ZnO nanoparticles were synthesized by co-precipitation with no capping agent followed by covering with ZnS using a solution-based chemical method at low temperature. By variation of the solution concentrations it was found that the fully-covering ZnS shell forms by a reaction of Na 2 S with ZnO NPs followed by the formation of ZnS nano-crystals by the reaction of Na 2 S with ZnCl 2. The mechanism that led to full coverage of the ZnO core is proposed to be the addition of ZnCl 2 at a later stage of the growth which guarantees a continuous supply of Zn ions to the core surface. Moreover, the ZnS nanocrystals that uniformly cover the ZnO NPs show no epitaxial relationship between the ZnO core and ZnS shell. The slow atomic mobility at the low reaction temperature is attributed to the non-epitaxial uniform ZnS shell growth. The rough surface of the ZnO grains provides initial nucleation positions for the growth of the ZnS shell nano-crystals. The low growth temperature also inhibits the abnormal growth of ZnS grains and results in the homogeneous coverage of ZnS nano-crystals on the ZnO core surface. The as-synthesized ZnO@ZnS core-shell nanoparticles were used as a photocatalyst to decompose Rose Bengal dye at three different pH values. ZnO@ZnS core-shell nanoparticles perform as a more active photocatalyst at a pH of 4, while pure ZnO nanoparticles are more efficient at a pH of 7.

In this work, electrosynthesis of Fe3O4 nanoparticles was carried out potentiostatically in an aqueous solution of C4H12NCl which acts as supporting electrolyte and electrostatic stabilizer. γ-Fe2O3 nanoparticles were synthesized by controlling oxidation of the electrooxidized Fe3O4 nanoparticles at dierent temperature. Finally the phase transition to α-Fe2O3 nanoparticles was performed at high temperatures using sintering treatment. The synthesized particles were characterized using X-ray diraction, Fourier transformation, infrared scanning electron microscopy with energy dispersive X-ray analysis, and vibrating sample magnetometry. Based on the X-ray diraction results, the transition from Fe3O4 to cubic and tetragonal γ-Fe2O3 was performed at 200• C and 650• C, respectively. Furthermore, phase transition from metastable γ-Fe2O3 to stable α-Fe2O3 with rhombohedral crystal structure was approved at 800• C. The existence of the stabilizer molecules at the surface of Fe3O4 nanoparticles was conrmed by Fourier transformation infrared spectroscopy. According to scanning electron microscopy images, the average particles size was observed around 50 nm for electrooxidized Fe3O4 and γ-Fe2O3 nanoparticles prepared at sintering temperature lower than 900• C, however by raising sintering temperature above 900• C the mean particles size increases. Energy dispersive X-ray point analysis revealed that the nanoparticles are almost pure and composed of Fe and O elements. According to the vibrating sample magnetometry results, saturation magnetization, coercivity eld, and remnant magnetization decrease by phase transition from Fe3O4 to Fe2O3.

Using density functional theory calculations, we determine the band structure and DOS of graphene and silicene supercell models. We also study the adsorption mechanism of Li metal atoms and Li-ions onto free-standing silicene (buckled, θ = 101.7°) and compare the results with those of graphene. In contrast to graphene, interactions between Li metal atoms and Li-ions with the silicene surface are quite strong due to its highly reactive buckled hexagonal structure. As a consequence of structural properties the adsorption height, the most stable adsorption site and energy barrier against Li diffusion are also discussed here to outline the prospects of using silicene in electronic devices such as Li ion batteries (LiBs), hydrogen storage and molecular machines. However, in most LiBs, graphene layers are used as anode electrodes. Here, it is shown that graphene has very limited Li storage capacity and low surface area than silicene. As our models are in good agreement with previous predictions, this finding presents a possible avenue for creating better anode materials that can replace graphene for higher capacity and better cycling performance of LiBs.