Investigations on structural and optical properties of starch capped ZnS nanoparticles synthesized by microwave irradiation method

Photocatalytic Evaluation of the Ternary Composite CdSO4-ZnAl LDH/ZnS in Hydrogen Production without a Sacrificial Reagent

In this work, a layered double hydroxide support modified with cadmium was synthesized by a one-pot coprecipitation method. Then, it was sulfured in different percentages by a solvothermal method. Next, the samples were analyzed using various characterization techniques like XRD, DRS, FTIR, N2 physisorption, PL spectroscopy, TEM, and SEM. Finally, the synthesized and uncalcined materials were assessed in hydrogen production from water and a methanol-water solution under UV-light irradiation. The results showed that the sulphuration improves the photocatalytic activity, reaching a maximum rate constant of hydrogen production of 7403 µmol/g∙h in a methanol-water solution and 1326 µmol/g∙h in water.

Sulfidogenic Bioreactor-Mediated Formation of ZnS Nanoparticles with Antimicrobial and Photocatalytic Activity

The use of sulfidogenic bioreactors is a biotechnology trend to recover valuable metals such as copper and zinc as sulfide biominerals from mine-impacted waters. In the present work, ZnS nanoparticles were produced using "green" H₂S gas generated by a sulfidogenic bioreactor. ZnS nanoparticles were physico-chemically characterized by UV-vis and fluorescence spectroscopy, TEM, XRD and XPS. The experimental results showed spherical-like shape nanoparticles with principal zinc-blende crystalline structure, a semiconductor character with an optical band gap around 3.73 eV, and fluorescence emission in the UV-visible range. In addition, the photocatalytic activity on the degradation of organic dyes in water, as well as bactericidal properties against several bacterial strains, were studied. ZnS nanoparticles were able to degrade methylene blue and rhodamine in water under UV radiation, and also showed high antibacterial activity against different bacterial strains including Escherichia coli and Staphylococcus aureus. The results open the way to obtain valorous ZnS nanoparticles from the use of dissimilatory reduction of sulfate using a sulfidogenic bioreactor.

Synergistically Assembled Cobalt-Telluride/Graphene Foam with High-Performance Electromagnetic Wave Absorption in Both Gigahertz and Terahertz Band Ranges

Electromagnetic wave (EMW)-absorbing materials have a great impact on civil use and national defense. In this paper, a novel composite, RGO@6CoTe₂-300 (the mass ratio of reduced graphene oxide to CoTe₂ is 1:6, annealed at 300 °C), has been obtained through a facile melt-diffusion method and solvothermal method. The as-prepared samples have shown excellent reflection losses (RL) and effective adsorption bandwidth (EAB) by controlling the loading of CoTe₂ and the annealing temperature. The sample has exhibited a RL of -62.2 dB at 13.04 GHz with the matching thickness of 3.53 mm, and the EAB reaches 8.2 GHz at 2-18 GHz. Moreover, excellent terahertz (THz) absorption property is also obtained at 0.2-2.0 THz. A RL of 54.07 dB is acquired, and the EAB covers 100% of the entire measured bandwidth. Thus, RGO@6CoTe₂-300 can be considered as a promising EMW absorption material in both gigahertz and terahertz band ranges.

Green synthesis of starch-capped Cu2O nanocubes and their application in the direct electrochemical detection of glucose

Glucose determination is an essential procedure in different fields, used in clinical analysis for the prevention and monitoring of diabetes. In this work, modified carbon paste electrodes with Cu₂O nanocubes (Cu₂O NCs) were developed to test electrochemical glucose detection. The synthesis of the Cu₂O NCs was achieved by a green method using starch as the capping agent, obtaining cubic-like morphologies and particle sizes from 227 to 123 nm with increasing amounts of the capping agent, as corroborated by electron microscopy analysis. Their crystalline structure and purity were determined by X-ray diffraction. The capability of starch as a capping agent was verified by Fourier-transform infrared spectroscopy, in which the presence of functional groups of this biopolymer in the Cu₂O NCs were identified. The electrochemical response to glucose oxidation was determined by cyclic voltammetry, obtaining a linear response of the electrical current as a function of glucose concentration in the range 100–700 μM, with sensitivities from 85.6 to 238.8 μA mM⁻¹ cm⁻², depending on the amount of starch used in the synthesis of the Cu₂O NCs.

Starch-capped Cu₂O nanocubes were used as an active electrochemical element to directly detect glucose.

Changes in structural and optical properties due to γ-irradiation of MgO nanoparticles

In this research, the influence of γ-irradiation on the optical and structural properties of magnesium oxide (MgO) nanoparticles was studied. The MgO nanoparticles were irradiated with doses 100 Gy, 1 kGy, 10 kGy and 20 kGy from 60Co source. The as-synthesized samples of MgO nanoparticles prepared by the sol-gel technique were analyzed by XRD which suggested the double phase; cubic and hexagonal structures of the material. The crystal defects that produced in the cubic and hexagonal lattice were studied before and after 60Co γ-irradiation in a gamma cell by different dose rates in order to report the changes in structural properties of the MgO nanoparticles. The irradiated and un-irradiated samples were characterized by XRD and UV–Vis. The XRD pattern of MgO nanoparticles is showed that the crystal size of MgO nanoparticles being increased with increasing the γ-ray dose rate. For optical absorption, the UV–Visible absorption spectra of MgO nanoparticles are showed that when the dose rate is increased, the value of band gap is decreased. Also, the experimental values of the mass attenuation coefficient of MgO nanoparticles have been calculated before and after γ-irradiation by using the gamma spectroscopy method. Therefore, the results are showed that γ-ray irradiation has various effects on structural, morphological and optical properties.