Ultrasensitive visual detection of hydrazine hydrate using a Au nanoparticles-based colorimetric sensing system (ANCSS) is reported for the first time, which is based on the hydrogen bonding recognition and the modality change of hydrogen bonding from “linear” (simple hydrogen bond interactions) to “nonlinear” (a complicated hydrogen bond network) between as-modified Au nanoparticles (Au NPs).

A polyhedral oligomeric silsesquioxanes (POSS) modified 8-hydroxyquinoline derivative (denoted as Q-POSS) was synthesized and used as a ligand to coordinate with lanthanide ions to obtain a series of lanthanide complexes Ln(Q-POSS)₃ (Ln = Er³⁺, Yb³⁺, Nd³⁺). The as-prepared lanthanide complexes have been characterized by FT-IR, UV–Vis, and elemental analysis. All these complexes showed the characteristic near-infrared (NIR) luminescence originated from the corresponding lanthanide ions under excitation. Compared with the unmodified counterparts LnQ₃ (HQ = 8-hydroxyquinoline), the Ln(Q-POSS)₃ complexes showed obviously increased emission intensity, which was ascribed mainly to the steric-hindrance effects of the POSS moiety in the ligands. It is believed that the POSS group could suppress undesired excimer formation and intermolecular aggregation, thus decreasing the concentration quenching effect of the corresponding lanthanide complexes.