Table 4: Summary of sensing performance of metal oxide functionalized CNT sensors. (Note: N/S = Not-stated.)

Metal oxideCNT typeSensor configurationTargeted analytesDetection limitResponse time Recovery timeReference

SnO2SWCNTsResistorNO2N/S9 min1.5 min[65]
SnO2SWCNTsResistorH2300 ppm2–5 s (200– C)3–5 s (200– C)[66]
SnO2SWCNTsResistorNH310 ppm 100 s 3.2 min[67]
SnO2MWCNTsResistorLPG, C2H5OH10 ppmN/SN/S[68]
SnO2MWCNTsResistorC2H5OH10 ppm 1 s ( C) 10 s ( C)[69]
SnO2MWCNTsResistorNO2100 ppbN/S20 min ( C)[70]
SnO2MWCNTsResistorNH360 ppm 5 min 5 min[71]
SnO2MWCNTsResistorformaldehyde0.03 ppm100 s ( C)90 s ( C)[72]
WO3MWCNTsResistorNO2, CO, NH3500 ppb NO2, 10 ppm CO, 10 ppm NH3N/SN/S[73]
TiO2MWCNTsResistoracetone, NH3N/S10–40 s (acetone)10–300 s (acetone)[74]
TiO2CNTsResistorO210 ppm5–8 min (350– C) 20 min ( C)[75]
SnO2, TiO2SWCNTs, MWCNTsResistorC2H5OH100 ppm 10 s (210– C) 10 s (210– C)[76]