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We use CeO x -TiO2 hetero-interfaces generated on the surface of CeO x -TiO2 hybrid oxide supporting powders to stabilize Au single-atoms (SAs) with excellent low-temperature activity toward CO oxidation. Based on intriguing density functional theory calculation results on the preferential formation of Au-SAs at the CeO x -TiO2 interfaces and the high activity of Au-SAs toward the Marsâ€"van Krevelen type CO oxidation, we synthesized a Au/CeO x -TiO2 (ACT) catalyst with 0.05 wt.% of Au content. The Au-SAs stabilized at the CeO x -TiO2 interfaces by electronic coupling between Au and Ce showed improved low-temperature CO oxidation activity than the conventional Au/TiO2 control group catalyst. However, the light-off profile of ACT showed that the early activated Au-SAs are not vigorously participating in CO oxidation. The large portion of the positive effect on the overall catalytic activity from the low activation energy barrier of ACT was retarded by the negative impact from the decreasing active site density at high temperatures. We anticipate that the low-temperature activity and high-temperature stability of Au-SAs that stand against each other can be optimized by controlling the electronic coupling strength between Au-SAs and oxide clusters at the Au-oxide-TiO2 interfaces. Our results show that atomic-precision interface modulation could fine-tune the catalytic activity and stability of Au-SAs. [ABSTRACT FROM AUTHOR]

The formation of the insulating A1O[sub x] tunnel barrier is a critical and sensitive process in magnetic tunnel junctions. Both the natural oxidation and the plasma oxidation methods were employed to fabricate the A1O[sub x] insulating layer in this study. In the natural oxidation, the A1 layer was exposed to pure oxygen gas at 20 Torr for up to 50 min to produce the A10[sub x] tunnel barrier. It was revealed by high resolution transmission electron microscopy that the oxidation occurred preferentially through the grain boundary of A1 grains. Also, the A10[sub x] grains expanded isotropically when fully oxidized, thereby making the surface of the A1O[sub x] layer modulated. In plasma oxidation, the oxygen plasma was used at 20 mTorr of pure oxygen gas for up to 30 s and the flat A10[sub x] layer formed uniformly on the A1 layer. It had sharp interfaces with the underlying metallic A1 and the rate of oxide layer growth decreased as the oxidation proceeded. [ABSTRACT FROM AUTHOR]

Aggregates of amyloidogenic peptides are involved in the pathogenesis of several degenerative disorders. Herein, an iridium(III) complex, Ir-1, is reported as a chemical tool for oxidizing amyloidogenic peptides upon photoactivation and subsequently modulating their aggregation pathways. Ir-1 was rationally designed based on multiple characteristics, including 1) photoproperties leading to excitation by low-energy radiation; 2) generation of reactive oxygen species responsible for peptide oxidation upon photoactivation under mild conditions; and 3) relatively easy incorporation of a ligand on the IrIII center for specific interactions with amyloidogenic peptides. Biochemical and biophysical investigations illuminate that the oxidation of representative amyloidogenic peptides (i.e., amyloid-β, α-synuclein, and human islet amyloid polypeptide) is promoted by light-activated Ir-1, which alters the conformations and aggregation pathways of the peptides. Additionally, their potential oxidation sites are identified as methionine, histidine, or tyrosine residues. Overall, our studies on Ir-1 demonstrate the feasibility of devising metal complexes as chemical tools suitable for elucidating the nature of amyloidogenic peptides at the molecular level, as well as controlling their aggregation. [ABSTRACT FROM AUTHOR]

To synthesize low-cost, highly conductive metal nanoparticles for inkjet printing materials, we synthesized Sn-Ag bimetallic nanoparticles using a polyol process with poly(vinyl pyrrolidone). Because a surface oxidation layer forms on Sn nanoparticles, various compositions of Sn- xAg [ x = 0, 20, 40, 60, 80, 100 (wt%)] nanoparticles were synthesized and characterized for the purpose of removing the β-Sn phase. The results of XPS, TEM, and XRD analyses confirm that the formation of a bimetallic phase, such as AgSn or AgSn, hinders the β-Sn phase and, consequently, leads to the removal of the surface oxidation layer. To measure the sheet resistance of various compositions of Sn-Ag nanoparticles, we made the ink that contains Sn-Ag by dispersing 10 wt% of Sn-Ag nanoparticles in methanol. The sheet resistance is decreased by the conductive Sn-Ag phases, such as the fcc, AgSn, and AgSn phases, but sharply increased by the low-conductive Sn nanoparticles and the surface oxidation layer on the Sn nanoparticles. The sheet resistance results confirm that 80Ag20Sn and 60Ag40Sn bimetallic nanoparticles are suitable candidates for inkjet printing materials. [ABSTRACT FROM AUTHOR]

In a magnetic tunnel junction, the formation of an insulator is sensitive and critical to the stable performance and reproducibility of the junction. The oxidation path and the microstructural change with time of the insulator in natural oxidation have been studied by the high-resolution transmission electron microscopy. It has been observed that the oxidation path is primarily through the grain boundary at an early stage of oxidation and then through the grains at a later stage. The morphology of the oxide layer was rugged and modulated. There also occurred an isotropic volume expansion with increased oxidation. It was observed that the ferromagnetic Co layer below an insulator was partially oxidized because of the preferred grain boundary oxidation. When this multilayer was annealed, the locally oxidized Co layer was reduced and the metallic layer formed as a continuous film type, thereby improving the interface. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of Ti x WTaVCr alloys for high-temperature and fusion plasma-facing applications are presented in this study. Specimens of Ti x WTaVCr containing 0 to 7 at% Ti were prepared via spark plasma sintering of an elemental powder mixture at 1500 °C. Characterization of sintered samples via X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy revealed increased formation of a BCC solid solution due to the addition of up to 7 at% Ti. Mechanical characterizations of the Ti x WTaVCr alloys indicate that they are harder and stronger than several reported high-entropy alloys. The alloy that contained 7 at% Ti also exhibited improved oxidation resistance in air at 1000 °C. Its improved strength, hardness, and oxidation resistance suggest future applications for this high-entropy alloy in high-temperature and nuclear applications. [ABSTRACT FROM AUTHOR]