Construction of mesoporous silica-implanted tungsten oxides for selective acetone gas sensing

Abstract

As a key biomarker for noninvasive diagnosis of diabetes, the selective detection of trace acetone in exhaled gas using a portable and low-cost device remains a great challenge. Semiconductor metal oxide (SMO) based gas sensors have drawn signification attention due to their potential in miniaturization, user-friendliness, high cost-effectiveness and selective real-time detection for noninvasive clinical diagnosis. Herein, we propose a one-pot solvent evaporation induced tricomponent co-assembly strategy to design a novel ordered mesoporous SMO of silica-implanted WO₃ (SiO₂/WO₃) as sensing materials for trace acetone detection. The controlled co-assembly of silicon and tungsten precursors and amphiphilic diblock copolymer poly(ethylene oxide)-block-polystyrene (PEO-b-PS), and the subsequent thermal treatment enable the local lattice disorder of WO₃ induced by the amorphous silica and the formation of ordered mesoporous SiO₂/WO₃ hybrid walls with a unique metastable ε-phase WO₃ framework. The obtained mesoporous SiO₂/WO₃ composites possess highly crystalline framework with large uniform pore size (12.0–13.3 nm), high surface area (99–113 m²/g) and pore volume (0.17–0.23 cm³/g). Typically, the as-fabricated gas sensor based on mesoporous 2.5 %SiO₂/WO₃ exhibits rapid response/recovery rate (5/17 s), superior sensitivity (R_air/R_gas = 105 for 50 ppm acetone), as well as high selectivity towards acetone. The limit of detection is as low as 0.25 ppm, which is considerably lower than the thresh value of acetone concentration (>1.1 ppm) in the exhaled breath of diabetic patients, demonstrating its great prospect in real-time monitoring in diabetes diagnosis. Moreover, the mesoporous 2.5 %SiO₂/WO₃ sensor is integrated into a wireless sensing module connected to a smart phone, providing a convenient real-time detection of acetone.