The Preparation Of Organic/Inorganic Nanocomnosites And Their Applications In Biosensing

Nanomaterials are endowed with special physical and chemical properties that are different from macroscopic materials due to their unique microstructure,which has attracted interests of a large number of researchers in the past decades.The field of organic/inorganic nanocomposites is a rapidly growing area of research in advanced functional materials science.These materials are made of nanoscaled organic and inorganic counterparts,wherein the interaction at molecular level generates unique properties at the interface.This thesis bases on the nanocomposites of two-dimensional nanomaterials,macrocyclic supramolecular compounds,metal nanoparticles,metal halides and other nanomaterials.These materials via covalent/non-covalent interactions to construct a series of organic/inorganic nanocomposite materials.Subsequently,the integration of two-dimensional nanomaterials,macrocyclic supramolecular compounds,metal nanoparticles,metal halides and other nanomaterials was studied for the application in the field of electrochemical sensing,fluorescence/visible light sensing and other fields for detection of the biologically related analytes.The following four parts are the main content of this thesis:In the first part,BPene nanosheets were prepared using the assay of liquid exfoliation from bulk BP.Then,dopamine was in situ polymerized on the BPene surface to construct the BPene@PDA nanocomposite.Furthermore,SCX8 was functionalized with BPene@PDA to produce BPene@PDA-SCX8 nanocomposite.The constructed nanocomposite can bind to folic acid(FA)and form a stable BPene@PDA-SCX8·FA conjugate through host-guest recognition.Cancer cells can bind to the BPene@PDA-SCX8·FA modified electrode through FA and the folic receptor(FR)on the cancer cells by forming an SCX8-FA-FR sandwich-type conjugate,resulting in increased impedance that was proportional to the cell amount.The cytosensor exhibited a linear relation with LNCa P cells concentration within the range of 2×10~2to 1×10~5 cells/m L with a detection limit of 36 cells/m L.The proposed cytosensing platform sensing was successfully used to determin actual samples and with a good potential in clinical application.In the second part,the covalent organic frameworks(COFs)prepared via a solvent-thermal method.Then,the Au NPs supported COFs nanozyme(COFs@Au)was synthesized via reduction of HAu Cl₄ in situ.The prepared COFs@Au with excellent mimic nitro-reductase and glucose-oxidase activity.According to the catalytic properties of the COFs nanozyme,the p-nitrophenol introduced as the substrate,which can be transformed to p-nitroaniline for UV-visible assay.Moreover,the COFs@Au nanozyme catalyzes glucose while generating hydrogen peroxide to oxidize Fe²⁺to Fe³⁺,which converts the MIL(Al)-MOF to MIL(Fe)-MOF through ion exchange,thereby quenching the fluorescence of MIL(Al)-MOF.For Circulating tumor cells(CTCs)detection,the CTCs were separated by folic acid(FA)modified magnetic nanoparticles through the interaction between FA and the folate receptor(FR)overexpressed on the tumor cells membrane surface with the aptamer-based COFs nanozyme as a probe for CTCs capture and signal amplification.The cytosensor exhibited a linear relation with MCF-7 cells concentration within the range of 50 to 2×10~4 cells/m L with a detection limit of 17cells/m L.The constructed cytosensing platform with the specific enrichment and separation of CTCs,and has potential application prospects in cancer identification and diagnosis.In the third part,the TPA-COFs was prepared via a solvent-thermal method.Then,TPA-COFs Ns were prepared using the assay of liquid exfoliation from TPA-COFs.Subsequently,the gold nanoparticles loaded on the surface of TPA-COFs Ns to obtain Au@TPA-COF Ns.Finally,the sulfhydryl Rh B-C2 peptide was modified on the surface of Au@TPA-COF Ns through Au-S bond to prepare Pep-Au@TPA-COF Ns complex.When there is no analysis target chymosin,the fluorescence of Rh B is quenched due to the FRET effect between TPA-COF Ns and the Rh B fluorescent molecule modified on the peptide.The specific cleavage of the peptide by chymosin makes Rh B Being released leads to the recovery of its fluorescence.The"Turn on"type fluorescent sensor is constructed by the complex to realize the detection of chymosin.The constructed fluorescence sensor has a linear range of 0.05-60?g/m L for daily detection of chymosin with a detection limit of 0.02?g/m L.The proposed fluorescence sensing platform can be used for the detection of chymosin in dairy products.In the last part,the Cs Pb Br₃/Cs₄Pb Br₆ composite nanocrystal(Cs Pb Br₃/Cs₄Pb Br₆)with ultrahigh stable were successfully synthesized via a simple chemical solvent-assisted mothed.Compared with conventional perovskites,the as-prepared Cs Pb Br₃/Cs₄Pb Br₆retain excellent water oxygen-resistant characteristics with 42%and 80%photoluminescence intensity remaining after 28 days under water and air conditions,respectively.Moreover,a special response to biomolecules from fingerprints was observed due to the electrostatic interactions between the Cs Pb Br₃/Cs₄Pb Br₆ NCs surface functional groups(amine and carboxylic)and the secretion from the thin layer of fluid left on the surface upon its direct contact with human fingers.Clear LFPs images were visualized in a bright environment by staining the prepared Cs Pb Br₃/Cs₄Pb Br₆composite NCs powder under UV light of wavelength 365 nm.The images were also obtained on porous and non-porous surfaces such as metal,plastic,wood,glass,and paper products.These perovskite nanocrystals are expected a stable and bright luminescent labeling agent for LFPs visualization and,have potential application in crime scene and personal identifications.