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Liquid phase oxidation of 2-methylnaphthalene (2-MN) is a common synthetic route for the preparation of 2-methyl-1,4-naphthoquinone (2-MNQ). Metal-free carbon materials doped with heteroatoms have been proven to have excellent catalytic potential in various reaction fields. In this paper, the catalytic performance of N, F co-doped benzoxazine carbon materials for the selective oxidation of 2-MN was studied. The results show that the catalyst obtained at a carbonization temperature of 700 °C has the best catalytic performance. Under optimized conditions, the 2-MN conversion is 97.9%, and the 2-methyl-1,4-naphthoquinone selectivity is 84.3%. In addition, this catalyst still exhibits good catalytic activity after five cycles. Based on the experimental and characterization results, graphitic nitrogen species play a key role in the catalytic reaction and there is an almost linear relationship between the F content and the selectivity of 2-MNQ. This work provides a greener and more efficient method for the preparation of 2-MNQ with N/F co-doped mesoporous carbon. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemically active Oxygen doped carbon (O-PCNs) was fabricated by superbase templated method. • The template basicity on the functionalities and the supercapacitor performances of the derived O-PCNs were disclosed. • The O-PCN-20 is rich in porosity, large in surface area (930 m2/g) and high in active oxygen content (11.4 atom%). • · The O-PCN-20 electrode exhibits large capacitance of 375 F/g@1.0 A/g and energy density of 25.7 Wh/kg@900 W/kg. Templating techniques have been widely adopted for the synthesis of porous carbons, such as oxygen-doped porous carbon nanosheets (O-PCNs), but the effect of the surface characteristics of templates on the surface functionality and performance of a derived carbon has not been well studied. Herein, a series of laboratory-made superbases of K/Mg(OH) 2 with different K/Mg ratios were employed as template to fabricate nanocarbon materials. The aim is to find out how the strength of template basicity could influence the surface functionalities and the supercapacitor performances of the derived O-PCNs. The resulting materials are rich in conjugated hydroxyl and carbonyl groups that are electrochemically active owing to the protection of the conjugated hydroxyl group by KOH and the dehydrogenation step catalyzed by magnesium oxide. Systematic investigations revealed that with the increase of basic strength, the content of the derived electrochemically active oxygen species in the forms of conjugated carbonyl (C O) and hydroxyl (C OH) first increases from 8.4 atom% to 11.4 atom% then decreases to 9.25 atom%. Moreover, the microporosity of the O-PCNs stepwise increases with the rise of KOH loading, ascribable to the effect of KOH etching on the carbon skeleton. The O-PCN-20 templated by 20 % K/Mg(OH) 2 is rich in porosity, large in surface area (930 m2/g) and high in active oxygen content (11.4 atom%). With high active surface area and extra Faradaic capacitance, O-PCN-20 exhibited superior supercapacitor performances including large specific capacitance of 375 F/g@1.0 A/g, high rate capability of 81.1 % (from 1.0 A/g to 20 A/g), energy density of 25.7 Wh/kg@900 W/kg and excellent cycling stability with near 100 % capacitance retentions after 10 000 cycles and more than 86.2 % capacitance retention over 20 000 cycles at large current density of 10 A/g, indicating O-PCN-20 has potential to be used as electrode material for energy storage devices. [ABSTRACT FROM AUTHOR]

Abstract The transport and thermoelectric properties of the LaO 1 − x F x BiPbS 3 compounds are studied. On the transport part, fluorine doping effectively reduces the electrical resistivity, and transforms the transport behavior from semiconducting-like to metallic-like. An evident enhancement of thermoelectric performance (power factor) is achieved in LaO 0.6 F 0.4 BiPbS 3 , with an obviously larger absolute value of Seebeck coefficient (| S |) compared to the parent compound. Hall coefficient measurements reveal the depression of effective carrier density for all the doped samples at high temperatures. The present results suggest that electron carriers alone can not explain the improvement of thermoelectric properties by fluorine doping, the conduction of ionic carriers should be taken into account. [ABSTRACT FROM AUTHOR]

A C-band erbium doped fiber ring laser is proposed and investigated. With the use of two sub-ring cavities and a saturable absorber, a high quality and stable fiber ring laser is obtained for high optical signal to noise ratio operation in lightwave transmission. As different fiber Bragg gratings are employed as the wavelength filter, a narrow 3 dB-bandwidth is necessary for the high quality operation. The fiber ring laser is evaluated in lightwave transmission. The Q factor and eye diagrams are also measured and discussed. [ABSTRACT FROM AUTHOR]

In rare-earth-doped single crystalline CaFe2As2, the mysterious small volume fraction which superconducts up to 49?K, much higher than the bulkTc?~?30?s?K, has prompted a long search for a hidden variable that could enhance theTcby more than 30% in iron-based superconductors of the same structure. Here we report a chemical, structural and magnetic study of CaFe2As2systematically doped with La, Ce, Pr and Nd. Coincident with the highTcphase, we find extreme magnetic anisotropy, accompanied by an unexpected doping-independentTcand equally unexpected superparamagnetic clusters associated with As vacancies. These observations lead us to conjecture that the tantalizingTcenhancement may be associated with naturally occurring chemical interfaces and may thus provide a new paradigm in the search for superconductors with higherTc. [ABSTRACT FROM AUTHOR]

We have studied the transport and magnetic properties of the TlKFeZnSe (nominal ratio 0.01≤ x≤0.15) single crystal samples. It is found that although Zn doping leads to a decrease of charge carrier density, it does not affect the superconductivity significantly when x≤0.1. The doped superconductors exhibit properties similar to the parent compound (TlKFeSe), e.g., the almost unchanged superconducting transition temperature ( T) and the 'hump'-like behavior in the resistivity curves, which denotes the transition from insulating phase to metallic phase. As the doping density rises, the hump obviously shifts to low temperature region, implying the quick enlargement of the ratio of insulating phase. The most plausible explanation for the above phenomena is that the Zn impurities prefer entering into the insulating phase only, therefore, merely hindering the formation of superconducting phase without directly changing its properties. The ESR measurement gives low signal-to-noise ratio and just weak paramagnetic signals, revealing strong itinerancy of the Zn doped superconductor. [ABSTRACT FROM AUTHOR]

[Display omitted] • An all-solid-state (ASS) strategy without using any solvents and activators was developed. • The ASS strategy derived carbon owns abundant nitrogen species and large packing density. • The resultant product show superior supercapacitor performances with both high gravimetric and volumetric performances. Template synthesis of porous carbon with rich functionalities by a scalable strategy without using any solvents and activators will be a green and promising route. Herein, we reported an all-solid-state synthesis strategy by mixing glucose and graphitic carbon nitride (g -C 3 N 4) by milling and then undergoing a segmented carbonization in which first at low temperature of 573 K to polymerize sucrose onto g -C 3 N 4 , then at high temperature of 973 K to carbonized the composite to obtain a porous carbon (denoted as GNC) with abundant nitrogen species over 20 atom% and large packing density (0.91–1.25 g cm−3). Due to the features of large packing density and rich electrochemically-active N species, as electrode for supercapacitive energy storage, the developed GNC exhibit a comparable energy storage level with both high gravimetric energy density of 26.8 Wh kg−1@1000 W kg−1 and volumetric energy density of 30.8 Wh L−1@1150 W L−1, suggesting a potentiality in energy storage field. Importantly, the present strategy owns characteristics of ease of operation, green and scalable, which would be a promising synthesis route towards the fabrication of functional carbon utilizing in many fields like sorption & separation, catalysis, energy storage and so on. [ABSTRACT FROM AUTHOR]

[Display omitted] • A solvent-freely polymerizing catechol and paraformaldehyde method was developed. • The present method derived carbon owns high nitrogen functionalties of 21.7 atom%. • The derived carbon achieves high energy density of 34.5 Wh L−1@1370 W/L. Fabrication of nitrogen functionalized carbon with high nitrogen content (over 10 atom%) by a route with simplified and solvent-free procedures would be both economically and environmentally scalable. We demonstrate here a simple solvent-free route towards synthesizing porous carbon doped by nitrogen functionalties (21.7 atom%) involving solid state catalytic polymerization of catechol and paraformaldehyde with g -C 3 N 4 as catalyst. Upon high-temperature treatment, the vaporized catechol and paraformaldehyde would be in situ polymerized on the surface of g -C 3 N 4 forming the composite of g -C 3 N 4 @resin. During the following carbonization process, the resin was carbonized to carbon skeleton, while the g -C 3 N 4 would be decomposed in situ doping the carbon skeleton. In our design, the avoidance of solvents in the whole synthesis procedure and the usage of g -C 3 N 4 in the preparation not only reduces the waste production, but also introduces high nitrogen species (21.7 atom%). As electrode for supercapacitor, the resultant SFC based electrode achieves a large specific capacitance of 391F cm−3@1.0 A/g and high energy density of 34.5 Wh/L@1370 W/L, suggesting a potential as electrode for energy storage. And more, the developed method offers a promising and alternative route for the fabrication of new materials in manner of green and environmentally friendly. [ABSTRACT FROM AUTHOR]

As an industrial material for supercapacitive energy storage, commercial activated carbons (AC) could achieve a satisfactory gravimetric performances by electric double layered capacitance (EDLC) due to their rich microporosity, but the volumetric performances are usually poor resulted from the low packing density. Herein, we presented a strategy to address this tradeoff relationship and to achieve both high gravimetric and volumetric performance by filling the macro/mesoporosity with extra nitrogen doped carbon. The reconstructed activated carbon could inherit most of microporosity from the parent AC, while the macro/mesoporosity of them was greatly decreased, resulting in increase of packing density and the improvement of surface hydrophilicity. Benefited from the increase of packing density and maintenance of microporosity, the resultant activated carbon achieves greatly enhanced energy storage level including three times higher capacitance of 384 F cm−3@ 1.0 A/g (vs 128 F cm−3@ 1.0 A/g for pristine AC), high rate capability of 73.4% (vs 59.2% for pristine AC), larger energy density of 27.5 Wh L−1@ 900 W L−1 (vs 10.0 Wh L−1@747 W L−1). Importantly, the present strategy provides a facile and unique method to process activated carbon, which offers a possibility improving the energy storage level of the commercial activated carbon. [Display omitted] • Commercial activated carbon (AC) was processed by filling the macro/mesoporosity. • The filled AC owns increased packing density and more nitrogen functionalities. • The filled AC achieves greatly enhanced supercapacitor performances. [ABSTRACT FROM AUTHOR]

The effect of main gas flow rate and gas type of carrier gas on the electrical and optical properties of Ga-doped ZnO films deposited by atmospheric pressure plasma jet was investigated. Adding Ar and H 2 in the carrier gas reduces the sheet resistance of the films from 230 to 90 Ω/□ and increases the deposition rate by 38% due to the incorporation of hydrogen as a shallow donor and the lower breakdown potential of Ar, respectively. The effect of the main gas flow rate is less significant compared with the gas type of the carrier gas, but a proper flow rate is required to produce the film with lower resistivity. The lowest resistivity of 1.25 × 10 − 3 Ω cm was achieved with a carrier gas mixture percentage of 75% and a main gas flow rate of 30 slm at a substrate temperature of 180 °C in open air. All the samples presented in this study exhibit average transmittance above 80% in the visible region and low haze below 5.5%. [ABSTRACT FROM AUTHOR]