Upcycling waste zirconia block dental powders: towards a facile and highly selective on-off optical probe for sensing Zn²⁺ and Hg²⁺ in aqueous media

Upcycling waste materials to produce high-value-added substances can pave the way for sustainable development. Waste block dental powders (WBDPs), a valuable source of zirconia, represent a significant portion of dentistry wastage and are valuable candidates for upcycling. Herein, a highly selective and facile optical probe based on upcycled WBDPs with surface interaction of 8-hydroxyquinoline-5-sulfonate (8-HQS) was developed to produce a powerful solid-state optical chemo-probe for sensing Zn²⁺ and Hg²⁺ in aqueous media. ZrO₂-8-HQS provided high selectivity for sensing Zn²⁺ over a wide range of cations and anions, with a remarkable fluorescence intensity enhancement (<i>λ</i> _em = 517 nm) over a wide pH range (4-10). The as-prepared optical probe had a remarkable sensitivity, with a limit of detection (LoD) of 5.2 μM for Zn²⁺. The fluorescence of the Zn²⁺ probe complex was quenched in the presence of aqueous solutions of Hg²⁺, allowing the as-prepared chemo-probe to sense Hg²⁺ in aqueous media (LoD of 0.8 μM for Hg²⁺). The Stern-Volmer equation revealed static and dynamic mechanisms in the quenching process, and the (<i>K</i> _S × <i>K</i> _D) and (<i>K</i> _S + <i>K</i> _D) values were 0.0012 and 0.0076, respectively.