CdS QD Research Articles

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.

Photocurrent switchable dual-target bioassay: Signal distinction and interface reconfiguration via pH-responsive triplex DNA programming

Most multiplexed photoelectrochemical (PEC) sensors require additional instrumentation and cumbersome electrode modification and surface partitioning, which limits their portability and instrument miniaturization. Herein, a pH-responsive programmable triple DNA nanomachine was developed for constructing a reconfigurable multiplex PEC sensing platform. By programming the base sequence, T-A·T-riched triple DNA was designed to construct integrated nano-controlled release machine (INCRM) for simultaneous recognition of multiple targets. The INCRM enables to recognize two targets in one step, and sequentially separate the signal labels by pH adjustment. The detached signal label catalyzes glucose to produce gluconic acid, causing the C-riched DNA fold into a triple structure on the electrode surface. As a result, one target can be detected relying on the enhanced photocurrent due to accelerated electron transfer between the CdS QD labeled at the end of C-riched DNA and the electrode. The triplex DNA dissociation in pH 7.4 buffer reconfigures the electrode interface, which can be continued to detect another target. The feasibility of the multiplexed sensor is verified by the detection of extensively coexisting antibiotics enrofloxacin (ENR) and ciprofloxacin (CIP). Under the optimal conditions, wide linear range (10 fg/mL ∼ 1 μg/mL) and low detection limit (3.27 fg/mL and 9.60 fg/mL) were obtained. The pH-regulated programmable triplex DNA nanomachine-based sensing platform overcomes the technical difficulties of conventional multiplexed PEC assay, which may open the way for miniaturization of multiplexed PEC sensors.

A label-free photoelectrochemical biosensor for silver ions based on Zn-Co doped C and CdS QD nanomaterials.

A sensitive photoelectrochemical (PEC) biosensor for silver ions (Ag+) was developed based on Zn-Co doped C and CdS quantum dot (CdS QD) nanomaterials. Hydrophobic modified sodium alginate (HMA), which could stabilize and improve the PEC performance of CdS QDs, was also used for the construction of PEC sensors. Especially, Zn-Co doped C, CdS QDs and HMA were sequentially modified onto an electrode surface via the drop-coating method, and a C base rich DNA strand was then immobilized onto the modified electrode. As the C base in DNA specifically recognized Ag+, it formed a C-Ag+-C complex in the presence of Ag+, which created a spatial steric hindrance, resulting in a reduced PEC response. The sensing platform is sensitive to Ag+ in the range of 10.0 fM to 0.10 μM, with a limit of detection of 3.99 fM. This work offers an ideal platform to determine trace heavy metal ions in environmental monitoring and bioanalysis.

Carbon dots-cadmium sulfide quantum dots nanocomposite for 'on-off' fluorescence sensing of chromium(vi) ions.

This work involves fluorescent probe which is composed of carbon dots (CD) and cadmium sulfide quantum dots (CdS QD) for the sensitive and selective fluorescence detection of chromium(vi) ions. The blue fluorescent carbon dots were synthesized by hydrothermal method from natural precursor apricot. The carbon dots-cadmium sulfide quantum dots (CD-CdS QD) nanocomposite was synthesized and all as-synthesized products were characterized using different characterization techniques. It showed white fluorescence under UV light which was quenched selectively in the presence of chromium(vi) ions due to the inner filter effect (IFE). The linear decrease in the white fluorescence was observed in the concentration range 2-120 μM of chromium(vi) ions with the limit of detection 2.07 μM. This is novel probe for the sensitive, selective and rapid detection of chromium(vi) ions.

Comparison of effect of CdS QD and ZnS QD and their corresponding salts on growth, chlorophyll content and antioxidative capacity of tomato

When applied in the same concentration to tomato plants, cadmium sulfate (CdSO4) and zinc sulfate (ZnSO4) were transported from soil to roots and from roots to shoots more readily than their nano counterparts: cadmium sulfide quantum dots (CdS QD) and zinc sulfide quantum dots (ZnS QD). Compared to the CdS QD, he higher rate of transport of CdSO4 resulted in a greater negative effect on growth, chlorophyll content, antioxidant properties, lipid peroxidation and activation of antioxidant defence systems. Although ZnSO4 was transported more rapidly than ZnS QD, the overall effect of Zn addition was positive (increase in total plant mass, stem length, antioxidant content and decrease in lipid peroxidation). However, these effects were more pronounced in the case of ZnS QD, suggesting that the mechanisms underpinning the activity of ZnS QD and ZnSO4 were different. Thus, the risk of phytotoxicity and food chain transfer of the two elements depended on their form (salt or nanoform), and consequently their effects on plants’ growth and physiology were different.

Soft ferromagnetic effect in FePc/CdS hybrid diluted magnetic organic/inorganic quantum dots

Manipulating magnetic interactions in diluted magnetic quantum dots (DMQDs) is a fundamental research field due to the potential for developing robust magnetic semiconducting materials that can operate effectively in various environmental conditions. Here we design a new class of DMQDs via hybridization of inorganic CdS QDs with organic iron phthalocyanine (FePc) molecules. By a combination of X-ray photoemission, Mӧssbauer spectroscopies, and vibrating sample magnetometry, we demonstrate that FePc molecules alter the original diamagnetic nature of CdS QDs. They turn them into room-temperature soft-ferromagnets, while preserving the CdS QD structure from further oxidation in a more efficient way than the standard Fe doping of CdS QDs. These hybrid materials open up new possibilities for the design of DMQDs of tunable and robust magnetism for optomagnetic and spintronic applications.

Semiconducting CdS quantum dots as a guest in a four ring bent-core nematic medium: modified dielectric and elastic properties

The nematic phase of the bent-core family proves to be particularly fascinating due to its distinct properties in comparison to its calamitic counterpart. Here we revealed after the dispersion of semiconducting CdS QD an achiral unsymmetrical (4′-fluoro phenyl azo) phenyl-4-yl 3-[N-(4′-n-hecyloxy two hydroxybenzylidene)amino]-2-methylbenzoate (6-2M-F) a bent-core nematic (BCN) liquid-crystalline medium made of bent-shaped molecules with short cores and low bend angles. These molecules are on the cusp between conventional bent-core molecules and rod-like molecules, with characteristics somewhere in between, resembling hockey sticks. The threshold voltage dielectric permittivity and elastic constants of pure BCN have been considerably influenced by semiconductor nanoparticles. The threshold voltage of nano-disperse BCN has decreased with QD doping, and we know that the low operation voltage is one of the key considerations in the development of mobile liquid crystal display technology. Similar to other BCNs with smectic-like clusters previously described, the elastic anisotropy for 6-2M-F is negative; however, the insertion of CdS QDs causes the anisotropy to become very positive (bend elastic constant > splay elastic constant ). While the parallel component of permittivity has declined with doping, the perpendicular component of permittivity has increased, leading to a considerable reduction in dielectric anisotropy in the nanocomposite, which implies the effect on nematic ordering due to the interaction between CdS QDs and the LC molecules.

A novel DNA-quantum dot nanostructure electrochemiluminescence aptamer sensor by chain reaction amplification for rapid detection of trace Cd2.

This work proposes a new enzyme-free electrochemiluminescence (ECL) sensing platform based on a novel DNA-quantum dot (QD) nanostructure and hybridization chain reaction (HCR) amplification for the trace detection of Cd2+. First, the Cd2+ aptamer triggers the HCR amplification circuit, so abundant biotin-labeled DNAs are introduced to the electrode, and then biotin as a linker specifically captures a large number of streptavidin (SA)-CdS QD complexes, showing very high ECL signals. After the present Cd2+ binds to its aptamer on the electrode, it causes the linear DNA structure loaded with a large number of QDs to break away from the electrode, resulting in a significantly decreased ECL response. This method combines the HCR-amplified DNA structure-QD signal with the specificity of the biotin-avidin reaction, enabling the rapid detection of Cd2+ in complex water. Therefore, this sensor provides a novel and competitive strategy for detecting heavy metal ions in actual samples, which extends its application to practical settings, such as environmental monitoring and biomedical diagnostics.

Label-Free Ratiometric Electrochemiluminescent (ECL) Immunosensor for the Determination of Prostate Specific Antigen (PSA) in Serum

A spatial- and potential-resolved ratiometric electrochemiluminescent (ECL) immunosensor was developed for prostate specific antigen detection in a label-free mode. CdS quantum dots (CdS QDs) and luminol-gold nanoparticles (luminol-Au NPs) were the potential-resolved electrochemiluminescence emitters and H2O2 was used as a co-reactant. The cathodic signal from the CdS QD electrode served as the working signal and the anodic signal from luminol-Au NPs as the reference. For prostate specific antigen detection, several concentrations of prostate specific antigen were immobilized on the CdS QDs modified electrode and a fixed concentration of the prostate specific antigen was modified on the luminol-Au NPs modified electrode. The prostate specific antigen levels were quantified by the electrochemiluminescence signal ratio of the cathodic and anodic (ECLcathodic/ECLanodic). Under the optimized conditions, the ratio of the cathodic and anodic signals (ECLcathodic/ECLanodic) had a linear relationship with the logarithm of (C, g mL−1) of prostate specific antigen concentration from 1.0 × 10−11 to 1.0 × 10−7 g mL−1. The detection limit was 5.0 × 10−12 g mL−1. Prostate specific antigen was determined in human serum and the recoveries were from 80.0% to 107.0%. The label-free electrochemiluminescence immunosensor offers simplicity and reliability for human serum with potential for clinical application.

Engineered Nanomaterial Exposure Affects Organelle Genetic Material Replication in Arabidopsis thaliana.

Mitochondria and chloroplasts not only are cellular energy sources but also have important regulatory and developmental roles in cell function. CeO2, FeOx ENMs, ZnS, CdS QDs, and relative metal salts were utilized in Murashige-Skoog (MS) synthetic growth medium at different concentrations (80-500 mg L-1) and times of exposures (0-20 days). Analysis of physiological and molecular response of A. thaliana chloroplasts and mitochondrion demonstrates that ENMs increase or decrease functionality and organelle genome replication. Exposure to nanoscale CeO2 and FeOx causes an 81-105% increase in biomass, whereas ZnS and CdS QDs yielded neutral or a 59% decrease in growth, respectively. Differential effects between ENMs and their corresponding metal salts highlight nanoscale-specific response pathways, which include energy production and oxidative stress response. Differences may be ascribed to ENM and the metal salt dissolution rate and the toxicity of the metal ion, which suggests eventual biotransformation processes occurring within the plant. With regard to specific effects on plastid (pt) and mitochondrial (mt) DNA, CdS QD exposure triggered potential variations at the substoichiometric level in the two organellar genomes, while nanoscale FeOx and ZnS QDs caused a 1- to 3-fold increase in ptDNA and mtDNA copy numbers. Nanoparticle CeO2 exposure did not affect ptDNA and mtDNA stoichiometry. These findings suggest that modification in stoichiometry is a potential morpho-functional adaptive response to ENM exposure, triggered by modifications of bioenergetic redox balance, which leads to reducing the photosynthesis or cellular respiration rate.

INFLUENCE OF TECHNOLOGICAL CONDITIONS OF SYNTHESIS ON THE FORMATION OF PHOTOLUMINESCENCE SPECTRA OF CdS QDs

Here are presented the results of influence of two parameters of synthesis process of quantum dots sulfide cadmium (CdS QD) on the spectrum luminescence, namely, the acid-base balance of the growth solution and the correlation of reaction components (cadmium and sulfur salts). Carried out the syntheses in which the pH solution was changed in the interval of values from 2 to 10. There were also synthesized CdS QD with different ratios of the initial components. The results obtained by evidence of the fact that the technological process has a significant impact on the formation of bands luminescence CdS QDs.

Photovoltaic study of TiO2 films sensitized with Cu2O and CdS QDs for applications in a solar cell

The effect of the Cu2O and CdS QD particles on the photoconversion efficiency of the TiO2 solar cell was analyzed. The Cu2O particles were synthesized using the chemical reduction method, and the CdS QDs were prepared using the SILAR method. The JV curves indicated that the photocurrent of the TiO2/ZnS solar cell was 0.04 ​mA/cm2, while the introduction of Cu2O particles in the TiO2/Cu2O/ZnS configuration showed that the cell exhibited a photocurrent forty times higher, of 1.82 ​mA/cm2. With the introduction of CdS QD in the following TiO2/Cu2O/CdS/ZnS and TiO2/CdS/ZnS/Cu2O solar cell configurations, the current increased to 5.34 ​mA/cm2 and 5.57 ​mA/cm2, respectively, being three times higher compared to TiO2/Cu2O/ZnS. Although the values of FF and Voc decreased in the TiO2 solar cells sensitized with Cu2O and CdS, probably due to the introduction of new defects, the photogenerated current increased significantly. These results lead to an improvement in photoconversion efficiency, η=0.38% for TiO2/Cu2O/CdS/ZnS and η ​= ​0.65% for TiO2/CdS/ZnS/Cu2O which is due to an increase in the absorption range. Cu2O particles contribute as a sensitizer probably improves the alignment of the conduction band between the different materials and the defect passivation effect of CdS on the surface of TiO2.

Diluted-CdS Quantum Dot-Assisted SnO2 Electron Transport Layer with Excellent Conductivity and Suitable Band Alignment for High-Performance Planar Perovskite Solar Cells.

An electron transport layer (ETL) with excellent conductivity and suitable band alignment plays a key role in accelerating charge extraction and transfer for achieving highly efficient planar perovskite solar cells (PSCs). Herein, a novel diluted-cadmium sulfide quantum dot (CdS QD)-assisted SnO2 ETL has been developed with a low-temperature fabrication process. The slight addition of CdS QDs first enhances the crystallinity and flatness of SnO2 ETLs so that it provides a promising workstation to obtain high-quality perovskite absorption layers. It also amazingly increases the conductivity of the SnO2 ETL by an order of magnitude and regulates the energy level matching between the SnO2 ETL and perovskite. These outstanding properties greatly accelerate the charge extraction and transfer. Thus, the MAPbI3-based PSCs with such a diluted-CdSQD-assisted SnO2 ETL achieve a maximum power conversion efficiency of 20.78% and obtain a better stability of devices in air. These findings testify the importance and potential of semiconductor QD modification on ETLs, which may pave the way for developing such composite ETLs for further enhancing photovoltaic performance of planar PSCs.

X-ray Photoelectron Spectroscopy Analysis of Chitosan-Graphene Oxide-Based Composite Thin Films for Potential Optical Sensing Applications.

In this study, X-ray photoelectron spectroscopy (XPS) was used to study chitosan–graphene oxide (chitosan–GO) incorporated with 4-(2-pyridylazo)resorcinol (PAR) and cadmium sulfide quantum dot (CdS QD) composite thin films for the potential optical sensing of cobalt ions (Co2+). From the XPS results, it was confirmed that carbon, oxygen, and nitrogen elements existed on the PAR–chitosan–GO thin film, while for CdS QD–chitosan–GO, the existence of carbon, oxygen, cadmium, nitrogen, and sulfur were confirmed. Further deconvolution of each element using the Gaussian–Lorentzian curve fitting program revealed the sub-peak component of each element and hence the corresponding functional group was identified. Next, investigation using surface plasmon resonance (SPR) optical sensor proved that both chitosan–GO-based thin films were able to detect Co2+ as low as 0.01 ppm for both composite thin films, while the PAR had the higher binding affinity. The interaction of the Co2+ with the thin films was characterized again using XPS to confirm the functional group involved during the reaction. The XPS results proved that primary amino in the PAR–chitosan–GO thin film contributed more important role for the reaction with Co2+, as in agreement with the SPR results.

Photoinduced charge transfer interaction between citrus limon extract passivated colloidal CdS with Methyl Violet & Beta Vulgaris dyes

Recently, use of different plant extracts for the green synthesis of CdS nanoparticles has appealed significant attention throughout the world. The components contained in antioxidant rich citrus fruits e.g. orange and lemon have attracted significant attention due to their chemical and biological properties. To date, the the synthesis of CdS nanoparticles using citrus limon extract as a surface functionalizing agent has not been explored. In the present study a reliable green synthesis method was developed by introducing Citrus Limon Extract (CLE) as a new surface functionalizing agent for the development of colloidal CdS quantum dots (CCQDs). Photo induced interaction between CLE functionalized colloidal CdS quantum dots with Methyl Violet (MV) & Beta Vulgaris (BV) dyes have been explored. Dyes adsorption on CdS surface results in quenching of dye molecules emission intensity. UV–Visible spectroscopic studies evidently reveal idiosyncratic photo-induced charge transfer interaction of CdS QDs with Methyl Violet (MV) dye noticeably differs from its interaction with Beta Vulgaris (BV) dye. Beta vulgaris dye shows H-aggregation on CLE capped CdS QD surface. Photo-induced quenching of both the dyes attributed to electron (e-) transfer to the conduction band (CB) of CdS from the excited state of the dyes.

Effect of Mn doping in CdS quantum dot sensitized solar cells grown by SILAR method

The manganese-doped cadmium sulfide (Mn-doped CdS) quantum dots on titanium dioxide nanoparticles was fabricated using the successive ionic layer absorption and reaction (SILAR) method. The quantum dots were applied to photovoltaic cells. The mixing percentage of manganese in cadmium sulfide precursors was in the range of 1–20 mol%. The study of transport mechanisms and photovoltaic properties of the Mn-doping into CdS QD were investigated using a solar simulator (AM 1.5 G) and current–voltage (J-V) measurements in the dark and under illumination conditions (100 mW/cm2) at room temperature. The photovoltaic performance results indicate that Mn-doped in CdS ratio of 15 mol% exhibits the photovoltaic performance maximum convention efficiency (PCE) is 0.33%. The X-ray diffraction (XRD) patterns of Mn/CdS photoanodes show the nanoparticle average grain size in the range of 4–5 nm, which the formation of the nanoparticles was confirmed by scanning electron microscopy (SEM). The energy dispersion spectroscopy (EDS) shows that Mn is doped into the lattice of CdS QDs. The optical property of the quantum dots was investigated by UV–VIS absorption spectroscopy. The optical band gap was obtained and found to be 2.19 eV from Tauc's plot technique..

White Light Emitting CdS Quantum Dot Devices Coated with Layers of Graphene Carbon Quantum Dots

AbstractCadmium sulfide quantum dots (CdS QDs) are semiconductor nanoparticles having sizes in the order of nanometers. They are materials that have outstanding properties for down conversion applications. These nanostructures have been used in the fabrication of white light emitting diodes (WLEDs) in the last years. However, inhomogeneous deposition of CdS QD conversion materials allows unwanted UV light escape. In addition, low efficiency due to strong self-quenching effect, incompatibility between CdS QD solution/crystal polyester resin matrix and reabsorption are common problems that need to be solved. In this work, we try to address the incompatibility between the CdS QD solution/crystal polyester resin matrix by using a solvent exchange procedure. To block the unwanted UV-light escape, we coated our devices with a mixture of graphene carbon quantum dot (GCQD) solution/crystal polyester resin matrix. The QDs and the WLED prototypes were characterized by absorption and photoluminescence (PL) spectroscopy. The QDs embedded in the matrix shown a good homogeneous dispersion. On the other hand, the mixture shown a rapid solidification. These facts indicate a good compatibility between the CdS QDs and the crystal polyester resin. We also observed a considerable reduction of unwanted near UV-light. White light emission from WLED devices with common crystal polyester resin and low-cost materials has been achieved.

Cu1.8S@CuS composite material improved the photoelectric efficiency of cadmium-series QDSSCs

Abstract An efficient and newly-built strategy is demonstrated in this page to produce counter electrode, which contains two mixtures (Cu1.8S and CuS), for QDSSCs. Compared with those of Cu2S CE, the higher electrochemical activity and lower charge transfer resistance of solar cells equipped with Cu1.8S@CuS CE result in a prominent development in photovoltaic characteristics. All the η, Voc and FF exhibit remarkable improvements whether in CdS or Mn2+–CdS QD sensitization system. In CdS QD sensitization system, current–voltage curve results indicate that the η and Voc of cells with Cu1.8S@CuS-120 CE are 1.49 and 1.17 times higher than those with Cu2S CE, respectively. FF is increased from 0.32 to 0.40. Besides, in Mn2+–CdS QD sensitization system, the η and Voc of cells with Cu1.8S@CuS-120 CE are 1.52 and 1.15 times higher than those with Cu2S CE, respectively. Furthermore, FF is increased from 0.33 to 0.42. Electrochemical impedance testing results reveal that the QDSSCs prepared with composite Cu1.8S@CuS-120 CE have lower resistance qualities.

Proteomic Analysis Identifies Markers of Exposure to Cadmium Sulphide Quantum Dots (CdS QDs).

The use of cadmium sulphide quantum dot (CdS QD)-enabled products has become increasingly widespread. The prospect of their release in the environment is raising concerns. Here we have used the yeast model Saccharomyces cerevisiae to determine the potential impact of CdS QD nanoparticles on living organisms. Proteomic analyses and cell viability assays performed after 9 h exposure revealed expression of proteins involved in oxidative stress and reduced lethality, respectively, whereas oxidative stress declined, and lethality increased after 24 h incubation in the presence of CdS QDs. Quantitative proteomics using the iTRAQ approach (isobaric tags for relative and absolute quantitation) revealed that key proteins involved in essential biological pathways were differentially regulated over the time course of the experiment. At 9 h, most of the glycolytic functions increased, and the abundance of the number of heat shock proteins increased. This contrasts with the situation at 24 h where glycolytic functions, some heat shock proteins as well as oxidative phosphorylation and ATP synthesis were down-regulated. It can be concluded from our data that cell exposure to CdS QDs provokes a metabolic shift from respiration to fermentation, comparable to the situation reported in some cancer cell lines.

Effect of PbS quantum dot-doped polysulfide nanofiber gel polymer electrolyte on efficiency enhancement in CdS quantum dot-sensitized TiO2 solar cells

Quantum dot-sensitized solar cells (QDSSCs) are among the most promising low cost third generation solar cells. Semiconductor quantum dots have unique properties such as high molar extinction coefficients, tunable energy gap by the quantum confinement effect and the ability of multiple exciton generation. In this study, stable CdS QDSSCs were fabricated by using polysulfide liquid electrolyte and also by using cellulose acetate nanofiber-based gel electrolyte. Incorporation of PbS Q dots to the liquid or gel electrolyte showed a significant enhancement in solar cell efficiency. Under the simulated light of 100 mW cm−1 the efficiency of the polysulfide liquid electrolyte based CdS QD solar cells increased from 1.19% to 1.51% and the efficiency of the nanofibre gel electrolyte based CdS QD solar cells increased from 0.94% to 1.46% due to the incorporation of 5% (wt/wt) PbS Q dots into the respective electrolytes. The efficiency increase has been attributed to the increase in short circuit photocurrent density due to increased sulfide ion (S2−) conductivity evidently caused by indirect ionic dissociation facilitated by PbS QDs.