Synthesis Of Anthraquinone-based Long-wave High-brightness Carbon Dots And Their Applications

Long-wave carbon dot（CD）have gained much attention for their excellent performance in low-power illumination,high-resolution flexible displays,and ultra-sensitive multimodal bio/chemical detection.Long-wave CD are generally derived from their internal macroconjugated structures,and the precursors with macroconjugated structures retain their electron-dissociation properties（or structures）due to the"precursor memory"effect in carbon dot synthesis,so polycyclic or dense-ring compounds with macroconjugated structures such as anthracene,phenanthrene,pyrene,biphenyl,etc.are mostly used in the synthesis of long-wave CD.In this paper,three anthraquinone-based CD with long wavelength and high fluorescence quantum yield were prepared by solvent thermal and solvent-free methods;the anthraquinone-based CD were characterized by transmission scanning electron microscopy（TEM）,infrared spectroscopy,ultraviolet spectroscopy,Raman spectroscopy and X-ray photoelectron spectroscopy（XPS）,and the luminescence mechanism and the effect of graphitization degree on the fluorescence quantum yield of anthraquinone-based CD were investigated;finally It was applied to ion detection,pesticide detection,coating indication and dynamic encryption anti-counterfeiting as follows:（1）Green fluorescent CD with high fluorescence quantum yield（41.3%）was prepared by solvothermal method using 1,4-dihydroxyanthraquinone as a precursor.using the switching effect of this CD fluorescence on Cu²⁺and glyphosate（GP）,an ultra-sensitive GP nanosensor with a low detection limit of 0.8 ng·m L^-1 and good selectivity was prepared and used for GP residue detection on vegetable surface The construction of the ultrasensitive glyphosate sensor and the preparation of the smart package provide new exploration and ideas for the application of carbon dots in food and environmental safety.（2）A red（600 nm）carbon dot with high fluorescence quantum yield（42.83%）and narrow half-peak width（33 nm）was synthesized in one step by solvent-free method using rhodopsin as the precursor;the good quenching effect of Fe³⁺on the CD fluorescence was found,and a fluorescent probe was constructed for the detection of Fe³⁺with a low detection limit of 0.026μg·L^-1;meanwhile,using the sensitive variation of this CD in p H=6-8 The sensitive variation of this CD in the range of p H=6-8 was used to prepare microspheres by combining CD with PMMA,and the application of damage self-indicating smart coating of CD was developed.The high fluorescence quantum yield and narrow half-peak width of CD were found based on the characterization results of IR mapping,Raman mapping,XPS,etc.The high graphitization（I_D/I_G=0.96）and the hydrogen bonding formed by a large number of amino and carboxyl groups on the surface of CD may be the reason for the high fluorescence quantum yield and long wavelength emission of CD.This part of work accumulates new experiences and additions to the synthesis method,luminescence mechanism and detection and damage application of CD.（3）The orange-red fluorescent CD with high yield（60%）and ultra-high quantum yield（91.47%）was prepared in one step by solvent-free method using 1,5-diamino-4,8-dihydroxy-9,10-anthracenedione（DAQ）and acetamide as carbon and nitrogen sources;the resulting CD fluorescence was found to have H⁺/OH^-reversible redshift effect,and this optical feature was utilized to apply it to red LED and dynamic information encryption anti-counterfeiting;based on the characterization of TEM and IR spectra,it was confirmed that the addition of H⁺to CD led to the protonation of amino groups in the amide and then the formation of O=C=N intermediate transition state under the electron-induced effect,resulting in the red-shift of CD;according to the analysis of the results of Raman spectroscopy,XPS mapping,and IR spectroscopy,it was concluded that the high graphitization（I_D/I_G=0.73）was the high fluorescence quantum yield of this CD the main reason.