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One-step assembled CdSe/CdS (core/shell) quantum dots (QDs) were deposited onto ZnO nanowires (NWs) and characterized for their structure, morphology and optical analyses. As deposited ZnO NWs array were wurtzite in structure. During a single hydrothermal cycle a layer of ∼4 nm CdSe/CdS QDs was formed onto ZnO NWs and overgrowth evidenced with an additional 2–5 layers due to which, (a) absorbance density, and (b) Raman Shift of 1LO mode (from 286 cm −1 to 296 cm −1 ) increased and (c) the photoluminescence intensity of the near band-edge emission peak at ∼379 nm decreased. Due to more accumulation of CdSe/CdS, photoelectrochemical cells of ZnO-based photoelectrodes designed for 1–4 cycles of CdSe/CdS onto indium-tin-oxide substrate demonstrated increasing power conversion efficiency trend from 0.18% to 1.29% whereas, for 5th cycle power conversion efficiency, due to an increased series resistance, decreased to 1.12% on account of an accumulation of several QDs. [ABSTRACT FROM AUTHOR]

Porous microspheres copper cobalt carbonate hydroxides (Cu x Co 2−x CH) pseudocapacitive electrode material comprised of nanoplates via a facile hydrothermal method were presented. Significantly, the crystalline structure, morphology and electrochemical performance of the Cu x Co 2−x CH can be readily manipulated by varying the Cu/Co molar ratios. Among various stoichiometries of Cu x Co 2−x CH porous microspheres studied, Cu 1.79 Co 0.21 CH consisted of nanoplates with a mean thickness of ∼35 nm showed a high specific capacitance of 789 F g −1 at a current destiny of 1 A g −1 and good rate ability. Furthermore, the optimized Cu 1.79 Co 0.21 CH electrode also exhibited remarkable high cycling stability, ca 77.5% after 3000 charge/discharge cycles at current density of 5 A g −1 . An asymmetric device was constructed from optimized Cu 1.79 Co 0.21 CH materials on nickel foam (NF) as cathode electrode and graphene on NF as anode electrode in a 6 M KOH electrolyte. The asymmetric Cu 1.79 Co 0.21 CH/NF//graphene/NF supercapacitor device delivered a specific capacitance of 60.5 F g −1 in a potential range of 0–1.6 V. A high energy density of 21.5 W h kg −1 was achieved at the power density of 200 W kg −1 . More significantly, the designed device exhibited excellent cycling stability with 73.3% capacity retention after 5000 cycles. [ABSTRACT FROM AUTHOR]

Al–Ni co-doped ZnO (NiAl:ZnO) thin films were deposited on glass substrates using a sol–gel method. Based on a previous study, Zn 1 − x Al x O (AZO; Al/Zn = 1.5 mol%) thin films optimized with a Ni content of 0.5 mol% were annealed at different temperatures from 450 to 600 °C in N 2 /H 2 (95/5) forming gas for 1 h. The effects of the annealing temperature on the structural, electrical and optical properties were determined. X-ray diffraction showed that NiAl:ZnO thin film annealed at 500 °C exhibited the best crystallization quality. XPS revealed the presence of metallic Ni and Ni 2 O 3 states, as well as Ni and Al atoms were successfully doped in NiAl:ZnO films, which did not result in a change in ZnO crystal structure and orientation. Scanning electron microscopy showed that the films were smooth and compact, and the grain size increased with increasing annealing temperature from ~ 23.8 nm to ~ 34.6 nm. According to the Hall Effect measurements, when the temperature reached 500 °C, the resistivity of the thin film showed the lowest value of 1.05 × 10 − 3 (Ω cm), which is the lowest resistivity reported for NiAl:ZnO films. The UV–Vis transmission spectra showed a high transmittance of more than 80% in the visible light range, and the band gap of the films was increased from 3.30 to 3.55 eV. This study showed that the annealing temperature in the forming gas is a vital factor affecting the quality of thin films. In addition, 500 °C was found to be the most appropriate annealing temperature for NiAl:ZnO films. This study provides a simple and efficient method for preparing high quality, high transparency and low resistivity NiAl:ZnO films for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Abstract: We reported on the facile synthesis of N-doped multilayer graphene (N-MLG) from milk powder that uses melamine as a nitrogen-doping source with Fe2+ ions as catalytic growth agents. We showed that milk powder could be used as a precursor for large-scale N-MLG synthesis through heat treatment at 1000°C under N2 atmosphere for 45–120min. In addition, heating time has a remarkable effect on N content and type in N-MLG. The resulting N-MLG exhibited higher catalytic activity than undoped graphene and carbon nanotubes (CNTs), as well as comparable catalytic activity to commercial Pt/C catalyst toward oxygen reduction reaction (ORR). Furthermore, the catalytic activity was sensitive to N content and type, particularly the ratio of pyridinic-N to total N atoms. Results showed that Fe atoms in N-MLG were found to function not as synergetic catalysts for ORR but as catalytic growth agents for N-MLG formation, thereby promoting and stabilizing N atoms. The present method could lead to the synthesis of bulk amounts of N-MLG, which is promising for applications in electrochemical energy devices, such as fuel cells and metal–air batteries. [Copyright &y& Elsevier]

Highlights: [•] Porous carbons were prepared using endothelium corneum gigeriae galli as precursor. [•] Surface and structural properties strongly depend on carbonization temperatures. [•] Resultant carbons possess nitrogen heteroatom and high surface areas. [•] ECGG-900 sample exhibits excellent electrochemical capacitive performances. [ABSTRACT FROM AUTHOR]

Highlights: [•] A green facile chemical approach to control the dimensions of Ag nanoparticles–graphene oxide (AgNPs/GO) composites was performed at room temperature. [•] With decreasing ultrasonication time, the size of the Ag nanoparticles decreased and became uniformly distributed over the surface of the GO nanosheets. [•] The as-prepared AgNPs/rGO composite films were then formed using a spin coating method and reduced at 500°C under N2/H2 gas flow for 1h. [•] The lowest sheet resistance of 270Ω/sq was obtained in the film corresponding to 1min of ultrasonication, which showed a 40 times lower resistivity than the rGO film (10.93kΩ/sq). [ABSTRACT FROM AUTHOR]

Abstract: A green chemical approach to control the dimensions of Ag nanoparticle-decorated graphene oxide (AgNP–GO) composites was proposed by in situ ultrasonication of a mixture of AgNO3 and GO solution with the assistance of vitamin C acting as an environmentally friendly reducing agent at room temperature. The AgNP–GO composites were characterized by X-ray diffraction, transmission electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, Raman spectra and ultraviolet–visible absorption spectra. The results demonstrated that Ag nanoparticles with an average diameter of ∼15nm were uniformly dispersed on the surface of GO nanosheets by in situ ultrasonication of 1min with vitamin C. Increasing the ultrasonication times resulted in Ag nanoparticles with tunable dimensions ranging from 15 to 55nm being formed on the surface of GO nanosheets. The amount of silver nitrate and the ultrasonication time play a key role in the control of the dimension of Ag nanoparticles on GO, and a formation mechanism of the as-prepared AgNP–GO composites is proposed. This study provides a guide to controlling the dimensions of AgNP–GO composites, which may hold promise as advanced materials for various analytical applications such as catalysis, sensors and microchips. [Copyright &y& Elsevier]

Highlights: [•] LiNi0.5Sm x Mn1.5−x O4 (x =0, 0.01, 0.03, and 0.05) spinel have been synthesized. [•] The Sm-doping improves the spinel structural stability. [•] LiNi0.5Sm x Mn1.5−x O4 exhibit enhanced cycling stability and rate performance. [•] LiNi0.5Sm x Mn1.5−x O4 display low charge transfer impedance. [ABSTRACT FROM AUTHOR]

Abstract: Spinel cobalt oxide (Co3O4) nanowires grown on Ni foam are successfully synthesized using a novel microwave-assisted template-free method. The effect of reaction temperature, concentration of reactants, and reaction time on the morphology and crystalline structures of the prepared nanowires is studied. The present work has demonstrated that uniform Co3O4 nanowires with diameters of 500–580nm and lengths of 6–8μm can be synthesized under proper reaction condition. Moreover, the proposed microwave-assisted template-free method can significantly reduce reaction time, increase reaction efficiency, and provide better control over the geometry of the nanostructures. [Copyright &y& Elsevier]

Abstract: High performance ultraviolet (UV) detectors based on ZnO metal–semiconductor–metal (MSM) and p–n heterojunctions, p-NiO/n-ZnO, were fabricated and their UV photo-responsivity was measured at room temperature. High-quality ZnO and NiO thin films were deposited on quartz substrates at room temperature under optimized RF reactive sputtering conditions. For ZnO-based MSM UV detectors using Al as a contact metal, the linear current–voltage (I–V) characteristics under a forward bias exhibited ohmic metal–semiconductor contact. A maximum photocurrent and photo-responsivity of 2.5mA and 1410A/W, respectively, at 365nm under 5V bias was observed, indicating the high photo-responsivity of the ZnO MSM detector. In comparison, a p-NiO/n-ZnO p–n heterojunction UV detector demonstrated clear rectifying I–V characteristics with an ideality factor, forward threshold voltage and photo-responsivity of 2, 0.9V and 0.09A/W, respectively, at 362nm under a reverse bias of 4V, which is close to that of the commercial GaN UV detector (∼0.1A/W). [Copyright &y& Elsevier]

Abstract: Highly transparent Cu2O-doped p-type Zn1−x Al x O (AZO; Al/Zn=1.5at%) conducting oxide films were synthesized on glass substrates using a cost effective low temperature sol–gel method. X-ray diffraction of the Cu2O-doped AZO (AZO:Cu2O) films revealed a polycrystalline Cu2O (110) peak. The I–V measurements of the p–n junction (ITO/AZO:Cu2O) revealed rectifying I–V characteristics, showing that these AZO:Cu2O films exhibit p-type conductivity. p-Type conductivity was achieved by annealing the AZO:Cu2O films in N2/H2 forming gas at 400°C. The hole concentration, hole mobility and resistivity of the 0.5–2mol% AZO:Cu2O films were 5.41×1018 to 1.99×1020 cm−3, 8.36–21.6cm2/Vs and 1.66×10−2 to 6.94×10−3 Ωcm, respectively. These results show that post-annealing in a forming gas is effective and practicable in producing p-type AZO. [Copyright &y& Elsevier]

Abstract: Methane is a potent greenhouse gas. It has a global warming potential (GWP) 23 times greater than carbon dioxide. Reducing methane emissions would lead to substantial economic and environmental benefits. This study investigated the performance of multi-transition-metal-(Cu, Cr, Ni, and Co)-ion-exchanged zeolite 13X catalysts in methane emissions abatement. The catalytic activity in methane combustion using multi-ion-exchanged catalysts was studied with different parameters including the molar percentage of metal loading, the space velocity, and the inlet methane concentration under atmospheric pressure and at a relatively low reaction temperature of 500 °C. The performance of the catalysts was determined in terms of the apparent activation energy, the number of active sites of the catalyst, and the BET surface area of the catalyst. This study showed that multi-ion-exchanged catalysts outperformed single-ion-exchanged and acidified 13X catalysts and that lengthening the residence time led to a higher methane conversion percentage. The enhanced catalytic activity in the multi-ion-exchanged catalysts was attributed to the presence of exchanged transition ions instead of acid sites in the catalyst. The catalytic activity of the catalysts was influenced by the metal loading amount, which played an important role in affecting the apparent activation energy for methane combustion, the active sites, and the BET surface area of the catalyst. Increasing the amount of metal loading in the catalyst decreased the apparent activation energy for methane combustion and also the BET surface area of the catalyst. An optimized metal loading amount at which the highest catalytic activity was observed due to the combined effects of the various factors was determined. [Copyright &y& Elsevier]

Abstract: This study investigates analytically and experimentally the influence of preheat temperature on flame propagation and extinction of premixed methane–air flame in single quartz tubes with inner tube diameters of 3.9, 3, 2 and 1mm respectively. The effects of preheat temperature, tube diameter, equivalence ratio and mixture flow rate on the flame speed and extinction conditions are determined. The analytical results show that high preheat temperature of the mixture can effectively suppress flame quenching, and the occurrence of stable solution in the slow flame branch extends the flammability limit leading to possible flame propagation in mini channels. Experimental results confirm that the flame speed increases and the flammability limit shifts toward the fuel lean direction either through increasing the preheat temperature or decreasing the mixture flow rate, or both. Decrease of propagating flame speed is observed before the stoichiometric equivalence ratio at high preheat temperatures. The analytical model provides insights into how propagating flame in mini channels can be sustained; however, the model is only good at predicting flame speed near the fuel lean branch. Influence of Cu2+ ions exchanged zeolite 13X catalyst on flame speed is also addressed. It is noted that the zeolite based catalyst can lower the preheat temperature requirement in order to sustain the flame propagation in narrow channels. [Copyright &y& Elsevier]

Abstract: Pure form, single phase and high crystalline zeolite 4A samples were synthesized by applying step-change of synthesis temperature during hydrothermal treatment of coal fly ash prepared solution. The results indicate that step-change of synthesis temperature during hydrothermal treatment plays an important role in reducing the overall synthesis time while maintaining a high degree of crystallinity for the samples. In order to obtain similar quality of zeolite 4A sample, a reduction by half of the total synthesis time could be achieved by applying step-change of synthesis temperature compared to using constant temperature throughout the synthesis process. Generally, the crystallinity of the synthesized zeolite 4A samples was in the range of 75–87%. The yielding (quantity) of pure zeolite 4A samples obtained in all the experiments was about 15–18%. In addition, crystals of smaller particle size existing in a narrower particle size distribution were synthesized. [Copyright &y& Elsevier]

Many 2D graphene-based catalysts for electrooxidation of glucose involved the use of binders and toxic reducing agents in the preparation of the electrodes, which potentially causes the masking of original activity of the electrocatalysts. In this study, a green method was developed to prepare binder-free 3D graphene aerogel/nickel foam electrodes in which bimetallic Pd-Pt NP alloy with different at% ratios were loaded on 3D graphene aerogel. The influence of Pd/Pt ratio (at%: 1:2.9, 1:1.31, 1:1.03), glucose concentration (30 mM, 75 mM, 300 mM, 500 mM) and NaOH concentration (0.1 M, 1 M) on electrooxidation of glucose were investigated. The catalytic activity of the electrodes was enhanced with increasing the Pd/Pt ratio from 1:2.9 to 1:1.03, and changing the NaOH/glucose concentration from 75 mM glucose/0.1 M NaOH to 300 mM glucose/1 M NaOH. The Pd 1 Pt 1.03 /GA/NF electrode achieved a high current density of 388.59 A g −1 under the 300 mM glucose/1 M NaOH condition. The stability of the electrodes was also evaluated over 1000 cycles. This study demonstrated that the Pd 1 Pt 1.03 /GA/NF electrode could be used as an anodic electrode in glucose-based fuel cells. [ABSTRACT FROM AUTHOR]

In this work, a facile two-step hydrothermal method was reported to grow hierarchical flower-like NiAl layered double hydroxide (LDH) directly on 3D nickel foam (NF) which was further coated with 2D graphene nanosheets (GNS) layers as binder-free supercapacitor electrode. The positive and negative effects of GNS on the electrochemical performance of LDH-NF electrode were investigated in detail. The prepared LDH-NF/GNS electrode maintained an enhanced specific capacity of 165.6 C g −1 after 4000 cycles at a high current density of 40 A g −1 . Furthermore, a hybrid supercapacitor, with LDH-NF/GNS and GNS-NF as the positive and negative electrodes, achieved an energy density (31.5 Wh kg −1 at a power density of 400 W kg −1 ) and super long-term cycle stability (a specific capacity of 67.2 C g −1 at 5 A g −1 after 5000 cycles with 80% retention). This study not only opens up the possibility of engineering LDH-NF/GNS into a promising electrode, but also highlights the positive and negative roles of GNS on LDH-NF as binder-free electrodes for further development of high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Highlights: [•] 3D Co(II) ions modified graphene aerogels were prepared by one-step hydrothermal process. [•] The aerogel electrodes showed hybrid supercapacitor behaviors. [•] The aerogel electrodes exhibited high rate capability and long-term cycling stability. [Copyright &y& Elsevier]

Highlights: [•] Ni–Al co-doped ZnO (NiAl:ZnO) composite thin films were deposited by DC magnetron sputtering at room temperature. [•] All films showed a highly preferential (002) c-axis orientation. [•] XPS revealed the presence of metallic Ni, NiO, and Ni2O3 states, and Ni atoms were successfully doped in the NiAl:ZnO films. [•] NiAl:ZnO (3wt% Ni) film showed the lowest electrical resistivity of 2.59×10−3 Ωcm. [•] Band gap widening (4.18eV) was observed in the NiAl:ZnO films with 5wt% Ni. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ni–Al co-doped ZnO (NiAl:ZnO) composite thin films were deposited by DC sputtering at low sputtering power. [•] All films showed a highly preferential (002) c-axis orientation. [•] NiAl:ZnO (5wt% Ni) film deposited at 40W at 6.0mTorr has the lowest resistivity of 2.19×10−3 Ωcm. [ABSTRACT FROM AUTHOR]

Abstract: “The Low Carbon, Green Growth” was declared as Korean national agenda in 2008. Korea has been enhancing the green growth for the sustainable economic development and fostering energy. To improve Korean national energy security and promote the “Low Carbon, Green Growth”, we established a long term strategic energy technology roadmap. In this paper, five criteria, such as economical impact, commercial potential, inner capacity, technical spin-off, and development cost, were used to assess the strategic energy technologies against high oil prices. We developed the integrated two-stage multi-criteria decision making (MCDM) approach which was used to evaluate the relative weights of criteria and measures the relative efficiency of energy technologies against high oil prices. On the first stage, the fuzzy analytic hierarchy process, reflecting the vagueness of human thought with interval values instead of crisp numbers, allocated the relative weights of criteria effectively instead of the AHP approach. On the second stage, the data envelopment analysis approach measured the relative efficiency of energy technologies against high oil prices with economic viewpoints. The relative efficiency score of energy technologies against high oil prices can be the fundamental decision making data which help decision markers to effectively allocate the limited R&D resources. [Copyright &y& Elsevier]

Abstract: ZnO thin films were deposited onto quartz substrates by radio frequency (RF) reactive magnetron sputtering using a Zn target. The structural and optical properties of the ZnO thin films were investigated comprehensively by X-ray diffraction (XRD), ultraviolet–visible and photoluminescence (PL) measurements. The effects of the oxygen content of the total oxygen–argon mixture and sputtering voltage in the sputtering process on the structural and optical properties of the ZnO films were studied systemically. The microstructural parameters, such as the lattice constant, crystallite size, stress and strain, were also calculated and correlated with the structural and optical properties of the ZnO films. In addition, the results showed that the crystalline quality of ZnO thin films improved with increasing O2/Ar gas flow ratio from 2:8 to 8:2. XRD and PL spectroscopy revealed 800V to be the most appropriate sputtering voltage for ZnO thin film growth. High-quality ZnO films with a good crystalline structure, tunable optical band gap as well as high transmittance could be fabricated easily by RF reactive magnetron sputtering, paving the way to obtaining cost-effective ZnO thin films transparent conducting oxides for optoelectronics applications. [Copyright &y& Elsevier]