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Speciation Analysis of Ag2S- and ZnS-Nanoparticles at ng/L Level in Environmental Waters by Cloud Point Extraction Coupled with LC-ICPMS
摘要： Toxicity and transport of metal-based nanoparticles (M-NPs) in environmental waters strongly depend on their speciation. A detailed understanding of the composition and speciation of M-NPs is necessary in order to move this field forward. Unfortunately, there is a shortage of analytical methods for metal-sulfide nanoparticles (MS-NPs) in the environment. In this work, a cloud point extraction (CPE) method combined with liquid chromatography hyphenated to inductively coupled plasma mass spectrometry (LC-ICPMS) is developed for sensitive determination of Ag2S- and ZnS-NPs. Under the condition of 0.15% (w/v) of Triton X-114 (TX-114), pH 5, 20 mM NaNO3, incubation temperature of 45 oC and time of 15 min, MS-NPs and non-MS-NPs were extracted into the surfactant-rich phase. With the sequent addition of 10 mM bis(p-sulfonatophenyl)phenylphosphane dehydrate dipotassium (BSPP) aqueous solution (100 μL) into the CPE-obtained extract, the non-MS-NPs were selectively dissociated into their ionic counterparts while maintaining the original size and shape of Ag2S- and ZnS-NPs. Interestingly, the micelle-mediated behavior suddenly disappeared with the addition of BSPP. Thus, the extract can be injected to LC-ICPMS for speciation analysis of trace Ag2S- and ZnS-NPs. This method exhibited excellent reproducibility (relative standard deviations < 4.9%), high sensitivity with the respective detection limits of 8 ng/L for Ag2S-NPs and 15 ng/L for ZnS-NPs, enabling recoveries of 81.3-96.6% for Ag2S-NPs and 83.9-93.5% for ZnS-NPs when they were spiked into three environmental water samples. Due to its potential applicability to low concentrations of Ag2S- and ZnS-NPs, this method is particularly convenient for monitoring the transformations of AgNPs and ZnO-NPs in the environment.
关键词： cloud point extraction,LC-ICPMS,environmental waters,metal-sulfide nanoparticles,speciation analysis
更新于2025-09-23 15:19:57
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Plasmonic-induced overgrowth of amorphous molybdenum sulfide on nanoporous gold: An ambient synthesis method of hybrid nanoparticles with enhanced electrocatalytic activity
摘要： Hybrid materials of earth abundant transition metal dichalcogenides and noble metal nanoparticles, such as molybdenum sulfide (MoSx) and gold nanoparticles, exhibit synergistic effects that can enhance electrocatalytic reactions. However, most current hybrid MoSx-gold synthesis requires an energy intensive heat source of >500 ○C or chemical plating to achieve deposition of MoSx on the gold surface. Herein, we demonstrate the direct overgrowth of MoSx over colloidal nanoporous gold (NPG), conducted feasibly under ambient conditions, to form hybrid particles with enhanced electrocatalytic performance toward hydrogen evolution reaction. Our strategy exploits the localized surface plasmon resonance-mediated photothermal heating of NPG to achieve >230 ○C surface temperature, which induces the decomposition of the (NH4)2MoS4 precursor and direct overgrowth of MoSx over NPG. By tuning the concentration ratio between the precursor and NPG, the amount of MoSx particles deposited can be systematically controlled from 0.5% to 2% of the Mo/(Au + Mo) ratio. Importantly, we find that the hybrid particles exhibit higher bridging and an apical S to terminal S atomic ratio than pure molybdenum sulfide, which gives rise to their enhanced electrocatalytic performance for hydrogen evolution reaction. We demonstrate that hybrid MoSx-NPG exhibits >30 mV lower onset potential and a 1.7-fold lower Tafel slope as compared to pure MoSx. Our methodology provides an energy- and cost-efficient synthesis pathway, which can be extended to the synthesis of various functional hybrid structures with unique properties for catalysis and sensing applications.
关键词： molybdenum sulfide,electrocatalytic activity,nanoporous gold,hydrogen evolution reaction,plasmonic
更新于2025-09-23 15:19:57
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Effect of thioglycolic acid molecules on luminescence properties of $$\hbox {Ag}_2$$Ag2S quantum dots
摘要： For monoclinic Ag2S nanocrystals (quantum dots, Ag2S/TGA QDs), the correlation between their luminescence properties and aspects of their passivation by thioglycolic acid (TGA) molecules is considered. The features of quantum confinement effect in the QDs absorption and photoluminescence spectra are analyzed for Ag2S QDs with an average size of 1.7–3.1 nm. We show that, in various conditions of passivation of QDs interfaces, the luminescence mechanism of Ag2S/TGA QDs is switched from recombination luminescence in the 870–1000 nm region to exciton luminescence with a band maximum at 620 nm. By means of FTIR spectra, two major types of interactions between TGA molecules and Ag2S QDs, arising due to changing the [Ag+]:[S2?] ratio from 1:0.9 to 1:1.43, are determined. Exciton luminescence (620 nm) occurs in case of using TGA as the sulfur source in Ag2S crystallization and the interface passivation agent, with [Ag+]:[S2?] = 1:1. The analysis of the FTIR spectra indicates bonding of TGA with the Ag2S surface by both thiol and carboxylic groups in this case. With increasing the sulfur concentration in the synthesis of Ag2S/TGA QDs, the exciton luminescence is suppressed. The employment of Na2S as the sulfur source in Ag2S crystallization with TGA acting as the surface passivation agent promotes the formation of recombination centers for IR luminescence. In this case, analysis of the FTIR spectra indicates passivation of Ag2S QDs by TGA molecules due to adsorption of thiol groups. It is found that the photodegradation or IR luminescence of Ag2S/TGA QDs upon exposure to exciting radiation is due to the photolysis of Ag2S nanocrystals with formation of luminescence quenching centers as well as due to photodestruction of TGA molecules.
关键词： Size dependence,Thioglycolic acid,Interaction mechanism,FTIR spectra,Trap state luminescence,Silver sulfide,Luminescence properties
更新于2025-09-23 15:19:57
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68Ga CdTe/CdS fluorescent quantum dots for detection of tumors: investigation on the effect of nanoparticle size on stability and in vivo pharmacokinetics
摘要： Background: Quantum dots (QDs)-based theranostics offer exciting new approaches to diagnose and therapy of cancer. To take advantage of the unique properties of these fluorescent QDs for different biomedical applications, their structures, size and/or surface chemistry need to be optimized, allowing their stability and functionalities to be tailored for different biomedical applications. Methodology: Cadmium telluride/Cadmium sulfide QDs (CdTe/CdS QDs) were synthesized and their structure, size, photostability and functionalities as a bioprobe for detection of Fibrosarcoma tumors were studied and compared with Cadmium telluride (CdTe) QDs. Hence, CdTe/CdS QDs were labeled with 68Ga radionuclide for fast in vivo biological nuclear imaging. Using gamma paper chromatography (γ-PC), the physicochemical properties of the prepared labeled QDs were assessed. In vivo biodistribution and positron emission tomography (PET) imaging of the 68Ga@ CdTe/CdS QDs nanocrystals were investigated in Sprague Dawley? rats bearing Fibrosarcoma tumor. Results: CdS shell on the surface of CdTe core increases the size and photostability against high energy radiations; therefore, CdTe/CdS QDs show prolonged fluorescence as compared to CdTe QDs. Conclusion: Excellent accumulation in tumor was observed for core/shell quantum dots, but this study showed that small changes in the size of the QDs (+1 nm), after adding the CdS shell around CdTe core, greatly change their biodistribution (especially the liver uptake).
关键词： core/shell quantum dots,PET,tumor imaging,68Ga,Cadmium telluride/Cadmium sulfide
更新于2025-09-23 15:19:57
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A facile hydrothemal synthesis of MoS2@Co3S4 composites based on metal organic framework compounds as a high-efficiency liquid-state solar cell counter electrode
摘要： A hollow Co3S4 polyhedral loads MoS2 nanosheet composite MoS2@Co3S4-0.5 is prepared by hydrothermal method using Co-based metal organic framework material ZIF-67 as precursor. Hollow Co3S4 polyhedron and uniformly distributed MoS2 nanosheet structure can not only prevent MoS2 aggregation, but also increase the specific surface area of the material and expose more catalytically active sites. The composites afford a promising synergistic effect on the catalyzing of triiodide reduction. As a counter electrode material applied to dye-sensitized solar cells, MoS2@Co3S4-0.5 exhibits excellent catalytic activity, achieving a photoelectric conversion efficiency of 7.86%, which is superior to 6.99% of Pt counter electrode performance in dye-sensitized solar cells. This indicates that MoS2@Co3S4-0.5 composite material can be used to replace precious metal Pt as an efficient and low-cost counter electrode material in dye-sensitized solar cells.
关键词： metal-organic framework,facile hydrothemal synthesis,transition metal sulfide,dye-sensitized solar cells,counter electrode
更新于2025-09-23 15:19:57
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Phosphorene as H <sub/>2</sub> S and CH <sub/>4</sub> Gas Sensor
摘要： First-principle calculations within density functional theory are carried out to investigate the adsorption of various gas molecules, including hydrogen sulfide and methane on two-dimensional monolayer phosphorene in order to fully exploit the gas sensing capabilities. The adsorption properties of different molecules in the environment on monolayer phosphorene base material is discussed in terms of the Mulliken charge transfer, energy band gap, adsorption energy. The prominent adsorption sites of methane, hydrogen sulfide, water, and oxygen on monolayer phosphorene are investigated at an atomistic level. Based on the results the transport properties of monolayer phosphorene exposed to these gas molecules are investigated both in zigzag and armchair direction using non-equilibrium Green function tuned with density functional theory. The results show that using both directions simultaneously as gas sensing can be an effective technique to distinguish hydrogen sulfide and methane gas molecules from others and demonstrate great selectivity.
关键词： phosphorene,methane,Green function,density functional theory,transport properties,device,hydrogen sulfide,gas sensors
更新于2025-09-23 15:19:57
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Structural transformation identification of sputtered amorphous MoS <sub/>x</sub> as efficient hydrogen evolving catalyst during electrochemical activation
摘要： Molybdenum sulfide MoSx is considered as attractive hydrogen evolution catalyst since it is free of noble metals and shows a low overpotential. Especially, amorphous molybdenum sulfide has attracted attention because of its high catalytic activity. However, the catalytic mechanism of the hydrogen evolution reaction is not yet fully understood. Therefore in our study, layers of MoSx were deposited by reactive magnetron sputtering varying the substrate temperature in the range from room temperature (RT) to 500°C. The morphology and structure of the films change significantly as a function of temperature, from an amorphous to a highly textured 2H-MoS2 phase. The highest catalytic activity was found for amorphous layers deposited at RT showing an overvoltage of 180 mV at a current density of -10 mAcm-2 in a 0.5 M sulfuric acid electrolyte (pH 0.3) after electrochemical activation. As detected by Raman spectroscopy the RT deposited catalyst consists of [Mo3S13]2- and [Mo3S12]2- entities which are interconnected via [S2]2- and S2- ligands. When sweeping the potential from 0.2 to -0.3 V vs RHE a massive release of sulfur in form of gaseous H2S was observed in the first minutes as detected by differential electrochemical mass spectroscopy (DEMS). After electrochemical cycling for 10 min, the chains of these clusters transform into a layer-type MoS2-x phase observed by in-situ Raman spectroscopy. In this transformation process, H2S formation gradually vanishes and H2 evolution becomes dominant. The transformed phase is considered as a sulfur deficient molybdenum sulfide characterized by a high number of molybdenum atoms located at the edges of nano-sized MoSx islands, which act as catalytically active centers.
关键词： hydrogen evolving catalyst,structural transformation,water splitting,molybdenum sulfide,sputtering
更新于2025-09-19 17:15:36
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Studying the Effect of Deposition Time on Optical Properties of CdS Thin Films
摘要： We have studied in this work the effect of deposition time on the absorption spectra and the optical energy gap of CdS thin film. That prepared by chemical bath deposition method (CBD) on glass substrate at temperature of (80 ± 5)°C. The structural features were examined by X-ray diffraction (XRD) is wurtzite structure for all samples. Transmittance spectra have been recorded in order to determine absorbance, reflectivity, absorption coefficient and the optical constants such as refractive index, extinction coefficient, real and imaginary part of dielectric constant. It was seen that all the parameters under investigation affected by deposition time (1,2 3, and 4) hours.
关键词： Cadmium sulfide,optical constants,chemical bath technique
更新于2025-09-19 17:15:36
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Nonlinear Optical Properties of CdS Semiconductor nanowires
摘要： In this work, we report on the nonlinear optical properties in single Cadmium sulfide nanowires (CdS NWs). The high qulity growth of CdS semiconductor nanowires were synthesized by chemical vapor deposition (CVD) method. The as-obtained products were characterized by X-ray diffraction (XRD) , Scanning electron microscopy (SEM), and the energy dispersive X-ray spectrom (EDS) was used to determine the specific elemental distribution and show purity of the CdS semiconductor nanowires . The excitation of femtosecond laser(800 nm, 50 fs, 80 MHz) was used to study the nonlinear optical properties of CdS nanowires, such as the Second Harmonic Generation(SHG) and optical waveguide effect. CdS NW has a second harmonic generation with a blue emission bands at a wavelength of 400 nm . Finally, based on the dark field image of the CCD taken and combined with the spectrum, it is proved that CdS NW has an optical waveguide effect.
关键词： Cadmium sulfide (CdS),Waveguide,nanowires (NWs),Second- Harmonic Generation (SHG),Chemical Vapor Deposition (CVD)
更新于2025-09-19 17:15:36
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Significant enhancement of stability for visible photocatalytic overall water splitting by assembling ultra-thin layer of NiO over Zn1-xCdxSX
摘要： Solar light driven water splitting into hydrogen and oxygen using visible light active photocatalyst has been considered as a clean, green, and renewable route to solar energy conversion and storage. Although Zn1-xCdxS catalyst shows comparatively higher activity for photocatalytic hydrogen generation under visible light irradiation, it suffers serious photocorrosion during the photocatalytic reaction. Deposition of protection layer over Zn1-xCdxS catalyst is believed to be an effective way to inhibit such photocorrosion. Nevertheless, seldom of protection layer exhibits satisfied catalytic properties for hydrogen evolution while presents good protection ability. In this work, a new Zn1-xCdxS photocatalyst has been developed for water splitting under visible light illumination by assembled an ultra-thin NiO layer over Zn0.8Cd0.2S via in-situ photodeposition method. By this strategy, NiO/Zn0.8Cd0.2S showed significant higher activity than Pt/Zn0.8Cd0.2S under same conditions without photocorrosion. The AQE of 0.66% for hydrogen evolution at 430 nm has been achieved and multi-cycle stability has been accomplished up to 12 hours without significant decay. Moreover, the strong electronic coupling between NiO layer and Zn1-xCdxS promoted efficient charge separation and migration.
关键词： Overall water splitting,sulfide semiconductor photocatalyst with thin NiO catalytic layer,enhanced charge separation and migration,significant enhanced stability,anti-photocorrosion
更新于2025-09-19 17:15:36