Controlled synthesis and catalytic activity of copper sulfide nanostructured assemblies with different morphologies

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.