Fabrication and characterization of poly(fullerene) thin films for gas sensors

Abstract

Ammonia, despite being a naturally generated compound in the metabolic process, can be harmful to health in higher concentrations. In this context, sensor devices are directly related to health and safety measurements to detect the presence of such substances. In this work, we study materials derived from fullerene, a material with a high electron affinity. We characterize three fullerene derivatives, namely PCBM, OPCBMMB and PPCBMB, and verify their applicability as ammonia sensors. The materials were studied in the form of thin films, produced by Langmuir–Schaefer and drop-casting techniques. Optical characterization was performed using UV–visible spectroscopy while morphological characteristics were studied using atomic force microscopy (AFM) and optical microscopy (OM). Current versus voltage and current versus time measurements were performed in order to determine the films' conductivities, electrical resistances and gas-sensing properties. UV–visible absorption was observed at lower wavelengths, with peaks in the UV region. In the electrical measurements, differences were observed between the deposition techniques, with the Langmuir–Schaefer films showing a higher conductivity than the drop-casting films. AFM and OM also showed differences in the film surfaces between the techniques, with a rougher surface on the drop-casting films. When exposed to ammonia, the materials showed electrical responses at every cycle, with a significant increase in their electrical responses. © 2024 Society of Chemical Industry.