Synthesis and photocurrent responsive properties of CdS/Se clusters integrated with methylviologen

Abstract

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.