Silver nanoparticles (NPs) have been the subjects of researchers because of their unique properties (e.g., size and shape depending optical, antimicrobial, and electrical properties). A variety of preparation techniques have been reported for the synthesis of silver NPs; notable examples include, laser ablation, gamma irradiation, electron irradiation, chemical reduction, photochemical methods, microwave processing, and biological synthetic methods. This review presents an overview of silver nanoparticle preparation by physical, chemical, and biological synthesis. The aim of this review article is, therefore, to reflect on the current state and future prospects, especially the potentials and limitations of the above mentioned techniques for industries.

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Synthesis of silver nanoparticles: chemical, physical and biological methods.

Due to the recent expanding interest in two-dimensional layered materials, molybdenum disulfide (MoS2) has been receiving much research attention. Having an ultrathin layered structure and an appreciable direct band gap of 1.9 eV in the monolayer regime, few-layer MoS2 has good potential applications in nanoelectronics, optoelectronics, and flexible devices. In addition, the capability of controlling spin and valley degrees of freedom makes it a promising material for spintronic and valleytronic devices. In this review, we attempt to provide an overview of the research relevant to the structural and physical properties, fabrication methods, and electronic devices of few-layer MoS2. Recent developments and advances in studying the material are highlighted.

Few-Layer MoS2: A Promising Layered Semiconductor

https://web.uvic.ca/~agbrolo/ACA_GFS_MF_2011.pdf

A review on the fabrication of substrates for surface enhanced Raman spectroscopy and their applications in analytical chemistry.

Transition metal phosphide hydroprocessing catalysts: A review

Highly active and low-cost catalysts for electrochemical reactions such as the hydrogen evolution reaction (HER) are crucial for the development of efficient energy conversion and storage technologies. Theoretical simulations have been instrumental in revealing the correlations between the electronic structure of materials and their catalytic activity, and guide the prediction and development of improved catalysts. However, difficulties in accurately engineering the desired atomic sites lead to challenges in making direct comparisons between experimental and theoretical results. In MoS2, the Mo-edge has been demonstrated to be active for HER whereas the S-edge is inert. Using a computational descriptor-based approach, we predict that by incorporating transition metal atoms (Fe, Co, Ni, or Cu) the S-edge site should also become HER active. Vertically standing, edge-terminated MoS2 nanofilms provide a well-defined model system for verifying these predictions. The transition metal doped MoS2 nanofilms show an increase in exchange current densities by at least two-fold, in agreement with the theoretical calculations. This work opens up further opportunities for improving electrochemical catalysts by incorporating promoters into particular atomic sites, and for using well-defined systems in order to understand the origin of the promotion effects.

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Transition-metal Doped Edge Sites in Vertically Aligned MoS2 Catalysts for Enhanced Hydrogen Evolution

Tungsten disulfide unsupported catalysts obtained by in situ decomposition of tetramethyl- and tetrabutylammonium thiosalts (TMATT and TBATT) presented better hydrodesulfurization performance than catalysts derived from the ammonium thiosalt (ATT). The reaction rate increased with the size of alkyl group in the precursor, however, no correlation of activity with surface area was observed. Auger analysis revealed that the surface concentration of sulfur and carbon varied with the precursor. The improved performance of WS2 catalysts derived from alkylammonium thiosalts in the HDS of DBT is attributed to the formation of tungsten carbide-sulfide species on the surface.

Catalytic properties of WS2 catalysts prepared by in situ decomposition of tetraalkyl-ammonium thiotungstates

Catalytic study of WS2 undergoing electron irradiation

Unsupported, carbon-containing molybdenum sulfide (MoS2) and bimetallic iron-molybdenum sulfide (FeMoS) catalysts are obtained by in-situ decomposition of (a) ammonium thiomolybdate (ATM), (b) Fe(III)-containing ATM, (c) hexyltrimethylammonium thiomolybdate (HTMATM), and (d) Fe(III)-containing HTMATM, labeled Mo-1, Mo-2, Mo-3 and Mo-4 catalysts. Their activity and selectivity are tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT). HDS activity of the novel bimetallic Mo-4 catalyst is nearly two times greater than that of the reference Mo-1 catalyst, with a less favorable selectivity towards hydrogenation products compared to the reference. Surface iron and carbon contents of the catalysts are found to affect their activity as follows; Mo-4 > Mo-3 ≈ Mo-1 > Mo-2.

Hydrodesulfurization of dibenzothiophene using novel unsupported FeMoS catalysts prepared by in-situ activation from Fe (III)-containing thiomolybdate salts

M. Del Valle

Papers

Catalytic properties of WS2 catalysts prepared by in situ decomposition of tetraalkyl-ammonium thiotungstates

Catalytic study of WS2 undergoing electron irradiation

Hydrodesulfurization of dibenzothiophene using novel unsupported FeMoS catalysts prepared by in-situ activation from Fe (III)-containing thiomolybdate salts