Reproducible strategy to generate ultra-large mesopores in spherical silica particles by chemical etching with triethanolamine

This work presents a simple and reproducible method for obtaining spherical silica particles with expanded mesopores. Porosity can be modulated gradually from small mesopores generated by surfactant micelles (around 2–3 nm) to ultra-large mesopores (ca. 14–15 nm). The methodology is based on a chemical attack of Stöber-type mesoporous silica particles (obtained with CTAB as surfactant) with triethanolamine. The control of simple parameters such as triethanolamine concentration and aging time allows for the modulation of porosity. In the case of short reaction times and/or low triethanolamine concentrations, silicas with hierarchical bimodal porosity are obtained, and a portion of the original mesopores are preserved. However, as the chemical degradation progresses, the original mesopore disappears, and mesoporous silicas with ultra-large pores are obtained. The process occurs without a significant decrease in particle size, accompanied by a degradation in volume, which also exhibits high homogeneity. The underlying principle of the process is the combination of a moderately basic pH generated by triethanolamine and its capacity to interact with Si. The successful expansion of the mesopores facilitates the adsorption of substantial quantities (ca. 400 mg/g) of medium-sized proteins, such as hemoglobin.