A BIO-INSPIRED POLYDOPAMINE APPROACH TO PREPARATION OF GOLD-COATED Fe₃O₄ CORE–SHELL NANOPARTICLES: SYNTHESIS, CHARACTERIZATION AND MECHANISM

Abstract

A biomimetic and facile approach for integrating Fe 3 O 4 and Au with polydopamine (PDA) was proposed to construct gold-coated Fe 3 O 4 nanoparticles (Fe 3 O 4 @AuÀPDA) with a coreÀshell structure by coupling in situ reduction with a seed-mediated method in aqueous solution at room temperature. The morphology, structure and composition of the coreÀshell structured Fe 3 O 4 @AuÀPDA nanoparticles were characterized by transmission electron microscopy (TEM), X-ray powder di®raction (XRD) and X-ray photoelectron spectrometry (XPS). The formation process of Au shell was assessed using a UV-Vis spectrophotometer. More importantly, according to investigating changes in PDA molecules by Fourier transform infrared spectroscopy (FTIR) and in preparation process of the zeta-potential data of nanoparticles, the mechanism of coreÀshell structure formation was proposed. Firstly, PDA-coated Fe 3 O 4 are obtained using dopamine (DA) self-polymerization to form thin and surface-adherent PDA¯lms onto the surface of a Fe 3 O 4 \core". Then, Au seeds are attached on the surface of PDA-coated Fe 3 O 4 via electrostatic interaction in order to serve as nucleation centers catalyzing the reduction of Au 3þ to Au 0 by the catechol groups in PDA. Accompanied by the deposition of Au, PDA¯lms transfer from the surface of Fe 3 O 4 to that of Au as stabilizing agent. In order to con¯rm the reasonableness of this mechanism, two veri¯cation experiments were conducted. The presence of PDA on the surface of Fe 3 O 4 @AuÀPDA nanoparticles was con¯rmed by the¯nding that glycine or ethylenediamine could be grafted onto Fe 3 O 4 @AuÀPDA nanoparticles through Schi® base reaction. In addition, Fe 3 O 4 @AuÀDA nanoparticles, in which DA was substituted for PDA, were prepared using the same method as that for Fe 3 O 4 @AuÀPDA nanoparticles and characterized by UV-Vis, TEM and FTIR. The results validated that DA possesses multiple functions of attaching Au seeds as well as acting as both reductant and stabilizing agent, the same functions as those of PDA.

A new strategy for utilization of NIR from solar energy—Promotion effect generated from photothermal effect of Fe3O4@SiO2 for photocatalytic oxidation of NO

“…), carbon-based materials (carbon nanotubes [16], graphene [9,17,18], etc.) and transition metal nanoparticles (Fe 3 O 4 [19][20][21], Cu 3 BiS 3 [22], Cu 9 S 5 [23] and Ti 8 O 15 [1], etc.) have been studied.…”

Gold-Coated Cobalt Ferrite Nanoparticles via Methionine-Induced Reduction

“…According to the first of them, gold seeds prepared separately can be attached to the surface of magnetic Nps by coprecipitation together with or after formation of a polymeric shell. 14,15 As a result, the true and hydrodynamic size of Nps increases drastically, frequently becoming not suitable for many biomedical applications. For example, it has been reported that the initial size of Fe 3 O 4 Nps (∼10 nm) and Co Nps (∼12 nm) increased up to 100 nm.…”

Preparation and optical properties of magnetic carbon/iron oxide hybrid dots

“…6, the observed absorption spectra of the aqueous dispersed PEG-C/Fe 3 O 4 -dots and PEI-C/Fe 3 O 4 -dots with PVP polymers for improved dispersion are generally similar to that of the neat PEI-CDots reported previously. 45 It should be pointed out that Fe 3 O 4 nanoparticles are colored, but their absorptivities in the visible spectral region are generally low, 48,49 and thus their contributions to the observed absorption spectra of the hybrid dots are insignicant. Fluorescence spectra of the aqueous dispersed PEG-C/Fe 3 O 4dots and PEI-C/Fe 3 O 4 -dots are similar in prole to those of neat CDots, as illustrated in Fig.…”