The SERS Of Amino Acids And Dipeptide Absorbed On Several New SERS Substrate

Light scattering phenomenon occurs when light passes through inhomogeneous medium including Rayleigh scattering and Raman scattering. Under irradiation of monochromatic light, different molecules come into being different Raman spectra,so Raman spectroscopy can be used to get molecular structure information and can be applied to qualitative analysis. Raman spectrum can also be used for quantitative analysis that the peak amplitude of Raman spectroscopy is related to the concentration of the molecular. The infrared spectra of molecular generate due to the changing of dipole moment and Raman spectroscopy comes from the polarization changes. Raman spectra vibration peaks of some molecular are not obvious while in infrared spectrum that can be very strong. Therefore, in the analysis of molecular structure, Raman spectrum and infrared spectrum are complementary, we can get more comprehensive information by using Raman spectrum in combination with infrared spectrum while for the inorganic molecular structure analysis, and Raman spectroscopy has more advantages. With the fast development of Raman spectra and SERS, they have been widely used in many new fields such as food security,criminal investigation, environmental analysis, and biomedicine.Surface enhanced Raman spectroscopy(SERS) refers to the intensity of Raman spectra peaks greatly enhanced when the molecules adsorbed on rough surface(including gold, silver, copper and other metals and other nanometer materials recent rapidly developed). Normal Raman spectrum has limitations when the concentration of sample is low because of the weak signal of Normal Raman spectrum. Some vibrational peaks wouldn’t appear in the normal Raman spectra while they canappear in the surface Raman spectra. That is why the SERS appears. It is good method to get a molecular fingerprint information by SERS on account of the high sensitivity of SERS. SERS base is the precondition of using surface enhanced Raman spectra for analysis. In recent years, the study of base is crucial, the base research of SERS is developing rapidly with the progress of nanotechnology. SERS substrate including precious metal sol, metal film substrate, rough electrode, solid nanoparticles, etc, which silver nano materials are the most widely used because of its larger enhancement factor. SERS is widely used in chemical, biological,environmental analysis, and food detection due to its high sensitivity and selectivity even though the enhancement mechanism of SERS is still unclear.In this paper, we introduced the history, mechanism, characteristics, application of Raman spectroscopy and surface enhanced Raman spectroscopy. Thus, three new kinds of nano materials were synthesized and applied to SERS analysis. The spectral information of D-carnitine and L-alanyl-L-glutamine(ala-gln) has been established by surface enhanced Raman spectroscopy combined with conventional Raman spectroscopy and infrared spectroscopy. Compared with the theoretical spectrum of ala-gln, spectrographic analysis method of ala-gln has been developed. The spectrographic way to identify the antipodal heterogeneous of the focal glutamate has also been developed. This paper includes the following parts:The first section introduces the development history, principles, characteristics and application of the Raman spectroscopy and surface enhanced Raman spectra. A comparison of the principle of infrared spectroscopy(IR) and Raman spectra is made.Their application similarities and differences in application are introduced. We summarized the development prospects and research direction of the SERS spectra application.In the second chapter, three new methods to synthesis SERS base were introduced. The base has been characterised. A fast and efficient way to synthesize a large number of silver nanowires was developed in this part, in which the reaction conditions were optimized. The silver nanowires synthesized in the condition which the concentration of AgNO3, NaCl, Cu(NO3)2 is 0.15 M, 0.3mM, 0.05 M respectively has the best enhancement effect of SERS. A water thermal way to synthesis Ag/Cu2 O base and Cu/Ag alloy base which also have good SERS effect is developed in this part. The detection of these basement can be single molecule level.In the third chapter, the solid normal Raman spectroscopy(NRS), Surfaceenhanced Raman spectroscopy(SERS) absorbed on Ag/Cu2 O base of two isomer of focal glutamic acid were studied. The SERS of the two isomer impacted with beta cyclodextrin(β-CD) absorbed on Ag/Cu2 O base was also got. The effect time and proportion of focal glutamic acid and beta cyclodextrin have been developed that the effect time of the two substance was one hour and the best ratio of the two substance was 1:7. We successfully developed a spectrographic way to distinguish the two isomer of focal glutamic acid. It also provides a new method to study the action mechanism of focal glutamic acid in biological function.In the fourth chapter, the theoretical calculation of the spectrum by density functional theory(DFT) including the molecular structure, infrared spectrum, Raman spectrum of the usual dipeptide L-alanyl-L-glutamine(ala-gln) were investigated.The Raman spectra,infrared spectra of ala-gln and the SERS of ala-gln absorbed on Cu/Ag alloy substrate were measured. After comparing theoretical spectrum and experimental spectrum, a comprehensive spectrographic information of ala-gln has been developed. The mayor vibrational peaks were assigned by the software called Gauss view 5.0. The way that ala-gln absorbed on Cu/Ag alloy substrate was speculated. It provides new research methods for the application of ala-gln on pharmacology.In the fifth chapter, the solid normal Raman spectroscopy(NRS), Raman spectroscopy of the D-carnitine solution whose concentration was 10-3 mol.L-1 and surface enhanced Raman Spectroscopy of D-carnitine by means of the silvernanowires base were obtained. The mayor vibrational peaks were assigned after comparing the NRS and SERS of D- carnitine. The analysis showed that the angle between the molecular and silver nanoparticles was nearly 180°. By the analysis of different concentration of D- carnitine absorbed on the silver nanowires,we found the minimum detection concentration of D- carnitine was 10-6 mol.L-1. The new way to analysis D- carnitine is rapid and characteristic and it will also provide an important guidance for the studies on pharmacology of D-carnitine.