Chitosan grafted polyacrylic acid doped MnO₂ nanocomposite an efficient dye degrader and antimicrobial agent

Manganese dioxide (MnO₂) nanorods and (3, 6, and 9 mL) chitosan grafted polyacrylic acid (CS-g-PAA) doped MnO₂ were prepared hydrothermally. The study objective is to decrease the recombination rate of MnO₂ upon doping to enhance the dye degradation efficiency and antimicrobial activity. The doping-dependent properties of CS-g-PAA on phase identification, functional groups, optical characteristics, elemental compositions, and morphological analyses of MnO₂ nanorods were conducted using systematic characterization techniques. XRD pattern shows that MnO₂ has a tetragonal structure, with increased crystallite size (15.87 to 29.36 nm) upon doping. The TEM analysis showed that MnO₂ has nanorods and that CS-g-PAA doped MnO₂ displayed nanoflakes-like structures. The decrease in electron-hole pair recombination rate on doping was verified by PL spectroscopy, demonstrating the enhanced catalytic activity. Moreover, adding grafted binary polymers to MnO₂ inhibits bacterial cell growth by binding with the negatively charged cell wall and preventing biofilm formation. The 9 mL doped sample displayed a maximum degradation (99.27 %) in a neutral medium and 85.84 % antimicrobial efficiency against E. coli. The enoyl-acyl carrier protein reductase (FabI_{E. coli}) and DNA gyrase_{(E. coli)} were inhibited by these CS-g-PAA doped MnO₂ nanostructures (NSs), as shown by in silico molecular docking studies.