Structural, morphological, optical, and antibacterial properties of Mn and (Ag, Mn) co-doped copper sulfide nanostructures

Pure, Mn-doped, and Mn/Ag-co-doped copper sulfide nanoflowers with a high surface area at different Ag concentrations (1%, 2%, and 3%), and a constant concentration value of Mn, were synthesized by hydrothermal technique. All nanoparticles were prepared and characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), zeta potential, UV–visible spectroscopy (UV–vis), and Fourier-transform infrared spectroscopy (FTIR). It was observed that copper sulfide doped with Mn and Ag plays a significant role in the crystallite size, lattice constant, and band gap energies of all samples. The results of the XRD characterization demonstrate that all the samples of interest have the covellite hexagonal polycrystalline structure with a (110) preferred orientation. The values of average crystallite size are in the range of 25.14–12.34 nm. The FE-SEM analysis confirms the formation of CuS nanoparticles as a hierarchical structure like a ball-flower shape. The deduced optical gap values from optical measurement are in the range of 3.19–2.24 eV. Antibacterial activities of pure CuS, Mn-doped, and Mn/Ag co-doped CuS against P. aeruginosa, S. aureus, and E. coli were assessed by inhibition zone. All the samples have high antibacterial activities, but the 3% Mn/3% Ag co-doped CuS displayed the highest antibacterial activity against negative and positive bacteria, with the maximum inhibitory concentration being 4 mg/ml.