Innovative environmentally friendly synthesis of graphene/AgNPs and AuNPs nanocomposites in one step: SERS performance and DFT-driven insights

Surface-enhanced Raman spectroscopy (SERS)-based sensors have gained attention because of their sensitivity and ease of implementation. The design and synthesis of substrates used in SERS poses a challenge in the search for a simple, affordable, and eco-friendly synthesis. Here, we report the use of Anemopsis californica extract to perform green synthesis of AgNPs and AuNPs , as well as the synthesis and functionalization by mechanical aqueous-surfactant exfoliation of graphite to obtain graphene. This one-step synthesis allows the formation of bionanocomposites of graphene/AgNPs and graphene/AuNPs, which are then evaluated as SERS substrates. The obtained nanocomposites showed different characteristics and properties depending on the surfactant used in the synthesis, and the interaction of A. californica in the nanocomposite remains unexplored. To this end, we correlated the experimental results with a DFT calculation of the interaction of the main A. californica extract compounds or surfactants (SDS or AOT) with the graphene monolayer. The DFT study revealed that the surfactant and A. californica compounds could be absorbed in the physisorption model on the graphene surface, which does not affect the graphene properties in relation to the indices of chemical reactivity and kinetic stability. SERS-based sensors are valued for their sensitivity and simplicity. We report a novelty one-step green synthesis of AgNPs and AuNPs using Anemopsis californica extract and mechanical exfoliation to produce graphene/AgNPs and graphene/AuNPs bionanocomposites as SERS substrates. Also, a DFT perspective correlates physicochemical properties to SERS application.