基于CdTe量子点的荧光猝灭-恢复法测定L-半胱氨酸

以巯基乙酸为稳定剂,合成了水溶性CdTe量子点(QDs),基于Ni~(2+)存在下,利用CdTe QDs荧光猝灭-恢复技术,建立了测定L-半胱氨酸的新方法。考察了缓冲溶液pH及Ni~(2+)浓度等对测定的影响。在pH=10.0的硼砂缓冲溶液中,Ni~(2+)浓度为40μmol/L条件下,L-半胱氨酸浓度在6.0×10~(-6)~5.0×10~(-5) mol/L范围内与量子点荧光恢复程度呈良好的线性关系,相关系数为0.9990,方法的检出限为2.1×10~(-6) mol/L。该方法应用于果汁和蜂蜜样品中L-半胱氨酸的检测,结果满意。     

β-环糊精存在下阳离子表面活性剂的毛细管电泳电导法测定

基于H3 BO3 与 β CD配合成大阴离子 ,与不同的阳离子表面活性剂作用不同 ,建立了快速分离检测阳离子表面活性剂的毛细管电泳电导法。研究了H3 BO3 与 β CD的浓度 ,缓冲液的酸度和浓度对分离的影响。在优化的实验条件下 ,溴化四丁基铵 (TBAB)、溴化十二烷基三甲基铵 (DTAB)、溴化十六烷基三甲基铵(CTMAB)阳离子表面活性剂 10min内完全分离 ,峰形良好。线性范围分别为TBAB 10 -3 ～ 10 -5mol/L ,DTAB1.0× 10 -3 ～ 5 .0× 10 -6mol/L ,CTMAB 1.0× 10 -3 ～ 5 .0× 10 -6mol/L。检测限分别为TBAB 7.5× 10 -6mol/L ,DTAB 1.7× 10 -6mol/L ,CTMAB 1.0× 10 -6mol/L。方法用于合成水样分析 ,结果令人满意     

水溶性CdTe量子点荧光法测定青霉素的研究

以巯基乙酸为稳定剂合成水溶性CdTe量子点(QDs),利用CdTe QDs荧光猝灭-恢复技术,建立了一种测定青霉素的新方法。考察了不同缓冲溶液、pH值、Co2+浓度等因素对体系的影响。结果表明,在pH=10的硼砂缓冲溶液中,Co2+能猝灭CdTe QDs的荧光,体系中加入青霉素后,CdTe QDs的荧光得到恢复且恢复强度与青霉素的浓度呈良好的线性关系,方法的线性范围为2.0×10-5~1.0×10-4 mol/L,检出限为2.2×10-6 mol/L,应用于实际样品测定,结果较好。     

栀子甙对碲化镉量子点的荧光淬灭作用

以3-巯基丙酸作为稳定剂,在水溶液中合成了CdTe量子点;采用荧光光谱法初步研究了栀子甙对巯基丙酸稳定的CdTe量子点的荧光淬灭作用,考察了量子点浓度、pH、反应时间等多种因素对量子点-栀子甙体系荧光强度的影响,确定了测定栀子甙的最佳实验条件;并初步探讨了栀子甙与该量子点相互作用的可能反应机理.结果表明,在最佳实验条件下,巯基丙酸稳定的CdTe量子点对栀子甙检测的线性范围为2×10-7~4×10-6 mol/L,检出限为1.4×10-7 mol/L,相对标准偏差为0.355%;且常见的金属阳离子、糖类和氨基酸对栀子甙的测定无显著影响.总体而言,该方法可用于人体体液中栀子甙的检测,且两者的作用过程可初步推断为动态淬灭过程.     

敏化光转化-化学发光法测定2,4-二氯苯酚的研究

基于2,4-二氯苯酚(2,4-DCP)在荧光素存在下光转化后产物与氧化剂N-溴丁二酰亚胺(NBS)反应产生化学发光的现象,建立了高灵敏度检测2,4-二氯苯酚的新方法。阳离子表面活性剂十六烷基三甲基溴化铵(CTMAB)作为增敏剂可以有效的增强体系的化学发光强度。方法对浓度为7.3×10-7~7.3×10-6mol/L及7.3×10-6~7.3×10-5mol/L的2,4-DCP分别有良好的发光响应线性关系,检出限可达4.5×10-7mol/L;通过富集浓缩可进一步降低了方法的检出限;该方法具有良好的选择性。对化学发光反应的机理做了初步探讨,认为敏化光解所产生的单线态氧与氯代酚反应生成了可发光的产物。     

功能性CdTe量子点荧光增敏法测定盐酸多巴胺

以CdTe量子点作为荧光探针,基于荧光增敏法对盐酸多巴胺进行了定量检测,考察了缓冲溶液体系、量子点浓度、反应时间等多种因素的影响。实验结果表明,在pH7.5的0.2 mol/L Na2HPO4-NaH2PO4缓冲液中,反应时间为20 min,盐酸多巴胺浓度为1.2×10-8~1.0×10-7mol/L时,其线性回归方程为△F=-27.47+25.54c(10-8mol/L),相关系数和检测限分别为0.9992和6×10-11mol/L。该方法为盐酸多巴胺的测定提供了新的方法。     

谷胱甘肽稳定的CdTe量子点荧光猝灭法测定痕量过氧化氢

以谷胱甘肽稳定的CdTe量子点作为荧光探针,基于荧光猝灭法对过氧化氢进行了定量检测,考察了缓冲溶液体系、量子点浓度、反应时间等多种因素的影响。实验结果表明,在pH=7.2的Na2HPO4-NaH2PO4缓冲液中,反应时间为15min,过氧化氢浓度为1.0×10-6～3.0×10-5 mol/L范围时,其线性回归方程为△F=9.78+7.56c(10-6 mol/L),线性相关系数和检测限分别为0.9992和1.27×10-8 mol/L。谷胱甘肽稳定的CdTe量子点荧光猝灭法已用于水样的测定,回收率在96%～103%之间,相对标准偏差RSD不大于3.3%,结果令人满意。     

基于CdTe量子点荧光增强测定阿米卡星

以水相中制备的巯基乙酸修饰CdTe量子点为荧光探针,基于N-羟基丁二酰亚胺(NHS)存在,阿米卡星能使合成的量子点荧光增强作用,建立了测定阿米卡星新的分析方法。考察了缓冲体系、量子点浓度、NHS浓度、反应时间等因素的影响,在最佳实验条件下,体系的F/F0与阿米卡星的浓度呈良好的线性关系,其线性范围为2.0×10-7~2.0×10-5mol/L,相关系数为0.9971,检出限为1.9×10-7mol/L。用于实际样品的检测,RSD≤2.1%(n=5),回收率为99.98%。     

水溶性CdTe量子点荧光猝灭法测定尼群地平的研究

以巯基乙酸为稳定剂,直接合成了水溶性CdTe量子点。基于尼群地平对合成量子点的荧光猝灭效应,建立了一种简便、快速和灵敏地测定尼群地平的分析方法。考察了缓冲体系、缓冲液浓度、缓冲液pH值、反应时间、量子点浓度对尼群地平测定的影响,在0.03 mol/L、pH值为8.3的Tris-HCl缓冲液中,当量子点的浓度为6.0×10-4mol/L、反应时间为5 min,体系的相对荧光强度与尼群地平的质量浓度呈良好线性关系,其线性范围为1.09~65.4 mg/L,线性系数为0.998 6,检出限(S/N=3)为0.11 mg/L。该方法已成功用于药片中尼群地平的测定,与中国药典中的标准方法比较,结果满意。同时该文对尼群地平与CdTe量子点的反应机理进行了初步探讨。     

一种提高双氢青蒿素电化学检测分辨率的新方法

采用电化学方法研究了阳离子表面活性剂对双氢青蒿素(DHA)在银电极表面伏安行为的影响,并探讨了其电极界面的电化学机理。随着阳离子表面活性剂十六烷基三甲基溴化铵(CTMAB)的加入,DHA的还原峰电位发生明显的变化。当CTMAB的浓度为1.0×10-5mol/L时,DHA的峰电位正移了102 mV,活化能降低,DHA的过氧键更容易断裂。当CTMAB的浓度继续增大至7.0×10-4mol/L,DHA的峰电位负移了108 mV,活化能增大,DHA的过氧键更稳定。同时,还研究了酸度、温度和不同结构的阳离子表面活性剂对DHA伏安行为的影响,并提出其作用机制,从而建立一种提高DHA电化学检测分辨率的新方法。     

Hydrophilization of CdSe quantum dots with surfactants

A procedure has been developed for hydrophilization of CdSe semiconductor quantum dots with anionic, cationic, and nonionic surfactants. Depending on the type of a surfactant, these particles may carry positive, negative, or no charges. In spite of the universality of the proposed procedure, the hydrophilization with specific surfactants must be carried out at specific concentrations of reagents and medium pH values. Under optimum conditions, the transfer of the quantum dots to water substantially increases the quantum yield of their luminescence. Conditions have been found under which the luminescence properties of the hydrophilic particles remain almost unchanged for a long time period.     

Synthesis of Multifunctional Mn‐Doped CdTe/ZnS Core/Shell Quantum Dots

The synthesis of a novel water‐soluble Mn‐doped CdTe/ZnS core‐shell quantum dots using a proposed ultrasonic assistant method and 3‐mercaptopropionic acid (MPA) as stabilizer is descried. To obtain a high luminescent intensity, post‐preparative treatments, including the pH value, reaction temperature, reflux time and atmosphere, have been investigated. For an excellent fluorescence of Mn‐doped CdTe/ZnS, the optimal conditions were pH 11, reflux temperature 100°C and reflux time 3 h under N₂ atmosphere. While for phosphorescent Mn‐doped CdTe/ZnS QDs, the synthesis at pH 11, reflux temperature 100°C and reflux time 3 h under air atmosphere gave the best strong phosphorescence. The characterizations of Mn‐doped CdTe/ZnS QDs were also identified using AFM, IR, powder XRD and thermogravimetric analysis. The data indicated that the photochemical stability and the photoluminescence of CdTe QDs are greatly enhanced by the outer inorganic ZnS shell, and the doping Mn²⁺ ions in the as‐prepared quantum dots contribute to strong luminescence. The strong luminescence of Mn‐doped CdTe/ZnS QDs reflected that Mn ions act as recombination centers for the excited electron‐hole pairs, attributing to the transition from the triplet state (⁴T₁) to the ground state (⁶A₁) of the Mn²⁺ ions. All the experiments demonstrated that the surface states played important roles in the optical properties of Mn‐doped CdTe/ZnS core‐shell quantum dots.     

Fluorescence-detecting cationic surfactants using luminescent CdTe quantum dots as probes

A novel fluorescence quenching method for the determination of cationic surfactants (CS), specifically cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and cetylpyridinium chloride (CPC), has been developed using water-soluble luminescent CdTe quantum dots (QDs) modified with thioglycolic acid (TGA). The possible interference from heavy and transition metals (HTM) has been efficiently eliminated through simple sample treatment with mercapto cotton made in-house. Under optimum conditions, the extent of fluorescence quenching of CdTe QDs is linearly proportional to the concentration of CS from 2.0 × 10⁻⁷ to 7.0 × 10⁻⁶ mol L⁻¹ with a detection limit of 5.0 × 10⁻⁸ mol L⁻¹. The relative standard deviation for 1.0 × 10⁻⁶ mol L⁻¹ CTAB is 2.5% (n = 6). The proposed method exhibits high sensitivity and selectivity and furthermore avoided the use of toxic organic solvents and tedious solvent extraction procedures. It has been applied to the determination of trace CS in natural river water and commodity samples with satisfactory results. Potential interference from heavy and transition metals is eliminated during photoluminescence detection of CS through simple sample pre-treatment with mercapto cotton     

Luminescence quenching in self-assembled adducts of [Ru(dpp)3]2+ complexes and CdTe nanocrystals

We have investigated chloroform solutions containing tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) and CdTe nanocrystal quantum dots (5.6 nm diameter). The electronic levels of these two components are such that the Ru complex can act as an energy donor towards the quantum dot, which can thus behave as an energy acceptor. Steady-state and time-resolved spectroscopic experiments indicate that the Ru complexes and the CdTe nanocrystals self-assemble to give stable 1?:?1 adducts, in which the luminescence of the former units is strongly quenched. Such a quenching can be ascribed to either energy transfer to the CdTe quantum dot, or to electron transfer from the CdTe valence band to the excited Ru complex. However, no supporting evidence for the occurrence of photoinduced energy transfer in the adduct could be found. The CdTe luminescence is also slightly quenched in the presence of the ruthenium complex. The strong association of the metal complexes with the nanocrystals suggests that self-assembly strategies may be effectively employed to achieve surface functionalization of semiconductor quantum dots with molecular units.     

Facile synthesis and application of highly luminescent CdTe quantum dots with an electrogenerated precursor

An electrogenerated precursor has been developed for green synthesis of highly luminescent aqueous CdTe quantum dots (QDs) with unique quantum yield and strong electrogenerated luminescence, which can access cellular targets via specific binding and have potential application as biolabels in highly sensitive biosensing and cell imaging.     

表面活性剂对CdSe量子点荧光性能的影响

通过添加不同类型的表面活性剂在水相中制备了CdSe量子点。用透射电子显微镜(TEM)、X射线衍射(XRD)、X-射线光电子能谱(XPS)对其进行了表征,并用紫外-可见(UV-Vis)和荧光(PL)分光光度法研究了不同类型的表面活性剂对CdSe量子点吸收光谱和荧光光谱的影响。结果表明,加入长链的非离子型和阴离子型表面活性剂制备的CdSe量子点颗粒只有几个纳米,分散性好,量子点的荧光强度也有明显的增强,而加入阳离子表面活性剂制备的量子点颗粒团聚明显,其荧光出现淬灭。     

CdTe/CdS半导体量子点作为农药百草枯的高灵敏传感器

用硫普罗宁(Tiopronin, TP)作为稳定剂合成了水溶性的高荧光CdTe/CdS量子点. 研究了该量子点与10种农药的相互作用. 实验发现, 当农药浓度为4.76×10^-6 mol/L时, 农药百草枯(Paraquat)能显著猝灭CdTe/CdS量子点的荧光, 使其荧光强度下降87.3%, 而分别加入乙酰甲胺磷及辛硫磷等其它9种农药, 仅能使CdTe/CdS量子点的荧光强度下降0.1%～5.1%, 显示了该CdTe/CdS量子点对百草枯的特异性传感作用. 采用吸收光谱和时间分辨荧光动力学研究了百草枯对CdTe/CdS量子点的荧光猝灭机理. 计算得出荧光强度猝灭的Stern-Volmer常数K为2.03×10⁶, 而寿命猝灭的Stern-Volmer常数K为4.25×10⁵. 结果表明, 百草枯对CdTe/CdS量子点的荧光猝灭主要为静态过程, 而动态过程的贡献较小. 利用二者的猝灭作用建立了对农药百草枯的高灵敏检测新方法, 校正曲线的线性范围为9.90×10^-9～1.50×10^-6 mol/L, 检出限为6.35×10^-9 mol/L, R=0.999. 用该方法对3种食品和3种水样中残留农药进行了检测, 加标回收率均在82.2%～98.5%之间, 其相对标准偏差为2.62%~8.35%.     

Chemiluminescence of CdTe nanocrystals induced by direct chemical oxidation and its size-dependent and surfactant-sensitized effect

CdTe nanocrystals (NCs) capped with thioglycolic acid (TGA) were synthesized via a microwave-assisted method. The chemiluminescence (CL) of CdTe NCs induced by directly chemical oxidation and its size-depended and surfactant-sensitized effect in aqueous solution were then investigated. It was found that oxidants, especially hydrogen peroxide and potassium permanganate, could directly oxidize CdTe NCs to produce strong CL emission in basic conditions. The oxidized CL of CdTe NCs displayed size-dependent effect and its intensity increased along with increasing the sizes of the NCs. Moreover, the CL intensity could, if surfactants CTAB or beta-cyclodextrin were added to the above CL system, be sensitized to some degree. The sensitized CL induced by CTAB and beta-cyclodextrin is mainly contributing to the formation of aggregate nanostructure and the micellar micronanoenvironment, respectively. The possible oxidized CL mechanisms were further examined by means of photoluminescence spectra, CL spectra, and transmission electron microscopy studies. The CL properties of CdTe NCs not only will be helpful to study physical chemistry properties of semiconductor nanocrystals but also are expected to find use in many fields such as luminescence devices, bioanalysis, and multicolor labeling probes.     

Optical properties of Ag/CdTe nanocomposite self-organized by electrostatic interaction

Ag/CdTe nanocomposite was prepared via self-organization process by electrostatic interaction between positively charged CdTe quantum dots and negatively charged Ag nanoparticles and examined with respect to their optical properties. The positively charged CdTe quantum dots and negatively charged Ag nanoparticles were synthesized separately by modifying nanoparticles surface with cationic and anionic thiol compounds, respectively. The result showed that the mixing ratio of Ag nanoparticles to CdTe quantum dots is an important parameter for controlling resulting composites. The resulting solution is optically transparent if one component is in excess. Photoluminescence of CdTe quantum dots undergoes considerably quenching if CdTe nanocrystals are in excess and SERS spectra of BVPP absorbed on Ag colloid became stronger if Ag nanoparticles are in excess. Nevertheless, while the ratio is approximately 1, micrometer-sized solid composite is obtained with the elapse of 1h after mixing. SERS spectra for solid composite only exhibit the signals of the CdS nanocrystal which reflected that prolonged refluxing during the synthesis leads to a partial hydrolysis of the thiols and to the incorporation of the sulfur from the thiol molecules into the the growing nanoparticles to form mixed CdTe(S) nanocrystal, similar to CdTe/CdS core/shell structure. From the results, we conclude that optical properties of Ag/CdTe are dependent on the mixing ratio of both nanoparticles.