Eco-Benign S-Doped g-C₃N₄ Nano-Architectonics for Rapid and Selective Fluorescent Detection of the Jaundice Biomarker

Abstract

Development of label-free biomolecular sensor probe without complicated pre-treatment is potential for advanced point-of-care clinical diagnosis. This study explores kinetic and thermodynamic behavior between fluorophore sulfur-doped graphitic carbon nitride (S-g-C₃N₄) and the analyte bilirubin (BIL). S-g-C₃N₄ was synthesized through a greener approach using thiourea as the source for sulfur and nitrogen. S-g-C₃N₄ exhibit strong blue fluorescence emission at 439.46 nm with a purity of 67.12%. Addition of target BIL leads to selective fluorescence quenching without the need for external label, following a synergistic static and dynamic mechanism. Static quenching occurs due to the formation of a ground-state complex through hydrogen bonding. Dynamic quenching is indicated by a reduction in the excited-state lifetime, which decreases from 2.17 ns to 1.71 ns. The probe demonstrates admirable sensitivity for BIL detection across a range of 0.04–70 µM, with a detection limit of 0.0256 µM. It performs reliably in both synthetic and real human urine samples. Practical applicability of the prepared fluorescence probe was further visualized by human fingerprint imaging. These comprehensive analyses substantiate the design of highly selective method for BIL detection, customizable into a simple, non-invasive, and stable diagnostic probe for biomolecular recognitions.