Synthesis of optically enriched cobalt-doped zinc oxide nanocomposites: Reduction of methylene blue dye

This study reports the synthesis of highly pure nanosized composite materials using a sol-gel self-combustion synthesis (SCS) approach. The complex generated within the polyvinyl alcohol and precursor(s) induces combustion once the ignition temperature is reached, resulting in a porous nanocatalyst as the gaseous by-products are removed. The XRD and TEM morphological analyses confirmed the crystalline nature, interstitial inclusion of cobalt into the ZnO lattice, and the nanoscale size range (20-50 nm) of the synthesized materials. The photoluminescence spectra of the doped nanocomposites showed a significant decrease in intensity as well as a high percentage of visible light absorption potential over pure ZnO NPs. This confirms the presence of better charge transfer and its significance in preventing electron-hole recombination processes. The UV-vis-DRS and Mot Schottky investigations showed better optoelectronic properties for the cobalt-doped ZnO composites (CZ-Cs) compared to that of the pure ZnO NPs. The indirect bandgap reduction (redshift) from 3.22 to 2.70 eV shows the perfect inclusion of cobalt in the ZnO lattice. It was revealed that the CZ-Cs showed better catalytic reduction potential for methylene blue dye within 12 min than ZnO. Thus, the solution combustion synthesis approach effectively synthesizes optoelectrically improved nanocomposite materials, which have promising prospects for catalysis, sensors, and biomedical applications.