C hapter 1 Nanomaterials and Nanotechnologies: an overview
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ion—cadium (Cd), for example—and a molecule that is able to
donate a selenium ion. This reaction generates crystals of cadmium
selenide (CdSe). The shape and size of quantum dots can be controlled by tuning the ratio of the molecules and by adding surfactants. Their size and shape are important because they determine
their electronic, magnetic, and optical properties.
The second important bottom-up method is the use of scanning
probes. One of the biggest steps toward nanoscale control occurred
in 1981 when researchers at the IBM research center in Switzerland,
led by Gerd Binning and Heinrich Rohre, developed the scanning
tunneling microscope (STM). The STM is, essentially, a fine tip that
scans over a material’s surface. Since the tip is only a few atoms
wide, electrons “tunnel” across the gap between the surface and
the tip as the tip sweeps over the surface (see Chapter 8). In this
way scientists developed several related instruments, now known as
scanning probe microscopes (SPMs), to collect images and analyze the
identities of atoms on a material’s surface. At the moment, SPMs
can do more than simply look at atoms. They can also be used to
move atoms. At IBM, Donald Eigler and Erhard Schweizer were able
to displace 35 xenon atoms onto a crystal of Ni and write the word
IBM (see Figure 1.7). These tools have opened up many new doors
for further scientific discovery.
The third relevant route for producing nanostructures using a
bottom-up approach is the use of biotechnology. By 1998, biotechnologists were able to make DNA sequences and assemble artificial
viruses, which are examples of molecular engineering. In addition,
several devices, which looked like biomolecular motors, sensors,
and actuators, could be integrated into systems made of molecular machines. One of the best biological examples of a molecular
machine is the ribosome, which is a remarkable nanoscale assembler.
The role of the ribosome is to act as a factory of proteins by combining amino acids in a very specific order. Section 2.2 discusses
ribosome self-assembly methods in more detail.
Figure 1.6
Cadmium selenide (CdSe) quantum dots of
different sizes and shapes in solution emit light at
different wavelengths. (Courtesy of M. J. Bawendi,
MIT.)
Figure 1.7 Xenon atoms arranged on a Ni
substrate by a scanning tunneling probe, forming
the word IBM. (Courtesy of IBM.)
8
ion—cadium (Cd), for example—and a molecule that is able to
donate a selenium ion. This reaction generates crystals of cadmium
selenide (CdSe). The shape and size of quantum dots can be controlled by tuning the ratio of the molecules and by adding surfactants. Their size and shape are important because they determine
their electronic, magnetic, and optical properties.
The second important bottom-up method is the use of scanning
probes. One of the biggest steps toward nanoscale control occurred
in 1981 when researchers at the IBM research center in Switzerland,
led by Gerd Binning and Heinrich Rohre, developed the scanning
tunneling microscope (STM). The STM is, essentially, a fine tip that
scans over a material’s surface. Since the tip is only a few atoms
wide, electrons “tunnel” across the gap between the surface and
the tip as the tip sweeps over the surface (see Chapter 8). In this
way scientists developed several related instruments, now known as
scanning probe microscopes (SPMs), to collect images and analyze the
identities of atoms on a material’s surface. At the moment, SPMs
can do more than simply look at atoms. They can also be used to
move atoms. At IBM, Donald Eigler and Erhard Schweizer were able
to displace 35 xenon atoms onto a crystal of Ni and write the word
IBM (see Figure 1.7). These tools have opened up many new doors
for further scientific discovery.
The third relevant route for producing nanostructures using a
bottom-up approach is the use of biotechnology. By 1998, biotechnologists were able to make DNA sequences and assemble artificial
viruses, which are examples of molecular engineering. In addition,
several devices, which looked like biomolecular motors, sensors,
and actuators, could be integrated into systems made of molecular machines. One of the best biological examples of a molecular
machine is the ribosome, which is a remarkable nanoscale assembler.
The role of the ribosome is to act as a factory of proteins by combining amino acids in a very specific order. Section 2.2 discusses
ribosome self-assembly methods in more detail.
Figure 1.6
Cadmium selenide (CdSe) quantum dots of
different sizes and shapes in solution emit light at
different wavelengths. (Courtesy of M. J. Bawendi,
MIT.)
Figure 1.7 Xenon atoms arranged on a Ni
substrate by a scanning tunneling probe, forming
the word IBM. (Courtesy of IBM.)