Structure-guided discovery of protein and glycan components in native mastigonemes.

Mastigonemes, the hair-like lateral appendages lining cilia or flagella, participate in mechanosensation and cellular motion, but their constituents and structure have remained unclear. Here, we report the cryo-EM structure of native mastigonemes isolated from Chlamydomonas at 3.0 Å resolution. The long stem assembles as a super spiral, with each helical turn comprising four pairs of anti-parallel mastigoneme-like protein 1 (Mst1). A large array of arabinoglycans, which represents a common class of glycosylation in plants and algae, is resolved surrounding the type II poly-hydroxyproline (Hyp) helix in Mst1. The EM map unveils a mastigoneme axial protein (Mstax) that is rich in heavily glycosylated Hyp and contains a PKD2-like transmembrane domain (TMD). Mstax, with nearly 8,000 residues spanning from the intracellular region to the distal end of the mastigoneme, provides the framework for Mst1 assembly. Our study provides insights into the complexity of protein and glycan interactions in native bio-architectures.

Revealing the Role of the Tetragonal Distortion in the Metal-Insulator Transition of Co- and Fe-Doped NiS.

Although the NiS exhibits the most widely adjustable metal-to-insulator (MIT) properties among the chalcogenides, the mechanisms, with respect to the regulations in their critical temperatures (TMIT), are yet unclear. Herein, we demonstrate the overlooked role associated with the structurally tetragonal distortion in elevating the TMIT of NiS; this is in distinct contrast to the previously expected hybridization and bandwidth regulations that usually reduces TMIT. Compared to the perspective of structure distortions, the orbital hybridization and band regulation of NiS are ∼19 times more effective adjustment in TMIT. As a result, the respective abruptions in both the electrical and thermal resistive switches across the TMIT of NiS can be better preserved in the low-temperature range (<273 K), shedding light on their optimum usage at cryogenic temperatures.

Manipulating the metal-to-insulator transitions of VO2 by combining compositing and doping strategies.

Vanadium dioxide (VO2) exhibits the most abrupt metal-to-insulator transition (MIT) property near room temperature among the representative 3d-orbital correlated oxides, and its structural variation during the MIT usually results in poor mechanical properties as bulk pellets. Moreover, compositing with highly resistive oxides has been reported to improve the mechanical strength of bulk VO2 since the generation and propagation of microcracks is suppressed upon thermocycling across the MIT; further, their respective impacts on electrical transportation are yet unclear. Herein, we demonstrate the role of these highly resistive oxide composites (e.g., HfO2, CoO and Al2O3) in reducing charge leakage along the microcracks within the insulating phase of VO2, leading to more abrupt MIT properties from the perspective of electrical transportation. This enables the possibility of simultaneously regulating the critical temperature and abrupt MIT transition, as well as the mechanical properties of the VO2 bulk pellets via compositing with oxides with different melting points using spark plasma-assisted reactive sintering (SPARS).

Reactive spark plasma-assisted synthesis of metastable rare-earth ferrites with widely tunable charge ordering transfer properties.

Although the d-band correlations within metastable rare-earth ferrites (ReFe2O4) enable charge ordering transition functionalities beyond conventional semiconductors, their material synthesis yet requires a reducing atmosphere that is toxic and explosive. Herein, we demonstrate a reactive spark plasma sintering (RSPS) strategy to effectively synthesize metastable ReFe2O4 (Re = Er, Tm, Yb, Lu) simply in coarse vacuum within a greatly shortened reaction period. High flexibility is gained in adjusting their rare-earth composition and thereby the charge ordering transition temperature within 218-330 K. Assisted by the temperature-dependent near edge X-ray absorption fine structure (NEXAFS) analysis, an elevation in the Fe3+/Fe2+ orbital configuration within ReFe2O4 was observed compared to previous reports, and it is consistent with their higher Mott temperature and activation energy observed in their electrical transportations. This work elucidates stabilization of the metastable phase (e.g., ReFe2O4) via the non-equilibrium processes of RSPS beyond the thermodynamic restrictions.

Revealing the Role of Hydrogen in Electron-Doping Mottronics for Strongly Correlated Vanadium Dioxide.

Hydrogen-associated electron-doping Mottronics for d-band correlated oxides (e.g., VO2) opens up a new paradigm to regulate the electronic functionality via directly manipulating the orbital configuration and occupancy. Nevertheless, the role of hydrogen in the Mottronic transition of VO2 is yet unclear because opposite orbital reconfigurations toward either the metallic or highly insulating states were both reported. Herein, we demonstrate the root cause for such hydrogen-induced multiple electronic phase transitions by 1H quantification using nuclear reaction analysis. A low hydrogenation temperature is demonstrated to be vital in achieving a large hydrogen concentration (nH ≈ 1022 cm-3) that further enhances the t2g orbital occupancy to trigger electron localizations. In contrast, elevating the hydrogenation temperatures surprisingly reduces nH to ∼1021 cm-3 but forms more stable metallic H0.06VO2. This leads to the recognition of a weaker hydrogen interaction that triggers electron localization within VO2 via Mottronically enhancing the orbital occupancies.

Revealing the role of interfacial heterogeneous nucleation in the metastable thin film growth of rare-earth nickelate electronic transition materials.

Although rare-earth nickelates (ReNiO3, Re ≠ La) exhibit abundant electronic phases and widely adjustable metal to insulator electronic transition properties, their practical electronic applications are largely impeded by their intrinsic meta-stability. Apart from elevating the oxygen reaction pressure, heterogeneous nucleation is expected to be an alternative strategy that enables the crystallization of ReNiO3 at low meta-stability. In this work, the respective roles of high oxygen pressure and heterogeneous interface in triggering ReNiO3 thin film growth in the metastable state are revealed. ReNiO3 (Re = Nd, Sm, Eu, Gd and Dy) thin films grown on a LaAlO3 single crystal substrate show effective crystallization at atmospheric pressure without the necessity to apply high oxygen pressure, suggesting that the interfacial bonding between the ReNiO3 and substrates can sufficiently reduce the positive Gibbs formation energy of ReNiO3, which is further verified by the first-principles calculations. Nevertheless, the abrupt electronic transitions only appear in ReNiO3 thin films grown at high oxygen pressure, in which case the oxygen vacancies are effectively eliminated via high oxygen pressure reactions as indicated by near-edge X-ray absorption fine structure (NEXAFS) analysis. This work unveils the synergistic effects of heterogeneous nucleation and high oxygen pressure on the growth of high quality ReNiO3 thin films.

Temperature-driven n-p conduction type switching without structural transition in a Cu-rich chalcogenide, NaCu5S3.

We report for the first time the discovery of reversible n-p conduction type switching in a chalcogenide, NaCu5S3, without structural transition. AC impedance and first-principles simulations of the ionic migration confirmed the local melting trends of the hexagonal copper lattice at high temperatures, which could result in superionic conductivity within NaCu5S3.

Electron-Doping Mottronics in Strongly Correlated Perovskite.

The discovery of hydrogen-induced electron localization and highly insulating states in d-band electron correlated perovskites has opened a new paradigm for exploring novel electronic phases of condensed matters and applications in emerging field-controlled electronic devices (e.g., Mottronics). Although a significant understanding of doping-tuned transport properties of single crystalline correlated materials exists, it has remained unclear how doping-controlled transport properties behave in the presence of planar defects. The discovery of an unexpected high-concentration doping effect in defective regions is reported for correlated nickelates. It enables electronic conductance by tuning the Fermi-level in Mott-Hubbard band and shaping the lower Hubbard band state into a partially filled configuration. Interface engineering and grain boundary designs are performed for Hx SmNiO3 /SrRuO3 heterostructures, and a Mottronic device is achieved. The interfacial aggregation of hydrogen is controlled and quantified to establish its correlation with the electrical transport properties. The chemical bonding between the incorporated hydrogen with defective SmNiO3 is further analyzed by the positron annihilation spectroscopy. The present work unveils new materials physics in correlated materials and suggests novel doping strategies for developing Mottronic and iontronic devices via hydrogen-doping-controlled orbital occupancy in perovskite heterostructures.

A d-Band Electron Correlated Thermoelectric Thermistor Established in Metastable Perovskite Family of Rare-Earth Nickelates.

The d-band electron correlations shed a light on bridging multiple functionalities within one material system, and this further extends the horizon in material designs and their emerging device applications. Herein, we demonstrate the combination of thermoelectric and thermistor functionalities within the perovskite family of correlated rare-earth nickelates (ReNiO3) having small rare-earth elements (i.e., YNiO3 and DyNiO3), in addition to their already known metal-to-insulator transitions. In contrast to conventional semiconductive materials, the electronic band structure of ReNiO3 split within the hybridized Ni3d-O2p is closely coupled to the structure of NiO6 octahedron. Based on such a distinguished feature, it is possible to achieve the coexistence of a large magnitude of thermopower (S) and negative temperature coefficient of resistance (NTCR) in the insulating phase of ReNiO3 with small Re and more distorted NiO6 octahedron. This establishes a thermoelectric thermistor that can be used for sensing the thermal perturbations by integrating the two distinguished detection modes within one system: the active mode utilizing the high NTCR, and the passive mode utilizing the large S. It is worth noticing that as-achieved S-NTCR relationship in ReNiO3 differs form the one for conventional semiconductors, in which cases enlarging the band gap enlarges S but reduces NTCR. As achieved thermoelectric thermistor combing thermistor and thermoelectric functionalities via electron correlation opens up a new direction to explore emerging energy/electronic devices for sensing the thermal perturbations. The temperature range that keeps a high thermoelectric thermistor performance (i.e., |TCR | >2%K-1 and meanwhile S > 100 µVK-1) of ReNiO3 with a small rare-earth radius is possible to cover most of the outdoor conditions on earth (i.e., -50 to 150 °C).

Revealing the role of lattice distortions in the hydrogen-induced metal-insulator transition of SmNiO3.

The discovery of hydrogen-induced electronic phase transitions in strongly correlated materials such as rare-earth nickelates has opened up a new paradigm in regulating materials' properties for both fundamental study and technological applications. However, the microscopic understanding of how protons and electrons behave in the phase transition is lacking, mainly due to the difficulty in the characterization of the hydrogen doping level. Here, we demonstrate the quantification and trajectory of hydrogen in strain-regulated SmNiO3 by using nuclear reaction analysis. Introducing 2.4% of elastic strain in SmNiO3 reduces the incorporated hydrogen concentration from ~1021 cm-3 to ~1020 cm-3. Unexpectedly, despite a lower hydrogen concentration, a more significant modification in resistivity is observed for tensile-strained SmNiO3, substantially different from the previous understanding. We argue that this transition is explained by an intermediate metastable state occurring in the transient diffusion process of hydrogen, despite the absence of hydrogen at the post-transition stage.

In-plane electric field controlled ferromagnetism and anisotropic magnetoresistance in an LSMO/PMN-PT heterostructure.

We report the in-plane electric field controlled ferromagnetism of La2/3Sr1/3MnO3 (LSMO) films epitaxially deposited on [Pb(Mg1/3Nb2/3)O3]0.7-(PbTiO3)0.3 (PMN-PT) (001), (011) and (111) single crystal substrates. The in-plane coercivities (H c∥) and remanences of the LSMO films greatly depend on the in-plane electric field applied on the PMN-PT (001) and (011) substrates. The experimental change of H c∥ is consistent with the Stoner-Wohlfarth model and first principle calculation with the electric field varying from -10 to 10 kV cm-1. Moreover, the Curie temperature and anisotropic magnetoresistance of the LSMO films can also be manipulated by an in-plane electric field. Finally, the LSMO/PMN-PT (001) heterostructure is designed to be a new kind of magnetic signal generator with the source of electric field.

Dipole-correlated carrier transportation and orbital reconfiguration in strain-distorted SrNbxTi1-xO3/KTaO3.

Strong electron-correlations can result in un-conventional transportation behaviour, such as metal-insulator transitions, high temperature superconductivity and bad metal conduction. Here we report a distinct transportation characteristic achieved by actively coupling the carriers with randomly distributed lattice-dipoles for strain-distorted SrNbxTi1-xO3. The strong electron correlations split the conduction band, and lead to a distinguished thermal-emitted carrier transportation with an activation energy of ∼10-2 eV. Further consistency was demonstrated by the respective changes in orbital configurations observed in near edge X-ray absorption fine structures. The present investigation demonstrates new mechanisms for regulating the carrier transportation using polaronic electron correlations.

Solid Conical Cap-closing Hollow Tube Growth by Axial Screw Dislocations.

Exploration of the mechanisms for growth of the nanostructures is the key point to achieve nanomaterial syntheses with precisely controlled morphology and structure. Herein, we reported a new mechanism that realized the growth of solid conical cap-closing hollow tube by axial screw dislocations in the formation α-Al2O3 nanowires. A hollow tube was firstly grown by axial screw dislocations in the formation α-Al2O3 nanowires through vapor-phase synthesis. Afterwards, the hollow tube was closed up by generating a solid conical cap with axial screw dislocations based on the competition between the surface energy and the strain energy of screw dislocation controlled by the growth environment. The solid conical cap-closing hollow tube growth model based on the axial screw dislocations is expected to be a general growth mechanism for nanowires within low supersaturation. This study enriches the fundamental understanding with respective to the kinetics of nanostructured crystal growth and provides guidance to the precise structure control in nanosynthesis and manufacturing.

Photo-induced enhancement of the power factor of Cu2S thermoelectric films.

Element doping is commonly used to adjust the carrier concentrations in semiconductors such as thermoelectric materials. However, the doping process unavoidably brings in defects or distortions in crystal lattices, which further strongly affects the physical properties of the materials. In this work, high energy photons have been used to activate the carriers in Cu2S thermoelectric films. As a result, the carrier concentrations, and the respective electrical conductivity as well as Seebeck coefficient are further changed. The photon-induced electrical transport properties are further analyzed utilizing a Parallel circuit model. Due to the realization of optimized carrier concentrations by photon activation, the power factor of Cu2S film is improved more than 900 times as compared with the dark data. As compared to the traditional doping process, the approach using photon activation can realize the tuning of carrier concentrations without affecting crystal lattice. This method provides an opportunity to investigate the intrinsic physical properties of semiconductor materials without involving traditional element doping process that usually brings in additional lattice defects or distortions.

Superlow thermal conductivity 3D carbon nanotube network for thermoelectric applications.

Electrical and thermal transportation properties of a novel structured 3D CNT network have been systematically investigated. The 3D CNT net work maintains extremely low thermal conductivity of only 0.035 W/(m K) in standard atmosphere at room temperature, which is among the lowest compared with other reported CNT macrostructures. Its electrical transportation could be adjusted through a convenient gas-fuming doping process. By potassium (K) doping, the original p-type CNT network converted to n-type, whereas iodine (I(2)) doping enhanced its electrical conductivity. The self-sustainable homogeneous network structure of as-fabricated 3D CNT network made it a promising candidate as the template for polymer composition. By in situ nanoscaled composition of 3D CNT network with polyaniline (PANI), the thermoelectric performance of PANI was significantly improved, while the self-sustainable and flexible structure of the 3D CNT network has been retained. It is hoped that as-fabricated 3D CNT network will contribute to the development of low-cost organic thermoelectric area.

Direct tuning of electrical properties in nano-structured Bi2Se0.3Te2.7 by reversible electrochemical lithium reactions.

Lithium intercalation and de-intercalation processes have been used to fabricate bulk Bi(2)Se(0.3)Te(2.7) with internal nanostructures. The doped Li content can be precisely controlled through this method. It provides a chance to directly optimize electrical properties when preparing nano-structured materials, leading to the optimum carrier concentration for improved thermoelectric figure of merit.

Top-down fabrication of nano-scaled Bi2Se(0.3)Te(2.7) associated by electrochemical Li intercalation.

A convenient top-down method for preparation of Bi(2)Se(0.3)Te(2.7) crystalline nano-particles has been demonstrated. It contains two steps: (1) lithium was intercalated between the van der Waals bonded quintuple-layers by electrochemical process inside lithium ion batteries with precisely controlled speed and amount; (2) subsequent alcohol exposure of Li(x)Bi(2)Se(0.3)Te(2.7) to make the intercalated Li atoms explode like atom-scaled bombs and exfoliate the original micro/macro scaled materials into nano-scaled single crystalline particles with sizes around 10 nm. The intercalation process does not cost external energy, and can be scaled up by amplification of the intercalation devices.

Biodegradation of Orange G by wood-rot fungi Phanerochaete sordida TXJ-1302A and Tyromyces lauteus TXJ-1302B.

Two strains isolated from the organic layers of forests on Zijin Mountain have indicated a strong capability of decolorization for Orange G on the solid plates. They were identified as Phanerochaete sordida and Tyromyces lauteus according to phenotypic and molecular techniques. Through this study, we try to find the suitable condition and cheapest way for decolorization by two strains. The result shows that malt extract and ammonium sulfate are the best N source for P. sordida and T. lauteus, respectively; 0.95 g per L glucose + 0.05 g per L ethonal are the best C source both for P. sordida and T. lauteus. Oxalate plays an important role as the organic acid chelator which can also enhance the decolorized capability of fungi.