The optical properties of gold and silver nanoparticles have been known for centuries, appearing in Roman glassware as well as medieval stained glass. An understanding of the phenomenon giving rise to these brilliant colors emerged in the last century: collective oscillations of conduction electrons called localized surface plasmon resonances (LSPRs) can be excited by light, leading to wavelength-dependent absorption and scattering. LSPRs have a broad technology potential as an attractive platform for surface-enhanced spectroscopies, non-bleaching labels, hyperthermal cancer therapy, waveguides, and so on. Excitingly, this light-matter interaction can be controlled by the size, shape, and dielectric environment of the nanoparticles; enabling the manipulation of LSPR energy, absorption/scattering ratio, light confinement, as well as far-field and near-field emission geometry, all important for specific applications.

Most plasmonic metals studied to date are composed of either Cu, Ag, and Au. The former two can pose significant challenges related to oxidation, the latter is often perceived as cost-prohibitive, and all three are rare. Recently, much attention has been focused on earth-abundant Al, which is an excellent plasmonic in the UV. This talk will briefly discuss colloidal Al nanoparticles as a plasmonic material, then report results on a new composition: magnesium. Mg nanoparticles are remarkably active plasmonics across the UV, Vis and NIR, as shown optically and with STEM-EELS. Surprisingly, they are stable in air for weeks owing to a self-limiting oxide layer. Colloidal Mg has potential on its own as a plasmonic structure, and can also be used as a scaffold for additional surface chemistry, sensing, and hybrid photocatalysts.

Electron tomography is a technique used in both materials science and structural biology to image features well below optical resolution limit. In this work, we present a new algorithm for reconstructing the three-dimensional(3D) electrostatic potential of a sample at atomic resolution from phase contrast imaging using high-resolution transmission electron microscopy. Our method accounts for dynamical and strong phase scattering, providing more accurate results with much lower electron doses than those current atomic electron tomography experiments. Our simulation results show that, for a wide range of experimental parameters, we can accurately determine both atomic positions and species, and also identify vacancies even for light elements such as silicon and disordered materials such as amorphous silicon dioxide and also identify vacancies. Our preliminary experimental results also show promising outcome of the method.

In the last century and defining the first two decades of this one, the development of novel materials and manufacturing processes has demanded the advancement of new characterization techniques. This characterization leveraged light in its many rich forms: While optical probes proved tractable in the first half of this timeframe, it took the emergence of synchrotrons and other X-ray sources and optics to penetrate matter and move to higher photon energies. Only in the very recent past, however, have innovators been able to successfully utilize the Vacuum region of the spectrum (VUV, EUV, and Soft X-ray) effectively in the laboratory. This long-overlooked region of the spectrum is proving to be a rich and promising probe for practical materials and devices—filling a void in the existing characterization and imaging space.

In this talk, we will discuss the advent of Coherent EUV light as the next technique to complement this correlative suite of instruments. Uniquely merging diffractive imaging, spectroscopic, and time-resolved measurements enables key applications that will unlock new avenues ranging from Semiconductor metrology, fundamental materials and device characterization. We will discuss how it takes a diverse and extensive team to bring such technology from an idea to impact. More importantly, we will discuss the evolution of a technology that has been taken from the limited confines of the Synchrotron community to very soon becoming a laboratory instrument available to augment the rich tool suite now relied upon by academic researchers and industrial microscopists alike.

Zinc-gallium oxynitride (Ga1-xZnx)(N1-xOx) exhibits visible absorption with a band gap that depends on composition (i.e., the value of x) and has been demonstrated to split water under visible irradiation. The origin of visible absorption in this solid solution material in this material is not understood. Furthermore, the local atomic-level distribution of the 4 elements, Ga, Zn, N, and O may play an important role in the optical properties of (Ga1-xZnx)(N1-xOx).

This presentation will focus on our use of scanning transmission electron microscopy (STEM) tools to characterize the local composition and electronic structure of these particles. I will describe the elemental distribution within (Ga1-xZnx)(N1-xOx) nanocrystals, measured by Energy Dispersive X-ray Spectroscopy (EDS) with sub-nm resolution, as well as the methods to control compositional disorder. Furthermore, I will describe our ongoing efforts to use Electron Energy Loss Spectroscopy (EELS) to correlate local composition with local electronic structure and elucidate the relationship between the two. Together, these tools allow us to postulate a comprehensive picture of the optical properties of (Ga1-xZnx)(N1-xOx) nanocrystals.

Cryo electron microscopy (cryoEM) has emerged as a tool of choice for determining three-dimensional (3D) structures of macromolecular complexes or biological nano-machines (>50 kDa) in their native forms. When such complexes can be isolated in microgram quantities, atomic models can now be obtained by cryoEM single-particle analysis and model building. Comparisons of atomic models obtained for the same complex at different functional states provide mechanistic insights for its functions. For pleomorphic complexes, such as those in their cellular or tissue environments, molecular resolution structures can be reconstructed by cryo electron tomography (cryoET). Examples will be presented to illustrate the power of cryoEM in visualizing 3D structures of nano-scale biological machines containing proteins, nucleic acids or lipids to inform such fundamental biological processes as genome transcription, molecular translocation and infectious diseases.

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