Construction Of The SERS Platform Of Graphene Nanocapsules And Application Of In-situ Bacterial Detection

Raman spectroscopy is based on the inelastic light scattering of the sample itself and contains the natural fingerprint information in the sample.Therefore,Raman spectroscopy has been successfully applied to the determination of chemical composition and molecular structure.However,the low sensitivity of Raman spectrum limits its wide application in biomedicine.The observation and confirmation of surface-enhanced Raman spectroscopy(SERS)phenomenon on rough silver metal surface in 1970 s greatly improved the detection sensitivity of Raman spectroscopy.In the fields of food safety,environmental monitoring and clinical diagnosis related to bacterial detection,SERS detection method has been reported,which has the advantages of strong selectivity,anti-bleaching and abundant molecular fingerprint information.However,the corrosion resistance of the traditional SERS enhanced base Au was weak,which would lead to the decline of the stability of SERS signal in practical application.Aiming at the above problems,this paper prepared a SERS detection platform with graphene nanocapsules(MACGs)with gold and cobalt particles in the graphene core.Combining the corrosion resistance advantage of graphene with the traditional enhanced base metal Au,it has the advantages of internal standard(SI),strong stability and high sensitivity.The platform was applied to in-situ detection of pseudomonas aeruginosa,which solved the disadvantages of long biochemical detection cycle and unstable SERS detection of traditional bacteria.The specific work content is as follows:(1)in chapter 2,MACGs nanoparticles were synthesized by chemical vapor deposition(CVD)to characterize the properties,magnetism and imaging stability of excellent SERS imaging of MACGs.Because the shell is graphene,it has a unique Raman peak,where the 2D peak can be used as an internal standard(SI)in the silent zone.(2)in chapter 3,a SERS detection platform for detecting pseudomonas aeruginosa secretions(pseudomonas aeruginosa and cyanogen)was established by using the advantages of MACGs nanometer substrate.In this chapter,the qualitative and quantitative detection of bacteria in situ and the detection of two secretions of pseudomonas aeruginosa were described,which increased the specificity and sensitivity of the detection.In the analysis of quantitative analysis results of analytes,2D peak of MACGs graphite shell can be used as SI to correct the interference factors,which can improve the quantitative accuracy.In addition,this chapter enhanced the sensitivity of SERS detection by magnetic absorption enrichment of bacteria,and the enhancement multiple was 4.46 times of that before magnetic absorption.In addition,the application of pseudomonas aeruginosa in the monitoring of physiological activities shows its great potential in bacterial typing and quantitative analysis.(3)in chapter 4,in order to further improve the sensitivity of SERS detection,the SERS enhanced effect of anions represented by cyanide root and halogen ions on GIAN/ detected and MACGs/ detected systems was explored.This enhanced effect is universal.In this paper,it has been found that more than a dozen anions have enhanced effect on all kinds of detected objects,and the enhancement multiple can reach up to 30 times,which has great potential in improving the SERS sensitivity and reducing the detection limit,and is suitable for application in all kinds of SERS detection systems.This chapter also briefly explores the mechanism of this enhancement effect.One possible mechanism is that anions adsorb on the surface of GIAN particles,thus causing changes in the conformation of the molecules under test on the surface of GIAN.It has been proved in this paper that anions can adsorb on the surface of GIAN particles.Another possible mechanism is that the particles are etched together,allowing the object to get closer to the "hot spot".In this paper,the ultraviolet absorption spectra and particle size changes of gold nanoparticles and GIAN particles mixed with halogen ions were investigated.The change of GIAN particle size is not obvious,and the mechanism of this part still needs to be further explored.