Revealing the plasmon coupling in gold nanochains directly from the near field

We studied the near-field properties of localized surface plasmon resonances in finite linear gold nanochains using photoemission electron microscopy(PEEM).The localization of the electromagnetic field in the near-field region was mapped at high spatial resolution.By tuning the excitation laser wavelength,we can obtain the near-field spectra,from which the energy splitting between longitudinal(L)and transverse(T)plasmon modes can be revealed.In particular,the L-mode red shifts and the T-mode blue shifts with increasing chain length.The red shift of the L-mode is highly dependent on the gap distance.In contrast,the T-mode almost remains constant within the range of gap distance we investigated.This energy splitting between the L-mode and the T-mode of metallic chains is in agreement with previous far-field measurements,where it was explained by dipole-dipole near-field coupling.Here,we provide direct proof of this near-field plasmon coupling in nanochains via the above-described near-field measurements using PEEM.In addition,we explore the energy transport along the gold nanochains under excitation at oblique illumination via PEEM measurements together with numerical simulations.

One-dimensional PtFe hollow nanochains for the efficient oxygen reduction reaction

Integration of electronic and strain effects with tailored structures is significant to tuning the electrocatalytic activity and stability of the electrocatalysts for the oxygen reduction reaction(ORR).In this study,onedimensional PtFe hollow nanochains are synthesized by a facile and effective method,which exhibit a highly open and porous structure.The modulated electronic and strain effects of Pt atoms are verified by extensive structural characterizations,and the mass and specific activities of the prepared catalyst are roughly 7.45 and 12.44 times higher than those of the commercial Pt/C catalyst,respectively.Remarkably,the catalyst demonstrates robust performance with negligible activity decay after an accelerated durability test for 30,000 cycles.The high activity of the catalyst is probably due to the optimized absorption affinity of Pt-O accelerating the reaction kinetics induced by the cooperation of Fe atoms as well as the unique hollow and curved structures.This study provides new insights into the rational design of high-performance ORR catalysts with considerable durability.

Synthesis and growth mechanism of SiC/SiO2 nanochains by catalyst-free thermal evaporation method in Ar/CO atmosphere

SiC/SiO2 nanochains were synthesized on a carbon fiber substrate by a catalyst-free thermal evaporation method in the Ar/CO atmosphere.X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)revealed that the as-synthesized SiC/SiO2 nanochains are composed of single-crystalline SiC nanowires and amorphous SiO2 beads.The introduction of CO can promote the formation of SiO2,so that the SiC/SiO2 nanochains are subsequently formed during cooling.In addition,the photoluminescence spectrum of SiC/SiO2 nanochains showed a broad emission peak at around 350 nm,which is ascribed to the oxygen discrepancy in the SiO2 beads as well as the SiC/SiO2 interfacial effect.These findings can provide guidance for further study of the vapor growth of 1D SiC-based materials.

Hydrogen evolution-assisted one-pot aqueous synthesis of hierarchical trimetallic PdNiRu nanochains for hydrazine oxidation reaction

A hydrogen evolution-assisted one-pot aqueous approach was developed for facile synthesis of trimetallic Pd Ni Ru alloy nanochain-like networks（Pd Ni Ru NCNs） by only using KBHas the reductant, without any specific additive（e.g. surfactant, polymer, template or seed）. The products were mainly investigated by transmission electron microscopy（TEM）, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS）. The hierarchical architectures were formed by the oriented assembly growth and the diffusioncontrolled deposition in the presence of many in-situ generated hydrogen bubbles. The architectures had the largest electrochemically active surface area（ECSA） of 84.32 mgPdthan Pd Ni nanoparticles(NPs,65.23 mgPd), Pd Ru NPs(23.12 mgPd), Ni Ru NPs（nearly zero）, and commercial Pd black(6.01 mgPd), outperforming the referenced catalysts regarding the catalytic characters for hydrazine oxygen reaction（HOR）. The synthetic route provides new insight into the preparation of other trimetallic nanocatalysts in fuel cells.

Autocatalytic reduction-assisted synthesis of segmented porous PtTe nanochains for enhancing methanol oxidation reaction

Morphology engineering has been developed as one of the most widely used strategies for improving the performance of electrocatalysts.However,the harsh reaction conditions and cumbersome reaction steps during the nanomaterials synthesis still limit their industrial applications.Herein,one-dimensional(1D)novel-segmented PtTe porous nanochains(PNCs)were successfully synthesized by the template methods assisted by Pt autocatalytic reduction.The PtTe PNCs consist of consecutive mesoporous architectures that provide a large electrochemical surface area(ECSA)and abundant active sites to enhance methanol oxidation reaction(MOR).Furthermore,1D nanostructure as a robust sustaining frame can maintain a high mass/charge transfer rate in a long-term durability test.After 2,000 cyclic voltammetry(CV)cycles,the ECSA value of PtTe PNCs remained as high as 44.47 m^(2)·gPt^(-1),which was much larger than that of commercial Pt/C(3.95 m^(2)·gPt^(-1)).The high catalytic activity and durability of PtTe PNCs are also supported by CO stripping test and density functional theory calculation.This autocatalytic reduction-assisted synthesis provides new insights for designing efficient low-dimensional nanocatalysts.

Fe_(2)TiO_(5)nanochains as anode for high-performance lithium-ion capacitor

The unique crystal structure and multiple redox couples of iron titanate(Fe_(2)TiO_(5)) provide it a high theoretical capacity and good cycling stability when used as an electrode. In this study, the electrospinning method is employed to synthesize one-dimensional(1 D) Fe_(2)TiO_(5) nanochains. The as-prepared Fe_(2)TiO_(5) nanochains exhibited superior specific capacity(500 mAh·g^(-1) at 0.10 A·g^(-1)),excellent rate performance(180 mAh·g^(-1) at 5.00 A·g^(-1)),and good cycling stability(retaining 100% of the initial specific capacity at a current density of 1.00 A·g^(-1) after1000 cycles). The as-assembled Fe_(2)TiO_(5)/SCCB lithiumion capacitor(LIC) also delivered a competitive energy density(137.8 Wh·kg^(-1))andpowerdensity(11,250 W·kg^(-1)). This study proves that the as-fabricated1 D Fe_(2)TiO_(5) nanochains are promising anode materials for high-performance LICs.

Facile one-step synthesis of PdPb nanochains for high-performance electrocatalytic ethanol oxidation

The widespread application of direct ethanol fuel cells is hampered due to the low activity,high cost and poor operation durability of electrocatalysts for ethanol oxidation reaction(EOR).Herein,we report a one-pot synthetic method to synthesize PdPb3 nanochains with well-defined shape,size and composition via a solution-phase reduction method.The morphology,composition distribution and structure characteristics of PdPb3 nanochains were investigated by transmission electron microscopy,X-ray photoelectron spectroscopy and X-ray diffraction.Thanks to the unique structure,the as-obtained PdPb3 nanochains can manifest much higher mass activity(2523 mA·mg-1)and higher operation durability than commercial Pd/C(1272 mA·mg-1)during the EOR measurements.More importantly,further CO-stripping measurements indicate that the incorporation of Pb species could favor the oxidative removal of CO intermediates on the Pd electrode at the negative potential and enhance the EOR activity and stability,making it possible to develop highly active and durable electrocatalysts.

Synthesis of magnetic core-shell iron nanochains for potential applications in Cr(Ⅵ)ion pollution treatment

Fe nanochains with diameters of 50-150 nm and average length of about 1μm were synthesized by titrating NaBH_(4)solution into FeCl_(2) aqueous solution(i.e.,reduction of Fe(II)ions).The microstructures and magnetic properties were studied by X-ray diffraction(XRD),transmission electron microscope(TEM),and vibrating sample magnetometer(VSM).The results reveal that the nanochains have a core-shell structure with a-Fe as the core and amorphous iron oxide as the shell.The Fe coreshell nanochains show the characteristic of soft magnetic materials,achieving the highest magnetization of200.74 mA-m^(2)·g^(-1).The influences of the titrating rate of NaBH_(4)aqueous solution on the morphology of the Fe nanochains were also studied.It reveals that low titrating rate is beneficial for synthesizing Fe nanochains with uniform morphology.The reduction experiments indicate that these Fe nanochains are of high reducibility.About 90%Cr(VI)ions are successfully removed after 10 min reaction of 100 mg Fe nanochains in the 100 ml K_(2)Cr_(2)O_(7) solution(100 mg·L^(-1))and more than 99%after 30 min.

Interface-rich Au-doped PdBi alloy nanochains as multifunctional oxygen reduction catalysts boost the power density and durability of a direct methanol fuel cell device

The development of cathode oxygen reduction reaction(ORR)catalysts with high characteristics for practical,direct methanol fuel cells(DMFCs)has continuously increased the attention of researchers.In this work,interface-rich Au-doped PdBi(PdBiAu)branched one-dimensional(1D)alloyed nanochains assembled by sub-6.5 nm particles have been prepared,exhibiting an ORR mass activity(MA)of 6.40 A·mgPd^(−1) and long-term durability of 5,000 cycles in an alkaline medium.The MA of PdBiAu nanochains is 46 times and 80 times higher than that of commercial Pt/C(0.14 A·mgPt^(−1))and Pd/C(0.08 A·mgPd^(−1)).The MA of binary PdBi nanochains also reaches 5.71 A·mgPd^(−1).Notably,the PdBiAu nanochains exhibit high in-situ carbon monoxide poisoning resistance and high methanol tolerance.In actual DMFC device tests,the PdBiAu nanochains enhance power density of 140.1 mW·cm^(−2)(in O_(2))/112.4 mW·cm^(−2)(in air)and durability compared with PdBi nanochains and Pt/C.The analysis of the structure–function relationship indicates that the enhanced performance of PdBiAu nanochains is attributed to integrated functions of surficial defect-rich 1D chain structure,improved charge transfer capability,downshift of the d-band center of Pd,as well as the synergistic effect derived from“Pd-Bi”and/or“Pd-Au”dual active sites.

One-dimensional nanochains consisting of magnetic core and mesoporous aluminosilicate for use as efficient nanocatalysts

Magnetic assembly at the nanoscale level brings potential possibilities in obtaining novel delicate nanostructures with unique physical, photonic or electronic properties. Interface surfactant micelle-directed assembly strategy holds great promising in fabricating ordered mesoporous materials with multifunctionality and pore parameter tunability. Combing these, herein, one-dimensional (1D) nanochains with well-aligned silica-coated magnetic particles as core and mesoporous aluminosilicate as shell are rational fabricated for the first time through magnetic field induced interface coassembly in biliquid system followed by the incorporation of Al species via in-situ chemical modification and transformation strategy. The obtained magnetic mesoporous aluminosilicate nanochains (MMAS-NCs) possess well-defined core-shell-shell sandwich nanostructure, tunable perpendicular mesopore channels in the shell (2.7–7.6 nm), high surface area (359 m^(2)·g^(-1)), abundant acidic sites, and superparamagnetism with a magnetization saturation of 13.8 emu·g^(-1). Thanks to the unique properties, the MMAS-NCs exhibit excellent performance in acting as magnetically recyclable superior solid acid catalysts and nanostirrers with high conversion of over 96.8%, selectivity of 95.0% in the deprotection reaction of benzaldehyde dimethylacetal to benzaldehyde. Moreover, MMAS-NCs exhibit an interesting pore size effect on the catalytic activity, namely, in the pore size range of 2–8 nm, the catalysts with larger pores show significantly enhanced catalytic activity due to the balanced mass transport and density of surface active sites.

In situ dynamics response mechanism of the tunable length-diameter ratio nanochains for excellent microwave absorber

Faster response benefits the high-performance of magnetic material in various live applications.Hence,enhancing response speed toward the applied field via engineering advantages in structures is highly desired.In this paper,the precise synthesis of Co nanochain with the tunable length-diameter ratio is realized via a magnetic-field-guided assembly approach.The Co nanochain exhibits enhanced microwave absorption performance(near to-60 dB,layer thickness 2.2 mm)and broader effective absorption bandwidth(over 2/3 of total S,C,X,Ku bands).Furthermore,the simulated dynamic magnetic response reveals that the domain motion in 1D chain is faster than that in 0D nanoparticle,which is the determining factor of magnetic loss upgrade.Meanwhile,based on the controllable magnetic field experiment via in situ transmission electron microscopy,the association between magnetic response and microstructure is first present at the nanometer-level.The real and imaginary parts of relative complex permeability are determined by the domain migration confined inside Co nanochain and the magnetic flux field surrounded outside Co nanochain,respectively.Importantly,these findings can be extended to the novel design of microwave absorbers and promising candidates of magnetic carriers based on 1D structure.

Heat treatment bimetallic PdAu nanocatalyst for oxygen reduction reaction

Pd-based nanocatalyst is a potential oxygen reduction oxidation(ORR)catalyst because of its high activity in alkaline medium and low cost.In this work,bimetallic Pd Au nanocatalysts are prepared by one-pot hydrothermal method using triblock pluronic copolymers,poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)(PEO19-PPO69-PEO19)(P123)as reducer and stabilizer,and heat-treatment method is applied to regulate catalyst structure and improve catalyst activity.The results show that the heat treatment can agglomerate the catalyst to a certain extent,but effectively improve the crystallinity and alloying degree of the catalyst.The ORR performance of the Pd Au nanocatalysts obtained under different heat treatment conditions is systematically investigated.Compared with commercial Pd black and Pd Au catalyst before heat treatment,the ORR performance of Au Pd nanocatalyst obtained after heat treatment for one hour at 500℃ has been enhanced.The Pd Au nanocatalysts after heat treatment also display enhanced anti-methanol toxicity ability in acidic medium.