Two-Step Synthesis of a Pullulan-Derived Polymeric Fluorophore with Metal Ion Sensing Abilities

Metal ions, which are naturally occurring in food, soil, and water, are present in every part of the environment. Therefore, it is imperative to identify those using accessible and economical methods. In this study, a novel two-step chemical modification process for pullulan, a natural polymer, is presented. This process yields a macromolecular derivative with considerably increased fluorescence, enabling efficient detection of specific metal ions. Furthermore, the recently synthesized polymer displays distinctly divergent characteristics in comparison with the native pullulan, a consequence of the undergone chemical reactions. These include the existence of fluorescence and solubility in organic solvents, which are lacking from the initial polymer. Subsequent to exhaustive thermal and spectral analysis, the synthesized polymer's capacity to discern disparate metal ions is investigated. The interaction between metal ions and the pullulan derivative is monitored to ascertain the extent of fluorescence quenching during this process. The synthesized polymer exhibits the greatest sensitivity to Fe³⁺ and Cu²⁺ among the various cations that are examined, while Pb²⁺ and the other ions demonstrate satisfactory results. The paper also discusses the underlying quenching mechanism and possible future applications.