Ⅱ-Ⅵ族量子点掺杂玻璃的光学性质及研究进展

由于量子限域效应,尺寸可调的Ⅱ-Ⅵ族量子点掺杂玻璃在光学滤波片、非线性光学器件上的应用已经被广泛研究。玻璃中量子点的光学性质主要由量子点的尺寸、表面状态和周围基质环境决定,通过提高Se/Cd比可以有效地对量子点的表面缺陷进行钝化,实现CdSe量子点的本征发光;进一步调整热处理制度可以促进Zn离子扩散进入CdSe量子点表面,形成CdSe/Cd_(1-x)Zn_xSe核壳结构,使得缺陷发光几乎完全猝灭,从而提高量子点的荧光量子效率;在玻璃中原位合成的CdS/ZnS核壳结构量子点的荧光量子效率可达到53%。随着基础研究中玻璃中Ⅱ-Ⅵ族量子点荧光效率的不断提高,发光二极管(LED)等小型发光器件的制造成为可能。为了满足实际需要,建立核壳结构中量子点表面钝化机理模型,进一步优化量子点荧光效率是下一步需要解决的问题。     

尺寸分布和界面混合对InAs/GaAs量子点光学性质的影响

研究了自组织生长模式(S-K modes)下量子点尺寸的不均匀分布对量子点发光性质的影响,对其光致发光峰进行了拟合计算.研究发现,量子点尺寸的不均匀分布导致了量子点发光峰的展宽以及发光峰位的红移.另一方面,后处理工艺中的退火及质子注入引起的界面混合导致了量子点PL谱发光峰的蓝移及半高宽的减小.     

静电自组装制备CdTe量子点纳米薄膜

以巯基丙酸为稳定剂, 在水相中合成了表面带负电荷、具有良好的分散性、平均粒径为5nm的CdTe量子点. 通过CdTe量子点与阳离子聚电解质聚二烯丙基二甲基氯化铵(PDDA)和阴离子聚电解质聚苯乙烯磺酸钠(PSS)之间的静电相互作用, 在石英基片表面通过层层静电自组装方法制备了多层CdTe量子点纳米薄膜. 以荧光分光光度计、UV-Vis、XPS、AFM等测试手段对所得的CdTe量子点纳米薄膜进行了表征. 研究结果表明, CdTe量子点自组装多层薄膜的UV-Vis吸光度与组装层数基本呈线性关系, 薄膜成膜质量良好. 自组装薄膜基本上规整并均匀地覆盖在石英基底表面, 但薄膜中存在部分CdTe量子点聚集现象. 通过在相邻的两层CdTe量子点之间引入基本结构单元为PDDA/PSS/PDDA的聚电解质复合层, 可有效提高CdTe量子点纳米薄膜的成膜质量. 所得的CdTe量子点纳米薄膜具有良好的荧光光致发光性.     

水相合成CdTe量子点及其性能表征

以NaTeO3为碲源,巯基乙酸(TGA)为稳定剂,合成CdTe量子点。研究Cd2+的浓度、Cd2+-TGA前驱体室温静置时间对CdTe量子点荧光光谱、荧光量子效率的影响,并用X射线粉末衍射仪和透射电子显微镜对其结晶性能、结构以及形貌进行表征。实验表明,所制备的CdTe量子点具有闪锌矿结构和球形形貌。且在Cd2+-TGA前驱体室温静置50min后参与回流,Cd2+浓度为0.00067mol/L时,荧光量子效率最高可达48.4%。     

高质量水溶性CdTe量子点的合成与表征

以CdCl2和TeO2为原料,硼氢化钠为还原剂,采用水相合成法制备巯基丁二酸稳定CdTe量子点。研究了反应时间、碲和镉的物质的量之比等实验条件对CdTe量子点发光性能的影响,并用X射线粉末衍射、透射电镜、红外光谱、紫外-可见吸收光谱和荧光光谱等分析技术对其进行表征。实验表明,合成的量子点为立方晶型,颗粒大小分布均匀。反应时间及碲和镉的物质的量之比对量子点的发光性能有明显影响,随着反应时间的延长,量子点的吸收与荧光光谱都向长波方向移动,在pH值为10.5的碱性条件下,当n(Cd)∶n(Te)∶n(MSA)=1∶0.05∶1.4时,在5h的时间内可获得发绿色到红色荧光的量子点,最高荧光量子产率为70.3%。     

基于量子点的分子灯塔探针的制备及其在DNA探针中的应用

根据荧光共振能量转移理论合成出一种新颖的分子灯塔探针.由于CdTe量子点（QD s）的荧光发射光谱与DABCYL的紫外-可见吸收光谱有很好的重叠性,所以此种探针采用CdTe量子点作为能量给体,DABCYL作为能量受体.通过水相法合成出直径为2.5 nm的CdTe量子点,并且在偶联剂1-乙基-3-（3-二甲基氨丙基）碳二亚氨盐酸盐（EDC）作用下,与5-′NH2-DNA-DABCYL连接得到了分子灯塔探针.实验发现探针的荧光强度相比CdTe-DNA有明显的下降,最大能量转移效率为68.3%,表明CdTe QD s和DABCYL之间发生了荧光共振能量转移.结果表明,此种探针体系对于互补DNA及其变种有着很好的特异性,且其检测极限为5.170×10^-9mol/L.     

磷化铟量子点合成的研究进展

综述了磷化铟量子点合成研究的最新进展。由于磷化铟量子点材料具有低毒性(不含铅镉等重金属有毒性元素),且具有优异的发光性质(如荧光发光峰在可见至近红外发光范围内可调,荧光量子产率高,稳定性好),在新型发光器件、显示器件、光检测器件和生物荧光成像中有广泛的应用前景。经过近三十年的发展,磷化铟量子点的合成研究取得了长足的进步,其光学性质已经可以和Ⅱ-Ⅵ和Ⅳ-Ⅵ族量子点材料的性能参数相媲美。围绕如何开发和优化磷化铟量子点的合成策略,提高材料的光学性能这一主题进行介绍,分别从磷化铟量子点的体相成分、表面配体、核壳结构的调控及优化等方面进行了阐述。最后对磷化铟量子点材料的目前合成研究存在的问题和未来趋势进行展望。     

微波辅助快速合成水溶性CdTe/CdSe核壳量子点

以巯基乙酸(TGA)作为稳定剂,用微波辅助法快速合成了水溶性CdTe/CdSe核壳量子点.比较了传统水热法和微波辅助法制备的量子点性能,研究了加热温度、反应物配比及CdTe量子点浓度对CdTe/CdSe核壳量子点的性能影响.研究结果表明,核壳结构的CdTe/CdSe量子点比单一的CdTe量子点具有更优异的光致发光强度和...     

零维氧化锌纳米量子点的水热法合成及其量子效应表征

介绍了一种以乙醇为溶剂,在低温、常压下水热制备零维氧化锌量子点(ZnO QDs)的简单方法,并运用该方法制备了尺寸均一、形貌规则的ZnO QDs。利用荧光分光光度计和紫外-可见分光光度计分析了其受激辐射特征波长的蓝移和深能级发光变化,证实其光学量子效应明显,光致发光的绿光发射增强。讨论了可能导致其绿光发射增强的原因并提出了有待验证的问题。     

碲化镉量子点/聚(3,4-乙撑二氧噻吩)-聚苯乙烯磺酸复合纳米微球的原位聚合与光学性质

通过原位种子聚合构筑了碲化镉量子点(CdTe QDs)/聚(3,4-乙撑二氧噻吩)-聚苯乙烯磺酸(PEDOT-PSS)复合纳米微球.利用扫描电镜、红外光谱,X射线光电子能谱、紫外可见吸收光谱及荧光发射光谱对其形貌、结构、光学吸收性质及光致发光性能进行了测试分析.研究结果表明,原位聚合的CdTe/PEDOT-PSS复合物...     

水溶性掺杂型CdZnTe量子点的制备及表征

以Zn离子为掺杂材料,L-半胱氨酸为稳定剂,采用高温高压的水热合成法制备出水溶性的掺杂型CdZnTe量子点,有效地减少了量子点表面的缺陷,降低了CdTe量子点的毒性,使得制备出的CdZnTe量子点的生物相容性良好,具有单分散性好、发射范围宽、量子产率高等优点,将会在生化检测及生物医学领域大有作为。     

Fe3O4/CdTe磁性荧光纳米复合物的逐步杂凝聚法合成及其表征

采用逐步杂凝聚法合成了Fe3O4/CdTe磁性荧光纳米复合物.以化学共沉淀法制备Fe3O4纳米颗粒,经油酸修饰后分散在表面活性剂中形成磁流体.CdTe量子点以巯基乙酸为稳定剂制得.最后以聚乙烯亚胺(PEI)为联接剂,成功制备了Fe3 O4 /CdTe磁性荧光双功能纳米复合物颗粒.该复合物颗粒平均尺寸为(30±5)nm,荧光产率为0.186,饱和磁化强度为15.745emu/g,该纳米粒子既具有优异的荧光特性,也具有较强的超顺磁性.     

Tuning spin properties of excitons in single CdTe quantum dots by annealing

Using polarization-resolved photoluminescence imaging in external magnetic fields we measure statistically significant distributions of exchange splitting, diamagnetic shift and effective g-factor of excitons in tens of single CdTe quantum dots. Comparison between the as-grown and annealed structures shows strong suppression of ensemble inhomogeneities, with the average exchange splitting reduced by half and significant narrowing of the g-factor distribution. Remarkably, the average value of the excitonic g-factor remains unchanged. This unique ability to yield highly uniform quantum dot ensembles without hampering the exciton Zeeman splitting makes annealing a highly attractive means for tuning the spin properties of quantum dot excitons.     

水溶性CdHgTe合金量子点的制备与表征

以巯基乙酸为稳定剂, 在水溶液中加热CdCl₂、HgCl₂ 和 NaHTe的混合物直接合成CdHgTe合金量子点. 分别用荧光光谱、红外光谱、X射线衍射及透射电镜对其光谱性能、表面基团和结构形貌进行了表征. 结果表明, 合金量子点的发射波长在536到688 nm范围内连续可调, 掺杂后量子点的发射光谱变宽, 半高峰宽为70~90 nm; CdHgTe的荧光量子产率介于1.5%到6.7%之间; 巯基与CdHgTe量子点表面的Cd²⁺离子发生键合, 而使巯基乙酸结合于量子点表面; 合金量子点具有闪锌矿结构; 量子点分散性好, 形貌呈颗粒状.     

Self-assembled InAs/GaAs quantum dots covered by different strain reducing layers exhibiting strong photo- and electroluminescence in 1.3 and 1.55 microm bands

The effect of different InGaAs and GaAsSb strain reducing layers on photoluminescence and electroluminescence from self-assembled InAs/GaAs quantum dots grown by metal-organic vapour phase epitaxy was investigated. The aim was to shift their luminescence maximum towards optical communication wavelengths at 1.3 or 1.55 microm. Results show that covering by InGaAs strain reducing layer provides stronger shift of photoluminescence maximum (up to 1.55 microm) as compared to GaAsSb one with similar strain in the structure. This is caused by the increase of quantum dot size during InGaAs capping and reduction of quantum confinement of the electron wave function which spreads into the cap. Unfortunately, the weaker electron confinement in quantum dots is a reason of a considerable blue shift of electroluminescence from these InGaAs structures since optical transitions move to InGaAs quantum well. Although strong electroluminescence at 1300 nm was achieved from quantum dots covered by both types of strain reducing layers, the GaAsSb strain reducing layer is more suitable for long wavelength electroluminescence due to higher electron confinement potential allowing suppression of thermal carrier escape from quantum dots.     

Photoluminescence and magnetophotoluminescence of circular and elliptical InAs/GaAs quantum dots

Photoluminescence, magnetophotoluminescence, and atomic force microscopy were used for the characterization of MOVPE prepared InAs/GaAs quantum dots. Significant differences in the behaviour of the first excited photoluminescence transition in magnetic field are explained by the different lateral shape of quantum dots. While the first excited luminescence peak of circular quantum dots splits with increasing magnetic field into two peaks, no splitting occurs for quantum dots with elliptic shape, only small red shift is observed. Theoretical calculations of energy levels in InAs/GaAs quantum dots with circular and elliptical shape with different elongations are presented and compared with experimental results.     

Luminescent quantum dots fluorescence resonance energy transfer-based probes for enzymatic activity and enzyme inhibitors

The paper describes the development and characterization of analytical properties of quantum dot-based probes for enzymatic activity and for screening enzyme inhibitors. The luminescent probes are based on fluorescence resonance energy transfer (FRET) between luminescent quantum dots that serve as donors and rhodamine acceptors that are immobilized to the surface of the quantum dots through peptide linkers. Peptide-coated CdSe/ZnS quantum dots were prepared using a one-step ligand exchange process in which RGDC peptide molecules replace trioctylphosphine oxide (TOPO) molecules as the capping ligands of the quantum dots. The peptide molecules were bound to the surface of the CdSe/ZnS quantum dots through the thiol group of the peptide cysteine residue. The peptide-coated quantum dots were labeled with rhodamine to form the FRET probes. The emission quantum yield of the quantum dot FRET probes was 4-fold lower than the emission quantum yield of TOPO-capped quantum dots. However, the quantum dot FRET probes were sufficiently bright to enable quantitative enzyme and enzyme inhibition assays. The probes were used first to test the enzymatic activity of trypsin in solution based on FRET signal changes of the quantum dot-based enzymatic probes in the presence of proteolytic enzymes. For example, exposure of the quantum dot FRET probes to 500 microg/mL trypsin for 15 min resulted in 60% increase in the photoluminescence of the quantum dots and a corresponding decrease in the emission of the rhodamine molecules. These changes resulted from the release of rhodamine molecules from the surface of the quantum dots due to enzymatic cleavage of the peptide molecules. The quantum dot FRET-based probes were used to monitor the enzymatic activity of trypsin and to screen trypsin inhibitors for their inhibition efficiency.     

Surfactant-dependent photoluminescence of CdTe/CdS nanocrystals

ABSTRACT

The photoluminescence of aqueously synthesised core/shell CdTe/CdS quantum dots (QDs) was investigated. Two molar ratios (2.4 and 1.3) of thioglycolic acid (TGA) to Cd²⁺ were compared to determine the best synthesis conditions for high photoluminescent quantum yield (PLQY) and photostability. A difference in the PLQY of the CdTe/CdS QDs was observed when CdS shells were grown with different TGA/Cd²⁺ ratios. The difference in the observed PLQY was attributed to the quality of the passivation of the CdTe during the CdS shell growth. At TGA/Cd²⁺ ratio of 1.3, the CdS shell forms through homogeneous nucleation, which is limited by diffusion of growth material from the solution onto the QDs surface. Due to the lattice mismatch of CdTe and CdS, the core will experience coherence strain resulting in dislocation sites and surface defects between nucleation sites which can result in non-radiative trap states. When the TGA/Cd²⁺ ratio is 2.0, the CdS shell grows epitaxially, minimising the number of surface trap states. Finally, we observed that the fluorescence intermittency was supressed for CdTe QDs after UV light illumination, attributed to annealing of deep surface trap states by UV light.     

Competition between surface trapping and nonradiative energy transfer to gold nanofilm

Nonradiative resonant energy transfer from CdSeS quantum dot to gold nanofilm was investigated by taking nanosecond and picosecond time resolved photoluminescence measurements. Surface plasma resonant absorption peak of gold nanofilm was adjusted to meet the near resonant conditions with the fluorescence peak of quantum dot by changing the thickness. Surface trapping state was proved to be the origin of the long lifetime component by comparing fresh and eight months aged quantum dot. It was observed that the excitonic state lifetime of the quantum dots was reduced by nonradiative resonant energy transfer to gold nanofilm. Nonradiative resonant energy transfer time, which was comparable with the surface trapping time, was calculated based on the data of picosecond photoluminescence measurements. No nonradiative energy transfer from surface trapping state to gold nanofilm, thus the lifetime of surface trapping state was not affected obviously. It is suggested that in the assembly combined with quantum dot and gold nanostructure, nonradiative energy transfer will occur after the population of excitonic state, and compete with surface trapping process. The interactions between surface trapping state and gold nanoflim were not exhibited.