Dual-functional 2D heterostructure Bi-Bi₂S₃ Nanosheets: Ultrasensitive folic acid biosensing and efficient methylene...

Monitoring folic acid (FA) and the degradation of organic dyes are important for promoting public health and environmental safety, by ensuring proper nutritional levels and reducing toxic pollutants in wastewater. We present the synthesis of heterostructure fluorescent 2D Bi-Bi₂S₃ nanosheets via a simple solvothermal and ultra-probe sonication approach. These heterostructure nanosheets exhibit a unique greenish-blue fluorescence, plasmonic characteristics with a narrow bandgap (1.18 eV), enabling dual functionality as a biosensor and photocatalyst. The nanosensor detects FA a biomarker linked to cancer and birth defects with exceptional sensitivity (detection limit: 2.98 nM) across a broad linear range (0 nM-1.9 μM), while effectively degrading toxic methylene blue (MB) under visible light. Rigorous evaluation confirmed high selectivity and robustness against interfering agents. Real-world applicability validation using human urine and blood serum yielded excellent recoveries (98-101 %). This work highlights the potential of 2D Bi-Bi₂S₃ nanosheets as a rapid, cost-effective, and versatile platform for biomedical diagnostics and environmental remediation.