Highly stable lanthanide cluster-based luminescent materials constructed from β-diketone to 1,10-phenanthroline exhibiting ultrahigh photoluminescence and efficient pesticide detection

Abstract

Simultaneously enhancing the photoluminescence quantum yield (PLQY) to reach a considerable value (>90%) and stability of lanthanide complexes holds tremendous significance for their practical applications. Here, we have successfully synthesized two series of luminescent lanthanide clusters: Ln_2b (Ln = Eu for Eu_2b and Gd for Gd_2b) and Ln_2p (Ln = Eu for Eu_2p and Gd for Gd_2p). Structural analysis revealed that compound Ln_2b with a chromophore/metal ratio of 3 : 1 exhibited a weak intermolecular π–π interaction, while compound Ln_2p with a higher ratio (4 : 1) of chromophore to metal exhibited strong intramolecular and intermolecular π–π interactions. Compound Eu_2p had an ultrahigh PLQY of (96.6 ± 0.3)%, surpassing the PLQY ((49.5 ± 0.5)%) of compound Eu_2b, and exhibited high thermal and solvent stability. The temperature-dependent emission spectra showed that the emission intensity of compound Eu_2p and Eu_2p-doped PMMA film did not decrease with increasing temperature. The Eu_2p-doped white light emitter achieved an impressive PLQY of (75.5 ± 0.5)%, outperforming commercial phosphors. Furthermore, the luminescent probe results showed the highly selective and sensitive nature of compound Eu_2p for DCN (2,6-dichloro-4-nitroaniline) detection, and the lowest detection limit of 0.12 μM, meeting the detection requirements for environmental protection and food safety. In general, this study synthesized two multi-functional lanthanide cluster-based luminescent materials with ultrahigh quantum yield and high solvent stability. The increase in chromophore–metal ratio and the enhancement of intramolecular and intermolecular interactions have provided insight into the structure–function relationship and represent a promising strategy for fabricating luminescent devices based on lanthanide clusters.