Gold nanorods assemble themselves into rings

Mar 09, 2007
Hybrid Nanorods
Transmission electron microscopy (TEM) image of a circular superstructure of hybrid nanorods templated by a water microdroplet. Credit: Bishnu Khanal

Rice University chemists have discovered that tiny building blocks known as gold nanorods spontaneously assemble themselves into ring-like superstructures.

This finding, which will be published as the inside cover article of the March 19 international edition of the chemistry journal Angewandte Chemie, could potentially lead to the development of novel nanodevices like highly sensitive optical sensors, superlenses, and even invisible objects for use in the military.

"Finding new ways to assemble nano-objects into superstructures is an important task because at the nanoscale, the properties of those objects depend on the arrangement of individual building blocks," said principal investigator Eugene Zubarev, the Norman Hackerman-Welch Young Investigator and assistant professor of chemistry at Rice.

Although ring-like assemblies have been observed in spherical nanoparticles and other symmetrical molecules, until now such structures had not been documented with rod-shaped nanostructures.

Like many nanoscale objects, gold nanorods are several billionths of a meter, or 1,000 times smaller than a human hair. Zubarev used hybrid nanorods for this research because attached to their surface are thousands of polymer molecules, which are flexible chainlike structures. The central core of the nanorods is an inorganic crystal, but the polymers attached to the outside are organic species. The combination of the inorganic and organic features resulted in a hybrid structure that proved to be critical to the study.

Working with Rice graduate student Bishnu Khanal, Zubarev placed the nanorods in a solution of organic solvent called chloroform. As the chloroform evaporated, its surface temperature dropped low enough to cause condensation of water droplets from the air, much like how dew forms. As thousands and thousands of microdroplets of water formed on the surface of the liquid chloroform, the nanorods that had been suspended in the solution started to press up against the round droplets and form rings around them. The polymer coating prevented the rods from being absorbed into the droplets because it is insoluble in water.

After the droplets evaporated, the nanorods remained in their ring formation.

"When nanorods are organized into a ring, significant changes in their optical and electromagnetic properties occur," Zubarev said. "These can have technological applications in the area of metamaterials, which have enormous potential in opto-electronics, communications and military applications." Zubarev said thousands of well-defined rings can be produced in a matter of seconds using the approach from his study. "This method is surprisingly simple and can be used for organizing nanocrystals of various shapes, size and chemical composition into circular arrays."

Source: Rice University

Explore further: Tiny wires could provide a big energy boost

Related Stories

Recommended for you

Tiny wires could provide a big energy boost

3 hours ago

Wearable electronic devices for health and fitness monitoring are a rapidly growing area of consumer electronics; one of their biggest limitations is the capacity of their tiny batteries to deliver enough ...

Graphene sheets enable ultrasound transmitters

3 hours ago

University of California, Berkeley, physicists have used graphene to build lightweight ultrasonic loudspeakers and microphones, enabling people to mimic bats or dolphins' ability to use sound to communicate ...

Project uses crowd computing to improve water filtration

21 hours ago

Nearly 800 million people worldwide don't have access to safe drinking water, and some 2.5 billion people live in precariously unsanitary conditions, according to the Centers for Disease Control and Prevention. ...

Engineering the world's smallest nanocrystal

Jul 06, 2015

In the natural world, proteins use the process of biomineralization to incorporate metallic elements into tissues, using it to create diverse materials such as seashells, teeth, and bones. However, the way ...

A stretchy mesh heater for sore muscles

Jul 03, 2015

If you suffer from chronic muscle pain a doctor will likely recommend for you to apply heat to the injury. But how do you effectively wrap that heat around a joint? Korean Scientists at the Center for Nanoparticle ...

Polymer mold makes perfect silicon nanostructures

Jul 03, 2015

Using molds to shape things is as old as humanity. In the Bronze Age, the copper-tin alloy was melted and cast into weapons in ceramic molds. Today, injection and extrusion molding shape hot liquids into ...

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.