Growth of ordered silver nanoparticles in silica film mesostructured with a triblock copolymer PEO–PPO–PEO

Elaboration of mesostructured silica films with a triblock copolymer polyethylene oxide–polypropylene oxide–polyethylene oxide, (PEO–PPO–PEO) and controlled growth of silver nanoparticles in the mesostructure are described. The films are characterized using UV–visible optical absorption spectroscopy, TEM, AFM, SEM, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). Organized arrays of spherical silver nanoparticles with diameter between 5 and 8 nm have been obtained by NaBH4 reduction. The size and the repartition of silver nanoparticles are controlled by the film mesostructure. The localization of silver nanoparticles exclusively in the upper-side part of the silica-block copolymer film is evidenced by RBS experiment. On the other hand, by using a thermal method, 40 nm long silver sticks can be obtained, by diffusion and coalescence of spherical particles in the silica-block copolymer layer. In this case, migration of silver particles toward the glass substrate-film interface is shown by the RBS experiment.