Organic-Transistor-Based NO2 Sensor Fabricated with Surface-Modified Faujasite-Type Zeolite as an Efficient Nanochannel for Gas Analytes

Recently, organic-transistor-based chemical gas sensors have attracted great interest; however, the properties of the sensor devices, such as their responsivity, response/recovery rates, and linearity, have not yet been fully developed to enable their practical and robust application. The poor device properties are, in principle, caused by the device configuration, which includes a thick and continuous active layer. In this study, we investigated the material properties of a multiscale porous faujasite-type framework, zeolite Y (FAU), which has been widely explored in industrial processes, and examined its potential as an analyte channel material inserted at an organic transistor active layer. A series of FAU powders were prepared via surface modification with organosilanes with different alkyl chain lengths, and the modified powders were subsequently compared. The microstructures, morphologies, and optical/electrical characteristics of polythiophene/surface-modified FAU hybrid films were systematically investigated. Organic-transistor-type nitrogen dioxide sensors based on the polythiophene/FAU hybrid films showed substantially improved sensing properties, including enhancements of their responsivity, response rate, and recovery rate. Moreover, the surface modification of the zeolite improved the sensor performance, possibly because of the optimized structural and surface characteristics of zeolitic cavity structures. These results provide invaluable information and keen insights into the design of transistor-type reactive gas sensors based on organic semiconductor/zeolite hybrid thin films.