[en] The Pt-Co-P ultrafine nanoparticles supported on carbon nanotubes (Pt-Co-P/CNT) have been successfully synthesized by a hypophosphite-assisted one-pot reduction strategy and used as the electrocatalysts for methanol oxidation reaction (MOR). Transmission electron microscope observation clearly indicates that the Pt-Co-P nanoparticles are highly dispersed onto the surface of CNT with a narrow particle size distribution. The average diameter of the Pt-Co-P nanoparticles with the different P contents can be controlled from 1.5 nm to 2.7 nm, probably by the assistance of in-situ phosphate capping agent for nanoparticle growth, which generated from simultaneous oxidation of sodium hypophosphite. The electrochemical measurement data indicate that the Pt-Co-P/CNT with the average particle diameter of 1.5 nm possesses superior electrocatalytic activity, outstanding tolerance against CO-like intermediates and excellent electrochemical stability, which is better than those of Pt-Co/CNT and commercial Pt/C. The improved electrochemical performance of Pt-Co-P/CNT can be attributed to the high electrochemical active surface area and rapid removal of CO-like intermediates arising from the ultrafine features of Pt-Co-P nanoparticles as well as the strong interaction among Pt, Co, and P. Therefore, the Pt-Co-P/CNT electrocatalysts prepared by a hypophosphite-assisted one-pot reduction strategy can be considered as a promising candidate for high performance MOR electrocatalyst.

[en] Highlights: • The nitrogen-doped hierarchical porous carbon was prepared from silkworm cocoon. • The NHPC possesses a unique porous structure and a high specific surface area. • The NHPC presents superior adsorption performance for Cr (VI). • The NHPC exhibits an excellent recyclability for the removal of Cr (VI). - Abstract: The development of highly efficient adsorbents is an effective way to remove Cr"6"+ from wastewater for environment protection. Herein, a high-specific-surface-area nitrogen-doped hierarchical porous carbon (NHPC) derived from silkworm cocoon was synthesized and applied as an efficient adsorbent for the removal of Cr"6"+ from wastewater. The resultant NHPC possesses a specific surface area as high as 3134 m"2 g"−"1 and a unique hierarchical porous structure with a large number of small mesopores (2–4 nm) and micropores (0.8–2 nm) embedded in the sidewall of bowl-like macropores (200–300 nm), in which sufficient exposure of adsorption sites and high-flow transfer of Cr"6"+ ions can be achieved. As a result, the NHPC exhibits a remarkable adsorption performance with a larger adsorption capacity (366.3 mg g"−"1), a higher adsorption rate (4 × 10"−"2 g mg"−"1 min"−"1) and a superior recyclability in comparison with the commercial adsorbent (Norit CGP). Thermodynamic and kinetic analyses indicate that the adsorption process is spontaneous and endothermic, which fits well with the pseudo-second-order kinetic model and Langmuir isotherm model. This biomass-based porous carbon with well-defined hierarchical porous structure can be applied as a promising adsorbent for the removal of Cr"6"+ from wastewater.

[en] The author introduces the means of using cesium-137 measurements to investigate soil erosion and sediment and the method of collecting and making radioactive soil samples. An actual example of collecting soil samples in the area of the Caohai lake in Guizhou is also given

[en] The authors have prepared the flexible Ag-sheated Bi(Pb)-Sr-Ca-Cu-O superconducting composites by the powder-in-tube process. The critical current density Jc has reached 5000 A/cm² (77K,OT), and the dependence of Jc on magnetic field is reduced to some extent. The improvement of the critical current density is considered due to the grain alignment and well connection between grains. Using these composites the authors succeeded in making gradient coils of magnetic flux transformers. Some results of bending test are also presented in this paper. (author). 14 refs., 6 figs., 1 tab

[en] In this paper, we propose a scheme that integrates quantum key distribution and private classical communication via continuous variables. The integrated scheme employs both quadratures of a weak coherent state, with encrypted bits encoded on the signs and Gaussian random numbers encoded on the values of the quadratures. The integration enables quantum and classical data to share the same physical and logical channel. Simulation results based on practical system parameters demonstrate that both classical communication and quantum communication can be implemented over distance of tens of kilometers, thus providing a potential solution for simultaneous transmission of quantum communication and classical communication.

[en] A digital calibration technique for an ultra high-speed folding and interpolating analog-to-digital converter in 0.18-μm CMOS technology is presented. The similar digital calibration techniques are taken for high 3-bit flash converter and low 5-bit folding and interpolating converter, which are based on well-designed calibration reference, calibration DAC and comparators. The spice simulation and the measured results show the ADC produces 5.9 ENOB with calibration disabled and 7.2 ENOB with calibration enabled for high-frequency wide-bandwidth analog input. (semiconductor integrated circuits)

[en] We present the enhanced photoluminescence (PL) of a corrugated Al₂O₃ film enabled by colloidal CdSe quantum dots. The colloidal CdSe quantum dots are fabricated directly on a corrugated Al₂O₃ substrate using an electrochemical deposition (ECD) method in a microfluidic system. The photoluminescence is excited by using a 150 nm diameter ultraviolet laser spot of a scanning near-field optical microscope. Owing to the electron transfer from the conduction band of the CdSe quantum dots to that of Al₂O₃, the enhanced photoluminescence effect is observed, which results from the increase in the recombination rate of electrons and holes on the Al₂O₃ surface and the reduction in the fluorescence of the CdSe quantum dots. A periodically-fluctuating fluorescent spectrum was exhibited because of the periodical wire-like corrugated Al₂O₃ surface serving as an optical grating. The spectral topographic map around the fluorescence peak from the Al₂O₃ areas covered with CdSe quantum dots was unique and attributed to the uniform deposition of CdSe QDs on the corrugated Al₂O₃ surface. We believe that the microfluidic ECD system and the surface enhanced fluorescence method described in this paper have potential applications in forming uniform optoelectronic films of colloidal quantum dots with controllable QD spacing and in boosting the fluorescent efficiency of weak PL devices. (paper)

[en] This work studied the effect of differential temperatures on the latent heat in the nucleation of CdSe quantum dots (QDs). The result showed that, by the formula of phase change, with increasing the reaction temperature, the latent heat in the nucleation of QDs reduced. CdSe QDs with the size-dispersion from 2.7 to 3.6 nm were synthesized via oleic acid-paraffin liquid system by controlling the reaction temperature from 180 to 220 °C. Synthesized QDs were characterized by UV–vis absorption spectra and X-ray diffraction (XRD). The result of UV–vis absorption spectra showed that with increasing of reaction temperature, the first absorption peak was red-shifted and the size of QD increased. The result of XRD showed that the synthesized QDs were zinc-blende structure. (paper)

[en] Highlights: • One-step conversion from NiFePPc to N-doped carbon supported Ni-Fe nanoparticles. • The [email protected] exhibits superior catalytic activity and durability for OER. • The resultant samples also exhibit high activity for HER. • The bi-functional [email protected] shows excellent performance in the symmetrical setup. As the two half-reactions in water splitting, the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) are traditionally carried out with high-cost and scarce precious metals (e.g., Ru, Ir and Pt) as the electrocatalysts, which hampers the large-scale applications in water splitting. Herein, we developed a low-cost and efficient method to prepare the nitrogen-doped carbon supported nickel-iron nanoparticle ([email protected]) electrocatalysts, simply by one-step conversion from cross-linked polyphthalocyanine under the direct pyrolysis treatment. The resultant [email protected] electrocatalysts exhibit the efficient catalytic activity and durability for both OER and HER as bi-functional electrodes in water splitting device. The water splitting device based on the same [email protected] electrocatalyst at both sides of anode and cathode can operate with lower cell voltage (1.81 V, at 10 mA cm⁻²) in 1 M KOH aqueous electrolyte, as well as excellent durability (over 15 h of operation at 8, 10 and 20 mA cm⁻²) and high reversibility. The excellent electrocatalytic performance indicates that [email protected] electrocatalysts can be the promising replacement of the precious metals for more practical and cost-efficient water splitting. This work develops a new method for the preparation of high efficient and low-cost Ni-based electrocatalysts for symmetrical water splitting devices.

[en] We studied an enhancement effect of defect fluorescence of ZnSe quantum dots (QDs) on a heterojunction of ZnSe QDs and gold nanoparticles. The photoluminescence (PL) of Au/ZnSe heterojunction is excited by using a 150 nm diameter ultraviolet laser spot of a scanning near-field optical microscope. Owing to the charge transfer of photon-generated carriers from ZnSe QDs, the enhanced PL effect is observed, which results from the increase of the built-in electric field to hinder the electron transfer to gold nanoparticles and is trapped by the defect states of ZnSe QDs. The broadening of defect fluorescence spectra and the reduction of excitonic fluorescence in multi-heterojunction of ZnSe QDs and gold nanoparticles are also observed which is attributed to an increase of their contact areas. We believe that enhanced defect fluorescence method described in this paper have potential applications in forming uniform optoelectronic heterojunction in controlling and boosting fluorescent efficiency of weak PL devices. (paper)