Environmental Engineering Reference
In-Depth Information
Michael Faraday was the first to provide a scientific description of the optical
properties of nanometric metal particles, in a paper he published in 1857 [
2
]. Turner
further revealed that leaving very thin gold or silver films on glassy surfaces heated
at 500
C changed both the properties of the deposited metals and those of the glass,
so that white light crossed the metallic film; this caused a marked reduction of
reflection, while electrical resistivity increased significantly [
3
]. Ten years later
(1867), James Clark Maxwell suggested a series of concepts of differentiation in
nanotechnology, but without using the word “nanotechnology” to define thin,
monomolecular layers [
4
].
The first accurate observations and measurements were made much later, by
Richard Adolf Zsigmondy, who used dark field ultramicroscopy which allows the
visualisation of particles smaller than monochromatic light wavelength (1914).
With this method, Zsigmondy was able to see 1/1,000,000-mm particles and he
was the first to apply the term “nanoparticles” explicitly to such particles [
5
].
Irving Langmuir and Katharine B. Blodgett, dealing with nanoparticle charac-
terisation and related phenomena that define interface in colloid science (1920),
introduced the concept of monolayer, a layer of material one molecule thick.
Langmuir received the Nobel Prize for his theoretical contributions in chemistry
in 1932 [
6
,
7
].
The shortest definition of nanoparticles [
8
-
10
], which is probably the most
intuitive one, takes into consideration only their size, which is limited convention-
ally to about 100 nm in any direction. This definition cannot be exhaustive, as it
does not give net values. But without a classification, no matter how general, it is
difficult to differentiate between the molecular and atomic field on the one hand and
the nanoparticle field on the other.
Nanoparticles can be classified based on the following criteria [
11
,
12
]:
- Origin:
• Natural
• Anthropogenic
- Size (as already shown):
• 1-10 nm
• 10-100 nm
• Over 100 nm
- Chemical composition:
• Inorganic substances
• Organic substances
• Elements of the living kingdom.
These criteria are presented synthetically in Fig.
1.1
[
13
].
The attempt to give a comprehensive definition of nanoparticles is generally the
object of physical chemistry, as nanoparticle behaviour depends both on
directly measurable quantities (mass, volume, electric charge) and their property
