A novel strategy for selective detection of Ag+ based on the red-shift of emission wavelength of quantum dots

Selective determination of Ag(I) ion was accomplished based on the red-shift of the emission band of quantum dots (QDs). Under optimal conditions, a linear relationship does exist between the red-shift of the emission and the concentration of Ag(I) in the range from 1.0?×?10^?7 to 1.5?×?10^?5 mol L^?1, with a detection limit of 5.0?×?10^?8 mol L^?1. The method has been successfully applied to the determination of Ag(I) ion in water samples. The possible reaction mechanism was investigated by ultraviolet–visible absorption, fluorescence, Raman spectroscopies and by high resolution transmission electron microscopy. The results suggest that the red-shift in emission be attributed to the stabilization of a charge-transfer state, but not due to the aggregation induced by AgI(I) ion.     

CdTe量子点荧光猝灭法测定奥沙利铂中微量银

以谷胱甘肽作为稳定剂,100℃恒温回流,直接合成水溶性CdTe量子点。基于Ag+对合成的CdTe量子点的荧光猝灭效应,建立了测定抗癌药物奥沙利铂中微量银的方法。考察了量子点浓度、缓冲液种类、缓冲液浓度、缓冲液pH和反应时间对银离子测定的影响。当量子点浓度为0.004 g/L时,在0.10 mmol/LpH7.4的磷酸缓冲溶液中,反应时间为5 min,体系的相对荧光强度与Ag+的质量浓度呈良好的线性关系,其线性范围为16.42～98.50μg/L,线性相关系数为0.9975,检出限为0.12μg/L。     

新荧光试剂双(2-苯并噻唑重氮氨基)-3,3′,5,5′-四甲基联苯的合成及其分析应用

将3,3′,5,5′-四甲基联苯胺和苯并噻唑类试剂结合, 并引入杂环三氮烯结构, 合成了新荧光试剂双(2-苯并噻唑重氮氨基) 3,3′,5,5′-四甲基联苯(BBTDTMB), 其结构经红外光谱、 核磁共振谱和元素分析证实. 研究结果表明, 在碱性介质中, 该试剂在λex/λem=342 nm/420 nm处产生强荧光, 并且Ag(Ⅰ)对其荧光有很好的猝灭作用, 因而建立了BBTDTMB测定Ag(Ⅰ) 的新荧光分析方法. 该方法的线性范围为1.0～240 μg/L, 检测限为 0.5 μg/L, 应用于人发、 茶叶中的Ag(Ⅰ) 的测定, 结果令人满意.     

Use of surface-modified CdTe quantum dots as fluorescent probes in sensing mercury (II)

Thioglycolic acid (TGA)-capped CdTe quantum dots (QDs) were synthesized in aqueous medium, and their interaction with metal cations was studied with UV-vis absorption, steady-state and time-resolved fluorescence spectra. The results demonstrated that Hg(II), Cu(II) and Ag(I) could effectively quench the QD emission based on different action mechanisms: Cu(II) and Ag(I) quenched CdTe QDs because they bound onto particle surface and facilitated non-radiative electron/hole recombination annihilation of QDs; electron transfer process between the capping ligands and Hg(II) was mainly responsible for the remarkable quenching effect of Hg(II). To prevent the approach of metal cations to QD core, the original TGA-capped CdTe QDs were further coated by denatured bovine serum albumin (dBSA). It was found that the dBSA-coated CdTe QDs could be quenched effectively by Hg(II), but Cu(II) and Ag(I) could hardly quench the QDs even at fairly higher concentration levels because the dBSA shell layer effectively prevented the binding of metal cations onto the QD core. On the basis of this fact, a simple, rapid and specific method for Hg(II) determination was proposed. Under optimal conditions, the quenched fluorescence intensity increased linearly with the concentration of Hg(II) ranging from 0.012 x 10(-6) to 1.5 x 10(-6) mol L(-1). The limit of detection for Hg(II) was 4.0 x 10(-9) mol L(-1). The developed method was successfully applied to the detection of trace Hg(II) in real samples.     

基于双发射免标记核酸探针的比率型荧光传感器用于银的检测

构建了一种新型免标记的双发射荧光比率核酸探针(GelRed/[G40]/Tb^3+)并用于Ag+的检测。对于GelRed/[G40]/Tb^3+探针,GelRed作为一种核酸染料嵌入到单链DNA-[G40]中,形成的GelRed/[G40]作为稳定的内置参照标准,在激发波长290 nm处,发射荧光强度固定不变的红色荧光(发射波长为635 nm),而[G40]/Tb^3+作为敏感的响应信号,随着Ag^+浓度的增加,产生的绿色荧光逐渐增强(发射波长为545 nm),[G40]/Tb3+与GelRed/[G40]发射的荧光强度比值也发生相应的改变,从而实现对Ag^+的定量检测。在优化的实验条件下,[G40]/Tb^3+与GelRed/[G40]荧光强度比值和Ag^+浓度在0~7.5μmol/L的范围内具有较好的线性关系,Ag^+检出限为0.156μmol/L。本传感器在10 min内就可完成对Ag^+的分析。方法已用于自来水样中Ag^+的检测,与ICP-MS法检测结果一致。     

紫外-可见吸收、荧光光谱研究CdTe/CdS量子点与盐酸药根碱的相互作用及其应用

合成了巯基乙酸（TGA）修饰的壳核型CdTe/CdS量子点（TGA-CdTe/CdS QDs）。 利用紫外-可见光谱吸收、荧光光谱研究TGA-CdTe/CdS QDs与盐酸药根碱（JH）的相互作用机理。 在pH值为7.4的tris-HCl缓冲溶液介质中,QDs与JH相互作用后使QDs的荧光呈线性猝灭,并有良好的线性关系（r=0.999 1）,线性范围0.011~10 mg/L,检出限（3σ）为3.3×10-3 mg/L,因此可以作为一种快速、简便、定量测定盐酸药根碱的新方法。     

Organic-inorganic hybrid fluorescent sensor thin films of rhodamine B embedded Ag-SBA 15 for selective recognition of Hg (Ⅱ) ions in water

Nowadays, the rapid and effective detection of low doses of heavy metal pollutants in contaminated water is a timely challenge in environmental pollution research. In this study, a rapid and highly sensitive assay for the detection of Hg~(2+)based on quenching of metal-enhanced fluorescence of rhodamine B(RB)has been fabricated. RB and silver nanoparticle were incorporated into the mesoporous siliceous framework spin cast on a quartz glass through post-synthetic incorporation method. The morphology and crystallinity of mesoporous structure and Ag nanoparticle were characterized by transmission electron microscopy and X-ray diffraction analyses. Photoluminescence assays on the hybrid thin film of RB-Ag-SBA15 showed a high enhancement when compared to the intensity of silver free SBA15-RB in the wavelength of 575 nm. The fluorescence of RB-Ag-SBA15 thin film decreased gradually with the increase in the concentration of Hg~(2+)and the detection limits were 10.54 nmol/L. Furthermore, the fluorescence intensity increased linearly with the concentration of Hg~(2+)in the range from 1.0 ? 10à8mol/L to10 ? 10à8mol/L, with a response time of a few seconds. In addition, this system offers a high selectivity over interfering cations such as Cd~(2+) and Pb~(2+). Overall, we have developed an optical assay having a wellordered mesoporous SBA15 containing Ag-RBfor selective detection of Hg~(2+)in aqueous solution. The scheme combines the advantages of specific binding interactions between Hg~(2+)and RB molecule and optical emission properties of RB. The method is suitable for a single-shot and irreversible analytical assay in a quartz glass/microtiter plate.     

纳米B2O3/TiO2复合材料的制备及其对痕量银的分离富集性能研究与应用

制备了新型纳米B2O3/TiO2吸附材料,并采用扫描电镜(SEM)及红外光谱(IR)对其进行表征,优化了纳米B2O3/TiO2复合材料对试液中痕量银的吸附和解吸条件,建立了纳米B2O3/TiO2分离富集-原子吸收光谱测定痕量银的新方法。当pH 4.3时,在22℃下振荡20 min,Ag+能被该材料快速吸附,其静态饱和吸附容量为11.72 mg/g,吸附在纳米B2O3/TiO2上的Ag+可用0.1 mol/L HNO3-0.05 mol/L硫脲(1∶4)完全洗脱。该方法的检出限为2.01μg/L,线性范围为0.01～4.00 mg/L,相对标准偏差(RSD)为1.8%,加标回收率为95%～105%。方法应用于实际矿渣样品中痕量银的测定,结果满意。     

Functionalized CdSe quantum dots as selective silver ion chemodosimeter

CdSe quantum dots (QDs) have been prepared and modified with mercaptoacetic acid. They are water-soluble and biocompatible. To improve their fluorescence intensity and stability in water solution, bovine serum albumin (BSA) was absorbed onto their surface. Based on the quench of fluorescence signals of the functionalized CdSe QDs in the 543 nm wavelength and enhancement of them in the 570-700 nm wavelength range by Ag(I) ions at pH 5.0, a simple, rapid and specific method for Ag(I) determination was proposed. In comparison with single organic fluorophores, these nanoparticles 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 Ag(I) between 4.0 x 10(-7) and 1.5 x 10(-5) mol L(-1), and the limit of detection is 7.0 x 10(-8) mol L(-1). The mechanism of reaction is also discussed.     

抗氧化剂没食子酸丙酯合成纳米银及其应用

在十六烷基三甲基溴化铵(CTAB)存在下, 硝酸银与没食子酸丙酯在碱性介质中发生还原反应, 制得纳米银; 考察了反应时间、 氢氧化钠浓度、 反应温度以及PG/Ag⁺浓度比等条件对合成纳米银粒子的影响. 利用扫描电子显微镜对纳米银颗粒形貌和尺寸进行了表征, 结果表明获得了分散性良好的球形粒子. 实验中还发现在还原银离子制备纳米银过程中会产生强烈的表面等离子共振峰, 用紫外-可见光谱监测制备过程得到的纳米银紫外吸收带范围为400~450 nm, 最大吸收波长为420 nm, 光谱强度与抗氧化剂的浓度成正比. 将纳米银的这一特性用于定量测定没食子酸丙酯(PG)、 二丁基羟基甲苯(BHT)、 叔丁基对羟基茴香醚(BHA)和叔丁基对苯二酚(TBHQ)等抗氧化剂, 所得检出限分别为0.0752, 0.1242, 0.0693和0.0701 mg/L, 线性范围分别为0.2~1.8, 0.2~3.4, 0.2~3.4和0.2~3.0 mg/L.     

Electochemiluminescence of CdTe/CdS Quantum Dots with Triproprylamine as Coreactant in Aqueous Solution at a Lower Potential and Its Application for Highly Sensitive and Selective Detection of Cu2+

Anodic electrochemiluminescence (ECL) of 3‐mercaptopropionic acid (MPA)‐ capped CdTe/CdS core‐shell quantum dots (QDs) with tripropylamine (TPrA) as the co‐reactant were studied in aqueous (Tris buffer) solution for the first time. The results suggest that the oxidation of TPrA at a glassy carbon electrode (GCE) surface participated in the ECL of QDs, and the onset potential and the intensity of ECL of CdTe/CdS QDs were affected seriously by TPrA, as the co‐reactant, in Tris buffer solution. The onset potential of ECL in this new system was about +0.5 V (vs. Ag/AgCl) and the ECL intensity greatly enhanced when TPrA was present. Various influencing factors, such as the electrolyte, pH, QDs concentration, potential range and scan rates on the ECL were studied. Based on the selective quenching by Cu²⁺ to the light emission from CdTe/CdS QDs/TPrA system, a highly sensitive and selective method for the determination of Cu²⁺ was developed. At the optimal conditions, the relative ECL intensity, I₀/I, was proportional to the concentration of Cu²⁺ from 14 nM to 0.21 μM with the detection limit of 6.1 nM based on the signal‐to‐noise ratio of 3. The possible ECL mechanism of QDs and the quenching mechanism of ECL were proposed.     

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 type-II core/shell CdTe/CdSe quantum dots for near-infrared fluorescent sensing of copper(II)

Type-II core/shell CdTe/CdSe quantum dots (QDs) were synthesized in aqueous medium by employing thiol-capped CdTe QDs as core template and CdCl(2) and Na(2)SeSO(3) as shell precursors, respectively. Compared with the original CdTe cores, the core/shell CdTe/CdSe QDs showed an obvious red-shifted emission with the color-tune capability to the near-infrared (NIR) wavelength, because of the formation of an indirect excitation. The prepared QDs exhibited high stability and moderate fluorescence quantum yields (10-20%), and their core/shell heterostructure was characterized by UV-vis absorption, steady-state and time-resolved fluorescence spectra, X-ray powder diffraction, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. The fluorescence of the core/shell QDs could be markedly quenched by Cu(II), and approximate concentrations of other physiologically important cations, such as Zn(II), Ca(II), Na(I) and K(I) etc., had no effect on the fluorescence. Based on this, a simple and rapid method for Cu(II) determination was proposed using the NIR CdTe/CdSe QDs as fluorescent probes. Under optimal conditions, the response was linearly proportional to the concentration of Cu(II) between 0.05 to 50.0 x 10(-6) mol L(-1), the limit of detection was 2.0 x 10(-8) mol L(-1). The developed method was successfully applied to the detection of trace Cu(II) in real samples.     

Modification of CdTe quantum dots as temperature-insensitive bioprobes

CdTe quantum dots (QDs) were synthesized in aqueous solution with 3-mercaptopropionic acid (MPA) as the stabilizer. The photoluminescence (PL) of CdTe QDs (3.5nm) is found to be temperature-dependent: as the temperature arising from 278K to 323K, the PL intensity declines to 50.2% of its original and PL emission peak shows obvious red-shift ( approximately 7nm). After modification of the QDs surface with denatured ovalbumin, the PL is more temperature-insensitive than before. The PL intensity retains more than 70% of its original and the emission peak shows less red-shift ( approximately 2nm). Moreover, it is found that the PL intensity and wavelength of denatured ovalbumin coated CdTe QDs are reversible during heating (323K)-cooling (278K) cycles. All the studies provide an important theoretical basis for searching temperature-insensitive bioprobes.     

石墨相氮化碳量子点的简易水热制备和荧光性能

本文以线状石墨相氮化碳(Lg-CN)为原料,在无需强酸加入的情况下,利用简单的纯水中的水热反应成功制得了氮化碳量子点(CN QDs),并利用傅里叶变换红外光谱、X射线粉末衍射、透射电镜、X射线光电子能谱等对所得量子点的形貌和结构进行了表征,进而解释了量子点的形成机理;利用紫外-可见吸收光谱和荧光光谱对其光学性质进行了研究。结果发现,所制备的CN QDs具有良好的光学性能,其荧光光谱不仅与激发波长有关,荧光发射位置和强度还受溶液pH的影响,在pH为7时,荧光强度最大。此外,Fe~(3+)对CN QDs的荧光具有良好的猝灭效果,可用于Fe~(3+)的选择性测定。该工作为CN QDs的制备提供了一种新的方法,既可避免繁琐的操作,也可避免强酸等的使用带来的危害。     

Determination of silver ion with cadmium sulfide quantum dots modified by bismuthiol II as fluorescence probe

CdS quantum dots (QDs) modified with bismuthiol II potassium salt is prepared in one step. Based on the characteristic fluorescence enhancement of CdS QDs at 480 nm by silver ions, simultaneously, a red shift of fluorescence emission bands of CdS QDs from 460 to 480 nm is observed. A simple, rapid, sensitive and specific detection method for silver ion is proposed. Under optimum conditions, the fluorescence intensity of CdS QDs was linearly proportional to silver ion concentration from 0.01 to 5.0 micromol L(-1) with a detection limit of 1.6 nmol L(-1). In comparison with single organic fluorophores, functionalized CdS quantum dots are brighter, more stable against photobleaching and do not suffer from blinking. Furthermore, the proposed method shows higher sensitivity and selectivity. A possible fluorescence enhancement mechanism is also studied.     

Functionalized CdS quantum dots-based luminescence probe for detection of heavy and transition metal ions in aqueous solution

Strong luminescence CdS quantum dots (QDs) have been prepared and modified with l-cysteine by a facile seeds-assistant technique in water. They are water-soluble and highly stable in aqueous solution. CdS QDs evaluated as a luminescence probe for heavy and transition metal (HTM) ions in aqueous solution was systematically studied. Five HTM ions such as silver(I) ion, copper(II) ion, mercury(II) ion, cobalt(II) ion, and nickel(II) ion significantly influence the photophysics of the emission from the functionalized CdS QDs. Experiment results showed that the fluorescence emission from CdS QDs was enhanced significantly by silver ion without any spectral shift, while several other bivalent HTM ions, such as Hg(2+), Cu(2+), Co(2+), and Ni(2+), exhibited effective optical quenching effect on QDs. Moreover, an obvious red-shift of emission band was observed in the quenching of CdS QDs for Hg(2+) and Cu(2+) ions. Under the optimal conditions, the response was linearly proportional to the concentration of Ag(+) ion ranging from 1.25 x 10(-7) to 5.0 x 10(-6)molL(-1) with a detection limit of 2.0 x 10(-8)molL(-1). The concentration dependence of the quenching effect on functionalized QDs for the other four HTM ions could be well described by typical Stern-Volmer equation, with the linear response of CdS QDs emission proportional to the concentration ranging from 1.50 x 10(-8) to 7.50 x 10(-7)molL(-1) for Hg(2+) ion, 3.0 x 10(-7) to 1.0 x 10(-5)molL(-1) for Ni(2+) ion, 4.59 x 10(-8) to 2.295 x 10(-6)molL(-1) for Cu(2+) ion, and 1.20 x 10(-7) to 6.0 x 10(-6)molL(-1) Co(2+) ion, respectively. Based on the distinct optical properties of CdS QDs system with the five HTM ions, and the relatively wide linear range and rapid response to HTM ions, CdS QDs can be developed as a potential identified luminescence probe for familiar HTM ions detection in aqueous solution.     

Highly sensitive determination of iodide by ion chromatography with amperometric detection at a silver-based carbon paste electrode

A silver-based solid carbon paste electrode was developed for use as a detector in ion chromatography (IC) for the sensitive determination of iodide in real samples. Micro- and nano-particles of silver were investigated for the fabrication of different electrodes. The iodide assay was based on IC with amperometric detection (IC-AD) at a silver composite electrode polarized at +0.080 V versus Ag/AgCl. Free iodide and organoiodide compounds were studied. The detection process was characterized by studying the redox behavior of iodide ions at both silver and silver composite electrodes by cyclic voltammetry (CV). The presence of iodide ions in solution was found to considerably facilitate metallic silver oxidation, with response currents directly related to iodide concentration. The calibration curve at the selected silver carbon paste electrode was linear in the concentration range comprised between 0.635 microg/L and 63.5 microg/L iodide. The relative standard deviation (R.S.D.) for successive injections was below 3% for all iodide standard solutions investigated. The limit of detection (LOD) was 0.47 microg/L (3.7 nmol/L) for an injection volume of 20 microL, i.e. 74 fmol injected. The IC-AD method was successfully applied to the determination of iodide in complex real samples such as table salts, sea products and iodide bound drug compounds. The analytical accuracy was verified by the assay of iodide in milk powder from an iodide certified reference material (CRM) Community Bureau of Reference (BCR) 150.     

Ultrasmall near-infrared Ag2Se quantum dots with tunable fluorescence for in vivo imaging

A strategy is presented that involes coupling Na(2)SeO(3) reduction with the binding of silver ions and alanine in a quasi-biosystem to obtain ultrasmall, near-infrared Ag(2)Se quantum dots (QDs) with tunable fluorescence at 90 °C in aqueous solution. This strategy avoids high temperatures, high pressures, and organic solvents so that water-dispersible sub-3 nm Ag(2)Se QDs can be directly obtained. The photoluminescence of the Ag(2)Se QDs was size-dependent over a wavelength range from 700 to 820 nm, corresponding to sizes from 1.5 ± 0.4 to 2.4 ± 0.5 nm, with good monodispersity. The Ag(2)Se QDs are less cytotoxic than other nanomaterials used for similar applications. Furthermore, the NIR fluorescence of the Ag(2)Se QDs could penetrate through the abdominal cavity of a living nude mouse and could be detected on its back side, demonstrating the potential applications of these less toxic NIR Ag(2)Se QDs in bioimaging.     

纳米SiO_2分离富集-火焰原子吸收法测定水中痕量银

研究了纳米SiO_2分离富集-火焰原子吸收法测定水中痕量银的新方法.考察了溶液pH、吸附时间、洗脱条件和干扰离子等因素对Ag~+分离富集的影响,确定了纳米SiO_2对Ag~+吸附的最佳条件.结果表明:在pH 4.1时,纳米SiO_2能定量吸附银,吸附在纳米SiO_2上的Ag~+可用0.5 mol/L HCl+0.5 mol/L硫脲定量洗脱.该法对银的检出限为0.77 ng/mL(3σ,n=11);线性范围为0.005～1.5μg/mL,对0.5μg/mL的Ag~+标液进行7次测定,RSD为3.6%,回收率在94.0%～101.5%之间;方法可用于环境水样中痕量银的测定.