Nanosphere lithography (NSL) spans a wide variety of techniques for producing 2D arrays of hexagonal-close-packed (HCP) spheres (typically polystyrene, PS), which act as masks for subsequent fabrication. Our interests are in using these HCP masks on smooth gold substrates to produce large-area (≥1cm2) gold microcavity arrays (AuMCAs) via electrochemical deposition. We have previously shown that AuMCAs are effective enhancers of NIR-to-visible upconversion emission from lanthanide-doped nanoparticles. However, difficulties were encountered in using published NSL techniques to reproducibly generate large areas (≥1cm2) of the PS masks with high-quality, long-range order. Here, we describe the development of a NSL technique utilizing a Langmuir-Blodgett (LB) trough to quickly and reproducibly generate high-quality HCP masks with dimensions ≥10cm2. The technique is based on carefully controlled introduction of the PS onto the air-water interface using an inclined ‘ramp’. The pressure at the water surface is adjusted such that the HCP array of spheres is formed spontaneously as the spheres enter the water layer from the ramp. The parameters for the method were developed first at the petri-dish scale and then adapted to the LB trough. The free-standing monolayers were deposited onto hydrophilic gold substrates through automated LB software and monolayer quality was assessed using optical microscopy. This technique was shown to consistently provide large (≥10cm2) HCP masks of the PS with a high level of reproducibility and automation. Masked substrates were then subjected to electrochemical plating to produce large-area AuMCAs to be used as enhancing substrates for lanthanide ion-doped upconversion nanoparticles (UCNPs).

Self-assembly of micron-sized polystyrene colloids via Langmuir-Blodgett technique for highly reproducible fabrication of large-area gold microcavity arrays

2019 Spring National Meeting

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