Low-temperature annealing of 2D Ti3C2Tx MXene films using electron wind force in ambient conditions

Two-dimensional transition metal carbides and nitrides, known as MXenes, are layered materials with unique functionalities which make them suitable for applications such as energy storage devices, supercapacitors, electromagnetic interference shielding, and wireless communications. Since they are wet-processed, MXenes need annealing to improve their electrical conductivity. The extent of annealing highly depends on temperature; however, higher temperatures can also impact the resulting phases and structure. In this study, we present a non-thermal annealing process utilizing an electron wind force (EWF) method in ambient conditions. This process is demonstrated on freestanding Ti3C2Tx films, where we show up to 70% decrease in resistivity at temperatures below 120 °C compared to conventional thermal annealing methods. MXene structures before and after annealing are analyzed using Raman spectroscopy and ex situ and in situ X-ray diffraction. Surface terminations and intra-flake defects modification in Ti3C2Tx layers after EWF annealing impart better electrical conductivity to MXene film than the non-annealed films

Morphology Characterization of Argon-Mediated Epitaxial Graphene on C-face SiC

Epitaxial graphene layers were grown on the C-face of 4H- and 6H-SiC using an argon-mediated growth process. Variations in growth temperature and pressure were found to dramatically affect the morphological properties of the layers. The presence of argon during growth slowed the rate of graphene formation on the C-face and led to the observation of islanding. The similarity in the morphology of the islands and continuous films indicated that island nucleation and coalescence is the growth mechanism for C-face graphene.Comment: 12 pages, 4 figure

Emergent Spin Phenomena in Air-Stable, Atomically Thin Lead

A stable platform to synthesize ultrathin heavy metals, with a strong interfacial Rashba effect, could lead to high efficiency charge-to-spin conversion for next-generation spintronics. Here we report wafer-scale synthesis of air-stable, epitaxially registered monolayer Pb on SiC (0001) via confinement heteroepitaxy (CHet). The highly asymmetric interfacial bonding in this heavy metal system lends to strong Rashba spin-orbit coupling near the Fermi level. Additionally, the system's air stability enables ex-situ spin torque ferromagnetic resonance (ST-FMR) measurements that demonstrate charge-to-spin conversion in CHet-based 2D-Pb/ferromagnet heterostructures and a 1.5x increase in the effective field ratio compared to control samples.Comment: 17 pages, 4 figures. Supporting Information included (20 pages, 9 figures, 1 table

Multi-wavelength Raman microscopy of nickel-based electron transport in cable bacteria

Cable bacteria embed a network of conductive protein fibers in their cell envelope that efficiently guides electron transport over distances spanning up to several centimeters. This form of long-distance electron transport is unique in biology and is mediated by a metalloprotein with a sulfur-coordinated nickel (Ni) cofactor. However, the molecular structure of this cofactor remains presently unknown. Here, we applied multi-wavelength Raman microscopy to identify cell compounds linked to the unique cable bacterium physiology, combined with stable isotope labeling, and orientation-dependent and ultralow-frequency Raman microscopy to gain insight into the structure and organization of this novel Ni-cofactor. Raman spectra of native cable bacterium filaments reveal vibrational modes originating from cytochromes, polyphosphate granules, proteins, as well as the Ni-cofactor. After selective extraction of the conductive fiber network from the cell envelope, the Raman spectrum becomes simpler, and primarily retains vibrational modes associated with the Ni-cofactor. These Ni-cofactor modes exhibit intense Raman scattering as well as a strong orientation-dependent response. The signal intensity is particularly elevated when the polarization of incident laser light is parallel to the direction of the conductive fibers. This orientation dependence allows to selectively identify the modes that are associated with the Ni-cofactor. We identified 13 such modes, some of which display strong Raman signals across the entire range of applied wavelengths (405–1,064 nm). Assignment of vibrational modes, supported by stable isotope labeling, suggest that the structure of the Ni-cofactor shares a resemblance with that of nickel bis(1,2-dithiolene) complexes. Overall, our results indicate that cable bacteria have evolved a unique cofactor structure that does not resemble any of the known Ni-cofactors in biology.BT/Environmental Biotechnolog

Data from: Fat in the leg: function of the expanded hind leg in gasteruptiid wasps (Hymenoptera: Gasteruptiidae)

Among some of the most unusual traits of the gasteruptiid wasps is their unique hovering flight and the expansion of their hind tibiae. Tibial expansions in female parasitoid hymenopterans often involve an enlarged sensory structure for vibration detection, the subgenual organ, thus enabling refined substrate-borne detection of concealed hosts. In the present paper, we utilize a combination of microscopy, chemical analysis, gene expression, and behavior to explore the function of the expanded hind tibia of gasteruptiid wasps. We find that the expanded hind tibia of gasteruptiids is filled largely with fat body, a cell cluster thought not typically to occur in insect legs. Based on its position relative to flexible tibial structures and the subgenual organ, the gasteruptiid tibial fat body may function to amplify vibrational signals. We show the tibial fat body to be filled with both trophocytes and, depending on gasteruptiid lineage, oenocytes. Transcriptomics reveals enrichment for fat-related genes more than expected in an insect leg and raises several additional possibilities for functions of fat in the leg including detoxification. Finally, our flight observations support the hypothesis that this structure may also function in balance and maneuvering in the unusual leg-dangling flight behavior of this wasp

Transcriptome_Analysis_additional_files

Transcriptome_Analysis_additional_file