Heterogeneous Doping of Nanodiamond Grains with Exfoliated 2D NbSe₂ Nanostructures for Highly Sensitive Ammonia Gas Sensors at Room Temperature

Herein, a first-time report details the development of a heterogeneous nanodiamond (ND) grain-niobium diselenide (NbSe2) hybrid for room-temperature ammonia (NH3) gas sensing. Exfoliated NbSe2 nanorods, potentially formed via sonochemical exfoliation, exhibit semiconducting behavior with a band gap of 2.29 eV. The ND–NbSe2 hybrid demonstrates higher NH3 selectivity compared to pristine NbSe2 and ND. This hybrid achieves a significantly higher response of 11.3% with faster response and recovery times (81.2 and 70.6 s) than those of ND (5.9%) and NbSe2 (4.5%) at a lower concentration of 100 ppm. Also, the stability of the as-fabricated ND toward NH3 gas is exceptional when compared to that of NbSe2. This explains the level of influence of ND on the present ND–NbSe2 hybrid heterostructure. Moreover, the heterojunction formation with a change in the resistivity of the sample is involved in the sensing mechanism. This can be ascribed to the correlation of energy gaps between the ND grains (4.43 eV) and NbSe2 nanorods (2.29 eV), which promotes electron transportation from the conduction band of NbSe2 to ND at the applied voltage. In addition, the NbSe2–ND hybrids offer excellent stability for long-term gas detection. Furthermore, it is expected that this study will inspire the development of 2D-NbSe2–nanodiamond hybrid materials for advanced gas-sensing applications.