别嘌醇插层Zn/Al-NO3-LDH复合材料的组装及缓释性能

以共沉淀法和离子交换法制备别嘌醇插层Zn/Al-NO3-LDH复合材料,结合XRD、FT-IR、TG-DTA分析表明,别嘌醇进入LDH层间与层板相互作用形成超分子结构,提高了别嘌醇的耐酸性和热稳定性,且共沉淀法制备的别嘌醇插层LDH具有良好的缓释性能.提出了共沉淀法制备有机分子插层LDH过程中,存在易于客体进行离子交换和包埋的溶胶-凝胶中间形态的假设,可提高有机分子插层量.     

不同无机阴离子插层层状双金属氢氧化物的合成及其离子交换特性

层状双金属氢氧化物(LDH)是用于镁合金表面防腐蚀的新兴材料.但 LDH 层间具有较强亲和力的层间无机阴离子是否会与腐蚀性阴离子Cl－发生离子交换还存在争议,为解决该问题,本工作拟合成 3 种不同无机阴离子插层的 MgAl-X-LDHs(X=PO3－4 ,CO2－3 和SO2－4 )并开展离子交换实验.SEM和 XRD等测试结果表明,PO3－4 ,CO2－3 和 SO2－4 成功进入LDH层间,形成3 种不同阴离子插层的MgAl-X-LDHs.离子交换实验结果表明:当在 3.5%NaCl(质量分数)溶液中含有10 g/L MgCl2 时,Cl－可以将LDH层间的PO3－4 和CO2－3 交换出来;不含有 MgCl2 时,Cl－则难以与 LDH 层间的 PO3－4 和CO2－3 发生离子交换.而无论是否含有 Mg2+,高浓度 Cl－都可以将 LDH 层间的 SO2－4 交换出来,低浓度 Cl－则不会与SO2－4 发生明显离子交换.上述结果对于在镁合金表面设计和制备不同类型的LDH防腐涂层具有理论指导意义.     

聚马来酸/LDH插层型纳米复合材料的制备与表征

采用离子交换法将马来酸单体插入Mg/Al-Cl-LDH层间,然后通过热或氧化还原引发层间单体链式原位缩聚制备聚马来酸/水滑石(LDH)插层型纳米复合材料。研究了插层组装的条件和引发聚合的方法。采用X射线衍射(XRD)、红外光谱(FT-IR)、热重及差热分析(TG-DTA)和扫描电子显微镜(SEM)等手段对样品进行了表征与测试。结果表明,马来酸插层LDH使层间距由0.767 nm增大至1.19 nm,H2O2引发剂或热引发聚合使层间距由1.19 nm分别减小至1.114 nm和1.085 nm,产物粒径为50 nm~100 nm。聚马来酸分子进入LDH层间形成超分子结构,使其热稳定性提高100℃以上。     

有机酸阴离子/LDH复合材料的插层组装条件及热稳定性研究

以Mg/Al-CO_3-LDH为前体,采用离子交换法制备了脂肪酸(丁二酸、己二酸、癸二酸、酒石酸)和芳香酸(笨甲酸、水杨酸)柱撑水滑石复合材料,并利用XRD、FT-IR、TG和DTA技术对样品进行了结构表征和性能测试.结果表明,通过控制离子交换条件,6种有机酸根离子可以插入水滑石的层间完全取代CO_3~(2-),形成具有超分子结构稳定的有机酸阴离子/LDHs复合材料.     

磺基水杨酸插层Mg/Cu/Zn/Al-LDHs的组装、表征及紫外性能

以共沉淀法制备了磺基水杨酸插层Mg/Cu/Zn/Al-LDHs复合材料, 借助XRD、FT-IR、TG-DTA等手段对样品测试表明, 客体进入LDHs层间, 层间距由0.832 nm扩至1.125 nm, 推测了层间排列模型; EDS分析验证了插层后层板元素组成比接近理论比值, 插层组装仍能保持良好的层状结构, 且客体进入层间因静电和氢键等作用提高了热稳定性; 同时由UV-DRS结果可知, 插层LDHs复合材料对紫外线具有良好的屏蔽和吸收双重作用。     

基于氧化铝模板原位制备Ni/Al-LDHs薄膜的工艺及性能研究

采用电化学阳极氧化铝模板提供Al3+,在Ni(NO3)2和NH4NO3溶液中采用原位生长法制备了Ni/Al-NO3-LDHs薄膜,在弱酸性条件下通过离子交换将磺基水杨酸阴离子引入Ni/Al-NO3-LDHs薄膜层间,制备了磺基水杨酸/LDHs复合薄膜,优化了工艺条件,并借助XRD、FT-IR、SEM等手段对薄膜进行了结构和形貌分析。结果表明,磺基水杨酸阴离子成功插层于LDHs薄膜层间,层间距由0.883 nm增大为1.153 nm,NO-3离子在1 384 cm-1的特征峰基本消失,同时出现了磺基水杨酸的特征峰。SEM照片显示,LDHs晶片垂直于Al基底生长。电化学腐蚀和UV-Vis分析表明,LDHs薄膜具有良好的耐蚀性和优异的紫外阻隔性能。     

机械化学法合成羟基插层Mg/Fe型层状双氢氧化物

Mg/Fe型层状双氢氧化物(LDH)是一类可有效去除水中有害组分(特别是有害阴离子)的无机吸附材料.常用的共沉淀法在合成层状双氢氧化物过程中容易产生大量碱性废水,且合成产物通常结晶度较低.本文利用改进的机械化学合成法,选取MgO和无定形态的Fe(OH)3作为反应前驱物,成功制备出了羟基(-OH)插层的Mg/Fe型层状双...     

芬布芬插层Mg/Fe-NO3-LDHs复合材料的组装及其缓释性能的研究

采用共沉淀法合成Mg/Fe-NO3-LDHs前体,通过正交试验考察了镁铁物质的量比、pH值、反应温度及时间对产物结构和物相的影响,确定了最佳合成条件(Mg、Fe物质的量比为3,pH值为9,反应温度为65℃,反应时间为4h)。再以共沉淀法组装芬布芬-LDHs,利用XRD、FT-IR、UV、TG-DTA对产物进行了结构表征,插层量19.6%。测试芬布芬-LDHs在模拟肠液、生理盐水及蒸馏水中的缓释性能,结果表明其在不同的缓释介质中均具有较好的缓释效果。释放过程符合准二级动力学方程,芬布芬在LDHs层间的扩散是释放控制步骤。     

头孢拉定/蒙脱石插层化合物的制备

采用医药级蒙脱石和钠基蒙脱石作载体材料, 通过溶液插层法制备了头孢拉定/蒙脱石插层化合物. 采用紫外分光光度法定量计算其载药量, 采用X射线衍射和傅立叶红外光谱测试定性分析其结构, 研究其层间结构变化情况. 结果表明, 头孢拉定与蒙脱石发生插层反应主要是由于离子交换作用, 简单的物理混合不能使二者发生插层反应. 钠化后的医药级蒙脱石有较好的离子交换特性, 易于发生插层反应. 医药级蒙脱石和头孢拉定在水中进行插层反应后, 蒙脱石的层间距减小; 而钠基蒙脱石和医药级蒙脱石钠化改性后制备的插层化合物层间距均增大.     

甘氨酸-Mg_3Al水滑石的制备、剥离以及与蒙脱土的插层组装

用共沉淀法制备甘氨酸(简称Gly)插层Mg3Al水滑石(简称Gly-Mg3Al LDHs),利用甘氨酸等电点的性质实现了Mg3Al水滑石在pH=3~4水溶液中的剥离,并将剥离出的LDHs纳米片层与蒙脱土进行插层组装,制备出Mg3Al水滑石/蒙脱土层状复合材料。用X射线粉末衍射、红外光谱、N2吸附-脱附以及电泳仪等手段对样品进行了表征。结果表明,制备出的GlyMg3Al LDHs结构规整,晶相单一,甘氨酸以42°的倾角排列于水滑石层间。在nGly∶nNO3-=1∶2的条件下制备的Gly-Mg3Al LDHs剥离效果最好,剥离后形成的无机聚合粒子的zeta电位介于35 mV~40 mV之间,剥离液可以稳定存在72 h。所得层状复合材料的层间距为1.44nm,此值为单元LDHs片层与单元蒙脱土片层的厚度之和,证明LDHs纳米片层与蒙脱土进行了有序交叉叠层。     

Synthesis and characterisation of nanohybrids of olsalazine-intercalated Al–Mg layered double hydroxide

In this study, olsalazine (3,3′-azobis 6-hydroxy benzoic acid) was intercalated into Mg–Al layered double hydroxides (LDHs) by ion exchange or coprecipitation methods to obtain olsalazine–LDH nanohybrids. Powder X-ray diffraction (XRD), Fourier transform infrared spectra and elemental analyses indicate a successful intercalation of olsalazine with a vertical orientation. Intercalation of organic anion of olsalazine into Mg–Al LDH caused the interlayer spacing of LDH to increase from 0.884 to 1.665–1.666?nm as determined by XRD studies. Thermogravimetric analyses propose that the thermal stability of the intercalated organic anion of olsalazine is largely improved compared to the pure form before intercalation due to the host–guest interaction involving the hydrogen bond. Furthermore, in vitro drug release experiments in pH 7.4 phosphate buffer solution have been investigated. The drug molecules during dissolution were exchanged with anions in the medium, thus leading to a slow release, much slower than when the same matrix was used simply mixed with the drug.     

Intercalation of collagen and soybean peptides into Zn-Al layered double hydroxide

In order to develop a new type biocompatible organic/inorganic nanohybrid material, an intercalation of collagen peptides (CP) and soybean peptide (SP) into Zn-Al layered double hydroxide (LDH) by the coprecipitation reaction has been investigated. The peptide/LDH has been characterized by chemical analysis, powder X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis (TG) and transmission electron microscopy (TEM). According to the XRD patterns and Raman spectra, the solid products were found to contain peptide and to show broad diffraction peaks with LDH structures. The CP/LDH and SP/LDH possess the expanding LDH structure, d(00l) = 2-3 nm, confirming that both peptides were intercalated into the LDH interlayer space with low organized stacking arrangement.     

Synthesis and characterisation of a new stable organo-mineral hybrid nanomaterial: 4-Chlorobenzenesulfonate in the zinc–aluminium layered double hydroxide

4-Chlorobenzenesulfonate (4-CBS) was intercalated between layers of Zn–Al layered double hydroxides (LDHs). Two methods of incorporation were applied: (1) direct synthesis by coprecipitation of metal nitrates and sodium 4-CBS and (2) ion exchange of the LDH nitrate with the organic ion. The solids were characterized by X-ray diffraction and infrared spectroscopy. The direct method, effected at different pH values, led to a hybrid material with good degree of intercalation. In order to optimise the exchange conditions, particular attention was given to the effect of solution pH, 4-CBS/NO₃ ratio and exchange temperature. The total exchange was successful and a new stable hybrid nanostructured material was obtained at pH 8 and with a 4-CBS concentration of 0.0028 M. This solid was further characterised by chemical and thermal analyses.     

A critical assessment of the methods for intercalating anionic surfactants in layered double hydroxides

Anionic surfactant intercalated layered double hydroxides (LDH) of high purity are easily prepared via direct coprecipitation and also by the ion exchange method provided that the precursor contains a monovalent anion, e.g., LDH–Cl or LDH–NO₃. However, LDH–CO₃ is an attractive starting material as it is commercially available in bulk form owing to large-scale applications as a PVC stabilizer and acid scavenger in polyolefins. Thus, intercalation of dodecyl sulfate and dodecylbenzenesulfonate into a commercial (LDH) with approximate composition [Mg_0.654Al_0.346(OH)₂](CO₃)_0.173 · 0.5H₂O] was explored. Direct ion exchange is difficult as the carbonate is held tenaciously. In the regeneration method it is removed by thermal treatment and the surfactant form obtained by reaction with the layered double hydroxide that forms in aqueous medium. Unfortunately the resulting products are impure, poorly crystallized and only partial intercalation is achieved. Better results were obtained using water-soluble organic acids, e.g., acetic, butyric, or hexanoic acid, to aid decarbonation of LDH–CO₃. Intercalation proceeded at ambient temperatures with the precursor powder suspended in an aqueous dispersion of the anionic surfactant. The carboxylic acids are believed to assist intercalation by facilitating the elimination of the carbonate ions present in the anionic clay galleries.     

Incorporation of fluorophosphate into zinc–aluminium–nitrate layered double hydroxide by ion exchange

The intercalation of fluorophosphate (PO₃F^2???, FP) in the [Zn–Al] layered double hydroxides (LDHs) was investigated. A nitrate precursor was prepared by coprecipitaion at pH 9. An attempt to intercalate FP by direct coprecipitation reaction led to a poorly crystalline LDH phase. The effects of pH, aging time and anion concentration were studied and allowed to confirm that the best crystalline material, with high exchange extent, was obtained by carrying out the exchange at 25 °C in 0·1 M FP solution at pH 9 with at least 20 h of aging time.     

Mg–Al and Zn–Fe layered double hydroxides used for organic species storage and controlled release

Layered double hydroxides (LDH) containing (Mg and Al) or (Zn and Fe) were prepared by coprecipitation at constant pH, using NaOH and urea as precipitation agents. The most pure LDH phase in the Zn/Fe system was obtained with urea and in Mg/Al system when using NaOH. The incorporation of phenyl-alanine (Phe) anions in the interlayer of the LDH was performed by direct coprecipitation, ionic exchange and structure reconstruction of the mixed oxide obtained by the calcination of the coprecipitated product at 400 °C. The reconstruction method and the direct coprecipitation in a medium containing Phe in the initial mixture were less successful in terms of high yields of organic–mineral composite than the ionic exchange method. A spectacular change in sample morphology and yield in exchanged solid was noticed for the Zn₃Fe sample obtained by ionic exchange for 6 h with Phe solution. A delivery test in PBS of pH = 7.4 showed the release of the Phe in several steps up to 25 h indicating different host–guest interactions between the Phe and the LDH matrix. This behavior makes the preparation useful to obtain late delivery drugs, by the incorporation of the anion inside the LDH layer.     

Preparation for a new intercalated compound of acrylamide monomers and their in-situ polymerization in layered double hydroxides

A new intercalation compound based on Mg/Al-layered double hydroxide (Mg/Al-LDH) with polymerizable acrylamide (AM) which cannot be synthesized by direct coprecipitation reaction, was achieved via in-situ hydrothermal method with the existence of glycine. The well-crystallized AM-intercalated Mg/Al-LDH was characterized by XRD, FTIR, DTA and scanning electronic microscopy. Basal spacing of the Mg/Al-LDH intercalation compound is 1.32 nm. Polymerization of AM incorporated into Mg/Al-LDH interlayer space occurs after 160 °C heat treatment, which indicates that the preparation of PAM/LDH nanocomposite is feasible via in-situ polymerization route.     

Development of sustained-release tablets containing sodium valproate: in vitro and in vivo correlation

We have developed a 200 mg and 400 mg sustained-release sodium valproate tablet that allows effective blood concentration of the active drug with once-a-day dosing. The controlled dissolution or sustained release of the drug was attained by a membrane-controlled system. A single-coating system did not adequately control the dissolution rate, and therefore double-coated tablets were prepared and a human pharmacokinetic study was conducted. With the 200 mg VPA-Na tablets, the nonfasting C_max was only 20% higher than the fasting C_max. An in vitro dissolution test was conducted to predict the effects of food on drug dissolution after administration of this tablet. A relatively good correlation was observed between the absorption profiles and the dissolution profiles of the drug.     

pH sensitive organic-inorganic layered nanomaterials by self-assembly of indigocarmine between the inorganic layers

New pH sensitive organic-inorganic intercalation compounds having different interlayer spacing were prepared. Zn-Al layered double hydroxide (LDH) is an anion exchangeable inorganic layered compound whose interlayer spacing is 0.76 nm. In the reactions of indigocarmine (IDC) with the calcined Zn-Al LDH at pH = 7 (LDH-IDC7), interlayer spacing increased to 2.25 nm. The interlayer spacing of LDH-IDC7 decreased to 1.89 nm by the treatment in basic solution. In the reaction of IDC with the calcined Zn-Al LDH at pH = 10 (LDH-IDC10), interlayer spacing of the intercalation compounds was 1.89 nm. The interlayer spacing of these intercalation compounds was changed reversibly by the treatments in acidic or basic solution.