Multimetallic Nanoparticles Research Articles

Monodisperse Ultrasmall Manganese-Doped Multimetallic Oxysulfide Nanoparticles as Highly Efficient Oxygen Reduction Electrocatalyst.

The highly efficient and cheap non-Pt-based electrocatalysts such as transition-based catalysts prepared via facile methods for oxygen reduction reaction (ORR) are desirable for large-scale practical industry applications in energy conversion and storage systems. Herein, we report a straightforward top-down synthesis of monodisperse ultrasmall manganese-doped multimetallic (ZnGe) oxysulfide nanoparticles (NPs) as an efficient ORR electrocatalyst by simple ultrasonic treatment of the Mn-doped Zn-Ge-S chalcogenidometalate crystal precursors in H2O/EtOH for only 1 h at room temperature. Thus obtained ultrasmall monodisperse Mn-doped oxysulfide NPs with ultralow Mn loading level (3.92 wt %) not only exhibit comparable onset and half-wave potential (0.92 and 0.86 V vs reversible hydrogen electrode, respectively) to the commercial 20 wt % Pt/C but also exceptionally high metal mass activity (189 mA/mg at 0.8 V) and good methanol tolerance. A combination of transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical analysis demonstrated that the homogenous distribution of a large amount of Mn(III) on the surface of NPs mainly accounts for the high ORR activity. We believe that this simple synthesis of Mn-doped multimetallic (ZnGe) oxysulfide NPs derived from chalcogenidometalates will open a new route to explore the utilization of discrete-cluster-based chalcogenidometalates as novel non-Pt electrocatalysts for energy applications and provide a facile way to realize the effective reduction of the amount of catalyst while keeping desired catalytic performances.

VOCs combustion catalysts based on composites of exfoliated organo-Laponite and multimetallic (Mn, Al, Zr, Ce) hydrotalcites prepared by inverse microemulsion

Composites of exfoliated organo-Laponite and multimetallic (Mn, Al, Zr, Ce) hydrotalcite-like nanoparticles obtained by inverse microemulsion method were used as precursors of catalysts for total oxidation of toluene. The materials were characterized with XRF, XPS, XRD, HRSEM, TEM/HRTEM, H2 TPR, and N2 adsorption/desorption at −196 °C. Features of nanocrystalline hydrotalcite-like phase could be identified in all active phase precursors obtained by inverse micellar route, of poorer order in samples doped with Ce and/or Zr. Mn-Al active phase in calcined (600 °C) composites formed uniform particles of ca. 30–40 nm diameter, while upon addition of Zr and/or Ce the active phase disintegrated forming very fine oxide particles, rarely exceeding 10 nm. All composites were very active in the total oxidation of toluene, those promoted with Zr and/or Ce showing performance superior to the undoped counterpart. Beneficial role of Zr and Ce promoters was attributed to the improved dispersion and amorphization of the mixed oxide phase, accompanied by its enhanced reducibility and increase of the catalysts specific surface area and pore volume. Addition of Ce resulted in an increase of the surface contribution of Mn4+ ions, advantageous for combustion activity. Best catalytic performance was obtained for the composite of Laponite with Mn-Al active phase promoted with both Zr and Ce, which showed excellent activity and stability. Catalysts obtained by the novel design performed much better than the references prepared from conventionally synthesized hydrotalcites and sodium or cetyltrimethylammonium form of Laponite.

Experimental Investigation on the Multi-metallic Cu-Zn NanofluidsHeat Transfer Enhancement and Pressure Losses

Metallic nanofluidsare suspensions of metallic particles of nanometre size in base fluids. The combination of two kinds of metallic particles mixed at the same volume ratio is known as multi-metallic nanoparticles. These multiple metallic particles of nanometre size were suspended in deionized H2Ovia the use of ultrasonic vibratorsat varying volume fractions as well as variations in the ratios of metallic/metallic particles of nanometre size. In our study the dynamic viscosity, the nanofluid’s heat conductivities were determined for varying temperatures and volume fractions. The coefficient of thermal transmissionof the flowing nanofluid in the constant wall heat flux tube were determined experimentally in laminar condition. The results revealedhuge thermal transmission enhancement comparison to the base fluids. The pressure loses were illustrated for all nanofluids. The comparisons of the different metallic and multi-metallic types of the nanofluids were showed that Cu nanofluids have a greater coefficient ofthermal transmission compared with the Cu-Zn, Zn atequal volume fractions.

Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001) by the systematic control of composition, annealing temperature and time.

Multi-metallic alloy nanoparticles (NPs) can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25) hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa.

Ligand-Mediated Deposition of Noble Metals at Nanoparticle Plasmonic Hotspots.

We report the use of gold nanoparticle surface chemistry as a tool for site-selective noble metal deposition onto colloidal gold nanoparticle substrates. Specifically, we demonstrate that partial passivation of the gold nanoparticle surface using thiolated ligands can induce a transition from linear palladium island deposition to growth of palladium selectively at plasmonic hotspots on the edges or vertices of the underlying particle substrate. Further, we demonstrate the broader applicability of this approach with respect to substrate morphology (e.g., prismatic and rod-shaped nanoparticles), secondary metal (e.g., palladium, gold, and platinum), and surface ligand (e.g., surfactant molecules and n-alkanethiols). Taken together, these results demonstrate the important role of metal-ligand surface chemistry and ligand packing density on the resulting modes of multimetallic nanoparticle growth, and in particular, the ability to direct that growth to particle regions of impact such as plasmonic hotspots.

Size-dependent Optical Response of Magneto-plasmonic Core-shell Nanoparticles

Functional properties tunability prospect of multi-layered and multi-metallic nanoparticles with respect to their emerging applications has always been the area of attraction. Magneto-plasmonic nanoparticles (MPNPs) present the possibility to exhibit their tuneable magnetic and optical properties with broad applications in magnetic resonance imaging (MRI), cancer therapy, photovoltaic solar cells, biological microscopy, optical imaging, and biosensing. Present studies found that the optical properties (absorption and scattering efficiencies) of MPNPs using Fe, Co and Ni as magnetic materials coated with single noble metal (Au or Ag) or double (both Au & Ag) coating layer, can be effectively tuned with the controlled size of core and shell layers. It is found that absorption and scattering LSPR peaks occur in Ultraviolet (UV) and visible region of EM for single core-shell MNP@Ag nanoparticles respectively. The absorption LSPR are found in the visible region, and scattering LSPR found in NIR region and also get blue shifted for single core-shell of MNP@Au nanospheres. In case of double core-shell layers of MNP@Ag@Au nanoparticles, the absorption and scattering peaks show spectra in visible and NIR region of EM spectrum and the absorption LSPR peak shifts visible to UV region and scattering LSPR are found in NIR region with broadening peaks of EM spectrum. It is concluded that the LSPR peak depends upon the thickness of the shell, size of core and material. The shifting of optical peaks towards the longer wavelengths depends on gold shell thickness whereas optical efficiencies depend on silver (as core or shell) thickness.

Transformative Heterointerface Evolution and Plasmonic Tuning of Anisotropic Trimetallic Nanoparticles.

Multicomponent nanoparticles that incorporate multiple nanocrystal domains into a single particle represent an important class of material with highly tailorable structures and properties. The controlled synthesis of multicomponent NPs with 3 or more components in the desired structure, particularly anisotropic structure, and property is, however, challenging. Here, we developed a polymer and galvanic replacement reaction-based transformative heterointerface evolution (THE) method to form and tune gold-copper-silver multimetallic anisotropic nanoparticles (MAPs) with well-defined configurations, including structural order, particle and junction geometry, giving rise to extraordinarily high tunability in the structural design, synthesis and optical property of trimetallic plasmonic nanoantenna structures. MAPs can easily, flexibly integrate multiple surface plasmon resonance (SPR) peaks and incorporate various plasmonic field localization and enhancement within one structure. Importantly, a heteronanojunction in these MAPs can be finely controlled and hence tune the SPR properties of these structures, widely covering UV, visible and near-infrared range. The development of the THE method and new findings in synthesis and property tuning of multicomponent nanostructures pave ways to the fabrication of highly tailored multicomponent nanohybrids and realization of their applications in optics, energy, catalysis and biotechnology.

Structural Evolution of Three-Component Nanoparticles in Polymer Nanoreactors.

Recent developments in scanning probe block copolymer lithography (SPBCL) enable the confinement of multiple metal precursors in a polymer nanoreactor and their subsequent transformation into a single multimetallic heterostructured nanoparticle through thermal annealing. However, the process by which multimetallic nanoparticles form in SPBCL-patterned nanoreactors remains unclear. Here, we utilize the combination of PEO-b-P2VP and Au, Ag, and Cu salts as a model three-component system to investigate this process. The data suggest that the formation of single-component Au, Ag, or Cu nanoparticles within polymer nanoreactors consists of two stages: (I) nucleation, growth, and coarsening of the particles to yield a single particle in each reactor; (II) continued particle growth by depletion of the remaining precursor in the reactor until the particle reaches a stable size. Also, different aggregation rates are observed for single-component particle formation (Au > Ag > Cu). This behavior is also observed for two-component systems, where nucleation sites have greater Au content than the other metals. This information can be used to trap nanoparticles with kinetic structures. High-temperature treatment ultimately facilitates the structural evolution of the kinetic particle into a particle with a fixed structure. Therefore, with multicomponent systems, a third stage that involves elemental redistribution within the particle must be part of the description of the synthetic process. This work not only provides a glimpse at the mechanism underlying multicomponent nanoparticle formation in SPBCL-generated nanoreactors but also illustrates, for the first time, the utility of SPBCL as a platform for controlling the architectural evolution of multimetallic nanoparticles in general.

Electrochemical Activation of CO2 through Atomic Ordering Transformations of AuCu Nanoparticles.

Precise control of elemental configurations within multimetallic nanoparticles (NPs) could enable access to functional nanomaterials with significant performance benefits. This can be achieved down to the atomic level by the disorder-to-order transformation of individual NPs. Here, by systematically controlling the ordering degree, we show that the atomic ordering transformation, applied to AuCu NPs, activates them to perform as selective electrocatalysts for CO2 reduction. In contrast to the disordered alloy NP, which is catalytically active for hydrogen evolution, ordered AuCu NPs selectively converted CO2 to CO at faradaic efficiency reaching 80%. CO formation could be achieved with a reduction in overpotential of ∼200 mV, and catalytic turnover was enhanced by 3.2-fold. In comparison to those obtained with a pure gold catalyst, mass activities could be improved as well. Atomic-level structural investigations revealed three atomic gold layers over the intermetallic core to be sufficient for enhanced catalytic behavior, which is further supported by DFT analysis.

Multifaceted Gold-Palladium Bimetallic Nanorods and Their Geometric, Compositional, and Catalytic Tunabilities.

Kinetically controlled, seed-mediated co-reduction provides a robust and versatile synthetic approach to multimetallic nanoparticles with precisely controlled geometries and compositions. Here, we demonstrate that single-crystalline cylindrical Au nanorods selectively transform into a series of structurally distinct Au@Au-Pd alloy core-shell bimetallic nanorods with exotic multifaceted geometries enclosed by specific types of facets upon seed-mediated Au-Pd co-reduction under diffusion-controlled conditions. By adjusting several key synthetic parameters, such as the Pd/Au precursor ratio, the reducing agent concentration, the capping surfactant concentration, and foreign metal ion additives, we have been able to simultaneously fine-tailor the atomic-level surface structures and fine-tune the compositional stoichiometries of the multifaceted Au-Pd bimetallic nanorods. Using the catalytic hydrogenation of 4-nitrophenol by ammonia borane as a model reaction obeying the Langmuir-Hinshelwood kinetics, we further show that the relative surface binding affinities of the reactants and the rates of interfacial charge transfers, both of which play key roles in determining the overall reaction kinetics, strongly depend upon the surface atomic coordinations and the compositional stoichiometries of the colloidal Au-Pd alloy nanocatalysts. The insights gained from this work not only shed light on the underlying mechanisms dictating the intriguing geometric evolution of multimetallic nanocrystals during seed-mediated co-reduction but also provide an important knowledge framework that guides the rational design of architecturally sophisticated multimetallic nanostructures toward optimization of catalytic molecular transformations.

Synthesis of an excellent electrocatalyst for oxygen reduction reaction with supercritical fluid: Graphene cellular monolith with ultrafine and highly dispersive multimetallic nanoparticles

Abstract Graphene cellular monolith (GCM) can be used as an excellent support for nanoparticles in widespread applications. However, it's still a great challenge to deposit the desirable nanoparticles in GCM that have small size, controllable structure, composition, and high dispersion using the current methods. Here we demonstrate a green, efficient and large-scale method to address this challenge using supercritical fluid (SCF). By this superior method, graphene hydrogel can be transferred into GCM while being deposited with ultrafine and highly dispersive nanoparticles. Specifically, the bimetallic PtFe/GCM and the trimetallic PtFeCo/GCM catalysts are successfully synthesized, and their electrocatalytic performances toward oxygen reduction reaction (ORR) are also studied. The resultant PtFe/GCM shows the significant enhancement in ORR activity, including a factor of 8.47 enhancement in mass activity (0.72 A mgPt−1), and a factor of 7.67 enhancement in specific activity (0.92 mA cm−2), comparing with those of the commercial Pt/C catalyst (0.085 A mgPt−1, 0.12 mA cm−2). Importantly, by introducing the Co, the trimetallic PtFeCo/GCM exhibits the further improved ORR activities (1.28 A mgPt−1, 1.80 mA cm−2). The high ORR activity is probably attributed to the alloying structure, ultrafine size, highly dispersive, well-defined, and a better interface with 3D porous graphene support.

DNA-Mediated Morphological Control of Pd-Au Bimetallic Nanoparticles.

Recent reports have shown that different DNA sequences can mediate the control of shapes and surface properties of nanoparticles. However, all previous studies have involved only monometallic particles, most of which were gold nanoparticles. Controlling the shape of bimetallic nanoparticles is more challenging, and there is little research into the use of DNA-based ligands for their morphological control. We report the DNA-templated synthesis of Pd-Au bimetallic nanoparticles starting from palladium nanocube seeds. The presence of different homo-oligomer DNA sequences containing 10 deoxy-ribonucleotides of thymine, adenine, cytosine, or guanine results in the growth of four distinct morphologies. Through detailed kinetic studies by absorption spectroscopy, scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), we have determined the role of DNA in controlling Pd-Au nanoparticle growth morphologies. One major function of DNA is affecting various properties of the incoming metal atoms, including their diffusion and deposition on the Pd nanocube seed. Interestingly, nanoparticle growth in the presence of A10 follows an aggregative growth mechanism that is unique when compared to the other base oligomers. These findings demonstrate that DNA can allow for programmable control of bimetallic nanoparticle morphologies, resulting in more complex hybrid materials with different plasmonic properties. The capability to finely tune multimetallic nanoparticle morphology stems from the versatile structure that is unique to DNA in comparison to conventionally used capping agents in colloidal nanomaterial synthesis.

Hydrogen sensing properties of Pt-Au bimetallic nanoparticles loaded on ZnO nanorods

The mono-noble metal nanoparticles are often loaded onto the sensing materials to promote the gas sensing performance of the materils; however, there have been few reports concerning the effect of the multi-metallic nanoparticles on the sensing performance. It is reported that the multi-metallic nanoparticles shows different absorption and catalytic performance from their mono-metal analogues because of the geometric and electronic effect, so it is very necessary to investigate the gas sensing performance of the multi-metallic nanoparticles loaded materials. In this work, the Pt-Au alloying nanoparticles was prepared and supported on the ZnO nanorods, and this hybrid was used as the H2 sensor for the first time. The sensing testing results indicate that the alloying nanoparticles loaded ZnO exhibits higher sensing response than the mono-metallic nanoparticles loaded ZnO. The Pt-Au bimetallic nanoparticles loaded ZnO shows high sensitivity to ppm-level of hydrogen even at room temperature, and the sensing response of (Pt-Au)-loaded ZnO to 250ppm of H2 is 157, 47, and 9.6 times higher than that of pure ZnO, Pt-loaded ZnO, and Au-loaded ZnO, respectively. This superior performance of the (Pt-Au)-loaded ZnO to H2 is most probably due to the strong adsorption of H2 onto the Pt-Au bimetallic nanoparticles caused by the geometric and electronic effects between the two metals.

Controlled Dealloying of Alloy Nanoparticles toward Optimization of Electrocatalysis on Spongy Metallic Nanoframes

Atomic-level understanding of the structural transformations of multimetallic nanoparticles triggered by external stimuli is of vital importance to the enhancement of our capabilities to fine-tailor the key structural parameters and thereby to precisely tune the properties of the nanoparticles. Here, we show that, upon thermal annealing in a reducing atmosphere, Au@Cu2O core-shell nanoparticles transform into Au-Cu alloy nanoparticles with tunable compositional stoichiometries that are predetermined by the relative core and shell dimensions of their parental core-shell nanoparticle precursors. The Au-Cu alloy nanoparticles exhibit distinct dealloying behaviors that are dependent upon their Cu/Au stoichiometric ratios. For Au-Cu alloy nanoparticles with Cu atomic fractions above the parting limit, nanoporosity-evolving percolation dealloying occurs upon exposure of the alloy nanoparticles to appropriate chemical etchants, resulting in the formation of particulate spongy nanoframes with solid/void bicontinuous morphology composed of hierarchically interconnected nanoligaments. The nanoporosity evolution during percolation dealloying is synergistically guided by two intertwining structural rearrangement processes, ligament domain coarsening driven by thermodynamics and framework expansion driven by Kirkendall effects, both of which can be maneuvered by controlling the Cu leaching rates during the percolation dealloying. The dealloyed nanoframes possess large open surface areas accessible by the reactant molecules and high abundance of catalytically active undercoordinated atoms on the ligament surfaces, two unique structural features highly desirable for high-performance electrocatalysis. Using the room temperature electro-oxidation of methanol as a model reaction, we further demonstrate that, through controlled percolation dealloying of Au-Cu alloy nanoparticles, both the electrochemically active surface areas and the specific activity of the dealloyed metallic nanoframes can be systematically tuned to achieve the optimal electrocatalytic activities.

Gyroscopic behavior exhibited by the optical Kerr effect in bimetallic Au–Pt nanoparticles suspended in ethanol

The modification in the third-order nonlinear optical response exhibited by rotating bimetallic Au–Pt nanoparticles in an ethanol solution was analyzed. The samples were prepared by a sol–gel processing route. The anisotropy associated to the elemental composition of the nanoparticles was confirmed by high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy measurements. The size of the nanoparticles varies in the range from 9 to 13 nm, with an average size of 11 nm. Changes in the spatial orientation of the nanomaterials automatically generated a variation in their plasmonic response evaluated by UV–Vis spectroscopy. A two-wave mixing experiment was conducted to explore an induced birefringence at 532 nm wavelength with nanosecond pulses interacting with the samples. A strong optical Kerr effect was identified to be the main responsible effect for the third-order nonlinear optical phenomenon exhibited by the nanoparticles. It was estimated that the rotation of inhomogeneous nanostructures can provide a remarkable change in the participation of different surface plasmon resonances, if they correspond to multimetallic nanoparticles. Potential applications for developing low-dimensional gyroscopic systems can be contemplated.

Ultrafine Alloy Nanoparticles Converted from 2D Intercalated Coordination Polymers for Catalytic Application

Supported multimetallic alloy nanoparticles (NPs) have shown great potential for applications owing to combined functions of constituent metals, and more remarkably, enhanced physicochemical properties and even novel synergistic effects that are not possessed by their parent metals. Nevertheless, synthesizing this kind of nanocomposites has been a long‐standing challenge using conventional wet chemistry. Here, this study reports an efficient, versatile strategy for the preparation of multimetallic alloy NPs supported by layered double hydroxides (LDH) and/or layered double oxides (LDO). In this approach, different metal precursors are intercalated stepwise into the gallery space of LDH. Along with the coordination reaction between the metal precursors, 2D cyanide bridged coordination polymers (CP) are formed in the confined space. Afterward, supported multimetallic alloy NPs can be obtained via either liquid‐phase reduction or thermal autoreduction. Due to the homogeneous mixing of metals in the 2D CP, ultrafine alloy NPs can be obtained with high particulate uniformity and compositional tailorability. A large series of supported binary alloy NPs (FePd, FePt, CoPd, CoPt, NiPd, NiPt, and PtPd) and ternary alloy NPs (FePdPt, FeNiPt, FeCoPt, and NiCoPt) are successfully synthesized with this approach. The resulting supported multimetallic alloy NPs present great potential in numerous applications. To demonstrate their workability, one class of LDH/NiPd nanocomposite is explored as a model heterogeneous catalyst with respect to the carbon–carbon cross‐coupling reactions (Suzuki–Miyaura, Heck, and Sonogashira cross‐coupling reactions).

Constraints on the solid solubility of Hg, Tl, and Cd in arsenian pyrite

Arsenic-rich (arsenian) pyrite can contain up to tens of thousands of parts per million (ppm) of toxic heavy metals such as Hg, Tl, and Cd, although few data are available on their solid solubility behavior. When a compilation of Hg, Tl, and Cd analyses from different environments are plotted along with As in a M(Hg, Tl, and Cd)-As log-log space, the resulting wedge-shaped distribution of data points suggests that the solid solubility of the aforementioned metals is strongly dependent on the As concentration of pyrite. The solid solubility limits of Hg in arsenian pyrite—i.e., the upper limit of the wedge-shaped zone in compositional space—are similar to the one previously defined for Au by Reich et al. (2005) (CHg,Au = 0.02CAs+ 4 × 10–5), whereas the solubility limit of Tl in arsenian pyrite is approximated by a ratio of Tl/As = 1. In contrast, and despite a wedge-shaped distribution of Cd-As data points for pyrite in Cd-As log-log space, the majority of Cd analyses reflect the presence of mineral particles of Cd-rich sphalerite and/or CdS. Based on these data, we show that arsenian pyrite with M/As ratios above the solubility limit of Hg and Tl contain nanoparticles of HgS, and multimetallic Tl-Hg mineral nanoparticles. These results indicate that the uptake of Hg and Tl in pyrite is strongly dependent on As contents, as it has been previously documented for metals such as Au and Cu. Cadmium, on the other hand, follows a different behavior and its incorporation into the pyrite structure is most likely limited by the precipitation of Cd-rich nanoparticulate sphalerite. The distribution of metal concentrations below the solubility limit suggests that hydrothermal fluids from which pyrite precipitate are dominantly undersaturated with respect to species of Hg and Tl, favoring the incorporation of these metals into the pyrite structure as solid solution. In contrast, the formation of metallic aggregates of Hg and Tl or mineral nanoparticles in the pyrite matrix occurs when Hg and Tl locally oversaturate with respect to their solid phases at constant temperature. This process can be kinetically enhanced by high-to-medium temperature metamorphism and thermal processing or combustion, which demonstrates a retrograde solubility for these metals in pyrite.

Structural optimization and segregation behavior of quaternary alloy nanoparticles based on simulated annealing algorithm**Project supported by the National Natural Science Foundation of China (Grant Nos. 51271156, 11474234, and 61403318) and the Natural Science Foundation of Fujian Province of China (Grant Nos. 2013J01255 and 2013J06002).

Alloy nanoparticles exhibit higher catalytic activity than monometallic nanoparticles, and their stable structures are of importance to their applications. We employ the simulated annealing algorithm to systematically explore the stable structure and segregation behavior of tetrahexahedral Pt–Pd–Cu–Au quaternary alloy nanoparticles. Three alloy nanoparticles consisting of 443 atoms, 1417 atoms, and 3285 atoms are considered and compared. The preferred positions of atoms in the nanoparticles are analyzed. The simulation results reveal that Cu and Au atoms tend to occupy the surface, Pt atoms preferentially occupy the middle layers, and Pd atoms tend to segregate to the inner layers. Furthermore, Au atoms present stronger surface segregation than Cu ones. This study provides a fundamental understanding on the structural features and segregation phenomena of multi-metallic nanoparticles.

Making ultrafine and highly-dispersive multimetallic nanoparticles in three-dimensional graphene with supercritical fluid as excellent electrocatalyst for oxygen reduction reaction

A powerful method of supercritical fluid was demonstrated to controllably synthesize porous graphene-based electrocatalysts by depositing ultrafine multimetallic nanoparticles.

One-pot two-step rapid synthesis of 3-aminopropyltrimethoxysilane-mediated highly catalytic Ag@(PdAu) trimetallic nanoparticles

Synergistic interactions between individual components of multimetallic nanoparticles result in dramatic changes in important physical or chemical properties that outclass those of monometallic nanoparticles in many aspects.