Development of a Cholesterol Biosensor and Energy Storage system based on Polypyrrole Coated Polyoxometalate

Designing sustainable and environmentally acceptable multifunctional electrode materials is vital for various purposes, such as energy storage and healthcare. The redox property of polyoxometalates is attractive for different electrochemistry fields, such as sensors, energy storage, catalysis, etc. In this study, potassium 9-tungsto-2-molybdo-1-vanadosilicate K₅[α-SiMo₂VW₉O₄₀].10H₂O (hereafter acronym as SiMo₂VW₉) embedded on polypyrrole (PPy), which acts as a nanohybrid, was synthesized for supercapacitor and biosensor applications. The electrochemical analysis for both applications was carried out using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The PPy-SiMo₂VW₉ nanohybrid showed the highest specific capacitance of 174.5 F g^-1 with power and energy densities of 799.94 W kg^-1 and 15.51 Wh kg^-1, respectively, at 0.5 M H₂SO₄ electrolytic medium. The nanohybrid showed the diffusion-dominant charge storage mechanism with 92.24% at a 5 mV s^-1 scan rate, which refers to the battery-type material. Furthermore, electrochemical sensing for cholesterol was also carried out using the cyclic voltammetry approach in the range of 0.03 to 0.58 mM cholesterol concentration. The PPy-SiMo₂VW₉ nanohybrid showed a sensitivity of 7.97 mAmMcm^-2 with limit-of-detection (LOD) and limit-of-quantification (LOQ) of 0.06 and 0.2 mM, respectively. The outcomes show that PPy-SiMo₂VW₉ nanohybrid material is promising in sensing and supercapacitor studies.