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Transparent photodetectors (PDs) based on binary metal oxides have become a hot topic in the field of photodetection because of their ability to absorb and detect ultraviolet (UV) light. However, PDs constructed with pure binary metal oxides still have the problems of slow response time and high-voltage drive. In addition, due to its natural internal defects, it has the characteristics of an n-type semiconductor and is difficult to achieve p-type conversion. In this work, the top layer of the device is polyoxometalate (POM) modified ZnO NWs which showed the characteristics of p-type semiconductors, its UV absorption was increased by 36.9%, and the bottom layer of the PD is pure ZnO NWs. An interlayer p–n junction is formed between the two layers, which is not only conducive to carrier transmission, but also can complete photodetection without bias. The PD has a transparency of more than 70% in the visible light region. Under the conditions of zero bias and AM 1.5 illumination, the light–dark current difference (ΔI) reaches 23.76 μA, and the rise-fall time is 1.32 s/2.62 s, respectively. After 216 hours of cycling, it still maintains 70% of the original efficiency.

Cu-based quaternary chalcogenide compounds have been thermoelectric topic of interest among researchers, especially in recent years, due to their intrinsically low thermal conductivity. Recently plenty of work is done on thermoelectric properties of Cu2ZnSnSe4-based alloys emphasizing on importance of Cu2ZnSnSe4-based alloys in thermoelectric power generation. In this study, we report the effect of annealing temperature on microstructure and thermoelectric properties of Cu2.1Zn0.9SnSe4 alloys. Cu2.1Zn0.9SnSe4 compounds were synthesized by high-temperature melting followed by annealing at four different temperatures (600 °C, 650 °C, 700 °C and 725 °C). X-ray diffraction combined with Raman spectroscopy confirmed the presence of Cu2ZnSnSe4 phase along with ZnSe and CuSe secondary phases. The increased annealing temperature critically affected the microstructure of Cu2.1Zn0.9SnSe4 alloys. Successive increase in annealing temperature subsequently increases the average grain size from 7.3 for 600 sample to 12.1 μm for 725 °C sample by shifting grain size distribution toward higher range. Increased grain size results in reduced carrier scattering and decreases the electrical resistivity eventually improving power factor and maximum power factor of about 400 μWk−2 m−1 is obtained for 725 °C sample. Besides, the increased annealing temperature resulted in increased thermal conductivity attributing increased grain size resulting in low phonon scattering. 725 °C sample shows highest power factor and moderate thermal conductivity among all the samples which resulted in highest value of figure of merit for 725 °C sample of about 0.1 at 673 K.

The growing demands for optical anti-counterfeiting technology require the development of new environmentally friendly materials with single component, multimodal fluorescence and high stability. Herein, the Bi/Sb codoped Cs2Ag0.1Na0.9InCl6 lead-free double perovskite material is reported as an efficient multimodal luminescence material with excitation-wavelength-dependent emission. When excited by 360 nm UV light, dual-emission is observed at 455 and 560 nm, which comes from the 3P1-1S0 transition of Sb3+ ions and self-trapped excitons (STEs), respectively. Under the 320 nm UV lamp, the microcrystals show only a blue emission centered at 455 nm. Therefore, the Bi/Sb codoped Cs2Ag0.1Na0.9InCl6 double perovskite emits blue and yellow lights under the 320 and 360 nm UV lamp, respectively. Moreover, the obtained double perovskite shows a high PLQY up to 41% and excellent stability against both air and high temperature, which make it a promising anti-counterfeiting material.

In this work, magnetic dispersive micro-solid phase extraction (MDMSPE) coupled with dispersive liquid-liquid microextraction (DLLME) was developed for Se(IV) and Se(VI) followed by graphite furnace atomic absorption spectrometry. MDMSPE involved the use of magnetic ZnFe

Analytical band centrifugation (ABC) was first developed for the separation of macromolecules in centrifugation cells ~60 years ago. Since its development, ABC has been predominantly utilized to study macromolecular interactions or chemical reactions between two solutions in situ upon mixing. In this current study, we evaluated ABC separations on modern analytical ultracentrifugation (AUC) instruments for therapeutic adeno-associated viruses (AAVs). ABC provided sufficient separation between the genome-containing full AAV particle and the empty AAV capsid, which need to be controlled during the manufacturing process. Because ABC produces a physical separation, no complex algorithm or sophisticated software is needed to process the experimental raw data. ABC profiles, dubbed “centrifugrams”, can be analyzed with a similar approach as typically used for electrophoretic separations to produce relative percent area. Sedimentation coefficients (s) of analytes can also be determined from ABC. The relative area percent and s value obtained in ABC experiments were shown to be consistent with those determined by conventional sedimentation velocity AUC (SV-AUC). Additionally, the separation and quantification by ABC were found to be reproducible and did not appear to be sensitive to experimental variations of initial rotor temperature or cell misalignment. The robustness of the separation, ease of data processing, and universal applicability for analysis of different AAV serotypes make ABC a promising technique for routine analysis of empty and full AAV particle composition in therapeutic products., Graphical abstract, We demonstrated the use of analytical band centrifugation (ABC) for measuring a critical quality attribute of therapeutical AAV drug candidates, i.e., the empty and full particle ratio. The ABC method produced good linearity and reproducibility and was shown to be more robust than conventional sedimentation velocity analytical ultracentrifugation (SV-AUC).

Compared with widely studied lead halide perovskite, copper halide perovskite is toxic-free and combines better stability with comparable photoluminescence quantum yield. Cation doping has proven to be an effective way to manipulate optical and electronic properties of perovskite. Unlike lead halide perovskite able to act as the host of different kinds of dopant, copper halide perovskite acting as host material is still a great challenge. Herein, Mn was successfully doped into Cs $$_3$$ Cu $$_2$$ I $$_5$$ under room temperature via solid-state reaction. In addition to original self-trapped emission of Cs $$_3$$ Cu $$_2$$ I $$_5$$ at 445 nm, Mn dopant introduced characteristic emission at $$\sim $$ 550 nm and realized dual color emission tuned by feeding ratio, extending chroma of Cs $$_3$$ Cu $$_2$$ I $$_5$$ in blue region. Meanwhile, ultraviolet photo-electron spectra results confirmed that Mn $$^{2+}$$ ion replacing Cu $$^+$$ resulted in p-type doping in Cs $$_3$$ Cu $$_2$$ I $$_5$$ . The as-prepared Mn:Cs $$_3$$ Cu $$_2$$ I $$_5$$ microcrystals show excellent stability with almost unchanged PL intensity within 15 days. Synthesis of p-type Mn:Cs3Cu2I5 with dual-color emission through room-temperature grinding method.

Despite considerable effort, the dielectric constant of interfacial water at solid surfaces is still not fully understood, thus hindering our understanding of the ubiquitous physical interactions in many materials and biological surfaces. In this study, we used molecular dynamics simulations to show that the parallel dielectric constant at the solid/water interface depends on solid-water interactions as well as the interfacial water structure on various solid crystal faces. In particular, ordered water structures can lead to a significant reduction (∼44%) in the parallel dielectric constant at the solid/water interface compared with that of bulk water. This sharp decrease in the parallel dielectric constant can be attributed to the specific antiferroelectric ordered structure of interfacial water molecules, which significantly suppresses the amplitude of the dipolar fluctuation associated with both the number of hydrogen bonds and the degree of order of interfacial water.

In this work, a two-dimensional perovskite Rashba piezoelectrics (TPRP) is proposed by a density functional theory study. The Rashba spin splitting in TPRP is optimized via the dipole moment of A-s...

Although Mn2+-doped aqueous ZnSe nanocrystals (NCs) have been reported, the obtained doped NCs usually possess multiple emission peaks originated from nanocrystal bandgap, defects, and Mn-dopants. ...

Fast and accurately locating the heating or force bearing points is essential to the maintenance and diagnosis of nano/micro-electromechanical systems. Here, a knitted graphene sheet (KGS), prepared by knitting graphene nanoribbons, is proposed as a heat or force sensor to locate the spot with nanoscale precision under thermal or mechanical loadings. The heat flux transport among the ribbons in the KGS is more difficult than in the ribbon due to the weaker van der Waals interactions among ribbons, so the heat energy can be restricted in the directly loaded ribbons over a period of time. Molecular dynamics results demonstrate that the KGS can efficiently locate and evaluate the spots and sizes of heat/force sources with high accuracy dependent on the width of the ribbons in the KGS. Our research provides a new detection approach and sheds light on designing and assembling KGS-based nanosensors for locating thermal and mechanical loads.

Exploring the manipulation of magnetism in perovskite oxides is scientifically interesting and of great technical importance in next-generation magnetic memory. Dual control of magnetism in superlattices through epitaxial strain and ferroelectric polarization may induce rich physical properties. In this work, we demonstrated a strong magnetoelectric coupling that appears in an La0.75Sr0.25MnO3/BaTiO3 superlattice. Reversible transitions in ferromagnetism, ferrimagnetism and anti-ferromagnetism, with strong magnetoelectric coupling, are achieved by precisely controlling the magnitude and spin-direction of the magnetic moments of Mn. Half-metallicity is demonstrated in the MnO2 layers, accompanied by the spin polarization of the superlattice varying from 100% to 0%. We realize the coexistence of ferroelectric polarization and metallicity, i.e., "ferroelectric metal". The variation in strain and re-orientation of polarization lead to a change in interfacial Ti-O and Mn-O bond lengths, and hence a hybridization state, determining the magnetism of our system. The purpose-designed LSMO/BTO superlattice with intrinsic magnetoelectric coupling is a particularly interesting model system that can provide guidance for the development of spintronic devices.

The electron transport layer (ETL) transfers the photogenerated electrons generated by the perovskite layer to the conductive glass substrate, which plays a vital role in the performance of the perovskite-based photodetector. SnO2, as a wide bandgap semiconductor, is a promising ETL material, but the interface electronic recombination between it and the perovskite layer limits the improvement of device efficiency. It is hopeful that {Mo132} will solve this problem. Here, we doped SnO2 with {Mo132}, which can simultaneously adjust the energy level of SnO2 and increase the crystallinity of the perovskite crystal, thereby reducing interface electronic recombination. The conduction band of the obtained composite material moves down by 0.11 V, which is more conducive to the transfer of photogenerated carriers. Moreover, the doping of {Mo132} significantly increases the ultraviolet light absorption intensity of the composite material, which is conducive to the collection of sunlight. In addition, the oxygen vacancy content of the composite material is reduced, which is conducive to reducing the electron recombination center. Therefore, the photocurrent of the device is increased from 13.32 μA to 27.04 μA, an increase of about 1.03 times.

International audience; Piezoelectric charge coefficient (d33) and piezoelectric voltage coefficient (g33) are the two most critical parameters that define output performance of piezoelectric nanogenerators (PNGs). Herein, we propose a vacancy-ordered double perovskite of TMCM2SnCl6 (where TMCM is trimethylchloromethylammonium) with a large d33 of 137 pC/N and g33 of 980 × 10–3 V·m/N. The piezoelectric coefficients are considered from the halogen-bonding-mediated synergistic movements of atomic displacement in inorganic [SnCl6]2– octahedrons, as well as the molecular rotation of organic TMCM+, which is revealed by a combined density functional theory (DFT) and experimental study. The TMCM2SnCl6 possesses a high saturated polarization (Ps) of 8.7 μC/cm2, a high Curie temperature (Tc) of 365 K, and a low coercive field (Ec) of 0.6 kV/cm. The output voltage (Voc) and current (Isc) of the PNGs are 81 V and 2 μA at an applied mechanical excitation of (4.9 N, 40 Hz). We hope this work will provide guidance in energy harvesting by innovatively designing highly piezoelectric perovskites for the PNGs.

Magnetite nanotubes with an average diameter of about 140 nm were synthesized by an AAO templateassisted sol–gel autocombustion method. The entire synthetic process is convenient, low-cost and nontoxic. The crystalline structure of the magnetite nanotubes was investigated by X-ray diffraction. From the diffraction pattern, we conclude that pure phase magnetite nanotubes were obtained. Tubular morphologies of the products were observed by transmission electron microscope. The as-prepared magnetite nanotubes have a high aspect ratios. The magnetic properties of the nanotubes were measured by a Physical Property Measurement System. The magnetic measurements indicate that the nanotubes have superparamagnetic characteristic at room temperature, and have ferromagnetic characteristic with a coercivity of about 518 Oe at 5 K. The blocking temperature TB of the nanotubes are measured to be 95 K. The as-prepared magnetite nanotubes may find potential applications in bio-medicine.

The multimetallic cocktails provide vast compositional space with unlimited elemental combinations and structural possibilities for alloy design. The crystallographic metastability and thermodynamic instability offer opportunities for the activation of athermal transformations and intermetallic phase formation, particularly when exposed to mechanical perturbations and thermal input. Elemental interactions between the constituent and/or interstitial elements attribute to the remarkable interstitial strengthening effect. The associated strengthening mechanisms and strain-hardening mechanisms are also discussed. Here, we attribute the above-mentioned properties to cocktail effects, which is originated from the synergistic multicomponent alloying. These results provide the insights for the development of structural materials via cocktail effects.

SnO2 microbelt coating carbon composite was fabricated via electrospinning precursor, thermal treatment, and polymer adhesion process. Primarily, the solvent of electrospinning jet quickly evaporates in a relatively high-temperature environment; intermediate microtubules simultaneously form when the solute containing tin salt and binder converge on the skin of the jet; then, the microtubules collapse into flat microbelt product under the action of atmospheric pressure. Subsequently, SnO2 microbelts can be obtained by annealing the electrospinning products. Finally, the SnO2@C microbelts are synthesized by dopamine polymerization and carbonization process. The SnO2@C microbelts present a regular strip with width ~ 1.2 μm and thickness ~ 120 nm. Because of the synergy effect of carbon coating and SnO2 microbelt design project, the composite shows superior lithium storage of 504 mAh g-1 after 100 cycles at 0.2 A g-1. The SnO2@C microbelts are expected to be competitive alternative anode material of next-generation LIBs.

The strength-ductility paradox is a long-sought challenge for all engineering materials. In this study, we escaped the strength-ductility trade-off by engineering nano-scale heterogeneities carefully in the advanced nanostructured Fe-based alloys through alloying with Cu and Mn additions. We demonstrated a triple ductility enhancement by 20% together with a strength improvement of 100MPa compared to the alloys with sole Cu additions, overturning a common understanding of the strength-ductility trade-off. The strength-ductility enhancement is attributed to the complex interplay between the transformation induced plasticity (TRIP) and the coherent nano-scale Cu precipitates as well as the resultant heterogeneous stress–strain partitioning and dislocation interactions.

Unwinding the double helix of the DNA molecule is the basis of gene duplication and gene editing, and the acceleration of this unwinding process is crucial to the rapid detection of genetic information. Based on the unwinding of six-base-pair DNA duplexes, we demonstrate that a terahertz stimulus at a characteristic frequency (44.0 THz) can serve as an efficient, nonthermal, and long-range method to accelerate the unwinding process of DNA duplexes. The average speed of the unwinding process increased by 20 times at least, and its temperature was significantly reduced. The mechanism was revealed to be the resonance between the terahertz stimulus and the vibration of purine connected by the weak hydrogen bond and the consequent break in hydrogen bond connections between these base pairs. Our findings potentially provide a promising application of terahertz technology for the rapid detection of nucleic acids, biomedicine, and therapy.

The friction at the liquid-solid interfaces is widely involved in various phenomena ranging from nanometer to micrometer scales. By the molecular dynamic (MD) simulation, the friction properties of liquid-solid interfaces at the molecular level are calculated via the Green-Kubo relation. It is found that the system size will influence the value of the friction coefficient, especially for the solid surfaces with the larger polar charge. The value of the friction coefficient decreases with the increase in the system size and converges at large system sizes. The large polar charge will lead to a significant friction coefficient. However, the diffusion of water molecules on this surface is almost a constant, indicating that the diffusion coefficient seems to be independent of the system size and polar charge. This work provides insights for the selection of the system size in modeling the frictional properties of hydrophobic/hydrophilic surfaces.

To further improve the charge separation and photocatalytic activities of g-C3N4 and CdMoO4 under visible light irradiation, CdMoO4/g-C3N4 composites were rationally synthesized by a facile precipitation-calcination procedure. The crystal phases, morphologies, chemical compositions, textural structures, and optical properties of the as-prepared composites were characterized by the corresponding analytical techniques. The photocatalytic activities toward degradation of rhodamine B solution were evaluated under visible light irradiation. The results revealed that integrating CdMoO4 with g-C3N4 could remarkably improve the charge separation and photocatalytic activity, compared with those of pristine g-C3N4 and CdMoO4. This would be because the CdMoO4/g-C3N4 composites could facilitate the transfer and separation of the photoexcited electron-hole pairs, which was confirmed by electrochemical impedance spectroscopy, transient photocurrent responses, and photoluminescence measurements. Moreover, active species trapping experiments demonstrated that holes (h+) and superoxide radicals (·O2−) were the main active species during the photocatalytic reaction. A possible photocatalytic mechanism was proposed on the basis of the energy band structures determined by Mott-Schottky tests. This work would provide further insights into the rational fabrication of composites for organic contaminant removal.

Thermal transfer across solid–liquid interfaces is influenced by multiple factors such as surface wettability, interfacial water layer density, molecular structure, and mass density depletion length. However, the dominant factors in interfacial heat transport are yet to be investigated. In this work, we explore the contributions from these factors by employing the Pd-water model for water molecules forming ordered, partially ordered, and disordered structures on Pd (100), (110) and (111) surfaces, respectively. The results revealed that the ordered water layer on the (100) surface can introduce a “phonon bridge” at the solid–liquid interface to improve thermal transfer, while the partially ordered water layer on the (110) surface can further promote thermal transfer due to the enhanced interfacial friction. On the other hand, the decreased density depletion length also makes dominant contributions to the enhancement of interfacial thermal transfer. The results are explained by the interfacial friction coefficient, surface potential energy distribution and density depletion length. We also introduce an efficient technique by tuning the vacancy defects on the solid surface to tune the atomic structure as well as the thermal transfer. Our study reveals the complex relationship between the atomic structure of the crystal face, the water layer structure and the thermal boundary conductance, which will inspire more experimental and theoretical studies toward the improvement of interfacial thermal transport by tuning the structure of the water layer.

Compositing is viewed as a promising strategy to synergistically enhance the thermoelectric and mechanical properties of materials as compared with the element doping method. Herein, different volume percentages of nano SiC (1, 3, 5, and 10 vol%) powders were firstly composited with pristine SnTe. The SiC particles combined well with the SnTe matrix and dispersed homogeneously. The lattice interface effect increases the electrical conductivity up to 700 S m−1 at room temperature due to the increased carrier concentration with addition of 1 vol% SiC. Along with the decreased lattice thermal conductivity (0.67 W m−1 K−1 at 823 K), the maximum figure of merit for SnTe-1 vol% SiC is ∼0.7 which is 1.7 times that of pristine SnTe. And this value is comparable to the results obtained by traditional chemical doping. Additionally, the hardness for all SiC composited samples is also significantly enhanced. Thus nano SiC compositing is a promising way to enhance both the thermoelectric and mechanical properties of SnTe.

In nano-confined systems, the properties of a fluid are different from those of macroscopic systems, and the properties of a nanotube can significantly affect water transport. However, our knowledge of the effects of nanotube shape is far from adequate. In the present work, we study the properties of a fluid transporting in different nano-confined configurations by molecular dynamics simulations. This study is aimed at gaining insight into the transport of water molecules in carbon nanotubes with different configurations. We find that the closer of channel shape to the circular nanotube (more sides of the channel), the lower friction coefficient of the solid-liquid interface has and the friction coefficient of nanochannels increases with R when R1.0 nm. The friction coefficient converges to a stable value (close to the friction coefficient of graphene/water) when R1.0 nm. A variety of configurations leads to the variation of the fluid properties in nanotubes. Our results can be applied to the nanofluid properties of a complex channel structure and water nanochannel microscopic design.

Polyoxometalates (POMs) have been considered as an efficient catalyst for triiodide reduction in dye-sensitized solar cells (DSSCs). However, agglomeration of POMs limits the improvement in power conversion efficiency (PCE) of DSSCs. In this paper, we improve our previous synthesis process by a simple ultrasonic driving strategy. A series of highly dispersed POM nanoparticles periodically deposited on multi-walled carbon nanotube (MWCNT) nanocomposites (abbreviated as POMs/CNTs) is synthesized, which increases the active sites by improving the dispersion degree and inhibiting the aggregation of POM molecules. Additionally, CNTs as a conductive support skeleton and physical barrier promote the rapid electron transfer and protect POM molecules from chemical degradation. The nanocomposites exhibit well-distributed morphology, and highly dispersed POM nanoparticles about tens of nanometers in diameter are in intimate contact with CNTs. Powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy demonstrate that POM nanoparticles have been periodically deposited on CNTs. POM/CNT counterelectrodes (CEs) exhibit a more remarkable performance towards triiodide reduction than pure CNT CEs, indicating that POMs deposited on CNTs boost electrocatalytic triiodide reduction. Among these POM/CNT CEs, the Co4PW9/CNT CE exhibits the best photovoltaic behavior with a high power conversion efficiency (PCE) of 7.60%, which is superior to that of the Pt CE (6.59%). The excellent activity originates from the synergistic effect between the high redox activity of POMs and the excellent conductive ability of CNTs. This work provides a foundation for preparing advanced high-efficient CE catalysts of POM materials.

Simple chemical compositions are more suitable for practical applications of thermoelectric materials due to the high success rates of their syntheses and their higher stabilities. Here, n-type PbTe alloys doped with a small amount of Sb were synthesized, and the effects of slight doping on the thermoelectric properties were investigated. All samples have single-phase microstructures, uniform composition distributions, and non-uniform grain sizes on the micro- and nano-scales. A higher power factor of 22.5 μW K−2 cm−1 has been obtained for the composition Pb0.995Sb0.005Te, which was attributed to a reduction in resistivity and to the preservation of a relatively high Seebeck coefficient though tuning the carrier concentrations. In addition, the highly heterogeneous grain size distribution strengthens the grain boundary scattering, and the Sb doped and Te vacancies result in an enhancement in point defect scattering. These two main factors lead to a lower lattice thermal conductivity of 0.68 W m−1 K−1 for the Pb0.988Sb0.012Te alloy at 723 K. In the end, a maximum zT value of about 1.1 has been achieved for the Pb0.995Sb0.005Te alloy, which is comparable to that of Sb doped PbTe alloys with a high doping concentration.

2D materials have strong intermolecular van der Waals forces, and 2D superlattice heterostructures have exhibited many dramatic photo-electrochemical properties for energy conversion and storage. Herein, based on the excellent properties of reduced graphene and superlattice structures, we constructed a 2D flexible superlattice polyoxometalate/rGO heterojunction with enhanced electron-hole separation via interfacial self-assembly engineering to further fabricate DSSCs based on the heterojunction-modified photoanode, which exhibited good electron transport properties. Selecting two kinds of Dawson POMs (P2W15V3, P2W18 and the corresponding heteropoly blue) as the research object, the polyoxometalate superlattice structure was obtained by the self-assembly strategy, and characterized by IR, UV-Vis, XRD, EDX and XPS. The TEM and AFM results indicated that the monolayer POM superlattice structure and superlattice polyoxometalate/rGO heterojunction were successfully obtained. The superlattice P2W18(HPB)/rGO heterojunction was introduced into the DSSCs photoanode, and electrochemical tests indicated that the superlattice polyoxometalate/rGO heterojunction improved the electron-hole separation rate, inhibited the electron recombination, and improved the photoelectric conversion efficiency to 8.09%. The 2D superlattice heterojunction remarkably improved the electrochemical performances of the energy storage and conversion systems.

Large scale cesium lead-halide (CsPbX3, X = Cl, Br, and I) perovskite films have become the basis of laser applications. Common fabrication methods such as spin-coating and thermal evaporation have a trade-off between high quality and low cost. Herein, we reported a facile method for preparing a large area homogeneous perovskite CsPbBr3 film via a multiple centrifugal deposition and solvent annealing (MCDSA) method. This method is superior because it can control the thickness (180 nm to 880 nm) of the film, ensure the film is crack and pinhole free, has a large area (2.5 cm × 2.5 cm), and has a low surface roughness (a root mean square of 32 nm). Multiple times of centrifugation and solvent annealing in the MCDSA method are key to improving the quality of the film as well as the laser performance. With increased centrifugation cycles from one to four, the thickness of the film increases from 180 nm to 880 nm, leading to a decrease in the laser threshold from 18.1 μJ cm−2 to 14.2 μJ cm−2 and an increase in the gain coefficient from 78.5 cm−1 to 112.7 cm−1. When solvent annealing is employed, the gain coefficient is further increased to 122.7 cm−1.

Obtaining tunable magnetic states in geometrically frustrated multiferroic compound CoCr2O4 by tuning the sublattice magnetic coupling is indeed of high interest from the fundamental and applied points of view. In this work, Fe substitution effects in Co(Cr1-xFex)2O4 (0 ≤ x ≤0.5) are experimentally investigated through detailed measurements of the crystalline structure and magnetization. Our experiments reveal that the samples undergo a magnetic transition characterized by a sharp variation in magnetization from 94 K at x = 0 to 317 K at x = 0.5. The field-cooled process shows that a magnetization reversal phenomenon is observed under a stable positive magnetic field when the measurement undergoes the compensation temperature. A magnetic field-assisted switching effect is realized near the compensation temperature, which possesses the characteristics of high repeatability and stability. The molecular field coefficients are evaluated based on the ferrimagnetic Curie-Weiss fitting, and the exchange interactions within and between the sublattices show a relationship of |JAA| < |JAB| < |JBB|. The magnetization reversal in Co(Cr1-xFex)2O4 is considered to be attributed to the coexistence and competition of A-A, A-B and B-B magnetic interactions, as well as the weakening of spin frustration.

Inverse oxide/metal model systems are frequently used to investigate catalytic structure-function relationships at an atomic level. By means of a novel atomic layer deposition process, growth of single-site Fe1Ox on a Pt(111) single crystal surface was achieved, as confirmed by scanning tunneling microscopy (STM). The redox properties of the catalyst were characterized by synchrotron radiation based ambient pressure X-ray photoelectron spectroscopy (AP-XPS). After calcination treatment at 373 K in 1 mbar O2 the chemical state of the catalyst was determined as Fe3+. Reduction in 1 mbar H2 at 373 K demonstrates a facile reduction to Fe2+ and complete hydroxylation at significantly lower temperatures than what has been reported for iron oxide nanoparticles. At reaction conditions relevant for preferential oxidation of CO in H2 (PROX), the catalyst exhibits a Fe3+ state (ferric hydroxide) at 298 K while re-oxidation of iron oxide clusters does not occur under the same condition. CO oxidation proceeds on the single-site Fe1(OH)3 through a mechanism including the loss of hydroxyl groups in the temperature range of 373 to 473 K, but no reaction is observed on iron oxide clusters. The results highlight the high flexibility of the single iron atom catalyst in switching oxidation states, not observed for iron oxide nanoparticles under similar reaction conditions, which may indicate a higher intrinsic activity of such single interfacial sites than the conventional metal-oxide interfaces. In summary, our findings of the redox properties on inverse single-site iron oxide model catalyst may provide new insights into applied Fe-Pt catalysis.

Strong thermal stress caused by high temperature and difference of thermal expansion coefficient (CTE) will negatively influence the lifespan of the thermoelectric module. In this work, a new high-temperature CaMnO3-based U-type unileg thermoelectric module, combining a unileg structure with pn-junction, is proposed and investigated. The novel design avoids the device failure due to different CTEs and high temperature gradients. As a result, the maximal thermal stress (σmax,TEM) of 3.31 GPa and fatigue life of 41686 cycles are 46 % and 132 % of those of traditional modules at 6 W and 300 K, respectively. To further relieve stress concentration, the effect of rounded corners (ru, rl), Ag layer thickness (HAg) and length of right legs (LR), have been studied. It has been found that larger ru, and rl are suitable to relieve the local stress concentration, and the lowest σmax,TEM and highest power (Pmax) are achieved at (ru,rl)=(0.1,0) and (0,0.5). Moreover, larger LR and HA are beneficial for mechanical properties by decreasing the peak stress and dispersing the high thermal stress regions, while module performance is improved at lower LR and HAg. Results obtained from this U-type unileg thermoelectric module should influence and guide the design and optimization of high-temperature thermoelectric generators., The work is financially supported by National Key R&D Program of China of 2017YFE0195200, the Natural Science Fund of China under grant Nos. 51871134 and 52111530034, the Science Fund of Shandong Province under grant No. ZR2019MEM007, and Qilu Young Scholar Program of Shandong University. M. A. Madre, and A. Sotelo also acknowledge the MINECO-FEDER (MAT2017-82183-C3-1-R) and Gobierno de Aragón-FEDER (Research Group T54-17R) for funding.

Herein we describe a modeling work on gradient refractive index (GRIN) lenses which could be fabricated from utilizing a mixture of a photocurable (Hydroxyethyl) methacrylate and epoxy prepolymer resins. Simulations based on the polymer properties show measurable and tunable optical properties such as spherical aberrations.

The shear properties and fracture behavior of the Cu/Sn-37Pb/Cu solder interconnections at temperatures ranging from −196 °C to room temperature were investigated in the present study. With a decrement in the testing temperature, the shear strength of the solder interconnections gradually increased first, but then decreased after it reached a maximum value at −150 °C. The shear strength of Cu/Sn-37Pb/Cu interconnects at cryogenic temperatures (below −55 °C) was much higher than that at room temperature. With a decline in the testing temperature, the fracture position of the solder interconnections transformed from in the solder bulk to partially in the solder bulk and partially in the interfacial IMCs.

It has been suggested that irreversible adsorption at the gas/liquid interface of bulk nanobubbles will reduce the Laplace pressure, leading to their stability. However, most previous studies have focused on the stability of individual nanobubbles. Bulk nanobubbles are polydispersed suspensions, and gas molecules can diffuse between bubbles, leading to their collective dynamics, which may be crucial to understanding their formation process and stability. In this study, we proposed a mean-field theory for computing the evolution of the size-distribution function of bulk nanobubbles with size-dependent surface tension. We applied this theory to investigate the evolution of bulk nanobubbles with insoluble surfactants pinned at their gas/water interface. The results show that Ostwald ripening can be suppressed when enough surfactants are adsorbed. Bulk nanobubbles can be produced by the shrinkage of microbubbles in an air-saturated solution. The mean stable size is controlled by the amount of surfactants and the initial microbubble concentration; these predictions are qualitatively consistent with the experimental results of micro/nanobubbles produced using the microfluidic method.

Taking advantages of negligible reabsorption and no phase separation, single-component white-emitting phosphors are believed as new promising color conversion materials for white light-emitting diodes. As a potential candidate, Mn-doped lead halide perovskites are studied intensively, but rare works can realize pure white emission with a single component due to the challenge for realizing sufficient energy transfer efficiency from perovskite to Mn at the desirable emission wavelengths. In this work, we reported the synthesis of single-component white light halide perovskite quantum dots (QDs) by doping Mn into the host of CsPb(Cl/Br)3@CsPb(Cl/Br)x core–amorphous shell (CAS). The small size of zero-dimensional core in CAS structure has a strong quantum confinement effect, which can enhance the energy transfer efficiency from halide perovskite to Mn impurity dramatically. Our result shows 19.3 times higher energy transfer efficiency for Mn-doped CAS than that of ordinary Mn-doped CsPb(Cl/Br)3 nanocubes. As a result, as-prepared Mn-doped CAS QDs give rise to a white light emission with Commission Internationale de l’Eclairage (CIE) color coordinates of (0.37, 0.33). After blending with polystyrene (PS), Mn-doped CAS QDs can be used as a single-component color conversion material for assembling white light LEDs.

To investigate the deposition mechanism of the outermost electroless nickel plating layer in a three-layer composite coatings on the magnesium alloy surface, the electroless nickel plating layers with six different plating times (3, 5, 10, 30, 60, and 90 minutes) were selected as research targets. The transformations in microcosmic morphology, element composition and material structure of the samples electrolessly plated at six different plating times were characterized by SEM、EDS and XRD. The changes in corrosion resistance of samples with different electroless plating times were measured by polarization curve. It was concluded that the nickel-phosphorus deposition process on the activation composite coatings was a “cell-like three-dimensional” growth judging from the microscopic morphology of coating surface obtained by SEM. The elemental changes obtained from the EDS were consistent with the growth of nickel cells obtained SEM. The XRD results showed that the diffraction peaks of nickel were not detected on the surface at an electroless plating time of 3 minutes. Nickel peaks appeared after 5 minutes of electroless plating, and the nickel peak width broadened and the intensity increased as the electroless plating time increased. The corrosion resistance is greatly improved when the electroless plating is performed for 60 minutes due to the complete nickel coating without defects as shown in the SEM. It can be concluded that the deposition mechanism of electroless plating on the double-layer active surface is an initial ecological reduction [H] autocatalytic reduction deposition process according to the micromorphology and structure of the samples electrolessly plated at six different plating times.

High thermoelectric figure of merits have been achieved in lead telluride (PbTe) alloys recently, which are beneficial for future thermoelectric applications. In this study, a PbTe-based thermoelectric module is constructed by eight pairs of p-type PbTe–8%SrTe and n-type PbTe0.998I0.002–3%Sb legs with initial sizes of 3 × 3 × 3 mm3. The relationship between multiple geometric parameters and performance of module has been studied by finite-element simulation. The maximum output power (Pmax) of 7.6 W and efficiency (ηmax) of 15.3% have been achieved at ΔT = 500 K for ideal contacted PbTe-based thermoelectric module. Contact resistance must exist in experimental thermoelectric module, so it has been considered in simulation about geometry optimization. The cross-sectional area ratio (Ap/An) and height (H) show strong dependent relationship to optimize module performance. The larger Ap/An and relatively lower H are propitious to enhance the output power. Moreover, the efficiency is improved at an optimum Ap/An and relatively higher H. In this PbTe-based module, the Pmax = 4 W is achieved at Ap/An = 1.78 and H = 0.65 mm, while ηmax = 14% is achieved at Ap/An = 1.64 and H = 13 mm under ΔT = 500 K. The Pmax and ηmax are 20% and 65% larger than those of initial design sizes. Thus, geometric structure modification is a good way to improve the performance of thermoelectric applications.

We report the synthesis, crystal structure and magnetic properties of Rare-earth hexaaluminates REMgAl11O19 (RE = Pr, Nd) crystallized in a hexagonal structure with space group P63/mmc, where the magnetically coupled rare-earth ions form perfect two-dimensional triangular layers well separated along c-axis. The magnetic susceptibilities reveal the dominant antiferromagnetic (AFM) interactions and no magnetic ordering down to 2 K with Curie Weiss temperature ( θ C W ) θ C W = −6.4 K and θ C W = -3.4 K for RE = Pr and Nd, respectively. Furthermore, the AFM interactions are robust against the nonmagnetic dilution by doping Lanthanum (La3+) ions. The analysis of X-band electron spin resonance (ESR) spectra also supports the existence of AFM interactions in these two compounds. Our studies reveal a promising platform to investigate novel magnetic ground states in two-dimensional triangular lattice.

Miniaturized enzymatic biofuel cells (EBFCs) with high cell performance are promising candidates for powering next-generation implantable medical devices. Here, we report a closed-loop theoretical and experimental study on a micro EBFC system based on three-dimensional (3D) carbon micropillar arrays coated with reduced graphene oxide (rGO), carbon nanotubes (CNTs), and a biocatalyst composite. The fabrication process of this system combines the top–down carbon microelectromechanical systems (C-MEMS) technique to fabricate the 3D micropillar array platform and bottom–up electrophoretic deposition (EPD) to deposit the reduced rGO/CNTs/enzyme onto the electrode surface. The Michaelis–Menten constant KM of 2.1 mM for glucose oxidase (GOx) on the rGO/CNTs/GOx bioanode was obtained, which is close to the KM for free GOx. Theoretical modelling of the rGO/CNT-based EBFC system via finite element analysis was conducted to predict the cell performance and efficiency. The experimental results from the developed rGO/CNT-based EBFC showed a maximum power density of 196.04 µW cm−2 at 0.61 V, which is approximately twice the maximum power density obtained from the rGO-based EBFC. The experimental power density is noted to be 71.1% of the theoretical value., Enzymatic biofuel cells: power for medical devices A two-step process enables the fabrication of miniaturized enzymatic biofuel cells composed of nanomaterials for possible use as power sources in implantable devices. There is growing need for self-powered implanted medical devices. Enzymatic biofuel cells are attractive for this since they rely on bio-compatible and non-toxic materials. However, improvements in power cell density are needed, and agglomeration of nanomaterials on existing devices limits performance. Now, Yin Song and Chunlei Wang from Florida International University report a new process: top–down photolithography creates a high surface area micropillar array, followed by deposition of reduced graphene oxide, carbon nanotubes and enzymes onto the pillars. A maximum power density of 196.04 µW cm−2 at 0.61 V is achieved in the resulting devices, attributed to the combination of nanomaterials and conformal coating of the micropillars.

To further improve the light response range and photocatalytic activity of Bi2SiO5, the Bi2SiO5/BiOBr type-II heterojunction photocatalysts were constructed by in-situ partial ion exchange strategy using Bi2SiO5 as precursor. The crystal phases, morphologies, chemical compositions, optical properties and textural structures of as-synthesized Bi2SiO5/BiOBr photocatalysts were characterized by the corresponding analytical techniques. The photocatalytic activities of samples were evaluated by degrading Rhodamine B (RhB) solution under visible light irradiation. The results showed that the Bi2SiO5/BiOBr heterojunction photocatalysts significantly improved the photocatalytic performances, which would be ascribed to the extended light response, enhanced adsorption capacity, matched energy band structures and intimate interface contact. Construction of Bi2SiO5/BiOBr heterojunction facilitated the separation and transfer of photoexcited charge carriers, which were verified by the electrochemical impedance spectroscopy (EIS), transient photocurrent response and steady photoluminescence spectroscopy (PL) measurements. This work would offer a new insight into the design and preparation of Bi2SiO5-based heterojunction photocatalysts for the removal of organic contaminant.

热电材料利用Seebeck与Peltier效应可以实现热能和电能的相互转化, 是颇具潜力的新型功能材料. 本文聚焦四元硫属化合物Cu2BIICIVSe4 (其中, B位为 Zn, Cd, Mn, Hg, C位为Si, Ge, Sn)的热电性能. 此类材料具有复杂的晶格结构, 导致其具有较低的晶格热导率, 是一类具有本征低热导的热电材料. 本文系统地总结了各类优化四元硫属化合物电学及热学的方法. 首先, 非化学计量法、元素掺杂和 η =1定理用于改善其电学性能. 然后, 纳米结构工程可用于进一步降低其热导率. 最后, 基于文中的论述, 我们提出通过多种实验方法的结合使用, 协同调控四元硫属化合物的电、热性能, 以期进一步提高其热电性能.

Developing a reliable, simple, cost-efficient, and eco-friendly method for scale-up production of high-quality graphene-based materials is essential for the broad applications of graphene. In this study, bipolar electrochemistry concept is utilized to design a single-step and controllable process for simultaneously exfoliating a graphite source and depositing both graphene oxide and reduced graphene oxide layers on conductive substrates. The electrochemical analysis carried out on symmetric cells revealed an areal capacitance of 1.932 mF cm–2 for the high-quality reduced graphene oxide deposited on the negative feeding electrode, and 0.404 mF cm–2 for the graphene oxide deposited on the positive feeding electrode at a scan rate of 2 mV s–1. The devices also showed high stability for periodic and repeated constant current charging/discharging cycles which is suitable for energy storage in supercapacitors. In the frequency domain, cutoff frequencies of 1820 and 1157 Hz at −45° impedance phase angle were obt...

Thermoresponsive thiol-terminated poly(N-isopropylacrylamide) (PNIPAM) and diblock poly(ethylene glycol)-b-poly(N-isopropylacrylamide) (PEG-b-PNIPAM) were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization and aminolysis reaction. The lower critical solution temperature (LCST) of the polymers increases with the increase of PEG chain segment. Such polymers were used to modify gold nanoparticles (AuNPs) by Au–S bonds. The optical limiting property of the polymer-stabilized gold nanoparticles was investigated, and the results show that the thermoresponsive polymer-stabilized gold nanoparticles exhibit enhanced optical limiting effect relative to pristine AuNPs. The higher optical limiting energy threshold was observed for gold nanoparticles stabilized with polymers having higher LCST.

Sol–gel derived ormosil gel glass can act as matrix for different functional molecules or nanomaterials due to its many advantages. Gold and silver colloidal nanoparticles have great application potential in nonlinear optical field due to their ultrafast optical response. In this letter, the nanocomposites of gold nanorods and ormosil gel glass were prepared by a solvent-assisted dispersing process and characterized by UV–vis spectra, TEM, XRD and optical limiting measurement. The results showed that these gold/ormosil nanocomposites could preserve optical limiting property of gold nanorods and had enhanced thermostability due to thermostable silica matrix. Such nanocomposite material of metal-doped gel glass matrix could be considered as a promising candidate for optical limiter against tunable laser.

Lead-free tin telluride (SnTe) has been viewed as one promising solid thermoelectric material for recovering waste heat in recent years. In this work, SnTe alloys doped with excessive In and Sb have been synthesized by melting, quenching and spark plasma sintering. The Seebeck coefficient has been enhanced by synergistic effect based on resonant levels and increased carrier effective mass especially at low and middle temperature range, and then, the power factor is enlarged. With the reduced electrical and lattice thermal conductivity via co-doping, the total thermal conductivity is decreased. Intrinsic point defect and more grain boundaries lead to reduction in the lattice thermal conductivity through the co-doping. In addition, as the doping level is near the solubility limit, the 200–600 nm, In-rich precipitations have been detected in Sn0.848Sb0.14In0.012Te alloy, which can further reduce the lattice thermal conductivity. Thus, the lowest lattice thermal conductivity of 0.96 W m−1 K−1 is obtained at 800 K. Finally, the maximum figure of merit zT of ~ 0.8 at 800 K has been obtained for Sn0.848Sb0.14In0.012Te alloy, and a relative high average zT of ~ 0.45 in 300–800 K is achieved due to the zT improvement in the low and middle temperature range which indicated that SnTe is a promising candidate for the thermoelectric application.

Thermoelectric properties of n-type LnTSbO (Ln = lanthanides and T = Zn, Mn) were firstly investigated by the first-principles method and the semi-classical Boltzmann theory. The results show that a multiple-valley structure appears around the bottom of conduction band. The valley with a high band degeneracy consists of the bands with a weak band dispersion, leading to large magnitudes of the Seebeck coefficient but low electrical conductivity. The valley with a low band degeneracy is made up of the bands with an intense band dispersion, resulting in a high electrical conductivity but small magnitudes of the Seebeck coefficient. The thermoelectric properties are dominated by the energy difference, ΔE, between the valleys. The ΔE value of LnZnSbO linearly increases with the ionic radius of Ln. The thermoelectric properties are thus effectively modulated by varying the lanthanides. As a result, LnZnSbO (Ln = Ce-Nd) with the moderate values of ΔE shows a better thermoelectric performance. The multiple-valley effect is an effective way to modulate the thermoelectric properties of n-type LnTSbO. Keywords: Multiple-valley structure, Oxyantimonide, Thermoelectric, First principles

Lithium niobate (LiNbO3, LN) crystal is a multi-functional material with favorable piezoelectric, nonlinear optical and electro-optic properties. In this study, the electromechanical properties of the radial extensional (RE) and the thickness extensional (TE) modes of the congruent LN are studied and the temperature dependent behaviors are revealed. The RE mode electromechanical coupling factors (kp) for the Y- and Z-oriented discs are calculated and found to be 3.8% and 24.7%, respectively, which are nearly the same as the experimental results of 3.8% and 25.2%, respectively. The maximum RE and thickness shear (TS) modes electromechanical coupling factors are obtained to be 47.6% and 68.5% for the Yx/25° and Yx/167° crystal cuts, respectively. The LN crystal possesses good temperature stability of the electromechanical coupling factors (RE and TE modes) from 20 °C to 500 °C, where the variations of kp and kt for the Y-oriented discs are

We attempt to develop an optimized metallized layer and evaluate the performance for a SnTe uni-leg thermoelectric module by finite-element simulation. The maximum conversion efficiencies of 3.0% and 0.7% have been achieved under ideal and rough contacted thermoelectric modules at ΔT = 600 K. The Ag metal is found to be the optimized metallized layer. The module with metallized Ag layer shows the lowest contact resistance and the best performance. The efficiency reaches about 60% of ideal contacted module. Following that, the pressure forced on module and the surface roughness between the electrode, metallized layer and thermoelectric material have been simulated. With the increase of surface roughness slope, the contact and inner resistances of the thermoelectric module are decreased, and the voltage, maximum output power and efficiency are increased. When the average surface roughness slope is over 0.8, the efficiency reaches 90% of the ideal contacted module. The contact and inner resistances obviously decrease with increasing pressure, while the voltage, maximum output power and efficiency are enhanced. The greater than 90% efficiency of an ideal contacted module is achieved when the pressure is beyond 100 kPa. These simulated results will be beneficial for the fabrication of SnTe-based thermoelectric modules.