Characterization of SERS Platforms Designed by Electrophoretic Deposition of Au Nanoparticles on CVD Graphene and ITO/glass
Here we perform electrophoretic deposition (EPD) method to control the assembly of citrate-coated Au nanoparticles (NPs) onto graphene and ITO/glass. Monolayer graphene is obtained by CVD and transferred to ITO/glass free of polymer. A quick surface-enhanced Raman scattering (SERS) test determined that drop casting methylene blue (MB) onto Au NPs previously deposited by EPD (600 s) exhibited 150 x signal enhancement. Therefore, 600 s EPD of Au NPs becomes the optimal coverage of Au NPs for SERS; we proceeded the same way and deposited the same NPs under identical conditions on graphene/ITO/glass. We then tested both platforms upon immersion into 0.3 mM MB solution and found similar SERS intensity on the graphene- and ITO-containing platforms after 10 min and 66 h, respectively which clearly demonstrate the importance of the substrate. To characterize the platforms, linear scan voltammetry (LSV) and SEM were used as fingerprints for assigning the NPs oxidation peaks to their corresponding areas on the image. We find good agreement with respect to the number of NPs per µm2 counted by LSV and SEM. We encounter that EPD on graphene leads to six fold larger coverage than on ITO/glass. These Au NPs were mostly assembled in the form of agglomerates located on what it seems defects of graphene. If those agglomerates are dissolved by anodic stripping, no SERS signal was found from the MB analyte. It also demonstrates that the platform can be reused for further deposition and SERS analysis. This work provides a simple and controllable method upon the design of advanced SERS platforms.