Silica-based microspheres

Silica-based microspheres are typically between 5 and 200 j,m in diameter, have wall thicknesses of 0.5-20 pm and can be filled with up to 100 M Pa of H2. The spheres are formed by melting spray-dried microparticles in free fall and the evolving gases... 

It is also relevant that silica microspheres being readily biodegradable and of no toxicity, they will not contaminate the environment as the cmrent commercial trend in their use continues, production of increasing quantities of sol-gel-derived silica-based fimctional materials will inevitably result in the introduction of granules and microparticles made of amorphous silica (or organosilica) in environmental matrices and in the biosphere (Table 18.2). 

E., Sellergren, B., Courtois, J., Irgum, K., Dambies, L., Cormack, P. A. G., Sherrington, D. C., Lorenzi, E. D., Chromatographic Comparison of Bupivacaine Imprinted Polymers Prepared in Crushed Monolith, Microsphere, Silica-Based Composite and Capillary Monolith Formats,/. 1160,215-226. 

Mercury is a highly toxic element and its removal and analytical detection are important. Dithiocarbamate-incorporated monosized polystyrene-based microspheres (2 pm) have been prepared (2043) and used for the selective removal of mercury(ll) from aqueous solutions. The absorption ability increases with pH (2044). Related to this, dithiocarbamate grafted onto dried silica gel have been shown to be highly effective for the removal of mercury from waste solutions containing various complexing agents (145). 

As examples of microgels with a constant degree of crosslinking, poly (ferrocenylsilane)-based gel particles could be oxidized, which yielded an electrostatically driven attachment of silica nanoparticles [397, 398]. Larger micrometersized poly(ferrocenylsilane)-based microspheres were prepared using microfluidics [399]. 

An important demonstrated application of this artificial nose system is the high-speed detection of low levels of explosives and explosive-like vapors. Several sensors, based on Nile Red attached to silica microspheres, show high sensitivity to nitroaromatic compounds (NAC) within a mixture12. Different fluorescence response profiles were observed for several NAC s, such as 1,3,5-trinitrotoluene (TNT) and 1,3-dinitrobenzene (DNB), despite their similar structures. These responses were monitored at low concentrations of the NAC vapors (ca. 5 ppb) and at short vapor exposure... 

High-performance liquid chromatography (HPLC) is a variant of the simple column technique, based on the discovery that chromatographic separations are vastly improved if the stationary phase is made up of very small, uniformly sized spherical particles. Small particle size ensures a large surface area for better adsorption, and a uniform spherical shape allows a tight, uniform packing. In practice, specially prepared and coated silica microspheres of 10-25 /j.m size are often used. Only 15 g of these microspheres have a surface area the size of a football field ... 

An important demonstrated application of this artificial nose system is the high-speed detection of low levels of explosives and explosive-like vapours. Several sensors, based on Nile Red attached to silica microspheres, show high sensitivity to nitroaromatic compounds (NAC) within a mixture... 

As shown in Fig. 8.9A, a full-color photonic crystal device was designed and fabricated in a form of electrochemical cell (Arsenault et al., 2007). The device was based on a two-component composite, that is, silica microspheres and polyferrocenylsilane (PFS). The silica microspheres with an ordered self-assembly array were deposited on ITO glass substrate and served as the inactive structural scaffold. PFS with pendant unsaturated C=C bonds were incorporated into the lattice spacing of silica microspheres and polymerized... 

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