Improved Vapor Selectivity and Stability of Localized Surface Plasmon Resonance with a Surfactant-Coated Au Nanoparticles Film

Here, we report the use of tetraoctylammonium bromide (TOABr)-coated Au nanoparticles (NPs) for the optical sensing of volatile organic compounds (VOCs). We find that the film responded selectively to the presence of polar and nonpolar vapors by changes in the maximum wavelength (lambda(max)) toward higher and lower wavelengths, respectively, as determined by UV-visible spectroscopy. We also observed that the organic coating reorganizes when vapors partition into the film indicated by FT-IR and the film contracts in the presence of water indicated by scanning electron microscopy (SEM). In the present sensor, the metallic Au core serves as the plasmonic signal while the organic coating acts as the receptor material providing vapor selectivity and sensor stability. Correlating changes in (lambda(max)) with changes in the refractive index (RI) and nanoparticle-to-nanoparticle separation in the film is important both fundamentally and for improving selectivity in localized surface plasmon resonance (LSPR) sensors.