硅壳包裹核/壳型CdSe/CdS纳米晶的制备与性能研究

采用低温水热技术,分别以柠檬酸、聚乙二醇(PEG400)和甲硫氨酸为稳定剂,在水相中合成了核壳型CdSe/CdS量子点,研究了稳定剂、CdSe与CdS物质的量比对量子点发光性能和结构的影响。XRD结果表明,当CdSe∶CdS在1∶3~4时,CdS主要在CdSe的外延生长,形成核壳型纳米粒子,当比例达到1∶5时,CdS单独成晶现象严重。CdSe∶CdS=1∶4时,核壳型量子点具有较高的荧光发射效率。TEM研究表明CdS在CdSe外表面生长形成较为完整的壳层,有效钝化CdSe表面,减少表面缺陷,从而显著提高CdSe量子点的发光效率。CdSe核尺寸为2~3nm的核壳型纳米粒子外包裹一层SiO2壳后,荧光发射效率没有显著提高,发射峰位置无明显红移。量子点包壳后能有效提高该量子点的光化学稳定性,提高量子点的生物相容性。     

CdTe量子点与蛋白质相互作用的荧光猝灭效应

本文在水热法合成水溶性CdTe及核壳结构CdTe/CdS量子点的基础上,分别研究了细胞色素c对CdTe量子点及CdTe/CdS核壳量子点荧光的猝灭效应和CdTe量子点对牛血清白蛋白荧光的猝灭效应,并阐述了猝灭机理。结果显示,细胞色素c对CdTe量子点的荧光猝灭效应具有一定的粒径依赖性,粒径越小,猝灭效应越强;细胞色素c对CdTe/CdS核壳量子点的猝灭效应比对CdTe量子点的更强,揭示了受激电子的表面传递机理。CdTe量子点通过松散牛血清白蛋白的螺旋结构而猝灭其荧光。     

巯基乙酸稳定的CdSe/ZnS核壳结构量子点的制备与表征

用非均相成核原理,在水溶液中制备CdSe/ZnS核壳结构量子点,并研究合成工艺,包括前驱物的滴加方式和用量、CdSe核的水浴反应时间、CdSe与ZnS的摩尔比等因素对CdSe/ZnS核壳结构量子点荧光性能的影响.用透射电子显微镜和x射线衍射仪测试核壳结构量子点的形貌和结构.用紫外吸收光谱与荧光光谱表征CdSe/ZnS核壳结构量子点的荧光性能.结果表明:ZnS壳层在CdSe核量子点表面外延生长,形成了核壳结构;CdSe/ZnS核壳结构量子点的荧光性能明显高于单一的CdSe量子点;合成的工艺条件会显著影响CdSe/ZnS核壳结构量子点的荧光性能.     

Pickering乳液聚合法CdS/PS荧光复合微球的制备与表征

通过水相合成法制备水溶性硫化镉(CdS)纳米晶,以CdS纳米晶固体粒子为乳化剂,进行Pickering乳液聚合制得CdS/PS荧光复合微球。通过SEM、XRD、FTIR、UV-vis、PL对CdS/PS荧光复合微球的微观结构、结晶情况及光学性能进行了分析和表征。结果表明,该复合微球具有以PS为核、CdS纳米晶为壳的核壳结构;复合微球的平均粒径为450nm;在复合微球中,CdS纳米晶仍然保持其量子尺寸效应,复合微球表现出了较好的荧光性能。     

CdTe/CdS核壳型量子点的水相合成与荧光性质研究

在水相中制备了不同壳层厚度的核壳型半导体CdTe/CdS量子点,通过荧光光谱(PL)分析、原子力显微镜(AFM)和X-射线粉末衍射 (XRD)光谱分析对产物进行了表征.实验结果表明:反应时间、温度、硫化钠浓度和NaOH的量对CdTe/CdS量子点的壳层厚度和荧光强度都有很大影响.     

CdTe/CdS量子点对木犀草素与人血清白蛋白结合力的影响

用还原型谷胱甘肽(GSH)作硫源和稳定剂在水相中合成了生物相容性好、量子产率高的核壳型CdTe/CdS半导体量子点;同时模拟人体内生理环境,研究了CdTe/CdS量子点(QDs)对木犀草素与人血清白蛋白(HSA)相互作用的影响。结果表明,CdTe/CdS QDs可有规律地猝灭HSA荧光;在CdTe/CdS QDs存在条件下,木犀草素可使HSA荧光最大发射波长从341 nm红移到347 nm,红移程度明显大于无QDs存在时,同时木犀草素与HSA的表观结合常数和结合位点数均有增加,即CdTe/CdS QDs使木犀草素与HSA的结合力增强。     

CdS-QDs/PSt纳米复合材料的制备及荧光性能研究

采用液体-固体-溶液界面相转移和相分离法(LSS)制备单分散CdS量子点(CdS-QDs);通过自由基本体聚合合成单分散CdS量子点/聚苯乙烯(CdS/PSt)纳米复合材料,采用HRTEM、XRD、FTIR、PL对CdS纳米晶、CdS/PSt复合材料的微观结构、形貌、化学组成、光学性能进行了表征。结果表明:CdS纳米晶为单分散,粒径约为4nm;所制备的CdS/PSt纳米复合材料具有优越的荧光性能及荧光稳定性,其聚合物中的CdS纳米晶仍然保持很好的量子尺寸效应和良好的分散性。     

CdS/CdSe核壳结构半导体纳米晶结构及光谱特性

采用共沉淀法在水相中将CdS外延生长于CdSe半导体纳米晶(CdSe NCs)表面,制备了结晶形态较好的CdSc/CdS核壳结构半导体纳米晶(CdSe/CdS C/S NCs),并改善了CdSe NCs的荧光性能.通过X射线衍射,透射电镜和选区电子衍射分析证明了核壳结构的形成,并通过紫外可见光吸收光谱和荧光光谱分析证明了核壳结构对CdSe NCs荧光性能的改善.此外,实验结果表明:控制CdSe核合成中Cd前驱体溶液pH值能获得粒径分布较窄的CdSe/CdS C/S NCs;采用不同浓度比的Cd和Se前驱体溶液可以有效调节核壳结构半导体纳米晶的粒径;选择合适的CdSe与CdS摩尔比及壳层中Cd与S摩尔比能改善CdSe/CdS C/S NCs的荧光性能.     

多层核壳CuInS_2/ZnS量子点的有机相合成的研究

有机相反应体系中合成制备CuInS2量子点核壳结构,并对制备出的核以及核壳结构的材料进行表征。XRD结果显示成功合成纯度高、晶形较好的CIS量子点;通过TEM可以观察到量子点形貌以及尺寸的变化;荧光光谱和吸收光谱则清楚表明在反应过程中红移和蓝移情况以及量子效率的明显增加;最后,由光稳定性实验得出包覆了ZnS的CIS量子点稳定性得到提高。     

CdSe/CdS核壳型量子点的合成及性质研究

在三相体系中合成了核壳型CdSe/CdS量子点。在三相体系中,油酸和乙醇的混和物组成液相(L),油酸钠为固相(S),Cd2+溶液和乙醇组成溶液相(S)。量子点在两相的界面形成。所制备的量子点用TEM、XRD和FL进行表征。结果表明,量子点的粒径分布均匀,形貌规则,为立方型晶体。在核表面包覆上宽带隙的半导体后,其光量子产率极大提高,表明核的表面缺陷被消除。     

Synthesis of Aqueous CdTe/CdS/ZnS Core/shell/shell Quantum Dots by a Chemical Aerosol Flow Method

This work described a continuous method to synthesize CdTe/CdS/ZnS core/shell/shell quantum dots. In an integrated system by flawlessly combining the chemical aerosol flow system working at high temperature (200–300°C) to generate CdTe/CdS intermediate products and an additional heat-up setup at relatively low temperature to overcoat the ZnS shells, the CdTe/CdS/ZnS multishell structures were realized. The as-synthesized CdTe/CdS/ZnS core/shell/shell quantum dots are characterized by photoluminescence spectra, X-ray diffraction (XRD), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Fluorescence and XRD results confirm that the obtained quantum dots have a core/shell/shell structure. It shows the highest quantum yield above 45% when compared to the rhodamine 6G. The core/shell/shell QDs were more stable via the oxidation experiment by H₂O₂.     

CdS quantum dots sensitized ZnO spheres via ZnS overlayer to improve efficiency for quantum dots sensitized solar cells

This paper reports the preparation of three-dimensional ZnO spheres by using a hydrothermal method and their application to quantum dots sensitized solar cells (QDSSCs). After achieving the desired thickness of sensitized CdS quantum dots (QDs) for ZnO spheres, ZnS overlayer was deposited on the surface of CdS/ZnO photo-anodes to further improve the photoelectric properties. CdS QDs and ZnS overlayer were deposited by successive ionic layer adsorption and reaction (SILAR) method. The surface morphology and crystal structure of the samples were verified by field-emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The CdS QDs sensitized solar cells were ameliorated via using ZnS as a protection-layer between quantum dots and electrolyte. As a result, the power conversion efficiency (η) has been increased from 0.60 to 1.43% after being treated by ZnS overlayer for CdS/ZnO photo-anodes.     

A highly efficient ZnS/CdS@TiO2 photoelectrode for photogenerated cathodic protection of metals

Shell-core nanostructured ZnS/CdS quantum dots (QDs) were assembled uniformly on the surface of TiO₂ nanotube arrays by sequence chemical bath deposition (CBD) of CdS and ZnS in alcohol solution system. The morphology and chemical composition of the obtained composite thin films were characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The effect of solvent and immersion cycles for the photoanode preparation on the photoelectrochemical activity and photogenerated cathodic protection property was investigated. It is found that the nanostructured CdS QDs (20 cycles) coated on TiO₂ nanotube arrays show a remarkably enhanced photoelectrochemical activity. The coating of ZnS QD shells (5 cycles) is able to improve the stability of the CdS@TiO₂ photoanode under white-light irradiation. After the irradiation light is turned off, the photogenerated cathodic protection of 403 stainless steel (403SS) can be remained for several hours.     

One-Pot Synthesis of Biocompatible CdSe/CdS Quantum Dots and Their Applications as Fluorescent Biological Labels

We developed a novel one-pot polyol approach for the synthesis of biocompatible CdSe quantum dots (QDs) using poly(acrylic acid) (PAA) as a capping ligand at 240°C. The morphological and structural characterization confirmed the formation of biocompatible and monodisperse CdSe QDs with several nanometers in size. The encapsulation of CdS thin layers on the surface of CdSe QDs (CdSe/CdS core–shell QDs) was used for passivating the defect emission (650 nm) and enhancing the fluorescent quantum yields up to 30% of band-to-band emission (530–600 nm). Moreover, the PL emission peak of CdSe/CdS core–shell QDs could be tuned from 530 to 600 nm by the size of CdSe core. The as-prepared CdSe/CdS core–shell QDs with small size, well water solubility, good monodispersity, and bright PL emission showed high performance as fluorescent cell labels in vitro. The viability of QDs-labeled 293T cells was evaluated using a 3-(4,5-dimethylthiazol)-2-diphenyltertrazolium bromide (MTT) assay. The results showed the satisfactory (>80%) biocompatibility of as-synthesized PAA-capped QDs at the Cd concentration of 15 μg/ml.     

Surface plasmon enhanced energy transfer in metal-semiconductor hybrid nanostructures

We report a type of hybrid nanostructures composed of ZnO nanoparticles, CdSe/ZnS core/shell quantum dots (QDs), and Ag nanoprisms. With ultraviolet light illumination, the energy absorbed by ZnO nanoparticles was transferred to the CdSe/ZnS core/shell QDs inducing a photoluminescence (PL) emission. To enhance the PL emission, Ag nanoprisms were doped in the ZnO nanoparticles and the QDs. Enhanced energy transfer from the ZnO nanoparticles to the QDs via the surface plasmon effect of the Ag nanoprisms was also demonstrated. The PL emission dependence was investigated as a function of the doped Ag nanoprism concentration and a 7.4 times PL enhancement was obtained at an Ag nanoprism concentration of 5 × 10(-8) M.     

Preparation of High Photoluminescent Hybrid Polymer-CdS Nanoparticle with Chelating Functional Polymer

The hybrid CdS nanocluster/chelating poly(acrylates-co-2-methylacrylic acid 3-(bis-carboxymethylamino)- 2-hydroxy-propyl ester) microbeads were prepared and characterized in this study. The copolymer microbead was prepared by the method of soap-free emulsion polymerization and then the CdS nanocluster was generated by the chemical deposition method on the surface of copolymer microbead. The size and morphology of the CdS nanoparticles on the surface of the hybrid composites were examined by using UV/vis spectroscope and TEM observation. The mean particle sizes of the CdS nanocluster for all of samples, calculated from Henglein’s empirical curve, is in the range of 3.3 ∼ 5.8 nm, which are approaching to TEM observation. Interestingly, most of the spherical CdS nanoclusters were aggregated in rod-like shapes with a length of around 200 nm when it was oscillated by super sonic energy. Furthermore, the luminescent spectrum of the hybrid nanoparticles exhibits a red-shift from 500 to 520 nm with an accompanying broad band. However, the energy and bandwidth of the CdS PL bands are related to the mole ratio of methyl methacrylate/methyl acrylate (MMA/MA) in copolymer. A higher MMA/MA mole ratio corresponds to a lower intensity and bandwidth. Additionally, in the size quantization effect of the CdS nanocluster disappears as the mean size of the CdS nanocluster exceeds 6 nm in this study. An erratum to this article can be found at     

Synthesis and Luminescence Properties of Core/Shell ZnS:Mn/ZnO Nanoparticles

In this paper the influence of ZnO shell thickness on the luminescence properties of Mn-doped ZnS nanoparticles is studied. Transmission electron microscopy (TEM) images showed that the average diameter of ZnS:Mn nanoparticles is around 14 nm. The formation of ZnO shells on the surface of ZnS:Mn nanoparticles was confirmed by X-ray diffraction (XRD) patterns, high-resolution TEM (HRTEM) images, and X-ray photoelectron spectroscopy (XPS) measurements. A strong increase followed by a gradual decline was observed in the room temperature photoluminescence (PL) spectra with the thickening of the ZnO shell. The photoluminescence excitation (PLE) spectra exhibited a blue shift in ZnO-coated ZnS:Mn nanoparticles compared with the uncoated ones. It is shown that the PL enhancement and the blue shift of optimum excitation wavelength are led by the ZnO-induced surface passivation and compressive stress on the ZnS:Mn cores.