Abstract Electrochemical surface plasmon resonance (ESPR) has been employed as a probe of redox reactions at the interface between gold (Au) and ionic liquid (IL). Two redox couples, ferrocene (Fc)/Fc+ and (ferrocenylmethyl)trimethylammonium (FTA+)/FTA2+, and two ILs, trioctylmethylammonium bis(trifluoromethanesulfonyl)amide ([TOMA+][C1C1N−]) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C4mim+][C1C1N−]) have been studied. In the ESPR measurements, the shift of the SPR angle has been recorded simultaneously with cyclic voltammogram (CV). It has been revealed that the SPR angle shift reproduces CV when the former is semi-differentiated or the latter is semi-integrated, and, therefore, that the ESPR response probes the surface concentration of redox couples at the IL|Au interface. Among the four combination of the two redox couples and the two ILs, the case for Fc/Fc+ in [TOMA+][C1C1N−] shows significantly greater ESPR response than the other three cases. A model has been established for the relationship between the SPR angle shift and the surface concentration of redox species. The model predicts that the SPR angle shift becomes pronounced with increasing DR/DO, the diffusion coefficient ratio of the reduced (R) and oxidized (O) species when the reduced species is initially dissolved in the IL as is the case for the present study. Significantly greater DR/DO for Fc/Fc+ in [TOMA+][C1C1N−] than the three other cases has been confirmed from the DR and DO measurements by CV with a microdisk electrode. The trend of the measured DR and DO values agrees with recent findings by researchers that small neutral solutes in ILs composed of large ions diffuse fast beyond the prediction of the Stokes-Einstein relation.

中文翻译：

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电化学表面等离子体共振作为离子液体界面氧化还原反应的探针

摘要 电化学表面等离子体共振 (ESPR) 已被用作金 (Au) 和离子液体 (IL) 界面处氧化还原反应的探针。两个氧化还原对，二茂铁 (Fc)/Fc+ 和（二茂铁基甲基）三甲基铵 (FTA+)/FTA2+，以及两个 IL，三辛基甲基铵双（三氟甲磺酰基）酰胺（[TOMA+][C1ClN−]）和 1-丁基-3-甲基咪唑鎓双（已经研究了三氟甲磺酰基）酰胺（[C4mim+][C1C1N-]）。在 ESPR 测量中，SPR 角的偏移已与循环伏安图 (CV) 同步记录。已经表明，当前者半分化或后者半整合时，SPR 角位移再现 CV，因此，ESPR 响应探测 IL|Au 界面处氧化还原对的表面浓度。在两个氧化还原对和两个 IL 的四种组合中，[TOMA+][C1C1N-] 中 Fc/Fc+ 的情况比其他三种情况显示出明显更大的 ESPR 响应。建立了 SPR 角位移与氧化还原物质表面浓度之间关系的模型。该模型预测，当还原物质最初溶解在 IL 中时，SPR 角位移随着 DR/DO、还原 (R) 和氧化 (O) 物质的扩散系数比的增加而变得明显，正如本研究的情况. [TOMA+][C1C1N-] 中 Fc/Fc+ 的 DR/DO 显着高于其他三种情况，这已从使用微盘电极的 CV 测量的 DR 和 DO 得到证实。