Abstract
The purpose in this research is mainly to discussed the synthesis of the shaped core/Fe3O4 core-shell magnetic nanoparticles (MNPs), with different Fe atomic percentages in single FePt NP as core. The dissertation will cover three discussions, including the reaction mechanism of shaped Pt/Fe3O4 MNPs, the synthesis of FePt core with different Fe atomic percentages and the verification of the coating process with the extension of Fe3O4 growing onto different cores. In the first section, shaped Pt/Fe3O4 core-shell MNPs were synthesized successfully with the combination of modified hot-injection method and seed-mediated method. Pt NPs with 5.2 nm in diameter were prepared in thermal decomposition process. Fe3O4 shell grew onto Pt NPs in the present of reductant and surfactants, with the injection of Fe precursor in ether at the reacting temperature 290 oC. The product was Pt/Fe3O4 core-shell MNPs dispersed in hexane with the 16 nm in length for each MNP. The amount of reductant determines the nucleation path. Small amount of reductant reduces less Fe ions in precursor, leading to low Fe concentration in reaction solution. The low concentration is limited to help Fe atoms to overcome the critical level of homogeneous nucleation. Rather, Fe prefers to nucleate heterogeneously onto Pt seeds. As a result, Pt/Fe3O4 core-shell MNPs dominates in MNPs product. With the amount of reductant increasing, more Fe atoms are presented in the same time, facilitating Fe to nucleate homogeneously. Therefore, both Fe3O4 and Pt/Fe3O4 core-shell MNPs are obtained. The second section focuses on the synthesis of FePt NPs with different Fe atomic percentages. FePt NPs were synthesized with the same method as Pt NPs. As the reaction time increased, the Fe content in single FePt NP decreased because the Fe precursor involving in reaction evaporated to the atmosphere. Note that the size of NP, 4.1 nm in diameter, maintained the same even they had different Fe and Pt composition. The result was analyzed by ICP-MS. The extension to Fe3O4 coating process to different cores will be discussed in the last part. 15.7 nm Fe0.35Pt0.65/Fe3O4 core-shell MNPs nanocubes were obtained with the core size of 4 nm in diameter. The successful synthesis of shaped Fe0.35Pt0.65/Fe3O4 core-shell MNPs reveals that the coating process is determined not by the inter-surface energy of FexPt1-x (0 < x < 1) and Fe3O4 but by the kind of surfactant in both surface of seed and reaction environment.