Microwave-Assisted Synthesis of Carbonized Polymer Dots as Fluorescent Probes for Temperature and Nitrite Ion Detection

The widespread presence of nitrite ions in the environment and food poses significant health risks, as they can be converted into potent carcinogens within the human body. Therefore, the accurate detection of nitrite ions is imperative for safeguarding public health and safety. A new type of thermosensitive blue carbonized polymer dots (B-CPDs) were prepared from p-aminophenol and citric acid using microwave process. B-CPDS has a very small nanoscale size and the fluorescence quantum yield was 18.68%. On the basis of the internal filtration effect (IFE), the B-CPDs can be used as a fluorescent probe for the selective detection of nitrite ions with a detection limit as low as 1.05 μM. Under the irradiation of 365 nm ultraviolet light, the brightness and color of the blue fluorescent probe changed with the incorporation of different levels of nitrite. These changes can be directly observed with the naked eye and can be used for qualitative and semiquantitative analysis of nitrite content. The developed fluorescent sensor provides an effective, simple, rapid and low-cost analytical method for sensitive and intuitive detection of nitrite in the aqueous environment. In addition, the fluorescence is reversible and reproducible over the temperature range of 20–80 °C, and has the potential to be used as a temperature sensor.