Carbon dots embedded nanofiber films: Large-scale fabrication and enhanced mechanical properties

Valuable application prospects and large-scale production technologies are powerful driving forces for the development of materials science. Carbon dots(CDs) are a kind of promising carbon-based fluorescent nanomaterials, which possess wide application prospects based and even beyond the fluorescence properties. Herein, we report the fast and high-yield synthesis of CDs and the large-scale preparation of fluorescent nanofiber films with enhanced mechanical properties. CDs were prepared from magn...     

Discovery and Characterization of a Novel Method for Effective Improvement of Cyclodextrin Yield and Product Specificity

Cyclodextrins(CDs) are widely used in food,phamiaceuticals, drug delivery, and chemical industries and in agriculture and environmental engineering. To improve the yield and selectivity of CDs, this work presented a tacile, scalable and efficient enzymatic synthesis of β-CD from starch using β-cyclodextrin glycosyltransferase (CGTase, EC2.4.1.19) from Bacillus cereus. First, we found that the pretreatment of starch dramatically influenced CDs yield that was related to the structure and molecular weight of the substrate starch. Second, alcohol solvents influenced the yield and product selectivity of CDs;tertiary alcohols enhanced CDs yield(from 54.95% to 68.21%) and secondary alcohols increased the product selectivity(β-CD/γ-CD changed from 6.25 to 8.05). Fluorescence quenching analysis showed that the binding constants and entropy of the solvents influenced the yield and product selectivity, respectively. In conclusion, the results demonstrate that this study provides a promising method for the industrial production of β-CD.     

HPLC Determination of Neurotoxin β-N-oxalyl-L-α,β -diaminopropionic acid and Its α -Isomer in Lathyrus sativus by Precolumn Derivatization with 1-Fluoro-2,4-dinitrobenzene

A rapid and simple method is presented for determining β-N-oxalyl-α,β-diaminopropionic acid (β-ODAP) and its much less toxic α-isomer (α-ODAP) in Lathyrus sativus. Seed and foliage extracts of Lathyrus sativus were treated with 1-fluoro-2,4-dinitrobenzene (FDNB) and a reversed-phase high-performance liquid chromatographic method for the separation of the derivatives in the pmol range is reported.     

EFFECTS OF K_2O AND MnO PROMOTERS ON THE PRODUCTION OF LIGHT ALKENES VIA SYNGAS OVER Fe/SILICALITE-2 CATALYST IL REDUCIBILITY OF K-Fe-MnO/SILICALITE-2 CATALYST

K_2O and MnO are two kinds of necessary promoters to theselective production of light alkenes from CO hydrogenation over silicalite-2(Si-2) zeolite supported Fe catalyst. The addition of both K_2O and MnOpromoters into Fe/Si-2 catalyst leads to a remarkable increase in the COconversion and the selectivity to light oletins. Silicalite-2 zeolite as Fe-MnOcatalyst support can suppress the formation of α-Fe_2MnO_3 or/andα-Fe_(2-y)Mn_yO_3 as Well as α-Fe_2O_3 and/or α-Mn_2O_3, being favorable for(?)ncreasing the dispersion of active metal component. So MnO can promotethe reduction of Fe~(3-) and enhance the capacity of CO adsorption, which canimprove the activity of the activity of the catalyst for CO hydrogenation. While K_2Opromoter is unfavorable for reduction of Fe~(3-) to some degree with formation of Fe~(2-) as a new species after reduction. However, K_2O promoter can enhance the capacity and strength of CO adsorption greatly.So K_2O can alsoimprove the activity of catalyst for CO hydrogenation.     

Synthesis of porous hematite nanorods loaded with CuO nanocrystals as catalysts for CO oxidation

Porous hematite (α-Fe2O3) nanorods with the diameter of 20-40 nm and the length of 80-300 nm were synthesized by a simple surfactant-assisted method in the presence of cetyltrimethylammonium bromide (CTAB).The α-Fe2O3 nanorods possess a mesostructure with a pore size distribution in the range of 5-12 nm and high surface area,exhibiting high catalytic activity for CO oxidation.CuO nanocrystals were loaded on the surface of porous α-Fe2O3 nanorods by a deposition-precipitation method,and the catalysts exhibited superior activity for catalytic oxidation of CO,as compared with commercial α-Fe2O3 powders supported CuO catalyst.The enhanced catalytic activity was attributed to the strong interaction between the CuO nanocrystals and the support of porous α-Fe2O3 nanorods.     

α-FACTOR-DIRECTED SYNTHESIS AND SECRETION OF β-SUBUNIT OF HUMAN CHORIOGONADOTROPIN (β-hCG)IN YEAST S. cerevisiae

A couple of sbuttle vectors (pYNA and pYNB), containing a sequence coding for the leader regionof the α-factor precursor (α-factor leader sequence) and the origin of 2μm circle, were constructed. ThecDNA for the β-hCG (145aa) was fused in phase to the 3'-end of the α-factor leader sequence andtransformed into the yeast Saccharomyces cercvisiae. The yeast cells carrying this hybrid gene synthesizedand secreted a protein with the immunoactivity of β-hCG in an amount of 45μg per liter of culture. Thepreliminary characterization of this protein is also reported in this paper.     

Carbon dots and polyurethane composite for photo-induced elimination of uranium under air atmosphere

Uranium is the main fuel of nuclear power and elimination uranium from nuclear wastewater is significant both in environmental protection and fuel recycle. Here we report for the first time the synthesis of carbon dots/polyurethane(CDs/PU) composite materials for the photoinduced elimination of uranium from water. Irradiated with visible light, CDs/PU could eliminate uranium efficiently with the generation of(UO₂)O₂·2H₂O as solid products in air. The further inve...     

Carbon dots/Bi_2WO_6 composite with compensatory photo-electronic effect for overall water photo-splitting at normal pressure

Overall water photo-splitting is a prospective ideal pathway to produce ultra-clean H_2 energy by semiconductors.However,the band structure of many semiconductors cannot satisfy the requirement of H_2 and O_2 production at the same time.Herein,we illustrate that carbon dots(CDs)/Bi_2 WO_6 photocatalyst with compensatory photo-electronic effect has enhanced activity for overall water photo-splitting without any sacrificial agent.In this complex photocatalytic system,the photo-potential provided by CDs makes the CDs/Bi_2 WO6(C-BWO) composite could satisfy the band structure conditions for overall water photo-splitting.The C-BWO composite(3 wt% CDs content) exhibits optimized hydrogen evolution(oxygen evolution) of 0.28 μmol/h(0.12 μmol/h) with an approximate 2:1(H_2:O_2) stoichiometry at normal pressure.We further employed the in-situ transient photovoltage(TPV) technique to study the photoelectron extraction and the interface charge transfer kinetics of this composite catalyst.     

A facile enantioselective synthesis of (+)-rolipram via C-H insertion process

Rolipram, (±)-4-(3-cyclopentyloxyl-4-methoxylphenyl)-2-pyrrolidinone,is known as a potent and selective inhibitor of phosphodiesterase type IV(PDE IV)1.In fact, although both enantiomers are active, the levorotatory isomer, for which several synthesis has been recently reported2, has proved to be the most active one. Hashimoto and Jung have repored rolipram,s synthesis via intramolecular C-H insertion reaction of α-methoxylcarbonyl-α-diazoacetamide and α-phenylsulfonyl-α-diazoacetamid…     

Carbon-coated manganese dioxide nanoparticles and their enhanced electrochemical properties for zinc-ion battery applications

In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnO_2nanoparticles(α-MnO_2@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO_2@C was prepared via a gel formation, using maleic acid(C_4H_4O_4) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnO_2 nanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO_2@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO_2@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnO_2 electrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.     

WAXD STUDY OF POLYMORPHOUS ISOTACTICPOLYPROPYLENE BY COMPUTER PEAK-RESOLUTION METHOD

Polymorphous i-PP containing a and βphases were studied by WAXD and computer peak-resolution method (CPRM). The asymmetric Gaussian-Cauchy functions (a-GC) were adoptedto fit the profiles of both amorphous and crystalline peaks. For the crystalline peaks, the fitting resultsof a-GC are better than the symmetric-GC; for the amorphous peaks, they are better than polynomialand exponential functions, etc. Using the retarded least-square procedure (RLSP) on microcom-puter the results of peak-resolution are rather satisfatory. For the polymorphous samples containingαand βphases, the relations between phase-state, crystallinity, crystalline size, the ratio of α,βrelativecontent and the crystallization temperature T_c were studied by CPRM. The ratio of α,βrelativecontents obtained by CPRM and Turner-Jones eq. have been carefully compared. There are manyimprovements in this work. A simple estimation method of WAXD peak areas, both for amorphousand crystalline peaki, is suggested.     

Study on Synthesis and Intercalation Behavior of Layered Zirconium Proline-N-methylphosphonate-phosphate

Zirconium proline-N-methylphosphonate-phosphate (α-ZPMPP) was prepared in the presence of HF for the first time. The α-ZPMPP sample is highly crystallized with interlayer distance of 1.52nm. The interlayer distance of complex of α-ZPMPP with n-butylamine (α-ZPMPP-BA) is in 0.45 nm larger than that of α-ZPMPP. The α-ZPMPP possesses different intercalation behavior of host-guest compound from α-ZP.     

TRIPLICATED α-GLOBIN GENE LOCI IN A CHINESE FAMILY

Utilizing restriction endonuclease mapping and blot bybridization, we have determined the arrangement of the α-globin genes in a Chinese family. The father and mother had no obvious α-thalassemia symptoms, but their twin daughters suffered from HbH disease. The gene analysis showed that the mother had three α-globin genes in one chromosome and no α-globin gene in the other (ααα/--), the father was a heterozygote of α-thal2 (αα/-α). Their twin daughters were double heterozygotes of α-thall and the rightward deletion genotype α-thal2 (--/-α)     

Oxidative Rearrangement via Oxycerication with Ce(IV) Salt

α-Arylpropanoic acids are pharmaceutically interesting compounds, some of them exhibit anti-flammatory and analgestic activities1. Even the enormous progress made in the synthesis of α-arylpropanoic acids by 1,2-aryl rearrangement of arylpropanone using thalium (III) nitrate1,2, silver (I) compounds,3,4 lead (IV) acetate5,6 and iodinate7 during the last decades. The route is, however, unsuitable for the preparation of pharmaceutical products (Naproxen, Ibuprofen and so on) because of the …     

PREPARATION AND CHARACTERIZATION OF INCLUSION COMPLEXES OF TWO-ARM LINEAR AND FOUR-ARM STAR-SHAPED POLY(ε-CAPROLACTONE)S WITH α-CYCLODEXTRIN

Both four-arm star-shaped poly(ε-caprolactone) (4sPCL) and two-arm linear PCL (2LPCL) were synthesized and their inclusion complexation with α-cyclodextrin (α-CD) were studied. The inclusion complexes (ICs) formed between the PCL polymers and α-CD were characterized by 1H-NMR, DSC, TGA, WAXD, and FT-IR, respectively. Both branch arm number and molecular weight of the PCL polymers have apparent effect on the stoichiometry (CL:CD, mol:mol) of these ICs. All these analytical results indicate that the branch arms of the PCL polymers are incorporated into the hydrophobicα-CD cavities and their original crystalline properties are completely suppressed. Moreover, the inclusion complexation between two-arm linear or four-arm star-shaped PCL polymers and α-CD not only enhances the thermal stability of the guest PCL polymers but also improves that of α-CD.     

Palladium(0)catalyzed reactions of propargylic carbonates and dialkyl cycloalkanone-α,α-dicarboxylates

Propargylic carbonates reacted with dialkyl cycloalkanone-α,α′-dicarboxylates under thecatalysis of Pd(0)complex to give bicyclic compounds in high yields.The two electron-withdrawinggroups at α and α′positions of cycloalkanone rings are essential for the annulation reaction.     

Effects of local matrix environment on the spectroscopic properties of ensemble to single-particle level carbon dots

Carbon dots(CDs), because of their unique properties, are being rapidly developed as important luminescent materials for imaging, sensing, and use in photonic devices. However, most of the reported fundamental properties of the CDs are results of investigations conducted in the solution state, which may be completely different from those conducted in the solid state. In this work, we study the luminescence properties, photostability, and the dynamics of CDs in different matrix environments, from...     

Cobalt oxide and carbon modified hematite nanorod arrays for improved photoelectrochemical water splitting

Given the proper band gap, low cost and good stability, hematite(α-Fe_2O_3) has been considered as a promising candidate for photoelectrochemical(PEC) water splitting, however suffers from the sluggish surface water oxidation reaction kinetics. In this study, a simple dip-coating process was used to modify the surface of α-Fe_2O_3 nanorod arrays with cobalt oxide(CoO_x) and carbon(C) for the improved PEC performance, with a photocurrent density at 1.6 V(vs. reversible hydrogen electrode, RHE) increased from 0.10 mA/cm~2 for the pristine α-Fe_2O_3 to 0.37 mA/cm~2 for the CoO_x/C modified α-Fe_2O_3 nanorods. As revealed by electrochemical analysis, thanks to the synergistic effect of CoO_x and C, the PEC enhancement could be attributed to the enhanced charge transfer ability, decreased surface charge recombination, and accelerated water oxidation reaction kinetics. This study serves as a good example for improving PEC water splitting performance via a simple method.     

Comparison of the Contributions of Tetrahydrofurfuryl Alcohol and PEG to α-Chymotrypsin Renaturation with High Performance Hydrophobic Interaction Chromatography

The contributions of tetrahydrofurfuryl alcohol(THFA) and polyethylene glyco(PEG) to the renature efficiency of α-chymotrypsin were investigated and compared with each other,The maximum increments of bioactivity recovery of α-Chy were found to be 25.1% for THFA,10.4% for PEG,respectively.The experimental results indicated that the denaturant solution containing THFA contributed more to the renaturation of α-Chy in high performance hydrophobic interaction chromatography(HPHIC) than that containing PEG,when the concentration of THFA was 3.2%,the bioactivity recovery of α-Chy is the highest.     

Cluster-Slabbing EHMO Study of Active-Site Model of Fe-Catalyst for Ammonia Synthesis

The 4-Fe/α-Fe(111) or (211)-surface cluster model of active sites of iron catalysts for ammonia synthesis and the two probable multinuclear coordination modes of dinitro-gen suggested previously were examined by means of improved cluster-slabbing EHMO calculations. The results are in favor of the suggested model of the active site and the corresponding modes of multinuclear coordination-activation of dinitrogen, and may be used rationally to explain the difference in catalytic activity of ammonia synthesis over the three crystal surfaces, (111), (211) and (100), of α-Fe.