Poly(amino acid)s-mediated synthesis of spatially organized Pt nanoparticles

Nanometer-sized noble metal particles are being increasingly studied for use in various applications including photochemistry, electrochemistry, optics, and catalysis. Recently, extensive efforts have been made to improve nanoparticle dispersion to enhance its performance using various surfactants, dendrimers and polyelectrolytes which can tune colloidal interactions. However, it is still challenging to establish a technology in which spatial organization of metal nanoparticles is finely controlled at varied length scales. Here we present that in situ sol-gel polymerization of metal precursors incorporated into self-assembling poly(amino acid) nanostructure would generate metal nanoparticles with regular spacing at the nanometer scale. This hypothesis was examined using poly(amino acid)s substituted with alkyl chains to form various morphologies from a spherical micelle to a bilayer structure. Platinum precursors (K₂PtCl₄) were mixed with alkyl-substituted poly(amino acid)s solution followed by reduction to activate sol-gel polymerization to form Pt particles. Specifically, alkyl-substituted poly(amino acid)s with DS of 5 % were assembled into a vesicle with an average diameter of 100 nm, and also presented Pt nanoparticles with diameter of 2 to 5 nm exclusively within a bilayer of the vesicle. Furthermore, the resulting Pt nanoparticles showed a significantly enhanced electro-catalytic activity as compared with Pt particles polymerized via bulk sol-gel polymerization. Taken together, the results of this study demonstrated that the size and spacing of metallic particle can be controlled using a self-assembling polymeric template. The resulting particles present strong potentials to significantly improve performance of a variety of energy storage and generation systems.