[en] Highlights: • Ethylene was decomposed by a photoelectrocatalytic (PEC) process. • A pulsed direct current square-wave (PDCSW) potential was applied to the PEC cell. • An electrode of TiO_2 or modified TiO_2 and activated carbon fiber (ACF) was used. • TiO_2/ACF photocatalyst electrodes were modified by gamma radiolysis. • Efficiencies of the PEC process were higher than those of the process using DC. - Abstract: Removing ethylene (C_2H_4) from the atmosphere of storage facilities for fruits and vegetable is one of the main challenges in their postharvest handling for maximizing their freshness, quality, and shelf life. In this study, we investigated the photoelectrocatalytic (PEC) degradation of ethylene gas by applying a pulsed direct current DC square-wave (PDCSW) potential and by using a Nafion-based PEC cell. The cell utilized a titanium dioxide (TiO_2) photocatalyst or γ-irradiated TiO_2 (TiO_2"*) loaded on activated carbon fiber (ACF) as a photoelectrode. The apparent rate constant of a pseudo-first-order reaction (K) was used to describe the PEC degradation of ethylene. Parameters of the potential applied to the PEC cell in a reactor that affect the degradation efficiency in terms of the K value were studied. These parameters were frequency, duty cycle, and voltage. Ethylene degradation by application of a constant PDCSW potential to the PEC electrode of either TiO_2/ACF cell or TiO_2"*/ACF cell enhanced the efficiency of photocatalytic degradation and PEC degradation. Gamma irradiation of TiO_2 in the electrode and the applied PDCSW potential synergistically increased the K value. Independent variables (frequency, duty cycle, and voltage) of the PEC cell fabricated from TiO_2 subjected 20 kGy γ radiation were optimized to maximize the K value by using response surface methodology with quadratic rotation–orthogonal composite experimental design. Optimized conditions were as follows: 358.36 Hz frequency, 55.79% duty cycle, and 64.65 V voltage. The maximum K value attained was 4.4 × 10"−"4 min"−"1

[en] The spherical shape Ag nanoparticles synthesized via gamma-ray radiolysis were observed with the transmission electron microscope (TEM). Diameters of Ag nanoparticles were measured from the TEM photographs. Statistical analysis showed that the particle diameter complied with a linear-converted Poisson distribution. The distribution parameter, which was the average of diameters, was related to the ultraviolet–visible spectrum peak position of the nanosilver collosol. An empirical equation was established to predicting size distribution of Ag nanoparticles with the peak position. Nanosilver of different sizes could be synthesized by adjusting the intensity of γ-irradiation, the kind and the addition amount of the stabilizing agent. Because particle size affects the physiochemical properties of nanosilver material, results of this paper would be of practical significance for the application of nanosilver. - Highlights: • Ag nanoparticles were produced by reduction using "6"0Co gamma radiolysis. • Observed Ag nanoparticles by using the transmission electron microscope. • Deduced a quasi-Poisson size distribution for the Ag nanoparticles. • Empirical equation for measuring the size of Ag nanoparticles with UV–vis spectrum. • Size-controlled synthesis of spherical Ag nanoparticles

[en] A novel consensus control protocol for multi-agent nonholonomic systems has been proposed in this paper. With the aid of non-smooth analysis and algebraic graph theory, the proposed linear protocol can ensure leader-follower results and three flocking rules without position measurement. Besides, it is proved that there exist a range of control gain to preserve the connectedness of the communication network and realize consensus. Finally, some numerical simulations are given to validate the above theoretical results. (paper)

[en] This study presents a proposal for textured ZnO grown by liquid phase deposition (LPD) to improve the efficiency of GaInP/(In)GaAs/Ge solar cells. The experimental and calculated results show that the photocurrent density and conversion efficiency of GaInP/(In)GaAs/Ge solar cells with a textured liquid-phase-deposited zinc oxide (LPD-ZnO) window layer are dependent on the root-mean-square (RMS) roughness of LPD-ZnO, as determined by the hydrochloric acid (HCl) concentration and deposition temperature. The optimal RMS-roughness range for textured LPD-ZnO is 90–100 nm. The GaInP/(In)GaAs/Ge solar cells with the 95 nm LPD-ZnO window layer have a higher open circuit voltage (2.41 V), short circuit current density (14.88 mA cm⁻²), and conversion efficiency (29.8%) than those without the LPD-ZnO textured window layer. They also have high external quantum efficiency at light wavelengths between 300 and 1000 nm because of high photocurrent density, resulting from the low reflectivity between air and textured LPD-ZnO. Additionally, the temperature characteristics for GaInP/(In)GaAs/Ge solar cells without and with the textured LPD-ZnO window layer are similar, indicating that ambient temperature does not degrade the solar cells with the textured LPD-ZnO window layer while they are operating outside. (paper)

[en] Surface-exposed uniformly doped silicon-on-insulator channels are fabricated to evaluate the accuracy of Kelvin Probe Force Microscopy (KPFM) measured surface potential and reveals the role of surface charge on the exposed channel operated in the ambient environment. First, the quality of the potential profile probed in the vacuum environment is assessed by the consistency of converted resistivity from KPFM result to the resistivity extracted by the other three methods. Second, in contrast to the simulated and vacuum surface potential profile and image, the ambient surface potential is bent excessively at the terminals of the channel. The excessive bending can be explained by the movement of surface charge under the drive of geometry induced strong local electric field from the channel and results in non-uniform distribution. The dynamic movement of surface charges is proved by the observation of time-dependent potential drift in the ambient measurement. The result suggests the surface charge effect should be taken into account of the measurement of the surface potential in the ambient environment and the design of charge sensitive devices whose surfaces are exposed to air or in ambient conditions in their operation. (paper)

[en] The performance of an InGaP/GaAs superlattice-emitter bipolar transistor with InGaAs/GaAs superlattice-base structure is demonstrated by experimental results. The injecting electrons from superlattice emitter are easy to transport into the superlattice-base region for promoting the collector current by tunneling behavior. Furthermore, the average energy gap of base regime is substantially reduced by the use of InGaAs/GaAs superlattice structure for the requirement of low turn-on voltage. Experimentally, the transistor exhibits a maximum common-emitter current gain of 295 and a relatively low collector-emitter offset voltage of only 16 mV. In particular, the ideality factor of collector current near to unity is obtained.

[en] Influence corresponding to the position of δ-doped supplied layer on InGaP/GaAs high electron mobility transistors is comparatively studied by two-dimensional simulation analysis. The simulated results exhibit that the device with lower δ-doped supplied layer shows a higher gate potential barrier height, a higher saturation output current, a larger magnitude of negative threshold voltage, and broader gate voltage swing, as compared to the device with upper δ-doped supplied layer. Nevertheless, it has smaller transconductance and inferior high-frequency characteristics in the device with lower δ-doped supplied layer. Furthermore, a knee effect in current-voltage curves is observed at low drain-to-source voltage in the two devices, which is investigated in this article.

[en] Molybdenum sulfide has great potential for the electrocatalytic hydrogen evolution, but its structural instability in acidic media and high barriers in alkaline/neutral media limits its practical applications. Herein, the design of monodispersed sandwich-structured MoO${}_2$/MoS${}_2$/C hollow nanoreactors is reported with a triple layer "conductor/catalyst/protector" configuration for efficient electrochemical hydrogen evolution over all pH values. Metallic MoO${}_2$ substrates with ultrahigh pristine electroconductivity can promote the charge transfer while sulfur vacancies are introduced to activate the highly exposed (002) facets of MoS${}_2$. The optimized MoO${}_2$/MoS${}_2$/C nanoreactor exhibits overpotentials of 77, 91, and 97 mV (10 mA cm${}^{-<!--\; ???\; -->2}$) and Tafel slopes of 41, 49, and 53 mV dec${}^{-<!--\; ???\; -->1}$ in acidic, alkaline, and neutral media, respectively, which are much better than most of the MoS${}_2$-based electrocatalysts. Moreover, defective carbon shells are in situ generated, preventing the electrocatalysts from corrosion in acidic and alkaline media; the structural stability is verified via in situ Raman and XRD characterizations. Based on the density functional theory calculations, vacancy engineering can regulate the band structures, electron density differences, total density of states, and the H* and H${}_2$O adsorption-dissociation ability over the entire pH range. The findings may shed light on the rational development of practical pH-universal electrocatalysts for durable hydrogen evolution. (© 2021 Wiley-VCH GmbH)

[en] Lithium-sulfur batteries (LSBs) have tremendous attractive interest for their high theoretical energy density, natural abundance, and environmental friendliness. However, the commercialization remains constrained by the shuttle effect and sluggish kinetics of polysulfides. Herein, a spraying/discharging strategy is employed to fabricate binder-free $\mathrm{\omega <!--\; ??\; -->}$-Li${}_3$V${}_2$O${}_5$ ($\mathrm{\omega <!--\; ??\; -->}$-LVO) catalytic network with multi-polarization centers by intercalating Li-ions into tetrahedral V${}_2$O${}_5$ for addressing the mentioned issues. Li (0.51 eV) and V (0.57 eV), which have a strong positive electric potential, and O(-0.57 eV), which has a strong negative electric potential, exhibit high polarity that can capture polysulfides effectively. In addition, the amounts of the polarity sites would be significantly increased because the catalyst is composed of light elements. Therefore, the $\mathrm{\omega <!--\; ??\; -->}$-LVO octahedron can catalyze polysulfides to short-chains sufficiently. The blue shift in synchronous ultraviolet-visible spectra and ultra-low Tafel plots of 34 and 20 mV dec${}^{-<!--\; ???\; -->1}$ at two discharge plateaus demonstrate excellent kinetics behavior even with a low catalyst loading. Furthermore, the conductive networks facilitate electronic/ionic transmission and thereby boost their electrochemical performances. This work offers an efficacious method to promote kinetics behaviors and lessen the gap between theoretical specific capacities and future commercialization of LSBs. (© 2021 Wiley‐VCH GmbH)

[en] Lunar Penetrating Radar (LPR) is one of the important scientific instruments onboard the Chang'e-3 spacecraft. Its scientific goals are the mapping of lunar regolith and detection of subsurface geologic structures. This paper describes the goals of the mission, as well as the basic principles, design, composition and achievements of the LPR. Finally, experiments on a glacier and the lunar surface are analyzed