Sustainably engineered pollen-derived carbon dots for efficient multi metal-ion sensing

Carbon dots (CDs) derived from biomass have garnered considerable attention as an environmentally friendly alternative for metal ion detection. This study presents a novel approach for synthesizing CDs from natural pollen sources: Hibiscus rosa-sinensis (H-CDs) and Sphagneticola trilobata L. (S-CDs), for heavy metal ion detection. Using a rapid and scalable microwave-assisted method, the structural and optical characteristics of the synthesized CDs were examined using UV–Vis spectroscopy, X-ray diffraction (XRD), and Fourier Transform Infrared (FTIR) spectroscopy. High-Resolution Transmission Electron Microscopy (HRTEM) confirmed the quasi-spherical morphology and crystallinity, revealing an interlayer spacing of 0.32 nm and an average particle size below 15 nm. Fluorescence analysis revealed that S-CDs (quantum yield: 23.6 %) selectively detected Fe²⁺ and Co²⁺, while H-CDs (quantum yield: 21.3 %) targeted Fe²⁺ and Ni²⁺. The quenching mechanism involved both static and dynamic interactions. The detection limits were 0.22 ppm (Ni²⁺) and 0.24 ppm (Fe²⁺) for H-CDs, and 0.34 ppm (Fe²⁺) and 0.38 ppm (Co²⁺) for S-CDs. This is the first study on pollen-derived CDs for optical applications, demonstrating their potential as eco-friendly, sustainable and efficient metal ion sensors.