Synthesis of Water-Soluble Iron−Gold Alloy Nanoparticles

Abstract

In this study, a synthetic method to produce water-soluble iron-gold (Fe-Au) alloy nanoparticles is described. The diameter of the alloy nanoparticles is 4.9 ( 1.0 and 3.8 ( 1.0 nm for two different precursors of iron, ferrous sulfate heptahydrate (Fe 2+ ) and iron pentacarbonyl (Fe 0 ). The X-ray powder diffraction of the alloyed nanoparticles shows an appreciable shift in 2θ peak positions relative to pure gold or iron. Using Vegard's law, we estimated the particle's iron content to be 14.8 ( 4.7 mol %. The lattice constant of the alloy nanoparticles is found to be 4.0449 ( 0.0375 Å. The high-resolution transmission electron microscopy images show the presence of icosahedral structures in agreement with the previous high temperature synthesis of the Fe-Au alloy nanoparticles. The optical absorption of the alloy nanoparticles is distinctive from pure gold nanoparticles and shows a relatively narrow absorption band in the range of 642-662 nm depending upon the amount of gold precursor used.

Superparamagnetic Nanoparticles as High Efficiency Magnetic Resonance Imaging T2 Contrast Agent

“…Furthermore, the Au/Fe NPs retain the localized surface plasmon resonance (LSPR) characteristic of pure Au NPs, as evidenced by a lack of attenuation or shift in the position of Au/Fe NPs' plasmon peak (Supporting Information Figure S1c). This is in agreement with similar properties of low-iron content, chemically synthesized Au−Fe alloy NPs, 14 (Figure 2d). As compared to iron and iron oxide nanoparticles of the same size, these Au/Fe NPs have similar blocking temperature but a smaller magnetization, which is mainly contributed by the small Fe portion and its wide distribution.…”

“…14 Chemical reduction of metal ions by sodium borohydrides has previously been used to prepare nanocrystalline magnetic materials, nanoalloys, and amorphous metals. 34,35 In this work, we report a new two-step synthesis to prepare magnetoresponsive gold/iron nanoparticles (Au/Fe NPs) with two mixed-ligand coatings, either mercaptopropionylsulfonic acid:-o c t a n e t h i o l ( M P S A : O T ) o r m e r c a p t o u n d e c y lsulfonate:octanethiol (MUS:OT).…”

Coexistence of plasmonic and magnetic properties in Au89Fe11 nanoalloys

“…22 At the nanoscale, the attempts to synthesize gold-iron alloy nanoparticles on substrates or in solution have been limited so far. AuFe alloy nanoparticles (AuFeNPs) were obtained by sequential ion implantation of iron in AuNPs embedded in a silica matrix, 15,31,32 by simultaneous reduction of Au salts and decomposition of Fe compounds in the presence of capping molecules dissolved in liquid solutions, [33][34][35][36][37][38][39][40][41][42] by electrodeposition on amorphous carbon electrodes from an aqueous solution of electrolytes, 43 in high-vacuum chambers by pulsed laser deposition 44,45 or by evaporation of a bulk alloy on a liquid hydrocarbon substrate. 46 Reports on structure-property relationships of these nanoparticles have produced conicting information, particularly regarding their plasmonic and magnetic responses.…”

“…31,34,35,39,40,45 This is a relevant point, since bottom-up synthetic approaches oen yield byproducts such as clustered iron atoms in the gold matrix, [36][37][38][39][40]47 iron-gold core-shell structures 11,34,35 or iron oxidegold heterostructures and agglomerates, [39][40][41]44 owing to the unfavorable thermodynamics in the formation of Au-Fe alloys. 28 Moreover, the AuFeNPs obtained by all previous methods were found to have problems related to surface accessibility, 15,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] which is important to catalytic applications [18][19][20] and for conjugation with functional molecules. [11][12][13] Thus, new low-cost and non-toxic synthetic methods that allow the synthesis of large amounts of well-dispersed and accessible nanoparticles avoiding the thermodynamic limitations to alloy formation are needed.…”

Facile growth of monocrystalline gold–iron nanocrystals by polymer nanoemulsion

“…Ascribing to its marvelous magnetic properties and readiness to be converted to bio-friendly oxides, the element iron is an excellent candidate for a wide range of applications such as magnetic recording, magnetic seals, printing, magnetic resonance imaging, drug delivery, biodetection, and cell tagging and separation [7][8][9][10]. Appreciably, amalgamation of Au and Fe into one AuFe alloy or intermetallic nanostructure can be more fascinating than the corresponding monoelements, offering potential functions in both magnetic and optical properties in addition to the biological compatibility and easy linkage to biomolecules endowed by the constituents [1,2,[11][12][13]. In such nanostructures, particle size and distribution, shape, composition, crystallinity, microstructure, surface properties, and aqueous solubility are vital.…”