CdS Quantum Dots Research Articles

Hole-scavenging in photo-driven N2 reduction catalyzed by a CdS-nitrogenase MoFe protein biohybrid system

The light-driven reduction of dinitrogen (N2) to ammonia (NH3) catalyzed by a cadmium sulfide (CdS) nanocrystal‑nitrogenase MoFe protein biohybrid is dependent on a range of different factors, including an appropriate hole-scavenging sacrificial electron donor (SED). Here, the impact of different SEDs on the overall rate of N2 reduction catalyzed by a CdS quantum dot (QD)-MoFe protein system was determined. The selection of SED was guided by several goals: (i) molecules with standard reduction potentials sufficient to reduce the oxidized CdS QD, (ii) molecules that do not absorb the excitation wavelength of the CdS QD, and (iii) molecules that could be readily reduced by sustainable processes. Earlier studies utilized buffer molecules or ascorbic acid as the SED. The effectiveness of ascorbic acid as SED was compared to dithionite (DT), triethanolamine (TEOA), and hydroquinone (HQ) across a range of concentrations in supporting N2 reduction to NH3 in a CdS QD-MoFe protein photocatalytic system. It was found that TEOA supported N2 reduction rates comparable to those observed for dithionite and ascorbic acid. HQ was found to support significantly higher rates of N2 reduction compared to the other SEDs at a concentration of 50 mM. A comparison of the rates of N2 reduction by the biohybrid complex to the standard reduction potential (Eo) of the SEDs reveals that Eo is not the only factor impacting the efficiency of hole-scavenging. These findings reveal the importance of the SED properties for improving the efficiency of hole-scavenging in the light-driven N2 reduction reaction catalyzed by a CdS QD–MoFe protein hybrid.

Photocatalytic removal of imidacloprid pesticide from wastewater using CdS QDs passivated by CQDs containing thiol groups

Over the past decade, CdS QDs have become versatile semiconductors. Surface modification of CdS QDs has become an interesting case study, as it can eliminate surface defects and improve their photochemical properties. In this study, we report a new strategy of using carbon quantum dots containing a large number of thiol groups (CQDs-SH) as a passivating agent for the stabilization of CdS quantum dots (QDs). Various characterization techniques have clearly revealed that the CdS QDs have been successfully passivated by CQDs-SH. The photocatalytic performance of CQDs-SH/CdS QDs was investigated for the degradation of the insecticide imidacloprid from an aqueous solution. Parameters affecting the photodegradation process, including the light source, photocatalyst amount, initial concentration of the pollutant, radiation time, pH, oxidizing agent, and temperature, were investigated. Furthermore, the HPLC technique was applied to quantitatively analyze imidacloprid and its degradation products. The results of the HPLC analysis revealed that under simulated visible light at pH 9, imidacloprid scarcely existed after 90 min of irradiation (90.13% degradation). The LC–MS method was also used to detect the degradation products and investigate the mechanism of photodegradation of the pesticide. The results showed that the CQDs-SH/CdS QDs composite was a promising photocatalyst for the degradation of imidacloprid in wastewater.

Enhancement of Spontaneous Photon Emission in Inverse Photoemission Transitions in Semiconductor Quantum Dots.

Inverse photoemission (IPE) is a radiative electron capture process where an electron is transiently captured in the conduction band (CB) followed by intraband de-excitation and spontaneous photon emission. IPE in quantum dots (QDs) bypasses optical selection rules for populating the CB and provides insights into the capacity for electron capture in the CB, the propensity for spontaneous photon emission, intraband transition energies where both initial and final states are in the CB, and the generation of photons with frequencies lower than the bandgap. Here, we demonstrate using time-dependent perturbation theory that judicious application of electric fields can significantly enhance the IPE transition in QDs. For a series of CdSe, CdS, PbSe, and PbS QDs, we present evidence of field-induced enhancement of IPE intensities (188% for Cd54Se54), field-dependent control of emitted photon frequencies (Δω = 0.73 eV for Cd54Se54), and enhancement of light-matter interaction using directed Stark fields (103% for Cd54Se54).

Carbon sphere doped CdS quantum dots served as a dye degrader and their bactericidal behavior analysed with in silico molecular docking analysis.

We have employed a co-precipitation method to synthesize different concentrations of carbon spheres (CSs) doped with cadmium sulfide (CdS) quantum dots (QDs) for catalytic reduction and antibacterial applications. Various morphological and structural characterization techniques were used to comprehensively analyze the CS effect on CdS QDs. The catalytic reduction efficiency of CS-doped CdS QDs was evaluated using rhodamine B dye. The antibacterial efficacy was also assessed against the pathogenic microorganism Escherichia coli (E. coli), and substantial destruction in the inhibitory zone was measured. Finally, the synthesized CS-doped CdS QDs demonstrated favorable results for catalytic reduction and antibacterial applications. Computational studies verified the suppressive impact of these formed QDs on DNA gyrase and β-lactamase of E. coli.

A novel layered double hydroxide-based ternary nanocomposite for the effective photocatalytic degradation of rhodamine B.

Photocatalytic degradation of organic pollutants is a green and effective route of wastewater treatment. Zinc oxide was initially used for this purpose; however, calcined zinc/chromium layered double hydroxide (ZnCr-LDO) and cadmium sulfide quantum dots (CdSQDs)-based nanocomposites proved as superior alternatives. Herein, we report a green sonochemical method for the sol-gel fabrication of novel CdSQDs@ZnCr-LDO/ZnO ternary nanocomposite that exhibited exceptional photocatalytic activity for the degradation of rhodamine B dye (RhB), in wastewaters, under UV-A-irradiation. The features of the ternary nanocomposite were investigated using various physicochemical techniques, including XRD, SEM, TEM, EDX, XPS, BET, zeta potential, DRS, and PL measurements. The RhB dye % removal was 38.02, 40.2, and 98% using pristine ZnO, ZnCr-LDO and the ternary CdSQDs@ZnCr-LDO/ZnO-based nanomaterials, respectively, reflecting the superior ternary nanocomposite's photocatalytic activity that made it an excellent competitor to commonly reported photocatalysts. Additionally, an investigation was carried out to determine the key reactive species in the photocatalytic degradation of RhB, considering both scavenger's type and concentration. The prevailing mechanism was found to be the reductive photodegradation pathway. Furthermore, several models were utilized to describe the kinetics of photocatalytic performance of the ternary nanocomposite and a typical Z-scheme type-II photocatalytic heterojunction mechanism was inferred.

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.

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.

Bi-ligand-fabricated CdS quantum dots to photo-induce aqueous-phase aldol condensation for biomass-derived carbonyl compounds.

CdS QDs were fabricated using bi-ligands 11-sulfanylundecanoic acid and proline for photo-induced aqueous-phase aldol condensation of biomass-derived furfural compounds and ketones, and they displayed acceptable selectivity, activity and recycling properties for generation of a wide range of products with diverse applications. This work facilitates understanding the molecular-level design concepts of semiconductor photocatalysts.

Triplet energy transfer from quantum dots increases Ln(iii) photoluminescence, enabling excitation at visible wavelengths.

Europium(iii) complexes are promising for bioimaging because of their long-lived, narrow emission. The photoluminescence (PL) from europium(iii) complexes is usually low. Thus, the effective utilization of low-energy light >400 nm and enhancement of PL are long-standing goals. Here, we show for the first time that 1-naphthoic acid triplet transmitter ligands bound to CdS quantum dots (QDs) and europium(iii) complexes create an energy transfer cascade that takes advantage of the strong QD absorption. This is confirmed by transient absorption spectroscopy, which shows hole mediated triplet energy transfer from QDs to 1-NCA, followed by triplet transfer from 1-NCA to europium(iii) complexes with an efficiency of 65.9 ± 7.7%. Smaller CdS QDs with a larger driving force lead to higher triplet transfer efficiency, with Eu(iii) PL intensity enhanced up to 21.4 times, the highest value ever reported. This hybrid QD system introduces an innovative approach to enhance the brightness of europium complexes.

Probing surface interactions in CdSe quantum dots with thiocyanate ligands.

Surface chemistry dictates the optoelectronic properties of semiconductor quantum dots (QDs). Tailoring these properties relies on the meticulous selection of surface ligands for efficient passivation. While long-chain organic ligands boast a well-understood passivation mechanism, the intricacies of short inorganic ionic ligands remain largely unexplored. This study sheds light on the surface-passivation mechanism of short inorganic ligands, particularly focusing on SCN- ions on CdSe QDs. Employing steady-state and time-resolved infrared spectroscopic techniques, we elucidated the surface-ligand interactions and coordination modes of SCN--capped CdSe QDs. Comparative analysis with studies on CdS QDs unveils intriguing insights into the coordination behavior and passivation efficacy of SCN- ions on Cd2+ rich QD surfaces. Our results reveal the requirement of both surface-bound (strong binding) and weakly-interacting interfacial SCN- ions for effective CdSe QD passivation. Beyond fostering a deeper understanding of surface-ligand interactions and highlighting the importance of a comprehensive exploration of ligand chemistries, this study holds implications for optimizing QD performance across diverse applications.

Resonant tunneling in a colloidal CdS semiconductor quantum-dot single-electron transistor based on heteroepitaxial-spherical Au/Pt nanogap electrodes.

Semiconductor quantum dots (QDs) have unique discrete energy levels determined by the particle size and material. Therefore, they have potential applications as novel optical and electronic devices. Among those, colloidal group II-VI semiconductor quantum dots stand out for their facile synthesis and band gaps aligned with the visible light spectrum. However, the electrical characterization studies of an individual quantum dot necessitate the size of nanogap electrodes being equal to the size of the quantum dot, which has conventionally been evaluated using techniques such as scanning tunneling microscopy (STM) and nanogaps fabricated by electromigration. The complexity of device fabrication has restricted research in this area. Here, we present a pioneering approach for the electrical characterization of single-QD: heteroepitaxial-spherical (HS) Au/Pt nanogap electrodes. We fabricated transistors through chemisorption, an anchoring colloidal CdS QD (3.8 nm) between the HS-Au/Pt nanogap electrodes (gap separation: 4.5 nm). The resulting device functions as a quantum-dot single-electron transistor (QD-SET), showing resonant tunneling-an inherent characteristic of the QD. A steep current increase was observed at a negative voltage, apart from the theoretical single-electron tunneling current by Coulomb blockade phenomena, which agreed with the theoretical resonant tunneling current through a discrete energy level of the QD. This underscores the promise of HS-Au/Pt nanogap electrodes in realizing single-QD devices, offering a pathway toward unlocking their full potential.

The In Vitro Toxicity Profile of ZnS and CdS Quantum Dots in Polysaccharide Carriers (Starch/Chitosan).

Nanocomposites are an emerging technology for ensuring food safety and quality. Their unique properties, attributed to nanoparticle presence, facilitate the development of sophisticated sensors and biosensors for detecting harmful substances, microbial growth, and environmental changes in food products. Smart and/or active food packaging development also benefits from the use of nanocomposites. This packaging, or portions of it, provide active protection for its contents and serve as sensors to promptly, simply, and safely identify any detrimental changes in stored food, without elaborate techniques or analyses. Films made from potato starch and chitosan were produced and quantum dots of zinc sulfide (ZnS) and cadmium sulfide (CdS)were synthesized in them for this study. The presence and dimensions of the QDs (quantum dots) were examined with scanning electron microscopy (SEM) and ultraviolet-visible (UV-VIS) spectroscopy. The study aimed to establish the toxicity profile of a starch-chitosan bionanocomposite integrated with ZnS and CdS quantum dots. Cytotoxic and genotoxic features were assessed through cytogenetic instability assessments, consisting of the alkaline comet assay, erythrocyte micronucleus assay, and peripheral blood cell viability analysis of a laboratory mouse model.

Synthesis and characterization of Ag-doped CdS quantum dots for enhanced photovoltaic performance of quantum dot sensitized solar cells

In this work, Ag-doped and undoped CdS quantum dots (QDs) were prepared via successive ionic layer adsorption and reaction (SILAR) technique, followed by their characterization. The synthesized QDs were employed in the devices based on iodide/triiodide (I−/I3−) and polysulfide (Sx2−/S2−) electrolytes, while carbon (C) and platinum (Pt) were used as counter electrodes (CEs). The structural properties of the synthesized QDs were examined using X-ray diffraction (XRD), while to analyze the elemental composition of the samples, energy-dispersive X-ray (EDX) spectroscopy technique was employed. To study absorption properties, UV–Visible spectroscopy was performed. The influence of Ag on passivation of defects in CdS QDs was investigated via photoluminescence spectroscopy. Photovoltaic performance and impedance spectroscopic measurements on the fabricated QDSSCs were made under an AM1.5G illumination and dark, respectively. The photovoltaic studies on the devices revealed an increase of efficiency by 131 %, 161 %, 151 %, and 93 % for Ag–CdS QDs/Iodolyte/Pt, Ag–CdS QDs/Polysulfide/Pt, Ag–CdS QDs/Iodolyte/C, Ag–CdS QDs/Polysulfide/C type devices, respectively. The doped device with a polysulfide electrolyte and C as counter electrode (CE) revealed superior performance, exhibiting an efficiency of 1.72 %, followed by the doped polysulfide-based device with Pt as CE, revealing 1.67 % efficiency. The stability test conducted on the fabricated devices demonstrated a long-term stability for the doped device containing polysulfide electrolyte and C as CE, retaining 80 % of its initial efficiency for 12 days, and then falling to 0 % in 22 days. Moreover, the impedance spectroscopic measurements revealed lowest series resistance (Rs) and Series Capacitance (Cs) for the superior performance device.

Living Materials Based Dynamic Information Encryption via Light-Inducible Bacterial Biosynthesis of Quantum Dots.

Microbial biosynthesis, as an alternative method for producing quantum dots (QDs), has gained attention because it can be conducted under mild and environmentally friendly conditions, distinguishing it from conventional chemical and physical synthesis approaches. However, there is currently no method to selectively control this biosynthesis process in a subset of microbes within a population using external stimuli. In this study, we have attained precise and selective control over the microbial biosynthesis of QDs through the utilization of an optogenetically engineered Escherichia coli (E. coli). The recombinant E. coli is designed to express smCSE enzyme, under the regulation of eLightOn system, which can be activated by blue light. The smCSE enzymes use L-cysteine and Cd2+ as substrates to form CdS QDs. This system enables light-inducible bacterial biosynthesis of QDs in precise patterns within a hydrogel for information encryption. As the biosynthesis progresses, the optical characteristics of the QDs change, allowing living materials containing the recombinant E. coli to display time-dependent patterns that self-destruct after reading. Compared to static encryption using fluorescent QD inks, dynamic information encryption based on living materials offers enhanced security.

Living Materials Based Dynamic Information Encryption via Light‐Inducible Bacterial Biosynthesis of Quantum Dots

AbstractMicrobial biosynthesis, as an alternative method for producing quantum dots (QDs), has gained attention because it can be conducted under mild and environmentally friendly conditions, distinguishing it from conventional chemical and physical synthesis approaches. However, there is currently no method to selectively control this biosynthesis process in a subset of microbes within a population using external stimuli. In this study, we have attained precise and selective control over the microbial biosynthesis of QDs through the utilization of an optogenetically engineered Escherichia coli (E. coli). The recombinant E. coli is designed to express smCSE enzyme, under the regulation of eLightOn system, which can be activated by blue light. The smCSE enzymes use L‐cysteine and Cd2+ as substrates to form CdS QDs. This system enables light‐inducible bacterial biosynthesis of QDs in precise patterns within a hydrogel for information encryption. As the biosynthesis progresses, the optical characteristics of the QDs change, allowing living materials containing the recombinant E. coli to display time‐dependent patterns that self‐destruct after reading. Compared to static encryption using fluorescent QD inks, dynamic information encryption based on living materials offers enhanced security.

Arylation of Allylic C(sp3)–H Bonds Promoted by Single Nickel Atom-Decorated CdS Quantum Dots

Arylation of Allylic C(sp3)–H Bonds Promoted by Single Nickel Atom-Decorated CdS Quantum Dots

Sensitive detection of furazolidone and nitrofurantoin by fluorescent nanoprobe coated with 3-mercaptopropionic acid on CdS quantum dots

Cadmium sulfide quantum dots (CdS QDs) were synthesized with 3-mercaptopropionic acid (MPA) as protective agent, which were characterized by TEM, UV–vis, fluorescence, XRD and TGA. Based on the fluorescence quenching of 3-MPA-CdS QDs, the indirect methods for the determination of furazolidone (FZD) and nitrofurantoin (NFT) were established. The interaction between FZD/NFT and CdS QDs was investigated by using fluorescence, resonance light scattering, UV–vis and FT-IR. The analyses of Stern-Volmer and fluorescence lifetime indicated that the two quenching systems were all static. The binding constant (Ka) of FZD/NFT-CdS QDs was 1.20 × 104/1.81 × 104 L/mol at 293 K, respectively. Hydrogen bond or van der Waals force was the main binding force between CdS QDs and drugs. Under optimum experimental conditions, the concentration of FZD/NFT was respectively highly correlated with the fluorescence intensity ratio in the range of 0.27 – 36.03/0.57 – 28.58 μg mL−1. The interference experiments showed that the methods had good selectivity. The limit of detection (LOD) for FZD/NFT was 0.02/0.01 μg mL−1. The contents of FZD and NFT in fish samples were determined, and the recoveries were 97.41–99.52 % and 96.64–100.49 %, respectively.

Synthesis of highly efficient (Cr, Gd) co-doped CdS quantum dots for photocatalytic H2 evolution beneath artificial solar light irradiation

To meet the future energy demand, the design, and development of novel, economical with efficient hydrogen (H2) fuel production rate and more stable photocatalytic material are most crucial and necessary. Numerous sunlight-active semiconductor nanostructures have been materialized for photocatalytic reactions towards hydrogen evolution. Nevertheless, their reliable application has been restricted through less photocatalytic efficiency and less stability provoked by the recombination of charge carriers. In the direction of to minimize the recombination rate among the charge carriers and enhance photocatalytic water splitting mechanism towards hydrogen evolution Co-doping of transition and rare earth elements to the host lattice is a promising strategy in functional material engineering to minimize the recombination rate among the charge carriers and enhance the photocatalytic water splitting mechanism towards hydrogen evaluation. In this view, herein, the chemical synthesis, structural, optical, and photocatalytic characteristics of pristine CdS, CdS:Cr (1 at%), CdS: (Cr, Gd (1 at%)) and CdS: (Cr, Gd (2 at%)) quantum dots for competent photocatalytic H2 fuel evolution. Furthermore, the rate of H2 of CdS: (Cr, Gd (2 at%)) quantum dots is almost 23 times greater than that of pristine CdS quantum dots with more stability. Hence, we strongly believe that, CdS: (Cr, Gd (2 at%)) quantum dots are reliable and potential semiconductor compounds for efficient photocatalytic hydrogen evolution for environmental purification.

Cellulose nanofibril/titanate nanofiber modified with CdS quantum dots hydrogel with 3D porous structure: A stable photocatalytic adsorbent for Cr(VI) removal

A novel cellulose nanofibril/titanate nanofiber modified with CdS quantum dots hydrogel (CTH) was synthesized as an effective, stable, and recyclable photocatalytic adsorbent using cellulose nanofibril (CN), titanate nanofiber (TN), and CdS quantum dots. Within the CTH structure, CN formed an essential framework, creating a three-dimensional (3D) porous structure that enhanced the specific surface area and provided abundant adsorption sites for Cr(VI). Simultaneously, TN modified with CdS quantum dots (TN-CdS) served as a nanoscale Z-type photocatalyst, facilitating the efficient separation of photoinduced electrons and holes, further increasing the photocatalytic efficiency. The morphological, chemical, and optical properties of CTH were thoroughly characterized. The CTH demonstrated the maximum theoretical adsorption capacity of 373.3 ± 14.2 mg/g, which was 3.4 times higher than that of CN hydrogel. Furthermore, the photocatalytic reduction rate constant of the CTH was 0.0586 ± 0.0038 min−1, which was 6.4 times higher than that of TN-CdS. Notably, CTH displayed outstanding stability, maintaining 84.9 % of its initial removal efficiency even after undergoing five consecutive adsorption–desorption cycles. The remarkable performance of CTH in Cr(VI) removal was attributed to its 3D porous structure, comprising CN and TN-CdS. These findings provide novel insights into developing a stable photocatalytic adsorbent for Cr(VI) removal.

In@CdS sensitized TiO2 nano-rod for enhanced photocatalytic and photoelectrochemical performance under visible light

Titanium dioxide (TiO2) nano-rod are synthesized by one step hydrothermal method while cadmium sulphide (CdS) and Indium (In) doped CdS quantum dots (QDs) are sensitized on the surface of TiO2 nano-rod by using successive ionic layer adsorption and reaction (SILAR) approach. Characterization of this material was done using XRD, XPS, FE-SEM, EDX, HR-TEM, Raman, UV-DRS, PL, EPR. XRD pattern attributed that the preferential orientation of TiO2 grains is along the (101) plane perpendicular to the FTO substrate. XRD pattern also reveals the sensitization of CdS QDs in form of hexagonal CdS QDs and doping of In into CdS QDs. FE-SEM analysis suggests that the TiO2 nano-rod are uniform, thick and grown vertically on the FTO plate. Detailed investigations of the ‘In’ sensitization in 2%In-CdS/TiO2 were carried out by HR-TEM studies. UV-DRS analysis shows decrease in the band gap energy as doping of In in CdS/TiO2 nano-rod increases. EPR analysis reveals the presence of oxygen vacancies due to sensitization of ‘In’ on CdS/TiO2 matrix. The photoelectrochemical and photocatalytic performance of In doped CdS QDs embellished on the surface of TiO2 nano-rod photoanode was investigated by varying the concentration of In. The photo electrochemical (PEC) and photocatalytic H2 generation performance under natural sunlight of as prepared photoanode are explored in terms of photocurrent density and amount of H2 generation. 2% In-CdS/TiO2/Pt/FTO nano-rod shows highest 22.12 ml/h/g of hydrogen generation and photocurrent density of 4.78 (mA/cm2).