水溶性CdTe/CdS纳米晶表面SiO2壳层的反相胶束法包覆

"提出了一种水相中制备CdTe/CdS核壳结构纳米粒子的方法.用Te粉作为碲源,用Na2S作为硫源,在50 ℃下制备了CdTe/CdS核壳结构纳米粒子. 用紫外可见吸收光谱和荧光光谱分析了CdS壳层对CdTe核的影响. 随CdS壳层厚度的增加,紫外可见吸收光谱和荧光光谱均发生了红移. CdS壳层厚度较薄时,CdTe/CdS纳米晶的荧光强度较CdTe纳米粒子有显著提高;而CdS壳层厚度较厚时,CdTe/CdS纳米晶的荧光强度会逐渐降低. 用反相胶束法在CdTe/CdS核壳结构纳米粒子的表面包被一层SiO2,     

表面修饰的CdS纳米荧光探针的研究

采用溶胶-凝胶法合成硫脲表面修饰的硫化镉纳米粒子[CdS/SC(NH₂)₂],研究硫脲的用量对其粒径的影响,用X射线粉末衍射、透射电子显微镜,红外光谱以及荧光光谱等手段进行了表征。并研究了小牛胸腺DNA的加入对该纳米粒子荧光光谱的影响。实验结果表明,硫脲的用量对该纳米粒子的粒径大小及发光特性有明显影响,随反应物中硫脲与镉离子的物质的量的比值增加,CdS/SC(NH₂)₂纳米粒子粒径变小,其发射波长蓝移,表现出明显的量子尺寸特性;小牛胸腺DNA的加入使CdS/SC(NH₂)₂纳米粒子的发射光谱强度减弱,实验推测该纳米粒子与小牛胸腺DNA存在静电相互作用, 该研究结果可望用于DNA的分析测定。     

纳米CdS-磺化聚苯胺（SPAn）多层复合膜的光学特性研究

研究了利用层-层自组织生长法制备的磺化聚苯胺-CdS纳米晶体复合膜的光学特性.研究发现，随样品中CdS 纳米晶体尺寸的减小，量子尺寸效应明显增强；在紫外吸收谱中表现为吸收边出现了明显蓝移；在光致发光谱中，不仅激子直接复合产生的带边发射产生了蓝移，而且陷阱态复合产生的宽带发射也发生了蓝移.还发现样品经低温退火处理后，激子复合产生的带边发射显著增强，发射带宽随纳米尺寸的减小而变窄.这说明退火后CdS 纳米晶粒的有序性和均匀度显著增加. 关键词： CdS 纳米晶体 SPAn 吸收 发光     

CdS半导体纳米晶体高强度激发下光谱特性研究

CdS半导体微晶作为代表性介观材料(mesoscopic material)其光学吸收和发光与量子尺寸效应的关系已经得到广泛研究[1-4],发现随着CdS微晶尺寸减小,CdS本征吸收和发射带呈现显著蓝移.Rossetti等人[3]和Y.Wang等人[4]分别通过对溶胶、沸石、聚合物和玻璃中CdS纳米晶体的光致发光测量研究了发光来源以及发光与尺寸的关系,确定了两个宽带发光分别属于带隙发光(350-500nm)和表面态或缺陷发光(500-700nm).本文首次报道了利用溶胶凝胶方法制备的钠硼硅中纳米尺寸CdS晶体高激发功率条件下的发光光谱测量结果,观察到随激发功率增加发光光谱兰移和线宽明显宽化,讨论了其物理机制.     

反相微乳液模板原位聚合制备纳米氯化银/聚甲基丙烯酸甲酯及其结构表征

用甲基丙烯酸甲酯 (MMA)作油相 ,反相胶束微乳液作为模板 ,制备了纳米氯化银 (AgCl)粒子 ,再进行原位聚合制备了纳米氯化银 /聚甲基丙烯酸甲酯 (AgCl/PMMA)复合材料 .透射电镜 (TEM )分析表明 ,纳米AgCl的尺寸为 2 0～ 80nm .扫描电镜 (SEM )测试表明纳米AgCl粒子均匀地存在于PMMA基材中 .红外分析证明 ,胶束中水和表面活性剂AOT的羰基在MMA聚合后微观环境发生变化 ,纳米粒子同聚合物之间有吸附行为 .动态力学 (DMTA)分析复合材料 ,发现纳米AgCl粒子与聚合物之间存在强烈相互作用 ,形成了中间相层 (interphaselayer) ,改变了聚合物的动态力学性能 .     

CdTe,核 壳型CdTe/CdS及CdTe/ZnS量子点的合成及表征

在水相中制备了半导体CdTe纳米晶,核 壳型CdTe/CdS和CdTe/ZnS纳米晶（即量子点;QDs）.利用扫描隧道显微镜（STM）和荧光光谱(FS)对合成的纳米晶量子点进行了研究,并且根据FS的数据进行了量子效率的计算.STM的结果表明合成的量子点直径约为3 nm并且分布良好.为了提高量子效率,对Cd2+浓度和Cd2+∶S2－比例等反应条件进行了研究,结果表明随着回流时间的增加,核 壳型量子点CdTe/CdS的量子效率总体上呈下降趋势.CdTe/CdS在pH8.5,Cd2+∶S2－=10∶1（摩尔比）时可获得80.0%的最大量子效率.同时制备了核 壳型量子点CdTe/ZnS,其最大发射波长由551 nm（CdTe）红移到635 nm（CdTe/ZnS）表明量子点的尺寸在增长,但是量子效率下降到14.4%. 当前研究的量子点可适用于生物标记,生物成像,以及基于共振能量转移的生物传感研究.     

掺杂CdS纳米粒子聚合物的光折变效应研究

研究了掺杂CdS纳米粒子的有机聚合物体系的光折变效应,体系中以CdS纳米粒子为光敏剂,聚乙烯咔唑(PVK)为载流子输运剂,4-(4-硝基苯偶氮)苯胺染料(DO3)为非线性生色团,9-乙基咔唑(ECZ)为增塑剂。反胶束法合成的CdS胶束颗粒采用紫外可见吸收光谱和透射电子显微镜(TEM)表征,结果表明,具有纳米尺寸和量子限制效应。研究了PVK-CdS薄膜的光电导特性,实验结果表明,CdS纳米粒子与PVK之间的电荷转移可以有效的提高PVK的光电导率。双光束耦合实验证明了该体系的光折变特性,在无外加电场下,获得二波耦合增益系数78.4 cm-1,分析表明聚合物薄膜具有强的光致取向增强效应;样品在两相干光束作用下,可建立折射率光栅,其衍射效率达到4.4%。     

YVO_4∶Eu~(3+)@SiO_2核壳结构纳米复合材料的合成与表征

用沉淀法制备了尺寸约为8 nm的YVO4∶Eu3+纳米粒子,然后用反相微乳液法在YVO4∶Eu3+纳米粒子的表面包覆了一层Si O2壳。利用XRD、TEM、UV-Vis吸收光谱和光致发光光谱对合成的样品进行了表征。得到的复合物具有较好的核壳结构,通过改变硅酸四乙酯的用量可以改变Si O2壳的厚度。研究了Si O2壳对YVO4∶Eu3+发光性质的影响,结果表明:包覆和未包覆的样品在紫外光激发下都有Eu3+的特征发射;随着Si O2壳厚度的增加,发光强度和量子效率越来越低,Eu3+格位对称性越来越高。     

Zno纳米晶的室温紫外受激发射特征

ZnO的激子特性对制备氧化锌基的光电子器件至关霞要,因此对ZnO量子点中激子的发光性质及其跃迁过程进行研究显得十分必要.采用溶胶-凝胶法制备了ZnO纳米晶,X射线衍射(XRD)结果表明样品具有六角纤锌矿多晶结构.研究了在不同泵浦功率激发下ZnO纳米晶的紫外发射的时间积分光谱和时间分辨光谱,观察到自南激子发光,激子-激子碰撞和电子-空穴等离子体引起的受激发射,研究了在不同泵浦功率激发下自由激子及激子-激子碰撞随泵浦功率依赖的动力学过程.研究结果对理解激子带边发射有一定帮助,对ZnO材料在短波长半导体光电器件方面有潜在的应用价值.     

不同厚度CdSe阱层的表面上自组织CdSe量子点的发光性质

利用变温和变激发功率分别研究了不同厚度CdSe阱层的自组织CdSe量子点的发光。稳态变温光谱表明:低温下CdSe量子阱有很强的发光,高温猝灭,而其表面上的量子点发光可持续到室温,原因归结于量子点的三维量子尺寸限制效应;变激发功率光谱表明:量子点激子发光是典型的自由激子发光,且在功率增加时。宽阱层表面上的CdSe量子点有明显的带填充效应。通过比较不同CdSe阱层厚度的样品的发光,发现其表面上量子点的发光差异较大,这可以归结为阱层厚度不同导致应变弛豫的程度不同,直接决定了所形成量子点的大小与空间分布^[1]。     

Optical and IR study of CdS nanoparticles dispersed in a new confined p-phenylenevinylene

In the present study we have synthesized CdS semiconducting quantum dots by reverse micelle method using dodecanthiol (C₁₂H₂₆S) as the capping agent. The synthetic medium consists of a quaternary water/Sodium dodecyl sulfate (SDS)/buta-1-ol/hexane microemulsion. The size of the particles was controlled by changing the molar ratio W=[H₂O]/[SdS], where [H₂O] and [SdS] are the molar concentrations in hexane of water and SdS respectively. The CdS nanoparticles were embedded in a new PPV derivate named Fluorinated Bisphenol A P-phenylenevinylene (BPAF-PPV). Fourier transform infrared spectroscopy (FT-IR) showed a strong interaction of thiol groups with CdS nanoparticles. Blue shift of the optical absorption onset is observed due to quantum size effect. The band gap and particle sizes of the nanoparticles were deduced from optical absorption spectra and the use of an effective mass approximation (EMA) model. Photoluminescence spectroscopy evidenced a charge transfer process via the interface between BPAF-PPV/CdS nanoparticles.     

利用Cd(OH)_2选择性包覆与光分解腐蚀缩小CdS纳米微粒的尺寸分布的研究

提出结合Ｃｄ（ＯＨ）２ 选择性包覆与光分解腐蚀法缩小ＣｄＳ纳米微粒的尺寸分布, 并通过对ＣｄＳ纳米微粒发射光谱的研究证实了这一设计思想． 以多聚磷酸钠（ＨＭＰ）为稳定剂合成ＣｄＳ纳米微粒, 再通过Ｃｄ２＋ 与ＯＨ－ 的选择性包覆在大粒径的ＣｄＳ纳米微粒表面形成一层Ｃｄ（ＯＨ）２, 然后溶液置于日光下辐照处理, 数天后, 未经包覆的小粒径ＣｄＳ纳米微粒被日光腐蚀分解, 溶液中只剩下被Ｃｄ（ＯＨ）２ 包覆的大粒径ＣｄＳ纳米微粒, 这样即可达到缩小ＣｄＳ纳米微粒尺寸分布的目的．     

ZnS:Ag/CdS: a new family of color-tunable quantum dots

ZnS:Ag/CdS quantum dots (QDs) have been synthesized by a reverse micelle process under ambient environment. Excited by 350?nm, the emission peak of ZnS:Ag/CdS QDs changes from 425 to 625?nm with increasing the thickness of CdS shells. Although the quantum yields of QDs decrease with CdS shells thickening, the luminescent brightness remains stable throughout. Compared with the traditional color-tunable CdSe QDs, the synthesis of ZnS:Ag/CdS QDs is less toxic and more economic. Therefore, this synthesis process can be regarded as an efficient way to fabricate a series of luminescent nanostructures for a variety of applications.     

Photoluminescence quantum and surface states of excitons in ZnSe and CdS nanoclusters

The optical spectra of quantum dots (QDs) of CdS and ZnSe grown in borosilicate glass by the sol-gel method are obtained and analyzed. It is found that at concentrations of the two semiconductors x<0.06% the emission spectra are due to annihilation of free (internal) excitons in quantum states. The mean size of the quantum dots for a given concentration of ZnSe and CdS is calculated and found to be in good agreement with the X-ray data, and the exciton binding energy is calculated with allowance for the dielectric mismatch between the semiconductor and matrix. It is proposed that this mismatch may be the cause giving rise to the exciton percolation level that is observed in QD arrays for both systems at x>0.06%. The emission from the surface level of CdS QDs in the region ~2.7 eV, formed by the outer atoms with dangling bonds, is observed for the first time, as is the emission band from surface localized states. The relation between the position of the maximum of this band and the energy of the 1S state of the free exciton is established. It is shown that the properties of surface localized states are largely similar to the analogous properties of localized states of 3D (amorphous semiconductors, substitutional solid solutions of substitution) and 2D (quantum wells and superlattices) structures.     

不同激发密度下CdS晶体的光致发光和受激发射

本文主要研究在77-111K温度范围内、不同激发密度的N2激光器的337.1nm谱线激发下,激子-激子(Ex-Ex)、激子-载流子(Ex-e)的相互作用和发射一个LO声子(Ex-1LO)、两个LO声子(Ex-2LO)的自由激子的辐射复合行为.并在77K温度下观测到由Ex-Ex发射产生的受激发射.     

CdS量子点的酿酒酵母仿生合成及光谱表征

以酿酒酵母为载体,常温下利用仿生法成功合成了CdS量子点。荧光发射光谱、紫外吸收光谱以及荧光显微镜照片证明,该方法合成的CdS量子点的荧光发射峰位置在443nm,在紫外灯下能发蓝绿色荧光。透射电子显微镜(TEM)表征结果表明,该仿生法合成的CdS量子点为六方纤锌矿结构。以荧光发射和紫外吸收光谱为性能指标,考察了酿酒酵母生长时期、Cd2+的反应浓度以及反应时间等条件对合成CdS量子点的影响。当酿酒酵母处于生长稳定期初期时,与浓度为0.5mmol.L-1的Cd2+共培养24h后所合成的CdS量子点荧光最强。实验中观察到,换液培养可有效提高酿酒酵母合成CdS量子点的产量。     

Photoluminescence properties of ZnS/CdS/ZnS quantum dot–quantum wells doped with Ag<Superscript>+</Superscript> ions

Enhanced photoluminescence and postirradiation luminescence is reported from Ag⁺-doping ZnS/CdS/ZnS quantum dot–quantum wells (QDQWs) prepared via a reverse micelle process. Controlling the final mole ratio of water-to-surfactant in H₂O/Heptane system, the size of a QDQW was estimated to be ~6 nm. Compared to undoped QDQWs, the doped QDQWs exhibited a much stronger orange emission, with a peak blue shift from 615 to 590 nm; the quantum yield was increased from 2.63 to 9.31%, and the remaining luminescence intensity after 2 h ultraviolet irradiation was increased from 71.2 to 94.7%. This improved quantum yield and postirradiation luminescence intensity for doped QDQWs was ascribed to the introduction of Ag⁺ ions to CdS wells.     

Growth mechanism and optical property of CdS nanoparticles synthesized using amino-acid histidine as chelating agent under sonochemical process

Using amino-acid histidine as chelating agent, CdS nanoparticles have been synthesized by sonochemical method. It is found that by varying the ultrasonic irradiation time, we can tune the band gap and particle size of CdS nanoparticles. The imidazole ring of histidine captures the Cd ions from the solution, and prevents the growth of the CdS nanoparticles. The deviation in the linear relation in between cube of radius of nanoparticles and ultrasonic irradiation time confirms the growth of CdS nanoparticles occur via two process; one is the diffusion process of the reactants as well as reaction at the surface of the crystallite. CdS nanoparticles synthesized using histidine as organic chelating agent have band edge emission at 481 nm and have greater photoluminescence intensity with blue-shift to higher energy due to typical quantum confinement effect.     

Surface-defect-states photoluminescence in CdS nanocrystals prepared by one-step aqueous synthesis method

CdS nanocrystals were prepared by a simple one-step aqueous synthesis method using thioglycolic acid (TGA) as the capping molecule, and characterized by X-ray powder diffraction (XRD), UV-vis absorption spectra and photoluminescence (PL) emission spectroscopy. The effects of both TGA/Cd and Cd/S molar ratio on the surface-defect-state PL intensity of CdS nanocrystals have been investigated. It was found that all of the as-prepared CdS nanocrystals showed a strong broad emission in the range of 450-700 nm centered at 560 nm, which was attributed to the recombination of an electron trapped in a sulfur vacancy with a hole in the valance band of CdS. The surface-defect-states emission intensity of CdS nanocrystals significantly increased with the increase of Cd/S molar ratio, and showed a maximum when Cd/S molar ratio was 2.0. If Cd/S molar ratio continued to increase, namely more than 2.0, the surface-defect-states emission intensity would decrease. It was found that the surface-defect-states emission intensity increased with the increase the TGA/Cd molar ratio, and showed a maximum when the TGA/Cd molar ratio was equal to 1.8, and a further increase of the TGA/Cd molar ratio would lead to the decrease of the surface-defect-states emission intensity.     

CdTe/CdS核壳结构量子点超快载流子动力学

在水相合成CdTe以及CdTe/CdS核壳结构量子点基础上, 利用基于抽运-探测技术的瞬态差分透射技术研究了CdTe量子点以及不同CdS壳层厚度的CdTe/CdS量子点的最低激子能态的超快激发与弛豫动力学. 研究表明:相比于CdTe,CdTe/CdS量子点的电子空穴由于空间分离,其所需的激发时间要长于电子空穴空间重叠态所需要的激发时间.随着壳层厚度的增加, 量子点表面的钝化有效地减少了表面态相关弛豫机理,并延长相对应的弛豫时间.