ENHANCED ADSORPTIVE REMOVAL OF METHYLENE BLUE USING GRAPHENE OXIDE-DOPED MNO₂ NANORODS

Abstract

Background: Graphene oxide (GO)-modified manganese dioxide (MnO₂) nanostructures have attracted considerable attention owing to their enhanced catalytic and antimicrobial properties resulting from improved charge transport and increased surface activity.

Objective: To synthesize GO-modified MnO₂ nanorods and evaluate the effect of GO incorporation on their structural, optical, catalytic, and antibacterial characteristics.

Materials and Methods: Pristine and GO-doped MnO₂ nanorods containing 2 and 6 wt% GO were synthesized through a facile chemical precipitation method under ambient conditions. The synthesized nanomaterials were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis) spectroscopy, photoluminescence (PL) analysis, and energy-dispersive spectroscopy (EDS). Catalytic activity was assessed through methylene blue (MB) degradation in the presence of sodium borohydride (NaBH₄) under different pH conditions.

Results: XRD analysis confirmed the formation of phase-pure monoclinic MnO₂ with an average crystallite size of approximately 36.4 nm and no detectable impurity phases. FTIR spectra verified the presence of characteristic O–H, C=C, C–O, and Mn–O functional groups, confirming successful GO incorporation. UV-Vis studies revealed a prominent absorption band near 300 nm with a band gap of approximately 4.1 eV, while GO addition induced a noticeable blue shift in the absorption edge. PL measurements showed reduced emission intensity for GO-doped samples, indicating suppressed charge carrier recombination and enhanced charge separation. Catalytic degradation studies demonstrated a substantial improvement in MB reduction efficiency following GO incorporation. The 6 wt% GO–MnO₂ nanocomposite exhibited the highest catalytic performance, achieving approximately 94% degradation in acidic medium and 95% degradation in neutral medium. The enhanced activity was attributed to the synergistic interaction between conductive GO sheets and MnO₂ nanorods, facilitating efficient electron transfer and increasing the number of active catalytic sites.

Conclusion: GO incorporation significantly improves the optical and catalytic properties of MnO₂ nanorods by promoting charge separation and enhancing electron transport. The synthesized GO–MnO₂ nanocomposites exhibit excellent catalytic efficiency and promising antibacterial activity, making them suitable candidates for environmental remediation and biomedical applications.