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: From tobacco to cyberwood

Related Stories

Ultra-small block 'M' illustrates big ideas in drug delivery

Feb 26, 2015

By making what might be the world's smallest three-dimensional unofficial Block "M," University of Michigan researchers have demonstrated a nanoparticle manufacturing process capable of producing multilayered, precise shapes.

Magnetic nanoparticles enhance performance of solar cells

Feb 25, 2015

Magnetic nanoparticles can increase the performance of solar cells made from polymers - provided the mix is right. This is the result of an X-ray study at DESY's synchrotron radiation source PETRA III. Adding ...

Recommended for you

From tobacco to cyberwood

7 hours ago

Swiss scientists from ETH Zurich have developed a thermometer that is at least 100 times more sensitive than previous temperature sensors. It consists of a bio-synthetic hybrid material of tobacco cells and nanotubes.

Scientists convert microbubbles to nanoparticles

10 hours ago

Biomedical researchers led by Dr. Gang Zheng at Princess Margaret Cancer Centre have successfully converted microbubble technology already used in diagnostic imaging into nanoparticles that stay trapped in tumours to potentially ...

'Atomic chicken-wire' is key to faster DNA sequencing

14 hours ago

An unusual and very exciting form of carbon - that can be created by drawing on paper- looks to hold the key to real-time, high throughput DNA sequencing, a technique that would revolutionise medical research ...

3-D images of tiny objects down to 25 nanometres

15 hours ago

Scientists at the Paul Scherrer Institute and ETH Zurich (Switzerland) have created 3D images of tiny objects showing details down to 25 nanometres. In addition to the shape, the scientists determined how ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.