Construction of multicolor solid state fluorescence carbonized polymer dots from pyromellitic dianhydride by HCCC method and their multiple applications

In this research, four CPDs with different solid-state fluorescence were successfully synthesized through a one-step hydrothermal condensation cross-linking carbonization (HCCC) approach employing pyromellitic dianhydride (PMDA) and ethylenediamine (EDA) as the polymerization monomers. It was proposed that there are two competing reaction pathways in the formation stage of polymers, and regulation of reaction conditions can affect this competitive relationship to acquire CPDs with different solid-state fluorescence. The morphology and surface structure of four kinds of CPDs were characterized in detail using several characterization techniques. These four CPDs not only possessed small particle sizes of 1.83–2.36 nm, but also exhibited excellent fluorescence stability. Results displayed that CPDs-1, CPDs-2, CPDs-3, and CPDs-4 solid powders exhibited fluorescent yellow, yellow, brownish-yellow, and brown fluorescence under 365 nm UV lamp, which could fabricate fluorescent films and apply in LED devices. Interestingly, it was noticed that the modulation of the content of CPDs in CPDs/PVA composite films or the surface of LED chips could greatly adjust the color of composite film and LED light emission. In sensing studies, CPDs-2 could serve as fluorescence probe to construct a sensitive and selective sensor for the detection of luteolin, the linear range was 0–100 µM and the detection limit was 30 nmol/L. In practical sample analysis, the recovery rate and the RSD were 94.96 %–107 % and 0.54 %–3.52 %, respectively. In addition, CPDs-3 was used to construct a fluorescence sensing platform for the detection of water in the range of 0 % to 90 %. Moreover, as a potential nano-fluorescent probe, CPDs-2 showed low cytotoxicity and good biocompatibility in cancer cell imaging research and plant seed growth processes.