In situ synthesis of cylindrical spongy polypyrrole doped protonated graphitic carbon nitride for cholesterol sensing application

Herein, we demonstrate the exfoliation of bulk graphitic carbon nitrides (g-C₃N₄) into ultra-thin (~3.4 nm) two-dimensional (2D) nanosheets and their functionalization with proton (g-C₃N₄H⁺). The layered semiconductor g-C₃N₄H⁺ nanosheets were doped with cylindrical spongy shaped polypyrrole (CSPPy-g-C₃N₄H⁺) using chemical polymerization method. The as-prepared nanohybrid composite was utilized to fabricate cholesterol biosensors after immobilization of cholesterol oxidase (ChOx) at physiological pH. Large specific surface area and positive charge nature of CSPPy-g-C₃N₄H⁺ composite has tendency to generate strong electrostatic attraction with negatively charged ChOx, and as a result they formed stable bionanohybrid composite with high enzyme loading. A detailed electrochemical characterization of as-fabricated biosensor electrode (ChOx-CSPPy-g-C₃N₄H⁺/GCE) exhibited high-sensitivity (645.7 µAmM⁻¹ cm⁻²) in wide-linear range of 0.02–5.0 mM, low detection limit (8.0 μM), fast response time (~3 s), long-term stability, and good selectivity during cholesterol detection. To the best of our knowledge, this novel nanocomposite was utilized for the first time for cholesterol biosensor fabrication that resulted in high sensing performance. Hence, this approach opens a new prospective to utilize CSPPy-g-C₃N₄H⁺ composite as cost-effective, biocompatible, eco-friendly, and superior electrocatalytic as well as electroconductive having great application potentials that could pave the ways to explore many other new sensors fabrication and biomedical applications.