Search results for "ANTENNA"
showing 10 items of 250 documents
A Co-monosubstituted Keggin polyoxometalate with an antenna ligand and three cobalt(II) chains as counterion
2009
Abstract A Co-monosubstituted Keggin polyoxometalate with an antenna ligand linked to the Co(II) center with a Co(II)-containing cation has been prepared. The title compound, formulated as {Co(H 2 O) 4 (4,4′-bpy)} 2 (4,4′-Hbpy) 2 [SiW 11 Co(4,4′-bpy)O 39 ] · 5H 2 O ( 1 ) (4,4′-bpy = 4,4′-bipyridine), was synthesized and characterized by elemental analysis, IR spectra, TG analysis, X-ray single crystal structure analysis and magnetic measurements. As far as we know, the title compound represents the first Co(II) substituted Keggin polyoxometalate with an antenna ligand structurally and magnetically characterized.
Bis- and trisporphyrin bio-inspired models for bacterial antennas and photosystems
2011
This review presents the synthetic aspects and photophysical properties of trimeric systems constructed with a first unit consisting of a cofacial porphyrin and then of another porphyrin attached as a side arm. Two scenarios are dealt with. The first one is the case where the three chromophores are different, called donor 1–donor 2–acceptor, specifically where the cofacial fragment is composed of donor 1 and donor 2, and the side arm is the acceptor. They are considered as models for the apo-proteins used in the LH II (light harvesting device) in the purple photosynthetic bacteria. The second one is the case where the chromophores of the cofacial bisporphyrin residue are identical and are …
B,B-Diporphyrinbenzyloxy-BODIPY dyes: synthesis and antenna effect.
2012
B,B-Diporphyrinbenzyloxy-BODIPY derivatives have been prepared in high yields, and the photophysical properties are reported. Singlet energy transfers from BODIPY to the porphyrin units have been analyzed.
A Dataset of Annotated Omnidirectional Videos for Distancing Applications
2021
Omnidirectional (or 360°) cameras are acquisition devices that, in the next few years, could have a big impact on video surveillance applications, research, and industry, as they can record a spherical view of a whole environment from every perspective. This paper presents two new contributions to the research community: the CVIP360 dataset, an annotated dataset of 360° videos for distancing applications, and a new method to estimate the distances of objects in a scene from a single 360° image. The CVIP360 dataset includes 16 videos acquired outdoors and indoors, annotated by adding information about the pedestrians in the scene (bounding boxes) and the distances to the camera of some point…
Optimal matching between optical rectennas and harvester circuits
2017
This paper deals with optimal coupling issues between rectennas and harvesting circuits. An optical rectenna consists of a nanoantenna usually coupled with an ultra-high speed rectifier. These devices aim to receive and convert solar and thermal radiation in a DC voltage, while a harvester circuit provides the energy to be stored. The rectenna impedance is influenced both by its structure and by the rectifying diode, the harvester circuit impedance has to be matched to optimize the power transfer. The purpose of this contribution is to discuss the best impedance conditions by taking into account the constraints that are due to the individual devices the conversion system consist of. Finally…
Trade-off Performance of Optical Nanoantennas for Solar Energy Harvesting Applications
2019
In this paper, the optimum behaviour of optical nanoantennas, in terms of impedance, directivity, available power, and field enhancement, at a resonance frequency of about 350 THz, will be shown. Optimum configurations are obtained by varying nanoantennas geometry in order to maximize the available power, enhancing the electric field in gap proximity and so the absorptivity. Moreover, the simulation results for aluminum nanoantennas on a three-layers substrate, will be reported, and a trade-off performance comparison among different antennas will be discussed. This study can guide both the engineering and the fabrication of plasmonic nanoantennas.
A High-Efficiency Optical Energy Harvester based on a Low-Impedance Plasmonic Nanoantenna
2022
In this paper, for the first time, an investigation in terms of efficiency of an energy harvester based on a plasmonic nanorectenna array is proposed. The novel proposed mirrored-arrowhead nanoantenna presents a very low impedance value at the resonant frequency which reduces the mismatching between the antenna and rectifier circuit. Simulation results carried out by the CST 2020 Studio show a resistance value equal to 1.1 kohms at about 350 THz and a very wide bandwidth as the equivalent RF rhombic antenna. This study paves the way to nanoantennas for high-efficiency electromagnetic energy harvesting applications overcoming the photovoltaic technology.
Advanced Techniques for Powering Wireless Sensor Nodes through Energy Harvesting and Wireless Power Transfer
2020
This paper presents three different techniques for efficiently powering an energy-autonomous wireless sensor (EAWS) through both energy harvesting (EH) and RF wireless power transfer (WPT). The aim of the paper is to provide effective strategies and techniques to reduce, as far as possible, the cost of wiring of the automotive production process due to the continuous and constant increase in the use of sensors. The techniques employ a highly integrated state-of-the-art, ultra-low power 2.5 mu W system-on-chip (SoC) system, designed for multi-source RF wireless energy harvesting and power transfer and are designed with the goal of minimizing and, where possible, eliminating the costly mainte…
Progress in THz Rectifier Technology: Research and Perspectives
2022
Schottky diode (SD) has seen great improvements in the past few decades and, for many THz applications, it is the most useful device. However, the use and recycling of forms of energy such as solar energy and the infrared thermal radiation that the Earth continuously emits represent one of the most relevant and critical issues for this diode, which is unable to rectify signals above 5 THz. The goal is to develop highly efficient diodes capable of converting radiation from IR spectra to visible ones in direct current (DC). A set of performance criteria is investigated to select some of the most prominent materials required for developing innovative types of electrodes, but also a wide variet…
Improving nanoscale terahertz field localization by means of sharply tapered resonant nanoantennas
2020
Abstract Terahertz resonant nanoantennas have recently become a key tool to investigate otherwise inaccessible interactions of such long-wavelength radiation with nano-matter. Because of their high-aspect-ratio rod-shaped geometry, resonant nanoantennas suffer from severe loss, which ultimately limits their field localization performance. Here we show, via a quasi-analytical model, numerical simulations, and experimental evidence, that a proper tapering of such nanostructures relaxes their overall loss, leading to an augmented local field enhancement and a significantly reduced resonator mode volume. Our findings, which can also be extended to more complex geometries and higher frequencies,…