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Fig. 6.12 Room temperature magnetization of bare magnetite and mesoporous magnetic
nanocomposite particles
magnetization and high specific surface area for their applications as magnetic
sorbents. The dense-liquid method followed by the template-assisted sol-gel
process resulted in the formation of a uniform, mesoporous thin silica coating
on magnetite particles. The resultant particles are well protected for iron
leaching from cores, while providing surface amenable for functionalization
via well-defined silane-coupling reactions. The functionalized particles have
potential applications in a variety of science and engineering disciplines.
6.4.5 Silanation on Mesoporous Silica-Coated Magnetic Particles
As mentioned earlier, the synthesized mesoporous magnetic particles exhibited
the necessary attributes of strong magnetization, high specific surface area and
good protection of magnetic cores for applications as magnetic sorbents. Based on
previous success of functionalizing silica surfaces using APTES to obtain reactive
amino groups of high affinity for metals [6, 112], APTES was the common choice
as silane-coupling agent. Furthermore, use of this short-chain alkane amine
minimized blockage of pore channels.
The self-assembly of silane-coupling agents by silanation is a multistep
process. In addition to complex interactions among the substrate, silane, and
solvent, many other parameters need to be considered. According to Feng et al.
[112], the number of surface silanol groups and the amount of adsorbed water
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