Electrochemically Deposited Silver Nanostructures on Reduced Graphene Oxide Aerogels as Sensitive SERS Substrates

Abstract

Surface-enhanced Raman scattering (SERS) pushes the boundaries of Raman spectroscopy as an analytical technique, allowing improved sensitivity and high discriminatory ability in analyte detection. Here, we introduce a SERS substrate using reduced graphene oxide aerogels as scaffolds. Reduced graphene oxide aerogels are hydrophobic, electrically conductive, and easily formable, providing a versatile platform for silver dendritic nanostructure growth via electrochemical deposition. We show that the electrochemical growth conditions (applied voltage, reduction time) have a significant effect on both the morphology and coverage of the silver nanostructures, which in turn have a strong effect on the SERS performance of the substrate. The importance of Ag dendrite morphology to the SERS substrate's performance is also confirmed by finite-difference time-domain simulations. Under silver growth conditions of 10 V applied voltage at 10 Hz for 120 min, we obtained a limit of detection of 3.16 × 10^-5 ppm for thiram, which is lower than the testing requirements set by food and environmental regulatory agencies. Moreover, the substrates showed high silver coverage (85.6%), reproducibility (relative standard deviation ∼6% for substrates produced under the same conditions), and relative stability (∼20% change) of the obtained signal over one month. In view of their SERS capabilities and relative ease of preparation, we consider this new class of substrates a strong candidate for meeting detection and quantification challenges for a broad spectrum of analytes.