Graphene Oxide (GO) Coating on Reticulated Open-Cell Mullite (ROM) Foams for Enhancing Antibacterial Activity

Graphene oxide (GO) was synthesized by a modified Hummers' method to study its antibacterial activity in two forms: powders and coating agents. Reticulated open-cell mullite (ROM) foams, fabricated by a replica method using polymer foam as the pore template, were enhanced in their antibacterial activity by coating them with the synthesized GO dispersed in aqueous solutions. To fabricate the mullite foams, nano silica (nSiO₂), derived from rice husk (RH), was mixed with commercial alumina (Al₂O₃) and sintered at 1500 °C for 4 h. The sintered foams were pretreated with HCl acid and dip-coated in GO aqueous solutions prepared with a fixed ratio of GO and deionized water. The dip-coating process was performed 3, 5, and 10 cycles to obtain GO multilayers on the surface of the mullite foams. X-ray computed tomography (XCT) analysis was used to investigate the external and internal microstructures of GO-coated foams and to determine GO layer thicknesses. Antibacterial activities against Gram-negative bacteria (<i>Escherichia coli</i>) and Gram-positive bacteria (<i>Staphylococcus aureus</i>) by the synthesized GO powders and GO-coated foams were determined based on the standard test ASTM E2149. The synthesized GO powders showed effective antibacterial properties. Microstructural analysis of the GO-coated foams confirmed the successful coating process due to the presence of multilayered GO on the foam surfaces. Ten cycles of GO coating on the foams showed the most effective antibacterial activities against both <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>.