title: Tip-Enhanced Raman Voltammetry: Coverage Dependence and Quantitative Modeling.
abstract: Electrochemical atomic force microscopy tip-enhanced Raman spectroscopy (EC-AFM-TERS) was employed for the first time to observe nanoscale spatial variations in the formal potential, E0', of a surface-bound redox couple. TERS cyclic voltammograms (TERS CVs) of single Nile Blue (NB) molecules were acquired at different locations spaced 5-10 nm apart on an indium tin oxide (ITO) electrode. Analysis of TERS CVs at different coverages was used to verify the observation of single-molecule electrochemistry. The resulting TERS CVs were fit to the Laviron model for surface-bound electroactive species to quantitatively extract the formal potential E0'at each spatial location. Histograms of single-molecule E0'at each coverage indicate that the electrochemical behavior of the cationic oxidized species is less sensitive to local environment than the neutral reduced species. This information is not accessible using purely electrochemical methods or ensemble spectroelectrochemical measurements. We anticipate that quantitative modeling and measurement of site-specific electrochemistry with EC-AFM-TERS will have a profound impact on our understanding of the role of nanoscale electrode heterogeneity in applications such as electrocatalysis, biological electron transfer, and energy production and storage.
authors.forename: Michael
authors.identifier: 0000-0002-8276-5562
authors.initials: M
authors.lastname: Mattei
authors.forename: Gyeongwon
authors.initials: G
authors.lastname: Kang
authors.forename: Guillaume
authors.initials: G
authors.lastname: Goubert
authors.affiliation: Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Dhabih V
authors.initials: DV
authors.lastname: Chulhai
authors.forename: George C
authors.identifier: 0000-0001-5837-4740
authors.initials: GC
authors.lastname: Schatz
authors.affiliation: Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Lasse
authors.initials: L
authors.lastname: Jensen
authors.forename: Richard P
authors.identifier: 0000-0001-8861-2228
authors.initials: RP
authors.lastname: Van Duyne
mesh_terms: D055664:Electrochemical Techniques; D018625:Microscopy, Atomic Force / Q000379:methods*; D008962:Models, Theoretical; D010078:Oxazines / Q000737:chemistry*; D010084:Oxidation-Reduction; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013499:Surface Properties; D017971:Tin Compounds / Q000737:chemistry
chemical_list: D010078:Oxazines; D017971:Tin Compounds; C008619:Nile Blue; C109984:indium tin oxide
keywords: Laviron model; Tip-enhanced Raman spectroscopy (TERS); cyclic voltammetry; single-molecule electrochemistry