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The synthesis and electrochemical anionsensing properties of a diaminobutane poly(propyleneimine) dendrimer functionalized with biferrocenyl units 2 are presented. The redox activity of the ferrocenyl centers in 2 has been characterized by cyclic voltammetry. Cyclic and square wave voltammetric investigations demonstrate that tetraferrocenyl compound 2 and the reference compound 1 show electrochemical anion-sensing action: they display a cathodic shift of the ferrocene−ferrocenium redox couple with dihydrogenphosphate and hydrogensulfate anions in solution and immobilized onto electrode surfaces.

The main target of this work is the preparation of nanostructurated surfaces with size-controlled gold nanoparticles to obtain effective electrocatalytic surfaces. In this paper, we show that dispersed Au nanoparticles (AuNPs) having diameters of less than 3 nm can be synthesized in situ with aminoferrocenyl-and amidoferrocenyl-poly(propyleneimine) (PPI) dendrimers previously electrodeposited onto electrode surfaces. Dendrimers of first, third and fifth generation have been studied and good dispersed non aggregated nanoparticles were obtained in all the cases. In a similar way than in homogeneous media, inter-dendrimer Au nanoparticles have been obtained when first or third generation dendrimer modified electrodes were used, while smaller nanoparticles were obtained with fifth generation dendrimer, indicating that intra-dendrimer Au nanoparticles have been synthesized. The AuNPs were obtained from a HAuCl 4 solution after chemical reduction with NaBH 4 . The formation of AuNPs was followed by UV-Vis spectroscopy; electrochemistry and ultra-high resolution scan electron microscopy (HRSEM). The obtained electrodes have been successfully used for the tetraelectronic oxygen reduction reaction (ORR) with a low onset potential (0.00 V vs. SCE), high kinetic current densities and also high heterogeneous electron transfer rate constants.

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