N-acetyle cysteine assisted synthesis of core⿿shell Ag2S with enhanced light transmission and diminished reflectance: Surface modifier for c-SiNx solar cells

Effect of sulphidation process on the structure, morphology and optical properties of GO/AgNWs composites

In this study, composite materials composed of graphene oxide (GO) synthesized by a modified Hummers' method and silver nanowires (AgNWs) synthesized by a modified polyol method were prepared. The prepared composites were subjected to sulfidation under the influence of H2S gas. Structural changes in the samples were evaluated using X-ray diffraction (XRD). The binding nature of the composite was characterized using FT-IR spectroscopy. Optical properties and band gap values were investigated using ultraviolet-visible (UV-Vis) spectroscopy. The morphology of the composites was analyzed by transmission electron microscopy (TEM). A simple method using H2S gas was applied for the sulphidation process of the samples. The sulfidation process was successful under the influence of H2S gas, resulting in an increased distance between the GO layers and a decrease in the band gap value for the composite post-sulfidation. In addition, AgNWs were observed to decompose into Ag2S nanoparticles under the influence of H2S gas. It was determined that the value of the band gap of the sample changes because of sulphidation.

Structural, optical, morphological, sun-light driven photocatalytic and antimicrobial investigations of Ag2S and Cu/Ag2S nanoparticles

This study focusses on the preparation of silver sulphide (Ag2S) and Cu-doped Ag2S (Cu/Ag2S) nanoparticles (NPs) by sol-gel method and demonstrated their photocatalytic and antibacterial applications. The X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) analysis demonstrated that the prepared NPs are effectively crystallized in the polycrystalline single-phase monoclinic geometry of Ag2S. The optical bandgap is significantly reduced, and for both the sample the average grain size is observed to have narrowed from 42 nm to 23 nm. Both NPs were confirmed to be spherical nature as observed by scanning electron microscopy (SEM), and the energy dispersive X-ray (EDX) spectroscopy analysis validated the presence of all necessary components at the expected concentrations in the obtained samples. Under the irradiation of sunshine, the photocatalytic properties of each sample were investigated for their ability to facilitate the photodegradation of a hazardous methylene blue (MB) dye in an aqueous solution. Cu/Ag2S sample possesses a profound photocatalytic reaction for the destruction of MB dye. Furthermore, the Cu-doped Ag2S NPs suppress the proliferation of Staphylococcus aureus and Escherichia coli. In comparison to pure Ag2S NPs, Cu/Ag2S showed enhanced antibacterial activity against both the bacteria. Current study suggests that the Cu doped Ag2S NPs could be a promising material for wastewater treatment and antimicrobial agents.

Highly Conductive Strong Healable Nanocomposites via Diels-Alder Reaction and Filler-Polymer Covalent Bifunctionalization

Healable stretchable conductive nanocomposites have received considerable attention. However, there has been a trade-off between the filler-induced electrical conductivity (σ) and polymer-driven mechanical strength. Here significant enhancements in both σ and mechanical strength by designing reversible covalent bonding of the polymer matrix and filler-matrix covalent bifunctionalization are reported. A polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene grafted with maleic anhydride forms the strong reversible covalent bonding with furfuryl alcohol through the Diels-Alder reaction. Small (7.5 nm) and medium (117 nm) nanosatellite particles are generated by in situ etching of silver flakes, enabling electron tunneling-assisted percolation. The filler-polymer covalent bifunctionalization is achieved by 3-mercaptopropanoic acid. Altogether, this results in high σ (108 300 S m^-1 ) and tensile strength (16.4 MPa), breaking the trade-off behavior. A nearly perfect (≈100%) healing efficiency is achieved in both σ and tensile strength. The conductive nanocomposite figure of merit (1.78 T Pa S m^-1 ), defined by the product of σ and tensile strength, is orders of magnitude greater than the data in literature. The nanocomposite may find applications in healable strain sensors and electronic materials.

Impact of a Model Soil Microorganism and of Its Secretome on the Fate of Silver Nanoparticles

Sulfidation is a key process for silver nanoparticles released from consumer products in the environment. This study focuses on the impact of a model soil microorganism, Bacillus subtilis, on the fate of pristine and already sulfidized Ag-NPs. The nanoparticles were incubated with the initial growth medium, isolated secretome, and living bacteria, and characterized for their size and morphology, agglomeration state, structure, and Ag speciation. No Ag internalization or sorption on the cell wall was detected. A partial sulfidation, leading to an Ag-Ag₂S core-shell structure, was observed in the presence of the secretome, and the rate limiting step of the reaction was the oxidation of Ag⁰, and it was favored near the crystal dislocations. The sulfidation was complete in the presence of the living bacteria and followed an indirect pathway. Both crystalline Ag₂S and amorphous Ag₂S and/or Ag-thiol were identified. At the opposite, the bacteria had no impact on Ag₂S. These results suggest that microorganisms participate in the sulfidation of Ag-NPs in aerobic systems such as unsaturated soils, and thus affect the bioavailability of Ag. It is important to take these transformations into account during exposure experiments, since they drastically change the exposure conditions. Finally, the secretome of B. subtilis might be used for the green synthesis of Ag-Ag₂S core-shell nanoparticles.