Regulating the luminescence of tetraphenylethene (TPE)-based lanthanide nanoparticles in the presence of organic amines/acids

Abstract

Two novel lanthanide-based energy transfer systems were established by the combination of a single ligand with aggregation-induced emission (AIE) properties or dual ligands with AIE and aggregation-caused quenching (ACQ) behaviors and poly(styrene sulfonic acid) sodium salt (PSS)-coated EuVO₄ nanoparticles, respectively, in which 4-methyl-1-(4-(1,2,2-triphenylvinyl)benzyl)pyridin-1-ium bromide (TPE-Py-Me) was selected as the AIE ligand and 4,4,4-trifluoro-1-phenyl-1,3-butanedione (ABM) behaved as the ACQ ligand. In both systems (TPE-Py-Me@PSS@EuVO₄ nanoparticles and TPE-Py-Me@PSS/ABM@EuVO₄ nanoparticles), the TPE motif was immobilized and its AIE luminescence was activated due to the electrostatic interaction between PSS and TPE-Py-Me. However, the emission peak located at 614 nm assigned to the typical emission of Eu³⁺ in TPE-Py-Me@PSS/ABM@EuVO₄ nanoparticles enhanced significantly when compared with TPE-Py-Me@PSS@EuVO₄ nanoparticles, owing to that ABM was a more effective sensitizer. Excitingly, two materials show different luminescence responses to organic amines and acids, respectively. In the presence of several amines, TPE-Py-Me@PSS@EuVO₄ nanoparticles have potential for application in detecting aniline, for which a unique peak located at 370 nm associated with the π–π interaction between PSS and aniline appeared. Differently, TPE-Py-Me@PSS/ABM@EuVO₄ nanoparticles can sensitively identify the citric acids among several organic acids, wherein the intensity of Eu³⁺ emission declined and the AIE behaviour of the TPE motif remained unchanged. This discovery may provide a facile approach to design and prepare more promising candidates as tunable optical composite materials.