RESUMO
The effects of sintering conditions on the microstructure, giant dielectric response, and electrical properties of Na1/2Y1/2Cu3Ti3.975Ta0.025O12 (NYCTTaO) were studied. A single phase of Na1/2Y1/2Cu3Ti4O12 and a high density (>98.5%) were obtained in the sintered NYCTTaO ceramics. First-principles calculations were used to study the structure of the NYCTTaO. Insulating grain boundaries (i-GBs) and semiconducting grains (semi-Gs) were studied at different temperatures using impedance and admittance spectroscopies. The conduction activation energies of the semi-Gs and i-GBs were Eg ≈ 0.1 and Egb ≈ 0.6 eV, respectively. A large dielectric constant (ε' ≈ 2.43-3.89 × 104) and low loss tangent (tanδ ≈ 0.046-0.021) were achieved. When the sintering temperature was increased from 1070 to 1090 °C, the mean grain size slightly increased, while ε' showed the opposite tendency. Furthermore, the breakdown electric field (Eb) increases significantly. As the sintering time increased from 5 to 10 h, the mean grain size did not change, whereas ε' and Eb increased. Variations in the dielectric response and non-linear electrical properties were primarily described by the intrinsic (Egb) and extrinsic (segregation of Na-, Cu-, Ta-, and O-rich phases) properties of the i-GBs based on the internal barrier layer capacitor effect.
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The Comment on our publication [Prasongkit et al., RSC Adv., 2016, 64, 59299] is puzzling since it is well known that biphenyl is fairly non-reactive. Hence, it's not surprising we have low binding energies when the gas molecules were adsorbed on biphenyl dithiol (BPDT). The large binding energy of NO2 chemisorbed onto BPDT (â¼2.04 eV) in the Comment conflicts with existing theoretical and experimental evidence. Grigoriev et al. have attempted to compare their results to our findings, employing different approximation schemes under the density functional theory (DFT) framework. Here, the effect of taking into account van der Waals (vdW) interactions upon the adsorption mechanism of small aromatic molecules has been discussed.
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Recently magnetic tunnel junctions using two-dimensional MoS2 as nonmagnetic spacer have been fabricated, although their magnetoresistance has been reported to be quite low. This may be attributed to the use of permalloy electrodes, injecting current with a relatively small spin polarization. Here we evaluate the performance of MoS2-based tunnel junctions using Fe3Si Heusler alloy electrodes. Density functional theory and the non-equilibrium Green's function method are used to investigate the spin injection efficiency (SIE) and the magnetoresistance (MR) ratio as a function of the MoS2 thickness. We find a maximum MR of ~300% with a SIE of about 80% for spacers comprising between 3 and 5 MoS2 monolayers. Most importantly, both the SIE and the MR remain robust at finite bias, namely MR > 100% and SIE > 50% at 0.7 V. Our proposed materials stack thus demonstrates the possibility of developing a new generation of performing magnetic tunnel junctions with layered two-dimensional compounds as spacers.
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Fast, cost effective, single-shot DNA sequencing could be the prelude of a new era in genetics. As DNA encodes the information for the production of proteins in all known living beings on Earth, determining the nucleobase sequences is the first and necessary step in that direction. Graphene-based nanopore devices hold great promise for next-generation DNA sequencing. In this work, we develop a novel approach for sequencing DNA using bilayer graphene to read the interlayer conductance through the layers in the presence of target nucleobases. Classical molecular dynamics simulations of DNA translocation through the pore were performed to trace the nucleobase trajectories and evaluate the interaction between the nucleobases and the nanopore. This interaction stabilizes the bases in different orientations, resulting in smaller fluctuations of the nucleobases inside the pore. We assessed the performance of a bilayer graphene nanopore setup for the purpose of DNA sequencing by employing density functional theory and non-equilibrium Green's function method to investigate the interlayer conductance of nucleobases coupling simultaneously to the top and bottom graphene layers. The obtained conductance is significantly affected by the presence of DNA in the bilayer graphene nanopore, allowing us to analyze DNA sequences.
Assuntos
DNA/genética , Grafite/química , Análise de Sequência de DNA , DNA/química , Simulação de Dinâmica Molecular , NanoporosRESUMO
The fabrication of nanopores in atomically thin graphene has recently been achieved, and translocation of DNA has been demonstrated. Taken together with an earlier proposal to use graphene nanogaps for the purpose of DNA sequencing, this approach can resolve the technical problem of achieving single-base resolution in electronic nucleobase detection. We have theoretically evaluated the performance of a graphene nanogap setup for the purpose of whole-genome sequencing, by employing density functional theory and the nonequilibrium Green's function method to investigate the transverse conductance properties of nucleotides inside the gap. In particular, we determined the electrical tunneling current variation at finite bias due to changes in the nucleotides orientation and lateral position. Although the resulting tunneling current is found to fluctuate over several orders of magnitude, a distinction between the four DNA bases appears possible, thus ranking the approach promising for rapid whole-genome sequencing applications.