Biomedical Engineering Reference
In-Depth Information
Fig. 6.14
Schematic graph showing the formation of CaCO
3
under the SA monolayer: (
a
) isolated
ACC particles are formed during the initial compression, (
b
) the primary ACC particles grow in
number density and remain stable during the continuous compression, (
c
) with prolongation of the
reaction time, the ACC particles continue to nucleate and grow and tend to aggregate together,
(
d
) when the reaction time is further increased, the ACC particles and the aggregates gradually
transform into calcite. (Reproduced from [
98
], Copyright © 2009, American Chemical Society)
monolayer at the air-water interface has been studied by Yang and co-workers
[
98
]. It is found that the final calcium carbonate crystals are transformed from
ACC rather than directly from the solvated ions under the compressed stearic
acid monolayer. The precursors, which are uniform spherical particles with sizes
smaller than 100 nm, are produced in an early stage of mineralization and can
be stabilized for at least 0.5 h. Subsequently, the ACC particles tend to aggregate
and are eventually transformed into the calcite phase with the elapse of time. In
addition, the Kitano method is used to form the ACC. Furthermore, the observation
of the crystallization of ACC is important to the understanding of the detailed
biomineralization mechanisms of cell membranes. According to the experiment
results, the crystallization process of calcium carbonate under the SA monolayer
can be illustrated as in Fig.
6.14
[
98
].
Moreover, the ACC can be obtained on a self-assembled monolayer (SAM) of
hydroxyl-terminated alkanethiols on a gold surface [
99
]. Then, it can be stored in
a dry atmosphere as a reservoir for ions and be induced to crystallize by water and
a secondary surface that is functionalized with carboxylic acid-terminated SAM.
This secondary surface is the template for oriented and patterned nucleation of
CaCO
3
. Using this method, various oriented crystalline arrays and micropatterned
films are formed (Fig.
6.15
)[
99
]. Foreign ions and molecules can be doped
