Highly selective room temperature detection of NO2 enabled by vanadyl oxygen vacancies in novel bilayer V2O5

• Future directions and perspectives for development of conjugated polymers-based gas sensors. The primary challenge in developing a gas sensor is achieving high selectivity for the target gas. Most sensor materials respond to multiple gases, making it difficult to discern between various toxic gases. The present study reports the enhancement of the selectivity towards NO 2 gas by introducing vanadyl oxygen (O I ) vacancies in novel 2D V 2 O 5 . The chemical exfoliation process, which is utilized in the present study to synthesize bilayer nanosheets of V 2 O 5 , intrinsically generates O I vacancies. The presence of O-vacancy defects, predominantly O I vacancies, in the sample is confirmed using X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and Raman spectroscopy. The bilayer 2D V 2 O 5 showed a highly selective chemiresistive response towards NO 2 gas at room temperature unlike normally observed higher temperature sensor response by V 2 O 5 , typically above 100°C. Along with the effect of high surface to volume ratio, the room temperature gas sensing performance by 2D V 2 O 5 stems from the presence of O I vacancy defects and the consequent increase in the surface activity. In addition, the presence of O I vacancies leads to highly selective response to NO 2 , since NO 2 is a highly oxidizing gas with a pair of lone electrons. Hence, the present study is the first to reveal novel bilayer V 2 O 5 sensor with a highly selective response to NO 2 at ambient temperature.