Delving into the dissimilarities in electrochemical performance and underlying mechanisms for sodium and potassium ion storage in N-doped carbon-encapsulated metallic Cu_(2)Se nanocubes

The large volumetric variations experienced by metal selenides within conversion reaction result in inferior rate capability and cycling stability,ultimately hindering the achievement of superior electrochemical performance.Herein,metallic Cu_(2)Se encapsulated with N-doped carbon(Cu_(2)Se@NC)was prepared using Cu_(2)O nanocubes as templates through a combination of dopamine polymerization and hightemperature selenization.The unique nanocubic structure and uniform N-doped carbon coating could shorten the ion transport distance,accelerate electron/charge diffusion,and suppress volume variation,ultimately ensuring Cu_(2)Se@NC with excellent electrochemical performance in sodium ion batteries(SIBs)and potassium ion batteries(PIBs).The composite exhibited excellent rate performance(187.7 mA h g^(-1)at 50 A g^(-1)in SIBs and 179.4 mA h g^(-1)at 5 A g^(-1)in PIBs)and cyclic stability(246,8 mA h g^(-1)at 10 A g^(-1)in SIBs over 2500 cycles).The reaction mechanism of intercalation combined with conversion in both SIBs and PIBs was disclosed by in situ X-ray diffraction(XRD)and ex situ transmission electron microscope(TEM).In particular,the final products in PIBs of K_(2)Se and K_(2)Se_(3)species were determined after discharging,which is different from that in SIBs with the final species of Na_(2)Se.The density functional theory calculation showed that carbon induces strong coupling and charge interactions with Cu_(2)Se,leading to the introduction of built-in electric field on heterojunction to improve electron mobility.Significantly,the theoretical calculations discovered that the underlying cause for the relatively superior rate capability in SIBs to that in PIBs is the agile Na~+diffusion with low energy barrier and moderate adsorption energy.These findings offer theoretical support for in-depth understanding of the performance differences of Cu-based materials in different ion storage systems.

Hydrogen generation from ammonia electrolysis on bifunctional platinum nanocubes electrocatalysts

The ammonia electrolysis is a highly efficient and energy-saving method for ultra-pure hydrogen generation, which highly relies on electrocatalytic performance of electrocatalysts. In this work, high-quality platinum(Pt) nanocubes(Pt-NCs) with 4.5 nm size are achieved by facile hydrothermal synthesis. The physical morphology and structure of Pt-NCs are exhaustively characterized, revealing that Pt-NCs with special {100} facets have excellent uniformity, good dispersity and high crystallinity. Meanwhile, the electrocatalytic performance of Pt-NCs for ammonia electrolysis are carefully investigated in alkaline solutions, which display outstanding electroactivity and stability for both ammonia electrooxidation reaction(AEOR) and hydrogen evolution reaction(HER) in KOH solution. Furthermore, a symmetric Pt-NCs||Pt-NCs ammonia electrolyzer based on bifunctional Pt-NCs electrocatalyst is constructed, which only requires 0.68 V electrolysis voltage for hydrogen generation. Additionally, the symmetric Pt-NCs||Pt-NCs ammonia electrolyzer has excellent reversible switch capability for AEOR at anode and HER at cathode, showing outstanding alternating operation ability for ammonia electrolysis.

Facile Synthesis of Porous Zn–Sn–O Nanocubes and Their Electrochemical Performances

Porous Zn–Sn–O nanocubes with a uniform size were synthesized through a facile aqueous solution route combined with subsequent thermal treatment. The chemical composition, morphology, and microstructure of Zn–Sn–O nanocubes, which have significant effects on the lithium storage performances, were easily tuned by adjusting the calcination temperature in preparation processes of ZnSn(OH)6solid nanocubes. Further studies revealed that porous Zn–Sn–O nanocubes prepared at 600 °C exhibited a good rate capability and a high reversible capacity of 700 m Ah g^(-1)at a current density of 200 m Ag^(-1)after 50 cycles, which may be a great potential as anode materials in Lithium-ion batteries.

Core-shell-structured Co@Co4N nanoparticles encapsulated into MnO-modified porous N-doping carbon nanocubes as bifunctional catalysts for rechargeable Zn–air batteries

Designing the highly catalytic activity and durable bifunctional catalysts toward oxygen reduction/evolution reaction(ORR/OER) is paramount for metal–air batteries. Metal–organic frameworks(MOFs)-based materials have attracted a great deal of attention as the potential candidate for effectively catalyzing ORR/OER due to their adjustable composition and porous structure. Herein, we first introduce the Mn species into zeolitic-imidazole frameworks(ZIFs) and then further pyrolyze the Mn-containing bimetallic ZIFs to synthesize core-shell-structured Co@Co4N nanoparticles embedded into MnO-modified porous N-doped carbon nanocubes(Co@Co4N/MnO–NC). Co@Co4N/MnO–NC exhibits the outstanding catalytic activity toward ORR and OER which is attributed to its abundant pyridinic/graphitic N and Co4N,the optimized content of MnO species, highly dispersed catalytic sites and porous carbon matrix. As a result, the Co@Co4N/MnO–NC-based Zn–air battery exhibits enhanced performances, including the high discharge capacity(762 mA h gZn-1), large power density(200.5 mW cm-2), stable potential profile over 72 h, low overpotential(<1.0 V) and superior cycling life(2800 cycles). Moreover, the belt-shaped Co@Co4N/MnO–NC cathode-based Zn–air batteries are also designed which exhibit the superb electrochemical properties at different bending/twisting conditions.

Cuprous Chloride Nanocubes Grown on Copper Foil for Pseudocapacitor Electrodes

In this paper, for the first time, we report the synthesis of nanoscale cuprous chloride(Cu Cl) cubic structure by a facile hydrothermal route. A possible mechanism for the growth of those nanostructures is proposed based on the experimental results. It is discovered that the existence of HCl could affect the surface of Cu Cl nanocubes. This unique cube-like nanostructure with rough surface significantly enhances the electroactive surface areas of Cu Cl, leading to a high special capacitance of 376 m F cm-2at the current density of 1.0 m A cm-2. There is still a good reversibility with cycling efficiency of 88.8 % after 2,000 cycles, demonstrating its excellent long-term cycling stability and might be the promising candidates as the excellent electrode material.

Controllable Synthesis of Ag Nanocubes via a Polyol Method

The controllable synthesis of uniform silver nanocubes with high purity is pivotal for the fundamental study of self-assembly and further research on the hollow nanostructures,gold nanocages for instance.Here,Ag nanocubes of different sizes were synthesized by an improved polyol method.With addition of HCl solution,Ag nanocubes with size about 100 nm were obtained under an air atmosphere.And Ag nanocubes with size around50 nm can be produced in a short time under Argon atmosphere with the presence of NaHS instead of HCl.Meanwhile,uniform Ag nanocubes with size larger than 100 nm were also synthesized successfully via adjusting experiment parameters.Results of transmission electron microscopy(TEM)combined with selected area electron diffraction(SAED)show that the Ag nanocubes are single crystalline with six(200)surface plane.In the UV-Vis-NIR optical absorption spectrum,the diple moment resonance absorption peak is changed in the range of 420—500nm with the increase of Ag nanocubes size.

Formation and Growth of Silver Nanocubes upon Nanosecond Pulsed Laser Irradiation: Effects of Laser Intensity and Irradiation Time

Silver nanoparticles (AgNPs) were fabricated by repetitive irradiation of near ultraviolet (UV) nanosecond laser pulses (355 nm, 5 ns) in an aqueous solution of silver nitrate in the absence of stabilizing agents. A broad absorption peak was observed in the visible region showing the formation of a variety of AgNPs in the solution. Among the variety of products, it was found that silver nanocubes (AgNCs) grew in size with longer laser irradiation time. The size of AgNCs also increased with higher laser intensity. The average size of AgNCs, investigated by a scanning electron microscope (SEM) was in the range of 75 - 200 nm. The number of reduced atoms in AgNCs as a function of laser intensity showed that the AgNCs are apparently produced by a four photon process, implying that the formation of dimer silver atoms is essential for the formation.

Synthesis of monodisperse palladium nanocubes and their catalytic activity for methanol electrooxidation

The single crystalline palladium nanocubes with an average size of 7 nm were prepared in the presence of poly （vinyl pyrrolidone） （PVP） and KBr using the polyol method. The as-prepared Pd nanocubes were highly uniform in both size and shape. The ordered packing structures including monolayer and multilayer can be fabricated via the rate-controlled evaporation of solution solvent. The electrochemical catalytic activity of these Pd nanocubes towards methanol oxidation was found to be higher than that of spherical Pd nanoparticles of similar size.

Enhanced detection of ppb-level NO_(2)by uniform Pt-doped ZnSnO_(3)nanocubes

ZnSnO_(3) nanocubes(ZSNCs)with various Pt concentrations(i.e.,1 at%,2 at%,and 5 at%)were synthesized by a simple one-pot hydrothermal method.The microstructures of pure and Pt-doped ZSNCs were characterized by X-ray diffractometry,scanning electron microscopy,transmission electron microscopy,energy-dispersive X-ray spectroscopy,and X-ray photoelectron spectroscopy.Results showed that the pure ZSNCs have a perovskite structure with a side length of approximately 600 nm;this length was reduced to 400 nm after Pt doping.Following doping,PtO_(x)(PtO and PtO_(2)) nanoparticles with a diameter of approximately 5 nm were uniformly coated on the surface of the ZSNCs.Systematic investigation of the gas-sensing abilities of the nanocubes showed that the Pt-doped ZSNCs have excellent sensing properties toward nitrogen dioxide(NO_(2)) gas in the operating temperature range of 75-175℃.Among the sensors prepared,that based on 1 at%Pt-doped ZSNCs exhibited the best response of 16.0 toward 500 ppb NO_(2) at 125℃;this response is over 11 times higher compared with that of pure ZSNCs.The enhanced NO_(2) sensing mechanism of the Pt-doped ZSNCs may be attributed to the synergistic effects of catalytic activity and chemical sensitization by Pt doping.

Optical binding forces between plasmonic nanocubes： A numerical study based on discrete-dipole approximation

Plasmonic nanocubes are ideal candidates in realizing controllable reflectance surfaces, unidirectional nanoantennas and other plasmon-associated applications. In this work, we perform full-wave calculations of the optical forces in threedimensional gold nanocube dimers. For a fixed center-to-center separation, the rotation of the plasmonic nanocube leads to a slight shift of the plasmonic resonance wavelength and a strong change in the optical binding forces. The effective gap and the near field distribution between the two nanocubes are shown to be crucial to this force variation. We further find that the optical binding force is dominated by the scattering process while the optical forces in the wavevector direction are affected by both scattering and absorption, making the former relatively more sensitive to the rotation of(an effective gap between) the nanocubes. Our results would be useful for building all-optically controllable meta-surfaces.

A Solvothermal Route to Cu_2O Nanocubes and Cu Nanoparticles

Cu2O nanocubes and Cu nanoparticles were prepared by reducing Cu（ Ⅱ ） salt with ethanol as the reducing agent and solvent in the presence of multidentate ligand poly（vinylpyrrolidone） （PVP） under different conditions. The morphologies and the crystalline structures of the products were characterized by using scanning electron microscopy （SEM）, transmission electron microscopy（TEM）, selected-area electron diffraction（ SAED）, and powder X-ray diffraction（XRD）. In particular, the influences of the solvothennal reaction temperature and alkalinity on the products were investigated. A lower temperature and a lower alkali concentration favor the formation of the Cu2O phase, whereas a higher temperature and a higher alkali concentration generally lead to the formation of the Cu phase.

B and Fe co-doped Co_(2)P hollow nanocubes for nitrate electroreduction to ammonia

Nitrate(NO_(3)^(−))electroreduction reaction(NO_(3)^(−)RR)provides an attractive and sustainable route for NO_(3)^(−)pollution mitigation or energy-saved ammonia(NH3)synthesis.In this work,high-quality B and Fe co-doped Co_(2) P hollow nanocubes(B/Fe-Co_(2) P HNCs)are successfully synthesized though simultaneous boronation-phosphorization treatment,which reveal outstanding selectivity,activity,stability for the NO_(3)^(−)to NH_(3) conversion in neutral electrolyte because of big surface area,fast mass transport,superhydrophilic surface,and optimized electronic structure.B/Fe-Co_(2) P HNCs can achieve the high NH3 yield rate(22.67 mg h^(−1) mg_(cat)^(−1))as well as Faradaic efficiency(97.54%)for NO_(3)^(−)RR,greatly outperforming most of non-precious metal based NO_(3)^(−)RR electrocatalysts.

Mesoporous Cu_(3−x)Zn_(x)(BTC)_(2)nanocubes synthesized in deep eutectic solvent and their catalytic performances

To develop high-performance metal-organic frameworks(MOFs)for catalysis is of great importance.Here,we synthesized the mesoporous Cu_(3−x)Zn_(x)(BTC)_(2)(BTC=benzene-1,3,5-tricarboxylate)nanocubes in a deep eutectic solvent of ZnCl_(2)/ethylene glycol solution.The route can proceed at room temperature and the reaction time needed is shortened to be 30 min,which is superior to the conventional solvothermal route that usually needs high temperature and long reaction time.The formation mechanism of the mesoporous Cu_(3−x)Zn_(x)(BTC)_(2)nanocubes in deep eutectic solvent(DES)was investigated by in situ synchrotron X-ray diffraction/small angle X-ray scattering/X-ray absorption fine structure conjunction technique.The mesoporous Cu_(3−x)Zn_(x)(BTC)_(2)nanocubes exhibit high catalytic activity and reusability for cyanosilylation reaction of benzaldehyde and aerobic oxidation reaction of benzylic alcohol.

Solar-driven CO_(2) conversion to methane and methanol using different nanostructured Cu_(2)O-based catalysts modified with Au nanoparticles

This work describes the use of TiO_(2)nanotubes-based electrodes(TNT)modified with Cu_(2)O nanostructures and gold nanoparticles for the photoelectroreduction of CO_(2)to produce value-added compounds.A thin layer of polydopamine was used as both an adherent agent and an electron transfer mediator,due to itsπ-conjugated electron system.The highest production yield was achieved using a TNT@PDA/Nc/Au40%electrode,with Faradaic efficiencies of 47.4%(110.5μM cm^(-2))and 27.8%(50.4μM cm^(-2))for methanol and methane,respectively.The performance of the photoelectrodes was shown to be Cu_(2)O facet-dependent,with cubic structures leading to greater conversion of CO_(2)to methanol(43%)and methane(27%),compared to the octahedral morphology,while a higher percentage of metallic gold on the nanostructured Cu_(2)O surface was mainly important for CH4production.Density functional theory(DFT)calculations supported these findings,attributing the superior photoelectrocatalytic performance of the TNT@PDA/Nc/Au40%electrode for CH4generation to the formation of an OCH3intermediate bonded to Au atoms.Studies using isotope-labeling and analysis by gas chromatograph-mass(GC-MS)demonstrated that13CO_(2)was the source for photoelectrocatalytic generation of13CH3OH and13CH313CH2OH.

In situ construction of surface defects of carbon-doped ternary cobalt-nickel-iron phosphide nanocubes for efficient overall water splitting

The ternary cobalt-nickel-iron phosphide nanocubes (P-Co0.9Ni0.9Fe1.2 NCs) with high intrinsic activity, conductivity, defect concentration and optimized ratio have been realized through a facile phosphorization treatment using ternary cobalt-nickel-iron nanocubes of Prussian blue analogs (PBA) as a precursor. The scanning electron microscopy and transmission electron microscopy results show that the P-Co0.9Ni0.9Fe1.2 NCs maintain a cubic structure with a rough surface, implying the rich surface defects as exposed active sites. The thermal phosphorization of the ternary PBA precursor not only provids carbon doping but also leads to the in situ construction of surface defects on the NCs. The carbon doping from the PBA precursor lowers the charge transfer resistance and optimizes the electronic transformation. The synergistic effect among the ternary metal ions and rich defects contributes to the enhanced electrocatalytic performance . The P-Co0.9Ni0.9Fe1.2NCs achieve low overpotentials of -200.7 and 273.1 mV at a current density of 10 mA cm^-2 for the hydrogen evolution reaction and the oxygen evolution reaction, respectively. The potential of overall water splitting reaches 1.52 V at a current density of 10 mA cm^-2. The longterm stability of the electrocatalysts was also evaluated. This work provides a facile method to design efficient transitionmetal- based bifunctional electrocatalysts for overall water splitting.

Metal-organic framework-derived CoSn/NC nanocubes as absorbers for electromagnetic wave attenuation

Metal-organic framework-derived composites have been widely used in electromagnetic wave(EMW)absorption,but the traditional synthetic strategy greatly limits the structure and species of MOFs.This research provided a solvent-free method to synthesize Co-MOF and its derivatives.Using CoSnO_(3)as the precursor,the preparation of Co-MOF is achieved by bridging the cobalt(II)ion of CoSnO_(3)and the 2-methylimidazole skeleton.The CoSn/N-doped carbon(CoSn/NC)composites derived from CoSnO_(3)-MOF(Co-MOF with CoSnO_(3)as Co source)retain the original morphology of CoSnO_(3).Besides,the polarization effect produced by the N-doped carbon layers also benefits the excellent EMW absorption performance of the CoSn/NC composites.It is reflected in the minimum reflection loss(RL)of-48.2 dB at 2.2 mm and the effective bandwidth(EBA)of 5.84 GHz.This work provides a new channel to the construction of Co-MOFs,which could be extended to other Co-based oxides and vastly expand the species of MOFs based on metallic Co.

Doxorubicin-Ioaded Fe3O4@MoS2-PEG-2DG nanocubes as a theranostic platform for magnetic resonance imaging- guided chemo-photothermal therapy of breast cancer

Molybdenum disulfide （MoS2）, a typical transition-metal dichalcogenide, has attracted increasing attention in the field of nanomedicine because of its preeminent properties. In this study, magnetic resonance imaging （MRI）-guided chemo-photothermal therapy of human breast cancer xenograft in nude mice was demonstrated using a novel core/shell structure of Fe3O4@MoS2 nanocubes （IOMS NCs） via the integration of MoS2 （MS） film onto iron oxide （IO） nanocubes through a facile hydrothermal method. After the necessary PEGylation modification of the NCs for long-circulation purposes, such PEGylated NCs were further capped by 2-deoxy-D-glucose （2-DG）, a non-metabolizable glucose analogue to increase the accumulation of the as-prepared NCs at the tumor site, as 2-DG molecules could be particularly attractive to resource-hungry cancer cells. Such 2-DG- modified PEGylated NCs （IOMS-PEG-2DG NCs） acted as drug-carriers for doxorubicin （DOX）, which could be easily loaded within the NCs. The obtained IOMS-PEG（DOX）-2DG NCs exhibited a 3？2 relaxivity coefficient of 48.86 （mM）^-1·s^-1 and excellent photothermal performance. 24 h after intravenous injection of IOMS-PEG（DOX）-2DG NCs, the tumor site was clearly detected by enhanced T2-weighted MRI signal. Upon exposure to an NIR 808-nm laser for 5 rain at a low power density of 0.5 W·cm^-2 a marked temperature increase was noticed within the tumor site, and the tumor growth was efficiently inhibited by the chemo-photothermal effect. Therefore, our study highlights an excellent theranostic platform with great potential for targeted MRI-guided precise chemo-photothermal therapy of breast cancer.

Vacuum-tuned-atmosphere induced assembly of Au@Ag core/shell nanocubes into multi-dimensional superstructures and the ultrasensitive IAPP proteins SERS detection

Utilizing vacuum-tuned-atmosphere induced dip coating method,we achieve the cross-dimensional macroscopic diverse self-assemblies by using one building block with one chemical functionality.Coordinated modulating the vacuum degree,colloid concentration and evaporation atmosphere,Au@Ag core/shell nanocubes (NCs) can controllably assemble into diverse multi-dimensional superstructures.Under 0.08 MPa,we obtained the two-dimensional (2D) stepped superstructures with continuously tunable step width.In addition,we generated a series of tailorable nanoscale-roughened 2D Au@Ag NCs superstructures at 0.04 MPa,which exhibited the label-free ultrasensitive SERS detection for the different mutants of IAPP8-37 proteins.Under 0.01 MPa,we obtained the cross-dimensional tailorable Au@Ag NCs assemblies from random to macroscale 2D and three-dimensional (3D) densest superstructures by adjusting the capping ligand-environmental molecule interactions.This is a flexible method to generate as-prepared Au@Ag core/shell NCs into well-defined macroscopic diverse superstructures and to promote the exploitation into biological applications.

Evolution of surface of Pd-Rh bimetallic nanocubes and its correlation with CO oxidation

Typically, varying pretreatment conditions probably results in the different catalytic performances for the bimetallic catalysts, and this originates from the surface evolution of catalysts during catalytic process. Hence, it is crucial to correlate surface chemistry(e.g., composition, chemical valence, etc.) of bimetallic nanocatalysts with their corresponding performances upon different pretreatments for the fundamental understanding of catalysis. Herein, compositionvaried(100) facet terminated Pd-Rh nanocubes(NCs) with the similar shape and sizes were prepared by a facile one-pot hydrothermal method to exclude the possible size and shape effect. Surface composition and valence state of these Pd0.8 Rh0.2, Pd0.6 Rh0.4, and Pd0.2 Rh0.8 NCs were tracked under different reaction conditions and during catalysis using a homebuilt ambient pressure X-ray photoelectron spectrometer(APXPS). The correlation of active surface of Pd-Rh NCs and their corresponding catalytic performance was established.

Replacing PVP by macrocycle cucurbit[6]uril to cap sub-5 nm Pd nanocubes as highly active and durable catalyst for ethanol electrooxidation

Pd nano cubes(NCs)en closed by six{100}facets are fasci nating model materials for both fun dame ntal studies and practical applicati ons.However,the only available method to prepare well-defined sub-10 nm Pd NCs was developed by Xia et al.more than 10 years ago,un avoidably using polyvinyl pyrrol id one(PVP)polymer to preve nt particle aggregati on.The strongly adsorbed PVP extremely deteriorates the catalysts*efficiency because of the high coverage of accessible surface-active sites.Numerous efforts have been devoted to replacing PVP with weaker capping agents but with limited progress predominately due to the difficulties in tuning the growth kinetics of Pd NCs.For the first time,we report that macrocycle cucurbit[6]uril(CB[6])can replace PVP in the synthesis of Pd NCs by dedicatedly controlling the growth parameters.CB[6]capped Pd NCs showed 1.1-1.5 times in creased specific surface area compared to the surfactant-free commercial Pd catalysts.Moreover,X-ray photoelectron spectroscopy dem on strated the modified electronic structure of Pd NCs through the carb onyl group of CB[6].Consequently,compared to the commercial catalysts,the obtained Pd NCs exhibited 7 times higher current density towards ethanol oxidation reaction.Remarkably,after 17 h of continuous work,it reduced deactivation by up to 1-4 orders of magnitude.