Prussian blue (PB) particles with the size of ca. 5 nm were synthesized and immobilized in a multilayer structure, as a strategy for the potential development of an amperometric transducer for oxidase-enzyme-based biosensors. Multilayer films composed of PB and poly(allylamine hydrochloride) (PAH) were prepared via layer-by-layer (LbL) sequential deposition. The process was carefully monitored by UV-vis spectroscopy and cyclic voltammetry. The increase of the redox current peaks during the layer-by-layer deposition demonstrated that charge propagation within the film occurs. Linear increase of UV-vis absorbance with the number of deposited bilayers indicates that well-organized systems have been elaborated. ITO electrodes coated with PB/PAH films were used successfully for detecting H2O2, sensitivity being dependent on the number of PB/PAH layers.

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In this study, Pt and Pd catalysts (in the absence and presence of Fe) and a Pt−Pd alloy were generated on a polycrystalline Au surface by means of a direct electrodeposition approach. The electrochemical profile of these materials was investigated using cyclic voltammetry and microgravimetry (electrochemical quartz crystal microbalance). The electrocatalytic activity toward oxygen reduction reaction (ORR) was studied using hydrodynamic cyclic voltammetry. Physical characterization of samples was performed using scanning electron microscopy, energy dispersive X-ray microanalysis, and atomic force microscopy. Electrodeposited catalysts containing Pt exhibited high electrocatalytic activity toward ORR, stability in terms of specific activity, and repeatability of responses, even at low Pt concentrations in the electrodeposition solution, thus suggesting the possibility of applying these catalysts to acid fuel cells. The Au electrode modified with Pt(0.75)/Fe(0.25) exhibited a nanorounded, low-roughness structure, whereas the Au electrode modified with Pd(0.75)/Fe(0.25) showed poor electrocatalytic activity, a nanospaghetti-shaped structure, and enhanced roughness.

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Nanoparticles of a Prussian blue (PB) analogue, copper hexacyanoferrate, were synthesized by using ultrasonic radiation and characterized by spectroscopic and electrochemical techniques. The nanoparticles (ca. 10 nm diameter) were immobilized onto transparent indium tin oxide electrodes by electrostatic layer-by-layer deposition. These modified electrodes showed interesting electrochromic properties, changing the coloration during the redox process from brown to orange when oxidized. The nanostructured electrode presented high stability, in contrast to that observed for PB nanoparticles; this fact must be related to the maintenance of the electrostatic assembly because the oxidized compound, CuII/FeIII(CN)6, still possesses a negative excess of charge due to the high number of cyanide groups that link the nanoparticles with the polycation, assuring the integrity of the whole electrostatic assembled film.

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A copper containing Prussian Blue analogue was incorporated into a conducting polypyrrole film. The modified electrode was synthesized through an electrochemical two-step methodology leading to very stable and homogeneous hybrid films. These electrodes were proved to show excellent catalytic properties towards H 2 O 2 detection, with a performance higher than those observed for Prussian Blue and other analogues. Electrochemical impedance spectroscopy experiments demonstrated that the excellent performance of these hybrid films is strongly related to the electronic conductivity of the polymeric matrix that is wiring the copper hexacyanoferrate sites. A glucose biosensor was built-up by the immobilization of glucose oxidase; the sensitivity obtained being higher than other biosensors reported in the literature even in Na + containing electrolytes.