Utilizing plasma modified SnO2 paper gas sensors to better understand gas-surface interactions at low temperatures

Abstract

Developing low temperature, low cost metal oxide gas sensors remains a critical but elusive goal. Additionally, a better understanding of gas-metal oxide interactions during sensing is required to achieve this goal as well as improving the performance of these devices. Here, the authors describe a paper-based gas sensor (PGS) utilizing SnO2 nanoparticles to detect ethanol, CO, and benzene. Proof-of-concept sensor data indicate that the response was increased and viable operating temperature was lowered (≤50 °C) via plasma surface modification techniques using an Ar/O2 gas mixture at a range of applied rf powers and precursor pressures. Temperature dependent response also demonstrates that sensor selectivity can be tuned with plasma treatment parameters. Ethanol response and recovery behavior at operating temperatures ≤50 °C indicate that sensors demonstrate real-time response at relatively low temperatures. Additionally, although the resistance of the PGS does not fully recover postgas exposure, the signal stability and continued response to ethanol with subsequent exposures indicate that sensors could potentially be used multiple times. Optical emission spectroscopy identified species involved in plasma surface modification processes and x-ray photoelectron spectroscopy elucidated how these changes in surface chemistry correlate to PGS performance. The combination of these techniques provides insight into the driving factors controlling the gas detection process. This approach to produce PGSs shows great promise for the fabrication of flexible, inexpensive devices capable of operating at much lower temperatures than current metal-oxide based sensors.