Polarization-Independent Second Harmonic Generation in 2D Van Der Waals Kagome Nb3 SeI7 Crystals.

Second harmonic generation (SHG) of 2D crystals has been of great interest due to its advantages of phase-matching and easy integration into nanophotonic devices. However, the polarization-dependence character of the SHG signal makes it highly troublesome but necessary to match the laser polarization orientation relative to the crystal, thus achieving the maximum polarized SHG intensity. Here, it is demonstrated a polarization-independent SHG, for the first time, in the van der Waals Nb3 SeI7 crystals with a breathing Kagome lattice. The Nb3 triangular clusters and Janus-structure of each Nb3 SeI7 layer are confirmed by the STEM. Nb3 SeI7 flake shows a strong SHG response due to its noncentrosymmetric crystal structure. More interestingly, the SHG signals of Nb3 SeI7 are independent of the polarization of the excitation light owing to the in-plane isotropic arrangement of nonlinear active units. This work provides the first layered nonlinear optical crystal with the polarization-independent SHG effect, providing new possibilities for nonlinear optics.

A π-Conjugated Polyimide-Based High-Performance Aqueous Potassium-Ion Asymmetric Supercapacitor.

Aqueous asymmetric supercapacitor has captured widespread attention as a sustainable high-power energy resource. Organic electrode materials are appealing owing to their sustainability and high redox reactivity, but suffer from structural instability and low power density. Here the π-conjugated polyimide-based organic electrodes with different lengths of alkyl chains are explored to achieve high rate capability and long lifespan in an aqueous K+ -ion electrolyte. The fabricated asymmetric supercapacitor exhibits high capacities of 107 mAh g-1 at 2 A g-1 and 67 mAh g-1 at 90 A g-1 . A specific capacity of 65 mAh g-1 over 70% of the initial performance is obtained after 65 000 cycles. Molecular engineering of long alkyl chains in polyimide can reduce the degree of π-conjugation and spatially block the π-conjugated imide bond with limited redox activity but improved stability against chemical degradation. Further electrochemical quartz crystal microbalance, ex-situ Fourier transformed infrared spectroscopy, and X-ray photoelectron spectroscopy characterizations reveal the pseudocapacitance behavior originating from the π-conjugated polyimide-based redox reaction with potassium ions and hydrated potassium ions. A promising polyimide-based polymer with extended π-conjugated system for high-performance asymmetric supercapacitor is showcased.

Structure Re-determination and Superconductivity Observation of Bulk 1T MoS2.

2H MoS2 has been intensively studied because of its layer-dependent electronic structures and novel physical properties. Though the metastable 1T MoS2 with a [MoS6 ] octahedron was observed over the microscopic area, the true crystal structure of 1T phase has not been strictly determined. Moreover, the true physical properties have not been demonstrated from experiments owing to the challenge for the preparation of pure 1T MoS2 crystals. 1T MoS2 single crystals were successfully synthesized and the crystal structure of 1T MoS2 re-determined from single-crystal X-ray diffraction. 1T MoS2 crystallizes in the space group P3‾ m1 with a cell of a=b=3.190(3) Šand c=5.945(6) Å. The individual MoS2 layer consists of MoS6 octahedra sharing edges with each other. More surprisingly, the bulk 1T MoS2 crystals undergo a superconducting transition of Tc =4 K, which is the first observation of superconductivity in pure 1T MoS2 phase.

Enhanced Superconductivity in Restacked TaS2 Nanosheets.

Since interface superconductivity was discovered at the interface between two insulating layers LaAlO3 and SrTiO3, such interface-induced superconducting systems have been a research hotspot in superconductivity. Here, we report homogeneous interfaces formed by stacking chemically exfoliated monolayer TaS2 nanosheets randomly. Enhanced superconductivity of Tc = 3 K is observed, compared with 0.8 K of parent 2H-TaS2. The measurement of heat capacity shows the increase of electronic specific-heat coefficient γ of restacked TaS2 nanosheets compared to parent 2H-TaS2 crystals. Density functional theory calculations indicate that increase and delocalization of electron states near the Fermi surface due to the homogeneous interfaces effects could account for the enhanced superconductivity.

New Graphene Form of Nanoporous Monolith for Excellent Energy Storage.

Extraordinary tubular graphene cellular material of a tetrahedrally connected covalent structure was very recently discovered as a new supermaterial with ultralight, ultrastiff, superelastic, and excellent conductive characteristics, but no high specific surface area will keep it from any next-generation energy storage applications. Herein, we prepare another new graphene monolith of mesoporous graphene-filled tubes instead of hollow tubes in the reported cellular structure. This graphene nanoporous monolith is also composed of covalently bonded carbon network possessing high specific surface area of ∼1590 m(2) g(-1) and electrical conductivity of ∼32 S cm(-1), superior to graphene aerogels and porous graphene forms self-assembled by graphene oxide. This 3D graphene monolith can support over 10 000 times its own weight, significantly superior to CNT and graphene cellular materials with a similar density. Furthermore, pseudocapacitance-active functional groups are introduced into the new nanoporous graphene monolith as an electrode material in electrochemical capacitors. Surprisingly, the electrode of 3D mesoporous graphene has a specific capacitance of 303 F g(-1) and maintains over 98% retention after 10 000 cycles, belonging to the list for the best carbon-based active materials. The macroscopic mesoporous graphene monolith suggests the great potential as an electrode for supercapacitors in energy storage areas.

Enhanced electron transport in Nb-doped TiO2 nanoparticles via pressure-induced phase transitions.

Anatase TiO2 is one of the most important energy materials but suffers from poor electrical conductivity. Nb doping has been considered as an effective way to improve its performance in the applications of photocatalysis, solar cells, Li batteries, and transparent conducting oxide films. Here, we report the further enhancement of electron transport in Nb-doped TiO2 nanoparticles via pressure-induced phase transitions. The phase transition behavior and influence of Nb doping in anatase Nb-TiO2 have been systematically investigated by in situ synchrotron X-ray diffraction and Raman spectroscopy. The bulk moduli are determined to be 179.5, 163.3, 148.3, and 139.0 GPa for 0, 2.5, 5.0, and 10.0 mol % Nb-doped TiO2, respectively. The Nb-concentration-dependent stiffness variation has been demonstrated: samples with higher Nb concentrations have lower stiffness. In situ resistance measurements reveal an increase of 40% in conductivity of quenched Nb-TiO2 in comparison to the pristine anatase phase. The pressure-induced conductivity evolution is discussed in detail in terms of the packing factor model, which provides direct evidence for the rationality of the correlation of packing factors with electron transport in semiconductors. Pressure-treated Nb-doped TiO2 with unique properties surpassing those in the anatase phase holds great promise for energy-related applications.

1D Insertion Chains Induced Small-Polaron Collapse in MoS2 2D Layers Toward Fast-Charging Sodium-Ion Batteries.

Molybdenum disulfide (MoS2 ) with high theoretical capacity is viewed as a promising anode for sodium-ion batteries but suffers from inferior rate capability owing to the polaron-induced slow charge transfer. Herein, a polaron collapse strategy induced by electron-rich insertions is proposed to effectively solve the above issue. Specifically, 1D [MoS] chains are inserted into MoS2 to break the symmetry states of 2D layers and induce small-polaron collapse to gain fast charge transfer so that the as-obtained thermodynamically stable Mo2 S3 shows metallic behavior with 107 times larger electrical conductivity than that of MoS2 . Theoretical calculations demonstrate that Mo2 S3 owns highly delocalized anions, which substantially reduce the interactions of Na-S to efficiently accelerate Na+ diffusion, endowing Mo2 S3 lower energy barrier (0.38 vs 0.65 eV of MoS2 ). The novel Mo2 S3 anode exhibits a high capacity of 510 mAh g-1 at 0.5 C and a superior high-rate stability of 217 mAh g-1 at 40 C over 15 000 cycles. Further in situ and ex situ characterizations reveal the in-depth reversible redox chemistry in Mo2 S3 . The proposed polaron collapse strategy for intrinsically facilitating charge transfer can be conducive to electrode design for fast-charging batteries.

An electron-blocking interface for garnet-based quasi-solid-state lithium-metal batteries to improve lifespan.

Garnet oxide is one of the most promising solid electrolytes for solid-state lithium metal batteries. However, the traditional interface modification layers cannot completely block electron migrating from the current collector to the interior of the solid-state electrolyte, which promotes the penetration of lithium dendrites. In this work, a highly electron-blocking interlayer composed of potassium fluoride (KF) is deposited on garnet oxide Li6.4La3Zr1.4Ta0.6O12 (LLZTO). After reacting with melted lithium metal, KF in-situ transforms to KF/LiF interlayer, which can block the electron leakage and inhibit lithium dendrite growth. The Li symmetric cells using the interlayer show a long cycle life of ~3000 hours at 0.2 mA cm-2 and over 350 hours at 0.5 mA cm-2 respectively. Moreover, an ionic liquid of LiTFSI in C4mim-TFSI is screened to wet the LLZTO|LiNi0.8Co0.1Mn0.1O2 (NCM) positive electrode interfaces. The Li|KF-LLZTO | NCM cells present a specific capacity of 109.3 mAh g-1, long lifespan of 3500 cycles and capacity retention of 72.5% at 25 °C and 2 C (380 mA g-1) with an average coulombic efficiency of 99.99%. This work provides a simple and integrated strategy on high-performance quasi-solid-state lithium metal batteries.

Core-shell nanostructured "black" rutile titania as excellent catalyst for hydrogen production enhanced by sulfur doping.

Modification of rutile titanium dioxide (TiO2) for hydrogen generation and water cleaning is a grand challenge due to the chemical inertness of rutile, while such inertness is a desired merit for its stability in photoelectrochemical applications. Herein, we report an innovative two-step method to prepare a core-shell nanostructured S-doped rutile TiO2 (R'-TiO2-S). This modified black rutile TiO2 sample exhibits remarkably enhanced absorption in visible and near-infrared regions and efficient charge separation and transport. As a result, the unique sulfide surface (TiO(2-x):S) boosts the photocatalytic water cleaning and water splitting with a steady solar hydrogen production rate of 0.258 mmol h(-1) g(-1). The black titania is also an excellent photoelectrochemical electrode exhibiting a high solar-to-hydrogen conversion efficiency of 1.67%. The sulfided surface shell is proved to be an effective strategy for enhancing solar light absorption and photoelectric conversion.

Gray TiO2 nanowires synthesized by aluminum-mediated reduction and their excellent photocatalytic activity for water cleaning.

Not always black and white: Gray TiO2 nanowires with high photocatalytic activity have been successfully synthesized by aluminum-mediated reduction in a two-zone furnace. These wires, which possess a core (TiO(2-x))/shell (TiO2 ) structure, exhibit visible-light and even IR absorption with high photocatalytic activity, far exceeding that of commercial Degussa P25. They show high stability in air and water under solar-light irradiation.

Nested order-disorder framework containing a crystalline matrix with self-filled amorphous-like innards.

Solids can be generally categorized by their structures into crystalline and amorphous states with different interactions among atoms dictating their properties. Crystalline-amorphous hybrid structures, combining the advantages of both ordered and disordered components, present a promising opportunity to design materials with emergent collective properties. Hybridization of crystalline and amorphous structures at the sublattice level with long-range periodicity has been rarely observed. Here, we report a nested order-disorder framework (NOF) constructed by a crystalline matrix with self-filled amorphous-like innards that is obtained by using pressure to regulate the bonding hierarchy of Cu12Sb4S13. Combined in situ experimental and computational methods demonstrate the formation of disordered Cu sublattice which is embedded in the retained crystalline Cu framework. Such a NOF structure gives a low thermal conductivity (~0.24 W·m-1·K-1) and a metallic electrical conductivity (8 × 10-6 Ω·m), realizing the collaborative improvement of two competing physical properties. These findings demonstrate a category of solid-state materials to link the crystalline and amorphous forms in the sublattice-scale, which will exhibit extraordinary properties.

Electrodes with Electrodeposited Water-excluding Polymer Coating Enable High-Voltage Aqueous Supercapacitors.

Aqueous supercapacitors are powerful energy sources, but they are limited by energy density that is much lower than lithium-ion batteries. Since raising the voltage beyond the thermodynamic potential for water splitting (1.23 V) can boost the energy density, there has been much effort on water-stabilizing salvation additives such as Li2SO4 that can provide an aqueous electrolyte capable of withstanding ~1.8 V. Guided by the first-principles calculations that reveal water can promote hydrogen and oxygen evolution reactions, here, we pursue a new strategy of covering the electrode with a dense electroplated polymerized polyacrylic acid, which is an electron insulator but a proton conductor and proton reservoir. The combined effect of salvation and coating expands the electrochemical window throughout pH 3 to pH 10 to 2.4 V for both fast and slow proton-mediated redox reactions. This allows activated carbon to quadruple the energy density, a kilogram of nitrogen-doped graphene to provide 127 Watt-hour, and both to have improved endurance because of suppression of water-mediated corrosion. Therefore, aqueous supercapacitors can now achieve energy densities quite comparable to that of a lithium-ion battery, but at 100 times the charging/discharging speed and cycle durability.

Boron-Induced Nitrogen Fixation in 3D Carbon Materials for Supercapacitors.

Nitrogen-rich carbon materials attract great attention because of their admirable performance in energy storage and electrocatalysis. However, their conductivity and nitrogen content are somehow contradictory because good conductivity requires high-temperature heat treatment, which decomposes most of the nitrogen species. Herein, we propose a facile method to solve this problem by introducing boron (B) to fix the nitrogen in a three-dimensional (3D) carbon material even at 1000 °C. Besides, this N-rich carbon material has a high content of pyrrolic nitrogen due to the selective stabilization of B, which is favorable in electrochemical reactions. Density functional theory (DFT) investigation demonstrates that B reduces the energy level of neighboring N species (especially pyrrolic nitrogen) in the graphene layer, making it difficult to escape. Thus, this carbon material simultaneously, achieves high conductivity (30 S cm-1) and nitrogen content (7.80 atom %), thus showing an outstanding capacitance of 412 F g-1 and excellent rate capability.

A Facile Approach To Improve Electrochemical Capacitance of Carbons by in Situ Electrochemical Oxidation.

A facile approach of in situ electrochemical oxidation has been utilized to modify carbons, including activated carbon, mesoporous few-layer carbon, graphite, carbon fiber, and carbon nanotube, which induces oxygen-containing functional groups on its surface and simultaneously enhances its wettability, contributing to the improvement of capacitance. By this approach, the capacitance of commercialized activated carbon is increased by 86% in an acidic electrolyte, reaching 320 F g-1, of which more than 96% was maintained after 10 000 cyclic tests. The huge improvement stems from electrochemical redox reactions enabled by oxygen-associated groups, which do not adversely affect the porous structure and electrical conductivity. Such improvement will put carbon-based electrochemical capacitors into more practical application areas.

Extraordinary Porous Few-Layer Carbons of High Capacitance from Pechini Combustion of Magnesium Nitrate Gel.

Highly capacitive carbons are viewed as promising commercial materials for supercapacitors, but few species satisfy the requirements of high capacitance and low cost. Here, we demonstrate an extraordinary porous few-layer carbon by facile Pechini combustion of magnesium nitrate gel, which combined salicylic acid as a complexing agent with magnesium nitrate as an inorganic metal salt. The as-synthesized carbon material delivers a capacitance of 415 F g-1, mostly stemming from a large specific surface area (∼1312 m2 g-1), a fluent channel for transport of the electrolyte, as well as electrochemical redox reactions at O,N-associated active sites. Such porous few-layer carbons may accelerate the adoption of carbon-based supercapacitors for commercial high-power energy storage applications.

Improving the Visible-Light Photocatalytic Activity of Graphitic Carbon Nitride by Carbon Black Doping.

Hydrogen production by water splitting and the removal of aqueous dyes by using a catalyst and solar energy are an ideal future energy source and useful for environmental protection. Graphitic carbon nitride can be used as the photocatalyst with visible light irradiation. However, it typically suffers from the high recombination of carriers and low electrical conductivity. Here, we have developed a facile mix-thermal strategy to prepare carbon black-modified graphitic carbon nitrides, which possess high electrical conductivity, a wide adsorption range of visible light, and a low recombination rate of carriers. With the help of carbon black, highly crystallized graphitic carbon nitrides with built-in triazine and heptazine heterojunctions are obtained. Improved photocatalytic activities have been achieved in carbon black-modified graphitic carbon nitride. The dye removal rate can be three times faster than that of pristine graphitic carbon nitride and the photocatalytic H2 generation is 234 µmol h-1 g-1 under visible light irradiation.

A New Green Titania with Enhanced NIR Absorption for Mitochondria-Targeted Cancer Therapy.

A new kind of green titania (G-TiO2-x ) with obvious green color was facilely synthesized from black titania (B-TiO2-x ) through subsequently strong ultrasonication. Comparatively, this stable G-TiO2-x shows much enhanced near infrared (NIR) absorption, especially around 920 nm, which can be ascribed to the obvious change of TiO2-x lattice order owing to the effect of ultrasonication. This feature enables G-TiO2-x to be stimulated with 980 nm laser in the combined photodynamic therapy (PDT) and photothermal therapy (PTT), which is greatly beneficial for improving tissue penetration depth. Furthermore, since mitochondria are preferred subcellular organelles for PDT/PTT, G-TiO2-x was further designed to conjugate with triphenylphosphonium (TPP) ligand for mitochondria-targeted PDT/PTT to obtain precise cancer treatment. Attributing to the high mitochondria-targeting efficiency and simultaneously synergistic PDT/PTT, high phototherapeutic efficacy and safety with a much lower laser power density (980 nm, 0.72 W cm-2) and low materials dosage were achieved both in vitro and in vivo. In addition, negligible toxicity was found, indicating high biocompatibility. This novel G-TiO2-x could provide new strategies for future precise minimal/non-invasive tumor treatment.

Controllable reduced black titania with enhanced photoelectrochemical water splitting performance.

Black titania prepared by metal-reduction methods is systematically studied and found the best controllable Mg-reduction method. Colored titania products from white, light blue, dark blue, to black were obtained with a crystalline/amorphous core-shell structure. The black titania shows a five times higher H2 production rate in photoelectrochemical (PEC) water splitting.

A Robust and Conductive Black Tin Oxide Nanostructure Makes Efficient Lithium-Ion Batteries Possible.

SnO2 -based lithium-ion batteries have low cost and high energy density, but their capacity fades rapidly during lithiation/delithiation due to phase aggregation and cracking. These problems can be mitigated by using highly conducting black SnO2-x , which homogenizes the redox reactions and stabilizes fine, fracture-resistant Sn precipitates in the Li2 O matrix. Such fine Sn precipitates and their ample contact with Li2 O proliferate the reversible Sn → Li x Sn → Sn → SnO2 /SnO2-x cycle during charging/discharging. SnO2-x electrode has a reversible capacity of 1340 mAh g-1 and retains 590 mAh g-1 after 100 cycles. The addition of highly conductive, well-dispersed reduced graphene oxide further stabilizes and improves its performance, allowing 950 mAh g-1 remaining after 100 cycles at 0.2 A g-1 with 700 mAh g-1 at 2.0 A g-1 . Conductivity-directed microstructure development may offer a new approach to form advanced electrodes.

[Analysis and Forecasting of Population Mortality and Life Lost Trend due to 
Lung Cancer among Xiamen Residents].

BACKGROUND: In recent years, the incidence and mortality of lung cancer is rising. It has become the leading cause of death of malignant tumors in China. The aim of this study is to explore the trend of mortality and years of life lost due to lung cancer in residents in Xiamen, so as to provide the basis data on preventing lung cancer in Xiamen. METHODS: The data of residents in Xiamen dying of lung cancer from 2005 to 2014 was collected and cleared up to calculate the evaluation indexes including the mortality rate, the average potential life lost (AYLL), and the average percentage change (APC) of mortality rate. GM(1,1) model was used to predict the future mortality and AYLL. RESULTS: From 2005 to 2014, the average mortality rate of lung cancer in residents in Xiamen was 28.58 per 100,000 persons, of which in male was 2.90 times as that in female. The APC was 4.86%. The AYLL, which was 7.8 years, had decline trend from 2005 to 2014. The mean absolute percentage errors between observed values and fitted values were 2.16%-8.83%. The mortality rate and AYLL of lung cancer in residents in Xiamen would increase from 2015 to 2019. CONCLUSIONS: The mortality of lung cancer increased year by year in Xiamen. There are both increasing trend of mortality and years of life lost in future. So we should pay more attentions on preventing and curing of lung cancer.