Upcycling agroindustrial waste into graphene oxide supports for gold nanoparticles: toward sustainable nanomaterials

The aim of this work is to develop a sustainable route for producing graphene oxide-based materials from agroindustrial waste and to evaluate their structural and chemical properties in comparison with conventional graphene oxide (GO) and reduced graphene oxide (rGO). Agroindustrial waste-derived graphene oxide (Agro-GO) was synthesized from peanut shells and spent coffee grounds via a ferrocene-assisted green pyrolysis-oxidation approach. The resulting materials were compared with GO prepared via the Marcano-modified Hummers' method and its hydrazine-reduced counterpart (rGO). Comprehensive characterization was performed using UV-vis, ATR-FTIR, XPS, XRD, and Raman measurements, complemented by TGA and TEM to assess optical properties, surface chemistry, and structural and morphological features. Additionally, gold nanoparticles (AuNPs) were photochemically deposited onto Agro-GO to evaluate its potential for nanotechnology-related applications. The results reveal that Agro-GO exhibits tunable oxidation levels, diverse surface functionalities, and morphologies comparable to those of conventional GO; these properties strongly depend on the type of agroindustrial waste precursor used. These findings demonstrate the feasibility of transforming agroindustrial waste into high-value graphene-based nanomaterials and highlight the potential of sustainable synthesis routes for advancing environmentally responsible carbon-based technologies.