2021 MRS Spring Meeting

Tutorial SM07: Probing Self-Assembly via Advanced Microscopic Techniques

Saturday, April 17, 2021
1:00 PM - 7:45 PM

Self-assembly is an important phenomenon on the formation of minerals in nature and has been become to a popular method to synthesize advanced materials in both lab and industrial scales. Up to now, plentiful materials prepared via self-assembly have been applied in various fields such as energy, catalysis, biomedicine, and electrics. For instance, advanced super lattice materials have been prepared via self-assembly of nanoparticles.

The tutorial aims to bring the attendees updated information on probing self-assembly via advanced microscopic techniques. It is also designed for the experienced researchers to reinforce their knowledge on the scopes of development of new generation of microscopic techniques for studying self-assembly of molecular, clusters, and nanoparticles. Eight top experts in the field will deliver lectures and consulting sections, providing a unique platform for the attendees to learn from the professionals and foster dynamic and scientific exchange via exciting cross-disciplinary discussions. The tutorials will be conducted using interesting illustrations and simple languages, which will greatly benefit junior researchers and graduate students.

In Situ and Liquid TEM for Investigating Nanpoarticles
Jungwon Park, Seoul National University

Molecular or atomistic mechanistic understanding of nucleation, growth, and structural changes of nanoparticles have not achieved enough at the nanoscale or below. It is mainly because of a lack of appropriate analytical methods that can obtain in-situ structural information with a spatial resolution at such small length scale along with sub-msec temporal resolution. The in situ, both in liquid phase and dry state, transmission electron microscopy (TEM) offers an opportunity to directly observe diverse classes of chemical reactions. Here we introduce technical developments for those techniques. Topics will cover fabrication processes for TEM liquid cells with thin film window materials such as graphene and silicon nitride, and data processing of large sized in situ TEM images. In addition, we also present application of in situ TEM to study chemistry of colloidal nanoparticles. We reveal that the early stage of nanoparticle formation is driven by reversible transition between disordered and ordered phases before crystalline phase is stable above a certain size. It is also frequently observed that different types of non-classical pathway, including two-step nucleation, amorphous-to-crystalline transition, and coalescence of clusters, are heavily involved in different conditions of nanoparticle formation. We also present a new development using liquid phase TEM to investigate 3D atomic structures of nanoparticles directly in the colloidal synthesis batch.

Dynamics of Interface-Driven Nucleation and Assembly
James De Yoreo, Pacific Northwest National Laboratory

Heterogeneous distributions of ions and water at interfaces have a strong impact on processes of nucleation and assembly. This talk will introduce how to investigate these phenomena and their relationship to interfacial structure for a number of mineral systems in aqueous electrolyte solutions via using a combination of in situ imaging techniques such as in situ liquid cell atomic force microscopy (AFM) and in situ liquid phase scanning/transmission electron microscopy (S/TEM) and computational methods.

Real Time Imaging of Dynamic Behavior of Individual Nanocrystals During Superlattice Phase Transformations using In Situ Liquid Phase Transmission Electron Microscopy
Haimei Zheng, Lawrence Berkeley National Laboratory

Nanocrystals have attracted considerable attention because of their potential applications in catalysis, energy storage, microelectronic devices, biomedicines, etc. Monodisperse nanocrystals could form superlattices with emergent collective properties. Although there have been intensive studies on nanocrystal superlattices, how individual nanocrystals change and how they interact with each other during superlattice transformations are unclear. Direct observation with high spatial and temporal resolution using transmission electron microscopy (TEM) provides the opportunity to address these questions. This talk will introduce the development of high-resolution carbon-film liquid cells, which allow to directly observe nanocrystal superlattice transitions using TEM.

Quantum Dot Nanomaterials—Synthesis, Assembly and Applications
Ou Chen, Brown University

Nanocrystal materials are emerging as an important class of tools that are revolutionizing both fundamental science and technological applications due to their many unique properties. In particular, quantum dots nanocrystals have demonstrated their great potential to be applied in a wide variety of applications as a unique emissive material.  In my talk, I will describe our experimental efforts for the synthesis and characterization of high-quality quantum dot nanocrystals. These dots combine, in one material, great optical performance metrics desired in quantum dot nanomaterials. Then, I will show how we can use colloidal quantum dot nanocrystals as building blocks to generate higher-order architectures in assemblies. At last, several quantum dot based applications studied in my lab will be discussed.

Pressure Induced Nanoparticle Aggregation
Hongyou Fan, Sandia National Laboratories

This talk will summarize recent progress on the studies of pressure Induced nanoparticle aggregation behavior. This talk starts with a brief overview of high pressure characterization techniques, coupled with synchrotron X-ray scattering, Raman, fluorescence, and absorption. Then, the pressure Induced nanoparticle aggregation behavior including size dependent aggregation and threshold pressures using several typical NP material systems as examples. Finally, outlooks with future directions are discussed.

Self-Assembly in Colloidal Nanoparticle Systems—Thermodynamics, Interaction Softness and Kinetics
Xingchen Ye, Indiana University

Nanoparticle superstructures are versatile materials platforms for fundamental study of colloidal assembly and exploration of technologically relevant applications. In this talk, I will describe our recent progress on kinetically controlled assembly of multicomponent superstructures using spherical nanoparticles with tunable softness. Characterization of kinetically arrested intermediates reveals a multistep crystallization pathway defying the classical nucleation theory. Next, I will present our work on assemblies of shape-anisotropic nanoparticles with tunable softness. The interplay between particle shape and interaction softness leads to rich phase behaviors.

Direct Observation of Oriented Attachment in Nanoparticle Growth
Dongsheng Li, Pacific Northwest National Laboratory

The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials. This talk will introduce the background of oriented attachment and the application of high-resolution fluid cell transmission electron microscopy (TEM) to directly observe oriented attachment of several nanoparticle systems, including iron oxyhydroxids, Au, Ag, and Pt.

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