Study On Synthesis And Properties Of Multi-color Chiral Carbon Dots And Their Composite Materials

Chirality is one of the most remarkable characteristics of nature,and is important in areas of chemistry,physics,biology and medicine.The outstanding properties of carbon dots(CDs),including biocompatibility,low toxicity,photoluminescence,and easy synthesis and modification,make them strong competitors to traditional semiconductor quantum dots.The application of chirality to CDs generates a new class of potentially valuable CDs materials,chiral CDs(Ch-CDs),that may be useful in areas such as enantiomeric recognition and separation,chiral catalysis,bioimaging,and biomedicine.At present,the emission wavelengths of Ch-CDs are concentrated in the blue-green light region,and no reports involve the challenging preparation of redemitting and wavelength-tunable Ch-CDs.In recent years,Ch-CDs composite materials have developed vigorously and have important applications in many fields.The heterostructure of all-inorganic halide perovskite quantum dots also exhibits many unique properties.However,the heterostructure integration of Ch-CDs with the CsPbBr3 nanocrystals has not yet been explored.In response to these urgent problems,this article will conduct in-depth research on the preparation of long-wavelength ChCDs,photoluminescence tunable Ch-CDs and chiral CDs-CsPbBr3 perovskite quantum dots heterostructures.The specific work is as follows:(1)A two-step synthesis method was used to prepare Ch-CDs with red emission.Precursors with conjugated structure(o-phenylenediamine)were selected,and the carbonization of H2SO4 was used to prepare achiral carbon core with red emission.Then modified with the chiral ligand alanine,Ch-CDs with red emission were prepared.The emission wavelength was at 603 nm,the full width at half maximum(FWHM)was 39.5 nm,and the quantum yield was 46.03%.(2)A one-step synthesis method was used to prepare multi-color Ch-CDs and endow them with corresponding circularly polarized luminescence.The synthesis of red-and multi-color emitting Ch-CDs using the common precursors L-/D-tryptophan and o-phenylenediamine and a solvothermal approach at one temperature.The quantum yield of the Ch-CDs was between 31%and 54%.Supramolecular self-assembly provided multi-color-emitting Ch-CDs showing novel circularly polarized luminescence,with the highest dissymmetric factor(glum)of-1 × 10-2.Importantly,circularly polarized white-emitting CDs were fabricated for the first time by tuning the mixing ratio of the three colored Ch-CDs in a gel.Our strategy affords exciting opportunities for designing functional chiroptical materials.(3)The room temperature ligand assisted reprecipitation method was used to prepare the chiral CDs-CsPbBr3 heterostructure.Ch-CDs was prepared by hydrothermal method using L-/D-serine as precursor.The emission peak of chiral CDsCsPbBr3 heterostructure is at 515 nm,the quantum yield is 89.87%,and it has excellent photoluminescence properties and special chiroptical properties.