Preparation Of Triangular Silver Nanoprisms And Their Applicatons In Surface-enhanced Raman Spectroscopy

Noble metal nanoparticles show great potential for various applications due to their unique optical, electrical, and chemical properties. Triangular silver nanoprisms(TSNPRs) as one kind classical noble metal nanoparticle, have many applications in surface-enhanced Raman spectroscopy(SERS), solar cell, bio-applications. These applications depend not only on the intense tunable plasmonic band of TSNPRs, but also heavily on the sharp tip morphology. On one hand, sharp tip morphology has huge electric field enhancement around the prism. Recently, bowtie nanoantenna forming the “hot spots” which consists of two triangular nanoparticles facing tip to tip has been demonstrated to drastically amplify the electric field between the two tips.On the other hand, the position of their local surface plasmon resonance(LSPR) peak of TSNPRs are sensitive to the sharpness of their tips. Utilization of these sharp tips,TSNPRs exhibit ultra-high LSPR sensitivity for chemical/biological sensing.However, preparation of TSNPRs with well-defined tips is difficult, especially in a relatively simple method which is favorable for practical applications. In addition,SERS has shown many potential to chemical/biological sensing due to its ultrahigh sensing sensitiviey, narrow vibrational spectral bands, low photobleaching. How to utilize the excellent properties of TSNPRs to design SERS detection system is also a difficult question, which needs to be solved. This dissertation devoted to solve these questions above.Firstly, simple one-step plasmon-mediated method was developed to preparemonodispersed TSNPRs with high quality. In this approach, the sole surface capping agent was the easily removable trisodium citrate. Different from common strategy using complex polymers, OH- ions were used to improve the monodispersity of silver seeds, as well as to control the growth process through inhibiting the oxidation of silver nanoparticles. From plasmon band shift versus refractive index, ultra-high local surface plasmon resonance sensitivity(413 nm·RIU-1 or 1.24 e V·RIU-1, figure of merit(FOM) =4.59) was reached at ~630 nm, making these materials promising for chemical/biological sensing applications.Secondly, we explored the SERS activity of TSNPRs. Compared the EF of good and poor TSNPRs, well-defined TSNPRs have higher enhancement effect of SERS than poor TSNPRs. Irradiation with high powers(>250 m W) of 785 nm laer could induce aggregate of TSNPRs to obtain high SERS spectra of analytes(4-mercaptobenzoic acid,4-MBA). Using these monodispersed high quality TSNPRs as building blocks, self-assembled TSNPRs consisting of six-tip based “hot spots”were realized for the first time as demonstrated in a high enhancement(~107) of SERS.Thirdly, one hand, by virtue of the six tip-based hot spots of self-assembled structure of TSNPRs, label-free detections of antigens and antibodies have been fulfiled. We characterized the self-assembled structure of TSNPRs. Antigens,antibodies and their immune reaction products were detected through SERS based on the self-assembled structure. We also discriminated the attributions of all the Raman spectra peaks. On the other hand, in vivo SERS detection based on combining TSNPRs and optical fibre biosensor has been achieved. Optical fiber biosensor with TSNPRs and anti-Ig G at one of its end was coupled with Raman detection system for in vivo SERS detection of labeled- antigen. In vivo SERS detection was demonstrated.Firstly, labeled-antigens were injected into the body of mice. Then, optical fiber SERS biosensors were inserted into the rat tail vein to catch the Raman tags labeled antigen, which fulfill the in vivo SERS detection.