非均相电子转移的探讨

本文用ESR方法研究了六种新的双吡啶盐(PQ⁺⁺)与CdS的水及非水悬浮体系间的非均相光诱导单电子转移过程。结果表明,在λ<520nm的光照射下,CdS价带中的电子被激发至导带,再转移至PQ⁺⁺使之还原为PQ⁺⁺自由基,呈现明显的ESR信号。当体系中有电子给体EDTA存在时,有电子从EDTA转移至CdS价带的正空穴,价带中的电子吸收光子跃迁至导带再转移至PQ⁺⁺,以生成更多的PQ⁺⁺,从而使ESR信号大大增强。

ESR STUDY OF PHOTOINDUCED ELECTRON TRANSFER PROCESS IN HEFEROGENEOUS SYSTEMS

Photoinduced electron transfet of aqueous and non-aqueous Cadmium Sulfide (CdS) dispersions in the presence of electron acceptors such as PQ⁺⁺ have been studied by means of ESR. The results show that upon irradiation of light (λ<517nm) the electron in the valence band (VB) of CdS can be excited to the conduction band (CB) giving rise to an electron-hole pair and the electron transfer from CB to PQ⁺⁺ to form free radical PQ⁺⁺ which can be detected by ESR.When electron donor such as EDTA is added to the systems, there is enhancement in the formation of PQ⁺⁺ which suggests that this hole is neutralized through the oxidation of EDTA.This returns the system to its original state thus allowing the CdS particles to be functional again in the photoproduction of PQ⁺⁺. Hence the CdS darticles are playing a catalytic role and in fact can be considered as a photocatalytic pump in which electrons are transfered from EDTA to PQ⁺⁺.