SnO2 with oxygen vacancies, an n-type gas sensing material used commercially as resistive sensors at high temperatures, suffers from the drift in voltage, contact resistances and poor selectivity. These prevailed defects in rutile SnO2 offer excellent optical properties which remain to be explored for the gas sensor. Apart from advantage of contactless operation with no direct voltage application, an optical method with the varied light energies is highly beneficial for excitations of the deep electronic states at ease, with opportunity to improve the sensor response measurement quickly in selective manner. In this direction, we report the synthesis and characterization of SnO2 nanostructures with emphasis on their Raman and photoluminescence properties. In subsequence, the crucial role of various defects in displaying the improved optical responses and selectivity for ammonia are highlighted.