Fine nanostructure design of metal chalcogenide conversion-based cathode materials for rechargeable magnesium batteries.

Magnesium-ion batteries (MIBs) a strong candidate to set off the second-generation energy storage boom due to their double charge transfer and dendrite-free advantages. However, the strong coulombic force and the huge diffusion energy barrier between Mg2+ and the electrode material have led to need for a cathode material that can enable the rapid and reversible de-insertion of Mg2+. So far, researchers have found that the sulfur-converted cathode materials have a greater application prospect due to the advantages of low price and high specific capacity, etc. Based on these advantages, it is possible to achieve the goal of increasing the magnesium storage capacity and cycling stability by reasonable modification of crystal or morphology. In this review, we focus on the application of a variety of sulfur-converted cathode materials in MIBs in recent years from the perspective of microstructural design, and provide an outlook on current challenges and future development.

Multifunctional Zincophilic Hydrogel Electrolyte with Abundant Hydrogen Bonds for Zinc-Ion Capacitors and Supercapacitors.

The new-generation flexible Zn-ion capacitors (ZICs) require multifunctionality and environmental adaptability for practical applications. This essentially means that hydrogel electrolytes are expected to possess superior mechanical properties, temperature resistance, and tunable interface properties to resist flexibility loss and performance degradation over a wide operating temperatures range. Herein, a multifunctional polyzwitterionic hydrogel electrolyte (PAM/LA/PSBMA) with wide operating temperatures, excellent tensile ability, high water retention, and self-adhesion is designed. Molecular dynamics simulations and experimental results show that polar functional groups (-COO-, -SO3-, -C═O, and -NHCO-) in the hydrogel can form abundant hydrogen bonds with water molecules, which can destroy the original hydrogen bonds (HBs) network between the water molecules and have a low freezing point. It can also form coordination with Zn2+, so that the deposition of Zn2+ electric field homogenization effectively alleviates the growth of Zn dendrites. On this basis, the constructed Zn//Zn cell can be stably cycled 290 h at 10 mA cm-2 (1 mA h cm-2). The constructed ZICs and supercapacitor have a high specific capacitance, excellent energy density, good ionic conductivity, and long cycling stability. This study provides guidance on molecular design for the development of integrated multifunctional smart electronic devices that are environmentally adaptable, resistant to drying, and highly flexible.

Title High Solar-Thermal Conversion Aerogel for Efficient Atmospheric Water Harvesting.

The shortage of freshwater is a global problem, however, the gel that can be used for atmospheric water harvesting (AWH) in recent years studying, suffer from salt leakage, agglomeration, and slow water evaporation efficiency. Herein, a solar-driven atmospheric water harvesting (SAWH) aerogel is prepared by UV polymerization and freeze-drying technique, using poly(N-isopropylacrylamide) (PNIPAm), hydroxypropyl cellulose (HPC), ethanolamine-decorate LiCl (E-LiCl) and polyaniline (PANI) as raw materials. The PNIPAm and HPC formed aerogel networks makes the E-LiCl stably and efficiently loaded, improving the water adsorption-desorption kinetics, and PANI achieves rapid water vapor evaporation. The aerogel has low density ≈0.12-0.15 g cm-3, but can sustain a weight of 1000 times of its own weight. The synergist of elements and structure gives the aerogel has 0.46-2.95 g g-1 water uptake capability at 30-90% relative humidity, and evaporation rate reaches 1.98 kg m-2 h-1 under 1 sun illumination. In outdoor experiments, 88% of the water is harvesting under natural light irradiation, and an average water harvesting rate of 0.80 gwater gsorbent -1 day-1. Therefore, the aerogel can be used in arid and semi-arid areas to collect water for plants and animals.

Covalent Organic Frameworks as Electrode Materials for Alkali Metal-ion Batteries.

Covalent organic frameworks (COFs) are a class of porous crystalline polymeric materials constructed by linking organic small molecules through covalent bonds. COFs have the advantages of strong covalent bond network, adjustable pore structure, large specific surface area and excellent thermal stability, and have broad application prospects in various fields. Based on these advantages, rational COFs design strategies such as the introduction of active sites, construction of conjugated structures, and carbon material composite, etc. can effectively improve the conductivity and stability of the electrode materials in the field of batteries. This paper introduces the latest research results of high-performance COFs electrode materials in alkali metal-ion batteries (LIBs, SIBs, PIBs and LSBs) and other advanced batteries. The current challenges and future design directions of COFs-based electrode are discussed. It provides useful insights for the design of novel COFs structures and the development of high-performance alkali metal-ion batteries.

Generation of 978†nm dispersion-managed solitons from a polarization-maintaining Yb-doped figure-of-9 fiber laser.

Restricted by the narrow gain bandwidth of Yb3+ near 980 nm, it is challenging to generate dispersion-managed (DM) solitons at this wavelength. In this work, we demonstrate the generation of DM solitons at 978 nm in a polarization-maintaining (PM) figure-of-9 fiber laser. Highly coherent pulses with 14.4 nm spectral bandwidth and 175 fs pulse duration are experimentally obtained. To the best of our knowledge, this is the shortest ∼980 nm pulse ever reported in an Yb-doped mode-locked fiber laser. Numerical simulations are performed to reveal the DM solitons' temporal and spectral evolution inside the figure-of-9 cavity under the condition of a narrow gain bandwidth. This robust and cost-effective 978 nm femtosecond laser is a promising light source for applications such as underwater communication and biophotonics.

Generation of 1.3†µm femtosecond pulses by cascaded nonlinear optical gain modulation in phosphosilicate fiber.

Nonlinear optical gain modulation (NOGM) is a simple and effective approach to generate highly coherent ultrafast pulses with a flexible wavelength. In this work, we demonstrate 34 nJ, 170 fs pulse generation at 1319 nm through a piece of phosphorus-doped fiber by two-stage cascaded NOGM with a 1064 nm pulsed pump. Beyond the experiment, numerical results show that 668 nJ, 391 fs pulses at 1.3 µm can be produced with up to 67% conversion efficiency by increasing the pump pulse energy and optimizing the pump pulse duration. This would offer an efficient method to obtain high-energy sub-picosecond laser sources for applications such as multiphoton microscopy.

Efficient single-frequency 972†nm Yb-doped fiber amplifier with core pumping and elevated temperature.

In this work, we present a monolithic single-frequency, single-mode and polarization maintaining Yb-doped fiber (YDF) amplifier delivering up to 6.9 W at 972 nm with a high efficiency of 53.6%. Core pumping at 915 nm and elevated temperature of 300 °C were applied to suppress the unwanted 977 nm and 1030 nm ASE in YDF, so as to improve the 972 nm laser efficiency. In addition, the amplifier was further used to generate a single-frequency 486 nm blue laser with 590 mW of output power by single-pass frequency doubling.

Alleviating Zn Dendrites by Growth of Ultrafine ZnO Nanowire Arrays through Horizontal Anodizing for High-Capacity, Long-Life Zn Ion Capacitors.

Zn ion capacitors (ZICs) composed of a carbon-based cathode and a Zn anode are one of the most promising energy storage devices due to their inherent safety and high-power output. However, their poor cycling stability originating from the Zn dendrites' formation and low energy density limited by insufficient activated carbon properties remain major challenges for development of high-performance ZICs. Hence, we constructed a facile and effective strategy to alleviate "edge effects" and suppress Zn dendrites by growing ZnO nanowire arrays on Zn foil (ZnO@Zn) using a horizontally potentiostatic anodizing technique. The electrochemical characterizations and in situ optical microscopy observation revealed that the introduction of ZnO nanowire arrays can significantly suppress the growth of Zn dendrites and enhance the cycling stability of the Zn anode. The superfine and interlaced ZnO nanowire arrays provide uniform nucleation sites and high electrical conductivity for the Zn metal anode, reducing the local current density and promoting the rapid diffusion and migration of Zn ions on the Zn anode surface. As a result, the ZnO@Zn electrode has a very low nucleation overpotential and excellent cycle stability, far superior to the bare Zn anode. Furthermore, a ZnO@Zn//NPHC ZIC assembled with an N, P-codoped hard carbon (NPHC) cathode delivers a high specific capacity of 110.3 mAh g-1 at 0.1 A g-1 and achieves outstanding cycling stability with 90% capacity retention together with ∼100% Coulombic efficiency after 20000 cycles.

Numerical simulation of nonlinear optical gain modulation in a Raman fiber amplifier.

Nonlinear optical gain modulation (NOGM) in a Raman fiber amplifier is numerically simulated with the generalized nonlinear Schrödinger equation. In the NOGM setup, a single frequency continuous wave seed laser is gain modulated into femtosecond pulses by an ultrafast pump, which can induce strong stimulated Raman scattering in a piece of single mode optical fiber. Different parameters regarding seed, pump and nonlinear gain medium (Raman fiber) are investigated in detail to find the best condition for higher Raman conversion efficiency. Simulated results reveal that the walk-off between pump and Raman pulses due to dispersion is one of the most important factors affecting the NOGM pulse's performance. Only when the speed of walk-off matches with the one of Raman conversion process can the conversion efficiency be optimized. This work offers a guild-line for the design of a fiber-based NOGM laser, which is able to produce wavelength-agile, femtosecond laser pulses with µJ-level pulse energy under more than 85% efficiency.

Three-dimensional nanoporous activated carbon electrode derived from acacia wood for high-performance supercapacitor.

Herein, the novel acacia wood based hierarchical porous activated carbons (AWCs) are easily prepared, low cost and have excellent characterization, such as special biomass nanopores via structural stability and large specific surface areas. Activating agents such as KOH, ZnCl2, and H3PO4 have been used to convert acacia wood carbon into active carbons such as AWC-K, AWC-Z, and AWC-P, respectively, which are named after the activating agent. As a supercapacitor electrode, the AWC-K sample has a high yield was 69.8%, significant specific surface area of 1563.43 m2g-1 and layer thickness of 4.6 mm. Besides that, it showed specific capacitance of 224.92 F g-1 at 0.5 A g-1 in 2 M KOH as electrolyte. In addition, the AWC-K//AWC-K symmetrical supercapacitor device displays high energy density of 23.98 Wh kg-1 at 450 W kg-1 power density with excellent cycling number stability was 93.2% long lifetime of 10,000 cycles using 0.5 M Na2SO4 as electrolyte. The high electrochemistry performance mainly contributed the special biomass pores structure. Therefore, the presented approach opens new avenues in supercapacitor applications to meet energy storage.

Cascaded nonlinear optical gain modulation for coherent femtosecond pulse generation.

Nonlinear optical gain modulation (NOGM) is a method to generate high performance ultrafast pulses with wavelength versatility. Here we demonstrate coherent femtosecond Raman pulse generation through cascaded NOGM process experimentally. Two single-frequency seed lasers (1121 and 1178 nm) are gain-modulated by 117 nJ 1064 nm picosecond pulses in a Raman fiber amplifier. Second-order (1178 nm) Stokes pulses are generated, which have a pulse energy of 76 nJ (corresponding to an optical conversion efficiency of 65%) with a pulse duration of 621 fs (after compression). Dynamic evolution of both pump and cascaded Stokes pulses within the Raman amplifier are investigated by numerical simulations. The influences of pump pulse duration and energy are studied in detail numerically. Moreover, the simulations reveal that NOGM pulses with higher energy and shorter pulse duration could be obtained by limiting the impact of walk-off effect between pump and Raman pulses. This approach can offer a high energy and wavelength-agile ultrafast source for various applications such as optical metrology and biomedical imagining.

Robust single-frequency 589 nm fiber laser based on phase modulation and passive demodulation.

A robust 20-W continuous-wave single frequency 589 nm laser is developed to aim for sodium guide star in astronomy. The source is based on applying π-depth binary phase modulation to a single frequency seed laser along with 3 steps of strain in the gain fiber to suppress the stimulated Brillouin scattering in the high power 1178 nm amplifier and realizing the recovery of single frequency after frequency doubling in a periodically poled LiTaO3 crystal. The efficiency of frequency doubling reaches up to 41.6%. To the best of our knowledge, it is the highest power reported for continuous-wave 589 nm laser generation by single-pass frequency doubling. The approach significantly simplifies the sodium guide star laser design and improves robustness.

Spectral compression by phase doubling in second harmonic generation.

In second harmonic generation, the phase of the optical field is doubled, which has important implications. Here, the phase-doubling effect is utilized to solve a long-standing challenge in the power scaling of single-frequency laser. (-π/2, π/2) binary phase modulation is applied to a single-frequency seed laser to broaden the spectrum and suppress the stimulated Brillouin scattering in a high-power fiber amplifier. The second harmonic of the phase-modulated laser returns to single frequency because the (-π/2, π/2) modulation is doubled to (-π, π) for the second harmonic. A compression-to-single-frequency rate as high as 95% is demonstrated in experiments limited by the electronic bandwidth of the setup. Such phase manipulation in wave-mixing processes may open up a new field of development in nonlinear optics and laser technology.

Spectral and RIN properties of a single-frequency Raman fiber amplifier co-pumped by ASE source.

Spectral and relative intensity noise (RIN) characteristics of a single-frequency Raman fiber amplifier co-pumped by amplified spontaneous emission (ASE) sources are investigated experimentally. Due to the relatively lower intensity noise of ASE sources compared to usual fiber laser pumps, the full width at half maximum (FWHM) linewidth of the signal laser increases negligibly. But there is significant increase in RIN and spectral wings due to the noise transfer at high frequency from the ASE source during the Raman amplification. The deterioration can be suppressed to some extent with ASE of broader linewidth, which has lower intensity noise.

An asymmetric supercapacitor based on controllable WO3 nanorod bundle and alfalfa-derived porous carbon.

A novel asymmetric supercapacitor (ASC) is assembled on the basis of an inerratic hexagonal-like WO3 nanorod bundle as a negative electrode and graphene-like alfalfa-derived porous activated carbon (APAC) as the positive electrode in 1 M H2SO4 aqueous electrolyte. The WO3 nanostructures prepared at pH of 1.6, 1.8, 2.0, 2.5 and 3.0 display hexagonal disc-like, nanorod bundle, inerratic hexagonal-like, sphere-like, and needle-shaped nanorod morphology. WO3-2.0, which was prepared at a pH of 2.0, exhibits high specific capacitance (415.3 F g-1 at 0.5 A g-1). APAC-2, which had the mass ratios of dried alfalfa and ZnCl2 as 1 : 2, showed a 3D porous structure, large surface area (1576.3 m2 g-1), high specific capacitance (262.1 F g-1 at 0.5 A g-1), good cycling stability with 96% of initial specific capacitance after 5000 consecutive cycles. The ASC assembled with WO3-2.0 and APAC-2 exhibits high energy density (27.3 W h kg-1 at a power density of 403.1 W kg-1), as well as good electrochemical stability (82.6% capacitance retention after 5000 cycles). Such outstanding electrochemical behavior implies that the electrode materials are promising for practical energy-storage systems.

Resonant frequency doubling of phase-modulation-generated few-frequency fiber laser.

Resonant frequency doubling of periodically phase-modulated single-frequency fiber laser is investigated as a method for power scaling of visible fiber lasers. Sinusoidal phase modulation is applied to generate few-frequency lasers at 1064 nm in the proof of principle experiments. By adjusting the modulation frequency to match the free spectral range of a doubling cavity, a resonant enhancement condition can be achieved and a near 30 W 532 nm laser is generated with a maximum conversion efficiency above 80%. The indistinguishable conversion efficiencies between the single-frequency and few-frequency cases prove the feasibility of the approach. Interesting spectral evolvement of the phase-modulated laser in second-harmonic generation is analyzed theoretically and observed in the experiment.

Effects of inverse ratio ventilation combined with lung protective ventilation on pulmonary function in patients with severe burns for surgery.

OBJECTIVE: To investigate the effects of inverse ratio ventilation combined with lung-protective ventilation on pulmonary function and inflammatory factors in severe burn patients undergoing surgery. Populations and Methods: Eighty patients with severe burns undergoing elective surgery were divided randomly into two groups: control (CG, n = 40) and experiment (EG, n = 40). The CG had conventional ventilation, whereas the EG were ventilated with tidal volume (TV) of 6-8 ml/kg, I (inspiration): E (expiration) of 2:1, and positive end-expiratory pressure (PEEP) 5 cm H2O. The following variables were evaluated before (T0), 1 h after start of surgery (T1) and after surgery (T2): oxygenation index (OI), partial pressure of carbon dioxide (PaCO2), TV, peak airway pressure (Ppeak), mean airway pressure (Pmean), PEEP, pulmonary dynamic compliance (Cdyn), alveolar-arterial difference of oxygen partial pressure D(A-a)O2, lactic acid (Lac), interleukin (IL)-6 and IL-10, and lung complications. Results: At T1 and T2 time points, the OI, Pmean and Cdyn were significantly greater in the EG than in the CG while the TV, Ppeak, D(A-a)O2, IL-6 and IL-10 were significantly smaller in the EG than in the CG. At the end of the surgery, the Lac was significantly smaller in the EG than in the CG (1.28 ± 0.19 vs. 1.40 ± 0.23 mmol/L). Twenty-four hours after the surgery, significantly more patients had hypoxemia (27.5 vs. 10.0%), increased expectoration (45.0 vs. 22.5%), increased lung texture or exudation (37.5 vs. 17.5%) in the CG than in the EG. Conclusions: Inverse ratio ventilation combined with lung-protective ventilation can reduce Ppeak, increase Pmean and Cdyn, improve the pulmonary oxygenation function, and decrease ILs in severe burn surgery patients.

Synthesis of porous carbon material based on biomass derived from hibiscus sabdariffa fruits as active electrodes for high-performance symmetric supercapacitors.

Carbon-based materials are manufactured as high-performance electrodes using biomass waste in the renewable energy storage field. Herein, four types of hierarchical porous activated carbon using hibiscus sabdariffa fruits (HBFs) as a low-cost biomass precursor are synthesized through carbonization and activation. NH4Cl is used as a chemical blowing agent to form carbon nanosheets, which are the first types of hibiscus sabdariffa fruit-based carbon (HBFC-1) sample, and KOH also forms a significant bond in the activation process. The prepared HBFC-1 is chosen to manufacture the symmetric supercapacitor due to its rough surface and high surface area (1720.46 m2 g-1), making it show a high specific capacity of 194.50 F g-1 at a current density of 0.5 A g-1 in a three-electrode system. Moreover, the HBFC-1 based symmetric supercapacitor devices display a high energy density of 13.10 W h kg-1 at a power density of 225.00 W kg-1, and a high specific capacity of 29 F g-1 at 0.5 A g-1. Additionally, excellent cycle life is observed (about 96% of capacitance retained after 5000 cycles). Therefore, biomass waste, especially hibiscus sabdariffa fruit based porous carbon, can be used as the electrode for high-performance supercapacitor devices.

More than 20 W fiber-based continuous-wave single frequency laser at 780†nm.

We demonstrate a 21.2 W continuous-wave single frequency 780 nm laser by utilizing single-pass frequency doubling of a 49.8 W 1560 nm fiber amplifier in a periodically-poled magnesium-oxide-doped lithium niobate (MgO: PPLN) crystal. The conversion efficiency of the frequency doubling reaches up to 42.6%. The high power 1560 nm Erbium-doped fiber amplifier (EDFA) is in-band pumped by a 1480 nm Raman fiber laser. Maximum output power of 49.8 W is obtained at an incident 1480 nm laser of 60.6 W, corresponding to an amplification efficiency of 79.7%. To the best of our knowledge, this is the highest reported continuous-wave single frequency 780 nm laser, which is developed for advanced quantum technology with Rb cold atoms.

2 W single-frequency, low-noise 509 nm laser via single-pass frequency doubling of an ECDL-seeded Yb fiber amplifier.

A single-frequency low-noise green laser at 509 nm is developed for the study of cesium Rydberg atoms. The laser is generated by single-pass second-harmonic generation of a Yb fiber amplifier seeded with an external cavity diode laser (ECDL) at 1018 nm in a periodically poled MgO-doped lithium-niobate crystal. An up to 2.03 W, 509 nm laser is obtained from a 10.04 W incident 1018 nm laser with a conversion efficiency of 20.2%. The linewidth of the 509 nm laser is estimated to be 40 kHz according to the measured linewidth of 20 kHz of the 1018 nm fundamental laser. The relative intensity noise is 0.038% rms integrated from 10 Hz to 10 MHz.