Functionalization and characterization of porphyrincapped iron oxide-gold core-shell nanoparticles

Abstract

This paper describes the synthesis of Fe2O3@Au-NPs, deposition of 5,10,15,20-tetrakis[(3-thioacetoxy-1- propyloxy)phenyl]porphyrin and characterization of the NPs. Fe2O3@Au-NPs were synthesized in aqueous solution by overgrowing the gold shell onto Fe2O3seeds. Shaking the resulting solution with a dichloromethane solution of the porphyrin leads to transfer of the Fe2O3@Au-NPs and deposition of the porphyrin onto the Au surface. TEM showed well dispersed NPs with broad size distribution; d = 34–54 nm (44.26± 6.93), σ = 0.16. AFM confirmed the dispersion observed with TEM. HRTEM showed the core-shell structure and the porphyrin layer. XRD confirmed the presence of Au and Fe. SQUID magnetometry of the porphyrincapped Fe2O3@Au-NPs (2-300 K) gave TB =15.7 ± 0.1 K, negligible hysteresis at room temperature, and significant hysteresis below TB. Kinetic studies showed rapid transfer of the Fe2O3@Au-NPs from the aqueous to the organic phase in the presence of dissolved porphyrin and no such transfer in the absence of dissolved porphyrin, suggesting that the phase transfer of the Fe2O3@Au-NPs was followed by binding of the porphyrin to the surface of the NPs in the organic phase. Binding of the porphyrin to the gold surface of the NPs, was also studied with FT-IR.