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nanomaterials. Nanomaterials of this type, especially intentionally produced ones,
are known as Engineered Nanomaterials (ENMs).
Another classification is carried out with regard to dimensions of materials.
Zero-dimensional (0D) nanomaterials are materials whose all three dimensions are
smaller than 100 nm like nanoparticles quantum dots (QDs). One-dimensional (1D)
ones are materials whose only one dimension is bigger than 100 nm, (e.g., nanotubes, nanowires, and nanorods). Two-dimensional (2D) nanomaterials have two
dimensions bigger than the upper limit of nanoscale such as nanofilms, nanolayers,
and nanocoatings. Three-dimensional (3D) nanomaterials or bulk nanomaterials
have no dimensions at nanoscale, but these 3D structures may consist of various
nanostructures. All of nanomaterials regardless of their dimension can be metallic,
ceramic, or polymeric. Because classification is out of scope of this chapter, we will
skip the topic.
In broad sense, two approaches are used in producing nanomaterials. First one is
top-down in which starting bulk material is mechanically or chemically reduced to
nanoscale material. In this case, a chunk of material of interest is ground or dissolved in an appropriate acid until the desired product is obtained. The second
approach is called bottom-up in which nanoparticles are manufactured by chemical
processes of atoms or molecules. Because the bottom-up method provides relatively
much more control over process, it enables us to carry out the process in a more
efficient way and, in turn, reduce pollution.
What makes nanomaterials so appealing is not only their dimensions, but also
their intrinsic behavior and functionality due to decrease in size. The behavior of
nanomaterials is determined by various parameters, especially size, shape, and
quantum confinement effect. For example, metal particles consisting of 50–100
atoms with a diameter between 1 and 2 nm start losing their metallic behavior and
tend to become semiconductors (Simon et al. 1993). The parameters affecting
behavior of nanomaterials will be explained concisely. It is useful to divide the
parameters as physical and chemical parameters.
Physical Parameters
• Size, shape, specific surface area, and aspect ratio
• Aggregation and clustering
• Size distribution of nanoparticles
• Surface morphology
• Crystallinity and defects
• Solubility
Chemical Parameters
• Chemical formula and molecular structure
• Composition
• Phase
• Surface chemistry (surface charge, reactivity, photo-catalytic feature, and zeta
potential)
• Hydrophilicity and hydrophobicity
2 Nanomaterials and Human Health
nanomaterials. Nanomaterials of this type, especially intentionally produced ones,
are known as Engineered Nanomaterials (ENMs).
Another classification is carried out with regard to dimensions of materials.
Zero-dimensional (0D) nanomaterials are materials whose all three dimensions are
smaller than 100 nm like nanoparticles quantum dots (QDs). One-dimensional (1D)
ones are materials whose only one dimension is bigger than 100 nm, (e.g., nanotubes, nanowires, and nanorods). Two-dimensional (2D) nanomaterials have two
dimensions bigger than the upper limit of nanoscale such as nanofilms, nanolayers,
and nanocoatings. Three-dimensional (3D) nanomaterials or bulk nanomaterials
have no dimensions at nanoscale, but these 3D structures may consist of various
nanostructures. All of nanomaterials regardless of their dimension can be metallic,
ceramic, or polymeric. Because classification is out of scope of this chapter, we will
skip the topic.
In broad sense, two approaches are used in producing nanomaterials. First one is
top-down in which starting bulk material is mechanically or chemically reduced to
nanoscale material. In this case, a chunk of material of interest is ground or dissolved in an appropriate acid until the desired product is obtained. The second
approach is called bottom-up in which nanoparticles are manufactured by chemical
processes of atoms or molecules. Because the bottom-up method provides relatively
much more control over process, it enables us to carry out the process in a more
efficient way and, in turn, reduce pollution.
What makes nanomaterials so appealing is not only their dimensions, but also
their intrinsic behavior and functionality due to decrease in size. The behavior of
nanomaterials is determined by various parameters, especially size, shape, and
quantum confinement effect. For example, metal particles consisting of 50–100
atoms with a diameter between 1 and 2 nm start losing their metallic behavior and
tend to become semiconductors (Simon et al. 1993). The parameters affecting
behavior of nanomaterials will be explained concisely. It is useful to divide the
parameters as physical and chemical parameters.
Physical Parameters
• Size, shape, specific surface area, and aspect ratio
• Aggregation and clustering
• Size distribution of nanoparticles
• Surface morphology
• Crystallinity and defects
• Solubility
Chemical Parameters
• Chemical formula and molecular structure
• Composition
• Phase
• Surface chemistry (surface charge, reactivity, photo-catalytic feature, and zeta
potential)
• Hydrophilicity and hydrophobicity
2 Nanomaterials and Human Health