A nonsymmetrical salamo-like fluorescence chemical sensor for selective identification of Cu²⁺ and B₄O₇^2- ions and...

An innovative salamo-like fluorescent chemical sensor H₂L, has been prepared that can be utilized to selectively detect Cu²⁺ and B₄O₇^2- ions. Cu²⁺ ions can bind to oxime state nitrogen and phenol state oxygen atoms in the chemosensor H₂L, triggering the LMCT effect leading to fluorescence enhancement. The crystal structure of the copper(II) complex, named as [Cu(L)], has been achieved via X-ray crystallography, and the sensing mechanism has been confirmed by further theoretical calculations with DFT. Besides, the sensor H₂L recognizes B₄O₇^2- ions causing an ICT effect resulting in bright blue fluorescence. Moreover, the sensor has relatively high selectivity and sensitivity for Cu²⁺ and B₄O₇^2- ions, and the detection limits are 1.02 × 10^-7 and 2.06 × 10^-7 M, respectively. In addition, the good biocompatibility and excellent water solubility of the sensor H₂L make it very advantageous in practical applications, using H₂L powder for fingerprint visualization, using H₂L to identify the phenomenon of B₄O₇^2- ions emitting bright blue fluorescence, making it an ink that can print encrypted messages on A4 paper, in addition to this, based on H₂L, the real water sample was tested for Cu²⁺ ion recognition, and finally the test strip experiment was carried out.