CONICET | Buscador de Institutos y Recursos Humanos

Electrochemical modulation to induce controlled fluctuations in surface enhanced Raman signals is introduced as a method to discriminate and isolate different contributions to the spectra. The electrochemical modulation, that can be changed in potential range and amplitude, acts as a controllable switch to turn on, to turn off or to change specific Raman signals. As we do know the profile of the external electrochemical modulation we look for this profile in the fluctuations of each peak in the Raman spectra by different fluctuation analysis techniques. Those peaks that are following the electrochemical modulation profile are assigned to the species that is electrochemically active in that potential range. Principal component analysis, either by itself or assisted by fast Fourier transform prefiltering, are shown to provide viable tools to isolate the different components of the spectra. Electrochemical modulation provides therefore a technique to study complex cases of coadsorption and to resolve problems of spectral congestion in surface enhanced Raman spectroscopy. Electrochemical modulation and signal discrimination could become a very important tool in areas like bioelectrochemistry. It allows to isolate the signals from different species in redox active sites in samples where one cannot choose at will the purity or spectral characteristics of all the components. The situation of overlapping peaks or much larger signals from spurious molecules can prevent the isolation of the interesting spectra displaying, for example, an oxidation/reduction cycle. Therefore the technique applies particularly well to cases of coadsorption, that is a classic phenomenon in the electrochemistry of complex multi-component systems like biological systems.