Novel Microwave-Induced Combustion Synthesis of SnO₂ Nanoparticles for Selective Sensing of CO Using Tin Chloride

A novel technique of chloride solution combustion synthesis (CSCS) is employed for preparation of SnO₂ nanoparticles, using SnCl₄ and sorbitol as a novel precursor and a fuel, respectively. Ammonium nitrate is also used as a combustion aid. The solution combustion synthesis is a single-step and simple method for nanoparticles synthesis. However, it commonly uses nitrate precursors. In this study tin chloride is used in CSCS method for the first time, employing ammonium nitrate as a combustion aid. The nanoparticles are characterized by means of XRD, SEM, EDS and BET and applied in sensing of carbon monoxide and methane. The molar ratio of fuel plus oxidant to SnCl₄ (Ψ) and the ratio of fuel-to-oxidant (φ) were varied in the modified CSCS technique. The smallest nanoparticles size, i.e., 3.9 nm with 220 m²·g⁻¹ obtained at Ψ = 1 and φ = 1. The sensor fabricated based on the SnO₂ nanoparticles obtained by CSCS method shows 2–3 times higher sensitivity to CO than the one obtained by the conventional sol–gel method. The CSCS sensors show high sensitivity to CO at temperatures lower than 300 °C, at which insignificant sensitivity to methane is observed. This makes the sensor selective to CO in presence of methane.