Optimization of synthesizing leucine-binding nano-sized magnetite by a two-step transformation

Abstract

The optimum conditions for synthesizing leucine (Leu)-binding nano-sized magnetite (NSM) particles by a two-step transformation (TST) process were studied. The formation and magnetization of as-synthesized NSM particles were investigated through variation of the acidity, the type of surface modifier, and the nature of the acid for pH adjustment. With increased acidity, the saturation magnetization of the NSM particles decreased, but the amount of Leu coated on the surface of NSM particles increased. After the influence of hydroxyl (OH − ) groups on the sur- face of NSM particles was removed by using the dicarboxyl anion (C2O4 2− ) as a ligand in the first step, Leu was suc- cessfully bound with NSM particles in the second step. However, when polyethylene glycol (PEG) was used as a sur- face modifier, it was difficult to form the Leu-to-NSM particle complex. In terms of the acid used to modify pH, H2SO4 was slightly less effective than HCl in achieving saturation magnetization because the coordination for SO4 2− anions is stronger than that of Cl − anions. The preparation of other amino acid-binding NSM particles can be optimized in an analogous manner.