Simplified Lead Detection: Graphene-Based Potentiometric Sensors for Pb(II) Monitoring

Lead contamination remains a significant environmental and public health concern, creating a demand for analytical platforms that combine sensitivity, simplicity, and long-term stability. In this work, a graphene-containing molecular membrane matrix was developed for the fabrication of single-piece all-solid-state potentiometric sensors for Pb(II) detection. The sensing membrane consisted of poly(vinyl chloride), plasticizers, a Pb(II)-selective ionophore, lipophilic ionic sites, and dispersed graphene nanostructures, forming an integrated molecular sensing interface. Within the membrane phase, selective complexation of Pb(II) ions by the ionophore was coupled with graphene-assisted ion-to-electron transduction, enabling efficient signal generation without the need for a separate solid-contact layer. The influence of graphene incorporation and membrane thickness on sensor performance was systematically investigated. Among the tested configurations, a membrane prepared from 40 µL of sensing cocktail provided the best overall performance, combining high electrical capacitance, favorable surface properties, and superior potential stability. SEM imaging revealed a homogeneous membrane morphology without large graphene agglomerates, indicating effective dispersion of graphene within the polymer matrix. The optimized sensor exhibited a near-Nernstian slope of 30.3 mV dec^-1, a linear response range from 1.0 × 10^-7 to 1.0 × 10^-2 M, a detection limit of 6.3 × 10^-8 M, and a potential drift of only 0.35 mV h^-1. These results demonstrate that direct incorporation of graphene into an ion-selective membrane is an effective strategy for constructing robust and scalable single-piece potentiometric sensors for Pb(II) monitoring and highlight the potential of developed membrane materials for electrochemical sensing applications.