PH response luminescence reversible lanthanide-2,6-pyridinedicarboxylic acid complex with tunable multi-color and white light emission for fluorescent anti-counterfeiting labels and LED

Abstract

Lanthanide-2,6-pyridinedicarboxylic acid complex (DPA-Lanthanide) is a simple complex, and its structure has been reported by many researchers. However, people often overlook the luminescence properties of DPA-Lanthanide because of its simple structure and 2,6-pyridinedicarboxylic acid (DPA) as a smaller ligand. In this work, we synthesized a series of DPA-Lanthanidex complexes (1-14) by a simple hydrothermal method, and studied their luminescence properties. We have found that DPA-Lanthanide complexes with either single rare earth ions or double rare earth ions have good fluorescence emission properties. Among them, by changing the ratio of Eu3+ to Tb3+ in the DPA-Lanthanide complex of double rare earth ions can tune the color of fluorescence emission. Fluorescence emission of diversified colors can be obtained. In particular, DPA-Dy (14) can achieve single-component white light emission under 296 nm excitation, and emit blue fluorescence under 375 nm excitation. Because DPA-Lanthanide complexes have strong fluorescence emission intensity, long life, good color rendering, and good heat resistance, they have achieved good results in applications such as fluorescent anti-counterfeiting and LEDs. Interestingly, we found that the fluorescence emission intensity of DPA-Lanthanide complexes is not only affected by pH, but this effect is reversible. Moreover, it is interesting that the color of the emition light of DPA-Eu + Tb (7) changes with the influence of pH. This opens up possibilities for pH sensing.