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Immobilization of l-alanine into natural kaolinite via amidation catalyzed by boric acid for the development of biohybrid materials
Journal of Solid State Chemistry ( IF 3.2 ) Pub Date : 2020-04-02 , DOI: 10.1016/j.jssc.2020.121332
Alexandre Fernando da Silva , Gabriel Silva de Pádua , Denis Talarico de Araújo , Carlos Alexandre Vieira , Emerson H. de Faria

The natural amino acid l-alanine was immobilized on the interlayer space and surface of the natural Brazilian São Simão's kaolinite using two different routes. In the first 3-aminopropyltriethoxysilane was previously grafted into kaolinite interlayer space resulting into aminofunctionlized kaolinite that was further employed as reactive sites on kaolinite surfaces to bond l-alanine via amidation reaction. In the second route 3-aminopropyltriethoxysilane was first modified by l-alanine via amidation reaction catalyzed by boric acid and the modified alkoxide grafted into kaolinite using kaolinite-dimethylsulfoxide resulting on the biohybrid. In both strategies the amino acid was covalently bounded using the carboxylic acid from the amino acids and amine groups present on the kaolinite surfaces resulting in amide bonds. In both routes, the reaction was catalyzed by boric acid. Results confirms that the nature and loading of immobilized l-alanine changes depending of the route employed. X-ray diffraction confirmed the expansion of the interlayer spaces of the grafted solids resulting in 8.3 Å and 10.8 Å respectively for grafted materials routes one and two respectively. Reaction effectivity was kinetically evaluated by infrared vibrational spectroscopy that confirms the presence of amide bonds in both products due to the bands at 1560 cm−1, due to carbonyl (N–CO) stretching, and 1490 cm−1, ascribed to N–H plane vibrations and C–N stretching. The typical vibration of inner surface aluminol groups at 938 cm−1 (for purified kaolinite) is absent for both routes employed after grafting reactions confirming the attachment of the modified alkoxide into aluminol groups via covalent bonds resulting in bonds type Al–O–Si. Thermal analysis showed the typical reduction of dehydroxylation temperature from 510 °C on pure kaolinite to 480 and 450 °C, respectively, on the biohybrid materials and confirmed the functionalization in both routes, the amount of organic content was quantified and was 0.193 and 0.298 mol of organic unit per 1 mol of kaolinite minimal formulae using route of previous grafting of kaolinite with amine groups and direct grafting of modified alkoxide into kaolinite dimethyl sulfoxide respectively. Specific surface area analysis by N2 adsorption-desorption isotherms (BET method), cationic exchange capacity, and total specific surface area by the methylene blue method also confirmed the reduction of specific surface area from kaolinite grafted derivatives induced by amidation reaction. The solids obtained was tested as matrix to incorporate acetyl salicylic acid and ibuprofen and reveal that grafted clays incorporate a higher amount of both drugs (qt = 210 mg/g) The model that explain the adsorption kinetic mechanism was the pseudo-second order that reveal the higher affinity between adsorbent and acetyl salicilSalicylic acid and ibuprofen using the grafted kaolinite with alanine.



中文翻译:

硼酸催化酰胺化将l-丙氨酸固定化为天然高岭土,用于开发生物杂化材料

天然氨基酸1-丙氨酸通过两种不同的途径固定在天然巴西圣西蒙高岭石的层间空间和表面上。首先,将3-氨基丙基三乙氧基硅烷预先接枝到高岭石层间空间中,得到氨基官能化的高岭石,其进一步用作高岭石表面上的反应位点以通过酰胺化反应键合1-丙氨酸。在第二路线3-氨丙基三首先由改性硼酸催化酰胺化反应生成-丙氨酸,然后用高岭石-二甲基亚砜将改性的醇盐接枝到高岭石上,生成生物杂化物。在两种策略中,使用来自高岭石表面上存在的氨基酸和胺基团的羧酸使氨基酸共价键合,从而产生酰胺键。在两种途径中,反应均由硼酸催化。结果证实了固定化l的性质和负载-丙氨酸根据所采用的途径而变化。X射线衍射证实了接枝固体的层间空间的扩大,分别导致了接枝材料路线一和二的分别为8.3埃和10.8埃。通过红外振动光谱动力学评估了反应的有效性,该反应证实了两种产物中酰胺键的存在,这归因于在1560 cm -1处的带(由于羰基(N –C O)拉伸)和在1490 cm -1处的归因于N – H平面振动和C–N拉伸。内表面铝醇基团在938 cm -1处的典型振动(对于纯净高岭石而言)在接枝反应后均没有使用这两种途径,这证实了改性的醇盐通过共价键键合形成Al–O–Si型键而结合到铝铝基团中。热分析表明,在生物杂化材料上,脱羟基温度通常从纯高岭石上的510°C分别降至480和450°C,并证实了这两种途径的功能化,对有机物含量进行了定量,分别为0.193和0.298 mol。 1摩尔高岭土基本配方中的有机单位的计算方法是,先用胺基接枝高岭石,然后将改性醇盐直接接枝到高岭土二甲亚砜中。用N 2分析比表面积吸附-解吸等温线(BET法),阳离子交换容量和亚甲基蓝法测定的总比表面积也证实了酰胺化反应导致高岭石接枝衍生物的比表面积降低。测试获得的固体作为基质,以掺入乙酰基水杨酸和布洛芬,并揭示接枝粘土掺入的两种药物的含量更高(qt = 210 mg / g)。使用接枝的高岭石和丙氨酸,吸附剂与乙酰水杨酸,水杨酸和布洛芬之间的亲和力更高。

更新日期:2020-04-03
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