Resonance-based detection of perilous sulphur dioxide using TiO2 nanoparticles and unit-cell ring resonator

Abstract SOx gases are the emissions from the industrial belt, ship exhausts, burning of fossil fuels and also a product for propellants and high-energy materials. Not only are these emissions hazardous to human health, but are toxic to the environment. Due to their ozone depletion and acid raineffects, these are extremely detrimental to the sensitive ecosystem. Detection of traces of such gaseous emissions is a challenge; which has sought various solutions; however, the answer is not satisfactory, especially in terms of selectivity and low-concentration detections. Titanium dioxide nanoparticles, which are conventionally known to exhibit gas sensing properties, due to their oxygen vacancies, have been used in ourstudies to demonstrate extremely sensitive, selective and rapid detection of SOx gaseous moieties, using a resonant frequency approach. TiO2 nanoparticles interact with entrapped SO2 molecules to form unique signatures of SO4− and shift in hydroxyl group (Ti−OH), thereby generating shifts in the resonant frequency signatures of the complementary split-ring resonator (CSRR) sensor designed for430 MHz. The duly simulated CSRR unit cell sensor is designed on copper clad with FR4 substrate. The electromagnetic waves passing through the waveguide are intercepted by the resonant structure, creating distinct resonant dips at the detector. These are manipulated by the changes in the dielectric constant of the various concentrations of SO2-entrapped-TiO2 nanoparticles subjected to the sensor surface. The sensor shows the sensitivity of ∼ 17.3 KHz/ppm with discrete and selective variations in the range of 0–300 ppm of SO2 gas moieties. The two-unit device is hence demonstrated, exhibiting a room-temperature, sensitive, selective, rapid and re-usable sensor. Using effective permittivity calculations of the SO2-entrapped-TiO2 nanoparticles, the sensor is duly calibrated for a probable device application.