Preparation of Quantum Dot-Embedded Photonic Crystal Hydrogel and Its Application as Fluorescence Sensor for the Detection of Nitrite.

The development of fluorescence sensing platforms with excellent photoluminescence capabilities is of great importance for their further application. In this work, a photonic crystal structure was successfully applied to enhance the luminescence performance of fluorescent hydrogel, and the application of the obtained hydrogel as a fluorescence sensor was explored. A polystyrene photonic crystal template was constructed via vertical deposition self-assembly; then, the precursor solution containing polyethylenimine-capped CdS quantum dots (PEI-CdS QDs) and monomers filled in the gap of the template. After the polymerization process, the desired hydrogel was obtained. PEI-CdS QDs endowed the hydrogel with its fluorescence property, while interestingly, the photonic crystal structure showed a significant enhancement effect on the fluorescence-emission capability. The mechanism of this phenomenon was revealed. Moreover, this hydrogel could be used as a reusable fluorescence sensor for the detection of nitrite in water with good selectivity. The limit of detection was determined to be 0.25 μmol/L, which is much lower than the maximum limit for nitrite in drinking water.