| As a rising star of fluorescent nanomaterials,carbon dots(CDs)have been sought after by scientific researchers because of its advantages such as simple synthesis,excellent fluorescence performance,low toxicity,and easy functionalization.In the past,researchers have obtained and reported a lot of CDs by using biological and chemical materials,but most of these CDs are with blue fluorescence.As is known to all,the biological tissue itself is easy to absorb short wavelength fluorescence strongly,and some proteins can even emit blue fluorescence itself,which makes detection subject to serious background interference and may greatly limits the application of CDs in biological aspects.At the same time,the long wavelength fluorescence has strong penetrating ability,which is more conducive to the application of CDs in the actual detection.Therefore,in order to make the CDs applicable to more fields,the preparation of long wavelength fluorescent CDs and the improvement of quantum yield are the focus of current research.In this paper,three kinds of long-wavelength fluorescent CDs were prepared,and their emission wavelengths were 520 nm,550 nm and 580 nm respectively,and different applications were realized according to the different characteristics of each CDs.Specific research contents are as follows:1.Using L-tartaric acid as carbon source and urea as nitrogen source,a new yellow luminescent carbon point(Y-CDs)was synthesized by solvothermal method.The YCDs emits yellow fluorescence at 550 nm wavelength under 450 nm excitation light with a quantum yield of 16.7%.At the same time,Y-CDs has excitation dependence,optical stability,and good dispersion.Y-CDs can effectively and selectively detect vitamin B12 in the range of 0～200 μM by fluorescence "off" phenomenon.There was a good linear relationship between the emission fluorescence intensity of Y-CDs and the concentration of vitamin B12.The correlation coefficient is 0.997,and the detection limit is 2.045 μmol/L.Furthermore,Y-CDs can be used as a cell imaging probe for MDA-MB-231 cells.The results show that Y-CDs can be used as a variety of probes and has a broad application potential in different biological studies.2.Using betaine hydrochloride and sulfadiazine as carbon sources,green carbon dots(G-CDs)were synthesized by simple green hydrothermal method.The G-CDs has excellent luminescence stability of excitation dependence and has different properties at different pH values,salt concentrations and temperatures.G-CDs can successfully detect Pb(Ⅱ)in the range of 0～200 μM.The concentration of Pb(II)showed a good linear relationship with the fluorescence intensity of G-CDs,the correlation coefficient was 0.993,and the detection limit was 3.0174 μmol L-1.Due to its good biocompatibility,G-CDs can be successfully applied to zebrafish imaging and cell imaging,and the results show that G-CDs is more suitable for zebrafish embryo imaging.The results showed that the obtained G-CDs could be used as a multifunctional probe and have a broad application potential in different biological research fields.3.A silicon-doped orange fluorescent carbon dots(O-CDs)was synthesized by hydrothermal method from o-phenylenediamine and ethyl orthosilicate.By doping silicon element,the quantum yield of the O-CDs is increased by 25%compared with the CDs without doping silicon element,and the quantum yield of the O-CDs is 64.10%.Different from other CDs,the O-CDs has good stability under different pH values,different temperatures,and different ionic environments.The O-CDs can be used as a fluorescent ink by adding glycerin for lubrication.When the O-CDs is used to write the code,it will emit orange luminescence.After acid treatment,the fluorescence will disappear,and after alkali treatment,the fluorescence will recover,to achieve the function of encryption and decryption.At the same time,the O-CDs can be prepared as phosphors and fluorescent hydrogels,showing good fluorescence effect under UV lamp. |
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