Rutin-grafted carbon nanofibers derived from Clitoria ternatea flower-extract for bio-friendly voltammetric pH sensing applications.

Clitoria ternatea (commonly known as sangu poo (SP) in South Indian languages) is a plant rich in natural flavonoids, particularly rutin, offering a sustainable source of electroactive molecular compounds for electrochemical applications. In this study, rutin from Clitoria ternatea was in situ grafted onto a carbon nanofibre (CNF)-modified glassy carbon electrode (GCE), forming a composite designated as GCE/CNF@SP-Redox, where SP-Redox refers to the redox-active form of sangu poo. This composite was employed in the development of a green, eco and bio-friendly electrochemical sensor for instant preparation and real-time pH monitoring. The sensor demonstrated excellent redox behavior, high stability, and a strong pH-dependent electrochemical response, attributed to the surface-confined electroactivity of grafted rutin. The successful grafting of rutin, as a plausible electroactive species, onto the CNF surface was validated through High-Performance Thin-Layer Chromatography (HPTLC) using an organic solvent extraction method and by several control experiments. Comprehensive characterization of the GCE/CNF@SP-Redox composite was carried out using FTIR, Raman spectroscopy, FE-SEM, Scanning Electrochemical Microscopy (SECM), Electrochemical Quartz Crystal Microbalance (EQCM) measurements, and various electrochemical techniques. These analyses confirmed the successful functionalization, nanoscale surface morphology, localized redox behavior, mass changes during electron transfer, and improved electrochemical performance. To demonstrate practical utility, a portable electrochemical sensing device was fabricated for on-site and point-of-care applications. Notably, the sensor was successfully applied to monitor pH variations in rat wound models, capturing dynamic pH fluctuations associated with different stages of wound healing. As a proof of concept, the system was further validated using various real sample matrices, confirming its versatility and reliability.