Exhaled VOCs sensing properties of WO_3 nanofibers functionalized by Pt and IrO_2 nanoparticles for diagnosis of diabetes and halitosis

摘要

This work presents a simple synthetic route to produce WO_3 nanofibers functionalized by catalytic Pt and IrO_2 nanoparticles and their superior acetone and H_2S sensing characteristics, demonstrating the potential use of Pt and IrO_2 nanoparticles in applications as sensors of biomarkers of diabetes and halitosis, respectively, in exhaled breath. The individual WO_3 fiber, calcined at 500℃, was composed of small nanoparticles with a size distribution in the range of 30-100 nm. Networks of WO_3 fibers exhibited a high surface-to-volume ratio and unique morphologies, thus facilitating efficient gas transport into the entire fiber layers. Pt (4-7 nm) and Ir (4-8 nm) nanoparticles were synthesized by polyol methods and were used as additives to decorate the surface of the WO_3 fibers. After a heat treatment, those catalyst particles were partially or fully oxidized to Pt/PtO_x and IrO_2, respectively. To investigate the advantages of Pt-decorated WO_3 fibers (PtWO_3) and IrO_2-decorated WO_3 (IrO_2-WO_3) fibers as acetone (CH_3COCH_3) and H_2S sensing materials, respectively, we carried out gas-sensing measurements in a highly humid atmosphere (RH 75%) similar to that of an oral cavity. The Pt-WO_3 fibers showed a high acetone response (R_(air)/R_(gas)= 8.7 at 5 ppm) at 350℃ and a superior H_2S response (R_(air)/R_(gas)=166.8 at 5 ppm) at 350℃. Interestingly, IrO_2-WO_3 fibers showed no response to acetone, while the gas response to H_2S exhibited temperature-insensitivity, which has never been reported in any other work. Thus, the highly selective cross-response between H_2S and acetone was successfully achieved via the combination of IrO_2 particles on WO_3 fibers. This work demonstrates that accurate diagnosis of diabetes and halitosis by sensing exhaled breath can be realized through the use of electrospun WO_3 fibers decorated with Pt and IrO_2 catalysts.