Surface-enhanced Raman scattering (SERS) has been shown to be capable of single molecule detection and distinction of analytes in complex mixtures through molecular fingerprints. However, sensitivity for low analyte concentrations is still a crucial challenge that needs to be addressed to further increase the measuring capabilities of a SERS sensor. Drawing the target molecules within the electromagnetic (EM) hotspots is an initial obstacle that hinders the further enhancement of SERS signals. Here, we explore the possibility of using electrostatic force as a means of guiding charged molecules in solution toward SERS active substrate for enhanced SERS signals. We use a device consisting of a polytetrafluoroethylene (PTFE) chamber with a SERS substrate, in-between two electrodes. In this setup, the SERS substrate acts as anode, attracting negative charge carriers, when a potential is applied. We demonstrate electrokinetic preconcentration of the analyte molecules in solution on the SERS substrates under a constant DC electric field of at least +100mV/mm for 60 minutes. The electrokinetic preconcentration provides full benefits in migrating the electrically charged molecules for the spatial confinement by applying an electrical potential. Our results show the migration of negatively charged molecules directed to the SERS substrate. The electrochemically enhanced analyte-surface interaction results in significantly higher SERS intensities, allowing for lower limits of detection. Extending our approach to different charged molecules, our work provides new directions for ultrasensitive SERS applications.

Electromigration of charged molecules in solution for highly intense surface enhanced Raman scattering

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.