Application of silver decorated carbon nanotubes for environmental ozone sensing

This work reports a gas sensor development based on multi-walled carbon nanotubes (MWCNTs) decorated with silver nanoparticles and fabricated by vapor phase impregnation decomposition method (VPID). The sensitive material was deposited on a substrate type resistor by drop coating. The gas sensing behavior of multiwalled carbon nanotubes-silver (MWCNTs-Ag) was evaluated using a calibrated commercial ozone generator. After a 1 min ozone exposure, MWCNTs-Ag showed electric resistance changes at different operation temperatures. The sensor was evaluated at 300 ppb and lower than 100 ppb. Results show that the MWCNTs-Ag exhibits the best sensitivity response at room temperature. The sensor response depends on the ozone concentration as the electric resistance increases with higher gas concentration, reporting p-type characteristics upon gas exposures. Raman spectroscopy was used to study the quality of MWCNTs after being subjected to an oxidative process. High resolution transmission electron microscopy (HRTEM) was employed to investigate structural and morphological features as well as size and distribution of nanoparticles (NPs). The responsiveness of MWCNTs decorated with different NPs, i.e. platinum (Pt), palladium (Pd), and silver (Ag) is compared at room temperature, 120 and 200 °C. The best performance was from MWCNTs-Ag at room temperature, while at 120 and 200 °C MWCNTs-Pd reported the best behavior.