Synthesis Of CdS Quantum Dots Research Articles

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.

Green synthesis of CdS Quantum dots for photocatalytic and anti-corrosive applications in aqueous media

Inorganic pollutants are the leading cause of water pollution, which harms human health and the environment. The most highly efficient nanoparticles with enhanced photocatalytic activity are semiconductor quantum dots (QDs). The heterogeneous photocatalysis using UV radiation on quantum dots is a fascinating technique for treating polluted sewage with a naturally available plant-based product. In this study, CdS QDs were synthesized using a facile green synthetic protocol in the presence of Coccinia grandis (CG) and Punica granatum (PG) fruit sap as capping and stabilizing agents. XRD, HR-TEM, FT-IR, UV-DRS, and photoluminescence spectroscopy were used to analyze the synthesized CdS QDs. The photocatalytic degradation activity of CdS quantum dots was performed against anionic and cationic dyes under UV light irradiation. The results revealed that PG-capped CdS QDs have the best photocatalytic activity compared to CG-capped CdS QDs.Further, the pseudo-first-order model is used to analyze the kinetics studies. Moreover, the electrochemical measurements of pure zinc and CdS QDs coated Zn (Zn/CdS QDs) plate were tested in three electrolytes: sodium chloride, potassium hydroxide, and hydrochloric acid, which demonstrated the corrosion inhibition ability of prepared CdS QDs. The electrochemical impedance spectra, Tafel plot, and in-situ SPM analysis depict the improving corrosion resistance of the Zn metal plate due to the prepared CdS QDs coatings. Based on the results, the prepared CdS QDs by the green method can be a potential candidate in the water purification and corrosion resistance field.

Designing and fabricating a CdS QDs/Bi2MoO6 monolayer S-scheme heterojunction for highly efficient photocatalytic C2H4 degradation under visible light

Achieving efficient photocatalytic degradation of atmospheric volatile organic compounds (VOCs) under sun-light is still a significant challenge for environmental protection. The S-scheme heterojunction with its unique charge migration route, high charge separation rate and strong redox ability, has great potential. However, how to regulate interfacial charge transfer of the S-scheme heterojunction is of significant importance. Here, density functional theory (DFT) calculations were first conducted and predicted that an S-scheme heterojunction could be formed in the CdS quantum dots/Bi2MoO6 monolayer system. Subsequently, this novel heterojunction is constructed by in-situ hydrothermal synthesis of CdS quantum dots on monolayer Bi2MoO6. Under visible-light, this novel S-scheme system gives a high-efficiency photocatalytic degradation rate (6.04 × 10−2 min−1) towards C2H4, which is 30.3 times higher than that of pure CdS (1.99 × 10−3 min−1) and 41.7 times higher than pure Bi2MoO6 (1.45 × 10−3 min−1). Strong evidence for the S-scheme charge transfer path is provided by in-situ XPS, PL, TRPL and EPR.

Structural, optical and dielectric studies of wurtzite-type CdS quantum dots green synthesised using Ocimum sanctum (Tulsi) leaf extract

Present study reports the synthesis of CdS quantum dots (QDs) using Ocimum sanctum (Tulsi) leaf extract by green chemical method. The as-prepared QDs are characterised by different analytical methods. FTIR analysis indicates that the phytochemicals present in Tulsi leaf extract play an important role in controlling the size of the particle and its morphology. The structural properties and surface morphology studies are carried out by powder XRD and SEM with EDX. PXRD patterns revealed the hexagonal structure (wurtzite) for all CdS QDs. The average crystallite size lies in the range of 3.6–3.0 nm which decreases with the increase of the extract concentration. The lattice parameters of the pure and capped CdS QDs are found to be smaller than that of their bulk analogue. The EDAX study confirms the purity of all the prepared samples. The optical study is done by UV-vis spectroscopy and the particle sizes are estimated by an empirical method, which are in good agreement with those obtained from PXRD analysis. Dielectric constant of the QDs is obtained at room temperature at different frequencies where the frequency dependence is pronounced at the lower frequencies. It is noted that the band gap of the capped CdS QDs systematically increases with the increase of the extract concentration whereas the particles size and dielectric constant of these samples decreases with the increasing amount of the extract.

Superficial Synthesis of CdS Quantum Dots for an Efficient Perovskite-Sensitized Solar Cell

In this paper, a thorough investigation of cadmium sulfide nanoparticle characteristics has been studied as a result of the wide attention and enormous application in a solar cell. Perovskite-sensitized solar cells (PSSCs) are a favorably effectual and sanitary hybrid, organic–inorganic solar cell device. The simple way uses synthesized cost-effective CdS quantum dots (QDs) via the sol–gel approach and also investigates their structural, electronic, and vibrational properties of CdS nanoparticles with the density functional theory method in B3LYP. Moreover, we use high-resolution transmission electron microscopy (HRTEM) techniques to confirm our calculations and acquire good agreement to the structural analysis of CdS QD formation. The maximum grain diameter is obtained from a HRTEM image, at ∼4 nm. The particle size analyzer that obtained ∼4 nm of CdS QD nanoparticles was determine via a dynamic light scattering study. The results demonstrated that the fabricated CdS QD-based dye-sensitized solar cell and PSSC represented a maximum power conversion efficiency (η) of 0.5 and 1.8% at 1 sun condition. This efficiency was improved by approximately 72%, associated with that of the reference cell.

Aggregation-Induced Emission Properties of Glutathione and L-Cysteine Capped CdS Quantum Dots and their Application as Zn(II) Probe.

Targeting to obtain better water solubility and stability and less aggregation-caused quenching effects of quantum dots, two kinds of thiol molecules, glutathione and L-cysteine, were firstly united to offer stabilizing ligands for aqueous synthesized CdS quantum dots, which exhibited sensitive aggregation-induced emission properties. Fluorescent intensity of the CdS quantum dots was enhanced about 5 folds by simple solvent exchange from water to 90vol% PEG200. Restriction of intramolecular motions in an aggregate state was probably the main cause of the phenomenon. At the same time, fluorescent intensity of CdS quantum dots in the presence of zinc ions was able to be enhanced about 2.2 folds. Based on the researches, a handy metal enhanced fluorescent probe for detecting zinc ions was established. And the detection limit was 0.58μmol/L. Zinc ions as a bridge among CdS quantum dots to form aggregates limited motions of CdS quantum dots to a certain extent and simultaneously enhanced their fluorescence emission intensities. Meanwhile, activation of surface states of CdS quantum dots also led to emission enhancement. Both of the two factors together contributed to the fluorescence enhancement and ultimately to the sensitivity to zinc ion sample detection.

Synthesis of CdS QDs with single cubic and hexagonal lattice for blue-light-blocking nanocomposite films with a narrow absorbing transitional band

It is highly expected to develop blue-light-blocking filters with narrow absorbing transitional band, so as to filter out only harmful blue light below 455 nm. In this paper, CdS quantum dots (QDs) with single cubic and hexagonal lattice were synthesized by a solvothermal method using mercaptoethanol as capping agent. The results show that hexagonal-type CdS QDs with a diameter about 2.5 nm was synthesized after 10 min of reaction, and then grow slowly up at low temperature (80 °C). Higher temperature (160 °C) helps to synthesize cubic-type CdS that grows rapidly to a final size about 4 nm. Hexagonal and cubic CdS all show separated energy level structure corresponding to a band gap of 3.59 eV and 3.1 eV, respectively. CdS QDs were compounded into poly(N,N-dimethacrylamide) matrices to prepare transparent nanocomposite films, in which the optical properties of CdS QDs can be preserved, and the nanocomposite films, especially ones with 30 wt% of cubic CdS, shows a narrow blue-light-absorbing transitional band. The wavelength span from 5 % to 80 % of maximum transmittance is only 20 nm (440−460 nm), indicating a potential application in ocular protection by sealing it between two layers of glass panels as blue-light-blocking filter due to its sharp cut on/off and wavelength-dependent blue transmittance.

Role of Alcohol in the Synthesis of CdS Quantum Dots

The proper choice of the solvent is an important parameter in wet-chemical syntheses. Here, we highlight the use of 1-tetradecanol, a fatty alcohol, as an excellent solvent for the synthesis of hig...

One-pot biosynthesis of CdS quantum dots through in vitro regeneration of hairy roots of Rhaphanus sativus L. And their apoptosis effect on MCF-7 and AGS cancerous human cell lines

Development of green based synthesis of nanoparticles has been regarded as a novel and safe alternative method compared to conventional methods. Semiconductor cadmium sulfide quantum dots (CdS QDs) possess unique biological and medical applications includes labeling cells, diagnosing of diseases and imaging intercellular events. The present paper reports the biosynthesis of CdS QDs through aqueous extracts of the regenerated hairy roots of Rhaphanus sativus L. as the organic source for both reducing and stabilizing of Cd and S precursor ions. The characterization of synthesized QDs showed maximum absorbance peak of 460 nm and fluorescence spectrum of cadmium sulfide at 530 nm. The results of Transmission Electron Microscope (TEM) and EDS analysis demonstrated that the particles were morphologically spherical with size distribution between 2–7 nm and confirmed presence of CdS QDs. Fourier transform infrared spectroscopy (FT-IR) also showed the active presence of aromatic, amino, and carboxyl groups on the surface of quantum dots. Cytotoxicity effect of the synthesized CdS QDs on two cell lines include MCF-7 breast cancer and AGS gastric cancer were assayed through MTT assay. The results showed significant inhibitory effects of synthesized QDs on treated cells in a dose dependent manner. It was also concluded that CdS QDs had more apoptosis effect on MCF-7 cells rather than AGS cell lines. The obtained results clearly illustrated that the synthesis of CdS quantum dots with standard features would be possible through cost-effective, reliable, environmentally friendly and less toxic alternative method compared to chemical and physical processes and the MTT toxicity assay also illustrated the significant apoptotic effects of synthesized CdS QDs on carcinogenesis.

Facile synthesis of CdS Quantum dots for QDSSC with high photo current density

Environment-friendly and cost effective green CdS Quantum Dots (QDs) are synthesized using Azadirachta Indica extract as a novel non-toxic stabilizing agent and to excogitate its light harvesting potentiality for QD Sensitized Solar Cells (QDSSCs). The effect of different configuration of green CdS based QDSSCs viz (i) different phase of TiO2 photoanodes (ii) with and without ZnS passivating layer (iii) with Platinum counter electrodes (CE) and (iv) CuS CE have been investigated. Despite tralatitious SILAR CdS based QDSSC showed better efficiency (1.93%) than green CdS based QDSSC (0.77%), the later unveil higher photocurrent density (10.61 mA) possibly due to effective encapsulation of Azadirachta Indica which suppresses the surface defects in green CdS QDs favoring the transport of photo generated carriers. The work facilitate scope for cost effective and environment-friendly green synthesized CdS QDs that significantly modulated photovoltaic properties of QDs based solar cells in an inviolable condition.

Strategies for Tuning Optoelectronic Properties of TiO2 Nanomaterials for Solar Photovoltaic Studies

Third generation solar cells are mainly focusing on the use of nanomaterials as host components for solar-to-electrical conversions. Among the various nanomaterials, TiO2 is one of the most promising candidates used in solar devices due to their remarkable structural and opto-electrical properties. However, bare TiO2 nanomaterials have the various constraints in efficient solar energy conversions. In the present research endeavors, TiO2 nanomaterials have been modified with the different strategies such as dyad anchoring, dye-quantum dot sensitization, composites of carbon nanostructures with sensitizers, metal ion doping with sensitizers so as to tune its optoelectronic properties for efficient solar energy harvesting. In addition, the interconnectivity between the various components and their optoelectronic properties of modified TiO2 for solar energy conversions have been studied in detail. In the dyad system, a supramolecular ruthenium(II)phthalocyanine··peryleneimide (RuPc···PI) has been anchored on the surfaces of TiO2 and thereafter these TiO2-dyad sensitized solar cells have assembled in a bottom-up fashion. Upon photo-irradiation at air-mass (AM) 1.5, the dyad-based solar devices convert solar light to electricity of 2.1%; which is higher than that of individual dyes. In next strategies, the synthesized CdS quantum dots (QDs) have connected electrostatically to the surfaces of TiO2 nanoparticles (NPs) and thereafter, this binary hybrid heterojunction is further self-assembled physically with N719 dye to form ternary TiO2 NPs-CdS QDs-N719 photoelectrodes. These co-sensitization devices reported the solar energy conversion efficiency (η) up to 2.35 %. In addition, anatase TiO2 NPs is anchored on the surface of functionalized carbon nanostructures (MWCNTs or RGO); which is further sensitized with Ru(II) dyes for solar devices having efficiency reached to 6.21%. In another modification, Cr(III) as well as Mo(VI) ions are inserted into TiO2 host lattice and then their composites with CNs are further sensitized for boosting the solar energy conversions and reached up to 7.69 % of efficiency. Figure 1

In-situ synthesis of CdS quantum dots on CdCO3 cubic structure for enhanced photocatalytic hydrogen production performance

Abstract The CdCO3 cubic structure was firstly synthesized by hydrothermal method. Then CdS quantum dots (QDs) were in-situ deposited on the CdCO3 to form CdCO3/CdS QDs composite photocatalyst to explore its photocatalytic hydrogen production performance. Physical characterization results show that cubic CdCO3 consists of nanoflake structures, and CdS QDs are uniformly dispersed on the surface of CdCO3 nanoflakes to form heterostructures. Under visible light irradiation, CdCO3/CdS QDs photocatalyst exhibits excellent photocatalytic performance with the photocatalytic H2 production rate of 1.93 mmol·h−1·g−1. The cubic CdCO3 can provide a large number of activity sites for CdS QDs, which is conducive to the photocatalytic hydrogen production process.

Visible-light-driven polydopamine/CdS QDs hybrid materials with synergistic photocatalytic activity

An ultrasensitive photoelectrochemical (PEC) sensor for progesterone (P4) detection was synthesized based on electrochemical synthesis of CdS quantum dots (QDs) and then equipped chemically with polydopamine (PDA) to decorate PDA@CdS QDs/Ti structure on the Ti substrate. It was found that the sensitizers can significantly enhance the photocurrent and the as-prepared PDA@CdS QDs hybrid materials displayed much higher photocatalytic activity than the CdS QDs/Ti and PDA/Ti due to the synergic effect between CdS QDs and PDA. In detection process, P4 acts as an electron donor to scavenge the hole and inhibit the charge recombination. Therefore, the sensor can exhibit charge-transfer upon light illumination and achieve the detection purpose via the intensity of the photocurrent. The resulting photoelectrode showed good sensitivity and selectivity PEC response to P4. Under the optimized conditions, a good linear relationship was obtained between the increased photocurrent and logarithm of P4 concentrations ranging from 2.0 to 280 nM and the detection limit was down to 1.54 nM. Additionally, the sensor had relatively good stability and reproducibility, and it could be applied to the determination of P4 in human serum sample.

Complete genome sequence of Raoultella sp. strain X13, a promising cell factory for the synthesis of CdS quantum dots.

A novel cadmium-resistant bacterium, Raoultella sp. strain X13, recently isolated from heavy metal-contaminated soil, and this strain can synthesize CdS quantum dots using cadmium nitrate [Cd(NO4)2] and l-cysteine. Biomineralization of CdS by strain X13 can efficiently remove cadmium from aqueous solution. To illuminate the molecular mechanisms for the biosynthesis of CdS nanoparticle, the complete genome of Raoultella sp. strain X13 was sequenced. The whole genome sequence comprises a circular chromosome and a circular plasmid. Cysteine desulfhydrase smCSE has been previously found to be associated with the synthesis of CdS quantum dots. Bioinformatics analysis indicated that the genome of Raoultella sp. strain X13 encodes five putative cysteine desulfhydrases and all of them are located in the chromosome. The genome information may help us to determine the molecular mechanisms of the synthesis of CdS quantum dots and potentially enable us to engineer this microorganism for applications in biotechnology.

CdS Quantum Dots Obtained by “Green” Synthesis: Comparative Analysis of Toxicity and Effects on the Proliferative and Adhesive Activity of Human Cells

A novel alternative approach for extracellular synthesis of CdS quantum dots using Escherichia coli bacteria, the fungus Pleurotus ostreatus, and the plant Linaria maroccana as biological matrices was previously developed. The nanoparticles obtained had stable luminescent properties and diameters of 2–10 nm. This paper presents the results of MTT assay- and flow cytometry-based analysis of cytotoxic/cytostatic effects, proliferative activity, and the ability of the CdS quantum dots synthesized to adhere to HeLa cells (human cervical cancer), malignized human T- and B-lymphocytes, and tumor cells of the AGS line (stomach cancer). The toxicity of the CdS quantum dots obtained by the “green” synthesis method was lower than that of inorganic cadmium sulfide, and this makes the quantum dots attractive candidates for a new type of nontoxic luminescent probes for bioimaging in cytological studies.

Quantum Dot-Sensitized Solar Cells via Integrated Experimental and Modeling Study

The solar energy is one of the potential renewable green energy source considering the availability of sunlight in abundance and the need for clean and renewable source of energy. Quantum dots are semiconductor nanocrystals having considerable interest in photovoltaic research areas. Cadmium sulfide-sensitized solar cells are synthesized by Chemical bath deposition and titanium nanowires were fabricated by hydrothermal method. The synthesized CdS quantum dots are sensitized to nanoporous TiO2 films to form quantum dots-sensitized solar cell applications. The introduction of TNWs enables the electrolyte to penetrate easily inside the film which increases the interfacial contact between the nanowires, the quantum dots and the electrolyte results in improvement in efficiency of solar cell. The goal of our research is to understand the fundamental physics and performance of quantum dot-sensitized solar cells with improved photoconversion efficiency at the low cost based on selection of TiO2 nanostructures, sensitizers and electrodes through an integrated experimental and modeling study.

Luminescence of CdS:Ag Quantum Dots in a Polymethacrylate Matrix

Semiconductor quantum dots (QDs) exhibit intense luminescence and reproduce optical characteristics. Doping with metal ions has a positive effect on their properties. Introduction of QDs into polymer matrices leads to the formation of a required morphology of composites. There is a problem in synthesis of optically transparent polymer composites containing QDs of the А2В6 group that consists in the extremely low solubility of metal chalcogenides and most of their precursors in monomers. To solve this problem, we used colloidal synthesis. CdS QDs were synthesized by the method of appearing reagents in situ in methylmethacrylate (MMA). Doping with Ag+ ions was performed by adding a silver salt into the reaction mixture during the synthesis of CdS QDs. The PMMA/CdS:Ag luminescent polymer glasses were synthesized by radical block polymerization of MMA. The transparency of the composites at wavelengths exceeding 500 nm reaches 92% (5 mm). The luminescence excitation is related to the interband electron transitions in CdS crystals. Luminescence in the range of 500–600 nm is observed due to electron relaxation via a system of levels in the band gap of doped CdS crystals. The positions and intensities of the spectral bands depend on the Ag+ concentration, particle size, excitation wavelength, and other factors. The formation of Cd(Ag)S/Ag2S structures at Ag+ concentrations higher than 5.0 × 10–3 mol/L quenches the luminescence.

Viscoelastic wormlike micelles formed by ionic liquid-type surfactant [C16imC8]Br towards template-assisted synthesis of CdS quantum dots.

In this paper, viscoelastic wormlike micelles consisting of cationic liquid-type surfactant, 1-hexadecyl-3-octyl imidazolium bromide ([C16imC8]Br), water and different additives were utilized for the synthesis of CdS quantum dots. First, the influence of different additives, such as [Cd(NH3)6]Cl2 and ethanethioamid (precursors for the synthesis of CdS quantum dots), and temperature on the viscoelasticity of the [C16imC8]Br aqueous solution was studied by dynamic and steady rheology. Furthermore, the synthesized CdS quantum dots and their photoluminescence properties were characterized by transmission electron microscopy (TEM), UV-Vis absorption spectroscopy, X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). In the end, the mechanism for the synthesis of CdS quantum dots in [C16imC8]Br wormlike micelles is proposed.

Synthesis of CdS quantum dots in an imidazolium based ionic liquid

A solution protocol to synthesize CdS quantum dots (QDs) using 1-ethyl-3-methylimidazolium methanesulfonate ionic liquid is described in this work. Various reaction parameters such as temperature and injection protocols were varied to study the optical and structural properties of the obtained particles. X-ray diffraction (XRD) studies confirmed the formation of cubic and hexagonal phases depending on the reaction conditions. Peak broadening in the diffraction patterns revealed the formation of small sized quantum dots and the morphological studies further showed formation of nano-sized particles in the range of 2–15nm, with close to spherical shaped morphologies. Blue-shifted band gaps further confirmed formation of very small CdS nanoparticles, which dependent on the reaction temperatures.

Absorption boost of TiO2 nanotubes by doping with N and sensitization with CdS quantum dots

A process of obtaining N-doped TiO2 nanotubes sensitized by CdS nanoparticles is presented, including detailed characterizations performed along the synthesis. Transparent TiO2 films consisting of nanotubes, 2.5 µm long and of ~60 nm inner diameter, were obtained after anodization of a titanium film deposited onto FTO glass substrate. N-doping was achieved by annealing of TiO2 film in ammonia. X-ray Photoelectron Spectroscopy measurements showed that nitrogen was substitutionally incorporated in the TiO2 matrix, with the N:Ti concentration ratio of 1:100. The doping changed the optical properties of the material in such a way that the absorption edge was shifted from 380 nm to 507 nm, as observed from diffuse reflectance spectra. The influence of the microwave (MW) irradiation on the synthesized CdS quantum dots and their optical properties was investigated. It was shown that the diameter of CdS nanoparticles was increased due to releasing of S2- ions from dimethyl sulfoxide (DMSO) as a consequence of the MW treatment. The (N)TiO2 films were then used as substrates for matrix assisted pulsed laser deposition of the CdS quantum dots with DMSO as a matrix. The laser parameters for the deposition were optimized in order to preserve the nanotubular structure open, the latter being an important feature of this type of photoanode. The structure obtained under optimized conditions has an additional absorption edge shift, reaching 603 nm.