Effects of Ultra-sonification Assisting Polyethylene Glycol Pre-treatment on the Crystallinity and Accessibility of Cellulose Fiber

In order to prepare the advanced cellulosic super-absorbent polymer with high grafting level, we tried the novel ultrasound wave assisting polyethylene glycol (PEG) pre-treatment method to decrease the crystallinity and increase the accessibility of cellulose fiber. The effects of ultrasonification assisting PEG method on the crystallinity and swelling capacity of cellulose fiber were investigated. To optimize the experimental condition, the Taguchi method was employed in the treatment process. The influence factors such as ultrasonic wave power, ultrasonic wave time and PEG molecular weight relative to the crystallinity of cellulose fiber were studied systematically. The degree of crystallinity of cellulose fiber was measured by wide-angle X-ray diffraction (WAXD). The morphology of cellulose fiber was observed by environment scanning electron microscopy (ESEM). The effects of pre-treatment variables on the water absorbency and water retention values of cellulose fiber were also investigated. The research results revealed that, under the optimal experimental condition (ultrasonic powder, 500 W; ultrasonic time, 150 s; PEG molecular weight, 600 g/mol), the crystallinity of cellulose fiber decreased from 72.16 to 42.95%. Accordingly, the absorbency of cellulose fiber increased from 1.436 to 2.063 g/g, and the water retention value increased from 47.21 to 113.4%. However, the morphology of cellulose fiber did not change thoroughly compared with the original cellulose fiber. It can be hypothesized that the original inter- and intra-macromolecular hydrogen bonds in cellulose network were weakened, resulting from the high level dispersion of PEG within cellulose network without breaking the surface morphology of fiber.     

Study on the BODIPY-triazine-based tripod fluorescent systems: various structures from similar procedure

We report a small library of fluorophore-triazine tripod fluorescent system that can accommodate a combination of three different functional groups, such as fluorophore (BODIPY), ligand (or ligands) and auxiliary group. Syntheses, photophysical properties as well as binding properties towards metal ions of these BODIPY-triazine derivatives are described.     

Highly sensitive detection of mercury (II) in aqueous media by tetraphenylporphyrin with a metal ion receptor

We provide a highly sensitive and selective assay to detect Hg²⁺ in aqueous solutions using a novel β-functionalised porphyrin-based chemosensor 5 at room temperature. The binding properties of the chemosensor 5 for cations were examined by UV–vis spectroscopy and ¹H NMR. The results indicate that a 1:1 stoichiometric complex is formed between chemosensor 5 and mercury (II) ion. The recognition mechanism between chemosensor 5 and metal ion was discussed based on their absorbance changes and the chemical shift changes when they interact with each other. Control experiments revealed that chemosensor 5 has a selective response to mercury (II) ion compared with other metal ions.     

Determination of 20(S)-protopanaxadiol in rat plasma by LC-MS/MS and its application to the pharmacokinetic study: A comparative study of its solution and two oral formulations

A high-performance liquid chromatography — tandem mass spectrometry method was used in a comparative pharmacokinetic study on 20(S)-protopanaxadiol in its solution, pharmacosomes and hydroxy-propyl-β-cyclodextrin inclusion compound. The calibration linearity range was 2.5–5000 ng/mL and the limit of quantification was 2.5 ng/mL. The intra- and inter-assay coefficients of variation were less than 7% and the recoveries were 67.4, 63.3 and 69.6% at 5, 250 and 4500 ng/mL. In contrast to 20(S)-protopanaxadiol solution, its pharmacosomes and hydroxypropyl-β-cyclodextrin inclusion compound improved the oral bioavailability to different extent and meanwhile were much safer in clinical use.     

Hydrothermal synthesis and structural characterization of a one-dimensional coordination polymer [Zn(Pydc)(Dppz)] n (H2Pydc = 2,6-pyridinedicarboxylic acid, Dppz = dipyrido[3,2-a:2′,3′-c]phenazine)

A new metal-organic coordination polymer [Zn(Pydc)(Dppz)] _n (I) (H₂Pydc = 2,6-pyridinedicarboxylic acid, Dppz = dipyrido[3,2-a:2′,3′-c]phenazine) was hydrothermally synthesized and characterized by elemental analysis, IR and X-ray single-crystal diffraction. The X-ray diffraction analysis reveals that I crystallizes in the monoclinic system, space group P2₁/c. The Pydc^2? ligands adopt O,N,O′-tridentate chelating and monodentate bridging coordination mode to link two adjacent Zn2+ ions to form a one-dimensional (1D) zigzag chain. The adjacent chains are further linked through hydrogen bonds and π-π stacking interactions, forming a three-dimensional (3D) supramolecular framework. The unit cell parameters for I: a = 7.332(3) Å, b = 36.023(9) Å, c = 7.8838(13) Å, β = 105.65(3)^○, V = 2005.1(10) ų, Z = 4.     

Solvothermal synthesis and structural characterization of a new one-dimensional metal-organic framework [Co(Atibdc)(Dpa)] n (H2Tibdc = 5-amino-2,4,6-triiodoisophthalic acid, Dpa = 2,2′-dipyridylamine)

The title cobalt(II) coordination polymer, [Co(Atibdc)(Dpa)] _n (I) (H₂Atibdc = 5-amino-2,4,6-triiodoisophthalic acid, Dpa = 2,2′-dipyridylanine), has been synthesized under solvothermal conditions and characterized by elemental analysis, IR, and X-ray crystallography structural analysis. Complex I exhibits a one-dimensional chain structure in which 5-amino-2,4,6-triiodoisophthalate as a bridging ligand interconnects adjacent two Co(II) centers to form a helical chain structure. The asymmetric unit includes one Co(II) center, one atibdc ligand, and one Dpa ligand. Each Co(II) center is five-coordinated and surrounded by two nitrogen atoms and three oxygen atoms from one Dpa ligand and two individual Atibdc ligands, leading to distorted trigonal bipyramid geometry. Adjacent chains are further linked through hydrogen bonds, C-H-π and π-π stacking interactions to form a three-dimensional supramolecular framework.     

Study on thermodynamic properties of glyphosate by oxygen-bomb calorimeter and DSC

The combustion enthalpy of glyphosate was determined by XRY-1C oxygen-bomb calorimeter at a constant volume. The standard mole combustion enthalpy and the standard mole formation enthalpy have been calculated to be ?1702.19 and ?1478.36 kJ mol^?1, respectively. For testing the reliability of instrument, glycine and naphthalene were used as reference materials by comparing the measured values with the literature values, the absolute error and relative error are 2.58 kJ mol^?1 and 0.26 % for glycine, respectively, and these of naphthalene are 4.08 kJ mol^?1 and 0.08 %, respectively. Moreover, the constant-pressure heat capacities c _p of glyphosate were measured by differential scanning calorimetry in the temperature range 303.15–365.15 K, and the relationship between c _p and temperature was established. These related studies can provide a thermodynamic basis for their further application.     

Effect of functionalized multiwall carbon nanotubes on the curing kinetics and reaction mechanism of bismaleimide–triazine

Functionalized multiwall carbon nanotubes (f-MWCNTs) with varying functionalization degrees were prepared by chemical methods. The effect of f-MWCNTs on the cure kinetics of bismaleimide–triazine (BT) resin was studied through nonisothermal differential scanning calorimetry (DSC) methods. The reaction activation energy (E _α ) was determined by Flynn–Wall–Ozawa method. The results show that f-MWCNTs have more acceleration ability than pristine MWCNTs, due to more groups on the surface of f-MWCNTs than that of pristine MWCNTs. The activation energy was decreased from a value of 91.3 kJ mol^?1 for the neat BT resin to 74.2 kJ mol^?1 at the small mass loading (1.0 %) of f7-MWCNTs. The effect of f-MWCNTs on the reaction mechanism has been investigated. It shows that the f-MWCNTs accelerate the cure reaction of BT resin by providing the Lewis acids (H⁺) to make the “Diels–Alder” reaction and “ENE” reaction of BT resins more efficient. These findings offer useful insights into the cure technology of thermosetting resin filled with f-MWCNTs, without negative effect on the cure reaction.     

Excellent electrochemical performance of nitrogen-enriched hierarchical porous carbon electrodes prepared using nano-CaCO3 as template

Recently, tremendous research efforts have been concentrated on developing high-performance electrode materials to meet the ever-increasing energy and power demands in supercapacitors. Herein, we presented a high-capacity supercapacitor material based on nitrogen-enriched hierarchical porous carbons (NHPCs) synthesized by the carbonization of melamine formaldehyde resins using eco-friendly and inexpensive nano-CaCO₃ as template. The effects of carbonization temperature and template content on the porous structure and electrochemical characteristics were compared and discussed in detail. The prepared NHPCs possessed large surface area up to 834 m² g^?1 and high nitrogen content up to 20.94 wt %. As electrode material for supercapacitors, NHPCs exhibited superior electrochemical performances with high specific capacitance (190 F g^?1 at 20 A g^?1), outstanding rate capability (80 %), and excellent cycling stability (over 2,000 cycles at 5 A g^?1) in 1 M sulfuric acid media. The excellent electrochemical performances are due to the synergic effects of unique hierarchical porous microstructure, abundant nitrogen and oxygen functionalities, as well as high degree of graphitization framework.