液体石蜡体系中CdSeS三元量子点的制备及性能

采用液体石蜡为反应溶剂, 油酸为Cd源的溶剂和配体, 在无磷条件下通过用高温热解法合成了高质量的CdSeS三元合金量子点. 用透射电子显微镜(TEM), X射线粉末衍射仪(XRD)和能量色散X射线分析仪(EDX)等对产物的性能进行了表征. 结果表明, 反应温度、 反应时间和Se与S的比例等因素均对量子点的生长过程及光学性能产生影响. 采用该方法制得的CdSeS三元合金量子点均为立方闪锌矿结构, 且形成了一种内富S外富Se的成分梯度结构, 其最大发射波长可在370~595 nm(近紫外~橙红色)范围内连续可调, 量子效率最高可达65%. 该体系下制备的CdSeS三元量子点具有良好的热稳定性和光稳定性.     

谷胱甘肽稳定水溶性CdTe/ZnTe量子点的制备与表征

用还原型谷胱甘肽(GSH)作为稳定剂, 合成了水溶性的CdTe/ZnTe核壳结构的半导体量子点. 考察了Zn/Cd反应物配比及GSH用量对CdTe/ZnTe量子点的性能影响. 用高分辨透射电子显微镜(HRTEM)和X射线粉末衍射(XRD)光谱对CdTe和CdTe/ZnTe的形貌和晶体结构进行了表征. 荧光光谱结果表明, 核壳结构的CdTe/ZnTe量子点比单一的CdTe量子点具有更高的荧光量子产率和更好的光活化性能.     

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。     

水合肼还原二氧化碲水相合成CdTe量子点

以巯基乙酸为稳定剂, 氯化镉为镉源, 二氧化碲为碲源, 水合肼为还原剂, 一步合成了CdTe量子点. 研究了反应时间、 碲与镉的摩尔比及巯基乙酸与镉的摩尔比等实验条件对CdTe量子点生长过程的影响. 采用荧光光谱、 X射线粉末衍射和透射电子显微镜等对量子点的性能进行了表征. 结果表明, 反应时间及反应物的相对用量对量子点的生长和荧光光谱有明显影响, 所得CdTe量子点具有立方晶型, 发光颜色从绿色到红色连续可调, 荧光量子产率可达26%.     

CdTe/CdSe核壳量子点的合成及其在指纹显现中的应用

以CdCl2和Te粉为原料,在水相中合成了CdTe量子点核;通过外延生长在CdTe量子点核上包覆一层CdSe量子点,得到具有良好荧光性能的CdTe/CdSe核壳量子点;采用X射线衍射仪、透射电镜、高分辨透射电镜分析了不同反应条件下合成的CdTe/CdSe核壳量子点的晶体结构和微观结构,并对其进行了荧光光谱等测试和指纹显现分析.结果表明,合成的CdTe和CdTe/CdSe量子点粒径在3～5nm之间,粒径分布窄,水分散性良好;可以通过控制反应时间和Te/Se比等得到在500～700nm显示荧光发射峰的CdTe/CdSe核壳量子点.此外,核壳CdTe/CdSe量子点可以有效地和指纹物质结合,可应用于对铝合金油潜指纹的鉴别.     

水热法合成AgInS2/ZnS核/壳结构量子点及其荧光性能

以硫脲为硫源,采用谷胱甘肽(GSH)和柠檬酸钠(SC)为配体,通过水热法制备了水溶性AgInS2/ZnS(AIS/ZnS)核/壳结构量子点。系统研究了反应温度和配体用量对量子点的合成及其荧光性能的影响。采用X射线衍射(XRD)、透射电子显微镜(TEM)、紫外可见吸收光谱(UV-Vis)和光致发光光谱(PL)分别对量子点的物相、形貌和光学性能进行了表征,并考察了量子点的稳定性。实验结果表明,随着反应温度从70℃升高至90℃,促进了ZnS壳层的形成,有效地钝化了量子点的表面缺陷,获得的AIS/ZnS核/壳量子点的发光强度显著提高,发光峰位从600 nm蓝移至580 nm。配体的添加可以有效地平衡Zn^2+的化学反应活性,减缓ZnS壳层的生长,抑制核壳界面缺陷的形成,还能消除量子点的表面态,当nGSH/nZn^2+=2.0,nSC/nZn^2+=2.5时,AIS/ZnS量子点的荧光性能最佳。此外,AIS/ZnS核/壳结构量子点还具有优异的光学稳定性。     

油胺/油酸稳定的CdSe量子点的绿色合成

以液体石蜡为高温反应溶剂,油酸和油胺为混合稳定剂,利用高温热解法一步合成了高质量的CdSe量子点。通过紫外-可见吸收光谱、荧光发射光谱、红外光谱和X射线衍射等手段对量子点的光学性质和结构进行了表征。结果表明,油胺/油酸混合表面活性剂稳定的量子点吸收光谱峰形更尖锐,荧光发射光谱半峰宽更窄。反应温度和反应时间均对量子点的生长过程和光学性质有明显影响,220℃下反应15 min,荧光量子产率可达26%。得到的CdSe量子点为立方晶型,表面同时包覆了油酸和油胺,具有良好的光稳定性。该方法无需使用三烷基膦,价廉环保,且合成的CdSe量子点性质稳定、性能优越,有利于其在分析检测领域中的应用。     

溶液环境中CdSeS量子点与金纳米颗粒相互作用

选用不同发射波长的合金型CdSeS量子点(QDs), 研究溶液状态下量子点和金纳米颗粒(AuNPs)相互作用及离子强度、pH值、距离等诸多因素对相互作用的影响, 在此基础上对相互作用的机理进行了分析. 在溶液状态下, 金纳米颗粒可以高效地淬灭量子点, Stern-Volmer 淬灭常数K_sv值在108 L·mol^-1数量级. 这种淬灭效应与距离、光谱之间叠合程度等密切相关, 受溶液极性、离子强度、pH值的影响较小. 金纳米颗粒与量子点相互作用的机理较为复杂, 以能量转移为主. 研究结果对设计更高效的生物传感器及更全面认识金纳米颗粒与量子点相互作用的机理具有重要意义.     

肿瘤细胞内CdS纳米量子点的仿生化合成

以宫颈癌HeLa细胞为载体,细胞内源性谷胱甘肽为保护剂和稳定剂,在细胞生命代谢活动驱动下合成性质优良的CdS量子点。光学性能表征显示,该CdS量子点在波长为450nm左右有发射峰,其荧光产率为5.2%。透射电镜表征显示CdS量子点粒径约为3.0nm,X射线衍射光谱表明该CdS量子点为立方晶型结构。     

水溶性InP/ZnS量子点的合成及其在指纹显现中的应用

以磷化锌、氯化铟为原料,以十二烷胺为溶剂,在150～200℃下合成了InP量子点,通过相转移和紫外光照得到了巯基乙酸修饰的水溶性InP/ZnS量子点.利用X射线衍射仪、透射电镜、高分辨透射电镜、荧光光谱仪等分析了不同温度下合成的量子点的粒径、形貌、荧光性能及指纹显现效果.结果表明,合成的InP和InP/ZnS量子点为球...     

Synthesis of Cysteine-Capped Zn(x)Cd(1)(-)(x)Se alloyed quantum dots emitting in the blue-green spectral range

Alloyed ZnxCd1-xSe quantum dots (QDs) have been successfully prepared at low temperatures by reacting a mixture of Cd(ClO4)2 and Zn(ClO4)2 with NaHSe using cysteine as a surface-stabilizing agent. The photoluminescence (PL) spectra of the alloyed QDs are determined on the basis of the Zn2+/Cd2+ molar ratio, reaction pH, intrinsic Zn2+and Cd2+ reactivities toward NaHSe, concentration of NaHSe, and the kind of thiols. A systematic blue shift in emission wavelength of the alloyed QDs was found with the increase in the Zn mole fraction. This result provides clear evidence of the formation of ZnxCd1-xSe QDs by the simultaneous reaction of Zn2+ and Cd2+ with NaHSe, rather than the formation of separate CdSe and ZnSe nanocrystals or core-shell structure CdSe/ZnSe nanocrystals. The size and inner structure of these QDs are also corroborated by using high-resolution transmission electron microscopy and X-ray powder diffraction. To further understand the formation mechanism, the growth kinetics of Zn0.99Cd0.01Se was studied by measuring the PL spectra at different growth intervals. The results demonstrated that, in the initial stage of growth, Zn0.99Cd0.01Se has a structure with a Cd-rich core and a Zn-rich shell. The post-preparative irradiation of these QDs improved their PL properties, resulting in stronger emission.     

Synthesis of imidazolium‐functionalized ionic polyurethane and formation of CdTe quantum dot–polyurethane nanocomposites

A series of positively charged imidazolium‐functionalized ionic polyurethanes (IPUs) were prepared in one‐step polymerization process by polymerization of presynthesized short‐chain imidazolium‐based ionic diol, polyethylene glycols with different molecular weights as long‐chain diols, and toluylene‐2,4‐diisocyanate. The structures of IPUs are confirmed by ¹H NMR analysis, and the thermogravimetric analysis measurement indicates that the IPUs have high degradation temperature. Fluorescent nanocrystal–polymer composites CdTe–IPU can be prepared conveniently, by the electrostatic interaction between positively charged IPUs and the negatively charged aqueous CdTe quantum dots (QDs). UV–vis absorption and photoluminescence spectra indicate the photochemical stability and strong fluorescent emission of CdTe–IPU composites. The quantum yields (QYs) of the composites are high and basically restore the QYs of the pure QDs. In addition, the transmission electron microscopy photographs show that the QDs in composites are uniform (about 3 nm in diameter) and monodisperse. The obtained nanocomposites are powder or elastomers with good film building. The casted CdTe–IPU films are transparent under visible light, and the colors of the composites and their films are vivid under a UV lamp. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Photocatalytic property of surface-modified TiO<Subscript>2</Subscript> nanobelts under visible light irradiation

A novel plasmonic photocatalyst, i.e., acid-etched TiO₂ nanobelts attached with Ag/AgI nanoparticles (NPs) was prepared by deposition–precipitation-photoreduction method. Such surface-modified nanobelts had larger area than the normal one. Ag NPs were formed from AgI by photo-reduction under Xenon lamp irradiation. X-ray diffraction, scanning electron microscopy analysis, UV–Vis diffuse reflectance spectra and fluorescence spectra were used to characterize the structure and optical properties of the sample. The obtained sample exhibited strong photodegradation of methyl orange (MO) under visible light irradiation, which were attributed to both the surface plasmon resonance of Ag NPs and the visible light actived AgI. The photodegradation was accomplished by the transfer of photoexcited electrons from the Ag NPs to the acid-etched TiO₂ nanobelts. After four cycles of photodegradation the photocatalyst was still stable. This novel photocatalyst had a high potential application in wastewater-treatment and biomedical engineering.     

Quantum Dot Photoluminescence Quenching by Cr(III) Complexes. Photosensitized Reactions and Evidence for a FRET Mechanism

Reported are quantitative studies of the energy transfer from water-soluble CdSe/ZnS and CdSeS/ZnS core/shell quantum dots (QDs) to the Cr(III) complexes trans-Cr(N(4))(X)(2)(+) (N(4) is a tetraazamacrocycle ligand, X(-) is CN(-), Cl(-), or ONO(-)) in aqueous solution. Variation of N(4), of X(-), and of the QD size and composition allows one to probe the relationship between the emission/absorption overlap integral parameter and the efficiency of the quenching of the QD photoluminescence (PL) by the chromium(III) complexes. Steady-state studies of the QD PL in the presence of different concentrations of trans-Cr(N(4))(X)(2)(+) indicate a clear correlation between quenching efficiency and the overlap integral largely consistent with the predicted behavior of a F?rster resonance energy transfer (FRET)-type mechanism. PL lifetimes show analogous correlations, and these results demonstrate that spectral overlap is an important consideration when designing supramolecular systems that incorporate QDs as photosensitizers. In the latter context, we extend earlier studies demonstrating that the water-soluble CdSe/ZnS and CdSeS/ZnS QDs photosensitize nitric oxide release from the trans-Cr(cyclam)(ONO)(2)(+) cation (cyclam = 1,4,8,11-tetraazacyclotetradecane) and report the efficiency (quantum yield) for this process. An improved synthesis of ternary CdSeS core/shell QDs is also described.     

Synthesis of NAC capped near infrared-emitting CdTeS alloyed quantum dots and application for in vivo early tumor imaging

The synthesis of water-soluble near-infrared (NIR)-emitting quantum dots (QDs) has recently received extensive attention for non-invasive detection of biological information in living subjects. Highly fluorescent CdTeS alloyed QDs for biological application are introduced in this paper. QDs were synthesized by a hydrothermal method and coated with N-acetyl-l-cysteine (NAC) as both bioactive ligand and sulfur source for biocompatibility and biological stability. The optical properties, morphology and structure of CdTeS alloyed QDs were characterized. The in vitro and in vivo toxicity was intensively investigated. Furthermore, the dynamics and bio-distribution of CdTeS alloyed QDs on living mice were studied. To explore biomedical application, folate-polyethylene glycol (FA-PEG) was used to decorate the CdTeS alloyed QDs (FP-CdTeS QDs) for targeted imaging of tumors over-expressing the folate receptor (FR). The tumor targeting capability of FP-CdTeS QDs on tumor bearing nude mice was demonstrated. The results showed that the prepared CdTeS QDs have excellent optical properties and low toxicity, which makes them an ideal inorganic material for biomedical imaging. In addition, the folate-PEG conjugated NIR-QDs displayed good biocompatibility as well as excellent sensitivity and specificity for optical imaging of tumors which can extend the application of CdTeS 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.     

Correlating natural ageing and Xenon irradiation of Paraloid B72 applied on stone

The ageing of Paraloid^® B72, an acrylic copolymer extensively used in conservation of works of art, has been investigated either under artificial irradiation (Xenon lamp) or in natural environment (external exposure) with the aim to correlate the results of the accelerate test with the real situation. For a better understanding of the involved mechanisms some acrylic homo-polymers were also subjected to the artificial ageing test. Molecular changes induced by ageing were followed by infrared spectroscopy (FT-IR) and size exclusion chromatography (SEC), while the efficiency of the treatment was checked by water capillary absorption test and colour determinations. The results obtained indicate that it is possible to discriminate, easily and within reasonable laboratory time experiment, between polymers that can be used in Conservation, and the macromolecules that should not be employed due to short efficacy life-times.     

新型低毒AgInS2量子点的制备和表征以及对肿瘤细胞的成像

在水相中快速合成AgInS2( AIS)量子点,并对其紫外-可见吸收光谱及荧光发射光谱进行了表征,通过电感耦合等离子体发射光谱仪分析了其元素组成,采用高分辨透射电镜观察其形貌与分布,并验证了它相对于传统的CdTe量子点在光稳定性和细胞毒性方面的优势。在AgInS2表面连接了叶酸实现了对肿瘤细胞的靶向成像。     

Optimized Synthesis and Fluorescence Spectrum Analysis of CdSe Quantum Dots

An optimized synthesis route was applied for controlling the preparation of CdSe quantum dots (QDs) in an aqueous solution. Some key factors which influencing the properties of CdSe QDs, such as initial pH, stabilizers, ratio of precursor, etc. were investigated. The size, shape, crystal structure, and optical property of CdSe QDs were also characterized by TEM, XRD, UV-Vis, and fluorescence (FL) spectra. The result showed that high-quality cubic CdSe QDs with 3 nm were obtained. The experiments also confirmed that thioglycolic acid (TGA), under the conditions of weak acid, is a better stabilizer than others. The ratio of [Cd²⁺] to [SeSO₃ ^2?] played an important role in the formation of CdSe QDs. The mechanisms about the influence factors were also presented.