into ordered arrays in one, two and three dimensions under the right conditions.
Lattices of nanocrystals consist of interacting nanocrystals and may exhibit novel
properties arising out of such interactions. The ability to engineer such assemblies
thus extends the reach of current lithographic techniques and holds promise for a
new generation of electronics of the nanoworld [29]. In this context, synthesis and
programmed assembly of nanocrystals assumes significance.
In this chapter, we discuss the structure and stability of mesoscopic organizations of nanocrystals in one, two and three dimensions, obtained by using a variety
of surfactants. We also examine certain unusual organizations such as clusters of
nanocrystals and microcolloidal crystals. Collective properties of nanocrystal organization are presented.
4.2
Synthetic Strategies
4.2.1
General Methods
Chemical synthesis of sols of metals and semiconductors results in nanoparticles
embedded in a layer of ligands or stabilizing agents, that prevent the aggregab
a
c
d
e
f
g
h
Fig. 4.1. The emission spectra of CdSe
nanocrystals of different sizes (a) 2.4 nm;
(b) 2.5 nm; (c) 2.9 nm; (d) 3.3 nm (e) 3.9 nm;
(f ) 4.1 nm; (g) 4.2 nm; (h) 4.4 nm. The change
in the emission width is due to decrease in
the nanocrystals diameter distribution with
increase in diameter (reproduced with
permission from [27]).
4.2 Synthetic Strategies 53