Enhanced antimicrobial activity of Cu-decorated graphene nanoplatelets and carbon nanotubes

• Published in: Surfaces and interfaces 2024-10, Vol.53, p.105074, Article 105074
• Main Authors: Assis, Marcelo, Santos, Jeziel R., Cipriano, Matheus H.L., Reis, Roberta Y.N., Ribeiro, Lara K., Mascaro, Lucia H., Longo, Elson, Andrés, Juan
• Format: Article
• Language: English
• Subjects: Antimicrobial coatings; Cu-decorated carbon materials; DFT calculations
• ISSN: 2468-0230
• DOI: 10.1016/j.surfin.2024.105074

New materials with antimicrobial properties are necessary to combat the proliferation and transmission of pathogenic microorganisms. In this work, graphene nanoplatelets (GPN) and multi-walled carbon nanotubes (CNT) decorated with Cu nanoparticles (Cu NPs) were synthetized by microwave-assisted hydrothermal method, varying the Cu content from 1 to 10 wt.%. These materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, and scanning and transmission electron microscopy (SEM and TEM) and their antimicrobial activity against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) were evaluated. The sample with 10 wt.% Cu at CNTs is more effective compared to GPNs. Then, brass coatings with pure and Cu-decorated (10 wt.%) CNTs and GPNs were prepared by spin coating to evaluate the antimicrobial activity of these surfaces. It was observed that coatings with the carbon matrices reduced microbial growth by 2 logs, whereas decoration with Cu NPs amplified this value, especially for the Cu/CNT coating, achieving up to a 6-log reduction after 24 h of contact. The stability of the antimicrobial activity of these coatings was evaluated over 5 successive 24-h cycles, demonstrating high stability. DFT calculations on a simplified model, based on a Cu atom adsorbed on GPN and CNT, reveal a thermodynamically favorable pathway to explain the antibacterial activity. The results show a mechanism that could promote the formation of the precursors of hydroxyl (⦁OH), superoxide (⦁O2−), and hydroperoxyl (⦁OOH) radicals, which are adsorbed strongly on GPN and CNT surfaces. This study highlighted the critical role of Cu NPs-loaded on carbon materials, GPN and CNT, in enhancing the antibacterial activity. [Display omitted]