Hussein Mohd Zobir Bin, Sarijo Siti Halimah, Yahaya Asmah Hj, Zainal Zulkarnain
Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), University Putra Malaysia, 43400 Serdang, Selangor, Malaysia.
J Nanosci Nanotechnol. 2007 Aug;7(8):2852-62. doi: 10.1166/jnn.2007.613.
Layered organic-inorganic hybrid nanocomposite material was synthesised using 4-chlorophenoxyacetate (4CPA) as guest anion intercalated into the Zn-Al layered double hydroxide inorganic host by direct co-precipitation method at pH = 7.5 and Zn to Al molar ratio of 4. Both PXRD and FTIR results confirmed that the 4CPA was successfully intercalated into the Zn-AI-LDH interlayer. As a result, a well-ordered nanolayered organic-inorganic hybrid nanocomposite, with the expansion of the basal spacing from 8.9 angstroms in the layered double hydroxide to 20.1 angstroms in the resulting nanocomposite was observed. The FTIR spectrum of the nanocomposite (ZAC) showed that it composed spectral features of Zn-AI-LDH (ZAL) and 4CPA. The nanocomposites synthesized in this work are of mesoporous-type containing 39.8% (w/w) of 4CPA with mole fraction of Al3+ in the inorganic brucite-like layers (xAI) of 0.224. The release studies showed a rapid release of the 4CPA for the first 600 min, and more sustained thereafter. The total amount of 4CPA released from the nanocomposite interlayer into the aqueous solution were 21%, 66%, and 72% in 0.0001, 0.00025, and 0.0005 M sodium carbonate, respectively. In distilled water, about 75, 35, and 57% of 4CPA could be released in 1000 min, when the pH of the release media was set at 3, 6.25, and 12, respectively. In comparison with a structurally similar organic moiety with one more chlorine atom at the 2-position of the aromatic ring, namely 2,4-dichlorophenoxyacetate (24D), the 4CPA showed a slower release rate. The slightly bulkier organic moiety of 24D together with the presence of chlorine atom at the 2-position presumably had contributed to its higher release rate, and it seems that these factors may be exploited for tuning the release rate of intercalated guest anions with similar properties. This study suggests that layered double hydroxide can be used as a carrier for an active agent and the chemical structure of the intercalated moiety can be used to tune the desired release kinetics of the beneficial agent.
采用直接共沉淀法，在pH = 7.5、锌与铝的摩尔比为4的条件下，以4 - 氯苯氧乙酸酯（4CPA）作为客体阴离子插入到锌铝层状双氢氧化物无机主体中，合成了层状有机 - 无机杂化纳米复合材料。粉末X射线衍射（PXRD）和傅里叶变换红外光谱（FTIR）结果均证实4CPA成功插入到锌铝层状双氢氧化物（Zn - AI - LDH）的层间。结果观察到形成了一种有序的纳米层状有机 - 无机杂化纳米复合材料，其层间距从层状双氢氧化物中的8.9埃扩展到所得纳米复合材料中的20.1埃。纳米复合材料（ZAC）的FTIR光谱表明它具有Zn - AI - LDH（ZAL）和4CPA的光谱特征。本工作中合成的纳米复合材料为介孔型，含有39.8%（w/w）的4CPA，无机类水镁石层中Al3 + 的摩尔分数（xAI）为0.224。释放研究表明，4CPA在前600分钟快速释放，之后释放更为持续。纳米复合材料层间释放到水溶液中的4CPA总量在0.0001 M、0.00025 M和0.0005 M碳酸钠中分别为21%、66%和72%。在蒸馏水中，当释放介质的pH分别设定为3、6.25和12时，1000分钟内4CPA的释放量分别约为75%、35%和57%。与在芳环2位多一个氯原子的结构相似有机部分即2,4 - 二氯苯氧乙酸酯（24D）相比，4CPA的释放速率较慢。24D稍大的有机部分以及2位氯原子的存在可能导致其释放速率较高，似乎这些因素可用于调节具有相似性质的插入客体阴离子的释放速率。本研究表明层状双氢氧化物可作为活性剂的载体，插入部分的化学结构可用于调节有益剂所需的释放动力学。
