scholarly journals A Universal Approach for Maximizing Terahertz Wave Absorption in Graphene Cut-Wires

2021 ◽  
Vol 8 ◽  
Author(s):  
Hongjia Zhu ◽  
Ximiao Wang ◽  
Zhaolong Cao ◽  
Huanjun Chen ◽  
Shaozhi Deng
Keyword(s):  
High Efficiency ◽  
Terahertz Wave ◽  
Duty Ratio ◽  
Geometrical Parameters ◽  
Practical Applications ◽  
Wave Absorption ◽  
Thz Wave ◽  
Universal Approach ◽  
Thz Absorption ◽  
Thz Applications

Graphene micro-/nanostructures and their arrays have attracted considerable attention in infrared (IR) and terahertz (THz) applications due to their strong plasmon responses. However, as too many parameters, including geometry, carrier concentration, frequency, and adjacent substrate, can affect the plasmonic behaviors of the micro-/nanostructures, the optimization of the THz-IR responses, such as absorption and reflection, of these structures and their arrays require tremendous computations on parameter scanning. Here, we propose a theoretical approach to design graphene cut-wires with maximized THz wave absorption. Analytical expression describing the THz absorption/reflection of graphene cut-wires is derived. Accordingly, a maximum THz wave absorption of the array, regardless of its operating frequencies and geometrical parameters, can be achieved by simply tuning the cut-wires duty ratio. The analytical results are further validated by numerical simulations. This intuitive design manner is of significance for the design of graphene arrays with high-efficiency THz responses as well as promoting their practical applications in THz functional devices.

scholarly journals Unusual terahertz-wave absorptions in δ/α-mixed-phase FAPbI3 single crystals: interfacial phonon vibration modes

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Inhee Maeng ◽  
Seungjun Lee ◽  
E. Q. Han ◽  
Yurou Zhang ◽  
Seung Jae Oh ◽  
...  
Keyword(s):  
Single Crystals ◽  
Terahertz Wave ◽  
Mixed Phase ◽  
Vibration Modes ◽  
Phonon Modes ◽  
Inorganic Hybrid ◽  
Wave Absorption ◽  
Thz Wave ◽  
Hybrid Perovskite ◽  
Chemical States

AbstractThe terahertz (THz)-wave absorption properties in organic-inorganic hybrid perovskite (OHP) materials are investigated with the in-depth development of OHP-based THz applications. In the THz range from 0.5 to 3 THz, OHPs typically show several interesting phonon modes such as transverse, longitudinal, and halogen self-vibrations. To modulate these frequencies, the density changes in defect-incorporated structures and element mixtures were tested and confirmed. In the literature, the origin of phonon modes in OHP materials have been mostly explained. However, we found new phonon vibration modes in formamidinium (FA)-based hybrid perovskite structures. FAPbI3 single crystals, organic–inorganic hybrid perovskites, of the δ-, δ/α-mixed-, and α-phases were prepared. We intriguingly found that the δ/α-mixed-phase exhibited significant THz-wave absorption peaks at 2.0 and 2.2 THz that were not related to any phonon modes from either the δ- or α-phases, although the δ/α-mixed-phase sample was confirmed to be formed by a physical combination of the δ- and α-phases without the creation of any new chemical states. Our theoretical study performed with ab initio calculations provides an explanation for these unusual THz-wave absorption behaviors; they originate from the novel vibration modes excited at the seamless interfaces in the mixed phase of FAPbI3.

A flexible and ultra-broadband terahertz wave absorber based on graphene–vertically aligned carbon nanotube hybrids

2020 ◽  
Vol 8 (21) ◽  
pp. 7244-7252 ◽  
Author(s):  
Dongyang Xiao ◽  
Minmin Zhu ◽  
Qian Wang ◽  
Leimeng Sun ◽  
Chun Zhao ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Terahertz Wave ◽  
Wave Absorption ◽  
Thz Wave ◽  
Vertically Aligned ◽  
Broadband Terahertz

A flexible THz wave absorber based on G-VACNT hybrids is demonstrated for ultra-broadband THz wave absorption and imaging applications.

scholarly journals Broadband THz Absorption of Microbolometer Array Integrated with Split-Ring Resonators

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Shuming Fan ◽  
Jun Gou ◽  
Qingchen Niu ◽  
Zheyuan Xie ◽  
Jun Wang
Keyword(s):  
Periodic Structure ◽  
Wide Spectrum ◽  
Wide Frequency Range ◽  
Ring Resonators ◽  
Split Ring ◽  
Small Unit ◽  
Split Ring Resonators ◽  
Wave Absorption ◽  
Thz Wave ◽  
Thz Absorption

AbstractIn this paper, a periodic structure based on metallic split-ring resonators is integrated into micro-bridge structures of THz microbolometer array to achieve high THz wave absorption in a wide frequency range. With a small unit size of 35 μm × 35 μm, the effect of split-ring structure on THz wave absorption characteristics of the multilayer structure array is studied to manipulate the resonance absorption frequencies. The absorption bandwidth is effectively increased by integrating a combined structure of split-ring and metallic disk. Broadband THz absorption is formed by coupling the absorption peaks of different structures. The periodic structure of dual-ring combined with a metallic disk provides a broadband THz wave absorption in the range of 4–7 THz. The highest absorption in the band reaches 90% and the lowest absorption is higher than 40%. The designed structure is process-compatible and easy to implement for small-pixel THz microbolometers with high absorption in a wide spectrum range. The research provides a scheme for broadband THz sensing and real-time imaging at room temperature.

scholarly journals Chemical Modification of Combusted Coal Gangue for U(VI) Adsorption: Towards a Waste Control by Waste Strategy

2021 ◽  
Vol 13 (15) ◽  
pp. 8421
Author(s):  
Yuan Gao ◽  
Jiandong Huang ◽  
Meng Li ◽  
Zhongran Dai ◽  
Rongli Jiang ◽  
...  
Keyword(s):  
Structural Analysis ◽  
High Efficiency ◽  
Low Cost ◽  
Chemical Activation ◽  
Cost Effective ◽  
Coal Gangue ◽  
Order Kinetic ◽  
Practical Applications ◽  
Detailed Structural Analysis ◽  
Alkaline Conditions

Uranium mining waste causes serious radiation-related health and environmental problems. This has encouraged efforts toward U(VI) removal with low cost and high efficiency. Typical uranium adsorbents, such as polymers, geopolymers, zeolites, and MOFs, and their associated high costs limit their practical applications. In this regard, this work found that the natural combusted coal gangue (CCG) could be a potential precursor of cheap sorbents to eliminate U(VI). The removal efficiency was modulated by chemical activation under acid and alkaline conditions, obtaining HCG (CCG activated with HCl) and KCG (CCG activated with KOH), respectively. The detailed structural analysis uncovered that those natural mineral substances, including quartz and kaolinite, were the main components in CCG and HCG. One of the key findings was that kalsilite formed in KCG under a mild synthetic condition can conspicuous enhance the affinity towards U(VI). The best equilibrium adsorption capacity with KCG was observed to be 140 mg/g under pH 6 within 120 min, following a pseudo-second-order kinetic model. To understand the improved adsorption performance, an adsorption mechanism was proposed by evaluating the pH of uranyl solutions, adsorbent dosage, as well as contact time. Combining with the structural analysis, this revealed that the uranyl adsorption process was mainly governed by chemisorption. This study gave rise to a utilization approach for CCG to obtain cost-effective adsorbents and paved a novel way towards eliminating uranium by a waste control by waste strategy.

scholarly journals Vacancy tuned thermoelectric properties and high spin filtering performance in graphene/silicene heterostructures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zainab Gholami ◽  
Farhad Khoeini
Keyword(s):  
Electric Fields ◽  
High Spin ◽  
High Efficiency ◽  
Practical Applications ◽  
External Electric Fields ◽  
Ferromagnetic Exchange ◽  
High Spin Polarization ◽  
Filtering Effect ◽  
Spin Switching ◽  
Spin Filtering

AbstractThe main contribution of this paper is to study the spin caloritronic effects in defected graphene/silicene nanoribbon (GSNR) junctions. Each step-like GSNR is subjected to the ferromagnetic exchange and local external electric fields, and their responses are determined using the nonequilibrium Green’s function (NEGF) approach. To further study the thermoelectric (TE) properties of the GSNRs, three defect arrangements of divacancies (DVs) are also considered for a larger system, and their responses are re-evaluated. The results demonstrate that the defected GSNRs with the DVs can provide an almost perfect thermal spin filtering effect (SFE), and spin switching. A negative differential thermoelectric resistance (NDTR) effect and high spin polarization efficiency (SPE) larger than 99.99% are obtained. The system with the DV defects can show a large spin-dependent Seebeck coefficient, equal to Ss ⁓ 1.2 mV/K, which is relatively large and acceptable. Appropriate thermal and electronic properties of the GSNRs can also be obtained by tuning up the DV orientation in the device region. Accordingly, the step-like GSNRs can be employed to produce high efficiency spin caloritronic devices with various features in practical applications.

scholarly journals Ruthenium Sensitizers and Their Applications in Dye-Sensitized Solar Cells

2012 ◽  
Vol 2012 ◽  
pp. 1-21 ◽  
Author(s):  
Yuancheng Qin ◽  
Qiang Peng
Keyword(s):  
Solar Cells ◽  
High Efficiency ◽  
Low Cost ◽  
Dye Sensitized Solar Cells ◽  
Ruthenium Complexes ◽  
Practical Applications ◽  
Photovoltaic Energy ◽  
Dye Sensitized ◽  
Sensitized Solar Cells ◽  
Excellent Stability

Dye-sensitized solar cells (DSSCs) have attracted considerable attention in recent years due to the possibility of low-cost conversion of photovoltaic energy. The DSSCs-based ruthenium complexes as sensitizers show high efficiency and excellent stability, implying potential practical applications. This review focuses on recent advances in design and preparation of efficient ruthenium sensitizers and their applications in DSSCs, including thiocyanate ruthenium sensitizers and thiocyanate-free ruthenium sensitizers.

scholarly journals Synergistic Interfacial and Doping Engineering of Heterostructured NiCo(OH)x-CoyW as an Efficient Alkaline Hydrogen Evolution Electrocatalyst

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Ruopeng Li ◽  
Hao Xu ◽  
Peixia Yang ◽  
Dan Wang ◽  
Yun Li ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
High Efficiency ◽  
Low Voltage ◽  
Electrochemical Etching ◽  
Synergistic Effects ◽  
Release Kinetics ◽  
Water Electrolysis ◽  
Water Dissociation ◽  
Practical Applications ◽  
Environmentally Friendly Process

AbstractTo achieve high efficiency of water electrolysis to produce hydrogen (H2), developing non-noble metal-based catalysts with considerable performance have been considered as a crucial strategy, which is correlated with both the interphase properties and multi-metal synergistic effects. Herein, as a proof of concept, a delicate NiCo(OH)x-CoyW catalyst with a bush-like heterostructure was realized via gas-template-assisted electrodeposition, followed by an electrochemical etching-growth process, which ensured a high active area and fast gas release kinetics for a superior hydrogen evolution reaction, with an overpotential of 21 and 139 mV at 10 and 500 mA cm−2, respectively. Physical and electrochemical analyses demonstrated that the synergistic effect of the NiCo(OH)x/CoyW heterogeneous interface resulted in favorable electron redistribution and faster electron transfer efficiency. The amorphous NiCo(OH)x strengthened the water dissociation step, and metal phase of CoW provided sufficient sites for moderate H immediate adsorption/H2 desorption. In addition, NiCo(OH)x-CoyW exhibited desirable urea oxidation reaction activity for matching H2 generation with a low voltage of 1.51 V at 50 mA cm−2. More importantly, the synthesis and testing of the NiCo(OH)x-CoyW catalyst in this study were all solar-powered, suggesting a promising environmentally friendly process for practical applications.

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