Nanomaterials: Properties, Preparation and Applications - Environmental and Human Health Impacts of Nanotechnology - page 64

Block copolymer

Hydrophilic section

Hydrophobic section

Nanoparticle Polymersome

Aqueous
core

Hydrophobic
area

Hydrophilic area

Figure 2.19 A block copolymer for the preparation of a nano-drug delivery system. Particles
(bottom left) and polymersomes (bottom right) may be formed depending on composition
and processing methods.

Clearly the preparation of nanoparticles is only part of the challenge. Often the
next challenge is analysing them. As complex mixtures there are many different
factors to consider. Conventionally, particle size and behaviour in various media
are routine. Crystal phase, capping material and purity, however, are key factors
which cannot be ignored. Various methods for determining these factors are out-
lined in detail in Chapter 6. As a minimum it is recommended that the following
information is critical, although in some cases more information may be required:

• Particle size and distribution (including surface area).
• Hydrodynamic size.
• Crystal phase of the particle.
• Nature of the capping agent/surface functionalisation (including surface charge).
• Purity.

2.6 Applications of Nanoparticles and Nanotechnology

2.6.1 The Past

The use of nanomaterials is not new. They were employed by nature long before
man even thought about technology. Even man has been employing them for thou-
sands of years. The Egyptians often added gold or cobalt to molten glass to colour
it and make costume jewellery. The glass took on a red (gold) colour due to the
surface plasmon resonances of the particles it contained. Lamp back has been used
as a pigment for inks for thousands of years before carbon black particles saw more