Tunable 2D Binary Colloidal Alloys for Soft Nanotemplating
Miguel Ángel Fernández-Rodríguez, Roey Elnathan, Ran Ditcovski, Fabio Grillo, Gaurasundar Marc Conley, Flavia Timpu, Astrid Rauh, Karen Geisel, Tal Ellenbogen, Rachel Grange, Frank Scheffold, Matthias Karg, Walter Richtering, Nico H. Voelcker, Lucio Isa:
Nanoscale, 10, 22189-22195 (2018)
doi: 10.1039/C8NR07059H  
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The realization of non-close-packed nanoscaled patterns with multiple feature sizes and length scales via colloidal self-assembly is a highly challenging task. We demonstrate here the creation of a variety of tunable particle arrays by harnessing the sequential self-assembly and deposition of two differently sized microgel particles at the fluid-fluid interface. The two-step process is essential to achieve a library of 2D binary colloidal alloys, which are kinetically inaccessible by direct co-assembly. These versatile binary patterns can be exploited for a range of end-uses. Here, we show that they can for instance be transferred to silicon substrates, where they act as masks for the metal-assisted chemical etching of binary vertically aligned silicon nanowires (VA-SiNWs) with fine geometrical control. In particular, continuous binary gradients in both NW spacing and height can be achieved. Notably, these binary VA-SiNW platforms exhibit interesting anti-reflective properties in the visible range, in agreement with simulations. The proposed strategy can also be used for the precise placement of metallic nanoparticles in non-close packed arrays. Sequential depositions of soft particles enable therefore the exploration of complex binary patterns, e.g. for the future development of substrates for biointerfaces, catalysis and controlled wetting.