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Waveguide Components and Aperture Antennas with Frequency-and Time-Domain Selectivity Properties
摘要： Filtering modules are essential devices of modern microwave systems given their capability to improve the signal-to-noise ratio of the received signal or to eliminate the unwanted interferences. For discriminating between different components, a filter exhibits a frequency-selective response that, however, is not able to distinguish between different signals whose spectrum falls within the pass-band of the filter itself. In this regard, some electromagnetic structures exhibiting, at the same frequency, different responses depending on the waveform of the incoming waves have been recently proposed. In this paper, we extend the aforementioned approach to the case of a standard waveguide filtering module. In particular, by loading a band-pass filtering iris with a proper lumped-element circuit, we design a waveguide component able to distinguish between different pulsed waves, even at the same frequency, depending on their pulse width. Moreover, by using this filter for capping an open-ended rectangular waveguide, a radiating element with both frequency- and time-domain selectivity properties is presented. The structures discussed in this paper may pave the way to a new class of microwave systems that, being both frequency and time selective, are less sensitive to noise and interferences.
关键词： filtering modules,time-domain response,waveguide components,waveform selectivity
更新于2025-09-23 15:21:01
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Simulation of Silicon Heterojunction Solar Cells for High Efficiency with Lithium Fluoride Electron Carrier Selective Layer
摘要： In this work, to ameliorate the quantum e?ciency (QE), we made a valuable development by using wide band gap material, such as lithium ?uoride (LiFx), as an emitter that also helped us to achieve outstanding e?ciency with silicon heterojunction (SHJ) solar cells. Lithium ?uoride holds a capacity to achieve signi?cant power conversion e?ciency because of its dramatic improvement in electron extraction and injection, which was investigated using the AFORS-HET simulation. We used AFORS-HET to assess the restriction of numerous parameters which also provided an appropriate way to determine the role of diverse parameters in silicon solar cells. We manifested and preferred lithium ?uoride as an interfacial layer to diminish the series resistance as well as shunt leakage and it was also bene?cial for the optical properties of a cell. Due to the wide band gap and better surface passivation, the LiFx encouraged us to utilize it as the interfacial as well as the emitter layer. In addition, we used the built-in electric and band o?set to explore the consequence of work function in the LiFx as a carrier selective contact layer. We were able to achieve a maximum power conversion e?ciency (PEC) of 23.74%, ?ll factor (FF) of 82.12%, Jsc of 38.73 mA cm?2, and Voc of 741 mV by optimizing the work function and thickness of LiFx layer.
关键词： electric ?eld,silicon heterojunction solar cell,lithium ?uoride,electron selectivity contact layer,work function
更新于2025-09-23 15:21:01
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Spectroscopic analysis of radioactive strontium with low isotopic abundance using laser resonance ionization
摘要： Strontium-90 (90Sr, half-life of 28.8 years) is one of the major fission products released in the Fukushima Daiichi Nuclear Power Plant accident in Japan. Due to the high concentrations of Sr stable isotopes in marine products, an upper limit for 90Sr isotopic abundance in them is of the order of 1 ppb or less. Resonance ionization technique using narrow linewidth lasers is suitable for analysis requiring high elemental and isotopic selectivity. In this study, we have investigated on 689.4 nm - 487.4 nm - 393.8 nm three-step resonance ionization of Sr atoms, where the 90Sr isotope shifts in the second and third transitions were predicted using a King plot approach to evaluate the optical isotopic selectivity. As the first step in measuring real samples, the influence of coexisting elements in seawater was also derived.
关键词： Strontium,Coexisting elements,Resonance ionization,Isotopic selectivity
更新于2025-09-23 15:21:01
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Ni Metal-Organic Frameworks Monolayers for Photoreduction of Diluted CO2: Metal Nodes-Dependent Activity and Selectivity
摘要： Photocatalytic conversion of diluted CO2 into solar fuel is highly appealing yet still in its infancy. Herein, we demonstrate the metal nodes-dependent performance for photoreduction of diluted CO2 by constructing Ni metal-organic frameworks monolayers (Ni MOLs). In diluted CO2 (10%), Ni MOLs exhibits a highest apparent quantum yield of 1.96% with a spectacular CO selectivity of 96.8%, which not only exceeds reported systems in diluted CO2 but also is superior to most catalysts in pure CO2. Whereas its isostructural Co MOLs is almost inactive in diluted CO2, indicating the performance is dependent on the metal nodes. Experimental and theoretical investigations show that strong CO2 binding affinity of Ni MOLs is the crucial factor, which is beneficial to stabilize the Ni-CO2 adducts and facilitates CO2-to-CO conversion. The universality of the superiority of Ni for CO2 photoreduction can be extended to other Ni MOFs, providing an effective general strategy for the design of inorganic-organic complexes for artificial photosynthesis.
关键词： low concertation,MOFs,CO2 photoreduction,monolayers,selectivity
更新于2025-09-23 15:21:01
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Harnessing sun for catalyst and sensitizer free regio- and stereo-selective [2+2] cycloaddition
摘要： Presence of cyclobutane rings in bioactive natural products makes them a popular synthetic target. Most common strategy for synthesizing cyclobutanes is [2+2] cycloaddition, which is usually facilitated by using ultraviolet radiation and catalysts. Herein we report the design and synthesis of densely functionalized cyclobutanes by alleviating these drawbacks and using sunlight. Further, we identified the putative mechanism of the transformation based on kinetic, fluorescence and crystallographic studies and evaluated biological activities of the products against MCF7 cell lines. The rational design of the olefinic substrates was based on their UV-vis spectra. The generic aspect of the reaction was elucidated by the syntheses of diverse analogs of cyclobutanes. Further, crystal structures and UV-vis spectra of the olefinic partners assisted us in rationalizing the stereoselectivity of the heterodimers. We believe this energy-efficient mild approach will provide a substantial contribution to the existing repertoire of strategies to regio- and stereoselectively access cyclobutanes.
关键词： Cycloaddition,Photocatalysis,Photodimerization,Self-sensitizer,Regio-selectivity
更新于2025-09-23 15:21:01
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Central-to-Helical-to-Axial-to-Central Transfer of Chirality with a Photoresponsive Catalyst
摘要： Recent advances in molecular design have displayed striking examples of dynamic chirality transfer between various elements of chirality, e.g. from central to either helical or axial chirality and vice versa. While considerable progress in atroposelective synthesis has been made, it is intriguing to design chiral molecular switches able to provide selective and dynamic control of axial chirality with an external stimulus to modulate stereochemical functions. Here, we report the synthesis and characterization of a photoresponsive bis(2-phenol)-substituted molecular switch 1. The unique design exhibits a dynamic hybrid central-helical-axial transfer of chirality. The change of preferential axial chirality in the biaryl motif is coupled to the reversible switching of helicity of the overcrowded alkene core, dictated by the fixed stereogenic center. The potential for dynamic control of axial chirality was demonstrated by using (R)-1 as switchable catalyst to direct the stereochemical outcome of the catalytic enantioselective addition of diethylzinc to aromatic aldehydes, with successful reversal of enantioselectivity for several substrates.
关键词： atropisomers,photoresponsive catalyst,chirality transfer,photoisomerization,dynamic selectivity control,molecular switches
更新于2025-09-23 15:21:01
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A dual colorimetric and near-infrared fluorescent turn-on probe for Hg2+ detection and its applications
摘要： The increasing Hg2+ contamination in environment and ecosystem has gained wide attention and thus demands for its facile and effective detection. In this study, we constructed a new fluorescent probe (E)-2-(2-(3-(1,3-dithian-2-yl)-4-hydroxystyryl)-4H-chromen-4-ylidene)malononitrile (DCM-Hg) for Hg2+ detection by incorporating the 1, 3-dithiane group to the dicyanomethylene-4H-pyran fluorophore for the first time. This probe can selectively detect Hg2+ via the Hg2+-triggered deprotection reaction of thioacetals, which leads to a distinct color change from purple to pink and obvious fluorescence enhancement in the near-infrared (NIR) region. The NIR fluorescence intensity increased linearly with Hg2+ level within the range from 0 to 100 μM and the detection limit of DCM-Hg for Hg2+ was found to be 6.8 × 10-8 mol/L. Moreover, the probe could sense Hg2+ on paper strips and image Hg2+ in living cells with low cytotoxicity, which demonstrates its potential application in environment and biological science.
关键词： Selectivity,Near-infrared,Imaging,Color change,Hg2+
更新于2025-09-23 15:21:01
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Pd-Pt bimetallic Nb-doped TiO2 for H2 photo-production: Gas and liquid phase processes
摘要： The performance of binary PtPd co-catalysts supported on Nb-TiO2 was tested in the gas and liquid phase photo-reforming of methanol. Co-catalyst formulations having Pt:Pd ratios from 2:1 to 1:4 were tested and the activity measured through the calculation of the quantum efficiency. Characterization of the initial and post-reaction materials showed that optimum activity is achieved in both processes by samples containing binary co-catalysts where Pd suffers an oxidation process and a PtPd alloying metallic phase is formed under reaction conditions. The analysis of catalytic output through an experimental design considering tree factors (methanol:water ratio, irradiance level, and catalyst volumetric concentration at liquid phase or surface concentration at gas phase) shows that the liquid phase process presents a rather high quantum efficiency value compared with the gas phase but the latter process displays higher atom efficiency as well as renders products with lower toxicity.
关键词： Carbon selectivity,Bimetallic co-catalyst,Quantum efficiency and yield
更新于2025-09-23 15:21:01
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Novel ?2-1,3-D-glucan porous microcapsule enveloped folate-functionalized liposomes as a Trojan horse for facilitated oral tumor-targeted co-delivery of chemotherapeutic drugs and quantum dot
摘要： In this study, a new type of β-1,3-D-glucan porous microcapsule (GPM)-enveloped and folate conjugated chitosan-functional liposome (FCL), FCL@GPM, was developed for the potential oral co-delivery of chemotherapeutic drugs and quantum dots (QDs) with facilitated drug absorption and antitumor efficacy. In this dual-particulate system, multiple FCLs serve as the cores for effective loading, folate-mediated tumor-targeting, facilitated intracellular accumulation, and pH-responsive controlled release of chemotherapeutic agents, while a GPM acts as the shell for affording macrophage-mediated tumor selectivity. Gefitinib (GEF) was selected as a chemotherapeutic agent, while acid degradable ZnO QDs were selected due to its dual role both as an anticancer agent for synergistic chemotherapy and as a fluorescent probe for potential cancer cellular imaging. The GEF and ZnO QDs co-loaded FCL@GPMs (GEF/ZnO-FCL@GPMs) have a prolonged release manner with limited release before uptake by intestinal cells. Furthermore, the Peyer’s patches uptake, macrophages uptake, cytotoxicity, and biodistribution of FCL@GPMs were tested. In addition, GEF and ZnO QDs co-loaded FCLs (GEF/ZnO-FCLs) not only have a tumor acidity responsive release property, but also induce a superior cytotoxicity on cancer cells as compared to GEF. Moreover, a 1.75-fold increase in the bioavailability of GEF delivered from GEF/ZnO-FCL@GPMs as compared to its trademarked drug (Iressa?). As a result, GEF/ZnO-FCL@GPMs exerted a superior antitumor efficacy (1.47-fold) as compared to its trademarked drug in mice. Considered together, the developed FCL@GPMs, combining the unique physicochemical and biological benefits of FCLs and GPMs, possess a great potential as an efficient delivery system for the co-delivery of chemotherapeutic agents and quantum dots.
关键词： chemotherapeutic drugs,pH-responsive controlled release,tumor-targeting,oral co-delivery,macrophage-mediated tumor selectivity,β-1,3-D-glucan porous microcapsule,folate conjugated chitosan-functional liposome,quantum dots
更新于2025-09-23 15:19:57
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Efficiency and spectral performance of narrowband organic and perovskite photodetectors: a cross-sectional review
摘要： The capability of detecting visible and near infrared light within a narrow wavelength range is in high demand for numerous emerging application areas, including wearable electronics, the Internet of Things, computer vision, artificial vision and biosensing. Organic and perovskite semiconductors possess a set of properties that make them particularly suitable for narrowband photodetection. This has led to rising interest in their use towards such functionality, and has driven remarkable progress in recent years. Through a comparative analysis across an extensive body of literature, this review provides an up-to-date assessment of this rapidly growing research area. The transversal approach adopted here focuses on the identification of: (a) the unifying aspects underlying organic and perovskite narrowband photodetection in the visible and in the near infrared range; and (b) the trends relevant to photoconversion efficiency and spectral width in relation to material, device and processing strategies. A cross-sectional view of organic and perovskite narrowband photodetection is thus delineated, giving fresh insight into the status and prospects of this research area.
关键词： narrowband organic photodetectors,narrowband perovskite photodetectors,NIR photodetectors,colour sensors,spectral selectivity
更新于2025-09-23 15:19:57