CdS Quantum Dots Research Articles

Heterostructures of Ni(II)-doped CdS quantum dots and β-Pb0.33V2O5 nanowires: Enhanced charge separation and redox photocatalysis via doping of QDs

Heterostructures of Ni(II)-doped CdS quantum dots and β-Pb0.33V2O5 nanowires: Enhanced charge separation and redox photocatalysis via doping of QDs

Numerical study of P3HT-based hybrid solid-state qantum dot solar cells with CdS quantum dots employing different metal oxides using SCAPS-1D

This study presents a comprehensive numerical investigation into solid-state quantum dot solar cells (SSQDSCs) utilizing P3HT poly(3-hexylthiophene) as both a hole transport and absorber layer employing SCAPS-1D simulation software, the research explores the performance of cells composed of FTO (Fluorine-doped Tin Oxide) as the front contact, integrated with different metal oxides (Titanium dioxide (TiO2), zinc oxide (ZnO), and tin dioxide (SnO2), CdS (Cadmium sulfide )quantum dots, P3HT, and Pt (platinum )as the back contact namely Hybrid solar cell. The thickness of each layer is systematically optimized, and the influence of various CdS quantum dots sizes is thoroughly examined. The study also dived into the characterization of interface defects at the P3HT/CdS junction, involving modifications to the electron affinity of P3HT. Additionally, the impact of metal work function variations was also investigated analyzing at each case critical parameters such as open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (FF), power conversion efficiency (PCE) and quantum efficiency. The results demonstrate that optimization of these parameters has the potential to elevate solar cell efficiency to 18%. These simulation findings offer valuable insights for comparative analysis and a deeper understanding of the challenges encountered in experimental research.

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.

Poole-Frenkel conduction in CdS single-layered and CdS/SnS2 heterojunction electrode system

In this communication, the prevalence of Poole-Frenkel conduction mechanism in two distinct semiconductor systems, CdS single-layered and CdS/SnS2 heterojunction electrode systems, is reported. X-ray diffraction (XRD) exhibits the formation of CdS quantum dots (QDs). A High resolution transmission electron microscopy (HRTEM) shows a discrete particle distribution of SnS2, tends to assemble into nanosheets. Poole-Frenkel conduction arises due to the trap distribution of CdS dots, modified by SnS2 sheets. Furthermore, the formation of heterojunctions with SnS2 shows promising enhancement in charge transport, characterized by reduced trap density and improved conductivity compared pristine CdS. The findings provide valuable insights into the fundamental charge transport processes in CdS/SnS2 system and offer potential avenues for optimizing the performance of electronic devices.

Fluorescent Nanocomposites of Cadmium Sulfide Quantum Dots and Polymer Matrices: Synthesis, Characterization, and Sensing Application

Fluorescent materials for sensing have gained attention for the visual detection of different substances as metals and pesticides for environmental monitoring. This work presents fluorescent nanocomposites in solution, film, and paper obtained without capping and stabilizing agents, coming from quantum dots of cadmium sulfide (CdS QDs) and anionic–cationic polymer matrices. Fluorescent films were formed by casting and fluorescent paper by impregnation from the solutions. The optical properties of CdS QDs in solution showed absorption between 418 and 430 nm and a maximum emission at 460 nm. TEM analysis evidenced particle size between 3 and 6 nm and diffraction patterns characteristic of CdS nanocrystals. Infrared spectra evidenced changes in the wavenumber in the fluorescent films. The band gap values (2.95–2.82 eV) suggested an application for visible transmitting film. Fluorescent solutions by UV-vis and fluorescence evidenced a chemical interaction with glyphosate standard between 1 and 100 µg/mL concentrations. The analysis of red, green, and blue color codes (RGB) evidenced a color response of the fluorescent paper at 10 and 100 µg/mL, but the fluorescent films did not show change. Nanocomposites of chitosan and pectin, in solution and on paper, exhibited a behavior “turn-on” sensor, while carboxymethylcellulose had a “turn-off” sensor. This methodology presents three fluorescent materials with potential applications in visual sensing.

Sonochemical synthesis of mesoporous ZnyCd1-yS quantum dots: Composition-dependent optical, electrical, dielectric, and hydrogen-generation characteristics

Mesoporous ZnyCd1-yS quantum dots (QDs) with mixed cubic–hexagonal phases prepared by sonochemical technique at varying Zn content. Incorporating Zn ions in the CdS lattice reduced the crystalline size and enhanced the corresponding surface areas at increasing Zn contents. The increase of Zn content in ZnyCd1-yS QDs increased the bandgap from 2.52 eV to 3.83 eV and enhanced the corresponding Urbach energy from 72 meV to 279 meV. ZnyCd1-yS QDs exhibited small electrical activation energies ranging from 249 mV to 361 mV. The effect of Zn content on the catalytic activity of ZnyCd1-yS QDs toward hydrogen production through NaBH4 hydrolysis was investigated at different temperatures. Ternary alloys ZnCdS QDs exhibited higher catalytic activity than pure ZnS and CdS QDs, with Zn0.5Cd0.5S QDs displaying the highest hydrogen generation rate of 96 mL∙min−1∙g−1. The increase of reaction temperature from 30°C to 60°C enhanced the rate constant of hydrogen production from 0.071 to 0.36 min−1. Based on the pseudo-first-order equation, the estimated apparent activation energy of Zn0.5Cd0.5S QDs was 45.3 kJ∙mol−1. Overall, the obtained results underscored the potential of ZnyCd1-yS QDs as promising catalysts for hydrogen generation.

Memristive behaviour of Al/rGO-CdS/FTO device at different temperatures: A MATLAB-integrated study

In the present work, a comprehensive study is carried out to investigate the memristive behaviour of reduced graphene oxide (rGO) conjugated cadmium sulphide quantum dot (CdS QD) nanocomposites (rGO-CdS), offering insights into their dynamic response under varying thermal conditions. The study integrates experimental analysis with MATLAB simulation to provide a detailed understanding of the complex interplay between different operating temperature (300K, 350K, 400K, and 450K) and memristive behavior in rGO-CdS nanocomposites. Different structural and chemical characterizations were carried out which confirms the formation of rGO-CdS nanocomposites. A sandwich structured device was fabricated with the synthesized rGO-CdS nanocomposites using Aluminum (Al) as top and Fluorine doped tin oxide (FTO) as bottom electrode. The influence of operating temperature on hysteresis behaviour of the fabricated Al/rGO-CdS/FTO device was investigated using Keithley 2450 source meter by sweeping a direct current (dc) voltage (−5 V → 5 V → −5 V). Notably, we observe a positive temperature coefficient in the device current, with maximum and minimum recorded current of |1.29mA| and |0.66mA| at 450K and 300K respectively. The current-voltage (I-V) behavior observed in the device reveals that in the low resistance state (LRS), conduction is dominated by bulk-limited mechanisms. However, in the high resistance state (HRS), conduction involves contributions from both Schottky barriers and the Pool-Frenkel effect. A MATLAB based linear drift model was used to simulate the device responses at different temperatures using the experimental data. The study provides first comprehensive analysis of temperature dependent hysteresis behaviour of Al/rGO-CdS/FTO device, integrating MATLAB simulation to glean valuable insights into its operation and possible applications as memristive material across different temperature regimes.

Long-lived carriers-promoted photocatalytic deuteration of halides with D2O as the deuterium source over Cu doped quantum dots

Deuterium labeling is a highly valuable yet challenging subject of research in various scientific fields. Conventional deuteration methods often involve harsh reaction conditions and suffer from limited reactivity and selectivity. Herein, we report a visible light–driven C–X (X = halogen) to C–D (D = deuterium) exchange strategy over copper-doped cadmium sulfide quantum dots (Cu-CdS QDs) under mild conditions, eliminating the need for noble metal catalysts and expensive deuterium sources. The conversion of aryl halides into deuterated products using Cu-CdS QDs reaches up to 99%, which is four times higher than that achieved using pristine CdS QDs. The substantial enhancement in the photocatalytic activity of the QDs can be primarily attributed to the generation of long-lived charge carriers (approximately 6 μs) induced by Cu doping. Mechanistic studies reveal that the Cu dopants considerably retard the recombination of photoinduced carriers by creating intermediate energy levels that serve as hole trapping centers in CdS QDs, thereby improving the electron utilization efficiency in energetically demanding photoreduction reactions. Additionally, the introduction of Cu increases the energy offset between the conduction band of CdS QDs and molecular acceptors, facilitating the electron transfer process. Upon visible light irradiation, a series of aryl halides can be efficiently converted into the desired deuterated compounds using D2O as the deuterium source. This work demonstrates that regulating charge carrier dynamics in ultrasmall QD-based photocatalysts is a promising strategy for promoting organic transformations.

Synthesis and Characterization of CdS and Sr-Doped CdS Quantum Dots: Impedance Analysis for Nano-Tuned Electronic Applications

This study reports the synthesis and comprehensive characterization of cadmium sulfide (CdS) and strontium-doped CdS quantum dots (QDs) using a straightforward chemical precipitation method. N, N-Dimethylformamide served as the stabilizing agent, while specific metal precursors facilitated the formation of the nanostructures. The incorporation of strontium into the CdS matrix aimed to enhance the electronic properties of the quantum dots. Energy Dispersive X-ray Analysis (EDAX) confirmed the successful doping of Sr into the CdS QDs. X-ray Diffraction (XRD) analysis verified the high-crystallinity of the synthesized quantum dots, with the mean crystal sizes determined to be 3.18 nm for pure CdS and 3.99 nm for Sr-doped CdS (2mM and 4mM concentrations). Impedance spectroscopy was utilized to study the frequency-dependent electrical properties of the QDs at room temperature, revealing significant variations in impedance with frequency. The results demonstrated that both pure and Sr-doped CdS QDs exhibit capacitive admittance, which is indicative of their potential application in nano-tuned electronic devices. The ability to fine-tune the resonant frequency by controlling the size and doping level of the quantum dots presents a significant advantage for their use in advanced electronic applications. The study highlights the promising application of CdS and Sr-doped CdS quantum dots in the development of high-performance, frequency-tunable nanoscale electronic devices.

Boosting Photocatalytic CO2 Methanation through Interface Fusion over CdS Quantum Dot Aerogels.

In the field of photocatalytic CO2 reduction, quantum dot (QD) assemblies have emerged as promising candidate photocatalysts due to their superior light absorption and better substrate adsorption. However, the poor contacts within QD assemblies lead to low interfacial charge transfer efficiency, making QD assemblies suffer from unsatisfactory photocatalytic performance. Herein, a novel approach is presented involving the construction of strongly interfacial fused CdS QD assemblies (CdS QD gel) for CO2 reduction. The novel CdS QD gel demonstrates outstanding photocatalytic performance for CO2 methanation, achieving a CH4 generation rate of ≈296 µmol g-1 h-1, with a selectivity surpassing 76% and an apparent quantum yield (AQY) of 1.4%. Further investigations reveal that the robust interfacial fusion in these CdS QDs not only boosts their ability to absorb visible light but also significantly promotes charge separation. The present work paves the way for utilizing QD gel photocatalysts in realizing efficient CO2 reduction and highlights the critical role of interfacial engineering in photocatalysts.

Large-scale continuous synthesis of CdS quantum dots using an impinging jet mixer

Quantum dots (QDs) have gained significant attention as next-generation display materials due to their high color purity, narrow emission wavelength, and extended lifespan compared to organic materials. However, the conventional batch process hinders their large-scale production due to the need for re-optimization of the reaction process when increasing the size of the reactor. In this study, we demonstrated the continuous synthesis method for CdS QDs using an impinging jet mixer, enabling large-scale production even without heating and continuous flow of nitrogen during the rapid nanoprecipitation of CdS QDs. The impinging jet mixer was prepared using conventional tube fittings and tubings, simplifying the fabrication process. Through this continuous synthesis method, we achieved a high nanoparticle production rate of 5.154 g/min which is relevant to 2.7 tons/year when the Reynolds number (Re) was set at 300. The synthesized CdS QDs were characterized using various analytical techniques, confirming their high quality and uniformity. This scalable production technique paves the way for the efficient and reliable synthesis of diverse QDs with potential use in displays, solar cells, biosensors, lighting, and optoelectronics.

Detection of Escherichia coli based on CdS QDs nanomarkers and its application in food hygiene and safety

With the continuous exposure of major food safety issues in recent years, food safety has become the focus of people’s attention. As a widely distributed bacterium, excessive levels of Escherichia coli in food may cause gastrointestinal discomfort symptoms, as well as adverse consequences such as food poisoning, acute gastroenteritis, food allergies, and gastric ulcers. Therefore, to ensure food safety and achieve rapid detection of E. coli, this study uses CdS quantum dots (QDs) nanomarkers to detect E. coli in water. Moreover, electrochemical square wave voltammetry is used to determine the relationship between Cadmium (Cd) ion concentration and E. coli concentration in the complex after enzyme-linked immunosorbent reaction. The experiment showed that the average particle size of CdS QDs nanoparticles was 5 nm and they had good biocompatibility. The current magnitude of electrochemical square wave voltammetry was positively correlated with the concentration of Cd ions and E. coli. When the concentration of E. coli was 50-1.0 × 105cfu/mL, its concentration was linearly positively correlated with the magnitude of the current, with a linear correlation coefficient of 0.9873. Compared to the flat plate counting method, its relative error did not exceed 10%, and in addition, the detection time was only 2 h. The above results indicate that CdS QDs nanomarkers can achieve rapid detection of E. coli, effectively improve the detection sensitivity of E. coli, and weaken non-specific adsorption.

Precise Optical Fiber-Based Ammonia Sensor Using CdS Quantum Dots Decorated with ZnO at Heterointerface

Precise Optical Fiber-Based Ammonia Sensor Using CdS Quantum Dots Decorated with ZnO at Heterointerface

Extremely Long-Lived Charge Donor States Formed by Visible Irradiation of Quantum Dots.

Using cyclic voltammetry under illumination, we recently demonstrated that CdS quantum dots (QDs) form charge donor states that live for at least several minutes after illumination ends, ∼12 orders of magnitude longer than expected for free carriers. This time scale suggests that the conventionally accepted mechanism of charge transfer, wherein charges directly transfer to an acceptor following exciton dissociation, cannot be complete. Because of these long time scales, this unconventional pathway is not readily observed using time-resolved spectroscopy to probe charge transfer dynamics. Here, we investigated the chemical nature of these charge donor states using cyclic voltammetry under illumination coupled with NMR spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and optical spectroscopy. Our data reveal that charges are stored locally rather than as free carriers, and the number of charges stored is dependent on the QD surface ligation and stoichiometry. Altogether, our results confirm that electrons are stored at ligated surface Cd, these sites are competent charge donors, and this storage is charge balanced by X-type ligand desorption. We found that charge storage occurs in every QD system studied, including CdS, CdSe, and InP capped with carboxylate and phosphonate ligands.

CRISPR-Enhanced Photocurrent Polarity Switching for Dual-lncRNA Detection Combining Deep Learning for Cancer Diagnosis.

Abnormal expression in long noncoding RNAs (lncRNAs) is closely associated with cancers. Herein, a novel CRISPR/Cas13a-enhanced photocurrent-polarity-switching photoelectrochemical (PEC) biosensor was engineered for the joint detection of dual lncRNAs, using deep learning (DL) to assist in cancer diagnosis. After target lncRNA-activated CRISPR/Cas13a cleaves to induce DNAzyme bidirectional walkers with the help of cofactor Mg2+, nitrogen-doped carbon-Cu/Cu2O octahedra are introduced into the biosensor, producing a photocurrent in the opposite direction of CdS quantum dots (QDs). The developed PEC biosensor shows high specificity and sensitivity with limits of detection down to 25.5 aM for lncRNA HOTAIR and 53.1 aM for lncRNA MALAT1. More importantly, this platform for the lncRNA joint assay in whole blood can successfully differentiate cancers from healthy people. Furthermore, the DL model is applied to explore the potential pattern hidden in data of the established technology, and the accuracy of DL cancer diagnosis can acquire 93.3%. Consequently, the developed platform offers a new avenue for lncRNA joint detection and early intelligent diagnosis of cancer.

CdS quantum dots modified two-dimensional MXene photocatalytic membrane for efficient removal of organic dyes from aquatic systems

MXene, a novel two-dimensional (2D) material, has been applied for the removal of dye molecules from wastewater; owing to its ability to stack into unique interlayer permeation channels. However, the narrow interlayer permeation channels of MXene limit its high permeability, and the dye contaminants tend to block the channels on the membrane surface as well as between the laminae. In view of this, CdS quantum dots (QDs) were incorporated with photocatalytic ability into the MXene channels, and the fabricated CdS QDs@MXene/PVDF photocatalytic composite membrane had high separation efficiency by using PVDF polymer as the support layer. The results manifested that; the CdS QDs were homogeneously dispersed in the MXene separation layer, and the introduction of CdS QDs optimized the interlayer permeation channels of MXene, with permeate flux of 502.6 L·m−2·h−1. The composite membrane exhibited an excellent removal of Congo red and Rhodamine B (CR and Rh B) dyes under the coupling of membrane separation and photocatalytic process, with the optimal removal ratio of 97.3 % for CR and 98.5 % for Rh B, respectively. Moreover, the CdS QDs endowed the membrane with self-cleaning ability, superior permeability and selectivity under five consecutive photocatalytic cycles, demonstrating the great in-situ resistance to contamination. After five intermittent cycles, the dye retention rate still exceeded 90 % and the permeate flux reached 388.0 L·m−2·h−1. This study provides an exceptional reference for quantum dots modified two-dimensional MXene membranes.

Potential-Resolved Ratio Electrochemiluminescence Biosensor Based on Perylene Diimide-MOF and DNA Nanoflowers-CdS Quantum Dots for Detection of Dual Targets.

BRCA1 gene and carcinoembryonic antigen (CEA) are important markers of breast cancer, so accurate detection of them is significant for early detection and diagnosis of breast cancer. In this study, a potential-resolved ratio electrochemiluminescence (ECL) biosensor using perylene diimide (PDI)-metal-organic framework and DNA nanoflowers (NFs)-CdS quantum dots (QDs) was constructed for detection of BRCA1 and CEA. Specifically, PDI-MOF and CdS QDs can generate potential-resolved intense ECL signals only using one coreactant, so the detection procedure can be effectively simplified. PDI-MOF was first attached to the electrode by graphene oxide, and the dopamine (DA) probe was linked to quench the ECL signal by DNA hybridization. In the presence of target BRCA1, it can form a bipedal DNA walker, so the quenching molecules (DA) were detached from the electrode via the walker amplification process aided by Mg2+, so that the PDI signal at -0.25 V was restored for the BRCA1 assay. Moreover, CdS QDs@DNA NFs as amplified signal probes were formed by self-assembly, and the target CEA-amplified product introduced the CdS QDs@DNA NFs to the electrode, so the QD ECL signal at -1.42 V was enhanced, while the ECL signal of PDI is unchanged; thus, CEA detection was achieved by the ratio value between them. Therefore, the detection accuracy is guaranteed by detection of two cancer markers and a ratio value. This biosensor has a great contribution to the development of new ECL materials and a novel ECL technique for fast and efficient multitarget assays, showing great significance for the early monitoring and diagnosis of breast cancer.

CdS Quantum Dot Gels as a Direct Hydrogen Atom Transfer Photocatalyst for C-H Activation.

Here, we report CdS quantum dot (QD) gels, a three-dimensional network of interconnected CdS QDs, as a new type of direct hydrogen atom transfer (d-HAT) photocatalyst for C-H activation. We discovered that the photoexcited CdS QD gel could generate various neutral radicals, including α-amido, heterocyclic, acyl, and benzylic radicals, from their corresponding stable molecular substrates, including amides, thio/ethers, aldehydes, and benzylic compounds. Its C-H activation ability imparts a broad substrate and reaction scope. The mechanistic study reveals that this reactivity is intrinsic to CdS materials, and the neutral radical generation did not proceed via the conventional sequential electron transfer and proton transfer pathway. Instead, the C-H bonds are activated by the photoexcited CdS QD gel via a d-HAT mechanism. This d-HAT mechanism is supported by the linear correlation between the logarithm of the C-H bond activation rate constant and the C-H bond dissociation energy (BDE) with a Brønsted slope α=0.5. Our findings expand the currently limited direct hydrogen atom transfer photocatalysis toolbox and provide new possibilities for photocatalytic C-H activation.

CdS Quantum Dot Gels as a Direct Hydrogen Atom Transfer Photocatalyst for C−H Activation

AbstractHere, we report CdS quantum dot (QD) gels, a three‐dimensional network of interconnected CdS QDs, as a new type of direct hydrogen atom transfer (d‐HAT) photocatalyst for C−H activation. We discovered that the photoexcited CdS QD gel could generate various neutral radicals, including α‐amido, heterocyclic, acyl, and benzylic radicals, from their corresponding stable molecular substrates, including amides, thio/ethers, aldehydes, and benzylic compounds. Its C−H activation ability imparts a broad substrate and reaction scope. The mechanistic study reveals that this reactivity is intrinsic to CdS materials, and the neutral radical generation did not proceed via the conventional sequential electron transfer and proton transfer pathway. Instead, the C−H bonds are activated by the photoexcited CdS QD gel via a d‐HAT mechanism. This d‐HAT mechanism is supported by the linear correlation between the logarithm of the C−H bond activation rate constant and the C−H bond dissociation energy (BDE) with a Brønsted slope α=0.5. Our findings expand the currently limited direct hydrogen atom transfer photocatalysis toolbox and provide new possibilities for photocatalytic C−H activation.

A self-powered photoelectrochemical and non-enzymatic glucose sensor based on ERGO/ZnONWs/CdS photoanode

We have developed an efficient, self-powered, non-enzymatic photoelectrochemical (PEC) glucose sensor operating in the visible spectrum. The sensor is based on electrochemically reduced graphene oxide (ERGO) and zinc oxide (ZnO) nanowalls (NWs) decorated with cadmium sulfide (CdS) quantum dots (QDs). We used a one-pot electrochemical process to grow vertically aligned ZnONWs on ERGO, followed by using the sequential ionic layer adsorption and reaction (SILAR) technique to decorate the ZnONWs with CdS QDs. The resulting ERGO/ZnONWs/CdS photoelectrode exhibits a three-dimensional hierarchical morphology, providing a large surface area for enhanced surface-substrate interactions and increased optical path length, leading to high absorptivity at visible light. Under one solar light illumination without a bias voltage, the electrode generated a significantly higher photocurrent density (1150 µAcm-2) in the presence of glucose (15.00 mM) than in the absence of glucose (150 µAcm-2). As a PEC glucose sensor, the ERGO/ZnONWs/CdS photoelectrode demonstrated two linear correlations in the glucose concentration range of 0.01–1.00 mM and 1.00–15.00 mM. The sensor has 430.06 and 25.75 µA cm-2mM-1 sensitivities and a low detection limit (1.1 µM). This novel visible light-mediated self-powered electrochemical sensing platform is cost-effective, reproducible, and stable for non-enzymatic glucose detection.