Development of a gas sensor for Eucalyptol supervision: supporting tool for extreme wildfire management

Extreme fire is not fully understood, and its data has not yet been accounted into the current wildfires’ prediction models. Recent research on flammable gases (i.e., volatile organic compounds, VOC) released by the heated vegetation has shown that, under specific conditions (e.g., extreme heat, humidity, wind, and topography), VOC might foster fire ignition sources and explain sudden changes in fire behaviour, particularly in the most susceptible and flammable forests (eucalypt forests).

The so-called electronic noses are instruments, “capable of recognising complex gases, which comprise an array of electronic sensors with partial specificity and an appropriate pattern-recognition system”, are suited to most monitoring applications as they provide high sensitivity, as well as accurate and swift responses for VOC concentrations. However, forest environments consist of a complex mixture of gases; the most suitable sensor must classify and quantify the target VOC. To improve the sensor’s sensitivity, different nanomaterials can be used as coatings. The ability to tune nanostructured thin films' composition enhances the sensor's intrinsic (chemical or physical) properties.

This work aims to develop a sensor array to monitor eucalyptol (from eucalyptus tree) levels (100 to 1000 ppm). The development of different nanostructures for sensor coating to find the best combination to the target compound will be evaluate through layer-by-layer films and simple or functionalized (e.g., COOH functional group) Multiwalled carbon nanotube based films produced by RF-magnetron sputtering. The detection of the target compound was achieved by measuring the impedance spectra of thin-films when in contact with the gas inside a custom made vacuum chamber system. The impedance spectra will be accessed with a Solartron 1260 Impedance Analyzer in the frequency range of 1 Hz to 1 MHz, by applying 25 mV. The sensor devices array forming the e-nose concept, consist of ceramic or BK7 solid support with deposited gold interdigitate electrodes, coated with the films aforementioned.