基于CdTe量子点荧光探针测定水样中痕量Cd2+

本文以巯基乙酸为稳定剂,在水相中合成水溶性的CdTe量子点(CdTe QDs),并基于QDs荧光增强原理,建立了QDs荧光探针测定水中痕量Cd2+的新方法。研究表明,在pH为7.8的硼酸-硼砂缓冲溶液和吐温-40的存在下,Cd2+能够显著增强CdTe QDs的荧光强度,且Cd2+浓度在2.0×10-7～5.5×10-5g/L范围内与CdTe QDs荧光增强强度呈现良好的线性关系,相关系数为0.9988,检出限(3s/k)为3.2×10-8 g/L。该方法简单便捷,灵敏度高,应用于实际水样的检测,回收率为96.0%～102.5%。     

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。     

核酸荧光探针检测铅离子的研究

将8-17 DNAzym e增加2个"G-C"碱基对进行增强热稳定性的结构修饰,并标记上1个荧光基团"FAM"和2个荧光猝灭基团"Dabcyl",设计成双猝灭Pb2+荧光探针。研究了该探针对Cd2+、Zn2+、Mg2+、Cu2+、Mn2+、Pb2+6种二价金属离子的响应,结果表明探针对Pb2+具有很强的特异性,在探针浓度为2.5×10-7mol/L时,Pb2+浓度在8.5×10-8~7.5×10-6mol/L范围内和探针的荧光强度呈线性关系,检出限为8.5×10-8mol/L。该探针可用于Pb2+的定性和定量检测。     

一种定量测定Pb^2＋的新型荧光探针的合成及性能

以氟化硼络合二吡咯甲川类(BODIPY)染料为荧光团,二(2-羟基乙基)亚胺为识别体合成了一种新的对Pb2+具有高选择性的Pb2+荧光探针.在HEPES缓冲溶液(pH 7.4)中,当Pb2+浓度达到1.0×10-5 mol/L时肉眼可观察到探针荧光强度明显增强;当Pb2+浓度达到3.0×10-4 mol/L时,探针荧光强度增大20倍以上,且识别作用不受其它金属离子(Na+、Mg2+、Ca2+、Cu2+、Fe2+、Hg2+、Ag+、Cd2+、Cr3+、Fe3+)干扰.Pb2+浓度在0.2×10-5～5.0×10-5 mol/L范围内,探针荧光强度与Pb2+浓度有较好的线性关系,相关系数为0.998,检出限为0.2 μmol/L.     

基于水溶性硅量子点的汞离子荧光传感器

本文基于Hg~(2+)对水溶性硅量子点(Si QDs)的荧光猝灭效应,构建了一种简单、快捷的Hg~(2+)荧光传感器。实验发现,当Si QDs表面的氨基与Hg~(2+)结合形成配合物时,Si QDs的荧光被猝灭,根据荧光猝灭程度与Hg~(2+)的浓度关系,可实现Hg~(2+)的检测。在优化的实验条件下,Si QDs的荧光猝灭程度与Hg~(2+)浓度在5.0×10-8~1.0×10-6 mol/L范围内呈良好的线性关系(R2=0.9978),检出限(3σ)为2.2×10-8 mol/L。在此基础上,借助Hg~(2+)易于与巯基结合形成稳定配合物的原理,选用治疗Hg~(2+)中毒的药品二巯基丙磺酸钠(DMPS)为模型,利用该巯基化合物可使Hg~(2+)猝灭Si QDs的荧光恢复的特性,建立了一种检测DMPS的新方法。     

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。     

Cr3+比色荧光探针的合成及细胞成像应用

以2,3,3-三甲基-3H-苯并[e]吲哚和对二甲氨基苯甲醛为原料, 乙醇作溶剂, 在酸性催化条件下, 通过一步反应合成了比色荧光探针B. 在EtOH/HEPES(pH=7.4)体积比为9∶1的混合体系中, 向探针B溶液中加入Cr ³⁺后, 溶液颜色由淡黄色变为紫红色, 说明探针B可以对Cr ³⁺进行裸眼识别. 紫外-可见吸收光谱和荧光发射光谱分析表明, 探针B对Cr ³⁺的选择性好、 灵敏度高且对EDTA有良好的接力识别. 探针B对Cr ³⁺的结合常数K_a=0.28×10 ² mol/L, 检出限为1.90×10 ^-8 mol/L, 该检出限低于世界卫生组织(WHO)规定的饮用水中Cr ³⁺的最大含量(9.60×10 ^-8 mol/L). 利用荧光发射光谱对实际水样中Cr ³⁺的浓度进行了定量检测. 探针B也可应用于对活细胞中Cr ³⁺的检测, 具有较好的应用前景和实用价值.     

利用salen型荧光探针测定Cr3+

研究了salen型席夫结构的荧光探针N,N’-二(2-羟基-1-萘甲醛)-l,2-苯二胺(NAPPDIH)对Cr3+的响应。Cr3+能够使该探针的荧光猝灭。研究表明,在pH3.5(乙酸胺-盐酸)和DMSO/H2O(V/V,8:2)的条件下,8.0×10-6 mol/L的Cr3+可以导致NAPPDIH 65%的荧光猝灭。并且,Cr3+的浓度在5.0×10-7～8.0×10-6 mol/L的范围内,与荧光强度的变化值呈良好的线性关系,检出限为3.7×10-7 mol/L。方法可用于直接检测水样中的Cr3+。     

1,8-二（2-羟乙基）亚氨基蒽醌荧光探针用于Fe3+的高选择性测定

在蒽醌荧光团上修饰乙醇胺分子,合成了用于铁离子识别检测的新的荧光探针.实验结果表明,在乙醇∶水=4∶1,pH值为7.20的条件下,Fe3+的加入使体系荧光猝灭,荧光强度和Fe3+浓度在4.0×10-5—3.0×10-4 mol/L范围内呈线性关系,由此可以实现在乙醇/水体系中对Fe3+离子的高选择性检测.检测限为3.8×10-7 mol/L.     

3-巯基丙酸修饰的CdTe量子点荧光探针用于碘酸根离子的检测

以3-巯基丙酸(MPA)为稳定剂,采用水相合成法制备了CdTe量子点(QDs)。基于IO-3可使CdTe QDs荧光显著猝灭的特性,建立了一种检测IO-3的荧光分析新方法。优化了实验条件,在pH=6.0、三酸缓冲溶液浓度为30mmol/L、QDs溶液浓度为8.66×10-6 mol/L、反应时间为24min最佳实验条件下,检测IO-3的线性范围为6.0×10-8~7.2×10-6 mol/L,检出限为4.92×10-8 mol/L,方法相对标准偏差为2.37%。实验表明,IO-3对CdTe QDs的荧光猝灭有较好的选择性。方法用于自来水中IO-3的回收率实验,回收率为92.17%~103.29%。对可能的机理进行了探讨。     

高灵敏CdTe量子点探针的构建及与金属离子的作用

采用变性的牛血清白蛋白(dBSA)对水相合成的CdTe量子点进行修饰, 构建了高灵敏金属离子探针, 研究了其对重金属离子的检测性能并对机理进行了探讨. 通过优化反应条件, 合成了具有高量子产率的以巯基乙酸为稳定剂的水溶性CdTe量子点, 并采用变性的牛血清白蛋白分别对不同粒径的CdTe量子点进行修饰, 确定变性的牛血清白蛋白与不同粒径量子点之间的最佳比例. 在纯化变性的牛血清白蛋白修饰的量子点(dBSA-QDs)的基础上, 研究了该量子点与不同金属离子的作用. 结果表明, 量子点经修饰后, 其量子产率、 抗光漂白性及稳定性得到显著提高; 而且dBSA-QDs的荧光可被重金属离子有效猝灭, 与巯基乙酸稳定的量子点(TGA-QDs)相比, 检测灵敏度显著提高.     

基于L-半胱氨酸/CdTe量子点修饰电极的电化学传感器的制备及其对Pb~(2+)的检测

成功制备了由L-半胱氨酸和CdTe量子点作为修饰材料的电化学传感器并用于水体中Pb~(2+)的检测。巯基丙酸修饰的CdTe量子点通过水相合成,表面含有大量羧基,与L-半胱氨酸表面的氨基形成酰胺键,修饰于金电极表面。通过荧光分光光度计、透射电子显微镜、红外光谱、X射线衍射对L-Cys/CdTe QDs复合材料进行表征。采用循环伏安法(CV)研究了L-Cys/CdTe QDs修饰成分在金电极上的电化学性能及CdTe量子点的最佳自组装时间。采用差分脉冲溶出伏安法(DPSV)研究了铅离子在修饰电极上的电化学行为。在优化实验条件下,Pb~(2+)浓度在1.0×10~(-6)~1.0×10~(-2) mol/L范围内与其峰电流呈良好的线性关系,相关系数(r2)为0.993 8,检出限(3σ,n=5)为4.0×10~(-7) mol/L。该传感器具有良好的重现性和稳定性,有望用于实际水样中铅离子的检测。     

Ligand displacement-induced fluorescence switch of quantum dots for ultrasensitive detection of cadmium ions

This paper reports the construction of a simple CdTe quantum dots (QDs)-based sensor with 1,10-phenanthroline (Phen) as ligand, and the demonstration of a novel ligand displacement-induced fluorescence switch strategy for sensitive and selective detection of Cd²⁺ in aqueous phase. The complexation of Phen at the surface quenches the green photoluminescence (PL) of QDs dominated by a photoinduced hole transfer (PHT) mechanism. In the presence of Cd²⁺, the Phen ligands are readily detached from the surface of CdTe QDs, forming [Cd(Phen)₂(H₂O)₂]²⁺ in solution, and as a consequence the PL of CdTe QDs switches on. The detection limit for Cd²⁺ is defined as ∼0.01 nM, which is far below the maximum Cd²⁺ residue limit of drinking water allowed by the U.S. Environmental Protection Agency (EPA). Two consecutive linear ranges allow a wide determination of Cd²⁺ from 0.02 nM to 0.6 μM. Importantly, this CdTe QDs-based sensor features to distinctly discriminate between Cd²⁺ and Zn²⁺, and succeeds in real water samples. This extremely simple strategy reported here represents an attempt for the development of fluorescent sensors for ultrasensitive chemo/biodetection.     

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.     

Simple and sensitive detection method for chromium(VI) in water using glutathione—capped CdTe quantum dots as fluorescent probes

Water-soluble and stable CdTe quantum dots (QDs) were synthesized in aqueous solution with glutathione (GSH) as the stabilizer. GSH is employed by nature to detoxify heavy metal ions. As a result of specific interaction, the fluorescence intensity of GSH-capped QDs is selectively reduced in the presence of Cr(VI). Under the optimum conditions, the relative fluorescence intensity decreases linearly with the Cr(VI) concentration in the range from 0.01 to 1.00?µg mL^?1, and the detection limit is 0.008?µg mL^?1. The luminescence response of the QDs to ions markedly depended on the particle size, and a new strategy for tuning the selectivity of luminescent QDs to certain ions without changing the capping layer of the QDs can be achieved by changing the crystallite size of the QDs.     

Quantum dot-based "turn-on" fluorescent probe for detection of zinc and cadmium ions in aqueous media

Health or environmental issue caused by abnormal level of metal ions like Zn²⁺ or Cd²⁺ is a worldwide concern. Developing an inexpensive and facile detection method for Zn²⁺ and Cd²⁺ is in urgent demand. Due to their super optical properties, fluorescent quantum dots (QDs) have been developed as a promising alternative for organic dyes in fluorescence analysis. In this study, a CdTe QDs-based sensitive and selective probe for Zn²⁺ and Cd²⁺ in aqueous media was reported. The proposed probe worked in fluorescence “turn-on” mode. The initial bright fluorescence of CdTe QDs was effectively quenched by sulfur anions (S²⁻). The presence of Zn²⁺ (or Cd²⁺) can “turn-on” the weak fluorescence of QDs quenched by S²⁻ due to the formation of ZnS (or CdS) passivation shell. Under optimal conditions, a good linear relationship between the fluorescence response and concentration of Zn²⁺ (or Cd²⁺) could be obtained in the range from 1.6 to 35 μM (1.3–25 μM for Cd²⁺). The limit of detection (LOD) for Zn²⁺ and Cd²⁺ were found to be 1.2 and 0.5 μM, respectively. Furthermore, the present probe exhibited a high selectivity for Zn²⁺ and Cd²⁺ over other metal ions and was successfully used in the detection of Zn²⁺ or Cd²⁺ in real water samples.     

Probing the mechanism of the interaction between l‐cysteine‐capped‐CdTe quantum dots and Hg2+ using capillary electrophoresis with ensemble techniques

A good understanding of the mechanism of interaction between quantum dots (QDs) and heavy metal ions is essential for the design of more effective sensor systems. In this work, CE was introduced to explore how l ‐cysteine‐capped‐CdTe QDs (l ‐cys‐CdTe QDs) interacts with Hg²⁺. The change in electrophoretic mobility can synchronously reflect the change in the composition and property of QDs. The effects of the free and capping ligands on the system are discussed in detail. ESI‐MS, dynamic light scattering (DLS), zeta potential, and fluorescence (FL) were also applied as cooperative tools to study the interaction mechanism. Furthermore, the interaction mechanism, which principally depended on the concentration of Hg²⁺, was proposed reasonably. At the low concentration of Hg²⁺, the formation of a static complex between Hg²⁺ and the carboxyl and amino groups of l ‐cys‐CdTe QDs surface was responsible for the FL quenching. With the increase of Hg²⁺ concentration, the capping l ‐cys was stripped from the surface of l ‐cys‐CdTe QDs due to the high affinity of Hg²⁺ to the thiol group of l ‐cys. Our study demonstrates that CE can reveal the mechanism of the interaction between QDs and heavy metal ions, such as FL quenching.     

The synthesis of mono-6-thio-β-cyclodextrin capped CdTe QDs and its interaction with neutral red

This paper presents a novel method for the synthesis of CdTe quantum dots (QDs) capped with β-cyclodextrin in aqueous solution using both TGA and mono-6-thio-β-CD as stabilizers. The interaction between mono-6-thio-β-CD-CdTe QDs and neutral red (NR) was studied with fluorescence, UV-absorption and the resonance Rayleigh scattering spectrum. When its concentration was over 7.5 × 10^?6 mol/L, the neutral red began to aggregate on the surface of the mono-6-thio-β-CD-CdTe QDs, which resulted in the mono-6-thio-β-CD-CdTe QDs particle size increasing, the sharply quenched fluorescence, and the marked increase of RRS intensity.     

Cadmium sulfide quantum dots modified by chitosan as fluorescence probe for copper (II) ion determination

CdS quantum dots (QDs) have been prepared and modified with chitosan. Based on the quenching of fluorescence signals of the functionalized CdS QDs at 531 nm wavelength and enhancement of signals the 400–700 nm wavelength range by Cu²⁺ at pH 4.2, a simple, rapid and specific method for Cu²⁺ determination is presented. Under optimum conditions, the relative fluorescence intensity of CdS QDs is linearly proportional to copper concentration from 8.0 nmol L^?1 to 3.0 μmol L^?1 with a detection limit of 1.2 nmol L^?1. The mechanism can be explained in terms of strong binding of Cu²⁺ onto the surface of CdS, resulting in a chemical displacement of Cd²⁺ ions and the formation of CuS on the surface of the QDs.     

An ultrasensitive method for the determination of melamine using cadmium telluride quantum dots as fluorescence probes

An ultrasensitive and simple method for the determination of melamine was developed based on the fluorescence quenching of thioglycolic acid (TGA) capped CdTe quantum dots (QDs) at pH 11.0. In strong alkaline aqueous solution, the selectivity of the method has been greatly improved due to most heavy metal ions show no interference as they are in the precipitation form or in their anion form. Furthermore, CdTe quantum dots have higher quantum yields at higher pH. The method has a wider concentration range and lower detection limit. The influence factors on the determination of melamine were investigated and the optimum conditions were determined. Under optimum conditions, the fluorescence intensity change of TGA coated CdTe quantum dots was linearly proportional to melamine over a concentration range from 1.0 × 10⁻¹¹ to 1.0 × 10⁻⁵ mol L⁻¹ with a correlation coefficient of 0.9943 and a detection limit of 5 × 10⁻¹² mol L⁻¹. The mechanism of fluorescence quenching of the QDs has been proposed based on the infrared spectroscopy information and electrophoresis experiments in presence of melamine under alkaline condition. The proposed method was employed to detect trace melamine in milk powder and pet feeds with satisfactory results.