Synthesis of carbon nanotubes by direct liquid injection chemical vapor deposition method and its relevance for developing an ultra-sensitive room temperature based CO2 sensor

The present paper reports the synthesis and characterization of Multiwalled Carbon Nanotube (MWCNT) based thin film and its application as a CO2 gas sensor. The MWCNT was prepared by direct liquid injection chemical vapor deposition method (DLICVD) using ethanol as a precursor in the presence of argon gas atmosphere and furnace temperature at 750 degrees C. The thin film of MWCNT was prepared by using the spin coating technique and characterized using Scanning electron microscope (SEM), UV-Visible spectrometer, Particle size analyzer and X-ray diffractometer (XRD). The vibrational and rotational spectra were observed through Fourier Transform Infra-Red Spectroscopy (FTIR) and Raman Spectroscopy. The SEM image of the thin film exhibited the nanotubular structure grown throughout the surface. From XRD, the minimum crystallite size was found to be 14 nm. The optical energy band gap of the nanotube-based thin film was found as 3.6 eV. The synthesized CNT-based thin film was employed for the CO2 sensing at room temperature. The sensor response of the sensor was found as 2.1 and the results were found 98% reproducible. The response and recovery times were found to be 30.2 and 49.6 s, respectively. Theoretical calculations were also performed in the support of CO2 sensing through the MWCNT. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.