Biology Reference
In-Depth Information
These properties are associated with the short-range order
of superparticles, and their cross-linkable surface ligands (ADT).
Grzybowski
demonstrated an excellent application of these
unique superparticles in the fabrication of freestanding, macroscopic
materials (Fig. 13.7).
et al.
22
These materials are plastic and moldable
against designed templates, and they can be thermally cross-linked
into polycrystalline metal structures with controlled porosity
(Fig. 13.7). In addition, macroscopic gold particle assemblies are
electrically conductive and exhibit Ohmic characteristics under an
electric field from 2
×
5
22
10
V/m down to 20 V/m.
13.4
Supercrystalline Superparticles
The formation of supercrystalline superparticles requires that the
interaction fields between nanocrystal building blocks are uniform
through the entire superparticle. Imperfect surface functionalization
and/or partial solvent inclusions induced by solvophilic interactions
between ligand and solvent molecules often create a nonuniform
interparticle interaction environment, leading to the formation
of superparticles with short-range order and sometimes loose
structures.
−
has observed the
conversion of short-range order superparticles into supercrystalline
crystals by increasing solvophobic interactions; however, this process
cannot prevent unlimited superparticle growth, thus resulting in
large particle assemblies (Fig. 13.6A).
22,33
36
Indeed, Grzybowski
et al.
36
In this section, we discuss
two general approaches for making colloidal supercrystalline
superparticles:
25,38
microemulsion-template
synthesis
and
1,20,21
controlled induction of solvophobic interactions (CIS).
13.4.1
Microemulsion-Template Synthesis
Microemulsion-template
synthesis
is
a
heterophase
reaction
developed by Li
, which is based on an oil-in-water (O/W)
microemulsion system (Fig. 13.8).
et al.
In this synthesis, nanocrystal
building blocks are dispersed in low boiling point, nonpolar organic
solvents such as cyclohexane, while surfactants are dissolved in the
water phase. Under stirring or sonication, these two phases are
mixed to form stable O/W microemulsions, and then the organic
solvent is evaporated at a chosen temperature, which does not
22
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