Inherently fluorescent polystyrene microspheres as a fluorescent probe for highly sensitive determination of chromium (VI) and mercury (II) ions

Nowadays developing fluorescent probes that are cheaper, nontoxic, robust and easy to use for determination of heavy metal ions with high selectivity and sensitivity is still an ongoing challenge. In this paper, inherently fluorescent aminated polystyrene microspheres (PS-NH2) were fabricated from cross-linked polystyrene (PS) microspheres through acetylation, oximation and reduction, which can serve as a selective and sensitive fluorescence (FL) probe for the determination of chromium (VI) (Cr(VI)) and mercury (II) (Hg2+) ions. The photostability, selectivity and sensitivity of the fluorescent PS-NH2 microspheres were studied in detail. The feasibility of PS-NH2 microspheres as a fluorescent probe was conducted by determining Cr(VI) or Hg2+ in real water samples. Results revealed that no photoleaching or leaking issues were observed on PS-NH2 microspheres. The fluorescent probe could analyze Cr(VI) and Hg2+ separately in water samples with high sensitivity and good accuracy in the range of 0.01–1 μM. The detection limits for Cr(VI) and Hg2+ were 9.1 nM and 9.9 nM, respectively. Additionally, two possible FL quenching mechanisms were proposed for Cr(VI) and Hg2+. This work provides a new platform for accurate determination of Cr(VI) and Hg2+ in environmental fields.