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This work presents a simple process for the development of flexible acetone gas sensors based on zinc oxide/graphene/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate). The gas sensors were prepared by inkjet printing, which was followed by a metal sparking process involving different sparking times. The successful decoration of ZnO nanoparticles (average size ~19.0 nm) on the surface of the graphene–PEDOT:PSS hybrid ink was determined by characterizations, including Raman spectroscopy, Fourier transform infrared spectroscopy, field-emission transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffractometry. The ZnO nanoparticle-decorated graphene–PEDOT:PSS with a sparking time of 2 min exhibited the highest response of 71.9% at 10 ppm of acetone, above those of samples treated with other sparking times and the undecorated control. In addition, the optimal sensor revealed high selectivity for acetone over several other kinds of gases, such as ammonia, toluene, dimethylformamide, ethanol, methanol, and benzene, at room temperature. The gas sensor also revealed a low limit of detection (0.4 ppm), high sensitivity (6.18 ppm−1), and high stability (5-week long-term) to acetone. The response and recovery times of the sensor were found to be 4.6 min and 4.2 min, respectively. The acetone-sensing mechanism was attributed to the formation of p-n heterojunctions, which were responsible for the significantly enhanced sensitivity. [ABSTRACT FROM AUTHOR]

Functionalized multi-walled carbon nanotubes dispersed in a polymer mixture of poly (3,4- ethylenedioxythiophene): poly (styrenesulfonate) (f-MWCNT-PEDOT:PSS) have been presented as a functional ink for fabrication of room-temperature gas sensor. The ink was deposited onto the flexible substrates with silver interdigitated electrodes by a handwriting method. The sensor shows the sensitivity and selectivity to NH3 at room-temperature. The high performance of sensor has attributed to the functionalized effect in the increment of extra active area for gas adsorption. The sensor can be worked without noticeable reduction in gas response although it is bent to the heavy disorder. The sensing mechanisms of sensor have proposed based on the reaction between NH3 molecules and oxygen species on the surface of f-MWCNTs. The direct charge-transfers and the film swelling of polymer have been also proposed as possible NH3- sensing mechanisms. From these findings, the direct ink writing is an effective method for preparing the sensing film of gas sensor. Furthermore, the f-MWCNT-PEDOT: PSS ink has the high potential to be selected as a good material for flexible NH3-sensing applications. [ABSTRACT FROM AUTHOR]