Abstract:The polyoxometalate ions P M O , ,~, ,~~, PW~,O,~-, and S~W,,O,;-are incorporated in polymeric ruthenium(II)(vinyl)bipyridine (poly-~u(vbpy),2+) films from aqueous and dioxane-water electrolytes. Despite their large mass the ions exist as freely diffusing species that compensate for up to 30% of the chage in poly~u ( v b~~)~~~. An investigation of the effect of environmental conditions on electrochemical behavior reveals that the first two one-electron reduction waves of s~w,,o,,~-coalesce into a single two-electron reaction and those of PW,,O,,,-shift significantly in potential upon a change from pure aqueous to 50(v/v)% dioxanelwater solvent. The observation is attributed to destabilization of the one-electron reaction products as the solvent is enriched is dioxane. Incorporation of polyoxometalates in protonated poly(viny1)pyridine and poly~u ( v b~~) ,~~ films from dioxane-water solvent results in differences in electrochemical behavior. Polyoxometalate anions incorporated in poly-~u(vbpy)3'f films catalyze the electrochemical reduction of hydrogen ion.Key words: polyoxometalate, electrochemistry, poly-~u(vbpy)32+, electrocatalysis, immobilization.RCsumC : On a incorporC les ions polyoxomCtallates PMO,~~,,", PW,,~,," et Siwl,O4,4-dans des films polymCriques de mthCnium(II)(vinyl)bipyridine (poly-~u(vbpy),") 2 partir d'Clectrolytes en solutions dans l'eau ou dans un mClange eau~lioxane. MalgrC leurs masses importantes, les ions existent sous la forme d'espkces qui diffusent librement et ils peuvent compenser Clectrostatiquement jusqu'i 30% de la chage du poly-~u(vbpy)33+. Une Ctude de l'effet des conditions environnementales sur le comportement Clectrochimique rCvkle que le potentiel des deux premikres vagues de rCduction du s~w ,~o , ,~-par un Clectron est fortement modifiC lorsqu'on passe de I'eau pure i un mClange de solvants form6 i 50% (vlv) de dioxaneleau. On attribue ces observations i la destabilisation des produits de rCduction par un Clectron lorsqu'on enrichit le solvant en dioxane. L'incorporation de polyoxomCtallates dans des films de poly(viny1)pyridine ou de poly~u ( v b~~) ,~+ protonCs B partir de solvants mixtes dioxane-eau provoque des diffkrences dans le comportement Clectrochimique. Les anions polyoxomCtallates incorporCs dans les films de poly-~u(vbpy)33f catalysent la rCduction Clectrochimique de l'ion hydrogkne.

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Colloidal Cu 2 O solutions were used to explore photonic activities at the semiconductor/electrolyte interface. Fluorescence spectroscopic studies were performed on Cu 2 O colloidal particles modified with some conjugated organic monomers such as 2-amino-phenyl pyrrole (2-APPy), tri-phenyl amine (TPA), or 2-thionyl pyrrole (2-Th-Py) to investigate the quantum absorbance efficiency at this inorganic/organic interface (IOI). Our study shows that colloidal p-type Cu 2 O possesses a bandgap with direct transition of ≈ 2⋅2 eV and indirect transition of 1⋅85 eV. The recorded rates of charge injection into colloidal Cu 2 O, k ct , were 2⋅31 × 10 9 s -1 , 5⋅05 × 10 8 s -1 , and 7⋅22 × 10 8 s -1 for 2-APPy, TPA and 2-Th-Py, respectively. The studied systems show more stability in colloidal form than in thin solid form. Results were interpreted using the optical and electrical parameters of the organic monomer such as ionization potential (IP), electron affinity (EA) and energy bandgap (Eg), and the barrier height at the IOI interface. Stability of the colloidal system is attributed to the physical dimensions of the photoactive system. The nano-colloidal particle offers a condition where its size is less than √Dt.

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