A low humidity sensor made of quartz crystal microbalance coated with multi-walled carbon nanotubes/Nafion composite material films

A low humidity sensor was made of a quartz crystal microbalance (QCM) coated with multi-walled carbon nanotubes/Nafion (MWCNTs/Nafion) composite material films. The microstructure of the MWCNTs/Nafion composite material films showed strong interaction between MWCNTs and Nafion. The MWCNTs/Nafion composite material films coated on the gold electrode of QCM showed excellent sensitivity (3.56 −ΔHz/Δppmv at 23.4 ppmv), linearity (R2 = 0.9604) and short response time (23 s at 83.5 ppmv). The water vapor molecules adsorbed onto the MWCNTs/Nafion films showed higher frequency shift than Nafion and single-walled carbon nanotubes/Nafion (SWCNTs/Nafion) films. The adsorption dynamic analysis, molecular mechanics calculation (association constant), was used to elucidate the effect of adding SWCNTs and MWCNTs into Nafion on the increased sensitivity of low humidity sensing.