Assessment of Morphological and Optical Properties of Molecularly Mediated Thin Film Assembly of Gold Nanoparticles

Abstract

This paper reports the results of an investigation of the optical properties of molecularly mediated thin film assemblies of nanoparticles. Thin film assemblies of gold nanoparticles of different sizes that are linked by dithiols and carboxylic acid functionalized thiols of different alkyl chain lengths are studied as a model system. These thin films have been assembled on different substrates for the systematic measurements of the morphological and optical properties. The correlation of the d -spacing values between the experimental and theoretical results has revealed the presence of ordered nanostructures in the thin film assemblies. The wavelength of the surface plasmon resonance band of the nanoparticles in these thin film assemblies is shown to be linearly dependent on the particle size and the interparticle linker chain length. The analyses of the optical properties theoretically using Mie theory and experimentally using reflectometry and spectroscopic ellipsometry have provided important information for the assessment of the optical constants for these nanostructured thin films. Implications of the results to the understanding of the interparticle structural properties are also discussed.