43879-G10
Single Molecule Raman Detection with a Composite Microresonator and Metal Nanocavity System
Surface enhanced Raman spectroscopy (SERS) is a widely-studied technique capable of adding single-molecule detection capability to the rich information provided by Raman spectroscopy. In the proposal, we proposed to combine the whispering gallery modes (WGMs) of ring resonator with nanocavities formed by metallic nanoparticle cluster to achieve multiplicative enhancement in Raman signal that enables single molecule Raman detection.
In a recent publication from our lab (“SERS-based detection in an optofluidic ring
resonator platform”, Optics Express, 15, 17433-17442), we demonstrated a cavity enhanced SERS in a liquid core optical ring resonator (LCORR). The sample used was Rhodamine 6G at a concentration of 400 pM. The sample volume is approximately 8 pL. Therefore, we were able to detect the Raman signal down to 2000 R6G molecules. The SERS enhancement was approximately 10^8 on average and the cavity enhancement was estimated to be 1000. As a result, the combined enhancement is on the order of 10^11. Given the signal strength obtained in the experiment, we believe that our system is capable of detecting Raman signal from a single molecule.
After demonstration of the cavity SERS effect, we moved to two applications. The first was to demonstrate opto-fluidic Raman laser, especially, we were aimed to achieve Raman lasing with the enhancement from silver nanoclusters. To date, we have successfully demonstrated the Raman lasing from the first Stokes band of carbon disulfide, when carbon disulfide was flowed through the LCORR. Our next step is to add silver nanoclusters to reduce the Raman laser threshold.
The second effort was to detect single virus using cavity SERS. At the time when this report is prepared, we have successfully demonstrated detection of virus down to 1000 pfu/mL. The results were published in Analyst 2008 (“Opto-fluidic micro-ring resonator for sensitive label-free viral detection” Analyst, 132, 356-360). Given the small sample volume used in the experiment, we estimated that only tens of virus particles existed in the sample. Our next step will be to mix the virus with silver nanoclusters to perform SERS.
In the past two year, the PI has tremendously benefited from the PRF grant, which not only supported the proposed research, but also partially supported a few graduate students as well as a post-doctor. It has helped the PI to overcome the hurdle in his early career as a tenure track assistant professor. During the support of this grant, the PI was able to establish his research program and obtain external grants. To date, he has received three NSF grants, including the prestigious NSF-CAREER award, and an NIH grant to support one of his post-doctors (who now is an assistant professor at the University of
