Morphology-dependent NO2 gas sensing for needle-like In2O3 chemiresistor nanosensors

One-dimensional In2O3 nanoneedles, i.e., nanoicicle and nanotower structures, have been prepared so that the interplay of surface facet and aspect ratio to gas-sensing behavior can be elucidated. The electrical resistance toward a model NO2 gas of 10 to 30 ppm concentration appears to depend critically on surface facet and aspect ratio of the nanoneedle sensors over a working temperature range from 50 to 200 °C. Sensing response (Rg/Ra) shows an interesting bell-shaped dependence with the aspect ratio. A maximum increase of the sensing response by nearly 4 times (i.e., Rg/Ra changes from 8.8 to 35.0) has been obtained when the aspect ratio was increased from 5.8 to 16.1 for the nanoicicle sensor against 10 ppm NO2 at 100 °C. This contrasts with the response increase of merely 1.5 times (i.e., Rg/Ra changes from 20.9 to 29.6) when the aspect ratio was varied from 4.3 to 10.5 for the nanotower counterpart.