A self-cleaning strategy for electrochemical oxidation of a-pinene with minimal electrode fouling

This work focusses on the electrochemical oxidation of a-pinene, a key semiochemical found in plants, insects, and other organisms that plays a vital role in ecological interactions within natural environments'-. This study may then aid in developing a sensitive and selective method for field monitoring of a-pinene. In our work, by coupling electrochemistry with spectroscopy, we have identified 4,6,6-trimethyl-bicyclo [3.1.1] hept-3-en-2-one and N-(4,6,6-trimethyl-bicyclo [3.1.1] hept-3-en-2-yl) acetamide as the primary oxidation products of a-pinene at a glassy carbon electrode in the presence of the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate (EMIM)[ESO,]) in acetonitrile as a supporting electrolyte. However, accumulation of these oxidation products at the electrode surface was found to hinder the oxidation of a-pinene, leading to severe electrode fouling that significantly compromised detection sensitivity and accuracy. Meanwhile, cyclic voltammetry of an electrolyte consisting of a similar imidazole-based ionic liquid at an electrode is known to involve the oxygen-superoxide redox reactions. In this work, we have exploited these redox reactions in a self-cleaning protocol to generate a reproducible electrode surface for the oxidation of a-pinene. This strategy effectively prevents detection signal degradation over repeated electrochemical scans, making it feasible to detect a-pinene through multiple oxidation scans. This fundamental work is expected to advance the current understanding of a-pinene electrochemistry, while offering guidelines for the design of robust electrochemical sensors for detecting volatile organic compounds that are essential for environmental and biosecurity monitoring.