Stabilization of Ruthenium(II) Polypyridyl Chromophores on Nanoparticle Metal-Oxide Electrodes in Water by Hydrophobic PMMA Overlayers

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• 作者：Kyung-Ryang Wee ; M. Kyle Brennaman ; Leila Alibabaei ; Byron H. Farnum ; Benjamin Sherman ; Alexander M. Lapides ; Thomas J. Meyer
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：October 1, 2014
• 年：2014
• 卷：136
• 期：39
• 页码：13514-13517
• 全文大小：254K
• ISSN：1520-5126

文摘

We describe a poly(methyl methacrylate) (PMMA) dip-coating procedure, which results in surface stabilization of phosphonate and carboxylate derivatives of Ru(II)-polypyridyl complexes surface-bound to mesoporous nanoparticle TiO₂ and nanoITO films in aqueous solutions. As shown by contact angle and transmission electron microscopy (TEM) measurements, PMMA oligomers conformally coat the metal-oxide nanoparticles changing the mesoporous films from hydrophilic to hydrophobic. The thickness of the PMMA overlayer on TiO₂鈥揜u(II) can be controlled by changing the wt % of PMMA in the dipcoating solution. There are insignificant perturbations in electrochemical or spectral properties at thicknesses of up to 2.1 nm with the Ru(III/II) couple remaining electrochemically reversible and E_1/2 values and current densities nearly unaffected. Surface binding by PMMA overlayers results in stable surface binding even at pH 12 with up to a 鈭?00-fold enhancement in photostability. As shown by transient absorption measurements, the MLCT excited state(s) of phosphonate derivatized [Ru(bpy)₂((4,4鈥?(OH)₂PO)₂bpy)]²⁺ undergo efficient injection and back electron transfer with pH independent kinetics characteristic of the local pH in the initial loading solution.