CTNFI · Charge transfer at Nanofunctionalised Interfaces

Final Activity Report Summary - CTNFI (Charge transfer at nanofunctionalised interfaces)

This project dealt with the fabrication, characterisation and investigation of charge transfer processes of several classes of nano-systems which are widely used in fuel cells and sensors applications. We investigated different nanoscale systems grouped in three main objectives. Objective 1: Fabrication of functional nanostructured films.(a) We developed a novel methodology for fabricating functional ultra-thin films of Nafion with incorporated redox mediators and we investigated the charge transfer processes of such systems. The knowledge of charge transfer processes inside such ultra-thin films is of paramount importance for practical applications in sensing and catalysis. These systems have been proved to be very useful in biosensing applications, in particular for the detection of amino acids (tripropylammine) and oxalate using electrochemical detection methods such as electrochemelectrochemiluninescence (ECL). We found interesting physico-chemical properties such as unusual low values of the diffusion coefficents and the presence of a kinetic barrier within these ultra-thin films. However, these films (in the order of 10-50 nm) showed remarkable stability over time.(b) We developed a novel procedure to incorporate both "naked" and positively charged palladium nanoparticles with Nafion LS films. Metal nanoparticles have interesting catalytic properties which are useful to develop cleaner energy resources using hydrogen. These systems were investigated for the catalysis of hydrogen oxidation and hydrogen evolution reactions using a novel scanning electrochemical microscopy (SECM) approach. The results obtained evidenced good catalytic properties towards hydrogen oxidation and the hydrogen evolution reaction. Objective 2: Electrochemical properties of self-assembled monolayers (SAMs) of metallo-complexes. (a) Monolayers of RuBpySH have been formed on micro and macro platinum electrodes by spontaneous adsorption from solutions. The monolayers can be reversibly switched between the Ru2+ and the Ru3+ forms. Dry monolayers displayed luminescence properties similar to those of powder samples of the complex, indicating that the monolayer has characteristics of the solid-state sample rather than the solution sample of the complex. Significantly, efficient electrochemiluminescence has been generated using tripropylamine as the coreactant. This provides a platform for the possible future use of these materials as molecular wires. Objective 3: Electrochemistry at single-walled carbon nanotubes electrodes. We investigated, for the first time, the electrochemistry of a SWNT network using cyclic voltammetry. The results obtained showed (world first) the possibility to detect unprecedented trace (nanomolar) levels of a redox mediator using cyclic voltammetry. To investigate the possibility to use such system in biosensing applications, SWNT networks were used to detect an important neurotransmitter (dopamine). The results demonstrated the potentiality of the SWNTs to achieve high sensitivity. These results provide a basis for further effort using polymeric functionalisation and pulsed voltammetric techniques in order to enhance the detection limits of SWNTs network and to achieve high selectivity.

Data: CORDIS, © European Union