Decai Huang

Luminescent sensing profiles based on anion-responsive lanthanide(III) quinolinecarboxylate materials: solid-state structures, photophysical properties, and anionic species recognition

Lanthanide complexes based on the quinolinecarboxylate ligand 2-phenyl-4-quinolinecarboxylic acid (PQC), namely, Ln2PQC6 (Ln = La3+, Pr3+, Nd3+, Sm3+ and Eu3+) were synthesized by a convenient solvothermal reaction, and the related crystal structures were determined. These complexes are isostructural and feature a discrete dinuclear moiety, in which solvent molecules act as coligands and the Ln3+ centre exhibits distorted tricapped trigonal prism geometry. By the introduction of the PQC ligand, the europium sample Eu2PQC6 (5) showing intense red emission in the solid state and solution, with both the replaceable coordination environment and potential hydrogen-bonding-accepting site, can be explored as a luminescent probe for sensing various anions. Among the tested ions (F−, Cl−, Br−, I−, NO3−, ClO4−, SCN−, HCO3−, HSO4− and H2PO4−), HSO4− and H2PO4− possess a strong response in the Eu3+ emitting behaviour leading to a unique quenching with a low detection limit of 15.3 and 8.3 nM, respectively, and a quick response time of less than 30 s. The different recognition mechanisms for two anions, including O–H⋯N hydrogen bonding and metal coordination modes have been proposed, which are supported by UV-vis, fluorescence spectroscopy, nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) measurements. In addition, density functional theory (DFT) calculations were carried out to verify the two recognition mechanisms of Eu2PQC6 in depth. As an extended research, Eu2PQC6 interaction with the nucleoside phosphates adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) in mixed aqueous solution was investigated, which can act as a special luminescent sensor for all three phosphates. The strong quenching by ADP (99.5%), has been ascribed to the strong bonding affinity (log Ka = 5.99) based on electrostatic attractions and steric effects.

Effect of Yb3+ concentration on upconversion luminescence of AlON:Er3+ phosphors

Abstract AlON:1.6 mol.%Er 3+ , x mol.%Yb 3+ ( x =0, 2.6, 3.1, 3.6, 4.1, 4.6) phosphors were synthesized successfully by aluminothermic reduction and nitridation (ATRN) method and characterized by X-ray diffraction (XRD), scanning electron microscopy (FESEM) and upconversion photoluminescence (UCPL) emission spectra. Under the excitation of diode laser 980 nm, the green (556 nm) and red (655 nm) upconverted emissions were observed, attributed to the 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transition of Er 3+ respectively. The emission intensity increased with increasing Yb 3+ concentration due to the energy transfer (ET) between Yb 3+ and Er 3+ . The upconverted emission reached the highest as x =3.6, and was pump-power dependent involving a two-photon process.