Formation Of Nanodomains Research Articles

Which Moiety Drives Gangliosides to Form Nanodomains?

Gangliosides are important glycosphingolipids involved in a multitude of physiological functions. From a physicochemical standpoint, this is related to their ability to self-organize into nanoscopic domains, even at molar concentrations of one per 1000 lipid molecules. Despite recent experimental and theoretical efforts suggesting that a hydrogen bonding network is crucial for nanodomain stability, the specific ganglioside moiety decisive for the development of these nanodomains has not yet been identified. Here, we combine an experimental technique achieving nanometer resolution (Förster resonance energy transfer analyzed by Monte Carlo simulations) with atomistic molecular dynamic simulations to demonstrate that the sialic acid (Sia) residue(s) at the oligosaccharide headgroup dominates the hydrogen bonding network between gangliosides, driving the formation of nanodomains even in the absence of cholesterol or sphingomyelin. Consequently, the clustering pattern of asialoGM1, a Sia-depleted glycosphingolipid bearing three glyco moieties, is more similar to that of structurally distant sphingomyelin than that of the closely related gangliosides GM1 and GD1a with one and two Sia groups, respectively.

MgO (1 0 0) as an affordable support for heteroepitaxial growth of high-quality β-Ga2O3 thin films and related highly-sensitive solar-blind UV photodetectors

Heteroepitaxial growth of high-quality β-Ga2O3 thin films on foreign substrates is of crucial importance for achieving high-performance power-electronic and optoelectronic devices with affordable prices. Herein, we demonstrate realization of heteroepitaxial growth of high-quality β-Ga2O3 films on MgO(100) via pulsed laser deposition, and achievement of related highly-sensitive solar-blind ultraviolet photodetectors (SBUVPDs). Under optimized oxygen pressure (7 Pa), single-phase, (100)-oriented, and atomically-smooth β-Ga2O3 films were grown epitaxially on MgO(100), consisting of unique 8–12 nm-wide columnar nanodomains. Atomically-resolvable aberration-corrected transmission electron microscopy unveiled initial growth of a cubic γ-phase transition layer of ∼ 8 nm thickness, and directly visualized occurrence and preferable location of oxygen vacancies at domain walls in the further grown β-Ga2O3 film. Density-functional-theory simulations rationalized the formation of columnar nanodomains in terms of energetics, and presumably identified the nanodomains interface orientations as (112¯)/(11¯2¯). The heteroepitaxial β-Ga2O3(100)/MgO(100) film-based photodetector demonstrates excellent performance, featured with exceedingly-low dark current, remarkably-high light-to-dark current ratio, and ultrahigh responsivity and detectivity (Idark = 0.6 pA, Ilight/Idark = 1.47 × 107, R = 191 A/W, D*=3.08 × 1015 Jones) as well as fast response speed towards 255 nm-UV detection. This work highlights MgO(100) as a suited yet affordable foreign substrate for heteroepitaxial growth of high-quality β-Ga2O3 films towards further development of high-performance devices such as SBUVPDs.

Excellent Energy-Storage Performance of (0.85 – x)NaNbO3–xNaSbO3–0.15(Na0.5La0.5)TiO3 Antiferroelectric Ceramics through B-Site Sb5+ Driven Phase Transition

NaNbO3-based relaxor antiferroelectric (AFE) ceramics are receiving more and more attention for high power pulse applications. A commonly used design strategy is to add complex perovskites with lower tolerance factors. Herein, a new lead-free AFE system of (0.85 - x)NaNbO3-xNaSbO3-0.15(Na0.5La0.5)TiO3 was specially designed considering the substitution of Sb5+ for Nb5+ reduces the polarizability of B-site ions but increases the tolerance factor. The formation of nanodomains with stable AFE orthorhombic R phase symmetry contributes to a slim and double-like polarization-field hysteresis loop, while the increased resistivity and activation energy as a result of sintering aids lead to an enhanced breakdown strength. Therefore, an excellent energy density Wrec ≈ 6.05 J/cm3, a high energy efficiency η ≈ 80.5%, and good charge-discharge performances (power density PD ≈ 155 MW/cm3 and discharging rate t0.9 ≈ 44.6 ns) were achieved in MnO2-doped x = 0.03 ceramics. The experimental results demonstrate that the B-site Sb5+ driven orthorhombic P-R phase transition and increased local structure disorder should provide a new strategy to design high-performance NaNbO3-based relaxor AFE capacitors.

The local density of H3K9me3 dictates the stability of HP1α condensates-mediated genomic interactions

The human genome can be demarcated into domains based on distinct epigenetic states. The trimethylation of histone H3 lysine 9 (H3K9me3) is essential for the formation of constitutive heterochromatin nanodomains. However, the extent to which genomic regions require specific densities or degrees of H3K9me3 for stable interactions remains unclear. Here, we utilize CRISPR-based DNA imaging to investigate the role of endogenous or ectopic H3K9me3 in chromatin dynamics and genomic interactions. We select three loci (IDR3, TCF3, and PR1) with distinct levels of H3K9me3 to examine the genomic interactions and association with endogenous Heterochromatin Protein 1 (HP1α) condensates. Our results demonstrate a positive correlation between the levels of H3K9me3 at the loci and their association with HP1α condensates. By dual-color labeling and long-term tracking of IDR3 and PR1 loci, we find a periodical association between the two ranging from one to three hours. Epigenetic perturbation-induced Genome organization (EpiGo)-KRAB introduces ∼20 kilobases of H3K9me3 at the TCF3 locus, which is sufficient to establish a stable association between TCF3 and HP1α condensates. In addition, EpiGo-mediated H3K9me3 also leads to stable genomic interaction between IDR3 and TCF3. Briefly, these data suggest that the density of H3K9me3 could dictate the stability of interactions between genomic loci and HP1α condensates.

Large electrical strain in lead-free K0.5Na0.5NbO3-based ceramics by heterovalent doping

Heterovalent doped (K0.48-0.07xNa0.52-0.43xBi0.5x)(Nb0.95-0.95xSb0.05-0.05xZrx)O3 ceramics were fabricated using conventional solid-state reaction. Then, the phase structures, dielectric, ferroelectric, and electric-strain properties were investigated. The compositions were tuned to be located at polymorphic phase boundary with increasing heterovalent Bi3+ and Zr4+ doping levels. A large strain of 0.19% was obtained at relatively low electric fields of 30 kV/cm in the composition of x = 0.04. The normalized large-signal d33∗ values were approximately 633 pm/V under a low driving electric field of 30 kV/cm, which were comparable or larger than the values reported for other lead-free families. The large strains obtained can be attributed to the formation of nanodomains and high-density domain walls, which were confirmed by the observations of domain morphology using transmission electron microscopy (TEM) technique. Excellent temperature stability of the strain properties of the x = 0.04 sample could be ascribed to the sluggish behaviour for the local structural heterogeneity in heterovalent-ion doped KNN ceramic. Theoretical simulations revealed that the Zr4+ produce the local stress at the BO6 octahedra and Bi3+ could yield off-centering of AO12 ployhedron due to the nature of Bi 6s lone pair electrons, which induced lattice expansion and local distortions in the sample. The local displacements are strongly anisotropic in heterovalent-ion doped system. It is believed that random local fields exist in these compositions owing to the eixstence of charge distribution. Such heterovalent doping of Bi3+ and Zr4+ could destory simultaneously the orthorhombic symmetry and the short-range ferroelecctric order, leading to the formation of complex nanodomains and local structral hetergenenity. Heterovalent doping may, therefore, offer a new avenve to design novel K0.5Na0.5NbO3 (KNN) -based materials for their mutifunctional applications.

Electrical and Recombination Properties of Polar Orthorhombic κ-Ga2O3 Films Prepared by Halide Vapor Phase Epitaxy

In this study, the structural and electrical properties of orthorhombic κ-Ga2O3 films prepared using Halide Vapor Phase Epitaxy (HVPE) on AlN/Si and GaN/sapphire templates were studied. For κ-Ga2O3/AlN/Si structures, the formation of two-dimensional hole layers in the Ga2O3 was studied and, based on theoretical calculations, was explained by the impact of the difference in the spontaneous polarizations of κ-Ga2O3 and AlN. Structural studies indicated that in the thickest κ-Ga2O3/GaN/sapphire layer used, the formation of rotational nanodomains was suppressed. For thick (23 μm and 86 μm) κ-Ga2O3 films grown on GaN/sapphire, the good rectifying characteristics of Ni Schottky diodes were observed. In addition, deep trap spectra and electron beam-induced current measurements were performed for the first time in this polytype. These experiments show that the uppermost 2 µm layer of the grown films contains a high density of rather deep electron traps near Ec - 0.3 eV and Ec - 0.7 eV, whose presence results in the relatively high series resistance of the structures. The diffusion length of the excess charge carriers was measured for the first time in κ-Ga2O3. The film with the greatest thickness of 86 μm was irradiated with protons and the carrier removal rate was about 10 cm-1, which is considerably lower than that for β-Ga2O3.

Epitaxially grown silicon-based single-atom catalyst for visible-light-driven syngas production

Improving the dispersion of active sites simultaneous with the efficient harvest of photons is a key priority for photocatalysis. Crystalline silicon is abundant on Earth and has a suitable bandgap. However, silicon-based photocatalysts combined with metal elements has proved challenging due to silicon’s rigid crystal structure and high formation energy. Here we report a solid-state chemistry that produces crystalline silicon with well-dispersed Co atoms. Isolated Co sites in silicon are obtained through the in-situ formation of CoSi2 intermediate nanodomains that function as seeds, leading to the production of Co-incorporating silicon nanocrystals at the CoSi2/Si epitaxial interface. As a result, cobalt-on-silicon single-atom catalysts achieve an external quantum efficiency of 10% for CO2-to-syngas conversion, with CO and H2 yields of 4.7 mol g(Co)−1 and 4.4 mol g(Co)−1, respectively. Moreover, the H2/CO ratio is tunable between 0.8 and 2. This photocatalyst also achieves a corresponding turnover number of 2 × 104 for visible-light-driven CO2 reduction over 6 h, which is over ten times higher than previously reported single-atom photocatalysts.

Synergistic enhanced energy storage performance of NBT-KBT ceramics by K0.5Na0.5NbO3 composition design

(1–x)(0.8Na0.5Bi0.5TiO3-0.2K0.5Bi0.5TiO3)-xK0.5Na0.5NbO3 (x = 0, 0.1, 0.2, 0.3, 0.4) (NBT-KBT-KNN) ceramic solid solution was synthesized by solid phase method through designing KNN composition. XRD, Raman and SEM results show that NBT-KBT-KNN ceramics form solid solutions with a stable perovskite structure. The dielectric temperature spectrum and impedance spectrum analysis confirmed that the relaxor ferroelectrics (RFE) properties enhanced with increasing KNN content. The piezoresponse force microscopy (PFM) results reveal that the introduced KNN disrupts the microdomains of NBT-KBT ceramics and promotes the formation of nanodomains, leading to enhanced energy storage properties. The breakdown electric field strength (BDS) was also increased with increasing KNN content, and maximum value was obtained at x = 0.2. The addition of KNN can obviously improve energy storage performance (ESP). At 255 kV cm–1, x = 0.2 produced excellent ESP with recoverable energy storage density (Wrec), amazingly normalized response (ξ), efficiency (η) and maximum polarization (Pmax) are 3.38 J cm–3, 132.55 J kV–1 m–2, 85.4 %, and 45.76 μC cm–2, respectively. ESP is also stable in terms of frequency and temperature at (1–100 Hz) and (20–140 °C). At 120 kV cm–1, the discharge energy density (Wdis), power density (PD), Current density (CD) and time for releasing 90 % of total energy density (t0.9), are 0.202 J cm–3, 23.43 MW cm–3, 390.42 A cm–2, and 56.6 ns. These findings demonstrate that NBT-KBT-KNN ceramics have the ability to be reliable energy storage and pulse power capacitors.

Domain-Enhanced Energy Storage, Piezoelectric, and Dielectric Properties in Pb(Zr0.52Ti0.48)O3/SrTiO3 Ferroelectric Superlattices

The domain structure and ferroelectric properties are highly sensitive to interfacial strain and electrostatic interaction in the ferroelectric superlattices. Here, we fabricated a series of [Pb(Zr0.52Ti0.48)O3]m/[SrTiO3]3 (PZTm/STO3) ferroelectric superlattices (m = 2, 3, 6... unit cells) on SrTiO3 (001) substrates by pulsed laser deposition. Compared with pure PZT films, the energy storage density, piezoelectric properties, and dielectric constant of the superlattice are improved. Particularly, the energy storage density, which is increased by about 158%. The modulation of PZT/STO superlattice period thickness effectively improves its dielectric and relaxation properties, which in turn enhances its energy density and efficiency. The mechanism underlying the excellent energy storage properties was revealed by the formation of nanodomains analyzed by a piezoresponse force microscope. Adjusting the electrostatic interactions by changing the periodic thickness of ferroelectric superlattices provides a promising strategy for the design of high-performance sensors and energy-storage devices.

Pattern formation in nanodomain aggregates of membrane proteins.

Transmembrane proteins, including receptors for growth factors and adhesion, play an important role in cell growth and migration; aberrant spatiotemporal signaling of these membrane proteins may underlie many diseases. Recent studies found that the accurate signaling of these membrane proteins is governed by the nanodomain formations; examples include the formation of synaptic receptor domains and receptor nanodomains encaged in flat clathrin lattice (FCL). However, the underlying physical mechanisms for the formation of such nanodomains still remain unknown. In this work, we compared three different model formulations for nanodomain formation, including 1) deterministic Turing model, 2) stochastic Turing model, and 3) particle-based model, to explore how the biophysics underlying these different models can capture different aspects of nanodomain formation. These nanodomains do not have a large occupancy but are long-term stable, and exhibit changed size and number under extracellular stimulus. Although the deterministic Turing model can generate a stable pattern, it fails to capture the property of changing pattern size and number under stimulus. The stochastic version of Turing model compensates for this shortcoming in the deterministic formulation, but the amount of new nanodomain number is still much less than that observed in the experiment. However, the particle-based model is able to generate more new nanodomains than above Turing models, indicating that the diffusion of each molecule may be driven by a more precise way than the concentration gradient. These findings may shed light on the mechanisms of nanodomain formation of membrane proteins.

Nanoscopic lipid diffusion in the live cell plasma membrane revealed by ultrafast single-molecule tracking.

Membrane organization and dynamics underlie various molecular interactions required for membrane functions. Although the importance of investigating biological membranes at the nanoscale is well recognized, resolving nanoscopic structures and dynamics is technically challenging. In this work, we employ ultrafast single-particle tracking techniques to measure single phospholipid diffusion in the plasma membrane of live cells. We attach a monovalent gold nanoparticle to the headgroup of biotinylated phospholipid and record its diffusive motion on microsecond resolution and nanometer precision by advanced optical interference microscopy. We find that both saturated and unsaturated phospholipids (biotin-PEG-DSPE and biotin-PEG-DOPE, respectively) undergo anomalous subdiffusion in the length scale below 100 nm. The unsaturated lipid diffuses only slightly more freely than the saturated lipid. Moreover, the nanoscopic lipid diffusion is highly heterogeneous in space and time. With statistical analyses, we find that the apparent dual-mobility subdiffusion can describe measured diffusion. The subdiffusion agrees well with the hop diffusion model that describes a Brownian diffuser moving in periodic and partially permeable barriers created by the cytoskeleton. Inhibition of actin polymerization by the chemical drug CK-666 reduces confinement's effective size and strength. Furthermore, we examine the effect of cholesterol on lipid subdiffusion by manipulating the cholesterol concentration. Cholesterol depletion by methyl-b-cyclodextrin leads to a more restricted lipid diffusion. We attribute the more confined diffusion to the formation of solid-like gel-phase nanodomains that move slowly and act as diffusion obstacles. Lowing the system temperature shows similar effects on lipid diffusion, suggesting that the cholesterol-dependent lipid diffusion connects to the nanoscopic phase separation. Overall, this study provides experimental evidence that lipid diffusion in the cell membrane is heterogeneous at the nanoscale and regulated by the membrane cholesterol and actin cytoskeleton.

Photocarrier-induced persistent structural polarization in soft-lattice lead halide perovskites.

The success of the lead halide perovskites in diverse optoelectronics has motivated considerable interest in their fundamental photocarrier dynamics. Here we report the discovery of photocarrier-induced persistent structural polarization and local ferroelectricity in lead halide perovskites. Photoconductance studies of thin-film single-crystal CsPbBr3 at 10 K reveal long-lasting persistent photoconductance with an ultralong photocarrier lifetime beyond 106 s. X-ray diffraction studies reveal that photocarrier-induced structural polarization is present up to a critical freezing temperature. Photocapacitance studies at cryogenic temperatures further demonstrate a systematic local phase transition from linear dielectric to paraelectric and relaxor ferroelectric under increasing illumination. Our theoretical investigations highlight the critical role of photocarrier-phonon coupling and large polaron formation in driving the local relaxor ferroelectric phase transition. Our findings show that this photocarrier-induced persistent structural polarization enables the formation of ferroelectric nanodomains at low temperature, which suppress carrier recombination and offer the possibility of exploring intriguing carrier-phonon interplay and the rich polaron photophysics.

Nanoscale Iron Redistribution during Thermochemical Decomposition of CaTi1-x Fe x O3-δ Alters the Electrical Transport Pathway: Implications for Oxygen-Transport Membranes, Electrocatalysis, and Photocatalysis.

Potential applications of the earth-abundant, low-cost, and non-critical perovskite CaTi1-x Fe x O3-δ in electrocatalysis, photocatalysis, and oxygen-transport membranes have motivated research to tune its chemical composition and morphology. However, investigations on the decomposition mechanism(s) of CaTi1-x Fe x O3-δ under thermochemically reducing conditions are limited, and direct evidence of the nano- and atomic-level decomposition process is not available in the literature. In this work, the phase evolution of CaTi1-x Fe x O3-δ (x = 0-0.4) was investigated in a H2-containing atmosphere after heat treatments up to 600 °C. The results show that CaTi1-x Fe x O3-δ maintained a stable perovskite phase at low Fe contents while exhibiting a phase decomposition to Fe/Fe oxide nanoparticles as the Fe content increases. In CaTi0.7Fe0.3O3-δ and CaTi0.6Fe0.4O3-δ, the phase evolution to Fe/Fe oxide was greatly influenced by the temperature: Only temperatures of 300 °C and greater facilitated phase evolution. Fully coherent Fe-rich and Fe-depleted perovskite nanodomains were observed directly by atomic-resolution scanning transmission electron microscopy. Prior evidence for such nanodomain formation was not found, and it is thought to result from a near-surface Kirkendall-like phenomenon caused by Fe migration in the absence of Ca and Ti co-migration. Density functional theory simulations of Fe-doped bulk models reveal that Fe in an octahedral interstitial site is energetically more favorable than in a tetrahedral site. In addition to coherent nanodomains, agglomerated Fe/Fe oxide nanoparticles formed on the ceramic surface during decomposition, which altered the electrical transport mechanism. From temperature-dependent electrical conductivity measurements, it was found that heat treatment and phase decomposition change the transport mechanism from thermally activated p-type electronic conductivity through the perovskite to electronic conduction through the iron oxide formed by thermochemical decomposition. This understanding will be useful to those who are developing or employing this and similar earth-abundant functional perovskites for use under reducing conditions, at elevated temperatures, and when designing materials syntheses and processes.

Regional consistency between cation displacement and oxygen octahedral tilt in nanodomain of BNKT-SBT relaxor ferroelectrics revealed by atomic-resolution AC-STEM

Since being discovered, relaxor ferroelectrics have attracted continued interest due to their unusual properties. Relaxor behavior is attributed to nanodomains or PNRs. Therefore, nano-scale even atomic-scale structural analysis is crucial to understanding the relaxor properties. However, the atomic-scale nanodomain structure has not been fully understood. For Bi0.5Na0.5TiO3, cation displacement and oxygen octahedral tilt are two common structural distortions. However, the relationship between them has not been proved experimentally. Here, the cation displacement and octahedral tilt were both investigated based on aberration-corrected STEM images. Cation displacement vectors illustrate a vortex structure. Octahedral tilt is regionally consistent with cation displacement that both of them increase gradually from the domain wall to the interior of the nanodomain. The formation of nanodomains may originate from their combined effect, thereby producing relaxor properties. Moreover, oxygen octahedral displacement stemmed from the complex coordinating environments was observed. These findings provide further insights into the nanodomain structure.

Structural determinants of REMORIN nanodomain formation in anionic membranes

Remorins are a family of multigenic plasma membrane phosphoproteins involved in biotic and abiotic plant interaction mechanisms, partnering in molecular signaling cascades. Signaling activity of remorins depends on their phosphorylation states and subsequent clustering into nanosized membrane domains. The presence of a coiled-coil domain and a C-terminal domain is crucial to anchor remorins to negatively charged membrane domains; however, the exact role of the N-terminal intrinsically disordered domain (IDD) on protein clustering and lipid interactions is largely unknown. Here, we combine chemical biology and imaging approaches to study the partitioning of group 1 remorin into anionic model membranes mimicking the inner leaflet of the plant plasma membrane. Using reconstituted membranes containing a mix of saturated and unsaturated phosphatidylcholine, phosphatidylinositol phosphates, and sterol, we investigate the clustering of remorins to the membrane and monitor the formation of nanosized membrane domains. REM1.3 promoted membrane nanodomain organization on the exposed external leaflet of both spherical lipid vesicles and flat supported lipid bilayers. Our results reveal that REM1.3 drives a mechanism allowing lipid reorganization, leading to the formation of remorin-enriched nanodomains. Phosphorylation of the N-terminal IDD by the calcium protein kinase CPK3 influences this clustering and can lead to the formation of smaller and more disperse domains. Our work reveals the phosphate-dependent involvement of the N-terminal IDD in the remorin-membrane interaction process by driving structural rearrangements at lipid-water interfaces.

Energy storage performance of SrSc0.5Nb0.5O3 modified (Bi,Na)TiO3‐based ceramic under low electric fields

AbstractDielectric ceramics with a high recoverable energy density (Wrec) and high efficiency are desirable for the development of pulsed power capacitors under low electric fields. In this study, through the introduction of SrSc0.5Nb0.5O3 into (Bi0.5Na0.5Ti0.95Al0.025Nb0.025O3) [(1‐x)BNTA‐xSSN], a considerable recoverable energy storage density (Wrec) of approximately 2.7 J/cm3 and energy storage efficiency (η) of approximately 76 % at 210 kV/cm are achieved at x = .1; additionally, η is further improved to 85 % at x = .2. Moreover, η and Wrec of .9BNTA‐.1SSN exhibit outstanding stability (thermal and frequency stability) at 150 kV/cm, which is superior to that of other lead‐free ceramics. The excellent energy storage performance is attributed to the increased relaxation degree and the formation of ferroelectric nanodomains, whereas the enhanced Eb is ascribed to the increased electrical resistivity and decreased grain size upon modification. These results indicate the potential of (1‐x)BNTA‐xSSN as an ideal candidate for energy‐storage applications.

The Effect of Thermal Treatment on Microstructure and Thermal-Induced Martensitic Transformations in Ni44Fe19Ga27Co10 Single Crystals

Heat treatments of single crystals of Ni44Fe19Ga27Co10 (at.%) shape memory alloys cause various microstructures of the high-temperature phase. The nanodomain structure, consisting of regions of the L21- and B2-phases, and nanosized particles are the main parameters that change during heat treatments and determine the mechanism of nucleation and growth of martensite crystals, the size of thermal-induced martensite lamellae, the temperature Ms, and the temperature intervals of the martensitic transformation. In the as-grown single crystals, the high-temperature phase has only the L21-structure and the MT occurs at low (Ms = 125 K) temperatures due to the motion of the practically single interphase boundary in narrow temperature ranges of 3–7 K. The reduction in the volume fraction of the L21-phase to 40% and the formation of nanodomains (20–50 nm) of the L21-and B2-phases due to annealing at 1448 K for 1 h with quenching causes an increase in the MT temperatures by 80 K. The MT occurs in wide temperature ranges of 40–45 K because of multiple nucleation of individual large (300–500 µm) martensite lamellae and their growth. After aging at 773 K for 1 h, the precipitation of nanosized particles of the ω-phase in such a structure additionally increases the MT temperatures by 45 K. The MT occurs due to the multiple nucleation of packets of small (20–50 μm) martensite lamellae.

Engineering Transport Properties in Interconnected Enargite-Stannite Type Cu2+x Mn1-x GeS4 Nanocomposites.

Understanding the mechanisms that connect heat and electron transport with crystal structures and defect chemistry is fundamental to develop materials with thermoelectric properties. In this work, we synthesized a series of self-doped compounds Cu2+x Mn1-x GeS4 through Cu for Mn substitution. Using a combination of powder X-ray diffraction, high resolution transmission electron microscopy and precession-assisted electron diffraction tomography, we evidence that the materials are composed of interconnected enargite- and stannite-type structures, via the formation of nanodomains with a high density of coherent interfaces. By combining experiments with ab initio electron and phonon calculations, we discuss the structure-thermoelectric properties relationships and clarify the interesting crystal chemistry in this system. We demonstrate that excess Cu+ substituted for Mn2+ dopes holes into the top of the valence band, leading to a remarkable enhancement of the power factor and figure of merit ZT.

Engineering Transport Properties in Interconnected Enargite‐Stannite Type Cu2+xMn1−xGeS4 Nanocomposites

AbstractUnderstanding the mechanisms that connect heat and electron transport with crystal structures and defect chemistry is fundamental to develop materials with thermoelectric properties. In this work, we synthesized a series of self‐doped compounds Cu2+xMn1−xGeS4 through Cu for Mn substitution. Using a combination of powder X‐ray diffraction, high resolution transmission electron microscopy and precession‐assisted electron diffraction tomography, we evidence that the materials are composed of interconnected enargite‐ and stannite‐type structures, via the formation of nanodomains with a high density of coherent interfaces. By combining experiments with ab initio electron and phonon calculations, we discuss the structure–thermoelectric properties relationships and clarify the interesting crystal chemistry in this system. We demonstrate that excess Cu+ substituted for Mn2+ dopes holes into the top of the valence band, leading to a remarkable enhancement of the power factor and figure of merit ZT.

Nanoarchitectonics of self-assembled chessboard-like structures by recurrent phase separation and coalescence of nano domains in CoFeMn oxide

Self-assembled chessboard-like (CB-like) nanostructures in oxides are potential candidate materials for high density memory and energy storage devices. The evolution of CB-like nanostructures has been studied by combining transmission electron microscopy and 3D atom probe tomography in spinel-forming CoFeMn oxide. CB-like nanostructures evolve through a complex process of twinning, subdomain formation through recurrent pseudo-spinodal decomposition and domain coalescence along specific crystallographic axes. It initiates with the cross-penetration of compound deformation twins with subtle chemical composition separation between different domains, which ultimately results in the polymorphic transformation of cubic and tetragonal phases. The requirement of interfacial strain minimization leads to the formation of two tetragonal and two cubic spinel domains of different compositions which are rotationally orientated. In the CB-like nanostructure, cubic and tetragonal domains are connected along 〈022〉 directions. Cubic with cubic domains, and tetragonal with tetragonal domains, are connected along 〈040〉 or 〈004〉 directions. Recurring pseudo-spinodal decomposition within the CB-like domains leads to the formation of finer CB-like nanodomains. The formation of cuboid shaped domains of the cubic and tetragonal phases to rod shape morphology with four {220} and two {001} faces can give rise to 2D CB-like nanostructures. Combined transmission electron microscopy and atom probe tomography analysis indicates that CB-like nanostructures can also form in 3D, and a new model for this has been proposed based on the octahedral/cuboidal shape of the compositionally separated domains. The coalescence of such nanostructures along 〈004〉 directions gives rise to a rod-like morphology. The proposed model is expected to lead to a paradigm shift in the current understanding of CB-like nanostructures.