MXene-enhanced ion-selective electrodes for real-time electrolyte monitoring with ultra-Nernstian response

Monitoring electrolytes in biological fluids is critical for assessing cardiovascular health, as even minor cation imbalances within narrow physiological ranges can trigger life-threatening arrhythmias. Conventional Ion-Selective Electrode (ISE) are constrained by the theoretical limits of the Nernst equation. Modern medicine requires early detection of dangerous electrolyte imbalances and personalized real-time feedback. This demands high-sensitivity and rapid response (<10s for continuous monitoring) that conventional ISEs struggle to achieve. Here, we report a MXene-enhanced ISE achieving ultra-Nernstian and real-time sensing performance through one-step assembly. This approach enables homogeneous integration of two-dimensional MXene nanosheets within the ion recognition layer, creating well-defined nanoconfinement zones that locally enrich cations inside the MXene interlayer galleries. The synergistic effects of MXene's electronegativity and nanoconfinement geometry amplify ion-carrier complexation. These effects also accelerate charge transfer across the highly conductive MXene nanochannels. This dual mechanism yields ultra-Nernstian slope responses of 102.2 mV dec −1 for K + and 88.4 mV dec −1 for Na + (average of forward/reverse cycles), and fully accounts for the disparate sensitivity enhancements observed in K + versus Na + detection. It represents 43–69% enhancement over conventional ISEs, while reducing response time from 20 to 30 s to 8.8 s. The combination of simple fabrication, nanoconfinement-induced sensitivity enhancement, and the shortened response time address scalability and precision challenges under physiological conditions. This work demonstrates that one-step assembled MXene-enhanced ISEs with nanoconfinement-amplified ultra-Nernstian response represent significant advancement in analytical electrochemistry for real-time physiological monitoring.