Chemistry Weekly Seminar - Dr. Alex Boika

Title: Hot Microelectrodes: Past, Present, and Future

Abstract:

Alternating current (ac) polarized microelectrodes, called hot microelectrodes, have been pioneered by Baranski in the early 2000s. A distinctive feature of his approach is the use of a high-frequency waveform, typically on the order of 100 MHz. As a result, such perturbation does not affect the measured electrochemical signal appreciably, and it is thus possible to do electrochemistry under the elevated temperature and fast mass transfer conditions. Early studies performed by Boika and Baranski have concentrated on understanding the exact nature and workings of phenomena observed at hot microelectrodes. In particular, it has been established that the simultaneous presence of high temperature and ac electric potential gradients in an electrolyte solution leads to the electrothermal fluid flow (ETF), while the ac electric field by itself is responsible for the phenomenon of dielectrophoresis (DEP). Currently, in the Boika lab, ETF and DEP phenomena have been utilized to improve the electrochemical detection of pM (10^-12 M) and sub-pM concentrations of metal nanoparticles (Ag, Pt) and E. coli bacteria. In addition, a novel technique called hot-tip scanning electrochemical microscopy (HT-SECM) has been developed. It is based on the use of a hot microelectrode in the arrangement for SECM, and so it is now possible to perform SECM measurements at elevated temperatures. The outlook on the future of the developed methodologies will also be provided.