made. In this case the specifications for this now singularly important class of
materials emerged in the 1930s. It is important for the chemist to remember that
the parameters defining the functional properties of such bulk materials: principally mobility and carrier type and concentration are defined by concentrations of
impurities or dopants which are very small. The determination of bulk properties
from such small concentrations made the initial proper definition of the intrinsic
properties of silicon difficult, the history of this problem has been discussed recently [6].
This chapter will be structured as follows:
. The types of nanodimensional materials now routinely prepared, their structures and how these might be defined.
. The emergent uses for nanodimensional materials and how these lead to a
market pull for volume manufacture.
. The general methods available for the synthesis of nanodimensional materials.
. The suitability of such methods for scaling.
. Conclusions and perspectives on the future.
In preparing this chapter we have tried to give a perspective on what is an emerging area. Due to constraints of space the referencing has been limited to key papers
and indications of a number of major secondary sources are given. Examples have
been drawn from the work of one author’s own group at Imperial College and
latterly in Manchester. The synthesis of nano-dispersed metals and oxides is not
considered in detail, although some key references are provided. There are two
reasons for omitting metals: Firstly, the problems in scale up are much greater for
semiconductors than for metals and hence there is more scope for discussion.
Secondly, gold in particular is readily available and widely used in nano-dispersed
form [7]. For oxides in terms of well-defined processable nano-materials analogous
of quantum dots there are relatively few reports, but for an outstanding example
see [8], in contrast crude nanopowders of oxides are commonly available. A very
useful review of nanodimensional magnetic materials has just appeared [9].
2.2
Defining Nanodimensional Materials
For the purposes of this article we will limit our discussion to particles defined by a
minimum of two dimensions less than 100 nm but usually with 2-dimenions less
than 10 nm. Current interest in these materials can principally be traced to work
by Luis Brus in the mid-1980s in which he pointed out that the band gap of a
simple direct band gap semiconductor such as CdS should be dependent on its
size once its dimensions were smaller than the Bohr radius [10]. Experimental
work confirmed this suggestion. Initial samples were prepared by low temperature
2.2 Defining Nanodimensional Materials 13
materials emerged in the 1930s. It is important for the chemist to remember that
the parameters defining the functional properties of such bulk materials: principally mobility and carrier type and concentration are defined by concentrations of
impurities or dopants which are very small. The determination of bulk properties
from such small concentrations made the initial proper definition of the intrinsic
properties of silicon difficult, the history of this problem has been discussed recently [6].
This chapter will be structured as follows:
. The types of nanodimensional materials now routinely prepared, their structures and how these might be defined.
. The emergent uses for nanodimensional materials and how these lead to a
market pull for volume manufacture.
. The general methods available for the synthesis of nanodimensional materials.
. The suitability of such methods for scaling.
. Conclusions and perspectives on the future.
In preparing this chapter we have tried to give a perspective on what is an emerging area. Due to constraints of space the referencing has been limited to key papers
and indications of a number of major secondary sources are given. Examples have
been drawn from the work of one author’s own group at Imperial College and
latterly in Manchester. The synthesis of nano-dispersed metals and oxides is not
considered in detail, although some key references are provided. There are two
reasons for omitting metals: Firstly, the problems in scale up are much greater for
semiconductors than for metals and hence there is more scope for discussion.
Secondly, gold in particular is readily available and widely used in nano-dispersed
form [7]. For oxides in terms of well-defined processable nano-materials analogous
of quantum dots there are relatively few reports, but for an outstanding example
see [8], in contrast crude nanopowders of oxides are commonly available. A very
useful review of nanodimensional magnetic materials has just appeared [9].
2.2
Defining Nanodimensional Materials
For the purposes of this article we will limit our discussion to particles defined by a
minimum of two dimensions less than 100 nm but usually with 2-dimenions less
than 10 nm. Current interest in these materials can principally be traced to work
by Luis Brus in the mid-1980s in which he pointed out that the band gap of a
simple direct band gap semiconductor such as CdS should be dependent on its
size once its dimensions were smaller than the Bohr radius [10]. Experimental
work confirmed this suggestion. Initial samples were prepared by low temperature
2.2 Defining Nanodimensional Materials 13