Page 120 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

106 Principles and Methods

in the release of Cd ions, the toxicity of which is well known. However,
when CdSe nanoparticles are covered with organic molecules, the cyto-
toxicity is reduced (see Chapters 11 and 12). Adsorptive interactions
involving nanomaterials (Chapter 10), the effects of nanoparticle sur-
face chemistry on particle stability and mobility (Chapter 7), and pho-
tocatalytic properties (Chapter 5) are also covered in greater detail later
in this book.

Principles of Light-Material Interactions,
Atomic Force Microscopy, and Scanning
Tunnel Microscopy
Phenomena resulting from the interaction between electromagnetic
radiation and matter can be interpreted to yield a great deal of infor-
mation on nanomaterials. Light (e.g., X-ray, UV-vis, infrared) is an
oscillating electromagnetic field. It is a wave that is characterized by
S
a specific frequency (v 5 2pn 0 ) and a radiation wave vector ( k 0 ).
0
However, light is also a particle called a photon, where each photon
carries a packet of energy that is proportional to its frequency. Light
can also be associated to particulate beams like electron beams. An
electron beam also interacts with matter in a similar fashion to that
of photons. The interaction between light and matter can occur in a
variety of different scenarios, which can be summarized as follows
(see also Figure 4.1):

Figure 4.1 Examples of the various manners of interac-
tions between light and electron beams with matter.