Fabrication Of Gold Core Silver Shell Nanorods And Their Applications In Surface Enhanced Raman Spectroscopy

Surface enhanced Raman scattering(SERS) has attracted tremendous interest in surface science, food safety testing, biological detection and many other fields due to its powerful advantages including ultrahigh sensitivity, negligible interference from water and providing fingerprint spectrum information of the analyte. Generally speaking, the SERS based analytical technique is based on the metal nanostructures supporting localized surface plasmon resonances. Gold-silver bimetallic nanomaterials have very wide applications such as catalysis and SERS sensor for their unique physical and chemical properties. Herein, gold core silver shell nanorods were prepared via a seed-mediated method and used as SERS active substrate, which showed a good application performance in catalytic monitoring and label detection of the specific gene fragment. The main work contents are as follows:1.Firstly, chitosan stabilized gold core silver shell nanoparticles were synthesized using the gold nanorods as seed. And a series of characterizations such as UV-vis spectrum, TEM, Raman spectrum were conducted to evaluate the optical property, morphology and SERS activity of the nanorods. Then the catalytic performance of nanoparticles were studied by UV-vis spectrum, and SERS technique was used to monitor the catalytic reduction reaction of p-nitrothiophenol. The study found that the dosage of AgNO3 had an effect on the morphology, catalytic efficiency and SERS activity of the nanorods. In addition, the changes of molecular structural could be observed by using SERS technique to monitor the intensity of Raman characteristic peaks during reduction action.2.Seed-mediated growth approach was used to prepare Raman reporter embedded gold core silver shell nanorods. Then biotin-modified hairpin structure DNA was attached to the Au@Ag NRs as the SERS signal probe and streptavidin-modified magnetic beads was used as the capture probe. The hairpin would open after adding target DNA sequence and expose biotin, so that SERS probe would attach to the magnetic beads to form a SERS sensor for the detection of specific DNA fragment. The research showed that surface plasmon resonance property and SERS activity of nanorods would change with the AgNO3 dosage, hence the maximum SERS effect could be attained by adjusting to the optimal dosage of AgNO3 to 150 μL. Furthermore, a few experimental parameters were optimized to improve the specificity and sensitivity of target DNA SERS assay.