One electron oxidation of ascorbic acid facilitated by ionic liquid-doped poly (3, 4-ethylenedioxythiophene) as artificial enzyme

Ke Qu, Wentao Dai, Yuqi Bai, Yuhan Chen, Zeqin Chen, MiaoDeng

College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059, PR China.

Abstract

Ascorbic acid (AA) play vital roles in various physiological processes and its two-electron oxidation pathway is typically documented. In this study, we reported that ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl) imide served as unique dopant to tune the surface electrical properties of poly (3, 4-ethylenedioxythiophene) (PEDOT), with a charge reversal from initially positively charged surface to partially negative after IL doping, as evidenced by cyclic voltammetry tests using redox probes (Ru(NH₃)₆Cl₃ and K₃Fe(CN)₆). The IL-doped PEDOT were characterized via SEM, AFM and XPS techniques and functionalized as artificial enzyme to enable precisely one electron oxidation of ascorbic acid toward ascorbyl radical. For two other interferences, uric acid (UA) and dopamine (DA), IL-doped PEDOT displayed one-electron oxidation behavior as well. The fabricated IL-doped PEDOT artificial enzyme enabled the simultaneous electrochemical sensing of AA, DA and UA with wide linear ranges (50–1000 μM for AA, 2.5–1000 μM for DA and 4–350 μM for UA). The underlying catalytic mechanism was approached with molecular calculation, revealing that strong π-π and hydrogen bond interactions at the molecular level contributed to the enhanced catalytic effect. In general, this study innovatively reveals the inherent catalytic activity of IL-doped conductive polymer as artificial enzyme for sensing application.

Keywords: Artificial enzyme, One electron oxidation, Ascorbic acid, Ionic liquid, Poly (3, 4-ethylenedioxythiophene).