Acid Capped Cadmium Sulfide Quantum Research Articles

Thioglycolic acid capped cadmium sulphide quantum dots as a turn-on fluorescence sensor for the determination of 5-hydroxyindoleacetic acid

A simple and highly selective turn-on fluorescence sensor has been developed for 5-hydroxyindoleacetic acid (5-HIAA) using thioglycolic acid capped cadmium sulphide quantum dots (TGA-CdS QDs). 5-HIAA enhances the fluorescence intensity of CdS QDs via aggregation-induced emission enhancement mechanism [AIEE]. Different sensor conditions have been optimized and under such conditions, the sensor achieved the quantification of 5-HIAA in the range of 2.5 × 10−6 M to 8.0 × 10-5 M with a limit of detection (LOD) of 8.4 × 10-7 M. The reliability of the sensor towards 5-HIAA detection has been proved by its successful application in synthetic urine and blood serum.

Highly sensitive cadmium sulphide quantum dots as a fluorescent probe for estimation of doripenem in real human plasma: application to pharmacokinetic study.

Thioglycolic acid-capped cadmium sulphide quantum dots (TGA-CdS QDs) have been synthesized and utilized as a fluorescent probe for the estimation of doripenem (DOR). Monitoring of DOR in different biological fluids is required to estimate the efficient dose to avoid bacterial infections and resistance. The investigated method is based on the measurement of fluorescence quenching of TGA-CdS QDs after the addition of DOR. The synthesized TGA-CdS QDs were characterized using transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD) and ZETA sizer. The TGA-CdS QDs showed unique photophysical properties with high quantum yield (0.32) using a comparison method with rhodamine B. Different experimental parameters affecting the synthesis process of the TGA-CdS QDs and their behavior with the studied drug DOR were examined and optimized. The values of the fluorescence quenching were linearly correlated to DOR concentration over the range of 10–500 ng mL−1 with a good correlation coefficient of 0.9991. The proposed method showed higher sensitivity over several reported methods, with LOD reaching 2.0 ng mL−1. The method was effectively applied for the estimation of DOR in human plasma and urine with good recovery results ranged from 95.16% to 99.51%. Furthermore, the stability of DOR in the human plasma was studied and a pharmacokinetic study of DOR in real human plasma was conducted.

A fluorescent sensor based on thioglycolic acid capped cadmium sulfide quantum dots for the determination of dopamine

A fluorescent sensor based on thioglycolic acid-capped cadmium sulfide quantum dots (TGA-CdS QDs) has been designed for the sensitive and selective detection of dopamine (DA). In the presence of dopamine (DA), the addition of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) activates the reaction between the carboxylic group of the TGA and the amino group of dopamine to form an amide bond, quenching the fluorescence of the QDs. The fluorescence intensity of TGA-CdS QDs can be used to sense the presence of dopamine with a limit of detection of 0.68μM and a working linear range of 1.0–17.5μM. This sensor system shows great potential application for dopamine detection in dopamine drug samples and for future easy-to-make analytical devices.

Synthesis and Characterization of Mercaptoacetic Acid Capped Cadmium Sulphide Quantum Dots.

This paper reports the facile synthesis and detailed characterization of mercaptoacetic acid capped cadmium sulphide (CdS) quantum dots using various cadmium precursors. The mercaptoacetic acid capped CdS quantum dots were prepared by facile and simple wet chemical method and characterized by several techniques such as energy dispersive spectroscopy (EDS), X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, UV-vis. spectroscopy, photoluminescence spectroscopy, high-resolution transmission microscopy (HRTEM) and thremogravimetric analysis. The EDS studies revealed that the prepared quantum dots possess higher atomic percentage of sulfur compared to cadmium due to the coordination of thiolate to the quantum dots surfaces. The X-ray and absorption analyses exhibited that the size of quantum dots prepared by cadmium acetate is larger than the quantum dots prepared by cadmium chloride and cadmium nitrate. The increase in size can be attributed to the low stability constant of cadmium acetate in comparison with cadmium chloride and cadmium nitrate. The FTIR and thermogravimetric analysis showed that the nature of capping molecule on the surface of quantum dots are different depending on the cadmium precursors which affect the emission from CdS quantum dots. Photoemission spectroscopy revealed that the emission of quantum dots prepared by cadmium acetate has high intensity band edge emission along with low intensity trapping state emission. However the CdS quantum dots prepared by cadmium chloride and cadmium nitrate produced only trapping state emissions.

Speciation of arsenic (III) and arsenic (V) based on quenching of CdS quantum dots fluorescence using hybrid sequential injection–stopped flow injection gas–diffusion system

A hybrid sequential injection–stopped flow injection system was developed for the speciation of arsenic based on the quenching of mercaptoacetic acid capped cadmium sulfide quantum dots (CdS–MAA QDs) fluorescence intensity. The analytical procedure involves the generation of arsine from As(III) by sodium borohydride in acetate buffer medium pH 6.0. The generated arsine (donor stream) diffuses across the PTFE membrane of the gas–diffusion unit into an acceptor stream and then interacts with CdS–MAA QDs. Total arsenic was determined after pre-reduction of As(V) to As(III) with 1% (m/v) mercaptoacetic acid. Concentration of As(V) in the sample solutions can be deduced from the difference of total arsenic and As(III). Optimization of the experimental conditions and instrumental parameters were investigated. Under optimal conditions, limits of detection were 20μgL−1 for As(III) and 40μgL−1 for As(V). Recoveries in the range 84–103% were obtained from sediment sample.

Determination of arsenic based on quenching of CdS quantum dots fluorescence using the gas-diffusion flow injection method

A sequential injection analysis system for determination of arsenic based on hydride generation and fluorescence quenching of mercaptoacetic acid capped cadmium sulfide quantum dots (CdS–MAA QDs) is described. The generated arsine diffused across the PTFE membrane in a gas-diffusion unit and subsequently interacted with CdS–MAA QDs. The parameters affecting the arsine generation and the fluorescence quenching of QDs were studied. Under the optimum conditions, it was observed that a increase in the concentration of As(III) corresponded well to a decrease in fluorescence intensity according to the Stern–Volmer relationship. The extent of quenching was dependent on the concentration of arsenic in the range of 0.08–3.20 mmol L −1, with the detection limit of 0.07 mg L −1. The precision (%RSD) from eight replicates of the determination of As(III) 1.0 mg L −1 was found to be 1.4%. The proposed method was applied to the determination of arsenic in ground water samples with satisfactory recoveries.