Temperature-modulated porous gadolinium micro-networks with hyperchrome-enhanced fluorescence effect

Porous and luminescent functional materials having well-controlled morphology are crucial in the field of adsorption, catalysis, and drug release. Herein, we propose the mechanism of hyperchrome-enhanced fluorescence (HEF) for the synthesis of highly fluorescent gadolinium micro-networks (Gd-MNs) via a facile one-pot hydrothermal treatment of almost non-luminescent Gd³⁺ ions / citric acid (Gd³⁺/CA) complexes. It is found that after high-temperature polymerization, a strong π-π* transition occurs in the Gd-MNs, which significantly enhances the absorption of light. So, our proposed HEF effect as a new photoactivation strategy can efficiently improve the fluorescence (FL) emission of optical materials by creating a large π-conjugated structure. Surprisingly, the FL of Gd-MNs is 152 times higher compared to that of Gd³⁺/CA complexes. In particular, porous Gd-MNs (P-Gd-MNs) having tunable porosity can be obtained by changing the reaction temperature, as the formation of the porous structure is strongly dependent on the release of H₂O molecules, coordinated with Gd³⁺ ions. Because of their porous structure and good FL properties, P-Gd-MNs is an ideal material for white light-emitting diodes (WLEDs) with adjustable correlation color temperature, by embedding fluorescent carbon dots into their pores. Besides, P-Gd-MNs can also be transformed into a peroxidase-like catalyst by directly reducing the Cu²⁺ ions of the porous surface. Moreover, Cu coated P-Gd-MNs can also be used for catalysing the degradation of rhodamine 6G dye with a degradation efficiency of about 100%. Hence, the facile synthesis of P-Gd-MNs opens new avenues for its potential applications in WLEDs fabrication and biocatalysis.