Synthesis Of Nitrogen And Sulfur Co-Doped Carbon Dots Fluorescent Probes And Applications In Drug Detection And Temperature Sensing

As a rising star in the field of fluorescent nanomaterials,carbon dots,which have the advantages of excellent fluorescence performance,good biocompatibility and convenient preparation processes,are widely used in scientific research and application.Combined with other nanomaterials with mesoporous,fluorescent,and magnetic properties,the performance of composite materials is superior to that of single-component materials,further expanding the application range of carbon dots In recent years,carbon dots and their composites have made some progress in the research of drug analysis and detection,drug loading and delivery,biological imaging,disease diagnosis,temperature sensing and so on.But the application method of carbon dots in the field of medicine still needs further research and development.In this paper,a new type of nitrogen and sulfur co-doped carbon dots(cys-CD)was prepared,while its structure and fluorescence properties were discussed.Based on the fluorescence quenching effect of baicalein on carbon dots,a new method for determining baicalein was established.In addition,the capabilities of cys-CD in cell imaging had also been proven.Moreover,the prepared carbon dots were combined with rhodamine B to prepare core-shell nanospheres with good biocompatibility for high sensitivity ratiometric fluorescence temperature sensing.The specific research is as follows:1.Nitrogen and sulfur co-doped blue fluorescent carbon dot(cys-CD)was synthesized by an one-step hydrothermal method,using L-cysteine as a nitrogen source and sulfur source,sodium citrate dodecahydrate as a carbon source.Characterization of cys-CD showed that its particle size was about 3.8 nm,with good biocompatibility,stable fluorescence performance and high quantum efficiency(QE=66%).Cys-CD was successfully used to image SKOV-3 human ovarian cancer cells.After 6 h of incubation with cys-CD,both cytoplasm and nucleus had bright blue fluorescence.Based on the quenching of carbon dot fluorescence by baicalein,we designed a quick-response and sensitive baicalein quantitative detection method with good detection effect between baicalein concentration of 0 μM and 30 μM.The detection limit was as low as 33 nM.It was verified that the quenching mechanism of baicalein on carbon dot fluorescence is static quenching effect and internal filtration effect.The method was used for detection in actual samples with favorable recovery.2.The blue fluorescent cys-CD uniformly dispersed Gd(OH)CO3 was used as the core,and mesoporous silica with red fluorescent rhodamine B was used as the shell layer,a core-shell nanosphere Gd(OH)CO3-cys-CD@mSiO2-RhB with blue-red dual fluorescence emission under single excitation was constructed.It was known through a series of characterization methods that the nanospheres had a particle size of～600 nm with good dispersion and clear core-shell structure.Cell viability experiments proved that the nanospheres also had good biocompatibility.Using rhodamine B’s temperature-sensitive red fluorescence as a probe,and the thermally stable blue fluorescence as the internal standard after solidification of cys-CD,a novel dual-fluorescence temperature-sensing nanomaterial based on dual emission was constructed.The results showed that Gd(OH)CO3-cys-CD@mSiO2-RhB had excellent temperature sensing performance,with the wide application range(283 K-373 K),good sensitivity(Sa=2.01%K-1,Sr=1.39%K-1),high resolution(>0.012 K)and other characteristics,was expected to use as a new type ratiometric fluorescent temperature sensor for medical,pharmacy,biology and other research.