Polyaniline-based flexible sensors for pH monitoring
Résumé
Advancements in pH sensor technology offer opportunities for improved sensitivity, accuracy, and miniaturization, enabling real-time monitoring in diverse environments, such as aqueous solutions, biological systems, and harsh industrial conditions. More specifically, oxidizing media, characterized by the presence of substances that readily accept electrons, such as chlorine or hypochlorite, are prevalent in various industrial processes like chemical manufacturing, water treatment, and environmental monitoring. pH measurement in such environments is crucial for ensuring product quality, process efficiency, and environmental safety. With this in mind, we set out to develop flexible sensors using electrodeposited polymer films as pH-sensitive layers to manufacture pH sensors that are effective even in oxidizing environments. On one hand, the choice to use flexible sensors is explained by the fact that flexible sensors are becoming more and more important today due to their lightness, conformability, wearability, customizability, and versatility [1]. On the other hand, conductive polymers, such as polyaniline (PANI), are lightweight, resistant and can be deposited on flexible substrates either by chemical oxidation if the flexible substrate is insulating or by electrochemistry if the substrate is conductive [2]. Considering the advantages of using polyaniline and flexible electrodes, we therefore developed a potentiometric flexible sensor using a polyaniline film electrodeposited on a Cu/Ni/Au stack as the pH-sensitive material was developed. The pH sensor exhibited interesting detection performances in aqueous solution, leading to sensitive (73.4 mV per unit pH) and reproducible responses for pH values going from 3 to 8. However, these sensors were ineffective in solutions containing oxidizing hypochlorite ions, which made it necessary to incorporate Tritonx100 surfactant during the electrodeposition of the polyaniline film to make the sensitive material more stable in an oxidizing environment. The pH sensors based on polyaniline and Tritonx100 surfactant were then proved to be sensitive (62.3 mV per pH unit) and reproducible in aqueous solutions containing hypochlorite ions