Magnetic nanoparticles assembled into long chains

Oct 20, 2005
Magnetic nanoparticles assembled into long chains

Chains of 1 million magnetic nanoparticles have been assembled and disassembled in a solution of suspended particles in a controlled way, scientists at the National Institute of Standards and Technology (NIST) report. Such particles and structures, once their properties are more fully understood and can be manipulated reliably, may be useful in applications such as medical imaging and information storage.

Image: Colorized transmission electron micrograph showing chains of cobalt nanoparticles. Image credit: G. Cheng, A.R. Hight Walker/NIST

The NIST work, scheduled to be featured on the cover of an upcoming issue of Langmuir* (an American Chemical Society journal), is the first to demonstrate the formation and control of centimeter-long chains of magnetic nanoparticles of a consistent size and quality in a solution. The researchers spent several years learning how to make cobalt particles with controllable size and shape, and they hope to use this knowledge to eventually "build" useful structures.

The researchers induce the nanoparticles to form linear chains by subjecting them to a weak magnetic field--about the same strength as a refrigerator magnet. The particles line up because the nanoparticles act like tiny bar magnets, all facing the same direction as the applied field. Once this alignment occurs, the attraction between particles is so strong that reversing the direction of the applied magnetic field causes the whole chain to rotate 180 degrees. When the magnetic field is turned off, the chains fold into three-dimensional coils. When the solution is lightly shaken, the chains fall apart into small rings. NIST scientists used optical and transmission electron microscopes to characterize these structures.

Magnetic particles have already been used in medical imaging and information storage, and nano-sized particles may offer unique or improved properties. For example, magnetic nanoparticle dyes may improve contrast between healthy and diseased tissue in magnetic resonance imaging (MRI), a possibility under study by a different NIST research group. The authors of the Langmuir paper are now developing methods to improve the biocompatibility of these magnetic nanoparticles.

*G. Cheng, D. Romero, G.T. Fraser, and A.R. Hight Walker. 2005. Magnetic-field-induced assemblies of cobalt nanoparticles. Langmuir. December. Posted online Oct. 12.

Source: NIST

Explore further: A crystal wedding in the nanocosmos

add to favorites email to friend print save as pdf

Related Stories

The science that stumped Einstein

Jul 01, 2014

In 1908, the physics world woke up to a puzzle whose layers have continued to stump the greatest scientists of the century ever since. That year, Dutch physicist Kamerlingh Onnes cooled mercury down to -450° ...

Recommended for you

A crystal wedding in the nanocosmos

4 hours ago

Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the Vienna University of Technology and the Maria Curie-Skłodowska University Lublin have succeeded in embedding nearly perfect semiconductor ...

PPPL studies plasma's role in synthesizing nanoparticles

Jul 22, 2014

DOE's Princeton Plasma Physics Laboratory (PPPL) has received some $4.3 million of DOE Office of Science funding, over three years, to develop an increased understanding of the role of plasma in the synthesis ...

User comments : 0