Biomedical Engineering Reference
In-Depth Information
The technology revolution in the twenty-first century is defined by the discovery
and design of new materials that are systematically engineered at the atomic level
to achieve unique physico-chemical properties that can be exploited for a vari-
ety of applications. Recent developments in chemistry and material science have
resulted in the engineering control enabling the miniaturization trend in nano-
technology. Among the components of nanotechnology to date, various types of
nanomaterials (NMs) offer the widest number of selections and the widest area of
possible applications.
NMs come in different chemical compositions, different sizes, different
shapes, different intrinsic properties that make them unique, and different func-
tional groups making them even more versatile. Their preparation or synthesis
processes vary as well from one chemical composition to another or even within
the same composition.
Some NMs exhibit optical properties while others have magnetic properties.
The optical properties may be due only to absorbance of light while others
may be caused by the NMs ability to absorb and emit light. These properties of
NMs are largely depended on their chemical composition and their size, shape,
crystal structure, and surface characteristics. These parameters, especially the
shape and size within the same chemical components, can be manipulated to
alter their unique characteristics. For example, the shape of an NM controls
its dimensions and reduction of its size results in the infinitesimal increase of
the electronic band of semiconductor nanoparticles (NPs) leading to changes
in its optical properties such as in the case of quantum dots (QDs), which are
made of semiconductor elements. High quality QDs, which exhibit stable spec-
troscopic properties, including high photoluminescence yield, have been stud-
ied and reported extensively in the literature.
1
A narrow size distribution in a
sample of NMs can minimize the broadening of spectroscopic properties that
can conceal details of the size-dependent properties.
2,3
To date, NMs of differ-
ent shapes and different sizes have emerged and with different properties than
those which are spherical.
4-10
Various methods for the synthesis of the sophis-
ticated shapes (e.g., nanorods, nanowires, and tetrapods) have emerged as well
as for the modifications to introduce various functionalities making the NMs
more versatile.
8-17
The controlled synthesis of these various NMs provides new
applications.
9,10,17,18
A long list of novel NMs forms and different compositions exhibiting unique
properties have been grown over the past two to three decades involving differ-
ent numerous synthetic routes of preparation. Development of novel synthetic
methods for preparation of new NMs requires control of experimental param-
eters in order to control their various effects on the growth process. As more and
more NMs emerged using different routes of synthesis, various mechanisms for
controlling the size, shape, and structure have been proposed and demonstrated.
These mechanisms serve as a guide for the design of new synthetic routes.
Today, there are no standard procedures to precisely engineer NMs unlike
synthetic organic chemistry, which is accurately controlled and reproducible.
