Preparation Of Several Carbon-based Fluorescent Probes And Their Application

Compared with traditional light-emitting materials,carbon-based fluorescent nanomaterials are widely used in the fields of fluorescence sensing and biological imaging due to their unique light-emitting properties,excellent chemical stability,good biocompatibility and easily-modification.As a new type of fluorescent material,graphitic carbon nitride（g-C₃N₄）possesses various advantages such as low-cost,good biocompatibility,high quantum yield and excellent stability.Carbon quantum dots are superior in terms of aqueous solubility,functionalizability,resistance to photobleaching,toxicity,biocompatibility and exhibit broader photoluminescence profiles.In this paper,highly sensitive and selective fluorescent sensing platforms were constructed based on carbon-based fluorescent nanomaterials（graphitic carbon nitride or carbon quantum dots）for quantitative detection of nitro aromatic explosives and small biological molecules.The contents are mainly divided into the following four parts:1.In this work,a novel fluorescent sensor based on g-C₃N₄ nanofibers for the sensitive detection of dopamine（DA）has been proposed.We synthesized g-C₃N₄ nanofibers by directly hydrolyzing bulk g-C₃N₄ in the alkaline atmosphere（3 M Na OH）.The obtained ultrathin g-C₃N₄ nanofibers were verified by characterizations of Transmission electronic microscope（TEM）,X-ray diffractometer（XRD）,Fourier transformation-infrared（FT-IR）and X-ray photoelectron spectroscopy（XPS）.The obtained g-C₃N₄ nanofibers have an ultra-thin thickness and functional groups such as a hydroxyl group and an amino group.It was found that the fluorescence intensity of g-C₃N₄ nanofibers was obviously quenched by DA.Fluorescence resonance energy transfer（FRET）between DA and g-C₃N₄ nanofibers led to the fluorescence reduction of g-C₃N₄ nanofibers.The fluorescent probe of g-C₃N₄ nanofibers exhibits remarkable sensitivity for DA in the range of 0～20μM,and the limit of detection（LOD）value is lower to 17 n M.The fluorescent probe shows excellent stability,good selectivity and can be successfully applied in real samples with satisfactory recoveries.2.In this work,a highly sensitive and selective fluorescence sensor based on carbon nitride quantum dots（g-CNQDs）for the determination of 2,4-dinitroanisole（DNAN）has been first constructed.The g-CNQDs fluorescent probe was prepared by one-step low-temperature solid-phase method.Transmission electron microscopy and infrared spectroscopy showed that g-CNQDs were uniformly dispersed,the size of particle was small,and rich groups were on the surface.The fluorescence of g-CNQDs can be effectively quenched by DNAN based on the strong inner filter effect（IFE）between DNAN and g-CNQDs.The PL intensity of g-CNQDs displayed a good linear relationship with the concentration of DNAN in the range of 0～30μM,and detection limit is 0.33μM.In addition,the fluorescence sensor was successfully applied in actual samples with a satisfactory recovery rate.3.In this work,a highly sensitive fluorescence sensor based on carbon nitride quantum dots embedded in metal-organic framework（g-CNQDs@Zn-MOF）fluorescent probe for sensitive and selective detection of riboflavin（RF）has been proposed.The g-CNQDs@Zn-MOF composite fluorescent material was prepared by ultrasonic mixing method.The composite material combined the excellent properties of host Zn-MOF and guest g-CNQDs.The g-CNQDs@Zn-MOF fluorescent probe has a strong and rapid fluorescence response to riboflavin（RF）based on the fluorescence resonance energy transfer（FRET）.The fluorescence intensity displayed a good linear relationship with the concentration of RF in the range of 0～1.0μM.The detection limit was lower down 15 n M.The fluorescence sensor also has good selectivity and stability.More importantly,the fluorescence sensor was successfully applied in milk and vitamin B₂ tablets for RF detection.4.In this work,a highly sensitive fluorescence sensor based on boron and nitrogen co-doped carbon quantum dots（BN-CDs）for the determination of 1,1-diamino-2,2-dinitroethylene（FOX-7）was firstly constructed.The BN-CDs fluorescent probe was prepared by one-pot hydrothermal carbonization method.The preparation process was simple and green,and the cost was low.The BN-CDs had strong fluorescence properties and the size was about 3 nm.Infrared spectrum and X-ray photoelectron spectroscopy showed that B and N elements were successfully doped into the carbon network.Under the optimal p H 7,the linear range of BN-CDs fluorescent probe for FOX-7 detection was 0～80μM,and the detection limit was 0.41μM.It was found that the decreased fluorescence of BN-CDs was ascribed to IFE between BN-CDs and FOX-7.The fluorescent sensor has excellent selectivity and stability,and can be successfully applied in actual water samples（tap water or lake water）with satisfactory recovery.