UV-activated room temperature NO2 gas sensing using In2Ge2O7 nanofiber sensors

In2Ge2O7 nanofibers were synthesized using a thermal evaporation technique. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction revealed that the nanofibers were single crystals and 50–100 nm in diameter and up to a few hundreds of micrometers in length. The sensing properties of multiple networked In2Ge2O7 nanofiber sensors toward NO2 gas at room temperature under UV irradiation were examined. The In2Ge2O7 nanofiber gas sensors showed a remarkably enhanced response to NO2 gas at room temperature under ultraviolet (UV) light illumination. The response of the In2Ge2O7 nanofibers to NO2 gas at room temperature increased from ∼104 to ∼601% with increasing the UV light illumination intensity from 0 to 1.2 mW/cm2. The significant improvement in the response of the In2Ge2O7 nanofibers to NO2 gas by UV irradiation is attributed to the increased change in resistance due to the increase in the number of electrons participating in the reactions with NO2 molecules by photo-generation of electron–hole pairs.