Wearable smart yarn sensor based on ZnO/SnO2 heterojunction for ammonia detecting

Metal–oxide–semiconductor gas-sensing materials, due to their high operating temperatures and often using rigid materials as substrates, limit their application in the field of wearable electronic devices. In this work, a skin–core structure electrospun nanofiber core-spun yarn (ES-PY) with polypropylene yarn (PY) as the core yarn and polyvinylidene fluoride (PVDF) nanofibers as the wrapping layer was prepared by a coaxial electrospinning nanofiber yarn-forming technique. The yarn sensor (ZS-PY) was prepared by compounding it with ZnO/SnO2 N–n-type metal–oxide–semiconductor heterojunction gas-sensing material prepared by a two-step hydrothermal method. The obtained yarn sensor utilized the synergistic effect of ZnO and SnO2, and the nanostructure effect of nanofibers and exhibited excellent gas-sensing performance for ammonia (NH3). The response to 100 ppm NH3 can reach 60.41%, with rapid response/recovery time even when exposed to an ammonia concentration as low as 10 ppm at room temperature. In addition, it has excellent gas selectivity and stability. Meanwhile, the yarn sensor retains the mechanical strength and flexibility of its core yarn, so it can be processed into specific electronic textiles using various textile molding techniques and is expected to be applied to the development of wearable smart textiles.