Flexible and disposable ultrasensitive liquid sensors based on CNTs and CNTs/ZnO-NPs spray-coated cellulose fiber frameworks

Abstract Here we report the facile and scalable spray coating of carbon nanotubes as well as carbon nanotubes/zinc oxide nanoparticles on cellulose fiber frameworks for the fabrication of flexible liquid sensors. The surface morphology of the deposited coatings is investigated using scanning electron microscope and their elemental analysis is carried out through energy dispersive x-ray spectroscopy. The flexible films are used for the fabrication of liquid sensors which are tested for three different analytes: drinking water, isopropyl alcohol and milk. The sensors show notable response for all the analytes. The response time is recorded as low as 0.5 s for isopropyl alcohol and sensitivity as high as 97,400 for milk. The exceptionally higher sensitivity is attributed to the swelling behavior of cellulose matrix and surface functionalization of carbon nanotubes/zinc oxide nanoparticles.