Exploring different carbon allotrope thermoplastic composites for electrochemical sensing

Composite electrodes are an effective and cheap way to utilise a wide range of carbon materials to make electrodes. More recently thermoplastics have been widely used as the binder to make carbon composite electrodes, as varying fabrication approaches, such as 3D printing, can make highly reproducible electrodes. However, there is a clear need to understand how the electrochemical performance of different carbon allotrope materials varies when made into sensors. We accessed polylactic acid (PLA) thermoplastic filaments containing carbon black, graphite, graphene, multiwall carbon nanotube (MWCNT) and carbon fiber using various electrochemical techniques. Graphite/PLA and graphene/PLA electrodes showed the best electron transfer kinetics. Graphene/PLA electrodes had the greatest sensitivity and lowest limit of detection for the measurement of serotonin. CB/PLA was least prone to electrode fouling from oxidative by-product generated from the oxidation of serotonin. 3D printing was used to make various carbon allotrope materials into complex shapes to evaluate the batch uniformity of the printed parts. Of all the materials explored, CB/PLA had the best resolution and batch uniformity when compared to PLA. Overall, our study highlights that the type of the carbon allotrope plays as much influence as amount of carbon on the electrochemical performance of carbon thermoplastic electrodes. These findings will provide significant guidance on the appropriate choice of carbon thermoplastic composite materials when designing electrodes for a wide range of applications.