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Photoelectrocatalytic decolorization of azo dyes with nano-composite oxide layers of ZnO nanorods decorated with Ag nanoparticles.
摘要： Photoelectrocatalysis provides an excellent frame for the application of photocatalytic nanostructured materials on easy recoverable supports. This study reports the two-step synthesis of hierarchically nanostructured ZnO/Ag composite photoelectrodes. Wutzite ZnO was selectively electronucleated as spheroidal seeds on fluor doped tin oxide substrates and nanodecorated with Ag nanoclusters under electrochemical control. Hirearchically organized nanorods were selectively chemically grown on the plane (002) perpendicular to the substrate from ZnO/Ag seeds. Solutions emulating dye effluents with the usual contents of 0.1 M of NaCl and a model azo dye (Methyl Orange) were decolorized using ZnO/Ag nanorods in different treatments. Photocatalysis attained discrete decolorizations of 8% whereas photoelectrocatalysis completely decolorized solutions after 60 min. The influence of the metal/semiconductor interface (ZnO/Ag) as introduced Schottky barrier is studied demonstrating a four-fold enhancement on decolorization kinetics respect bare ZnO nanorods. The influence of the seed growth control on the final photoelectrocatalytic response is reported to control the hierarchical organization of nanorods. This resulted in different decolorization kinetics as result of the differences on the efficient use of the delivered photons conditioned by the photoelectrode structure.
关键词： photocatalysis,photocathode,nano-coating,electrochemical water treatment,Metallic/semiconductor composite photocatalysts
更新于2025-09-10 09:29:36
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The effect of manganese doping on structural, optical, and photocatalytic activity of zinc oxide nanoparticles
摘要： In this work, polyethylene glycol-6000 (PEG-6000) capped ZnO nanoparticles (NPs) were synthesized by doping with varying levels of Mn (0, 1, 2, 3, and 4 wt.%; 0% implies no doping). The crystalline sizes of the hexagonal wurtzite-structured nanoparticles, when measured with (4%) and without Mn doping (0%), were 30 and 28 nm, respectively. The Mn doping led to a shift of the ZnO optical band gap from 3.36 to 3.51 eV. The Mn2+ ions from the doping agent caused tail states in the absorbance spectrum of ZnO NPs, allowing them to be used as effectual UV photocatalysts for the degradation of organic contaminants (e.g., methyl orange (MO), methylene blue (MB), and congo red (CR)). This effect was optimized when doped with 4% Mn. When comparing 0 and 4% Mn doping, the degradation efficiency of the three contaminants was approximately 87/93.5 (MO), 85/88 (MB), and 86/93 (CR)%, respectively. Accordingly, Mn doping on ZnO NPs was found to significantly enhance their photo-degradation efficiency.
关键词： Mn-ZnO,photocatalytic degradation,organic contaminants,UV irradiation,semiconductor nanoparticles
更新于2025-09-10 09:29:36
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Enhanced Sensing Performance to Toluene and Xylene by Constructing NiGa2O4-NiO Heterostructures
摘要： The selective detection of methyl benzene (e.g. toluene and xylene) using oxide semiconductor-based gas/vapor sensors is highly desirable but limited by the low chemical reactivity of the benzene compounds. Exploiting p-type semiconductor oxides (e.g., NiO) which provide distinctive catalytic activities for methyl benzene detection is an essential approach. However, the intrinsic responses of p-type semiconductor oxides are often low. In this paper, high-performance toluene and xylene detection has been realized by a sensor based on novel p-p heterojunction NiGa2O4-NiO nanospheres. Construction of optimized p-p heterojunctions, which resulting from the rationally controlling of the NiGa2O4 content in NiGa2O4-NiO, leads to significantly promoted sensing properties for toluene and xylene detection. It is found that the sensor based on 50% NiGa2O4-NiO exhibits the best sensing performances. Its highest response (Rg/Ra = 12.7 to toluene; Rg/Ra = 16.3 to xylene) is almost 10 times higher than that of the pure NiO (Rg/Ra < 2) to 100 ppm toluene and xylene at 230 oC. More importantly, the sensor exhibits superior selectively for detection of the methyl benzene even against more reactive interfering gases/vapors, such as formaldehyde and ethanol. The p-p oxide heterojunction suggests a promising sensing material for toluene and xylene detection with high response, excellent selectivity, good stability and rapid response/recover time.
关键词： Composite semiconductor,NiO,NiGa2O4,Heterojunction,Xylene,Toluene
更新于2025-09-10 09:29:36
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Monolithic axial and radial metal-semiconductor nanowire heterostructures
摘要： The electrical and optical properties of low dimensional nanostructures depend critically on size and geometry and may differ distinctly from those of their bulk counterparts. In particular, ultra-thin semiconducting layers as well as nanowires have already proven the feasibility to realize and study quantum size effects enabling novel ultra-scaled devices. Further, plasmonic metal nanostructures attracted recently a lot of attention because of appealing near-field mediated enhancement effects. Thus, combining metal and semiconducting constituents in quasi 1D heterostructures will pave the way for ultra-scaled systems and high-performance devices with exceptional electrical, optical and plasmonic functionality. This paper reports on the sophisticated fabrication and structural properties of axial and radial, Al-Ge and Al-Si nanowire heterostructures, synthesized by a thermally induced exchange reaction of single-crystalline Ge-Si core-shell nanowires and Al pads. This enables a self-aligned metallic contact formation to Ge segments beyond lithographic limitations as well as ultra-thin semiconducting layers wrapped around monocrystalline Al core nanowires. High-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and μ-Raman measurements proved the composition and perfect crystallinity of these metal-semiconductor nanowire heterostructures. This exemplary selective replacement of Ge by Al represents a general approach for the elaboration of radial and axial metal-semiconductor heterostructures in various Ge-semiconductor heterostructures.
关键词： metal-semiconductor heterostructure,germanium,aluminum,transmission electron microscopy,nanowire
更新于2025-09-10 09:29:36
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Semiconductor opening switch generator with a primary thyristor switch triggered in impact-ionization wave mode
摘要： The results of the investigation involving a thyristor switch triggered in the impact ionization wave mode are presented. This switch is intended for operation as a primary switch in a nanosecond pulse generator with a semiconductor opening switch (SOS). The thyristor switch is based on commercial low-frequency tablet thyristors stacked in a joint assembly of up to 6 pieces connected in series. At a charging voltage of 2–12 kV and switching energy of up to 16 J, the switch operates with a discharge current of up to 8 kA, a current rise rate in the range from 14 to 54 kA/μs, and a switching ef?ciency of ～0.9. It is shown that an increase in a voltage rise rate on thyristors at the triggering stage reduces energy loss in the thyristor switch during the current ?ow. The SOS pumping circuit contains one magnetic element—a pulse transformer, which simpli?es the generator and increases its ef?ciency. The SOS generator has an output voltage of up to 300 kV and a peak power of up to 250 MW with a pulse duration of ～50 ns. The thyristor switch in the generator operates at a voltage of 12 kV and provides current ?ow with the amplitude of up to 7.5 kA with a duration of ～500 ns and a current rise rate of ～54 kA/μs. The pulse repetition frequency of the generator is 1 kHz in the burst mode of operation.
关键词： semiconductor opening switch,nanosecond pulse generator,thyristor switch,impact ionization wave
更新于2025-09-10 09:29:36
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European Microscopy Congress 2016: Proceedings || Insight on the fine structure of semiconductor nanowires down to single atom detection: correlation to their physical properties
摘要： Nanotechnology allows modifying the structure of nanoobjects down to the atomic scale. Low dimensional quantum structures can be embedded in a nanowire system in order to modify its properties at will. Electronic and optoelectronic devices benefit from the new advances in growth methodologies, with a fine control of the elemental species locally deposited. In the present work, we will present how an accurate knowledge on the atomic positions, down to single atom detection, may help to deeply understand the improved properties of our complex nanowire heterostructures. We will show how from scanning transmission electron microscopy (STEM), it is possible to obtain precise 3D atomic models that can be used as input for the simulation of its physical properties. Finally, these theoretical properties will be cross-correlated to the experimental measurements obtained locally on our nanowire systems. Some of the presented works will include: the effect of the isotope distribution on the phononic behavior of nanowires, the measurement of the internal electric fields in quantum structures and the influence of doping on the compensation of the polarization field, or the influence of polarity and the atomic arrangement on the photonic and electronic properties of single heterostructured nanowires.
关键词： polarity,physical properties,atomic scale,non-planar nanostructures,Semiconductor Nanowires
更新于2025-09-10 09:29:36
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Defects and their reduction in Ge selective epitaxy and coalescence layer on Si with semicylindrical voids on SiO<formula><tex>$_{2}$</tex></formula> masks
摘要： Formation of semicylindrical voids on SiO2 masks in Ge layers selectively grown on Si has positive impacts for reduction of threading dislocation density (TDD). Semicylindrical voids are formed through selective epitaxial growth (SEG) and coalescence of SEG Ge layers. A cross-sectional transmission electron microscope (TEM) observation reveals that a threading dislocation (TD) is terminated at a semicylindrical void, resulting in the reduction of TDD. The semicylindrical voids also contribute to the suppression of two-dimensional defects generated at the coalesced interfaces between the SEG Ge layers, which were widely observed in previous reports. Plan-view TEM observations reveal that there are TDs inclined to be parallel to the semicylindrical voids, and plan-view TEM observations show a large (4 μm × 4 μm) TD-free area in the Ge layer with the semicylindrical voids.
关键词： silicon photonics,threading dislocation density,germanium (Ge),semiconductor epitaxial layers,Epitaxial growth
更新于2025-09-10 09:29:36
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Artificial neuron based on nonlinear polarization rotation in a semiconductor optical amplifier
摘要： We experimentally demonstrated an optoelectronic artificial neuron model, which can perform sigmoid transfer function. The proposed optoelectronic circuit can mimic the behavior of continuous sigmoidal neuron based on the nonlinear polarization rotation (NPR) in a single semiconductor optical amplifier (SOA). Because the current-induced NPR is anti-parallel to the optical power-induced NPR, excitatory and inhibitory stimuli to the proposed artificial neuron can be implemented by optical injection and electrical modulation, respectively. The response of the proposed neuron to excitatory inputs and inhibitory inputs are related to the initial state of polarization (SOP), bias current and power of probe beam. By adjusting the initial SOP, the neuron can be more likely to be excited or inhibited.
关键词： Semiconductor optical amplifier,Optical processing devices,Optical neural systems
更新于2025-09-10 09:29:36
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Tuning of the defect mode in a 1D superconductor-semiconductor crystal with hydrostatic pressure dependent frequency of the transverse optical phonons
摘要： This study aims to investigate a transmittance spectrum in a one-dimensional photonic crystal, which is surrounded by air and composed of alternating layers of a superconductor (HgBa2Ca2Cu3O8+δ) and a semiconductor (GaAs), using the transfer matrix and two-fluid models. Herein, we considered the pressure-dependence of the superconductor’s critical temperature and the pressure-dependence, in the semiconductor, in both the angular frequency of the transverse optical phonons and the thickness of layers. Initially, we found that increasing the pressure for fixed thickness values of the superconductor results in a shift in the larger frequencies of the transmittance spectrum and the photonic band gaps. With an increase in the thickness of the superconductor layer at a fixed pressure and thickness values of the semiconductor, an increase in the width of the photonic band gaps was observed. When a defective GaAs semiconductor layer was inserted into the structure due to the dissipative features of the semi-conductor, a defective mode with a transmittance of less than 1.0 was found inside the photonic band gaps. When the thickness of the superconductor layer was increased, while keeping the pressure and thickness of the semiconductor constant, the defect mode shifted to shorter frequencies. It was also found that the shift and the number of defective modes in the photonic band gaps increase when the thickness of the defective semiconductor layer increases.
关键词： superconductor,transfer-matrix method,semiconductor,defect mode,Photonic crystal
更新于2025-09-10 09:29:36
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Synthesis of ultra-narrow PbTe nanorods with extremely strong quantum confinement
摘要： Monodisperse, high-quality, ultra-narrow PbTe nanorods were synthesized for the first time in a one-pot, hot-injection reaction using trans-2-decenoic acid as the agents for lead precursors and tris(diethylamino)phosphine as the telluride precursors. High monomer reactivity, rapid nucleation and fast growth rate derived from the new precursors led to the anisotropic growth of PbTe nanocrystals at low reaction temperatures (< 150 oC). In addition, the aspect ratio of PbTe nanorods could be largely adjusted from 4 to 15 by tuning the Pb to Te precursor molar ratio and reaction temperatures. Moreover, the synthesized ultra-narrow PbTe nanorods exhibited extremely strong quantum confinement and presented unique optical properties. We revealed that the diameter and length of PbTe nanorods could significantly affect their optical properties, which potentially offer them new opportunities in the application of optoelectronic and thermoelectric devices and make them desired subjects for multiple exciton generation and other fundamental physics studies.
关键词： optical properties,PbTe nanorods,Colloidal semiconductor nanocrystals
更新于2025-09-10 09:29:36