CNTs/ZnO and CNTs/ZnO/Ag multilayers spray coated on cellulose fiber for use as an efficient humidity sensor

The exceptional high surface area and wide band gap ranges of semiconductor metal oxide nanostructures owe unique chemical, optical and physical properties that have grabbed their utilization for humidity sensing applications. In this framework, cost-effective sensors have been fabricated using a simple spray coating technique. Initially, the sonication was carried out for all the conductive inks such as carbon nanotubes (CNTs), zinc oxide (ZnO) and silver (Ag) nanoparticles (NPs) for 15 min in each case and then sprayed over conducting cellulose polymer substrate. Surface study demonstrated conducting networks of CNTs and cellulose polymer, and layers of ZnO and Ag NPs, as well. The analysis of elemental composition confirmed the required stoichiometric contents. Sensing measurement of CNTs/ZnO/Ag sample showed smaller resistance and enhanced current as compared to CNTs/ZnO sample. Hence, the device showed an efficient activity to sense humidity.