Excitation‐Wavelength‐Dependent Luminescence of Chemically and Physically Mixed Europium and Terbium Phosphonates: Color‐Tunable Luminescence, Near‐White‐Light Emission, and Selective Fe³⁺ Detection

Abstract

Molecular lanthanide phosphonates [Ln 2 (H 3 tpmm) 2 (H 2 O) 6 ] • xH 2 O (Ln=Eu, EuP; Ln=Tb, TbP) were synthesized. Single-crystal X-ray diffraction confirmed that EuP has a sandwich-like dinuclear structure, in which the Eu(III) center adopts a {EuO 8 } distorted dodecahedral geometry. XRPD patterns prove that TbP and EuP are isomorphous and isostructural.EuP and TbP are highly thermally stable approaching 450 °C and exhibit red-and green-light emissions from the characteristic 4 f-4 f transition of the Eu 3 + and Tb 3 + , respectively. Interestingly, luminescence modulation is achieved for the chemically mixed Eu/Tb phosphonate analogues, c-Eu x Tb 2-x P (x = 1.5, 1, 0.5), and physically mixed Eu/Tb phosphonate materials, p-yEuP : zTbP (y : z = 3 : 1, 1 : 1, 1 : 3), with varying the excitation wavelength. Of particular note, near-white-light emission is also achieved for c-EuTbP, p-EuP : TbP, and p-EuP : 3TbP when excited at 365 nm. Therefore, these dinuclear molecular lanthanide phosphonates emitting excitation wavelength and Eu 3 + : Tb 3 + ratio dependent luminescence might be potential candidates for color-tunable luminescence materials and white-light-emitting materials. On the other hand, the bright green-light emission makes TbP to be an excellent reusable luminescence sensor for selective detection of Fe 3 + with Stern-Volmer quenching constant (K SV ) of 9.66 × 10 3 M À 1 and detection limit (DL) of 0.42 μM through absorption competition caused luminescence quenching effect.

Assembly of One-, Two-, and Three-Dimensional Cu(I)-Based Coordination Frameworks for Tunable White Light Emission and Effective Fluorescence Sensing

“…It is displayed in Figure S20 that unlike other metal cations, the solution of Fe 3+ presents an intense absorption band in 280–400 nm in the UV–vis spectrum, showing a large overlap with the excitation band of solid 1 . Thus, the competitive energy absorption may explain this interesting phenomenon, as the Fe 3+ rather than 1 has absorbed the majority of excitation energy, leading to the consequent quenching effect. − …”