Mesoporous Silica

Abstract

Mesoporous silica (MS), which provides highly ordered, scalefine tunable mesopores (pore diameter of from 2 to 50 nm) and nanopores (pore diameter smaller than 2 nm), has excellent properties. These include an extremely large surface area (∼1000 m 2 /g), high thermal stability (∼900 C), and transparency to visible light. 1 The most significant property of MS concerns its controllable and uniform porosity, because the utility of porous materials is largely due to the structure and size of their pores. Highly ordered porous structures are synthesized using a surfactant, such as block copolymers, as a template for pores that form a periodic structure in a self-organizing manner in a solution. 2,3 It has been about thirty years since Yanagisawa et al. first reported the synthesis of MS in 1990 (pore diameter of from 1.8 to 3.2 nm), 3 but it has still attracted considerable interest in many different fields due to its great potential for wide ranging applications. These include separation, catalytic processes, molecular supports, chemical reaction fields, adsorbents, and sensors. For these applications, it is significant to understand any difference in the molecular behaviors between in pores and in the bulk phase. MS is synthesized in various forms: powder, thin-films, fibers, rods, monoliths, and spheres. Recently, Ohta et al. reported on a pore-size effect on a formation of pharmaceutical crystals from solution incorporated in the pores of MS by using Raman spectroscopy. 5 Because MS exhibits an excellent transmittance in the visible wavelength region, it enables us to perform optical measurements of molecules in the pores of MS. Sato et al. reported on the diffusion of fluorescent dye in a micrometer-sized spherical MS particle by using confocal fluorescence micro spectroscopy.

Surface Modification of Mesoporous Silica Nanoparticles for Application in Targeted Delivery Systems of Antitumour Drugs

“…Mesoporous silica nanoparticles are promising nanoscale carriers due to the ease with which they can be synthesized and their homogeneous structure, tuneable size (50–200 nm) [ 67 ], and large pore volume (0.6–1.4 cm 3 /g) [ 68 , 69 ]. With a high specific surface area (700–1000 m 2 /g) [ 70 , 71 ], MSNs have high drug loading capacity.…”