Fast Assembly of Gold Nanoparticles in Large-Area 2D Nanogrids Using a One-Step, Near-Infrared Radiation-Assisted Evaporation Process

Abstract

When fabricating photonic crystals from suspensions in volatile liquids using the horizontal deposition method, the conventional approach is to evaporate slowly to increase the time for particles to settle in an ordered, periodic close-packed structure. Here, we show that the greatest ordering of 10 nm aqueous gold nanoparticles (AuNPs) in a template of larger spherical polymer particles (mean diameter of 338 nm) is achieved with very fast water evaporation rates obtained with near-infrared radiative heating. Fabrication of arrays over areas of a few cm(2) takes only 7 min. The assembly process requires that the evaporation rate is fast relative to the particles' Brownian diffusion. Then a two-dimensional colloidal crystal forms at the falling surface, which acts as a sieve through which the AuNPs pass, according to our Langevin dynamics computer simulations. With sufficiently fast evaporation rates, we create a hybrid structure consisting of a two-dimensional AuNP nanoarray (or "nanogrid") on top of a three-dimensional polymer opal. The process is simple, fast, and one-step. The interplay between the optical response of the plasmonic Au nanoarray and the microstructuring of the photonic opal results in unusual optical spectra with two extinction peaks, which are analyzed via finite-difference time-domain method simulations. Comparison between experimental and modeling results reveals a strong interplay of plasmonic modes and collective photonic effects, including the formation of a high-order stopband and slow-light-enhanced plasmonic absorption. The structures, and hence their optical signatures, are tuned by adjusting the evaporation rate via the infrared power density.

Stratification and Size Segregation of Ternary and Polydisperse Colloidal Suspensions during Drying

“…When we have small numbers of the small particles, they clearly accumulate at the top but without forming a layer. They fill the spaces between the intermediate-size particles in a similar fashion to the case we reported in Ref 42. for binary mixtures.…”

Stratification in binary colloidal polymer films: experiment and simulations

“…Films were formed in static air at a room temperature of approximately 22 1C and relative humidity of 50%. Under these conditions, the evaporation rate, E, of water in a latex film has been reported to be 1.1 Â 10 À7 m s À1 (expressed as the velocity of the falling surface), 47 and this is taken as the value in our calculations that follow.…”

Broadband light scattering and photoluminescence enhancement from plasmonic Vogel's golden spirals

“…We further note that the enhancement is only dependent on the amplitude of the Fourier transform and not the phase. Therefore, similar ideas could be pursued in other structures with similar strongly banded rotationally symmetric structure factors, such as hyperuniform lattices .…”