Effective dual-mode turn-on sensing of phosphates enabled by the twisted “head-to-head” self-assembly of a platinum(ii)-terpyridyl complex with close Pt–Pt packing

Abstract

The dual-mode sensing strategy reveals greatly improved accuracy with visual cross-validation, satisfying the strict requirement of trace sensing in complex environments. However, the dual-mode probe design for phosphates with a single component, significant signaling, and hypersynchronous response remains a great challenge. Herein, a dual-mode colorimetric/fluorescent “signal-on” sensing of phosphates was achieved using a well-designed platinum(II) complex probe with a short hydrogen bond recognition site guiding its self-assembly triggered by phosphates. The unique packing assisted by the hydrogen bond between the probe and phosphate anions resulted in metal–metal-to-ligand charge transfer (MMLCT)-related deep blue (596 nm) and bright red (715 nm) emission of the 1D aggregates formed. The platinum(II) complex could be employed for anionic phosphate sensing with proper dual-mode sensitivity (colorimetric LOD of 5.73 μM and fluorescent LOD of 2.25 nM), instant response (<2 s), and remarkable selectivity and anti-interference performance for over 20 interferents. Besides, a facile dual-mode test strip constructed based on the proposed probe achieved the direct onsite visualization of the phosphate additives in 5 beverages, revealing its promising practical application in the real world. The proposed non-bonding interaction-induced self-assembly with dual-mode turn-on behavior is also expected to find a variety of applications for optoelectronic material design and photophysical mechanism-dominated chemical sensing benefited by non-bonding interactions.