Extended visible photosensitivity of carboxyethyltin functionalized polyoxometalates with common organic dyes enabling enhanced photoelectric performance

Abstract

A kind of broad spectral responsive photoelectrode has been assembled from open-chain carboxyethyltin functionalized Dawson sandwich-type polyoxometalates (POMs) [{Sn(CH₂)₂COO}₂M₂(P₂W₁₅O₅₆)₂]¹⁶⁻ (SnR-M-P₂W₁₅, M = Mn, Co, Cu and Zn) and organic dyes such as rhodamine B (RhB) and methylene blue (MB) through the layer-by-layer (LBL) self-assembly method. SnR-M-P₂W₁₅ shows strong adsorption towards RhB and MB. The adsorption capacity of SnR-Co-P₂W₁₅ towards RhB and MB reached 217.36 and 288.76 mg g⁻¹ in 10 min, respectively. Compared to Keggin sandwich-type open-chain carboxyethyltin–POM and closed-ring carboxyethyltin–POM derivatives such as [Zn₂{Sn(CH₂)₂COO}₂[(PW₉O₃₄)₂]¹⁰⁻ (SnR-Zn-PW₉) and [K₃{Sn(CH₂)₂COO}₂(PW₉O₃₄)₂]¹¹⁻ (SnR-PW₉), and the parent POMs [M₄(H₂O)₂(P₂W₁₅O₅₆)₂]¹⁶⁻ (M-P₂W₁₅, M = Mn, Co, Cu and Zn), SnR-M-P₂W₁₅-based photoelectrodes showed significantly enhanced photocurrent owing to their greater visible light harvesting. Also, the photoelectric performances of LBL multilayer films can be adjusted by controlling the number of deposited layers, adsorbed dye types and incorporated transition metal ions in the POMs.