Ultra-sensitive and selective NH room temperature gas sensing induced by manganese-doped titanium dioxide nanoparticles.

The study of the fabrication of ultra-high sensitive and selective room temperature ammonia (NH) and nitrogen dioxide (NO) gas sensors remains an important scientific challenge in the gas sensing field. This is motivated by their harmful impact on the human health and environment. Therefore, herein, we report for the first time on the gas sensing properties of TiO nanoparticles doped with various concentrations of manganese (Mn) (1.0, 1.5, 2.0, 2.5 and 3.0mol.% presented as S1, S2, S3, S4 and S5, respectively), synthesized using hydrothermal method. Structural analyses showed that both undoped and Mn-doped TiO crystallized in tetragonal phases. Optical studies revealed that the Mn doped TiO nanoparticles have enhanced UV→Vis emission with a broad shoulder at 540nm, signifying induced defects by substituting Ti ions with Mn. The X-ray photoelectron spectroscopy and the electron paramagnetic resonance studies revealed the presence of Ti and singly ionized oxygen vacancies in both pure and Mn doped TiO nanoparticles. Additionally, a hyperfine split due to Mn ferromagnetic ordering was observed, confirming incorporation of Mn ions into the lattice sites. The sensitivity, selectivity, operating temperature, and response-recovery times were thoroughly evaluated according to the alteration in the materials electrical resistance in the presence of the target gases. Gas sensing studies showed that Mn doped on the TiO surface improved the NH sensing performance in terms of response, sensitivity and selectivity. The S1 sensing material revealed higher sensitivity of 127.39 at 20 ppm NH gas. The sensing mechanism towards NH gas is also proposed.