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Qiaofeng Yao, Tiankai Chen, Xun Yuan, Jianping Xie
Total synthesis, where desired organic- and/or biomolecules could be produced from simple precursors at atomic precision and with known step-by-step reactions, has prompted centuries-lasting bloom of organic chemistry since its conceptualization in 1828 (Wöhler synthesis of urea). Such expressive science is also highly desirable in nanoscience, since it represents a decisive step toward atom-by-atom customization of nanomaterials for basic and applied research. Although total synthesis chemistry is less established in nanoscience, recent years have witnessed seminal advances and increasing research efforts devoted into this field...
May 24, 2018: Accounts of Chemical Research
Michael Boyarsky, Timothy Sleasman, Laura Pulido-Mancera, Aaron V Diebold, Mohammadreza F Imani, David R Smith
Through aperture synthesis, an electrically small antenna can be used to form a high-resolution imaging system capable of reconstructing three-dimensional (3D) scenes. However, the large spectral bandwidth typically required in synthetic aperture radar systems to resolve objects in range often requires costly and complex RF components. We present here an alternative approach based on a hybrid imaging system that combines a dynamically reconfigurable aperture with synthetic aperture techniques, demonstrating the capability to resolve objects in three dimensions (3D), with measurements taken at a single frequency...
May 20, 2018: Applied Optics
Mohammad Mehrabi, Hamid Rajabalipanah, Ali Abdolali, Majid Tayarani
Because of exhibiting extraordinary features, metamaterial absorbers have captured considerable attention in recent years, especially at visible frequencies. In this paper, a new design of a metamaterial-inspired perfect visible absorber (MIPVA) is investigated, which exhibits ultra-broadband, polarization-independent, and wide-angle performances. The proposed MIPVA provides a flat and near unity absorbance (>99%) in an ultra-broad range of radiation wavelengths from λ=500 to 625 nm, while retaining its convincing absorptivity over the entire visible wavelengths...
May 10, 2018: Applied Optics
Rolf Szedlak, Thomas Hisch, Benedikt Schwarz, Martin Holzbauer, Donald MacFarland, Tobias Zederbauer, Hermann Detz, Aaron Maxwell Andrews, Werner Schrenk, Stefan Rotter, Gottfried Strasser
We demonstrate the on-chip generation of twisted light beams from ring quantum cascade lasers. A monolithic gradient index metamaterial is fabricated directly into the substrate side of the semiconductor chip and induces a twist of the light's wavefront. This significantly influences the obtained beam pattern, which changes from a central intensity minimum to a maximum depending on the discontinuity count of the metamaterial. Our design principle provides an interesting alternative to recent implementations of microlasers operating at an exceptional point...
May 22, 2018: Scientific Reports
Yanpei Tian, Alok Ghanekar, Matt Ricci, Mikhail Hyde, Otto Gregory, Yi Zheng
Radiative thermal transport of metamaterials has begun to play a significant role in thermal science and has great engineering applications. When the key features of structures become comparable to the thermal wavelength at a particular temperature, a narrowband or wideband of wavelengths can be created or shifted in both the emission and reflection spectrum of nanoscale metamaterials. Due to the near-field effect, the phenomena of radiative wavelength selectivity become significant. These effects show strong promise for applications in thermophotovoltaic energy harvesting, nanoscale biosensing, and increased energy efficiency through radiative cooling in the near future...
May 22, 2018: Materials
Zhen Gao, Lin Wu, Fei Gao, Yu Luo, Baile Zhang
Advances in metamaterials have offered the opportunity of engineering electromagnetic properties beyond the limits of natural materials. A typical example is "spoof" surface plasmon polaritons (SPPs), which mimic features of SPPs without penetrating into metal, but only with periodic corrugations on metal surfaces. They hold considerable promise in device applications from microwaves to the far infrared, where real SPP modes do not exist. The original spoof SPP concept is derived from the description of corrugated surfaces by a metamaterial that hosts an effective plasma frequency...
May 21, 2018: Advanced Materials
Tao Zhang, Caroline Hartl, Kilian Frank, Amelie Heuer-Jungemann, Stefan Fischer, Philipp C Nickels, Bert Nickel, Tim Liedl
3D crystals assembled entirely from DNA provide a route to design materials on a molecular level and to arrange guest particles in predefined lattices. This requires design schemes that provide high rigidity and sufficiently large open guest space. A DNA-origami-based "tensegrity triangle" structure that assembles into a 3D rhombohedral crystalline lattice with an open structure in which 90% of the volume is empty space is presented here. Site-specific placement of gold nanoparticles within the lattice demonstrates that these crystals are spacious enough to efficiently host 20 nm particles in a cavity size of 1...
May 18, 2018: Advanced Materials
Yan Zhao, Sarawuth Chaimool
In this paper, we apply a relativistic finite-difference time-domain (FDTD) method by using the Lorentz transformation to analyze metamaterials moving at a high speed. As an example, we consider a slab of left-handed metmaterial (LHM) with both relative permittivity and permeability equal to -1. Simulation results show that when the LHM slab moves at a high speed, its electromagnetic responses are drastically different from the static case. Specifically, when the LHM slab moves toward the source, for the case of normal incidence, there exists a special velocity at which fields experience a zero spatial phase delay through the LHM slab; while for the oblique incidence, above a certain velocity fields inside the LHM become evanescent...
May 16, 2018: Scientific Reports
Bo Liu, Chaojun Tang, Jing Chen, Ningyan Xie, Huang Tang, Xiaoqin Zhu, Gun-Sik Park
It is well known that a suspended monolayer graphene has a weak light absorption efficiency of about 2.3% at normal incidence, which is disadvantageous to some applications in optoelectronic devices. In this work, we will numerically study multiband and broadband absorption enhancement of monolayer graphene over the whole visible spectrum, due to multiple magnetic dipole resonances in metamaterials. The unit cell of the metamaterials is composed of a graphene monolayer sandwiched between four Ag nanodisks with different diameters and a SiO2 spacer on an Ag substrate...
May 16, 2018: Nanoscale Research Letters
Qianqian Shi, Debabrata Sikdar, Runfang Fu, Kae Jye Si, Dashen Dong, Yiyi Liu, Malin Premaratne, Wenlong Cheng
The electronic, optical, thermal, and magnetic properties of an extrinsic bulk semiconductor can be finely tuned by adjusting its dopant concentration. Here, it is demonstrated that such a doping concept can be extended to plasmonic nanomaterials. Using two-dimensional (2D) assemblies of Au@Ag and Au nanocubes (NCs) as a model system, detailed experimental and theoretical studies are carried out, which reveal collective semiconductor n/p-doping-like plasmonic properties. A threshold doping concentration of Au@Ag NCs is observed, below which p-doping dominates and above which n-doping prevails...
May 14, 2018: Advanced Materials
Saman Jahani, Sangsik Kim, Jonathan Atkinson, Justin C Wirth, Farid Kalhor, Abdullah Al Noman, Ward D Newman, Prashant Shekhar, Kyunghun Han, Vien Van, Raymond G DeCorby, Lukas Chrostowski, Minghao Qi, Zubin Jacob
Ultra-compact, densely integrated optical components manufactured on a CMOS-foundry platform are highly desirable for optical information processing and electronic-photonic co-integration. However, the large spatial extent of evanescent waves arising from nanoscale confinement, ubiquitous in silicon photonic devices, causes significant cross-talk and scattering loss. Here, we demonstrate that anisotropic all-dielectric metamaterials open a new degree of freedom in total internal reflection to shorten the decay length of evanescent waves...
May 14, 2018: Nature Communications
Andrés Concha, David Aguayo, Paula Mellado
Materials that have hysteretic response to an external field are essential in modern information storage and processing technologies. A myriad of magnetization curves of several natural and artificial materials have previously been measured and each has found a particular mechanism that accounts for it. However, a phenomenological model that captures all the hysteresis loops and at the same time provides a simple way to design the magnetic response of a material while remaining minimal is missing. Here, we propose and experimentally demonstrate an elementary method to engineer hysteresis loops in metamaterials built out of dipolar chains...
April 13, 2018: Physical Review Letters
Samuel Savitz, Mehrtash Babadi, Ron Lifshitz
For many years, quasicrystals were observed only as solid-state metallic alloys, yet current research is now actively exploring their formation in a variety of soft materials, including systems of macromolecules, nanoparticles and colloids. Much effort is being invested in understanding the thermodynamic properties of these soft-matter quasicrystals in order to predict and possibly control the structures that form, and hopefully to shed light on the broader yet unresolved general questions of quasicrystal formation and stability...
May 1, 2018: IUCrJ
Hua Zheng, Rong-Jun Zhang, Da-Hai Li, Xin Chen, Song-You Wang, Yu-Xiang Zheng, Meng-Jiao Li, Zhi-Gao Hu, Ning Dai, Liang-Yao Chen
The optical properties of aluminum-doped zinc oxide (AZO) thin films were calculated rapidly and accurately by point-by-point analysis from spectroscopic ellipsometry (SE) data. It was demonstrated that there were two different physical mechanisms, i.e., the interfacial effect and crystallinity, for the thickness-dependent permittivity in the visible and infrared regions. In addition, there was a blue shift for the effective plasma frequency of AZO when the thickness increased, and the effective plasma frequency did not exist for AZO ultrathin films (< 25 nm) in the infrared region, which demonstrated that AZO ultrathin films could not be used as a negative index metamaterial...
May 12, 2018: Nanoscale Research Letters
André Soffiatti, Yuri Max, Sandro G Silva, Laércio M de Mendonça
This article proposed to build a system founded on metamaterial sensor antennas, which can be used to evaluate impurities in aqueous substances according to the quality of transmission between the sensor antennas. In order to do this, a dedicated setup with tests in several frequencies was deployed so as to monitor the behavior of transmission variation between sensors. These sensors are microstrip antennas with a ground plane of resonant cleaved metallic rings; the substrate functions as a metamaterial for the irradiating element...
May 11, 2018: Sensors
Zenghui Xu, Dong Wu, Yumin Liu, Chang Liu, Zhongyuan Yu, Li Yu, Han Ye
We propose and numerically demonstrate an ultra-broadband graphene-based metamaterial absorber, which consists of multi-layer graphene/dielectric on the SiO2 layer supported by a metal substrate. The simulated result shows that the proposed absorber can achieve a near-perfect absorption above 90% with a bandwidth of 4.8 Thz. Owing to the flexible tunability of graphene sheet, the state of the absorber can be switched from on (absorption > 90%) to off (reflection > 90%) in the frequencies range of 3-7...
May 9, 2018: Nanoscale Research Letters
Jorge R Mejía-Salazar, Sabrina A Camacho, Carlos J L Constantino, Osvaldo N Oliveira
The strong enhancement and localization of electromagnetic field in plasmonic systems have found applications in many areas, which include sensing and biosensing. In this paper, an overview will be provided of the use of plasmonic phenomena in sensors and biosensors with emphasis on two main topics. The first is related to possible ways to enhance the performance of sensors and biosensors based on surface plasmon resonance (SPR), where examples are given of functionalized magnetic nanoparticles, magnetoplasmonic effects and use of metamaterials for SPR sensing...
2018: Anais da Academia Brasileira de Ciências
Qin Xie, Guangxi Dong, Ben-Xin Wang, Wei-Qing Huang
Quad-band terahertz absorber with single-sized metamaterial design formed by a perforated rectangular resonator on a gold substrate with a dielectric gap in between is investigated. The designed metamaterial structure enables four absorption peaks, of which the first three peaks have large absorption coefficient while the last peak possesses a high Q (quality factor) value of 98.33. The underlying physical mechanisms of these peaks are explored; it is found that their near-field distributions are different...
May 8, 2018: Nanoscale Research Letters
Mengdi Lu, Long Hong, Yuzhang Liang, Benjamin Charron, Hu Zhu, Wei Peng, Jean-François Masson
2D nanoplasmonic substrates excited in transmission spectroscopy are ideal for several biosensing, metamaterials, and optical applications. We show that their excellent properties can be further improved with plasmonic coupling of Au nanoparticles (AuNPs) on gold-coated nanodisk arrays excited at large incidence angles of up to 50o. The Bragg modes (BM) thereby strongly couple to AuNP immobilized on the plasmonic substrate due to shorter decay length of the plasmon at higher incidence angles, leading to a further enhanced field between the AuNP and the plasmonic substrate...
May 8, 2018: Analytical Chemistry
Ashish Chanana, Xiaojie Liu, Chuang Zhang, Zeev Valy Vardeny, Ajay Nahata
The ability to control the response of metamaterial structures can facilitate the development of new terahertz devices, with applications in spectroscopy and communications. We demonstrate ultrafast frequency-agile terahertz metamaterial devices that enable such a capability, in which multiple perovskites can be patterned in each unit cell with micrometer-scale precision. To accomplish this, we developed a fabrication technique that shields already deposited perovskites from organic solvents, allowing for multiple perovskites to be patterned in close proximity...
May 2018: Science Advances
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