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.     

CdTe/CdS荧光探针测定痕量铜(Ⅱ)

以巯基乙酸为稳定剂,在水溶液中合成CdTe/CdS量子点,基于量子点与Cu2+混合后发生荧光猝灭作用,建立CdTe/CdS量子点作为荧光探针检测微量铜的新方法。在pH 4.60的HAc-NaAc缓冲溶液中,反应时间为10 min时,Cu2+质量浓度在0.01～1.00μg/mL范围与CdTe/CdS量子点的荧光猝灭程度呈良好的线性关系,相关系数为0.9978,检出限为9.90×10-3μg/mL。方法可以用于雨水、自来水和延河水中Cu2+的分析。     

Functionalized cadmium sulfide quantum dots as fluorescence probe for silver ion determination

CdS quantum dots (QDs) modified with l-cysteine has been prepared by one step. They are water-soluble and biocompatible. To improve CdS QDs stability and interaction between silver ion and functionalized CdS QDs in aqueous solution, some amounts of fresh l-cysteine were added to functionalized CdS solution. Based on the characteristic fluorescence enhancement of CdS QDs at 545 nm by silver ions in the presence of some amounts of fresh l-cysteine, simultaneously, a gradual red shift of fluorescence emission bands of CdS QDs from 545 to 558 nm was observed. A simple, rapid, sensitive and specific detection method for silver ion was proposed. Under optimum conditions, the fluorescence intensity of CdS QDs is linearly proportional to silver concentration from 2.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol/L with a detection limit of 5.0 × 10⁻⁹ mol/L. In comparison with single organic fluorophores, functionalized CdS quantum dots are brighter, more stable against photobleaching, and don’t suffer from blinking. Furthermore, owing to the fluorescence enhancement effect of CdS QDs by silver ion, the proposed method showed lower detection blank and higher sensitivity. Possible fluorescence enhancement mechanism was also studied.     

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.     

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。     

11-巯基烷酸修饰cdse/cds纳米晶的合成及荧光增敏法测定溶菌酶

巯基烷酸;纳米晶;量子点;cdse/cds;溶菌酶     

水溶性CdSe/CdS纳米晶合成条件的优化研究

以巯基乙醇为修饰剂,在水溶液中合成了稳定的CdSe/CdS纳米晶,应用单因素法和多目标单纯形法探索合成条件。通过透射电镜观察所合成的纳米晶的形貌和大小,用紫外-可见吸收光谱和荧光光谱对其光学特性进行了表征。并且以L-色氨酸荧光量子产率0.14为标准,测量了合成的CdSe/CdS纳米晶的荧光量子产率为0.37。     

Use of CdSe/ZnS core-shell quantum dots as energy transfer donors in sensing glucose

In the present work, CdSe/ZnS core-shell quantum dots were synthesized and conjugated with enzymes, glucose oxidase (GOD) and horseradish peroxidase (HRP). The complex of enzyme-conjugated QDs was used as QD-FRET-based probes to sense glucose. The QDs were used as an electron donor, whereas GOD and HRP were used as acceptors for the oxidation/reduction reactions involved in oxidizing glucose to gluconic acid. Electron transfer between the redox enzymes and the electrochemical reduction of H₂O₂ (or O₂) occurred rapidly, resulting in an increase of the turnover rate of the electron exchange between the substrates (e.g. glucose, H₂O₂ and O₂) and the enzymes (GOD, HRP), as well as between the QDs and the enzymes. The transfer of non-radiative energy from the QDs to the enzymes resulted in the fluorescence quenching of the QDs, corresponding to the increase in the concentration of glucose. The linear detection ranges of glucose concentrations were 0–5.0 g/l (R = 0.992) for the volume ratios of 10/5/5, 0.2–5.0 g/l (R = 0.985) for the volume ratios of 10/5/3 and 1.0–5.0 g/l (R = 0.982) for the volume ratios of 10/5/0. Temperature (29–37 °C), pH (6–10) and some ions (NH₄⁺, NO₃⁻, Na⁺, Cl⁻) had no interference effect on the glucose measurement.     

柠檬酸盐稳定的水溶性CdSe量子点的合成及表征

以柠檬酸三钠为稳定剂在水溶液中合成了水溶性CdSe量子点,用X射线粉末衍射、透射电镜、紫外-可见吸收光谱和荧光发射光谱对CdSe量子点的结构、形貌及其荧光性质进行了表征.结果表明合成的CdSe量子点为立方闪锌矿结构,呈球形,分散性良好,平均尺寸约为2.6nm,具有窄且对称的荧光发射光谱,半峰宽为45nm.     

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。     

CdSe量子点荧光探针检测生活饮用水中的痕量六价铬

采用胶体化学方法合成还原性谷胱甘肽(GSH)稳定的Cd Se纳米量子点,所合成的Cd Se量子点对痕量的六价铬具有灵敏的荧光猝灭作用。以Cd Se量子点为荧光探针,建立一种简单快速测定生活饮用水中痕量六价铬的检测方法。在0.05~2.0μg·L-1范围内,Cd Se量子点的荧光强度变化值与生活饮用水中六价铬的含量呈线性关系,方法的检出限为0.01μg·L-1,样品测定的相对标准偏差小于5%,加标回收率在97~104%之间。该方法能够快速灵敏检测生活饮用水中的痕量六价铬,具有重现性好,定量准确灵敏等优点。     

CdSe/CdS量子点荧光猝灭法测定芹黄素的研究

以巯基乙酸为稳定剂,在水溶液中合成了具有特殊光学性质的水溶性CdSe/CdS量子点。以该量子点为荧光探针,基于荧光猝灭法对芹黄素进行了定量检测。考察了缓冲体系、反应时间、量子点浓度等多种因素的影响。实验结果表明,在0.001 mol/L、pH为6.80的KH2PO4-Na2HPO4缓冲液中,当量子点浓度为1.2×10^-4mol/L、反应时间为20 min时,该方法的线性范围为0.16-27.02μg/mL,其线性回归方程为F0/F=0.99665＋0.11067ρ（μg/mL）,相关系数r=0.998,检出限为0.13μg/mL,并用于合成样品的分析。     

Resonance Rayleigh scattering and resonance non-linear scattering method for the determination of aminoglycoside antibiotics with water solubility CdS quantum dots as probe

In pH 6.6 Britton–Robinson buffer medium, the CdS quantum dots capped by thioglycolic acid could react with aminoglycoside (AGs) antibiotics such as neomycin sulfate (NEO) and streptomycin sulfate (STP) to form the large aggregates by virtue of electrostatic attraction and the hydrophobic force, which resulted in a great enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum scattering peak was located at 310 nm for RRS, 568 nm for SOS and 390 nm for FDS, respectively. The enhancements of scattering intensity (ΔI) were directly proportional to the concentration of AGs in a certain ranges. A new method for the determination of trace NEO and STP using CdS quantum dots probe was developed. The detection limits (3σ) were 1.7 ng mL⁻¹ (NEO) and 4.4 ng mL⁻¹ (STP) by RRS method, were 5.2 ng mL⁻¹ (NEO) and 20.9 ng mL⁻¹ (STP) by SOS method and were 4.4 ng mL⁻¹ (NEO) and 25.7 ng mL⁻¹ (STP) by FDS method, respectively. The sensitivity of RRS method was the highest. The optimum conditions and influence factors were investigated. In addition, the reaction mechanism was discussed.     

Interaction of CdTe/CdS quantum dots with antibodies

In the study,we observed the strong adsorption of CdTe/CdS QDs to antibodies and the formation of QDs-antibodies conjugates. Capillary electrophoresis with laser-induced fluorescence detection(CE-LIF),fluorescence spectrometry and fluorescence correlation spectroscopy(FCS) were used to characterize the QDs conjugates with antibody.We found that the QDs-antibody conjugates possessed high fluorescence,small hydrodynamic radii and good stability in aqueous solution.     

Ultrasensitive cysteine sensing using citrate-capped CdS quantum dots

The importance of cysteine (Cys) in biological systems has stimulated a great deal of efforts in the development of analytical methods for the determination of this amino acid. In this work, a novel fluorescent probe for Cys based on citrate (Cit)-capped CdS quantum dots (QDs) is reported. The Cit-capped CdS QDs fluorescent probe offers good sensitivity and selectivity for detecting Cys. A good linear relationship was obtained from 1.0 × 10⁻⁸ mol L⁻¹ to 5.0 × 10⁻⁵ mol L⁻¹ for Cys. The detection limit was calculated as 5.4 × 10⁻⁹ mol L⁻¹. The proposed method was applied to detect Cys in human urine samples, which showed satisfactory results. This assay is based on both the lability of Cit and the strong affinity of thiols to the surface of CdS QDs. The addition of Cys improved the passivation of the surface traps of CdS QDs and enhanced the fluorescence intensity.     

A novel fluorescent assay for edaravone with aqueous functional CdSe quantum dots

Aqueous thiol-capped CdSe QDs with a narrow, symmetric emission were prepared under a low temperature. Based on the fluorescence enhancement of thiol-stabilized CdSe quantum dots (QDs) caused by edaravone, a simple, rapid and specific quantitative method was proposed to the edaravone determination. The concentration dependence of fluorescence intensity followed the binding of edaravone to surface of the thiol-capped CdSe QDs was effectively described by a modified Langmuir-type binding isotherm. Factors affecting the fluorescence detection for edaravone with thiol-stabilized CdSe QDs were studied, such as the effect of pH, reaction time, the concentration of CdSe QDs and so on. Under the optimal conditions, the calibration plot of C/(I − I₀) with concentration of edaravone was linear in the range of (1.45–17.42) μg/mL (0.008–0.1 μmol/L) with correlation coefficient of 0.998. The limit of detection (LOD) (3σ/κ) was 0.15 μg/mL (0.0009 μmol/mL). Possible interaction mechanism was discussed.     

A novel method for iodate determination using cadmium sulfide quantum dots as fluorescence probes

We have developed a novel method for the determination of iodate based on the carboxymethyl cellulose-capped CdS quantum dots (QDs). Factors affecting the iodate detection were investigated, and the optimum conditions were determined. Under the optimum conditions, the relative fluorescence intensity of CdS quantum dots was linearly proportional to IO₃⁻ over a concentration range from 1.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol L⁻¹ with a correlation coefficient of 0.9987 and a detection limit of 6.0 nmol L⁻¹. Iodide, being oxidized by bromine to form iodate, was detected indirectly. The method was successfully applied to the determination of iodate and total amount of iodine in table salt samples. The related mechanism was also discussed.     

A sensitive sensor for anthraquinone anticancer drugs and hsDNA based on CdTe/CdS quantum dots fluorescence reversible control

Based on CdTe/CdS quantum dots (CdTe/CdS QDs) fluorescence (FL) reversible control, a new and sensitive FL sensor for determination of anthraquinone (AQ) anticancer drugs (adriamycin and daunorubicin) and herring sperm DNA (hsDNA) was developed. Under the experimental conditions, FL of CdTe/CdS QDs can be effectively quenched by AQ anticancer drugs due to the binding of AQ anticancer drugs on the surface of CdTe/CdS QDs and photoinduced electron transfer (PET) process from CdTe/CdS QDs to AQ anticancer drugs. Addition of hsDNA afterwards brought the restoration of CdTe/CdS QDs FL intensity, as AQ anticancer drugs peeled off from the surface of CdTe/CdS QDs and embedded into hsDNA double helix structure. The liner ranges and the detection limits of FL quenching methods for two AQ anticancer drugs were 0.33-9 μg mL⁻¹ and 0.09 μg mL⁻¹ for ADM and 0.15-9 μg mL⁻¹ and 0.04 μg mL⁻¹ for DNR, respectively. The restored FL intensity was proportional to concentration of hsDNA in the range of 1.38-28 μg mL⁻¹and the detection limit for hsDNA was 0.41 μg mL⁻¹. It was applied to the determination of AQ anticancer drugs in human serum and urine samples with satisfactory results. The reaction mechanism of CdTe/CdS QDs FL reversible control was studied.     

Characterizing mixed phosphonic acid ligand capping on CdSe/ZnS quantum dots using ligand exchange and NMR spectroscopy

The ligand capping of phosphonic acid functionalized CdSe/ZnS core–shell quantum dots (QDs) was investigated with a combination of solution and solid‐state ³¹P nuclear magnetic resonance (NMR) spectroscopy. Two phosphonic acid ligands were used in the synthesis of the QDs, tetradecylphosphonic acid and ethylphosphonic acid. Both alkyl phosphonic acids showed broad liquid and solid‐state ³¹P NMR resonances for the bound ligands, indicative of heterogeneous binding to the QD surface. In order to quantify the two ligand populations on the surface, ligand exchange facilitated by phenylphosphonic acid resulted in the displacement of the ethylphosphonic acid and tetradecylphosphonic acid and allowed for quantification of the free ligands using ³¹P liquid‐state NMR. After washing away the free ligand, two broad resonances were observed in the liquids' ³¹P NMR corresponding to the alkyl and aromatic phosphonic acids. The washed samples were analyzed via solid‐state ³¹P NMR, which confirmed the ligand populations on the surface following the ligand exchange process. Copyright © 2015 John Wiley & Sons, Ltd.