Lithium dendrite intrusion in solid-state batteries limits fast charging and causes short-circuiting, yet the underlying regulating mechanisms are not well-understood. Here we discover that heterogeneous Ag+ doping dramatically affects lithium intrusion into Li6.6La3Zr1.6Ta0.4O12 (LLZO), a brittle solid electrolyte. Nanoscale Ag+ doping is achieved by thermally annealing a 3-nm-thick metallic coating on LLZO, inducing Ag–Li ion exchange and Ag diffusion into grains and grain boundaries. Density functional theory calculations and experimental characterization show negligible impact on the electronic properties and surface wettability from Ag+ incorporation. Mechanically, nanoindentation experiments show a fivefold increase in the mechanical force required to fracture the surface Ag+-doped LLZO, indicating substantial doping-induced surface toughening. Operando microprobe scanning electron microscopy experiments show that the Ag+-doped LLZO surface exhibits improved lithium plating at >250 mA cm−2 and an electroplating diameter that is expanded by over fourfold, even under an extreme indentation stress of 3 GPa. This demonstrates enhanced defect tolerance in LLZO, rather than electronic or adhesion effects. Our study reveals a chemo-mechanical mechanism via surface heterogeneous doping, complementing present bulk design rules to minimize mechanical failures in solid-state batteries. Short-circuiting during fast charging through lithium dendrite intrusion into electrolytes is a major challenge in solid-state batteries. Here, using thermally annealed 3-nm-thick Ag coatings, lithium penetration into brittle electrolyte Li6.6La3Zr1.6Ta0.4O12 is inhibited at local current densities of 250 mA cm−2 due to an increase in surface fracture toughness.

Organic-inorganic perovskites are an emerging class of photovoltaic materials. Despite achieving power conversion efficiencies surpassing 26%, the challenge of perovskite stability including degradation during exposure to operational conditions such as light, heat, humidity, water, oxygen, and electric fields is well known. Related, perovskite instability has limited high-resolution electron imaging and characterization techniques that can be used for understanding degradation mechanisms. Here, we demonstrate perovskite device cross-section preparation using mechanical polishing in a water-free environment with cryogenic Ar ion milling. Scanning electron microscopy was then used in both backscattered electron and secondary electron imaging modes to obtain information about layer structure, grain aggregate structure, and compositional heterogeneity. Monte Carlo CASINO simulations inform optimum beam conditions and image acquisition parameters and the effects of accelerating voltage, dwell times, and frame averaging for practical image acquisition are reported.

Multiple quantum well (MQW) light-emitting diodes (LEDs) provide precise wavelength control, making them ideal light sources. However, achieving simultaneous short-wavelength infrared (SWIR, 1-3 µm) and mid-wavelength infrared (MWIR, 3-5 µm) emission from a single LED presents significant technical challenges due to lattice mismatch and reduced quantum efficiency when MQW structures with distinct bandgap energies are integrated onto a single substrate. As a result, most LEDs typically operate in only one IR band. In this study, monolithic multi-band MQW LEDs capable of simultaneous SWIR and MWIR emission are demonstrated. Strain engineering via Sb doping in the QWs induces well-distributed local lattice distortions, such as modulations of atomic bond angles and lengths, leading to balanced strain compensation and coherent epitaxy with atomically sharp interfaces within the MQWs. Reducing the QW thickness of InAsSb enhances quantum confinement, enabling simultaneous SWIR and MWIR emission at 2.87 and 3.18 µm. To further extend the emission range, a simulation-based fabrication feasibility map is developed, and an additional monolithic LED that emits simultaneously at 2.63 and 3.34 µm is fabricated. The monolithic integration of multi-band emission into a single device not only reduces size and complexity but also facilitates multispectral analysis for future optoelectronic devices.

Transition metal perovskite oxides are employed as air electrode catalysts for solid-oxide fuel cells and electrolyzers. However, degradation linked to cation segregation and precipitation involving alkaline-earth substituents limits their commercialization. In this work, we engineered a multilayer electrode consisting of an ultrathin (La1_xSrx)FeO3_s catalyst overlayer (x = 0, 0.5), a cation-migration-suppression Pr0.1Ce0.9O2_ s layer, and a bulk-transport (La0.5Sr0.5)FeO3_ s layer. This "trilayer" electrode structure enables the surface reactivity and stability to be optimized independently from the bulk transport: an architecture that mitigates the segregation of available Sr and other cations from the bulk reservoir and their subsequent precipitation at the solid-gas interface. This trilayer architecture reduced surface reaction resistance and long-term degradation by over an order of magnitude at 650 degrees C over 48 h. The approach offers a general pathway for designing multilayer electrode coatings with decoupled catalytic and transport functionalities.

This study investigates the bending fatigue performance of Vacuum Arc Remelted/Electron Beam Refined (VAR/EBR) Nitinol for cardiovascular applications. Diamond-shaped fatigue specimens were manufactured from ultra-clean VAR/EBR Nitinol tubing with inclusion sizes below 10 μm and tested under physiologically relevant conditions to 100 million cycles. Testing included multiple combinations of mean strains (0–7

The ability to freeze and stabilize reaction intermediates in their metastable states and obtain their structural and chemical information with high spatial resolution would be very powerful to unravel the fundamentals in many important materials technologies such as catalysis and batteries. Here, we develop an electrified operando-freezing methodology for the first time to preserve these metastable states under electrochemical reaction conditions for cryogenic electron microscopy (cryo-EM) imaging and spectroscopy. Using Cu catalysts for CO2 reduction as a model system, we observe restructuring of the Cu catalyst in a CO2 atmosphere while the same catalyst remains intact in an air atmosphere at the nanometer scale. Furthermore, we discover the existence of single valance Cu (1+) state and C-O bonding at the electrified liquid-solid interface of the operando-frozen samples, which are key reaction intermediates that traditional ex situ measurements fail to detect. This work highlights our novel technique to study the local structure and chemistry of electrified liquid-solid interfaces, which has broad impact for many electrochemical reactions.

Abstract Transcatheter heart valve replacement is a key advancement in the cardiovascular device industry and provides an alternative to open surgical procedures for patients that suffer from severe symptomatic stenosis and/or regurgitation. The functions and boundary conditions of the four heart valves are unique and must be considered separately. It is essential that the structural durability of these high-risk valve replacement implants is thoroughly assessed through testing and analysis. As such, ISO 5840 outlines a comprehensive device durability approach that incorporates worst-case boundary conditions, computational stress/strain analyses, and benchtop fatigue testing. The present study is focussed on 100,000,000-cycle fatigue testing of custom-designed “diamond-shaped” coupons of process-optimized high purity VAR/EBR Nitinol. Benchtop testing was coupled with finite element analysis (FEA) and microstructural characterization to provide an in-depth understanding of durability.

Atomic scale, scanning transmission electron microscopy (STEM) analysis of the moiré structures in twisted epitaxial gold nanodiscs encapsulated in twisted bilayer molybdenum disulfide is presented. High angle annular dark field STEM imaging reveals that the period of the moiré patterns between gold and molybdenum disulfide varies with different twist angles of the bilayer molybdenum disulfide, ranging from 1.80 nm (epitaxial alignment of gold) to 1.53 nm (twisted epitaxial alignment of gold). Additionally, bright field STEM imaging reveals a faint, larger "moiré of moiré" structure in cases where the bilayer molybdenum disulfide twist angle is small (∼6°), arising from the overlapping three-layers, which is not visible in conventional transmission electron microscopy images. Our experiments indicate that scanning transmission electron microscopy as a suitable tool for moiré analysis of twisted multilayer planar heterostructures, complementary to information provided by conventional transmission electron microscopy and diffraction.

We expand the concept of epitaxy to a regime of “twisted epitaxy” with the epilayer crystal orientation between two substrates influenced by their relative orientation. We annealed nanometer-thick gold (Au) nanoparticles between two substrates of exfoliated hexagonal molybdenum disulfide (MoS 2 ) with varying orientation of their basal planes with a mutual twist angle ranging from 0° to 60°. Transmission electron microscopy studies show that Au aligns midway between the top and bottom MoS 2 when the twist angle of the bilayer is small (<~7°). For larger twist angles, Au has only a small misorientation with the bottom MoS 2 that varies approximately sinusoidally with twist angle of the bilayer MoS 2 . Four-dimensional scanning transmission electron microscopy analysis further reveals a periodic strain variation (<|±0.5%|) in the Au nanodisks associated with the twisted epitaxy, consistent with the Moiré registry of the two MoS 2 twisted layers.

Diamond color centers have proven to be versatile quantum emitters and exquisite sensors of stress, temperature, electric and magnetic fields, and biochemical processes. Among color centers, the silicon-vacancy (SiV[Formula: see text]) defect exhibits high brightness, minimal phonon coupling, narrow optical linewidths, and high degrees of photon indistinguishability. Yet the creation of reliable and scalable SiV[Formula: see text]-based color centers has been hampered by heterogeneous emission, theorized to originate from surface imperfections, crystal lattice strain, defect symmetry, or other lattice impurities. Here, we advance high-resolution cryo-electron microscopy combined with cathodoluminescence spectroscopy and 4D scanning transmission electron microscopy (STEM) to elucidate the structural sources of heterogeneity in SiV[Formula: see text] emission from nanodiamond with sub-nanometer-scale resolution. Our diamond nanoparticles are grown directly on TEM membranes from molecular-level seedings, representing the natural formation conditions of color centers in diamond. We show that individual subcrystallites within a single nanodiamond exhibit distinct zero-phonon line (ZPL) energies and differences in brightness that can vary by 0.1 meV in energy and over 70% in brightness. These changes are correlated with the atomic-scale lattice structure. We find that ZPL blue-shifts result from tensile strain, while ZPL red shifts are due to compressive strain. We also find that distinct crystallites host distinct densities of SiV[Formula: see text] emitters and that grain boundaries impact SiV[Formula: see text] emission significantly. Finally, we interrogate nanodiamonds as small as 40 nm in diameter and show that these diamonds exhibit no spatial change to their ZPL energy. Our work provides a foundation for atomic-scale structure-emission correlation, e.g., of single atomic defects in a range of quantum and two-dimensional materials.

Journal Article Twisted Epitaxial Growth of Gold Nanodiscs Confined in Twisted Bilayer Molybdenum Disulfide Get access Yi Cui, Yi Cui Department of Materials Science and Engineering, Stanford University, Stanford, CA, United States Search for other works by this author on: Oxford Academic Google Scholar Robert Sinclair, Robert Sinclair Department of Materials Science and Engineering, Stanford University, Stanford, CA, United States Corresponding authors: bobsinc@stanford.edu, yicui@stanford.edu Search for other works by this author on: Oxford Academic Google Scholar Yi Cui Yi Cui Department of Materials Science and Engineering, Stanford University, Stanford, CA, United States Corresponding authors: bobsinc@stanford.edu, yicui@stanford.edu Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Pages 1657–1658, https://doi.org/10.1093/micmic/ozad067.853 Published: 22 July 2023

MicroRNAs are critical regulators of cancer initiation, progression, and dissemination. Extensive evidence suggests that the inhibition of over-expressed oncogenic miRNA function can be a robust strategy for anticancer therapy. However, in vivo targeted delivery of miRNA therapeutics to various types of cancers remains a major challenge. Inspired by their natural synthesis and cargo delivery capabilities, researchers have exploited tumor cell-derived extracellular vesicles (TEVs) for the cancer-targeted delivery of therapeutics and theranostics. Here, we investigate a TEV-based nanoplatform for multimodal miRNA delivery and phototherapy treatments as well as the magnetic resonance imaging of cancer. We demonstrated loading of anti-miR-21 that blocks the function of endogenous oncogenic miR-21 over-expressed in cancer cells into and subsequent delivery by TEVs derived from 4T1 cells. We also produced Cy5-anti-miR-21-loaded TEVs from two other cancer cell lines (HepG2 and SKBR3) and confirmed their robust homologous and heterologous transfection efficiency and intracellular Cy5-anti-miR-21 delivery. Additionally, TEV-mediated anti-miR-21 delivery attenuated doxorubicin (DOX) resistance in breast cancer cells with a 3-fold higher cell kill efficiency than in cells treated with DOX alone. We then investigated TEVs as a biomimetic source for the functionalization of gold iron oxide nanoparticles (GIONs) and demonstrated nanotheranostic properties of TEV-GIONs in vitro. TEV-GIONs demonstrated excellent T2 contrast in in vitro magnetic resonance (MR) imaging and resulted in efficient photothermal effect in 4T1 cells. We also evaluated the biodistribution and theranostic property of anti-miR-21 loaded TEV-GIONs in vivo by labeling with indocyanine green near-infrared dye. We further validated the tumor specific accumulation of TEV-GIONs using MR imaging. Our findings demonstrate that the distribution pattern of the TEV-anti-miR-21-GIONs correlated well with the tumor-targeting capability as well as the activity and efficacy obtained in response to doxorubicin combination treatments. TEVs and TEV-GIONs are promising nanotheranostics for future applications in cancer molecular imaging and therapy.

The oxygen reduction reaction (ORR) is rate-limiting in polymer electrolyte fuel cells over a wide range of overpotentials. To improve our understanding of the underlying physics and chemistry of ORR, we created a model system with atomically-ordered interfaces that allows us to distinguish between bulk and electronic effects on catalytic behavior. Specifically, we developed a facile way of growing thin, epitaxial Pt nanostructures on graphene, which serves as both growth substrate and electrode. Rotating disc electrode measurements showed a high specific activity relative to platinum on glassy carbon. The enhanced ORR activity was observed despite consistent measurements that show a small electrochemically-active surface area arising from the fact that virtually all carbon atoms in monolayer graphene are surface atoms. This talk will address the reasons for the increase of ORR activity in view of the new ground state of atomically thin platinum on graphene.

Silicon-vacancy (SiV$^-$) centers in diamond are promising candidates as sources of single-photons in quantum networks due to their minimal phonon coupling and narrow optical linewidths. Correlating SiV$^-$ emission with the defect's atomic-scale structure is important for controlling and optimizing quantum emission, but remains an outstanding challenge. Here, we use cathodoluminescence imaging in a scanning transmission electron microscope (STEM) to elucidate the structural sources of non-ideality in the SiV$^-$ emission from nanodiamonds with sub-nanometer-scale resolution. We show that different crystalline domains of a nanodiamond exhibit distinct zero-phonon line (ZPL) energies and differences in brightness, while near-surface SiV$^-$ emitters remain bright. We correlate these changes with local lattice expansion using 4D STEM and diffraction, and show that associated blue shifts from the ZPL are due to defect density heterogeneity, while red shifts are due to lattice distortions.

The development of inexpensive and abundant catalysts with high activity, selectivity, and stability for the oxygen reduction reaction (ORR) is imperative for the widespread implementation of fuel cell devices. Herein, we present a combined theoretical-experimental approach to discover and design first-row transition metal antimonates as promising electrocatalytic materials for the ORR. Theoretically, we identify first-row transition metal antimonates – MSb2O6, where M = Mn, Fe, Co, and Ni – as non-precious metal catalysts with promising oxygen binding energetics, conductivity, thermodynamic phase stability and aqueous stability. Among the considered antimonates, MnSb2O6 shows the highest theoretical ORR activity based on the 4e− ORR kinetic volcano. Experimentally, nanoparticulate transition metal antimonate catalysts are found to have a minimum of a 2.5-fold enhancement in intrinsic mass activity (on transition metal mass basis) relative to the corresponding transition metal oxide at 0.7 V vs RHE in 0.1 M KOH. MnSb2O6 is the most active catalyst under these conditions, with a 3.5-fold enhancement on a per Mn mass activity basis and 25-fold enhancement on a surface area basis over its antimony-free counterpart. Electrocatalytic and material stability are demonstrated over a 5 h chronopotentiometry experiment in the stability window identified by Pourbaix analysis. This study further highlights the stable and electrically conductive antimonate structure as a promising framework to tune the activity and selectivity of non-precious metal oxide active sites for ORR catalysis.

Current clinical brain tumour therapy practices are based on tumour resection and post-operative chemotherapy or X-ray radiation. Resection requires technically challenging open-skull surgeries that can lead to major neurological deficits and, in some cases, death. Treatments with X-ray and chemotherapy, on the other hand, cause major side-effects such as damage to surrounding normal brain tissues and other organs. Here we report the development of an integrated nanomedicine-bioelectronics brain-machine interface that enables continuous and on-demand treatment of brain tumours, without open-skull surgery and toxicological side-effects on other organs. Near-infrared surface plasmon characteristics of our gold nanostars enabled the precise treatment of deep brain tumours in freely behaving mice. Moreover, the nanostars' surface coating enabled their selective diffusion in tumour tissues after intratumoral administration, leading to the exclusive heating of tumours for treatment. This versatile remotely controlled and wireless method allows the adjustment of nanoparticles' photothermal strength, as well as power and wavelength of the therapeutic light, to target tumours in different anatomical locations within the brain.