Application Of Polydopamine Functionalized Surface Plasmon Array In The Detection Of Weakly Absorbed Molecules

In recent years,with the continuous development of science and technology,people’s living standards have been improving day by day,and more and more food problems,environmental pollution,drug abuse and other problems have gradually become prominent,which seriously threaten people’s health.It is very important to establish analytical methods to detect these toxic and harmful substances.The traditional analysis and detection methods are mostly detection methods such as chromatography and mass spectrometry.These detection methods often require expensive instruments and complicated pre-processing,which greatly limits the possibility of rapid in-situ detection.Therefore,it is urgent to develop new detection technologies to achieve rapid in-situ trace detection of analytes.Surface enhanced spectroscopy(SES)technology is a powerful analysis technology that can realize ultratrace detection of substances,the most widely used are Surface Enhanced Raman Spectroscopy(SERS)and Surface Enhanced Fluorescence Spectroscopy(SEF).This analysis technology combines the high sensitivity provided by the surface-enhanced substrate(metal nanostructure)with the characteristic spectral characterization of the substance by the molecular spectrum analysis technology(such as Raman spectroscopy and fluorescence spectroscopy).It can realize ultra-sensitive quantitative analysis and detection of analytes,and has broad application prospects in environmental monitoring,food and drug monitoring,and biological detection.The mechanism of surface enhancement originates from the surface plasmon resonance(SPR)phenomenon caused by the interaction of gold and silver nanostructures with incident light.The generation of SPR is accompanied by the enhancement of the strong electromagnetic field on the gold and silver nanostructures.This is the most important way for surface enhancement spectroscopy to achieve signal amplification.The development of surface-enhanced substrates is an important basis for surface spectroscopy research.Common surface-enhanced substrates include gold and silver nanoparticles with various morphologies.However,it is difficult to control the size and uniform spacing of nanoparticles due to the synthesis and assembly process of nanoparticles,resulting in large inhomogeneities in the signal.Our research group has prepared an enhanced substrate with both high sensitivity and uniformity through ultraviolet holographic lithography technology.The substrate also has the characteristics of a large area and uniformity and is suitable for mass production,and is suitable for practical applications.However,in the process of applying the substrate to the actual molecule detection process,due to the distribution characteristics of the enhanced electromagnetic field on the surface of the metal nanostructure,the signal of molecules far away from the metal surface drops sharply.The measured molecule needs to be close to the surface within10 nm to achieve signal enhancement.That is,the molecules need to be adsorbed on the surface.The precious metal itself can only achieve the adsorption of some special molecules(such as sulfhydryl molecules,etc.).For weakly adsorbed molecules,it is necessary to functionally modify the surface of the precious metal substrate,and achieve quantitative analysis and detection by specifically interacting with the molecule to be tested.As a new type of polymer coating material,polydopamine has good adhesion characteristics,mild reaction conditions,excellent chemical properties,and is rich in a variety of active functional groups.It can be used as a good adsorption layer material.The work of this thesis is the first to successfully synthesize a polydopamine filmcoated gold periodic nanoarray substrate(PDA-SERS)and a polydopamine film-coated silver periodic nanoarray substrate(PDA-SEF),used for SERS and SEF detection respectively,expanding the application range of nano-array substrates.The substrate has a good enhancement effect and uniformity.Among them,the polydopamine film is used as a functional adsorption layer to successfully achieve the surface adsorption of some conjugated molecules,and the auxiliary surface enhancement spectroscopy realizes its quantitative analysis and detection,and further explored the detection range of the PDA-SERS substrate.In addition,in the PDA-SEF research,the adsorption of fluorescent molecules such as crystal violet and enhanced fluorescence detection have been successfully achieved.PDA-SERS and PDA-SEF substrates will play an important role in the quantitative analysis and detection of more weakly adsorbed molecules.