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

## TL;DR

Graphene oxide (GO) coatings on mullite foams significantly enhance antibacterial activity against both Gram-negative and Gram-positive bacteria.

## Contribution

A novel method of enhancing antibacterial properties of mullite foams through multilayer GO coatings is presented.

## Key findings

- GO-coated foams showed effective antibacterial activity against Escherichia coli and Staphylococcus aureus.
- Ten coating cycles produced the most effective antibacterial performance.
- XCT analysis confirmed successful multilayer GO coating on foam surfaces.

## Abstract

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 (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) 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 Escherichia coli and Staphylococcus aureus.