Crumpled and Exfoliated Graphene as Transducers in High Sensitivity Potentiometric Nitrate Sensors

This work presents a comparative study of two graphene morphologies-crumpled graphene (CG) and liquid-phase exfoliated graphene (LPE)-as transducer materials in fully printed electrochemical potentiometric nitrate sensors. Electrochemical sensors composed of CG and LPE as the active layer in the working electrode were fabricated on polyimide substrates using both aerosol jet and inkjet printing. The working electrodes were both functionalized using a nitrate ion-selective membrane. Both sensor types demonstrated super-Nernstian sensitivities of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-\mathbf{9 6. 4 5 m V} /$</tex> dec and -94.58 mV/dec for CG and LPE, respectively, with sub-5-second response times and low micromolar limits of detection (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\sim 2.1 \mu \mathrm{M}$</tex> for CG and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\sim 3.2 \mu \mathrm{M}$</tex> for LPE). Despite differences in morphology, both graphene materials exhibited comparable performance, which suggests that electrical double layer (EDL)-driven transduction dominates sensor performance. These findings highlight the potential of crumpled and exfoliated graphene for scalable, high-performance nitrate sensing applications.