Composition and substrate effects on Mn3O4@zeolitic imidazolate framework-67 heterostructures for extended-gate field-effect transistor-based electrochemical sensing of pH and glucose

Carbon cloth (CC) and carbon paper (CP) were systematically investigated as conductive substrates to construct Mn 3 O 4 @zeolitic imidazolate framework-67 (Mn 3 O 4 @ZIF-67) heterostructures via a single-step hydrothermal strategy. These advanced composite layers were subsequently integrated into extended-gate field-effect transistor (EGFET) devices to evaluate their potential for non-enzymatic electrochemical pH and glucose sensing applications. The impacts of the Co/Mn molar ratio and underlying substrate architecture on material morphology, interfacial bonding characteristics, nucleation kinetics, and analytical sensing performance were rigorously examined. Scanning electron microscopy verified the successful formation of regular rhombic dodecahedral ZIF-67 crystal templates, while the strategic incorporation of mixed-valence Mn 3 O 4 produced highly compact heterointerfaces and shifted the composite layer growth from a crystal-growth-dominated to a nucleation-dominated pathway. Among the investigated configurations, a Co/Mn molar ratio of 3:1 yielded the most favorable interfacial architecture, establishing a synergistic layout that optimized charge separation and enhanced continuous catalytic turnover. For potentiometric pH monitoring, the optimized 3:1/CP sensor achieved an outstanding voltage sensitivity of 8.43 mV/pH, representing a notable 122% enhancement over the 1:1/CC configuration. For non-enzymatic glucose detection, the same 3:1/CP platform exhibited an excellent current sensitivity of 1.396 mA/(mg·mL −1 ) and a voltage-shift sensitivity of 8.7 mV/(mg·mL −1 ), outperforming the 3:1/CC device by 22% and 10%, respectively. This significant performance boost is primarily credited to the three-dimensional macroporous network and superior electron transport capabilities of the CP substrate, which facilitate uniform material coverage and minimize kinetic barriers. Furthermore, the optimized EGFET platform demonstrated excellent signal reversibility with low hysteresis and minimal drift over prolonged testing, indicating reliable operation for continuous biochemical tracking.