Environmental Engineering Reference
In-Depth Information
to strongly acidic or alkaline by grafting different functional groups. Thus it can
promise for a wide range of surface catalytic systems with various types of
chemical reactions for industrial, biological, and pharmacological processes.
The industrial processes like flotation, flocculation, and ceramic processing,
etc., which chiefly depend on the nature of the interface, can be controlled by
manipulating surface characteristics. The surface charge and wettability of the
silica-coated magnetite surfaces can also be tuned by the adsorption of surfac-
tants, which can be beneficial for controlling dispersion and flocculation in
various industrial processes. Silica surface can act as a template for the synthesis
of high molecular weight polymers and bio-molecules of medical importance.
Using this template, drug-delivery technique can be developed whereby specific
drugs can be applied directly to localized area thus resulting in an enhanced
remedy without affecting other parts of the body. Photosensitive compounds
adsorbed on silica surface can be subjected to external irradiations and their
reaction mechanisms can be studied in great detail with better profoundness.
Such study can be utilized in developing photo-sensitized chemical machines
which can replace electronic chips and can produce pollution-free micro machi-
neries [145]. With magnetic property, the difficulties in recovery and recycling
for some applications can be overcome.
In addition, co-condensation reactions, introduction of organic moieties
within the silicate framework may increase the flexibility of mesoporous silica
coating. The flexibility in choosing organic, inorganic, or hybrid building
blocks, and combinations of templates allows one to control the materials'
properties and to optimize them for each desired application. Periodic meso-
porous organosilicas (PMOS) were independently initiated by three groups
(Inagaki group [146], Ozin group [147], and Stein group [148]) in 1999. This
category of materials is synthesized using organic molecules having multiple
alkoxysilane groups such as bis(triethoxysilyl)ethane and bis(triethoxysilyl)-
benzene [149]. Unlike in organic functionalized mesoporous silica phases
obtained via grafting or co-condensation procedures the organic groups in
PMOS are direct parts of the 3D framework structure, thus giving raise to
enormous possibilities to turn their chemical and physical properties in desig-
nated ways by varying the structure of the precursors [150]. It is worth to
integrate PMOS with magnetic nanoparticles.
6.7 Conclusion
Magnetic nanocomposites were successfully synthesized by SA. By controlling
the reactivity of functional groups with surface, MHA was anchored onto
g-Fe
2
O
3
surface through chemical bonding between the carboxylic head
group of surfactant and iron on the surface, leaving the thiol or disulfide groups
reactive. The molecular orientation of MHA self-assembled on g-Fe
2
O
3
was
inferred fromXPS, DRIFTS and film flotation. This SA film is resistant to acid
and base attack.
