Understanding and Controlling the Crystallization Process in Reconfigurable Plasmonic Superlattices

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Nanomaterial crystallization is crucial for solid-state photonic structures used in optoelectronics.
• Colloidal crystallization is well-studied, but noncolloidal nanoparticle (NP) freezing remains unexplored.

Purpose of the Study:

• To investigate the noncolloidal crystallization (freezing) of reconfigurable nanoparticle assemblies.
• To understand the impact of preparation and processing on the structure and properties of NP solids.

Main Methods:

• Utilized in situ and ex situ techniques including X-ray diffraction (XRD), transmission electron microscopy (TEM), HAADF-STEM tomography, AFM, and UV-vis spectroscopy.
• Employed in situ heating with HAADF-STEM tomography for 3D single-particle analysis.
• Performed ensemble measurements with small-angle XRD and ex situ TEM imaging.

Main Results:

• Small-angle XRD showed correlation length dependence on heating/cooling cycles and cooling rate.
• Ex situ TEM revealed controllable domain size (over 2 orders of magnitude) and structure dependent on sample preparation.
• HAADF-STEM tomography provided 3D positional order evolution, highlighting anisotropic assembly behavior.
• TEM identified interface importance in polydomain structures, explaining UV-vis spectral differences.

Conclusions:

• The combination of in situ HAADF-STEM tomography, XRD, and ex situ TEM is effective for studying NP freezing.
• Disorder in solid-state NP aggregates significantly impacts their plasmonic properties.
• This research provides foundational understanding for designing photonic nanomaterials for optoelectronics.