Nanohybrid objects based on polymer and platinum nanoparticles are of great interest for applications in fuel cells or as biosensors. The polymer part can help first to stabilize and to organize the particles, second to increase the amount of chemical functions available in the organic corona, and, finally, to improve or to mask the properties of the particles. The method to introduce the polymer consists of using both the "grafting from" technique and controlled radical polymerization (atom transfer radical polymerization). Small-angle neutron scattering (SANS) is a well-suited technique for the study of these objects, particularly due to the possibility to use contrast matching to see either the particle or the polymer corona. Polymerization kinetics was followed by SANS and the polymer corona spectra showed a plateau at small q which attested that the objects are individual and well-dispersed. These systems were exempt of free polymers, so the characterization via SANS could lead to quantitative data such as the radius of gyration of the object, the amount of grafted chains and the molecular weight of the chains, using a star model to fit the data. Langmuir films have then been obtained directly from the polymer-grafted-nanoparticles solutions, and compression isotherms have been recorded followed by transmission electron microscopy (TEM) characterization of the films at different pressures. A good correlation has therefore been observed from the distances between objects calculated using the compression isotherms or observed via TEM and the objects' dimensions determined from SANS study.
International audienceFunctionalized platinum nanoparticles (PtNPs) possess catalytic properties towards H202 oxidation, which are of great interest for the elaboration of electrochemical biosensors. To improve the understanding of phenomena involved in such systems, we designed platinum-polymer-enzyme model nanostructures according to a bottom-up approach. These structures have been elaborated from elementary building units based on polymer-grafted PtNPs obtained from surface initiated-atom transfer radical polymerization. This paper describes the polymerization of ter-butyl methacrylate from PtNPs and its subsequent hydrolysis to obtain a water-soluble corona, followed by an activated ester modification to introduce an enzyme (glucose oxidase). The structure of the objects, the molecular weight and the grafting density of the polymer chains were principally elucidated by small angle neutron scattering (SANS). After the grafting of the enzyme, the final hybrid structures were characterized by both microscopy and SANS to attest for the covalent grafting of the enzyme. Composition and enzyme activity of the nanohybrid objects, have also been determined by UV spectroscop
Hybrid nanoparticles based on platinum nanoparticles (PtNPs) are of great interest for applications in fuel cells or as biosensors. Polymer chains covalently attached to the PtNPs may improve both the (bio)compatibility, solubility, and stability of the PtNPs, without inhibiting their electrochemical properties. First, we performed a copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "grafting to" method to graft either poly(ethylene glycol) (PEG) or poly(ε-caprolactone) (PCL) onto PtNPs to create new hybrid nanoparticles with a biocompatible corona. Second, we combined both surface-atom transfer radical polymerization "grafting from" copolymerization of azide-functionalized monomers and CuAAC "grafting to" coupling of PEG or PCL to construct more complex polymer architectures. These approaches afforded a large library of nanostructures with varying chemical nature, microstructure, radius, and morphology of the polymer corona. Infrared spectroscopy, thermogravimetric analysis, and more detailed SANS experiments proved that these methodologies are simple, efficient, and wide in scope for the preparation of highly functional metal nanoparticles with tunable properties.
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.
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