Stability and Morphology of Gold Nanoisland Arrays Generated from Layer-by-Layer Assembled Nanoparticle Multilayer Films: Effects of Heating Temperature and Particle Size.

This article reports the effects of heating temperature and composition of nanoparticle multilayer films on the morphology, stability, and optical property of gold nanoisland films prepared by nanoparticle self-assembly/heating method. First, nanoparticle-polymer multilayer films are prepared by the layer-by-layer assembly. Nanoparticle multilayer films are then heated at temperature ranging from 500 °C to 625 °C in air to induce an evaporation of organic matters from the films. During the heating process, the nanoparticles on the solid surface undergo coalescence, resulting in the formation of nanostructured gold island arrays. Characterization of nanoisland films using atomic force microscopy and UV-vis spectroscopy suggests that the morphology and stability of gold island films change when different heating temperatures are applied. Stable gold nanoisland thin film arrays can only be obtained after heat treatments at or above 575 °C. In addition, the results show that the use of nanoparticles with different sizes produces nanoisland films with different morphologies. Multilayer films containing smaller gold nanoparticles tend to produce more monodisperse and smaller island nanostructures. Other variables such as capping ligands around nanoparticles and molecular weight of polymer linkers are found to have only minimal effects on the structure of island films. The adsorption of streptavidin on the biotin-functionalized nanoisland films is studied for examining the biosensing capability of nanoisland arrays.