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Li2TiSiO5 receives much interest recently in lithium-ion battery anodes because of its attractive Li-insertion/extraction potential at 0.28 V (vs. Li+/Li), which bridges the potential gap between graphite and Li4Ti5O12. However, Li2TiSiO5 suffers from the low intrinsic electronic conductivity and sluggish Li-ion transfer kinetics. In this work, we report lithium-ion insertion kinetics of Li2TiSiO5 by Na doping, achieving high-rate capability. Rietveld refinement of X-ray diffraction results reveals that Na doping can enlarge the space of Li slabs, thus reducing the Li-ion transfer barrier and enhancing the Li-ion diffusion kinetics. According to first-principles calculations, Na doping can tune the band structure of Li2TiSiO5 from indirect to direct band, leading to improved electronic conductivity and electrochemical performance. In particular, the Na-doped Li2TiSiO5 (Li1.95Na0.05TiSiO5) electrode exhibits outstanding rate capability with a high capacity of 101 mA h g−1 at 5 A g−1 and superior cyclability with a reversible capacity of 137 mA h g−1 under 0.5 A g−1 over 150 cycles.

Solid-state electrolytes (SSEs) with high ionic conductivities are the key components in solid-state batteries, and the ionic conductivities of SSEs are strongly related to their underlying crystal...

Plasmonic excitations, consisting of collective oscillations of the electron gas in a conductive film or nanostructure coupled to electromagnetic fields, play a prominent role in photonics and optoelectronics. While traditional plasmonic systems are based on noble metals, recent work has established graphene as a uniquely suited materials platform for plasmonic science and applications due to several distinctive properties. Graphene plasmonic oscillations exhibit particularly strong sub-wavelength confinement, can be tuned dynamically through the application of a gate voltage, and span a portion of the infrared spectrum (including mid-infrared and terahertz (THz) wavelengths) that is not directly accessible with noble metals. These properties have been studied in extensive theoretical and experimental work over the past decade, and more recently various device applications are also beginning to be explored. This review article is focused on graphene plasmonic nanostructures designed to address a key outstanding challenge of modern-day optoelectronics – the limited availability of practical, high-performance THz devices. Graphene plasmons can be used as a means to enhance light–matter interactions at THz wavelengths in a highly tunable fashion, particularly through the integration of graphene resonant structures with additional nanophotonic elements. This capability is ideally suited to the development of THz optical modulators (where absorption is switched on and off by tuning the plasmonic resonance) and photodetectors (relying on plasmon-enhanced intraband absorption or rectification of charge-density waves), and promising devices based on these principles have already been reported. Novel radiation mechanisms, including light emission from electrically excited graphene plasmons, are also being explored for the development of compact narrowband THz sources.

Most Li+/Na+-conducting solid electrolytes are unstable in moisture, and the formed hydroxides and carbonates on their surfaces result in the increase of the interfacial resistance between solid el...

In this study, a facile and green route was designed using hydrolyzed chitosan as precursor to fabricate superior molecular state fluorophores based on the Maillard reaction (MR). The fluorophores ...

The vision system of arthropods such as insects and crustaceans is based on the compound-eye architecture, consisting of a dense array of individual imaging elements (ommatidia) pointing along different directions. This arrangement is particularly attractive for imaging applications requiring extreme size miniaturization, wide-angle fields of view, and high sensitivity to motion. However, the implementation of cameras directly mimicking the eyes of common arthropods is complicated by their curved geometry. Here, we describe a lensless planar architecture, where each pixel of a standard image-sensor array is coated with an ensemble of metallic plasmonic nanostructures that only transmits light incident along a small geometrically-tunable distribution of angles. A set of near-infrared devices providing directional photodetection peaked at different angles is designed, fabricated, and tested. Computational imaging techniques are then employed to demonstrate the ability of these devices to reconstruct high-quality images of relatively complex objects., The compound eyes of arthropods provide a visual advantage by seeing a wide range of angles all at once, but cameras that mimic them are usually curved and bulky. Here, the authors develop a flat, plasmonic image sensor array that enables high-quality wide-angle vision without lenses or curvature.

LAGP (Li1.5Al0.5Ge0.5P3O12) is a promising solid-state electrolyte (SSE) for all solid-state lithium-ion batteries (ASS-LIBs) with its favorable lithium ionic conductivity and good performance on inhibiting lithium dendrite. However, the ultrahigh interfacial resistance between lithium metal anode and LAGP SSEs greatly hinders its application. In this work, a thin film of metallic Bi was sputtered on LAGP to improve the chemical/physical properties of the Li/SSE interface. It is found that the Bi buffer not only inhibits the unfavorable reaction between LAGP SSEs and Li metal, but also improved their compatibility. As a result, the Li/LAGP interfacial resistance was effectively reduced from 2255.6 to 92.8 Ω cm2 at 30 °C. Furthermore, a good performance solid state full cell with a LiFePO4 cathode had been demonstrated. This work provides an effective avenue to address the interfacial challenges between Li metal and LAGP SSE.

The sodium (Na) anode suffers severe interfacial resistance and dendrite issues in a classic NASICON-type Na3Zr2Si2PO12 (NZSP) electrolyte, resulting in poor electrochemical performance for solid-state Na metal batteries. There has been little success in the reduction of interfacial resistance in recent years. The exact mechanism of this resistance has not been fully understood because of little information about the interface. In this work, we effectively address the large interfacial resistance issue and the metal dendrite problem between the Na anode and NZSP by introducing a TiO2 film as an active interphase. We employ quasiinsitu X-ray photoelectron spectroscopy (XPS) to uncover the interphase formation mechanism at the Na/TiO2–NZSP electrolyte interface. Our quasiinsitu XPS results confirm the formation of a sodiated-TiO2 interphase upon stepwise Na evaporation on the surface of the NZSP electrolyte. Further investigation by molten Na contact angle measurements, impedance spectroscopy and DFT calculations demonstrates that the sodiated-TiO2 interphase promotes Na ion transport between the Na anode and NZSP electrolyte. Moreover, the electrostatic potential formed at the NZSP/NaxTiO2 interface can effectively reduce electronic conductivity at the interface and hence prevent the growth of sodium dendrites. A representative paradigm for interphase design is provided to address the interface contact for developing stable solid-state batteries with high performance.

Graphene is a promising materials system for basic studies and device applications in THz optoelectronics with several key functionalities, including photodetection and optical modulation, already ...

Ni-rich layered oxides (LiNi1-x-yCoxMnyO2, 1-x-y ≥ 0.5) are attracting great attention due to their high capacity and operating voltage. However, Ni-rich layered oxides still face long-standing challenges, such as incomplete capacity release and fast capacity fade, especially at high C rates. Herein, we implement a wet chemical method to dope Ti into LiNi0.8Co0.1Mn0.1O2 (NCM811). We discover that NCM811 with the homogeneously distributed Ti can effectively enhance ion transfer kinetics and thus greatly improve capacity delivery at high C rates. The Ti-doped NCM811 exhibits a capacity of 196 mAh/g and 157 mAh/g at 0.5C and 2C in voltage range of 2.8–4.6 V, 5% higher (188 mAh/g at 0.5C) and 15% higher (136 mAh/g at 2C) than the pristine NCM811. Ti-doped NCM811 cathodes also exhibit enhanced cycling stability with capacity retention of 84% after 100 cycles at 1C, which shows that our methodology for Ti doping is potentially competitive for a practical production of Ni-rich layered oxides.

Nickel-rich Li(NixCoyMn1-x-yO2) (x ≥ 0.6) is considered to be a predominant cathode for next-generation lithium-ion batteries (LIBs) due to its towering specific energy density. Unfortunately, serious structural degradation causes rapid capacity degradation with the increase in nickel content. Herein, a Co and Ti co-modified LiNi0.8Co0.1Mn0.1O2 (NCM-811) cathode ameliorates the reversible capacity together with the rate capability by obviously alleviating the lattice structure degradation and microscopic intergranular cracks. Further studies show that the titanium doping effectively reduces the cation mixing and also stabilizes the crystal structure, while the spinel phase formed at the surface by a cobalt oxide coating is much stable than the layered phase at high voltage, which can alleviate the generation of micro-cracks. After 0.5% Co oxide coating and 1% Ti doping (T1Co0.5-NCM), a superior rate capability (121.75 mA h g-1 at 20 C between 2.7 and 4.5 V) and predominant capacity retention (74.2%) are observed compared with the pristine NCM-811 (59.5%) after 400 cycles between 2.7 and 4.7 V. This work supplies an eminent design of high-voltage and high-rate layered cathode materials and has a huge application prospect in the next generation of high-energy LIBs.

Replacing organic porous separators with an inorganic solid-state electrolyte (SSE) is a promising strategy to suppress lithium dendrite and inhibit polysulfide dissolution in lithium-sulfur (Li-S) batteries. However, the realization of such a concept is still limited by the large interfacial resistance between SSE and lithium anode. Herein, a new electrolyte additive, copper fluoride (CuF2), is used in liquid electrolytes to construct a stable interphase between Li1.5Al0.5Ge1.5(PO4)3 (LAGP) SSE and Li metal for a quasi-solid-state Li-S battery. A Li||Li symmetric cell with ultralong life over 1500 h (at 0.1 mA cm-2) proves the excellent stability of the as-formed interphase. As a result, the assembled Li-S full cell presents high coulombic efficiency and stable cycling (750 mA h g-1 after 50 cycles) at room temperature with lean liquid electrolytes. This strategy provides an effective method for improving the electrochemical performance of Li-S batteries.

The development of environmentally friendly and durable gel materials based on biomass is becoming critical today. In this paper, a kind of self-healing ion gel based on acylhydrazone bonds was firstly prepared by eco-friendly polysaccharide materials. The gel can achieve rapid self-healing within minutes after cutting and has properties such as free-shapeable and adhesive properties, and it can also be used as a solid electrolyte in supercapacitors. On this basis, we introduced Fe3O4 to the gel precursor and produced a kind of ion gel (OSA-PAM-Fe3O4-CNCs ion gel) which can realize self-healing instantly by combining acylhydrazone bond with metal coordination bond for the first time. Moreover, the strength of ion gel is more than 10 times than before. With the good Mechanical and electrochemical properties, the self-healing ion gels is expected to be used in the field of wearable flexible sensing.

Na2Zn2TeO6 is a potential sodium solid electrolyte of all-solid-state sodium-ion batteries. In this work, Na+ ion conductivity and electrochemical performance of layered Ca-doped Na2Zn2-xCaxTeO6 (x = 0–0.05) (NZTO-Cx) electrolytes have been investigated. The highest conductivity has been achieved 7.54 × 10−4 S cm−1 in NZTO-Cx at x = 0.02, at room temperature due to grain-boundary modification and interlayer-interface elimination. Meanwhile, chemical stability with metallic Na anode and electrochemical window of NZTO-Cx are improved by Ca doping. Furthermore, the cycle stability of Na3V2(PO4)3/NZTO-Cx/Na solid-state batteries have been successfully increased by Ca doping. These advantages highly demonstrate good potential application prospect of NZTO-Cx in all-solid-state sodium-ion batteries.

We are presenting a sol–gel method for building novel nanostructures made of nanosized F-doped Na1–2xTi2(PO4)3–xFx (NTP-Fx, x = 0, 0.02, 0.05, and 0.10) particles embedded in three-dimensional (3D)...

Recently perfect absorbers (PAs) have received significant interest due to their characteristics of complex electric permittivity (e) and magnetic permeability (μ). By rationally designing these artificial structures, the impedance of the perfect absorber can be matched to free space with an independent adjustment in the electric and magnetic resonances, where this structure leads to strong absorption from mid- to near-IR wavelength. In this article, we proposed a multiband PA platform, which simultaneously operates with a near unity absorption at different resonances that could be an ideal candidate for multiple sensing of molecular fingerprints. We numerically analyzed the dependence of the optical response of the PA platform through finite-difference time domain (FDTD) simulations for a fine-tuning mechanism of the PA platform. We theoretically demonstrated the surface enhanced infrared absorption (SEIRA) capability of our PA platform by studying its optical response with a thin protein bilayer and a polymethyl-methacrylate (PMMA) film. As an initial step we experimentally showed the vibrational modes of a thin PMMA film. We believe, our findings could open new avenues for reliable SERIA platforms through providing multiple vibrational finger print information compared to its conventional counterparts relying only on a single sensing data.

Summary Similar to graphite and graphene, aromatic rings are ultra-stable configurations with highly delocalized sp2-hybridized electrons, which are the basic units for most organic electrode materials. However, the aromatic rings in organic electrode materials are inaccessible for Na+-ion storage. Here, we have designed a wavy-layered 3D structure of metal-organic compound zinc perylenetetracarboxylates (Zn-PTCA) with stretched space between adjacent perylene planes, which enables aromatic rings activated as Na+-ion storage sites. Such Zn-PTCA delivers a high specific capacity of 357 mAh g−1 at a current density of 50 mA g−1 within the potential range of 0.01–2 V versus Na+/Na, corresponding to an eight-electron-transfer process. Experiments and calculations revealed that both C=O groups and aromatic rings are involved in the Na insertion processes. We believe that the present strategy can open up an avenue for developing a big family of 3D open-framework-structured organic materials for application in high-capacity Na+-ion batteries.

LiNi0.6Co0.2Mn0.2O2 has attracted considerable attention as a high-performance cathode material for lithium ion batteries due to its relatively high specific capacity and low cost. However, structural instability and side reactions at the surface, which occur during the charge/discharge process, largely limit its performance. Here, we introduce a nanoscale nitrogen-doped carbon layer at the surface of the LiNi0.6Co0.2Mn0.2O2 particles by using simple mechanical activation and pyrolysis methods. Systematic characterization indicates that a nitrogen-doped carbon layer approximately 16 nm thick is uniformly coated on the LiNi0.6Co0.2Mn0.2O2 particles. It has been proved beneficial to stabilize the layered structure of the LiNi0.6Co0.2Mn0.2O2 with less cation disorder and residual lithium at the surface. The nitrogen-doped carbon-coated LiNi0.6Co0.2Mn0.2O2 exhibited a capacity retention of 92% after 100 cycles from 3.0 to 4.5 V at 1 C, and a discharge capacity of 156 mAh g−1 at 5 C (78% of the capacity at 0.2 C), which is superior to the pristine LiNi0.6Co0.2Mn0.2O2 in this work and most other reported LiNi0.6Co0.2Mn0.2O2 cathodes. The improved electrochemical properties of the nitrogen-doped, carbon-coated cathode can be attributed to the higher degree of cation ordering, relieved side reactions between the cathode and electrolyte, and increased electronic conductivity.

Tin selenide (SnSe) has been explored as a promising anode material for sodium ion batteries (SIBs) but its electrochemical performance is strictly limited by the large volume variation during charge/discharge process and relatively low electronic conductivity. In this work, hierarchical Cu doped SnSe nanoclusters were prepared by a cost-efficient and nontoxic method and demonstrated as a high-performance anode for SIBs. Under optimized Cu doping degree (10 wt% Cu), the developed Cu-SnSe anode exhibits excellent rate performance with a high capacity of 330 mAh/g at 20 A/g and outstanding stability with a capacity of 304 mAh/g after 1000 cycles at 5 A/g (0.1–3.0 V vs. Na/Na+). The enhanced electronic conductivity, facilitated sodiation/desodiation process, and relieved volume change during cycling in Cu doped SnSe benefited from Cu doping and the unique hierarchical structure should account for its extraordinary sodiun storage performance.

Gated graphene superlattices, where in-plane variations in the potential-energy profile are introduced with a periodic patterning of the gate electrode or dielectric, provide new opportunities for tailoring the electronic and optical properties of two-dimensional materials. Here we present a numerical study of the optical transitions between minibands derived from the same energy band (conduction or valence) in these systems. Giant absorption peaks at voltage-tunable THz frequencies are obtained, associated with van Hove singularities in the joint density of states of select pairs of minibands. Furthermore, we describe the possibility of interminiband THz gain in the same systems under external carrier injection, resulting from a local population inversion at specific symmetry points of the mini-Brillouin zone, even in the absence of a global inversion. These results highlight the great potential of engineered graphene superlattices for THz optoelectronic device applications, including modulators, tunable...

Hard carbon (HC) is one of the most promising anode materials for sodium-ion batteries (SIBs) due to its suitable potential and high reversible capacity. At the same time, the correlation between carbon local structure and sodium-ion storage behavior is not clearly understood. In this paper, the two series of HC materials with perfect spherical morphology and tailored microstructures were designed and successfully produced using resorcinol formaldehyde (RF) resin as precursor. Via hydrothermal self-assembly and controlled pyrolysis, RF is a flexible precursor for high-purity carbon with a wide range of local-structure variation. Using these processes, one series of five representative RF-based HC nanospheres with varying degrees of graphitization were obtained from an RF precursor at different carbonization temperatures. The other series of HC materials with various microscopic carbon layer lengths and shapes was achieved by carbonizing five RF precursors with different cross-linking degrees at a single c...

A novel solid sodium-ion conductor, Na2Mg2TeO6 (NMTO) with a P2-type honeycomb-layered structure, has been synthesized for the first time by a simple solid-state synthetic route. The conductor of NMTO exhibits high conductivity of 2.3 × 10-4 S cm-1 at room temperature (RT) and a large electrochemical window of ∼4.2 V (versus Na+/Na). The conductor is remarkably stable, both in the ambient environment and within its metallic Na anode. This facile sodium-ion conductor displays potential for use in all-solid-state sodium-ion batteries (SS-SIBs).

Li-ion capacitors, comprising a battery anode and a supercapacitor cathode, have been expected to bridge the gap between batteries and supercapacitors. However, the kinetics mismatch between the an...

Here, a P2-type layered Na2 Zn2 TeO6 (NZTO) is reported with a high Na+ ion conductivity ≈0.6×10-3 S cm-1 at room temperature (RT), which is comparable to the currently best Na1+n Zr2 Sin P3-n O12 NASICON structure. As small amounts of Ga3+ substitutes for Zn2+ , more Na+ vacancies are introduced in the interlayer gaps, which greatly reduces strong Na+ -Na+ coulomb interactions. Ga-substituted NZTO exhibits a superionic conductivity of ≈1.1×10-3 S cm-1 at RT, and excellent phase and electrochemical stability. All solid-state batteries have been successfully assembled with a capacity of ≈70 mAh g-1 over 10 cycles with a rate of 0.2 C at 80 °C. 23 Na nuclear magnetic resonance (NMR) studies on powder samples show intra-grain (bulk) diffusion coefficients DNMR on the order of 12.35×10-12 m2 s-1 at 65 °C that corresponds to a conductivity σNMR of 8.16×10-3 S cm-1 , assuming the Nernst-Einstein equation, which thus suggests a new perspective of fast Na+ ion conductor for advanced sodium ion batteries.

NASICON-structure Na3V2(PO4)3 (NVP) is a potential cathode material for sodium ion battery, which is still confronted with low rate performance because of its poor conductivity. To address this problem, high-valance Mo6+ ion was introduced into NVP. The crystal structure, electrochemical performances, sodium ion diffusion kinetics and ion transfer mechanism of high valence Mo-doped Na3−5xV2−xMox(PO4)3/C (0 < x < 0.04) were investigated. X-ray diffraction, electron microscopy and XPS data confirmed high purity NASICON phosphate phases. The Na ion diffusion process was identified through CV measurement, which clearly shows rapid sodium ion transportation in the Mo-doped NASICON materials. Moreover, DFT calculations proved that Na ion diffusion is promoted by Mo doping. Benefiting from the superior Na ion kinetics, Na2.9V1.98Mo0.02(PO4)3 exhibited a performance of 90 mA h g−1 at 10C and preserved 83.5% of the original capacity after 500 cycles. Our studies demonstrate that high-valence Mo doped Na3V2(PO4)3/C is a promising cathode material for sodium ion batteries with super-high rate capability and stable cycle life.

Sodium iron hexacyanoferrate (Fe-HCF) has been proposed as a promising cathode material for sodium-ion batteries (SIBs) because of its desirable advantages, including high theoretical capacity (∼170 mAh g–1), eco-friendliness, and low cost of worldwide rich sodium and iron resources. Nonetheless, its application faces a number of obstacles due to poor electronic conductivity and structural instability. In this work, Fe-HCF nanospheres (NSs) were first synthesized and fabricated by an in situ graphene rolls (GRs) wrapping method, forming a 1D tubular hierarchical structure of Fe-HCF NSs@GRs. GRs not only provide fast electronic conduction path for Fe-HCF NSs but also effectively prevent organic electrolyte from reaching active materials and inhibit the occurrence of side reactions. The Fe-HCF NSs@GRs composite has been used as a binder-free cathode with a capacity of ∼110 mAh g–1 at a current density of 150 mA g–1 (∼1C), the capacity retention of ∼90% after 500 cycles. Moreover, the Fe-HCF NSs@GRs cathode ...

Pronounced terahertz emission peaks originating from current-driven plasmonic oscillations in graphene nanoribbons are measured. The emission frequency can be tuned by design through the ribbon width and actively by varying the applied gate voltage.

We investigate the ability of gradient metasurfaces to promote directional light emission from an ensemble of dipole sources (colloidal quantum dots) in their near field. Well-collimated ouqrut beams along geometrically tunable directions are measured.

Electro-synthesis of ammonia at ambient environment is a promising alternative of the industrial Haber-Bosch process operated under critical conditions. In this work, we have systematically investigated the electro-reduction of nitrate (NO3−RR) to ammonia catalyzed by fluorine doped carbon (FC) synthesized from the pyrolysis of the discarded cigarette filter saturated with polytetrafluoroethylene (PTFE) solution. FC electrocatalyst shows an exceptional NO3−RR catalytic performance with Faradaic efficiency of 20% associated with ammonia production rate of 23.8 mmol h−1 gcat−1, 2 and 4-fold better than bare C electrocatalyst. Furthermore, a stable NO3−RR activity is also achieved for FC electrocatalyst. Density functional theory (DFT) results suggest that F dopants efficiently reduce the energy barriers of NO3− hydrogenation and suppress the competitive hydrogen evolution reaction (HER). This observation will be beneficial for constructing a high-performance metal-free electrocatalyst to electro-synthesize ammonia from NO3−RR.

A composite of graphitic carbon nitride and TiO 2 (g-C 3 N 4 /TiO 2 ) with enhanced photocatalytic hydrogen evolution capacity was achieved by calcining melamine and TiO 2 sol-gel precursor. Characterization results reveal that heating temperature had a great influence on the structure, surface area and properties of the composites. Compared with the polycondensation of pure melamine, the presence of TiO 2 precursor can promote the formation of melon at a low temperature. The highest photocatalytic activity of g-C 3 N 4 /TiO 2 (400) was achieved when the calcination was performed at 400 °C, exhibiting H 2 production rate of 76.25 μmol/h under UV–vis light irradiation (λ > 320 nm) and 35.44 μmol/h under visible light irradiation (λ > 420 nm). The highest photocatalytic performance of g-C 3 N 4 /TiO 2 (400) can be attributed to: (1) the strong UV–vis light absorption due to the narrow bandgap caused by synergic effect of TiO 2 and g-C 3 N 4 , (2) high surface area and porosity, (3) the effective separation of photo-generated electron-holes owing to the favorable heterojunction between TiO 2 and g-C 3 N 4 .

Nitrogen-rich hierarchical mesoporous polymers with photocatalytic activity for H 2 evolution from water were prepared, which was based on aminal bonds constructed by catalyst-free Schiff-base condensation. The effects of the reaction time, concentration of terephthaldehyde and the mole ratio of aldehyde to amine groups on the structure and properties of polymers were discussed. By tuning reaction conditions, the surface area of these polymers changed from 216.83 to 569.04 m 2 /g. Among all these materials, the polymer with moderate surface area (391.76 m 2 /g), the smallest average pore size (4.27 nm) and low intensity peak of photoluminescence showed the highest H 2 evolution rate of 18.56 μmol·h − 1 . When loaded with palladium, it exhibited enhanced H 2 evolution rate of up to 43.58 μmol·h − 1 . The results demonstrated that the nitrogen-rich porous polymer has a good potential for H 2 evolution from water under UV–Vis light irradiation (λ = 380–780 nm). This study expanded the scope of porous polymers in photocatalysis applications. The outstanding advantages of the polymers presented here include their low price, commercially available starting compounds and the easy method of synthesis. This kind of porous polymer has promise for further applications.

Plasmonic excitations in graphene nanostructures provide a particularly effective means to enhance light–matter interactions at THz frequencies. Here, we investigate the use of graphene nanoribbons for narrowband THz light emission based on the excitation of plasmonic oscillations under current injection and their resonant decay into free-space radiation. A detailed theoretical model of the underlying plasmon-enhanced thermal emission mechanism is presented, whose predictions are in good agreement with the recent experimental demonstration of this phenomenon. This model highlights the key role played by the nanostructure absorption efficiency to maximize the output radiation at the plasmonic resonance frequency. Based on this idea, we explore the integration of graphene nanoribbons with nearby metallic antennas in an open cavity configuration in order to promote critical coupling to free-space radiation and correspondingly enhance the absorption (and, therefore, radiation) efficiency by up to two orders of magnitude. The simulation results indicate that this approach is promising for the development of novel THz sources with technologically relevant emission characteristics.

With the increasing abuse of fentanyl and its derivatives, it is urgent to develop techniques that can rapidly detect these compounds in different types of matrices. In this work, we developed a miniature mass spectrometer-based method for the fast and on-site analysis of fentanyl compounds. Optimization of several direct sampling procedures such as paper capillary spray cartridge with a miniature mass spectrometry system enables sensitive analysis of multiple fentanyl compounds. This system was evaluated by analysis of fentanyl and its derivatives in several types of beverage, showing limits of detection (LODs) as low as 10 ppb. It has also been applied into analysis of fentanyl compounds on the surface of a dusty plastic bag, showing LODs of 1 ng/cm2. A precursor ion scan method was also developed for fast screening of multiple fentanyl compounds. This system has also been applied in the analysis of fentanyl in urine samples.

Lithium–sulfur batteries are believed to be potential next-generation electrochemical devices which will satisfy the increasing market demands due to their high energy density, low cost and environmental friendliness. However, the practical application of Li–S batteries is still hindered by poor cycle stability and rate capability caused by the low electronic conductivity of sulfur and dissolution of intermediate polysulfides. Here, we employ easily-obtained titanium nitride (TiN) as a highly efficient immobilizer to trap polysulfides via a chemical mechanism. TiN also possesses high electronic conductivity which helps in achieving a high sulfur utility and an excellent rate capability. At 0.5C, the TiN-based sulfur composite cathode demonstrates a high initial reversible capacity of 1012 mA h g−1 and a long cycle life of over 200 cycles with a decay rate of 0.2% per cycle. Even at 5C, the reversible discharge capacity is still higher than 550 mA h g−1. The outstanding electrochemical performance is ascribed to the strong chemisorption effect between TiN and polysulfides.

Paiella, Roberto/0000-0002-7183-6249; Swan, Anna/0000-0002-3978-7993 WOS: 000408077800018 Graphene provides a promising materials platform for fundamental studies and device applications in plasmonics. Here we investigate the excitation of THz plasmon polaritons in large-area graphene samples on standard oxidized silicon substrates, via diffractive coupling from an overlying periodic array of metallic nanoparticles. Pronounced plasmonic absorption features are measured, whose frequencies can be tuned across a large portion of the THz spectrum by varying the array period. At the same time, the ability to tune these resonances actively via electrostatic doping is found to be strongly limited by the presence of large carrier density variations across the sample area induced by the underlying SiO2, which are measured directly by Raman microscopy. These results highlight the importance of minimizing charge "puddles" in graphene plasmonic devices, e.g., through the use of more inert substrates, in order to take full advantage of their expected dynamic tunability for applications in THz optoelectronics. National Science FoundationNational Science Foundation (NSF) [DMR-1308659]; Royal Thai Government Fellowship; Turkey Ministry of Education Fellowship; Division of Materials ResearchNational Science Foundation (NSF)NSF - Directorate for Mathematical & Physical Sciences (MPS) [1411008] Funding Source: National Science Foundation This work was supported by the National Science Foundation under Grant DMR-1308659. K.T. and H.D. acknowledge partial support by a Royal Thai Government Fellowship and by a Turkey Ministry of Education Fellowship, respectively.

Pronounced plasmonic absorption features at terahertz frequencies are measured in large-area graphene sheets coupled to periodic arrays of metallic nanoparticles, and limitations on their tunability caused by carrier density inhomogeneities are investigated.