Hexagonal spiral growth in the absence of a substrate

TL;DR

This study demonstrates the spontaneous formation of hexagonal spirals from cadmium nanocrystals in solution, driven by a novel dislocation mechanism without substrate assistance, revealing new insights into nanoparticle growth dynamics.

Contribution

It introduces a substrate-independent growth mechanism involving a dynamic dislocation, termed the 'feeder', in nanoparticle spiral formation.

Findings

Hexagonal spirals form without substrate constraints.

Growth involves a dense nanocrystal aggregate called the 'feeder'.

Spiral growth occurs via a dynamic dislocation mechanism.

Abstract

Experiments on the formation of spiraling hexagons (350 - 1000 nm in width) from a solution of nanoparticles are presented. Transmission electron microscopy images of the reaction products of chemically synthesized cadmium nanocrystals indicate that the birth of the hexagons proceeds without assistance from static screw or edge dislocatons, that is, they spiral without constraints provided by an underlying substrate. Instead, the apparent growth mechanism relies on what we believe is a dynamical dislocation identified as a dense aggregate of small nanocrystals that straddles the spiraling hexagon at the crystal surface. This nanocrystal bundle, which we term the "feeder", also appears to release nanocrystals into the spiral during the growth process.