Wavelength-shift-based visual fluorescence sensing of aspartic acids using Eu/Gd-MOF through pH triggering

Area of Science:

• Materials Science
• Analytical Chemistry
• Nanotechnology

Background:

• Existing luminescence sensors face limitations in meeting on-site detection demands due to self-reference capacities for non-analyte factors.
• Metal-organic frameworks (MOFs) are explored for luminescence sensing, but novel strategies are needed for improved performance.

Purpose of the Study:

• To develop a novel wavelength shift-based luminescence sensor for on-site detection.
• To design a sensor, Eu/Gd(TCPP), exhibiting dual-emission from Eu³⁺ ions and aggregation-induced emission (AIE) ligands H₄TCPP.
• To achieve sensitive and selective visual detection of acidic aspartic acid.

Main Methods:

• A simple, green, and fast plasma synthesis method was employed to prepare the Eu/Gd(TCPP) sensor.
• Characterization data were utilized to verify the luminescence switching mechanism.
• The sensor's short-range pH response property was leveraged for detection.

Main Results:

• The Eu/Gd(TCPP) sensor demonstrated dual-emission from Eu³⁺ and H₄TCPP ligands.
• A specific wavelength shift and visual color change (red to blue) were observed within a pH range of 4 to 3.
• The luminescence switching mechanism was attributed to H⁺-induced crystal structure collapse and ligand untwisting, hindering the antenna effect and restricting AIE.

Conclusions:

• The developed Eu/Gd(TCPP) sensor effectively utilizes wavelength shift and visual color change for pH detection.
• The sensor enables highly sensitive and selective on-site visual detection of acidic aspartic acid.
• The findings present a promising approach for developing advanced luminescence sensors for practical applications.