A Naked Eye and Turn‐On Fluorescence Detection of Zn 2+ Ion by Imidazole‐Quinoline‐Based Fluorophore and Its Application in Live‐Cell Imaging

Imidazole Compounds: Synthesis, Characterization and Application in Optical Analysis

Imidazole is a five-membered heterocyclic ring containing three carbon atoms, two nitrogen atoms, and two double bonds. Among two nitrogen atoms, one of which carries with a hydrogen atom is a pyrrole-type nitrogen atom, another is a pyridine type nitrogen atom. Hence, the imidazole ring belongs to the π electron-rich aromatic ring and can accept strong suction to the electronic group. Moreover, the nitrogen atom of the imidazole ring is coordinated with metal ions to form metal-organic frameworks. In recent years, because of imidazole compounds' unique optical properties, their applications have attracted more and more attention in optical analysis. Thus, this review has summarized the synthesis, characterization, and application with emphasis on the research progress of imidazole compounds in optical analysis, including fluorescence probe, colorimetric probe, electrochemiluminescence sensor, fiber optical sensor, surface plasmon resonance, etc. This paper will suggest the direction for the development of imidazole-containing sensors with high sensitivity and selectivity.

Thiophene-phenylquinazoline probe for selective ratiometric fluorescence and visual detection of Fe(iii) and turn-off fluorescence for I- and its applications

A 2,5-bis(4-phenylquinazolin-2-yl)thiophene (BQT) probe is designed, synthesized and explored for selective ratiometric fluorescence and visual detection of Fe³⁺ and as a turn-off fluorescence probe for I^- anion. BQT is colorless and has blue emission in CH₃CN solution. BQT selectively complexes with Fe³⁺, turns its solution from colorless to greenish yellow and enables the ratiometric sensing of Fe³⁺ with limit of detection (LOD) and limit of quantitation (LOQ) of 2 × 10^-8 M and 6.1 × 10^-8 M, respectively. Binding constant of BQT with Fe³⁺ is found to be 4.1 × 10^-4 M^-1. BQT is also able to sense I^- anion present in aqueous solution by selectively turning colorless to yellow and fluorescence quenching with a LOD of 1.7 × 10^-7 M and LOQ of 5.2 × 10^-7 M. BQT sensing ability is not influenced by the presence of other metal ions and anions in the vicinity. The BQT-Fe³⁺ complex is thoroughly characterized using MALDI-TOF, NMR and Job's plot. A reversibility experiment with EDTA suggests BQT is a reversible fluorescent chemosensor for Fe³⁺ ions. The spectroscopic data of BQT and its complexes are employed to construct a field test kit for qualitative analysis and INHIBIT logic gate.