Ultrasensitive Colorimetric and Ratiometric Detection of Cu²⁺: Acid-Base Properties, Complexation, and Binding...

Area of Science:

• Analytical Chemistry
• Materials Science
• Coordination Chemistry

Background:

• Development of selective and sensitive chemosensors is crucial for environmental monitoring and biological analysis.
• Copper ions (Cu²⁺) play vital roles in biological systems but can be toxic at elevated levels, necessitating accurate detection methods.

Purpose of the Study:

• To synthesize and characterize a new chemosensor, 5-(diethylamino)-2-(2,3-dihydro-1H-perimidin-2-yl)phenol (HL).
• To evaluate the efficacy of HL for the selective and sensitive detection of Cu²⁺ in aqueous methanol solutions.

Main Methods:

• Synthesis of HL via condensation of 4-(diethylamino)salicylaldehyde and 1,8-diaminonaphthalene.
• Spectrophotometric and spectrofluorometric measurements for sensing studies.
• Spectrophotometric pH titrations, high-resolution electrospray ionization mass spectrometry (ESI-HRMS), and Job's plot experiments for binding and speciation analysis.

Main Results:

• HL exhibits selective and ratiometric detection of Cu²⁺.
• Achieved a low limit of detection (LOD) of 3.7 nM for Cu²⁺ using spectrophotometry.
• Demonstrated naked-eye detection capability for Cu²⁺ at concentrations as low as 2.5 μM.
• Established a 1:1 stoichiometry for Cu²⁺ binding to HL.
• Tentatively assigned a square pyramidal coordination geometry for the Cu²⁺ complex.

Conclusions:

• The synthesized chemosensor HL is highly effective for the selective and sensitive detection of Cu²⁺.
• The sensor's dual detection modes (spectrophotometry and naked-eye) offer versatility.
• The findings contribute to the development of advanced analytical tools for copper ion determination.