(CdO)$_{1-x}$(Mn$_3$O$_4$)$_x$ ($x$ = 0.0/0.25/ 0.50/0.75/1.0) nanocrystals: preparation by a facile method, physicochemical properties and applications

High phase pure (CdO)$_{1-x}$(Mn$_3$O$_4$)$_x$ ($x$ = 0.0/0.25/0.50/0.75/1.0) nanocrystals (including multiphased nanocomposites) were prepared by using a simple microwave-assisted solvothermal method, and characterized structurally, chemically, optically and electrically by carrying out X-ray diffraction, electron microscopic (SEM/TEM), energy dispersive X-ray absorption spectral, optical (UV-Vis) absorption spectral and AC electrical (at various temperatures and frequencies) measurements. Samples prepared exhibit crystalline nature, high chemical purity, nearly uniform spherical morphology, considerable particle sizes (within 47 nm), higher optical band gap energies (4.0 – 5.3 eV) and normal dielectric behavior. Studies were made to understand their capability in photocatalytic degradation (evaluated using Methylene Blue (MB) dye under UV-visible irradiation) and antimicrobial activity against gram positive Bacillus Subtilis (BS), gram negative Escherichia Coli (EC) and fungal Candida Albicans (CA). Results indicate a higher photocatalytic degradation with MB dye for the three multi-phased (CdO)$_{1-x}$(Mn$_3$O$_4$)$_x$ nanocomposites (with $x$ = 0.25/0.50/0.75) prepared (with light of wavelength around 665 nm), and a higher antimicrobial activity with the bacteria (BS and EC) than with the fungus (CA); however, the phase pure Mn$_3$O$_4$ (with $x$ = 1.0) nanocrystal has been found to be more active with all the three microbes considered.