Argyrodite-Li6PS5Cl/Polymer-based Highly Conductive Composite Electrolyte for All-Solid-State Batteries.

Solid-state batteries (SSBs) that incorporate the argyrodite-Li6PS5Cl (LPSCl) electrolyte hold potential as substitutes for conventional lithium-ion batteries (LIBs). However, the mismatched interface between the LPSCl electrolyte and electrodes leads to increased interfacial resistance and the rapid growth of lithium (Li) dendrites. These factors significantly impede the feasibility of their widespread industrial application. In this study, we developed a composite electrolyte of the LPSCl/polymer to enhance the contact between the electrolyte and electrodes and suppress dendrite formation at the grain boundary of the LPSCl ceramic. The monomer, triethylene glycol dimethacrylate (TEGDMA), is utilized for in situ polymerization through thermal curing to create the argyrodite LPSCl/polymer composite electrolyte. Additionally, the ball-milling technique was employed to modify the morphology and particle size of the LPSCl ceramic. The ball-milled LPSCl/polymer composite electrolyte demonstrates slightly higher ionic conductivity (ca. 2.21 × 10-4 S/cm) compared to the as-received LPSCl/polymer composite electrolyte (ca. 1.65 × 10-4 S/cm) at 25 °C. Furthermore, both composite electrolytes exhibit excellent compatibility with Li-metal and display cycling stability for up to 1000 h (375 cycles), whereas the as-received LPSCl and ball-milled LPSCl electrolytes maintain stability for up to 600 h (225 cycles) at a current density of 0.4 mA/cm2. The SSB with the ball-milled LPSCl/polymer composite electrolyte delivers high specific discharge capacity (138 mA h/g), Coulombic efficiency (99.97%), and better capacity retention at 0.1C, utilizing the battery configuration of coated NMC811//electrolyte//Li-Indium (In) at 25 °C.

Ultrahigh-resolution scanning microwave impedance microscopy of moiré lattices and superstructures.

Two-dimensional heterostructures composed of layers with slightly different lattice vectors exhibit new periodic structure known as moiré lattices, which, in turn, can support novel correlated and topological phenomena. Moreover, moiré superstructures can emerge from multiple misaligned moiré lattices or inhomogeneous strain distributions, offering additional degrees of freedom in tailoring electronic structure. High-resolution imaging of the moiré lattices and superstructures is critical for understanding the emerging physics. Here, we report the imaging of moiré lattices and superstructures in graphene-based samples under ambient conditions using an ultrahigh-resolution implementation of scanning microwave impedance microscopy. Although the probe tip has a gross radius of ~100 nm, spatial resolution better than 5 nm is achieved, which allows direct visualization of the structural details in moiré lattices and the composite super-moiré. We also demonstrate artificial synthesis of novel superstructures, including the Kagome moiré arising from the interplay between different layers.

Controlled Assembly of Upconverting Nanoparticles for Low-Threshold Microlasers and Their Imaging in Scattering Media.

Micron-sized lasers fabricated from upconverting nanoparticles (UCNP) coupled to whispering gallery mode (WGM) microresonators can exhibit continuous-wave anti-Stokes lasing useful for tracking cells, environmental sensing, and coherent stimulation of biological activity. The integration of these microlasers into organisms and microelectronics requires even smaller diameters, however, which raises threshold pump powers beyond practical limits for biological applications. To meet the need for low lasing thresholds and high fidelity fabrication methods, we use correlative optical and electron microscopy to uncover the nanoparticle assembly process and structural factors that determine efficient upconverted lasing. We show that 5 µm microspheres with controlled submonolayer UCNP coatings exhibit, on average, 25-fold lower laser thresholds (1.7 ± 0.7 kW/cm2) compared to the mean values of the lowest threshold UCNP lasers, and variability is reduced 30-fold. WGMs are observed in the upconversion spectra for TiO2-coated microspheres as small as 3 µm, a size at which optical losses had previously prevented such observations. Finally, we demonstrate that the WGM signatures of these upconverting microlasers can be imaged and distinguished through tissue-mimicking phantoms. These advances will enable the fabrication of more efficient upconverting lasers for imaging, sensing, and actuation in optically complex environments.

Polymer-metal coating for high contrast SEM cross sections at the deep nanoscale.

In scanning electron microscopy (SEM), imaging nanoscale features by means of the cross-sectioning method becomes increasingly challenging with shrinking feature sizes. However, obtaining high quality images, at high magnification, is crucial for critical dimension and patterned feature evaluation. Therefore, in this work, we present a new sample preparation method for high performance cross-sectional secondary electron (SE) imaging, targeting features at the deep nanoscale and into the sub-10 nm regime. Different coating architectures including conductive and non-conductive polymer, carbon and metal are compared on their ability to discern etching feature profiles and materials interfaces of densely packed nano-patterned features. A stacked coating of polymer and metal produced better visibility mainly due to enhancement of contrast between feature and background. Contrast was evaluated by using histograms of intensity of gray levels directly derived from SE images, obtained by the SE in-lens detector. In polymer-metal coatings (PMC), optimization of contrast is explored by varying the thickness of the metal layer and results are discussed in terms of the effectiveness of the metal layer in reducing the escape of secondary electrons (SE) generated in the polymer layer and feature. Other advantages of PMCs are their cleanroom compatibility and ease of coating removal.

Low irradiance multiphoton imaging with alloyed lanthanide nanocrystals.

Multiphoton imaging techniques that convert low-energy excitation to higher energy emission are widely used to improve signal over background, reduce scatter, and limit photodamage. Lanthanide-doped upconverting nanoparticles (UCNPs) are among the most efficient multiphoton probes, but even UCNPs with optimized lanthanide dopant levels require laser intensities that may be problematic. Here, we develop protein-sized, alloyed UCNPs (aUCNPs) that can be imaged individually at laser intensities >300-fold lower than needed for comparably sized doped UCNPs. Using single UCNP characterization and kinetic modeling, we find that addition of inert shells changes optimal lanthanide content from Yb3+, Er3+-doped NaYF4 nanocrystals to fully alloyed compositions. At high levels, emitter Er3+ ions can adopt a second role to enhance aUCNP absorption cross-section by desaturating sensitizer Yb3+ or by absorbing photons directly. Core/shell aUCNPs 12 nm in total diameter can be imaged through deep tissue in live mice using a laser intensity of 0.1 W cm-2.

Peptoid nanosheets as soluble, two-dimensional templates for calcium carbonate mineralization.

Nacre-mimetic materials are of great interest, but difficult to synthesize, because they require the ordering of organic and inorganic materials on several length scales. Here we introduce peptoid nanosheets as a versatile two-dimensional platform to develop nacre mimetic materials. Free-floating zwitterionic nanosheets were mineralized with thin films of amorphous calcium carbonate (of 2-20 nm thickness) on their surface to produce planar nacre synthons. These can serve as tunable building blocks to produce layered brick and mortar nanoarchitectures.

Catalyst-directed crystallographic orientation control of GaN nanowire growth.

In this work, we demonstrate that catalyst composition can be used to direct the crystallographic growth axis of GaN nanowires. By adjusting the ratio of gold to nickel in a bimetallic catalyst, we achieved selective growth of dense, uniform nanowire arrays along two nonpolar directions. A gold-rich catalyst resulted in single-crystalline nanowire growth along the ⟨11̅00⟩ or m axis, whereas a nickel-rich catalyst resulted in nanowire growth along the ⟨112̅0⟩ or a axis. The same growth control was demonstrated on two different epitaxial substrates. Using proper conditions, many of the nanowires were observed to switch direction midgrowth, resulting in monolithic single-crystal structures with segments of two distinct orientations. Cathodoluminescence spectra revealed significant differences in the optical properties of these nanowire segments, which we attribute to the electronic structures of their semipolar {112̅2} or {11̅01} sidewalls.

Engineering bright sub-10-nm upconverting nanocrystals for single-molecule imaging.

Imaging at the single-molecule level reveals heterogeneities that are lost in ensemble imaging experiments, but an ongoing challenge is the development of luminescent probes with the photostability, brightness and continuous emission necessary for single-molecule microscopy. Lanthanide-doped upconverting nanoparticles overcome problems of photostability and continuous emission and their upconverted emission can be excited with near-infrared light at powers orders of magnitude lower than those required for conventional multiphoton probes. However, the brightness of upconverting nanoparticles has been limited by open questions about energy transfer and relaxation within individual nanocrystals and unavoidable tradeoffs between brightness and size. Here, we develop upconverting nanoparticles under 10 nm in diameter that are over an order of magnitude brighter under single-particle imaging conditions than existing compositions, allowing us to visualize single upconverting nanoparticles as small (d = 4.8 nm) as fluorescent proteins. We use advanced single-particle characterization and theoretical modelling to find that surface effects become critical at diameters under 20 nm and that the fluences used in single-molecule imaging change the dominant determinants of nanocrystal brightness. These results demonstrate that factors known to increase brightness in bulk experiments lose importance at higher excitation powers and that, paradoxically, the brightest probes under single-molecule excitation are barely luminescent at the ensemble level.

Gold nanocone near-field scanning optical microscopy probes.

Near-field scanning optical microscopy enables the simultaneous topographical and subdiffraction limited optical imaging of surfaces. A process is presented for the implementation of single individually engineered gold cones at the tips of atomic force microscopy cantilevers. These cantilevers act as novel high-performance optical near-field probes. In the fabrication, thin-film metallization, electron beam induced deposition of etch masks, and Ar ion milling are combined. The cone constitutes a well-defined highly efficient optical antenna with a tip radius on the order of 10 nm and an adjustable plasmon resonance frequency. The sharp tip enables high resolution topographical imaging. By controllably varying the cone size, the resonance frequency can be adapted to the application of choice. Structural properties of these sharp-tipped probes are presented together with topographical images recorded with a cone probe. The antenna functionality is demonstrated by gathering the near-field enhanced Raman signature of individual carbon nanotubes with a gold cone scanning probe.

Single-walled carbon nanotubes under the influence of dynamic coordination and supramolecular chemistry.

A dynamic coordinative-directed solubilization of single-walled carbon nanotubes (SWNTs) in aqueous solutions has been achieved through a combination of a Zn(II) metalloporphyrin complex and a cis-protected Pd(II) complex, which are believed to form charged acyclic and/or cyclic adducts on or around the side walls of SWNTs. The solubilization of SWNTs in aqueous solution only occurs when these acyclic and/or cyclic complexes are allowed to enter simultaneously into a self-assembly process with SWNTs under mild conditions. The aqueous solubility properties that these dynamic complexes confer upon SWNTs are believed to involve noncovalent bonding interactions between the two entities. They have been probed in solution using ultraviolet and visible absorption spectroscopy and in thin films using high-resolution transmission electron microscopy. The supramolecular electronic effects that the individual components of their acyclic and/or cyclic complexes impart upon a single semiconducting SWNT have been probed within a nanotube field-effect transistor device.

Electronic detection of the enzymatic degradation of starch.

[reaction: see text] The enzymatic degradation of starch can be monitored electronically using single-walled carbon nanotubes (SWNTs) as semiconducting probes in field-effect transistors (FETs). Incubation of these devices in aqueous buffer solutions of amyloglucosidase (AMG) results in the removal of the starch from both the silicon surfaces and the side walls of the SWNTs in the FETs, as evidenced by direct imaging and electronic measurements.