SnO₂ Nanoribbons as NO₂ Sensors:  Insights from First Principles Calculations

SnO 2 nanoribbons with exposed (1 0 1̄) and (0 1 0) surfaces have recently been demonstrated to be highly effective NO 2 sensors even at room temperature. The sensing mechanism is examined here through first principles density functional theory (DFT) calculations. We show that the most stable adsorbed species involve an unexpected NO 3 group doubly bonded to Sn centers. Significant electron transfer to the adatoms explains an orders-of-magnitude drop in electrical conductance. X-ray absorption spectroscopy indicates predominantly NO 3 species on the surface, and computed binding energies are consistent with adsorbate stability up to 700 K. Nanoribbon responses to O 2 and CO sensing are also investigated.