Thin and continuous films with controlled bi- and tri-modal porosities by embedment of zeolitenanoparticles in a mesoporous matrix

Abstract

Continuous, well-adhered silicon dioxide thin films (∼100 nm) with multi-mode porosity (micro/meso/macro) have been fabricated through a series of inorganic–organic self-assembly techniques, in essence, combining zeolite nanoparticles and a 2D hexagonal structured mesoporous system in a facile but effective approach. Silicalite-1 nanoparticles (average particle size ∼60 nm) were added to a mixture of block co-polymer (Pluronic 123 and Brij 56) and tetraethoxyorthosilane (TEOS) and the resulting solution deposited as a thin film viaspin coating techniques. Under low loadings of zeolite nanoparticles, the calcined films retain their conventional 2D hexagonal array of pores but at high concentrations of nanoparticles, part of the mesoporous structure is converted to a macroporous structure as a result of accumulating intrinsic stress within the thin film. Nanoparticle loaded thin films with concentrations close to 70% were possible as the mesoporous structure functions as an adhesion promoter for the zeolite nanoparticles and, crucially, it does not interfere with the accessibility of the zeolite nanoparticles. Furthermore, we explore the pore diffusion and templating properties of these novel films by infilling with germanium nanocrystalsvia supercritical fluid inclusion methods within the channels of the mesoporous segments of the films.