Peter Ercius

A correlative analysis combining three‐dimensional (3D) electron tomography and small convergence angle convergent‐beam electron diffraction acquired in four‐dimensional scanning transmission electron microscopy (4D‐STEM) mode is used to investigate the structure, crystallographic orientation, and strain distribution in thermally welded silver nanowire (AgNW) junctions. High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) tomography enables reconstruction of the asymmetric and faceted morphology of AgNW welds, revealing distinct ridge continuity and facet‐specific junction geometries. Complementary diffraction mapping demonstrates orientation inheritance across the junction and crystallographic continuity within the welded region. Full‐field strain maps derived from nanobeam 4D‐STEM reveal minimal coherent strain (typically <0.5%) and small rotational distortions associated with nanowire bending. This multidimensional correlation of geometry, crystallography, and strain provides insight into weld formation mechanisms and interfacial behavior beyond the limits of conventional two‐dimensional and localized atomic‐resolution studies.

Achieving high‐energy‐density and long‐term cycling stability in Mn‐redox‐based cathodes is a critical step toward advancing Ni‐ and Co‐free Li‐ion chemistries to diversify supply chains and lower battery costs. Here, we demonstrate an unusually high performance benchmark for Mn‐redox cathodes using near‐micron single‐crystalline δ‐phase cation‐disordered rocksalt (δ‐DRX), derived from Mn‐rich DRX, delivering ≈640 Wh kg ⁻¹ with ≈97% capacity retention over 400 cycles. The very high energy density and cycle life were achieved by using a high Mn content, to suppress oxygen redox activity, and careful control of the synthesis parameters to tune single crystal particle size. Using high‐throughput automated electron microscopy, we identify interparticle compositional heterogeneity present in the early stage of phase‐pure DRX formation as the origin of orthorhombic LiMnO ₂ impurity formation during cooling, a finding that rationalizes the long high‐temperature dwell times required and the associated particle coarsening in conventional synthesis. We demonstrate that an accelerated cooling strategy kinetically suppresses localized impurity formation, reducing long high‐temperature exposure, and enables downsizing of single‐crystalline Mn‐rich DRX particles to the near‐micron regime (D50 = 1.5 µm). This work provides a mechanistic basis for particle‐size control in Mn‐rich DRX synthesis, and presents δ‐DRX as a stable, sustainable, high‐performance, Ni‐ and Co‐free cathode material.

C-H terminated nanometer scale diamonds (d = 1 to 15 nm) are synthesized from 1-fluoroadamantane at high pressure (6-8 GPa) and high temperature (500-1500 °C) in a multianvil press. High resolution transmission electron microscopy, X-ray diffraction, Raman, diffuse reflectance Fourier transform infrared, and X-ray absorption spectroscopies demonstrate the excellent crystallinity and atomically flat C-H terminated surfaces of nanodiamonds with (111) and (110) facets. The importance of hydrogen to the synthesis of nanodiamond and its faceting is discussed. Following vacancy generation, annealing and oxidation of the nanodiamonds, optically detected magnetic resonance and electron spin resonance coherence times (T₂ = 0.9 and 2.1 μs) of nitrogen vacancy (NV) centers are measured. The obtained T₂ values are equivalent to the shallow NV centers (depth <10 nm) in bulk diamond crystals and larger nanocrystals prepared by mechanical milling.

The development of functional nanomaterials with controlled morphologies is essential for advancements in medicine, electronics and computing, energy, catalysis, and environmental applications. However, conventional synthesis methods often demand high energy input and pose significant environmental challenges. Urease-based biomineralization presents an efficient, eco-friendly alternative for nanomaterial production under mild conditions. In this study, we engineered Escherichia coli (E. coli) to express a urease gene cluster from Sporosarcina pasteurii using CRAGE-Duet technology. The engineered strain successfully synthesized calcium carbonate and calcium phosphate crystals. Expanding the approach, we synthesized metal oxide nanoparticles, including hematite (Fe₂O₃), and nanocrystalline anatase titanium dioxide (TiO₂). These nanomaterials were characterized by electron microscopy, demonstrating the potential of E. coli as a sustainable and versatile platform for green nanomaterial synthesis.

Electron microscopy (EM) is fundamental to nanocrystal characterization, but some structures degrade quickly under electron beams, limiting advanced structural characterization. Here, we introduce a synthetic strategy that combines layer-by-layer shell growth with in situ annealing to produce NaYb_0.8Er_0.2F₄ alloyed upconverting nanoparticles (UCNPs) with enhanced structural stability and optical properties. Using an automated synthesis platform to control precursor delivery and annealing cycles, high rare-earth ion concentrations are maintained during shell growth and annealing at high temperature, reducing luminescence quenching and degradation under electron beams. This in situ annealing layer-by-layer (ISA-LBL) approach gives rise to alloyed UCNPs (aUCNPs) with exceptional electron-beam stability, reducing beam-induced fractures and voids by >90% compared to conventionally synthesized aUCNPs. ISA-LBL aUCNPs also exhibit enhanced photoluminescence intensity and extended lifetimes, consistent with fewer quenching defects. This demonstrates a synthetic route to nanocrystals with enhanced structural integrity, increasing their compatibility with EM studies and their utility in ionizing environments.

Diamine functionalization of the metal–organic framework Mg₂(dobpdc) (dobpdc^4– = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) significantly enhances its selectivity for CO₂ capture from flue gases and air. The structure and CO₂ capacity of such materials are typically assessed using bulk techniques that rely on averaging signal over large ensembles of unit cells, obscuring local heterogeneities, such as variations in CO₂ occupancy across individual nanocrystals. To resolve this limitation, we demonstrate a multimodal, nanoscale characterization of Mg₂(dobpdc) appended with 1,3-diaminopropane. By employing recently developed characterization techniques at progressively smaller length scales, we uncover insights from correspondingly smaller populations of unit cells. First, we use parallel-beam 3D electron diffraction (3D ED) to identify a prominent expansion in lattice parameters upon desorption of CO₂, as observed at the level of single nanocrystals. Second, we use convergent-probe 4D scanning transmission electron microscopy (4D-STEM) to quantify associated differences in lattice strain as a function of gas loading and diamine appending. These measurements sample small subvolumes within individual nanocrystals. Finally, we apply infrared scattering scanning near-field optical microscopy (IR s-SNOM) to confirm variable CO₂ chemisorption across adsorption sites at the surface of single nanocrystals. This multimodal, multiscale approach allows us to map heterogeneity within individual nanocrystals. Collectively, these findings emphasize the importance of local, nanoscale characterization of metal–organic frameworks in revealing previously unresolvable features that impact their performance.

Despite their adaptability and mechanical stability, Pickering emulsions based on the interfacial assembly of colloidal particles have not found use in iontronics, since the dense interfacial packing of micron-sized particles precludes functional connectivity between two droplets. Here, we introduce a chemically reconfigurable droplet interface bilayer (DIB) platform based on the interfacial assembly of nanoparticle-surfactants (NPSs) that enables spontaneous or field-induced formation of ion-conducting nanochannels, eliminating the need of ionophores or nanochannel-forming proteins. These nanoscopic channels emerge from packing defects in the jammed interfacial assemblies of the charged NPSs and support size and charge selective, hysteretic ion transport governed by interfacial electrostatics and dimensional constraints. The NPS-DIBs show short-term and long-term plasticity, hallmarks of neuromorphic behavior, that are mediated by the structural and chemical design of the bilayer. These assemblies establish a versatile, chemically tunable platform that couples soft-matter mechanics with interfacial ionic functionality, offering a robust foundation for soft iontronic systems.

Macromolecular crystallography has historically inferred models of internal crystal architecture from reciprocal-space measurements of Bragg reflections. Nevertheless, direct real-space visualization of crystallographic disorder remains elusive, particularly at the nanoscale. Using a 15-nanometer probe, here we apply both ambient-temperature and cryogenic four-dimensional scanning transmission electron microscopy (4D–STEM) to map the topography of coherently diffracting domains (CDDs) in lysozyme and myoglobin microcrystals at length scales 100× finer than conventional X-ray and electron beams. Virtual dark-field reconstructions from individual Bragg reflections reveal that each peak arises from spatially distinct subvolumes. Subdomain analysis demonstrates that these CDDs behave as orientationally monolithic units analogous to single mosaic blocks. Under sustained irradiation, protein CDDs undergo continuous rearrangements spanning several micrometers of internal movement. Furthermore, pinpoint high-dose “impact crater” experiments reveal delocalized radiolytic damage propagating hundreds of nanometers from primary irradiation sites, behavior similar to small-molecule crystals but amplified in both rate and magnitude. Together, these results establish macromolecular microcrystals as dynamic assemblies whose internal architecture continuously reorganizes during irradiation, laying the foundation for realistic models of mosaicity directly informed by both real-space and reciprocal-space observations.