Growth by heat treatment of silver nanorods inside mesostructured silica thin films: synthesis, colours of thin films, study of some experimental parameters and characterization

In this paper we report a soft route leading to spherical or rod nanoparticles confined in SBA-15 thin films exhibiting a hexagonal mesostructure. For that purpose, these transparent mesoporous silica thin films are elaborated in the presence of a non ionic triblock copolymer P123 as structure directing agent. After soaking in a silver salt solution, they are heat treated to grow silver structures. In function of several experimental parameters as the immersion time in the silver salt solution, the solvent of the silver salt solution or the heat treatment temperature, nanorods and/or nano spherical particles can be obtained. These coloured samples are characterized by X-ray diffraction (XRD), ultraviolet–visible (UV–vis) absorption and Fourier transformed infrared (FTIR) spectroscopies, atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of the nanorods has been showed by using polarized UV–vis spectroscopy. The results show that most of silver nanoparticles grow inside the film thickness.