Department of Chemistry, University of Bath, Bath BA2 7AY, UK.
Langmuir. 2011 May 17;27(10):6471-7. doi: 10.1021/la2010584. Epub 2011 Apr 13.
Voltammetric responses of pentoxyresorufin in 4-(3-phenylpropyl)-pyridine (PPP) microdroplets immersed in aqueous electrolyte are investigated in the absence and in the presence of light. The reduction of pentoxyresorufin to leuco-pentoxyresorufin in the dark is shown to occur in a two-electron, two-proton process sensitive to the aqueous pH and the PPP|aqueous electrolyte interfacial tension. No significant net photoelectrochemical current responses are observed, although transient responses indicative of distinct electron and hole charge carriers are seen in the presence of pentoxyresorufin. EPR evidence confirms the formation of radical intermediates upon illumination. As a coreactant, duroquinone in the PPP microdroplet phase is investigated and also shown to undergo two-electron, two-proton reduction (to duroquinol) without significant photoelectrochemical activity. When investigated in combination, pentoxyresorufin acts as a photocatalyst for the oxidation of duroquinol to duroquinone. Wavelength-resolved photovoltammetry experiments clearly implicate pentoxyresorufin as the primary photoexcited intermediate. The photoelectrochemical mechanism is explained on the basis of the presence of a long-lived (possibly charge-separated) photoexcited intermediate in the PPP microphase. Implications for light-energy harvesting are discussed.
在不存在和存在光的情况下，研究了沉浸在水电解质中的 4-(3-苯丙基)-吡啶 (PPP) 微滴中的戊氧基-resorufin 的伏安响应。黑暗中戊氧基-resorufin 向 leuco-pentoxyresorufin 的还原被证明是一个两电子、两质子过程，对水的 pH 和 PPP|水电解质界面张力敏感。尽管在存在戊氧基-resorufin 的情况下观察到指示明显电子和空穴载流子的瞬态响应，但没有观察到显著的净光电化学电流响应。EPR 证据证实了光照下自由基中间体的形成。作为共反应物，研究了 PPP 微滴相中存在的二氢醌，并发现它也经历了两电子、两质子还原（形成二氢醌醇），但没有显著的光电化学活性。当联合研究时，戊氧基-resorufin 充当二氢醌醇氧化为二氢醌的光催化剂。波长分辨光电伏安法实验清楚地表明戊氧基-resorufin 是主要的光激发中间体。光电化学机制是基于 PPP 微相中存在长寿命（可能是电荷分离）的光激发中间体来解释的。讨论了对光能收集的影响。
