Highly sensitive and selective nanoengineered PtO₂-BNNT heterostructures for ppb level ammonia gas sensing

Ammonia is a frequently used gas in many industrial sectors which is both poisonous and highly corrosive to our human environment. In this study, boron nitride nanotubes (BNNTs) decorated PtO₂ nanoparticles (NPs) were used to form a heterojunction for enhancing the room temperature (RT, 28 °C) gas sensing towards dry NH₃ gas varying from 0.05 to 10 ppm. The BNNT was synthesized by boron oxide-assisted chemical vapor deposition (BOCVD). The fabrication of PtO₂-BNNT heterostructures was done by RF sputtering of Pt NPs and subsequent deposition of BNNTs using slurry casting and annealing. The existence of BNNT-PtO₂ heterostructure was confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and energy spectroscopy (EDS) compositional analysis. The integration of PtO₂ NPs onto BNNTs provides a synergistic effect, enabling enhanced NH₃ sensing capabilities. According to the results, the response time of the PtO₂-BNNT sensor to -decorated BNNT sensor to 1 ppm NH₃ is 19 s with a low detection limit of 5 ppb NH₃ as compared to the pristine PtO₂ sensor. Extended modulation of conduction channels by BNNTs functionalized with PtO₂ facilitated the large sensor response and selectivity of PtO₂–BNNTs sensor with high repeatability, excellent resistance against humidity, and long-term stability.