Bin Wang

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.

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

Glycidol‐modified polyethylenimine (PEI‐OH)‐capped carbon dots (PEI‐OH‐CDs) were prepared and applied for selectively and sensitively detecting folic acid in food samples. PEI‐OH‐CDs were firstly synthesized by a one‐pot hydrothermal method using PEI‐OH and citric acid as precursors, and the transmission electron microscopy characterization reveals that the PEI‐OH‐CDs were of spherical shape with diameters of 2–3 nm and well dispersed in solution. The PEI‐OH‐CDs have high fluorescence and exhibit ultrastrong stability against pH, ion strength, and UV light irradiation. In a wide pH range higher than pH 6, the fluorescence of PEI‐OH‐CDs can be effectively quenched by folic acid through static quenching process and inner filter effect but is not affected by many typical chemicals including cations, anions, amino acids, and vitamins. A good linear relationship was found between the F₀/F and the concentration of folic acid in the range from 0.1 to 100 μM, and the detection limit of folic acid is 0.07 μM. The PEI‐OH‐CDs were successfully applied for sensitive determination of folic acid in orange juice, fresh pear, grape spinach, and celery samples at pH 7.2, which is helpful to the stability of folic acid and provides a new strategy for accuracy detection of folic acid in food samples.

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.