A simple, template-free and mild solution chemistry route was employed to synthesize diverse copper sulfide (CuS) nanostructured assemblies at 70 °C by varying the solvent (water or ethylene glycol, or their ratios (3:1, 1:1 and 1:3)). The CuS structures in the shape of spheres and nanotubes were found to be assemblies of either nanoplates or nanoparticles. The nanotube formation was elaborately studied by varying the synthesis parameters such as temperature, reaction duration, precursor's ratio, and counterions. Counterions such as NO3(-) and SO4(2-) were found to be suitable for nanotube formation whereas in the presence of Cl(-) and OAc(-) ions, CuS flake-like and nanoparticle assemblies are obtained, respectively. The optical bandgaps for the CuS with different morphologies were measured to be in the range of 1.88-2.16 eV. The bandgap of CuS in the visible region of electromagnetic radiation prompted it to be used as photocatalyst in the past under natural light. However, we demonstrate here the similar catalytic performance of as-synthesized CuS nanostructures for the degradation of methylene blue in the dark, suggesting that light does not play a role in its catalytic behavior.

Herein we demonstrate the synthesis and formation mechanism of copper sulfide (CuS and Cu 2 S) by a simple hydrothermal process in the temperature range of 150-250 1C. The molar concentration ratio of copper nitrate to sodium thiosulfate precursor, and the reaction temperature play important roles in determining the morphology and composition of the product. At a higher thiosulfate concentration, elemental sulfur precipitates out along with CuS. However, the elemental sulfur is degraded with increasing of the reaction temperature. The morphology of the as-synthesized product is primarily a sphere-like agglomeration of either nanoparticles and/or nanoplates. The surfactant is found to be indispensable for obtaining dispersed nanocrystals. The stability of CuS and the formation of different copper compounds at higher temperature are studied in detail using thermal analysis and X-ray diffraction (XRD). The phase pure CuS is found to be completely converted to CuO upon calcining in air at 800 1C. However, the in situ high temperature XRD measurements in a vacuum show complete conversion of CuS to Cu 2 S at 600 1C without any intermediate phases. The optical bandgap of the as-synthesized CuS nanocrystals is measured to be B1.7 eV.

Ni-Doped CuS synthesized by a facile solvothermal method is demonstrated as an efficient oxygen evolution catalyst in alkaline medium.

The effective surface area of the nanostructured materials is known to play a prime role in catalysis. Here we demonstrate that the shape of the nanostructured materials plays an equally important role in their catalytic activity. Hierarchical CdS microstructures with different morphologies such as microspheres assembled of nanoplates, nanorods, nanoparticles, and nanobelts are synthesized using a simple hydrothermal method by tuning the volume ratio of solvents, i.e., water or ethylenediamine (en). With an optimum solvent ratio of 3:1 water:en, the roles of other synthesis parameters such as precursor's ratio, temperature, and precursor combinations are also explored and reported here. Four selected CdS microstructures are used as photocatalysts for the degradation of methylene blue and photoelectrochemical water splitting for hydrogen generation. In spite of smaller effective surface area of CdS nanoneedles/nanorods than that of CdS nanowires network, the former exhibits higher catalytic activity under visible light irradiation which is ascribed to the reduced charge recombination as confirmed from the photoluminescence study.