Super Nernstian pH response and enzyme-free detection of glucose using solgel derived RuOx on PET flexible-based extended-gate field-effect transistor

In this paper, we fabricated a sol-gel derived RuOx, with low-temperature thermal oxidation, on polyethylene terephthalate (PET) flexible based extended-gate field-effect transistor (EGFET) as a pH sensor for the assessment of glucose for the first time. Structural identification, surface morphology, and film composition of the sensing membrane were investigated by X-ray diffraction, atomic force microscopy, and X-ray photoelectron microscopy, respectively. The RuOx on PET based EGFET sensor exhibited a pH sensitivity of 65.11 mV/pH in the wide range of pH 2-12 with an excellent linearity of 0.999. This sensor showed good reversibility in terms of a lower hysteresis voltage of similar to 1 mV and a better stability for 12 h named as drift rate similar to 2.08 mV/h. The RuOx-based EGFET sensor also demonstrated a high selective response towards H+. In addition, the pH performace of this RuOx EGFET flexible sensor kept unchanged after 500 repeated bending cycles. Subsequently, the RuOx on PET based EGFET was functionalized by 4-carboxyphenyl boronic acid (4-CPBA), which is a synthetic receptor for covalent attachment of glucose on the sensing surface. The sensitivity of glucose was 6.89 mV/mM with the linearity of 0.993 within the glucose concentration from 1 to 8 mM. The concentration of serum glucose measured by our 4-CPBA functionalized RuOx EGFET biosensor is comparable to that determined by commercial blood glucose monitoring system. In addition, this RuOx EGFET biosensor exhibited an elevated reference voltage shift response to glucose compared with other saccharides (e.g. fructose, sucrose and mannose).