Surface-enhanced Raman Spectroscopy Technique And Application

Surface-enhanced Raman spectroscopy can amplify Raman signals by several orders of magnitude and depress the fluorescence background in a certain extent, which make it suitable to characterize the properties of biological system.Appropriate substrate is very important for obtaining high enhancement. In this thesis,we synthesized several kinds of Ag sol by chemical reduction, and used UV-VIS absorption spectrum to characterize the products. The Raman signals of L-tryptophan (L-Trp) enhanced by using different substrates were compared. We also applied SERS technique to characterize L-Trp and Trp-containing dipeptides,analyzed the interaction mechanism and found the rules of the spectrum.The details are the followings:1.Gray and yellow transparent Ag sols were fabricated by traditional methods.Their concentration,size,shape,homogeneity were characterized by UV-VIS absorption spectrum. After a comparison, we found that the yellow Ag sol was better the gray one in enhancing the SERS signals of L-Trp.2. Ag nanoprisms were prepared using dual-reductant method. The size of the Ag sol and the position of its surface plasmon resonance (from-400nm to near infrared region) could be adjusted. However, the enhancement to L-Trp was disappointing. We conjectured that the addition of PSSS, which was used as a stabilize in the preparation of Ag sol, interfered the contact and interaction between the adsorbate and the surface.3. Two kinds of experimental scheme were designed for synthesizing improved Ag sol. The one which had triangular Ag nanoparticles proved by UV-VIS absorption spectrum exhibited a better enhancement to L-Trp than the yellow Ag sol. The enhance mechanism is under study.4. The normal Raman spectra of L-Trp both in solid powder and aqueous solution and its SERS spectum were obtained. The vibration assignment of the spectrum was displayed. We also studied the interacting site of L-Trp on the surface of Ag sol. 5. The SERS spectrum of Trp-containing dipeptides (Trp-Trp,Trp-Tyr,Tyr-Trp,Trp-Gly,Gly-Trp) were also detected. In the studying of the enhance mechanism, we found that the SERS spectra of all of these dipeptides were nearly identical with the spectrum of the dipeptides of their N-terminal residues, regardless of their C-terminal residues.