Single Domain Structure Research Articles

Enhanced Bulk Photovoltaic Effect of Single-Domain Freestanding BiFeO3 Membranes.

The bulk photovoltaic effect (BPVE), which uniquely exists in non-centrosymmetric materials, has been received extensive attention recently due to its potential to overcome the theoretical Shockley-Queisser limit in traditional p-n junction solar cells. Here, freestanding single-domain BiFeO3 membranes are exfoliated from miscut SrTiO3 substrates by dissolving Sr3Al2O6 sacrificial layers, and transferred on SiO2/Si substrates. This study finds that the freestanding BiFeO3 membranes maintain the single-domain structure and exhibits the significantly enhanced bulk photovoltaic response (≈200% enhancement), compared to the strained BiFeO3 films. The comprehensive atomic imaging analyses manifest that the freestanding BiFeO3 membrane demonstrates the bigger noncentral ion (Fe) displacement, which results in the larger in-plane ferroelectric polarization and substantial increase in the BPVE photocurrent. This work not only provides an effective approach to enhance the BPVE of ferroelectric oxide films, but also can potentially promote the exploration of BPVE of oxide membranes integrated with silicon-based or 2D electronics.

Single-domain structure of Fe3O4 nanoparticles encapsulation by magnetic surfactant M(AOT)2 (M=Co, Ni)

Investigating the magnetic nanoparticle size and the effective magnetic interactions that form the magnetic domain can lead us to nanoparticles with targeted applications, such as targeted drug delivery and higher resolution MRI imaging. In this study magnetic susceptibility and coercive field properties, and the structure size range of single-domain magnetic capsules with high magnetization were obtained by structural analysis of volumetric DLS properties. In this regard, the role of exchange, anisotropy, and magnetostatic interaction was investigated in the structure of a magnetic capsule containing Fe3O4 nanoparticles (MCap-NPs). The stable capsules were synthesized in an emulsion solution with magnetic surfactants M(AOT)2 (M = Co, Ni). Vibrating Sample Magnetometer (VSM) and capsule relative volume (CRV) of Dynamic Light Scattering (DLS) were used to determine the magnetic properties of the single-domain (SD) structure. The produced emulsion samples were found to have superparamagnetic properties property with saturation magnetization in the range of 2–6 × 10−3emu/g for NiCap-NPs, and 5-13 × 10−3emu/g for CoCap-NPs. The results show that nanoparticles have the most significant effect on magnetization. The coercive field, the anisotropy energy values, and the SD of M(AOT)2 were determined using magnetic susceptibility distribution. The outcome results show that the surface of the magnetic capsule plays an essential role in forming a single-domain structure. It was also found that the saturation magnetization of the samples in the emulsion solution is proportional to the nanoparticle density and not to the mass of nanoparticles. All produced samples have distinct peaks in CRV versus capsule size, and each peak follows a log-normal distribution. For both samples, except for the samples with molar ratios ω of 23 (Co3 and Ni4 samples), the positions of the second and third relative volume peaks were constant at 269 ± 3 nm and 424±6 nm, respectively. The behavior of the CRV function normalized to the peak size showed a proportionality between the coercive field and the CRV.

Biophysical and structural studies of fibulin-2

Fibulin-2 is a multidomain, disulfide-rich, homodimeric protein which belongs to a broader extracellular matrix family. It plays an important role in the development of elastic fiber structures. Malfunction of fibulin due to mutation or poor expression can result in a variety of diseases including synpolydactyly, limb abnormalities, eye disorders leading to blindness, cardiovascular diseases and cancer. Traditionally, fibulins have either been produced in mammalian cell systems or were isolated from the extracellular matrix, a procedure that results in poor availability for structural and functional studies. Here, we produced seven fibulin-2 constructs covering 62% of the mature protein (749 out of 1195 residues) using a prokaryotic expression system. Biophysical studies confirm that the purified constructs are folded and that the presence of disulfide bonds within the constructs makes them extremely thermostable. In addition, we solved the first crystal structure for any fibulin isoform, a structure corresponding to the previously suggested three motifs related to anaphylatoxin. The structure reveals that the three anaphylatoxins moieties form a single-domain structure.

The Ferroelectric Effects of Rhombohedral and Tetragonal BiFeO3 in Photoelectrochemical Water Splitting.

The phase of BiFeO3 (BFO) as well as its domain configuration can be tuned by strain engineering. Phase change may greatly influence the properties of the polarization field and hence charge separation. However, the photoelectrochemical properties of different BFO phases have rarely been addressed. Here, the photoelectrochemical study of tetragonal (T-) and rhombohedral (R-) phase BFO films was conducted under visible light illumination. The photocurrent density of R-BFO is 5 times that of T-BFO. A ferroelectric domain study shows that T-BFO features single domain structure in contrast to the polydomain structure of R-BFO. Higher charge separation efficiency is achieved in R-BFO, dominated by the domain walls as conducting pathways for efficient charge separation and transfer. This work provides a fundamental understanding of the photoelectrochemical properties of T- and R-BFO, offering valuable insights for the development of BFO-based materials for solar energy conversion.

Highly oriented epitaxial Cu2O (011) thin film grown on MgO (001) substrate by dynamic aurora PLD method

The epitaxial Cu2O films are grown on MgO (001) substrates by the dynamic aurora pulsed laser deposition (PLD) method. The structure and epitaxial growth of the as-prepared thin films at different substrate temperatures (25 °C to 600 °C) were investigated. The thin film prepared at room temperature (RT, 25 °C) exhibits (111) plane of monoclinic CuO phase with poor crystallinity. The thin films deposited at 200 °C to 600 °C show single-phase cubic Cu2O with good crystallinity. The highly oriented epitaxial Cu2O thin film on the MgO substrate is achieved at low temperatures of 200 °C by applying an induced electromagnetic field during thin film growth. The quality and crystallinity of epitaxial Cu2O thin films remarkably improved with increasing temperature from 200 °C to 600 °C and all these thin films exhibited an out-of-plane epitaxial relationship of Cu2O (011) ‖ MgO (001). The CuO thin film grown on MgO substrate at RT shows a single domain structure, as observed by RHEED. In constrast, Cu2O films grown at 200 °C to 600 °C exhibit two different kinds of domain structure with corresponding in-plane epitaxial relationship of Cu2O [100] ‖ MgO [110] and Cu2O [100] ‖ MgO [11¯0]. This report reveals, for the first time, the feasibility of epitaxial growth of highly oriented Cu2O (011) thin film achieved at the low temperature of 200 °C by the dynamic aurora PLD method. The quality of epitaxial Cu2O (011) is significantly enhanced with increasing substrate temperature from 200 °C to 600 °C.

Effect of lightly substituted samarium ions on the structural, optical, magnetic and dielectric properties of the sonochemically synthesized M-type Sr-hexaferrite nanoparticles

In this study, the role of sonochemical treatment followed by a combustion process adopted for the synthesis of SrSmxFe12-xO19 (x = 0.01 to 0.03) hexaferrites. We have investigated effect of lightly Sm substitutions on structural, magnetic, optical and dielectric properties in Strontium hexaferrites. X-ray diffraction analysis show M as major phase with impurity. The FTIR analysis shows that the value of force constant increased on both sides (tetra hederal and octa hederal) with the increase of samarium content. The band gap was calculated using Tauc method from UV–Visible spectra. Result shows that as the samarium content increases from x = 0.01 to 0.03 the band gap gradually increases from 2.50 eV 2.91 eV respectively. The surface morphology of prepared Sm substituted SrM nanoparticles was examined using field emission scanning electron microscopy, an average particle size was found to 301 nm, 254 nm, and 285 nm for x = 0.01, 0.02, and 0.03 compositions respectively. High values of Ms (53.104 emu/g.) and Mr (29.0 emu/g) observed in x = 0.03 sample with low Hc of 53.104 Oe. Mr/Ms values of all samples are >0.5 show that of formed hexaferrite nanoparticles possess single magnetic domain structure. The Sm-doped of the SrFe12O19 compound exhibits a low dielectric constant (ε′) ∼ 20 at low frequencies, while it increased with increasing temperature and reached 100 when the Sm content was 0.01, but less than 150 in x = 0.02 and 0.03. The temperature and frequency-dependent dielectric constant confirmed the contributions of different polarization mechanisms.

Pioneering preparation and analysis of a clean surface on a microcrystal, mined by a focused ion beam

We demonstrate a series of procedures to prepare a clean surface of micro-sized graphite, mined from a bulk flake and securely affixed onto a macroscopic Si plate by focused ion beam scanning electron microscope. Analyses of structure and electronic (chemical) states were made using micro-beam X-ray photoelectron spectroscopy and angle-resolved photoemission spectroscopy. At the surface of the micro graphite, the band dispersion from a single-domain structure was observed. The proposed methodology showcases its capability to produce clean and high-quality micro samples suitable for surface-sensitive analyses. This technique paves the way to investigate surfaces of unexplored microcrystals embedded in complex materials.

Genome-wide identification, characterization, and expression analysis of m6A readers-YTH domain-containing genes in alfalfa

Eukaryotic messenger RNAs (mRNAs) are often modified with methyl groups at the N6 position of adenosine (m6A), and these changes are interpreted by YTH domain-containing proteins to regulate the metabolism of m6A-modified mRNAs. Although alfalfa (Medicago sativa) is an established model organism for forage development, the understanding of YTH proteins in alfalfa is still limited. In the present investigation, 53 putative YTH genes, each encoding a YT521 domain-containing protein, were identified within the alfalfa genome. These genes were categorized into two subfamilies: YTHDF (49 members) and YTHDC (four members). Each subfamily demonstrates analogous motif distributions and domain architectures. Specifically, proteins encoded by MsYTHDF genes incorporate a single domain structure, while those corresponding to MsYTH5, 8, 12, 16 who are identified as members of the MsYTHDC subfamily, exhibit CCCH-type zinc finger repeats at their N-termini. It is also observed that the predicted aromatic cage pocket that binds the m6A residue of MsYTHDC consists of a sequence of two tryptophan residues and one tyrosine residue (WWY). Conversely, in MsYTHDF, the binding pocket comprises two highly conserved tryptophan residues and either one tryptophan residue (WWW) or tyrosine residue (WWY) in MsYTHDF.Through comparative analysis of qRT-PCR data, we observed distinct expression patterns in specific genes under abiotic stress, indicating their potential regulatory roles. Notably, five genes (MsYTH2, 14, 26, 27, 48) consistently exhibit upregulation, and two genes (MsYTH33, 35) are downregulated in response to both cold and salt stress. This suggests a common mechanism among these YTH proteins in response to various abiotic stressors in alfalfa. Further, integrating qRT-PCR with RNA-seq data revealed that MsYTH2, MsYTH14, and MsYTH16 are highly expressed in leaves at various development stages, underscoring their potential roles in regulating the growth of these plant parts. The obtained findings shed further light on the biological functions of MsYTH genes and may aid in the selection of suitable candidate genes for future genetic enhancement endeavors aimed at improving salt and cold tolerance in alfalfa.

A Ferroelectric Nonlinear Optical Crystal for Deep‐UV Quasi‐Phase‐Matching

AbstractPhase matching is indispensable for high efficiency of second‐order nonlinear optical (NLO) crystals. Thousands of these crystals rely on birefringence phase matching, whereas only a few of them are quasi‐phase matching without the restriction of birefringence. Herein, using oriented seeds inch‐sized LiNH4SO4 (LAS) single crystals are successfully grown. LAS is NLO‐active with a very short deep‐UV absorption edge of 171 nm and high laser damage threshold up to 1.47 GW cm−2 at 1064 nm, 10 ns, but its birefringence is merely 0.0078@532 nm, which is too small to realize birefringence phase matching in deep‐UV region. Fortunately, P−E hysteresis loop, variable‐temperature NLO tests, and ferroelectric domain observations confirm that LAS is ferroelectric. Furthermore, LAS exhibits small refractive index dispersion resulting in a relatively long periodic length of 1.4 µm and its single domain structure can be easily obtained by electrical poling. These attributes make LAS a scarce NLO candidate for deep‐UV quasi‐phase matching. This work highlights the longly overlooked potential of sulfates and provides new opportunities for deep‐UV NLO materials.

Laser single-shot magnetization reversal in Co1−xLux nanostructures

The magnetic properties of $\mathrm{Pt}\text{/}{Co}_{1\ensuremath{-}x}{\mathrm{Lu}}_{x}\text{/}\mathrm{Pt}$ thin films have been investigated. For an alloy thickness of 3 nm, the saturation magnetization linearly decreases from 830 kA/m to 400 kA/m for $x$ varying between 18% and 40%, including the proximity-induced moment in platinum. Furthermore, we show that ${\mathrm{Co}}_{1\ensuremath{-}x}{\mathrm{Lu}}_{x}$ alloys 3 nm thick thin films have a perpendicular magnetic anisotropy for a concentration ranging between 25% and 40%. A single femtosecond laser shot leads to a demagnetized state with a domain size that increases with the decrease of saturation magnetization. Patterning the layer into dots leads to a single domain structure that can be fully reversed using a single laser pulse. The statistics and the origin of the nondeterministic reversal are discussed based on the atomistic model.

Boosting Photocatalytic Water Oxidation on Photocatalysts with Ferroelectric Single Domains.

Ferroelectric materials are considered as promising photocatalysts due to their efficient charge separation via apolarization-induced built-in electric field. However, the polydomain structures hinder spatial charge separation and transfer due to the cancellation of polarization vectors in the domains. Inthiswork, taking BiFeO3 (BFO) as a prototype, single-domain BFO nanosheets with visible-light absorption are prepared, as evident by piezoresponse force microscopy (PFM), spatially resolved surface photovoltage spectroscopy (SRSPS), and photodeposition experiments. The single-domain BFO nanosheets show nine times activity in photocatalytic water oxidation reaction under visible-light irradiation, compared with that of the polydomain BFO particles. With the asymmetric driving force for charge separation in a single domain, selective deposition of cocatalysts further enhances the photocatalytic activity of single-domain ferroelectric BFO nanosheets. These results demonstrate the role of thesingle-domain structure in constructing the driving force of charge separation in ferroelectric photocatalysts. The fabrication of single-domain structures in ferroelectric photocatalysts to achieve enhanced photocatalytic activity offers a path to efficiently utilize the photogenerated charges in solar energy conversion.

Effects of Pr3+ ion doping on magnetic features of Ni–Co nanospinel ferrites synthesized via sonochemical approach

The praseodymium ion (Pr3+) substituted Ni0.5Co0.5Fe2O4 nanospinel ferrites, (Co0.5Ni0.5PrxFe2-xO4 (Pr → CoNi) (x ≤ 0.10) NSFs), were synthesized via sonochemical route. XRD confirmed the single cubic structure of all samples with the crystallite size within the range of 9–11 nm.The morphology of (Pr → CoNi) (x ≤ 0.10) NSFs) particles was analyzed by SEM and TEM and showed the spherical shape. Mossbauer study showed that the larger Pr3+ ions prefer the B site. According to the magnetic study, the superparamagnetic character increased with increase of Pr3+ions. The magnetic characteristics are elucidated through both hysteresis curves and temperature (T) dependence of magnetization (M). Magnetization (M) vs external field (H) hysteresis curves were performed at both 300 (RT) and 10 K. It is revealed that Pr → CoNi NSFs exhibit superparamagnetic (SPM) nature performed at RT. Saturation magnetization (Ms), magnetic moment (nB), squareness ratio (SQR), remanence (Mr), and coercivity (Hc) were determined. The Hc of Pr → CoNi (x ≤ 0.10) NSFs was found to be larger than that of the host material. On the other hand, at both temperatures, the magnetization data demonstrates the crucial impact of Pr3+ ions which diminish the Ms, Mr and nB of the host material. The magnetic parameters for Pr → CoNi (x ≤ 0.10) NSFs barely fluctuate and depend on the cation distribution. At 10 K, the SQR of all samples is calculated to be ∼ 0.5 which reflects the uniaxial symmetry and a single-domain structure formation. For Pr → CoNi (x ≤ 0.10) NSFs, much lower SQR values are attained at room temperature (RT), indicating a decrease in the exchange interaction, and suggesting a multi-domain wall structure. For Pr → CoNi (x ≤ 0.10) NSFs, the M values through field-cooling (FC) curves exhibit a slight decrease with increasing T. Their zero field-cooling (ZFC) curves display a nonmonotonic decrease with the decreasing T and result in a low magnetization at low Ts. ZFC and FC curves of Pr → CoNi (x ≤ 0.10) NSFs indicate a large irreversibility.

Decisive role of microstrains in the formation of the domain structure in multiwall carbon nanotubes

The present paper deals with the structure of carbon nanotubes of various diameters. The results of X-ray diffractometry and transmission electron microscopy are analyzed in detail. It is shown that the studied carbon nanotubes have one or several types of domain boundaries (zigzag, armchair). The role of uniaxial microstrains in the formation of the domain structure in carbon nanotubes is great. The number of significant independent microstrains determines the number of the domain types in the MWCNT structure. Tubes experiencing only the εzz strain have a single-domain structure. Multiwall carbon nano-tubes with strains εzz and εxx have a multidomain structure. Nonequilibrium microstrains at interfaces during energy dissi-pation can lead to the hysteresis of thermal and mechanical properties.

Pulsed Lased Deposition of Single-Crystalline (001) Oriented Pb(Zr0.5T0.5)O3 Thin Film on PrScO3 Substrate

High quality thin films are important for domain engineering applications such as on-volatile memory applications. Single crystalline (001) oriented Pb (Zr0.5T0.5)O3 thin films have been grown by pulsed laser deposition on PrScO3 with strontium ruthenate (SRO) electrodes. Thin films were prepared from PZT ceramic targets with 15% excess PbO to compensate for lead loss at high deposition temperature. Layer by layer/step flow growth mode observed on AFM images has been realised by using a single terminated PrScO3 substrate as well as optimized deposition parameters. XRD measurements have confirmed the highly (001) oriented tetragonal symmetry. Furthermore, analysis conducted using piezoresponse force microscopy has shown that the thin films are monodomain with spontaneous ferroelectric polarization preferentially pointing upwards, i.e., away from the substrate. The absence of ferroelastic domains and the observed single ferroelectric domain structure are the results of both relatively small compressive misfit strain as well as favourable electrical boundary conditions.
 Keywords: PZT; Pulsed Laser Deposition; Epitax; Thin film

Resonance behavior of embedded and freestanding microscale ferromagnets

The ferromagnetic resonance of a disordered A2 Fe60Al40 ferromagnetic stripe, of dimensions 5 µm × 1 µm × 32 nm, has been observed in two vastly differing surroundings: in the first case, the ferromagnetic region was surrounded by ordered B2 Fe60Al40, and in the second case it was free standing, adhering only to the oxide substrate. The embedded ferromagnet possesses a periodic magnetic domain structure, which transforms to a single domain structure in the freestanding case. The two cases differ in their dynamic response, for instance, the resonance field for the uniform (k = 0) mode at ~ 14 GHz excitation displays a shift from 209 to 194 mT, respectively for the embedded and freestanding cases, with the external magnetic field applied along the long axis. The resonant behavior of a microscopic ferromagnet can thus be finely tailored via control of its near-interfacial surrounding.

I-TASSER-MTD: a deep-learning-based platform for multi-domain protein structure and function prediction.

Most proteins in cells are composed of multiple folding units (or domains) to perform complex functions in a cooperative manner. Relative to the rapid progress in single-domain structure prediction, there are few effective tools available for multi-domain protein structure assembly, mainly due to the complexity of modeling multi-domain proteins, which involves higher degrees of freedom in domain-orientation space and various levels of continuous and discontinuous domain assembly and linker refinement. To meet the challenge and the high demand of the community, we developed I-TASSER-MTD to model the structures and functions of multi-domain proteins through a progressive protocol that combines sequence-based domain parsing, single-domain structure folding, inter-domain structure assembly and structure-based function annotation in a fully automated pipeline. Advanced deep-learning models have been incorporated into each of the steps to enhance both the domain modeling and inter-domain assembly accuracy. The protocol allows for the incorporation of experimental cross-linking data and cryo-electron microscopy density maps to guide the multi-domain structure assembly simulations. I-TASSER-MTD is built on I-TASSER but substantially extends its ability and accuracy in modeling large multi-domain protein structures and provides meaningful functional insights for the targets at both the domain- and full-chain levels from the amino acid sequence alone.

Influence of RE-Gd3+ ion substitution on structure, morphology, optical, and magnetic analysis of Cu-Cd based nano ferrites synthesized by low-temperature citrate sol–gel auto combustion method

The current study focused on the influence on physical, thermal, spectral, optical, and magnetic properties with the replacement of Fe3+ ions by large ionic radii rare-earth Gd3+ ions in CuCdFe2O4 nano-ferrites. The Gd3+ doped CuCdFe2O4 ferrite samples with chemical composition Cu0.8Cd0.2GdxFe2-xO4 (x = 0, 0.025, 0.05, 0.075 and 0.1) were produced by citrate sol–gel auto combustion route from the metal nitrates of the corresponding compounds. With the help of Thermo-gravimetric and differential thermal (TG-DTA) analysis, the temperature-dependent spinel phase formation and weight loss percentages were examined. The results of Powder X-ray diffraction patterns and FTIR spectra revealed the development of a cubic single-phase structure with α-Fe2O3 secondary phase, and stretching of metal ion bonds with the addition of Gd3+ ion in CuCdFe2O4 ferrites. From XRD data the observed lattice parameter was in the range of 8.323–8.469 Å and the average crystalline size was increased from 13 to 18 nm. “Field emission scanning electron microscopy” (FE-SEM) and “high-resolution transmission electron microscopy” (HR-TEM) analysis was used to give the particle size, shape, clear agglomeration, and dense structure of Gd3+ doped Cu-Cd nanoparticle. The semiconducting nature of the fabricated samples were confirmed from the characteristic UV–Vis spectra and the respective optical band gap values (1.70–1.74 eV). Electron spin resonance spectroscopy (ESR) analysis was provided the information about the various factors including g-value, peak to peak line width (ΔHPP), resonance field (Hr), and time relaxation (T2). The magnetic characteristic hysteresis loops of synthesised samples at 300 K and 15 K temperatures were obtained by VSM. The results showed that all Gd3+ doped samples exhibited a ferromagnetic nature at 300 K and enhanced hard magnetic nature at 15 K. The maximum saturation magnetisation (MS) was observed for x = 0.025 at both the temperatures (31.66 emu/g at 300 K and 39.65 emu/g at 15 K). The HC values were found in the range of 169.23–557.29 Oe at 300 K and 374.69–749.85 Oe at 15 K. The observed SQR (Mr/Ms) values revealed the single domain structure of prepared samples.

Effect of κ-carbides on the mechanical properties and superparamagnetism of Fe–28Mn–11Al-1.5/1.7C–5Cr lightweight steels

The effect of κ-carbides on the mechanical properties and superparamagnetism of Fe–28Mn–11Al-1.5/1.7C–5Cr (wt.%) lightweight steels in hot-rolled and solution-treated samples were investigated by scanning electron microscopy (SEM), electron back-scatter diffraction (EBSD), X-ray diffraction (XRD), transmission electron microscopy (TEM), vibratory sample magnetometer (VSM) and magnetic force microscopy (MFM). The grain sizes of the hot-rolled samples are similar. Compared with 1.5C steel, 1.7C steel not only has more and larger intragranular κ-carbides but also submicron-sized intergranular κ0-carbides, which leads to the higher strength. At the initial stage of deformation, the slip bands are gradually refined, and the smaller spacing of slip band in 1.7C steel results in a higher strain hardening rate than 1.5C steel. When the strain reaches or exceeds 25%, the microbands only arise in 1.7C steel, while three non-coplanar slip bands appear in 1.5C steel. After solution treatment at 1100 °C for 30min, the grain size of the solution-treated samples grows significantly, but is still close. The volume fraction and average size of intragranular κ-carbides are reduced, and the intergranular κ0-carbides are mostly dissolved in 1.7C steel. The strength of two lightweight steels is decreased but the elongation increased obviously. Meanwhile, the yield phenomenon of 1.5C steel disappears because the precipitation strengthening of κ-carbides is no longer the most significant strengthening mechanism. The results show that the volume fraction and average size of intragranular κ-carbides in 1.7C steel are both higher than that in 1.5C steel, and the intergranular κ0-carbides are only formed on the grain boundaries of 1.7C steel. The precipitation strengthening of κ-carbides is the most significant strengthening mechanism except for the solution-treated sample of 1.5C steel, which leads to yield phenomena. At the initial stage of deformation, the slip bands of the hot-rolled samples are gradually refined, and the spacing between slip bands of 1.7C steel is smaller than 1.5C steel. When the strain reaches or exceeds 25%, the microbands only arise in 1.7C steel, while three non-coplanar slip bands appear in 1.5C steel. The difference of deformation mechanism between the two samples is due to the presence of submicron-sized intergranular κ0-carbides and the size effect of intragranular κ-carbides. In addition, the hysteresis loops of two lightweight steels at room temperature exhibit superparamagnetic property due to the single domain structure of κ-carbides. Moreover, the values of saturation magnetization are proportional to the volume fraction of intragranular κ-carbides. The blocking temperature increases with the decrease of the intragranular κ-carbides volume fraction and average size because of the effect of shape anisotropy and surface anisotropy.

DEMO2: Assemble multi-domain protein structures by coupling analogous template alignments with deep-learning inter-domain restraint prediction.

Most proteins in nature contain multiple folding units (or domains). The revolutionary success of AlphaFold2 in single-domain structure prediction showed potential to extend deep-learning techniques for multi-domain structure modeling. This work presents a significantly improved method, DEMO2, which integrates analogous template structural alignments with deep-learning techniques for high-accuracy domain structure assembly. Starting from individual domain models, inter-domain spatial restraints are first predicted with deep residual convolutional networks, where full-length structure models are assembled using L-BFGS simulations under the guidance of a hybrid energy function combining deep-learning restraints and analogous multi-domain template alignments searched from the PDB. The output of DEMO2 contains deep-learning inter-domain restraints, top-ranked multi-domain structure templates, and up to five full-length structure models. DEMO2 was tested on a large-scale benchmark and the blind CASP14 experiment, where DEMO2 was shown to significantly outperform its predecessor and the state-of-the-art protein structure prediction methods. By integrating with new deep-learning techniques, DEMO2 should help fill the rapidly increasing gap between the improved ability of tertiary structure determination and the high demand for the high-quality multi-domain protein structures. The DEMO2 server is available at https://zhanggroup.org/DEMO/.

Solution epitaxy of single-crystal and single-domain KNbO3 film with a great photovoltaic current

As a classic ferroelectric material, orthorhombic perovskite KNbO3 demonstrates a large electro-optical coefficient, high refractive index, and excellent nonlinear optical property. These make single-crystal KNbO3 films being long-pursued for lead-free sensor or optoelectronic device applications. However, it remains a challenge to obtain high-quality single-crystal KNbO3 films because of the volatility of potassium at a high growth temperature. In this work, single-crystal KNbO3 films with a tunable thickness have been successfully fabricated by a low-temperature (∼220 °C) hydrothermal epitaxy on cubic single-crystal Nb:SrTiO3 substrates. Interestingly, the KNbO3 film was investigated to adopt a single-domain structure with a polarization direction pointing to the substrate. In-depth characterization reveals an intriguing disordered region of approximately 0.6–1.2 nm because of partial Nb substitution of Ti near the interface, giving rise to the coexistence of Ti3+ and Ti4+ ions. Such region is proposed to release a large interface strain energy from a large lattice misfit (∼2.3%) between {011}KNbO3 and {100}Nb:SrTiO3 and reduce interfacial electrostatic energy via screening of the positive polar surface of KNbO3. This allows to drive a hydrothermal epitaxy of single-crystal and single-domain KNbO3 without forming a typical dislocation. The films demonstrate a great photovoltaic short-circuit current of 15.65 μA/cm2 under the 375 nm laser irradiation of 500 mW/cm2 light intensity, and the corresponding photoresponsivity is the highest among the emerged KNbO3-based materials. Such improvement in the photoresponsivity has been attributed to a successful low-temperature solution epitaxy of single-crystal and single-domain KNbO3 films, where K deficiency can be significantly suppressed. These findings suggest that a solution epitaxy strategy is effective in producing high-quality ferroelectric films for lead-free optoelectronic or self-powered photodetector device applications.