Organic vapour sensing using localized surface plasmon resonance spectrum of metallic nanoparticles self assemble monolayer

The response of localized surface plasmon resonance (LSPR) spectra of gold and silver nanoparticles, and gold nanoshells to organic vapors was investigated. The surface area of nanomaterials was sufficiently high for quantitative adsorption of volatile organic compounds (VOCs). Surface adsorption and condensation of VOCs caused the environmental refractive index to increase from n = 1.00 in pure air to as high as n = 1.29 in near saturated toluene vapor. The extinction and wavelength shift of the LSPR spectra were very sensitive to changes in the surface refractive index of the nanoparticles. Responses of the LSPR band were measured with a real-time UV–vis spectrometer equipped with a CCD array detector. The response of silver nanoparticles to organic vapors was most sensitive in changes in extinction, while gold nanoshells exhibited red-shifts in wavelength (∼250 nm/RIU) when exposed to organic vapors. The LSPR spectral shifts primarily were determined by the volatility and refractive indices of the organic species. The T90 response time of the VOC–LSPR spectrum was less than 3 s and the response was completely reversible and reproducible.