A New, Extremely Sensitive, Turn-Off Optical Sensor Utilizing Schiff Base for Fast Detection of Cu(II)

Area of Science:

• Analytical Chemistry
• Materials Science
• Environmental Science

Background:

• Heavy metal ion detection is crucial for environmental monitoring and human health.
• Copper(II) ions (Cu(II)) are essential but toxic at elevated levels, necessitating accurate detection methods.
• Existing sensors often lack selectivity, sensitivity, or reversibility.

Purpose of the Study:

• To design and develop a novel optical sensor for the selective and sensitive detection of Cu(II) ions.
• To investigate the sensing mechanism using theoretical calculations.
• To evaluate the sensor's performance in real-world conditions.

Main Methods:

• Synthesis of the (4-mercaptophenyl) iminomethylphenyl naphthalenyl carbamate (MNC) sensor probe.
• Fluorescence and UV-Vis absorption spectroscopy for sensing experiments.
• Density Functional Theory (DFT) and time-dependent DFT (TDDFT) for theoretical analysis.
• Interference studies with various metal ions and reversibility tests using EDTA.

Main Results:

• The MNC sensor probe demonstrated a highly sensitive 'turn-off' fluorescent response to Cu(II) ions.
• The sensor exhibited excellent selectivity for Cu(II) over other common metal ions.
• Theoretical calculations confirmed that Internal Charge Transfer (ICT) is responsible for the luminescence quenching and selectivity.
• A low Limit of Detection (LOD) of 1.45 nM was achieved within a narrow dynamic range (0-1.2 µM Cu(II)).
• The sensor's reversibility was confirmed using EDTA.

Conclusions:

• The developed MNC sensor is a promising tool for the accurate and reliable detection of Cu(II) ions.
• Its unique optical properties, high sensitivity, selectivity, and reversibility make it suitable for environmental and biological applications.
• The combination of experimental and theoretical approaches provides a deep understanding of the sensing mechanism.