A terahertz electromagnetically induced transparency (EIT) metamaterial, consisting of single-layer graphene cut wire resonator arrays with closely placed graphene closed ring resonator arrays, was ...designed and numerically investigated in this paper. A distinct transparency window resulting from the near field coupling between two resonators can be obtained in the transmission spectrum. More importantly, since two resonator elements of all unit cells connect respectively with the corresponding metallic pads (Pad 1 and Pad 2) by the separated graphene wires, the location and amplitude of the transparency window, and the associated group delay and delay bandwidth product can be actively controlled by the selective doping graphene. Moreover, compared with other separated graphene patterns, a more convenient and fast modulation can be realized by applying gate bias voltage. In addition, a two-particle model was employed to theoretically study EIT behaviors of the graphene metamaterial with different doping states, and the analytic results agree excellently with our numerical results. Therefore, the work could offer a new platform for exploring actively tunable slow light terahertz devices such as modulators, buffers, and optical delays.
A terahertz electromagnetically induced transparency (EIT) metamaterial, consisting of single-layer graphene cut wire arrays with closely placed graphene closed ring arrays, was designed and numerically investigated in this paper. A distinct transparency window can be obtained in the transmission spectrum. More importantly, the location and amplitude of the transparency window, and the associated group delay and delay bandwidth product can be actively controlled by the selective doping graphene. Display omitted
Lead-free halide perovskites have recently evoked considerable interest in illumination and display, due to their intriguing optical properties. Herein, we present an efficient and facile strategy to ...prepare Cs2InCl5-xBrx·H2O (x = 0–5) perovskites. The preparation was performed at a low temperature of 80 °C under atmospheric pressure, and required no complex technological process. Comparing with that prepared by the traditional hydrothermal method, the emission intensity of the prepared Cs2InX5·H2O (X = Cl/Br) perovskites were increased by two times. Besides, Sb3+ ions were successfully doped into the matrix of Cs2InX5·H2O (X = Cl/Br) by our method. After doping with Sb3+, the emission intensities of Cs2InX5·H2O were greatly enhanced, with enhanced by a factor of ∼187 and ∼102, respectively. Importantly, the PLQYs were greatly improved, reaching 79.6% and 42.7%, respectively. Additionally, the effects of Br− on luminescent properties of Cs2InCl5-xBrx·H2O:Sb3+ (x = 0–5) were also investigated in this work. Though the control of the Br− content, tunable emissions from 575 nm to 630 nm were achieved. These results indicate the prepared samples could be promising environmentally-friendly materials for lightings. Furthermore, this work presents a reliable and simple method for preparing high-quality perovskites.
•Phase-pure Cs2InCl5-xBrx·H2O(x = 0–5) perovskites were prepared at a low temperature of 80 °C under atmospheric pressure.•Effects of Sb3+ ions on Cs2InX5·H2O(X = Cl/Br) were investigated in this work.•Cs2InCl5-xBrx·H2O:Sb3+(x = 0–5) perovskites with tunable emissions from 575 nm to 630 nm were achieved.•Providing a reliable and simple method for preparing high-quality perovskites.
P2-type Fe/Mn-based oxides are considered as the competitive cathode materials for sodium-ion batteries because of high specific capacity and low material cost. However, it suffers from poor cycling ...stability and unsatisfactory rate capability. Herein, the lithium-doped Na0.67Li0.1Fe0.4Mn0.5O2 microspheres are successfully synthesized via a three-step method. Benefiting from the synergetic effect of the double modification through the morphology controlling and lithium doping, the Na0.67Li0.1Fe0.4Mn0.5O2 delivers an improved cycling stability and rate performance. Moreover, fluorine is successfully introduced to further improve the electrochemical performance of the Na0.67Li0.1Fe0.4Mn0.5O2. Fluorine doping can boost the stability of the material crystal structure because of the strong electronegativity of fluorine and the stable fluorine-metal bond. Meanwhile, fluorine doping avoids the formation of extra O3 phase by reducing the average valence of transition metals. Most importantly, P2-type 10 mol% F-Na0.67Li0.1Fe0.4Mn0.5O2 shows a high discharge specific capacity of 182.0 mAh g-1 at 20 mA g-1, excellent capacity retention of 90.0% after 50 cycles and outstanding rate performance of 128.7 mAh g−1 at 400 mA g-1. Apparently, such a modification strategy apparently promotes the electrochemical performances of the P2-type Fe/Mn-based oxide and increases the commercial application possibilities of this cathode material in sodium-ion batteries.
•P2/O3-type Li-doped NLFMO microspheres are successfully synthesized.•NLFMO microspheres delivers improved cycling stability and rate performance.•Pure P2-type NLFMO microspheres are synthesized by 10 mol% fluorine doping.•P2-type 10 mol% F-NLFMO displays higher specific capacity than NLFMO.•P2-type 10 mol% F-NLFMO also shows better cyclic stability and rate capability.
Mesoporous carbons (MCs) are highly porous materials, which offer high surface area and higher electrochemical performance than traditional carbon materials. Doped carbons are particularly ...interesting materials due to their possible use as metal-free ORR catalysts. In this paper, nitrogen and sulfur doped or co-doped MCs were prepared according to a hard template approach consisting in pyrolysis of powders obtained by liquid impregnation of mesoporous silica with different heterocyclic condensed aromatic precursors. The synthetized MCs show round shaped particles with mesoporosity of 3–4 nm diameter, a BET surface area higher than 850 m2/g and nitrogen and sulfur contents ranging between 3–8% and 4–14%, respectively. Final doping has been demonstrated by core level photoemission spectra. The effect of the pyrolysis temperature on the physico-chemical properties of the resulting MCs has been investigated as well as the role of the dopant heteroatoms on their catalytic performances towards oxygen reduction reaction (ORR). Electrochemical tests show that both the oxygen-, sulfur- and nitrogen-containing groups can induce an electrocatalytic activity of MCs for ORR. The catalytic activity shows a linear dependence from the nitrogen content and a prevalent 2 electron reduction process leading to the formation of hydrogen peroxide, both in acid and alkaline solution.
•Nitrogen/sulfur co-doped carbon is designed by a facile template method.•Interconnected honeycomb-like structure essentially boosts fast K+/e− transport.•Porosity engineering coupled with heteroatom ...doping endows outstanding K+ storage.
Carbonaceous materials are selected as promising anodes for potassium-ion batteries (PIBs). Nevertheless, it is still a significant bottleneck to fabricate an ideal carbonaceous material with impressive rate capability and cycling performance due to the sluggish kinetics of K+. Herein, a hard template-assisted strategy is reported for designing a class of rhodanine-derived nitrogen/sulfur co-doping honeycomb-like carbons as anodes for PIBs. The characteristics, including high nitrogen/sulfur content (6.28/3.3 at%), high surface area (560 m2 g−1), and interconnected honeycomb-like structure, play significant roles in boosting potassium ion storage by offering more electroactive sites and shorting the ion transfer distance, resulting in ultrahigh reversible capacity of 443.3 mA h g−1 at 100 mA g−1, exceptional rate capability (182.5 mA h g−1at 10 A g−1), and superior cyclability (97% retention ratio at 2 A g − 1 over 1000 cycles). Moreover, the electrochemical kinetic analysis manifests the fast capacitive-dominated potassium storage mechanisms. The fabricated potassium ion capacitor delivers a promising energy and power density (76.8 W h kg−1 and 10,413.7 W kg−1)), and simultaneously ultra-long lifespan (∼91% capacity retention over 2000 cycles). Such a work highlights that structure engineering coupled with doping engineering could effectively enhance K+ adsorption, providing a facile pathway of material design for high-performance PIBs.
The nitrogen and sulfur co-doped honeycomb-like carbon (NSC) is synthesized as anode for PIBs by a facile hard template-assisted strategy. The characteristics, including high nitrogen/sulfur content, interconnected honeycomb-like structure, and large surface area, result in the superior potassium ion storage. Display omitted
High-voltage spinel Li1+xNi0.5Mn1.5O4-xClx (0 ≤ x ≤ 0.04) cathode materials with different contents of Li+ and Cl− co-doping were obtained through a solid-state process. Scanning electron microscopy ...and transmission electron microscopy images indicate that pure LiNi0.5Mn1.5O4 (LNMO, space group Fd-3 m) particles possess an octahedral morphology, predominantly exhibiting {111} crystallographic planes. While the specimens with Li+ and Cl− co-doping display not only {111} crystal facets but also positive {100} and {110} facets (i.e. truncated octahedral shape) that could facilitate Li+ transport and stabilize the spinel structure. Compared to the pure LNMO, the Li+ and Cl− co-doped LNMO electrodes display superior electrochemical performances. For example, the Li1.03Ni0.5Mn1.5O3.97Cl0.03 exhibits the superior rate capability, with discharge capacities of 92.3 and 52.6 mA h g−1 at 7C and 10C, respectively, which are much higher than those of pure LNMO (54.2 and 7.8 mA h g−1 at 7C and 10C). An improved electrochemical properties of LNMO-Cl0.03 is attributable to its relatively larger portion of {100} and {110} facets, lower charge-transfer resistance and electrode polarization, and higher Li+ diffusion coefficient.
•The Li and Cl co-doping not only changes particle morphologies but also make the particle size become slightly larger.•LNMO-Cl0.03 exhibits a superior rate performance and cycling stability than that of pure LNMO.•The relatively larger portion of {100} and {110} facets in LNMO-Cl0.03 may be favorable for Li+ diffusion.
Constructing electrode materials with fast ions and electrons transport channels is an effective solution to achieve high‐power‐density and long‐cycle potassium‐ion batteries (PIBs). Herein, ...completely opening radial pores in N/O dual‐doped carbon nanospheres (RPCNSs) are constructed as anode for high‐power PIBs. The RPCNS with hierarchical structure (micro/meso/macropores and radial channels) and N/O dual‐doping permits speedy ions and electrons transportation within the carbon nanospheres anode, achieving a reversible capacity of 346 mAh g−1 at 50 mA g−1 after 360 cycles and long‐term cycling life over 2000 cycles without obvious capacity attenuation. The in situ Raman and kinetic analysis (in situ electrochemical impedance spectroscopy and galvanostatic intermittent titration) suggest that the exquisitely designed pore structure and heterodoping enable highly reversible electrochemical reaction and fast de/intercalation kinetics. Moreover, the full cells packaged with RPCNS anode can be fully charged in 10 s and exhibit the highest charge power density of 24 866 W kg−1 and longest cycling endurance of 5000 cycles in reported PIBs. The unique structural engineering provides a new way for high‐power density potassium‐ion storage devices.
A radial channel is constructed, and in situ nitrogen/oxygen doping in carbon nanospheres is introduced to assemble a high power density and ultralong cycling life potassium‐ion full battery anode. The hierarchical channels and N,O dual‐doping can significantly shorten the ion conveyance pathway and highly accelerate the electrons conduction, which are availed to the kinetics of electrode reactions.
Cation doping is an effective strategy for improving the cyclability of layered oxide cathode materials through suppression of phase transitions in the high voltage region. In this study, Mg and Sc ...are chosen as dopants in P2‐Na0.67Ni0.33Mn0.67O2, and both have found to positively impact the cycling stability, but influence the high voltage regime in different ways. Through a combination of synchrotron‐based methods and theoretical calculations it is shown that it is more than just suppression of the P2 to O2 phase transition that is critical for promoting the favorable properties, and that the interplay between Ni and O activity is also a critical aspect that dictates the performance. With Mg doping, the Ni activity can be enhanced while simultaneously suppressing the O activity. This is surprising because it is in contrast to what has been reported in other Mn‐based layered oxides where Mg is known to trigger oxygen redox. This contradiction is addressed by proposing a competing mechanism between Ni and Mg that impacts differences in O activity in Na0.67MgxNi0.33‐xMn0.67O2 (x < 0 < 0.33). These findings provide a new direction in understanding the effects of cation doping on the electrochemical behavior of layered oxides.
Beyond the well‐known P2 to O2 phase transition, oxygen redox is a main bottleneck for capacity retention. Using synchrotron‐based methods, it is revealed that competing mechanisms between Ni and Mg (or Li, Zn, and Cu) are critical for controlling the degree of oxygen redox in doped Ni–Mn based layered oxides in Na‐ion batteries.
To enable graphene-integrated interconnects in modern VLSI circuits, a major roadblock is developing an efficient Back End of Line (BEOL) compatible doping technique. In this paper, we demonstrate ...metal-induced doping of graphene in graphene-ruthenium hybrid structures. We study doping by systematically performing different material characterization techniques – Internal Photoemission Spectroscopy (IPE), Raman Spectroscopy and Kelvin Probe Force Microscopy (KPFM) to gain a deeper understanding on the charge transfer at the graphene-Ru interface. In IPE, we measure the relative band alignment of graphene and Ru, the interface potential barrier and effective work function of 4.9eV. With Raman spectral mapping, we report p-type doping in single layer graphene on Ru film with carrier density 1.9E13cm−2. And with KPFM, Fermi-level shift of ∼420 meV (wrt intrinsic graphene) is observed implying downward shift of Fermi level in the graphene valence band. Electrically, graphene capping results in ∼19 % drop in sheet resistance of Ru accompanied by significant decrease in contact resistance. Moreover, the temperature coefficient of resistance reduces after graphene capping indicating better response to thermal fluctuations. By performing an extensive study using different material and electrical techniques, our results provide a viable and practical basis for integrating graphene as a conductor in advanced interconnects.
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