Thiourea Functionalised Receptor for Selective Detection of Mercury Ions and its Application in Serum Sample

A thiourea functionalised fluorescent probe 1-phenyl-3-(pyridin-4-yl)thiourea was synthesized and utilised as a fluorescent turn-on chemosensor for the selective recognition of Hg²⁺ ion over competitive metal ions including Na⁺, Mn²⁺, Li⁺, Cr²⁺, Ni²⁺, Ca²⁺, Cd²⁺, Mg²⁺, K⁺, Co²⁺, Cu²⁺, Zn²⁺, Al³⁺ and Fe²⁺ ions based on the inter-molecular charge transfer (ICT). Intriguingly, the receptor demonstrated unique sensing capabilities for Hg²⁺ in DMSO: H₂O (10:90, v/v). The addition of Hg²⁺ ions to the sensor resulted in a blue shift in the absorption intensity and also enhancement in fluorescence intensity at 435 nm. Fluorescence emission intensity increased linearly with Hg²⁺ concentration ranging from 0 to 80 µL. The detection limit and binding constant were determined as 0.134 × 10^–6 M and 1.733 × 10⁷ M⁻¹, respectively. The sensing behavior of Hg²⁺ was further examined using DLS, SEM and FTIR. The probe could detect Hg²⁺ ions across a wide pH range. Furthermore, the receptor L demonstrated good sensing performance for Hg²⁺ in bovine serum albumin and actual water samples.