| Carbon dots are a type of fluorescent nanoparticles with a size of less than 10 nm.Because of their unique fluorescent properties,good biocompatibility and high photostability,they have received more and more attention.In general,the precursors of carbon dots are derived from chemical materials,but due to economic and environmental requirements,in recent years,researchers have focused on the use of biomass waste to synthesize carbon dots.In addition,as a new type of fluorescent nanomaterials,tungsten disulfide quantum dots arouse the interest of researchers due to their excellent optical,electrochemical and catalytic properties,and are widely used in sensing,photocatalysis,energy,biomedicine and other related fields.This thesis has carried out a series of research work combining the advantages of carbon dots,tungsten disulfide quantum dots and optical sensing technology,and the specific contents are as follows:1.A fluorescence sensing method based on nitrogen,sulfur and phosphorus codoped carbon dots were used for the detection of ferric ions.This chapter proposed a method to synthesize fluorescent carbon dots using biomass waste as a precursor.Green pepper seeds were used as raw materials to prepare fluorescent nitrogen,sulfur and phosphorus co-doped carbon dots(NSP-CDs)through a one-step hydrothermal method.Fe3+ can selectively quench their fluorescence.Therefore,based on the fluorescence quenching characteristics of Fe3+ on NSP-CDs,a fluorescent "turn-off" sensing method was constructed for sensitive detection of Fe3+.The linear range of this method was 1500 pM,and the detection limit was 0.1 ?M.NSP-CDs have low toxicity and good biocompatibility,and can be used for intracellular Fe3+ detection.This strategy is simple,economical,and green.It realizes the comprehensive utilization of biomass waste,has huge economic and environmental benefits,and expands the various applications of green and sustainable preparation of high-fluorescence nanomaterials.2.A fluorescent "turn-off" sensing method based on tungsten disulfide quantum dots were used for the detection of alkaline phosphatase activity.In this chapter,tungsten disulfide quantum dots(WS2 QDs)were synthesized by a one-step hydrothermal method,and their fluorescence can be quenched by the internal filtration effect.Studying the mechanism found that in the presence of alkaline phosphatase(ALP),disodium p-nitrophenyl phosphate(PNPP)was converted to p-nitrophenol(PNP),and there was a certain degree between the absorption spectrum of PNP and the excitation spectrum of WS2 QDs.As a result,the internal filtration effect occurred,and finally the fluorescence of WS2 QDs was quenched,through the change of fluorescence signal,the sensitive detection of ALP was realized.The linear range of this method was 0.01-50 U L'1,and the detection limit was 0.002 U L"1.In addition,the detection method proposed in this experiment had been successfully used for the detection of ALP in serum and cells,and for the screening of ALP inhibitors.The results of serum sample analysis and inhibitor screening showed that the sensing method proposed in this chapter can be used for ALP activity detection in biochemical applications and ALP inhibitor screening in drug discovery.3.The dual-mode sensing method based on tungsten disulfide quantum dots and cobalt oxyhydroxide nanosheets is used for the detection of a-glucosidase.This chapter used the oxidase-like properties of CoOOH nanosheets to develop a sensing method for ratiometric fluorescence and colorimetric dual-mode detection of a-Glu activity.Due to the overlap between the absorption spectrum of the cobalt oxyhydroxide(CoOOH)nanosheets and the excitation spectrum of WS2 QDs,the fluorescence of WS2 QDs were quenched by the internal filter effect.O-phenylenediamine(OPD)is a typical oxidase chromogenic substrate,which can be oxidized in CoOOH nanosheets solution.The resulting oxidation product 2,3-diaminophenazine(DAP)showed yellow and emitted orange fluorescence.When ?-glucosidase(?-Glu)was present,the substrate 2-O-?-D-glucopyranosyl-L-ascorbic acid(AAG)was hydrolyzed into ascorbic acid(AA)that can decompose CoOOH nanosheets.Due to the decomposition of CoOOH nanosheets,the quenching of WS2 QDs and the oxidation of OPD were inhibited,resulting in an increase in the fluorescence of WS2 QDs at 450 run,and a decrease in the fluorescence of DAP at 560 nm.Using fluorescence intensity ratio and ultraviolet absorption peak as signal readout,a selective and sensitive dual-mode determination of ?-Glu activity was successfully realized,and the analysis results were more reliable.At the same time,this research also provides new ideas for the application of CoOOH nanosheets in the development of sensitive sensing strategies. |
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