Highly selective and robust nanocomposite-based sensors for potassium ions detection

Abstract Ion-selective electrodes are employed in technological important fields, such as medical diagnosis, or water quality evaluation. Plasticized polymeric membranes containing ionophores are typically used in these devices. However, the low mechanical hardness and limited robustness of these electrodes combined with their low selectivity limit their use in high precision applications. In the present work, PVC-functionalised silica nanoparticles incorporated in a plasticized PVC film have been integrated into ion sensors for the first time applied to the detection of K+ in solution. This approach was used for the design of highly specific and mechanically robust systems using a fluidic chamber. The device presented a hardness in the range of 5.2 GPa, being 2 orders of magnitude higher than the one reported for plasticized PVC (0.059 GPa), and could measure the concentration of K+ with high specificity when compared to Ca2+ and Na+ ions compared to the conventional approach. The interactions of the sensing films with the ions in solution were systematically studied for different degrees of PVC functionalisation to allow the rational design of a robust and selective sensor. The final device exhibited one of the lowest signal drift ever reported, with 1.3 µV h−1. The system operated under fluid pressure and shear stress conditions of 45 mbar for at least 8 h while the control experiment, fabricated using the conventional composition without nanoparticles showed a significantly higher noise (circa 115.6 µV h−1) and degraded after 4 h of continuous measurements. The sensors here reported could also be used for the accurate determination of the concentration of K+ inside complex mixtures of ions such as simulated body fluids and human serum, leading to a plethora of applications in healthcare for the diagnosis and monitoring of diseases.