Preparation and L-Tryptophan sensing performance of Tb³⁺ decorated fluorescent MOF

Abstract

For selectively sensing Tryptophan(Trp), the fluorescent Tb3+@UiO-66-(COOH)2 was prepared through loading Tb3+ into UiO-66-(COOH)2 via post-synthesis method. Transmission electron microscope (TEM), X-ray powder diffractometer (XRD), specific surface area analyzer, and X-ray photoelectron spectroscope (XPS) were used to analysize the morphology, composition and pore characteristics of the porous materials. Meanwhile, ultraviolet-visible spectrophotometer (UV-Vis) and fluorescence spectrophotometer were used to study the fluorescence characteristics. The results show that the energy transfer from organic ligand to Tb3+ leads to a bright green fluorescence. Among the 13 amino acids, only Tryptophan has obvious fluorescence quenching effect. This is because there appears a large overlap between UV-Vis absorption spectrum of Trp and excitation spectrum of the MOF, which indicates a strong competition effect for UV light. The absorption to UV light of Tb3+@UiO-66-(COOH)2 is decreased by Trp,leading to the weak fluorescence. Further investigation indicates the material can sensitively sense Trp (LOD, 5.53 μmol/L) and owns excellent anti-interference ability from other co-existing amino acids. Thus, this work not only demonstrates Tb3+@UiO-66-(COOH)2 can serve as a selective and sensitive sensor for Trp, but also provides a guideline for designing novel sensors for amino acids in the future.

Keywords

• metal-organic framework
• post-synthesis modification
• tryptophan
• fluorescence quenching