Self-Assembled Ligand-Capped Plasmonic Au Nanoparticle Films in the Kretschmann Configuration for Sensing of Volatile Organic Compounds

Abstract

Films of close-packed Au nanoparticles are coupled electrodynamically through their collective plasmon resonances. This collective optical response results in enhanced light-matter interactions, which can be exploited in various applications. Here, we demonstrate their application in sensing volatile organic compounds, using methanol as a test-case. Ordered films over several cm2 were obtained by interfacial self-assembly of colloidal Au nanoparticles (~10 nm diameter) through controlled evaporation of the solvent. Even though isolated nanoparticles of this size are inherently non-scattering, when arranged in a close-packed film the plasmonic coupling results in a strong reflectance and absorbance. The in-situ tracking of vapor phase methanol concentration through UV-Vis transmission measurements of the nanoparticle film is first demonstrated. Next, in-situ ellipsometry of the self-assembled films in the Kretschmann (also known as ATR) configuration is shown to yield enhanced sensitivity, especially with phase difference measurements. Our study shows the excellent agreement between theoretical models of the spectral response of self-assembled films with experimental in-situ sensing experiments. At the same time, the theoretical framework provides the basis for the interpretation of the various observed experimental trends. Combining periodic nanoparticle films with ellipsometry in the Kretschmann configuration is a promising strategy towards highly sensitive and selective plasmonic thin-film devices based on colloidal fabrication methods for volatile organic compound (VOC) sensing applications.

19 pages

References in corpus (4)

• Observation of intrinsic size effects in the optical response of individual gold nanoparticles
• Coupled Plasmon Modes in 2D Gold Nanoparticle Clusters and their Effect on Local Temperature Control
• Effect of size distribution, skewness and roughness on the optical properties of colloidal plasmonic nanoparticles
• Selectivity in Ligand Functionalization of Photocatalytic Metal Oxide Nanoparticles for Phase Transfer and Self-assembly Applications