Separation and purification of polyprenols from Ginkgo biloba leaves by silver ion anchored on imidazole-based ionic liquid functionalized mesoporous MCM-41 sorbent.

Polyprenols (PPs) are compounds with excellent biological activities and are applied in food, pharmaceutical, and cosmetic industries. However, its strong non-polar nature makes it difficult to separate with many saturated impurities (such as saturated fatty acids) extracted together. Complexation extraction is an effective method for separating saturated and polyunsaturated compounds. In this study, mesoporous silica MCM-41 was modified by imidazole-based ionic liquids (IL) followed by coating these MCM-41-supported IL compounds with silver salt to construct π-complexing adsorbent (AgBF4/IL•MCM-41) to enrich PPs from Ginkgo biloba leaves (GBL) extract. The mesoporous π-complexing sorbent was characterized by small-angle X-ray scattering (SAXS), FTIR, and nitrogen adsorption-desorption. The effect of the ratio of silver salt to IL•MCM-41 on the adsorption capacity of polyprenols from GBL was compared, and the dosage of AgBF4 was determined to be 1.5 mmol/g IL•MCM-41. Adsorption isotherms and kinetics indicate that the π-complexing adsorbent has excellent PPs adsorption performance (153 mg/g at 30 °C) and a fast adsorption rate (the time to reach adsorption equilibrium is 210 s). The PPs were separated using the fixed bed after treatment for only one cycle with AgBF4/IL•MCM-41, and the content of PPs in the product was increased from 38.54% to 70.2%, with a recovery rate of 86.6%. The π-complexing adsorbent showed excellent reusability for ≥3 adsorption-desorption cycles.

Altering Ligand Microenvironment of Atomically Dispersed CrN4 by Axial Ligand Sulfur for Enhanced Oxygen Reduction Reaction in Alkaline and Acidic Medium.

Because of the instability and Fenton reactivity of non-precious metal nitrogen-carbon based catalyst when processing the oxygen reduction reaction (ORR), seeking for electrocatalysts with highly efficient performance becomes very highly desired to speed up the commercialization of fuel cell. Herein, chromium (Cr)-N4  electrocatalyst containing extraterrestrial S formed axial S1 -Cr1 N4  bonds (S1 Cr1 N4 C) is achieved via an assembly polymerization and confined pyrolysis strategy. Benefiting from the adjusting  coordination configuration and electronic structure of the metal center through axial coordination, S1 Cr1 N4 C exhibits enhanced the intrinsic activity (half-wave potential (E1/2 ) is 0.90 V versus reversable hydrogen electrode, RHE) compared with that of CrN4 C and Pt/C catalysts. More notably, the catalyst is almost inert in catalyzing the Fenton reaction, and thus shows the high stability. Density functional theory (DFT) results further reveal that the existence of axial S atoms in S1 Cr1 N4 C moiety has the better ORR activity than Cr1 N4 C moieties. The axial S ligand in S1 Cr1 N4 C moiety can break the electron localization around the planar Cr1 N4  active center, which facilitated the rate-limiting reductive release of OH* and accelerated overall ORR process. The present work opens up a new avenue to modulate the axial ligand type of the single-atoms (SAs) active center to enhance intrinsic SAs performances.

Preparation of Expanded Graphite and Graphite Nanosheets for Improving Electrical Conductivity of Polyester Coating Films.

Expanded graphite and graphite nanosheets were facilely prepared by the thermal expansion of expandable graphite at 800 °C and sand milling of expanded graphite in water, respectively. When the expandable graphite precursor was prepared by the oxidation and intercalation of natural graphite (5 g) using KMnO4 (6 g) as an oxidant in a concentrated sulfuric acid solution (120 mL) at room temperature (25 °C) for 8 h, the expanded graphite with a maximum volumetric rate of 317 mL g-1 was prepared after the thermal expansion of the expandable graphite precursor at 800 °C for 60 s. The oxidation extent of natural graphite with KMnO4 is crucial for the preparation of expanded graphite. The thicknesses of graphite nanosheets decreased from 8.9 to 3.2 nm when the sand milling time of the expanded graphite in deionized water was prolonged from 6 to 24 h. The prolonging of the sand milling time not only decreased the layer number of the graphite nanosheet but also increased the d002 spacing due to the shocking and shearing forces. The addition of the expanded graphite powder and graphite nanosheets in a polyester paint efficiently improved the electrical conductivity of the resultant polyester coating films.

Regulating Fe-spin state by atomically dispersed Mn-N in Fe-N-C catalysts with high oxygen reduction activity.

As low-cost electrocatalysts for oxygen reduction reaction applied to fuel cells and metal-air batteries, atomic-dispersed transition metal-nitrogen-carbon materials are emerging, but the genuine mechanism thereof is still arguable. Herein, by rational design and synthesis of dual-metal atomically dispersed Fe,Mn/N-C catalyst as model object, we unravel that the O2 reduction preferentially takes place on FeIII in the FeN4 /C system with intermediate spin state which possesses one eg electron (t2g4eg1) readily penetrating the antibonding π-orbital of oxygen. Both magnetic measurements and theoretical calculation reveal that the adjacent atomically dispersed Mn-N moieties can effectively activate the FeIII sites by both spin-state transition and electronic modulation, rendering the excellent ORR performances of Fe,Mn/N-C in both alkaline and acidic media (halfwave positionals are 0.928 V in 0.1 M KOH, and 0.804 V in 0.1 M HClO4), and good durability, which outperforms and has almost the same activity of commercial Pt/C, respectively. In addition, it presents a superior power density of 160.8 mW cm-2 and long-term durability in reversible zinc-air batteries. The work brings new insight into the oxygen reduction reaction process on the metal-nitrogen-carbon active sites, undoubtedly leading the exploration towards high effective low-cost non-precious catalysts.

Preparation of Hollow SiO2@BiOI Nanocomposites and Their Photocatalytic Performance in Ammonia Nitrogen Degradation.

Hollow SiO2 microsphere-supported bismuth oxyiodide (BiOI) nanocomposites were prepared using Bi(NO3)3 · 5H2O and KI as the precursors of BiOI at 80 °C in an aqueous solution by the liquid chemical deposition method. The BiOI nanosheets with the thicknesses of 25-40 nm and the widths of 1-2 µm were deposited on the hollow SiO2 microsphere surfaces. There were interactions between the BiOI nanosheets and hollow SiO2 microspheres, which enlarged the ban gap of the BiOI nanosheet as compared with the pure BiOI. The band gap energy increased with the increase in SiO2/BiOI weight ratios. The hollow SiO2@BiOI nanocomposites showed high photocatalytic activity in ammonia nitrogen degradation when the photocatalytic degradation reaction was performed in aqueous solution under visible light irradiation. The degradation extent of ammonia nitrogen was upto 81% when the ammonia nitrogen degradation reaction was photocatalyzed by the hollow SiO2@BiOI(100:10) nanocomposite at an initial concentration of ammonia nitrogen of 10 mg L-1 and 25 °C for 4 h. The reaction kinetics of ammonia nitrogen degradation was well simulated by the first-order reaction model.

Preparation of Different-Sized Copper Nanoparticles by Reducing Copper Hydroxide and Application in Lithium-Based Grease.

Copper nanoparticles with different average particle sizes of 61-139 nm were facilely prepared by the wet chemical reduction of copper hydroxide without or with the use of organic modifier. Sodium dodecyl benzene sulfonate as an organic modifier effectively decreased the sizes of copper nanoparticles as compared to sodium citrate. The presence of polyvinylpyrrolidone favored the formation of the small-sized copper nanoparticle. The tribological properties of lithium-based complex grease were effectively improved by addition of copper nanoparticles (≤2 wt%). The improvement of grease tribological properties could be attributed to deposition of soft copper nanoparticles and tiny bearing action on rubbing surfaces.

Oxidation of 1,2-Propanediol to Carboxylic Acid Over Hydroxyapatite Nanorod-Supported Metallic Cu0 Nanoparticles.

Hydroxyapatite nanorod-supported metallic Cu0 nanoparticle catalysts (Cux/HAP) were prepared by the wetness chemical reduction method. The metallic Cu0 nanoparticles were well dispersed on the surfaces of the HAP nanorods. The alkaline HAP nanorods inhibited the crystal growth of the metallic Cu0 nanoparticles. The HAP nanorods also retarded the oxidation of the metallic Cu0 nanoparticles. The Cux/HAP catalyst exhibited a higher catalytic activity for the oxidation of 1,2-propanediol with gaseous oxygen to lactic, acetic, and formic acids with the total selectivity of 70.3% even at a lower reaction temperature of 140 °C. The total selectivity of lactic, acetic, and formic acids reached 93.1% at a mild reaction temperature of 180 °C. However, the sole monometallic Cu0 nanoparticles or HAP nanorods had no catalytic activity for the oxidation of 1,2-propanediol. The metallic Cu0 nanoparticles and alkaline HAP nanorods in the Cux/HAP catalyst synergistically catalyzed the oxidation of 1,2-propanediol to carboxylic acid.

Functional characterization of bimetallic CuPdx nanoparticles in hydrothermal conversion of glycerol to lactic acid.

The crude glycerol from biomass represents an abundant and inexpensive resource which can be utilized in producing food additives such as lactic acid. The direct transformation of bioderived glycerol to lactic acid under the catalysis of bimetallic CuPdx nanoparticles as well as monometallic Cu and Pd was investigated in hydrothermal conditions. The properties of fresh and spent bimetallic CuPdx nanoparticles were characterized with various physicochemical techniques viz. XRD, TEM, HRTEM, XPS, and AAS measurements. Catalytic activity of the prepared CuPdx nanoparticles is superior to the monometallic ones due to the alloying trend and synergistic effects. At optimal experimental conditions (100 ml of glycerol and NaOH solution, catalyst/glycerol mass ratio 2:100, 220°C, and 2.0 hr), the desired lactic acid selectivity catalyzed by the bimetallic CuPd2 , CuPd3 , and CuPd4 catalysts reached 95.3%, 91.4%, and 90.9%, respectively. PRACTICAL APPLICATIONS: Lactic acid, a widely used food additive, was traditionally produced by fermentation. However, due to the limitation such as time-consuming and complex separation procedure, interest has been attracted in developing an alternative approach toward efficient production of lactic acid. An attempt was made in present study to use the biodiesel byproduct, glycerol, and chemical conversion to high-valued lactic acid. Compared with traditional biological fermentation route, it was evidenced that glycerol selective transformation to lactic acid involves a new chemical reaction path for commodity lactic acid with a large availability and economic efficiency. This finding is significant for sustainable development of biodiesel industry and elimination of environmental issues arising from the abandoned crude glycerol.

Morphology-controlled synthesis of calcium titanate particles and adsorption kinetics, isotherms, and thermodynamics of Cd(II), Pb(II), and Cu(II) cations.

CaTiO3 particles with different particle sizes and morphologies were synthesized starting from CaCl2 and titanium (IV) isopropoxide with or without the use of organic modifier by the hydrothermal synthesis method. Without the use of organic modifier, nanosized CaTiO3 particulates were mainly formed at the hydrothermal temperatures of 120 °C and 140 °C whereas CaTiO3 cuboids were predominantly formed at 180 °C. The utility of polyethylene glycol as an organic modifier favored the formation of small-sized CaTiO3 nanoparticulates. However, cetyltrimethyl ammonium bromide and trisodium citrate induced the formation of CaTiO3 cuboids. The adsorption of heavy metallic Cd(II), Pb(II), and Cu(II) cations on CaTiO3 powders was well illustrated by the pseudo-second-order adsorption kinetics. The Langmuir adsorption isotherm with the correlation coefficients (R2) of 0.9946-0.9967 well fitted their adsorption at equilibrium. The adsorption processes were spontaneous and endothermic. The CaTiO3 powders synthesized by the hydrothermal method had higher adsorption capacities for Cd(II) (82.6 mg g-1) and Pb(II) (261.8 mg g-1) cations than the porous CaTiO3 powders synthesized by the solid-state calcination method reported in literatures. The as-synthesized CaTiO3 powders by the hydrothermal method could have potential application in the removal of heavy metallic cations from waste water.

Hydrogenation of 1-Nitroanthraquinone to 1-Aminoanthraquinone Catalyzed by Bimetallic CuPtx Nanoparticles.

Bimetallic CuPtx nanoparticles were prepared in ethanol solution by the wet chemical reduction method using Cu(NO3)2 and H2PtCl6 as starting materials, hydrazine hydrate as a reductant, and polyvinyl pyrrolidone as an organic modifier. The average particle sizes of Cu and Pt nanoparticles were 60 nm and 3 nm, respectively. The small-sized Pt nanoparticles were evenly anchored at the surfaces of large-sized Cu nanoparticles, forming Cu@Pt core-shell structured nanocomposites. In the bimetallic CuPtx nanoparticles, electron was transferred from platinum to copper species, which increased the selectivity of 1-aminoanthraquinone by suppressing the high hydrogenation activity of metallic platinum. The CuPt0.1 bimetallic nanoparticles exhibited higher catalytic activity for the hydrogenation of 1-nitroanthraquinone to 1-aminoanthraquinone than both monometallic Cu and Pt nanoparticles. Over the CuPt0.1 catalyst, the selectivity of 1-aminoanthraquinone was 99.3% at the 1-nitroanthraquinone conversion of 98.9%.

Improvement of the Tribological Properties of a Lithium-Based Grease by Addition of Graphene.

Graphene with layer number less than seven, prepared by a mechanical exfoliation method, was used as a friction-reducing additive to a lithium-based grease. The graphene was characterized via AFM, TEM, and Raman spectroscopy. The as-prepared graphene had few defects according to the characterization analysis and appeared to be composed primarily of sheets averaging 1-4 atomic layers. When the graphene was added to a lithium-based grease, the lubrication and antiwear properties of the grease were improved, as quantified by friction coefficient and wear scar measurements. The weld point of the lithium-based grease increased proportionally with graphene loading. At the maximum graphene loading tested (2 wt%), the weld point was 1.6 times that of the pure lithium-based grease. Hence the mechanical properties of the graphene sheets played an important role in improving the tribological properties of the grease.

Bioinspired Synthesis of Au Nanostructures Templated from Amyloid ß Peptide Assembly with Enhanced Catalytic Activity.

Peptides have been regarded as useful biomolecule templates to control the synthesis of various inorganic nanomaterials in mild conditions. Inspired by this, the easily self-assembled amyloid ß (Aß) peptide was developed as an alternative template to prepare Au nanostructures for the enhanced catalytic activity, for instance, the reduction of 4-nitrophenol. The presence of Aß peptide assemblies with different structures could direct the nucleation of Au to form different Au nanostructures. Using the Aß25-35 monomers, nanoribbons, and nanofibrils prepared by the self-assembly in phosphate buffered (PB) solution at 0, 3, and 12 h, respectively, as templates could controllably prepare Au nanospheres, nanoribbons, and nanofibers, while the Aß25-35 monomers prepared by the self-assembly in water at 0 h could direct the synthesis of Au nanoflowers. The Aß25-35-templated Au nanostructures had different catalytic activities due to the size and structure effects, which however are significantly enhanced as compared with the template-free Au nanoparticles.

Catalytic Conversion of Glycerol to Lactic Acid Over Hydroxyapatite-Supported Metallic Ni0 Nanoparticles.

Catalytic conversion of low-priced biomass glycerol to value-added lactic acid is an alternative route to the conventional fermentation process using sugar as the starting material. Nanosized hydroxyapatite-supported metallic Ni0 nanoparticles (Nix/HAP) prepared by the wetness chemical reduction method effectively catalyzed the conversion of high-concentrated glycerol (1.5-3 mol L-1) to lactic acid in a NaOH aqueous solution. The Nix/HAP catalysts exhibited higher catalytic activity for glycerol conversion to lactic acid than the sole metallic Ni0 nanoparticles. When the reaction was carried out over the Ni0.2/HAP catalyst with the initial glycerol and NaOH concentrations of 2.0 and 2.2 mol L-1 at 200 °C for 2 h, the selectivity of lactic acid reached 94.7% at the glycerol conversion of 92.1%.

Selective Oxidation of 1,2-Propanediol to Carboxylic Acids Catalyzed by Copper Nanoparticles.

Copper nanoparticles with different particle sizes were prepared by a wet chemical reduction method in the presence of organic modifiers, such as citric acid (CA), hexadecyl trimethyl ammonium bromide, Tween-80 (Tween), and polyethylene glycol 6000. Selective oxidation of sustainable 1,2-propanediol with O2 to high-valued lactic, formic, and acetic acids catalyzed by the copper nanoparticles in an alkaline medium was investigated. The small-sized CuCA nanoparticles with the average particle size of 15.2 nm favored the formation of acetic and formic acids while the CuTween nanoparticles with the average particle size of 26.9 nm were beneficial to the formation of lactic acid. The size effect of copper nanoparticles on the catalytic oxidation of 1,2-propanediol to the carboxylic acids was obvious.

Direct reaction between silicon and methanol over Cu-based catalysts: investigation of active species and regeneration of CuCl catalyst.

When a CuCl/Si mixture was pretreated at 200-240 °C in a N2 atmosphere, trimethoxysilane was predominantly formed in the direct reaction of silicon with methanol. When the pretreatment temperatures were raised to 260-340 °C, tetramethoxysilane was favorably formed. The Cu x Si y Cl z species catalyzed the reaction between silicon and methanol to trimethoxysilane. Chlorination of the spent CuCl/Si mixture promoted the reaction between silicon and methanol to form both trimethoxysilane and tetramethoxysilane due to the recovery of the CuCl phase and the exposure of the metallic Cu0 phase. When Cu2O, CuO, and Cu0 were used as the catalysts, tetramethoxysilane was formed as the main product.

Conversion of Glycerol to Lactic Acid Catalyzed by Different-Sized Cu2O Nanoparticles in NaOH Aqueous Solution.

Different-sized Cu2O nanoparticles with the average particle sizes ranging from 115 to 423 nm were prepared starting from CuSO4 using ascorbic acid as the reductant at room temperature. When Cu2O nanoparticles were used as the catalysts for hydrothermal conversion of glycerol at 230 °C in a NaOH aqueous solution, Cu2O nanoparticles effectively catalyzed the hydrothermal conversion of glycerol to lactic acid as compared to the conventional hydrothermal conversion of glycerol in a "pure" NaOH aqueous solution. Small-sized Cu2O nanoparticles showed higher catalytic activity than the large-sized ones. In a wide glycerol concentration range of 1­2.5 mol/L and a low mole ratio of Cu2O nanoparticle to glycerol of 2.5:100, the glycerol conversion and lactic acid selectivity were more than 86.2% and 87.2%, respectively, after reacting at 230 °C for 2 h.

Catalytic Conversion of Glycerol to Lactic Acid Over Metallic Copper Nanoparticles and Reaction Kinetics.

Different-sized metallic Cu° nanoparticles were prepared by the wet chemical reduction method with organic modifiers. The small-sized Cu° nanoparticles (Cu(PEG)) prepared by using polyethylene glycol as the organic modifier exhibited high catalytic activity for the hydrothermal conversion of glycerol to lactic acid. When the reaction was carried out with the initial glycerol and NaOH concentrations of 1.0 and 1.1 mol L⁻¹ at 230 °C for 4 h, the lactic acid selectivity reached 91.9% at the glycerol conversion of 98.0%. Over CuPEG (36.9 nm) and Cublank (118.3 nm) catalysts, the reaction activation energies were 76.3 and 86.5 kJ mol⁻¹, respectively.

Fluoride Release from Hollow Silica Microsphere-Containing Dental Restorative Acrylate Resin.

Hollow silica microspheres with mesoporous shells were prepared by the sacrificial template method. Hollow silica microsphere-containing acrylate resin-based dental restoration materials were prepared by using hollow silica microspheres as NaF reservoirs. Fluoride release performances from naked hollow silica microspheres, acrylate resin, and hollow silica microsphere-containing acrylate resin-based dental restorative materials in an artificial saliva were investigated. The results showed that hollow silica microsphere-containing acrylate resin-based dental restorative materials had higher cumulative fluoride release quantities and sustained fluoride release rates than traditional acrylate resin-based dental restorative materials. Fluoride release could be tuned by changing the mesoporous shell thickness of hollow silica microsphere.

Synthesis of different sized and porous hydroxyapatite nanorods without organic modifiers and their 5-fluorouracil release performance.

Porous biocompatible hydroxyapatite (HAP) nanorods of various sizes were synthesized by the combination of chemical precipitation and hydrothermal method without the use of organic modifiers. The HAP nanorod samples were characterized by powder X-ray diffraction, transmission electron microscopy, and N2 adsorption/desorption techniques. HAP nanorods with average diameters and average lengths ranging from 8.5 to 26.6 nm and from 23.1 to 49.7 nm, respectively, could be controllably synthesized via these methods. Low autoclaving temperature and high pH value favored the formation of relatively small HAP nanorods. The TEM images showed that the nanorods possessed porous structures with average pore diameters ranging from 1.6 to 2.7 nm. These HAP nanoparticles effectively prolonged the release time of 5-fluorouracil up to 24h. The as-synthesized HAP nanorods displayed no cytotoxicity to bone marrow stem cells at low HAP concentration, indicating that these nanorod materials could serve as potential carriers for novel drug release systems.

Selective Chlorination of Toluene to p-Chlorotoluene Catalyzed by Nanosized Zeolite K-L Catalysts.

Nanosized zeolite K-L catalysts were synthesized by the hydrothermal method starting from silica sol and potassium aluminate. The crystallinities of the zeolite K-L catalysts increased with increasing the SiO2/Al2O3 mole ratio of reaction solution and prolonging the autoclaving time. Nanosized and well-dispersed zeolite K-L catalysts were synthesized when the SiO2/Al2O3 mole ratio was more than 26:1. Well-crystallized and nanosized zeolite K-L catalysts showed high catalytic activity for the chlorination of toluene to p-chlorotoluene. When the nanosized zeolite K-L catalyst was synthesized with the SiO2/Al2O3 mole ratio of 31:1 at the autoclaving temperature of 150 °C for 96 h, the selectivities of p-chlorotoluene and o-chlorotoluene were 76.2% and 20.0%, respectively, at the complete conversion of toluene.