Anodic TiO 2 as a Memristive pH‐Sensing Material

This work investigates anodically grown TiO 2 as an interface‐dominated memristive material for liquid‐phase pH sensing. The crossbar devices exhibit electroforming‐free and diode‐like switching behaviour over a broad pH range. With increasing alkalinity, a progressive opening of the hysteresis can be noted in the I‐U response, as well as an increase in high resistance state to low resistance state ratio. This pH‐dependent regulation of the resistive states hints that OH ‐ species are responsible for the sensing mechanism. Complementary X‐ray photoelectron spectroscopy shows an increase in high binding energy O components contribution after exposure to different pH solutions. This suggests that surface hydroxylation or adsorbate retention can alter the resistive switching behaviour behind the sensing process. The sensing performance of the TiO 2 anodic memristor was assessed. The sensitivity, limits of detection and quantification of the TiO 2 anodic memristor were obtained to be 0.16 pH −1 , 1.18 pH, and 3.57 pH, respectively.