Room-temperature (RT) operation sensors are constantly in increasing demand because of their low power consumption, simple operation, and long lifetime. However, critical challenges such as low sensing performance, vulnerability under highly humid state, and poor recyclability hinder their commercialization. In this work, sub-10 nm hollow, bimetallic Pt-Ag nanoparticles (NPs) were successfully formed by galvanic replacement reaction in bioinspired hollow protein templates and sensitized on the multidimensional SnO2-WO3 heterojunction nanofibers (HNFs). Formation of hollow, bimetallic NPs resulted in the double-side catalytic effect, rendering both surface and inner side chemical reactions. Subsequently, SnO2-WO3 HNFs were synthesized by incorporating 2D WO3 nanosheets (NSs) with 0D SnO2 sphere by c-axis growth inhibition effect and fluid dynamics of liquid Sn during calcination. Hierarchically assembled HNFs effectively modulate surface depletion layer of 2D WO3 NSs by electron transfers from WO3 to SnO2 stemming from creation of heterojunction. Careful combination of bimetallic catalyst NPs with HNFs provided an extreme recyclability under exhaled breath (95 RH%) with outstanding H2S sensitivity. Such sensing platform clearly distinguished between the breath of healthy people and simulated halitosis patients.
Keywords: breath sensor; hollow catalyst; humidity; room temperature; sub-10 nm.