Researchers find simpler way to deposit magnetic iron oxide onto gold nanorods

December 11, 2017

Researchers from North Carolina State University and MIT have found a simpler way to deposit magnetic iron oxide (magnetite) nanoparticles onto silica-coated gold nanorods, creating multifunctional nanoparticles with useful magnetic and optical properties.

Gold nanorods have widespread potential applications because they have a surface plasmon resonance - meaning they can absorb and scatter light. And by controlling the dimensions of the nanorods, specifically their aspect ratio (or length divided by diameter), the wavelength of the absorbed light can be controlled. This characteristic makes gold nanorods attractive for use in catalysis, security materials and a host of biomedical applications, such as diagnostics, imaging, and cancer therapy. The fact that the magnetite-gold nanoparticles can also be manipulated using a magnetic field enhances their potential usefulness for biomedical applications, such as diagnostic tools or photothermal therapeutics.

"The approach we outline in our new paper is simple, likely making it faster and less expensive than current techniques for creating these nanoparticles - on a small scale or a large one," says Joe Tracy, an associate professor of materials science and engineering at NC State and corresponding author of a paper on the work.

The new technique uses an approach called heteroaggregation. Silica-coated gold nanorods are dispersed in ethanol, a polar solvent. In ethanol, the hydrogen atoms are partially positively charged, and the oxygen atoms are partially negatively charged. The magnetite nanoparticles are dispersed in hexanes, a non-polar solvent, where the charges are not separated. When the two solutions are mixed, the magnetite nanoparticles bind to the gold nanorods - and the resulting magnetite-gold nanoparticles are removed from the solvent using a simple centrifugation process.

"We are able to take pre-synthesized, silica-coated gold nanorods and iron oxide nanoparticles and then combine them," says Brian Chapman, a Ph.D. student at NC State and lead author of the paper. "This is simpler than other techniques, which rely on either growing iron oxide nanoparticles on gold nanorods or using molecular cross-linkers to bind the iron to the silica coating of the nanorods."

"Our approach also results in highly uniform nanoparticles," Tracy says. "And by incorporating ligands called PEG-catechols, the resulting nanoparticles can be dispersed in water. This makes them more useful for biomedical applications.

"These are interesting, and potentially very useful, multifunctional nanoparticles," Tracy adds. "And hopefully this work will facilitate the development of applications that capitalize on them."
-end-
The paper, "Heteroaggregation Approach for Depositing Magnetite Nanoparticles onto Silica-Overcoated Gold Nanorods," is published in the journal Chemistry of Materials. The paper was co-authored by Wei-Chen Wu, a former Ph.D. student at NC State; and Qiaochu Li and Niels Holten-Andersen of MIT. The work was done with support from the National Science Foundation under grants DMR-1121107, DMR-1056653, and CBET-1605699.

North Carolina State University

Related Nanoparticles Articles from Brightsurf:

An ionic forcefield for nanoparticles
Nanoparticles are promising drug delivery tools but they struggle to get past the immune system's first line of defense: proteins in the blood serum that tag potential invaders.

Phytoplankton disturbed by nanoparticles
Products derived from nanotechnology are efficient and highly sought-after, yet their effects on the environment are still poorly understood.

How to get more cancer-fighting nanoparticles to where they are needed
University of Toronto Engineering researchers have discovered a dose threshold that greatly increases the delivery of cancer-fighting drugs into a tumour.

Nanoparticles: Acidic alert
Researchers of Ludwig-Maximilians-Universitaet (LMU) in Munich have synthesized nanoparticles that can be induced by a change in pH to release a deadly dose of ionized iron within cells.

3D reconstructions of individual nanoparticles
Want to find out how to design and build materials atom by atom?

Directing nanoparticles straight to tumors
Modern anticancer therapies aim to attack tumor cells while sparing healthy tissue.

Sweet nanoparticles trick kidney
Researchers engineer tiny particles with sugar molecules to prevent side effect in cancer therapy.

A megalibrary of nanoparticles
Using straightforward chemistry and a mix-and-match, modular strategy, researchers have developed a simple approach that could produce over 65,000 different types of complex nanoparticles.

Dialing up the heat on nanoparticles
Rapid progress in the field of metallic nanotechnology is sparking a science revolution that is likely to impact all areas of society, according to professor of physics Ventsislav Valev and his team at the University of Bath in the UK.

Illuminating the world of nanoparticles
Scientists at the Okinawa Institute of Science and Technology Graduate University (OIST) have developed a light-based device that can act as a biosensor, detecting biological substances in materials; for example, harmful pathogens in food samples.

Read More: Nanoparticles News and Nanoparticles Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.