乳液聚合法制备聚苯乙烯/Mg-Al层状双氢氧化物纳米复合材料

采用乳液聚合法制备阻燃性聚苯乙烯MgAl层状双氢氧化物(LDHs)纳米复合材料.通过对不同合成条件下复合材料的XRD谱,讨论了纳米复合材料的形成过程;经SEM图证实了LDHs是以剥离的纳米级层片分散在基体中的;TG和DSC谱图揭示了LDHs纳米层板可有效提高PS的热稳定性,并可使PS的玻璃化转化温度明显提高;当层状双氢氧化物在插层复合材料中含量为14.92%时,纳米复合材料的氧指数可达23.5%,其用量比在PS中直接添加纳米LDHs时要少约一倍.文中还分析了纳米复合材料的形成过程.     

LDHs薄膜基纳米荧光传感器的制备及其研究进展

层状复合氢氧化物(LDHs)是一种层板金属元素和层间离子可调的无机层状材料,利用其独特的插层组装特性,基于静电、氢键、范德华力等相互作用力,功能性荧光客体分子可与LDHs纳米片复合构筑多功能荧光薄膜材料.LDHs薄膜基荧光材料用于荧光传感器,在有机挥发性气体(VOCs)、温度、压力、重要生物分子等的检测中显示了良好性能.本文总结了LDHs复合薄膜的制备方法以及近年来其在纳米荧光传感领域的进展,并对其未来发展做出了展望.     

基于层状前驱体制备活性位高分散催化材料

综述了近年来以层状双金属氢氧化物(LDHs)为前躯体制备高分散催化剂的研究进展,基于LDHs层板金属阳离子以原子水平高度分散及层间阴离子以一定方式有序排布的结构特点,以LDHs材料作为单一前驱体,经层板剥离、晶格限域、插层组装及阵列化等途径制备催化活性位高度分散的多相催化材料具有显著的优势.     

层状双金属氢氧化物基光催化剂的研究进展

层状双金属氢氧化物(LDHs)具有组分可调、层板金属离子高度分散、层间阴离子可交换、拓扑转变等特性,使其可作为理想的光催化剂、催化剂载体或前驱体。作为一种新型多功能材料,LDHs基光催化剂在环境净化、能源储备、工业催化和生物医学等多个领域广泛应用。但是,选择合适的路径进一步优化LDHs基光催化剂的性能,以实现太阳能的高效利用及催化反应过程的高转化率和高选择性仍然具有很大的挑战性。本文依据LDHs的结构特点及活性组分引入方式,将LDHs基光催化剂的制备方法总结归纳为主体层板构筑法、客体插层敏化法、剥离层层组装法、复合材料杂化法四类,详细介绍了不同制备方法对光催化性能的影响,综述其最新研究进展;并结合LDHs基光催化材料的应用,介绍其光催化行为和机理;最后,对LDHs基光催化剂的应用前景进行分析和展望。     

层状双金属氢氧化物基光催化剂研究进展

层状双金属氢氧化物(LDHs)具有组分可调、层板金属离子高度分散、层间阴离子可交换、拓扑转变等特性,使其可作为理想的光催化剂、催化剂载体或前驱体。作为一种新型多功能材料,LDHs基光催化剂在环境净化、能源储备、工业催化和生物医学等多个领域广泛应用。但是,选择合适的路径进一步优化LDHs基光催化剂的性能,以实现太阳能的高效利用及催化反应过程的高转化率和高选择性仍然具有很大的挑战性。本文依据LDHs的结构特点及活性组分引入方式,将LDHs基光催化剂的制备方法总结归纳为主体层板构筑法、客体插层敏化法、剥离层层组装法、复合材料杂化法四类,详细介绍了不同制备方法对光催化性能的影响,综述其最新研究进展;并结合LDHs基光催化材料的应用,介绍其光催化行为和机理;最后,对LDHs基光催化剂的应用前景进行分析和展望。     

二维纳米片层孔洞化策略及组装材料在超级电容器中的应用

功率密度高、倍率性能优异和循环性能好等特性使得超级电容器在储能领域显示了巨大的应用前景。尽管二维层状材料剥离形成的纳米片层不仅可为电化学反应提供独特的纳米级反应空间,而且由其组装的层状纳米电极材料具有化学和结构上的氧化还原可逆性及纳米片层水平方向上离子或电子快速传输通道。但是,纳米片层组装电极材料在纳米片层垂直方向上离子或电子传输存在障碍,对于超级电容器功率密度和能量密度的提高及实现快速能量储存非常不利。因此,如何通过改善离子或电子的快速传输,实现超级电容器大功率密度下的高能量密度是超级电容器电极材料发展的方向之一。本文主要综述了二维层状材料剥离成纳米片层,纳米片层孔洞化策略及组装孔洞化材料在超级电容器电极材料中的应用。纳米层孔洞化技术是改善层状电极材料在纳米片层垂直方向离子或电子传输的有效手段,为实现高比电容下的高倍率性能超级电容器电极材料制备提供了方法学。最后,对开发大功率密度下的高能量密度超级电容器电极材料提出了展望。     

基于LDHs荧光材料的组装及二维限域效应研究

近年来,层状双金属氢氧化物(LDHs)因其特殊的二维结构及限域环境,作为主体材料构筑了一系列性能优异的插层结构材料,在发光、成像、传感等领域显示了广泛的应用前景.本文从插层客体、组装方法及LDHs的二维限域效应等方面详细介绍了基于LDHs荧光材料的最新研究进展,讨论了二维限域效应与发光性能的内在关联,并探讨了LDHs材料在该领域面临的挑战和发展趋势.     

层状材料及催化

LDHs（1ayered double hydroxides）是一类结构可调的阴离子层状及插层结构功能材料,近些年来在催化领域得到了广泛的关注．本文综述了有关LDHs材料构筑原则的理论研究、组装方法及其在多相催化领域应用的最新进展．     

新型纳米层状硅酸盐Magadiite主体材料的制备、表征、结构和生成机理研究

利用简单的插层反应方法成功地制备了四丁基氢氧化铵(TBAOH)插层的层状硅酸盐Magadiite纳米复合材料,在室温下该材料溶胶放置30d可以保持稳定,粉体长期保存结构稳定,而且反应时间短,只需30min.利用XRD,FTIR,SEM和HRTEM等方法对样品进行了结构表征.结果表明,TBA⁺离子在层间以双分子层排列,并与层状硅酸盐结合在一起,TBAOH插层后的纳米粒子在玻璃片上进行了重组,粒径分布在10～100nm之间;HRTEM电镜照片进一步证实了剥离的层状硅酸盐纳米粒子在玻璃片上的自组装过程.根据实验结果阐述了TBAOH插层反应形成纳米溶胶的机理.     

氟尿苷-层状双金属氢氧化物纳米杂化物制备及表征

采用共沉淀法将抗癌药物氟尿苷插入Mg-Al层状双金属氢氧化物(LDHs)的层间,合成了氟尿苷-LDHs纳米杂化物。依据氟尿苷分子大小和杂化物通道高度推测,氟尿苷分子是以长轴垂直或略倾斜于LDHs层片在LDHs层间呈双层排列。分别在pH=4.8和7.2的介质中研究了药物释放动力学,表明符合准二级动力学方程;释放速率随载药量增大而降低;氟尿苷-LDHs纳米杂化物具有良好的缓释效果。     

乙二胺四乙酸柱撑镁锌铝三元水滑石的制备与表征

采用共沉淀法合成了Mg2ZnAl-CO3水滑石;以其为前驱体,利用离子交换法进行插层组装得到Mg2ZnAl-EDTA三元柱撑水滑石;采用X射线衍射仪和傅立叶变换红外光谱仪对产物进行了表征.结果表明,合成的Mg2ZnAl-CO3水滑石纯度高、晶型良好,其层间CO32-可被乙二胺四乙酸(EDTA)阴离子取代形成Mg2ZnAl-EDTA三元柱撑水滑石;柱撑水滑石的层间距离明显增加,EDTA阴离子在层间倾斜排列.     

单层类水滑石纳米片的可控合成及规模生产展望

水滑石(LDHs)是一种阴离子黏土材料,由于其主体层板厚度的可调性,使其在光/电催化、电池、超级电容器、传感器以及生物医药等领域都具有广泛应用。降低层厚至单层可使材料的物理化学性质发生根本改变,从而优化催化性能。近期研究表明,利用自上而下,自下而上的方法,可以实现单层LDHs类材料的合成,但是受限于产量(g级)以及成本设备等问题,目前规模化制备高质量单层LDHs类材料还没有工业案例。成核晶化隔离法是目前唯一规模化合成纳米LDHs的工业化方法,具有成本低,产量可吨级放大等优点。本综述从合成方法、表征手段、应用三个角度讨论了单层及超薄LDHs的精准调控,详细论述了近期关于单层及超薄LDHs合成突破以及LDHs的规模化生产进展,并对其性能进行了总结,为后续设计高性能单层LDHs提供思路。     

二氟尼柳/水滑石插层组装结构、氢键及水合特性的分子动力学模拟

采用分子动力学方法模拟二氟尼柳插层水滑石(DIF/LDHs)的超分子结构, 研究复合材料主客体间形成的氢键以及水合膨胀特性.结果表明, 当水分子总数与DIF分子总数之比Nw≤3时, 层间距dc保持基本恒定, 约1.80 nm; 当Nw≥4时, 层间距逐渐增大, 且符合dc=1.2611Nw+13.63线性方程. 随着水分子个数增加, 水合能驻UH逐渐增大. 当Nw≤16时, 由于⊿UH<-41.84 kJ·mol-1, LDHs-DIF可以持续吸收水, 从而使材料层间距不断膨胀. 但当Nw≥24时, ⊿UH>-41.84 kJ·mol-1, 此时LDHs-DIF层间不能再进一步水合, 因此LDHs-DIF在水环境中膨胀具有一定的限度. 水滑石层间存在复杂的氢键网络. DIF/LDHs水合过程中, 水分子首先同步与层板和阴离子构成氢键; 当阴离子趋于饱和后, 水分子继续与层板形成氢键, 并逐步发生L-W型氢键取代L-A型氢键, 驱使阴离子向层间中央移动, 与层板发生隔离; 最后水分子在水滑石羟基表面形成有序结构化水层.     

Synthesis and Characterization of Poly(ethylene terephthalate)/Modified Lithium‐Aluminum‐Layered Double Hydroxide Nanocomposites Prepared Using In‐situ Polymerization

Layered double hydroxides are a type of layered stacked compound, which can be intercalated with organic‐molecule modifiers. An ion‐exchange process for layered double hydroxide (LDH) was used to intercalate water‐soluble sulfanilic acid salt (SAS) and dimethyl 5‐sulfoisopthalate (DMSI) into lithium aluminum layered double hydroxides (LiAl LDHs). In this work, a hydrothermal process was used to modify LiAl LDHs, and the modified LiAl LDHs were treated with either SAS or DMSI through an ion‐exchange process and were then intercalated using bis‐hydroxyethylene terephthalate (BHET). The results indicate that the modified LiAl LDHs improved the interlayer compatibility between the PET and LiAl LDH layers; thus, enabling the oligomer molecules to more easily enter the gallery of the LiAl LDH layers so that polymer chains could be included between the LDH layers during polymerization of the matrix. The better barrier, mechanical properties, and thermal stability of these new types of PET nanocomposites are discussed.     

二元类水滑石层板组成、结构与性能的理论研究

采用晶体学理论建立二元类水滑石(LDHs)微观结构模型与静电势能模型，将层板金属离子间距、层板电荷密度、层间阴离子间距等微观结构参数定量化，并将层间阴离子的静电势能表示成层板金属离子半径和物质的量之比、插层阴离子尺寸和电荷的函数。研究结果表明：LDHs层板金属离子间距应用离子紧密堆积来估算和孔径按阴离子平面六方点阵分布来计算是可行的；调变层板金属离子种类与物质的量之比影响层间阴离子的稳定性，势能计算值与文献报道的LDHs热稳定性次序一致。所以该模型可用于预测LDHs的微观结构参数以及热稳定性，为新型层状双羟基材料的定向合成提供思路。     

Recent progress on preparation and applications of layered double hydroxides

The properties of layered double hydroxides (LDHs), including the adjustability of cations in host layers, exchangeability of anions between layers, and tunability of the crystal structure, render them unique characteristics in preparation and applications. Relating to the structural characteristics of LDHs, this work analyzes the research status, advantages and disadvantages of the synthetic methods for LDHs, including hydrothermal, electrodeposition, co-precipitation and anion exchange methods. In addition, the application status and prospects are reviewed, such as photo/electrocatalysis, electrochemical energy storage, magnetic materials, pollutant adsorption, and other fields. Lastly, the critical issues and solutions in the developing process of LDHs are analyzed and proposed.     

A composite of layered double hydroxides obtained through random costacking of layers from Mg–Al and Co–Al LDHs by delamination–restacking: Thermal decomposition and reconstruction behavior

A composite of dodecylsulfate intercalated Mg–Al and Co–Al LDHs in which the layers of the two LDHs are randomly costacked was prepared starting from the monolayer colloidal dispersions of the individual surfactant intercalated LDHs obtained through delamination in 1-butanol. The surfactant ion of the composite could be exchanged for acetate ions. The thermal decomposition and reconstruction behavior of the acetate-intercalated composite was found to be different from those of an LDH in which each layer contains Mg, Co and Al and a physical mixture of Mg–Al and Co–Al LDHs. While the composite shows partial reconstruction to LDH phase even after heating up to 1000 °C the other samples do not show reconstruction beyond 800 °C.     

PREPARATION OF POLY（METHYL METHACRYLATE）/LAYERED DOUBLE HYDROXIDES NANOCOMPOSITES via in situ SOLUTION POLYMERIZATION

An exfoliated layered double hydroxides/poly(methyl methacrylate)(LDHs/PMMA)nanocomposite was prepared by in situ solution polymerization of methyl methacrylate(MMA)in the presence of 4-vinylbenzenesulfonate intercalated LDHs(MgAl-VBS LDHs).MgAl-VBS LDHs was prepared by the ion exchange method,and the structure and composition of the MgA1-VBS LDHs were determined by X-ray diffraction(XRD),infrared spectroscopy and elemental analysis.XRD and transmission electron microscopy(TEM)were employed to examine the structure of LDHs/PMMA nanocomposite.It was indicated that the LDHs layers were well exfoliated and dispersed in the PMMA matrix.The grafting of PMMA onto LDHs was confirmed by the extraction result and the weight fraction of grafted PMMA increased as the weight fraction of LDHs in the nanocomposites increased.     

层板金属离子不同的钴基双氢氧化物制备及其电化学性能

通过调变层板中的三价金属离子制备了层板金属离子不同的钴基双氢氧化物(LDHs),X-射线衍射(XRD)和傅里叶变换红外(FTIR)测试表明,层板中金属离子的变化对LDHs的物理结构有较大影响。电化学性能比较表明,三价金属离子的改变对材料的有效工作电位窗口和大电流稳定性及循环容量保持率均有很大影响。由于二价与三价金属离子在电化学过程中的作用不同,Co-AlLDHs在1A·g-1的电流密度下比容量达到447F·g-1;Co-InLDHs与Co-CrLDHs则具有很好的循环稳定性和电容性质。     

Effect of dispersion pH on the formation and stability of Pickering emulsions stabilized by layered double hydroxides particles

Using positively charged plate-like layered double hydroxides (LDHs) particles as emulsifier, liquid paraffin-in-water emulsions stabilized solely by such particles are successfully prepared. The effects of the pH of LDHs aqueous dispersions on the formation and stability of the emulsions are investigated here. The properties of the LDHs dispersions at different pHs are described, including particle zeta potential, particle aggregation, particle contact angle, flow behavior of the dispersions and particle adsorption at a planar oil/water interface. The zeta potential decreases with increasing pH, leading to the aggregation of LDHs particles into large flocs. The structural strength of LDHs dispersions is enhanced by increasing pH and particle concentration. The three-phase contact angle of LDHs also increases with increasing pH, but the variation is very small. Visual observation and SEM images of the interfacial particle layers show that the adsorption behavior of LDHs particles at the planar oil/water interface is controlled by dispersion pH. We consider that the particle-particle (at the interface) and particle-interface electrostatic interactions are well controlled by adjusting the dispersion pH, leading to pH-tailored colloid adsorption. The formation of an adsorbed particle layer around the oil drops is crucial for the formation and stability of the emulsions. Emulsion stability improves with increasing pH and particle concentration because more particles are available to be adsorbed at the oil/water interface. The structural strength of LDHs dispersions and the gel-like structure of emulsions also influence the stability of the emulsions, but they are not necessary for the formation of emulsions. The emulsions cannot be demulsified by adjusting emulsion pH due to the irreversible adsorption of LDHs particles at the oil/water interface. TEM images of the emulsion drops show that a thick particle layer forms around the oil drops, confirming that Pickering emulsions are stabilized by the adsorbed particle layers. The thick adsorbed particle layer may be composed of a stable inner particle layer which is in direct contact with the oil phase and a relatively unstable outer particle layer surrounding the inner layer.