A near-infrared squaraine dye for cascade recognition of copper ion and biological phosphate and its application in IMPLICATION logic gate

A near-infrared fluorescent chemosensor based on squaraine has been synthesized, and its cascade recognition for copper ion, biological phosphate PPi, and amino acids has also been investigated by spectroscopic techniques. SQ-1 exhibits high selectivity and sensitivity for sensing Cu2+ over other metal ions by reversibly forming a [SQ-1-Cu2+] complex. By tandem ligand exchange, PPi and amino acids can remove Cu2+ from the complex and restore the spectral signal of SQ-1, which can be used for cascade recognition of these biologically active species. Notably, an IMPLICATION logic gate can be constructed based on this bifunctional chemosensing system. (C) 2016 Elsevier B.V. All rights reserved.