In Situ Monitoring of the Change in Extinction of Stabilized Nanoscopic Gold Particles in Contact with Aqueous Phenol Solutions

Changes to the surface plasmon resonance band of stable nanoscopic gold particle films were monitored with a UV−vis spectrometer as the films come in contact with a host analyte of varying concentrations. The gold particle films were prepared via a sputtering and annealing method and were secured in a flow cell with enough stability to remain intact while analytes flow through the cell. Time scans are performed as pure water is passed over the film with plugs of phenol systematically introduced for quantitation. With increasing host concentration surrounding the film, a characteristic red-shift and increase in intensity is observed as expected from Drude theory and the Clausius−Mossotti equation for small metal particle polarizability. The reversible response was evaluated by baseline−peak extinction difference (Δ C ext ) and integrated peak area. In both methods of analysis, a linear agreement in Δ C ext is found in the 5 mM−0.4 M range. Gold particle films modified with octanethiol exhibit the same linearity in this range. However, the normalized Δ C ext is noticably enhanced.