Green synthesis of graphene quantum dots and silver nanoparticles compounds with excellent surface enhanced Raman scattering performance

• The Ag-GQDs compounds were successfully prepared via photochemical reaction.
• The Ag-GQDs compounds were then collected in a SiO2 microspheres-actived substrate.
• GQDs with the size of 1–4 nm in Ag-GQDs compounds can act as “hot spot” sites.
• GQDs favor the adsorption of Rhodamine 6G molecules and the charge transfer process.
• The SiO2 template provides a larger surface areas to adsorb more probe molecules.

Here, silica (SiO2) supported silver nano-particles (Ag NPs) and graphene quantum dots (GQDs) compounds were designed and synthesized via a “green” photochemical approach and an electrophoresis deposition technique in order to provide a highly active surface-enhanced Raman scattering (SERS) substrate. In this approach, the electrochemically prepared aqueous solution of GQDs was used as a solvent and a reducing agent to synthesize in-situ Ag-GQDs compounds under Ultraviolet (UV) irradiation. These compounds were collected on a SiO2 supported Si substrate through the electrophoresis deposition technique. Benefiting from their proper size (1–4 nm) and distribution in the spatial gaps between adjacent Ag NPs, GQDs could act as “hot spot” sites for lighting up the Raman scattering signals. Together with the enhanced adsorption of Rhodamine 6G (R6G) molecules through π-π stacking, the electrostatic interactions from GQDs, and the enlarged specific surface area provided by the SiO2 template, the as-prepared substrate exhibited a strong SERS signal with excellent reproducibility. The detection limit of R6G was pushed to 8.0 × 10−14 M. We hope our work provides a time-saving and facile approach for the design and creation of ultrasensitive SERS substrate for trace species detection.

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