In-situ impregnation/reduction/calcination synthesis of silver nanoparticle-graphene oxide nanocomposites

Graphene oxide–silver nanoparticles (GO+AgNPs) nanocomposites have gained significant interest for biomedical applications due to their synergistic antimicrobial and physicochemical properties. Nonetheless, developing environmentally benign synthesis routes that avoid strong reducing agents, limit nanoparticle aggregation, and enable precise control over particle size and distribution remains challenging. In this study, an in-situ thermal reduction at 300 °C was explored after wet impregnation of the precursors using either water (GO-Ag-300-W) or isopropanol (GO-Ag-300-I) to evaluate the effect of the solvent on the growth of AgNPs on graphene oxide. Micrographic analysis revealed spherical AgNPs with average diameters of 7.8 nm for GO-Ag-300-W and 12.5 nm for GO-Ag-300-I, with greater size polydispersity in the latter, whereas agglomerate formation was more pronounced in GO-Ag-300-W. Spectroscopic results confirmed partial reduction of GO, defect-induced restructuring of sp 2 domains, and predominantly metallic silver with a crystalline oxidized surface layer, together with a stabilizing effect of the nanoparticles on the GO lattice, without full graphitic restoration at 300 °C. Thermal analysis indicated higher stability during the initial decomposition stage (183–253 °C) compared with pristine GO, whereas the final decomposition temperature decreased by 30–120 °C due to the catalytic effect of silver on carbon lattice degradation. A preliminary in vitro cytotoxicity test in human gingival fibroblasts, conducted with potential dental applications in mind, showed a concentration-dependent increase in cytotoxicity, with GO-Ag-300-I exhibiting the lowest growth inhibition. Overall, the findings provide fundamental elements to guide the optimization of GO+AgNPs nanocomposites for future use. • GO+AgNPs nanocomposites were synthesized via in-situ wet impregnation and calcination. • Water and isopropanol impregnation led to different AgNPs sizes and dispersion on GO. • The nanocomposites exhibited lower cytotoxicity than pristine GO in human gingival fibroblast assays.