Metal film over nanosphere (MFON) electrodes for surface-enhanced Raman spectroscopy (SERS): Improvements in surface nanostructure stability and suppression of irreversible loss

The stability and reproducibility of most SERS-active electrode surfaces are far from ideal. We have focused on this problem by developing and characterizing a metal film over nanosphere (MFON) electrode which solves these shortcomings. Atomic force microscopy (AFM), cyclic voltammetry, and surface-enhanced Raman spectroscopy (SERS) of representative molecules were used to characterize and evaluate the electrochemical and SERS performance of MFON electrodes. Tremendous stability to extremely negative potential excursions is observed for MFON electrodes as compared to standard metal oxidation reduction cycle (MORC) roughened electrodes. Consequently, irreversible loss of SERS intensity at negative potentials is not observed on these MFON electrodes. We conclude that MFON electrodes present a significant advantage over MORC electrodes because SERS enhancement is not lost upon excursion to extremely negative potentials. This work demonstrates that the MFON substrate, while easily prepared and temporally stable, offers unprecedented stability and reproducibility for electrochemical SERS experiments. Furthermore, one can conclude that irreversible loss is not a distinguishing characteristic of electrochemical SERS and consequently cannot be used as evidence to support the chemical enhancement mechanism.