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As a typical class of man-made nanoreactors, metal-loaded hollow carbon nanostructures (MHC nanoreactors) exhibit competitive potentials in the heterogeneous catalysis due to their tailorable microenvironment effects, in which the void-confinement effect is one of the most fundamental functions in boosting the catalytic performance. Herein this paper, Ru-loaded hollow carbon spheres are employed as nanoreactors with a crucial biomass hydrogenation process, levulinic acid (LA) hydrogenation into γ-valerolactone, as the probe reaction to further recognize the forming mechanism of this pivotal effect. We demonstrated that the void-confinement effect of the selected MHC nanoreactors is essentially driven by an integrating action of electronic metal-support interaction, reactant enrichment and diffusion, which are mainly ascribed to peculiar properties of hollow nanoreactors both in electronic and structural aspects, respectively. This work offers a distinct case for interpreting the catalytic behaviour of MHC nanoreactors, which could potentially promise broader insights into the microenvironment engineering strategies of hollow nanostructures.

NASICON-type NaTi2(PO4)3 (NTPO) is a promising anode for Na+ batteries owing to its excellent thermal stability, high Na+ conductivity, high theoretical capacity, low price, and good safety. However, the electronic conductivity of NTPO is not satisfactory for practical applications in rechargeable Na+ batteries. In this work, NTPO@C electrode anchored to B-doped graphene (BG) sheets is synthesized via a combination of facile sol-gel procedure and solid-state reaction at high temperature. As envisioned in the design step, the BG coupled with the carbon layer forms a network that improves the electronic conductivity of BG/NTPO@C anode, resulting in excellent Na+ storage properties. It provides a high specific capacity of 127.9 mAh g-1 at 0.1C in the potential range of 1.5–3.0 V. Furthermore, it displays a high reversible capacity of 103.4 mAh g-1 at 10C over 500 cycles while retaining 93.7% of the initial capacity. These electrochemical experiments demonstrate that the developed BG/NTPO@C composite is a promising novel anode for high-performance Na+ batteries.

The low photoluminescence (PL) quantum yields of transition metal dichalcogenide monolayers have been a limiting factor for their optoelectronic applications. Various and even inconsistent mechanisms have been proposed to modulate their PL efficiencies. Herein, we use PL/Raman microspectroscopy and the corresponding in situ mapping, atomic force microscopy, and field-effect transistor (FET) characterization to investigate the changes in the structural and optical properties of monolayer MoS2. Relatively low power density (

The hydrogenation of furfural (FUR), a typical bio-based furan derivative, is a critical reaction within the roadmap for upgrading lignocellulosic biomass into high value-added chemicals and liquid fuels, the performance of which is strongly correlated with the catalysts' intrinsic peculiarities. Metal catalysts with tailorable sizes, uniform dispersions and robust sintering resistance are generally recognized as a prerequisite for obtaining better hydrogenation activity, selectivity and stability, which has prompted intensive research into metal particle size effects and their regulation strategies. The roles of metal particle sizes and corresponding dispersions of metal catalysts used for FUR hydrogenation have been clearly recognized to be crucial over the past decade. In this regard, this systematic Minireview aims to provide profound insights into particle size effects in the metal-catalyzed hydrogenation of FUR, as well as conditional and structural approaches to regulating these effects. In addition, from the aspect of catalyst stability, the impacts and improvements of the metal particle sintering issue are analyzed. Moreover, several suggestions are proposed in response to the challenges in regulating particle size effects. Furthermore, the viewpoints presented herein would potentially contribute to the rational development of metal hydrogenation catalysts and further help to boost a more sustainable biomass refining system.

The poor cyclability and inferior capacity retention caused by severe Jahn–Teller effect and dissolution of Mn ions into electrolyte during cycling hinder the commercial application of spinel LiMn2O4 with low cost and non-toxic. Herein, hollow LiMn2O4 nanofibers composed of LiMn2O4 nanograins are proposed, forming 3D network framework with uniform distribution. The slender and firm nanofibers can effectively buffer the irreversible phase transitions triggered by Mn3+ disproportionation and Jahn–Teller distortion and lead to the extremely long cycle life of LiMn2O4 cathode. Meanwhile, the huge specific surface area provided by hollow structure ensures the full contact between the materials and electrolyte, being beneficial to the diffusion of Li ions and transfer of electron to maintain its capacity. It can be observed that the capacity retention is 97.5% after 1000 cycles at 1C. The structure design of the hollow nanofibers modified the LiMn2O4 cathode material at the micro-level, which greatly improves the long-term cycling stability of the material and provides reference for the modification in lithium ion batteries.

The mechanism of aggregation-induced emission, which overcomes the common aggregation-caused quenching problem in organic optoelectronics, is revealed by monitoring the real time structural evolution and dynamics of electronic excited state with frequency and polarization resolved ultrafast UV/IR spectroscopy and theoretical calculations. The formation of Woodward-Hoffmann cyclic intermediates upon ultraviolet excitation is observed in dilute solutions of tetraphenylethylene and its derivatives but not in their respective solid. The ultrafast cyclization provides an efficient nonradiative relaxation pathway through crossing a conical intersection. Without such a reaction mechanism, the electronic excitation is preserved in the molecular solids and the molecule fluoresces efficiently, aided by the very slow intermolecular charge and energy transfers due to the well separated molecular packing arrangement. The mechanisms can be general for tuning the properties of chromophores in different phases for various important applications.

Two-dimensional semiconductors could be used as a channel material in low-power transistors, but the deposition of high-quality, ultrathin high-κ dielectrics on such materials has proved challenging. In particular, atomic layer deposition typically leads to non-uniform nucleation and island formation, creating a porous dielectric layer that suffers from current leakage, particularly when the equivalent oxide thickness is small. Here, we report the atomic layer deposition of high-κ gate dielectrics on two-dimensional semiconductors using a monolayer molecular crystal as a seeding layer. The approach can be used to grow dielectrics with an equivalent oxide thickness of 1 nm on graphene, molybdenum disulfide (MoS2) and tungsten diselenide (WSe2). Compared with dielectrics created using established methods, our dielectrics exhibit a reduced roughness, density of interface states and leakage current, as well as an improved breakdown field. With the technique, we fabricate graphene radio-frequency transistors that operate at 60 GHz, and MoS2 and WSe2 complementary metal–oxide–semiconductor transistors with a supply voltage of 0.8 V and subthreshold swing down to 60 mV dec−1. We also create MoS2 transistors with a channel length of 20 nm, which exhibit an on/off ratio of over 107. Using a monolayer molecular crystal as a seeding layer, hafnium oxide dielectrics with an equivalent oxide thickness of only 1 nm can be deposited on graphene, molybdenum disulfide and tungsten diselenide.

A novel nanocrystal-embedded-insulator (NEI) ferroelectric field-effect transistor (FeFET) is demonstrated to function as a synaptic device for analog neural network (NN) applications. The NEI layer (down to 3.6 nm in thickness) comprises ferroelectric nanocrystals embedded in amorphous Al2O3, resulting in reduced operating voltages and depolarization effects as compared to conventional doped-HfO2 films. With fixed-amplitude 100 ns potentiation/depression pulses, an NEI FeFET synapse achieves weight update with small non-linearity ( $\alpha _{p}= {0.12}$ , $\alpha _{\text {d}}= -{0.09}$ ) and asymmetry factors, advantageous for analog-style NNs with online training. A convolutional NN is designed and emulated for an MNIST dataset, projecting an online training accuracy of 92%.

Lithium manganese oxide (LiMn2O4) is one of the most promising material as lithium-ion battery cathodes owing to its significant advantages such as nontoxicity and low cost at present. However, LiMn2O4 exhibits insufficient cycling stability in practical application, which is an urgent problem to be figured out. In order to overcome this shortcoming, a facile method is presented which synthesized a yttrium-doped spherical LiMn2O4 whose diameter is about 5–6 μm using cubic MnCO3 precursors. The doped LiMn2O4 samples were investigated by XRD and SEM, which indicated that the spherical LiYxMn2−xO4 is a porous structure composed of LiYxMn2−xO4 nanoparticles with an average size of about 60–80 nm. The LiYxMn2−xO4 shows an excellent cycling performance when x = 0.01. At the current density of 1C (1C = 140 mAh g−1), LiYxMn2−xO4 shows a discharge specific capacity of 120 mAh g−1 at 1C with a specific capacity retention of 96% after 650 cycles.

Catalysis is an effective way to improve the performance of lithium-sulfur (Li-S) batteries by enhancing the reaction kinetics of polysulfides. However, the bidirectional catalysis for discharging and charging processes in Li-S battery is still challenging. Herein, a (110) facet-dominated VO2 is prepared through the thermal-induced partial decomposition of (NH4)2V4O9 (NVO), forming a (110)VO2@NVO hybrid with the bidirectional catalysis ability. This (110) facet-dominated VO2 shows the ability to break the S-S bond to guide the Li2S deposition in the reduction process and reduce the delithiation barrier of Li2S to promote the oxidation process. The above hybrid is loaded on carbon nanofiber (CNF) to build an interlayer, where the 3D CNF and the conductive NVO ensure the fast electron transfer. The assembled battery with the above interlayer exhibits a high capacity of 1038 mAh g-1 after 300 cycles at 0.1 C (capacity retention: 70%). At a high rate of 5 C, a high capacity of 521 mAh g-1 after 1000 cycles is reached. Even under an ultrahigh sulfur loading of 10.3 mg cm-2 and a low electrolyte/sulfur ratio of 4 μL mgS-1, stable cycling performance with a high capacity of >3 mAh cm-2 is also achieved.

The hydrodeoxygenation (HDO) catalytic conversion of lignin has always been a hot research topic, and vacancy engineering is considered to be a new means to develop more efficient catalysts. Among them, oxygen vacancies and sulfur vacancies are widely used in HDO. Based on the current research status of vacancies in the field of lignin-derived oxygenates, this review discusses in detail the design methods of vacancy engineering, including surface activation, synergistic modification, and morphology control. Meanwhile, it is clarified that in the HDO reaction, vacancies can act as acidic sites, promote substrate adsorption and regulate product distribution, while for the catalysts, vacancies can enhance the stability and reducibility, improve metal dispersion, and improve the redox capacity. Finally, the characterization of vacancies is summarized, and feasible suggestions are proposed for the current deficiencies in this field.

Due to the absence of dangling bonds, the integration of ultra-thin dielectric on 2D semiconductors has become a huge challenge, and its reliability research has been blank before. For the first time, we report the high $-\mathcal{K}$ dielectric reliability on Mos2. By PTCDA crystal as interface layer, we demonstrated excellent reliability of HfO 2 /PTCDA gate stack, including EBD over 8.9 MV/cm, $\mathrm{E}_{\text{BD}}\ ^{10\text{yrs}}$ over 6.5 MV/cm and ultra-low BD rate, all of which show better reliability than HfO 2 /Si.

Hierarchically porous activated carbons with high specific surface areas are synthesized by chemical activation of the leaves of Schefflera octophylla. The specific surface areas of the materials are over 2300 m2 g−1 and the specific pore volume is as high as 1.92 cm3 g−1. The optimized material achieves a high specific capacitance of 336 F g−1 in 6 M KOH aqueous electrolyte at a current density of 0.5 A g−1, and it also shows excellent cycling stability with 97.5% capacitance retention after 10,000 cycles at a current density of 10 A g−1. The simple synthesis route of hierarchically porous activated carbon from renewable bio-wastes enables a promising strategy in both reducing wastes and producing useful energy storage materials.

A fiber-optic Fabry–Perot (F-P) sensor, based on a pendulum structure, for simultaneous measurement of tilt angle and vibration acceleration was proposed, which also has a high-tilt angle resolution. The real-time cavity lengths are absolutely measured using a fast demodulation algorithm. The tilt angle is estimated from the mean value of the real-time cavity lengths while the vibration acceleration derives from the alternating quantity of them. A series of experiments are conducted using a micro-tilt platform and a vibration table to simulate tilt angle chang. The experimental results show a tilt angle resolution of 0.023” in the measurement range from –2.8° to 2.6°. Meanwhile, the vibration acceleration results are obtained by using a spectral analysis to the alternating quantity and basing on a non-linear fitting curve of the frequency response of the acceleration sensibility, within the frequency range of 0 ~ 180 Hz.

This study reports a supramolecular self-healing material as a multi-functional binder for lithium–sulfur batteries. The spontaneously damage repair ability of such a binder can be applied to overcome the short cycle-life issue of lithium–sulfur batteries under low current density with deep galvanostatic cycling. Diamines and polybasic acids are used to synthesize the supramolecular self-healing material. 10 wt% amine groups in this designed material provide a large amount of chemical adsorption sites for polysulfides which can effectively inhibit the shuttling of polysulfides and maintain the content of sulfur species in cathode. This N-rich binder is mixed with the sulfur during preparation, which can improve the effective contacting surface of N function groups and sulfur locally. The cells with pure self-healing material binder achieve an initial capacity of 918 mAh g−1, and maintain a reversible capacity of 469 mAh g−1 after 200 cycles at 0.1C, twice higher than the retention capacity of cells with polyvinylidene fluoride binder. After optimization, the cells with a hybrid binder of self-healing material and polyvinylidene fluoride (weight ratio of 1:1) with a sulfur loading of 2.65 mg cm−2 achieve an initial capacity of 993 mAh g−1, and remain a reversible capacity of 571 mAh g−1 with a capacity fade of 0.2% per cycle after 200 cycles at 0.1C.

Cactus structure MnO2/N-rich carbon nanofiber composites were synthesized via an in situ redox reaction to be utilized as the interlayer in lithium–sulfur batteries. The exposed MnO2 nanosheets vertically aligned on carbon nanofibers provide a large amount of active sites for polysulfide adsorption and conversion. Unlike physical barriers or simple surface interactions, the MnO2 nanosheets generate an anchor and transfer mediator for polysulfides to dissolve into the electrolyte, and then control the deposition of Li2S2 or Li2S on the designed interlayer. This structure induces an arranged relocation of sulfur species during cycling, resulting in a shortened electron passage and an improved utilization of the active material. With a sulfur loading of 1.65 mg cm−2 and a sulfur content of 60% at the whole electrode level, the cell with the MnO2/carbon nanofiber interlayer delivered an initial discharge capacity of 1102 mA h g−1, 965 mA h g−1, and 712 mA h g−1 at 0.1C, 1C and 5C, respectively. It could maintain a reversible capacity of 646 mA h g−1 after 100 cycles at 1C and a specific capacity of 414 mA h g−1 after 1000 cycles at 5C with a fade rate of 0.04% per cycle.

A self-standing nitrogen/oxygen dual-doped carbon nanofiber matrix is prepared on the basis of polymer chain design and electrospinning followed by a one-step carbonization. The interlayer can subs...

A novel concept of acoustic fiber Bragg grating (AFBG) was conceived and experimentally validated as an effective technique for high-temperature sensing. Similar to the well-known optical fiber Bragg grating, the AFBG employs interactions between waves and periodic structures on an elongated waveguide. Acoustic waves reflected from periodic structures interfere with each other and result in the emergence of resonance frequency when acoustic wavelength matches with pitch length of the periodic structures. When the single-mode operation condition is satisfied, the resonance frequency location can be accurately resolved and thus be used as an effective indicator for temperature sensing. To demonstrate this concept, an AFBG sample was fabricated on a telecommunication optical fiber (125- $\mu \text{m}$ diameter) with femtosecond laser micromachining setup, and it demonstrated sensing capability up to 700 °C, which was limited by the fiber material (fused silica) and could be over 1400 °C if other material, such as sapphire, was used as the waveguide. With the features of various applicable material, low system cost, and potential multiplexing capability, this AFBG technology is a promising candidate for high-temperature sensing, even in a distributed manner.

Modern high-temperature processes, such as fossil energy production, nuclear reactors, and chemical reactors lack robust, distributed sensing systems to map temperatures in these high-value harsh-environment systems. Regular silica-fiber-based distributed temperature sensing systems usually only operate at temperatures below about 800 °C. In this paper, we present the design, implementation, and testing of a distributed ultra-high temperature sensing system using Raman scattering intensity, which operates from room temperature to above 1400 °C. Consideration is given to the impacts of thermal radiation, fluorescence, and the multimode nature of unclad single-crystal fiber to optimize the system. Results from picosecond and sub-nanosecond lasers were compared. Measurements were taken with a ∼2 m sapphire optical fiber, which represents the longest commercially available length. A spatial resolution of 12.4 cm and position standard deviation of 0.28 mm were achieved up to the maximum testing temperature of 1400 °C, which is a new record for distributed temperature sensing systems.

The commercial LiFePO4 cathode has attracted great attention for large-scale energy storage because of its high safety, low cost, low toxicity and excellent thermal stability. Unfortunately, the poor electronic conductivity of LiFePO4 leads to bad lithium storage property. In this work, the nitrogen-doped graphene-decorated LiFePO4 was prepared via a facile hydrothermal method followed by a conventional solid-state route. Benefiting from the advantages of nitrogen-doped graphene, the conductivity of LiFePO4 is greatly improved. Therefore, the obtained composite shows excellent electrochemical performances, including high reversible capacity (163.1 mAh g−1 at 0.1 C), good rate capability (113.7 mAh g−1 at 10 C) and stable cycle-life (111.6 mAh g−1 after 150 cycles at 10 C). These results reveal that the designed nitrogen-doped graphene-decorated LiFePO4 composite is a promising cathode material for rechargeable lithium-ion batteries.

Spinel Li4Ti5O12 material has been regarded as the next-generation anode for lithium-ion batteries owing to its excellent safety and good structural stability. Nevertheless, the low electrical conductivity and bad Li+-ion diffusion efficiency of pristine Li4Ti5O12 greatly limit its wide applications in electrochemical energy storage. Herein, the nanosized Li4Ti5O12 crystals are prepared via a simple sol-gel method to shorten the diffusion pathway of Li+-ion. Meanwhile, the conductive PEDOT layer is adopted to modify the electrical conductivity of Li4Ti5O12. The PEDOT-coated Li4Ti5O12 composite is successfully prepared by using the in-situ polymerization method. Benefit from the advantages of nanosized Li4Ti5O12 particles and conductive PEDOT coating, the obtained electrode exhibits enhanced electrochemical performances. It can deliver the initial discharge capacities of 169.6 and 125.2 mAh g−1 at 0.1 and 20 C. These results demonstrate that the designed composite is a potential electrode for high-rate electrochemical lithium storage.

We proposed a high-resolution dynamic fiber-optic inclinometer based on a Fabry-Perot (F-P) interferometer and a vertical cantilever structure with an inertial mass. The F-P cavity length variation approximates the vertical cantilever deflection corresponding to the tilt angle. As a fast demodulation mechanism is applied, the F-P cavity length is absolutely and dynamically measured. The tilt angle is obtained by extracting direct current component from the real-time signals of the F-P cavity length. An experiment is carried out by using an adjustable micro-tilt platform mounted on a vibration table. The experimental results show a high tilt resolution of 0.03″ within the measurement range of ±1°. The dynamic resolution of the tilt measurement in ambient vibration is also estimated to 0.66″ with the simulated vibration frequency and amplitude of 50 Hz and 20.9 μm. Due to the dynamic measurement method, the tilt angle readouts are tolerant of ambient vibration.

Sodium-ion batteries have been regarded as the most attractive alternative to lithium-ion batteries because of their low cost, abundance of sodium resources and promising applications for energy storage systems. In this work, boron-doped graphene decorated Na3V2(PO4)3@C (BG-Na3V2(PO4)3@C) composite is successfully synthesized for the first time by using a simple sol-gel assisted solid-state method. In this composite, the ultrafine Na3V2(PO4)3@C particles are uniformly distributed on the boron-doped graphene sheets. The carbon layer and boron-doped graphene greatly increase the electron/ion transport kinetics of Na3V2(PO4)3 and assure the material structure integrity, leading to excellent electrochemical performances in terms of high-rate capability and long cycle-life. It delivers a high reversible capacity of 94.7 mAh g−1 at 10C and keeps 96.4% of the capacity after 100 cycles. These preliminary results reveal that the as-fabricated BG-Na3V2(PO4)3@C composite is a new promising cathode material for sodium energy storage.

The development of organic thin-film transistors (OTFTs) with low power consumption and high gain will advance many flexible electronics. Here, by combining solution-processed monolayer organic crystal, ferroelectric HfZrOx gating and van der Waals fabrication, we realize flexible OTFTs that simultaneously deliver high transconductance and sub-60 mV/dec switching, under one-volt operating voltage. The overall optimization of transconductance, subthreshold swing and output resistance leads to transistor intrinsic gain and amplifier voltage gain over 5.3 × 104 and 1.1 × 104, respectively, which outperform existing technologies using organics, oxides and low-dimensional nanomaterials. We further demonstrate battery-powered, integrated wearable electrocardiogram (ECG) and pulse sensors that can amplify human physiological signal by 900 times with high fidelity. The sensors are capable of detecting weak ECG waves (undetectable even by clinical equipment) and diagnosing arrhythmia and atrial fibrillation. Our sub-thermionic OTFT is promising for battery/wireless powered yet performance demanding applications such as electronic skins and radio-frequency identification tags, among many others., Exploiting negative capacitance effects in organic thin-film transistors (OTFTs) is advantageous for enhancing device performance. Here, the authors report solution-processed sub-thermionic OTFTs and circuits with ferroelectric hafnium oxides that show ultra-low power and ultra-high gain.

Two-dimensional materials are promising candidates for future electronics due to unmatched device performance at atomic limit and low-temperature heterogeneous integration. To adopt these emerging materials in computing and optoelectronic systems, back end of line (BEOL) integration with mainstream technologies is needed. Here, we show the integration of large-area MoS2 thin-film transistors (TFTs) with nitride micro light-emitting diodes (LEDs) through a BEOL process and demonstrate high-resolution displays. The MoS2 transistors exhibit median mobility of 54 cm2 V−1s −1, 210 μA μm−1 drive current and excellent uniformity. The TFTs can drive micrometre-sized LEDs to 7.1 × 107 cd m−2 luminance under low voltage. Comprehensive analysis on driving capability, response time, power consumption and modulation scheme indicates that MoS2 TFTs are suitable for a range of display applications up to the high resolution and brightness limit. We further demonstrate prototypical 32 × 32 active-matrix displays at 1,270 pixels-per-inch resolution. Moreover, our process is fully monolithic, low-temperature, scalable and compatible with microelectronic processing. Low-temperature ultraclean integration of large-area MoS2 thin-film transistors with nitride micro-LEDs through a back end of line process enables the demonstration of displays with high resolution and uniformity.

2D semiconductors are considered to be one of the most promising channel materials to extend transistor scaling. However, the integration of ultra-thin dielectrics on 2D semiconductors has been challenging, and the reliability has not been investigated to date. Here, using monolayer 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) molecules as interface layer, we realize EOT as low as 1.7 nm on large-area monolayer CVD MoS 2 . The reliability of ultrathin high-κ dielectric on 2D semiconductors is systematically studied for the first time. The median breakdown (BD) field of HfO 2 /PTCDA stack is over 8.42 MV/cm, which is two times that of HfO 2 /Si under the same EOT. Through TDDB we project that the gate dielectric can work reliably for 10 years under E BD = 6.5 MV/cm, which shows 85% improvement than HfO 2 /Si. The BD current increase rate in our gate stack is several orders of magnitude smaller than HfO 2 /Si. The excellent reliability suggests that molecular interfacial layer is a promising dielectric technology for 2D electronics.

Lithium metal is a promising anode utilized in cutting-edge high-energy batteries owing to the low density, low electrochemical potential, and super high theoretical capacity. Unfortunately, continuous uncontrollable lithium dendrite growth and ‘dead’ lithium result in capacity decay, low coulombic efficiency and short circuit, severely hindering the practical utilization of lithium anode. Herein, we propose a three-dimensional porous lithiophilic current collector for lithium storage. The conductive 3D structure constructed by carbon fiber (CF) can well accommodate the deposited lithium, eliminating volume change between the lithium depositing/stripping process. Moreover, the polydopamine (PDA) coating on the CF surface possesses a large number of polar groups, which can homogenize Li+ ions distribution and apply as the sites for lithium deposition, decreasing nucleation overpotential. As a result, under the 1 mA cm−2 current density, the PDA coated CF (PDA@CF) electrode exhibits high CE (∼98%) for 1000 cycles. Galvanostatic measurements demonstrate that the Li anode using PDA@CF achieves 1000 h cycling life under 1 mA cm−2 with a low overpotential (

Surfactant-enhanced mobilization features in various complicated pore structures were rarely investigated. In this work, from the perspective of pore heterogeneity, taking conglomerate with complicated pore-throat distribution as an example, micromodels with three pore structures were fabricated, and polymer and polymer-surfactant (SP) solutions were compared to evaluate the effect of surfactant on the pore-scale mobilization. Furthermore, quantification methods of pore-throat sweep efficiency and recovery were established for the first time through a special image processing workflow. The microfluidics experiment results demonstrated that the solubilization of surfactant could significantly improve the pore-throat displacement efficiency, which contributed to the recovery of SP flooding 6–13% higher than that of polymer flooding. The pore-throat sweep efficiency features at the presence of surfactant varied significantly with displacement pattern. In the displacement pattern of ramified, surfactant would reduce the sweep efficiency of small pore-throat by 7–15% in comparison with polymer flooding, but the favorable displacement efficiency compensated for the difference in pore-throat recovery. In the displacement pattern of compact, surfactant exerted a positive role in expanding sweep efficiency in synergy with polymer, which contributes to promoting the sweep efficiency and recovery in the full range of pore-throat by 7–25%. Last of all, critical driven pore-throat (CDP) was defined, below which pore-throat recovery decreased significantly. The cumulative permeability contribution (CPC) method was utilized to realize CDP generalization in various pore-throat distributions. The CDP of polymer flooding and surfactant flooding corresponded to CPC of 96.21% and 98.71%, respectively. The results play an essential role in understanding how the pore-throat distribution impacts the fluid movement and application of surfactant flooding in the reservoir with complicated pore structures.

Lithium metal anodes (LMAs) have exceptional promises for rechargeable Li-metal batteries. However, their practical applications have long been hindered by the safety concerns related to excessive Li dendrite growth and huge volume expansion during cycling, especially in high-capacity cycles. In this work, we developed a new strategy to suppress the dendrite growth via a 3D reinforced lithium metal composite anode with a nanostick structured copper oxide @copper mesh. Such nanostick structured copper oxide would not only reduce the lithium nucleation overpotential to 11 mV, but also would uniformly accommodate lithium ions to suppress the dendrite effect. Moreover, the 3D structure of copper mesh could effectively alleviate the aggressive volume changes of the lithium metal electrode after hundreds of cycles. Based on CuO@copper mesh, highly reversible lithium stripping/plating are achieved for LMAs at current density of 1 mA cm–2 with a limited volume fluctuation of 13.6% after 1000 h. With ultrahigh capacity densities of 5 mAh cm−2, the CuO@Cu mesh/Li cell exhibits low overpotential of 12 mV and ultralong cycle life over 600 h, which is 2–3 times of the reported average cycling lifespan. The proposed preparation process is simple and easy to scale-up, demonstrating a promising prospect as a commercial Li metal anode with large capacity.

Efficient absorption of solar spectral radiation is a key requirement in solar heat utilization. In an effort to achieve this goal, this study investigated slow light effect and magnetic polaritons, and analyzed other physical model coupling mechanisms in photonic crystals. To construct a class of two-dimensional layers of Ni-Al2O3 as a pyramid array solar energy absorber, the high melting points of Ni and Al2O3 were utilized to create an arrangement of absorbers with good thermal stability, low sensitivity to angle of incidence, and polarization independence. Based on AM1.5 solar spectral data, a simulation study of the photothermal absorption characteristics of this type of absorber in the 0.3–2.5 µm band was conducted. The results showed that the photothermal conversion efficiency is as high as 96.45%. Compared with the traditional single physical effect design, the conversion efficiency of this photonic crystal structure is increased by ~11%. Furthermore, increasing the concentration factor allows the absorber to maintain high efficiency even at high temperatures, which provides theoretical evidence for the efficient use of solar radiation. This work will be beneficial in several areas, including solar thermal utilization, thermal photovoltaics, absorber design, and radiator design in radiant refrigeration systems.

This paper reports fabrication technique and demodulation algorithm developments to use multiplexable intrinsic Fabry-Perot interferometer (IFPI) fiber sensor array for distributed vibration measurements at high temperatures. Using femtosecond laser direct writing scheme, IFPI array were fabricated through laser-induced Type II scattering points in single mode fiber cores. Reflection spectra of IFPI array were demodulated in real-time using modified Bunemen frequency analysis. The demodulation algorithm, which was implemented using a photodetector-array spectrometer, achieves 64-ne dynamic strain resolution at 1-kHz spectral acquisition rate and 2-kHz maximum vibration bandwidth. Performance and stabilities of IFPI sensor array were characterized from room temperatures to 800 °C. The static strain resolution was 0.6 μe and the minimum detectable dynamic strain amplitude was 23 ne/√Hz at 800 °C. The multiplex performance was also tested by measuring dynamic strain in time domain through six IFPI sensor array fabricated in one fiber. This paper presents an integrated and low-cost sensing solution to perform distributed vibration measurements in harsh environments.

Silicon (Si) is a promising anode material for lithium-ion batteries (LIBs) owing to its very high lithium storage capacity; however, fragmentation of Si caused by drastic volume change during lithium insertion and extraction leads to serious capacity decay during cycling. In this work, we report a novel method to synthesize an in situ nanocomposite containing Si nanoparticles evenly embedded in an electrically conductive SiOx@C network (Si/SiOx@C) from one single polysiloxane precursor. In our process, Si nanocrystals were reduced from the polysiloxane precursor using a low temperature molten salt reduction method, and carbon segregated out in the SiOx@C phase which evolved during the subsequent pyrolysis. As an anode material for LIBs, the Si/SiOx@C nanocomposite showed a specific capacity up to 1292 mA h g−1 at a current density of 0.4 A g−1 and 81.84% capacity retention after 200 cycles. The high capacity and stable performance of Si/SiOx@C as an anode material can be attributed to the continuous SiOx@C matrix which provides reliable mechanical support, electronic and ionic conductivity, and a stable solid–electrolyte interphase (SEI). This work demonstrated the viability of deriving a homogenous nanocomposite from a single polymeric precursor, which creates a promising anode material for next-generation LIBs.

The development of advanced Li 4 Ti 5 O 12 anode with high capacity and long cycle-life is a central issue for rechargeable Li-ion batteries. In this study, we report that a novel composite, nanosized Li 4 Ti 5 O 12 particles supported by N-doped graphene sheets, has been successfully prepared by a facile and rapid strategy. Compared to the pure Li 4 Ti 5 O 12 anode, improved electronic conductivity, higher flexibility and enhanced mechanical strength are demonstrated in N-doped graphene modified Li 4 Ti 5 O 12 . When used as anode materials for Li-ion batteries, the specific discharge capacities of the pure and N-doped graphene modified Li 4 Ti 5 O 12 electrodes for the first cycle at a current density of 0.5 C between 1.0 and 2.5 V (vs. Li + /Li) are 163.6 and 171.2 mA h g −1 , respectively, and their capacity retentions over 100 cycles are 96.1% and 99.3%, respectively. Moreover, the high-rate capacities of N-doped graphene decorated anode are also much better than that of the pure Li 4 Ti 5 O 12 at various current densities. Even at 40 C, it can still achieve a high reversible capacity of 136.9 mA h g −1 and tolerate a long-term cycling with 1000 cycles. This design strategy provides a promising pathway for developing high-performance Li 4 Ti 5 O 12 anode for Li-ion batteries.

2D semiconductors are promising candidates for future electronic device applications due to their immunity to short-channel effects (SCE), but many issues regarding mobility, contact, interface and power consumption still remain (Fig. 1). We develop a low-field model to calculate the mobility of monolayer MoS 2 FETs. Guided by the model, high carrier mobility of 150 cm2/Vs and saturation current over $450 \mu \mathrm{A}/\mu \mathrm{m}$ are realized in long-channel monolayer MoS 2 FETs, through a series of interface optimization by high- $\boldsymbol{\kappa}$ dielectric and thiol chemical treatment. For low-power applications, we demonstrate hysteresis-free MoS 2 negative capacitance FETs (NCFETs) using ferroelectric HtZrO x (HZO) as gate dielectric, achieving sub-60m V/dec subthreshold slope (SS) over 6 orders of I D , minimum SS of 24 mV/dec and 107 on/off ratio under $V_{dd}=0.5\mathrm{V}$ . We further study the high frequency performance and show that sub-60mV/dec is maintained at least to 10 kHz without signs of degradation. Finally, by performing different gate sweeps we conclude that the steep slope is indeed due to NC effects rather than ferroelectric switching of HZO.

Zhundong coal as a high quality steam coal has not been widely utilized due to severe fouling and slagging problems during combustion. To promote clean utilization of Zhundong coal, combustion experiments of Zhundong coal were carried out in the drop tube furnace (DTF). The influence of novel phosphorus-based additive on ash deposition characteristics of Zhundong coal was studied. The appearance and phase composition of the raw coal and mixed coal ash deposits at different flue gas temperatures were researched respectively. The new prediction index of slagging tendency containing phosphorus was proposed, and the balance calculation were performed by FactSage thermodynamic software in different flue gas temperatures, including experimental temperatures selected. The results showed that the values of new indexes for predicting slagging tendency had obvious changes, and the phosphorus-based additive had a significant effect on the ash deposition behavior during the combustion process of Zhundong coal in DTF. Compared with the raw coal, the mixed coal with additive had higher ash fusion points and were in the form of loose, crisp, and porous powder, which was beneficial for soot blowing. When the flue gas temperature was 1000 °C or 1150 °C, there was much phosphate complex salt as the skeleton in the ash deposits of the mixed coal, such as Na2CaMg7(PO4)6. Phosphate captured Na and Ca, and effectively inhibited the low temperature eutectic mixtures of Ca with Si and Al, indicating that phosphorus-based additive had good effect on improving ash deposition characteristics of Zhundong coal.

Single-atomic-layered materials are important for future electronics. They allow optoelectronic devices to be fabricated at the single-atomic layer level. A single-atomic-layered two-dimensional (2D) transition metal dichalcogenide (TMD) film is usually composed of randomly orientated single-crystalline domains, and the size distribution of the domains on a large-area film has a significant impact on the applications of the film, but the impact is difficult to characterize. We report an approach to evaluate the size of the single-crystalline domains by measuring the second-harmonic generation divergence caused by the domains of different orientations. Using this method, domain size mapping on an 8 × 8 m m 2 region of a continuous M o S 2 film is achieved. This method provides a fast and efficient way of domain size characterization across a large area in a non-destructive and transfer-free manner for single-atomic-layered TMD films.

GVL (γ-valerolactone) is identified as an important biomass platform molecule due to its wide application. In this work, a series of novel supported Ni catalysts with different supports and Ni loading were synthesized via metal-organic chemical vapor deposition (MOCVD) method for the hydrogenation of EL (ethyl levulinate) to GVL. Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), nitrogen adsorption/desorption, inductively coupled plasma optical emission spectroscopy (ICP-OES) and transmission electron microscopy (TEM) were used to characterize the as-synthesized catalysts. The results showed that the 2 wt.% Ni/AC(MOCVD) presented superior catalytic activity when compared with the catalyst prepared by impregnation method. This behavior is explained in terms of the smaller Ni nanoparticles (4.28 nm) and higher dispersion on 2 wt.% Ni/AC(MOCVD). Among the catalysts, the 2 wt.% Ni/AC catalyst exhibited the best catalytic performance with 99.7 % EL conversion and 79.8 % GVL yield under 1 MPa initial H2 pressure (measured at room temperature) at 250 °C for 2 h. In addition, the reaction conditions were optimized and the stability of the catalyst were also investigated. The insights gained from this study in the design of high dispersed Ni particles with smaller particle size via MOCVD method will facilitate the metal-catalyzed hydrogenation of EL to GVL.

Hydraulic fracturing is required during development of tight oil reservoir. Flowback fluid, usually surfactant, is generally used in fracturing fluid to accelerate the fluid flow back. For the reservoir with matrix and fracture construction, this flow of surfactant is dynamic imbibition. Betaine surfactant has good salt and temperature tolerance. In this study, a betaine surfactant was characterized from interfacial tension and wettability. In order to simulate complex fracture conditions, a matrix-fracture network model was established. It was featuring adjustable fracture width from 476.5 to 72.8 μm through changing the confining pressure. Then series of experiments were carried out on the dynamic imbibition in tight oil fracture network model with the aid of surfactant. Various factors that impact on the oil recovery during dynamic imbibition of models were examined. The oil recovery by dynamic imbibition was gradually increased with the increasing concentration of surfactant, matrix permeability, and temperature. The oil recovery reached to 22.6% with surfactant concentration of 0.5 wt%. With various surfactant flow rate, the oil production reached to 18.1% at a flow rate of 0.1 mL/min during dynamic imbibition. The oil distribution in the matrix and fracture was analyzed using Magnetic Resonance Imaging (MRI) method. It showed that the surfactant can effectively improve the oil recovery in the matrix near fracture during dynamic imbibition. The study would provide further understanding for the dynamic imbibition with aid of surfactant in tight oil sandstone reservoir after fracturing.

In this study, nitrogen-doped carbon is coated on LiVPO 4 F electrode for the first time via a simple chemical refluxing process, using ethylenediamine (EDA) as the carbon and nitrogen source. The structure, morphology and microstructure of the as-prepared electrode are characterized by XRD, XPS, Raman spectra, SEM and TEM. The uniform coating of nitrogen-doped carbon improves the electronic conductivity of LiVPO 4 F. As cathode material for lithium-ion batteries, the nitrogen-doped carbon coated LiVPO 4 F composite exhibits superior rate capability and excellent cycle performance over the carbon coated LiVPO 4 F. The electrode delivers an initial discharge capacity of 109.6 mAh g − 1 at high rate of 10 C and 103.1 mAh g − 1 of capacity is retained after 100 cycles. Thus, this novel modification method of nitrogen-doped carbon coating is highly effective and could be widely used to optimize the electronic conductivity of other electrode materials for lithium-ion batteries.

Hierarchical micro/nanostructure surface structures with different spatial characteristics are achieved after irradiation of crystalline silicon via femtosecond (fs) laser pulses (800 nm, 120 fs, 1 kHz) with the sample submerged in ethanol. According to laser pulse energy and fabrication parameters (such as scanning speed and superimposed writing), a characteristic morphology evolution of ovoid-like smooth modified area, ripple-like, wave-like, and coral-like micro/nanostructures is demonstrated, and the underline principle is discussed. The amorphization of fs laser-modified area is verified and investigated by Raman spectroscope. These modified structures have potential applications in sensors, silicon photovoltaic cells, and sterilization.

Performing attenuation measurements in unclad single crystal sapphire fiber has traditionally been accomplished through use the cutback method. Because single-crystal sapphire fibers do not cleave easily like silica fibers, this method requires repeated cutting and polishing of the sapphire fiber sample; which is very time consuming and introduces uncertainty in each loss measurement. In this paper, we present a new method to measure attenuation in sapphire or other single-crystal fibers based on distributed sapphire Raman optical time domain reflectometry (OTDR). This method is both nondestructive, significantly faster than the cutback method, and capable of measuring the local loss along the entire length of the fiber.

To realize steep-slope MoS2 n-type FET, we fabricate negative capacitance FET (NCFET) structure using ferroelectric HfZrOx (HZO)/AlOx as dielectric layer. The MoS2 NCFET devices exhibit ultra-low subthreshold swing (SS) of 23 mV/dec, sub-60mV/dec over 6 orders of Id, nearly hysteresis-free up to V ds = 1V, small |V th | on /I off ratio >109, and small DIBL of 25 mV/V. Importantly, we can modulate 5 orders of Id using a gate drive of 232 mV, clearly demonstrating the potential of MoS2 NCFET for low-power electronics applications. Furthermore, compared to normal MoS 2 FET with 11.2 nm equivalent oxide thickness (EOT), the NCFET achieve 60% improvement in Id (250 μA/μm) and 4 times improvement in transconductance.

As a successful novel structure, FinFET has been a hot research area, whereas how Fin influences FinFETs' performance on the hypothetical silicon process limitation is still an open issue. In reported works, Fin shape was normally mixed with the change of other parameters, such as the size scaling, and its effect was confused by those. In this paper, we just focus on Fin shape's effect itself. A simple and quantitative two-incline-angle description of Fin shape is proposed. Using this method, four typical (trapezoidal, rectangular, convex and concave) Fins' control abilities upon the hypothetical silicon limitation process node (sub-10 nm) are analyzed, and their impacts on FinFETs' characteristics are discussed systematically. The results show that in this case the rectangle shape Fin is prior on both analog and digital characteristics. The Fin shape's influence on FETs' frequency characteristic is not obvious. As an in-depth exploration, a ratio factor between the effective channel width and the cross-section area of channel is pointed out. The proposed factor can quantitatively evaluate Fin's impact not only for the regular shape Fins but also for the irregular ones. This work gives a guidance of FinFET's design on both nano scale silicon FinFETs and other advanced material FinFETs.

Transition-metal dichalcogenides (TMDCs) are important class of two-dimensional (2D) layered materials for electronic and optoelectronic applications, due to their ultimate body thickness, sizable and tunable bandgap, and decent theoretical room-temperature mobility of hundreds to thousands cm2/Vs. So far, however, all TMDCs show much lower mobility experimentally because of the collective effects by foreign impurities, which has become one of the most important limitations for their device applications. Here, taking MoS2 as an example, we review the key factors that bring down the mobility in TMDC transistors, including phonons, charged impurities, defects, and charge traps. We introduce a theoretical model that quantitatively captures the scaling of mobility with temperature, carrier density and thickness. By fitting the available mobility data from literature over the past few years, we are able to obtain the density of impurities and traps for a wide range of transistor structures. We show that interface engineering such as oxide surface passivation, high-k dielectrics and BN encapsulation could effectively reduce the impurities, leading to improved device performances. For few-layer TMDCs, we analytically model the lopsided carrier distribution to elucidate the experimental increase of mobility with the number of layers. From our analysis, it is clear that the charge transport in TMDC samples is a very complex problem that must be handled carefully. We hope that this Review can provide new insights and serve as a starting point for further improving the performance of TMDC transistors., Comment: 61 pages, 9 figures, Advanced Functional Materials, in press

The nanoporous InGaN/GaN multiple quantum wells (MQWs) has been fabricated through rapid thermal annealing (RTA) and inductively coupled plasma (ICP) dry etching process using self-assembled Ni nanoporous masks. In comparison with the as-grown planar InGaN/GaN MQWs, both internal quantum efficiency and light extraction efficiency for nanoporous InGaN/GaN MQWs are increased, which can be concluded from the photoluminescence (PL) measurements. The thermal activation energy of nanoporous structure (107.44 meV) is significantly higher than that of the as-grown sample (33.02 meV) from temperature-dependent PL measurement, indicating that carriers are well confined and the non-radiative recombination caused by the dislocations and other defects has been reduced. Besides, enhanced light scattering in the disordered nanoporous system can further increase the output emission intensity. The enhanced performance of nanoporous InGaN/GaN MQWs reveals its promising applications for high-efficiency light-emitting devices.

Highly monodisperse, dendritic, and functionalized mesoporous silica nanospheres (MSNs) with sub-200 nm size were synthesized in a one-pot sol-gel reaction, by a dual-templating micelle system consisting of a partially fluorinated short-chain anionic fluorocarbon surfactant and cetyltrimethylammonium bromide. This kind of anionic fluorocarbon surfactant works simultaneously as a swelling agent to enlarge the pore of the MSNs, an ion-pair agent to the structure-directing silane in the preparation of amine-functionalized MSNs, and a surface tension reducing agent to make the system thermodynamically more stable for producing more uniform MSNs. The particle size and the morphology of the resultant MSNs can be fine-tuned by changing the amount of the fluorocarbon surfactant added and the ratio of the functional group containing organosilane to tetraethoxysilane. Subsequently, the as-prepared MSNs were used as base materials for the preparation of drug delivery nanomaterials through the surface grafting of a pH-sensitive drug-conjugated polymer and fluorescent nanomaterials through the embedding of europium(III) complex or the immobilization of large molecule fluorescein isothiocyanate-bovine serum albumin.