Cadmium Sulfide Nanocrystals Research Articles

Absorption in nanosystems containing cadmium sulfide nanocrystals in the ultraviolet spectral ranges

Absorption in nanosystems containing cadmium sulfide nanocrystals in the ultraviolet spectral ranges

Absorption by cadmium sulfide nanocrystals in the ultraviolet spectral ranges

Within the framework of the effective mass approximation, the energy of the ground state of an electron-hole pair was obtained by the variational method as a function of the radius of the nanocrystal of cadmium sulfide. Determined that the absorption peaks of the nanosystem are caused by interband transitions of electrons from quantum-confined energy levels, located in the valence band of a colloidal nanocrystal of cadmium sulfide, to quantum-confined energy levels, located in the conduction band of CdS nanocrystal.

2D kinetic Monte-Carlo model of nanocrystal aggregation within a liquid matrix: Simulation and experimental study

A stochastic model of nanocrystals (NC) aggregation governing mobilities both of individual nanocrystals and its clusters is developed. The influence of the model parameters on the NC morphology is considered and an analysis is made of the applicability of the model to describe various real physical systems. The model is applied to simulate an aggregation of cadmium sulfide nanocrystals upon evaporation of the Langmuir–Blodgett matrix and as a result a comparison of simulations and experimental results is carried out. We give a comprehensive analysis of the patterns simulated by the model, and study an influence of the surrounding medium (solvent) on the aggregation processes. This system is a typical example from real life and is noteworthy in that the morphology of NC after evaporation of the matrix cannot be described exactly by a model based only on the motion of individual nanocrystals or by a cluster–cluster aggregation model.

PVK-based LEDs doped by cadmium sulphide nanocrystals coated by mixed thiophenol and 1-decanethiol

Nanoparticles capped with more than one ligand have great potential to improve the properties of optoelectronic devices. To discuss this possibility, we synthesized cadmium sulphide nanocrystals coated by two different ligands, 1-decanethiol and thiophenol. In addition, as a reference, cadmium sulphide nanocrystals coated with thiophenol were synthesized. Photoluminescence and UV–Vis absorption measurements indicated that the maximum emission peaks of both cadmium sulphide nanoparticles were located around 600 nm and the absorption edges showed the existence of two different types of crystalline structure, cubic zinc blende and wurzite-type hexagonal. But the nanoparticles with both ligands had higher emission intensity than nanocrystals coated only by thiophenol. Finally, hybrid light-emitting devices have been manufactured with the following structure: Indium Tin Oxide/Poly(3,4-ethylenedi-oxythiophene): poly(styrene sulfonate)/poly(9-vinylcarbazole): cadmium sulphide/Aluminum. These devices presented an active layer composed of poly(9-vinylcarbazole) doped by cadmium sulphide nanocrystals coated only by thiophenol in one case and with thiophenol and 1-decanethiol in the other case. The inclusion of nanocrystals in the active layer increased the current density of these devices. In addition, the solubility in chlorobenzene of nanoparticles with both ligands was improved, due to the presence of 1-decanethiol on their surface. Moreover, the presence of the second ligand intensified the influence of nanoparticles in electroluminescence measurements compared to cadmium sulfide nanocrystals without 1-decanethiol.

Optical gain and lasing from bulk cadmium sulfide nanocrystals through bandgap renormalization.

Strongly confined colloidal quantum dots have been investigated for low-cost light emission and lasing for nearly two decades. However, known materials struggle to combine technologically relevant metrics of low-threshold and long inverted-state lifetime with a material gain coefficient fit to match cavity losses, particularly under electrical excitation. Here we show that bulk nanocrystals of CdS combine an exceptionally large material gain of 50,000 cm-1 with best-in-class gain thresholds below a single exciton per nanocrystal and 3 ns gain lifetimes not limited by non-radiative Auger processes. We quantitatively account for these findings by invoking a strong bandgap renormalization effect, unobserved in nanocrystals to date, to the best of our knowledge. Next, we demonstrate broadband amplified spontaneous emission and lasing under quasi-continuous-wave conditions. Our results highlight the prospects of bulk nanocrystals for lasing from solution-processable materials.

Synthesis and Characterization of CdS/CISe Quantum Dots with Core–Shell Structure

AbstractQuantum dots have received great interest due to their excellent optoelectronic properties. However, the surface defects of quantum dots affect the carrier transport and ultimately reduce the photovoltaic efficiency. In this paper, a core–shell quantum dot by hot‐injection method is prepared to grow a narrow‐band semiconductor layer (CuInSe2 (CISe) quantumdot) on the surface of a broad‐band core material (cadmium sulfide (CdS) nanocrystal). The composition, structure, optical properties, and decay lifetime of CdS/CISe core–shells are investigated in more detail by X‐ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL), UV–vis spectrophotometry, and fluorescence spectroscopy. The CdS/CISe core–shell structure has a broadened absorption range and still shows CISe‐related quantum effects. The increased size of the core–shell and the smaller specific surface area of the CISe shell layer lead to a lower carrier complexation chance, which improves the carrier lifetime.

Effect and mechanism of simultaneous cadmium-tetracycline removal by a self-assembled microbial-photocatalytic coupling system

Electrochemical bacteria Shewanella oneidensis MR-4 (MR-4) was used to biologically generate cadmium sulfide (bio-CdS) nanocrystals and construct a self-assembled intimately coupled photocatalysis-biodegradation system (SA-ICPB) to remove cadmium (Cd) and tetracycline hydrochloride (TCH) from wastewater. The characterization using EDS, TEM, XRD, XPS, and UV–vis confirmed the successful CdS bio-synthesis and its visible-light response capacity (520 nm). 98.4% of Cd2+ (2 mM) was removed during bio-CdS generation within 30 min. The electrochemical analysis confirmed the photoelectric response capability of the bio-CdS as well as its photocatalytic efficiency. Under visible light, SA-ICPB entirely eliminated TCH (30 mg/L). In 2 h, 87.2% and 43.0% of TCH were removed separately with and without oxygen. 55.7% more chemical oxygen demand (COD) was removed with oxygen participation, indicating the degradation intermediates elimination by SA-ICPB required oxygen participation. Biodegradation dominated the process under aerobic circumstances. Electron paramagnetic resonance analysis indicated that h+ and ·O2- played a decisive role in photocatalytic degradation. Mass spectrometry analysis proved that TCH was dehydrated, dealkylated, and ring-opened before mineralizing. In conclusion, MR-4 can spontaneously generate SA-ICPB and rapidly-deeply eliminate antibiotics by coupling photocatalytic and microbial degradation. Such an approach was efficient for the deep degradation of persistent organic pollutants with antimicrobial properties.

Luminescent properties of cadmium sulfide nanocrystals grown from gas phase

Photoluminescent (PL) properties of undoped nanocrystals of cadmium sulfide were investigated as a function of excitation power intensity. Room-temperature PL spectra of CdS nanocrystals grown from the gas phase revealed two emission bands: with peak positions at 510 nm (near-band-edge emission) and close to 690 nm (deep trap defects). Tunable photoluminescence of CdS nanocrystals with the exchange of the main radiative channel from relaxation through defect levels to direct near-band-edge relaxation with the change of the color was demonstrated. Nonlinear behavior of the intensities of near-band-edge and defect level emission lines as well as the blue shift of the peak of defect level emission are discussed and explained by the finite capacitance of the defect subzone in the forbidden gap. The origin of the red-light emission is due to native defects such as sulfur vacancies or twinning interfaces.

In-situ photodeposition of cadmium sulfide nanocrystals on manganese dioxide nanorods with rich oxygen vacancies for boosting water-to-oxygen photooxidation

Carrier separation and surface reaction kinetic are two main bottlenecks limiting photocatalytic efficiency of photocatalysts towards an industrial level. In this regard, heterostructures and defects engineering have been proven to be effective strategies for addressing the two issues. However, the integrated construction of heterostructures and defects has been reported rarely. Herein, a facile in-situ photodeposition strategy has been developed to grow CdS nanocrystals on MnO2-x nanorods with rich oxygen vacancies (VO) as a direct Z-scheme photocatalyst for boosting water oxidation. It has been found that the Cd2+ ions accept photoelectrons from MnO2-xunder irradiation for the in-situ growth of CdS nanocrystals, which enables a close contact between the two components, providing high-speed electron-transport channels for photocatalysis. Meanwhile, the photooxidation half reactions extract surface lattice oxygen, leading to the increase of VO content in MnO2-x, which supplies abundant active sites for oxygen evolution. Owing to the synergistic effects of VO and Z-scheme systems, the optimized MnO2-x/CdS photocatalyst displays a dramatically enhanced photocatalytic activity with an O2 production rate of 779 μmol g-1h-1 under visible-light irradiation without any cocatalysts, which is 2.33 times higher than the bare MnO2-x. This work reveals the cooperative manipulation of VO and CdS nanocrystals on MnO2-x for achieving efficient photocatalysis, providing new insights into the construction of high-performance photocatalysts via a combined strategy of Z-scheme heterostructures and surface defects.

Structural, morphological, and optical properties of CdS and nickel doped CdS nanocrystals synthesized via a bottom-up approach

The present work investigates the effect of nickel doping with pristine cadmium sulfide (CdS) on structural, morphological, and optical properties synthesized via a bottom-up approach. The crystallite structure, size, interplanar space, lattice constants, and volume of the unit cell have been estimated from the X-ray diffraction (XRD). The average crystallite size was found in a nano range and increased with nickel incorporation. XRD result confirmed the prepared nanocrystals of CdS and transition metal Nickel doped CdS are in the hexagonal wurtzite structural phase. Field emiision scanning electron microscopy(FESEM) micrographs indicate that the nanocrystals have a smooth surface and appear to be roughly spherical and are also found in the nano range. EDAX attached with FESEM mapping studies showed the presence of the homogenous distribution of individual elements. Absorption spectra of UV–Vis spectroscopy show an effective band gap decreases after doping. This work furnishes a gateway to improve the optical properties of CdS for optoelectronic device applications by selecting the suitable proportion of transition metal dopants.

Synthesis Route of Cadmium Sulphide Nanocrystals Coated by Mixed Thiophenol and 1-Decanethiol

Synthesis Route of Cadmium Sulphide Nanocrystals Coated by Mixed Thiophenol and 1-Decanethiol

Green synthesis, structural characterization and application of cadmium sulfide nanocrystals with fluorescent dyes for solar enhancement

Green synthesis, structural characterization and application of cadmium sulfide nanocrystals with fluorescent dyes for solar enhancement

Fabrication of nano battery from CdS quantum dots and organic polymer

Efficient energy storage systems are recharged from the nano batteries; however, the available energy of present nanomaterial batteries remains capable for many applications due to the limited basic charging capacity of the electrode materials. A cadmium sulfide (CdS) nanocrystal (NCs) or quantum dots (QDs) that was prepared by chemical reaction and were fabricated nano battery device using the PVV / Li: graphite / CdS / Al. The optical properties of the CdS QDs were described by the spectrometers of ultraviolet-visible (UV-Vis.) and photoluminescence (PL), the results are indicating that the CdS QDs prepared where nanocrystalline structures are formed. The energy gap (Eg) of CdS QDs measured from PL was found to be about 2.69 eV. The CdS QDs led to improving the performs of the nano battery in terms of enhancing the mobility of the carrier's charging and consequently the processes of recombination between CdS QDs and Li-ions. The characteristics of the current-voltage (I-V) indicate acceptable conditions for the generation of light at (3 Volt). The structures can be designed to determine the fundamentals of ion and electron transport for energy storage in nanostructures and to test the limits of three-dimensional nano battery technologies. The nano battery device from semiconductor substance (CdS QDs) with (Li) has been successful in operating the nano battery with a few voltages giving a good current. Fabrication of CdS QDs and Li nano battery devices was involved in enhancing the efficiency of the nano battery devices.

Selective and fast growth of CdS nanocrystals on zinc (II) metal–organic framework architectures for photoelectrochemical response and electrochemical immunosensor of foot-and-mouth disease virus

The integration of cadmium sulfide (CdS) and metal organic frameworks (MOFs) has shown promise in applications such as photocatalysis and sensing. Herein, a sensitive electrochemical immunosensor based on a room temperature, simple and fast aqueous synthetic strategy of in-situ selective growth nanocystalline CdS on zinc metal organic framework (CdS@Zn-MOF) is reported. We investigated the possibility of growth CdS on various MOFs, synthesizing by electrosynthesis or solution phase syntheses with different metal ions (e.g. Zn2+, Cu2+, Fe3+, Co2+, Zr4+) and organic ligands (e.g. 1,3,5-benzenetricarboxylic acid, 2-methylimidazole, 1,4-benzenedicarboxylic acid, 2-aminoterephthalic acid). This simple experiment process proved that CdS nanocrystalline can selectively grow on varied structures Zn-MOFs with different organic ligands. The synthesis, characterization and mechanisms involved in the formation of this composite material was explored carefully and thoroughly. The unique properties of this composite presented a promising photoelectrochemical and electrochemical applications. Therefore, a sensitive Zn-MOF-labeled amperometric immunosensor based on this strategy for the detection of foot-and-mouth disease virus (FMDV) was developed. The logarithm FMDV concentration was range from 0.5 fg mL−1 to 5 ng mL−1 with a low detection limit of 0.05 fg mL−1. Moreover, this proposed sensor with good selectivity, acceptable reproducibility, and stability was successfully applied to detect FMDV in actual blood sample. Furthermore, this method of growth the CdS nanocrystalline in situ on a Zn-MOF device structure or platform also provides a new horizon for future optoelectronic applications.

A stochastic model, simulation, and application to aggregation of cadmium sulfide nanocrystals upon evaporation of the Langmuir–Blodgett matrix

Abstract A stochastic model of nanocrystals clusters formation is developed and applied to simulate an aggregation of cadmium sulfide nanocrystals upon evaporation of the Langmuir–Blodgett matrix. Simulations are compared with our experimental results. The stochastic model suggested governs mobilities both of individual nanocrystals and its clusters (arrays). We give a comprehensive analysis of the patterns simulated by the model, and study an influence of the surrounding medium (solvent) on the aggregation processes. In our model, monomers have a finite probability of separation from the cluster which depends on the temperature and binding energy between nanocrystals, and can also be redistributed in the composition of the cluster, leading to its compaction. The simulation results obtained in this work are compared with the experimental data on the aggregation of CdS nanocrystals upon evaporation of the Langmuir–Blodgett matrix. This system is a typical example from real life and is noteworthy in that the morphology of nanocrystals after evaporation of the matrix cannot be described exactly by a model based only on the motion of individual nanocrystals or by a cluster-cluster aggregation model.

Calculation of lattice vibrational and thermal properties of cadmium sulfide nanocrystal and growth preference of cadmium sulfide powder during microwave‐hydrothermal process

AbstractCdS nanocrystal is investigated by first‐principles calculations and experiments. Based on phonon spectra, the wurtzite CdS structure is thermodynamically stable. Debye temperature, specific heat capacity and thermal expansion coefficient are calculated to be 221.51 K, 47.68 J·mol−1·K−1 and 1.95×10−4 K−1, respectively. Band gaps of CdS single crystal and monolayer CdS supercell calculated by GGA–mBJ function are 2.74 eV and 2.38 eV. CdS powder is synthesized by microwave‐hydrothermal process (140 °C + 15 min), with particle size ranging from 50 to 1000 nm. HRTEM shows the nanocrystal distance of 6.676 Å between the (0001) crystal faces and growth preference along the [002] direction. The band gap of CdS thin film evaluated by UV–Vis absorption spectra is 2.41 eV, close to 2.38 eV of monolayer supercell, which provides theoretical basis for CdS doping to improve photoanode performance of piezoelectric semiconductors.

Threonine dehydratase enhances bacterial cadmium resistance via driving cysteine desulfuration and biomineralization of cadmium sulfide nanocrystals

Biomineralization is often used by microorganisms to sequester heavy metal ions and provides a potential means for remediating increasing levels of heavy metal pollution. Bacteria have been shown to utilize cysteine for the biomineralization of metal sulfide. Indeed, in the present study, the supplement of L-cysteine was found to significantly improve both cadmium resistance and removal abilities of a deep-sea bacterium Pseudomonas stutzeri 273 through cadmium sulfide (CdS) nanoparticle biomineralization. With a proteomic approach, threonine dehydratase of P. stutzeri 273 (psTD) was proposed to be a key factor enhancing bacterial cadmium resistance through catalyzing L-cysteine desulfuration, H2S generation and CdS nanoparticle biomineralization. Consistently, deletion of the gene encoding psTD in P. stutzeri 273 resulted in the decline of H2S generation, decrease of cadmium resistance, and reduction of cadmium removal ability, confirming the unique function of psTD directing the formation of CdS nanoparticles. Correspondingly, the single-enzyme biomineralization of CdS nanoparticle driven by psTD was further developed, and psTD was shown to act as a capping reagent for the mineralization reaction, which controlling the size and structure of nanocrystals. Our results provide important clues for the construction of engineered bacteria for cadmium bioremediation and widen the synthesis methods of nanomaterials.

Sulfur to Cadmium Ratio-Dependent Studies on Properties of Solution-Processed CdS Nanocrystals

One of the most used metal chalcogenide semiconductor materials in the fabrication of photovoltaic devices is cadmium sulfide (CdS), due to its wide band gap, high carrier mobility, and proper energy levels. In this study, a solution-based method is introduced for the synthesis of CdS nanocrystals (NCs) at room temperature with different sulfur to cadmium ratios in wet synthesis media. The effect of the sulfur to cadmium ratio (S:Cd) in the synthesis media on the morphological, structural, and optical properties of CdS NCs has been investigated. FTIR analysis showed that Cd–S bonds formed in the room temperature synthesis process. It was found that, by reducing the S:Cd ratio, the band gap of the synthesized CdS NCs increases. Furthermore, XRD data revealed that the crystal structure of the synthesized CdS is more cubic at lower sulfur concentrations and hexagonal at higher concentrations. Moreover, it was found that the S:Cd ratio has an important effect on the stability of colloidal suspensions of CdS NCs. The CdS NCs synthesized with the highest sulfur to cadmium ratio (S:Cd = 8:1) in the synthesis media formed the most stable colloidal suspension of CdS NCs in dimethylformamide.

Reduced Graphene Oxide Inserted into PEDOT:PSS Layer to Enhance the Electrical Behaviour of Light-Emitting Diodes.

In this study, poly(9-vinylcarbazole) (PVK)-based LEDs doped with reduced graphene oxide (rGO) and cadmium sulphide (CdS) nanocrystals were fabricated by spin-coating. The hybrid LED structure was a layer sequence of glass/indium tin oxide (ITO)/PEDOT:PSS|rGO/PVK/Al. rGO was included in the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) layer due to its energy bands being close to PEDOT:PSS bands, and the possibility of using water for dispersing both polymer and flakes. Optical properties such as photoluminescence and UV-Vis absorption were not affected by the addition of rGO to the PEDOT:PSS solution. However, PVK-based LEDs with rGO showed increased current density compared to those without rGO in the hole transporting layer. Higher electroluminescence intensities were observed for rGO-enriched LEDs, although the shape of the spectrum was not modified. LEDs including CdS nanocrystals in the poly(9-vinylcarbazole) emissive layer did not show such dependence on the rGO presence. Though the addition of rGO to PEDOT:PSS still produces a slightly higher current density in CdS doped LEDs, this growth is no longer proportional to the rGO load.

Highly luminescent CdS nanoparticles synthesized using microwave irradiation of Dithiocarbazate ligand as a single molecular precursor source

In this paper, we have reported microwave-assisted synthesis of highly luminescent cadmium sulfide nanocrystals using dithiocarbazate Cd (II) chloride complex single-molecule precursor route. The precursors were heated using microwave irradiation to obtain CdS nanocrystals. The irradiation of precursor in DMSO environment played an important role in reducing reaction time, minimizing possibility of side reactions, and resulted in obtaining good quality particles. The obtained samples were analyzed using structural, morphological, and optical characterizations. X-ray diffraction studies confirm the hexagonal crystalline phase. High-resolution electron microscopy and transmission electron microscopy exhibit rod-shape structures with an average particle size of 80 nm. Sharp absorption edge at 320 nm indicates good quality of the particles. Strong luminescence peaks in the visible wavelength range 450–490 nm is observed in PL spectra. Another luminescence peak at 680 nm for excitation at 320 nm ensured the involvement of deep donor and acceptor levels in the crystals. The luminescence spectra show strong dependence on excitation wavelength which makes these particles suitable for various optoelectronic applications. The method reported here is a good candidate for obtaining large-scale high-quality CdS nanoparticles for optoelectronic applications.