Single- and double-thread activated carbon fibers for pH sensing

In this paper, activated carbon (AC) in the form of single and double threads is used for the first time as a pH sensor because of its intrinsic properties (high porosity, and conductivity). To determine its applicability as a pH sensor, this study characterizes the morphological features and measures the pH sensing characteristics of the AC threads. The pH sensing characteristics (sensitivity and hysteresis) of both single and double thread are: 19.66 mV/pH; 60.4 mV and 11.3 mV/pH; 144.6 mV, respectively. The AC single-thread exhibits a higher sensitivity for pH range of 2-12 with excellent linearity of 98.2%, and the lower hysteresis for pH (7-4-7-10-7) cycle. These values of pH sensitivity and hysteresis for AC single-thread make it a good EGFET candidate for use as a pH sensor. The high porosity and conductivity of the AC sensor explains its high pH sensing performance. Given the dependence of pH sensitivity on the ion-exchange between available [H+] in the electrolyte and the carbon ions available in the surface of the thread.