Abstract
A novel experimental methodology for studying silver particles deposited at the water∣nitrobenzene (W∣NB) interface is proposed by means of thin-film electrodes. The electrode assembly consists of a graphite electrode (GE) covered with a thin NB film containing decamethylferrocene (DMFC) as a redox probe. The W∣NB interface was modified with silver particles in an AgNO 3 aqueous solution, where a heterogeneous electron transfer reaction between DMFC (NB) and Ag ( W ) + takes place to form a Ag-deposit at the W∣NB interface, and DMFC + and NO 3 - in the organic phase. The Ag-modified thin-film electrode was inspected by voltammetry in a contact with an aqueous electrolyte free of Ag ( W ) + . The overall reaction at the thin-film electrode proceeds as a coupled electron–ion transfer reaction. Ag-particles deposited at the W∣NB interface affect significantly the ionic transfer, which provides the basis for a voltammetric inspection of the metal deposition at the W∣NB interface. When the concentration AgNO 3(W) is close to the concentration of DMFC (NB), a dense Ag-film is formed that prevents completely the ionic transport, hence resulting in a complete vanishing of the voltammetric response. In a presence of [ Fe ( CN ) 6 ] ( W ) 3 - , the response of the electrode is restored, having properties of a reductive catalytic electrode mechanism. The overall mechanism couples two simultaneous electron transfer reactions undergoing at separate interfaces, i.e. the reduction of DMFC ( NB ) + to DMFC (NB) at the GE∣NB interface and the heterogeneous redox reaction between DMFC (NB) and [ Fe ( CN ) 6 ] ( W ) 3 - to form DMFC ( NB ) + and [ Fe ( CN ) 6 ] ( W ) 4 - at the Ag-modified W∣NB interface. Under these conditions the Ag-film acts as an effective conductive medium for fast electron exchange between DMFC (NB) and [ Fe ( CN ) 6 ] ( W ) 3 - . The methodology proposed is particularly suited to inspect catalytic activities of metal particles deposited at the liquid∣liquid interface towards heterogeneous electron transfer reactions between reactants embedded in immiscible liquids.
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