Quartz crystal microbalance coated with carbon nanotube films used as humidity sensor

The possibilities and properties of multi-wall carbon nanotube (MWNT)-coated quartz crystal microbalance (QCM) as a humidity sensor are presented. In order to enhance effectively sensitivity of the sensor, the MWNTs coated on QCM are treated by means of ball milling and hydrogen plasma technique, respectively. The morphology and microstructure of MWNT films were characterized with SEM and TEM. It can be found that the frequency shift of the MWNT-coated QCM linearly decreases with increasing relative humidity over the range of 5-97% RH. The sensors have a response and recovery time of about 60 and 70 s, respectively. The experimental results prove that MWNT-coated QCM are usable as a humidity sensor and as an analytical device.