Structure, optical properties and antimicrobial activities of MgO–Bi2−xCrxO3 nanocomposites prepared via solvent-deficient method

MgO–Bi 2− x Cr x O 3 nanocomposites for x = 0 and 0.07 were fabricated using the solvent-deficient route. X-ray diffraction method, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA) and UV–Vis spectroscopy were employed to study the properties. The samples were also evaluated for the antibacterial activity. The x = 0 sample showed a dominant monoclinic crystalline structure of α -Bi 2 O 3 phase. No peaks attributed to MgO were observed. Cr-doped MgO - Bi 2 O 3 in which Bi was substituted showed that the tetragonal BiCrO 3 phase was also present in the MgO - Bi 2 O 3 composite. The Scherrer formula was employed to determine the crystallite size of the samples. The Cr-doped sample showed a decrease in the crystallite size. The microstructures of the non-doped MgO–Bi 2 O 3 and MgO–Bi 1.93 Cr 0.07 O 3 composites consisted of micrometer sized grains and were uniformly distributed. Direct transition energy gap, E g decreased from 3.14 to 2.77 eV with Cr-doping as determined from UV–Vis spectroscopy. The Cr-doped MgO - Bi 2 O 3 nanocomposites exhibited two energy gaps at 2.36 and 2.76 eV. The antibacterial activity was determined against gram-negative bacteria ( Salmonella typhimurium and Pseudomonas aeruginosa ) and gram-positive bacteria ( Staphylococcus aureus ) by disc diffusion method. Cr-doping led to a decrease in inhibitory activity of MgO–Bi 2− x Cr x O 3 nanocomposite against the various types of bacteria.