SiOC Phase Control and Carbon Nanoribbon Growth by Introducing Oxygen at Atom Level for Lithium-Ion Batteries.

Poor intrinsic conductivity and the presence of irreversible lithiation phase affect the electrochemical performance of silicon oxycarbide anode materials. Even though it can be improved by increasing free carbon content or composition, scarification of reversible capacity and initial Coulombic efficiency (ICE) remain as challenge. Here, polycarbosilane (PCS) with alternating distribution of silicon and carbon atoms is employed as precursor of SiOC ceramics. Air oxidation cross-linking is used to regulate the content of oxygen and carbon elements in PCS at atom level, so as to explore a solution to improve the intrinsic conductivity and reversible lithium phase content of SiOC ceramics. This strategy provides extremely excellent rate capability, areal/volumetric capacity, and ICE. This is also the first concept for feasible precursor structure design to control the SiOC glass phase and regulate the growth of C nanoribbon that can improve the intrinsic conductivity and reversible capacity of SiOC ceramic anode materials.

Investigation of the impact of supplemental reflective films to improve micro-light climate within tomato plant canopy in solar greenhouses.

The non-uniform growth and development of crops within Chinese Solar Greenhouses (CSG) is directly related to the micro-light climate within canopy. In practice, reflective films are used to improve micro-light climate within plant canopy by homogenizing light distribution and so increasing total plant light interception. However, as to our knowledge, the contributions to light distribution within canopy have not been investigated for passive reflector like reflective films. Field experiments dealing with light conditions and growth behavior over time, are complicated to carry out, time-consuming and hard to control, while however, accurate measurements of how reflective films influence the micro-light climate of canopy are an essential step to improve the growth conditions for any crop. Here, we propose a supplementary light strategy using reflective films to improve light distribution within plant canopy. Based on the example of CSG, a 3D greenhouse model including a detailed 3D tomato canopy structure was constructed to simulate the influence of supplementary reflective films to improve micro-light climate. Comparison of measured solar radiation intensity with predicted model data demonstrated that the model could precisely predict light radiation intensity over time with different time points and positions in the greenhouse. A series of reflective film configurations were investigated based on features analysis of light distribution in the tomato canopy on sunny days using the proposed model. The reflective film configuration scheme with the highest impact significantly improved the evenness of horizontal and vertical light distribution in tomato canopy. The strategy provided here can be used to configure reflective films that will enhance light conditions in CSG, which can be applied and extended in different scenarios.

Analyzing the Impact of Greenhouse Planting Strategy and Plant Architecture on Tomato Plant Physiology and Estimated Dry Matter.

Determine the level of significance of planting strategy and plant architecture and how they affect plant physiology and dry matter accumulation within greenhouses is essential to actual greenhouse plant management and breeding. We thus analyzed four planting strategies (plant spacing, furrow distance, row orientation, planting pattern) and eight different plant architectural traits (internode length, leaf azimuth angle, leaf elevation angle, leaf length, leaflet curve, leaflet elevation, leaflet number/area ratio, leaflet length/width ratio) with the same plant leaf area using a formerly developed functional-structural model for a Chinese Liaoshen-solar greenhouse and tomato plant, which used to simulate the plant physiology of light interception, temperature, stomatal conductance, photosynthesis, and dry matter. Our study led to the conclusion that the planting strategies have a more significant impact overall on plant radiation, temperature, photosynthesis, and dry matter compared to plant architecture changes. According to our findings, increasing the plant spacing will have the most significant impact to increase light interception. E-W orientation has better total light interception but yet weaker light uniformity. Changes in planting patterns have limited influence on the overall canopy physiology. Increasing the plant leaflet area by leaflet N/A ratio from what we could observe for a rose the total dry matter by 6.6%, which is significantly better than all the other plant architecture traits. An ideal tomato plant architecture which combined all the above optimal architectural traits was also designed to provide guidance on phenotypic traits selection of breeding process. The combined analysis approach described herein established the causal relationship between investigated traits, which could directly apply to provide management and breeding insights on other plant species with different solar greenhouse structures.

Microscopic origins of the crystallographically preferred growth in evaporation-induced colloidal crystals.

Unlike crystalline atomic and ionic solids, texture development due to crystallographically preferred growth in colloidal crystals is less studied. Here we investigate the underlying mechanisms of the texture evolution in an evaporation-induced colloidal assembly process through experiments, modeling, and theoretical analysis. In this widely used approach to obtain large-area colloidal crystals, the colloidal particles are driven to the meniscus via the evaporation of a solvent or matrix precursor solution where they close-pack to form a face-centered cubic colloidal assembly. Via two-dimensional large-area crystallographic mapping, we show that the initial crystal orientation is dominated by the interaction of particles with the meniscus, resulting in the expected coalignment of the close-packed direction with the local meniscus geometry. By combining with crystal structure analysis at a single-particle level, we further reveal that, at the later stage of self-assembly, however, the colloidal crystal undergoes a gradual rotation facilitated by geometrically necessary dislocations (GNDs) and achieves a large-area uniform crystallographic orientation with the close-packed direction perpendicular to the meniscus and parallel to the growth direction. Classical slip analysis, finite element-based mechanical simulation, computational colloidal assembly modeling, and continuum theory unequivocally show that these GNDs result from the tensile stress field along the meniscus direction due to the constrained shrinkage of the colloidal crystal during drying. The generation of GNDs with specific slip systems within individual grains leads to crystallographic rotation to accommodate the mechanical stress. The mechanistic understanding reported here can be utilized to control crystallographic features of colloidal assemblies, and may provide further insights into crystallographically preferred growth in synthetic, biological, and geological crystals.

Development of High-Capacity and Water-Lean CO2 Absorbents by a Concise Molecular Design Strategy through Viscosity Control.

The exponentially increasing viscosity of water-lean CO2 absorbents during carbon capture processes is a critical problem for practical application, owing to its strong correlation with systems' mass transfer properties, as well as convenience of transportation. In this work, a concise strategy based on structure-viscosity relationships is proposed and applied to construct a series of functionalized ethylenediamines as single-component absorbents for post-combustion CO2 capture. These nonaqueous absorbents have outstanding viscosities (50-200 cP, 25 °C) at their maximal CO2 capacities (up to 22 wt % or 4.92 mol kg-1 , 1 bar), and are readily regenerated at low temperatures (50-80 °C) under ambient pressure. Additional capture of CO2 through physisorption could also be achieved by operating at high pressures. The CO2 capture and release process is systematically investigated by means of 13 C NMR spectroscopy, differential scanning calorimetry (DSC), in situ FTIR analysis, and density functional theory (DFT) calculations, which could provide sufficient spectroscopic details to reveal the ease of reversibility and enable rational interpretation of the absorption mechanism.

Fabrication of double core-shell Si-based anode materials with nanostructure for lithium-ion battery.

Yolk-shell structure is considered to be a well-designed structure of silicon-based anode. However, there is only one point (point-to-point contact) in the contact region between the silicon core and the shell in this structure, which severely limits the ion transport ability of the electrode. In order to solve this problem, it is important that the core and shell of the core-shell structure are closely linked (face-to-face contact), which ensures good ion diffusion ability. Herein, a double core-shell nanostructure (Si@C@SiO2) was designed for the first time to improve the cycling performance of the electrode by utilising the unique advantages of the SiO2 layer and the closely contacted carbon layer. The improved cycling performance was evidenced by comparing the cycling properties of similar yolk-shell structures (Si@void@SiO2) with equal size of the intermediate shell. Based on the comparison and analysis of the experimental data, Si@C@SiO2 had more stable cycling performance and exceeded that of Si@void@SiO2 after the 276th cycle. More interestingly, the electron/ion transport ability of electrode was further improved by combination of Si@C@SiO2 with reduced graphene oxide (RGO). Clearly, at a current density of 500 mA g-1, the reversible capacity was 753.8 mA h g-1 after 500 cycles, which was 91% of the specific capacity of the first cycle at this current density.

Economical synthesis of composites of FeNi alloy nanoparticles evenly dispersed in two-dimensional reduced graphene oxide as thin and effective electromagnetic wave absorbers.

Developing electromagnetic wave absorbing materials prepared by a facile and economical way is a great challenge. Herein, we report a feasible route to synthesize a series of two-dimensional FeNi/rGO composites by a hydrothermal method followed by a carbonization process. The characterization confirms that nano-sized FeNi alloy nanoparticles are evenly supported onto graphene sheets without aggregation. The homogeneous dispersion of the nanoparticles may result from the introduction of glucose and the oxygen-containing groups on the surface of the graphene oxide. Measurements show that the microwave attenuation capability of the composites can be improved dramatically by adjusting the proportion of dielectric and magnetic components. Consequently, the two-dimensional magnetic material (FeNi/rGO-100) exhibits an excellent microwave absorption performance. In detail, the minimum reflection loss of -42.6 dB and effective bandwidth of 4.0 GHz can be reached with a thinner thickness of 1.5 mm. This study demonstrates that synergistic effects among the magnetic particles, reduced graphene oxide and amorphous carbon layers give rise to the highlighted microwave attenuation ability. Overall, the FeNi/rGO composite is a promising candidate to be used as a microwave absorber, and the feasible and economical method has shown potential application to construct multitudinous two-dimensional materials.

Massive preparation of pitch-based organic microporous polymers for gas storage.

A general challenge for preparing organic microporous polymers (MOPs) is to use cheap and sustainable building blocks while retaining the advanced functions. We demonstrate a strategy to massively prepare pitch-based MOPs, which are thermally and chemically stable. A maximum BET surface area of 758 m(2) g(-1) and high gas storage capacity were achieved.

Cu(II)-catalyzed esterification reaction via aerobic oxidative cleavage of C(CO)-C(alkyl) bonds.

A novel Cu(II)-catalyzed aerobic oxidative esterification of simple ketones for the synthesis of esters has been developed with wide functional group tolerance. This process is assumed to go through a tandem sequence consisting of α-oxygenation/esterification/nucleophilic addition/C-C bond cleavage and carbon dioxide is released as the only byproduct.

Highly efficient SO2 absorption/activation and subsequent utilization by polyethylene glycol-functionalized Lewis basic ionic liquids.

Up to now, flue-gas desulfurization (FGD) is one of the most effective techniques to control SO(2) emission from the combustion of fossil fuels. The conventional technology for FGD poses serious inherent drawbacks such as formation of byproducts and volatilization of solvents. In this work, polyethylene glycol (PEG)-functionalized Lewis basic ionic liquids (ILs) derived from DABCO were proved to be highly efficient absorbents for FGD due to its specific features such as high thermal stability, negligible vapor pressure, high loading capacity. Notably, PEG(150)MeDABCONTf(2) gave an extremely high SO(2) capacity (4.38 mol mol(-1) IL), even under 0.1 bar SO(2) partial pressure (1.01 mol mol(-1) IL), presumably owing to the strong SO(2)-philic characterization of the PEG chain. Furthermore, the absorbed SO(2) could be easy to release by just bubbling N(2) at room temperature, greatly reducing energy requirement for SO(2) desorption. In addition, SO(2)/CO(2) selectivity (110) of PEG(150)MeDABCONTf(2) is two times larger than the non-functionalized imidazolium IL (45). On the other hand, through activation of SO(2) with the tertiary nitrogen in the cation, Lewis basic ILs such as PEG(150)MeDABCOBr proved to be efficient catalysts for the conversion of SO(2) to some value-added chemicals such as cyclic sulfites without utilization of any organic solvent or additive. Thus, this protocol would pave the way for the development of technological innovation towards efficient and low energy demanded practical process for SO(2) absorption and subsequent transformation.

Equimolar CO2 capture by N-substituted amino acid salts and subsequent conversion.

Steric bulk controls CO(2) absorption: N-substituted amino acid salts in poly(ethylene glycol) reversibly absorb CO(2) in nearly 1:1 stoichiometry. Carbamic acid is thought to be the absorbed form of CO(2); this was supported by NMR and in situ IR spectroscopy, and DFT calculations. The captured CO(2) could be converted directly into oxazolidinones and thus CO(2) desorption could be sidestepped.

Synthesis and liquid crystallinity of dendronized carbohydrate liquid crystal.

A dendronized carbohydrate thermotropic liquid crystal was synthesized by attaching wedge-shaped mesogens onto a carbohydrate core. These molecules self-organize into chiral columnar hexagonal mesophase with each column slice (4.5 Å thicknesses) filled with average of two molecules. The supramolecular model was further optimized by molecular dynamics simulation. Moreover, chirality successfully expressed in columnar hexagonal mesophase by dendronized carbohydrate molecules may provide inspiration in searching for chiral mesophase of carbohydrate liquid crystals.

Tuning mesomorphic properties and handedness of chiral calamitic liquid crystals by minimal modification of the effective core.

Two pairs of calamitic liquid crystalline molecules, (+)-2-[4'-(S)-sec-butoxyphenyl]-5-(4'-hexoxyphenyl)toluene ((+)-S-1) and (+)-2-(4'-hexoxyphenyl)-5-[4'-(S)-sec-butoxyphenyl]toluene ((+)-S-2), (-)-2-[4'-(R)-sec-butoxyphenyl]-5-(4'-hexoxyphenyl)toluene ((-)-R-1) and (-)-2-(4'-hexoxyphenyl)-5-[4'-(R)-sec-butoxyphenyl]toluene ((-)-R-2), have been designed and synthesized. Each of the molecules consists of a p-terphenyl core substituted with a methyl group on the middle ring, a chiral sec-butoxy tail, and an achiral n-hexoxy tail. The geometrical difference between (+)-S-1 ((-)-R-1) and (+)-S-2 ((-)-R-2) lies only in the location of the methyl group on the effective mesogenic core. Yet, such a small change in the structure gives rise to remarkable differences in mesogenic properties and handedness. Both (+)-S-1 and (-)-R-1 have an enantiotropic cholesteric phase (N*) and a monotropic twist grain boundary C* phase (TGBC*), whereas (+)-S-2 and (-)-R-2 exhibit only a monotropic N* phase. Moreover, (+)-S-1 ((-)-R-1) and (+)-S-2 ((-)-R-2) have opposite handedness in the N* phase, and (+)-S-1 and (-)-R-1 even have a helical inversion from N* to TGBC* phase through a non-helical chiral mesophase.

Unusual chiral transfer in radical copolymerization of vinyl monomers bearing side-on p-terphenyl pendants.

Radical copolymerization of a chiral monomer, (+)-2,5-bis[4'-((S)-2-methylbutoxy)phenyl]styrene and an achiral monomer, 2,5-bis(4'-hexyloxyphenyl)styrene, is carried out in anisole at 90 degrees C with benzoyl peroxide as the initiator. The resultant optically active helical copolymers show an unusual linear relationship between optical activity and composition, in sharp contrast with Green's "sergeants-and-soldiers" and "majority" rules. Analysis of the polarimetry, circular dichroism, and chain extension results suggest that the weak steric interaction between the propagation helical radical and the incoming monomer drove the copolymer chain to grow in a specific direction. Moreover, the helical macroinitiator is successfully used to induce the helix-sense-selective atom transfer radical polymerization of an achiral analogous monomer to yield optically-active block copolymers, which indicate a convenient way to prepare helical polymers with an excess screw sense from an achiral monomer by means of radical polymerization.

Tuning the helicity of self-assembled structure of a sugar-based organogelator by the proper choice of cooling rate.

A novel sugar-appended low-molecular-mass gelator, 4''-butoxy-4-hydroxy-p-terphenyl-beta-D-glucoside (BHTG), was synthesized. It formed thermally reversible gels in a variety of aqueous and organic solvents. Three-dimensional networks made up of helical ribbons were observed in the mixture of H(2)O/1,4-dioxane (40/60 v/v). The handedness of the ribbons depended on the rate of gel formation. Fast-cooling process led to right-handed ribbons, while slow-cooling process led to left-handed ones. A combinatory analyses of microscopic, spectroscopic, and diffraction techniques revealed that BHTG formed a twisted interdigitated bilayer structure with a d spacing of 3.1 nm in gels through a kinetically controlled nucleation-growth process. There were two kinds of molecular orientations of BHTG in the nuclei, clockwise and anticlockwise, which dictated the growth of ribbons. One was metastable and formed first during the cooling process of gel formation. It was able to gradually transform into the more stable latter one with further decreasing temperature. Fast-cooling process did not leave enough time for the nuclei to evolve from metastable to stable state and the ribbons grown from them exhibited right-handedness. However, the metastable nuclei transformed into the stable one when cooled slowly and directed the molecules of BHTG to grow into left-handed aggregates.

Synthesis and characterization of near-infrared absorbing and fluorescent liquid-crystal chromophores.

This work demonstrates that the donor-acceptor-donor charge-transfer chromophores can be tailor-made to be near-infrared absorbing and fluorescent, as well as being liquid crystals. The chromophore containing an extremely strong acceptor of benzo[1,2-c:4,5-c']bis([1,2,5]thiadiazole) can form a columnar mesophase that absorbs at 890 nm and emits at 1160 nm in the solid state. These chromophores are readily soluble in common organic solvents and can form thin films by casting or spin coating, making them suitable for further device applications.

Quaternary ammonium bromide functionalized polyethylene glycol: a highly efficient and recyclable catalyst for selective synthesis of 5-aryl-2-oxazolidinones from carbon dioxide and aziridines under solvent-free conditions.

A quaternary ammonium bromide covalently bound to polyethylene glycol (PEG, MW = 6000), i.e., PEG(6000-)(NBu(3)Br)2, was found to be an efficient and recyclable catalyst for the cycloaddition reaction of aziridines to CO(2) under mild conditions without utilization of additional organic solvents or cocatalysts. As a result, 5-aryl-2-oxazolidinone was obtained in high yield with excellent regioselectivity. The catalyst worked well for a wide variety of 1-alkyl-2-arylaziridines. Besides, the catalyst could be recovered by centrifugation and reused without significant loss of catalytic activity and selectivity.

Solvent effect on the aggregation behavior of rod-coil diblock copolymers.

The water-induced aggregation behavior of rod-coil diblock copolymers based on poly(ethylene oxide) (PEO) and poly{(+)-2,5-bis[4'-((S)-2-methylbutoxy)phenyl]styrene} (PMBPS), PEO104-b-PMBPS53, was investigated in the common solvent THF and in the selective solvent dioxane. Before adding water, PEO104-b-PMBPS53 stayed as single polymer chains no matter what conformation the PEO block took (i.e., either the random coil conformation in THF or the compact globule conformation in dioxane). The critical water content ( approximately 6 wt %) at which PEO104-b-PMBPS53 began to aggregate was also similar in both solvents, indicating that PMBPS dominated the aggregation process. However, the size, the size distribution, and the morphology of aggregates in THF/water were quite different from those in dioxane/water. Narrowly distributed spheres with Rh approximately 20 nm were observed in dioxane, whereas in THF, a bimodal distribution peaked at 3 and approximately 300 nm, was observed. The results from 2D wide-angle X-ray diffraction and polarized optical microscopy demonstrated that the PMBPS blocks packed in a parallel pattern upon aggregation in dioxane/water. The anisotropic disclike structures observed in THF/water also indicated the orientation of the PMBPS blocks upon forming aggregates in dilute solution.

Controlled fabrication of cross-linked nanoparticles/polymer composite thin films through the combined use of surface-initiated atom transfer radical polymerization and gas/solid reaction.

A promising strategy for the controlled synthesis of inorganic/polymeric nanocomposites may be sustained by fabricating cross-linked PbS nanoparticles/polymer composite thin films through combining surface-initiated atom transfer radical polymerization (ATRP) and gas/solid reaction. The introduction of Pb ions through the extension of surface-initiated ATRP to the monomers containing metal ions provides an opportunity for generating nanoparticles on the substrate.