Novel Hydrogen-Bonding Cross-Linking Aggregation-Induced Emission: Water as a Fluorescent “Ribbon” Detected in a Wide Range

The development of efficient sensors for detection of the water content in a wide detection range is highly desirable for balance in many industrial processes and products. Presented herein are six novel different substituted Schiff base Zn­(II) complexes, which exhibit the remarkable capability to detect traces of water in a wide linear range (most can reach 0–94%, v/v), low detection limit of 0.2% (v/v), and rapid response time of 8 s in various organic solvents by virtue of an unusual water-activated hydrogen-bonding cross-linking AIE (WHCAIE) mechanism. As a proof-of-concept, the WHCAIE mechanism is explained well by single X-ray diffraction, absorption spectra, fluorescence spectra, dynamic light scattering, 1H NMR spectra, and theoretical calculations. In addition, the molecules demonstrated their application for the detection of humidity (42–80%). These Schiff base Zn­(II) complexes become one of the most powerful water sensors known due to their extraordinary sensitivity, fast response, and wide detection range for water.