In situ microscopy of the self-assembly of branched nanocrystals in solution.

Eli Sutter,Milena Arciniegas,Peter Sutter,Joost De Graaf,Alexei V Tkachenko,Liberato Manna,Roman Krahne

doi:10.1038/ncomms11213

Abstract

Solution-phase self-assembly of nanocrystals into mesoscale structures is a promising strategy for constructing functional materials from nanoscale components. Liquid environments are key to self-assembly since they allow suspended nanocrystals to diffuse and interact freely, but they also complicate experiments. Real-time observations with single-particle resolution could have transformative impact on our understanding of nanocrystal self-assembly. Here we use real-time in situ imaging by liquid-cell electron microscopy to elucidate the nucleation and growth mechanism and properties of linear chains of octapod-shaped nanocrystals in their native solution environment. Statistical mechanics modelling based on these observations and using the measured chain-length distribution clarifies the relative importance of dipolar and entropic forces in the assembly process and gives direct access to the interparticle interaction. Our results suggest that monomer-resolved in situ imaging combined with modelling can provide unprecedented quantitative insight into the microscopic processes and interactions that govern nanocrystal self-assembly in solution.

Highlights

Solution-phase self-assembly of nanocrystals into mesoscale structures is a promising strategy for constructing functional materials from nanoscale components
Using the example of the one-dimensional (1D) self-assembly of CdSe/CdS octapods, we demonstrate the ability of Liquid-cell electron microscopy (LCEM) to dynamically probe such solution-phase self-assembly processes in real space with nanometre resolution
Our findings illustrate the ability of in situ microscopy combined with modelling to obtain detailed quantitative insight into nanocrystal self-assembly processes in solution

Summary

Introduction

Solution-phase self-assembly of nanocrystals into mesoscale structures is a promising strategy for constructing functional materials from nanoscale components. Understanding the structure, formation and transformation of colloidal matter requires probing particle configurations from monomers to extended periodic or aperiodic assemblies Computer simulations provide this capability[16,17], but experiments are complicated by the need to interrogate processes in liquids that allow suspended particles to diffuse and interact freely. By real-time imaging with monomer resolution, the in situ LCEM observations reported here establish several key aspects of the self-assembly of ordered linear chains of octapods in solution. On the basis of the characteristics obtained from in situ microscopy, a statistical mechanics model is built that explains the chain-length distribution (notably the absence of stable dimers), establishes the relative importance of van der Waals and entropic forces in the self-assembly, and determines the strength of the particle–particle interaction. Our findings illustrate the ability of in situ microscopy combined with modelling to obtain detailed quantitative insight into nanocrystal self-assembly processes in solution

Methods

Results

Conclusion