Environmental Engineering Reference
In-Depth Information
50
45
Nanomachine (80)
Nanocomposites (10715)
Nanomaterials (4065)
Nanomedicine (268)
40
35
30
25
20
15
10
5
0
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Year
Figure 2.2
The relative number of publications describing various high profi le areas of
nanotechnology. Total number of publications shown in brackets. Clearly the area of nano-
medicine is currently seeing rapid growth; however, the area of nanocomposites is the longest
lived and largest of those presented here. (Source; MIMAS Web of Science.)
were not purposely produced but formed as a by-product of another process. In
addition, those which had been purposely prepared were not prepared in a form
that had been optimised for dispersion in liquid media (SCENIHR, 2005). The
concern with current developments in nanotechnology is that new particles will be
more active, more diverse and may be released into the environment by a wider
range of mechanisms than ultrafi ne particles.
A wide range of nanoparticles is formed in nature without the infl uence of man;
iron is stored in nanoparticles (ferritin), humic substances in soils and viruses are
all on the nanoscale. The application of nanotechnology by man is also not particu-
larly new. Man has been using nanotechnology for millennia; the ancient Egyptians
added gold to glass to give a red colour and recent studies of jewellery show that
this colour is due to the formation of nanoparticles of gold trapped in the glass.
Similarly, in 1857, Michael Faraday reduced gold salts using white phosphorous to
produce gold sols with deep red colours. Although Michael Faraday speculated on
the nature of the new gold material he had prepared it was not until the advent of
high resolution microscopy that these systems could be studied in detail. Towards
the end of the twentieth century the enabling technologies evolved and the common
tools of scanning electron microscopy (SEM), transmission electron microscopy
(TEM) and scanning probe microscopy (SPM) made imaging at atomic resolutions
possible. These are discussed in Chapter 6. In addition, new synthetic approaches
such as chemical vapour deposition and fast ion bombardment began to make
Search WWH ::
Custom Search