Capped Cadmium Sulfide Quantum Dots Research Articles

Integration of cadmium sulfide quantum dots with calcium alginate microbeads for dual-functional mercury (II) ion sensing and removal

Mercury contamination poses human health as well as ecosystem at significant risks. This study introduces a novel approach for the selective detection with removal of Hg2+ ions from aqueous media by developing a dual functional adsorbent that combines calcium alginate microbeads (FMCAB) with capped cadmium sulfide quantum dots (CdS QDs). CdS QDs immobilized on calcium alginate microbeads in magnetite facilitated efficient separation from the adsorption system under an external magnetic field. The fluorescence properties of CdS QDs remain largely unaffected before and after adsorption of Hg2+ ions on FMCAB, enabling selective monitoring of these ions. The adsorbent demonstrated a high adsorption capacity of around 160 μg/g and exhibited a quick and effective process. FMCAB evidenced selectivity over the other metal ions with limits of detection 12.9 μM. The results from this research pave the way for novel applications of FMCAB for heavy metal ions sensing probes and its removal.

Study on photoinduced charge transfer between Citrus Limon capped CdS quantum dots with natural dyes

The development of highly efficient Quantum dots-based Dye Sensitized Solar Cells (DSSCs) capable of absorbing a broader spectrum of solar light has garnered significant interest. In these systems, the proper selection of sensitizers plays a crucial role. Consequently, the exploration of highly efficient, cost effective and non-toxic sensitizer options has led to a growing focus on natural dyes. In this study, we investigated the credibility of natural dyes Beta Vulgaris, Ixora coccinea and Butea monosperma were explored as potential sensitizer in a Cadmium Sulphide (CdS) quantum dots-based system. Moreover, the effect of Citrus Limon Extract (CLE) as a capping agent through X-ray Photoelectron Spectroscopy (XPS) and Electron Paramagnetic Resonance (EPR) analyses. A Density Functional Theory (DFT) model was also presented to explore the charge accumulation on CdS surface due capping action. Quenching mechanism of CLE-CdS with different dyes under various irradiation conditions was studied and their mechanism were defined. Lastly, our finding demonstrates the effect of H-aggerated dye on CLE-CdS, indicating its potential in increasing solar light absorption.

Synthesis, characterization, and pharmacological evaluation of dextrin capped cadmium sulfide quantum dots conjugated with temozolomide for drug delivery and imaging application

Quantum dots (QDs) of cadmium sulfide semiconductor capped with dextrin and bioconjugated with temozolomide (CdS/Dx+TMZ) were used to target and provide imaging of glioma cells. CdS/Dx+TMZ QDs were in the range of 6.5 nm in size and exhibited an intense fluorescence emission in the green spectrum, which allowed us to monitor fluorescence imaging in a rat glioma cell line. The results showed that glioma cells efficiently took up the CdS/Dx+TMZ QDs, which had a large accumulation time in cells and were distributed in both the cytoplasm and nucleus, where the pharmacological drug effects were enhanced. CdS/Dx+TMZ QDs were more cytotoxic than TMZ and CdS/Dx alone. Glioma cells treated with 100 µM CdS/Dx+TMZ QDs showed both an increase in size (cytoplasm and nucleus) and in the number of cell deaths by apoptosis. The morphological analysis showed the presence of binucleated cells and membrane blebbing, as well as apoptotic bodies. This study confirmed the effective cellular uptake of CdS/Dx QDs bioconjugated with TMZ and their pharmacological effects in a glioma cell line. Our conclusion is that CdS/Dx+ TMZ QDs could be simultaneously used as drug delivery and cell monitoring system for the treatment of GBM and other brain tumors.

Octadecyl amine capped cadmium sulfide quantum dots: morphological studies, electrochemical properties, and its use as photocatalyst for the degradation of methylene blue dyes

We present the structural, optical, electrochemical, and photocatalytic studies of octadecyl amine capped CdS quantum dots (ODA-CdS). TEM micrographs showed CdS quantum dots with particle sizes of 1.9-5.2 nm. The optical bandgaps of the quantum dots are 2.03, 2.06 and 2.01 eV for ODA-CdS1, ODA-CdS2 and ODA-CdS3 respectively, which was less than the bandgap of the bulk CdS (2.42 eV). Photo-electrochemical band gaps of 2.60 V for ODA-CdS1, 2.24 V for ODA-CdS2 and 2.46 V for ODA-CdS3 were obtained from cyclic voltammetry. The photocatalytic degradation efficiency of methylene blue was 62% for ODA-CdS1, 80% for ODA-CdS2, 69% for ODA-CdS3.

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.

INTERACTION OF DEXTRIN CAPPED CADMIUM SULFIDE QUANTUM DOTS WITH BLOOD COMPONENTS: COAGULATION AND HEMOLYSIS STUDIES

Evaluate at interaction of dextrin capped cadmium sulfide quantum dots with blood components. The intravenous administration of quantum dots (QDs) has been widely reported as a promising alternative for delivery of drugs to specific cells. Therefore, previous studies have pointed out the importance of studying of, at least, factors like coagulation effect; and their hemolytic character when nanoparticles are intended to be administered for intravenous injection. The hemolytic activity and platelets aggregation of the nanoparticles was tested on isolated rat erythrocytes and platelets. Atomic force microscopy (AFM) facilitates the real‐time studies of blood cells and the morphological, structural, optical properties of the CdS‐dex QDs. In this work a methodology for erythrocytes and platelets study by platelet aggregation, hemolysis and AFM was developed. The results show that CdS‐Dex/QDs caused platelet aggregation at concentration‐dependent manner, this effect being greater at 1000 ug/mL, where the increase was up to 57% (p<0.05). The AFM measurements establish a more direct correlation between the surface topography of platelets with the surface nanostructure and reveal that modified the morphology of the platelets from the concentration of 0.01 ug/mL. The CdS‐Dex/QDs do not cause lysis of erythrocytes significantly, although they modified their morphology, suggesting that they can cause eriptosis. The CdS‐Dex/QDs, caused effects in oval and biconcave morphology of the erythrocytes, making it round and of edges not defined, semi‐flat and with cracks in its surface and lacking central depression in a concentration‐dependent manner and observed in its surface some artifacts that may correspond to agglomerated NPs. We found that CdS‐dex/QDs caused aggregation of rats platelets in vitro; however; there were both quantitative and qualitative differences depends to various concentrations.

Quantum dots based “On-Off” fluorescence probe for the selective detection of Cu2+ ion: Application to real sample analysis

Abstract Turn ‘On-Off’ quantum dot-based fluorescent probe has been developed for the selective detection of Cu2+. This strategy achieved by consecutively fluorescence enhancement and quenching of mercapto propionic acid (MPA) capped cadmium sulphide quantum dots (MPA-CdS QDs) by the addition of D-penicillamine (D-PA) and Cu2+ respectively. After successive addition of Cu2+in CdS QDs-(D-PA) system, the fluorescence intensity of quantum dots decrease due to the removal of D-PA molecules from the surface of QDs as well as selective ion exchange process takes place between Cu2+ and Cd2+ at the surface of QDs. At optimal conditions, probe offers a good response in the linear range between 4 ng/mL and 40 ng/mL with LOD 2.71 ng/mL. This reported strategy is a very simple and selective towards Cu2+. Hence, a new method for the potential detection of Cu2+ in real pharmaceutical samples can be developed by using QDs-based fluorescence probe.

Capped cadmium sulfide quantum dots with a new ionic liquid as a fluorescent probe for sensitive detection of florfenicol in meat samples.

The new ionic liquid capped CdS quantum dots (IL-CdS QDs) as a fluorescent probe was successfully synthesized by a hydrothermal method in a one step process and used for the facile and sensitive determination of florfenicol (FLF) in aqueous media. The new ionic liquid 3-(2-[(5-amino-1,3,4-thiadiazol-2-yl)thio]ethyl)-1-methyl-1H-imidazol-3-ium chloride (IL) was synthesized by introducing 5-amino-1,3,4-thiadiazole-2-thiol as a ligand onto the alkyl chain of the 1-chloroethyl-3-methylimidazolium chloride ILs. This task specific ionic liquid reagent was used for the capping of CdS QDs which played the role of recognition element of FLF. The IL-CdS QDs were characterized by Ultra Violet-Visible absorption -spectroscopy (UV-Vis absorption spectroscopy), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Quenching of fluorescence intensity of the IL-CdS QDs was in proportion to the addition of FLF concentration. Under the optimum conditions, the fluorescence intensity ratio of IL-CdS QDs in the presence and absence of FLF versus FLF concentrations gave a linear response according to the Stern-Volmer equation from 0.1 to 20 μg mL-1 (0.3 to 56 μmol L-1) with a limit of detection 0.035 μg mL-1 (0.098 μmol L-1). The developed method was applied to the determination of FLF in fish and chicken meats with satisfactory results. This method revealed some advantages such as high sensitivity, precision and wide linear range to FLF. The proposed method can be utilized for rapid screening the quality of meat products.

INTERACTION OF DEXTRIN CAPPED CADMIUM SULFIDE QUANTUM DOTS WITH BLOOD COMPONENTS: COAGULATION AND HEMOLYSIS STUDIES

Evaluate at interaction of dextrin capped cadmium sulfide quantum dots with blood components. The intravenous administration of quantum dots (QDs) has been widely reported as a promising alternative for delivery of drugs to specific cells. Therefore, previous studies have pointed out the importance of studying of, at least, factors like coagulation effect; and their hemolytic character when nanoparticles are intended to be administered for intravenous injection. The hemolytic activity and platelets aggregation of the nanoparticles was tested on isolated rat erythrocytes and platelets. Atomic force microscopy (AFM) facilitates the real‐time studies of blood cells and the morphological, structural, optical properties of the CdS‐dex QDs. In this work a methodology for erythrocytes and platelets study by platelet aggregation, hemolysis and AFM was developed. The results show that CdS‐Dex/QDs caused platelet aggregation at concentration‐dependent manner, this effect being greater at 1000 ug/mL, where the increase was up to 57% (p<0.05). The AFM measurements establish a more direct correlation between the surface topography of platelets with the surface nanostructure and reveal that modified the morphology of the platelets from the concentration of 0.01 ug/mL. The CdS‐Dex/QDs do not cause lysis of erythrocytes significantly, although they modified their morphology, suggesting that they can cause eriptosis. The CdS‐Dex/QDs, caused effects in oval and biconcave morphology of the erythrocytes, making it round and of edges not defined, semi‐flat and with cracks in its surface and lacking central depression in a concentration‐dependent manner and observed in its surface some artifacts that may correspond to agglomerated NPs. We found that CdS‐dex/QDs caused aggregation of rats platelets in vitro; however; there were both quantitative and qualitative differences depends to various concentrations.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Oleic acid capped cadmium sulphide (CdS) quantum dots: Discussions on synthesis, structural, optical and morphological behavior

Cadmium sulphide (CdS) quantum dots were synthesized via simple chemical precipitation technique under methanolic medium, while oleic acid is used as capping agent to control the particle size and to prevent agglomeration. The hexagonal wurtzite structure of the title compound was revealed through powder X-ray diffraction analysis. The CdS quantum dots exhibited strong absorption and luminescent properties in the visible region. Dynamic light scattering analysis gives the hydrodynamic diameter of the prepared CdS product. Field emission scanning electron microscope and transmission electron microscope analyses confirm the spherical morphology and give the particle size of the synthesized CdS sample. These findings would be helpful in determining the suitability of the CdS quantum dots to photovoltaic device applications.

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.

Fluorescence sensor based on d-penicillamine capped cadmium sulfide quantum dots for the detection of cysteamine

A fluorescence sensor for selective detection of cysteamine derived from D-penicillamine capped cadmium sulfide quantum dots (DPA-CdS QDs) is proposed. The DPA-CdS QDs were successfully synthesized via a simple method in a one-pot reaction. The morphology of DPA-CdS QDs was characterized by transmission electron microscopy (TEM) revealing spherical shapes with an average size of 3.2±0.5nm. In the presence of cysteamine, the fluorescence intensity of the DPA-CdS QDs was enhanced proportionally with increasing cysteamine concentration. The proposed fluorescence sensor can be used to detect cysteamine in a wide range of working concentrations up to 10μM and with a limit of detection of 0.07μM. Furthermore, this sensor can be efficiently used for the detection of cysteamine in real urine samples with high accuracy.

Enzyme free Thiol capped CdS Quantum dots based sensing method for the detection of Malathion

This study was focused to develop a cost effective and simple sensing method for Malathion using Thioglycolic acid (TGA) capped Cadmium Sulfide (CdS) quantum dots. Quantum dots (QDs) were synthesized by reflux condensation method and capped with TGA. QDs were characterized by UV-Vis spectroscopy, Spectrofluorometer, FT-IR and HR-TEM. Size of the TGA capped QDs were found to be 2.5 nm. Interaction of Malathion and quantum dots was analyzed by Spectrofluorometer based on photoluminescence (PL) quenching. The lowest detection limit of Malathion was found to be 2 ppb which was observed from the minimum interference it could cause in the PL spectrum.

Fluorescence Turn off Sensor for Brilliant Blue FCF- an Approach Based on Inner Filter Effect

A nanosensor with fluorometric readout based on L-cysteine capped cadmium sulphide quantum dots for discriminative detection and determination of Brilliant blue FCF (BB) (in 0.5M Tris buffer solution of pH9.5) over other synthetic food colourants is developed. Mechanism of the nanosensor is based on inner filter effect (IFE). The addition of BB into quantum dot solution might induce the quenching of fluorescence. The nanosensor described in this report reveals its simplicity and flexibility due to less laborious and more cost-effective synthesis. The developed fluorescence sensor showed excellent selectivity towards BB, and allows the detection as low as 3.50×10-7M. The developed sensor exhibited a linear concentration range of 4.00×10-5 to 4.50×10-6M. More importantly, the proposed sensor exhibit sensitive responses toward BB in food samples such as sports drink and candies, demonstrating its potential in food analysis, which might be significant in food quality control in the future.

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.

Controllable synthesis of CdS quantum dots and their photovoltaic application on quantum-dot-sensitized ZnO nanorods

Water-dispersible l-cysteine (l-cys)-capped cadmium sulfide (CdS) quantum dots (QDs) with a cubic structure and excellent crystallinity are synthesized by a one-pot method in aqueous solution, and the dots are subsequently used to grow QD-decorated zinc oxide (ZnO) nanorod (NR) heterostructures by the direct adsorption technique. Adjustment of the reaction time from 0.5 to 9 h allows tuning of the size of the synthesized CdS QDs from 2.30 to 2.78 nm. Quantum size effects lead to red shifting of the CdS QD absorption peak from 385 to 418 nm. The photoconversion efficiency (η) of CdS QD-sensitized ZnO NRs is enhanced by 250 % compared with that of unmodified ZnO NRs.

Circular dichroism sensor based on cadmium sulfide quantum dots for chiral identification and detection of penicillamine

A new chemical sensor based on the measuring of circular dichroism signal (CD) was fabricated from cysteamine capped cadmium sulfide quantum dots (Cys-CdS QDs). The chiral-thiol molecules, d-penicillamine (DPA) and l-penicillamine (LPA), were used to evaluate potentials of this sensor. Basically, DPA and LPA provide very low CD signals. However, the CD signals of DPA and LPA can be enhanced in the presence of Cys-CdS QDs. The CD spectra of DPA and LPA exhibited a mirror image profile. Parameters affecting the determination of DPA and LPA were thoroughly investigated in details. Under the optimized condition, the CD signals of DPA and LPA displayed a linear relationship with the concentrations of both enantiomers, ranging from 1 to 35 μM. Detection limits of this sensor were 0.49 and 0.74 μM for DPA and LPA, respectively. To demonstrate a potential application of this sensor, the proposed sensor was used to determine DPA and LPA in real urine samples. It was confirmed that the proposed detection technique was reliable and could be utilized in a broad range of applications.

Enhancement of Charge Transfer and Quenching of Photoluminescence of Capped CdS Quantum Dots.

Quantum dots (Q-dots) of cadmium sulfide (CdS) with three different capping ligands, 1-butanethiol (BT), 2-mercaptoethanol (ME) and benzyl mercaptan (BM) have been investigated. An external electric field of variable strength of 0.2–1.0 MV cm−1 was applied to the sample of capped CdS Q-dots doped in a poly(methyl methacrylate) (PMMA) films. Field-induced changes in optical absorption of capped CdS Q-dots were observed in terms of purely the second-derivative of the absorption spectrum (the Stark shift), indicating an enhancement in electric dipole moment following transition to the first exciton state. The enhancement depends on the shape and size of the Q-dots prepared using different capping ligands. Field induced-change in photoluminescence (PL) reveals similar changes, an enhancement in charge-transfer (CT) character in exciton state. PL of capped CdS Q-dots is significantly quenched in presence of external electric field. The strong field-induced quenching occurs as a result of the increased charge separation resulting exciton dissociation. Thus, understanding the CT character and field-induced PL quenching of CdS Q-dots is important for photovoltaic, LEDs and biological applications.

A circular dichroism sensor for Ni2+ and Co2+ based on l-cysteine capped cadmium sulfide quantum dots

A new circular dichroism sensor for detecting Ni2+ and Co2+ was proposed for the first time using chiral chelating quantum dots. The detection principle was based on changing of circular dichroism signals of the chiral quantum dots when forming a chiral complex with Ni2+ or Co2+. l-Cysteine capped cadmium sulfide quantum dots (l-Cyst-CdS QDs) were proposed as a chiral probe. The CD spectrum of l-Cyst-CdS QDs was significantly changed in the presence of Ni2+ and Co2+. On the other hand, other studied cations did not alter the original CD spectrum. Moreover, when increasing the concentration of Ni2+ or Co2+, the intensity of the CD spectrum linearly increased as a function of concentration and could be useful for the quantitative analysis. The proposed CD sensor showed linear working concentration ranges of 10–60μM and 4–80μM with low detection limits of 7.33μМ and 1.13μM for the detection of Ni2+ and Co2+, respectively. Parameters possibly affected the detection sensitivity such as solution pH and incubation time were studied and optimized. The proposed sensor was applied to detect Ni2+ and Co2+ in real water samples, and the results agreed well with the analysis using the standard ICP-OES.

A highly selective electrochemical sensor for l‐tryptophan based on a screen‐printed carbon electrode modified with poly‐p‐phenylenediamine and CdS quantum dots

ABSTRACTA new highly selective electrochemical sensor for the determination of l‐tryptophan was proposed by modifying the surface of screen‐printed carbon electrodes (SPCEs). The surface of SPCE was firstly modified by electropolymerization of p‐phenylenediamine (PPD). The polymer film was then covalently linked with cysteamine capped cadmium sulfide quantum dots (Cys‐CdS QDs) by using glutaraldehyde (GA) as a cross‐linker resulted in an organic–inorganic hybrid composite film (QDs/GA/PPD/SPCE). The modified electrode was applied as a working electrode for detecting various amino acids. It was found that the modified electrode gave an electrochemical response selectively to l‐tryptophan over other amino acids. The experimental parameters, including pH of solution, buffer types, electropolymerization cycles, scan rate, and accumulation time, were studied and optimized. The proposed sensor can be used to detect l‐tryptophan with a low detection limit of 14.74 µmol L−1 with good precision and the relative standard deviation less than 3.7%. The modified electrode was used to detect l‐tryptophan in beverage samples and gave satisfactory recoveries from 91.9 to 104.9%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40356.