CdTe量子点荧光猝灭法测定痕量叶酸

以CdTe量子点作为荧光探针,基于荧光猝灭法对叶酸进行了定量检测,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,在水中,反应时间为10min,叶酸浓度为2.5×10-7—1.5×10-6mol/L范围时,其线性回归方程为ΔF=47.67+129.88C(10-6mol/L),相关系数为0.9989。该方法检测范围宽,灵敏度高,为痕量叶酸的测定提供了新的方法。     

CdTe量子点荧光猝灭法测定微量铅

以CdTe量子点作为荧光探针,基于荧光猝灭法对铅进行了定量检测,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 7.5的0.2mol/L Na2HPO4-NaH2PO4缓冲液中,反应时间为10min,铅浓度为2.0×10-6—3.5×10-5mol/L范围时,其线性回归方程为ΔF=26.35+11.47C(×10-6mol/L),相关系数和检出限分别为0.9991和1.8×10-8mol/L。该方法灵敏度高,为铅的测定提供了新的方法。     

CdTe量子点荧光猝灭法测定钴

以CdTe量子点作为荧光探针,基于荧光猝灭法对钴(Ⅱ)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pH8.0的0.2mol/LNa2HPO4-NaH2PO4缓冲液中,反应时间为10min,钴(Ⅱ)浓度为1.6×10-5—20×10-5mol/L范围时,其线性回归方程为F0/F=1.45+0.096Q(10-5mol/L),检出限为3×10-7mol/L。该方法检测范围宽,灵敏度高,为钴的测定提供了新的方法。     

巯基乙胺稳定的CdTe量子点荧光猝灭法测定间苯二酚

以CdTe量子点作为荧光探针,基于荧光猝灭法对间苯二酚进行了定量检测,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 6.5的0.2mol/LNa<,2>HPO<,2>-NaH<,2>PO<,4>缓冲液中,反应时间为15min.间苯二酚浓度为1.6×10<'-6>-2.0×10<'-5>...     

单质碘对水溶性CdTe量子点的荧光猝灭研究

合成了不同尺寸的、巯基丙酸和半胱氨酸修饰的水溶性CdTe量子点,并研究了I2与CdTe量子点的相互作用,实验发现I2能够明显猝灭CdTe量子点的荧光,且猝灭程度与量子点的修饰剂有关,没有表现出明显的尺寸依赖效应。     

基于CdTe量子点荧光猝灭-恢复方法测定依诺沙星的研究

水相合成了巯基丙酸保护的CdTe量子点。根据在Cu2+存在的情况下,CdTe量子点荧光恢复程度与依诺沙星浓度成正比的现象,建立了基于CdTe量子点荧光猝灭-恢复测定依诺沙星的新方法。考察了溶液pH值以及Cu2+浓度等对检测体系的影响。在p H=10的硼砂缓冲溶液中,在Cu2+浓度为2.3×10-5mol/L的条件下,依诺沙星浓度在8.0×10-7~3.0×10-5mol/L范围内与量子点荧光恢复程度呈良好的线性关系,检出限为7.2×10-8mol/L。该方法用于实际样品中依诺沙星的检测,回收率为95.5%~105.0%。     

谷胱甘肽修饰的CdTe量子点荧光猝灭法测定化妆品中的铅

以谷胱甘肽(GSH)为稳定剂,在水溶液中制备稳定的CdTe纳米量子点.根据Pb(Ⅱ)对CdTe量子点的荧光具有较强的猝灭效应,建立一种简便灵敏的测定铅的新方法.考察了缓冲液体系、缓冲液pH、量子点的浓度和反应时间等对pb2+测定的影响.结果表明,在Tris缓冲液(pH8.8)中,CdTe量子点浓度0.0306mmol/L,反应时间5min,体系的相对荧光强度与pb2+浓度呈良好的线性关系,其线性范围为10-105μg/L,检出限0.27μg/L(3σ),加标回收率在97.6％-101.8％之间.此方法操作简便,快速,可用于化妆品中铅(Ⅱ)含量的测定.     

巯基琥珀酸修饰的CdTe量子点荧光猝灭法测定果蔬中的微量铜

以巯基琥珀酸(MSA)为稳定剂,在水溶液中制备稳定的CdTe量子点.基于Cu2+在磷酸盐缓冲液中对该量子点的荧光具有较强的猝灭作用,建立一种简便灵敏的测定铜的新方法.考察了量子点的浓度,缓冲液pH、和反应时间等对Cu2+测定的影响.结果表明,CdTe量子点浓度为0.0306mmol/L,在0.2mmol/L的磷酸盐缓冲液(pH7.4)中,反应时间为5min,体系的相对荧光强度与Cu2+浓度呈良好的线性关系,其线性范围为1.28-38.4μg/L,检出限为0.023μg/L(3σ).方法操作简便,快速,可用于果蔬中Cu2+含量的测定.     

碳量子点荧光猝灭法测定饮料中日落黄

以柠檬酸为碳源制备碳量子点(CQDs),所得碳量子点被394 nm的光激发后在484 nm处有较强的荧光发射,最大吸收波长为482 nm的日落黄能强烈猝灭碳量子点的荧光。基于该现象,发展了一种以碳量子点为荧光探针测定日落黄的分析方法,并探讨了荧光猝灭机理。在选定的实验条件下,该分析方法的线性检测范围为0.1~100μmol/L,检出限(3σ/k)为0.051μmol/L。     

茜素红S荧光猝灭法测定壳聚糖含量

在pH 5.0的NaAc-HAc缓冲液中壳聚糖对茜素红S的荧光强度具有明显的猝灭作用,且猝灭程度F0/F与加入的壳聚糖浓度成线性关系,据此建立一种测定壳聚糖含量的荧光猝灭法。确定了最佳测定条件,线性回归方程为F0/F=-0.438 37 0.436 27c(mg·L-1),线性范围为0-16.667 mg·L-1,r=0.996,检测限为0.473 mg·L-1;平均回收率为100.60％,测定了样品中壳聚糖的含量,并考察了干扰因素对测定的影响。采用该方法可测定复杂样品中微量壳聚糖含量。     

A simple fluorescence quenching method for roxithromycin determination using CdTe quantum dots as probes

A new method for the determination of roxithromycin based on the fluorescence quenching of 3-mercaptopropionic acid-capped CdTe quantum dots (MPA-CdTe QDs) was developed. In ethanol medium, the fluorescence of CdTe quantum dots at 552 nm was quenched in the presence of roxithromycin. Based on this a simple, sensitive, and selective method for rapid determination of roxithromycin was described. Reaction time, interfering substances on the fluorescence quenching, and mechanism of the interaction of CdTe QDs with roxithromycin were investigated. After optimization, the proposed method allows the determination of roxithromycin over the range 25.0-350.0 μg ml⁻¹. The detection limit is 4.6 μg ml⁻¹. The proposed method was successfully applied to commercial capsules and tablets with satisfactory results. The recovery of the method was in the range of 96.8-102.5%.     

低强度飞秒激光激发下CdTe和CdTe/CdS核壳量子点的荧光上转换研究

利用400 nm和800 nm不同波长的低强度飞秒激光,对CdTe和CdTe/CdS核壳量子点溶胶进行激发,研究其稳态和时间分辨荧光性质.800 nm飞秒激光激发下,CdTe和CdTe/CdS核壳量子点产生上转换发光现象,上转换荧光峰与400 nm激发下的荧光峰相比蓝移最多达15 nm,而且蓝移值与荧光量子产率有关.变功率激发确认激发光功率与上转换荧光强度间满足二次方关系,时间分辨荧光的研究表明荧光动力学曲线服从双e指数衰减.提出表面态辅助的双光子吸收模型是低激发强度上转换发光的主要机理.CdTe和CdT 关键词： CdTe量子点 CdTe/CdS核壳量子点 时间分辨荧光 上转换荧光     

Photoluminescence quenching of CdTe/CdS core-shell quantum dots in aqueous solution by ZnO nanocrystals

Photoluminescence (PL) properties of 3-mercaptopropionic acid (MPA) coated CdTe/CdS core-shell quantum dots (QDs) in aqueous solution in the presence of ZnO colloidal nanocrystals were studied by steady-state and time-resolved PL spectroscopy. The PL quenching of CdTe/CdS core-shell QDs with addition of purified ZnO nanocrystals resulted in a decrease in PL lifetime and a small red shift of the PL band. It was found that CdTe(1.5 nm)/CdS type II core-shell QDs exhibited higher efficiency of PL quenching than the CdTe(3.0 nm)/CdS type I core-shell QDs, indicating an electron transfer process from CdTe/CdS core-shell QDs to ZnO nanocrystals. The experimental results indicated that the efficient electron transfer process from CdTe/CdS core-shell QDs to ZnO nanocrystals could be controlled by changing the CdTe core size on the basis of the quantum confinement effect.     

Photoluminescence properties of a novel conjugate of water-soluble CdTe quantum dots to guanine

A novel conjugate of water-soluble CdTe quantum dots to a small biomolecule guanine has been obtained in aqueous phase. The photoluminescence property and the stability of the conjugate increased comparing to CdTe QDs. The interaction between CdTe QDs and guanine was studied by TEM, fluorescence microscope and photoluminescence (PL), IR, UV-Vis spectra. The effects of reflux time, pH value, ionic strength, and the ratio of CdTe QDs to guanine on the photoluminescence properties of conjugate were investigated in detail. The results show that guanine has a great influence on both the photoluminescence property and stability of thioglycolic acid-stabilized CdTe QDs. The formation of coordination and hydrogen bond between guanine molecules and CdTe including thioglycolic acid on its surface may effectively enhance the PL intensity and stability of CdTe QDs. The maximum PL intensity of the conjugate was obtained on the condition with lower ionic strength, less than 30 min reflux time, neutral pH value and 6/1 as molar ratio of guanine to CdTe.     

Study on the interaction of CdTe quantum dots with ferulic acid and protocatechuic aldehyde by optical spectroscopy

Luminescent CdTe quantum dots (QDs) were synthesized using thioglycolic acid (TGA) as a stabilizing agent in aqueous medium and were characterized by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and transmission electron microscopy (TEM). In weak basic media the fluorescence of TGA-CdTe QDs was quenched notably by ferulic acid (FA) and protocatechuic aldehyde (PA), and the quenching values were proportional to the concentration of the quenchers in a certain range. The addition of bovine serum albumin (BSA) to TGA-CdTe QDs-FA and TGA-CdTe QDs-PA systems rendered a large recovery of the fluorescence of TGA-CdTe QDs.     

水溶性CdTe量子点的三阶光学非线性极化特性

利用超短脉冲Z扫描技术和光学Kerr效应研究了以巯基丙酸为稳定剂的CdTe量子点水溶液的三阶光学非线性极化特性. 在532nm,30ps和800nm,130fs脉冲激光激发下, 发现分别具有正负相反取值的三阶光学非线性折射率,自由载流子吸收和双光子吸收分别是这两种脉冲激光激发下三阶光学非线性吸收的起因. 测量得到CdTe量子点的三阶光学非线性极化率约为CS₂的32倍, 在520—700nm光谱区的CdTe量子点的光学响应时间小于400fs. 关键词： CdTe量子点(QDs) Z扫描 三阶光学非线性极化特性 双光子吸收     

水溶性CdTe量子点的稳态和纳秒时间分辨光致发光光谱

报道了以飞秒脉冲激光为激发光源的水溶性CdTe量子点(QDs)的稳态荧光光谱和纳秒时间分辨荧光光谱.实验发现CdTe量子点的荧光光谱峰值位置随激发波长变化发生明显移动，激发脉冲波长越长，荧光峰位红移越大.荧光动力学实验数据显示，在400nm和800nm脉冲激光激发下，水溶性CdTe量子点的荧光光谱中均含有激子态和诱捕态两个衰减成分，两者的发射峰相距很近，诱捕态的发射峰波长较长.在800nm脉冲激光激发下的诱捕态成分占总荧光强度的比重比400nm激发下的约高3倍，其相对强度的这种变化导致了稳态荧光发射峰位的红移. 关键词： CdTe 量子点 时间分辨 荧光光谱 上转换荧光     

Investigation of ultrafast dynamics of CdTe quantum dots by femtosecond fluorescence up-conversion spectroscopy

The ultrafast carrier relaxation processes in CdTe quantum dots are investigated by femtosecond fluorescence upconversion spectroscopy.Photo-excited hole relaxing to the edge of the forbidden gap takes a maximal time of ～ 1.6 ps with exciting at 400 nm,depending on the state of the photo-excited hole.The shallow trapped states and deep trap states in the forbidden gap are confirmed for CdTe quantum dots.In addition,Auger relaxation of trapped carriers is observed to occur with a time constant of ～ 5 ps.A schematic model of photodynamics is established based on the results of the spectroscopy studies.Our work demonstrates that femtosecond fluorescence up-conversion spectroscopy is a suitable and effective tool in studying the transportation and conversion dynamics of photon energy in a nanosystem.     

Preparation and purification of l-cysteine capped CdTe quantum dots and its self-recovery of degenerate fluorescence

l-cysteine capped CdTe quantum dots (QDs) were prepared in aqueous solution by a simple and efficient method, showing many advantages such as short synthesis period, the broaden range of starting pH value and the wide fluorescence emission wavelength range. A novel purification process was designed to remove excess Cd²⁺ which has potential cytotoxicity for bio-analysis. Three-dimensional fluorescence charts of pre- and post-purification showed that the purified QDs were of better luminescent performance. The prepared QDs were of cubic crystal structure with an average size of 2-6 nm, which were characterized by XRD and HRTEM. It is confirmed by IR spectra that the l-cysteine ligands were conjugated with CdTe cores via covalent bond. The degenerate fluorescence of QDs can be self-recovered in the presence of l-cysteine without other processing steps.     

Study on the Interaction Between Water-Soluble CdTe Quantum Dots and Ovalbumin by Optical Spectroscopy

ABSTRACT

CdTe quantum dots (QDs) modified by 2-mercaptoethylamine hydrochloride (CA) and thioglycolic acid (TGA), respectively, were synthesized in aqueous medium. The interaction of CdTe QDs with ovalbumin has been investigated in depth by Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption, fluorescence-quenching spectrometry, and resonance Rayleigh scattering spectroscopy (RRS). Fluorescence data show that the quenching type of ovalbumin by CA-CdTe QDs is static quenching with the binding constant being 10^?4 M^?1, and the number of binding sites being one. The calculated thermodynamic parameters demonstrate that the main binding forces are hydrophobic interaction and electrostatic attraction. In contrast, the quenching style of ovalbumin by TGA-CdTe QDs is verified to be dynamic quenching. Under suitable acidity conditions, the interaction of CA-CdTe QDs or TGA-CdTe QDs with ovalbumin leads to the remarkable enhancement of RRS, and the increments are found to be proportional to the concentration of ovalbumin in a certain range. A simple and highly sensitive RRS approach for determining ovalbumin is developed. In addition, the causes for the enhancement of RRS and the quenching of fluorescence are investigated to shed light on the quenching mechanism.