181
Optical Properties
9
9.1
General Remarks
There are many applications of nanoparticles and nanocomposites exploiting the
special size-dependent optical properties. These applications have great importance in science and the economy. The most important groups of applications are:
• adjusting the index of refraction of a polymer;
• visually transparent UV-absorber;
• pigments;
• luminescent particles, primarily for applications in displays, medicine, and
biotechnology;
• photo- and electroluminescence;
• combined optical and magnetic applications.
The relative importance of these, characterized by revenues, is changing with time,
depending on the economic maturity of the different developments.
9.2
Adjustment of the Index of Refraction and Visually Transparent UV Absorbers
There are many applications of polymers where the index of refraction and the
optical dispersion of polymers must be adjusted precisely. This may be needed for
new optical systems or just for a glue connecting optical fibers for data transmission. Assuming a small concentration of particles with an index of refraction n particle
in a polymer matrix with an index of refraction n matrix , such a composite, with small
concentration c of particles, has a resulting index of refraction
n
c n
cn
n
c n
n
composite
matrix
particle
matrix
particle
mat
= −
(
)
+
=
+
−
1
r rix
(
).
(9.1)
This linear relationship of the index of refraction is experimentally very well
verified. As an example, Figure 9.1 displays the index of refraction of the composite titania, TiO 2 –polyvinyl alcohol, PVA as a function of the particle concentration [1].
Nanoparticles – Nanocomposites – Nanomaterials: An Introduction for Beginners, First Edition. Dieter Vollath.
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2013 by Wiley-VCH Verlag GmbH & Co. KGaA.