Robust Metallic Actuators Based on Nanoporous Gold Rapidly Dealloyed from Gold–Nickel Precursors

Dealloyed nanoporous gold (np-Au) has applications as oxygen reduction catalysis in Li-air batteries and fuel cells, or as actuators to convert electricity into mechanical energy. However, it faces the challenges of coarsening-induced structure instability, mechanical weakness due to low relative densities, and slow dealloying rates. Here, monolithic np-Au is dealloyed from a single-phase Au₂₅Ni₇₅ solid-solution at a one-order faster dealloying rate, ultra-low residual Ni content, and importantly, one-third more relative density than np-Au dealloyed from conventional Au₂₅Ag₇₅. The small atomic radius and low dealloying potential of the sacrificing element Ni are intrinsically beneficial to fast produce high relative density np-Au, as predicted by a general model for dealloying of binary alloys and validated by experiments. Stable, durable, and reversible actuation of np-Au takes place under cyclic potential triggering in alkaline and acidic electrolytes with negligible coarsening-induced strain-shift. The thermal and mechanical robustness of bulk np-Au is confirmed by two-order slower ligament coarsening rates during annealing at 300 °C and 45 MPa macroscopic yielding strength distinctive from the typical early onset of plastic yielding. This article opens a rich direction to achieve high relative density np-Au which is essential for porous network connectivity, mechanical strength, and nanostructure robustness for electrochemical functionality.     

CrN和CrN/Ag涂层的真空高温摩擦磨损性能*

为改善涂层在真空、高温等苛刻条件下的摩擦学性能，利用中频直流磁控溅射技术在硅片和316L不锈钢上沉积了CrN和CrN/Ag涂层，利用扫描电镜、透射电镜和X射线衍射仪对涂层的成分及相结构进行了表征，通过划痕测试仪、纳米压痕仪和摩擦磨损试验机测试了涂层的力学及摩擦学性能。结果表明：添加Ag元素以后，CrN/Ag涂层硬度及承载能力有所减小，但结合强度增加；真空高温环境下CrN与CrN/Ag涂层摩擦因数随温度升高呈下降趋势，其中CrN涂层通过软化镀层减小剪切强度和阻力，从而减小摩擦因数，CrN/Ag涂层主要通过高温产生的热驱动力诱导表面Ag润滑膜的形成来减小摩擦因数；CrN涂层依靠自身剪切特性参与摩擦，而CrN/Ag涂层在真空高温下具有自润滑和持续润滑性能，作为自润滑零部件具有潜在的应用价值。     

Selective and efficient hydrogen separation of Pd–Au–Ag ternary alloy membrane

The widespread demand for clean energy stimulates great interest to hydrogen energy with high energy density and conversion efficiency. Separation technologies by membranes are increasingly applied for hydrogen separation because of its excellent performance and low consumption. In this work, density functional theory simulations is used to study hydrogen separation of Pd–Au–Ag membrane, and the performance of Pd–Au alloy is also compared and discussed. The results indicate that Pd–Au alloy shows superior selectivity to H₂ gas over CO, N₂, CH₄, CO₂ and H₂S gases, which is in line with experimental results. In particular, the separation selectivity of Pd–Au–Ag to H₂ is significantly greater than those for Pd–Au alloy and several currently reported materials. Moreover, the permeability of H₂ in Pd–Au–Ag exceeds the limits for industrial production at deferent temperatures. Our calculations demonstrate that Pd–Au–Ag alloy present excellent performance as a promising membrane for hydrogen separation.     

碘化多壁碳纳米管制备含有Ag/MWCNTs复合材料的银-环氧树脂浆料

提出一种将多壁碳纳米管碘化后制备银/多壁碳纳米管（Ag/MWCNTs）复合材料的方法。通过球磨对碘化多壁碳纳米管进行了功能化，并通过透射电子显微镜（TEM）、X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、拉曼光谱和热重分析（TG）对其进行了表征。结果表明，经碘化处理后，银纳米粒子（Ag-NPs）能更好地粘附在碳纳米管表面，改善了银纳米粒子与碳纳米管之间的连接。羟基（-OH）基团的伸缩振动明显增强，激活了碳纳米管的表面，增加了碳纳米管表面Ag⁺形核的数量。在260 ℃以下，Ag/MWCNTs复合材料的质量损失小于MWCNTs的质量损失。最后，制备了银-环氧树脂浆料，发现使用Ag/MWCNTs复合物制备的浆料具有最低的电阻率和最高的热导率。     

Ultrathin Dual‐Scale Nano‐ and Microporous Membranes for Vascular Transmigration Models

Selective cellular transmigration across the microvascular endothelium regulates innate and adaptive immune responses, stem cell localization, and cancer cell metastasis. Integration of traditional microporous membranes into microfluidic vascular models permits the rapid assay of transmigration events but suffers from poor reproduction of the cell permeable basement membrane. Current microporous membranes in these systems have large nonporous regions between micropores that inhibit cell communication and nutrient exchange on the basolateral surface reducing their physiological relevance. Here, the use of 100 nm thick continuously nanoporous silicon nitride membranes as a base substrate for lithographic fabrication of 3 µm pores is presented, resulting in a highly porous (≈30%), dual‐scale nano‐ and microporous membrane for use in an improved vascular transmigration model. Ultrathin membranes are patterned using a precision laser writer for cost‐effective, rapid micropore design iterations. The optically transparent dual‐scale membranes enable complete observation of leukocyte egress across a variety of pore densities. A maximal density of ≈14 micropores per cell is discovered beyond which cell–substrate interactions are compromised giving rise to endothelial cell losses under flow. Addition of a subluminal extracellular matrix rescues cell adhesion, allowing for the creation of shear‐primed endothelial barrier models on nearly 30% continuously porous substrates.     

Thermal annealing induced cave in and formation of nanoscale pits in Ag–TiO2 plasmonic nanocomposite thin film

Ag–TiO₂ nanocomposite thin films on silica glass were prepared through thermal evaporation in combination with RF magnetron sputtering. Thermal annealing induced changes in the optical, morphological and structural properties of Ag–TiO₂ nanocomposites were examined using optical absorption, photoluminescence spectroscopy, Raman spectroscopy, FESEM, AFM and XRD. FESEM and AFM studies revealed cave in of the Ag–TiO₂ thin film at various places leading to the formation nanoscale pits upon thermal annealing at 600 °C. The computed average size of pits was found to be 54 nm. Raman studies indicated 600 °C annealing induced transformation of anatase phase of TiO₂ into anatase/rutile mixed phase TiO₂. Optical absorption spectra showed systematic changes due to the effects of mixed phase formation and variation in the plasmonic behavior upon annealing. PL results of the as deposited Ag–TiO₂ thin film showed peaks at 377, 402, 432 and 486 nm. PL studies of Ag–TiO₂ nanocomposites treated at different annealing temperatures revealed changes in defect concentration in TiO₂. The tentative mechanism for the creation of nanoscale pits in Ag–TiO₂ thin film through thermal annealing was proposed.     

Embedding Ag or Au nanoparticles within the nano-sized wall of YbPO4:Er3+ inverse opals and resulting enhanced upconversion luminescence

Metal nanoparticles preparation in the interior of nanoscale skeleton of inverse opals made up of crystallized matrix is more difficult than the preparation of pure inverse opals. In the present work, the Ag or Au nanoparticles embedded YbPO₄:Er³⁺ inverse opals were prepared by a simple approach, which involved the infiltration of opal template by using the transparent YbPO₄:Er³⁺ sol including silver nitrate or chloroauric acid and the sintering at high temperature. The 20–30?nm Au or 5–10?nm Ag nanoparticles were formed in the interior of nanoscale skeleton in the YbPO₄:Er³⁺ inverse opals, and the Ag or Au nanoparticles embedded YbPO₄:Er³⁺ inverse opals were prepared. The influence of Ag or Au nanoparticles on the upconversion photoluminescence of YbPO₄:Er³⁺ inverse opal was studied, and the upconversion luminescence enhancement induced by the Ag or Au nanoparticles was observed. The mechanisms of upconversion luminescence enhancement of YbPO₄:Er³⁺ inverse opals induced by Ag or Au nanoparticles were discussed. The enhancement of upconversion luminescence induced by Ag nanoparticles was attributed to the enhancement of the excitation field, and the enhancement of upconversion emission induced by Au nanoparticles was related to the increasing of the radiation decay rate of Er³⁺.     

Plasmonic-excitonic multi-hybrid glass-based nanocomposites incorporating Ag plus core-shell CdSe/CdS and alloyed CdSxSe1−x nanoparticles

Successful fabrication of glass-based hybrid nanocomposites (GHNCs) incorporating Ag, core-shell CdSe/CdS and CdS_xSe_1?x nanoparticles (NPs) is herein reported. Both metallic (Ag) and semiconductor (CdSe/CdS) NPs were pre-synthesized, suspended in colloids and added into the sol-gel reaction medium which was used to fabricate the GHNCs. During fabrication of the nanocomposites a fraction (20–60%) of core-shell CdSe/CdS NPs was alloyed into CdS_xSe_1?x (0.20 < x < 0.35) NPs without changing morphology. Modulation of in situ alloying is possible via the relative content of organics added into the sol-gel protocol. Within colloids Ag (core-shell CdSe/CdS) NPs presented average diameter and polydispersity index of 49.5 nm (4.2 nm) and 0.41 (0.21), respectively. On the other hand, the Ag (core-shell CdSe/CdS) NPs’ average diameter and polydispersity index assessed from the GHNCs were respectively 51.5 nm (4.1 nm) and 0.43 (0.25), revealing negligible aggregation of the nanophases within the glass template. The new GHNCs herein introduced presented two independent excitonic transitions associated to homogenously dispersed semiconductor NPs, peaking around 420 nm (core-shell CdSe/CdS) and 650 nm (CdS_xSe_1?x) and matching the plasmonic resonance (Ag NPs) in the 400–500 nm range. We envisage that the new GHNCs represent very promising candidates for superior light manipulation while illuminated with multiple laser beams in quantum interference-based devices.     

Electrodeposited and characterization of Ag–Sn–S semiconductor thin films

Thin film of silver tin sulfides (Ag–Sn–S) has been deposited on indium tin oxide coated glass (ITO) substrates using potentiostatic cathodic electrodeposition technique. New procedure for the growth of Ag–Sn–S film is presented. An electrolyte solution containing Silver Nitrate (AgNO₃), Tin(II) Chloride (SnCl₂) and Sodium Thiosulfate (Na₂S₂O₃)in acidic solution (pH ~2) and at temperature of the bath 55 °C were used for the growth of Ag–Sn–S thin film. Prior to the deposition, a cyclic voltammetry technique was performed in binary (Ag–S, Sn–S) and ternary (Ag–Sn–S) systems. This study was carried out to examine the behavior of electroactive species at the electrode surface. Based on these results, the cathodic applied potential was fixed at −1000 mV versus Ag/AgCl to obtain a uniform and good adhesion of ternary thin film. After that, structural, morphological and optical performances of films have been investigated. The X-ray diffraction patterns of the samples demonstrate the presence of the orthorhombic phase of Ag₈SnS₆ at applied potential of −1000 mV versus Ag/AgCl. Based on the scanning electron microscopy (SEM), it was found that the surface morphology and grain size were strongly influenced by the presence of Sn and/or Ag in the electrolyte bath. The band gaps of binaries and ternary compound are evaluated from optical absorption measurements. Band gap of Ag₈SnS₆ determined from transmittance spectra is in the range 1.56 eV. Flat-band potential and free carrier concentration have been determined from Mott–Schottky plot and are estimated to be around 0.18 V and 2.21×10¹⁴ cm⁻³ respectively. The photoelectrochemical test of Ag₈SnS₆ was studied and the experimental observations are discussed in detail.