High-performance field-effect transistor-type glucose biosensor based on nanohybrids of carboxylated polypyrrole nanotube wrapped graphene sheet transducer

We report a rapid-response and high-sensitivity field-effect transistor (FET)-based sensor with specificity towards glucose, based on reduced graphene oxide (rGO)-carboxylated polypyrrole (C-PPy) nanotube (NT) hybrids as the conductive channel. The rGO, C-PPy NTs, and rGO/C-PPy NT hybrids were characterized using Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results indicate that a well-organized structure was successfully prepared, based on specific interactions between the C-PPy NTs and the graphene sheets. Reliable electrical contacts were developed between the rGO/C-PPy NTs and the patterned-microelectrodes, which remained stable when exposed to the liquid-phase electrolyte. Liquid-ion-gated FETs composed of these rGO/C-PPy NT hybrids exhibited hole-transport behavior with higher conductivity than those of graphene sheets or C-PPy NTs because the C-PPy NTs formed a bridge between the graphene layers, resulting in effective electron transport. Glucose oxidase (GOx) was used as the capture probe, and was tightly combined with C-PPy NTs via a chemical coupling reaction, and glucose detection was performed via GOx, which catalyzes the oxidation of glucose in the rGO/C-PPy NTs hybrid FET biosensor. The FET biosensor provided a rapid response (< 1 s) with high sensitivity toward glucose with a limit of detection of 1 nM. This result is ca. 2–3 orders more sensitive than previous reported glucose sensor. The FET-type biosensor was highly reproducible and stable in air over a period of one month. Furthermore, the liquid-gated FET-type biosensor displayed specificity toward glucose in a mixed solution containing compounds found in biological fluids.

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