Dimethyl disulphide residue analysis and degradation kinetics determination in soil using gas chromatography–mass spectrometry

Dimethyl disulphide (DMDS) is a volatile sulphur compound and is used as a new type of soil fumigant. The objective of this study was to develop an effective method to extract and analyse DMDS residue in soil, then determine the degradation kinetics of DMDS in soil using the above method. The results showed that DMDS extraction from soil by ethyl acetate under static conditions for 60 min gave the best recovery. The extracted DMDS was analysed by gas chromatography–mass spectrometry (GC-MS), and the limit of quantification of DMDS in the soil was 5 μg/kg. The average recoveries of the DMDS at five different concentrations were in the range of 65.4–120.1% with all intra- and inter-day relative standard deviation less than 19.1 and 14.8, respectively. The degradation rates of DMDS in different soils were significantly different and were strongly influenced by the soil pH. The results in the present study will be useful for DMDS environmental behaviour study in future.     

Green Electrospun Silk Fibroin Nanofibers Loaded with Cationic Ethosomes for Transdermal Drug Delivery

Transdermal drug delivery system(TDDS) facilitates the controlled release of active ingredients penetrating through the skin, avoiding the liver first pass effect. Electrospinning is a simple process to fabricate ultrafine fibers with a higher specific surface area, making them excellent candidates for drug delivery. In current work, a novel silk fibroin(SF) nanofiber loaded with cationic ethosomes(CEs) was prepared via green electrospinning. The data of Fourier transform infrared spectroscopy(FTIR) and laser scanning confocal microscopy(LSCM) confirmed the existence of CEs in the SF nanofibers. The morphology of the nanofibers was not significantly affected by the incorporation of CEs as shown by scanning electron microscopy(SEM) images. The CEs-loaded SF nanofibrous patch (CEs-SFnP) showed good cytocompatibility as proved by both cell counting Kit-8(CCK-8) assay and SEM. Using doxorubicin hydrochloride(Dox) as a model drug, the transdermal performance of CEs-SFnP was evaluated through Franz diffusion cell against mouse skin. The results indicated that CEs-SFnP can effectively deliver drug into the skin, with a much higher permeation rate than the normal nanofibers without CEs. The as-spun CEs-SFnP in this study could find promising applications in TDDS.     

VPI-7分子筛的合成及生物学性能

采用水热法,通过调变反应溶胶的量合成了不同尺寸的不规则圆片状多孔锌硅分子筛VPI-7,并研究了其生物学性能.扫描电子显微镜观测结果表明,制备的样本由VPI-7条状晶体聚集成微球,并进一步相互交联形成微米级孔隙,其形貌可以促进钙磷化合物在样品表面的沉积,同时可以负载并缓释蛋白.细胞学检测结果表明,VPI-7分子筛有利于细胞黏附增殖,具有良好的生物相容性.     

Understanding the Solid Solution–Aqueous Solution Equilibria in the KCl + RbCl + H<Subscript>2</Subscript>O System from Experiments,Atomistic Simulation and Thermodynamic Modeling

The solid solution–aqueous solution (SSAS) equilibria in the KCl + RbCl + H₂O system were redetermined at 298.15 K. The experimental data for (K,Rb)Cl were consistent with the formation of a continuous solid solution without miscibility gaps. The Schreinemakers’ wet residues method and an XRD quantitative analysis technique based on the Vegard approach were applied to determine the chemical composition of the solid solution phase of (K,Rb)Cl. The compositions of (K,Rb)Cl derived from the Vegard approach are in accordance with those from the wet residues method. The thermodynamic properties of mixing of the (K,Rb)Cl solid solution were theoretically predicted using atomistic simulations. From these simulations, a regular solution behavior is recognized that is consistent with the knowledge of the thermodynamic properties of mixing of (K,Rb)Cl obtained from SSAS equilibrium studies, but the predicted regular solution model parameter A ₀ is significantly larger than that regressed from the SSAS equilibrium data. Finally, a thermodynamic model was developed for representing the SSAS equilibria and element partitioning in the KCl + RbCl + H₂O system as a function of temperature that can be used for predicting the SSAS equilibria in the studied system over the temperature range 273.15–373.15 K.     

Phase diagram of the NaCl–MgCl<Subscript>2</Subscript>–H<Subscript>2</Subscript>O system at 25–75°C and its application for MgCl<Subscript>2</Subscript> · 6H<Subscript>2</Subscript>O purification

The co-saturation line for the solid phases NaCl_(s) and MgCl₂ · 6H₂O_(s) in aqueous solution has been measured by a phase equilibrium at various temperatures. It was found that the Y _b (Y _b = w(NaCl)/(w(NaCl) + w(MgCl₂))) value of the co-saturation line increase with increasing temperature. A new recrystallization approach has been suggested for the purification of MgCl₂ · 6H₂O_(s) containing quite amount of impurity NaCl, i.e., dissolving the crude sample at low temperatures, followed by evaporating and phase separating at high temperatures. Applying the proposed approach a crude MgCl₂ · 6H₂O_(s) sample can be purified to the level of Y _b = 0.17% by only one crystallization process.     

有机化学知识在高分子材料合成创新实验中的运用——分享几个实例

针对目前教学中存在的理论课程之间、实验课程与理论课程之间关联不够紧密等问题,探索了通过"知识关联"将有机化学基本知识运用到高分子材料合成创新实验中的教学思路。以新试剂合成及应用、荧光聚酯合成、聚酰胺合成、聚酯水解等为例,介绍了如何将有机化学新理论、新方法、新试剂应用于本科高分子化学和高分子材料实验教学,以及如何将有机化学的理论知识和实验手段应用于高分子材料合成教学中。实践表明:通过"知识关联",将有机化学基础理论知识和实验技能应用于高分子合成实验中可以提高学生对所学知识的理解和运用能力,增强学生的实验探索兴趣,有效改进了高分子材料合成实验教学的课堂气氛。     

“高分子材料合成创新实验”线上教学探索与实践

Based on the platform of "QQ share screen + video live broadcast", through the combination of "online theory teaching", "development of home alternative experiment", "game type" experimental operation and "virtual simulation experiment", we carried out the online teaching of polymer material synthesis innovation laboratories, integrating "theory + practice" and "virtual + reality", which is also a good opportunity for labor education. These explorations and practices are expected to provide some references for online teaching of chemical laboratory courses during the COVID-19 epidemic.     

Axially Chiral TADF-Active Enantiomers Designed for Efficient Blue Circularly Polarized Electroluminescence

The use of a chiral, emitting skeleton for axially chiral enantiomers showing activity in thermally activated delayed fluorescence (TADF) with circularly polarized electroluminescence (CPEL) is proposed. A pair of chiral stable enantiomers, (−)-(S)-Cz-Ax-CN and (+)-(R)-Cz-Ax-CN, was designed and synthesized. The enantiomers, both exhibiting intramolecular π-conjugated charge transfer (CT) and spatial CT, show TADF activities with a small singlet–triplet energy difference (ΔE_ST) of 0.029 eV and mirror-image circularly polarized luminescence (CPL) activities with large g_lum values. Notably, CP-OLEDs based on the enantiomers feature blue electroluminescence centered at 468 nm with external quantum efficiencies (EQEs) of 12.5 and 12.7 %, and also show intense CPEL with g_EL values of −1.2×10⁻² and +1.4×10⁻², respectively. These are the first CP-OLEDs based on TADF-active enantiomers with efficient blue CPEL.     

α-Decay near the shell closure from ground and isomeric states

The modified two-potential approach (MTPA) is employed to study the exotic α-decay near the closed shells Z=82 and N=82, 126 within a deformed version of the cluster model. We perform systematic calculations on favored α-decay half-lives from both the ground states (g.s.) and the isomeric states (i.s.) by using the microscopic double-folding potential. The obtained α-decay half-lives are found to be in good agreement with the experimental data. This indicates that four types of α transitions among ground states and isomeric states (g.s. → g.s., g.s. → i.s., i.s. → g.s., i.s. → i.s.) are well described in a unified model. In addition, the unfavored α transitions in the Bi isotopes are investigated to pursue a further understanding of α-decay properties.     

Application of a low impedance contactless conductometric detector for the determination of inorganic cations in capillary monolithic column chromatography

Poly(glycidyl methacrylate) cation exchange monolithic column was prepared in fused-silica capillaries of 320 μm i.d. by thermally initiated radical polymerization and utilized in capillary ion chromatography. With 15 mM methanesulfonic acid as the mobile phase, the separations of a mixture of inorganic cations (Li⁺, Na⁺, NH₄⁺, K⁺) was tested by using a capacitively coupled contactless conductivity detector (C⁴D) and a low impedance C⁴D (LIC⁴D). The LIC⁴D is the series combination of a C⁴D and a quartz crystal resonator. At the resonant frequency of the series combination, the capacitor impedance from capillary wall was offset by the inductance impedance from the quartz crystal resonator. A minimum impedance was obtained in the impedance-frequency curve of the combination. The responses of the C⁴D and LIC⁴D were analyzed based on an equivalent circuit model. It was shown that the sensitivity of the C⁴D to the change in analyte concentration is rather poor due to the high ratio of the impedance from the capillary wall capacitor to the solution impedance. The LIC⁴D has the similar sensitivity as a contact conductivity detector but a much smaller cell volume. The on-column detection model was realized by LiC⁴D without preparation of optical detection window in monolithic column.