Synthesis of Dual-Responsive, Highly Fluorescent, Non-Conjugated Polymer Dots for Fe³⁺ Detection

Non-conjugated polymer dots (NC-PDs) are a new class of fluorescent nanoparticles that show desirable properties such as high fluorescence, excellent brightness, high photostability, and synthesis simplicity. In this work, we synthesized highly fluorescent non-conjugated polymer dots by a hydrothermal method from polyester prepared from polyethylene glycol (PEG) and di-anhydride EDTA (DA-EDTA). The synthesized NC-PDs display strong blue fluorescence with a high quantum yield (QY) of 45% in water and more than 45% in different solvents such as ethanol, dimethyl sulfoxide (DMSO), N, N-dimethyl formamide (DMF), and acetone. The optical and structural characteristics of the PDs were investigated by UV-Vis spectrophotometry, fluorescence spectrophotometry, EDX, FTIR, and TEM. The PDs were utilized as a sensitive fluorescence probe for detecting Fe³⁺ ions in the range of 0-250 µM, demonstrating a low detection limit of 1.28 µM. The fluorescence intensity also declines with rising temperature, allowing the synthesized PDs to function as thermometers at 20 to 70ºC. The spike recovery test validated the efficiency of the proposed method for analyzing Fe³⁺ ions in tap water.