Abstract: A novel Fe-N-CDs@PVP composite nanomaterial with dual-signal ratiometric colorimetric-fluorescent response was developed for the highly sensitive and visual dual-mode determination of curcumin in biological samples related to depression inhibition models. Firstly, iron and nitrogen co-doped carbon dots (Fe-N-CDs) were synthesized via a one-step hydrothermal method, followed by surface functionalization and hybridization using polyvinylpyrrolidone (PVP). The introduction of PVP not only enriched the luminescent states on the surface of the carbon dots but also significantly enhanced their dispersion stability. Under optimized conditions, a distinct inner filter effect (IFE) occurred between the target analyte, curcumin, and Fe-N-CDs@PVP. This interaction induced a red-shift in the ultraviolet (UV) absorption of the system, enabling colorimetric detection, while simultaneously triggering the fluorescence quenching of the composite material. The linear ranges of this method for the colorimetric and fluorescent detection of curcumin were 1–50 μmol/L and 0.1–10μmol/L, respectively, with a detection limit as low as 10 nmol/L. Furthermore, this dual-mode sensor was successfully applied to the precise quantitative tracking of trace curcumin in simulated biological fluids and antidepressant drug screening samples. This work provides a powerful visual analytical tool for evaluating the antidepressant efficacy of curcumin and advancing research into targeted diagnosis and treatment of depression.

Key words: Curcumin, Carbon dots, Polyvinylpyrrolidone, Colorimetric-fluorescence