Pore ordering in mesoporous matrices induced by different directing agents

Abstract

Mesoporous silica particles of MCM-41 type were synthesized by sol-gel method from tetraethyl orthosilicate (TEOS) in 2-methoxyethanol and deionized water mixture in base conditions at room temperature. Ammonia or sodium hydroxides were used as catalysts and cetyl-trimethylammonium bromide (CTAB) and n-dodecyl-trimethylammonium bromide (DTAB) as structure directing agents. The porosities and the ordered structure have been analyzed using transmission and scanning electron microscopy, small angle neutron and Xray diffraction, nitrogen adsorption, thermal analysis and FTIR spectroscopy. The samples consist of spherical particles of sub-micrometer size, with radially arranged pores. The comparison of the effect of the different surfactants and catalysts shows that by varying the surfactant type and their proportion, the pore sizes can be controlled. As compared to the commonly used ammonia catalyst, the use of NaOH as catalyst results in a much smaller porosity of the as-prepared materials. These materials are not resisting to the heat treatment at 700 ºC used for the template removal, and the ordered porous structure is completely lost.

Mesoporous silica obtained with methyltriethoxysilane as co-precursor in alkaline medium

“…The power exponent varied between -3.5 and -4.2, showing no regularity with MTES content or thermal treatment. Value of -4 would correspond to an ideally smooth interface, while the observed deviations from this value point to a rough particle surface [37,38]. The variation of the pore distance is similar to the XRD results, the trends being smoother due to the lower resolution ( Figure 6).…”

SiO2-PVA-Fe(acac)3 Hybrid Based Superparamagnetic Nanocomposites for Nanomedicine: Morpho-textural Evaluation and In Vitro Cytotoxicity Assay

“…At 120 • C calcination temperature, the scattering curve displays a flat incoherent background at high Q values, which is due to the residual water and organics content of the materials. At low Q, a single power law is seen, which is characteristic of the porous xerogel structures [63][64][65]. There is no evidence on the formation of crystallites, due to their small quantity.…”

TiO2 Nanoparticles Supported on Hierarchical Meso/Macroporous SiO2 Spheres for Photocatalytic Applications

“…Materials with H 3 hysteresis do not show any limiting adsorption at high P/Po associated with nonrigid aggregates of plate-like particles and have slit-shaped pores [30]. These particles have a complex porous structure (Figure 2d) with pores of 3.5 nm, resulting from the surfactant assemblies that define the pore structure of the walls [31], as derived from BJH analysis of adsorption-desorption isotherms. Additionally, there is a broad distribution of larger pores related to the lamellar structure unfolding toward the particle surface.…”