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.

Perfluorooctane sulfonate (PFOS), a ubiquitous persistent organic pollutant, has aroused growing concern due to its adverse effects on human health.

The modern surfactant industry demands more efficient and environmentally friendly products as environmental regulations become more stringent. Amino acid Gemini surfactants (AAGSs), as the emerging green surfactants of amino acid surfactants, together with the Geminis, which consist of two or more amphiphilic moieties chemically linked by a spacer group, are the most reliable of these efficient green chemicals. With the diversity of structure and topological configuration of the spacer group, AAGSs have stronger aggregation ability and multifarious molecular configuration and aggregation morphology. They are used in various fields such as pharmaceuticals, biomedicine, daily chemicals, oil recovery and environmental treatment. This review contains detailed discussions on the synthesis of AAGSs from natural and non-natural sources using reactions such as Hofmann alkylation and Schotten-Baumann condensation. The physicochemical properties such as low CMC, good emulsification, different micelle forms, high biodegradability, antibacterial ability and biocompatibility are presented. Future research directions of AAGSs are also suggested, including their optimized synthesis, clarification of structure-performance relationships, and exploration of new applications in a wider range of fields.