Porous silica microscaffolds for nanoparticle immobilization

Patrícia Isabel Pereira da Silva

Key information

Authors:

Patrícia Isabel Pereira da Silva (Patrícia Isabel Pereira da Silva)

Supervisors:

Ana Clara Lopes Marques (Ana Clara Lopes Marques)

Published in

01/26/2021

Abstract

The present work regards the enlightenment of porous silica microspheres formation and their suitability as microscaffolds for immobilization of nanoparticles with scope for photocatalysis applications. Such porous microspheres were prepared via sol-gel technique with a water-in-oil microemulsion as a template inducing phase separation through spinodal decomposition, which led to interconnected macroporosity. These materials have great potential since they can be loaded with different chemical species, depending on the application preferred. Besides, their hybrid feature due to tetraethoxysilane (TEOS) and (3-Glycidyloxypropyl)trimethoxysilane (GPTMS) as silica precursors, provide them multifunctionality. With the aim to find a precise approach that permits the control of pore size, shape, and morphology of the microspheres, two main methods were performed: condensation stimulated by pH and by temperature. Within those, the influence of various parameters in the reaction were evaluated, such as the addition of ammonia according to temperature, the amount of the precursor solution, the amount of surfactant, the hydrolysate addition’s rate to the emulsion, hydrolysis duration and the hydrolysate’s viscosity. The microspheres that exhibited the desired final properties were found for a 30-minute addition to the emulsion of a pre-hydrolysate with a viscosity of 9.20 cP, following a specific temperature profile during condensation. After the immobilization process, the presence of Aeroxide® P25 commercial TiO2 nanoparticles within the microspheres were confirmed by Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscopy (SEM-EDS) proving the capability of these microscaffolds as supports.