Lychee-like SnO2 hollow microspheres sensitized by carbon quantum dots for high-sensitivity ethanol sensor

In this work, the application of carbon quantum dots as known as CQDs for ethanol detection is pioneered, and a multi-fold improvement in gas sensor performance is achieved through the unique electron transport mechanism of carbon quantum dots. The lychee-like SnO2 hollow microspheres and CQDs are prepared by a solvent heat method. The composites are assembled by rapid grinding, ultrasonication, and stirring. The minimum detection limit is 500 ppb. The response/recovery time of the best mass percentage composite is 9 s/16 s to ethanol at 100 ppm with an optimum working temperature of 216? in the target gas-sensitive test. Such a fast response speed improvement is ascribed to the excellent electron transfer efficiency of the 5 nm diameter carbon quantum dots (CQDs).