Properties Of CdS Quantum Dots Research Articles

Engineering of Solar Energy Harvesting Tb3+-Ion-Doped CdS Quantum Dot Glasses for Photodissociation of Hydrogen Sulfide.

The photocatalytic properties of CdS quantum dots (Q-dots) and Tb3+-doped CdS Q-dots dispersed in a borosilicate glass matrix were investigated for the photodissociation of hydrogen sulfide (H2S) into hydrogen (H2) gas and elemental sulfur (S). The Q-dot-containing glass samples were fabricated using the conventional melt-quench method and isothermal annealing between 550 and 600 °C for 6 h for controlling the growth of CdS and Tb3+-ion-doped CdS Q-dots. The structure, electronic band gap, and spectroscopic properties of the Q-dots formed in the glass matrix after annealing were analyzed using Raman and UV-visible spectroscopies, X-ray powder diffraction, and transmission electron microscopy. With increasing annealing temperature, the average size range of the Q-dots increased, corresponding to the decrease of electronic band gap from 3.32 to 2.24 eV. For developing the model for photocatalytic energy exchange, the excited state lifetime and photoluminescence emission were investigated by exciting the CdS and Tb3+-doped CdS quantum states with a 450 nm source. The results from the photoluminescence and lifetime demonstrated that the Tb3+-CdS photodissociation energy exchange is more efficient from the excited Q-dot states compared to the CdS Q-dot glasses. Under natural sunlight, the hydrogen production experiment was conducted, and an increase of 26.2% in hydrogen evolution rate was observed from 0.02 wt % Tb3+-doped CdS (3867 μmol/h/0.5 g) heat-treated at 550 °C when compared to CdS Q-dot glass with a similar heat treatment temperature (3064 μmol/h/0.5 g). Furthermore, the photodegradation stability of 0.02 wt % Tb3+-CdS was analyzed by reusing the catalyst glass powders four times with little evidence of degradation.

Synthesis and characterization of CdS/ZnS heterostructures to improve the optical properties of CdS quantum dots

In this work, we performed the synthesis of CdS quantum dots (QDs) and CdS/ZnS heterostructures (HQDs) via a hot injection method. The chemical route influenced the growth control and the physicochemical stability of the QDs with great reproducibility. To better understand the optoelectronic properties of CdS QDs and CdS/ZnS HQDs, we studied their surface states by means of UV–Vis assays and evaluated the emission peaks of each state, thus determining the band gap energy, nanoparticle average size, photoluminescence with temperature variation, and decay rate. Our results suggest an improvement of the optical properties as indicated by the PLQY of up to 64% for encapsulated samples, showing the efficiency of the process performed. The improvement is also supported by an intensity reduction of emissions from surface defects and vacancy states, and an intensity increase of the excitonic transitions and decreasing in the mean lifetime of luminescence for all HQDs samples.

Development of multiple analytical labels for volatile organic compounds based on the results of sorption on CdS quantum dots in chitosan without and with modification with Rhodamine 6G

Analytical solutions using the luminescent labels for the analysis of gaseous media and the detection of volatile organic compounds are discussed. Such solutions can potentially be applied for the development of optical, sorption gas sensors, smart label fillers, test systems with various carriers for the detection of chemical biomarkers in living systems. To solve the problem it is proposed to develop and study the properties of modifiers based on cadmium sulfide quantum dots. The aim of the work is studying the sorption properties of CdS quantum dots prepared using a method improved in the direction of "green chemistry", with stabilizing chitosan shells (pure and modified with Rhodamine 6G). Sorption properties of various phases based on quantum dots were studied at a temperature of 22±1 °C by a highly sensitive direct piezo-quartz microweighting method with a resolution of up to 10–9 g by the mass of the sorbent in vapors of volatile compounds. The selectivity of phases based on cadmium sulfide quantum dots in low-mass chitosan (5–10 micrograms) with respect to volatile organic compounds of different classes was evaluated. The relative selectivity and sensitivity of vapor weighing on different phases were evaluated using the parameters A(i/j), showing how many times the sorption properties of CdS phases in chitosan differ without and with the addition of Rhodamine 6G. The method of direct weighing allows to estimate the rate of sorption and desorption, and the capacity of the sorbent phases. It was established that substances belonging to the same selectivity group in terms of A(i/j) values, for example, water and ethanol, have different sorption rates. This feature can be applied for solving the problems of separate detection of vapors, they can be identified at different moments of exposure of piezo balances with phases based on CdS quantum dots in chitosan without and with the addition of Rhodamine 6G. The use of cadmium sulfide quantum dots in chitosan as a sorbent of organic compound vapors significantly affects the kinetics and sorption efficiency. Modification of chitosan with Rhodamine 6G changes the sorption properties of quantum dots in chitosan, which can be used for engineering new sorbents for sensor systems. Simple algorithms are proposed for solving problems of vapor recognition of volatile compounds according to calculated parameters even for non-selective sorption systems. Programming the approach can significantly increase the expressiveness of decision-making in integrated analytical systems, for example, "electronic noses" based on sensors, including those with studied phases. It was found that the mass of the phase based on cadmium sulfide quantum dots in chitosan does not affect the sorption properties in the micromass range, which is traditional for nanostructures. Changes in the luminescent properties of phases based on cadmium sulfide, as a possible visually detectable analytical response, will be discussed in the next paper.

Effect of temperature on the morphological, optical, and photocatalytic properties of CdS quantum dots

Effect of temperature on the morphological, optical, and photocatalytic properties of CdS quantum dots

Synergistic effects of CdS QDs – Neutral red dye hybrid system on its nonlinear optical properties

One of the main goal in the area of nanophotonics is to reinforce the nonlinear optical effects at low input fluence. In this regard, nanohybrids have received special attention which render remarkable third-order nonlinear optical properties. Herein, we have studied the nonlinear optical properties of CdS Quantum Dots (QDs) - Neutral Red (NR) nanohybrid system using Z-scan technique and report the development of functional materials for optical limiting applications. Open aperture Z-scan results suggests that reverse saturable absorption is the predominant mechanism behind the observed nonlinear effects and it can be ascribed to enhanced triplet state population. A significant enhancement in the nonlinear absorption coefficient, nonlinear refraction and third-order nonlinear susceptibility is observed with the nanohybrids as compared to their individual components. The enhanced nonlinear properties can be attributed to cumulative effects of distinct nonlinear mechanisms.

Optical and Structural Properties of CdS Quantum Dots Synthesized Using (MW-CBD) Technique

In the present study, the microwave heating method was used to prepare cadmium sulfide quantum dots CdSQDs films. CdS nanoparticles size average obtained as (7nm). The morphology, structure and composition of prepared CdSQDs were examined using (FE-SEM), (XRD) and (EDX). Optical properties of CdSQDs thin films formed and deposited onto glass substrates have been studied at room temperature using UV/ Visible spectrophotometer within the wavelength of (300-800nm), and Photoluminescence (PL) spectrum. The optical energy gap (Eg) which estimated using Tauc relation was equal (2.6eV). Prepared CdS nanoparticles thin films are free from cracks, pinholes and have high adhesion to substrate.

Lanthanide-doped CdS quantum dots: luminescence and paramagnetic properties

Optical and magnetic properties of CdS quantum dots (QDs) doped with europium(II) and gadolinium(III) ions were studied. l-Cysteine stabilized nanoparticles were synthesized by the colloidal method in aqueous media. The QDs obtained have a hexagonal crystal lattice. The nanoparticle size varies from 3 to 14 nm. The EPR spectra of nanoparticles prepared in different conditions were measured and analyzed. Dependences of the optical properties of nanoparticles on the reaction time and pH values were studied. The dependence of the luminescence properties of CdS QDs on the dopant ion type was established. It was shown that the increase in the reaction time and medium pH values favors a bathochromic shift of maxima in the luminescence spectra of nanoparticles.

Influence of gadolinium (III) doping on the structural, optical, magnetic, and photocatalytic properties of CdS quantum dots

CdS, Cd0.98Gd0.02S, and Cd0.96Gd0.04S quantum dots (QDs) have been fabricated by solvothermal method and found to form in cubic phase. Raman spectra displayed first as well as second order longitudinal modes of CdS QDs. Transmission electron microscopy images depict the nearly spheroid particles of size in the range of 3.8–6.2 nm. Reflectance spectra showed that the absorption edge of the Cd0.98Gd0.02S and Cd0.96Gd0.04S QDs was red-shifted compared to that of CdS QDs. Electron paramagnetic resonance spectra of Cd0.98Gd0.02S and Cd0.96Gd0.04S reveal resonance signals at g ≈ 2.16 and 2.93 corresponding to the gadolinium (III) ions located at sites with frail as well as intermediate crystal field. Exploration of the magnetic property reveals that the Cd0.98Gd0.02S and Cd0.96Gd0.04S QDs show signs of superparamagnetism. The photocatalytic activity of CdS and Cd0.96Gd0.04S QDs was studied on malachite green oxalate dye under artificial solar light irradiation. The decomposition rate of CdS and Cd0.96Gd0.04S QDs evaluated on the malachite green oxalate dye is as follows: Cd0.96Gd0.04S > CdS.

Synthesis and optical properties of CdS quantum dots via paraffin liquid and oleic acid

In this study, an easy, low-cost, green, and environmentallyfriendlier reagents have been used to prepare CdS QDs, in chemicalreaction method by mixed different ratio of CdO and sulfur inparaffin liquid as solvent and oleic acid as the reacting media indifferent concentration to get the optimum condition of the reactionto formation CdS QDs. The results give an indication that thebehavior is at small concentration of 4ml of the oleic acid is bestconcentration which give CdS QDs of small about to 9.23 nm withnano fiber configuration.

Influence of ambient gas on the optical properties of CdS quantum dots prepared by plasma-liquid interactions

In this study CdS quantum dots were fabricated by injecting non-equilibrium plasma jet into the aqueous solution including Na2S2O3, CdSO4 and Thioglycolic acid (TGA) in the presence of an ambient gas such as nitrogen and oxygen gases. In order to investigate the structure, morphology, size and chemical nature of the prepared CdS nanocrystals in presence of ambient gas, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) were employed. The optical properties of CdS nanoparticles were characterized using UV–Vis absorption and photoluminescence (PL) spectroscopies. It was found that the presence of ambient gases especially oxygen, reduces the size and concentration of the synthesized nanoparticles, while the crystalline structure of these nanoparticles is not altered. It was also found that with the increase of flow rate of ambient gas, the PL emission intensity of quantum dots was reduced and the PL peak position as well as the absorption edge undergoes a blue shift.

Passivating effect of ternary alloyed AgZnSe shell layer on the structural and luminescent properties of CdS quantum dots

The surface passivation of luminescent CdS quantum dots (QDs) via epitaxial overgrowth of new alloyed ternary AgZnSe shell layer is reported here. Two synthetic fabrication strategies were used to tune the optical properties of CdS/AgZnSe core/alloyed shell QDs across the visible region. Transmission electron microscopy, powder X-ray diffraction, Raman, UV/vis and fluorescence spectrophotometric techniques were used to characterize the nanocrystals. Analysis of the internal structure of the QDs revealed that homogeneity of the particle reduced as the size increased, thus indicating that the QDs growth transitioned from an interfacial epitaxial homogenous state to a heterogeneous state. The crystal structure of the QDs revealed a distinct zinc-blende diffraction pattern for CdS while CdS/AgZnSe core/alloyed shell QDs kinetically favoured a phase change process from the zinc-blende phase to a wurtzite phase. Analysis of the photophysical properties revealed varying degrees of interfacial defect state suppression in CdS/AgZnSe QDs which was dependent on the QDs size. Specifically, the fluorescence quantum yield (QY) of CdS/AgZnSe QDs was at most ~5-fold higher than the CdS core and varied from 35% to 73%. We found that band gap modulation via the synthetic fabrication strategy employed, influenced the optical properties of the core/alloyed shell QDs. The CdS/AgZnSe QDs produced in this work hold great promise in light-emitting optoelectronic applications.

Optical Properties of CdS Quantum Dots on Graphene

Hybrid systems based on graphene and semiconductor quantum dots are prospective materials for optoelectronics and photonics. In this work, electronic structure and dielectric properties of small particles of cadmium sulfide on the surface of graphene were studied using the density functional theory. The optical spectrum of this hybrid structure depends on the orientation of the nanoparticle relative to graphene due to the interaction between electrons of sulfur atoms on the surface of the CdS particle and π-orbitals of carbon atoms.

Оптические свойства квантовых точек CdS на графене

Оптические свойства квантовых точек CdS на графене

Morphological and Optical Properties of CdS Quantum Dots Synthesized with different pH values

Morphological and Optical Properties of CdS Quantum Dots Synthesized with different pH values

Study of the nonlinear optical properties of CdS quantum dots in phosphate glass

CdS quantum dots (QDs) embedded in a phosphate glass matrix were investigated. The time-resolved Z-scan technique was used to determine the nonlinear refraction and absorption for different concentrations of CdS QDs. The results indicate that the nonlinear absorption presents a reverse saturable character, which is a desirable feature in the design of optical limiting devices. In addition, strong experimental evidence that the main contribution onto the refractive index variation is not of thermal origin was found. The observed variation presents a character similar to an electronic-like effect. These evidences are supported by numerical simulations.

Influence of hydrogen peroxide on the stability and optical properties of CdS quantum dots in gelatin

Influence of hydrogen peroxide on the stability and optical characteristics of CdS quantum dots obtained by aqueous synthesis in gelatin is investigated. It is shown that the action of hydrogen peroxide on the CdS quantum dots reduces the average particle size, increases monodispersity of particle size distribution, and also increases the photoluminescence intensity. A model that explains the behavior of CdS quantum dots photoluminescence with a decrease of particle size as a result of treatment with hydrogen peroxide is presented.

Effect of MPS concentration on ripening kinetics and structural properties of CdS quantum dots in self-assembled thin films

The colloidal CdS quantum dots (QDs) were synthesized with various molar ratios of 3-mercaptopropyltrimethoxysilane (MPS) molecules. The results show that the smaller size of CdS QDs was obtained at the higher molar concentration of MPS. Sol–gel spin coating method was used for deposition of the colloidal nanoparticles on a glass substrate. One pot production method was used to obtain self-assembled thin films of CdS QDs in SiO2 network and the grow kinetics of QDs were investigated. The samples were heat treated at various temperatures to observe the growth of the QDs. The sizes of the QDs were obtained in the range of 2–5 nm depending on the capping agent concentration and heat-treatment temperature. The activation energies for the Ostwald ripening process were found as 38.7, 56.4, 93,1 and 98.6 kJ/mol for the samples containing molar ratio of MPS:Cd = 0.25, 0.50, 1.00 and 2.00 respectively.

Surface passivation by l-arginine and enhanced optical properties of CdS quantum dots co-doped with Nd3+–Li+

l-Arginine-passivated Nd3+ and Li+ co-doped CdS quantum dots (QDs) were synthesized by chemical precipitation method. Ultraviolet–visible absorption spectra of prepared QDs show absorption in the range of 477–450 nm indicating huge blue shift in energy band gap as compared to the bulk CdS due to quantum confinement effect. The optical band gap is found increasing from 2.44 to 2.97 eV as the doping concentration increased from 1 to 5 wt%. Photoluminescence spectra showed that co-doped CdS QDs are highly luminescent and emit multiple intense violet (362, 371, 385, 395 nm) and blue (422, 445, 456 and 465 nm) coloured peaks with increasing intensity with co-dopant concentration. Fourier transform infrared study confirmed the interaction between CdS nanoparticles and l-arginine ligands. The structural and morphological study revealed the formation of orthorhombic crystal structure. The size of CdS QDs, as analysed by X-ray diffraction and high-resolution transmission electron microscopy, is found reducing with co-dopant concentration. The energy dispersive X-ray analysis shows no impurities present except dopants indicating high purity of the prepared samples. Based on the results, we proposed that this material is a new class of luminescent material suitable for optoelectronics devices’ application, especially in light emitting devices, electroluminescent devices and display devices.

Effect of coordinating ligand on spectral-luminescent properties of CdS quantum dots in microwave synthesis

The effect of the coordinating (capping) ligand benzyl mercaptan (BM) on the size and spectral-luminescent properties of CdS quantum dots (QDs) has been investigated. The QDs are synthesized from cadmium acetate and thiourea at a 1 × 1 molar ratio under microwave activation in dimethylformamide. Monodisperse QDs are obtained at a BM: CdS molar ratio of 1.5, which provides the complete coating of the QD surface by mercaptan molecules. The resulting QDs have a diameter of 2.4 nm; their absorption maximum is at 332 nm and the emission band is at 450 nm. The full width of the emission band at half maximum is 100 nm.

Genotoxic effects of CdS quantum dots and Ag2S nanoparticles in fish cell lines (RTG-2)

The increasing use of nanotechnologies will lead to significant releases of engineered nanoparticles into the aquatic environment, where their impact is still poorly characterized. In the present paper, the genotoxic and cytotoxic properties of CdS quantum dots (QDs) and silver sulphide (Ag2S) coated with methyl polyethylene glycol (M-PEG) were investigated in a rainbow trout cell line (RTG-2). The results showed that CdS QDs were highly cytotoxic at high concentrations (10 and 50μg/ml), and exhibited a concentration-dependent genotoxicity in the sub-toxic range (0.01–1μg/ml) after 24h exposure. Ag2S showed neither genotoxic nor cytotoxic effects.