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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Parameterization Models for Traceable Characterization of Planar CPW SOL Calibration Standards
摘要： Methods for traceable characterization and uncertainty evaluation of planar 1-port CPW short-open-load (SOL) devices are developed. The agreement of modelling and verification measurement results greatly supports the application of the proposed parameterization models and used FEM-based EM modelling of CPW structures for traceable characterization of planar CPW-based SOL devices in the frequency range between a few kHz up to 50 GHz.
关键词： traceability,co-planar waveguide,measurement uncertainty,VNA,nanostructures,on-wafer calibration,EM simulation,precision measurements
更新于2025-09-10 09:29:36
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Enhanced Oxygen Evolution Reaction Activity of Nanoporous SnO <sub/>2</sub> /Fe <sub/>2</sub> O <sub/>3</sub> /IrO <sub/>2</sub> Thin Film Composite Electrodes with Ultralow Noble Metal Loading
摘要： A conductive SnO2 layer and small quantities of IrO2 surface cocatalyst enhance the catalytic efficiency of nanoporous Fe2O3 electrodes in the oxygen evolution reaction at neutral pH. Anodic alumina templates are therefore coated with thin layers of SnO2, Fe2O3, and IrO2 by atomic layer deposition. In the first step, the Fe2O3 electrode is modified with a conductive SnO2 layer and submitted to different postdeposition thermal treatments in order to maximize its catalytic performance. The combination of steady-state electrolysis, electrochemical impedance spectroscopy, X-ray crystallography, and X-ray photoelectron spectroscopy demonstrates that catalytic turnover and e? extraction are most efficient if both layers are amorphous in nature. In the second step, small quantities of IrO2 with extremely low iridium loading of 7.5 μg cm?2 are coated on the electrode surface. These electrodes reveal favorable long-term stability over at least 15 h and achieve maximized steady-state current densities of 0.57 ± 0.05 mA cm?2 at η = 0.38 V and pH 7 (1.36 ± 0.10 mA cm?2 at η = 0.48 V) in dark conditions. This architecture enables charge carrier separation and reduces the photoelectrochemical water oxidation onset by 300 mV with respect to pure Fe2O3 electrodes of identical geometry.
关键词： iridium oxide,water splitting,nanostructures,iron oxide,atomic layer deposition
更新于2025-09-10 09:29:36
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Reversible Polarization Recording in As2S3–Se Multilayer Nanostructures
摘要： Polarization holographic recording of diffraction gratings and their subsequent erasure have been investigated on As2S3–Se multilayer nanostructures. The work investigates how preexposure to actinic laser radiation up to complete photoinduced changes in the optical properties affects the formation of diffraction gratings in the studied structure. It is shown that the preexposure of an As2S3–Se multilayer nanostructure (MNS) leads to photobleaching, and the maximum achievable diffraction efficiency (DE) of 35% does not change; however, the required exposure value is increased. It is also shown that exposure using one laser beam results in complete erasure of the diffraction grating recorded up to the maximum. Seven recording–erasure cycles show that the kinetics of the increase in diffraction efficiency and its maximum value do not change, which indicates that the As2S3–Se multilayer structure is capable of reversible holographic recording under orthogonal circular polarization. Study of the gratings recorded with an atomic-force microscope shows that the main factor determining the diffraction efficiency value is modulation of the relief, the depth of which is greater than 200 nm.
关键词： reversible holographic recording,chalcogenide multilayer nanostructures,diffraction efficiency,direct surface relief formation
更新于2025-09-10 09:29:36
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Electromagnetic field amplification in Al/Ag spherical nanostructures
摘要： The localized electromagnetic field of multilayered nanoshells is studied using quasi-static approach and plasmon hybridization theory. The absorption spectrum of concentric metal–dielectric–metal nanostructures shows three plasmon resonance peaks which are optimized by tuning the geometrical parameters. It has been found that the three-layered nanoshells present different surface plasmon mode when the metal type of inner core and outer shell is exchanged. Silver and aluminum metals have stronger and sharper plasmon modes than that of gold and the outer silver shell has a greater effect on the total plasmonic properties of nanoshell. Three separated plasmon peaks of absorption spectrum of Al–Dielectric–Ag nanoshell cover a wide range from UV to NIR region. In addition, the optimal geometry is discussed to obtain the highest electromagnetic field enhancement in Al–dielectric–Ag nanoshell with special properties.
关键词： Plasmon hybridization theory,SERS,Surface plasmon resonance,Al/Ag spherical nanostructures,Electromagnetic field amplification
更新于2025-09-10 09:29:36
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Applied Nanophotonics || Energy transfer processes
摘要： In this chapter, we introduce the general phenomenon of excitation energy transfer, explain radiative and nonradiative types of energy transfer, and derive the basic processes of energy transfer. We look at the F?rster resonance energy transfer (FRET) in particular. We also describe Dexter energy transfer, charge transfer, exciton diffusion, and exciton dissociation. Finally, we summarize the modifications of FRET when using nanostructures with mixed dimensionalities and in different assemblies.
关键词： F?rster resonance energy transfer,nanostructures,FRET,charge transfer,exciton diffusion,energy transfer,Dexter energy transfer,exciton dissociation
更新于2025-09-10 09:29:36
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Li2SnO3 branched nano- and microstructures with intense and broadband white-light emission
摘要： Exploiting the synergy between microstructure, morphology and dimensions by suitable nanomaterial engineering, can effectively upgrade the physical properties and material performances. Li2SnO3 elongated nano- and microstructures in form of belts, wires, rods and branched structures have been fabricated by a vapor-solid method at temperatures ranging from 700 to 900 °C using metallic Sn and Li2CO3 as precursors. The achievement of these new morphologies can face challenging applications for Li2SnO3, not only in the field of energy storage, but also as building blocks in optoelectronic devices. The micro- and nanostructures grown at 700 and 800 °C correspond to monoclinic Li2SnO3, while at 900 °C complex Li2SnO3/SnO2 core-shell microstructures are grown, as confirmed by X-ray diffraction and Raman spectroscopy. Transmission electron microscopy reveals structural disorder related to stacking faults in some of the branched structures, which is associated with the presence of the low-temperature phase of Li2SnO3. The luminescent response of these structures is dominated by intense emissions at 2, 2.5 and 3 eV, almost completely covering the whole range of the visible light spectrum. As a result, white-light emission is obtained without the need of phosphors or complex quantum well heterostructures. Enhanced functionality in applications such as in light-emitting devices could be exploited based on the high luminescence intensity observed in some of the analysed Li2SnO3 structures.
关键词： white light emitters,luminescence,nanostructures,lithium oxides
更新于2025-09-10 09:29:36
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Synthesis and physical properties of un- and Zn-doped Ag2S nanoparticles
摘要： This study is devoted to the sonochemical synthesis of un- and Zn-doped silver sulfide (Ag2S) nanostructures and evaluation of the parameters that affect its structural, morphological and optical properties. To unravel any changes in the characteristics of the particles, the XRD and FESEM techniques, in addition to photoluminescence (PL), Raman and UV–Vis spectroscopies, were applied. According to the analyses, 15 min sonication using 200 W power can provide the highest quality of the Ag2S crystals. Moreover, it was found out that Zn doping shifts the XRD peaks of Ag2S to higher angles and declines crystallinity of the samples while it does not change the spherical shape of the Ag2S particles. The other impact of Zn presence in the crystal lattice of Ag2S was declared to be increasing the size of the Ag2S nanostructures. Importantly, based on the PL results, the un- and Zn-doped Ag2S particles present several emission bands lying in the visible spectrum of light due to their specific optical near band emission (NBE) and crystal defects. As the PL spectra demonstrated, increasing the Zn concentration decreases the optical band gap energy of the Ag2S nanostructures. Also, the Raman results unraveled the impact of synthesis conditions on the optical and crystalline properties of the grown structures.
关键词： Zn-doped,Optical properties,Sonochemical,Ag2S nanostructures,Synthesis parameters
更新于2025-09-10 09:29:36
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Highly efficient visible-light-assisted photocatalytic hydrogen generation from water splitting catalyzed by Zn0.5Cd0.5S/Ni2P heterostructures
摘要： Development of heterostructured photocatalysts which can facilitate spatial separation of photo-generated charge carriers is crucial for achieving improved photocatalytic H2 production. Consequently, herein, we report the synthesis of Zn0.5Cd0.5S/Ni2P heterojunction photocatalysts with varying amount of Ni2P, 0.5 (S1), 1 (S2), 3 (S3), 5 (S4) and 10wt% (S5) for the efficient visible-light-assisted H2 generation by water splitting. The heterostructures were characterized thoroughly by PXRD, FE-SEM, EDS, HR-TEM and XPS studies. FE-SEM and HR-TEM analyses of the samples unveiled the presence of Zn0.5Cd0.5S microspheres composed of smaller nanocrystals with the surface of the microspheres covered with Ni2P nanosheets and the intimate contact between the Zn0.5Cd0.5S and the Ni2P. Further, visible-light-assisted photocatalytic investigation of the samples showed excellent water splitting activity of the heterostructure, Zn0.5Cd0.5S/1wt%Ni2P (S2) with very high H2 generation rate of 21.19 mmol h?1 g?1 and the AQY of 21.16% at 450 nm with turnover number (TON) and turnover frequency (TOF) of 251,516 and 62,879 h?1 respectively. Interestingly, H2 generation activity of S2 was found to be about four times higher than that of pure Zn0.5Cd0.5S (5.0 mmol h?1 g?1) and about 240 times higher than that of CdS/1wt%Ni2P. The enhanced H2 generation activity of S2 has been attributed to efficient spatial separation of photo-generated charge carriers and the presence of highly reactive Ni2P sites on the surface of Zn0.5Cd0.5S microspheres. A possible mechanism for the enhanced photocatalytic H2 generation activity of Zn0.5Cd0.5S/1wt%Ni2P (S2) has been proposed and is further supported by photoluminescence and photocurrent measurements. Furthermore, the catalyst, S2 can be recycled for several cycles without significant loss of catalytic activity and photostability. Remarkably, the H2 generation activity of S2 was found to be even higher than the reported examples of ZnxCd1-xS doped with noble metal cocatalysts. Hence, the present study highlights the importance of Zn0.5Cd0.5S/Ni2P heterostructures based on non-noble metal co-catalyst for efficient visible-light-driven H2 production from water splitting.
关键词： Heterostructure,Transition metal phosphide,H2 generation,Visible-light photocatalysis,Zn0.5Cd0.5S nanostructures
更新于2025-09-10 09:29:36
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Wet-chemical preparation of TiO2-nanostructures using different solvents: Effect of CTAB concentration and tentative mechanism of particle formation
摘要： In this paper, TiO2 nanostructures (TiO2-NSs) were synthesized in a controlled way. The effects of the use of a surfactant, Cetyl trimethylammonium bromide (CTAB), and the nature of the solvent of synthesis (ethanol and toluene) on the characteristics of the final product were studied. For this, TiO2-NSs were characterized using IR spectroscopy, X-ray diffraction (XRD), Transmission and Scanning Electron Microscopy. The solid obtained, without heat treatment, presented an amorphous structure that crystallized when treated at 450 °C, giving anatase as crystalline phase, independent of the solvent of synthesis and the concentration of CTAB used. The size of the crystallite in the powders synthesized was 3-5 nm and was reduced on increasing CTAB concentration, regardless of the solvent used. Using ethanol, the primary particles had a spheroidal or needle type shape of nanometric size (<100 nm) and the agglomerates were spherical (1 to 5 μm), reducing in size on the addition of CTAB. On using toluene, irregular-shaped aggregates with acute edges were formed (10 to 20 μm), made up of primary particles nanometric (<100 nm) and with the presence of poros. Given the nature of the synthesis process, a mechanism was proposed to explain the formation of the TiO2-NSs.
关键词： toluene,mechanism of formation,ethanol,TiO2 nanostructures,synthesis,surfactant
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