Probe Mediated SERS-Based Ultrasensitive and Selective Detection of Targeted Analyte

This dissertation focuses on the development of probe-mediate method in detection of targeted analytes based on SERS. Even though SERS is capable of delivering detection of single molecule level concentration, the method still heavily relies on the interaction between the substrate and the analyte as well as the Raman cross-section of the analyte. Because SERS is notorious for extreme distance dependence requirement, many researchers are focused on improving the interaction between the analytes and the SERS substrate. However, in some cases, no appreciable SERS signal could be obtained even when the analytes is in direct contact with the SERS substrate due to the small Raman cross section. We solved this problem by introduction of a probe molecule which can specifically interact with the analyte yielding a complex with greater Raman cross section than the original analyte. We further simplified such scheme into two categories: in-situ detection and in vivo or in vitro detection and we showed the examples of detection hydrazine in-situ and hydrogen peroxide in vitro respectively. Although our proposed scheme is not perfect for every molecule that possesses small Raman cross section, it still provides a method to consider when analyzing such class of molecules.

Also, we will introduce a brand-new concept of releasing the molecules from plasmonic nanoparticle through a very efficient and well-known plasmon-driven reaction. Researchers in this field mainly focus on the mechanisms behind this classic plasmon-driven reaction model, para-aminothiphenol (PATP) to 4, 4’-dimercaptoazobenzene (DMAB), instead, we realized the reaction is not only limited to PATP but applies to all PATP derivatives. Bearing this mind, we coupled PATP with a fluorescent tag to demonstrate the release of the fluorescent molecule upon the excitation of plasmon using a CW laser. We believe this method will give inspiration in designing the next generation drug delivery systems.