Tuning the reflection band of ordered nanocomposites using direct laser writing.

Hierarchical ordering is common in Nature, where materials are organised in specific architectures across multiple scales, to achieve function-led design. Herein, we demonstrate multi-tiered organisation of silica nanoparticles (NPs), within a nanocomposite by employing direct laser writing (DLW). The hierarchical arrangement was optimised for wide-gamut reflected colour across the visible range by controlling NP size, NP type (core-shell and core-only), NP volume, and DLW fabrication parameters. The obtained microstructures were characterised using SEM, demonstrating retained order of non-close-packed NPs, and reproducible high-resolution fabrication with sub-micron features. We further used microspectroscopy to quantify the effect of fabrication parameters on structural colour, which is supported by FIB-SEM analysis, and exploited this effect to fabricate 3-dimensional multi-coloured images at the micro-scale. We demonstrate that this process can also be expanded to fabricate photonic nanocomposite microstructures using plasmonic core-shell NPs.