Fabrication of visible-active ZnO-gC₃N₄ nanocomposites for photodegradation and cytotoxicity of methyl orange and antibacterial activity towards drug resistance pathogens

Nanostructured ZnO is a well dynamic photocatalyst but it has few shortcomings like wide band gap and high recombination rate. To overcome these constraints herewith we report on modification of ZnO NPs with g-C3N4 in the different weight ratios (4:1, 3:1 and 2:1). The prepared nanocomposites were comprehensively charac-terized to study the structural, morphological and optical properties. The XRD patterns of the ZnO-gC(3)N(4) NCs exhibit analogous diffraction peaks of ZnO and g-C3N4 with hexagonal structure. The optical study shows decline in bandgap energies from 3.13 (p-ZnO) to 2.95eV (ZnO-gC(3)N(4) NCs) which demonstrates the nanocomposites are extended the light absorption towards visible region. BET surface area exhibit the ZnO-gC(3)N(4) NCs have a higher specific surface area (38.37 m(2)g(-1)) than that of p-ZnO and g-C3N4. The optimized ZnO-gC(3)N(4) NCs show the improved photodegradation efficiency of Methyl Orange (MO) under UV-Vis. and sunlight with more than 25% of increment compared to pristine samples of ZnO and g-C3N4. It is important that the nanocomposite is not only extended the absorptivity towards visible light with higher activity but also photo-stability after many cycles. The bactericidal property of ZnO-gC(3)N(4) NCs was studied against four bacterial strains by agar well diffusion method which showed that the gram negative bacteria are more sensitive than gram positive. Furthermore, the cytotoxicity study of MO by using meristematic root tip cells of Allium cepa was carried out. Thus, the result shows that the ZnO-gC(3)N(4) NCs are useful for dye degradation and bactericidal activity. The cytotoxicity studies of meristematic root tip cells of Allium cepa explored that the photodegraded product is less toxic than the MO.