Biomedical Engineering Reference
In-Depth Information
use as novel vehicles for drug delivery. Another medical application of fullerenes is related
to their use as a contrast agent in magnetic resonance imaging (MRI). Fullerenes are also
used in nonlinear optics, cosmetics, and surface coatings [39-41].
Another type of carbon nanostructure, CNTs, can be obtained by rolling graphene into
cylinders [31]. The resulting CNTs adopt various structures. Such structures differ in vital
parameters, including length, thickness, type of helicity, and number of layers. When a
carbon nanotube possesses one carbon layer it is called single-wall carbon nanotube
(SWNT). However, the diversity of their structures is quite remarkable and a coaxial assem-
bly of SWNT can also be arranged, called multiwall carbon nanotube (MWNT). Many
applications of CNTs originate from their extraordinary strength [42]. These characteristics
are used to improve various materials: textiles, concrete, polymers, and sport equipment.
Other applications, including magnets, conductive films, transistors, displays, solar cells and
ultracapacitors, utilize their unique electrical properties. The exceptional properties of
CNTs are also vital for chemical processes, and CNTs are used in water desalination, air fil-
ters, and hydrogen storage [43-50].
Due to the unique, one-layer structure of graphene, it has exceptional properties that can
be adjusted and controlled by chemical modifications of the parent species. Graphene is a
prospective material for nanoelectronics, and the electron transport in graphene is described
by a Dirac-like equation. Investigations of various processes involving bending, folding, and
scrolling of graphene sheets are producing rapid technological advances. An interesting
example of chemically modification is hydrogenated graphene, a graphene that represents a
two-dimensional hydrocarbon with one hydrogen atom attached to every site of the honey-
comb lattice [51]. The binding processes of H atoms on the graphene, especially modifica-
tion of the graphene surface by the addition of various metals, are of current interest and
there is an expectation that such systems could be used for hydrogen storage [38, 51, 52].
Metal and Metal Oxide Nanomaterials
Among the large groups of inorganic nanomaterials, nanometals and nanometal oxides are
currently very popular. They have been used in various industrial and commercial applica-
tions and their role and significance have been steadily growing over the past decade.
Gold nanoclusters are among the most recognized metal nanostructures. Perhaps,
together with the nanosilver, they have been the subject of the largest and most diverse
volume of comprehensive studies. In historical times, medieval craftsmen applied gold in its
nano form to stained glass. The red color of such processed glass is the effect of blending
gold chloride into glass during the melting process. Under applied conditions gold chloride
dissociates, forming nano-sized gold spheres, which adsorb and reflect sunlight, generating
burgundy, red, or purple colors, with the intensity and exact shade depending on the size
(and perhaps also shape) of metal aggregates.
One of the advantages of working with gold is its plasticity, which creates a potential to
produce various forms of Au nanostructures and clusters. Gold clusters and nanoparticles
assume many forms, including spheres, rods, discs, cubes, belts, pyramids, branched, and
stars, in various sizes. Of industrial importance is that the evolution of size and structure of
gold nanoparticles can be carried out carefully through well-controlled processes [53-55].
This facilitates accurate determination of size, classification, and segregation of useful por-
tions of the material. The possibility of fabrication and separation of desired fractions of
material creates interest in gold nanostructures from both basic science research and
commerce. The most important applications of gold nanomaterials include organic photo-
voltaics, various probes and sensors, therapeutic agents, biological and medical applications,
electronic conductors, catalysis, and fuel-cell applications [56-59].
