KCS

We have successfully prepared two different kinds of Amino Acid such as Phenylalanine (Phe) and Glutamic acid (Glu) into layered double hydroxide (LDH) via ion exchange reaction. At first, we synthesized Mg₂Al-(NO₃)-LDH at pH10 via coprecipitation. Since amino acids have different charge depending on the pH of the reaction solution, we carried out the ion-exchange reaction in the pH range of deprotonating the carboxylic acid group of amino acid, 7 ~ 10 for Phe and 7 ~ 11 for Glu. According to X-ray diffraction analysis, Phe is not intercalated into LDH at pH7, but Phe is successfully intercalated into LDH at pH 10, which is higher than pK_a2 of Phe (9.32) and the basal spacing was expanded to 1.8 nm compared to that of the pristine LDH (0.88 nm), indicating that Phe lattice with bilayer structure. On the other hand, Glu is intercalated into LDH at the range of pH 7 ~ 11, and the basal spacing is ~0.95 nm regardless of pH, since dicarboxylic acid group in Glu were completely deprotonated above pH 6 to be negatively charged. The difference of basal spacing between Phe-LDH and Glu-LDH nanohybrid was caused by the different interlayer structure of amino acid through the different total net charge,indicating that Phe is incorporated into LDH with paraffin-type interdigited bi-layer structure, but Glu is intercalated into LDH with parallel mono layer structure to the ab plane of LDH.