Preparation of porous superabsorbent particles based on starch by supercritical CO2 drying and its water absorption mechanism.

The slow water-absorption speed of starch-based superabsorbent resin (St-SAP) limits its application. In this study, porous St-SAP (P-St-SAP) was prepared by inverse suspension polymerization and supercritical CO2 drying, the aim is to provide a preparation method of fast absorbent resin. The P-St-SAP at 33 % starch content had an interpenetrating porous structure with macropores, mesopores and micropores, and the surface area, pore volume and average pore diameter were 32.06 m2·g-1, 0.116 cm3·g-1 and 21.6 nm, respectively. The water-absorption process included rapid-section, medium-section and slow-section, according with internal diffusion, double-constant and quasi second-order kinetic models, respectively. In the initial 30 s, a water-absorption speed of 262.6 g·g-1·min-1 in distilled water was much higher than some previous research results, and the equilibrium absorption value of 517.9 g·g-1 in distilled water and 72.9 g·g-1 in 0.9 % saline was better than that of non-porous St-SAP at similar starch content. Moreover, at the same stage the percentage of saline absorption ratio to equilibrium absorption value was 1.0- 2.0 times higher than that of distilled water. These research results indicate that the P-St-SAP has fast water-absorption speed and good salt resistance, which will have greater application prospects in sanitary materials, building concrete pouring, and flood control blocking piping.

Orderly Arranged Dipoles Regulate Anion-Derived Solid-Electrolyte Interphase for Stable Lithium Metal Chemistry.

Lithium (Li) metal batteries are considered the most promising high-energy-density electrochemical energy storage devices of the next generation. However, the unstable solid-electrolyte interphase (SEI) derived from electrolytes usually leads to high impedance, Li dendrites growth, and poor cyclability. Herein, the ferroelectric BaTiO3 with orderly arranged dipoles (BTOV) is integrated into the polypropylene separator as a functional layer. Detailed characterizations and theoretical calculations indicate that surface oxygen vacancies drive the phase transition of BaTiO3 materials and promote the ordered arrangement of dipoles. The strong dipole moments in BTOV can adsorb TFSI- and NO3 - anions selectively and promote their preferential reduction to form a SEI film enriched with inorganic LiF and LiNxOy species, thus facilitating the rapid transfer of Li+ and restraining the growth of Li dendrites. As a result, the Li-Li cell with the BTOV functional layer exhibits enhanced Li plating/stripping cycling with an ultra-long life of over 7000 h at 0.5 mA cm-2/1.0 mAh cm-2. The LiFePO4 || Li (50 µm) full cells display excellent cycling performance exceeding 1760 cycles and superior rate performance. This work provides a new perspective for regulating SEI chemistry by introducing ordered dipoles to control the distribution and reaction of anions.

The Role of Surveillance Inspections in Reducing False-Positives of SARS-CoV-2 Omicron Variants during the COVID-19 Epidemic.

Objective: This study aims to assess the effectiveness of surveillance inspections conducted by the provincial health committee in Quanzhou city during a COVID-19 outbreak in reducing false-positive results in SARS-CoV-2 RT-PCR assays. Method: The team conducted on-site inspections of laboratories that participated in mass screening, recording any violations of rules. Results: The positive cases in five rounds of mass screening were 23, 173, and 4 in Licheng District, Fengze District, and Luojang District, respectively. The false-positive rates in the five rounds of mass screening were 0.0099%, 0.0063%, 0.0018%, 0.0006%, and 0%, respectively. The study also recorded that the number of violations in the seven selected laboratories was 36, 68, 69, 42, 60, 54 and 47. The corresponding false-positive rates were 0.0012%, 0.0060%, 0.0082%, 0.0032%, 0.0060%, 0.0027%, and 0.0021%, respectively. The study found a positive correlation between false-positive rates and the number of violations (r = 0.905, P=0.005), and an inverse correlation between false-positive rates and the frequency of surveillance inspections (r = -0.950, P < 0.001). Conclusion: Daily surveillance inspection in laboratories can remind laboratories to strictly comply with standard procedures, focus on laboratory quality control, and reduce the occurrence of false-positive cases in SARS-CoV-2 nucleic acid tests to some extent. This study recommends that government decision-making departments establish policies and arrange experts to conduct daily surveillance inspections to improve laboratory quality control.

In Situ Formed Heterostructure Interface and Well-Tuned Electronic Structure Ensuring Long Cycle Stability for 4.9 V High-Voltage Li-Rich Layered Oxide Cathodes.

High-voltage lithium-rich manganese-based layered oxides (LMLOs) are considered as the most competitive cathode materials for next-generation high-energy-density lithium-ion batteries (LIBs). However, LMLOs still suffer from irreversible lattice oxygen release, uncontrollable interface side reactions, and surface structural degradation. Herein, we propose an integration strategy combining La/Al codoping and LixCoPO4 nanocoating to improve the electrochemical performance of LMLOs comprehensively. La/Al codoping regulates the electronic structure to enhance the redox activity of anions and cations and inhibit structural degradation. The LixCoPO4 nanocoating formed by in situ reaction with the surface residual lithium can not only promote Li-ion migration but also reduce interfacial side reactions. The induced Layered@Rocksalt@LixCoPO4 heterostructure suppresses lattice volume variation and structural degradation during cycling. Under the synergistic effect of the heterostructure interface and well-tuned electronic structure, the capacity retention rate of comodified LMLO materials reaches 80.06% after 500 cycles (2.0-4.65 V) and 75.1% after 340 cycles at 1C under a high cut-off voltage of 4.9 V.

A separator modified by barium titanate with macroscopic polarization electric field for high-performance lithium-sulfur batteries.

The detrimental "shuttling effect" of lithium polysulfides and the sluggish kinetics of the sulfur redox reaction in lithium-sulfur batteries (LSBs) impede the practical application. Considering the high polar chemistry facilitates the anchoring of polysulfides, ferroelectric materials have gradually been employed as functionalized separators to suppress the "shuttling effect". Herein, a functional separator coated with BaTiO3 with a macroscopic polarization electric field (poled-BaTiO3) is designed for retarding the problematic shuttle effect and accelerating redox kinetics. Theoretical calculations and experiments revealed that resultant positive charged alignments on the poled-BaTiO3 coating can chemically immobilize polysulfides, effectively improving the cyclic stability of LSBs. Moreover, the simultaneous reinforcement of the built-in electric field in the poled-BaTiO3 coating can also improve Li-ion transportation for accelerating redox kinetics. Benefiting from these attributes, the as-developed LSB attains an initial discharge capacity of 1042.6 mA h g-1 and high cyclic stability of over 400 cycles at 1 C rate. The corresponding LSB pouch cell was also assembled to validate the concept. This work is anticipated to provide new insight into the development of high-performing LSBs through engineering ferroelectric-enhanced coatings.

Characterization of Modified Mechanically Activated Cassava Starch Magnetic Porous Microspheres and Its Adsorption for Cd(II) Ions.

The magnetic polymer microsphere is a promising adsorbent due to its high adsorption efficiency and good regeneration ability from wastewater. Cassava starch magnetic porous microspheres (AAM-MSMPMs) were synthesized by graft copolymerization in inverse emulsion. Mechanically activated cassava starch (MS) was used to graft skeletons, vinyl monomers [acrylic acid (AA) and acrylamide (AM)] as copolymerized unsaturated monomers, methyl methacrylate (MMA) as the dispersing agent, and polyethylene glycol/methanol (PEG2000/MeOH) as the porogen. It was found that the AAM-MSMPM adsorbent is superparamagnetic, the saturation magnetization is 14.9 emu·g-1, and it can be rapidly and directionally separated from Cd(II) ions in aqueous solution. The FTIR indicated that the carboxyl and hydroxyl groups were grafted into MS. The AAM-MSMPM had good speroidization and a uniform size. After the porogen was added, the particle size of the AAM-MSMPM decreased from 19.00 to 7.00 nm, and the specific surface area increased from 7.00 to 35.00 m2·g-1. The pore volume increased from 0.03 to 0.13 cm3·g-1. The AAM-MSMPM exhibited a large specific surface area and provided more adsorption active sites for Cd(II) ions. The maximum adsorption capacity of the AAM-MSMPM for Cd(II) ions was 210.68 mg·g-1, i.e., 81.02% higher than that without porogen. Additionally, the Cd(II) ion adsorption process on the AAM-MSMPM can be described by Langmuir isothermal and pseudo-second-order kinetic models. A chemical reaction dominated the Cd(II) ion adsorption process on the AAM-MSMPM, and chemisorption was the rate-controlling step during the Cd(II) ion adsorption process. The AAM-MSMPM still had excellent stability after five consecutive reuses.

Dual Active Sites of Oversaturated Fe-N5 and Fe2 O3 Nanoparticles for Accelerating Redox Kinetics of Polysulfides.

The shuttling effect and sluggish reaction kinetics are the main bottlenecks for the commercial viability of lithium-sulfur (Li-S) batteries. Metal-nitrogen-carbon single atom catalysts have attracted much attention to overcoming these obstacles due to their novel electrocatalytic activity. Herein, a novel cooperative catalytic interface with dual active sites (oversaturated Fe-N5 and polar Fe2 O3 nanocrystals) are co-embedded in nitrogen-doped hollow carbon spheres (Fe2 O3 /Fe-SA@NC) is designed by fine atomic regulation mechanism. Both experimental verifications and theoretical calculations disclose that the dual active sites (Fe-N5 and Fe2 O3 ) in this catalyst (Fe2 O3 /Fe-SA@NC) tend to form "FeS" and "LiN/O" bond, synchronically enhancing chemical adsorption and interface conversion ability of polysulfides, respectively. Specially, the Fe-N5 coordination with 3D configuration and sulfiphilic superfine Fe2 O3 nanocrystals exhibit the strong adsorption ability to facilitate the subsequent conversion reaction at dual-sites. Meanwhile, the nitrogen-doped hollow carbon spheres can promote Li+ /electron transfer and physically suppress polysulfides shuttling. Consequently, Li-S battery with the Fe2 O3 /Fe-SA@NC-modified separator exhibits a high capacity retention of 78% after 800 cycles at 1 C (pure S cathode, S content: 70 wt.%). Furthermore, the pouch cell with this separator shows good performance at 0.1 C for practical application (S loading: 4 mg cm-2 ).

Integrating a Ferroelectric Interface with a Well-Tuned Electronic Structure in Lithium-Rich Layered Oxide Cathodes for Enhanced Lithium Storage.

Li-rich layered oxides (LLOs) are considered promising candidates for new high-energy-density cathode materials for next-generation power batteries. However, their large-scale applications are largely hindered by irreversible Li/O loss, structural degradation, and interfacial side reactions during cycling. Herein, we demonstrate an integration strategy that tunes the electronic structure by La/Al codoping and constructs a ferroelectric interface on the LLOs surface through Bi0.5Na0.5TiO3 (BNT) coating. Experimental characterization reveals that the synergistic effect of the ferroelectric interface and the well-tuned electronic structure can not only promote the diffusion of Li+ and hinder the migration of On- but also suppress the lattice volume changes and reduce interfacial side reactions at high voltages up to 4.9 V vs Li+/Li. As a result, the modified material shows enhanced initial capacities and retention rates of 224.4 mAh g-1 and 78.57% after 500 cycles at 2.0-4.65 V and 231.7 mAh g-1 and 85.76% after 200 cycles at 2.0-4.9 V at 1C, respectively.

Preparation and Drug-Loading Properties of Amphoteric Cassava Starch Nanoparticles.

Based on the characteristics of charge reversal around the isoelectric point (pI) of amphoteric starch-containing anionic and cationic groups, amphoteric cassava starch nanoparticles (CA-CANPs) are prepared by a W/O microemulsion crosslinking method using (3-chloro-2-hydroxypropyl) trimethyl ammonium chloride as a cationic reagent and POCl3 as an anionic reagent, and the effects of preparation conditions on the particle size of the CA-CANPs are studied in detail in the present study. CA-CANPs with a smooth surface and an average diameter of 252 nm are successfully prepared at the following optimised conditions: a crosslinking agent amount of 15 wt%, an aqueous starch concentration of 6.0 wt%, an oil-water ratio of 10:1, a total surfactant amount of 0.20 g·mL-1, and a CHPTAC amount of 4.05 wt%. The pH-responsive value of the CA-CANPs can be regulated by adjusting the nitrogen-phosphorus molar ratio in the CA-CANPs. By using CA-CANPs with a pI of 6.89 as drug carriers and the paclitaxel (PTX) as a model drug, the maximum loading rate of 36.14 mg·g-1 is achieved, and the loading process is consistent with the Langmuir isotherm adsorption, with the calculated thermodynamic parameters of ΔH° = -37.91 kJ·mol-1, ΔS° = -10.96 J·mol-1·K-1 and ΔG° < 0. By testing the release rate in vitro, it is noted that the release rates of PTX in a neutral environment (37.6% after 96 h) and a slightly acidic environment (58.65% after 96 h) are quite different, suggesting that the CA-CANPs have the possibility of being a targeted controlled-release carrier with pH responsiveness for antitumor drugs.

High-Precision Temperature Inversion Algorithm for Correlative Microwave Radiometer.

In order to achieve high precision from non-contact temperature measurement, the hardware structure of a broadband correlative microwave radiometer, calibration algorithm, and temperature inversion algorithm are innovatively designed in this paper. The correlative radiometer is much more sensitive than a full power radiometer, but its accuracy is challenging to improve due to relatively large phase error. In this study, an error correction algorithm is designed, which reduces the phase error from 69.08° to 4.02°. Based on integral calibration on the microwave temperature measuring system with a known radiation source, the linear relationship between the output voltage and the brightness temperature of the object is obtained. Since the metal aluminum plate, antenna, and transmission line will have a non-linear influence on the receiver system, their temperature characteristics and the brightness temperature of the object are used as the inputs of the neural network to obtain a higher accuracy of inversion temperature. The temperature prediction mean square error of a back propagation (BP) neural network is 0.629 °C, and its maximum error is 3.351 °C. This paper innovatively proposed the high-precision PSO-LM-BP temperature inversion algorithm. According to the global search ability of the particle swarm optimization (PSO) algorithm, the initial weight of the network can be determined effectively, and the Levenberg-Marquardt (LM) algorithm makes use of the second derivative information, which has higher convergence accuracy and iteration efficiency. The mean square error of the PSO-LM-BP temperature inversion algorithm is 0.002 °C, and its maximum error is 0.209 °C.

Engineering Fe-N Coordination Structures for Fast Redox Conversion in Lithium-Sulfur Batteries.

Critical drawbacks, including sluggish redox kinetics and undesirable shuttling of polysulfides (Li2 Sn , n = 4-8), seriously deteriorate the electrochemical performance of high-energy-density lithium-sulfur (Li-S) batteries. Herein, these challenges are addressed by constructing an integrated catalyst with dual active sites, where single-atom (SA)-Fe and polar Fe2 N are co-embedded in nitrogen-doped graphene (SA-Fe/Fe2 N@NG). The SA-Fe, with plane-symmetric Fe-4N coordination, and Fe2 N, with triangular pyramidal Fe-3N coordination, in this well-designed configuration exhibit synergistic adsorption of polysulfides and catalytic selectivity for Li2 Sn lithiation and Li2 S delithiation, respectively. These characteristics endow the SA-Fe/Fe2 N@NG-modified separator with an optimal polysulfides confinement-catalysis ability, thus accelerating the bidirectional liquid-solid conversion (Li2 Sn ↔Li2 S) and suppressing the shuttle effect. Consequently, a Li-S battery based on the SA-Fe/Fe2 N@NG separator achieves a high capacity retention of 84.1% over 500 cycles at 1 C (pure S cathode, S content: 70 wt%) and a high areal capacity of 5.02 mAh cm-2 at 0.1 C (SA-Fe/Fe2 N@NG-supported S cathode, S loading = 5 mg cm-2 ). It is expected that the outcomes of the present study will facilitate the design of high-efficiency catalysts for long-lasting Li-S batteries.

A labyrinth-like network electrode design for lithium-sulfur batteries.

The volume expansion of sulfur and the dissolution of polysulfides into the electrolyte are the key issues to be solved in the development of lithium-sulfur batteries. In this work, a labyrinth electrode material design is presented to overcome these difficulties in lithium-sulfur batteries. The shell of NiO-Co3O4 hollow spheres as the "wall" to prevent the polysulfide dissolution cross-links into a labyrinth network as a sulfur host. The 3D labyrinth network not only provides enough inner space to load sulfur but also adapts to its large volume expansion during lithiation and delithiation. In addition, the polar NiO-Co3O4 shells can promote the chemical adsorption of polysulfides, while NiO-Co3O4 shells can promote the conversion of polysulfides into Li2S. With this unique design, the 3D labyrinth-like NiO-Co3O4@S electrode presents a good electrochemical performance, delivering high capacity with a stable cycling life of up to 200 cycles at 1C and the attenuation rate of each cycle is only 0.1%.

Novel CdFe Bimetallic Complex-Derived Ultrasmall Fe- and N-Codoped Carbon as a Highly Efficient Oxygen Reduction Catalyst.

During the development of oxygen reduction reaction electrocatalysts, transition-metal nanoparticles embedded in N-doped graphene have attracted increasing attention owing to their low-priced, minimal environmental impact, and satisfying performance. In this study, a new organic-cadmium (Cd) complex formed through Cd2+ coordination with p-phenylenediamine (PPD) was used to synthesize highly active Fe-embedded N-doped carbon catalysts for the first time. It is significant that with the decreasing molar ratio of Cd/Fe, an obvious microstructure evolution was observed in Cd-Fe-PPD from diamond-like blocks to thick flakes, and further bloomed into flowerlike shapes with ultrathin petals and then eventually exhibited large block starfish-like shapes. After carbonization, Cd was removed, slack and porous N-doped carbon was formed, and Fe was assembled in the N-doped carbon. Similar phenomenon was also observed in Co-PPD. The optimized Fe/NPC-2 material featuring uniform and well-dispersed 3-5 nm Fe nanoparticles embedded in two-dimensional ultrathin carbon nanosheets delivered excellent electrocatalytic performance ( Eonset: 0.96 V vs reversible hydrogen electrode (RHE), E1/2: 0.84 V vs RHE), which is very close to those of commercial platinum on carbon (Pt/C) ( Eonset: 0.95 V vs RHE, E1/2: 0.84 V vs RHE), and its methanol tolerance and durability also surpass those of Pt/C.

High-Rate and Long-Life Sodium-Ion Batteries Based on Sponge-like Three-Dimensional Porous Na-Rich Ferric Pyrophosphate Cathode Material.

Sponge-like three-dimensional porous carbon-encapsulated Na3.32Fe2.34(P2O7)2 nanoparticles (labeled to NFPO@SC) were manufactured by a sol-gel method followed by multistage calcinations and utilized as the cathode material for sodium-ion batteries. The excellent electrochemical performance of the NFPO@SC cathode can be attributed to its unique porous structure, which facilitates electrolyte penetration, reduces the diffusion path of sodium ions, and increases electronic conductivity. In addition, the full battery is assembled by NFPO@SC and hard carbon, which are employed as cathode and anode electrodes, respectively. The full battery delivers a high discharge capacity (112.2 mA h g-1 at 0.5 C) and maintains 93.9% stable capacity over 1000 cycles at 5 C.

Nitrogen-Doped Carbon as a Host for Tellurium for High-Rate Li-Te and Na-Te Batteries.

A nitrogen-doped hierarchical porous carbon sponge, used as a matrix for tellurium accommodation, was designed and prepared in this work. The porosity of the matrix played an important role in enhancing the electrochemical performance of Li/Na-Te batteries. Specifically, the mesopores could accommodate active materials whereas the macropores provided sufficient space for partial Te accommodation and volume expansion in discharge. In addition, N heteroatoms in carbon species could enhance the electrical conductivity and widen its application in lithium/sodium storage. The monolithic and flaky architecture of the nitrogen-doped hierarchical porous carbon sponge/tellurium composite offered a highly conductive network for fast electron transportation. As a result, the nitrogen-doped hierarchical porous carbon sponge/tellurium composite achieved a superior rate performance for Li-Te and Na-Te batteries.

Self-Supported FeCo2S4 Nanotube Arrays as Binder-Free Cathodes for Lithium-Sulfur Batteries.

Inhibiting the shuttle effect, buffering the volume expansion, and improving the utilization of sulfur have been the three strategic points for developing a high-performance lithium-sulfur (Li-S) battery. Driven by this background, a flexible sulfur host material composed of FeCo2S4 nanotube arrays grown on the surface of carbon cloth is designed for a binder-free cathode of the Li-S battery through two-step hydrothermal method. Among the rest, the interconnected carbon fiber skeleton of the composite electrode ensures the basic electrical conductivity, whereas the FeCo2S4 nanotube arrays not only boost the electron and electrolyte transfer but also inhibit the dissolution of polysulfides because of their strong chemical adsorption. Meanwhile, the hollow structures of these arrays can provide a large inner space to accommodate the volume expansion of sulfur. More significantly, the developed composite electrode also reveals a catalytic action for accelerating the reaction kinetic of the Li-S battery. As a result, the FeCo2S4/CC@S electrode delivers a high discharge capacity of 1384 mA h g-1 at the current density of 0.1 C and simultaneously exhibits a stable Coulombic efficiency of about 98%.

Substrate-Controlled Domino Reactions of Crotonate-Derived Sulfur Ylides: Synthesis of Benzothiophene Derivatives.

Substrate-controlled domino reactions between thioaurones or their analogues and crotonate-derived sulfur ylides were developed and produced a broad spectrum of benzothiophene-fused pyran derivatives, substituted chromene derivatives. In these reactions, crotonate-derived sulfur ylides acting as two-carbon synthons (α and ß carbons or ß and γ carbons) in annulation reactions are reported for the first time. These investigations nicely complement and expand previously studied reactions of crotonate-derived sulfur ylides. In addition, reaction mechanisms for these domino reactions are proposed, one of which is supported by DFT calculations.

Solvent-Controlled Switchable Domino Reactions of MBH Carbonate: Synthesis of Benzothiophene Fused α-Pyran, 2,3-Dihydrooxepine, and Oxatricyclodecene Derivatives.

Solvent-controlled switchable domino reactions between 2-alkylidenebenzothiophene-3(2H)-ones and Morita-Baylis-Hillamn (MBH) carbonate were developed. All domino reactions exhibited excellent regioselectivity, producing a broad spectrum of benzothiophene-fused α-pyran, 2,3-dihydrooxepine, and oxatricyclodecene derivatives. Furthermore, [4 + 2], [4 + 3], and related domino reactions from identical substrates can be controlled.

Correction: Direct N-H/α,α,ß,ß-C(sp3)-H functionalization of piperidine via an azomethine ylide route: synthesis of spirooxindoles bearing 3-substituted oxindoles.

Correction for 'Direct N-H/α,α,ß,ß-C(sp3)-H functionalization of piperidine via an azomethine ylide route: synthesis of spirooxindoles bearing 3-substituted oxindoles' by Yanlong Du et al., Chem. Commun., 2017, 53, 1684-1687.

Selenium Encapsulated into Metal-Organic Frameworks Derived N-Doped Porous Carbon Polyhedrons as Cathode for Na-Se Batteries.

The substitution of Se for S as cathode for rechargeable batteries, which confine selenium in porous carbon, attracts much attention as a potential area of research for energy storage systems. To date, there are no reports about metal-organic frameworks (MOFs) to use for Na-Se batteries. Herein, MOFs-derived nitrogen-doped porous carbon polyhedrons (NPCPs) have been obtained via facile synthesis and annealing treatment. Se is encapsulated into the mesopores of carbon polyhedrons homogeneously by melt-diffusion process to form Se/NPCPs composite, using as cathode for advanced Na-Se batteries. Se/NPCPs cathode exhibits excellent rate capabilities of 351.6 and 307.8 at 0.5C and 2C, respectively, along with good cycling performance with high Coulombic efficiency of 99.7% and slow decay rate of 0.05% per cycle after 1000 cycles at 2C, which result from the NPCPs having a unique porous structure to accommodate volumetric expansion of Se during discharge-charge processes. Nitrogen doping could enhance the electrical conductivity of carbon matrix and facilitate rapid charge transfer.