BACKGROUNDWork in recent years-first described in this journal 1 -involving the irreversible entrapment of organic molecules, polymers, catalysts, and enzymes in metal matrixes has led to the establishment of a new family of composite materials, the organics@metals family. 2À7 To allow the intact entrapment of the organic element, termed a "dopant", a room-temperature, one-pot methodology has been developed. This involves the reduction of metal ions from solution, which leads to the formation of metal nanocrystallites and subsequently to their aggregation into mesoporous, metallic matrixes. The products preserve some of their metal properties such as metallic sheen and crystalline tight-packed structure. The porosity is primarily interstitial, that is, pores are formed in between tightly aggregated, pure-metal crystals. As a result of being present in the solution of metal ions before and during reduction and aggregation, the dopant is incorporated intact into inter-crystallite cages. Furthermore, its removal by subsequent washing with the solvent used for the synthesis is rendered practically impossible, despite the fact that the dopant is originally soluble in this solvent. This is termed "entrapment". However, dopants have been found to remain accessible, via diffusion through the metal matrix pore system, to extraction with more effective solvents 1,6,8 and to reactions with external reagents. 1,3,4,9,10 So far, entrapment of a variety of organic molecules has been successfully achieved in several different metals, from aqueous and organic media, and with reduction carried out by homogeneous reductants (e.g., sodium hypophosphite 1 or N,N-dimethylformamide 11 ), by dispersed metal powders according to the electrochemical series, 8 or electrolytically. 6 The diversity of these conditions demonstrates the ubiquity of the entrapment phenomenon. The amount of organic content varies according to synthesis conditions, but is generally estimated to be about 1% weight, or a few hundred metal atoms per one organic unit, and at most about 10% in weight. 11 Entrapment allows the fine-tuning of metal properties and their tailoring with induced properties from the huge selection of organic and biological molecules at the disposal of science today. Several studies have demonstrated the alteration of the metal matrix' physical properties: the metal composite's electrical conductivity has been shown to be a function of its loading and the nature of the dopant, 5,11 and the entrapment of chiral dopants has led to the induction of chirality in bulk metal (which is of course normally achiral). 4,12 In addition, it has been found that the inherent catalytic behavior of a metal may be modified by doping. 4,13 In this research, it is demonstrated that the electrode behavior of a metal, and in particular its apparent electrode potential, may also be altered by doping it with an organic element. This is done mainly through the examination of potentiometric and voltammetric behavior of silver, pure or doped with Congo red (CR). Th...