Self-assembly, which is one of the important terms used in nanoscience,
describes a process in which a collection of disordered building blocks
(molecules or nano-objects) come together to form an organized structure. One common example is the crystallization of small ions into a
definite lattice structure. Techniques such as x-ray diffraction show that
such highly organized structures are comprised of a repetition of smaller
“unit cells” of nanoscale dimension. Self-assembled structures may also
result from just a few molecules, but the cooperative interplay between
these molecules within the structure may impart a specific function or
property.
It is also worthwhile to note that self-assembly may lead to discrete or
extended entities. A discrete entity is well defined in terms of the number
of molecules it contains. A simple example is the dimer that is formed
when two nucleic acids interact through hydrogen bonding to form a
DNA base pair (Figure 1.5). Another example, which is discussed in
detail in later chapters, is a micelle—a stable, often spherical aggregate of
a few hundred amphilic molecules, which have one polar/hydrophilic
end and one nonpolar/hydrophobic end; the hydrophobic ends cluster
together to minimize energy and surface area. Extended nanosystems are
undefined in scale in at least one dimension; they can be either 1D, 2D,
or 3D nanosystems. Polymers (1D) and thin films (2D) are examples
of extended nanosystems. Nanotechnology exploits both discrete and
extended systems to perform specific functions.
Self-assembled systems are commonly found in nature as well as in
engineered materials. The folding of proteins and other biomacromolecules and the formation of lipid bilayer cell membranes are examples of
natural self-assembly in biology. Artificial methods may involve covalent
building blocks based on chemically robust starting materials or may
H
H
O
N
N
R
O
H
N
N
N
R
N
N
Figure 1.5 A dimer of the nucleic acid bases adenine and thymine, two of the
key components of DNA. The dashed lines represent hydrogen bond interactions
(discussed in Chapter 5) between the carbonyl oxygen and amine hydrogens. The
dimer is an example of a discrete entity, which could form a larger nanostructure as
part of a DNA double helix.
CHAPTER 1: A Brief Introduction to Nanoscience
10
describes a process in which a collection of disordered building blocks
(molecules or nano-objects) come together to form an organized structure. One common example is the crystallization of small ions into a
definite lattice structure. Techniques such as x-ray diffraction show that
such highly organized structures are comprised of a repetition of smaller
“unit cells” of nanoscale dimension. Self-assembled structures may also
result from just a few molecules, but the cooperative interplay between
these molecules within the structure may impart a specific function or
property.
It is also worthwhile to note that self-assembly may lead to discrete or
extended entities. A discrete entity is well defined in terms of the number
of molecules it contains. A simple example is the dimer that is formed
when two nucleic acids interact through hydrogen bonding to form a
DNA base pair (Figure 1.5). Another example, which is discussed in
detail in later chapters, is a micelle—a stable, often spherical aggregate of
a few hundred amphilic molecules, which have one polar/hydrophilic
end and one nonpolar/hydrophobic end; the hydrophobic ends cluster
together to minimize energy and surface area. Extended nanosystems are
undefined in scale in at least one dimension; they can be either 1D, 2D,
or 3D nanosystems. Polymers (1D) and thin films (2D) are examples
of extended nanosystems. Nanotechnology exploits both discrete and
extended systems to perform specific functions.
Self-assembled systems are commonly found in nature as well as in
engineered materials. The folding of proteins and other biomacromolecules and the formation of lipid bilayer cell membranes are examples of
natural self-assembly in biology. Artificial methods may involve covalent
building blocks based on chemically robust starting materials or may
H
H
O
N
N
R
O
H
N
N
N
R
N
N
Figure 1.5 A dimer of the nucleic acid bases adenine and thymine, two of the
key components of DNA. The dashed lines represent hydrogen bond interactions
(discussed in Chapter 5) between the carbonyl oxygen and amine hydrogens. The
dimer is an example of a discrete entity, which could form a larger nanostructure as
part of a DNA double helix.
CHAPTER 1: A Brief Introduction to Nanoscience
10