Henri Perez

Direct Electrocatalytic Activity of Capped Platinum Nanoparticles toward Oxygen Reduction

This paper reports on the original and promising electrocatalytic properties of thiol-capped platinum nanoparticules toward O2 reduction in acidic medium. The nanoparticles were initially functionalized by 4-mercaptoaniline, and were further derivatized with 2-thiophenecarbonyl chloride leading to high stabilization of the organic crown. Ultrathin films of these particles were built up by the LB technique on gold. Their electrochemical behavior was studied. These assemblages were also characterized by X-ray photoelectron spectroscopy before and after oxygen reduction experiments. An electrocatalytic activity was established without any activation treatment. Our results show that the organic crown of the nanoparticles does not prevent their electrochemical activity

Immunoglobulin immobilization by the Langmuir-Blodgett method

Abstract A systematic study of immunoglobulin G (IgG) immobilization on Langmuir-Blodgett films has been carried out with the aim of characterizing the immobilization efficiency and the protein activity. A quantitative evaluation of the amount of immobilized protein has been carried out by IR spectroscopy. Maximum IgG immobilization (400–900 ng cm −2 ) has been obtained with buffers of low ionic strength (0.005 M) and pH near but below the isoelectric point of the protein. No desorption has been observed in pure water, but in buffers desorption increases with the ionic strength of the buffer. The probable mechanism of desorption is a screening of the charges responsible for protein attachment, by small ions from the buffer. As expected, this desorption leads to high non-specific binding (75% in 0.1 M buffer) by dynamic protein exchange.

Direct Electrochemical Activity and Stability of Capped Platinum Nanoparticles

4-mercaptoaniline functionalised platinum particles of 2 nm diameter were synthesised and over-grafted with 2-thiophenecarbonyl chloride. The derivative particles were dispersed in DMSO and gave long term stable suspensions. The Langmuir-Blodgett technique was then used to build up stable Langmuir-Blodgett films and the electrochemical behaviour of these ultra-thin films towards oxygen reduction was investigated in an acidic medium. It revealed direct activity without any previous activation treatments despite of the presence of the organic shell at the particle surface. Furthermore, XPS experiments revealed that the organic crown was not significantly destroyed on prolonged cycling. The results open a way to study original and versatile platinum-based nanocomposites.

Electrocatalytic (Bio)Nanostructures Based on Polymer-Grafted Platinum Nanoparticles for Analytical Purpose

Functionalized platinum nanoparticles (PtNPs) possess electrocatalytic properties toward H2O2 oxidation, which are of great interest for the construction of electrochemical oxidoreductase-based sensors. In this context, we have shown that polymer-grafted PtNPs could efficiently be used as building bricks for electroactive structures. In the present work, we prepared different 2D-nanostructures based on these elementary bricks, followed by the subsequent grafting of enzymes. The aim was to provide well-defined architectures to establish a correlation between their electrocatalytic properties and the arrangement of building bricks. Two different nanostructures have been elaborated via the smart combination of surface initiated-atom transfer radical polymerization (SI-ATRP), functionalized PtNPs (Br-PtNPs) and Langmuir-Blodgett (LB) technique. The first nanostructure (A) has been elaborated from LB films of poly(methacrylic acid)-grafted PtNPs (PMAA-PtNPs). The second nanostructure (B) consisted in the elaboration of polymer brushes (PMAA brushes) from Br-PtNPs LB films. In both systems, grafting of the glucose oxidase (GOx) has been performed directly to nanostructures, via peptide bonding. Structural features of nanostructures have been carefully characterized (compression isotherms, neutron reflectivity, and profilometry) and correlated to their electrocatalytic properties toward H2O2 oxidation or glucose sensing.