3D structure of individual nanocrystals in solution by electron microscopy

Park, Jungwon,Elmlund, Hans,Ercius, Peter,Yuk, Jong Min,Limmer, David T.,Chen, Qian,Kim, Kwanpyo,Han, Sang Hoon,Weitz, David A.,Zettl, A.,Alivisatos, A. Paul American Association for the Advancement of Scienc 2015 Science Vol.349 No.6245

<P><B>Looking at teeny tiny platinum particles</B></P><P>Electron microscopy is a powerful technique for taking snapshots of particles or images at near-atomic resolution. Park <I>et al.</I> studied free-floating platinum nanoparticles using electron microscopy and liquid cells (see the Perspective by Colliex). Using analytical techniques developed to study biological molecules, they reconstructed the threedimensional features of the Pt particles at near-atomic resolution. This approach has the scope to study a mixed population of particles one at a time and to study their synthesis as it occurs in solution.</P><P><I>Science</I>, this issue p. 290; see also p. 232</P><P>Knowledge about the synthesis, growth mechanisms, and physical properties of colloidal nanoparticles has been limited by technical impediments. We introduce a method for determining three-dimensional (3D) structures of individual nanoparticles in solution. We combine a graphene liquid cell, high-resolution transmission electron microscopy, a direct electron detector, and an algorithm for single-particle 3D reconstruction originally developed for analysis of biological molecules. This method yielded two 3D structures of individual platinum nanocrystals at near-atomic resolution. Because our method derives the 3D structure from images of individual nanoparticles rotating freely in solution, it enables the analysis of heterogeneous populations of potentially unordered nanoparticles that are synthesized in solution, thereby providing a means to understand the structure and stability of defects at the nanoscale.</P>

Direct Observation of Wet Biological Samples by Graphene Liquid Cell Transmission Electron Microscopy

Park, Jungwon,Park, Hyesung,Ercius, Peter,Pegoraro, Adrian F.,Xu, Chen,Kim, Jin Woong,Han, Sang Hoon,Weitz, David A. American Chemical Society 2015 Nano letters Vol.15 No.7

<P>Recent development of liquid phase transmission electron microscopy (TEM) enables the study of specimens in wet ambient conditions within a liquid cell; however, direct structural observation of biological samples in their native solution using TEM is challenging since low-mass biomaterials embedded in a thick liquid layer of the host cell demonstrate low contrast. Furthermore, the integrity of delicate wet samples is easily compromised during typical sample preparation and TEM imaging. To overcome these limitations, we introduce a graphene liquid cell (GLC) using multilayer graphene sheets to reliably encapsulate and preserve biological samples in a liquid for TEM observation. We achieve nanometer scale spatial resolution with high contrast using low-dose TEM at room temperature, and we use the GLC to directly observe the structure of influenza viruses in their native buffer solution at room temperature. The GLC is further extended to investigate whole cells in wet conditions using TEM. We also demonstrate the potential of the GLC for correlative studies by TEM and fluorescence light microscopy imaging.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-7/acs.nanolett.5b01636/production/images/medium/nl-2015-01636y_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5b01636'>ACS Electronic Supporting Info</A></P>

Rational design and observation of the tight interface between graphene and ligand protected nanocrystals

Kim, Byung Hyo,Bae, Hyeonhu,Park, Hyesung,Lee, Hoonkyung,Ercius, Peter,Park, Jungwon The Royal Society of Chemistry 2019 Physical chemistry chemical physics Vol.21 No.1

<P>Heterostructures constructed of graphene and colloidal nanocrystals provide a unique way to exploit the coupled physical properties of the two functional building blocks. Studying the interface structure between the two constituent materials is important to understand the formation mechanism and the resulting physical and chemical properties. Along with <I>ab initio</I> calculations, we elucidate that the bending rigidity and the strong van der Waals interaction of graphene to the metal surface guide the formation of a tight and conformal interface. Using theoretical foundations, we construct colloidal nanocrystal-graphene heterostructures with controlled interfacial structures and directly investigate the cross-sectional structures of them at high resolution by using aberration-corrected transmission electron microscopy. The experimental method and observations we present here will link the empirical methods for the formation of nanocrystal-graphene heterostructures to the mechanistic understanding of their properties.</P>

Subnanometer Vacancy Defects Introduced on Graphene by Oxygen Gas

Yamada, Yasuhiro,Murota, Kazumasa,Fujita, Ryo,Kim, Jungpil,Watanabe, Ayuko,Nakamura, Masashi,Sato, Satoshi,Hata, Kenji,Ercius, Peter,Ciston, Jim,Song, Cheng Yu,Kim, Kwanpyo,Regan, William,Gannett, Wil American Chemical Society 2014 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.136 No.6

<P>The basal plane of graphene has been known to be less reactive than the edges, but some studies observed vacancies in the basal plane after reaction with oxygen gas. Observation of these vacancies has typically been limited to nanometer-scale resolution using microscopic techniques. This work demonstrates the introduction and observation of subnanometer vacancies in the basal plane of graphene by heat treatment in a flow of oxygen gas at low temperature such as 533 K or lower. High-resolution transmission electron microscopy was used to directly observe vacancy structures, which were compared with image simulations. These proposed structures contain CO, pyran-like ether, and lactone-like groups.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2014/jacsat.2014.136.issue-6/ja4117268/production/images/medium/ja-2013-117268_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja4117268'>ACS Electronic Supporting Info</A></P>

Observation of Anisotropy in Thermal Conductivity of Individual Single-Crystalline Bismuth Nanowires

Roh, Jong Wook,Hippalgaonkar, Kedar,Ham, Jin Hee,Chen, Renkun,Li, Ming Zhi,Ercius, Peter,Majumdar, Arun,Kim, Woochul,Lee, Wooyoung American Chemical Society 2011 ACS NANO Vol.5 No.5

<P>The thermal conductivity of individual single-crystalline Bi nanowires grown by the on-film formation of nanowires (ON–OFF) has been investigated. We observed that the thermal conductivity of single-crystalline Bi nanowires is highly anisotropic. Thermal conductivity of nanowires (diameter ∼100 nm) in the off-axis [1̅02] and [110] directions exhibits a difference of ∼7.0 W/m·K. The thermal conductivity in both growth directions is diameter-dependent, which indicates that thermal transport through the individual Bi nanowires is limited by boundary scattering of both electrons and phonons. This huge anisotropy in thermal conductivities of Bi nanowires suggests the importance of direction-dependent characterization of charge, thermal transport, and thermoelectric properties of Bi nanowires.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-5/nn200474d/production/images/medium/nn-2011-00474d_0006.gif'></P>

Graphene Veils and Sandwiches

Yuk, Jong Min,Kim, Kwanpyo,Alemá,n, Benjamí,n,Regan, William,Ryu, Ji Hoon,Park, Jungwon,Ercius, Peter,Lee, Hyuck Mo,Alivisatos, A. Paul,Crommie, Michael F.,Lee, Jeong Yong,Zettl, Alex American Chemical Society 2011 NANO LETTERS Vol.11 No.8

<P>We report a new and highly versatile approach to artificial layered materials synthesis which borrows concepts of molecular beam epitaxy, self-assembly, and graphite intercalation compounds. It readily yields stacks of graphene (or other two-dimensional sheets) separated by virtually any kind of “guest” species. The new material can be “sandwich like”, for which the guest species are relatively closely spaced and form a near-continuous inner layer of the sandwich, or “veil like”, where the guest species are widely separated, with each guest individually draped within a close-fitting, protective yet atomically thin graphene net or veil. The veils and sandwiches can be intermixed and used as a two-dimensional platform to control the movements and chemical interactions of guest species.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-8/nl201647p/production/images/medium/nl-2011-01647p_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl201647p'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl201647p'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl201647p'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl201647p'>ACS Electronic Supporting Info</A></P>

Amorphous-Phase-Mediated Crystallization of Ni Nanocrystals Revealed by High-Resolution Liquid-Phase Electron Microscopy

Yang, Jiwoong,Koo, Jahyun,Kim, Seulwoo,Jeon, Sungho,Choi, Back Kyu,Kwon, Sangwoo,Kim, Joodeok,Kim, Byung Hyo,Lee, Won Chul,Lee, Won Bo,Lee, Hoonkyung,Hyeon, Taeghwan,Ercius, Peter,Park, Jungwon American Chemical Society 2019 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.141 No.2

<P>Nonclassical features of crystallization in solution have been recently identified both experimentally and theoretically. In particular, an amorphous-phase-mediated pathway is found in various crystallization systems as an important route, different from the classical nucleation and growth model. Here, we utilize high-resolution <I>in situ</I> transmission electron microscopy with graphene liquid cells to study amorphous-phase-mediated formation of Ni nanocrystals. An amorphous phase is precipitated in the initial stage of the reaction. Within the amorphous particles, crystalline domains nucleate and eventually form nanocrystals. In addition, unique crystallization behaviors, such as formation of multiple domains and dislocation relaxation, are observed in amorphous-phase-mediated crystallization. Theoretical calculations confirm that surface interactions can induce amorphous precipitation of metal precursors, which is analogous to the surface-induced amorphous-to-crystalline transformation occurring in biomineralization. Our results imply that an unexplored nonclassical growth mechanism is important for the formation of nanocrystals.</P> [FIG OMISSION]</BR>