Carbon nanotubes immobilized on gold electrode as an electrochemical humidity sensor

Abstract Multi-walled carbon nanotubes (MWCNTs) were fabricated on a gold electrode to develop a resistance-sensing humidity sensor with low resistance. Core-shell-structured nanohybrids were prepared using Chitosan-MWCNT to obtain good hydrophilicity, resulting in a highly responsive humidity sensor. We also measured resistance, which changes due to hydrogen bonding between the amine group of chitosan and H2O. The structure of the fabricated chitosan-MWCNT core–shell-structured nanohybrid was measured. Furthermore, we determined the highest response and linearity of the CS-MWCNT25 nanohybrids based on the number of coats on the electrode and the composition ratio of chitosan and MWCNTs. The fabricated CS-MWCNT25 nanohybrid humidity sensor exhibited good electrical efficiency without voltage or frequency dependence and a low-temperature dependency with a temperature coefficient (RH/°C) of 0.187%. Finally, a fast recovery time of 40 s between 30% and 100% RH, a maximum humidity hysteresis of less than 0.300 ± 0.001%, and long-term stability for 2 months indicated that this is an excellent humidity sensor.