LAUSR

Herein luminescent lanthanide supramolecular assemblies were constructed via coordination of a crown-connected bis-terpyridine (L1) and Ln3+ ions, which can self-assemble to form homogeneous spherical nanoparticles with an average diameter of 700 nm on a silicon plate surface upon slow evaporation of solvents. Potassium ions are shown to give rise to obvious enhancement in the luminescence of Ln3+ (Ln = Eu, Tb) ions in the lanthanide assemblies. The changes are the consequence of the capture of the cations by the crown moieties via cation–π interactions, increasing the triplet excited energy level of L1 and thus favoring the population of the lanthanide's excited state from the antenna triplet state by means of an energy transfer. Besides, energy transfer from Tb3+ to Eu3+ was observed in the luminescent Eu3+/Tb3+ bimetallic assemblies (Eu/Tb·L1) and the efficiency can be tuned by potassium concentration. Thus, Eu/Tb·L1 can serve as a self-calibrating sensor, which can selectively and quantitatively detect potassium by linearly correlating the K+ concentration to the emission intensity ratio of 5D4 → 7F5 transition (Tb3+) to 5D0 → 7F2 transition (Eu3+).