Triple the steady-state reaction rate by decorating the In_(2)O_(3)surface with SiO_(x)for CO_(2)hydrogenation

Indium oxide(In_(2)O_(3)),as a promising candidate for CO_(2)hydrogenation to C_(1) products,often suffers from sintering and activity decline,closely related to the undesirable structural evolution under reaction conditions.Based on the comprehension of the dynamic evolution,this study presents an efficient strategy to alleviate the agglomeration of In_(2)O_(3)nanoparticles by the surface decoration with highly dispersed silica species(SiO_(x)).Various structural characterizations combined with density functional theory calculations demonstrated that the sintering resulted from the over-reduction,while the enhanced stability originated from the anchoring effect of highly stable In-OSi bonds,which hinders the substantial formation of metallic In(In^(0))and the subsequent agglomeration.0.6Si/In_(2)O_(3)exhibited CO_(2)conversion rate of10.0 mmol g^(-1)h^(-1)at steady state vs.3.5 mmol g^(-1)h^(-1)on In_(2)O_(3)in CO_(2)hydrogenation.Enhanced steady-state activity was also achieved on Pd-modified catalysts.Compared to the traditional Pd/In_(2)O_(3)catalyst,the methanol production rate of Pd catalyst supported on 0.6Si/In_(2)O_(3)was enhanced by 23%,showing the potential of In_(2)O_(3)modified by SiO_(x)in serving as a platform material.This work provides a promising method to design new In_(2)O_(3)-based catalysts with improved activity and stability in CO_(2)hydrogenation.

Microstructure and battery performance of Mg-Zn-Sn alloys as anodes for magnesium-air battery

Four Mg-x Zn-y Sn(x=2,4 and y=1,3 wt.%)alloys are investigated as anode materials for magnesium-air(Mg-air)battery.The self-corrosion and battery discharge behavior of these four Mg-Zn-Sn alloys are analyzed by electrochemical measurements and Mg-air battery tests.The results show that addition of Sn stimulates the electrochemical activity and significantly improves the anodic efficiency and specific capacity of Mg-Zn alloy anodes.Among the four alloy anodes,Mg-2Zn-3Sn(ZT23)shows the best battery discharge performance at low current densities(≤5 m A cm^(-2)),achieving high energy density of 1367 m Wh g^(-1)at 2 mA cm^(-2).After battery discharging,the surface morphology and electrochemical measurement results illustrate that a ZnO and SnO/SnO_(2)mixed film on alloy anode surface decreases self-corrosion and improves anodic efficiency during discharging.The excessive intermetallic phases lead to the failure of passivation films,acting as micro-cathodes to accelerate self-corrosion.

Recent Advances in Simple Model for 4f-5d Transitions of Lanthanide Ions in Solids

The simple model for 4f-5d transitions of lanthanide ions in crystals was extended to deal with the case of the octahedral crystal field, where for the t2 component of 5d orbitals the spin-orbit interaction could not be neglected due to incomplete quenching of the 5d orbital angular momentum. The energy levels for the 4fN-15d configuration and the relative line strengths for the 4fN4fN-15d transition were calculated in detail. The result was applied to the interpretation of the low-temperature 4f-5d excitation spectrum of Cs2NaYCl6∶Tb3+.

Data inversion of multi-dimensional magnetic resonance in porous media

Since its inception in the 1970s,multi-dimensional magnetic resonance(MR)has emerged as a powerful tool for non-invasive investigations of structures and molecular interactions.MR spectroscopy beyond one dimension allows the study of the correlation,exchange processes,and separation of overlapping spectral information.The multi-dimensional concept has been re-implemented over the last two decades to explore molecular motion and spin dynamics in porous media.Apart from Fourier transform,methods have been developed for processing the multi-dimensional time-domain data,identifying the fluid components,and estimating pore surface permeability via joint relaxation and diffusion spectra.Through the resolution of spectroscopic signals with spatial encoding gradients,multi-dimensional MR imaging has been widely used to investigate the microscopic environment of living tissues and distinguish diseases.Signals in each voxel are usually expressed as multi-exponential decay,representing microstructures or environments along multiple pore scales.The separation of contributions from different environments is a common ill-posed problem,which can be resolved numerically.Moreover,the inversion methods and experimental parameters determine the resolution of multi-dimensional spectra.This paper reviews the algorithms that have been proposed to process multidimensional MR datasets in different scenarios.Detailed information at the microscopic level,such as tissue components,fluid types and food structures in multi-disciplinary sciences,could be revealed through multi-dimensional MR.

Spin-Split Joint Density of States in GdN

We present an investigation of the optical constants of the near stoichiometric GdN films. Transmission and reflection spectra are collected for the paramagnetic and the ferromagnetic GdN in the photon energy range of 0.5-5.5 eV. In the ferromagnetic phase, behaviors of minority and majority spin states are specifically focussed on, which indicate spin-split joint density of states. The results confirm the LSDA＋U estimates of energy gap associated with the majority-spins and also the magnitude of spin splitting.

Large-scale synthesis of N-doped carbon capsules supporting atomically dispersed iron for efficient oxygen reduction reaction electrocatalysis

The large-scale synthesis of platinum-free electrocatalysts for the oxygen reduction reaction(ORR)remains a grand challenge.We report the large-scale production of stable and active ORR electrocatalysts based on iron,an earth-abundant element.A core–shell zeolitic imidazolate framework–tannic acid coordination polymer composite(ZIF-8@K-TA)was utilized as the catalyst precursor,which was transformed into iron atoms dispersed in hollow porous nitrogen-doped carbon capsules(H-Fe-N_(x)-C)through ion exchange and pyrolysis.H-Fe-N_(x)-C fea-tures site-isolated single-atom iron centers coordinated to nitrogen in graphitic layers,high levels of nitrogen doping,and high permeability to incoming gases.Benefiting from these characteristics,H-Fe-N_(x)-C demonstrated efficient electrocatalytic activity(E_(1/2)=0.92 V,vs.RHE)and stability towards the ORR in both alkaline and acidic media.In ORR performance,it surpassed the majority of recently reported Fe-N-C catalysts and the standard Pt/C catalyst.In addition,H-Fe-N_(x)-C showed outstanding tolerance to methanol.

Converging Cooperative Functions into the Nanospace of Covalent Organic Frameworks for Efficient Uranium Extraction from Seawater

The extraction of uranium from seawater is challenging though it offers tremendous potential for the sustainable production of nuclear fuel for the energy sector.Herein,we report a new strategy for efficient extraction of uranium from seawater via converging the cooperative functions of adsorption-photocatalysis into the nanospace of covalent organic frameworks(COFs).Functionalization of the organic linkers in the multicomponent COFs allowed exploration of the relationship between material composition and adsorption-photocatalytic activity for uranium extraction.The presence of amidoxime groups in the COFs offered selective binding sites for uranyl,whilst triazine units and bipyridine-Pd groups acted cooperatively to photocatalytically reduce adsorbed U(Ⅵ)to a U(Ⅳ)solid product(UO2)for facile collection.One of our developed COFs,4-Pd-AO,displayed exceptional performance in sequestering and reducing uranyl from natural seawater,with a high extraction capacity of 4.62 mg U/g per day(average data)under visible light irradiation.Mechanistic studies revealed that 4-Pd-AO not only reduced adsorbed uranyl(Ⅵ)to U(Ⅳ)O_(2),but also generated ^(1)O_(2) and superoxide radicals under visible light excitation,thus affording excellent antibacterial and antialgal activities(i.e.,antibiofouling properties)for sustained efficient uranium extraction performance.This proof-ofconcept study establishes multicomponent COFs as promising candidates for efficient uranium extraction from seawater.

Role of phase separation in nanocomposite indium-tin-oxide films for transparent thermoelectric applications

We report that oxygen vacancies have a profound impact on phase separation and thermoelectric properties of ITO films grown at room temperature.Oxygen vacancies in non-stoichiometric In1.8Sn0.2O2.5 films aided the formation of In-rich metallic clusters.It yields a high electrical conductivity s=1540 Scm1 and Seebeck coefficient|a|=27.2 mVK1,which resulted in the highest power factor(a2 s=113.8 mW m1 K2)but low optical transmission(Top-25%).An increase in oxygen partial pressure resulted in stochiometric In1.8Sn0.2O3 films which improved the optical transparency by 300%(Top-75.4%),but power factor was reduced by-85%due to a decrease in a and s.A decrease in a was due to the lack of energy filtering of charge carriers in the stoichiometric ITO film which did not have In-rich metallic clusters.XPS results showed that the valence band energy shifts with a change in oxygen partial pressure due to a decrease in carrier density,which implied a change in Fermi energy due to the reverse Moss-Burstein effect.Our results showed that phase separation can be obtained in nanocomposite ITO films by tuning their stoichiometry simply by varying the oxygen partial pressure during deposition of thermoelectric materials at low temperatures.

Recent review of surface plasmons and plasmonic hot electron effects in metallic nanostructures

Plasmonic resonators are widely used for the manipulation of light on subwavelength scales through the near-field electromagnetic wave produced by the collective oscillation of free electrons within metallic systems,well known as the surface plasmon(SP).The non-radiative decay of the surface plasmon can excite a plasmonic hot electron.This review article systematically describes the excitation progress and basic properities of SPs and plasmonic hot electrons according to recent publications.The extraction mechanism of plasmonic hot electrons via Schottky conjunction to an adjacent semiconductor is also illustrated.Also,a calculation model of hot electron density is given,where the efficiency of hot-electron excitation,transport and extraction is discussed.We believe that plasmonic hot electrons have a huge potential in the future development of optoelectronic systems and devices.

联吡啶嗡盐共价有机框架材料合成与选择性捕获放射性高鍀酸根

具有高比表面积及规则孔道结构的离子型共价有机框架(COF)材料表现出广泛的应用前景.本文设计合成了一种基于联吡啶嗡盐的阳离子型COF材料(PS-COF-1).PS-COF-1比表面积为2703 m^(2) g^(-1),高于目前报道的其他离子型COF材料.PS-COF-1具有固定的一维通道(~4.5 nm)、良好的化学稳定性和耐辐照稳定性,表现出优异的吸附ReO_(4)^(-)(最大吸附量为1262 mg g^(-1))和^(99)TcO_(4)^(-)性能.进一步研究表明,PS-COF-1在高离子强度下表现出快速吸附动力学、高吸附容量和对^(99)TcO_(4)^(-)和ReO_(4)^(-)的高选择性,在模拟美国汉福德低活性废物流条件下成功选择性去除了^(99)TcO_(4)^(-).此外,PS-COF-1能够在10 min内将ReO_(4)^(-)和^(99)TcO_(4)^(-)污染水净化至饮用水级别.密度泛函理论计算表明,PS-COF-1对低电荷密度阴离子ReO_(4)^(-)和^(99)TcO_(4)^(-)具有强的亲和力(优于其他常见阴离子,如Cl^(-),NO_(3)^(-),SO_(4)^(2-),CO_(3)^(2-)),阐明了PS-COF-选择性吸附^(99)TcO_(4)^(-)的机理.本文展示了一种用于选择性捕获放射性核素新型阳离子COF吸附剂,为放射性污染治理提供了重要的理论依据和指导.

ZIF-8的高温热解: 锌(Ⅱ)单原子中心从四面体构型到类卟啉构型的演变

高温热解金属有机骨架(ZIFs)是一种合成含类卟啉单原子碳材料的有效方式.理解煅烧产物中单原子位点在热解过程中的构型变化,对实现高性能单原子催化材料具有重要意义.因此,本工作系统地研究了在ZIF-8煅烧过程中(500~900℃)锌单原子中心的构型演变.同步辐射吸收谱结果表明:ZIF-8前驱体中四面体构型的锌单子中心在600℃时开始转变为类卟啉锌中心(锌中心凸出卟啉平面);并随着温度升高至900℃,锌中心逐渐接近N4卟啉平面.由于Zn N4中心位点的几何构型变化改变了锌中心原子的电子密度分布,因此其在降解H2O2中表现不同的催化活性(800℃煅烧得到的锌单原子产物性能最优).本工作为理解ZIF煅烧中单原子的构型演变以及其催化性能提供了新思路.

Capillaric field effect transistors

Controlling fluid flow in capillaric circuits is a key requirement to increase their uptake for assay applications.Capillary action off-valves provide such functionality by pushing an occluding bubble into the channel using a difference in capillary pressure.Previously,we utilized the binary switching mode of this structure to develop a powerful set of fundamental fluidic valving operations.In this work,we study the transistor-like qualities of the off-valve and provide evidence that these structures are in fact functionally complementary to electronic junction field effect transistors.In view of this,we propose the new term capillaric field effect transistor to describe these types of valves.To support this conclusion,we present a theoretical description,experimental characterization,and practical application of analog flow resistance control.In addition,we demonstrate that the valves can also be reopened.We show modulation of the flow resistance from fully open to pinch-off,determine the flow rate-trigger channel volume relationship and demonstrate that the latter can be modeled using Shockley's equation for electronic transistors.Finally,we provide a first example of how the valves can be opened and closed repeatedly.