Electrochemical sensing of caffeic acid on natural biomass-pyrrole-functionalized magnetic biochar (PFMB) as promising SPE material.

A peanut shell-modified screen-printed carbon electrode (SPE) was developed for the sensing of caffeic acid (CA) in saliva samples using cheap miniaturized analyzer composed of a laptop and an electrochemical workstation. Peanut shells, sourced from abundant biomass residues, were used to fabricate magnetic biochar (MB) and pyrrole-functionalized magnetic biochar (PFMB) with varying pyrrole/Fe ratios through a hydrothermal process. The surface morphology and electrochemical properties of the synthesized PFMB material were analyzed using XRD, FTIR, Raman, SEM, VSM, cyclic voltammetry, and differential pulse voltammetry techniques. The PFMB-modified SPE displayed excellent electrocatalytic response towards CA in a wide linear range from 10 to 600 μM with a low limit of detection of 0.08 μM. The enhanced electrocatalytic response could be ascribed to the synergistic effect of pyrrole-functionalized biochar and FeO on the newly designed probe. Moreover, the fabricated sensor was successfully utilized for real-time detection of CA in various samples. Quantum chemical modeling was performed to confirm the relevant findings to clarify the structure-activity relationship of CA adsorption on biochar.