光谱增强的物理机制,从而为进一步提高光谱信号稳定性及定量化分析的精确度提供有力的理论支持。     

PX5与Fe(CO)5分子结构的比较

以群论为基础对PX5及Fe(CO)5的分子结构进行比较,对其差异进行剖析.PX5及Fe(CO)5分子均为三角双锥结构,但是前者轴向键键长略长于平伏键,其键的强度小于平伏键,而Fe(CO)5则恰恰相反.本文从杂化轨道的类型、Berry拟转动机理、量子化学计算及NMR、X射线衍射结果等多角度做了说明和解释     

A Model on the Mn^2＋ Luminescence Band Redshift with Mn（Ⅱ） Doping and Aggregation within CdS＇Mn Microwires ＊

We report the microphoto-luminescence band redshifts with individual and multi-Mn（Ⅱ） ion emissions within CdS microwires. The localized exciton magnetic polaxons （LEMPs） corresponding to the d-d optical transitions of Mn（Ⅱ） account for this shift. This LEMP emission from the double-, three- and four-Mn（Ⅱ） ions with ferromag- netic coupling after photoexeitation can happen in diluted magnetic semiconductors, except for the individual Mn（Ⅱ） doping. In addition, a simple spin-exchange polaronic model is established to account for these emission peaks well. Through this model, we can verify the local geometry of the Mn（Ⅱ） ions in CdS microwires.     

Formation and spectroscopic characterization of mono-dispersed CdSe nanocrystals

In this article, mono-dispersed hexagonal structure CdSe nanocrystals with polyhedron shape were prepared by an open solvent thermal reaction. They show a discrete excitonic transition structure in the absorption spectra and the minimal photoluminescence （PL） peak full-width at half-maximum of 19nm. The PL quantum yield is about 60%. Transmission electron micrographs, high-resolution transmission electron micrographs, x-ray powder diffraction patterns, UV-vis absorption spectra and PL spectra were obtained for the as-prepared CdSe nanocrystals. The size of the CdSe nanocrystals can be tuned by changing the reaction temperature or time. Due to the improved synthesis method, a different growth mechanism of the CdSe nanocrystals is discussed.     

Y型沸石分子筛的水热法制备及表征——综合性研究型实验设计

介绍一个综合性研究型实验——Y型沸石分子筛的制备及表征。该实验以水热条件下溶胶-凝胶法合成分子筛为理论基础,采用导向剂法合成Y型沸石分子筛,并采用XRD、IR等手段对产物进行表征。该实验时间和步骤安排合理,可操作性强,可以在本科及研究生实验教学中推广。     

Enhancing the photo-luminescence stability of CH3NH3PbI3 film with ionic liquids

The methylammonium lead triiodide (CH₃NH₃PbI₃)-based perovskite shows a great alluring prospect in areas of solar cells, lasers, photodetectors, and light emitting diodes owing to their excellent optical and electrical advantages. However, it is very sensitive to the surrounding oxygen and moisture, which limits its development seriously. It is urgent to spare no effort to enhance its optical and electrical stability for further application. In this paper, we synthesize the MAPbI₃ perovskite film on the glass substrate with/without the ionic liquid (IL) of 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) by a simple two-step sequential solution method. The additive of BMIMBF₄ can improve the quality of crystal structure. Moreover, the photo-luminescence (PL) intensity of MAPbI₃ film with BMIMBF₄ is much stronger than the pure MAPbI₃ film after a week in the air, which is almost ten-fold of the pure one. Meanwhile, under the illumination of 405-nm continuous wave (CW) laser, the fluorescent duration of the MAPbI₃ film with BMIMBF₄ is approximately 2.75 min, while the pure MAPbI₃ film is only about 6 s. In fact, ionic liquid of BMIMBF₄ in the perovskite film plays a role of passivation, which prevents the dissolution of MAPbI₃ into CH₃NH₃ and PbI₂ and thus enhances the stability of environment. In addition, the ionic liquid of BMIMBF₄ possesses high ionic conductivity, which accelerates the electron transport, so it is beneficial for the perovskite film in the areas of solar cells, photodetectors, and lasers. This interesting experiment provides a promising way to develop the perovskite's further application.     

新型便携式激光诱导击穿光谱系统综述

本文主要综述了国内外便携式激光诱导击穿光谱(LIBS)系统的研究进展和应用情况。目前该系统主要针对金属元素进行检测,对非金属等轻元素的定量分析需要较大能量的激光激发,但受限于激光器和光谱仪等组件体积的影响,研发便携式、高精度LIBS系统有较高难度。本文针对全元素检测便携设备的研发,利用限域和高压放电脉冲得到了增强的LIBS信号,降低了激光能量,从物理机理上给出了便携式LIBS设备研发的新方向。     

Ⅱ-Ⅵ族稀磁半导体微纳结构中的激子磁极化子及其发光

自旋是基本粒子(电子、光子)角动量的内在形式.固体中体现自旋特征的集体电子行为如拓扑绝缘体等是当前凝聚态物理领域关注的焦点,是基态行为.激子作为电子空穴对的激发态且寿命很短,可复合发光,它是否能体现自旋极化主导的行为?对此人们的认识远不如针对基态的电子.激子磁极化子(exciton magnetic polaron, EMP)是由磁性半导体微结构中铁磁自旋耦合态与自由激子相互作用形成的复合元激发,但其研究很有限.本文概述了我们在稀磁半导体微纳米结构中的EMP及其发光动态学光谱、自旋极化激子凝聚态的形成方面取得的一些进展,展望了未来可能在自旋光电子器件、磁控激光、光致磁性等量子技术方面的潜在应用.     

Lasing behaviour from the condensation of polaronic excitons in a ZnO nanowire

Atoms under optical and magnetic trapping in a limited space at a very low temperature can lead to Bose-Einstein condensation (BEC),even in a one-dimensional (1D) optical lattice. However,can the confinment of dense excitons in a 1D semiconductor microstructure easily reach the excitonic BEC A lightly Mn(Ⅱ)-doped ZnO nanowire under a femtosecond laser pulse pump at room temperature produces single-mode lasing from coherent bipolaronic excitons,which is much like a macroscopic quantum state due to the condensation of the bipoaronic excitons if not real BEC. In this process,longitudinal biphonon binding with the exciton plays an important role. We revisit this system and propose possibility of bipolaronic exciton condensation. More studies are needed for this condensation phenomenon in 1D microcavity systems.     

粉煤灰提取氧化铝的技术进展

粉煤灰中含有丰富的铝,从粉煤灰中提取铝对于节约资源,改善环境,提高经济效益,实现资源优化配置和实现可持续发展都具有重要的意义.本文通过对国内外粉煤灰提铝技术的分析,讨论了各种技术的优劣及可行性.