Highly enhanced acetone sensing performance of porous C-doped WO3 hollow spheres by carbon spheres as templates

WO3-based gas sensors have received considerable attention in breath acetone analysis for their great potential in the clinical diagnosis of diabetes. However, several key challenges, especially sensitivity, selectivity and stability, should be further addressed before WO3-based materials are capable of applying for acetone analysis. Herein, C-doped WO3 sensing materials were synthesized by coupling carbon sphere templates with post-heat treatment method. The resulting materials are composed mainly of epsilon-WO3, a phase with high selectivity to acetone, and featured with porous hollow sphere structure. The as fabricated sensors based on the C-doped WO3 materials show high sensitivity to acetone down to 0.2 ppm. By contrast, the sensors show substantially lower response to other gases including ethanol, methanol, toluene, NH3, NO and CO. In addition, the effect of the relative humidity (RH) on the sensing property was studied and it was found that the response distinction to acetone even at 90% RH was sufficient to separate diabetics from healthy people. More attractively, the epsilon-phase WO3 could maintain its acetone sensing activity at 350 degrees C over 3 months, suggesting excellent long-term stability. The results gained herein may be useful for rational design of new types of highly selective and stable acetone sensing materials. (C) 2016 Elsevier B.V. All rights reserved.