Biplane Ion-Pairing Induced Supramolecular Assembly for High-Performance Uranium Detection

It is still challenging to directly recognize the anionic species [UO₂(CO₃)₃]^4-, the dominant species in the environment (82%-93%), using current optical probes because of the adverse effects of its thick hydration shell on binding interactions. In this study, a water-soluble Pt(II) methylated terpyridine complex ([Pt(CH₃-tpy)NCO]⁺) supramolecular probe is designed to directly target [UO₂(CO₃)₃]^4- by a new strategy of thick hydration shell overlapping arrangement. The optical response demonstrates excellent selectivity among ≈30 investigated interfering substances, along with rapid response (≈15 s), high sensitivity (64.1 nm) and dual-signals. It is confirmed both experimentally and theoretically that the superior detection performance is attributed to the formation of a unique supramolecular structure featuring biplane-like building block, bicolumnar stacking and water-bridged anionic networks, via the overlap of thick hydration shells of aligned [UO₂(CO₃)₃]^4- to boost a superentropic driving force, and the distinguishable dual-signals arises from the emergence of four types of Pt-Pt interactions, generating low-energy metal-to-metal charge transfer adsorption/emission. In addition, a [Pt(CH₃-tpy)NCO]⁺-based hydrogel platform is constructed for detecting both anionic and cationic uranium, with a detection limit of 14.89 fg. This work unlocks not only a way to directly detect [UO₂(CO₃)₃]^4-, but also a new idea for sensing ions with extreme thick hydration layers.