Electrostatically Tuned Microdomain Morphology and Phase-Dependent Ion Transport Anisotropy in Single-Ion Conducting Block Copolyelectrolytes

Block copolyelectrolytes are solid-state single-ion conductors which phase separate into ubiquitous microdomains to enable both high ion transference number and structural integrity. Ion transport in these charged block copolymers highly depends on the nanoscale microdomain morphology; however, the influence of electrostatic interactions on morphology and ion diffusion pathways in block copolyelectrolytes remains an obscure feature. In this paper, we systematically predict the phase diagram and morphology of diblock copolyelectrolytes using a modified dissipative particle dynamics simulation framework, considering both explicit electrostatic interactions and ion diffusion dynamics. Various experimentally controllable conditions are considered here, including block volume fraction, Flory–Huggins parameter, block charge fraction or ion concentration, and dielectric constant. Boundaries for microphase transitions are identified based on the computed structure factors, mimicking small-angle X-ray scattering patterns. Furthermore, we develop a novel “diffusivity tensor” approach to predict the degree of anisotropy in ion diffusivity along the principal microdomain orientations, which leads to high-throughput mapping of phase-dependent ion transport properties. Inclusion of ions leads to a significant leftward and upward shift of the phase diagram due to ion-induced excluded volume, increased entropy of mixing, and reduced interfacial tension between dissimilar blocks. Interestingly, we discover that the inverse topology gyroid and cylindrical phases are ideal candidates for solid-state electrolytes in metal-ion batteries. These inverse phases exhibit an optimal combination of high ion conductivity, well-percolated diffusion pathways, and mechanical robustness. Finally, we find that higher dielectric constants can lead to higher ion diffusivity by reducing electrostatic cohesions between the charged block and counterions to facilitate ion diffusion across block microdomain interfaces. This work significantly expands the design space for emerging block copolyelectrolytes and motivates future efforts to explore inverse phases to avoid engineering hurdles of aligning microdomains or removing grain boundaries

Axonal morphological changes demonstrated by in vivo tracing in the different brain areas after transient cerebral ischemia/reperfusion.

<p>Right panels were high magnification views of the areas in left panels in A–E (single arrow), respectively. Typical swollen axons or varicosities (arrowheads) could be seen in the primary sensory cortex (Psc) (A), primary motor cortex (Pmc) (B), hippocampus (Hi) (C) and caudoputamen (Cpu) (D) of the ischemic hemisphere after transient cerebral ischemia/reperfusion. No obvious axonal changes were noticed in the primary sensory cortex from the sham group (E). Scale bars: 20 µm for left panels and 5 µm for right panels in A–E.</p

Semi-quantitative analysis of the degree of axonal changes in different brain regions in transient cerebral ischemia/reperfusion and control rats from axonal tracing evaluation.

<p>The numbers (1–3) represent the degree of axonal changes (see also in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0033722#s4" target="_blank">method</a>). MCAO: middle cerebral artery occlusion and reperfusion; Psc: primary sensory cortex; Pmc: primary motor cortex; Hi: hippocampus; Cpu: caudoputamen; Per-C: perilesional cortex; ND: not detected.</p

Transient cerebral ischemia/reperfusion induces early and chronic axonal changes.

<p>Representative axonal changes (swellings of axons and varicosities) can be seen at 6 h, 24 h, 1 w, 2 w, 3 w and 4 w after transient cerebral ischemia/reperfusion in different brain regions, including the ischemic primary sensory cortex (Psc) (A), primary motor cortex (Pmc) (B), hippocampus (Hi) (C), caudoputamen (Cpu) (D) and peri-lesional cortex (E). Arrowheads in each figure mark the swollen axons or varicosities. Scale bars: 5 µm for A–E.</p

Tracing and immunohistochemical double staining show the tracer-labeled neurons and the expression of hyperphosphorylated Tau induced by transient cerebral ischemia/reperfusion.

<p>B, D and F are the magnification of an area in A, C and E, respectively. Some staining for AT8 (brown color) was found in the ischemic cortex (A) and AT8 labeled neuronal bodies could be noticed (B, arrowheads). The arrows in B indicate the tracer-labeled neurons (dark blue color). Strong staining for Tau-5 (brown color) was found in the ischemic cortex (C) and the extensive Tau-5 labeled neurons (D, arrows) and swollen axons (D, arrowheads) were noticed. Inserted figure in C showed the magnification of an area (arrowhead), demonstrating the tracer-labeled neurons (dark blue color). Only very weak staining could be observed for P-tau (E) and tracer-labeled neurons presented the morphological changes as cell shrinkage occurred. Scale bars: 10 µm for B, D, and F, 100 µm for A and C, 200 µm for E.</p

Western blot testing shows the expression of hyperphosphorylated Tau induced by transient cerebral ischemia/reperfusion.

<p>The level of Tau protein increased in the ischemic cortex of the transient cerebral ischemia/reperfusion subgroup compared to the corresponding region in the sham group (A through D). The levels of AT8 and Tau-5 increased obviously at 1 w after transient cerebral ischemia/reperfusion (B and D), whereas a similar increase was detected in the level of P-tau only at 6 h after transient cerebral ischemia/reperfusion (C). The asterisk indicates a significant difference (P<0.05) between this subgroup and the other five subgroup.</p

Thinning Segregated Graphene Layers on High Carbon Solubility Substrates of Rhodium Foils by Tuning the Quenching Process

We report the synthesis of large-scale uniform graphene films on high carbon solubility substrates of Rh foils for the first time using an ambient-pressure chemical vapor deposition method. We find that, by increasing the cooling rate in the growth process, the thickness of graphene can be tuned from multilayer to monolayer, resulting from the different segregation amount of carbon atoms from bulk to surface. The growth feature was characterized with scanning electron microscopy, Raman spectra, transmission electron microscopy, and scanning tunneling microscopy. We also find that bilayer or few-layer graphene prefers to stack deviating from the Bernal stacking geometry, with the formation of versatile moiré patterns. On the basis of these results, we put forward a segregation growth mechanism for graphene growth on Rh foils. Of particular importance, we propose that this randomly stacked few-layer graphene can be a model system for exploring some fantastic physical properties such as van Hove singularities

Atomic-Scale Morphology and Electronic Structure of Manganese Atomic Layers Underneath Epitaxial Graphene on SiC(0001)

We report the fabrication of a novel epitaxial graphene(EG)/Mn/SiC(0001) sandwiched structure through the intercalation of as-deposited Mn atoms on graphene surfaces, with the aid of scanning tunneling microscope, low energy electron diffraction, and X-ray photoelectron spectroscopy. We found that Mn can intercalate below both sp³-hybridized carbon-rich interface layer and monolayer graphene, along with the formation of various embedded Mn islands showing different surface morphologies. The unique trait of the sandwiched system is that the strong interaction between the carbon-rich interface layer and SiC(0001) can be decoupled to some degrees, and contemporaneous, an <i>n</i>-doping effect is observed by mapping the energy band of the system using angle-resolved photoemission spectroscopy. Moreover, what deserves our special attention is that the intercalated islands can only evolve below monolayer graphene when a bilayer coexists, accounting for an intriguing graphene thickness-dependent intercalation effect. In the long run, we believe that the construction of graphene/Mn/SiC(0001) systems offers ideal candidates for exploring some intriguing physical properties such as the magnetic property of two-dimensional transition metal systems

Tunable Spin–Orbit Interaction in Trilayer Graphene Exemplified in Electric-Double-Layer Transistors

Taking advantage of ultrahigh electric field generated in electric-double-layer transistors (EDLTs), we investigated spin–orbit interaction (SOI) and its modulation in epitaxial trilayer graphene. It was found in magnetotransport that the dephasing length <i>L</i>_ϕ and spin relaxation length <i>L</i>_so of carriers can be effectively modulated with gate bias. As a direct result, SOI-induced weak antilocalization (WAL), together with a crossover from WAL to weak localization (WL), was observed at near-zero magnetic field. Interestingly, among existing localization models, only the Iordanskii–Lyanda-Geller–Pikus theory can successfully reproduce the obtained magnetoconductance well, serving as evidence for gate tuning of the weak but distinct SOI in graphene. Realization of SOI and its large tunability in the trilayer graphene EDLTs provides us with a possibility to electrically manipulate spin precession in graphene systems without ferromagnetics

Structure and Magnetic and Magneto-Optical Properties of a New Cubic Ce₃Sc₂Ga₃O₁₂ Garnet Crystal with Heavy Ce³⁺ Concentration

Based on the thermal stability analysis by density functional theory and the crystal phase optimization by tolerance factor, the crystal structure was designed. So, a new cubic Ce3Sc2Ga3O12 (CSGG) garnet material with a high Ce3+ concentration was synthesized. The centimeter-scale CSGG crystal was grown by the Czochralski method. CSGG exhibits fine magneto-optical properties, which are attributed to the stable valence and high concentration of rare-earth Ce3+ ions. Compared with commercial Tb3Ga5O12 (TGG), CSGG is also paramagnetic, but its magneto-optical properties are better. The Verdet constants of CSGG in 532, 635, 1064, and 1550 nm are −380.0, −258.8, −47.5, and −22.4 rad/T·m, respectively, which are from 1.2 to 2.0 times that of TGG. Moreover, the CSGG crystal has high transmittance in 1500–2300 nm to make up for the poor transmittance of TGG crystal in this band. Also, considering its low raw material cost, the CSGG crystal presents promising application potential. It could be qualified as an essential material for magneto-optical isolators, circulators, and switches within the visible to mid-infrared band