Synthesis and photocurrent responsive properties of CdS/Se clusters integrated with methylviologen†
Cadmium chalcogenido C1 (Cd17) CdQ (Q = S, Se) clusters with MV2+ cations (MV = methylviologen) are prepared under solvothermal conditions, using thiourea and selenourea as S and Se sources. The anions ([Cd17Q4(SPh)24Br4]2−) are discrete homosized nano-clusters with about a 1.5 nm scale. The selenide cluster can be considered as a nano-CdSe/CdS core–shell particle with a CdSe4 core and a [Cd16(SPh)24Br4] shell. The electronic spectra show the characteristic peaks of charge transfer bands. Cyclic voltammetry exhibits a low-potential-shift due to the charge transfer from the cadmium chalcogenido cluster to the MV2+ cation. Photocurrent responses of compounds 1 and 2 are studied using a three electrode cell. The results are as follows. (1) The current intensities of the MV–CdQSPh clusters are significantly larger than those of the CdQSPh clusters with quaternary ammonium cations; (2) the photocurrent directions of 1 and 2 can change from positive to negative when the irradiation wavelength is changed from UV light to visible light due to the different photocurrent conversion mechanism. The effect of MV2+ on these properties is discussed.