The Preparation And Modification Of Mesoporous Silica Nanoparticles And Its Applications

In recent years, the mesoporous silica nanoparticles (MSNs) have attracted considerable attention because of their potential applications in the fields of catalysis, adsorption and separation and drug delivery. Enormous studies have shown that the framework composition, internal porous structure, and external morphology of mesoporous silica nanoparticles have significant influence on their practical applications. Moreover, many functionalized mesostructure materials are synthesized, due to they can provide the possibility of combining the tunable functionality of organic moieties with the advantages of large surface areas and high stability inorganic framework. In the paper, we put forward some new ideas for synthesis of mesoporous silica materials, and successfully prepared a series of small size of mesoporous silica and functionalized counterparts, meanwhile apply them to practical application. The details are as follows:1.A series of small particle size of monodisperse silica particles have been first successfully synthesized by using different small organic amines (SOAs) and nitrogen containing heterocyclic compounds (NCHCs) as the catalyst in the presence of TEOS as silicon source and CTAB as surfactant. For the product synthesized by N,N,N’,N’-Tetrakis(2-hydroxyethyl)ethylenediamine (THEEDA) as catalysts, we not only study the dispersion and anti-reflection/anti-fog application, but also study the impact on the structure and morphology by changing the ratio of THEEDA/TEOS. The experimental results indicate that we have first successful synthesized a series of small size of monodisperse silica particles by using the eight kinds of catalyst, and could effectively adjust the particles size, pore size and specific surface area by selecting different SOAs and NCHCs as basic catalysts. Meanwhile, for the product synthesised by THEEDA as catalysts, the particle size, pore size and specific surface area can be controlled by changing the molar ratio of THEEDA/TEOS, the degree of the channel structure ordering is significantly improved. In addition, the research also further demonstates that the sol prepared using the mesoporous material synthesised by THEEDA as catalysts has a good dispersibility, stability, anti-reflection and anti-fog application property.2. Colloidal suspensions of monodispersed nanoporous silica particles were first successfully synthesized by using THEEDA as catalyst; and then, the functionalization nanoporous silica particles were also synthesized by applying mercapto modification in a similar way. These nanoporous silica particles were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), nitrogen adsorption-desorption and X-ray diffraction. Experimental results indicate that the spherical functionalized nanoporus silica particles are uniform (with the size of about 30-40 nm) and have large specific surface area (about 500 m2/g), large pore volume (> 1.6 cm3g-1) and narrow pore sizes distribution (< 3nm). Furthermore, they could be adopted as adsorbent for the removal of Hg2+ and Au3+ ions in water, having a promising application in removal of the metal ions.3. Organic functional groups were immobilized to SiO2 surface by the co-condensation of tetraethoxysilane (TEOS) and the hydrophobic organoalkoxysilanes RSi(OR’)3 (R=Ci2H25) in the presence of a cationic surfactant CTAB as the structure directing agents and sodium hydroxide as catalyst in the pure water system. These alkyl-functionalized mesoporous nanoparticles were characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption. The results indicate that the spherical functionalized mesostructures silica particles are ordered 2D hexagonal mesophases with large specific surface area (> 1000 m2/g), larger pore volume (> 1.2 cm3g-1), narrow pore sizes distribution (about 2.7 nm) and uniform small size (about 110 nm). Furthermore, with increasing the amount of DTES and the chain length of the organic group, the size and pore structure of the mesoporous silica could be effectively adjusted. Moreover, after being coated by the prepared sol (0.05g/25ml ethanol) containing dodecyl-functionalized mesoporous silica particles, the coated glass substrate showed good antifogging and superhydrophilic property.