Evaluation of dyes diffusion of different charges in TiO2 mesoporous thin films

ZAMBRANO, ISKRA; HODAK, JOSE; GONZALEZ SOLVEYRA, ESTEFANIA; SOLER-ILLIA, GALO J. A. A.

Exposición; RCSPoster; 2023

The possibility of creating materials of controlled porosity and functionality at the nanoscale offers enormous potential for several applications. In this study we focused on understanding the transport processes of this type of systems by means of fluorescent probes of different charges within the pores. For this purpose, mesoporous films of titanium oxide (TiO2) were synthesized. Diffusion phenomena in nanopores were characterized by measurements of characteristic diffusion times using Fluorescence Correlation Spectroscopy (FCS). The probes were incorporated into the mesoporous films at 99% humidity. The parameters of interest in these experiments are the ionic strength and the pH within the pores. From the experiments, it appears that the dye molecules do not show conventional 2D diffusion within the pores. On the contrary, its diffusion can be described by means of the “stick and diffuse” model, in which there is a fraction of molecules that diffuses freely while others suffer strong adsorption on the pore walls. Finally, it is observed that the diffusion varies with the charge of the dye molecule and the pH of the solution in contact with the pores.