Development of humidity sensor using modified curved MWCNT based thin film with DFT calculations

One-dimensional carbon nanostructures e.g. Carbon nanotubes (CNTs) possess outstanding physical properties owing to their unique structure and atomic arrangement. High electrical conductivity, highly exposed surface area and stability of these carbon nanostructures introduce them as the leading choice of nanomaterials for a number of electrical and industrial applications like humidity and gas sensing. The conductance or capacitance of CNTs varies greatly with the adsorption-desorption of molecules such as hydroxyl (OH-) ions. In this paper, we report the preparation of carbon nanotubes based thin film using a CVD technique which has been characterized by using Scanning Electron Microscopy (SEM), UV-vis microscopy and X-ray diffraction technique. The characterized film was investigated as a humidity sensor. In the experimental part, the variations in the impedance of film were observed by Impedance Analyzer 6440 B on varying the humidity levels. In the theoretical part, we have simulated the CNTs using Ab initio density functional theory (DFT) calculations to investigate the formation of endohedral complexes among CNTs and OH- groups. The binding energy, dipole moment, electronegativity and HOMO-LUMO gaps were monitored by increasing the hydroxyl group levels, which results in its better use in developing a robust and cost-effective humidity sensor.