Self-Assembly Fluorescent Cationic Cellulose Nanocomplex via Electrostatic Interaction for the Detection of Fe³⁺ Ions

In this work, an aggregation-induced emission (AIE) sensor for the detection of Fe³⁺ ions was fabricated through the electrostatic interaction between 1,1,2-triphenyl-2-[4-(3-sulfonatopropoxyl)-phenyl]-ethene sodium salt (SPOTPE) and quaternized cellulose (QC). The structure and properties of the SPOTPE/QC nanocomplex were studied by using ¹H NMR, spectrofluorophotometer, transmission electron microscopy (TEM), and dynamic laser light scattering (DLS). An aqueous solution of SPOTPE and QC resulted in a remarkably enhanced cyan fluorescence in comparison to that of the SPOTPE solution. Strong through-space electrostatic interaction between SPOTPE and QC is the main cause for the fluorescence emerging. The fluorescence of the SPOTPE/QC solutions show good stability over a wide pH range of 5.0⁻10.0. When introducing Fe³⁺ ions into the SPOTPE/QC solution, the fluorescence quenched within 5 s. SPOTPE/QC solutions exhibited high selectivity and sensitivity for the detection of Fe³⁺ ions with ignored interferences from other ions, and the detection limit was determined to be 2.92 × 10^-6 M. The quenching mechanism was confirmed to be the consequence of the binding interactions between Fe³⁺ ions and SPOTPE/QC complex.