Free-standing SWNT films (FSFs), an excellent example of air-filtering CNTs, were fabricated by Nasibulin et al. [61], as shown in
Fig. 6a. The nanotubes have 10 mm lengths and
1.3–2 nm diameters with a few micrometer’s
thickness. Figure 6b shows the filtration efficiency
Airborne Nanoparticles: Control and Detection,
Fig. 5 SEM images of MWNT-coated filters. (a) Fibrous
filter morphology. (b) The cross-sectional view shows a
continuous MWNT film ($1–2 mm thick, as seen in (c)) on
top of the cellulose layer. (Reprinted with permission [27])
Airborne Nanoparticles: Control and Detection, Table 4 Characteristics of cellulose filters and MWNT-coated
filters. (Reprinted with permission [27]). Note: cellulose filter II consists of five cellulose layers in series
Sample
Coverage of
MWNTs
[mg cm
À2
]
Pressure drop after
filtration [kPa]
Filter efficiency for
dp ¼ 300 nm [%]
Filter quality for
dp ¼ 300 nm [kPa
À1
]
Cellulose
filter I
–
0.45
66.45
2.42
MWNT I
0.07
2.10
99.96
4.12
MWNT II
0.11
3.00
99.978
3.36
MWNT III
0.14
3.77
99.9976
3.56
MWNT IV
0.22
5.42
99.9994
2.75
Cellulose
filter II
–
2.11
98.76
2.65
Airborne Nanoparticles: Control and Detection
99