CPM-4 SERS and UV-Vis of Rhodamine B on Au and Ag Nanoparticles
Abstract
This project predominantly focuses on the effects of pH on the plasmonics of silver and gold nanoparticles (NP) when attached to rhodamine B. Unlike their bulk component, silver and gold nanoparticles possess a unique ability for the surface electrons to become excited and resonate upon irradiation with visible light. This property, known as surface plasmon resonance (SPR), can be utilized in the technique, surface-enhanced Raman spectroscopy (SERS). With SERS, the Raman signal of a molecule is enhanced tremendously when the molecule is within close proximity of a metal nanoparticle’s surface due largely to the SPR of the nanoparticles. With 100-10,000 times enhancements routinely achieved, silver and gold nanoparticles are the most commonly used SERS optical substrates. In this project, aqueous suspensions of silver and gold nanoparticles were prepared by reducing the metal salts in the presence of a weak reducing agent. Rhodamine B, was chosen as a model SERS analyte specifically for its strong SERS enhancement and for its fluorescent property, which could also be monitored. Furthermore, rhodamine-B is an FDA-regulated dye toxic to mammals. An immediate goal of this project included (1) maximizing conditions for detecting rhodamine B and (2) better understanding the analyte-surface interactions between silver and gold with rhodamine B by developing a SERS- binding isotherm. In particular, significant variations in signal strength have been observed by adjusting the system’s pH. We hope this research will have implications in testing levels of rhodamine B and other FDA regulated molecules in substances such as foods, spices, and beverages.
Keywords
Chemistry, Physical Chemistry, Metal Nanoparticles, Surface Plasmon Resonance, SERS, UV-Vis
CPM-4 SERS and UV-Vis of Rhodamine B on Au and Ag Nanoparticles
University Readiness Center Greatroom
This project predominantly focuses on the effects of pH on the plasmonics of silver and gold nanoparticles (NP) when attached to rhodamine B. Unlike their bulk component, silver and gold nanoparticles possess a unique ability for the surface electrons to become excited and resonate upon irradiation with visible light. This property, known as surface plasmon resonance (SPR), can be utilized in the technique, surface-enhanced Raman spectroscopy (SERS). With SERS, the Raman signal of a molecule is enhanced tremendously when the molecule is within close proximity of a metal nanoparticle’s surface due largely to the SPR of the nanoparticles. With 100-10,000 times enhancements routinely achieved, silver and gold nanoparticles are the most commonly used SERS optical substrates. In this project, aqueous suspensions of silver and gold nanoparticles were prepared by reducing the metal salts in the presence of a weak reducing agent. Rhodamine B, was chosen as a model SERS analyte specifically for its strong SERS enhancement and for its fluorescent property, which could also be monitored. Furthermore, rhodamine-B is an FDA-regulated dye toxic to mammals. An immediate goal of this project included (1) maximizing conditions for detecting rhodamine B and (2) better understanding the analyte-surface interactions between silver and gold with rhodamine B by developing a SERS- binding isotherm. In particular, significant variations in signal strength have been observed by adjusting the system’s pH. We hope this research will have implications in testing levels of rhodamine B and other FDA regulated molecules in substances such as foods, spices, and beverages.