MCM-41 mesoporous silica is one of the most widely employed mesoporous silicas due to its large specific surface area, tunable pore diameter and high porosity.mcm-41 mesoporous silica It has attracted attention in the field of drug delivery and sensing because of its versatile properties. In this context, its functionalization with various organic groups enables the immobilization of drugs in the mesopores and their release upon application. Hence, the identification of a simple, reliable and effective method for the modification of mesoporous MCM-41 is crucial to its practical applications.
Most of the published methods for the preparation of mesoporous MCM-41 MSNs rely on complex and hazardous chemical reactions.mcm-41 mesoporous silica Moreover, they require high concentrations of surfactants, which may not be environmentally friendly or easily obtainable. Furthermore, these methods are difficult to scale-up for industrial applications. Recently, a simple, safe and efficient procedure for the synthesis of MCM-41 like MSNs has been developed by applying a modified Stober methodology to the calcination of cetyltrimethylammonium halide (CTAB) in an isotropic aqueous solution of sodium carbonate (NaCO3). This synthesis method is easy to apply and it can be operated under ambient conditions with good reproducibility and high yields. Furthermore, it does not involve toxic reagents and requires less time than other methodologies.
However, the MCM-41 morphologies obtained by different synthesis conditions differ substantially, and even the same morphology may be influenced by the synthesis parameters.mcm-41 mesoporous silica This is mainly due to the variation of fluid dynamics near the stirrer during the process, which leads to a variation in the concentration of surfactant present in the reactor and thus to different meso-order formations.
To address these problems, we developed a new mesoporous MCM-41 synthesis protocol that allows the elaboration of highly ordered MCM-41-like MSNs with a uniform morphology. This methodology consists of a two-step reaction procedure. In the first step, TEOS is dropwise added to a CTAB/NaCO3 solution that has been thermally stabilized at 80 degC. This mixture is then heated under a gentle flow of air to permit silica condensation.
After the completion of the reaction, the MCM-41 nanoparticles are purified by precipitation from the aqueous solution. The purified MCM-41 is then characterized by X-ray diffraction, FTIR and N2 adsorption experiments.
The morphology of the MCM-41 and its functionalized derivatives was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The unmodified MCM-41 displays a regular sphere-shaped structure with smooth surfaces, while the MCM-41-NH2 samples show agglomerated particles (Figure 5a).
In addition to this, the specific surface areas and pore volume/diameter of the MCM-41 and MCM-41-NH2 were determined by N2 adsorption measurements. The results demonstrate that the mesoporous MCM-41 maintains its mesostructure after functionalization with aminopropyl groups. This is important for the future application of mesoporous MCM-41 in diverse fields such as adsorption/desorption, surface chemistry, and cellular uptake of drug molecules. Furthermore, the MCM-41 NH2 shows high hydrothermal stability which renders it an attractive candidate for dye impregnation in water-based systems, where its luminescent ability was demonstrated.
Tags:mcm-41 catalyst | mesoporous mcm41 | zeolite mcm-41
