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

Abstract

Throughout this research, a unique optical sensor for detecting one of the most dangerous heavy metal ions, Cu(II), was designed and developed. The (4-mercaptophenyl) iminomethylphenyl naphthalenyl carbamate (MNC) sensor probe was effectively prepared. The Schiff base of the sensor shows a “turn-off” state with excellent sensitivity to Cu(II) ions. This innovative fluorescent chemosensor possesses distinctive optical features with a substantial Stocks shift (about 114 nm). In addition, MNC has remarkable selectivity for Cu(II) relative to other cations. Density functional theory (DFT) and the time-dependent DFT (TDDFT) theoretical calculations were performed to examine Cu(II) chelation structures and associated electronic properties in solution, and the results indicate that the luminescence quenching in this complex is due to ICT. Chelation-quenched fluorescence is responsible for the internal charge transfer (ICT)-based selectivity of the MNC sensing molecule for Cu(II) ions. In a 1:9 (v/v) DMSO-HEPES buffer (20 mM, pH = 7.4) solution, Fluorescence and UV-Vis absorption of the MNC probe and Cu(II) ions were investigated. By utilizing a solution containing several metal ions, the interference of other metal ions was studied. This MNC molecule has outstanding selectivity and sensitivity, as well as a low LOD (1.45 nM). Consequently, these distinctive properties enable it to find the copper metal ions across an actual narrow dynamic range (0–1.2 M Cu(II)). The reversibility of the sensor was obtained by employing an EDTA as a powerful chelating agent.

SERS detection of dopamine using metal-chelated Ag nanoshell

“…[40][41][42] Moreover, a decrease in the absorption peak from 785 nm to 734 nm suggests the formation of a bond between copper and dopamine. 43 Similar to the previously reported study results, 39,[44][45][46] these spectral changes indicate the formation of metalchelation bonds between copper and dopamine.…”

Strategies for Improving Selectivity and Sensitivity of Schiff Base Fluorescent Chemosensors for Toxic and Heavy Metals

“…The coordination between the Schiff base's cation and the imine group disrupts the fluorescent properties. This quenching effect can arise due to energy transfer, electron transfer, or other quenching mechanisms associated with coordination with the hazardous cation [45]. (3) Fluorescence Recovery: The fluorescence quenching of the Schiff base upon cation binding provides the basis for sensing hazardous cations.…”

Lanthanide‐Based Single‐Chain Nanoparticles as “Visual” Pass/Fail Sensors of Maximum Permissible Concentration of Cu2+ Ions in Drinking Water

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