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Sensors of volatile organic compounds (VOCs) play a vital role in environmental monitoring. Although much progress has been made to develop new sensing materials, it remains challenging to detect a particular VOC selectively and without the interference of humidity. Herein, we report the effect of In2O3 nanoparticles on the VOC-sensing performance of ZnO twin-rods. The VOC-sensing tests were carried out in dry air and at a relative humidity (RH) of 26, 59, and 98%. The results indicated that the In2O3/ZnO heterostructure exhibited an improved sensing performance to triethylamine (TEA) compared to ZnO. In dry air, the responses to 100 ppm of TEA at 350 °C were 60.2 for the In2O3/ZnO heterostructure and 39.2 for pure ZnO. In2O3/ZnO even exhibited a high response of 6.2 to 1 ppm of TEA. Moreover, In2O3/ZnO exhibited a response to TEA up to 46.2 times higher than those of the other VOCs, indicating excellent selectivity. At 98% RH, the In2O3/ZnO heterostructure still had a high sensitivity to TEA, showing a response of 21.2 to 100 ppm of TEA with a response time of 1 s. The improved TEA-sensing performance of the In2O3/ZnO heterostructure can be attributed to the formation of the n-n heterojunction.

The purpose of this study was to produce composite particles, consisting of core starch particles coated with glycine, by liquid–liquid interfacial crystallization with an ultrasonic spray nozzle and to investigate the effect of operating conditions on glycine particle morphology. We confirmed that ultrasonic irradiation could improve the coating efficiency of the core starch particles during the crystallization process. We also investigated the transformation between different polymorphs of glycine crystals that covered the starch surface. The coating efficiency of the fine glycine crystals on the starch particles was improved by using an ultrasonic spray nozzle rather than anti-solvent crystallization without an ultrasonic spray nozzle. The glycine crystals on the surface of starch particles transformed from unstable to stable forms according to the solution-mediated mechanism and Ostwald rule of stages. The interaction between the core particles and guest particles was found to be a key factor in producing the composite particles. The results indicate that this crystallization process using the ultrasonic spray nozzle is promising for efficiently producing composite particles. [ABSTRACT FROM AUTHOR]