CdS量子点的一步法合成及量子产率

以油酸为配体,十八烯为溶剂,采用一步法合成了CdS量子点,研究了反应温度、反应时间和Cd/S的摩尔比对量子点光谱性能的影响.X射线衍射(XRD)和高分辨透射电镜(HRTEM)测试结果表明,所获得的CdS量子点为立方闪锌矿结构,且尺寸分布均一,结晶度高,其较强的带边发光、尖锐的紫外吸收峰以及狭窄的荧光发射峰进一步表明量子...     

Fine tuning of the morphology of copper oxide nanostructures and their application in ambient degradation of methylene blue

A low-cost, green, and reproducibly non-injection one-pot synthesis of high-quality CdS quantum dots (QDs) is reported. The synthesis was performed in the open air by mixing precursors cadmium stearate and S powder into a new solvent N-oleoylmorpholine. An overlapped nucleation-growth stage followed by a dominated growth stage was observed. The resulting QDs exhibited well-resolved absorption fine substructure and a dominant band-edge emission with a narrow size distribution (the full width at half maximum (fwhm) was only 22-24nm). The maximum photoluminescence (PL) quantum yield (QY) was as high as 46.5%. Highly monodispersed CdS QDs with tunable sizes and similar PL fwhm and QYs could also be obtained from the CdS QDs in a large-scale synthesis. The high-resolution transmission electron microscopy (HRTEM) images and powder X-ray diffraction (XRD) pattern suggested that the as-prepared QDs with high crystallinity had a cubic structure. A significant PL improvement and a continuous QY increase for the CdS QDs were observed during a long storage time in air and in a glovebox under room temperature. A slow surface reconstruction was proposed to be the cause for the PL enhancement of CdS QDs.     

Photoassisted synthesis of CdSe and core-shell CdSe/CdS quantum dots

This paper describes the synthesis of core-shell CdSe/CdS quantum dots (QDs) in aqueous solution by a simple photoassisted method. CdSe was prepared from cadmium nitrate and 1,1-dimethylselenourea precursors under illumination for up to 3 h using a pulsed Nd:YAG laser at 532 nm. The effects that the temperature and the laser irradiation process have on the synthesis of CdSe were monitored by a series of experiments using the precursors at a Cd:Se concentration ratio of 4. Upon increasing the temperature (80-140 degrees C), the size of the CdSe QDs increases and the time required for reaching a maximum photoluminescence (PL) is shortened. Although the as-prepared CdSe QDs possess greater quantum yields (up to 0.072%) compared to those obtained by microwave heating (0.016%), they still fluoresce only weakly. After passivation of CdSe (prepared at 80 degrees C) by CdS using thioacetamide as the S source (Se:S concentration ratio of 1) at 80 degrees C for 24 h, the quantum yield of the core-shell CdSe/CdS QDs at 603 nm is 2.4%. Under UV irradiation of CdSe/CdS for 24 h using a 100-W Hg-Xe lamp, the maximum quantum yield of the stable QDs is 60% at 589 nm. A small bandwidth (W1/2 < 35 nm) indicates the narrow size distribution of the as-prepared core-shell CdSe/CdS QDs. This simple photoassisted method also allows the preparation of differently sized (3.7-6.3-nm diameters) core-shell CdSe/CdS QDs that emit in a wide range (from green to red) when excited at 480 nm.     

CdTe/CdS量子点的Ⅰ-Ⅱ型结构转变与荧光性质

制备了壳层厚度可以精确控制的CdTe/CdS核壳量子点, 利用紫外-可见吸收光谱、光致发光光谱、透射电镜和时间分辨光谱等技术, 分析了CdS壳层厚度对CdTe量子点的荧光量子产率和光谱结构的影响规律. 发现了不同于CdSe/CdS, CdSe/ZnS, CdTe/ZnS等核壳量子点的荧光峰展宽、大幅度红移以及荧光寿命大幅度增加现象. 根据能带的位置关系, 随着CdS厚度的增加, CdTe从Ⅰ型结构逐渐过渡到Ⅱ型核壳结构. 对于Ⅱ型CdTe/CdS核壳量子点, 不仅存在CdTe核区导带电子与价带空穴间的直接复合, 还存在CdS壳层导带电子与CdTe核价带空穴界面处的间接复合, 发光机制的变化导致荧光峰的展宽、明显红移和荧光寿命的增加. 当壳层过厚时, 壳层表面新引入的缺陷会阻碍荧光寿命和量子产率的进一步提高.     

低温水相合成巯基化聚乙烯醇/CdS量子点纳米复合物及用于测定环境水样中痕量Cu~(2+)

采用水相合成法,在低温N2气保护条件下,以巯基化聚乙烯醇(PVA)为基体材料合成一种环境友好型PVA/CdS量子点纳米复合物,并通过红外光谱(IR)、X射线粉末衍射(XRD)、透射电子显微镜(TEM)、热重(TG)、荧光光谱(PL)和紫外可见光谱(UV-Vis)等技术手段对复合物进行结构表征和光学性能研究。测试结果表明,复合物中CdS量子点为立方晶型结构,形状为球形,粒径小于5nm,具有很好的稳定性、分散性及发光性质。此外,Cu~(2+)对PVA/CdS水溶液荧光具有良好的猝灭作用,其荧光猝灭程度与Cu~(2+)浓度在1~1000nmol/L范围内呈良好的线性关系,线性相关系数为0.9923,方法检出限为0.12nmol/L。该纳米复合物荧光分析方法简便快速、灵敏度高、检出限低,已应用于实际黄河水样中痕量Cu~(2+)的分析与检测。     

温度对聚酰胺-胺树形分子模板法制备CdS量子点的影响

为了研究温度对聚酰胺-胺(PAMAM)树形分子的模板法制备硫化镉(CdS)量子点的影响, 以4.5代(G4.5, 64个甲酯端基)PAMAM树形分子为模板, 在－10～30 ℃的温度范围内制备了分散良好的CdS量子点. 用透射电子显微镜(TEM)表征了CdS量子点的形貌、尺寸; 用紫外-可见光谱(UV-Vis)和光致发光光谱(PL)表征了CdS量子点的光学性能. 发现在相同条件下, 制备温度从－10 ℃升高到30 ℃, CdS量子点粒径从1.8 nm增大到3.4 nm, 其中在10 ℃时制备的量子点的尺寸分布最窄; CdS量子点的吸收和发射光谱均随温度增大而红移, 其中10 ℃时制备的量子点的室温光致发光效率最高. 这表明制备温度决定了树形分子的配位基团与Cd^2＋的分离速度, 并影响了CdS量子点的成核和生长过程, 从而最终决定了CdS量子点的尺寸及尺寸分布、光致发光颜色和发光效率.     

Impact of FRET between Molecular Aggregates and Quantum Dots

Energy transfer has been employed in third‐generation solar cells for the conversion of light into electrical energy. Long‐range nonradiative energy transfer from semiconductor quantum dots (QDs) to fluorophores has been demonstrated by using CdS QDs and thiophene?BODIPY (boron dipyrromethene, abbreviated as TG2). TG2 shows a broad photoluminescence (PL) spectrum, which varies with concentration. At very low concentrations, monomeric units are present; then, upon increasing the concentration, these monomers form a mixed (J‐/H‐)aggregated state. Energy transfer between the CdS QDs and TG2 was confirmed by separately investigating the interactions between CdS and the monomer of TG2 and between CdS and the aggregated states of TG2. Size‐dependent PL quenching confirmed that nonradiative Förster resonance energy transfer (FRET) from photoexcited CdS QDs to the J‐aggregate state of TG2 was the major energy‐relaxation channel, which occurred on the timescale of hundreds of fs. These results have broad applications in the field of light harvesting based on the assembly of molecular aggregates.     

金属离子对CdS量子点/聚酰胺-胺树形分子纳米复合材料光致发光性能的影响

以聚酰胺-胺树形分子为模板制备了分散好、尺寸均匀的CdS量子点，并用分光光度滴定法研究了Cd²⁺、Zn²⁺、Pb²⁺、Cu²⁺、Mn²⁺几种金属离子对其光致发光性能的影响。发现不同离子对CdS量子点的发光性能影响不同:Cd²⁺和Zn²⁺使量子点荧光增强，Pb²⁺、Cu²⁺和Mn²⁺使其荧光有不同程度淬灭。这归因于金属离子对CdS量子点表面的修饰作用。Cd²⁺能减少由S^2-悬键构成的非辐射复合中心，增强树形分子对量子点表面缺陷的钝化作用，并能在量子点周围形成类肖特基能垒，从而显著增大CdS量子点的光致发光效率。由于ZnS与CdS的晶格参数非常接近，Zn²⁺能起到与Cd²⁺类似的作用，使CdS量子点的发光效率大大增强。Pb²⁺和Cu²⁺能取代Cd²⁺在CdS量子点表面生成窄带隙的壳层，对其发光有很强的淬灭作用。由于块体PbS的带隙比块体CuS窄，故Pb²⁺的淬灭能力强于Cu²⁺。Mn²⁺能破坏Cd²⁺与PAMAM树形分子的配位键，降低树形分子对CdS量子点表面缺陷的钝化作用，且其本身在量子点表面构成了新的荧光淬灭中心，但Mn²⁺也能形成较弱的类肖特基能垒，故对量子点的发光淬灭作用较弱。     

CdTe/CdS核壳量子点与蛋白质荧光标记

利用连续离子层吸附技术合成了水溶性的CdTe／CdS核壳量子点．通过CdS壳层的包覆,量子点的量子效率由原来的15％（裸核）提高到38％（核壳）,这种核壳结构量子点的化学和光学性质具有更好的稳定性,可以用于生物标记．本文采取共价连接与静电吸附两种方法,实现了量子点的生物标记,电泳技术已证明,应用这种量子点成功地实现了对蛋白质分子的生物标记．通过对量子点与蛋白质偶联前后的荧光光谱分析,发现量子点与蛋白质作用后荧光增强是由于蛋白质对量子点进行了表面修饰,从而降低了表面缺陷引起的非辐射跃迁几率所致．通过共价连接量子点的荧光峰位红移,主要是由于偶极-偶极相互作用引起的;量子点与蛋白质静电吸附作用引起的荧光峰位蓝移主要起因于量子点表面电荷量的降低．     

基于GSH-CdTe/CdS量子点的荧光变化研究hsDNA与盐酸洛美沙星-Cu(Ⅱ)配合物的相互作用

采用水相法合成了谷胱甘肽(GSH)修饰的CdTe/CdS量子点(GSH-CdTe/CdS QDs). 透射电子显微镜表征结果表明, GSH-CdTe/CdS QDs的粒径分布均匀, 分散性好. 在Tris-HCl(pH=7.6)缓冲液中, 由于静电引力作用, 带正电的盐酸洛美沙星(LMFH)-Cu(Ⅱ)配合物[LMFH-Cu(Ⅱ)]吸附到带负电的GSH-CdTe/CdS QDs表面形成基态复合物, 导致GSH-CdTe/CdS QDs的荧光猝灭. 随后, 向GSH-CdTe/CdS QDs-LMFH-Cu(Ⅱ)配合物体系中加入鲱鱼精DNA(hsDNA), hsDNA可诱导LMFH-Cu(Ⅱ)配合物从GSH-CdTe/CdS QDs表面脱落而嵌入到hsDNA的双螺旋结构中, 使GSH-CdTe/CdS QDs的荧光恢复. 通过对GSH-CdTe/CdS QDs荧光的可逆调控, 利用荧光光谱、 紫外-可见吸收光谱和共振瑞利散射光谱研究了hsDNA与LMFH-Cu(Ⅱ)配合物的相互作用. 通过对比GSH-CdTe/CdS QDs与LMFH相互作用的光谱性质, 讨论了GSH-CdTe/CdS QDs-LMFH-Cu(Ⅱ)-hsDNA的相互作用机理, 模拟了作用过程, 从而建立了一种研究氟诺喹酮类药物的金属配合物与核酸相互作用机制的光谱方法.     

Effect of CdS Interlayer on Properties of CdTe Based Quantum Dots

Highly luminescent thioglycolic acid-capped CdTe-based core/shell quantum dots (QDs) were synthesized through encapsulating CdTe QDs in various inorganic shells including CdS, ZnS and CdZnS. CdTe/CdS core/shell QDs exhibited a significant redshift of emission peaks (a maximum emission peak of 652 nm for the core/shell QDs and 575 nm for CdTe cores) with increasing shell thickness. In contrast, the redshift of photoluminescence (PL) peak wavelength of CdTe/ZnS QDs was less than 15 nm. The PL peak wavelengths of the core/shell QDs depended strongly on core size and shell thickness. The PL quantum yields (QYs) of the CdTe/CdS core/shell QDs are up to 67 % while that of CdTe/ZnS core/shell QDs is 45 %. A composite CdZnS shell made CdTe cores a high PL QY up to 51 % and broadly adjusted PL spectra (a maximum PL peak wavelength of 664 nm). The epitaxial growth of the shell was confirmed by X-ray powder diffraction analysis and luminescence decay experiments. Because of high PL QYs, tunable PL spectra, and low toxicity from a ZnS surface layer, CdTe/CdZnS core/shell QDs will be great potential for bioapplications.     

足球状CdS微米球的合成与发光性能的初步研究

应用化学水浴沉淀法,合成了具有特殊形貌的由纳米颗粒组成的Cds微米球,通过改变反应温度实现了对产物尺寸的控制．XRD测试结果表明生成产物为结晶良好的六角结构CdS,PL谱测试说明了产物有较好的光致发光性能．利用TEM,SAED,FEG-SEM和紫外吸收谱分析等测试手段对其结构和形成机理进行了研究．     

Controllable fabrication of nanocrystal-polymer hybrids via the catalytic chain transfer polymerization process

A facile catalytic chain transfer polymerization (CCTP) technique has been developed to synthesize covalently linked CdS nanocrystal-polymer hybrids with good optical properties. The in situ polymerization of methyl methacrylate (MMA) on the surface of modified CdS nanocrystals (NCs) with diameter of 5 nm via CCTP process yielded CdS-polymethylmethacrylate (PMMA) hybrid nanocomposites; while the incorporation of hydroxyl-coated CdS NCs into poly(methacryloxypropyltrimethoxysilane) (PMPS)-co-PMMA matrices prepared by CCTP afforded CdS-PMPS-co-PMMA hybrid nanocomposites, which were further cross-linked by free radical polymerization to form CdS NC-polymer network. The spectroscopic studies indicate that as-prepared CdS NC-polymer hybrids show good photoluminescence (PL) and the NC-polymer network exhibits highly enhanced PL property with respect to that before cross-linking. Also described are the probable mechanism for the catalytic chain transfer polymerization on the surface of modified nanocrystal and the measurement of chain transfer constants.     

水溶性的高荧光CdTe/CdSeⅡ型核壳量子点的合成与表征

用L-半胱氨酸(L-cysteine)作为稳定剂,以制备的CdTe量子点为核模板,水相合成了具有近红外发光的Ⅱ型核壳CdTe/CdSe半导体量子点。实验考察了合成温度,核模板的尺寸和组分比等因素对合成高质量的CdTe/CdSe量子点的影响。用紫外-可见吸收和荧光光谱研究了合成的量子点的光学性质。在优化的合成条件下,荧光发射光谱在586～753nm范围连续可调,荧光量子产率高达68%;通过X-射线衍射(XRD),X射线光电子能谱(XPS)和透射电镜(TEM)对合成的Ⅱ型核壳CdTe/CdSe量子点进行了结构和形貌表征。     

第二近红外窗口荧光Ag2Te量子点的合成

以巯基辛烷为表面配体, 通过调控Ag前体和Te前体的比例, 制备了第二近红外窗口荧光Ag₂Te量子点. 采用透射电子显微镜(TEM)、 X射线衍射光谱(XRD)、 X射线光电子能谱(XPS)、 紫外-可见-近红外吸收光谱和荧光光谱等对产物进行了表征. 结果表明, 制得了粒径均一、 分散性好的油溶性Ag₂Te量子点, 其最大荧光发射波长位于1320 nm, 荧光量子产率高达4.2%.     

Biomimetic interactions of proteins with functionalized cadmium sulfide quantum dots

Interactions between various modified semiconductor nanocrystal, cadmium sulfide quantum dots (CdS QDs) and bovine serum albumin (BSA) and lysozyme (LZY) were investigated. CdS QDs capped with mercaptoethanol (MPA), l-cysteine (Lcys) and glutathione (GSH) were synthesized in aqueous solution and characterized by UV-vis and fluorescence spectrum. Circular dichroism (CD) and fluorescence spectrum were used to detect the interactions between as-prepared CdS QDs and protein molecules. The interaction parameters, including binding constant (K_b), binding site number (n) and quench constant (K_q), were determined by fluorescence spectrum. The changes of secondary structures of the proteins were detected by CD. The results imply that CdS QDs modified by different agents have dramatically different binding strength with protein molecules. The results obtained here analyze the biosafety of CdS QDs in terms of the biological behavior of biomolecules and could serve as basis for the application of CdS QDs to bioscience.     

油溶性CuInS2/ZnS量子点的制备及其温敏性聚丙烯酰胺胶束介导的水相转移

采用非热注法成功制备了高质量的油溶性CuInS2/ZnS核壳量子点,量子点的荧光发射峰在可见光到近红外范围内可调(550～800 nm),且荧光量子产率最高达80%。本文进一步利用具有温敏特性的聚丙烯酰胺胶束作相转移剂,成功地将油溶性的CuInS2/ZnS核壳量子点转移入水相。水相中自组装形成的CuInS2/ZnS量子点-胶束复合物不仅具有良好的荧光性质,而且胶束原有的灵敏的热响应性被保留。这些研究初步表明,无镉的低毒的CuInS2/ZnS量子点可作为纳米胶束的荧光示踪探针。     

油溶性CuInS2/ZnS量子点的制备及其温敏性聚丙烯酰胺胶束介导的水相转移

采用非热注法成功制备了高质量的油溶性CuInS₂/ZnS核壳量子点, 量子点的荧光发射峰在可见光到近红外范围内可调(550~800 nm), 且荧光量子产率最高达80%。本文进一步利用具有温敏特性的聚丙烯酰胺胶束作相转移剂, 成功地将油溶性的CuInS₂/ZnS核壳量子点转移入水相。水相中自组装形成的CuInS₂/ZnS量子点-胶束复合物不仅具有良好的荧光性质, 而且胶束原有的灵敏的热响应性被保留。这些研究初步表明, 无镉的低毒的CuInS₂/ZnS量子点可作为纳米胶束的荧光示踪探针。     

超声电化学快速制备近红外CdTe量子点与细胞成像

针对当前水溶性量子点合成路线复杂、量子产率低的现状, 在无需N₂保护的条件下, 采用简便的超声电化学方法快速合成了CdTe量子点前驱体;并对不同条件下制得的前驱体加热回流, 得到水溶性、高质量的近红外CdTe量子点。产物的形貌、结构和组成通过高分辨透射电子显微镜(HRTEM)、X-射线粉末衍射(XRD)等手段进行了表征。考察了超声电化学参数和回流条件对量子点荧光性质的影响。通过控制电流脉冲宽度、反应时间、反应温度等参数, 实现了CdTe量子点前驱体的可控制备;通过调节加热回流条件得到不同荧光发射波长的量子点;选用602 nm近红外发射波长的CdTe量子点标记了子宫颈癌细胞(Hela), 并采用共聚焦技术实现了肿瘤细胞的显微成像观察。和传统的量子点合成方法相比, 超声电化学方法具有合成路线简单、参数易调可控的特点;为高品质量子点的快速制备提供了新的思路, 拓展了超声电化学在纳米材料制备领域的应用。     

CdS量子点的制备及细胞膜初步荧光标记

以巯基乙酸为稳定剂,通过控制反应温度、反应时间及pH值,在水相中合成了稳定的受激发出紫光、蓝光、绿光、黄光和红光的CdS量子点;通过紫外可见吸收光谱、荧光光谱和X射线衍射谱(XRD)对产物的光学性能和晶体结构进行了表征,结果表明所合成的CdS量子点分散性较好,量子产率为8%,为立方晶型,粒径约1 nm;利用荧光倒置显微镜观察了量子点在洋葱内表皮细胞膜上聚集及受激发射荧光行为,实现细胞膜初步标记.