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internal structural dimensions and external surface dimensions are independent variables for the categorization of 2-D
nanomaterials.
The way 2-D nanomaterials are produced adds to the complexity of their categorization. Generally, 2-D nanomaterials, like the
one shown in Figure 6.1, are deposited on a substrate or support
with typical dimensions above the nanoscale. In these cases, the
overall sample thickness dimensions become a summation of the
film’s and substrate’s thickness. When this occurs, the 2-D nanomaterial can be considered a nanocoating (see Figure 6.9). Yet at
times when the substrate thickness does have nanoscale dimensions or when multiple layers with thicknesses at the nanoscale
are deposited sequentially, the 2-D nanomaterial can be classified
as a multilayer 2-D nanomaterial (see Figure 6.10). Within each
layer, the internal structure can be at the nanoscale or above it
(Figure 6.10).
Figure 6.6
Three-dimensional space showing the relationships among 0-D, 1-D, 2-D, and 3-D
nanomaterials.
Figure 6.7
Two-dimensional nanomaterial with thickness and
internal structure at the nanoscale.
0-D
1-D
2-D
z
x
y
0-D: All dimensions at the nanoscale
1-D: Two dimensions at the nanoscale,
one dimension at the macroscale
2-D: One dimension at the nanoscale,
two dimensions at the macroscale
3-D: No dimensions at the nanoscale,
all dimensions at the macroscale
t ≤ 100 nm
Nanocrystalline
Figure 6.8
Two-dimensional nanomaterial with thickness
at the nanoscale and internal structure at the
microscale.
t ≤ 100 nm
Microcrystalline
Figure 6.9
Two-dimensional nanomaterials with thickness at
the nanoscale, internal structure at the nanoscale/
microscale, and deposited as a nanocoating on a
substrate of any dimension.
t n ≤ 100
nm
t n ≤ 100
nm
Nanocrystalline
Microcrystalline
Classification of Nanomaterials