Biological Detection Based On Perovskite Nanocrystals And Their Application With MOF Composites

Perovskite nanocrystals(NCs)have attracted extensive attention in recent years due to their excellent physical and chemical properties such as simple synthesis,narrow emission band width,wide visible light coverage and high fluorescence quantum yield.One can predict that perovskite NCs will also have the same potential for bioanalysis as their quantum dot counterparts.Although perovskite NCs show great potential in the field of biosensing due to its excellent fluorescence properties,its application is still greatly limited due to its lack of targeting,poor stability in aqueous solution and no signal in detection mode,which can easily lead to false positive signal or even detection failure.Making it difficult to explore new understandings or new applications.In addition,there are few reports on exploring the intrinsic enzyme activity of perovskite NCs to develop biosensors for macromolecular detection.In this paper,the ligand OPA was selected to modify CsPbBr3 NCs to improve its stability in water phase,and the appropriate strategy was selected to prepare composite materials,and a variety of different types of biosensors were constructed.Furthermore,the nano-enzyme properties of CsPbBr3 NCs were further explored,which proved that it has a broad application background in the field of biosensing.Specific research contents are as follows:Part One,a ratio fluorescence sensor based on CsPbBr3@Eu-BTC was constructed for the detection of Hg and GSH in aqueous solutionCsPbBr3 NCs were in situ grown into Eu-BTC by solvothermal method,and dualemission CsPbBr3@Eu-BTC composite material was synthesized.A novel ratio fluorescence sensor based on CsPbBr3@Eu-BTC was prepared for the rapid,sensitive and intuitive detection of Hg2+ and GSH in aqueous solution.The successful preparation of CsPbBr3@EuBTC composites was verified by transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and gas adsorption(BET).At the same time,CsPbBr3@Eu-BTC nanocomposites maintain high fluorescence properties and stability in aqueous solution.After the addition of Hg2+,the green fluorescence of CsPbBr3 was quenched,while the red fluoresceacc of Eu3+ remained unchanged,so the color changed from green to red obviously.The fluorescence lifetime,Stern-Volmer quenching constant and XPS analysis were used to verify the dynamic quenching and electron transfer.After the addition of GSH,the green fluorescence of CsPbBr3 was restored,while the red fluorescence of Eu3+remained unchanged,and the color changed from red to green again.The ratio type fluorescence sensor has high analytical performance for Hg2+ and GSH.More importantly,a novel paper-based sensor based on the CsPbBr3@Eu-BTC ratio probe was successfully prepared for the visual detection of Hg2+ and GSH by naked eye.This novel ratio fluorescence sensor shows great potential for point-of-care diagnosis(POCT)applications.Part Two,ratio fluorescence sensor based on CsPbBr3@Zr-MOF composite material for ascorbic acid detectionA novel ratio type fluorescence biosensor based on CsPbBr3@Zr-MOF was constructed by loading CsPbBr3 onto the Zirconium matrix(Zr-MOF)surface by a simple stirring method at room temperature for the quantitative detection of ascorbic acid(AA).By comparing the fluorescence intensity and fluorescence lifetime of CsPbBr3 before and after modification of MOF materials,the protective effect of Zr-MOF on CsPbBr3 was verified.The strong interaction between AA and Zr-O clusters destroys the crystal structure of Zr-MOF and releases BDC-NH2,which enhances the fluorescence intensity of Zr-MOF ligand at 450 nm and weakens the fluorescence intensity of CsPbBr3 at 520 nm.Resulting in a gradual decrease in fluorescence intensity ratio(I520/I450)with a distinguishable color transition from green to blue.The mechanism of AA detection was further determined by fluorescence lifetime and TEM analysis.In order to meet the requirements of POCT,we produce a paper-based device based on CsPbBr3@Eu-BTC nanoprobe,which is integrated with the portable sensor platform of smart phone to read RGB values,so as to realize the fluorescence visual quantitative detection of AA.This design aims to develop a field,sensitive and rapid detection system for personalized medicine and clinical diagnosis.Part Three,study on enzyme-like activity of perovskite based on CsPbBr3 and its application in colorimetric determination of ascorbic acidIt was found that OPA-CsPbBr3 NCs had oxidase-like and ascorbate-like enzyme activities,and it was applied in biological cascade catalytic reaction for colorimetric detection of AA.Firstly,CsPbBr3 NCs were prepared with amphiphilic polymer-octylamine grafted polyacrylic acid(OPA)as ligand coating layer,which showed high stability in aqueous solution.Importantly,OPA-CsPbBr3 showed oxidase-like and ascorbate-like catalytic activity.By means of DFT simulation,the reaction process of ascorbic acid(AA)catalyzed by OPACsPbBr3 nanase was studied,that is,O2 was activated to produce superoxide radical(O2·-)through the oxidase-like pathway,and then O2·-directly oxidized AA to produce hydrogen peroxide(H2O2).Furthermore,by cascading OPA-CsPbBr3 with oxidase properties and Prussian blue(PB)with peroxidase properties,a whole nano-enzyme cascade system was constructed,and combined with portable paper-based device,the colorimetric detection of AA was realized.This work for the first time realized the application of all inorganic CsPbBr3 nanomases in biomimetic cascade catalytic reactions and verified its application in clinical diagnosis of POCT.