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。     

Biomolecule-quantum dot systems for bioconjugation applications

In the present work, it is reported for the first time the bioconjugation of CdS quantum dots (QDs) directly with bovine serum albumin (BSA) using a one-step procedure via aqueous route at room temperature by methods of colloidal chemistry. Essentially, the bioconjugates were developed based on BSA as capping ligand for the nucleation and stabilization of CdS nanoparticles using cadmium perchlorate and thioacetamide as precursors. UV-visible spectroscopy was used to characterize the kinetics and the relative stability of CdS nanoparticles. The CdS nanocrystals were produced with the calculated average particle size below 4.0 nm, indicating they were in the so-called "quantum-size confinement range". The results have clearly indicated that BSA was effective on nucleating and stabilizing the colloidal CdS quantum dots.     

Fluorescence quenching of bovine serum albumin.

The fluorescence emission spectra and 3D fluorescence spectra of bovine serum albumin (BSA) in cetyltrimethylammonium bromide (CTAB) reversed micelles were affected by the microenvironment. Blue shifts of the fluorescence emission peaks were found when BSA was present in CTAB reversed micelles. The fluorescence intensity changed with the water content. Similar changes in the peak regions of the 3D fluorescence spectra were also observed. CdS nanoparticles prepared in CTAB reversed micelles quenched the fluorescence of BSA significantly. The fluorescence of BSA was more effectively quenched by negative CdS nanoparticles than by positive or neutral CdS ones. The quenching degree increased linearly with increasing the concentration of negative CdS nanoparticles over the range of 5.0 x 10(-6) - 3.0 x 10(-5) mol L(-1). The quenching mechanism is discussed and the quenching constant is 1.32 x 10(4) L mol(-1).     

Determination of Albumin Using CdS/SiO2 Core/shell Nanoparticles as Fluorescence Probes

CdS quantum dots (QD) were capped with SiO₂ via a microemulsion method for reducing the toxicity and imparting the biocompatibility of the CdS QD. The resulting CdS/SiO₂ core/shell nanoparticles (NP) showed an improved water‐solubility and stability even in pH 4.0 acidic medium. Their fluorescence could be effectively enhanced in the presence of bovine serum albumin (BSA), due to the passivation effect of BSA on the surface of the NP. Furthermore, the concentration dependence of the fluorescence intensity obeys the Langmuir‐type binding isotherm. Thus a novel fluorescence enhancement method for the determination of BSA has been developed using the less‐toxic CdS/SiO₂ core/shell NP as probes. Under optimal conditions, the linear range of calibration curve is 0.6–30 µg·mL^?1, and the detection limit is 0.18 µg·mL^?1. Compared with the water‐soluble CdS NP without SiO₂ shell, the CdS/SiO₂ core/shell NP exhibited slightly lower fluorescence response to BSA as well as other coexisting substances, such as heavy and transition metals, due to the inhibition of SiO₂ shell. The proposed method was applied to the quantification of BSA in synthetic and serum samples with satisfactory results.     

An Electrochemical Aptasensor for Detection of Thrombin based on Target Protein‐induced Strand Displacement

A sensitive electrochemical aptasensor for detection of thrombin based on target protein‐induced strand displacement is presented. For this proposed aptasensor, dsDNA which was prepared by the hybridization reaction of the immobilized probe ssDNA (IP) containing thiol group and thrombin aptamer base sequence was initially immobilized on the Au electrode by self‐assembling via Au? S bind, and a single DNA labeled with CdS nanoparticles (DP‐CdS) was used as a detection probe. When the so prepared dsDNA modified Au electrode was immersed into a solution containing target protein and DP‐CdS, the aptamer in the dsDNA preferred to form G‐quarter structure with the present target protein resulting that the dsDNA sequence released one single strand and returned to IP strand which consequently hybridized with DP‐CdS. After dissolving the captured CdS particles from the electrode, a mercury‐film electrode was used for electrochemical detection of these Cd²⁺ ions which offered sensitive electrochemical signal transduction. The peak current of Cd²⁺ ions had a good linear relationship with the thrombin concentration in the range of 2.3×10^?9–2.3×10^?12 mol/L and the detection limit was 4.3×10^?13 mol/L of thrombin. The detection was also specific for thrombin without being affected by the coexistence of other proteins, such as BSA and lysozyme.     

Continuous tuning of cadmium sulfide and zinc sulfide nanoparticle size in a water-in-supercritical carbon dioxide microemulsion

The size and size dispersion of cadmium sulfide and zinc sulfide semiconductor nanoparticles can be continuously tuned over a wide range of values by adjusting the density of the fluid phase in water-in-supercritical CO2 microemulsions. The average size of the ZnS nanoparticles decreases linearly from approximately 9.1 to 1.9 nm with increasing fluid density from 0.86 to 0.99 g cm(-3) at a water-to-surfactant ratio (W value) of 10. At a W value of 6, the particle size can be tuned from 7.0 to 1.5 nm in the same density range. In the case of CdS nanocrystals, the size varied from 7.1 to 2.0 nm when the W value was 10 and from 4.0 to 1.3 nm when the W value employed was 6, in the same density range. Monodispersive CdS and ZnS nanoparticles were synthesized by chemical reaction of cadmium or zinc nitrate with sodium sulfide, using two water-in-supercritical CO2 microemulsions as nanoreactors followed by protection with a fluorinated-thiol stabilizer. The stabilizer is introduced at 6 and 16 minutes after the mixing of the two microemulsions where the intensity of the characteristic absorption peak due to the quantum confinement properties of the CdS and ZnS nanoparticles (280 and 360 nm) reaches a maximum, respectively. The supercritical CO2 microemulsion method represents a simple approach to use a density-tunable solvent for synthesizing size-controlled semiconductor nanoparticles over a broad range of values.     

聚乙烯烷酮修饰CdS纳米微粒的制备及其光电转移特性

以聚乙烯烷酮（PVP）为修饰剂,制备了CdS纳米微粒。实验结果表明PVP与CdS纳米微粒间存在着强的相互作用,PVP和CdS纳米微粒的荧光都在很大程度上发生淬灭。其原因在于作为修饰剂的PVP与CdS纳米微粒子间发生了特殊缔合．受激时形成共振激发态,电子能量弛豫被延迟。     

CdS aerogels: Effect of concentration and primary particle size on surface area and opto-electronic properties

Porous aerogels of CdS that exhibit quantum confined optical properties have been prepared by supercritical drying of wet CdS gels prepared by oxidative stripping of nanoparticle capping groups. The water-to-surfactant ratio (W) employed in the preparation of the nanoparticles is found to have a large impact on the surface areas of resultant aerogels, with W=5 samples producing mesoporous samples with the highest surface areas and cumulative pore volumes. In contrast, the concentration of the CdS sol employed in the gelation has only a small effect on the porosity characteristics, but a large impact on the apparent crystallite and chromophore sizes in as-prepared aerogels. Higher concentrations of the sol result in larger crystallite sizes and lower degrees of quantum confinement, as evidenced by a red shift in the absorbance spectra.     

Preparation and application of functionalized nanoparticles of CdS as a fluorescence probe

CdS nanoparticles have been prepared and modified with mercaptoacetic acid. The functionalized nanoparticles are water-soluble and biocompatible. They could be used as a fluorescence probe in the determination of bovine serum albumin (BSA), which was proved to be a simple, rapid and specific method. In comparison with single organic fluorophores, these nanoparticle probes are brighter, more stable against photobleaching, and do not suffer from blinking. Under the optimum conditions, the response is linearly proportional to the concentration of BSA between 0.1 and 3.2 μg ml⁻¹, and the limit of detection is 0.08 μg ml⁻¹.     

Solid state morphology and band gap studies of ETS-10 supported CdS nanoparticles

Engelhard titanosilicate (ETS-10) supported cadmium sulphide (CdS) nanoparticles were synthesized and characterized by various solid state techniques including: XRD, DR UV-Vis, TEM and FESEM. The effect of different synthesis routes of CdS nanoparticles on its physicochemical character was studied. It was observed that CdS nanoparticles prepared by both in situ sulphur reduction (CdS-IS) and reverse micelle (CdS-RM) methods showed similar roperties. However, CdS-IS nanoparticles are more feasible and economically practical. The reflectance measurements of the as-synthesized CdS nanoparticles are apparently blue-shifted compared to bulk CdS. This phenomenon of blue-shifted absorption edge has been ascribed to an increase in bandgap energy with a decrease in particle sizes. The bandgap of the as-synthesized CdS samples was calculated from the linear correlation of [F(R) hν]² and hν. The bandgap of CdS in ETS-10 was noticeably slightly reduced when compared with the as-synthesized CdS (8 nm) due to the formation of cluster arrays on the pores of ETS-10.     

Enhancement of Raman Scattering of 1,4-Benzenedithiol by CdS Nanoparticles Assembled on a Silver Surface

CAS nanoparticles were assembled on the smooth surface of a piece of silver by using 1,4-benzenedithiol as coupling molecules. The SEM and resonance Raman spectroscopic characterizations demonstrate that the nanosized structure of CdS was still preserved upon assembly, and a two-dimensional structure of CdS nanoparticles was formed on the substrate surface. The FT-Raman spectra indicate that 1,4-benzenedithiol was coupled between CAS nanoparticles and the silver surface with a tilted orientation. The Raman scattering of 1,4-benzenedithiol was substantially enhanced by the assembled CdS nanoparticles, probably due to the alteration of the polarizability of 1,4-benzenedithiol and the electromagnetic interaction between the dipoles of the CdS particle with its image in the metal substrate.     

溶剂对反胶束法合成CdS纳米粒子粒径的影响

以磺基琥珀酸二辛酯钠盐(AOT)为保护剂,利用反胶束法在不同烷烃溶液中合成了CdS纳米粒子.采用紫外-可见光谱、透射电子显微镜、荧光光谱法对其进行表征.研究表明:在不同烷烃溶液中合成的CdS纳米粒子,其粒子大小和荧光强度都随溶剂而改变.     

Composites comprising CdS nanoparticles and poly(ethylene oxide): optical properties and influence of the nanofiller content on the thermal behaviour of the host matrix

Tri-n-octylphosphine oxide-capped CdS nanoparticles were synthesized with the cadmium(II) complex of thiocarbohydrazide as a precursor. Nanocomposites were prepared by mixing a toluene solution of poly(ethylene oxide) (PEO) and the obtained CdS nanoparticles. The ultraviolet-visible spectroscopy measurements showed a blue shift of the onset of optical absorption, compared to bulk CdS, which confirmed the presence of nanostructured CdS. A transmission electron microscopy micrograph of the nanocomposite depicted that the nanoparticles are well dispersed in the PEO matrix. Differential scanning calorimetry analysis revealed hindered crystallization of PEO in the presence of CdS nanoparticles. It was also found that increasing the nanoparticle content led to the shift of the onset of decomposition of the matrix towards higher temperature.     

用丝素膜制备的纳米CdS及其光催化活性研究

根据蚕丝丝素蛋白等电点约4.5的特性,以CdCl_2·2.5H_2O和CH_3CSNH_2为原料,将CdCl_2用明胶包覆后置于定制的丝素膜反应器中,在pH=6条件下制得纳米 CdS。经 UV、AFM表征,CdS的平均粒径为 5～10 nm,其对活性染料 KD-8B有较好的光催化降解活性。     

Mesoporous Silica Nanoparticles Functionalized with Amino Groups for Biomedical Applications

The synthesis and characterization of amino-functionalized mesoporous silica nanoparticles are presented following two different synthetic methods: co-condensation and post-synthesis grafting of 3-aminopropyltriethoxysilane. The amino groups’ distribution on the mesoporous silica nanoparticles was evaluated considering the aggregation state of a grafted photosensitizer (Verteporfin) by using spectroscopic techniques. The homogeneous distribution of amino groups within the silica network is a key factor to avoid aggregation during further organic functionalization and to optimize the performance of functionalized silica nanoparticles in biomedical applications. In addition, the formation of a protein corona on the external surface of both bare and amino-functionalized mesoporous silica was also investigated by adsorbing Bovine Serum Albumin (BSA) as a model protein. The adsorption of BSA was found to be favorable, reducing the aggregation phenomena for both bare and amino-modified nanoparticles. Nevertheless, the dispersant effect of BSA was much more evident in the case of amino-modified nanoparticles, which reached monodispersion after adsorption of the protein, thus suggesting that amino-modified nanoparticles can benefit from protein corona formation for preventing severe aggregation in biological media.     

硫化镉钠米微粒在聚合物网络中的组装

硫化镉钠米微粒在聚合物网络中的组装黄金满，杨毅，杨柏，刘式墉，沈家骢（吉林大学分子光谱与分子结构重点实验室、集成光电子国家重点实验室，长春，１３００２３）关键词组装，纳米微粒，离子交换，透射电子显微镜，电子衍射由于纳米半导体微粒的物理和化学性质介于分...     

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.     

Size tunable synthesis of cysteine-capped CdS nanoparticles by gamma-irradiation

Highly water soluble and biocompatible L-cysteine-capped CdS nanoparticles having narrow size distribution were synthesized for the first time by gamma-irradiation technique without using any additional stabilizer. FTIR study shows that CdS nanoparticles are capped through mercapto-group of cysteine amino acid while its free amino and carboxylate groups make it amenable to bio-conjugation. Size and luminescence of the nanoparticles can be well controlled by varying the parameters like radiation dose, pH and concentration of cysteine. The observed results suggest that pH 7 can be optimum for the synthesis of L-cysteine-capped CdS nanoparticles. CdS nanoparticles synthesized with molar ratio of Cd(2+):cysteine, 1:60 at pH 7 were found to be most luminescent. All nanoparticles formed lie in the size quantization regime and exhibit good crystallinity. Remarkable improvement in stability and luminescence was achieved on changing pH of as-prepared nanoparticles from 7 to 11.     

In situ synthesis of water dispersible bovine serum albumin capped gold and silver nanoparticles and their cytocompatibility studies

A simple and convenient one step room temperature method is described for the synthesis of bovine serum albumin (BSA) capped gold and silver nanoparticles. BSA reduces silver ions to silver nanoparticles but does not directly reduce gold ions to gold nanoparticles at room temperature and varying pH conditions. However, when silver and gold ions are simultaneously added to BSA, silver ions get reduced to metallic silver first and these in turn reduce gold ions to gold nanoparticles through a galvanic exchange reaction. The so synthesized silver and gold nanoparticles are easily water dispersible and can withstand addition of salt even at high concentrations. It is shown that the capped protein retains its secondary structure and the helicity to a large extent on the nanoparticles surface and that the protein capping makes the nanoparticles cytocompatible.     

Preparation of CdS nanoparticles by hydrothermal method in microemulsion

CdS nanoparticles with good crystallinity were prepared by hydrothermal method in microemulsion composed of polyoxyethylene laurylether/water/cyclohexane/butanol. The structure and the size of the CdS nanoparticles were analyzed by TEM and XRD. The UV-Vis optical absorption of the samples was also investigated. The results show that hydrothermal treatment is an effective method to prepare CdS nanoparticles of hexagonal structure at lower temperature. The particles were in dimensional uniformity. The diameter of the CdS nanoparticles decreased with the increase of the molar ratio of water to surfactant. The minimum diameter of the CdS nanoparticles prepared in this work was about 10 nm. Obvious blue shift appeared in the UV-Vis absorption spectra. Translated from Chinese Journal of Inorganic Chemistry, 2006, 22(5): (in Chinese)