Improvement in metrological performances of phthalocyanine-based QCM sensors for BTX detection in air through substituent’s effect

Abstract

Molecular engineering in macrocyclic materials like metallophthalocyanines (MPc) is a powerful strategy to tune the thin film properties that can be relevant to develop high performance gas sensors. In this context, the present work reports the enhancement in BTX sensing properties of MPc-based quartz crystal microbalance (QCM) sensors through exploiting the large surface area of tertiary-butyl (ttb) substituent grafted at the periphery of CuPc. Thin films of CuPc and ttb-CuPc reveal distinct morphologies and microstructures, in which the former presents a locally organized columnar structure, while the latter has an amorphous structure, containing agglomeration of molecular clusters. Such structural variation of the MPc films has huge implications on benzene, toluene and xylenes (BTX) sensing properties of the QCM sensors, utilizing these materials as sensing layers. Responses of ttb-CuPc-based QCM sensor are amplified by ca. 4-times and response time is reduced, compared to CuPc-based sensor. Moreover, ttb-CuPc-based QCM sensor displays high repeatability, resolution better than 20 ppm, negligible hysteresis and high sensitivity with limit of detection to 2 ppm, 1 ppm and 0.7 ppm for benzene, toluene and xylenes, respectively. Such favorable metrological characteristics combined with negligible interference from other gases make this microsensors suitable for BTX detection in real environment at concentrations below the recommended guidelines.