One-pot synthesis of manganese oxide/graphene composites via a plasma-enhanced electrochemical exfoliation process for supercapacitors.

In this work, a feasible one-pot approach to synthesize manganese oxide/graphene composites, the so-called plasma-enhanced electrochemical exfoliation process (PE3P), has been developed. Herein, a composite of graphene decorated with manganese oxide nanoparticles was prepared via PE3P from a KMnO4 solution and graphite electrode under a voltage of 70 V in an ambient environment. By controlling the initial KMnO4 concentration, we obtained distinct MnO2/graphene samples. The prepared samples were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and Raman spectroscopy. The electrochemical measurements of the MnO2/graphene composites revealed that the specific capacitance of the samples is approximately 320 F g-1 at a scan rate of 10 mV s-1, which is comparably very high for manganese oxide/carbon-based supercapacitor electrode materials. Considering the simple, low-cost, one-step and environmentally friendly preparation, our approach has the potential to be used for the fabrication of MnO2/graphene composites as the electrode materials of supercapacitors.

Fractional quantum Hall effects in In0.75Ga0.25As bilayer electron systems observed as "Finger print".

Observations of fractional quantum Hall (FQH) plateaus are reported in bilayer electron gas system in wide (>80 nm) In0.75Ga0.25As wells. Several q/p (p = 5, 3, and 2, q > 5) QH states are confirmed at high temperatures (~1.6 K) when the critical conditions including an electron density imbalance as well as a dynamical resistance behavior at the bilayer-monolayer transition are properly satisfied. The former leads to a quantum limit in either of the layers and the latter might bring a meta-stable nature into FQH phenomena. Such a behavior occurs as a probability process associating with impurities or defects in the wells, they inevitably reflect the local structural landscapes of each sample. This is verified by the new finding that the kinds of fractional plateaus (what set of fractional filling factors) appeared are different depending on the samples, that is, they are the "finger print" in each sample.

Chemical Simultaneous Synthesis Strategy of Two Nitrogen-Rich Carbon Nanomaterials for All-Solid-State Symmetric Supercapacitor.

Present work demonstrates a single step process for simultaneous synthesis of metal-nanoparticle-encapsulated nitrogen-doped bamboo-shaped carbon nanotubes (M/N-BCNTs) and graphitic carbon nitride (G-C3N3). The synthesis of two different carbon nanostructures in a single step is recognized for the first time. This process involves the use of inexpensive and nontoxic precursors such as melamine as carbon and nitrogen sources for the growth of G-C3N3 and M/N-BCNTs. In this technique, the utilization of unwanted gases such as ammonia and hydrocarbons released during the decomposition of melamine is the key to grow M/N-BCNTs over the catalyst along with the formation of G-C3N4. The implementation of M/N-BCNTs as the electrode material for all-solid-state symmetric supercapacitor results in a maximum specific capacitance of ∼368 F g-1 with excellent electrochemical stability with 97% capacity retention after 10 000 cycles. Furthermore, fabricated symmetric supercapacitor shows maximum high energy and power density up to 10.88 W h kg-1 and 2.06 kW kg-1, respectively. The superior electrochemical activity of M/N-BCNTs can be attributed to its high surface to area volume ratio, unique structural characteristics, ultrahigh electrical conductivity, and carrier mobility.

Enhanced ferromagnetism of ZnO@Co/Ni hybrid core@shell nanowires grown by electrochemical deposition method.

The hybrid structure of ZnO NWs with the presence of different dopants recently has drawn many interests from researchers due to the possibility to integrate multiple functionalities into one single structure. In this article, we investigated the morphology, crystal structure and ferromagnetism of the ZnO@Co/Ni hybrid core@shell NWs prepared by a facile electrochemical deposition method. The results show that a thin layer of Ni and Co coated on the surface of ZnO NWs (confirmed by XRD, EDS, TEM and Raman scattering) can create a significant improvement of ferromagnetic property in such hybrid core@shell NWs. In which, for the coating time of 10, 15, 20 min, the value of M s is around 0.67, 0.88 and 2.56 emu g-1 for ZnO@Co NWs, and about 0.013, 0.022 and 0.031 emu g-1 for ZnO@Ni NWs, respectively, in comparison with the number of 0.016 emu g-1 for pure ZnO NWs. Interestingly, we also found the temperature dependence of ferromagnetism of such Co/Ni coated ZnO NWs. These results reveal the possibility to employ such hybrid core@shell NWs for many applications, e.g. spin field effect transistors.

Nitrogen Gas Field Ion Source (GFIS) Focused Ion Beam (FIB) Secondary Electron Imaging: A First Look.

The recent technological advance of the gas field ion source (GFIS) and its successful integration into systems has renewed the interest in the focused ion beam (FIB) technology. Due to the atomically small source size and the use of light ions, the limitations of the liquid metal ion source are solved as device dimensions are pushed further towards the single-digit nanometer size. Helium and neon ions are the most widely used, but a large portfolio of available ion species is desirable, to allow a wide range of applications. Among argon and hydrogen, $${\rm N}_{2}^{{\plus}} $$ ions offer unique characteristics due to their covalent bond and their use as dopant for various carbon-based materials including diamond. Here, we provide a first look at the $${\rm N}_{2}^{{\plus}} $$ GFIS-FIB enabled imaging of a large selection of microscopic structures, including gold on carbon test specimen, thin metal films on insulator and nanostructured carbon-based devices, which are among the most actively researched materials in the field of nanoelectronics. The results are compared with images acquired by He+ ions, and we show that $${\rm N}_{2}^{{\plus}} $$ GFIS-FIB can offer improved material contrast even at very low imaging dose and is more sensitive to the surface roughness.