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Charge transfer dynamics and catalytic performance of a covalently linked hybrid assembly comprising a functionalized cobalt tetraazamacrocyclic catalyst and CuInS <sub/>2</sub> /ZnS quantum dots for photochemical hydrogen production
摘要： Although the cobalt complex, [Co(CR)X2]+ (CR ? 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene), has been studied as a catalyst for electro- and photochemical H2 generation and CO2 reduction for more than thirty years, only the unfunctionalized one was used as a free catalyst in bulk solutions. Considering that the immobilization of functionalized molecular catalysts (MCs) on the surface of light harvesting materials through a stable covalent linkage was often an effective strategy to boost the activity of semiconductor/MC hybrid photocatalytic systems, we prepared the first anchoring group-functionalized [Co(CR)X2]+ complex (C1, X ? Br), which bears a (20,60-dicarboxypyridin-40-yl) group at position 15 of the macrocyclic ligand. The covalent attachment of C1 to the surface of CuInS2/ZnS (CISZ) core–shell quantum dots (QDs) afforded the C1@CISZ hybrid assembly. Comparative studies on the visible-light-induced H2 evolution performances of C1@CISZ and the non-bonded reference system comprising the unfunctionalized [Co(CR)Br2]+ complex (C2) and CISZ QDs (denoted as C2+CISZ) revealed that the photocatalytic activity of C1@CISZ was twice to thrice as high as that of C2+CISZ under the same conditions. Appealingly, the isolated C1@CISZ assembly was more stable than the C2+CISZ system in long-term photolysis. Moreover, photoluminescence (PL) and transient absorption (TA) spectroscopic studies demonstrated that covalent immobilization of C1 on the surface of CISZ QDs accelerated the electron transfer from QDs to the catalyst and meanwhile retarded the charge recombination process on the surface of QDs. The evidently improved charge separation efficiency resulted in the higher activity of the hybrid assembly C1@CISZ than that of C2+CISZ for photocatalytic hydrogen production.
关键词： photochemical H2 generation,cobalt complex,photocatalytic hydrogen production,CO2 reduction,charge transfer dynamics,CuInS2/ZnS quantum dots
更新于2025-09-16 10:30:52
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Evaluation for adverse effects of InP/ZnS quantum dots on the in vitro cultured oocytes of mice
摘要： So far, cadmium-containing quantum dots (QDs), such as cadmium telluride (CdTe), have been known for causing time- and dose-dependent toxicity for cells, tissues or organs in living organisms. Yet, there has been no a unified conclusion whether indium phosphide (InP) QDs, a kind of non-cadmium QDs, have the same effects on these structures, especially on female germ cells. In this work, we evaluated the adverse effects of InP/ZnS based core/shell QDs on oocytes of the Kunming mice. The immature oocytes were co-cultured with InP/ZnS QDs at concentrations of 0, 0.2 μg/mL, 2 μg/mL, and 20 μg/mL for 16 hours, respectively. The statistics of morphology showed that InP/ZnS QDs significantly (P<0.05) affected the maturation rate of oocytes at concentrations above 2 μg/mL, while measurements of diameter didn’t seem to display difference between the groups. Fluorescence images showed that the uptakes of QDs by granulosa cells increased with the increasing concentration, but no fluorescence signal of QDs was detected inside the oocytes. The abnormality rate of both spindles and chromosomes in control group was the same as that in experimental groups. However, two hormone levels were both disturbed by InP/ZnS QDs. These results indicated that InP/ZnS QDs decreased the oocytes maturation in a dose-dependent manner by changing the culture environment, which was similar to the effects of cadmium-containing QDs. This study provides the reproductive toxicology data of InP/ZnS QDs, which is useful for biomedical safe application of QDs in future.
关键词： quantum dots,InP/ZnS,oocytes,adverse effects,in vitro
更新于2025-09-16 10:30:52
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Numerical Analysis of Potential Buffer Layer for Cu2ZnSnS4 (CZTS) Solar Cells
摘要： In this work, CZTS solar cell with heterojunctions CdS/CZTS and ZnS/CZTS have been simulated using the Solar Cell Capacitance Simulator (SCAPS-1D). The effect of thickness and doping concentration on the performances of both structures has been investigated. It is obtained that the optimum thickness is about 30 nm and the best doping concentration is around 5E16 cm-3 and 5E17 cm-3 for CdS/CZTS and ZnS/CZTS structures respectively. By using the buffer layers optimum parameters (thickness and doping concentration), the electrical efficiency of CZTS solar cell is boosted from 12.03% to 12.38 % for CdS/CZTS structure and from 12.51% to 12.78% for ZnS/CZTS structure. The obtained results reveal some valued insights for manufacturing Cd_free CZTS solar cells.
关键词： Thin film,SCAPS-1D,Solar cell,CdS,CZTS,ZnS
更新于2025-09-16 10:30:52
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Solution-processed QD-LEDs in visible range: Modulation bandwidth enhancement
摘要： Light-emitting diodes based on quantum dots (QD-LEDs) have attracted much attention not only due to their usage in lighting and display applications but also as the light sources in visible light communication (VLC). One of the most important parameters of a QD-LED as a light source is the improvement of modulation bandwidth in order to increase the data transfer rate. Here, three sets of QD-LEDs are presented for which some parameters such as frequency response are investigated, once for the devices with similar structure but different homogeneities and then for those with minor changes in the structure. It was found that by changing the homogeneity of QDs in the same structure based on CdSe/ZnS and using the ZnO shell instead of ZnS, the modulation bandwidth varied between 2 and 8 MHz. Furthermore, for the structure based on CdSe/ZnS, the modulation bandwidth of 8 MHz is achieved which is fairly a wide bandwidth for a QD-LED. The idea of manipulation in the structure of nanomaterials can be an important step toward increasing the modulation bandwidth. According to calculated results, the carrier density in different layers is calculated and then the recombination current-voltage characteristics are compared with the experimental results, indicating high conformity.
关键词： Light emitting diode,Frequency response,CdSe/ZnS,Quantum dots,Modulation bandwidth
更新于2025-09-16 10:30:52
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Facile and efficient 3-chlorophenol sensor development based on photolumenescent core-shell CdSe/ZnS quantum dots
摘要： Quantum dots (QDs) are semiconducting inorganic nanoparticles, tiny molecules of 2–10 nm sizes to strength the quantum confinements of electrons. The QDs are good enough to emit light onto electrons for exciting and returning to the ground state. Here, CdSe/ZnS core/shell QDs have been prepared and applied for electrochemical sensor development in this approach. Flat glassy carbon electrode (GCE) was coated with CdSe/ZnS QDs as very thin uniform layer to result of the selective and efficient sensor of 3-CP (3-chlorophenol). The significant analytical parameters were calculated from the calibration plot such as sensitivity (3.6392 μA μM?1 cm?2) and detection limit (26.09 ± 1.30 pM) with CdSe/ZnS/GCE sensor probe by electrochemical approach. The calibration curve was fitted with the regression co-efficient r2 = 0.9906 in the range of 0.1 nM ～ 0.1 mM concentration, which denoted as linear dynamic range (LDR). Besides these, it was performed the reproducibility in short response time and successfully validated the fabricated sensor for 3-CP in the real environmental and extracted samples. It is introduced as a noble route to detect the environmental phenolic contaminants using CdSe/ZnS QDs modified sensor by electrochemical method for the safety of healthcare and environmental fields at broad scales.
关键词： CdSe/ZnS,Quantum dots,electrochemical sensor,3-chlorophenol,environmental safety
更新于2025-09-16 10:30:52
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Efficient UV photodetectors based on Ni-doped ZnS nanoparticles prepared by facial chemical reduction method
摘要： Ni-doped ZnS nanoparticles are synthesized by simple hydrothermal process for the utilization in UV photodetectors. Surface morphology of the prepared samples is investigated through high resolution transmission electron microscopy (HRTEM), which reveals that the prepared nanoparticles are smaller than 20 nm. The well visualized selected area electron diffraction rings suggests the nanocrystalline nature of the prepared nanoparticles with (hkl) planes (111), (220) and (311). The structural analysis is done by x-ray diffraction (XRD) studies; which reveal the decrease in crystallite size with increase in Ni-doping concentration. The device performance of the photodetectors is tested under UV-A light (wavelength ?365 nm) and found that the ability of the prepared devices increases with increase in Ni-doping concentration. This can be attributed to the enhanced surface to volume ratio and increase in charge carrier concentration. The adsorption-desorption of oxygen molecules on the nanoparticles’ surface is considered to be the mechanism for UV photodetection.
关键词： Hydrothermal process,UV-Photodetectors,ZnS nanoparticles
更新于2025-09-16 10:30:52
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Enhanced Photocatalytic Activity of ZnS:Mn2+ Quantum Dots
摘要： The photocatalytic activity of Mn2+ doped ZnS quantum dots stabilized by glutathione capping agent in aqueous media was studied in situ by photoluminescence spectroscopy. The methylene blue was chosen as model organic dye for photodecomposition under excitation in near UV-range. It is shown that the rate of photodegradation of the methylene blue depends strictly on the concentration of the manganese activator ions and the presence of its own intrinsic defects in the host ZnS crystal lattice. It is found that the most effective photocatalyst are ZnS quantum dots doped with 0.25 at % of Mn2+ providing the total dye decolorization within 5 minutes.
关键词： Mn doped ZnS,photocatalysis,nanocrystalline materials,luminescence
更新于2025-09-16 10:30:52
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Synthesis and application of a surface ionic imprinting polymer on silica-coated Mn-doped ZnS quantum dots as a chemosensor for the selective quantification of inorganic arsenic in fish
摘要： A novel room temperature phosphorescence chemosensor probe has been successfully developed and applied to the selective detection and quantification of inorganic arsenic (As(III) plus As(V)) in fish samples. The prepared material (IIP@ZnS:Mn QDs) was based on Mn-doped ZnS quantum dots coated with (3-aminopropyl) triethoxysilane and an As(III) ionic imprinted polymer. The novel use of vinyl imidazole as a complexing reagent when synthesizing the ionic imprinted polymer guarantees that both inorganic arsenic species (As(III) and As(V)) can interact with the recognition cavities in the ionic imprinted polymer. After characterization, several studies were performed to enhance the interaction between the targets (As(III) and As(V) ions) and the IIP@ZnS:Mn QDs nanoparticles. The optimization and validation process showed that the composite material offers high selectivity (high imprinting factor) for inorganic arsenic species. The limit of quantification for total inorganic As was 29.6 μg kg?1, value lower than the EU/EC regulation limits proposed for other foodstuffs than fish, such as rice. The proposed method is therefore simple, requires short analysis times and offers good sensitivity, precision (inter-day relative standard deviations lower than 10%), and quantitative analytical recoveries. The method has been successfully applied to assess total inorganic arsenic in several fishery products, showing good agreement with the total inorganic arsenic concentration (As(III) plus As(V)) found after applying other advanced and expensive methods such those based on high-performance liquid chromatography hyphenated to inductively coupled plasma-mass spectrometry.
关键词： Ionic imprinted polymer,Silica-coated Mn-doped ZnS quantum dots,Fish,Room temperature phosphorescence,Chemosensor probe,Inorganic arsenic
更新于2025-09-16 10:30:52
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Dielectric and electrical properties of annealed ZnS thin films. The appearance of the OLPT conduction mechanism in chalcogenides
摘要： The annealing temperature (Ta) dependence of the structural, morphological, electrical and dielectric properties of ZnS thin films was investigated. In this work, we consider the as-deposited and annealed ZnS thin films at different temperatures. The as-deposited films were amorphous in nature. However, the films annealed at Ta ≥ 673 K, exhibited a hexagonal structure with (002) preferential orientation. The post annealing caused an improvement in crystallinity. The best one was observed at Ta = 723 K. Grain size increased from 7 nm to 25 nm as annealing temperature was increased from 673 K to 723 K. The surface of annealed samples is homogenous and uniform and the rms roughness is dependent on the annealing temperature: it increases with temperature within the range 5–50 nm. The film electrical conductance is found to be dependent on frequency measurement and annealing temperature: the dc conductance exhibits semi-conductor behavior for all ZnS films over the explored range of temperature and the conductance was found to enhance with increasing annealing temperature up to 623 K. In addition, it was observed that the highest conductance and lowest activation energy of ZnS films were obtained at an annealing temperature of 623 K. The mechanism of alternating current ac conductance can be reasonably explained in terms of the overlapping-large polaron tunnelling (OLPT) model for samples annealed at 623 K and 673 K. To our knowledge, this conduction mechanism was rarely found in chalcogenide materials. A significant change of Nyquist plot with annealing temperature was noted permitting the correlation between the microstructure and its electrical properties. The impedance analysis investigated that the relaxation process is well pronounced for the both annealed films at 623 K and 673 K. The dielectric behavior was associated to the polarization effect, an improvement on the dielectric constant 30 and dielectric loss 300 with annealing was noticed.
关键词： electrical properties,dielectric properties,annealing temperature,OLPT conduction mechanism,ZnS thin films
更新于2025-09-16 10:30:52
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Effect of energy transfer on the optical properties of surface-passivated perovskite films with CdSe/ZnS quantum dots
摘要： Surface passivation is an effective method to protect the surfaces and improve the luminescence properties of perovskite (PS) films. CdSe/ZnS core-shell quantum dots (QDs) have been employed for surface passivation of PS films because of their size-dependent tunable bandgaps. Herein, the energy transfer (ET) behavior of CH3NH3PbI2Br PS films covered with CdSe/ZnS QDs (QD/PS hybrid structures) is characterized by using photoluminescence (PL) and time-resolved PL spectroscopy. The PL decay time and the integrated PL intensity of the QD/PS hybrid structure increase compared with those of the bare PS films, owing to ET from the QDs to the PS and reduced charge traps. The ET efficiency increases from ~7% to 63% for the QD/PS hybrid structure when the core diameter of the QDs decreases from 6.5 to 2.7 nm, respectively. This can be explained by the charge transfer rate enhancement due to the control of energy level alignment of QDs. These results allow us to understand fundamental mechanisms such as ET from QDs to PS films as a function of the size of the QD.
关键词： CdSe/ZnS quantum dots,perovskite films,energy transfer,photoluminescence,surface passivation
更新于2025-09-12 10:27:22