Bi 4 NdTi 3 Fe 0.7 Ni 0.3 O 15 (BNTFN) ceramics were fabricated via a modified solid‐state reaction method. Comprehensive magnetodielectric (MD) characterization revealed significant anisotropy for MD coupling in BNTFN. In the high‐frequency region, under identical frequency ( f ) and external magnetic field ( H ) conditions, MD coupling parallel to the c ‐axis (MD//) exhibited a weak positive effect, while that perpendicular to the c ‐axis (MD⊥) demonstrated a pronounced negative effect. When H < 5 kOe, MD// increased with H , whereas MD⊥ remained negligible. However, when H exceeded 5 kOe, MD// approached saturation, and MD⊥ began to rise progressively with further increases in H . Remarkably, at 1 MHz and under 10 kOe, MD⊥ was almost ten or twenty times stronger than MD// in BNTFN. More importantly, this work also elucidates the relationship between microstructure and MD coupling in four‐layered perovskite compounds, offering valuable insights for designing high‐sensitivity magnetocapacitance devices through strategic microstructure manipulation in layered oxide systems.

In this work, the NixFe1-x LDHs (x = 0.25, 0.5, 0.75, 0.8) samples were prepared by hydrothermal method. The morphology of NixFe1-x LDHs can be controlled and porous NixFe1-x LDHs "nanoflowers" were obtained at x = 0.75. The XRD patterns showed that pure NixFe1-x LDHs were produced when the nickel and iron salts were at a fixed ratio. By tuning the conductivity of LDHs, the current density of NixFe1-x LDHs/ acetylene black (AB) obviously increased. The Ni0.75Fe0.25 LDHs/AB showed good OER performance with Tafel slope of 31 mV/dec and low overpotential of 262.2 mV at current density of 20 mA/cm2.

Abstract FeCo nanoparticles were prepared by controlling the reaction temperature and addition of surfactant. With the increasing of reaction temperature, CoFe2O4 impurities disappeared and crystalline FeCo nanoparticles were got. High Ms of 218.5 emu/g and low Hc of 90.2 Oe were observed after reacting at 150 oC. The best OER (oxygen evolution reaction) properties with low onset potential (0.73 V) and small Tafel value (105 mV/dec) were found in FeCo nanoparticles prepared at 150 oC. With increasing the surfactant ratio, the purity of FeCo particles did not change. However, the repulsive forces between the polar ends of oleic acid molecules induced the formation of uniform small FeCo nanoparticles. Large Ms of 166.4 emu/g and small Hc of 75.0 Oe were observed when the surfactant ratio was 3:1. The best OER activity with low onset potential (0.63 V) and small Tafel value (67 mV/dec) were found in FeCo nanoparticles prepared with the surfactant ratio of 3:1. The improved OER activity was contributed to the impurity reduction, the better crystallization, the larger surface area and the better magnetic properties, which could provide small electric resistance, more active sites and easy electron transfer.

Photodynamic therapy (PDT) with selectivity and security has been widely acknowledged as a promising therapeutic option for cancer treatment. With the swift blossom of phototherapy and nanotechnology, nanotherapeutics for PDT have made great progress in recent years. Herein, we outline the latest updates in nanotherapeutics for facilitating PDT. First, the recent trends of nanotherapeutics for light transmitting in deep tumors are outlined, mainly including radiation ray-activated nanosystems, near-infrared ray-excitation nanosystems and sono-light dual excited nanoparticles. Then, the emerging nanotherapeutics for reversing tumor hypoxia are discussed, including nanosystems for exogenous oxygen delivery, oxygen in situ generations and oxygen consumption inhibition. Subsequently, nanotherapeutics for promoting photosensitizers delivery efficiency are presented, including photosensitizers nanocarriers and photosensitizers carrier-free nanoassemblies. Moreover, the design rationale, advantages and challenges of nanosystems for clinical therapy are highlighted.

为了研究A位掺杂对LaFeO3的结构及电化学性能的影响,本文中采用溶胶凝胶法制备并在空气中800℃退火获得La1-x,BixFeO3纳米颗粒.研究发现,随着Bi元素的掺杂,材料的氧还原(ORR)性能显著提升.通过一系列电化学测式发现,无论是起始电位、极限电流密度,还是Tafel斜率与未掺杂样品相比都有显著提升,并在x=0.15时得到最优的ORR性能.这可能是因为Bi的掺杂使得LaFeO3发生晶格畸变并导致材料中的氧空位增加,从而得到更优的ORR性能.

The OH¯/(Co2+, Fe2+) ratio and annealing temperature (Ta) have a great influence on the microstructure and magnetic properties of FeCo alloys. In this work, the OH¯/(Co2+, Fe2+) ratio was first changed from 10:1 to 30:1. When the OH¯/(Co2+, Fe2+) ratio was 20:1, pure FeCo powder samples were obtained. After annealing at 400 °C, the saturation magnetization (Ms), remnant magnetization (Mr), and coercivity (Hc) were 155 emu/g, 15 emu/g, and 210 Oe, respectively. Then the prepared FeCo samples were annealed in the range of 300 °C–600 °C for 5 h. With the increasing of Ta, the better magnetic properties of FeCo powders were observed. When the Ta was 600 °C, the Ms, Mr, and Hc were 202 emu/g, 12 emu/g, and 87 Oe, respectively. When the OH¯/(Co2+, Fe2+) = 20:1 and Ta was 400 °C, the real part of complex permittivity was between 8.2 and 9.5, and the corresponding imaginary part was between − 0.3 and 1.3. Furthermore, the maximum reflection loss (RL) value of FeCo powders (20–30 nm) was − 35.49 dB which showed great potential in corresponding industrial applications.

The catalysts are often used in fuel cells and metal-air batteries to speed up electrochemical reactions. In this study, we prepared CoFe2O4 nanoparticles with mainly inverse spinel structure and FeCo2O4 nanoparticles with mainly spinel structure as bifunctional catalysts by hydrothermal method. After annealing at 350 degrees C, pure CoFe2O4 and FeCo2O4 nanoparticles with uniform size distribution have been obtained. The CoFe2O4 nanoparticles showed high current density of 5.5 mA/cm(2) at -0.8 V in the ORR test. It's low Tafel slope of 83.0 mV/dec further confirmed the excellent ORR catalytic properties of CoFe2O4 nanoparticles. Furthermore, the CoFe2O4 nanoparticles also showed good OER properties with satisfied current density of 35.7 mV/cm(2) at l.0 V and low OER Tafel slope of 71.0 mV/dec. Both the ORR and OER properties of CoFe2O4 nanoparticles showed good time stability which were compared with FeCo2O4 nanoparticles. These results indicated that CoFe2O4 nanoparticles with mainly inverse spinel structure had better electrocatalytic performance than FeCo2O4 nanoparticles with mainly spinel structure. The CoFe2O4 nanoparticles with mainly inverse spinel structure show a significant potential application in rechargeable battery. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

A wide bandgap is one of the major obstacles that hamper the photoelectric application of ferroelectrics. This work reported the tunable band gaps of ferroelectric Aurivillius Bi3.15Nd0.52Ti3O2 (BNdT) by B-site X (X = Ni, Co, Cr Mn, or Fe) substitution. The analysis of the UV-vis absorption spectra showed a decrease in the band gap induced by substitution and the valence band XPS (VBXPS) spectra indicated that the substitution of X ions elevates the valence band maximum (VBM). The octahedral distortion was estimated qualitatively by Raman analysis and quantitatively through the structural refinements. It is found that the change of the energy band structure and the band gap tuning are proportional to the octahedral distortion induced by B-site substitution. To our knowledge it's the first time to relate the octahedral distortion to the band gap tuning quantitatively for ferroelectric Aurivillius compounds, and the present work will shed light on the mechanism of band gap tuning of ferroelectric oxides materials and provide an available way on manipulating oxide optoelectronics.

In this work, La1−xBixFeO3 powders (0 ≤ x ≤ 0.2) were prepared by sol–gel route. The orthorhombic Pbnm structure of the pure LaFeO3 powder was confirmed by X-ray diffraction. However, there was a changing tendency from the orthorhombic Pbnm structure into the rhombohedral R3c structure with the increase in Bi-doping. The structural and symmetric change of Bi-doped LaFeO3 samples was further verified by the Raman spectra which changed from fundamental 5 modes into 7 modes. The X-ray photoelectron spectra (XPS) revealed that more oxygen vacancies, Fe3+ and Fe4+, existed in Bi-doped LaFeO3 sample. Detailed CV, LSV and EIS analyses had provided conclusive evidence that the oxygen vacancy Fe3+ and Fe4+ played an important contribution to the electrocatalytic activity. The best ORR catalytic effect was observed in La0.85Bi0.15FeO3 catalyst. These results suggest that the Bi-doping is a significative effort to enhance the activities of perovskite electrocatalysts.

Ceramics of Mn-doped Bi4NdTi3Fe1−xMnxO15 (Mnx, x = 0.1, 0.3, 0.5 and 0.7) were synthesised by a multicalcination procedure. The substitution of Mn for Fe does not change the layered perovskite structure of Bi4NdTi3FeO15 (BNTF) except that small amounts of Mn3O4 appear in the samples. Plate-like morphology of the grains which is characteristic for layer-structure Aurivillius compounds was clearly observed for all the Mnx samples. The dielectric, ferroelectric and magentic properties of the samples were studied and it is found that the doping of Mn weakened the electric properties but improved the magnetic property. Especially, in Mn0.3 sample, the 2Mr value is about ten times of those in other samples. The present work is meaningful for compositional design of room temperature (RT) multiferroic materials based on four-layer structured Aurivillius compounds.

C-axis preferentially and randomly oriented Bi4NdTi3FeO15 (BNTF) ceramics were prepared by molten salt synthesis and conventional solid-state reaction methods, respectively. The ceramics with different orientations all exhibit Aurivillius structure containing four perovskite layers and the Lotgering factor f of c-axis preferentially oriented BNTF prepared by molten salt synthesis was calculated to be 0.865. BNTF powders show two absorption edges due to the electron excitations not only from valence band (VB) to Ti 3d conduction band (CB) but also to Fe eg CB. The ferroelectric and photovoltaic properties of BNTF ceramic samples were investigated. The ferroelectric performance of randomly oriented ceramic sample is better than that of c-axis preferentially oriented one. Significant photovoltaic effect was observed in both ceramic samples. Compared with the ceramic with c-axis preferred orientation, the randomly oriented ceramic exhibits a larger photocurrent Jsc and a smaller photovoltage Voc, which was discussed from the grain alignment in the two ceramics and the anisotropy of the crystal structure. The present work provides a new way to control photovoltaic properties of lead-free Bi5Ti3FeO15 (BTF) based compounds and accelerates their application in ferroelectric photovoltaic (FEPV) and energy fields.

Ceramics of Mn-doped Bi4NdTi3Fe1−xMnxO15 (Mnx, x = 0.1, 0.3, 0.5 and 0.7) were synthesised by a multicalcination procedure. The substitution of Mn for Fe does not change the layered perovskite structure of Bi4NdTi3FeO15 (BNTF) except that small amounts of Mn3O4 appear in the samples. Plate-like morphology of the grains which is characteristic for layer-structure Aurivillius compounds was clearly observed for all the Mnx samples. The dielectric, ferroelectric and magentic properties of the samples were studied and it is found that the doping of Mn weakened the electric properties but improved the magnetic property. Especially, in Mn0.3 sample, the 2Mr value is about ten times of those in other samples. The present work is meaningful for compositional design of room temperature (RT) multiferroic materials based on four-layer structured Aurivillius compounds.

Aurivillius Bi4NdTi3(Fe0.5M0.5)O-15 (M-BNTF, M = Cr, Ni, Fe, Co, Mn) thin films were prepared by a sol-gel method. Single-phase four-layered perovskite structure of all the M-BNTF thin films was characterized by X-ray diffraction and FT-IR spectra. Typical plate-like grains with different grain sizes were observed in the M-BNTF thin films. Optical properties were measured by a UV-vis spectrometer, and all the films have direct bandgaps. The bandgaps of the Cr-, Ni-, Fe-, Co- and Mn-BNTF films were calculated to be about 3.45, 2.84, 2.58, 2.47 and 2.37 eV respectively through the Tauc's power law. The bandgap tuning is attributed to the cationic disorder and the large distortion of MO6 octahedron by the M ions doping which was verified by the calculation of lattice parameters and Raman measurements. The present work may help shed light on the origin of the bandgap tunability for bismuth-contained Aurivillius ferroelectric compounds and promote them to get more extensively application in the new photovoltaic cells and other novel optoelectronic devices.(C) 2018 Elsevier B.V. All rights reserved.

Co2FeAl@C nanoparticles were prepared by co-precipitation and annealed in a gas mixture. Firstly, the effects of annealing temperature on the structure and magnetic properties of Co2FeAl@C nanoparticles were studied. Subsequently, the oxidation resistance of Co2FeAl@C nanoparticles was explored. When the annealing temperature was 400 degrees C, carbon-coated pure Co2FeAl alloy nanoparticles were prepared. With the increasing of annealing temperature, crystallization degree, grain size and saturation magnetization of Co2FeAl@C nanoparticles increased gradually. When the annealing temperature was 800 degrees C, the saturation magnetization of Co2FeAl@C nanoparticles reached a maximum value (149.6 emu/g). These Co2FeAl@C nanoparticles with good oxidation resistance have great potential in some industrial fields. (C) 2019 Elsevier B.V. All rights reserved.

In present work,ordered titanium dioxide nanotubes fabricated by anodization method. The crystalline structure and morphology were characterized with X-ray diffraction (XRD) and scanning electron microscopy (SEM),respectively. Three samples made of the pristine,the annealed and the reduced TiO2 nanotubes were analyzed and compared in terms of the performance and characteristic of galvanostatic charge-discharge. The experimental results show:1) the reduced TiO2nanotubes have the largest charging efficiency and energy density,whose performance is very close to ideal capacitor;2) the annealed TiO2nanotube is much higher energy density and efficiency of energy storage than the un-annealed one.

The Bi3.15Nd0.85Ti3O12 (BNdT) and Cr-doped BNdT films on quartz substrates were prepared by a sol-gel process and the effects of Cr doping on the structure and band gap of BNdT were examined. Cr-doping does not change the three-layered perovskite structure of BNdT but transforms the grain morphology from equiaxed grains to rectangular grains. The utilization of visible light is increased by Cr doping and the large band gap reduction (similar to 1.1 eV) was obtained, which is analyzed from the electronegativity and the distortion caused by substitution. The present work provides an available way to make ferroelectric (FE) BNdT getting more extensively applied in the new photovoltaic cells and other novel optoelectronic devices. (C) 2018 Elsevier B.V. All rights reserved.

First-principles calculations are performed to investigate pressure effects on structure, magnetism, martensitic phase transition and Curie temperatures of Mn2PtGa Heusler alloy in framework of the density functional theory. It is shown that Mn2PtGa prefer to crystallize in the inverse Heusler type structure. Besides, we predict an extraordinary occurrence of pressure induced metallic ferrimagnetism to half-metallic ferromagnetism transition in cubic phase of Mn2PtGa alloy under hydrostatic pressure up to 43 GPa and the half-metallic ferromagnetism is found to be robust even the lattice further compression to 90 GPa. However, with the pressure up to 100 GPa, the spin-down gap starts to close and the half metallicity begin to disappear, while with the pressure increasing from 100 GPa to 300 GPa, the alloy returns to metallic characteristic. In addition, the energy difference between the austenitic and martensitic phases is found to increase with increasing pressure followed by a decrease when pressure reaches to 43 GPa, which implies a variation trend of martensitic phase transition temperature. Furthermore, Curie temperatures in both austenitic and martensitic phases are estimated under pressure by using the standard mean-field approximation which agrees well with the theoretical results in literature. The robustness of the half metallicity, magnetic transition and the high Curie temperature under pressure make Mn2PtGa alloy a promising candidate for applications in spintronic devices.

Composite electrode materials were synthesized by mixing activated carbon with TiO2and the influence of mixing way and the ratio on the capacitance performance were studied.The results show that the specific capacity and energy density of the capacitor can be enhanced with the increase of activated carbon, The equivalent series resistance of TiO2/C capacitors decreased rapidly with the increase of the proportion of activated carbon.When the mass ratio of activated carbon and TiO2is 2:1, the specific capacitance is 24.2 F/g and energy density is 3.32 Wh/kg for the composite electrode material.

Surface clean,highly ordered TiO2nanotube arrays were prepared by electrochemical anodic oxidation method with a mixture of ethylene glycol and ammonium fluoride as solution and high purity titanium plate as electrodes. The influence of the ammonium fluoride concentration,anodic oxidation voltage and time on the size and morphology of TiO2nanotubes were studied systematically in this work. Results show that surface clean and highly order TiO2nanotube arrays with a length of 50 μm and a diameter of 90 nm can be prepared by the anodic oxidation method when the fluoride content,the voltage and time of anodic oxidation are 0.3%,60 V and 13 hours,respectively.

Here we report a facile solution-phase synthesis of Co2FeAl alloy nanostructures by controlling the reaction temperatures and reaction times. The use of Teflon autoclave ensured the formation of pure Co2FeAl alloy nanostructures even at a low reaction temperature of 60 degrees C. X-ray diffraction analysis confirmed the formation of good crystalline Co2FeAl alloy with average grain size of about 20-30 nm. Scanning electron microscope observations showed the evolution of Co2FeAl alloy nanostructures from cluster flower nanostructure to layered columnar nanostructure. Magnetic investigations showed high saturation magnetization of 189.2 emu/g and low coercivity of 23 Oe of Co2FeAl alloy nanostructures at 150 degrees C. These Co2FeAl alloy nanostructures with special structure morphologies and good soft magnetic properties have great potential in some industry fields. (C) 2017 Elsevier B.V. All rights reserved.