Recent advances in carbon dots-based chromatographic separation materials

Chromatographic column is the core of chromatographic separation, and chromatographic separation material is considered the soul of the chromatographic column. The type and characteristics of the chromatographic separation material directly determine the separation mode and performance of chromatographic columns. The development and preparation of separation materials with novel structures and good separation performance is an ongoing hotspot in chromatography research. Given rapid developments in nanoscience and technology, nanomaterials with unique surface functional groups and large specific surface areas have attracted extensive attention and great interest from researchers in the field of separation science. Carbon dots (CDs), a new type of zero-dimensional fluorescent carbon nanomaterials, have been widely used in bioimaging, light-emitting diodes, sensing, catalysis, drug delivery, and other applications since they were first reported in 2004. These nanomaterials present several advantages over other types of separation materials, including a simple preparation process, low toxicity, easy functionalization, excellent biocompatibility, and photobleaching resistance. In addition, compared with traditional carbon nanomaterials such as graphene and carbon nanotubes, CDs have abundant surface functional groups, nanoscale sizes, and moderate adsorption properties. Hence, when CDs-based new materials are applied as a stationary phase for column chromatography, they can provide rich reaction sites and ensure the uniformity of the chromatographic packing process. The use of CDs can effectively avoid the peak-tailing phenomenon caused by the strong interaction of large pi-conjugated systems with some analytes and improve the efficiency of the chromatographic column. As such, these nanomaterials show good application prospects in the field of chromatographic separation. In this review, the development history, classification, and synthesis strategies of CDs are briefly described. We then focus on the development of CDs-based chromatographic separation materials by systematically reviewing the recent advances in the use of CDs-based materials as a stationary phase for high-performance liquid chromatography (including hydrophilic interaction, reversed-phase, mixed-mode, and chiral chromatography), gas chromatography, and capillary electrochromatography, with special emphasis on the preparation methods and applications of various stationary phases. Finally, the development prospects of CDs and future research efforts on these materials are also analyzed and discussed. This review can provide guidance on the rational design and application of new CDs-based chromatographic separation materials.