Metamaterial-Based Ring Resonator Sensor for Detection of Poisonous Nitrogen Oxide (NO_X) Gas by Using Fe₃O₄ Doped MXene (Ti₃C₂T_x) Nanosheets

Detecting low concentrations of gaseous explosive formulations based on NOx derivatives has been challenging, especially when the hazard is extremely severe. MXene (e.g. Ti₃C₂T_x,) family of 2D layered compounds have shown promise for sensing gases due to their unique properties such as high surface area, strong metallic conductivity, high hydrophilicity, good mechanical properties and active surface chemistry. Ti₃C₂T_x is the most extensively researched MXene and in this work we have used a composite based on the same for NOx detection. Indeed, we have observed that selectivity for the NO₂ gas in Ti₃C₂T_X can be considerably improved by loading the same with Fe₃O₄nanoparticles. Fe₃O₄ gives the electron for the transition from NO₂ to NO₃^-, whilst Ti₃C₂T_X provides a large surface area for this reaction to take place and also aids in the provision of extra electrons. In this context, a metamaterial-inspired sensor is used to detect the NOx gas,wherein the sensor is made to interact with Fe₃O₄NPloaded MXene. The properties are studied as a function of variation of dielectric constant of Fe₃O₄-loaded -MXene as a result of the toxic gas interaction. The sensor is a complementary slit-ring resonator (CSRR) operating at 430 MHz, and is initially simulated for its resonant frequency and power using COMSOL software. The unit cell sensor is fabricated on a copper-clad with FR-4 substrate. Separately, Fe₃O₄-doped-MXene is exposed to the NOx gas (varying from 0 to 150 ppm) and the NOx-purged Fe₃O₄-doped-MXene is obtained; which is subjected to the CSRR device. A systematic shift, both in frequency and power is obtained as the purged gas concentration changes from 0 to 150 ppm. The sensor is studied for its sensitivity, accuracy, and recovery properties. The Fe₃O₄-doped-MXene is carefully evaluated for its structure, chemical composition and interaction with NOx molecules. A two-stage device is hence illustrated, for hazardous gas sensing. The details are discussed in this presentation.