Surface-engineered silica core-shell enables an ideal ratiometric fluorescent probe for highly selective Hg

Ratiometric fluorescence sensors, which intrinsically compensate for fluctuations in ambient and excitation light intensity, have garnered extensive interest for their enhanced analytical reliability. In this study, we report the design and fabrication of a novel nanohybrid dual-emission platform constructed by integrating CdTeS quantum dots with coumarin derivatives for the selective detection of Hg2+ ions. A ternary hollow nanostructured sensor was synthesized via sequential solvothermal processing, comprising core-shell silica microspheres decorated with CdTeS quantum dots and subsequently functionalized with coumarin moieties. The resulting nanohybrid exhibits two well-resolved emission bands at 475 and 680 nm, attributed to the intrinsic photoluminescence of coumarin moieties and CdTeS dots, respectively. Upon exposure to Hg2+, the 475 nm emission undergoes pronounced quenching, whereas the 680 nm signal remains largely invariant, enabling a robust ratiometric response. The fluorescence intensity ratio (I475/I680) displays a linear correlation with Hg2+ concentration, achieving a detection limit of 10.2 nM. Moreover, the nanosensor demonstrated reliable analytical performance in quantifying mercury levels in real samples. Overall, this work presents a versatile strategy for engineering multifunctional ratiometric fluorescent probes with promising applications in biomedical analysis and environmental monitoring.