The importance of nano-edges in atomic stencilling and chiroptically active assembly of patchy gold tetrahedra

Abstract

Molecular patterning of proteins with atomic precision encodes folding and recognition. Emulating this patterning on synthetic surfaces can integrate multifunctionality with directional interactions for catalysis, biomedicine, nanomanufacturing and agriculture. Here we extend recently reported atomic stencilling, where iodides mask Au{111} facets to direct polymer grafting, to gold nanotetrahedra. Despite all faces being {111}, unexpected patch patterns emerge due to nanoparticle edges. Tuning edge exposure, solvent polarity and polymer–polymer interactions leads to seven distinct patch patterns on a single tetrahedron shape. Polymer scaling theory and simulations that explicitly consider edge accessibility chart a phase diagram spanning more than 30 conditions and quantitatively matching experiments. The patchy nanotetrahedra self-assemble via corner-, edge- or face-sharing motifs analogous to molecular complexes, which exhibit plasmonic chiroptical activity confirmed by ultrafast electron microscopy and finite-difference time-domain calculations. These results show that atomic stencilling precision makes nanoscopic edge features critically important, offering scalable, multiplexed and site-selective functionalization. Patchy tetrahedra with seven distinct patterns are synthesized using atomic stencilling. The experimentally mapped phase diagram of more than 30 conditions is rationalized by polymer scaling theory and molecular dynamics simulations that account for the critical importance of nano-edges. It is found that polyelectrolyte complexation drives patch-to-patch assembly with emergent chiroptical properties.