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

AbstractMolecular lanthanide phosphonates [Ln2(H3tpmm)2(H2O)6] ⋅ xH2O (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 {EuO8} 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 Eu3+ and Tb3+, respectively. Interestingly, luminescence modulation is achieved for the chemically mixed Eu/Tb phosphonate analogues, c‐EuxTb2–xP (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 Eu3+ : Tb3+ 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 Fe3+ with Stern‐Volmer quenching constant (KSV) of 9.66×103 M−1 and detection limit (DL) of 0.42 μM through absorption competition caused luminescence quenching effect.