Regulation And Performance Study Of The Optimal Hotspots Of Dynamic Surfaced-enhanced Raman Spectroscopy

Since surface-enhanced Raman spectroscopy(SERS)was discovered in the 1970s,with the integration of unique spectroscopic fingerprint,nondestructive and ultrasensitive characteristics,SERS technique has become a powerful spectroscopic tool for chemical,biological,and environmental analyses.However,there are still many problems to be solved in the field of SERS.In recent years,our group developed the dynamic surfaced-enhanced Raman spectroscopy(D-SERS),which is based on nanoparticles transforming from the wet state to the dry state for SERS measurements.The D-SERS method with excellent reproducibility,stability and high sensitivity as well as the characteristics of real-time detection has gradually been concerned.As is known,SERS intensity typically depends on the nanomorphology of the substrate and nanomaterials can be synthesized in various different shapes.It is worth noting that anisotropic nanostructures,such as cubes,nanostars and triangles,exits wide size distribution in each batch,which will severely influence plasmonic propertiesof nanostructure and the reproducibility of detection.Therefore,it is important to synthetize monodisperse nanoparticles.This paper is based on the synthesis of monodisperse nanoparticles as SERS substrate,combined with the advantages of the D-SERS method to carry out a series of work.The basic concept,mechanism and substrate materials of SERS and application of SERS in medical,single molecule detection and public safety were presented in the first chapter.Due to the main work of this paper is based on the dynamic surface enhanced Raman spectroscopy(D-SERS),the development of and advantages of D-SERS detailedly introduced in this chapter,the existing problems and research ideas also presented.The second chapter is mainly based on the characteristics of D-SERS to achieve real-time detection,and then combined with the bianalyte method to study the competitive adsorption of dipyridyl isomerides 2,2'-Bpy and 4,4'-Bpy in real-time.Through the real-time monitoring of D-SERS,it is found that the adsorption of 2,2'-Bpy and 4,4'-Bpy is a dynamic competitive process.Such a dynamic change process of adsorption is not detectable in the ordinary dry state method,so the real-time D-SERS provide the significant advantage of observing the continuous SERS spectra of analyte,so that one can monitor the real-time competitive adsorption.In the third chapter,we put forward the concept of the optimal hotspots and establish a reliable quantitative analysis method based on the optimal hotspots.In situ small angle X-ray scattering(SAXS)was carried out to in situ real-time monitor the formation of the optimal hotspots.The results show that the optimal hotspots created from D-SERS.By using the SERS signal of 4-mercaptopyridine(4-mpy)as a stable internal calibration standard,the relative SERS intensity of CV demonstrated a linear response versus the negative logarithm of concentrations at the point of strongest SERS signals.With high stability and excellent reproducibility as well as advantage of quantitative analysis,the public drugs 3,4-methylenedioxymethamphetamine(MDMA),a-Methyltryptamine hydrochloride(a-MT)and melamine obtained precise analysis with internal standard D-SERS strategy.The fourth chapter is mainly based on the content of the third chapter to further explore.The optimal hotspots combined with internal standards-free were used to monitor special structural molecules.The special structure is referred to the molecule with larger scattering cross section and the special symmetrical structure,for example triphenylmethane dyes.CV are inexpensive triphenylmethane dyes effective against fungal and parasite infections in fish.Because of their mutagenic and teratogenic effects to humans,these substances are banned for use in aquaculture.Therefore,the precise determination of triphenylmethane dyes concentration is critical for food safety.The results show quantitative monitoring symmetric molecule could be possible achieved through this simple method.The last chapter is based on the contents of the chapter 3 and chapter 4 to explore the controllability of the optimal hotspots in the process of D-SERS.There are many advantages of the optimal hotspots in the process of D-SERS.However,the optimal hot spots are produced during the process of short,rapid and irreversible change.Therefore,we hope to be able to take some measures to fix the hotspots with different gap values.In situ Small angle X-ray scattering(SAXS)was carried outto in situ real-time monitor the controllability of the hotspots.The results show that the hotspots can be prolonged through the different time of sealing.In addition,the method of liquid seal is adopted to control the volatilization process.The results show that this method can also prolong the hotspots,which has important significance for D-SERS and SERS.