The Daily Bulletin

Please join the Chemistry Department for the seminar "Screening of Near-IR Surface-Enhanced Raman Scattering (SERS) Dyes Using Quick Freezing-Induced AuNP Aggregates (QFIAAs)," presented by Carleigh Cimmerer, a graduate forensic science student, on Thursday, April 14, from 12:15 to 1:30 p.m. in Science and Mathematics Complex 151.

Seminar Abstract
Near-IR (NIR) surface-enhanced Raman scattering (SERS) is an emerging bioimaging technique that can be a safe alternative with a resolution better than current bioimaging techniques, such as MRI, CT, and PET. These can be hazardous with long-term exposure due to powerful magnetic fields or ionizing radiation. The success of NIR SERS bioimaging partially lies in the selection of highly sensitive NIR Raman reporters, which is essential to achieve highly resolved bioimaging from the body system. Researchers have synthesized and screened NIR dyes that can be used for NIR SERS bioimaging.1,2 NIR Raman dyes must satisfy three important conditions: strong absorption in the NIR region, strong binding to the surfaces of gold nanoparticles (AuNPs), and excellent NIR SERS activity. AuNPs have been used as vital SERS substrates but must be aggregated to create "hot-spots" to produce strong SERS signals.

Thus, the AuNPs are often aggregated by adding salts or high-concentration of dye molecules themselves, which is largely due to the electrical neutralization of negatively-charged AuNP surfaces. However, these methods are difficult to control the aggregation of AuNPs, thus leading to unreliable SERS signals. We previously reported that moderate sizes of AuNP clusters could be prepared by quickly freezing citrate-capped AuNPs and thawing them at room temperature. 3 We discovered that QFIAAs prepared from AuNPs with an average diameter of 70 nm could not only act as excellent NIR SERS substrates but also remain suspended in a solution for a long time, so they could be used to detect analytes using NIR SERS. In addition, QFIAAs were stable without disintegration when stored for more than three months. This research has focused on the applications of QFIAAs in the screening of dye molecules with high throughput for NIR SERS bioimaging. In this talk, the effect of the capping agents on the formation of QFIAAs, the charge effect of dye molecules on their adsorption on QFIAAs, and the results of a proof-of-concept experiment on using QFIAAs to screen dye molecules for NIR SERS will be presented.