Metals Au Research Articles

Optical and thermoplasmonic properties of core (AuxAg1- x)- shell (Au) nanostructures

The optical and thermoplasmonic properties of bimetallic nanoparticles (NPs) offer a wide range of possibilities for designing functional materials and innovative nanotechnological devices. Their exploration is generating increasing interest in experimental and theoretical scientific research. The combination of noble metals such as gold (Au) and silver (Ag) within the same nanostructure, in the form of an alloy or core/shell arrangement, presents several advantages and potential applications. In this paper, the finite element method (FEM) is used to study the optical response and nanoscale heat generation capability of bimetallic core/shell nanospheres composed of a mixed alloy (AuxAg1−x)-core and an Au-shell. First, we studied the surface plasmon resonance (SPR) properties by generating absorption spectra. Our results show that the position and amplitude of the SPR peak of these nanospheres are strongly influenced by the fractions of Au and Ag metals composing the core, as well as by the Au-shell thickness. In particular, the SPR-peak position can be adjusted between 535nm and 1085nm depending on the composition and structure of these NPs. Secondly, we studied the ability of these NPs to convert absorbed light into heat when exposed to either a continuous wave (cw) laser or a femtosecond pulsed (fs-pulsed) laser. The results demonstrate the ability to control the temperature generated by these NPs based on the core composition, Au-shell thickness, illumination intensity, and the type of illumination (cw or fs-pulsed). In particular, under fs-pulsed illumination, the internal temperature of the NPs is significantly higher than under cw illumination. These findings are crucial for the use of these alloy-core and Au-shell nanoparticles in various thermoplasmonic applications.

Dual LSPR and CT synergy: 3D urchin-like Au@W18O49 enables highly sensitive in-situ SERS detection of dissolved furfural in insulating oils

Assessing the levels of furfural in insulating oils is a crucial technical method for evaluating the degree of aging and mechanical deterioration of oil-paper insulation. The surface-enhanced Raman spectroscopy (SERS) technique provides an effective method for enhancing the sensitivity of in-situ detection of furfural. In this study, a homogeneous three-dimensional (3D) urchin-like Au@W18O49 heterostructure was synthesized as a SERS substrate using a straightforward hydrothermal method. The origin of the superior Raman enhancement properties of the 3D urchin-like heterostructures formed by the noble metal Au and the plasmonic semiconductor W18O49, which is rich in oxygen vacancies, is analyzed experimentally in conjunction with density-functional theory (DFT) calculations. The Raman enhancement is further amplified by the remarkable dual localized surface plasmon resonance (LSPR) effect, which generates a strong local electric field and creates numerous "hot spots," in addition to the interfacial charge transport (CT). The synergistic effect of these factors results in the 3D urchin-like Au@W18O49 heterostructure exhibiting exceptionally high SERS activity. Testing the rhodamine 6G (R6G) probe resulted in a Raman enhancement factor of 3.41 × 10−8, and the substrate demonstrated excellent homogeneity and stability. Furthermore, the substrate was effectively utilized to achieve highly sensitive in-situ surface-enhanced Raman scattering (SERS) detection of dissolved furfural in complex plant insulating oils. The development of the 3D urchin-like Au@W18O49 heterostructure and the exploration of its enhancement mechanism provide theoretical insights for the advancement of high-performance SERS substrates.

Revealing the Effect of Dynamic Structural Evolution on Triple Junction Deformation Mechanism: Molecular Dynamics Simulations and an Energetic Model

Abstract Triple junction (TJ) migration is a plastic deformation mechanism in polycrystalline metals mediated by the interplay between neighboring grain boundaries (GBs). Compared with GB migration, the dynamic change of TJ structure during migration and its impact on subsequent TJ behavior is often overlooked. In this study, we explore the effect of dynamic TJ structure evolution on TJ deformation mechanism in a face-centered cubic metal Au model using molecular dynamics simulations. Our analysis reveals that the dislocation accumulation at TJ due to inconsistent disconnection nucleation from neighboring GBs can influence the stick-slip behavior of TJ migration. With the dynamic change of TJ structure, the velocity of TJ migration is gradually reduced, leading to a transition from TJ migration to dislocation emission from TJ. We have developed an energetic model to evaluate the critical stresses required for TJ migration and dislocation emission, providing an explanation of the competition between TJ migration and dislocation emission. Our findings deepen the understanding of TJ-governed plastic deformation mechanisms in polycrystalline materials.

C60 Fullerene-Induced Reduction of Metal Ions: Synthesis of C60-Metal Cluster Heterostructures with High Electrocatalytic Hydrogen-Evolution Performance.

Metal clusters, due to their small dimensions, contain a high proportion of surface atoms, thus possessing a significantly improved catalytic activity compared with their bulk counterparts and nanoparticles. Defective and modified carbon supports are effective in stabilizing metal clusters, however, the synthesis of isolated metal clusters still requires multiple steps and harsh conditions. Herein, we develop a C60 fullerene-driven spontaneous metal deposition process, where C60 serves as both a reductant and an anchor, to achieve uniform metal (Rh, Ir, Pt, Pd, Au and Ru) clusters without the need for any defects or functional groups on C60. Density functional theory calculations reveal that C60 possesses multiple strong metal adsorption sites, which favors stable and uniform deposition of metal atoms. In addition, owing to the electron-withdrawing properties of C60, the electronic structures of metal clusters are effectively regulated, not only optimizing the adsorption behavior of reaction intermediates but also accelerating the kinetics of hydrogen evolution reaction. The synthesized Ru/C60-300 exhibits remarkable performance for hydrogen evolution in an alkaline condition. This study demonstrates a facile and efficient method for synthesizing effective fullerene-supported metal cluster catalysts without any pretreatment and additional reducing agent.

Theoretical study of adsorption of gas (CO, CO2, NH3) by metal (Au, Ag, Cu)-doped single-layer WS2.

The adsorptions of gas (CO, CO2, NH3) by metal (Au, Ag, Cu)-doped single layer WS2 are studied by density functional theory. The doping of metal atoms makes WS2 behave as n-type semiconductors. The final adsorption sites for CO, CO2, and NH3 are close to the atomic sites of the doped metal. The adsorptions of CO and NH3 gases on Cu/WS2, Ag/WS2, and Au/WS2 are dominated by chemisorption. The doped metal atoms enhance the hybridization of the substrate with the gas molecular orbitals, which contributes to the charge transfer and enhances the adsorption of the gas with the material surface. The adsorptions of CO and NH3 on Cu/WS2 and Ag/WS2 allow favorable desorption in a short time after heating. The single-layer Cu/WS2 is proved to have the potential to be used as a reliable recyclable sensor for CO. This work provides a theoretical basis for developing high-performance WS2-based gas sensors. In this paper, the adsorption energy, electronic structure, charge transfer, and recovery time of CO, CO2, and NH3 in the doped system have been investigated based on the CASTEP code of density functional theory. The exchange correlation function used is the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The TS (Tkatchenko-Scheffler) dispersion correction method was used to involve the effects of van der Waals interaction on the adsorption energies for all adsorption system. The ultrasoft pseudopotentials are chosen and the plane-wave cut-off energies are set to 500eV. The k-point mesh generated by the Monkhorst package scheme is used to perform the numerical integration of the Brillouin zone and 5 × 5 × 1k-point grid is used. The tolerances of total energy convergence, maximum ionic force, ionic displacement, and stress component are 1.0 × 10-5eV/atom, 0.03eV/Å, 0.001Å, and 0.05 GPa, respectively.

M/BiOCl-(M=Pt, Pd, and Au) Boosted Selective Photocatalytic CO2 Reduction to C2 Hydrocarbons via *CHO Intermediate Manipulation.

Selective CO2 photoreduction to C2 hydrocarbons is significant but limited by the inadequate adsorption strength of the reaction intermediates and low efficiency of proton transfer. Herein, an ameliorative *CO adsorption and H2O activation strategy is realized via decorating bismuth oxychloride (BiOCl) nanostructures with different metal (Pt, Pd, and Au) species. Experimental and theoretical calculation results reveal that distinct *CO binding energies and *H acquisition abilities of the metal cocatalysts mediate the CO2 reduction activity and hydrocarbon selectivity. The relatively moderate *CO adsorption and *H supply over Pd/BiOCl endows it with the lowest free energy to generate *CHO, leading to its highest activity of hydrocarbon production. Specifically, the Pt cocatalyst can efficiently participate in H2O dissociation to deliver more *H for facilitating the protonation of the *CHO and *CHOH, thereby favoring CH4 production with 76.51% selectivity. A lower *H supply over Pd/BiOCl and Au/BiOCl results in a large energy barrier for *CHO or *CHOH protonation and thus a more thermodynamically favored OC─CHO coupling pathway, which endows them with vastly increased C2 hydrocarbon selectivity of 81.21% and 92.81%, respectively. The understanding of efficient C2 hydrocarbon production in this study sheds light on how materials can be engineered for photocatalytic CO2 reduction.

Releasing Au Electrons to Mo Site for Weakened Mo─H Bond of Mo2C MXene Cocatalyst Toward Improved Photocatalytic H2 Production.

Mo2C MXene (Mo2CTx) is one of the most promising noble-metal-free cocatalysts for photocatalytic H2 production because of its excellent electron transport capacity and abundant Mo sites. However, Mo2CTx typically exhibits a strong Mo─Hads bond, resulting in that the produced H2 difficultly desorbs from the Mo surface for the limited activity. To effectively weaken the Mo─Hads bond, in this paper, a regulation strategy of electron donor Au releasing electrons to the d-orbitals of Mo sites in Mo2CTx is proposed. Herein, the Mo2CTx-Au/CdS photocatalysts are prepared through a two-step process, including the initial loading of Au nanoparticles on the Mo2CTx surface and the subsequent in situ growth of CdS onto the Mo2CTx-Au surface. Photocatalytic measurements indicate that the maximal H2-production rate of Mo2CTx-Au/CdS reaches up to 2799.44µmol g-1h-1, which is 30.99 and 3.60 times higher than that of CdS and Mo2CTx/CdS, respectively. Experimental and theoretical data corroborate that metallic Au can transfer free electrons to Mo2CTx to generate electron-enriched Moδ- sites, thus causing the increased antibonding-orbital occupancy state and the weakened Mo─Hads bond for the boosted H2-production efficiency. This research provides a promising approach for designing Mo2CTx-based cocatalysts by regulating the antibonding-orbital occupancy of Mo sites for improved photocatalytic performance.

Enhancement of photocatalytic activity by thermal annealing of Au, Ag, and Cu implanted TiN thin films

The paper presents an investigation on the optoelectronic and photocatalytic properties of titanium-nitride (TiN) thin films, modified through the introduction of metal ions (Au, Ag, and Cu) during implantation, followed by thermal annealing. Employing high-resolution microscopic and spectroscopic techniques, we examined the microstructural and compositional features of the films in detail. The films exhibited a crystalline structure with distinct columnar patterns, attributed to defect release and recovery during annealing. Furthermore, metal nanoparticles were detected in samples implanted with gold and silver ions, indicating coalescence processes, while no such particles were observed in the case of Cu ions. Post-implantation annealing also led to surface oxidation and the formation of anatase TiO2, with a coexistence of TiO2, TiN, metallic Au and Ag, and CuO phases in subsurface regions. Comparative optical measurements revealed significant changes in photoluminescence efficiency and photocatalytic response of modified TiN. All implanted samples showed reduced photoluminescence intensity compared to pristine titanium-nitride, with the Au-implanted film exhibiting the most significant decrease, due to the presence of surface Au nanoparticles, thus resulting in the slower electron-hole recombination rates and enhanced photocatalytic activity.

Atomically Precise Ternary Cluster: Polyoxometalate Cluster Sandwiched by Gold Clusters Protected by N-Heterocyclic Carbenes.

Coinage metal (Au, Ag, Cu) cluster and polyoxometalate (POM) cluster represent two types of subnanometer "artificial atoms" with significant potential in catalysis, sensing, and nanomedicine. While composite clusters combining Ag/Cu clusters with POM have achieved considerable success, the assembly of gold clusters with POM is still lagging. Herein, we first designedly synthesized two cluster structural units: an Au3O cluster stabilized by diverse N-heterocyclic carbene (NHC) ligands and an amine-terminated POM linker. The subsequent reaction involved amine substitution in the POM linker for the central O atom in the Au3O cluster, resulting in the first ternary composite cluster - a POM cluster sandwiched by two Au clusters protected by NHCs. Single-crystal X-ray diffraction and other characteristic methods characterized their atomically precise structures. Furthermore, altering the NHC ligands decreased the number of gold atoms in the sandwich structures, accompanying the different protonated degrees of amine ligand in the terminal end of the POM linker. These composite clusters showed excellent performances in catalytic H2O2 conversion through the synergistic effect between gold clusters and POM clusters. This work opens a new avenue to functional composite metal clusters and would promote their enhanced catalysis applications through intercluster synergistic interactions within composite systems.

Updating Geological Information about the Metallogenesis of the Iberian Pyrite Belt

The Iberian Pyrite Belt (IPB) represents one of the largest districts of volcanogenic massive sulfide (VMS) deposits in the world, and is a critical source of base metals (Cu, Pb, and Zn) for Europe. Confirmed resources exceed 1700 Mt of massive sulfides with grades of around 1.2% Cu, 1% Pb, and 3% Zn as well as more than 300 Mt of stockwork-type copper mineralization. Significant resources of Sn, precious metals (Au and Ag), and critical metals (Co, Bi, Sb, In, and Se) have also been evaluated. The genesis of these deposits is related to a complex geological evolution during the late Devonian and Mississippian periods. The geological record of such evolution is represented by three main lithological units: Phyllite–Quartzite Group, the volcano–sedimentary Complex (VSC), and the so-called Culm Group. The sulfide deposits are located in the VSC, associated with felsic volcanic rocks or sedimentary rocks such as black shales. The massive sulfide deposits occur as tabular bodies and replacement masses associated with both volcanic and sedimentary rocks. Their mineralogical composition is relatively simple, dominated by pyrite, chalcopyrite, sphalerite, and galena. Their origin is related to three evolutionary stages at increasing temperatures, and a subsequent stage associated with the Variscan deformation. The present paper summarizes the latest developments in the IPB and revises research areas requiring further investigation.

Microplastic assessment in aquaculture feeds: Analyzing polymer variability across commercial fishfeeds from three continents

This study analysed ten widely used commercial fishfeeds in aquaculture from six countries spanning three continents to assess microplastic (MP) contamination. MPs with an average abundance of 1130 ± 259.07 particles/kg and an average length of 2.64 ± 0.62 mm ( ± SE) were found in aquaculture feeds, with fibres (85 %) and fragments (15 %). The majority of these MPs were black. The abundance of MPs varied among the samples, with the highest in feed SP (26 %), followed by IF, GA, ELS, NT, EW, TB, GR, VR, and the least in HCF (3 %). Polymers identified consisted of Polyethylene terephthalates (PET, 20 %), Polyamide (PA, 30 %), Polymethyl methacrylate (PMMA), Polyurethane (PU), and Polystyrene (PS) with 15 % each, and Polypropylene (PP, 5 %). SEM-EDX analysis of fibres showed flakes, cracks, and pits and the presence of heavy metals Ni, Cu, Zn, Cr, Au, Hg, Cd, Ti, and Pb. Additionally, some fragments contained Nb (Niobium) alongside the naturally occurring elements. The Polymer Hazard Index (PHI) for the polymers in ten feeds was calculated, and nine were in the highly hazardous category (IV and V) with PHI values ranging from 400–394825. The work showcases the graveness of MPs in fishfeeds and advocates control measures to curtail MPs in fishfeeds for sustainable aquaculture production.

Comparative study of Ti/Al and Ti/Al/Ti/Au ohmic contacts to AlGaN/GaN heterostructures

We investigated the electrical properties and the ohmic contact formation considering Ti/Al and Ti/Al/Ti/Au ohmic contact metallization schemes on AlGaN/GaN heterostructures. The specific contact resistance of contacts was determined by characterizing the current–voltage relation from TLM measurement. The lowest value for the specific contact resistivity was obtained using Ti/Al/Ti/Au metallization. An interfacial TiN layer was monitored at the contact-AlGaN interface. TiN phases were found at both contacts, but the thickness in the Ti/Al/Ti/Au contact reached 8 nm, while the thickness in Ti/Al was thinner and discontinuous. The surface roughness of the Ti/Al/Ti/Au contact was determined as 8.17 nm and that of the Ti/Al contact as 36.23 nm. It was found that the spesific contact resistance depends on the atomic structure of the metal–semiconductor interface and composition and structure of the ohmic contact layers. These results showed that it is possible to achieve higher reliability and uniformity as well as lower contact resistance in AlGaN/GaN HEMTs with Ti/Al/Ti/Au contact compared to Ti/Al contact.

Triple junction excess energy in polycrystalline metals

The energetics of triple lines are often negligible in polycrystalline systems, but may play a significant role in the finest nanocrystals, and in fact lower the excess defect energies of those polycrystals. This paper develops a methodology to assess polycrystalline average grain boundary and triple junction excess energies for pure fcc metals Ni, Cu, Al, Pd, Pt, Ag and Au using embedded atom method potentials. It is found that there are correlations between the triple line energy and physical quantities such as grain boundary and dislocation line energy, but with a negative sign indicating that triple junctions reduce intergranular excess energy per area on average. The relationship with grain boundary energy is of order ∼−4.5 × 10−10 m, and the triple junction energy is about −1/12 of the dislocation line energy. Despite their low energy, triple junctions can significantly affect total system energy due to their high density in the finest nanocrystals; for example, 6-nm Pd nanocrystals have an effective intergranular energy of ∼0.83 J/m2 (compared with the large grain size limit of 0.93 J/m2), translating to a measurable bulk excess enthalpy of ∼6 kJ/mol. Such excess enthalpy is experimentally assessable, and the present framework can be used to measure triple junction energies. For instance, re-analyzing data of Lu and Sun (Phil. Mag., 1997) we obtain grain boundary and triple junction energies of 0.33 J/m2 and −3.0 × 10−10 J/m respectively for Selenium nanocrystals, which can be compared with modeled values of 0.76 J/m2 and −1.02 × 10−10 J/m by using our method with a published bond-order potential for Se.

Rotating Disk Electrode Studies of Benzaldehyde Oxidation on Group Ib Metals

Water electrolysis is a green means of producing hydrogen gas to be used as a fuel or reactant in key industrial processes such as ammonia production. The conventional system of oxygen evolution (OER) and hydrogen evolution (HER) suffers from slow kinetics at the anode and a high cell voltage limited by thermodynamics. One solution is to replace OER with another reaction such as an organic oxidation reaction that has a lower equilibrium potential and produces a valuable organic byproduct at the anode. Recent work has demonstrated that biomass-derived aldehydes such as furfural and 5-hydroxymethylfurfural can be selectively oxidized to their corresponding carboxylates and H2 on Cu-based anodes at low potentials (~0.1 VRHE) in alkaline media. In alkaline media, a hydroxide ion adds to the carbonyl carbon of an aldehyde molecule forming a gem diolate in solution phase. It is argued that dehydrogenation becomes more facile due to the weaker C-H bond of the gem diolate compared to the aldehyde form of the molecule. This may enable oxidation without the need for coadsorbed-OH. Additionally, aldehyde oxidation is only active on Au, Ag, and Cu electrodes at higher pHs.The aim of this work is to identify the conditions under which low potential oxidation of aldehydes and high anodic Faradaic efficiency to H2 occurs, namely, electrode material and applied potential. To avoid polymerization side reactions of furans in alkaline media, we studied benzaldehyde as a model compound which has also been shown to exhibit low potential oxidation and anodic H2. The activity (rate of aldehyde consumption) and selectivity (to anodic H2 versus H2O) were compared for the group Ib metals (Au, Ag, Cu), each of which demonstrates a relatively early onset potential (<0.4 VRHE) and generates anodic H2 at certain potentials. Rotating disk electrode studies with Koutecky-Levich analysis were conducted to separate mass transfer effects from kinetic current to compare the intrinsic activity of each electrode. Additionally, the average number electrons transferred per aldehyde molecule consumed was estimated from Koutecky-Levich analysis; the one-electron pathway combines the aldehyde hydrogens to H2 while the two-electron pathway requires an additional electron per aldehyde molecule to oxidize the hydrogen from the surface to form H2O. Rotating ring disk electrode studies were used to further validate the anodic H2 generation as a Pt ring was still able to oxidize H2 despite the presence of benzaldehyde. This was used as an additional means of estimating the selectivity to H2 as a function of potential.CVs for benzaldehyde oxidation on each metal are shown in Figure a. Peak current followed the order of Au > Ag >> Cu. Au reached a mass transfer limiting current, and Ag also showed an RPM dependence but did not reach full mass transfer limitations. Cu was the least active and did not show any mass transfer dependence. On the other hand, Cu has the earliest onset potential followed by Ag then Au. The average number of electrons transferred per aldehyde molecule according to RRDE measurements is shown in Figure b, where one electron represents H2 and two electrons represents H-oxidation to H2O. Cu had 100% selectivity to H2 over its entire potential window of activity (up to 0.45 VRHE). Au and Ag have high selectivity to H2 at low potentials but decreases to near zero H2 production in the range of 0.6-0.8 VRHE; the decrease in selectivity to H2 on Ag occurs slightly earlier than Au (~0.1 V). H2 selectivity is related to the inability of each metal to oxidize H to H2O at low potentials. Figure 1

Next Generation Heterogeneous 3D IC Chip Packaging

The demand for a faster and more efficient IC has been steadily increasing more than ever to accommodate the trend of Artificial Intelligence, Industry 4.0, Machine Learning, and Big Data. Traditionally, the semiconductor industry has kept up with demand of faster and more efficient IC by shrinking the size of transistor. As we approach a 1 nm transistor the technological challenge will be challenging to overcome as quantum tunneling becomes more pronounced and would decrease the reliability of the chip. To overcome this technological challenge, an advance packaging of 3D IC chip technology has been developed and delivered to market such as CoWoS (Chip-on-Wafer-on-Substrate) and InFO (Integrated Fan-Out). However, the aforementioned technology have their drawbacks with CoWoS uses interposer and TSV (through-silicon substrate via) which make it costly, time consuming, and wastes a lot of energy and InFO is limited in the number of layers it can accommodate for chiplets. Both of those technology are currently limited to 2 or 3 layer of IC and difficult to be modularize. In this study, we aim to develop a heterogeneous 3D IC package that can overcome the aforementioned problem which is modular, cost-effective, able to integrate chip from different manufacturers, and capable to stack more than 3 layers of ICs. This study has successfully completed the first stage of development by employing an advanced package consisting of Epoxy substrate with 200Å Ti/500Å Pt/1000Å Au metal interconnects, previously fabricated as a base for 3D stacking. Keywords : 3D IC Package, Advance Packaging, Modulable IC Packaging, Heterogeneous Integration Figure 1

Real-Time Tunable Gas Sensing Platform Based on SnO2 Nanoparticles Activated by Blue Micro-Light-Emitting Diodes

HighlightsBlue micro-light-emitting diodes (μLED)-integrated gas sensors were fabricated as monolithic structure by directly loading sensing materials onto the μLED.SnO2 nanoparticles are activated by blue μLED and exhibit outstanding sensitivity to NO2 at μ-Watt power levels.Noble metal (Au, Pd, Pt)-decorated SnO2 showed the tunable gas selectivity for 4 target gases under blue light illumination.

Experimental study of thermal transport across metal/h-BN interfaces: Comparison with metal/graphite interfaces

The continuing miniaturization of layered material electronics highlights the increasingly significant role of interfacial thermal conductance (G) in the efficient nanoscale heat dissipation in these electronics. Despite its importance, the mechanisms of thermal transport across the interfaces of layered materials and the underlying substrate remain unclear. In this work, we comprehensively investigate the interfacial thermal and phonon transport across layered-material interfaces through our ultrafast pump-probe measurements and detailed calculations on G for the interfaces of hexagonal boron nitride (h-BN), one of the most promising layered materials. We first experimentally measure Gc for interfaces between four different metals (Al, Pd, Au and Ti) and h-BN along c-axis using time-domain thermoreflectance (TDTR) from 80 to 300 K. We successfully achieve high accuracy of our measurements with uncertainty <10 % through using the carefully chosen high modulation frequency (15.6 MHz) and relatively large laser spot size (22.5 μm). We find that the measured Gc for interfaces between metals (except Al) and (100) plane of h-BN is lower than that of metal/graphite interfaces, while Gc of Al/h-BN is comparable to that of Al/graphite interfaces. Furthermore, together with our proposed anisotropic model and the diffuse mismatch model (DMM), we determine the transmission probability for the various metal/h-BN interfaces and find that the strong bonding strength enhances the phonon transmission across Ti/h-BN or Ti/graphite interfaces. Finally, we predict the orientation-dependent thermal conductance (i.e., the different interfacial thermal transport along c-axis (Gc) and in-plane (Gab) crystallographic orientations) for both metal/h-BN and metal/graphite. We find Gab between metals and (001) plane is up to 2–3 times higher than Gc. This can be attributed to the highly anisotropic elastic properties in the h-BN and graphite. This work provides important insight into the phonon transmission mechanisms across metal/h-BN interfaces, and thus contributes significantly to the thermal management of layered material electronics.

Base Metals Induced Oxygen Migration and Adjustable Performance in Multifunctional Oxide Heterojunction Devices

AbstractThe chemical and electronic interactions at metal/oxide heterojunctions is pivotal in determining the electronic properties of oxide devices utilized in microelectronics, catalysis, and photovoltaic systems. In this study, interfacial oxidation migrations within a model heterostructure system, consisting of a La0.7Sr0.3MnO3 film overlaid by various metallic (Ti, Al, Cu, Ag, and Au) ultrathin layers are systematically investigated. It is experimentally demonstrated that at elevated deposition temperature, the oxygen‐active ultrathin overlayers of base metals such as Ti and Al significantly derive oxygen from the underlying La0.7Sr0.3MnO3 film, inducing a perovskite to brownmillerite phase transition in the underlying functional oxide film. Conversely, no structural transitions are observed for La0.7Sr0.3MnO3 film when it is capped by noble metals (Au, Ag), which possess relative high oxidation formation energy. These observations are crucial for the development of novel crystalline and electronic architectures in metal/oxide heterostructures, offering a refined approach to modulate interfacial reactivity without compromising the functionality of oxide‐based heterojunction devices.

Dynamic multicolor electrochromic skin in high-brightness flexible WO3/Au asymmetric Fabry–Perot nanocavity fabricated on Nylon 66 porous substrate

Recently, the Fabry–Perot (F–P) cavity electrochromic devices, which are constructed by combining nano-size inorganic electrochromic material WO3 and reflective metal layers, have attracted considerable attention due to their potentials in the fields of dynamic multicolor displays and active camouflage. However, in the few studies that have been reported, the peak reflectance of flexible F–P cavity multicolor electrochromic devices in the visible wavelength band is generally lower than 30 %, which limits their reflective display and camouflage effects in high-brightness environments. Thus, we have combined multicolor reflective electrochromic electrodes in WO3/Au asymmetric F–P nanocavity constructed by magnetron sputtering on a Nylon 66 porous substrate with a highly transparent UV-cured gel electrolyte and a PET plastic sealing procedure. As a result, a flexible and dynamic multicolor electrochromic skin with high reflectance (Rmax＞50 %) and excellent flexibility (bending radius of 4 mm) has been fabricated. The WO3 electrochromic layer at the top works as the dynamic dielectric layer in the broadband absorption Fabry–Perot cavity, and the inert metal Au layer at the bottom works as the reflective layer. The WO3/Au asymmetric F–P cavity can acutely capture the variation in optical constants of WO3 due to the thickness change and electric-driven effects. This cavity facilitates the selective reflection and absorption of the energy distribution of the spectrum after the induced interferometric resonance. As a result, the cavity exhibits a rich array of structural colors, including ocher, taupe, yellow, orange, green, and violet. The electrochromic skin exhibits a fast switching time and maintains 99.43 % of the optical modulation amplitude (ΔR) after 110 coloring/bleaching cycles. It provides a potential option in the field of flexible high-brightness reflective displays and dynamic camouflage in the future.

Spontaneous Emulsification of Organometallic Complexes Applied to the Synthesis of Nanocapsules Active for H2 Release from Ammonia-Borane.

Herein, we achieved spontaneous emulsification of organometallic precursors to elaborate subμm metal nanocapsules after interfacial reduction. Depending on the proportion of the three components, water, solvent, and the metal precursor, either thermodynamically stable "surfactant-free microemulsions" (SFME) or metastable Ouzo emulsions are formed. We investigated the catalytic transition metals Au, Pd, and Pt, individually or combined, and stabilized by various ligands. Upon reduction of the precursors, either shells of discrete nanoparticles (NPs) or continuous shells were obtained, for the SFME and Ouzo emulsions, respectively. The Au/Pd mixed emulsions lead to a unique structural morphology, in which the Au-Pd nanoparticles are embedded in a continuous submicronic metal shell. The AuNPs are available to grow larger particles within the NP shell using a seeded growth approach. The water-stable and surfactant-free nanocapsules are appealing as catalysts, and, as such, were evaluated for the hydrolysis of ammonia-borane as a promising catalytic strategy for H2 release from an H-high-content storage material. This work establishes for the first time a genuine activity of water-compatible gold colloids for this reaction.