Preparation of pH-Sensitive Polymers/Layered Double Hydroxide Hybrid Beads for Controlled Release of Insulin

The present work introduces new hybrid material based on the combination of layered double hydroxides (LDH) and a pH-sensitive polymer (PSP), alginate, a polysaccharide widely applied for encapsulating drugs to produce a LDH–polymer nanocomposite, able to act as an effective drug delivery system (DDS) in comparison to the Zn–Al LDH or the polymer alone. Insulin has been chosen as a model drug, being loaded in a Zn–Al LDH matrix. In vitro release profiles were established separately in both the presence and absence of glucose phosphate in pH 7. Drug release studies showed that the in the presence of glucose phosphate release rate increases.     

即时合成MgAl13-LDH处理高氟水的效果

高氟水在我国西北地区分布广泛,长期饮用高氟水易患全身性慢性疾病,甚至对人脑神经造成损害,使人丧失劳动能力。这不仅严重危害着当地人民的身体健康,也制约着当地的经济发展。层状双氢氧化物（LDH）具有优异的阴离子交换性能,在对高氟水的处理方面具有一定的优越性。通过以Al13即时合成的镁铝型LDH与以AlCl3即时合成的镁铝型LDH对高氟水进行处理进行对比,考察了各个影响因素以及反应条件对处理效率的影响。结果表明,该技术对含氟5 mg/L以下的高氟水地下水有良好的处理效率,在最佳反应条件下,出水可以达到世界卫生组织（WHO）所规定的饮用水卫生标准,降低高氟水给人体带来的危害。即时合成LDH较为适宜的反应条件为:溶液pH值为105,Mg2+浓度为48 mg/L,Al13浓度为006 mmol/L,Ca2+浓度为20 mg/L,即Mg2+/Ca2+为2∶〖KG-*2〗1,反应时间8 min,该条件下氟离子去除率可以达到70%左右。此时Mg2+和Al13水解较完全,综合去除效果最好,且生成固体中没有发现其他的物相。通过Mg/Al13/MgAl13-LDH的单独实验表明,相对于铝盐,即时合成LDH的去除效果更好。采用北大自来水为水样,在优化条件上,证明以Al13即时合成的镁铝型LDH比以AlCl3即时合成的镁铝型LDH对F-的去除率更优。该方法可以在水处理过程中即时合成LDH,既能达到处理高氟水的目的,又省去了LDH在实验室合成过程中的复杂且严格的条件控制、固液分离、干燥以及粉碎等步骤。采用絮凝性能更好的Al13为金属离子M3+即时合成MgAl-LDH,用以处理高氟水效果更好,为将LDH应用于实际水处理方面提供了参考。     

Fabrication of CdS/NiFe LDH heterostructure for improved photocatalytic hydrogen evolution from aqueous methanol solution

2D CdS/NiFe LDH (short for layered double hydroxide) heterostructures were designed and fabricated by following a facile in-situ growth method. The CdS nanoparticles are well dispersed on the surface of NiFe LDH to form nanoscale heterojunctions, as suggested from the TEM and elemental mapping images. The composites with optimum CdS amount (15 wt%) take on notably higher hydrogen evolution activity (469 μmol h^?1 g^?1) than the independent CdS and NiFe LDH from aqueous methanol solution under xenon lamp irradiation. The nano-heterojunction notably promotes the H₂ evolution kinetics and greatly suppresses the recombination of photo-induced electrons and holes, which is responsible for the enhanced photocatalytic activity of the composites, as demonstrated by the reducing onset potential and increasing photocurrent of the composites in the photoelectrochemical experiments. The possible photocatalytic mechanism is proposed on the basis of the defined position of energy band edges.     

Cobalt-based layered double hydroxides as oxygen evolving electrocatalysts in neutral eletrolyte

Co–M (M= Co, Ni, Fe, Mn) layered double hydroxides (LDHs) were successfully fabricated by a hexamethylenetetramine (HMT) pyrolysis method. Composite electrodes were made using a self-assembly fashion at inorganic/organic surface binder-free and were used to catalyze oxygen evolution reaction. Water oxidation can take place in neutral electrolyte operating with modest overpotential. The doping of other transitional metal cations affords mix valences and thus more intimate electronic interactions for reversible chemisorption of dioxygen molecules. The application of employing LDH materials in water oxidation process bodes well to facilitate future hydrogen utilization.     

不同工艺参数下6010铝板极限拉深高度变化的模拟分析

以6010铝板的圆筒形件拉深成形为例,利用Dynaform软件有限元模拟成形,研究了压机速度、摩擦系数和圆角半径等成形因素对极限拉深高度的影响。得到了当取压机速度8000mm／s～14000mm／s、摩擦系数0．2左右及冲模圆角半径13mm时效果最好。为电池壳、子弹壳等相关零件的拉深工艺参数设计,提供了理论依据。     

Kinetics and thermodynamics of Mn(II) removal from aqueous solutions onto Mg-Zn-Al LDH/montmorillonite nanocomposite

This study deals with the removal of Mn(II) from aqueous solutions by Mg-Zn-Al LDH/montmorillonite nanocomposite. LDH adsorbent was prepared by co-precipitation method and the composite was prepared by physical mixing of LDH and MMT using high-shear action. The data revealed that the maximum adsorption efficiency were 24.5, 26.4 and 28.9?mg/g at adsorbent mass of 0.25?g/L, pH of 6.0, initial Mn(II) concentration of 80?mg/L, stirring rate of 160?rpm, contact time of 75?min and different temperatures of 298, 308 and 318?K, respectively. Langmuir and Freundlich models were used to optimize the adsorption process and pseudo-first order and pseudo-second order models were used to evaluate the adsorption kinetics of Mn(II) ions onto Mg-Zn-Al (LDH)/MMT nanocomposite. The data indicated that Langmuir model fits the experimental data better than Freundlich model and pseudo-second order model is sufficient to depict the kinetics of Mn(II) onto Mg-Zn-Al (LDH)/MMT composite. Also, the data obtained from thermodynamics study; Gibbs free energy (ΔG°), Enthalpy change (ΔH°), and Entropy change (ΔS°) revealed that the adsorption process is spontaneous, endothermic and randomness at the solid-solution interface during the process of adsorption.     

小剂量γ射线对人体血清LDH及其同工酶的影响

为探讨小剂量γ射线对人体血清LDH及其同工酶的影响,本文对95例职业性~(137)铯探矿者血清LDH及其同工酶进行观察。结果表明受照组比对照组LDH总活性明显升高,LDH同工酶两组间差异不显著,未见其与职业工令及累积剂量间的相关性变化。     

Structural and thermal properties of polystyrene/CoAl-layered double hydroxide nanocomposites prepared via solvent blending: effect of LDH loading

Nanocomposites of polystyrene (PS) with modified CoAl-layered double hydroxide (CoAl–LDH) were prepared via simple solvent blending method and the effect of CoAl–LDH content on the structural and thermal properties was investigated. The structural and thermal properties of the nanocomposites were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The nano-scale dispersion of the CoAl–LDH layers in the PS matrix is verified by the (0?0?3) XRD reflection of the modified CoAl–LDH. The XRD data show that the exfoliated PS/CoAl–LDH nanocomposites can be obtained by controlling the LDH loading of about 5?wt%. TEM analysis also confirms the formation of exfoliated PS nanocomposites with 3?wt% and 5?wt% LDH loading. The thermal degradation temperature of the PS nanocomposite containing 5?wt% CoAl–LDH is found to be 12°C higher than that of pure PS when 50% weight loss is selected as a point of comparison. The glass transition temperature (T _g) of PS nanocomposites is about 14°C higher than that of pure PS.     

Enhanced corrosion resistance of layered double hydroxides/steam coating composite coating prepared by the hydrothermal method on LA43M magnesium–lithium alloy substrates

An excellent anticorrosion Mg–Al layered double hydroxide (LDH) composite coating was successfully fabricated on LA43M magnesium alloy substrates via an in situ steam coating (SC) process and a subsequent hydrothermal treatment at different temperatures. The microstructure, composition and phase formation of the composite coatings were studied via X-ray diffractometer, energy disperse spectroscopy, and scanning electron microscope, respectively. The corrosion resistance of composite coatings was further investigated using electrochemical measurements and corrosion test. The results showed that LDH/SC composite coating has typical nanosheets microstructure, which effectively seal the defects of SC. As the hydrothermal temperature increases, the thickness and density of nanosheets increases, and the corrosion resistance was significantly improved. Especially, the Mg–Al LDH/SC composite coating prepared at 100°C was the most dense and thickness, and exhibited the optimal and long-term anticorrosion resistance in 3.5 wt.% NaCl soultion. It has the lowest I_corr (1.767 × 10⁻⁸ A/cm²), which decreased by three and two orders of magnitude compared with the bare substrate and SC. Furthermore, it can maintain good chemical stability after immersion in the corrosion medium for 192 h and its hydrogen evolution rate (0.00416 mL·cm⁻²·h⁻¹) and weight lost rate (0.00266 mg·cm⁻²·h⁻¹) were the lowest compared with other samples.     

纳米水滑石(LDH)的有机化改性及其在高聚物中的分散

通过插层置换对水滑石（LDH）纳米粒子进行了有机化改性,并就改性纳米水滑石在PE、EVA树脂基体中的分散情况进行了研究。研究发现,经有机化改性的水滑石纳米粒子无论在极性的EVA基体中,还是在非极性的PE基体中都能达到很好的分散效果,为进一步制备高性能聚合物基纳米复合材料提供了一种新的分散方法。