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.