Copper Precursor Salt‐Dependent Antimicrobial Activity of Graphite Oxide Composites Against Escherichia coli and Staphylococcus Aureus: Synthesis and Characterization

Abstract

Graphite oxide (GrO) and GrO doped with 1.5 wt% Cu(NO3)2 (CuN/GrO) and 1.5 wt% CuSO4 (CuS/GrO) were synthesized by the Hummers and incipient impregnation methods, respectively. Face‐center cubic Cu, monoclinic CuO, and cubic Cu2O mixed crystalline phases were observed in CuN/GrO and CuS/GrO composites. In particular, CuSO4‐doped GrO composite showed higher relative crystallinity compared to Cu(NO3)2‐doped GrO composite. The ID/IG ratio on average was 1.0 for all composites, associated with similar structural disorders and defects. CuN/GrO and CuS/GrO composites increased the C: O ratio by 30% compared to GrO. In Cu(NO3)2‐doped and CuSO4‐doped GrO composites, the copper particle dispersion was on the GrO surface and GrO edges, respectively. By agar‐well diffusion assay, the CuN/GrO composite presented only inhibition against the Staphylococcus aureus microorganism at 10 mg mL‐1 per well. However, using the CuS/GrO composite, the minimum inhibitory concentration was 5 mg mL‐1 per well against Escherichia coli and S. aureus microorganisms. In general, the copper precursor salt influenced the copper particle localization in the GrO matrix in a different way, modulating the antimicrobial behavior. In this way, it is possible to establish a possible electrostatic adsorption caused by the Cu+ or Cu2+ ions and the negative charges of the bacterial cell membrane, where the adsorption and mass diffusion mechanisms between charged composites and Gram‐positive and Gram‐negative microorganisms were affected by the copper particle arrangement in the composites.This article is protected by copyright. All rights reserved.