紫外-可见吸收光谱和荧光光谱研究壳核型 CdTe/CdS量子点与盐酸巴马汀的相互作用及其分析应用

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-可见光谱和荧光光谱研究了TGA-CdTe/CdS QDs与盐酸巴马汀(PC)的相互作用机理. 结果表明, 在pH=7.4的Tris-HCl缓冲液中, QDs与PC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=0.997), 线性范围为25~1×10⁴ ng/mL, 检出限(3σ)为7.7 ng/mL. 建立了一种快速简便、 可定量测定PC的新方法.     

CdTe/CdS量子点与丝裂霉素的相互作用及其应用

在水相中合成了硫普罗宁(Tiopronin,TP)修饰的CdTe/CdS量子点(TP-CdTe/CdS QDs).利用紫外-可见吸收光谱、荧光光谱研究了TP-CdTe/CdS QDs与丝裂霉素(mitomycin C,MMC)的相互作用机理.在pH=7.6的tris-HCl缓冲溶液介质中,TP-CdTe/CdS QDs与MMC相互作用,使TP-CdTe/CdS QDs的荧光发生猝灭,并且QDs的荧光强度与MMC的浓度有良好的线性关系(r=0.9991),线性范围4.7×10-9～1.2×10-8g/mL,检出限(3σ)为1.4×10-g/mL.此方法快速简便,用于尿样中丝裂霉素的测定,实验结果令人满意.     

Silanized quantum dots as labels in lateral flow test strips for C-reactive protein

The paper describes the first use of silanized semiconductor core-shell quantum dots as fluorescent labels for macromolecule, C-reactive protein determination in blood plasma. The controlled synthesis of CdSe cores, with successive shells of CdS, CdZnS, ZnS and coating with transparent, stable, and inert silica shell, provides quantum dots with a narrow emission band, high quantum yield, and prolonged signal stability. Finally, the quantum dots were conjugated with specific antibodies via carboxylic groups on the silica surface. The method was further used for the immunochromatographic assay of C-reactive protein, a diagnostically important inflammatory biomarker. Assays with both the fluorescent QDs and a widely used colloidal gold label were developed in parallel and compared. The silanized quantum dots provide a more sensitive assay with a detection limit of 1?ng/mL for C-reactive protein in standard solutions, whereas the common assay has a detection limit of 10?ng/mL. The possibility of quantitative evaluation of analyte content by a portable device was demonstrated; the accuracy of the measurements was in the range of 5%–10%. The tests were used to determine C-reactive proteins in human plasma samples. The selected optimized protocol for these samples is based on a 4-fold dilution. The final working range of the assay, 4–1,200?ng/mL, covers practically all important interval of C-reactive protein values for the characterization of acute, chronic, and local inflammatory processes. Due to their high physical stability and inertness as well as intense, stable, and reproducible fluorescence, silanized quantum dots may be applied for high-sensitive assays for different analytes.     

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.     

A Novel Method for Uric Acid Determination Using CdS Quantum Dots as Fluorescence Probes

A novel method has been developed for uric acid analysis based on the quenching of fluorescence emission from CdS quantum dots by uric acid. Also, the effect of the presence of different surfactant agents, in order to improve the fluorescent signals of the CdS QDs, has been investigated, and the cetyltrimethyl ammonium bromide (CTAB) was selected. Under optimum conditions, the calibration graph was linear over the range of 0.1 ng/mL to 12.0 ng/mL (r = 0.9950). The limit of detection (S/N = 3) was 0.1 ng/mL. The RSD for ten determinations of 5.0 ng/mL uric acid was 3.5%. The method was applied to determine uric acid in human serum and urine sample with satisfactory results.     

量子点传感器测定水中微量银离子

选择铋试剂Ⅱ作为硫化镉(cds)量子点的修饰剂,合成了表面修饰的量子点,利用其有效官能团与银离子作用,导致修饰的量子点的荧光增强作用,建立了测定银离子的方法,开发了新型的银离子的传感器。结果表明,对水中银离子测定的线性范围为0.01~5.0μmol.L-1,相关系数为0.999 3,检测限达到1.6 nmol.L-1,对实际水样的分析获得了较满意的结果。     

Portable smartphone-based microfluidic electrochemical immunosensor for ultrasensitive detection of alpha-fetoprotein in human serum

Rapid and accurate tracing of biomarkers is essential for early detecting and diagnosing of cancer. Therefore, a valid and convenient strategy needs to be developed for efficient monitoring of cancer biomarkers. Herein, we constructed a portable microfluidic electrochemical immunosensor based on three-dimensional reduced graphene oxide (3D rGO) doped with gold nanoparticles (Au NPs) for ultrasensitive determination of alpha-fetoprotein (AFP). The designed microfluidic chip, with the advantages of small injection volume, detachable structure and high integration, was fabricated by 3D printing, which only needed 9 μL of reagent to realize the high sensitivity detection. In addition, the 3D Au NPs-rGO composites with high specific surface area and electrons transfer capacity can effectively increase electroactive sites and enhance electrochemical signals. Benefiting from these features, the 3D Au NPs-rGO microfluidic electrochemical immunochip showed a wide detection range between 0.1 pg/mL–200 ng/mL and a best detection limit of 0.045 pg/mL with the high sensitivity of 175.008 μA (ng/mL)⁻¹ cm⁻². Meanwhile, the proposed immunosensor exhibited reliable AFP detection in human serum samples, which demonstrated that this portable smartphone-based microfluidic electrochemical immunosensor hold great promises in clinical detection and huge potential in personalized healthcare.     

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。     

Simultaneous electrochemical DNA hybridization assay for PAT and FMV 35S gene sequence using quantum dots as labels

An electrochemical method for the simultaneous detection of two different DNA sequences from PAT and FMV 35S gene sequence using CdS and PbS quantum dots （QDs） as labels was described. The QDs were readily functionalized with oligonucleotides as electrochemical DNA probes and selectively hybridized to the complementary sequences immobilized on the microplate. The QDs anchored on the hybrids were dissolved in the solution by the oxidation of HNO3 and further detected by a sensitive differential pulse anodic stripping voltammetric method （DPASV）. The DPASV signals of the oxidation of Cd^2＋ and Pb^2＋ ions present in the solution were different and reflected the identity of corresponding ssDNA targets sequences.     

Thioglycolic Acid Capped CdS Quantum Dots as Fluorescence Probe for Ultrasensitive Determination of Tetracycline and Oxytetracycline

Water soluble CdS quantum dots (QDs) have been synthesized using thioglycolic acid (TGA) as surface modifying agent through a one step process by using safe and low cost materials. These TGA capped CdS QDs are highly stable in aqueous solution and applied for ultrasensitive tetracycline (TC) and oxytetracycline (OTC) sensing. The approach was based on the fluorescence of the QDs selectively quenched in the presence of TC and OTC, respectively. Under optimal conditions, the relative fluorescence intensities of CdS QDs were decreased linearly with increasing TC and OTC in the range of 0.05 to 10.0 μM and 0.1 to 10.0 μM, respectively. The limit of detection (S/N = 3) was 5.0 nM for TC and 10.0 nM for OTC, respectively. The RSD for eleven determinations of 5.0 μM TC was 1.26% and 5.0 μM OTC was 0.8%, respectively. There was no significant wavelength shift on the fluorescence‐quenched signals in the presence of the drugs. The effect of common foreign substances on the fluorescence of the QDs was examined to evaluate the selectivity and the results showed a high selectivity of the TGA capped CdS QDs towards TC and OTC. The method presented here is simple, rapid, inexpensive, sensitive and suitable for practical application.     

A novel method for ranitidine hydrochloride determination in aqueous solution based on fluorescence quenching of functionalised CdS QDs through photoinduced charge transfer process: spectroscopic approach

A novel method for the quantitative determination of ranitidine hydrochloride (RNH) based on the fluorescence quenching of functionalised CdS quantum dots (QDs) by RNH in aqueous solution was proposed. The method is simple, rapid, specific and highly sensitive with good precision. The thioglycolic acid (TGA)-capped CdS QDs were synthesized from cadmium nitrate and sodium sulfide in alkaline solution. Under the optimal conditions, the Stern-Volmer calibration plot of F(0)/F against concentration of RNH was linear in the range of 0.50-15.0 μg mL(-1) with a correlation coefficient of 0.996. The limit of detection (LOD) was 0.38 μg mL(-1). The method was satisfactorily applied to the direct determination of RNH in pharmaceutical formulations with no significant interference from excipients. The results were found to be in good agreement with those obtained by the reference method and the claimed value. The accuracy and reliability of the method were further ascertained by recovery studies via the standard-addition method, with percentage recoveries in the range of 98.47 to 102.30%. The possible fluorescence quenching mechanism for the reaction was also discussed.     

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.     

Fast self-assembly kinetics of quantum dots and a dendrimeric peptide ligand

Engineered peptide ligands with exceptionally high affinity for metal can self-assemble with nanoparticles in biological fluids. A high-affinity dendrimeric peptide ligand for CdSe-ZnS quantum dots (QDs) exhibited very fast association kinetics with QDs and reached equilibrium within 2 s. Here, we have combined a droplet-based microfluidic device with fluorescence detection based on F?rster resonance energy transfer (FRET) to provide subsecond resolution in dissecting this fast self-assembly kinetics in solution. This work represents the first application of microfluidic devices to ligand-particle assembly for the measurement of fast assembly kinetics in solution.     

Photoelectrochemical Immunosensor Array Based on Thioglycolic Acid Capped CdS Quantum Dots for Multiplexed Detection of Veterinary Drug Residues

A photoelectrochemical immunosensor based on multi‐electrode array was developed for simultaneous and sensitive determination of veterinary drug residues. In this system, poly(dimethyldiallylammonium chloride) (PDDA), Au nanoparticles (Au NPs) and thioglycolic acid (TGA)‐capped CdS quantum dots (QDs) were layer‐by‐layer assembled onto the home‐made Au electrode array. The assembling process of the (CdS/PDDA/Au NPs/PDDA)_n multilayer was characterized by electrochemical impedance spectroscopy. And then the antibodies for clenbuterol (CB), ractopamine (RAC) and chloramphenicol (CAP) were covalently immobilized onto the Au electrode array by 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide (EDC) coupling reaction, respectively. The concentrations of CB, RAC and CAP were measured based on the photoelectrochemical effects of CdS QDs. Under the optimal conditions, the limits of detection (LOD) for CB, RAC and CAP were 25, 50 and 2.2 pg/mL (3Δ), respectively, with acceptable recovery over the range of 95.40%–105.5% in pig liver samples. All results indicate that the immunosensor array system has potential application for practical, effective and high throughput analysis of veterinary drugs residues.     

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。     

Enhancement of sensitivity and specificity of the fluoroimmunoassay of Hepatitis B virus surface antigen through “flexible” coupling between quantum dots and antibody

Quantum dots (QDs) are widely used in the immune detection. Yet, the sensitivity and specificity of the immune detection are not satisfactory because the binding sites of QDs onto antibody (Ab) are often arbitrary and the influence of the large surface electronic potential energy of QDs on the directly conjugated Ab is nonnegligible. In this work, we provide a “flexible” coupling method, in which protein G (PG) is selected as the flexible bridge between the QDs and the Hepatitis B virus surface antibody (HBsAb), to improve the sensitivity and specificity of the fluoroimmunoassay compared to the directly covalent conjugation. Successful coupling of the HBsAb to our highly luminescent CdTe/CdS core/shell QDs is proven with Gel electrophoresis and atomic force microscopy (AFM). The assay results, based on the microelisa well plate as matrix to immobilize the sandwich structure, show that both sensitivity and specificity can be improved greatly through the flexible coupled QDs-PG-Ab conjugates.     

Electrochemical and Photoelectrochemical Sensing of NADH and Ethanol Based on Immobilization of Electrogenerated Chlorpromazine Sulfoxide onto Graphene‐CdS Quantum Dot/Ionic Liquid Nanocomposite

Here, a simple one‐step solvothermal procedure was employed to synthesize a nanocomposite containing graphene‐nanosheets and CdS quantum dots (GNs‐CdS QDs). The electrochemical oxidation of chlorpromazine (CPZ) to chlorpromazine‐sulfoxide (CPZ‐SO) onto a GNs‐CdS QDs/ionic liquid (IL) nanocomposite modified glassy carbon (GC) electrode give rise to redox‐active products which showed excellent electrocatalytic and photoelectrocatalytic activity toward NADH oxidation at reduced overpotential. A linear response up to 200 µM was obtained for photoamperometric determination of NADH with detection limit 1 µM. Immobilizing alcohol dehydrogenase(ADH) onto the modified electrode via a simple cross linking procedure, the photoelectrochemical capability of the proposed system toward ethanol biosensing was clearly shown.     

The electrochemical behavior of core-shell CdSe/CdS magic-sized quantum dots linked to cyclodextrin for studies of the encapsulation of bioactive compounds

Semiconductor nanocrystal quantum dots have been the subject of extensive investigations in different areas of science and technology in the past years. In particular, there are few studies of magic-sized quantum dots (MSQDs), even though they exhibit features such as extremely small size, fluorescence quantum efficiency, molar absorptivity greater than traditional QDs, and highly stable luminescence in HeLa cell cultures, thereby enabling monitoring of biological or chemical processes. The present study investigated the electrochemical behavior of free CdSe/CdS MSQDs using glassy carbon electrode and CdSe/CdS MSQDs immobilized on a gold electrode modified with a self-assembled cyclodextrin monolayer. The MSQDs showed two peaks in aprotic medium. The functionalized film modifier was prepared and characterized by means of cyclic voltammetry and electrochemical impedance spectroscopy using ferricyanide ions as a redox probe. The prepared modified electrode exhibited a stable behavior. The proposed method was successfully applied to encapsulation studies of mangiferin, a natural antioxidant compound, and cyclodextrin associated with the quantum dot, and the response was compared with that of the modified electrode without QD. The fluorescence study revealed that CdSe/CdS quantum dots emit blue light when excited by an optical source of wavelength of 350 nm and a significant increase in fluorescence and absorbance intensity is observed from the core-shell CdSe/CdS MSQDs when quantities of mangiferin are added to the solution containing thiolated cyclodextrin. CdSe/CdS MSQDs are optically and electrochemically sensitive and can be used for the detection and interaction of compounds encapsulated in cyclodextrin.     

Quantum dot based rapid tests for zearalenone detection

Three different kinds of immunosorbent assays with luminescence detection were developed for the determination of zearalenone (ZEN), a secondary toxic metabolite of Fusarium fungi. CdSe/ZnS core/shell quantum dots (QDs) were used as a label in quantitative micro-well plate immunoassays (fluorescent-labeled immunosorbent assay, FLISA) and in qualitative column test methods. As carriers for QD-based column tests, sepharose gel (for covalent binding of antibody) and polyethylene frits (for physical absorption of antibody) were used and compared. The application of QDs as a label resulted in a fourfold decrease in the IC(50) value with FLISA (0.1 ng mL(-1)) with a detection limit of 0.03 ng mL(-1) when compared with the traditional immunosorbent assay which makes use of horseradish peroxidase as the enzyme label. The cutoff levels for both qualitative column test methods were selected based on the maximum level for ZEN in unprocessed cereals established by the European Commission (100 μg kg(-1)) as 5 ng mL(-1) taking into account extraction and dilution. The different developed immumoassays were tested for ZEN determination in raw wheat samples. As a confirmatory method, liquid chromatography coupled to tandem mass spectrometry was used. The obtained results allow using FLISA and both qualitative column test methods for the analysis of analytes with very low established maximum limits, even in very complicated food matrices, owing to the high dilution of the sample extract.     

Thiourea functionalized CdSe/CdS quantum dots as a fluorescent sensor for mercury ion detection

CdSe/CdS quantum dots(QDs) functionalized by thiourea(TU) were synthesized and used as a fluorescent sensor for mercury ion detection.The TU-functionalized QDs were prepared by bonding TU via electrostatic interaction to the core/shell CdSe/CdS QDs after capping with thioglycolic acid(TGA).It was observed that the fluorescence of the functionalized QDs was quenched upon the addition of Hg~(2+).The quantitative detection of Hg~(2+) with this fluorescent sensor could be conducted based on the linear relationship between the extent of quenching and the concentration of Hg~(2+) added in the range of1-300 μg L~(-1).A detection limit of 0.56 μg L~(-1) was achieved.The sensor showed superior selectivity for Hg~(2+) and was successfully applied to the determination of mercury in environmental samples with satisfactory results.