Page 287 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

272 Principles and Methods

earlier in this section. Surface asperities act to increase the particle’s
adhesion lever arm while also reducing the shearing forces acting on the
deposited nanoparticle. The impact of surface roughness on the adhesion
between two interacting bodies has been explored at length [74–76,
78–80]. Even small asperities (< 1 nm) on a collector surface may dra-
matically increase the contact area between the nanoparticle and collec-
tor surfaces and, in turn, the adhesive lever arm for the nanoparticle
(Figure 7.25) [65]. This is in contrast with the case of larger particles
where the adhesion is reduced through a reduction in the contact area due
to the asperities [76, 81, 82]. For larger colloids, roughness may decrease

= 2500 nm
a p

350 nm
150 nm
0 µm 4 µm 8 µm
a p = 25 nm

350 nm
150 nm
0 µm 4 µm 8 µm

Contact
area
Figure 7.25 Scaled illustration of a large and small particle(s) on an
AFM-generated height profile of a rough surface. The surface had an average
roughness of 65 nm. The contact area between one of the small (a p 25 nm)
particles with the rough surface is highlighted.