Ag-NP-Decorated Carbon Nanostructures: Synthesis, Characterization, and Antimicrobial Properties

As the global urgency for effective antimicrobial agents intensifies, this work harnesses the widely demonstrated antimicrobial activity of silver nanoparticles (Ag-NPs) and proposes alternative synthesis approaches to metal-organic hybrid systems with antimicrobial activity. In this study, the proposed synthesis route involves decorating metallic nanoparticles into organic substrates without previous doping. The synthesis simultaneously uses polyethylene glycol for three crucial purposes: (1) acting as a mild reducing agent to generate Ag-NPs with a spherical shape and diameters ranging from 10 to just over 20 nm, (2) functioning as a dispersing agent for flakes of commercial nanostructured carbon supports, including reduced graphene oxide (rGO, ID-nano), and commercial carbon nanoplatelets from Sigma-Aldrich (GNPs, Sigma-Aldrich), and (3) serving as a promoter for the homogeneous anchoring of Ag-NPs in the carbon lattice without altering the conformation of the carbon lattice. This intricate interaction involves the π-orbitals from the sp² hybridization honeycomb and the d-orbitals from the Ag-NPs, leading to the constructive rehybridization of rGO and GNPs. In our study, Ag-NPs/rGO are compared with a support lacking oxygenated groups in the lattice, such as commercial GNPs (Sigma-Aldrich), to produce Ag-NPs/GNPs. This comparison maintains constructive sp² rehybridization, preserving the characteristic properties of rGO (ID-nano) and graphene nanoplatelets, including commercial GNPs (Sigma-Aldrich). Notably, oxygenated groups from rGO exhibit greater availability for exchanging oxo and hydroxy defects for Ag-NPs compared with GNPs (Sigma-Aldrich). The resulting Ag-NPs/rGO and Ag-NPs/GNP systems are thoroughly physicochemically characterized, employing techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and scanning transmission electron microscopy, revealing the successful integration of Ag-NPs with minimal alteration to the carbon lattice. Subsequent antimicrobial evaluation against Escherichia coli (E. coli) demonstrates significant activity, with Ag-NPs/rGO and Ag-NPs/GNPs registering similar minimum inhibitory concentrations of 50 μg mL^-1. This study underscores the potential of our metal-organic hybrid systems as antimicrobial agents and provides insights into the constructive rehybridization process, paving the way for diverse applications in the biomedical and environmental fields.