Charge transfer dynamical processes at graphene-transition metal oxides/electrolyte interface for energy storage: Insights from in-situ Raman spectroelectrochemistry

Hybrids consisting of supercapacitive functionalized graphene (graphene oxide; GO reduced graphene oxide; rGO multilayer graphene; MLG, electrochemically reduced GO; ErGO) and three-dimensional graphene scaffold (rGO HT ; hydrothermally prepared) decorated with cobalt nanoparticles (CoNP), nanostructured cobalt (CoO and Co 3 O 4 ) and manganese (MnO 2 ) oxide polymorphs, assembled electrochemically facilitate chemically bridged interfaces with tunable properties. Since Raman spectroscopy can capture variations in structural and chemical bonding, Raman spectro-electrochemistry in operando i.e. under electrochemical environment with applied bias is employed to 1) probe graphene/metal bonding and dynamic processes, 2) monitor the spectral changes with successive redox interfacial reactions, and 3) quantify the associated parameters including type and fraction of charge transfer. The transverse optical (TO) and longitudinal optical (LO) phonons above 500 cm -1 belonging to Co 3 O 4 , CoO, MnO 2 and carbon-carbon bonding occurring at 1340 cm -1 , 1590 cm -1 and 2670 cm -1 belonging to D, G, and 2D bands, respectively, are analyzed with applied potential. Consistent variation in Raman band position and intensity ratio reveal structural modification, combined charge transfer due to localized orbital re-hybridization and mechanical strain, all resulting in finely tuned electronic properties. Moreover, the heterogeneous basal and edge plane sites of graphene nanosheets in conjunction with transition metal oxide \u27hybrids\u27 reinforce efficient surface/interfacial electron transfer and available electronic density of states near Fermi level for enhanced performance. We estimated the extent and nature (n- or p-) of charge transfer complemented with Density Functional Theory calculations affected by hydration and demonstrate the synergistic coupling between graphene nanosheets and nanoscale cobalt (and manganese) oxides for applied electrochemical applications

Cross-species analysis of viral nucleic acid interacting proteins identifies TAOKs as innate immune regulators

The cell intrinsic antiviral response of multicellular organisms developed over millions of years and critically relies on the ability to sense and eliminate viral nucleic acids. Here we use an affinity proteomics approach in evolutionary distant species (human, mouse and fly) to identify proteins that are conserved in their ability to associate with diverse viral nucleic acids. This approach shows a core of orthologous proteins targeting viral genetic material and species-specific interactions. Functional characterization of the influence of 181 candidates on replication of 6 distinct viruses in human cells and flies identifies 128 nucleic acid binding proteins with an impact on virus growth. We identify the family of TAO kinases (TAOK1, -2 and -3) as dsRNA-interacting antiviral proteins and show their requirement for type-I interferon induction. Depletion of TAO kinases in mammals or flies leads to an impaired response to virus infection characterized by a reduced induction of interferon stimulated genes in mammals and impaired expression of srg1 and diedel in flies. Overall, our study shows a larger set of proteins able to mediate the interaction between viral genetic material and host factors than anticipated so far, attesting to the ancestral roots of innate immunity and to the lineage-specific pressures exerted by viruses. Whether there are conserved nucleic acid (NA) binding proteins across species is not fully known. Using data from human, mouse and fly, the authors identify common binders, implicate TAOKs and show that these kinases bind NAs across species and promote virus defence in mammalian cells.We further thank Korbinian Mayr, Igor Paron, and Gaby Sowa for maintaining mass spectrometers and the MPI-B core facility, especially Judith Scholz, Leopold Urich, Sabine Suppmann, and Stephan Uebel, for support..

Single-Molecule Electrochemical Transistor Utilizing a Nickel-Pyridyl Spinterface

Using a scanning tunnelling microscope break-junction technique, we produce 4,4′-bipyridine (44BP) single-molecule junctions with Ni and Au contacts. Electrochemical control is used to prevent Ni oxidation and to modulate the conductance of the devices via nonredox gatingthe first time this has been shown using non-Au contacts. Remarkably the conductance and gain of the resulting Ni-44BP-Ni electrochemical transistors is significantly higher than analogous Au-based devices. Ab-initio calculations reveal that this behavior arises because charge transport is mediated by spin-polarized Ni <i>d</i>-electrons, which hybridize strongly with molecular orbitals to form a “spinterface”. Our results highlight the important role of the contact material for single-molecule devices and show that it can be varied to provide control of charge and spin transport

Demonstrating the highest supercapacitive performance of branched MnO(2) nanorods grown directly on flexible substrates using controlled chemistry at ambient temperature

A simple and efficient route for the growth of branched MnO2 nanorods on a flexible substrate at ambient temperature without templates is reported. The capacitive characteristics of the MnO2 nanorods presented here can be applied to produce inexpensive and high‐performance flexible supercapacitors on a large scale. Practical demonstration could show technological interest for the design of flexible electrodes in the industry.Deepak P. Dubal, Jong Guk Kim, Youngmin Kim, Rudolf Holze and Won Bae Ki

Spinel LiNixMn2-xO4 as cathode material for aqueous rechargeable lithium batteries

Ni-doped spinel LiNixMn2-xO4 (x = 0, 0.05, 0.10) samples were prepared by a sol-gel method. Structure and morphology of the samples were characterized by X-ray diffraction, scanning electron microscopy, Brunnauer-Emmet-Teller method and inductively coupled plasma atomic absorption spectrometry. The electrochemical behavior as a cathode material (positive mass) for aqueous rechargeable lithium batteries (ARLBs) was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, capacity measurements and cycling tests. The results show that the LiNi 0.1Mn1.9O4 electrode presents the best rate and cycling performance but low reversible capacity. In contrast, the LiNi 0.05Mn1.95O4 electrode shows a higher reversible capacity and relatively good cycling behavior. At a current density of 150 mA g-1, LiNi0.05Mn1.95O4 delivers a reversible capacity of 102 mA h g-1. At the relative high current densities of 1500 and 3000 mA g-1, the LiNi 0.05Mn1.95O4 electrode still delivers reversible capacities of 95.0 and 88.7 mA h g-1, respectively. The Ni-doped samples show excellent cycling life in 0.5 mol L-1 Li 2SO4 aqueous solution. The capacity retention ratios for LiNi0.05Mn1.95O4 and LiNi0.10Mn 1.90O4 after 800 cycles at a current density of 1500 mA g-1 are 79.4% and 91.1%, respectively, much higher than that for the undoped LiMn2O4 at only 37.8%. 2013 Elsevier Ltd. 2013 Elsevier Ltd. All rights reserved

Surface Active Sites: An Important Factor Affecting the Sensitivity of Carbon Anode Material towards Humidity

In this paper, we report that various kinds of active sites on graphite surface including active hydrophilic sites markedly affect the electrochemical performance of graphite anodes for lithium ion batteries under different humidity conditions. After depositing metals such as Ag and Cu by immersing and heat-treating, these active sites on the graphite surface were removed or covered and its electrochemical performance under the high humidity conditions was markedly improved. This suggests that lithium ion batteries can be assembled under less strict conditions and that it provides a valuable direction to lower the manufacturing cost for lithium ion batteries