Abstract
The quantum size of materials is an effective property for specific physical applications. The theoretical approach helps in understanding the physical properties of these materials. SnO2 quantum crystals of similar to 1.8-6.0 nm are prepared by a hydrothermal method. The size of crystals is smaller than the Debye length reported for SnO2 at 250 degrees C. The emission spectra of the radiative recombination between conduction and valence bands show a blue shift, which confirms the electron confinement. The prepared materials are used for fabricating gas sensor tested for CH4 gas. The gas detecting measurements exhibited high sensitive quantum crystals, QCs, toward CH4. For the first time, a theoretical approach is formulated for the response of SnO2 toward CH4 to understand the sensing mechanism of the quantum crystals. The correlation between the theoretical and experimental results clarified the reason of the high response observed for the quantum crystals toward CH4. To conduct a high response, the crystal size should be comparable or less than the Debye length, which means that the crystal is fully depleted or in volume-depleted in the air. Thus, the high response obtained here is explained in terms of the proposed theoritical approach.