Biomedical Engineering Reference
In-Depth Information
2
μ
m
1
μ
m
5
μ
m
a
c
e
b
d
f
Figure 13.7
Upper left: structural schematic of MCM-41. The middle upper
fi gure: a schematic illustration of MCM-41 single crystal morphology-hexagonal
circular bicone-a combination form bounded by circular bicone faces and
hexagonal prism faces. Upper right: SEM image of a larger MCM-41 single
crystal the hexagonal feature is the view of a single crystal whose c-axis parallels
the line of vision. Lower fi gure: the SEM and TEM images of the as-synthesized
samples. (Reprinted with permission from [52-55])
adding Na
+
(sodium ions), K
+
(potassium ion), as well as vulcanization-
silane, respectively. We fi nd that if we change the adding factor (usually
as certain ions such as Fe
3+
, K
+
, etc.), the morphologies of product can be
controllably transformed from the MCM-single crystal to nanorod. And
the MCM-41 with different size can be controlled by adjusting the alka-
linity of the medium. Moreover, the morphology of the MCM-41 crystal
can be controllably modulated through the addition of alkali salts in the
synthetic system. Increasing the concentration of KCl can cause the aspect
ratio and the conical angle to increase consistently, and the result displays
monotonicity with a certain statistical deviation [57, 59].
Novel thiol-functionalized mesoporous silica nanorods or nanofi bers can
be controllably synthesized by adding of two assistant organoalkoxysilanes:
3-mercaptopropyl trimethoxysilane (MPTMS) and bis[3-(triethoxysilyl)
propyl]tetrasulfi de (TESPT) through a co-condensation method, in which
TEOS were used as silica precursors simultaneously [61, 62]. Results show
that the single-axis nanofi bers with diameters of about 60-80 nm are
obtained. The mesostructure of mesoporous silica nanofi ber corresponds
Search WWH ::
Custom Search