Selective ion sensing with high resolution large area graphene field effect transistor arrays

Real-time, high resolution, simultaneous measurement of multiple ionic species is challenging with existing chromatographic, spectrophotometric and potentiometric techniques. Potentiometric ion sensors exhibit limitations in both resolution and selectivity. Herein, we develop wafer scale graphene transistor technology for overcoming these limitations. Large area graphene is an ideal material for high resolution ion sensitive field effect transistors (ISFETs), while simultaneously enabling facile fabrication as compared to conventional semiconductors. We develop the ISFETs into an array and apply Nikolskii–Eisenman analysis to account for cross-sensitivity and thereby achieve high selectivity. We experimentally demonstrate real-time, simultaneous concentration measurement of K+, Na+, $${{\rm{NH}}}_{4}^{+}$$NH4+, $${{\rm{NO}}}_{3}^{-}$$NO3−, $${{\rm{SO}}}_{4}^{2-}$$SO42−, $${{\rm{HPO}}}_{4}^{2-}$$HPO42− and Cl− with a resolution of $$\sim\! 2\times 1{0}^{-3}\,{\mathrm{log}}\,$$~2×10−3log concentration units. The array achieves an accuracy of ±0.05 log concentration. Finally, we demonstrate real-time ion concentration measurement in an aquarium with lemnoideae lemna over three weeks, where mineral uptake by aquatic organisms can be observed during their growth.