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BACKGROUND Owing to their small particle size, good stability against photobleaching, high fluorescence stability, tunable fluorescence emission, easy surface functionalization, low toxicity and excellent biocompatibility, carbon dot (CD) has been widely applied in many fields including catalyst, cell imaging, drug delivery, fluorescence detection and photoelectronic devices. In recent years, synthetic methods for preparing high-performance fluorescent CD using different raw materials have attracted much attention. In addition, detection of trace metal ions by a fluorescent probe has been rapidly developed and widely used. The fluorescent probe can be constructed thus:the CD directly interact with the target analyte, the CD modified by the specific ligand interact with the target analyte, and the CD forming a complex with other substances interact with the target analyte. OBJECTIVES To provide references for researchers to synthesize CD and construct fluorescent probes based on CD for the determination of trace metal ions in complex samples. METHODS The optical properties and synthetic raw materials of CD were described. The process and characteristics of the commonly used top-down and bottom-up methods were summarized. The application progress of fluorescent probes constructed by the three interaction modes between CD and target analytes for the determination of biochemical reaction ions, Fe3+, Zn2+ and Cu2+, and other heavy metal ions such as Hg2+, As3+, Pb2+, Cr6+ and Cd2+ were reviewed. RESULTS Different raw materials had been utilized for synthesizing CD with different properties. The prepared CD were used to construct fluorescent probes for the determination of micro metal ions with high selectivity and sensitivity. CONCLUSIONS Further research on the determination mechanisms, development of new detection modes, construction of fluorescent probes for specific metal ions and sample components, and establishment of analytical methods, which can be applied to complex samples are the challenges and development orientation of the fluorescent probes based on CD.

Two new lignans, dolichanthin A (1) and dolichanthin B (2), were isolated from the EtOAc extract of Wikstroemia dolichantha. Their structures were elucidated by the analysis of 1D and 2D spectroscopic data as well as MS. The inhibitory activity of two isolates against acetylcholinesterase (AChE) revealed that compound 1 exhibited weak inhibitory activity. [ABSTRACT FROM AUTHOR]

Capillary electrochromatography (CEC) has received increased attention from the academic community because it combines the excellent selectivity of high performance liquid chromatography (HPLC) and the high efficiency of capillary electrophoresis (CE). Selecting the most appropriate stationary phase material is crucial to achieve better separation effects in CEC. In recent years, a considerable number of materials, such as graphene oxide, proteins, metal organic frameworks, and covalent organic frameworks (COFs), have been widely used as stationary phases in CEC to further improve its separation performance and extend its scope of potential applications. Among these materials, COFs have shown great application prospects in CEC owing to their unique properties, which include high porosity, large surface area, excellent stability, tunable pore size, and high designability of the framework structure. This review systematically summarizes published papers on the development and application of COFs in CEC from 2016 to 2023. First, two COF-based capillary columns (i. e., open-tube CEC columns and monolithic CEC columns) and their preparation methods are introduced. Second, the applications of CEC based on COF stationary phases in the separation of environmental endocrine disruptors, pesticides, aromatic compounds, amino acids, and drugs, particularly chiral drugs, are systematically summarized. The separation mechanism of CEC based on COF stationary phases is also introduced. At present, the good separation ability of COF-based CEC is mainly attributed to two factors: 1) The size exclusion effect of the pores of the COF stationary phase. Because of differences in the sizes of their organic molecular building units and side chains, COFs have varying pore sizes and topological structures. Thus, target analytes smaller than the pores of the COFs can enter the frameworks and interact with them during separation. On the other hand, target analytes larger than the pores of the COFs cannot enter the frameworks and interact with them during separation; thus, they can be separated. 2) The interactions between the target analytes and side chains (e. g., hydrophobic interactions, hydrogen bonding, π-π interactions, etc.) of the COFs. Since COFs usually contain alkyl side chains, aromatic structures, and oxygen and/or nitrogen atoms with high electronegativity, various interactions could occur between the COFs and target analytes. Finally, directions for the future development and strategic application of CEC based on COF stationary phases are proposed. We believe that future research in CEC based on COF stationary phases should focus on the following aspects: 1) The use of cheminformatics to design and construct COFs to improve the efficiency of COF capillary column preparation; 2) the development of milder methods to synthesize COFs that can meet the requirements of high performance COF capillary columns; and 3) in-depth research to explore the separation mechanism of CEC based on COF stationary phases to provide theoretical guidance for developing CEC methods suitable for the separation and analysis of complex samples.