水溶性CdSe/CdS量子点的合成及其与牛血清蛋白的共轭作用

用巯基乙酸(TGA)作为稳定剂，合成了水溶性的CdSe和核壳结构的CdSe/CdS半导体量子点。吸收光谱和荧光光谱研究表明，核壳结构的CdSe/CdS半导体量子点比单一的CdSe量子点具有更优异的发光特性。用TEM、电子衍射(ED)和XPS分别表征了CdSe和CdSe/CdS纳米微粒的结构、形貌及分散性。红外光谱和核磁共振谱证实了巯基乙酸分子中的硫原子和氧原子与纳米微粒表面的金属离子发生了配位作用。在pH值为7.4的条件下，将合成的CdSe和CdSe/CdS量子点直接与牛血清白蛋白(BSA)相互作用。实验发现，两种量子点均对BSA的荧光产生较强的静态猝灭作用；而BSA对两种量子点的荧光则具有显著的荧光增敏作用，存在BSA时CdSe/CdS量子点的荧光增强是不存在BSA时体系荧光强度的3倍。     

水溶性的CdSe/CdS/ZnS量子点的合成及表征

用L-半胱氨酸盐(Cys)作为稳定剂,合成了水溶性的双壳结构的CdSe/CdS/ZnS半导体量子点。吸收光谱和荧光光谱结果表明,双壳结构的CdSe/CdS/ZnS纳米微粒比单一的CdSe核纳米粒子和单核壳结构的CdSe/CdS纳米粒子具有更优异的发光特性。用透射电子显微镜(TEM)、ED、XRD、XPS和FTIR等方法对CdSe核和双壳层的CdSe/CdS/ZnS纳米微粒的结构、分散性及形貌分别进行了表征。     

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.     

双官能Fe3O4/CdSe/CdS荧光磁性复合物的制备和表征

采用化学共沉淀法, 以FeCl₂•4H₂O和FeC1₃•6H₂O为原料制备磁性Fe₃O₄纳米颗粒(MNPs), 采用氨基酸对其进行修饰使其表面连上氨基. 用巯基乙酸作为稳定剂合成了水溶性的CdSe/CdS量子点, 并利用偶联剂1-乙基-3-(3-二氨丙基)碳二亚胺盐酸盐(EDC)和N-羟基琥珀酰亚胺(NHS)连接氨基修饰的Fe₃O₄和带有羧基的CdSe/CdS, 成功制备了Fe₃O₄/CdSe/CdS荧光磁性纳米颗粒. 该荧光磁性纳米复合物保留了CdSe/CdS量子点优异的荧光特性, 平均粒径在40 nm左右; 磁化曲线表明此纳米复合物具有超顺磁性. 这种双官能复合纳米颗粒有望成为新型荧光磁性双标记复合微粒而广泛应用于免疫检测、荧光追踪、磁性分离等领域.     

CdS量子点与CdSe量子点间荧光共振能量转移研究

在有机相中合成了不同尺寸的CdS和CdSe量子点, 并利用Langmuir-Blodgett (LB)技术将相同尺寸的CdS和CdSe量子点组装成多层复合纳米有序结构. 采用荧光光谱研究了CdS和CdSe量子点在混合体系和多层复合纳米有序结构状态下的荧光共振能量转移(Fluorescence resonance energy transfer, FRET). 我们观察到CdS和CdSe量子点混合溶液与当溶剂挥发形成固态膜中, CdS量子点的荧光强度较溶液状态下强烈猝灭, 表明当颗粒间距离减小时CdS和CdSe量子点间产生较高效率的荧光共振能量转移. 在多层复合纳米有序结构中, 随着给体CdS量子点层数的增加, 单层受体CdSe量子点的荧光逐步增强, 这表明层间纵向能量转移率随给体层数的增加而提高.     

柠檬酸稳定的水溶性CdSe和CdSe/CdS量子点的荧光特性

用柠檬酸(citrate)作为稳定剂合成了尺寸分布集中、荧光性质良好的水溶性CdSe量子点。通过调节合成温度可以调控CdSe量子点的尺寸及相应的最大荧光发射波长。当温度由20 ℃增加到95 ℃时,合成的CdSe量子点的平均尺寸由2.0 nm增加到3.2 nm,相应的荧光发射峰由500 nm红移到570 nm,展现出明显的量子尺寸效应。进一步制备了CdSe/CdS核壳量子点,其荧光量子产率比CdSe增加了5～10倍。系统地研究了S/Se物质的量的比对CdSe/CdS量子点荧光特性的影响,通过XPS证实了CdSe/CdS量子点中CdS壳层的存在。利用红外光谱和核磁共振波谱表征了柠檬酸分子中的羧基和羟基氧原子与CdSe量子点表面的Cd离子的配位作用,进而揭示了柠檬酸分子对水溶性CdSe量子点溶液的稳定作用。     

水溶性量子点纳米微球的制备、表征及其在生物检测中的应用

通过超声乳化(O/W)法, 在CdSe/CdS荧光量子点外包覆一层双亲性高分子外壳, 制得水溶性量子点纳米微球. 用荧光发射光谱(PL)和透射电子显微镜(TEM)等手段对产品进行了表征. 结果表明, 此种方法简单易行, 制得的量子点纳米微球(70 nm)具有良好的水溶性、稳定性以及较强的荧光发射强度. 用这种改性后的量子点标记的免疫球蛋白分子能够识别专一抗原, 因此这种纳米粒子将有望进一步应用于生物检测.     

CdSe/CdS量子点荧光探针用于司帕沙星的测定

在规定的条件下和pH 11的碱性溶液中,通过镉（Ⅱ）、巯基乙酸（TGA）与硒化氢钾乙醇溶液之间的反应制得TGA修饰的CdSe量子点（QD′s）,再将此量子点和硫化钠溶液反应制得TGA修饰的CdSe/CdS量子点。基于喹诺酮类抗生素司帕沙星与CdSe/CdS量子点的荧光猝灭作用,用CdSe/CdS量子点作为荧光探针测定了...     

光谱法研究CdSe/CdS/ZnS量子点与壳聚糖的复合

通过CdSe/CdS/ZnS量子点与壳聚糖之间的静电作用,用共混法制备了壳聚糖-CdSe/CdS/ZnS复合物.用荧光光谱、紫外-可见光谱、红外光谱对所得的壳聚糖-CdSe/CdS/ZnS复合物进行了表征.研究结果表明:壳聚糖-CdSe/CdS/ZnS复合物具有良好的光学性能.     

荧光磁性双功能Fe_3O_4/Alendronate@CdSe/CdS纳米复合物的制备与表征

采用化学共沉淀法制备了磁性Fe3O4纳米颗粒,并用四甲基氢氧化铵(TMAOH)、阿伦磷酸钠、丙烯酸丁酯和无水乙二胺对Fe3O4纳米颗粒表面进行修饰,制备出3代表面胺基化的Fe3O4树状分子.采用油相合成的方法制备CdSe/CdS量子点,再用巯基乙酸进行修饰,使其具有良好的水溶性和较好的稳定性.将制备的Fe3O4树状分子与修饰后的量子点进行连接,制备出双功能树状Fe3O4/Alendronate@CdSe/CdS微球.通过这种方法得到的材料的荧光性能明显增强,但材料的荧光性能并不随代数成线性变化的.     

Aqueous synthesis of CdSe and CdSe/CdS quantum dots with controllable introduction of Se and S sources

A new and convenient route is developed to synthesize CdSe and core-shell CdSe/CdS quantum dots(QDs) in aqueous solution.The gaseous precursors,H2Se and H2S,generated on-line by reducing SeO 3 2à with NaBH 4 and the reaction between Na 2 S and diluted H2SO 4,are used to form high-quality CdSe and CdSe/CdS QDs,respectively.The synthesized water-soluble CdSe and CdSe/CdS QDs possess high quantum yield(3% and 20%) and narrow full-width-at-half-maximum(43 nm and 38 nm).The synthesis process is easily reproducible with simple apparatus and low-toxic chemicals,and can be readily extended to the large-scale aqueous synthesis of QDs.     

Probing cytotoxicity of CdSe and CdSe/CdS quantum dots

Toxicities of CdSe and CdSe/CdS quantum dots(QDs) synthesized by ultrasound-assisted methods were investigated in vitro and in vivo.Five human cell lines were used to assess the cytotoxicity of as-prepared CdSe and CdSe/CdS by assays of MTT viability,red blood cell hemolysis,flow cytometry,and fluorescence imaging.The results show that these QDs may be cytotoxic by their influence in S and G2 phases in cell cycles.The cytotoxicity of QDs depends on both the physicochemical properties and related to target cells.     

CdS/CdSe/TiO2多级空心微球光阳极中量子点覆盖度的提高

TiO₂多级空心微球(THHSs)具有高的比表面积、强的光散射效应以及良好的电子传输性质,以此作为光阳极材料,可以显著提升CdS/CdSe敏化太阳能电池(QDSSCs)的性能。但基于化学浴沉积方法获得的这一类电池中量子点在光阳极表面的覆盖度通常不高(50%左右),本文发展了一种基于表面选择性吸附原理的多步沉积方法,选取特定分子(正十二硫醇)限制已有量子点的生长,通过二次沉积成功提高了CdS/CdSe在TiO₂多级空壳微球表面的覆盖度。使用此方法最终得到高达85.4%的覆盖度。结果表明,量子点覆盖度的增加有效提高了电池对太阳光的利用率,使得光电流获得了明显的增加。同时,二氧化钛空白表面积的减小还可以抑制电子和空穴的复合。优化后的电池光电流密度为15.69 mA·cm^-2,填充因子为0.583,电压为0.605 V,最高光电转换效率为5.30%。     

The electrochemical behavior of core-shell CdSe/CdS magic-sized quantum dots linked to cyclodextrin for studies of the encapsulation of bioactive compounds

Semiconductor nanocrystal quantum dots have been the subject of extensive investigations in different areas of science and technology in the past years. In particular, there are few studies of magic-sized quantum dots (MSQDs), even though they exhibit features such as extremely small size, fluorescence quantum efficiency, molar absorptivity greater than traditional QDs, and highly stable luminescence in HeLa cell cultures, thereby enabling monitoring of biological or chemical processes. The present study investigated the electrochemical behavior of free CdSe/CdS MSQDs using glassy carbon electrode and CdSe/CdS MSQDs immobilized on a gold electrode modified with a self-assembled cyclodextrin monolayer. The MSQDs showed two peaks in aprotic medium. The functionalized film modifier was prepared and characterized by means of cyclic voltammetry and electrochemical impedance spectroscopy using ferricyanide ions as a redox probe. The prepared modified electrode exhibited a stable behavior. The proposed method was successfully applied to encapsulation studies of mangiferin, a natural antioxidant compound, and cyclodextrin associated with the quantum dot, and the response was compared with that of the modified electrode without QD. The fluorescence study revealed that CdSe/CdS quantum dots emit blue light when excited by an optical source of wavelength of 350 nm and a significant increase in fluorescence and absorbance intensity is observed from the core-shell CdSe/CdS MSQDs when quantities of mangiferin are added to the solution containing thiolated cyclodextrin. CdSe/CdS MSQDs are optically and electrochemically sensitive and can be used for the detection and interaction of compounds encapsulated in cyclodextrin.     

Thiourea functionalized CdSe/CdS quantum dots as a fluorescent sensor for mercury ion detection

CdSe/CdS quantum dots(QDs) functionalized by thiourea(TU) were synthesized and used as a fluorescent sensor for mercury ion detection.The TU-functionalized QDs were prepared by bonding TU via electrostatic interaction to the core/shell CdSe/CdS QDs after capping with thioglycolic acid(TGA).It was observed that the fluorescence of the functionalized QDs was quenched upon the addition of Hg~(2+).The quantitative detection of Hg~(2+) with this fluorescent sensor could be conducted based on the linear relationship between the extent of quenching and the concentration of Hg~(2+) added in the range of1-300 μg L~(-1).A detection limit of 0.56 μg L~(-1) was achieved.The sensor showed superior selectivity for Hg~(2+) and was successfully applied to the determination of mercury in environmental samples with satisfactory results.     

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.     

Near unity quantum yield of light-driven redox mediator reduction and efficient H2 generation using colloidal nanorod heterostructures

The advancement of direct solar-to-fuel conversion technologies requires the development of efficient catalysts as well as efficient materials and novel approaches for light harvesting and charge separation. We report a novel system for unprecedentedly efficient (with near-unity quantum yield) light-driven reduction of methylviologen (MV(2+)), a common redox mediator, using colloidal quasi-type II CdSe/CdS dot-in-rod nanorods as a light absorber and charge separator and mercaptopropionic acid as a sacrificial electron donor. In the presence of Pt nanoparticles, this system can efficiently convert sunlight into H(2), providing a versatile redox mediator-based approach for solar-to-fuel conversion. Compared to related CdSe seed and CdSe/CdS core/shell quantum dots and CdS nanorods, the quantum yields are significantly higher in the CdSe/CdS dot-in-rod structures. Comparison of charge separation, recombination and hole filling rates in these complexes showed that the dot-in-rod structure enables ultrafast electron transfer to methylviologen, fast hole removal by sacrificial electron donor and slow charge recombination, leading to the high quantum yield for MV(2+) photoreduction. Our finding demonstrates that by controlling the composition, size and shape of quantum-confined nanoheterostructures, the electron and hole wave functions can be tailored to produce efficient light harvesting and charge separation materials.     

Quantum dots co-sensitized solar cells: a new assembly process of CdS/CdSe linked to mesoscopic TiO2-nano-SiO2 hybrid film

A green and simple method was found to prepare CdS/CdSe co-sensitized photoelectrodes for the quantum dots sensitized solar cells application. All the assembly processes of CdS and CdSe quantum dots (QDs) were carried out in aqueous solution. CdS and CdSe QDs were sequentially assembled onto TiO₂-nano-SiO₂ hybrid film by two steps. Firstly, CdS QDs were deposited in situ over TiO₂-nano-SiO₂ hybrid film by the successive ionic layer adsorption and reaction (SILAR) process in water. Secondly, using 3-mercaptopropionic acid (3-MPA) as a linker molecule, the pre-prepared colloidal CdSe QDs (~3.0 nm) dissolved in water was linked onto the TiO₂-nano-SiO₂ hybrid film by the self-assembled monolayer technique with the mode of dropwise. The mode is simple and advantageous to saving materials and time. The results show that the photovoltaic performance of the cells is enhanced with the increase of SILAR cycles for TiO₂-nano-SiO₂/CdS photoelectrode. The power conversion efficiency of 2.15 % was achieved using the co-sensitization photoelectrode prepared by using 6 SILAR cycles of CdS plus CdSe (TiO₂-nano-SiO₂/CdS(6)/CdSe) under the illumination of one sun (AM1.5, 100 mW/cm²).