Carbon monoxide (CO) gas is an odorless toxic combustion product that rapidly accumulates inside ordinary places, causing serious risks to human health. Hence, the quick detection of CO generation is of great interest. To meet this need, high-performance sensing units have been developed and are commercially available, with the vast majority making use of semiconductor transduction media. In this paper, we demonstrate for the first time a fabrication protocol for arrays of printed flexible CO sensors based on a printable semiconductor catalyst-decorated reduced graphene oxide sensor media. These sensors operate at room temperature with a fast response and are deposited using high-throughput printing and coating methods on thin flexible substrates. With the use of a modified solvothermal aerogel process, reduced graphene oxide (rGO) sheets were decorated with tin dioxide (SnO2) nanoscale deposits. X-ray diffraction data were used to show the composition of the material, and high-resolution X-ray photoelectron spectroscopy (XPS) characterization showed the bonding status of the sensing material. Moreover, a very uniform distribution of particles was observed in scanning (SEM) and transmission electron microscopy (TEM) images. For the fabrication of the sensors, silver (Ag) interdigitated electrodes were inkjet-printed from nanoparticle inks on plastic substrates with 100 µm linewidths and then coated with the SnO2-rGO nanocomposite by inkjet or slot-die coating, followed by a thermal treatment to further reduce the rGO. The detection of 50 ppm of CO in nitrogen was demonstrated for the devices with a slot-die coated active layer. A response of 15%, response time of 4.5 s, and recovery time of 12 s were recorded for these printed sensors, which is superior to other previously reported sensors operating at room temperature.
Additive Manufacturing of a Flexible Carbon Monoxide Sensor Based on a SnO2-Graphene Nanoink
