Thermally Stable SnO2 Nanocrystals: Synthesis and Application to Gas Sensors

In this study, we prepared thermally stable SnO2 nanocrystals (ca. 4 nm) in a mixture of SnCl4, tetraethylene glycol (TEG), and tetrabutylammonium hydroxide (TBAH) under reflux and obtained a highly sensitive semiconductor gas sensor. It has been determined both theoretically and experimentally that the synthesis of oxide semiconductor nanoparticles is an important factor in highly sensitive semiconductor gas sensors. However, as-synthesized nanocrystals generally grow large during calcination at high temperature, and this thermal crystal growth reduces the sensor response. Therefore, to refine the response of the semiconductor gas sensor, we synthesized thermally stable SnO2 nanocrystals by heating under reflux a SnCl4-TBAH-TEG mixture. The obtained SnO2 nanocrystals exhibited high thermal stability even when calcined at a temperature up to 600 °C. The gas-sensing films fabricated from the thermally stable SnO2 nanocrystals exhibited a high sensor response to hydrogen due to their small crystal size, and...