Interfacial Phenomena at a Surface of Nanosilica

Fumed silicas (also named as nanosilicas, pyrogenic silicas, and highly disperse amorphous silicas) are synthesized by using high-temperature (HT) hydrolysis of SiCU SiCljCHj, or other similar 

Nanosilicas with a spherical shape of nonporous nanoparticles, controlled particle size distribution (PaSD), and specific surface area (Sbet) are appropriate nanosized materials to study the interfacial phenomena (without the strong distorting effects in nanopores) in different dispersion media. Nanosilicas are fully amorphous and can possess a larger 5bet value from 50 up to 500 mVg and a narrow PaSD (which becomes narrower at a greater Sbet value Her 1979, Ulrich 1984, Degussa 1997, Barthel et al. 1998a,b, Kammler and Pratsinis 2000, Kammler et al. 2004, Cabot Corporation 2011). 

FIGURE 1.1 Dispersion patterns of nanosilica CAB-O-SIL (CAB-O-SIL, a registered trademark of Cabot Corporation, copyright Cabot Corporation 2011). (Adapted from Cabot Corp. Boston, MA, 2011, www.cabot-corp.com/fmo. With permission.) 

FIGURE 1.2 HRSEM (a, b) (From Barthel, H. et al, Particle sizes of fumed silica, in An International Conference on Silica Science and Technology Silica 98 , Mulhouse, France, September 1-4, 1998, pp. 323-326) and HRTFM (c-f) (Adapted from Myronyuk, I.F. et al., Phys. Chem. Solid State, 11, 409, 2010. With permission) images of nanosilicas (a) agglomerate (375 nm in size) of primary nanoparticles A-200, (b) aggregate of agglomerates ( 6.5 pm), (c) A-50 (5 bet=52 mVg), (d-f) A-200 (Sbet= 179 mVg) (d, e) 1—nanopores, 2—narrow, and 3—broad mesopores (f) structures 1, 2, and 3 show the amorphous character of nanosilica. 

Nanosilica A-300 ( bet OO mVg) is used as a medicinal preparation of a high sorption capability possesses certain unique properties, which make it possible to use it effectively on treatment of different diseases (Chuiko 1993, 2003, Blitz and Gun ko 2006). These features of nanosilica are caused by several factors (i) chemical nature of amorphous nonporous primary nanoparticles passive in redox reactions and possessing weak reactivity in acid-base reactions (with participation of the =SiOH groups) and a low surface charge density at pH 8 (ii) a small size 

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