Teraflop 73 - Novembre - cesca

One of the great challenges of
modern science is how to fabricate
and manipulate materials
and devices at the molecular scale.
For example, nowadays most commercial
semiconductor technologies (such
as standard MOS technology) use bulk
material properties in order to produce
electronic circuits. Also current lithographic
methods used in production of
microchips may only operate with structures
of ~200 nm of more in size. Going
below this limit requires new experimental,
not currently in production, techniques.
Indeed, recently, there has been
an explosion of research on the
nanoscale behavior (nanoscale is defined
as objects of 1-100 nm in length).
Nanoscience and nanotechnology involve
studying and working with matter
on an ultra-small scale (a single human
hair is around 80,000 nm in width).
Nanoscience is an interdisciplinary field
of sciences which in the next 10-20
years is expected to have great impact
on technology and stretches across the
whole spectrum of science, influencing
medicine, biology, physics, engineering,
chemistry etc. Nanotechnology
which is mostly studied now includes
molecular electronics, nanocrystalline
materials, NEMS, nanoparticles, quantum
dots and nanotubes. From these
applications we will discuss only nanotubes
and their smaller counterparts,
fullerenes.
An unique character of nanoscience
is that it creates devices through
“bottom-up” instead of “top-down” approach
and major problem of nanoscience
is how we can study (observe)
the nanoobjects. Another reason for the
explosion in nanoscience, starting from
the late 90’s is the developments in the
80’s of different microscopy types, such
as STM, AFM, SEM and TEM. They
Single Wall Carbon Nanotube
Solubility and Novel C60 Materials
Michael Bendikov and Fred Wudl
Department of Chemistry and Biochemistry
Exotic Materials Institute
University of California, Los Angeles, California
provide the “eyes” and “fingers” for
nanoscale manipulation and measurements.
Recent progress in high performance
computers also allowed highly
sophisticated computer simulations
which are essential to enhance our
understanding of the processes occurring
on the nanoscale regime, as well
as to design “tailor-made” materials.
Structure of chemically modified fullerene,
1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C 61
(PCBM), which is used in plastic solar cells
(organic photodiodes), which is the most promising
applications of fullerenes.
The most abundant single carbon-carbon
bond is about 0.154 nm
long and most other chemical bonds
are shorter than 0.25-0.30 nm. Thus,
molecules are generally less than a nm
and we study them in chemistry. Condensed
matter physics deals with continuous
solids which much longer than
100 nm length-scale. Nanoscience
deals with the in-between meso-world.
Nanoword it is a lot of (usually more
than hundred) atoms, however, it is significantly
smaller than the wavelength
of visible light and any micro-device.
As different types of microscopy
are a breakthrough which opened
nanoscience from a technological direction,
the parent fullerene (C 60) might
be considered as introducer of nanoscience
from a chemical direction. C 60
is a special high symmetry carbon
cluster with a diameter of ca. 0.7 nm.
Its spherical π-electron surface has
provided scientists and engineers with
an unprecedented fundamental building
block with many promising electronic,
magnetic and optical properties.
However, it is only sparingly soluble in
most common solvents, which prevents
utilization of its unusual properties. It is
imperative that the cluster be derivatized
(functionalized) to be incorporated
into most familiar solids for materials
science applications. Great progress
has been made in chemical
modification of C 60, producing compounds
with modified properties and
greater solubility, which opens up possibility
for its technological use. However,
addition and cycloaddition reactions
are the only synthetic methods available
to functionalize C 60. Semiconducting,
magnetic and superconducting
properties of unmodified buckminsterfullerene
have been thoroughly investigated.
After nearly 20 years of fullerene
research, there are only two areas
where functionalized fullerenes have
had an impact: plastic solar cells and
optical limiting glasses, with lesser applications
in polymeric materials and
fullerene-modified traditional materials.
Real applications of fullerenes still have
to be discovered, but few exist now
and one of the important outcomes of
intensive studies of fullerenes is that it
opened the road to nanotubes.