Surface plasmonic spectroscopy revealing the oxidation dynamics of copper nanowires embedded in polycarbonate ion-track templates

Chemical stability of metal nanowires is a great concern for many practical applications. Metal nanowires deposited in the pores of various templates have been considered oxidization-resistant because the templates provide natural protection. Here we present the first ever attempt to investigate the oxidation behavior of copper nanowires supported in a template matrix using a surface-plasmon-based optical spectroscopy method combined with high-resolution transmission electron microscopy (TEM). Although the nanowires are protected by being embedded in the polymer template matrix, unexpected oxidation is clearly observed in TEM imaging, which unambiguously reveals the possible underlying oxidation mechanism responsible for the oxidation passivation. By measuring the optical properties with localized surface plasmon resonance spectroscopy, the oxidation behavior of the copper nanowires is studied as a function of storage time in both air and vacuum and thus uncovers the oxidation dynamics of copper. Finally, we demonstrate that the oxidation can be entirely prevented by sealing the open ends of the wires, which is confirmed by monitoring the electrical resistance of single nanowires. Our results have significant importance in understanding the oxidation behavior of metal nanostructures in general and also provide useful guidelines to estimate their electrical functionality in optoelectronic devices.Department of Applied Physic

Experimentalstudy of metasurface-based nanoantennas array fabricated using heavy ion tracking for biochemistry sensing

A novel metasurface-based nanoantennas array fabricated using a technique of heavy ion tracking is introduced. The technique has advantages of large area patterning, high aspect ratio of the nanoantennas, controllable length, and multi-choice of materials etc. Fabrication process, numerical calculation and optical near-field characterization of the structure are presented. Evidenced by probing results of our near-field scanning optical microscope, the sharp nanoantennas with high aspect ratio can scattering as tiny hot-spots with beam sopt size as small as 50 nm in near-field region. Sensitivity of 137 nm/RIU is obtained for sensing ethanol on the basis of spectroscopy results. Our theoretical and experimental results demonstrate that this structure not only is capbale of acting as a biochemistry sensors for immunoassay and cell/molecular spectrocopy, but also has potential applications in bioimaging due to the nanofocusing hot-spots formed by the sharp nano-pillars array with high-aspect ratio

Catalytic deoxygenation of carboxyl compounds in the hydrothermal liquefaction crude bio-oil via in-situ hydrogen supply by CuO-CeO2/gamma-Al2O3 catalyst

Hydrothermal liquefaction (HTL) has drawn great attention as a potential method to produce bio-oil from biomass waste. However, bio-crude from HTL shows undesired high-oxygen content and needs further deoxygenation upgrading. Herein, stearic acids as a model carboxylic compounds in HTL bio-crude was employed to investigate catalytic deoxygenation performance. Results showed that (CuO)(10)-CeO2/gamma-Al2O3 had the most superior catalytic deoxygenation performance for the stearic acids. The maximum stearic acid conversion rate (96.36%) and total hydrocarbon yield (88.79%) were obtained at 300 degrees C, 12 h, ratio of stearic acid to water 1 : 4. The main catalytic deoxygenation pathways were proposed: carbon monoxide generation (decarbonylation) - in-situ hydrogen generation (water-gas shift) - short-chain fatty acid generation (hydrogenolysis) - n-alkanes generation (decarboxylation, hydrodeoxygenation and hydrogenation). DFT calculation elucidated that CuO-CeO2 reduced the activation energy from 24.8 kcal mol(-1) (vacuum) to 15.0 kcal mol(-1) (catalytic). Thus, deoxygenation via CuO-CeO2/gamma-Al2O3 would be an effective method for upgrading HTL bio-crude

Temperature- and Angle-Dependent Magnetic Properties of Ni Nanotube Arrays Fabricated by Electrodeposition in Polycarbonate Templates

Parallel arrays of Ni nanotubes with an external diameter of 150 nm, a wall thickness of 15 nm, and a length of 1.2 ± 0.3 µm were successfully fabricated in ion-track etched polycarbonate (PC) templates by electrochemical deposition. The morphology and crystal structure of the nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Structural analyses indicate that Ni nanotubes have a polycrystalline structure with no preferred orientation. Angle dependent hysteresis studies at room temperature carried out by using a vibrating sample magnetometer (VSM) demonstrate a transition of magnetization between the two different magnetization reversal modes: curling rotation for small angles and coherent rotation for large angles. Furthermore, temperature dependent magnetic analyses performed with a superconducting quantum interference device (SQUID) magnetometer indicate that magnetization of the nanotubes follows modified Bloch’s law in the range 60–300 K, while the deviation of the experimental curve from this law below 60 K can be attributed to the finite size effects in the nanotubes. Finally, it was found that coercivity measured at different temperatures follows Kneller’s law within the premises of Stoner–Wohlfarth model for ferromagnetic nanostructures

Surface Modification and Damage of MeV-Energy Heavy Ion Irradiation on Gold Nanowires

Gold nanowires with diameters ranging from 20 to 90 nm were fabricated by the electrochemical deposition technique in etched ion track polycarbonate templates and were then irradiated by Xe and Kr ions with the energy in MeV range. The surface modification of nanowires was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations. Different craters with and without protrusion on the gold nanowires were analyzed, and the two corresponding formation mechanisms, i.e., plastic flow and micro-explosion, were investigated. In addition, the sputtered gold nanoparticles caused by ion irradiation were studied and it was confirmed that the surface damage produced in gold nanowires was increased as the diameter of the nanowires decreased. It was also found that heavy ion irradiation can also create stacking fault tetrahedrons (SFTs) in gold nanowires and three different SFTs were confirmed in irradiated nanowires. A statistical analysis of the size distribution of SFTs in gold nanowires proved that the average size distribution of SFT was positively related to the nuclear stopping power of incident ions, i.e., the higher nuclear stopping power of incident ions could generate SFT with a larger average size in gold nanowires

Arabidopsis Plastidial Folylpolyglutamate Synthetase Is Required for Seed Reserve Accumulation and Seedling Establishment in Darkness

<div><p>Interactions among metabolic pathways are important in plant biology. At present, not much is known about how folate metabolism affects other metabolic pathways in plants. Here we report a T-DNA insertion mutant (<i>atdfb-3</i>) of the plastidial folylpolyglutamate synthetase gene (<i>AtDFB</i>) was defective in seed reserves and skotomorphogenesis. Lower carbon (C) and higher nitrogen (N) content in the mutant seeds than that of the wild type were indicative of an altered C and N partitioning capacity. Higher levels of organic acids and sugars were detected in the mutant seeds compared with the wild type. Further analysis revealed that <i>atdfb-3</i> seeds contained less total amino acids and individual Asn and Glu as well as NO₃⁻. These results indicate significant changes in seed storage in the mutant. Defects in hypocotyl elongation were observed in <i>atdfb-3</i> in darkness under sufficient NO₃⁻ conditions, and further enhanced under NO₃⁻ limited conditions. The strong expression of <i>AtDFB</i> in cotyledons and hypocotyl during early developmental stage was consistent with the mutant sensitivity to limited NO₃⁻ during a narrow developmental window. Exogenous 5-formyl-tetrahydrofolate completely restored the hypocotyl length in <i>atdfb-3</i> seedlings with NO₃⁻ as the sole N source. Further study demonstrated that folate profiling and N metabolism were perturbed in <i>atdfb-3</i> etiolated seedlings. The activity of enzymes involved in N reduction and assimilation was altered in <i>atdfb-3</i>. Taken together, these results indicate that AtDFB is required for seed reserves, hypocotyl elongation and N metabolism in darkness, providing novel insights into potential associations of folate metabolism with seed reserve accumulation, N metabolism and hypocotyl development in Arabidopsis.</p></div