Preparation of Large Conjugated Polybenzimidazole Fluorescent Materials and Their Application in Metal Ion Detection

Preparation of fluorescent polyurethane microspheres and their applications as reusable sensor for 4-nitrophenol detection and as microplastics model for visualizing polyurethane in cells and zebrafish

Fluorescent microspheres are of significant interests due to their wide applications in biotechnology fields. However, their preparation presents several challenges, such as the need for dye labeling, the complexity of materials and often sophisticated preparation conditions. Here a simple process for hydrophilic and crosslinked polyurethane (CPU) microspheres, with carboxyl groups on the surface via one-step precipitation polymerization in 40 min, is presented. The microsphere size is easily adjusted by varying experimental conditions. CPU microspheres exhibit high thermal and pH stability with good redispersibility in water, and emit fluorescence without any modification or dye labeling. The emission mechanism is discussed. CPU microspheres are used as fluorescent probe to detect 4-nitrophenol (4-NP) based on their emission in UV light region, with excellent selectivity and sensitivity. In addition, they are reusable with detection limit unchanged after 7 cycles of reuses, a significant feature of this work. The mechanism of fluorescence detection is thoroughly explored and ascribed to the internal filtration effect. Based on the emission in visible light region, CPU microspheres are used as a model of PU microplastics (MPs) to visualize their biodistribution in HeLa and macrophage cells, as well as in zebrafish larvae, providing a reliable tracer for the visualization and tracking of PU MPs in organisms.

Incorporation of Rhodamine into a Host Polymer via In-Situ Generated Isocyanato Group and Application for the Detection of Cu2+ Ion

A rhodamine-based fluorescent polymer P(MMA-co-RB) has been synthesized via an intermediate NCO-containing polymer generated by the Lossen rearrangement reaction. The fluorescent property of P(MMA-co-RB) with regard to metal ions, such as Cu2+, Fe3+, Cr3+, Al3+, Zn2+, Co2+, Sn2+ and Ag+, was studied by fluorescence emission spectroscopy. The results demonstrate that the fluorescence intensity of P(MMA-co-RB) decreased gradually with an increase of the concentration of Cu2+ ion. Furthermore, a test strip made of P(MMA-co-RB) can be used for fast and quantitative determination of Cu2+ ion. In the presence of Cu2+ ion, the sensory tester undergoes distinct changes in fluorescence intensity and visible color.