3-巯基丙酸修饰的CdSe/ZnS量子点的合成及测定牛血清白蛋白的研究

以3-巯基丙酸作为修饰剂,在水溶液中合成了稳定的CdSe/ZnS量子点(QDs),透射电镜观察所合成量子点的形貌近似球形,粒径约为25 nm.吸收光谱与荧光光谱的研究表明,CdSe QDs在410 nm处有最大吸收峰,而CdSe/ZnS QDs的最大吸收峰在470 nm处,CdSe/ZnS QDs的荧光强度是CdSe QDs的11倍.考察了缓冲溶液的体积、pH值、反应温度、反应时间对体系荧光的影响.在最佳实验条件下,体系的荧光强度与BSA的浓度呈线性关系,线性响应范围为0.746×10-7～4.48×10-7 mol/L,检出限为3.846×10-10 mol/L.并且CdSe/ZnS QDs荧光强度基本保持稳定,可达两个多月.该方法应用于合成样品的测定,结果满意.     

Laser Assisted Catalytic Growth of ZnS/CdSe Core‐Shell and Wire‐Coil Nanowire Heterostructures

ZnS/CdSe core‐shell and wire‐coil nanowire heterostructures have been synthesized by chemical vapor deposition assisted with pulsed laser ablation. Measurements from high‐resolution transmission electron microscopy and selected area electron diffraction have revealed that both ZnS/CdSe core‐shell and wire‐coil nanowires are of single‐crystalline hexagonal wurtzite structures and grow along the [0001] direction. While the lattice parameters of ZnS and CdSe in the core‐shell nanowires are nearly equal to those of bulk ZnS and CdSe, change of the lattice parameters in the CdSe‐coil is attributed to the doping of Zn into CdSe, resulting in the relaxation of compressive strain at the interface between CdSe‐coil and ZnS‐wire. Composition variation across the interfacial regions in the ZnS/CdSe nanowire heterostructures ranges only 10–15 nm despite the pronounced lattice mismatch between ZnS and CdSe by ?11%. Growth mechanisms of the ZnS/CdSe nanowire heterostructures are discussed.     

水溶性的CdSe/ZnS纳米微粒的合成及表征

用L-半胱氨酸(Cys)作为稳定剂，合成了水溶性的CdSe/ZnS核壳结构的半导体纳米微粒。吸收光谱和荧光光谱表明，CdSe/ZnS纳米微粒比单一的CdSe纳米粒子具有更优异的发光特性。透射电子显微镜（TEM）、ED和XPS表征了CdSe/ZnS纳米微粒的结构、分散性及形貌。红外光谱证实半胱氨酸分子中的硫原子和氧原子参加了与纳米粒子表面的金属离子的配位作用。     

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。     

Photostability of complexes based on fluorescent CdSe/ZnS nanoparticles and polyelectrolytes

By means of fluorescence spectroscopy, it has been found that the oscillator strength of the electronic transition in CdSe/ZnS nanoparticles increases when the hydrophilic fluorescent CdSe/ZnS nanoparticles form complexes with cationic and anionic polyelectrolytes. However, an increase in the relative quantum yield and photostability is possible only in the complexes of the anionic shell-covered CdSe/ZnS nanoparticles with polycations. The mechanisms of the effect of ionic interactions on the probabilities and channels of electronic transitions in the nanoparticles are discussed.     

CdSe/ZnS量子点探针用于检测猪链球菌2型溶菌酶释放蛋白(MRP)抗原的新方法研究

合成了高发光效率的CdSe/ZnS量子点并制备了CdSe/ZnS量子点-溶菌酶释放蛋白(MRP)抗体探针, 利用凝胶电泳和分子光谱法研究了MRP抗体与CdSe/ZnS量子点的结合机理. 荧光光谱法优化了CdSe/ZnS量子点-MRP抗体探针制备的影响因素, 建立了一种测定MRP抗原的新方法, 其线性范围为5.0×10－8～1.5×10－6 mol/L, 线性相关系数为0.9976, 检测限为 1.9×10－8 mol/L.     

Optical properties of CdSe and CdSe/ZnS quantum dots dispersed in solvents of different polarity

Original organic capping TOPO/TOP groups of CdSe and CdSe/ZnS quantum dots (QDs), from mother solution were replaced with 2_mercaptoethanol, which was chosen as model compound, in order to achieve water solubility. Obtained water dispersions of CdSe and CdSe/ZnS QDs were characterized by UV/VIS absorption and luminescence techniques. Luminescence measurements revealed that bare cores are very sensitive to surface capping, transfer into water diminished emission intensity. Core/shell, CdSe/ZnS, QDs are much more resistant to changes of the capping and solvent, and significant part of emission intensity was preserved in water. The article is published in the original.     

Imaging pancreatic cancer using surface-functionalized quantum dots

In this study, CdSe/CdS/ZnS quantum dots (QDs) were used as optical contrast agent for imaging pancreatic cancer cells in vitro using transferrin and anti-Claudin-4 as targeting ligands. CdSe/CdS/ZnS was chosen because the CdSe/CdS/ZnS QDs have better photoluminescence (PL) efficiency and stability than those of CdSe/ZnS. The transferrin-mediated targeting is demonstrated in both a cell-free coprecipitation assay as well as using in vitro confocal microscopy. Pancreatic cancer specific uptake is also demonstrated using the monoclonal antibody anti-Claudin-4. This targeted QD platform will be further modified for the purpose of developing as an early detection imaging tool for pancreatic cancer.     

基于石英纳米孔道的单颗粒尺寸分布分析

发展了一种基于石英纳米孔道的单颗粒电化学动态分析方法, 用于单个CdSe/ZnS量子点纳米颗粒的尺寸分布分析. 其机制是向石英纳米孔道两端施加电压, 表面带有正电荷的单个CdSe/ZnS量子点纳米颗粒在电场力驱动下由管内向管外运动, 当量子点纳米颗粒穿过纳米孔道尖端狭小的限域空间时, 其表面正电荷使石英纳米孔道内电荷密度增加, 孔道内的电化学限域效应进一步将电荷密度增加的信息放大并转变为可读的离子流增强信号. 通过对动态离子流信号解析可实时获取具有2种不同尺寸的量子点纳米颗粒所导致的2类过孔事件信息, 从而对在限域空间内运动的纳米颗粒进行尺寸分布分析.     

Layer-by-layer quantum dot constructs using self-assembly methods

We describe the creation of CdSe/ZnS quantum dot assemblies using layer-by-layer construction strategies, using self-assembly. In the first approach, a dithiol linker was used to make multilayers of CdSe/ZnS quantum dots, while in the second biotin- and streptavidin-conjugated CdSe/ZnS quantum dots were used to make multilayer constructs. Both the chemical bonding nature and fluorescence spectroscopic properties of quantum dot films were characterized using X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy.     

Temperature-dependent photoluminescence of water-soluble quantum dots for a bioprobe

The photoluminescence of water-soluble CdSe/ZnS core/shell quantum dots is found to be temperature-dependent: as temperature arising from 280 K to 351 K, the photoluminescence declines with emission peak shifting towards the red at a rate of ∼0.11 nm K⁻¹. And the studies show that the photoluminescence of water-soluble CdSe/ZnS quantum dots with core capped by a thinner ZnS shell is more sensitive to temperature than that of ones with core capped by a thicker one. That is, with 50% decrement of the quantum yield the temperature of the former need to arise from 280 K to 295 K, while the latter requires much higher temperature (315.6 K), which means that the integrality of shell coverage is a very important factor on temperature-sensitivity to for the photoluminescence of water-soluble CdSe/ZnS quantum dots. Moreover, it is found that the water-soluble CdSe quantum dots with different core sizes, whose cores are capped by thicker ZnS shells, possess almost the same sensitivity to the temperature. All of the studies about photoluminescence temperature-dependence of water-soluble CdSe/ZnS core/shell quantum dots show an indispensable proof for their applications in life science.     

Highly Stable CdSe/CdS/ZnS Fluorophores in Acidic Environment: Acile Preparation and Modification of Core/shell/shell Nanocrystals

We described a facile method for preparing CdSe/CdS/ZnS core/shell/shell nanocrystals from air-stable single source precursors.The single source precursors of cadmium ethylxanthate and zinc ethylxanthate were used to form CdS and ZnS shell layers in octadecene.An efficient modification of CdSe/CdS/ZnS nanocrystals was subsequently performed to obtain hydrophilic nanocrystal fluorophores with good stability in a pH range of 1.6-10.     

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.     

Electrophoretic properties of BSA-coated quantum dots

Low toxic InP/ZnS quantum dots (QDs), ZnS:Mn²⁺/ZnS nanocrystals and CdSe/ZnS nanoparticles were rendered water-dispersible by different ligand-exchange methods. Eventually, they were coated with bovine serum albumin (BSA) as a model protein. All particles were characterised by isotachophoresis (ITP), laser Doppler velocimetry (LDV) and agarose gel electrophoresis. It was found that the electrophoretic mobility and colloidal stability of ZnS:Mn²⁺/ZnS and CdSe/ZnS nanoparticles, which bore short-chain surface ligands, was primarily governed by charges on the nanoparticles, whereas InP/ZnS nanocrystals were not charged per se. BSA-coated nanoparticles showed lower electrophoretic mobility, which was attributed to their larger size and smaller overall charge. However, these particles were colloidally stable. This stability was probably caused by steric stabilisation of the BSA coating.     

Super Sensitization: Grand Charge (Hole/Electron) Separation in ATC Dye Sensitized CdSe,CdSe/ZnS Type‐I,and CdSe/CdTe Type‐II Core–Shell Quantum Dots

Ultrafast charge‐transfer dynamics has been demonstrated in CdSe quantum dots (QD), CdSe/ZnS type‐I core–shell, and CdSe/CdTe type‐II core–shell nanocrystals after sensitizing the QD materials by aurin tricarboxylic acid (ATC), in which CdSe QD and ATC form a charge‐transfer complex. Energy level diagrams suggest that the conduction and valence band of CdSe lies below the LUMO and the HOMO level of ATC, respectively, thus signifying that the photoexcited hole in CdSe can be transferred to ATC and that photoexcited ATC can inject electrons into CdSe QD, which has been confirmed by steady state and time‐resolved luminescence studies and also by femtosecond time‐resolved absorption measurements. The effect of shell materials (for both type‐I and type‐II) on charge‐transfer processes has been demonstrated. Electron injection in all the systems were measured to be <150 fs. However, the hole transfer time varied from 900 fs to 6 ps depending on the type of materials. The hole‐transfer process was found to be most efficient in CdSe QD. On the other hand, it has been found to be facilitated in CdSe/CdTe type‐II and retarded in CdSe/ZnS type‐I core–shell materials. Interestingly, electron injection from photoexcited ATC to both CdSe/CdTe type‐II and CdSe/ZnS type‐I core–shell has been found to be more efficient as compared to pure CdSe QD. Our observation suggests the potential of quantum dot core–shell super sensitizers for developing more efficient quantum dot solar cells.     

High-quality ZnS shells for CdSe nanoparticles: rapid microwave synthesis

Using a domestic microwave oven and new, inexpensive precursors, a rapid and reliable synthesis of highly luminescent CdSe/ZnS NPs was developed. To evaluate the quality of our core/shell particles for varying shell thickness in comparison to that of CdSe/ZnS nanoparticles obtained commercially, the parameter fluorescence quantum yield is been used as well as a new, straightforward, thiophenol-based shell-quality test as a tool to ensure a dense ZnS shell without holes and cracks, which is a prerequisite for high luminescence and stability.     

Electrochemiluminescence immunosensor for the determination of ag alpha fetoprotein based on energy scavenging of quantum dots

An electrochemiluminescence (ECL) immunosensor for ultrasensitive detection of alpha fetoprotein (AFP) was fabricated using graphene-CdS quantum dots-alginate (G-CdS QDs-AL) as the immobilizing support and CdSe/ZnS QDs as the label. CdSe/ZnS QDs could effectively scavenge the ECL of G-CdS QDs-AL composite, and the quenched ECL intensity depended linearly on the logarithm for AFP concentration in the range from 0.05 to 500 fg/mL. The detection limit was 20 ag/mL. The proposed ECL immunoassay protocol for AFP detection is stable, specific, highly sensitive and promising for clinical application.     

Quantum-dot-sensitized solar cells fabricated by the combined process of the direct attachment of colloidal CdSe quantum dots having a ZnS glue layer and spray pyrolysis deposition

We were able to attach CdSe quantum dots (QDs) having a ZnS inorganic glue layer directly to a mesoporous TiO(2) (mp-TiO(2)) surface by spray coating and thermal annealing. Quantum-dot-sensitized solar cells based on CdSe QDs having ZnS as the inorganic glue layer could easily transport generated charge carriers because of the intimate bonding between CdSe and mp-TiO(2). The application of spray pyrolysis deposition (SPD) to obtain additional CdSe layers improved the performance characteristics to V(oc) = 0.45 V, J(sc) = 10.7 mA/cm(2), fill factor = 35.8%, and power conversion efficiency = 1.7%. Furthermore, ZnS post-treatment improved the device performance to V(oc) = 0.57 V, J(sc) = 11.2 mA/cm(2), fill factor = 35.4%, and power conversion efficiency = 2.2%.     

Spontaneous emission control of CdSe/ZnS nanoparticle monolayer in polymer nanosheet waveguide assembled on a one-dimensional silver grating surface

We present spontaneous emission control of a core-shell CdSe/ZnS nanoparticle array assembled with polymer ultrathin films consisting of polymer nanosheets on a silver grating substrate, which served as a unique and simple photonic cavity. The grating-coupled waveguide modes enabled 10(3) order luminescence enhancement and one-fourth spectral narrowing. The light emission from a CdSe/ZnS nanoparticle array can be controlled by tuning the film thickness of hybrid polymer nanoassemblies, which provides multiple emission performance with good tuning ability from red to green at low-power continuous wave laser excitation (～μW).     

核-壳结构CdSe/ZnS量子点的制备、硫醇修饰及其光学性能

采用高温有机相包覆技术制备了CdSe/ZnS核壳结构量子点材料,考察了包覆量对量子点材料的光学性能的影响,研究了含脂肪链和芳香基的双硫醇分子1,4-苯二甲硫醇和1,8-辛二硫醇对于具有核-壳结构的CdSe/ZnS量子点材料的修饰作用,考察了修饰作用对于量子点的量子效率和荧光强度等光学性能的影响.实验结果表明:随着硫化锌包覆量的增加,量子点的量子效率及其荧光发射强度明显提高;硫醇的修饰能显著增强量子点的发光强度,随着硫醇浓度的增加,其发光性能增强,但是达到一定程度后,光学性能基本不随硫醇浓度的变化而变化.根据固体核磁共振等实验结果推测:硫醇分子可能部分替代了量子点体系中的正三辛基氧膦配体,稳定了量子点体系,对量子点起修饰保护作用,从而提高了量子点的光学性能.