Analysis And Application Research Based On The Characteristics Of Black Phosphorus Quantum Dots Oxidation-mimicking Enzymes

As a new zero—dimensional nanomaterial.black phosphorus quantum dots(BP QDs)have attracted scientists' attention for their special structure,excellent electronic,optical characteristics and good biocompatibility.This thesis found that BP QDs exhibited an intense oxidase-mimicking activity for transferring typical enzyme substrate 3.3'.5.5'-tetramethylbenzidine(TMB)into blue-colored product(oxTMB).Based on the oxidase-mimicking activity of BP QDs.simple colorimetric methods were put forward for determination of biothiols and evaluation of acetylcholinesterase activity.These methods have important application value in pharmaceutical preparation and enzyme activity evaluating.Part one.Colorimetric determination of biothiols based on oxidase-mimicking activity of black phosphorus quantum dotsBP QDs with small size were synthesized through an easy to operate thermal method.It was found that BP QDs possess oxidase mimicking activity.They could catalyze the oxidation of substrate TMB to produce a blue-colored product even in the absence of hydrogen peroxide.Active oxygen species proved to be involved in the reaction through the experiments of radical scavenging and electron spin resonance.Biothiols including reduced glutathione and cysteine inactivated the oxidase-mimicking activity of BP QDs,concomitant with the fading of the blue solution.This work puts forward a colorimetric method for the determination of glutathione and cysteine.The decreased absorbance at 652 nm displayed linear response to the concentrations of glutathione ranging from 0.1 to 5.0 ?mol·L^-1.and cysteine from 0.1 to 10.0 ?mol·L^-1.The detection limits are 0.02 ?mol·L^-1 and 0.03 ?mol·L^-1 for glutathione and cysteine,respectively.Successive determination of 1.0 ?moI·L^-1 glutathione and 5.0 ?mol·L^-1 cysteine solution gave the relative standard deviations of 0.8%and 1.7%(n=11),respectively.As a preliminary application,the practicability of the method was evaluated by the determination of glutathione in pharmaceutical preparation.This work not only discovers a useful oxidase mimics,but also sets up a reliable platform based on BP QDs in colorimetric detection.Part two.Light-accelerating oxidase-mimicking activity of black phosphorus quantum dots for colorimetric detection of acetylcholinesterase activity and inhibitor screeningA feasible and sensitive colorimetric method was established for the assay of acetylcholinesterase(AChE)activity and evaluation of inhibitor screening,based upon oxidase-mimicking activity of BP QDs.BP QDs were synthesized through a thermal exfoliation method and characterized with various techniques.BP QDs exhibited an oxidase-mimicking catalytic activity on dissolved oxygen-mediating oxidation of TMB,a typical substrate of peroxidase/oxidase.This led to a transformation of TMB into its blue oxidized product,which owned a visible absorption peak at 652 nm.The exposure of 365 nm light irradiation significantly expedited the oxidase-mimicking activity of BP QDs and accelerated the reaction efficiency.AChE can specifically catalyze the decomposition of its substrate acetylthiocholine(ATCh)chloride to thiocholine.Thiocholine owns reducing capacity and can make a loss of the oxidase-mimicking activity of BP QDs.As a result,the oxidation of TMB was impeded and the blue solution became faded.The assay had a linear response ranging from 0.5 to 10.0 mU·mL^-1 and a detection limit of 0.17 mU·mL^-1 AChE.The assay was successfully applied to evaluate inhibitor screening with neostigmine as the model.In summary,BP QDs were synthesized through a thermal method.Two simple,reliable and sensitive colorimetric methods were established for the determination of biothiols and AChE based on oxidase-mimicking catalytic activity of BP QDs.This thesis not only discovers the oxidase-mimicking activity of BP QDs,but also sets up a reliable platform in pharmaceutical preparation and evaluation of AChE activity with its inhibitor screening.This research has important value for the development of black phosphorus quantum dots in the field of optical chemistry analysis.