Nanowires Designed by Electrophoretic Deposition of Core–Shell Silver-Graphene Quantum Dots Nanohybrids on Conductive Electrodes

In this work, we observe a template-free formation of nanowires (NWs) during electrophoretic deposition (EPD) of chemically synthesized core-shell Ag-graphene quantum dots (GQDs) hybrid nanoparticles (hNPs) with a diameter of ∼20 nm. The EPD method consists of a transparent ITO-glass electrode subjected to 1.0 V (vs SCE) and immersed in as-synthesized hNPs aqueous dispersion containing hydroquinone (HQ). During EPD, Ag-GQDs hNPs tend to align close to each other to ultimately form well-connected NWs comprised of ∼5.6 μm long and ∼20 nm width, consistent with the original diameter of the as-synthesized hNPs. The proposed mechanism involves the alignment of hNPs along the lines of the electric field, followed by electrochemical Ostwald ripening. From 1200 to 1800 s EPD, Ag⁺ seems to be reduced (solder) at the gaps between already deposited nanohybrids to ultimately form longer and consolidated Ag NWs. A control experiment performed with citrate-coated Ag nanoparticles (NPs) under the same experimental conditions exhibits few NP alignments with a very low yield of Ag NWs seen after long periods of time under EPD. This suggests that the presence of GQDs at the shell may play a role in the formation of NWs induced by Ostwald ripening. At 1800 s EPD, the as-formed film exhibits the highest SERS enhancement factor for detecting 1.0 × 10^-6 M Rhodamine 6G (Rh6G), highlighting their superior performance. This simple method of forming organic-metal hybrid NWs can be further exploited in next-generation electronics, touch screens, and sensors.