Single nanoparticle SERS probes of ion intercalation in metal-oxide electrodes

Probing ion-intercalating processes in electrodes is hugely important for batteries, supercapacitors, and photovoltaic devices. In this work we use single-nanoparticle (NP) probes to see real-time molecular changes correlated to electrochemically modulated ion-intercalation in metal-oxide electrodes. Using surface-enhanced Raman spectroscopy (SERS) transduced by single NP probes, we observe that the Raman frequencies and spectral intensities of the adsorbed molecules vary on cycling the electrochemical potential on a vanadium-oxide electrode. The potential-dependent frequency shifts in SERS from an electrochemically inert molecule are attributed to a Stark effect induced by chemical and structural changes as a result of ion-intercalation processes in vanadium oxide. Our study opens up a unique strategy to explore adsorbates and molecular reaction pathways on ion-intercalating materials and semiconducting interfaces.