Science as art: self-assembly of hybrid SiO2-coated nanocrystals

Abstract

Hybrid SiO₂-coated CdTe nanocrystals (NCs) show a drastic increase in fluorescence quantum yield with a significant red-shifted photoluminescence (PL) peak because of the hybrid shell containing CdS-like clusters which are very close to the CdTe core. With their hybrid SiO₂ shell, CdTe NCs reveal self-assembly activity which creates one-dimensional nanostructured materials (fibers) with bright PL. Additionally, we experimentally observed the self-assembly of the hybrid SiO₂-coated CdTe NCs into two-dimensional dendritic morphology and three-dimensional crystals through a droplet dewetting technique on a hydrophilic glass surface by using NaCl molecules as scaffolds. This phenomenon is ascribed to the domain growth of NaCl to form fractal structures through tip splitting and side branching dynamics. This is also due to a hydrodynamic mechanism through outward capiliary flow. The evaporation speed of solvent during droplet dewetting plays an important role in controlling the self-assembly of the hybrid SiO₂-coated CdTe NCs. The experimental parameters such as the amount of sample on the hydrophilic glass surface and dewetting time are key for getting assemblies with tunable morphologies. The present strategy provides a new approach to study the self-assembly of a variety of NCs. This has a potential application for pattern manufacture in a natural way.