Synthesis of Highly Ordered Mesoporous MCM-41: Selective External Functionalization by Time Control

Ana Claudia Da Silva,Noboru Hioka,Patrícia Cordeiro,Wilker Caetano,André Tessaro,Bianca Estevão,Hellmut Eckert,Murilo Moisés,Silvana Santin

doi:10.21577/0103-5053.20190058

Abstract

Sol-gel synthesis is commonly used to modify the surface of mesoporous silica nanoparticles (MSN) with organic groups through the co-condensation method. The template removal, and the site-controlled addition of organic groups and their partial occlusion inside the framework walls are still a challenge in the one-pot synthesis. Here, we optimize the synthesis of amino-modified MSN by the combination of efficient template removal methodology with the precise time of the amino precursor addition to achieve superb mesoporous material. The addition after the growth process produces a sample with a significantly higher amount of NH2 on the external surface when compared to the standard procedure. The template removal by reflux with isopropanol/H+ eliminated ca. 90% of cetyltrimethylammonium bromide (CTAB), and preserved the mechanical and thermal properties, even with thin walls (2.1 nm). The synthesized nanoparticles possess stability, appropriate size, and a positive surface. This makes them excellent nanocarriers, especially in the biomedical field.

Highlights

Mesoporous silica nanoparticles (MSN) possess high specific areas and ordered/regular pore distribution.[1,2,3] This makes them versatile materials that can be applied in adsorption, chromatography, catalysis, chemical sensors, and drug delivery systems in the biomedical field.[4,5] In Mobil composition of matter No 41 (MCM-41) synthesis, one of the most used silica mesoporous materials, the surfactant cetyltrimethylammonium bromide (CTAB) acts as the structure-directing agent
TEM images (Figure 2) show well-ordered mesoporous materials homogeneously distributed in spherical nanoparticles of an average size of 156 ± 21.3 nm
Even though the value is in line with the estimated by the N2 adsorption/desorption isotherm

Summary

Introduction

Mesoporous silica nanoparticles (MSN) possess high specific areas and ordered/regular pore distribution.[1,2,3] This makes them versatile materials that can be applied in adsorption, chromatography, catalysis, chemical sensors, and drug delivery systems in the biomedical field.[4,5] In Mobil composition of matter No 41 (MCM-41) synthesis, one of the most used silica mesoporous materials, the surfactant cetyltrimethylammonium bromide (CTAB) acts as the structure-directing agent (template). This indicates a narrow size distribution of cylindrical, uniform, and unidirectional mesoporous.[27] MSN_R12 is the only sample that presents a type IVa isotherm, in addition to the MSN_C used as a reference (Figure S3, SI section). Compared to the reflux used in the literature, MSN_R12 presented a specific area equal to that found by Wada et al.[14] In addition, it required half the extraction time.

Results

Conclusion