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Robust synthesis of Au-based multishell structures as plasmonic catalysts for selective hydrogenation of 4-nitrostyrene
摘要： In this paper, we describe a robust self-template strategy for facile and large-scale synthesis of porous multishell Au with controllable shell number, sphere size and in-situ surface modification. The process involved the rapid reduction of novel Au-melamine colloidal templates with a great amount of NaBH4 in presence of poly(sodium-p-styrenesulfonate) (PSS). After soaking the templates in other metal salt solution, the obtained bimetallic templates could also be generally converted into bimetallic multishell structures by same reduction process. In the hydrogenation of 4-nitrostyrene using NH3BH3 as a reducing agent, the porous triple-shell Au with surface modification (S-PTSAu) exhibited excellent selectivity (97 %) for 4-aminostyrene in contrast with unmodified triple-shell Au. Furthermore, it also showed higher enhancement of catalytic activity under irradiation of visible light as compared to similar catalysts with less shell number. This work opens up a new route in designing and synthesizing Au-based multishell structures for various applications.
关键词： Selectivity,Plasmonic catalysis,Self-sacrificial templates,Multishell Au,Hydrogenation
更新于2025-09-19 17:13:59
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Passivation, conductivity, and selectivity in solar cell contacts: Concepts and simulations based on a unified partial-resistances framework
摘要： Passivation, conductivity, and selectivity are often acknowledged as the three requirements for optimal contacts to photovoltaic solar cells. Although there are generally accepted definitions and metrics for passivation and conductivity, a common understanding of the concept of selectivity is emerging only now. In this contribution, we present a generalized model of solar cell contacts based on the distinct lumped resistances encountered by electrons and holes traversing a contact, which we refer to as partial specific contact resistances. The relations between electron and hole partial current densities, quasi-Fermi level separation, and external voltage are derived from these partial specific contact resistances, leading to simple metrics for the aforementioned contact properties: the sum of the electron and hole resistances is a metric for passivation, their ratio is a metric for selectivity, and the majority-carrier resistance is a metric for conductivity. Using PC1D, we validate our model by simulating 10 500 cases of homojunction contacts to crystalline silicon solar cells, although our framework is material agnostic and can be equally applied to any other type of absorber. In these simulations, the hole contact and absorber are assumed to be ideal, whereas we vary the partial specific contact resistances in the electron contact by orders of magnitude by adjusting the electron and hole mobilities, their densities (through variations of the donor doping density), and the contact thickness. The simulations confirm the finding of the model that, when the contact fraction cannot be adjusted—as is the case with full-area contacts—combined passivation and conductivity are necessary and sufficient for optimal solar cell performance, and they imply selectivity. However, the reciprocal is not true: contacts can be selective but lack conductivity—causing a deleterious drop in fill factor—or can be selective but provide poor passivation—leading to a reduction in implied open-circuit voltage and, hence, actual open-circuit voltage. Thus, selectivity is a meaningful metric in the sole case of partial-area contacts, where the contact fraction can be adjusted arbitrarily.
关键词： solar cell contacts,crystalline silicon,partial specific contact resistances,conductivity,selectivity,PC1D simulations,passivation
更新于2025-09-16 10:30:52
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Compact three-dimensional bandpass FSS with high selectivity based on split square coaxial waveguide
摘要： In this Letter, a compact three-dimensional (3D) frequency selective surface (FSS), exhibiting a bandpass filtering response with high selectivity, is proposed based on the split square coaxial waveguide (SSCW). The unit cell of the presented 3D FSS consists of one parallel-plate waveguide propagation path and one SSCW propagation path. In the SSCW path, two identical short SCWs are produced by employing a centred annular slot. Each short SCW intrinsically provides a square slot resonance. Owing to the electromagnetic coupling between these two square slot resonances, original single square slot resonant mode will split into even-/odd-resonant modes, resulting in a flat passband with two transmission poles. Moreover, two transmission zeros located at both sides of the passband are introduced for high selectivity, because the electromagnetic waves passing through these two different paths are combined out of phase. By investigating the electric-field distributions at the frequencies of the transmission zeros/poles, the operating principle of the proposed 3D FSS is described. A prototype of the proposed 3D FSS is fabricated and measured. The measured results show that the proposed design can achieve a stable response under the incident angles up to 60° for both TE and TM polarisations.
关键词： frequency selective surfaces,bandpass filtering,compact,split square coaxial waveguide,high selectivity
更新于2025-09-16 10:30:52
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[IEEE 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Bengaluru, India (2018.12.17-2018.12.19)] 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Improvement in Self-Powered GaN-based Symmetric Metal-Semiconductor-Metal Ultraviolet Photodetectors by Using Phenol-Functionalized Porphyrin Organic Molecules
摘要： Organic molecular monolayers have been used for improving the performance of various electronic device structures. In this work, the concept of organic molecular surface modification is applied for improving the performance and the self-power quality of GaN-based symmetric Metal-Semiconductor-Metal (MSM) Ultraviolet (UV) Photodetectors (PDs). Organic molecules of phenol-functionalized-metallated-Porphyrin (Zn-TPPOH) have been adsorbed on GaN epitaxial layers and Ni/Zn-TPPOH/GaN/Zn-TPPOH/Ni PD structures have been fabricated. This process has led to decrease in reverse bias dark current by ~ 10,000 times at 0V in comparison to the dark current values obtained for Ni/GaN/Ni MSM PDs. Photodetector parameters such as Photo-to-dark current ratio and Responsivity have increased from 8.8 and 0.004 A/W for Ni/GaN/Ni structures to 2.4×105 and 0.038 A/W for Ni/Zn-TPPOH/GaN/Zn-TPPOH/Ni structures, respectively at 0V. The spectral selectivity of the PDs has also improved at 0V, which means that the molecularly modified devices have become more responsive in UV spectral region and lesser in visible spectral region, if compared to bare-GaN based devices.
关键词： PDCR,Responsivity,Spectral selectivity
更新于2025-09-16 10:30:52
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Design of miniaturized high selectivity folded substrate integrated waveguide band pass filter with Koch fractal
摘要： This paper proposes the design of a novel double folded substrate integrated waveguide (FSIW) band pass filter (BPF) based on Koch space-filling curve (SFC). The folded SIW filter is incorporated with first and second iteration levels of Koch curve on central conducting layer. A prototype of second iteration Koch fractal FSIW BPF has been fabricated using substrate having dielectric constant 2.55 and thickness 0.508 mm for each layer and then tested. The fabricated second order filter has merits of compact size (0.204 λ0 2), high roll off rate (82.2 dB/GHz) and low insertion loss (<0.85 dB) in the X band.
关键词： Folded Substrate Integrated Waveguide (FSIW) Koch fractal,selectivity,Bandpass filter,miniaturization
更新于2025-09-16 10:30:52
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Hybrid III-Nitride Tunnel Junctions for Low Excess Voltage Blue LEDs and UVC LEDs
摘要： We report a 3-D-stackable 1S1R passive cross-point resistive random access memory (RRAM). The sneak (leakage) current challenge in the cross-point RRAM integration has been overcome utilizing a ?eld-assisted superlinear threshold selector. The selector offers high selectivity of >107, sharp switching slope of <5 mV/decade, ability to tune the threshold voltage, stable operation at 125 °C, and endurance of >1011. Furthermore, we demonstrate 1S1R integration in which the selector-subthreshold current is <10 pA while offering >102 memory ON/ OFF ratio and >106 selectivity during cycling. Combined with self-current-controlled RRAM, the 1S1R enables high-density and high-performance memory applications.
关键词： sneak path,cross-point memory,select device,resistive random access memory (RRAM),1S1R,selectivity
更新于2025-09-16 10:30:52
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Development of an interference-filter-type external-cavity diode laser for resonance ionization spectroscopy of strontium
摘要： A frequency tunable external-cavity diode laser (ECDL) using a narrow bandwidth (～0.3 nm) interference filter has been developed for resonance ionization spectroscopy of strontium (Sr) with high isotopic selectivity. Improved wavelength and single mode stabilities of this interference-filter-type ECDL (IF-ECDL) over a commonly used (also home-made) Littrow-type ECDL were theoretically expected and experimentally confirmed by both a wavelength meter and a home-made Fabry-Perot interferometer. The measured spectral profile of the dominant isotope 88Sr using our IF-ECDL in the 689.4 nm intercombination transition shows that the Lorentzian component (～1.3 MHz) of the spectrum width is consistent with the obtained fringe width of the interferometer. High 90Sr isotopic selectivity of ～104 with respect to 88Sr is expected in this transition, which indicates that even if the manufacturing accuracy is not comparable to commercial Littrow-type ECDLs, our compact IF-ECDL having sufficient wavelength stability is a promising laser source for background-free analysis of radioactive 90Sr in marine samples.
关键词： resonance ionization spectroscopy,interference filter,external-cavity diode laser,isotopic selectivity,strontium
更新于2025-09-12 10:27:22
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Substrate‐integrated waveguide filtering crossovers with improved selectivity
摘要： Two substrate-integrated waveguide (SIW) filtering crossovers with high selectivity are presented. The orthogonal degenerate TE201 and TE102 modes in center square cavity are employed to realize the cross transmission and channel isolation. The offset coupling positions are then exploited for surrounding TE101-mode rectangular cavities to produce transmission zeros (TZs) above the passband in the first crossover design or for TE201-mode oversized rectangular cavities to generate one TZ on each side of the passband in the second crossover design. The footprint of first crossover has greatly been reduced, while the selectivity of both crossovers has been greatly improved. Two prototypes centered at 20 GHz are designed, fabricated, and tested for demonstration, showing good agreement between the simulated and measured results.
关键词： filtering crossovers,orthogonal degenerate modes,substrate-integrated waveguide,high selectivity
更新于2025-09-12 10:27:22
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Additive‐Free Non‐Fullerene Organic Solar Cells
摘要： CeMnOx catalyst was synthesized by the combustion method, and the supported Ti/CeMnOx catalyst was subsequently prepared by wetness impregnation. Ti/CeMnOx catalyst exhibited higher N2 selectivity than CeMnOx catalyst in the selective catalytic reduction of NO by NH3 (NH3-SCR), and the generation of side products including in N2O and NO2 were discussed. N2 adsorption/desorption, X-ray di?raction (XRD), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (TPR), NH3 temperature-programmed desorption (TPD), and in situ di?use re?ectance infrared Fourier transform spectroscopy (DRIFTS) were carried out to reveal the promotion e?ect of TiO2 on the N2 selectivity of CeMnOx catalyst. Results indicated that loading TiO2 weakened the redox ability and enhanced the NH3 adsorption ability of CeMnOx catalyst, and thus inhibited NO/NH3 oxidation and facilitated the Eley?Rideal reaction pathways even at higher temperature.
关键词： TiO2,NH3 adsorption,redox ability,CeMnOx catalyst,N2 selectivity,NH3-SCR
更新于2025-09-11 14:15:04
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Burrs-Shelled SnO2@Al2O3 Nanocables for Detection of 3-Hydroxy-2-Butanone Biomarkers
摘要： Detection of 3-hydroxy-2-butanone (3H-2B) biomarker is a newly emerging and feasible way to monitor Listeria monocytogenes (LMs). Although progress has been made in gas-sensing methodology, the long-term adsorption of the intermediate products of the reaction onto the sensing materials leads to a decrease in stability and selectivity. Herein, we report highly selective and stable 3H-2B sensors, which are developed from a core-shell structure of tin oxide nanowire coated with alumina (SnO2@Al2O3 NCBs), via combining AAO template-confined electrodeposition and wet-chemical etching. As-built sensors exhibit high sensitivity of Ra/Rg = 43.3 to 5 ppm 3H-2B at 120 oC, which is around 6 ~ 40 times against other interfering gases. Also, our sensors exhibit excellent stability with 42 days’ evaluation. Furthermore, the sensors can detect as low as 0.1 ppm 3H-2B (Ra/Rg = 2.4; 120 oC), and the sensitivity reach Ra/Rg = 27.2 at 50 oC. Our SnO2@Al2O3 NCBs sensors are endowed with ppb-level detection limit, excellent selectivity and stability at low temperature, which is of great potential in future detection of LMs.
关键词： SnO2@Al2O3 nanocables,3-hydroxy-2-butanone,selectivity and stability,sensor,AAO template
更新于2025-09-11 14:15:04