Non-thiolated intermolecular and interfacial interactions near gold nanostars and their effect on SERS

How low amounts of molecules in solution vibrate are studied by mixing them with metal nanoparticles (sizes below 100 nanometers) and exposing the solution to a laser. Each molecule vibrates at a specific frequency allowing us to identify what molecules are present and how they interact with each other. This thesis first provides an overview of molecular vibration near nanoparticle surfaces and how these are utilized to study vibrations of molecules. The overview explains how vibrational signal is enhanced near a nanoparticle surface while identifying the current advantages and disadvantages of the technique. Next, nanoparticles are exploited to determine how tetrahydrofuran, a common organic solvent, affects the detection and vibration of aspirin, a common drug, near a gold surface. Tetrahydrofuran is shown to facilitate aspirin reaching the nanoparticle surface, enabling detection, by interacting and moving with aspirin in solution. Lastly, the molecular vibrations near a gold surface allow the metabolism of Δ9-tetrahydrocannabinol (THC) to be tracked through saliva and associated with how “high” a person feels at a given time after THC inhalation. Molecular vibration further supports that a long-lasting metabolite of THC is detected in saliva with the possibility of identifying whether a person is impaired by THC at a given time. Overall, this thesis discusses our progress towards minimizing the disadvantages of using molecular vibrations to understand what is around us and how it works.