Gold Nanoparticles covered with mesoporous films: growth and use as sensors

PAULA C. ANGELOMÉ; ISABEL PASTORIZA-SANTOS; JORGE PÉREZ-JUSTE; LUIS M. LIZ-MARZÁN

Sanxenxo

Workshop; International Workshop on Nanoplasmonics for energy and the Environment; 2011

The combination of mesoporous oxide thin films with metallic nanoparticles is of interest in various fields, including catalysis, biosensing and non linear optics. In most of the reported works, the metallic particles were embedded in the mesoporous materials and their morphology would be dictated by the pores structure. In this work, we have developed a new family of composite materials comprising two layers: a glass substrate with chemically attached gold nanoparticles and, on top, a mesoporous film. This film has two functions: it keeps the particles attached to the substrate and acts as a barrier between them and the outer medium. As a consequence, the access to the nanoparticles and their growth can be controlled by the thin film properties. The synthesis was performed in three steps: 1) chemical attachment of gold particles onto glass, 2) thin film deposition and stabilization, and 3) growth of gold particles by seed mediated method. Several initial nanoparticles shapes (spheres, stars, decahedra) and three types of mesoporous films (SiO2 with pore diameter around 6 and 12 nm and TiO2 with 12nm pores) were tested. The stability of both the film and the particles was studied during the synthesis and processing, demonstrating that, in most of the cases, both the shape of the particles and the mesoporous order are not deteriorated. In a first set of experiments, Au decahedra covered with different films were used as evaporation sensors. Solvent – thin films interaction were followed by means of the displacement in the LSPR band of the nanoparticles during solvent evaporation1. In a second set of experiments, particles’ seeded growth was performed by immersing the composite materials in a growth solution (Au+ complexed with CTAB) in several reaction conditions. This growth procedure allowed us to obtain anisotropic gold particles with different morphologies that were influenced by the pore size of the mesoporous film and the reaction conditions. The effect of the growth conditions on the final shape of the particles was evaluated and the key reaction parameters were determined. The obtained materials were characterized with UV-vis spectroscopy, electron microscopy and XPS.