The redox state, geometry and chemical conversion of molecular or biomolecular moieties in contact with an electrified interface can be tuned by adjusting the applied potential. To improve device design in biotechnology, molecular electronics or electrochemical energy conversion applications, detailed understanding of reaction-site specific interfacial electron transfer on the structural and physico-chemical properties of (bio)molecular adsorbates is required.
In this talk, I will present our recent development of electrochemical tip-enhanced Raman spectroscopy (EC-TERS) as a powerful tool to study electrified solid/liquid interfaces with molecular detail.[1-4] A combination of EC-STM and Raman spectroscopy, EC-TERS provides the potential-dependent chemical fingerprint of interfacial species and electrode surfaces with <10 nm spatial resolution, in combination with topographic information on the region of interest. In a proof-of-concept study, we have investigated the electrochemical behavior of less than 100 small, non-resonant adenine molecules at Au(111).[3,4] From the spectral changes observed as a function of potential, the conformational and chemical changes of the showcase DNA base, namely the adsorption state and geometrical reorientation following molecule (de)protonation were deduced by combining ECTERS experimental and theoretical simulation data.
Our results demonstrate the great potential that this unique addition to the electrochemical nanoscopy tool box holds to access electron-transfer triggered (bio)molecular chemistry in situ with unprecedented spatial and chemical resolution, for example, to unravel redox mechanisms of biophysical processes on the few- to single-moiety level for sensing or molecular electronics applications.
 N. Martín Sabanés, L. Driessen, K.F. Domke Anal. Chem. 88 (2016) 7108.
 N. Martín Sabanés, K.F. Domke ChemElectroChem 4 (2017) 1814.
 N. Martín Sabanés, A. Elizabeth, J.H.K. Pfisterer, K.F. Domke Faraday Disc. 205 (2017) 233.
 N. Martín Sabanés, T. Ohto, D. Andrienko, Y. Nagata, K.F. Domke Angew. Chem. Int. Ed. 56 (2017)