Rational tailoring of ZnSnO3/TiO2 heterojunctions with bioinspired surface wettability for high-performance humidity nanosensors

Abstract

We developed a novel kind of branched heterostructure by hydrothermal growth of ZnSnO₃ nanostructures on TiO₂ electrospun nanofibers, and demonstrated its enhanced ability to sense humidity through a sequential cactus-inspired tailoring of the ZnSnO₃ nanostructures. Combining these results with first-principles calculations, it is deduced that the concentration of water molecules adsorbed on the ZnSnO₃/TiO₂ heterojunction surface can be increased by reducing the surface potential barrier. Meanwhile, the bioinspired ZnSnO₃ nanoneedles, which form branches on the heterostructures, can further boost their adsorption abilities for water molecules via a water collection process. The adsorbed water molecules on the tips of the ZnSnO₃ nanoneedles desorb easily in a low-humidity environment due to the small area of the tips (1.5–2.5 nm). Thus, the optimal ZnSnO₃/TiO₂ heterostructure exhibits response and recovery times of ∼2.5 s and ∼3 s, respectively. Its good sensitivity may enable it to detect tiny fluctuations in moisture and relative humidity that may surround any high-precision instrument.