Biomedical Engineering Reference
In-Depth Information
Metal NPs
Small molecules
Silicates/silanes
Citrate salts
Surfactants
Synthetic polymers
PVP
Interface
Polyelectrolytes
Bio-polymers
Enzyme
Gelatin
Silica-coated
metal NPs
Figure 4.4
Silica-coating strategies [31].
liquid phases for stabilization of suspensions [30], and also as i llers in wide
range of polymer products, including dental materials [31]. Silica nanopar-
ticles are also used for the synthesis of various nanoshells are depicted in
Figure 4.4, consisting of a solid siliceous core and a nanoshell or vice versa
Silica particles having sizes ranging from 40 nm to several micrometers
by controlled hydrolysis of tetraethylortho-silicate (TEOS) in ethanol, fol-
lowed by condensation (polymerization) of the dispersed phase material.
h e reactions involved is
(hydrolysis) Si(OR)
4
+ 4H
2
O
Si(OH)
4
+ 4ROH
(condensation) Si(OH)
4
SiO
2
+ 4H
2
O
It was found that there are i ve primary parameters af ect on the size of
silica particles. h ese parameters were (1) concentration of TEOS (2) con-
centration of ammonia (3) concentration of water (4) alcohol used as the
solvent (5) reaction temperature.
Silica particles were synthesized by authors using Stöber procedure
[33, 34]. Hydrolysis and successive condensation of silica precursor TEOS
was carried out in alcoholic medium in a base catalyzed reaction using
ammonium hydroxide. In a typical preparation method mixture of ethanol
(15 mL), distilled water (3 mL) and ammonium hydroxide (0.75 mL) was
stirred for 30 mins to form a homogeneous solution. TEOS (1.2 mL) was
