Preparation of Gold Nanoisland Arrays from Layer-by-Layer Assembled Nanoparticle Multilayer Films

Abstract

This article introduces a facile nanoparticle self-assembly/annealing method for the preparation of nanoisland films. First, nanoparticle-polymer multilayer films are prepared with layer-by-layer assembly. Nanoparticle multilayer films are then annealed at ~ 500 o C in air to evaporate organic matters from the films. During the annealing process, the nanoparticles on the solid surface undergo nucleation and coalescence, resulting in the formation of nanostructured gold island arrays. By controlling the overall thickness (number of layers) of nanoparticle multilayer films, nanoisland films with various island density and different average sizes are obtained. The surface property of gold nanoisland films is further controlled by the self-assembly of alkanethiols, which results in an increased surface hydrophobicity of the films. The structure and characteristics of these nanoisland film arrays are found to be quite comparable to those of nanoisland films prepared by vacuum evaporation method. However, this self-assembly/annealing protocol is simple and requires only common laboratory supplies and equipment for the entire preparation process.

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

“…29,30 The nanoisland films prepared at 525 °C showed similar changes but with less extent (Δλ max = ~25 nm). The change was quite small but still clearly visible for the films generated at 550 °C (Δλ max = ~10 nm).…”

“…27,28 We have shown that the gold nanoisland arrays with various grain density and different average sizes could be obtained by controlling the overall thickness (number of layers) of nanoparticle multilayer films. 29 Gold nanoisland films obtained from the nanoparticle 2-layer films were quite polydisperse. Nanoisland films generated from the nanoparticle 8-layer films contained grains with higher density compared to the island films generated from the nanoparticle 5-layer films.…”

“…This spectral evolution agrees that the gold nanoparticles undergo nucleation and coalescence on the glass surface resulting in the formation of larger gold nanoparticle-like structures. 29,30 …”

“…9,29 To examine the stability of the produced nanoisland films at different temperatures, the nanoisland arrays were placed in 1.0 mM 11-mercaptoundecanoic acid solution in ethanol for at least 24 hours and then characterized with the UV-vis spectrophotometer (Figure 5). Thiol treatment is a simple and fast way to prove the stability of nanostructured films.…”

“…Since the SP band of gold in UV-vis spectra is very sensitive to the change in the structure of the nanostructured films, any morphological variation will result in the change in the intensity, peak width, and/or the wavelength of the SP band. 9,21,29 It is also known that the reflective index changes caused by MUA assembly could result in the shift and/or increase in plasmon band. Therefore, to confirm the changes caused by MUA assembly was due to the morphological changes of the island films, we have examined the response of island films generated at different temperature using the streptavidin/biotin model system (Figure S2 in Supporting Information).…”