Preparation And Application Of Heteratomic Doped Carbon Quantum Dot Fluorescent Probe

As a nano-scale carbon-based carrier,carbon quantum dots（CQDs）can be used in different fields by carrying various groups with different functions.CQDs have excellent physicochemical properties such as good biocompatibility,low toxicity,small size,environmental friendliness and easy surface functionalization,its own fluorescence characteristics also make it in the optical field,biomedical field have great research value.This paper uses olive leaves as biomass carbon source,thiourea as nitrogen source and sulfur source to synthesize nitrogen-sulfur co-doped carbon quantum dots（NS-CQDs）by hydrothermal method,then uses them as fluorescent probes to detect amphotericin B、Fe³⁺in water,and Fe³⁺and NS-CQDs as composite fluorescent probes to detect CO32-in water.The main contents were as follows:（1）Using olive leaves as carbon source,sulfuric acid as sulfur source,nitric acid as nitrogen source,thiourea as nitrogen source and sulfur source,respectively.CQDs、sulfur-doped carbon quantum dots（S-CQDs）,nitrogen-doped carbon quantum dots（N-CQDs）and NS-CQDs were prepared by one-step hydrothermal method.After exploring the reaction temperature,reaction time,material ratio,pretreatment and other conditions,the optimum preparation conditions were found.The as-prepared NS-CQDs showed good water solubility,good dispersity without agglomeration,size distribution between 2-5 nm,obvious excitation wavelength dependence,strong fluorescence stability in high ionic strength environment and pH values from the range of 4-12.（2）Microdetection of amphotericin B by NS-CQDs as fluorescent probe.The results showed that with the increase of amphotericin B concentration,the fluorescence intensity of NS-CQDs increased.When the concentration of amphotericin B was 0-100μM,the I/Io was linearly correlated with the concentrat ion of amphotericin.The theoretical detection limit was 9.9809.In order to detect the practicability,the NS-CQDs fluorescent probe was tested with common ions and small molecules.the results show that the NS-CQDs has strong anti-interference ability and can be used in complex environmental water bodies.（3）The NS-CQDs was used as a fluorescent probe to trace the Fe³⁺.The results show that the fluorescence intensity of NS-CQDs is quenched rapidly with the increase of Fe³⁺concentration.Because the absorption spectrum of NS-CQDs shows the same change as the emission spectrum,it can be judged that the quenching type is static quenching,that is,the reaction with NS-CQDs quickly after Fe³⁺entering the water body produces new non-luminescent substances,thus achieving the effect of rapidly quenching NS-CQDs fluorescence,and the quenching efficiency can reach up to 89.97%.When the Fe³⁺concentration is 0-700μmol/L,the Fe³⁺concentration is linearly related to the fluorescence intensity of the NS-CQDs,and the theoretical detection limit is calculated to be 7.415μmol/L.（4）When 700μmol/L Fe3 is present,the fluorescence intensity of the NS-CQDs fluorescent probe is quenched to the maximum extent.Because it is a static quenching mechanism,anions that can react with Fe3 can be added to release NS-CQDs to restore fluorescence.To use Fe3 and NS-CQDs as composite fluorescent probes to detect CO₃^2-.The detection results show that at 0-0.33333mol/L,the concentration xof CO₃^2-has a linear relationship with the fluorescence intensity of the composite fluorescent probes.The output limit is calculated as 0.02374mol/L.