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

Abstract

In this work, we observe a template-free formation ofnanowires (NWs) during electrophoretic deposition (EPD) ofchemically 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 electrodesubjected to 1.0 V (vs SCE) and immersed in as-synthesized hNPsaqueous dispersion containing hydroquinone (HQ). During EPD, Ag-GQDs hNPs tend to align close to each other to ultimately form wellconnectedNWs comprised of ∼5.6 μm long and ∼20 nm width,consistent with the original diameter of the as-synthesized hNPs. Theproposed mechanism involves the alignment of hNPs along the lines ofthe electric field, followed by electrochemical Ostwald ripening. From1200 to 1800 s EPD, Ag+ seems to be reduced (solder) at the gapsbetween already deposited nanohybrids to ultimately form longer and consolidated Ag NWs. A control experiment performed withcitrate-coated Ag nanoparticles (NPs) under the same experimental conditions exhibits few NP alignments with a very low yield ofAg NWs seen after long periods of time under EPD. This suggests that the presence of GQDs at the shell may play a role in theformation of NWs induced by Ostwald ripening. At 1800 s EPD, the as-formed film exhibits the highest SERS enhancement factorfor detecting 1.0 × 10−6 M Rhodamine 6G (Rh6G), highlighting their superior performance. This simple method of formingorganic-metal hybrid NWs can be further exploited in next-generation electronics, touch screens, and sensors.