In this article, morphology control of Aurivillius Bi11Fe3Ti6O33 (4.5-BFCTO) microcrystals was investigated in detail in the hydrothermal process, where NaOH concentration and citric acid play a critical role. When NaOH concentrations are 0.3–0.5 M, 0.6 M, and 0.7–1.5 M4.5-BFCTO microflowers, microsheets and truncated tetragonal bipyramid particles formed, respectively. For the 0.3–0.5 M-sample, (Bi2O2)2CO3(OH)2 intermediate product, rather than (Na/Bi)7FexCoyTi5−x−yO21−δ of 0.6 M and 0.7–1.5 M samples, acts as a template and is responsible for the morphology change due to the competition between OH− and CO32− ions originating from the decomposition of citric acid. For the 0.6 M and 0.7–1.5 M samples, the morphology was controlled by the Gibbs free energy along the [001] direction. Besides, the dependence of magnetic properties on the morphologies was also investigated. This research on the morphology control could serve as guidance to potentially synthesize larger BFCTO single crystals and shed light on further designing nanodevices.

•Co-doped La3Ni2O7 can be a promising cathode for proton conducting SOFCs.•Co-doped La3Ni2O7 samples keep much more oxygen vacancies at intermediate temperatures.•The covalence of B-O bonds in Co-doped samples can be largely improved.Co-doped La3Ni2O7 single phase mix-conductors are successfully fabricated and investigated as cathodes for solid oxide fuel cells. Electrochemical measurement suggests that the polarization resistance of the cell using such cathodes reduce largely when increasing the Co content in La3Ni2O7 cathodes, which is about 1.12 Ω cm2 for La3Ni1.9Co0.1O7 and 0.35 Ω cm2 for La3Ni1.6Co0.4O7 both measured at 650 °C. X-ray photoelectron spectroscopy analysis suggests that the Co-doped La3Ni2O7 samples keep much more oxygen vacancies at high temperatures when compared with those undoped samples, which can benefit both oxygen adsorption and oxygen ion diffusion process in the oxygen reduction reaction. Moreover, both conductivity and magnetic measurements indicate that the covalence of B-O bonds in Co-doped samples can be largely improved because of the more localized 3d electrons in the Co substituted samples, which can further help to accelerate the proton diffusion process. The findings in this research demonstrate that the Co-doped La3Ni2O7 with the two-layer structure can be a promising cathode for proton conducting SOFCs, due to its high activity toward the oxygen reduction reaction.

Light-sensitive electronic devices based on semiconductor P–N junctions have been widely used as photodetectors and solar cells. In order to improve the overall performance of such photosensitive devices, new yet simple design is required. In this work, a simple sandwich structure is proposed by combining a new ferroelectric oxide Bi6FeCoTi3O18 with graphene. A highly sensitive photodetector is then realized benefiting from the ferroelectric polarization assisted charge separation, as well as from the unique features of graphene such as the extreme sensibility, ballistic transportation, and broadband absorption. The new device has a remarkable on–off response as high as 2 × 103% under a Xe light-source irradiation. The ferroelectric polarization enhances the photoresponse by about 2 × 104% when compared with a reference sample. Additionally, the new device is sensitive to a wide-spectrum from visible to ultraviolet, and is tolerant to high power of the incident light. This unique design opens up a new way to develop next-generation photoelectric devices that can be both proficient and cost effective.

•A three-dimensional Au NP-1LG-Ag NDA hybrid structure was prepared.•Sub-10-nm gaps between the adjacent Ag NDs were formed.•3200-fold enhancement of the Raman response of graphene was obtained.•A detection limit of 0.1 pM for crystal violet molecules was achieved.We prepared a three-dimensional (3D) hybrid structure by assembling dense gold nanoparticles (Au NPs) on graphene supported on electron beam lithography-fabricated silver nanodisk arrays (Ag NDAs). Using the strategy of modulating the structure parameters via EBL system to sufficiently narrow the distances between adjacent disks, we successfully constructed sub-10-nm gaps between the horizontally patterned Ag NDs. Moreover, uniform nanometer-scale graphene gaps were obtained between Au NPs and Ag NDAs. Finite element numerical simulations revealed that the multi-dimensional plasmonic couplings in the 3D Au NP-graphene-Ag NDA system led to an electric field enhancement up to 112 times in graphene defined gaps. As demonstrated by our SERS measurements, the well-designed and fabricated 3D Au NP-graphene-Ag NDA hybrid structure exhibits 3200-fold enhancement of the Raman response of graphene, and sensitive SERS detection with a limit of 0.1 pM for crystal violet molecules, which can be attributed to the extremely strong electric field enhancement and chemical enhancement of graphene. This work represents a step towards high-sensitivity and strong-reproducibility SERS substrate fabrication, and opens a new avenue for rationally designing graphene-plasmonic hybrid structures for SERS sensing.

•The defect behaviors of TiO2 nanosheet array films were studied by positron annihilation spectroscopy.•Different bulk/surface defect ratios were realized by annealing at different temperature.•It was concluded that bulk defects are mainly Ti3+ vacancy defects.•The separation efficiency of photogenerated electrons and holes could be significantly improved by optimizing the bulk/surface defects ratio.The photocatalysis behavior of TiO2 nanosheet array films was studied, in which the ratio of bulk/surface defects were adjusted by annealing at different temperature. Combining positron annihilation spectroscopy, EPR and XPS, we concluded that the bulk defects belonged to Ti3+ related vacancy defects. The results show that the separation efficiency of photogenerated electrons and holes could be significantly improved by optimizing the bulk/surface defects ratio of TiO2 nanosheet films, and in turn enhancing the photocatalysis behaviors.

We report a novel graphene–metal hybrid system by introducing monolayer graphene between gold nanoparticles (Au NPs) and silver nanohole (Ag NH) arrays. The design incorporates three key advantages to promote the surface-enhanced Raman scattering (SERS) sensing capacity: (i) making full use of the single-atomic feature of graphene for generating uniform sub-nanometer spaces; (ii) maintaining the bottom layer of Ag nanoarrays with an ordered manner for facilitating the transfer of graphene films and assembly of the top layer of Au NPs; (iii) integrating the advantages of the strong plasmonic effect of Ag, the chemical stability of Au, as well as the mechanical flexibility and biological compatibility of graphene. In this configuration, the plasmonic properties can be fine-tuned by separately optimizing the horizontal or vertical gaps between the metal NPs. Exactly, sub-20 nm spaces between the horizontally patterned Ag tips constructed by adjacent Ag NHs, and sub-nanometer scale graphene gaps between the vertically distributed Au NP–Ag NH have been achieved. Finite element numerical simulations demonstrate that the multi-dimensional plasmonic couplings (including the Au NP–Au NP, Au NP–Ag NH and Ag NH–Ag NH couplings) promote for the hybrid platform an electric field enhancement up to 137 times. Impressively, the as-prepared 3D Au NP–graphene–Ag NH array hybrid structure manifests ultrahigh SERS sensitivity with a detection limit of 10−13 M for R6G molecules, as well as good reproducibility and stability. This work represents a step towards high-performance SERS substrate fabrication, and opens up a new route for graphene–plasmonic hybrids in SERS applications.

We report a novel graphene–metal hybrid system by introducing monolayer graphene between gold nanoparticles (Au NPs) and silver nanohole (Ag NH) arrays. The design incorporates three key advantages to promote the surface-enhanced Raman scattering (SERS) sensing capacity: (i) making full use of the single-atomic feature of graphene for generating uniform sub-nanometer spaces; (ii) maintaining the bottom layer of Ag nanoarrays with an ordered manner for facilitating the transfer of graphene films and assembly of the top layer of Au NPs; (iii) integrating the advantages of the strong plasmonic effect of Ag, the chemical stability of Au, as well as the mechanical flexibility and biological compatibility of graphene. In this configuration, the plasmonic properties can be fine-tuned by separately optimizing the horizontal or vertical gaps between the metal NPs. Exactly, sub-20 nm spaces between the horizontally patterned Ag tips constructed by adjacent Ag NHs, and sub-nanometer scale graphene gaps between the vertically distributed Au NP–Ag NH have been achieved. Finite element numerical simulations demonstrate that the multi-dimensional plasmonic couplings (including the Au NP–Au NP, Au NP–Ag NH and Ag NH–Ag NH couplings) promote for the hybrid platform an electric field enhancement up to 137 times. Impressively, the as-prepared 3D Au NP–graphene–Ag NH array hybrid structure manifests ultrahigh SERS sensitivity with a detection limit of 10−13 M for R6G molecules, as well as good reproducibility and stability. This work represents a step towards high-performance SERS substrate fabrication, and opens up a new route for graphene–plasmonic hybrids in SERS applications.

In recent years, much attention has been paid to layer-structured Bi4Bim−3Fem−3−xMxTi3O3m+3 (BFMTO, M = Co, Mn) compounds due to their potential as high temperature single phase multiferroic materials. However, BFMTO single crystals have been rarely reported in the past, though they are better candidates for studying the corresponding intrinsic multiferroics as well as the platform for making future devices, due to their structural complexity and difficulties in fabrication. In this article, Bi5Fe0.9Co0.1Ti3O15 single-crystalline nanoplates were synthesized by the hydrothermal method. The ferromagnetic domain structure of the nanoplate was investigated by electron holography. Denser phase contours were observed and the closed magnetic flux lines indicated a significant magnetic interaction between the neighboring nanoplates, which proved the ferromagnetic nature of the sample. Furthermore, M–H loops of the sample were also measured, in which the ferromagnetic Curie temperature reached ∼730.2 K. Besides, ferroelectric domains were also detected by using a piezoresponse force microscope. All the above-mentioned results indicate the first verification of the room temperature (RT) multiferroic behaviour in such single crystals, which will be useful for both future devices and understanding the underlining physics.

Limited by low volume energy density, high flammability and wide explosive limit of hydrogen fuel, SOFCs directly adopting hydrogen fuels are being gradually substituted by those using hydrocarbon fuels. Unfortunately, the large molecule of methanol makes it inconvenient to be transported to active sites for efficient anode reactions, and this indeed impedes the electrochemical performance of such hydrocarbon SOFCs. Herein, a new Ni–BaZr0.3Ce0.5Y0.2O3−δ (BZCY) anode substrate, possessing a relatively dense functional layer and large finger-like pores straight to the surfaces, is successfully fabricated using a new phase-inversion combined tape casting technology (PICTC). Fueled with 68% CH3OH–32% N2, the PICTC button cell using BaZr0.3Ce0.5Y0.2O3−δ electrolyte demonstrates a great electrochemical performance with peak power densities of 500 and 330 mW cm−2 measured at 700 and 650 °C, about 40% and 100% higher than those of the traditional cold-pressing cells, respectively. To the best of our knowledge, this is the first report of using liquid hydrocarbon fuels in proton conducting fuel cells (P-SOFCs). In contrast to the general opinion, impedance spectra analysis using distribution of relaxation time (DRT) method suggests that reactions taking place in anode contributed greatly to the total polarization resistances of the fuel cell, which is in good agreement with our observation on the electrochemical performance of the PICTC cell.

Multiferroic complex oxides with intergrowth aurivillius phases are gaining more and more attention due to the potential to greatly adjust their ferroelectricity (FE) and ferromagnetism (FM) using non-integer layer numbers. In this work, the 2 + 3 aurivillius intergrowth phases of Bi7Ti4−2xCoxNb1+xO21 were successfully synthesized via a solid reaction method. X-ray diffraction (XRD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) analyses clearly demonstrated that Co substituted Bi7Ti4−2xCoxNb1+xO21 keeps an intergrowth phase structure when x ≤ 0.3. A new analysis method that maps the linear brightness in HAADF images was used to give the clear Bi atom position, and this revealed that the lattice shrinkage in the c direction caused by Co substitution mainly occurred at the (BiTiNbO7)2− block in the (Bi3TiNbO9) layer, which was also confirmed by an investigation using Raman spectroscopy. Polarization–electric field (P–E) investigations and pulsed polarization positive-up negative-down (PUND) measurements indicated that Bi7Ti4−2xCoxNb1+xO21 (x = 0.1, 0.2, and 0.3) presents much enhanced properties compared with non-substituted Bi7Ti4NbO21. For example, 2Ec = 135.23 kV cm−1 and 2Pr = 9.33 μC cm−2 can be achieved when x = 0.3. Also with Co substitution, Bi7Ti4NbO21 changed from diamagnetic (χ < 0) to paramagnetic (χ ≈ 7 × 10−5). The calculated effective magnetic moments in the Bi7Ti4−2xCoxNb1+xO21 samples have similar values, suggesting that the cobalt atoms in the materials have almost the same efficient moment.

Driven by the mounting concerns on global warming and energy crisis, intermediate temperature solid-oxide fuel cells (IT-SOFCs) have attracted special attention for their high fuel efficiency, low toxic gas emission, and great fuel flexibility. A key obstacle to the practical operation of IT-SOFCs is their sluggish oxygen reduction reaction (ORR) kinetics. In this work, we applied a new two-layered Ruddlesden–Popper (R-P) oxide, Sr3Fe2O7-δ (SFO), as the material for oxygen ion conducting IT-SOFCs. Density functional theory calculation suggested that SFO has extremely low oxygen ion formation energy and considerable energy barrier for O2– diffusion. Unfortunately, the stable SrO surface of SFO was demonstrated to be inert to O2 adsorption and dissociation reaction, and thus restricts its catalytic activity toward ORR. Based on this observation, Co partially substituted SFO (SFCO) was then synthesized and applied to improve its surface vacancy concentration to accelerate the oxygen adsorptive reduction reaction rate. Electrochemical performance results suggested that the cell using the SFCO single phase cathode has a peak power density of 685 mW cm–2 at 650 °C, about 15% higher than those when using LSCF cathode. Operating at 200 mA cm–2, the new cell using SFCO is quite stable within the 100-h’ test.Keywords: cathode; density functional theory; Ruddlesden−Popper oxide; solid oxide fuel cells; surface exchange coefficient

•Bi5−xEuxFe0.95Co0.05Ti3O15 (BEFCTO) nanoflowers were synthesized with hydrothermal way.•BEFCTO nanoflowers show notable UV- and Vis-driven fully photo-degradation of RhB dye.•Ferromagnetism of BEFCTO nanoflowers enable the feasible recovery from water suspension with magnet.•Properties of Bi5−xEuxFe0.95Co0.05Ti3O15 were improved by optimizing the europium content.Nanomaterials with improved photocatalysis and magnetism may enrich their field implementation in actual situations where both high light activity and good room-temperature (RT) magnetic recyclability are required. Previously, composite structures formed by at least one magnetic component with a photocatalysis part are mainly used to realize magnetically retrievable photocatalysts. In this work, europium doped Bi5Fe0.95Co0.05Ti3O15, in the format of nanoflowers, exhibiting a significant ferromagnetism at the room temperature and the notable UV- and visible-light-driven degradation capability, were synthesized by the hydrothermal method. Both ferromagnetism and photocatalysis properties of the resulting Bi5−xEuxFe0.95Co0.05Ti3O15 were greatly improved by optimizing the doped europium content. Recyclability of such nanoflower photocatalysts in water solutions was demonstrated by simply applying a magnetic field at the RT environment, while a complete photocatalytic decompose of RhB dye was verified by the Fourier transform infrared spectra.

Methylammonium lead trihalide perovskites have become the harbinger in solar cells lately. However, many fundamental mechanisms, especially those related to the used materials, still need a deeper understanding, in order to further improve the cells’ stability and efficiency. This work discussed the influence of chlorine doping on the materials’ thermal stability and the energy loss by either releasing heat or emitting light in CH3NH3PbI3. The results indicated that CH3NH3PbI3–xClx had no phase transition in the range 25–100 °C, in contrast to CH3NH3PbI3 with a phase transition at ∼50 °C. It was discovered that the heat generated in absorbing photon processes in CH3NH3PbI3–xClx could be reduced, about 20% lower than that in CH3NH3PbI3. More heat released in CH3NH3PbI3 may cause the occurrence of the phase transition and then further decline the cell stability. Photoluminescence results also indicated that adding chlorine into CH3NH3PbI3 could further suppress the energy loss in the means emitting light.

A single-phase material where ferroelectricity and ferromagnetism coexist at room temperature (RT) is hardly available at present, and it is even more rare for such a material to further have an intrinsic and low magnetic field response magnetoelectric (ME) coupling at temperatures higher than RT. In this communication, a new single-phase Aurivillius compound, SrBi5Fe0.5Co0.5Ti4O18 has been discovered that exhibits a plausible intrinsic ME coupling. Remarkably, this property appears at a high temperature of 100 °C, surpassing all single-phase multiferroic materials currently under investigation. With a magnetocapacitance effect detectable at 100 °C and under a low response magnetic field, a RT functioning device was demonstrated to convert an external magnetic field variation directly into an electric voltage output. The availability of such a single-phase material with an intrinsic and low magnetic field response that is multiferroic at high temperature is important to the fundamental understanding of physics and to potential applications in sensing, memory devices, quantum control, etc.

Intermediate temperature solid-oxide fuel cells (IT-SOFCs) ), as one of the energy conversion devices, have attracted worldwide interest for their great fuel efficiency, low air pollution, much reduced cost and excellent longtime stability. In the intermediate temperature range (500–700 °C), SOFCs based on proton conducting electrolytes (PSOFCs) display unique advantages over those based on oxygen ion conducting electrolytes. A key obstacle to the practical operation of past P-SOFCs is the poor stability of the traditionally used composite cathode materials in the steam-containing atmosphere and their low contribution to proton conduction. Here we report the identification of a new Ruddlesden–Popper-type oxide Sr3Fe2O7−δ that meets the requirements for much improved long-term stability and shows a superior single-cell performance. With a Sr3Fe2O7−δ-5 wt% BaZr0.3Ce0.5Y0.2O3−δ cathode, the P-SOFC exhibits high power densities (683 and 583 mW cm−2 at 700 °C and 650 °C, respectively) when operated with humidified hydrogen as the fuel and air as the cathode gas. More importantly, no decay in discharging was observed within a 100 hour test.

{116} faceted single crystalline anatase nanosheet arrays could exhibit excellent electrochemical and photocatalytic performance. In order to optimize the performance, structures of the nanosheet arrays were studied by changing the growth parameters, including growth temperature, initial reactant concentration, precursors, additives, etc. The nanosheet array grown at high temperature and with an additional surfactant (CTAB) possesses a highly preferred {116} orientation and shows an upright diamond structure. The sample exhibits higher reduction capacity and electrochemical reversibility. In the growth of {116} faceted anatase nanosheet arrays, hydrofluoric acid was also found to act as the hydrolysis inhibitor rather than the capping agent. Extra hydrofluoric acid will suppress the degree of the preferred orientation.

By SiO2 shell coating and Nd3+ doping, layer-structured hexagonal phase Gd2O2CO3:Yb3+, Er3+ nanoparticles were synthesized successfully through a homogeneous precipitation method. The detailed mechanism was investigated and the results indicate that the SiO2 shell and Nd3+ doping ions can effectively prevent hexagonal phase Gd2O2CO3 from decomposing into cubic phase Gd2O3 during heat treatment, because the SiO2 shell limits the diffusion of CO2 gas and the Nd3+ doping increases the decomposition temperature of Gd2O2CO3. Compared with non-layer-structured GdVO4:20%Yb3+, 2%Er3+, 4%Nd3+ particles with similar diameters and morphologies and lower phonon energies, layer-structured Gd2O2CO3:20%Yb3+, 2%Er3+, 4%Nd3+/SiO2 hexagonal phase particles show much a stronger upconversion emission, suggesting that layer-structured materials are more appropriate as upconversion hosts. Furthermore, the paramagnetic properties of Gd2O2CO3:Yb3+, Er3+, Nd3+/SiO2 nanoparticles were also demonstrated.

A facile route was developed to fabricate Bi7Fe3−xCoxTi3O21 (BFCTO) ceramics in which the micrometer sized grains were highly [0 0 1] oriented. The preparation involved dry pressing nanoplates with high aspect ratio under low axial pressure (10 MPa), and subsequently sintering the green compact at high temperature without applied pressure. The formation mechanism and the effects of Co doping on the orientation were investigated. The results indicated that the orientation degree of BFCTO grains was depended on the aspect ratio of nanoplate powder, which increased with the increase of doping amount of Co. The degree of orientation was achieved as high as 0.91 in Bi7Fe2CoTi3O21 ceramic. The saturation magnetization (2 Ms) values were larger when surfaces of the oriented grains were perpendicular to the direction of applied magnetic field, indicating obvious anisotropic magnetism. This fabrication method provided an economical yet convenient approach to manufacture grain-oriented complex oxide ceramics with improved magnetic property.

Size and morphology are critical to monitoring the properties of nanocrystals. In this work, Bi6Fe1.9Co0.1Ti3O18 (BFCTO) nanocrystals, which are a visible-light active photocatalyst with room temperature ferromagnetism, were successfully synthesized through a hydrothermal process. Furthermore, the morphology dependent magnetism and band gap of the BFCTO-1.00/BFCTO-1.50/BFCTO-2.00 nanocrystals are studied by adjusting the NaOH concentration to 1.00 M/1.50 M/2.00 M in the hydrothermal process, respectively. As the {117} facet ratio increases, the absorption edge has an obvious red-shift by 32 nm and the corresponding bandgap is reduced from 2.58 to 2.42 eV. Remarkably, the specific surface area normalized degradation rate of BFCTO-1.50 was considerably higher than those of BFCTO-1.00 and BFCTO-2.00 due to the optimal ratio of {001} and {117} facets.

•The physical properties of the layer-structured BFTO could be greatly affected by the layer number n.•Partial substituted of Co for Fe could break the AFM or PFM state in pure BFTO at room temperature, thus exhibits ferromagnetization.•A systematic investigation of the influence of layer number n on the room temperature ferromagnetic properties of the Co-substituted BFTO has been done.Aurivillius Bi4Bin-3Fen-3.2Co0.2Ti3O3n+3 (BFCT, n=4–7) ceramics were prepared by the hot-press method. X-ray diffraction and high-resolution transmission electron microscopy analysis indicate a successful synthesis of pure phase BFCT samples. All samples show significant magnetic moments at the room temperature. Interestingly, the remanent magnetization (2Mr) increases with the increase of n, which was found to be 21.53 emu/mol, 413.49 emu/mol, 472.78 emu/mol and 727.03 emu/mol for n=4, 5, 6 and 7 ceramics, respectively. This phenomenon can be ascribed to the increased coupling probability of Fe-O-Co with increasing n. Besides, the odd-layered compounds are likely to be beneficial for enhancing the 2Mr, due to that their crystalline structures may endure larger distortions when compared with the even-layered compounds.

Solid oxide fuel cells (SOFCs) have been attracting remarkable attention as one of the most promising green energy conversion devices in the recent years. However, a high susceptibility of commonly used Ni-based anodes to carbon coking is a major challenge to the successful commercialization of SOFCs. In this study, a robust anode with Ni/TiO2−δ nano-network interfaces is reported, for low-cost SOFCs working at intermediate temperatures. This anode demonstrates an acceptable power density, and good stability with humidified (3% H2O) methane. X-ray diffraction (XRD) Rietveld refinement, X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and high resolution transmission electron microscopy (HRTEM) images reveal that the Ni/TiO2−δ network-composite anode forms from the in-situ reductive decomposition of NiTiO3. Numerous Ni/TiO2−δ interfaces that facilitate the water adsorption and the water-mediated carbon-removing reactions form during this decomposition process. Density functional theory calculations predict that at the Ni/TiO2−δ interfaces, the dissociated OH from H2O (adsorbed on TiO2−δ) reacts with C (locating on Ni) to produce CO and H species, which are then electrochemically oxidized (combined with O2−) to CO2 and H2O at the triple-phase boundaries of the anode.固体氧化物燃料电池是一种有应用前景的绿色能源转化装置, 目前得到了广泛关注, 然而传统的Ni基金属陶瓷阳极容易因积碳而失活是固体氧化物燃料电池商业化的一个发展瓶颈. 本研究基于低成本的中温固体氧化物燃料电池, 发展了一种稳健的具有纳米网状结构的Ni-TiO2−δ阳极材料, 以潮湿的甲烷为燃料展现了良好的电化学性能和长期稳定性. 结合X射线衍射, X射线光电子能谱, 电子顺谱共振及高分辨透射电镜等测试结果, 揭示了NiTiO3阳极支撑体原位还原形成了具有纳米网状结构的Ni-TiO2−δ新型阳极, 可以吸附大量的水, 从而可以通过水重整过程有效地实现积碳转移. 密度泛函理论计算解释了积碳转移过程, 在阳极的三相界面处, 被TiO2−δ吸附的水解离的OH与Ni吸附积碳发生电化学反应生成CO和H, 进而氧化成CO2和H2O.

The assertion that a new material could become a potential single-phase and room-temperature functioning multiferroic material may be confounded by the presence of minor amount of secondary magnetic inclusions, especially in the Aurivilliustype material system. In this study, we demonstrated that the derivative thermo-magneto-gravimetry (DTMG) technique can be a sensitive tool to identify an d quantify the magnetic secondary phases in the Bi7Fe2.25Co0.75Ti3O21 ceramic, which shows the potential to become a single-phase multiferroic material. The accuracy of this DTMG measurement experimentally reaches to ~0.5 wt.%, far below the detection limit of the traditional X-ray diffraction. The impurity identified in the specimen is the ferrimagnetic CoFe2O4 spinel phase with an amount of ~3.6 wt.%. Significantly, the room-temperature intrinsic magnetism of the ceramic was measured, which is sorely from the main phase.判断新的材料是否是一个室温单相多铁性材料需要认真的鉴定评价, 特别是对于Aurivillius 相多铁材料. 这类材料中易生 成微量的具有铁磁性的杂质, 从而混淆对其本征磁性能的判断. 本论文介绍了一种磁失重方法, 并应用该方法判断和量化了Aurivillius 相层状结构陶瓷Bi7Fe2.25Co0.75Ti3O21中的磁性杂质. 该方法的测量精度远高于X-射线仪器的精度, 能够辨别出含量仅为0.5%重量的杂质. 最终结果表明陶瓷B i7Fe2.25Co0.75Ti3O21中的磁性杂质是尖晶石相CoFe2O4, 其含量约占总质量的3.6%. 通过该方法同时确定了该陶瓷的室 温固有磁性. 本研究不仅展示了磁失重方法, 而且通过固有磁性和固有铁电性的鉴定, 证明了该陶瓷是一种新的室温单相多铁性材料.

Single-crystalline anatase TiO2 nanosheet arrays were synthesized on a transparent conductive fluorine-doped tin oxide (FTO) substrate with a unique one-step alcohol-thermal process. The nanosheets were nearly vertically grown on the FTO substrate along their <10> zone, and they were dominated by {116} facets. The as-fabricated {116} faceted single-crystalline anatase nanosheet arrays exhibit a much higher reduction capacity and a much better electrochemical reversibility than both {001} faceted anatase single-crystalline nanosheet arrays and P25 film. The results indicate a promising application potential for the new material in the photoelectrochemical field.

In this work, single-phase ferroelectric (FE) and ferromagnetic (FM) layer-structured semiconductive Aurivillius Bi7Fe3Ti3O21 nanoshelves with a direct band gap of ∼2.22 eV were controllably synthesized by a facile hydrothermal method. The nanoshelf structure could suppress the unwanted aggregation problem introduced by spontaneous polarization and ensure a high Brunauer–Emmett–Teller surface area. The Bi7Fe3Ti3O21 nanoshelves with co-existing FE and FM properties were demonstrated as visible-light-driven photocatalysts for decomposing Rhodamine B. This finding may open a window for developing new visible-light-driven photocatalysts because the used layer-structured Aurivillius phase has significant potential in elemental doping and further structural engineering applications.

Using the first-principles calculation and the electronic conductivity relaxation (ECR) experimental technique, we investigated the adsorption and dissociation behaviors of O2 on Pt-modified La0.625Sr0.375Co0.25Fe0.75O3−δ (LSCF) surface. Toward the O2 reduction, the calculation results show that the perfect LSCF (100) surface is catalytically less active than both the defective (100) surface and the perfect (110) surface. O2 molecule can weakly adsorb on the perfect LSCF (100) surface with a small adsorption energy of about −0.30 eV, but the dissociation energy barrier of the O2 molecule is about 1.33–1.43 eV. Doping of Pt cluster on the LSCF (100) surface can remarkably enhance its catalytic activity. The adsorption energies of O2 molecules become −1.16 and −1.89 eV for the interfacial Feint site and the Ptbri bridge site of Pt4-cluster, respectively. Meanwhile, the dissociation energy barriers are reduced to 0.37 and 0.53 eV, respectively. The migration energy barrier of the dissociated oxygen from the interfacial Pt to the LSCF surface is 0.66 eV, and it is 2.58 eV from the top site of the Pt cluster to the interfacial Pt site, suggesting that it is extremely difficult for oxygen to migrate over the Pt cluster. The Bader charge analysis results further indicate that the charges transferring from Pt cluster to LSCF surface promote the adsorption and dissociation of O2 molecules. Experimentally, a dramatic decrease of the surface oxygen exchange relaxation time was observed on Pt-modified LSCF cathode, with a chemical surface exchange coefficient increased from 6.05 × 10–5 cm/s of the bare LSCF cathode to 4.04 × 10–4 cm/s of the Pt-modified LSCF cathode, agreeing very well with our theoretical predictions.Keywords: density functional theory; LSCF; oxygen reduction; Pt modification; solid oxide fuel cells

Yttrium-modified Bi7Fe1.5Co1.5Ti3O21 Aurivillius phase oxides were synthesized using a modified Pechini method, and their multiferroic properties were investigated as a function of the Y content in the formula Bi7−xYxFe1.5Co1.5Ti3O21. X-ray diffraction investigation suggests the formation of a pure Aurivillius phase when the Y content is less than 1.25, and a Co-doped BiFeO3 impurity appears when the content exceeds 1.25. When the Y content is 1.25, the sample exhibits significantly improved room temperature multiferroic properties with a remanent polarization 2Pr of 11.72 μC cm−2 and a remanent magnetization 2Mr of 3.2 emu g−1. Derivative thermo-magneto-gravimetry measurement indicates that the measured magnetic properties mainly originate intrinsically from the Y-modified Aurivillius phases when the Y content is less than 1.25.

Bismuth layer-structured Bi7−xGdxFe3Ti3O21 (0.00 ≤ x ≤ 1.50) ceramics were synthesized by Pechini's method, in which gadolinium doping was used with a goal to enhance the magnetic response of the material. With increase in the Gd content of x, an obvious structural transformation, changing gradually from the originally designed six-layer structure to five-layers, was initially shown by X-ray diffraction patterns, and then by Raman scattering spectra and high-resolution transmission electron microscopy images. Substituting Bi sites with Gd3+ ions was found to be able to effectively suppress the leakage current, and its resistivity was found to be about two orders of magnitude higher than that of the un-doped sample. Improved magnetic properties and a clear magnetic anomaly were observed in the sample with a composition of x = 1.00, indicating the behaviour of transforming from anti-ferromagnetism with weak ferromagnetism at the room temperature into a complex magnetism at low temperature.

•Isopropanol (IPA)-treated PEDOT:PSS was incorporated as a new ETL in BHJ-PSC device.•The electron transport property of IPA-treated PEDOT:PSS was revealed.•PCE of ETL-incorporated device is quite comparable to that of the reference device.•An annealing treatment of IPA-treated PEDOT:PSS ETL led to an increase of PCE.Isopropanol (IPA)-treated poly(3,4-ethylenedioxithiophene):poly(styrene sulfonate) (PEDOT:PSS) was applied as a new electron transport layer (ETL) in P3HT:PCBM bulk heterojunction polymer solar cell (BHJ-PSC) devices for the first time, revealing the electron transport property of IPA-treated PEDOT:PSS in sharp contrast to the well known hole transport property of the untreated PEDOT:PSS. Under the optimized condition for incorporating PEDOT:PSS ETL, the power conversion efficiency (PCE) of the ITO/untreated PEDOT:PSS (HTL)/P3HT:PCBM/IPA-treated PEDOT:PSS (ETL)/Al device (3.09%) is quite comparable to that of the reference ITO/untreated PEDOT:PSS (HTL)/P3HT:PCBM/Al device without any ETL (3.06%), and an annealing treatment of PEDOT:PSS ETL at 120 °C for 10 min led to a PCE of 3.25%, which even slightly surpasses that of the reference device, revealing the electron transport property of IPA-treated PEDOT:PSS. The electron transport property of IPA-treated PEDOT:PSS is interpreted by the lowering of the work function of PEDOT:PSS upon IPA treatment and incorporation as ETL as probed by scanning Kelvin probe microscopy (SKPM).By incorporating isopropanol (IPA)-treated poly(3,4-ethylenedioxithiophene):poly(styrene sulfonate) (PEDOT:PSS) as a new electron transport layer (ETL) in P3HT:PCBM bulk heterojunction polymer solar cell (BHJ-PSC) devices, we revealed the electron transport property of IPA-treated PEDOT:PSS for the first time. The electron transport property of IPA-treated PEDOT:PSS is interpreted by the lowering of the work function of PEDOT:PSS upon IPA treatment and incorporation as ETL.

New Aurivillius phase Bi9Fe4.7Me0.3Ti3O27 (Me = Fe, Co, Ni, Mn) oxides have been prepared using a citrate combustion method. X-ray diffraction on powders and high-resolution transmission electron microscopy investigation confirmed that the Bi9Fe4.7Me0.3Ti3O27 samples are with an eight-layer structure. Both ferromagnetic and ferroelectric investigations suggested that Co or Ni substitution could enhance their multiferroic properties, while Mn substitution depressed them. Among all the samples, Bi9Fe4.7Co0.3Ti3O27 sample exhibits the largest remnant polarization of Pr ~3.8 μC/cm2, and the largest remnant magnetization of Mr ~0.06 μB/f.u. with a Curie temperature about 764 K, while the Bi9Fe4.7Ni0.3Ti3O27 sample has the largest spontaneous magnetization (0.26 μB/f.u.). The improved ferromagnetic properties of both Bi9Fe4.7Co0.3Ti3O27 and Bi9Fe4.7Ni0.3Ti3O27 can be ascribed to the spin canting of magnetic ion-based sublattices via the Dzyaloshinskii–Moriya interaction and also the magnetic ions exchanging interactions (Fe3+–O–Co3+ or Fe3+–O–Ni3+).

An anatase TiO2 nanosheet array (TNSA) assembled by {116} facet-oriented nanocrystallites with {116} facets parallel to the surface is synthesized directly on a fluorine-doped tin oxide substrate via a two-step process, and exhibits 50% higher photocatalytic activity than {001} facet-oriented TNSA. The precursor and TNSA are both suggested to be grown via the “oriented attachment” mechanism.

We propose a biosensor by exploiting localized plasmons in graphene and biomolecule adsorption on it. Numerical simulations demonstrate that the sensitivity of such a device can achieve a high value of up to 1697 nm/RIU (refractive index unit) when the wavelength shift at the plasmon resonance is detected. The transparent substrate supporting graphene can be chosen potentially from a wide range of materials including insulators, semiconductors, polymers, and gels. The plasmon resonance wavelength can be tuned with electrostatic doping and/or structure modulation of graphene. Furthermore, the device works in a wide angle range of incident light since the transverse magnetic (TM) polarization is independent of incident angles.

•SOFCs based on proton conducting electrolytes, La2Ce2O7, are fabricated.•SEM-EDX and Raman analysis suggest a BaCeO3-based reaction layer is formed.•Electronic conducting in LCO electrolyte is well blocked by the reaction layer.•The reaction layer affects the conducting behaviors of LCO electrolyte.A composite of NiO–BaZr0.1Ce0.7Y0.2O3−δ (NiO-BZCY) was successfully prepared by a simple one-step-combustion process and applied as an anode for solid oxide fuel cells based on stable La2Ce2O7 (LCO) electrolyte. A high open circuit voltage of 1.00 V and a maximum power density of 315 mW cm−2 were obtained with NiO-BZCY anode and LCO electrolyte when measured at 700 °C using humidified hydrogen fuel. SEM-EDX and Raman results suggested that a thin BaCeO3-based reaction layer about 5 μm in thickness was formed at the anode/electrolyte interface for Ba cations partially migrated from anode into the electrolyte film. Impedance spectra analysis showed that the activation energy for LCO conductivity differed with the anode materials, about 52.51 kJ mol−1 with NiO-BZCY anode and 95.08 kJ mol−1 with NiO-LCO anode. The great difference in these activation energies might suggest that the formed BaCeO3 reaction layer could promote the proton transferring numbers of LCO electrolyte.

•Co-doped NiFe2O4 spinels were applied as promising cathodes in SOFCs.•That Co taking octahedral interstitial sites is the stable structure for NiFe2−xCoxO4.•Electronic conductivity of NiFe2−xCoxO4 increases with x.•NiFe2−xCoxO4 (x ≤ 0.6) has a close TEC with electrolyte.•Conductivities in cathode materials are the key in the cathode reaction.In this work, Co-doped NiFe2O4 spinels (NFCO-x) are successfully fabricated and characterized as possible cathode materials for the intermediate-temperature solid oxide fuel cells (SOFC). Results of the binding energy calculations using the density functional theory suggest that the reverse spinel structure is stable when Co3+ occupies the octahedral interstitial sites. Total and ionic-only conductivities indicate that NFCO-x are a kind of mixed electronic-ionic conductors. Ionic transferring numbers are approximately 0.049 and 0.006 for NFCO-0.1 and NFCO-0.5, respectively, measured at 700 °C in air. Co dopant in the NFCO-x improves the electronic conductivity at the expense of the ionic conductivity. For NFCO-0.5, electronic and ionic conductivities are approximately 0.24 and 9.6 × 10−4 S cm−1, respectively, measured also at 700 °C in air. Unlike behaviour of the conductivities, the polarization resistance of symmetric cells with NFCO-x electrodes decreases when increasing the Co content (x) to a certain level, and then increases. The cell containing the NFCO-0.5 electrode exhibits the lowest polarization resistance (Rp), which is approximately 1.51 Ω cm2 at 650 °C. For single cells, the maximum power density is 320 mW cm−2 measured at 650 °C using a 38-μm-thick SDC electrolyte and an NFCO-0.5 cathode.

Layer-structured bismuth complex oxides Bi7Fe3−xNixTi3O21 (0 ≤ x ≤ 2) (BFNT) were synthesized using a low-temperature combustion synthesis method. X-ray diffraction patterns and high-resolution transmission electron microscopy analysis indicated that the samples presented a six-layer Aurivillius structure. Substituting Fe sites by Ni ions inside the lattice was found to be effective in enhancing the multiferroic properties at or above the room-temperature. The sample with a composition of x = 1 exhibited a large remnant magnetization (2Mr = 1.32 emu g−1) that is about five hundred times higher than that in un-substituted Bi7Fe3Ti3O21 ceramics. The work is an important step in the effort to find a single phase and a fully functioning multiferroic material.

•Large Au@SiO2 core/shell nanoparticles (NPs) were incorporated into BHJ-PSC devices.•Au@SiO2 NPs were penetrated into all organic layers and partially embedded in Al cathode layer.•Au@SiO2 NPs-incorporated device exhibits an enhancement on both light absorption and Jsc.•The SiO2 shell provides an insulating barrier and plays the role of “surfactant”.•An efficiency enhancement by ∼16 % was achieved due to the LSPR effect.We report the incorporation of Au@SiO2 core/shell nanoparticles (NPs) into bulk heterojunction polymer solar cell (BHJ-PSC) devices, leading to an obvious efficiency enhancement due to the localized surface plasmon resonance (LSPR) effect. The Au@SiO2 core/shell NPs comprise of large Au NPs with an approximate size of 70 nm coated by a ∼50 nm thick SiO2 shell. Such NPs were doped into the poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer of P3HT:PCBM BHJ-PSCs, resulting in that the large NPs penetrate into all organic layers including the PEDOT:PSS buffer layer and P3HT:PCBM active layer, and are partially embedded in the Al cathode layer. The power conversion efficiency (PCE) of the P3HT:PCBM BHJ-PSC devices incorporated with Au@SiO2 NPs increased from 3.29% to 3.80%, and such a ∼16% efficiency enhancement can be primarily attributed to the light absorption enhancement, originating from the LSPR effect induced by Au NPs as confirmed by the UV–vis absorption spectrocopic study. Contrarily, the analogous P3HT:PCBM BHJ-PSC devices incorporated with bare Au NPs exhibited a lower efficiency enhancement, indicating that the coating of dielectric SiO2 shell is beneficial for the LSPR effect.Graphical abstractLarge Au@SiO2 core/shell NPs were incorporated into P3HT:PCBM BHJ-PSC devices, resulting in the penetration of Au@SiO2 NPs into all organic layers. PCE of the device is enhanced by ∼16 % at the optimum Au@SiO2 NPs doping ratio of 2 wt%, and the efficiency enhancement is originated from the pure LSPR effect.

Calcium doped yttrium iron garnet, Y2.5Ca0.5Fe5O12−δ (YCFO), was studied as a new cathode material for intermediate temperature solid oxide fuel cells. Low polarization resistance of 0.55 Ωcm2 at 650 °C was realized with the use of YCFO–Ce0.8Sm0.2O1.9 (SDC, 40 wt.%) composite electrode. An investigation over limiting steps of the cathode reaction suggests that oxygen ion diffusion, oxygen dissociative adsorption, and gas-phase diffusion might be the rate-limiting steps for the YCFO–SDC cathode. Of a single cell using the YCFO–SDC composite cathode, the polarization resistance reduces to as low as 0.14 Ωcm2 measured at 650 °C, and the maximum power density reaches 438 mW cm−2 with a 40 μm – thick SDC electrolyte.Highlights► Low polarization resistance was achieved with YCFO-based composite cathode. ► The ionic conducting phase has a great effect on the polarization resistance. ► YCFO is a promising cathode material for its close TEC and good performance.

Samarium-doped ceria (SDC) is evaluated as electrolyte materials for intermediate temperature reversible solid oxide cells (RSOCs). The bulk resistances of cells with SDC thin-film electrolytes are 0.16 and 0.23 Ω cm2 when operating in solid oxide electrolysis cell (SOEC) mode and in solid oxide fuel cell (SOFC) mode, respectively. This result suggests that the electrolyte is reduced to a greater extent in the SOEC mode. New Ni-Ba1+xZr0.3Ce0.5Y0.2O3−δ (x = −0.04, 0 and 0.04) composites are applied as hydrogen electrode for RSOCs to prevent SDC reduction. With the new hydrogen electrodes, the bulk resistances of the RSOCs are approximately 0.37 Ω cm2 in both SOFC and SOEC modes, suggesting that reduction in the SDC electrolyte is successfully minimized. The energy dispersive X-ray mapping of the Ba element indicates that Ba cations partially transfer from the hydrogen electrode into the electrolyte layer.Highlights► Intensive reduction in doped ceria thin film electrolyte was observed when operating as solid oxide electrolysis cells (SOECs). ► Using new Ni-Ba1+xZr0.3Ce0.5Y0.2O3−δ (BZCY) composites as hydrogen electrodes, reduction of SDC electrolyte has been prevented. ► The polarization resistances of RSOCs increased with Ba content in the Ni-Ba1+xZr0.3Ce0.5Y0.2O3−δ hydrogen electrodes. ► RSOCs with the SDC electrolyte and the Ni-Ba1+xZr0.3Ce0.5Y0.2O3−δ hydrogen electrodes presented good electro-performance.

α-Fe2O3 nanorods with highly defective surfaces were used as a support to further synthesize hybrid Pt/α-Fe2O3 nanorods. Transmission electron microscopy analyses suggest that Pt nanoparticles are selectively deposited on the surface defects such as edge-steps. Pt nanoparticles in metallic and electron deficient states, as well as the correlation between chemisorbed oxygen species and the peripheral Pt area, were revealed by the X-ray photoelectron spectroscopy spectra. The hybrid nanorods with an optimized amount of Pt nanoparticles and a large peripheral Pt area exhibit far better visible light photocatalytic activity for degrading methylene blue than α-Fe2O3.

BaZr1−xCoxO3−δ (BZC-x, x = 0.1, 0.2, 0.3, 0.4, 0.5) are prepared and identified as single phase air electrode materials for reversible solid oxide cells. BZC-x shows a typical perovskite structure with x ≤ 0.4, and slight BaCoO3 second phase is observed with x = 0.5. Conductivity measurements suggest that BZC-x is an oxygen ion and electron mixed conductor in dry oxygen atmosphere. The electronic conductivity of BZC-x increases when increasing Co content in BZC-x specimen, while the ionic conductivity reduces. For BaZr0.6Co0.4O3−δ, the electronic and ionic conductivity are 5.24 S cm−1 and 1.20 × 10−3 S cm−1, respectively, measured at 700 °C in dry oxygen. With BZC-0.4 as a single phase air electrode, the discharging and electrolysis current densities of a single cell are 299 mA cm−2 (at 0.7 V) and −935 mA cm−2 (at 1.5 V), respectively, measured at 700 °C. The polarization resistance of cells using this new air electrode is only 0.19 Ω cm2, approximately 65% lower than that using a traditional Sm0.5Sr0.5CoO3−δ/BaCe0.5Zr0.3Y0.2O3−δ composite air electrode.Highlights► Cobalt-doped BaZrO3 is an ion–electron mixed conductor. ► BaZr0.6Co0.4O3−δ air electrode has good electro-performance. ► Single phase air electrode can improve the reaction rate operating in SOEC mode.

•Growth and structural characterization of epitaxial Bi6FeCoTi3O18 (BFCTO) films.•Effect of the substrates conductivity on the growth temperature of thin films.•The films grown on conductive layers have lower growth temperature and larger magnetization.The Aurivillius layered oxide homologous series attract wide interests due to their room temperature multiferroic properties. Unfortunately, the synthesis of such layered oxide epitaxial thin films has been a major challenge owing to the occurrence of growth defects and narrow growth temperature window. To obtain high quality epitaxial Bi6FeCoTi3O18 (BFCTO) thin films, the effects of insulating and conductive bottom layers were studied by laser molecular beam epitaxy. We found that the optimal deposition temperature for growth on conductive bottom layers is more than 90 °C lower than that on insulating bottom layers, which indicates the interface between BFCTO and conductive bottom layers has smaller interfacial energy than the interface between BFCTO and insulating bottom layers. The magnetic and ferroelectric properties of the optimized BFCTO thin films on insulating substrate and conductive bottom layers were studied. This study is important to control the growth of complex layered oxide thin films and exploit the applications for future room temperature multiferroic devices.

In order to reveal the solid relationship between oxygen vacancies and multiferroic properties, polycrystalline Bi4.25La0.75Fe0.5Co0.5Ti3O15 (BLFCT) ceramics were sintered in argon (BLFCT-Ar), air (BLFCT-air) and oxygen (BLFCT-O2) by conventional solid state reaction, respectively. Their microstructures, ferroelectric, magnetic properties and valence states of magnetic ions were investigated and compared. X-ray diffraction patterns confirmed a single phase crystal structure in all samples. The lattice constants were calculated and the minor variation of the lattice constants is attributed to the different oxygen vacancy concentration. Furthermore, different oxygen vacancy concentration may be responsible for the different values of RT-recorded remanant magnetization (2Mr), remanent polarization (2Pr) as well as magnetic phase transition temperatures (TCM). The magnetic response of sample sintered in argon (2Mr =0.52 emu/g, TCM=392 K) is significantly superior to that of the others, while the sample sintered in oxygen exhibits a better remnant polarization (2Pr =11.6 µC/cm2) at an applied electric field of 160 kV/cm. The BLFCT-Ar sample was then annealed in oxygen to further justified the dependence of 2Pr and 2Mr on oxygen vacancies. Finally, outcome of the XPS measurement manifested the ratios of Fe2+/Fe3+ and Co2+/Co3+, and reconfirmed the different oxygen vacancy concentration in three samples.

•Interfacial defects and magnetization of Bi7Fe2.75Co0.25Ti3O21 were studied.•Interfacial defects disappear slowly with the increase of annealing temperature.•Saturation magnetization decreased with increasing the annealing temperature.•Higher concentration of interfacial defects bring higher saturation magnetization.This paper investigated the effect of the annealing temperature on the interfacial defects and the magnetization of a single-phase multiferroic Bi7Fe2.75Co0.25Ti3O21. With the increase of annealing temperature, the average thickness of the nonaplates increased from 80 to 180 nm. But the magnetic property measurement shows that the saturation magnetization gradually decreases with the increase of the annealing temperature correspondingly. Positron annihilation measurements reveal that the interfacial defects disappear obviously when the annealing temperature increased, which is found to agree well with the variation of saturation magnetization. The results suggest that with the higher concentration of interfacial defects may bring about higher saturation magnetization for the Aurivillius phase material, opening a window to improve the magnetic performance through controlling the concentration of interfacial defects.

Intermediate temperature solid-oxide fuel cells (IT-SOFCs) ), as one of the energy conversion devices, have attracted worldwide interest for their great fuel efficiency, low air pollution, much reduced cost and excellent longtime stability. In the intermediate temperature range (500–700 °C), SOFCs based on proton conducting electrolytes (PSOFCs) display unique advantages over those based on oxygen ion conducting electrolytes. A key obstacle to the practical operation of past P-SOFCs is the poor stability of the traditionally used composite cathode materials in the steam-containing atmosphere and their low contribution to proton conduction. Here we report the identification of a new Ruddlesden–Popper-type oxide Sr3Fe2O7−δ that meets the requirements for much improved long-term stability and shows a superior single-cell performance. With a Sr3Fe2O7−δ-5 wt% BaZr0.3Ce0.5Y0.2O3−δ cathode, the P-SOFC exhibits high power densities (683 and 583 mW cm−2 at 700 °C and 650 °C, respectively) when operated with humidified hydrogen as the fuel and air as the cathode gas. More importantly, no decay in discharging was observed within a 100 hour test.

In this work, single-phase ferroelectric (FE) and ferromagnetic (FM) layer-structured semiconductive Aurivillius Bi7Fe3Ti3O21 nanoshelves with a direct band gap of ∼2.22 eV were controllably synthesized by a facile hydrothermal method. The nanoshelf structure could suppress the unwanted aggregation problem introduced by spontaneous polarization and ensure a high Brunauer–Emmett–Teller surface area. The Bi7Fe3Ti3O21 nanoshelves with co-existing FE and FM properties were demonstrated as visible-light-driven photocatalysts for decomposing Rhodamine B. This finding may open a window for developing new visible-light-driven photocatalysts because the used layer-structured Aurivillius phase has significant potential in elemental doping and further structural engineering applications.

An anatase TiO2 nanosheet array (TNSA) assembled by {116} facet-oriented nanocrystallites with {116} facets parallel to the surface is synthesized directly on a fluorine-doped tin oxide substrate via a two-step process, and exhibits 50% higher photocatalytic activity than {001} facet-oriented TNSA. The precursor and TNSA are both suggested to be grown via the “oriented attachment” mechanism.

We propose a biosensor by exploiting localized plasmons in graphene and biomolecule adsorption on it. Numerical simulations demonstrate that the sensitivity of such a device can achieve a high value of up to 1697 nm/RIU (refractive index unit) when the wavelength shift at the plasmon resonance is detected. The transparent substrate supporting graphene can be chosen potentially from a wide range of materials including insulators, semiconductors, polymers, and gels. The plasmon resonance wavelength can be tuned with electrostatic doping and/or structure modulation of graphene. Furthermore, the device works in a wide angle range of incident light since the transverse magnetic (TM) polarization is independent of incident angles.