Carbon-based quantum dots could mean 'greener' technology in medicine, biology

May 23, 2006
Bacterial spores illuminated with carbon-based quantum dots
Microscope image of bacterial spores (Bacillus subtilis) labeled with luminescent carbon nanoparticles. B. subtilis serves as a common model for anthrax research. These carbon nanoparticles, or carbon dots, could lead to safer, disposable biosensors to detect biological warfare agents. Measurement shown is 5 micrometers. Image courtesy of Dr. Ya-Ping Sun of Clemson University

Chemists at Clemson University say they have developed a new type of quantum dot that is the first to be made from carbon. Like their metal-based counterparts, these nano-sized "carbon dots" glow brightly when exposed to light and show promise for a broad range of applications, including improved biological sensors, medical imaging devices and tiny light-emitting diodes (LEDs), the researchers say.

The development, which could help broaden the use of quantum dot technologies, is described in a research communications published online today by the Journal of the American Chemical Society. The paper will appear in the journal's June 7 print edition.

The carbon-based quantum dots show less potential for toxicity and environmental harm and have the potential to be less expensive than metal-based quantum dots, the scientists say. Cheap disposable sensors that can detect hidden explosives and biological warfare agents such as anthrax also are among the possibilities envisioned by the researchers.

"Carbon is hardly considered to be a semiconductor, so luminescent carbon nanoparticles are very interesting both fundamentally and practically," says study leader Ya-Ping Sun, Ph.D., a chemist at the university, located in Clemson, S.C. "It represents a new platform for the development of luminescent nanomaterials for a wide range of applications."

Quantum dots have generated much interest in recent years, especially for potential applications in biology and medicine. These tiny particles -- thousands of times smaller than the width of a human hair -- have been developed from compounds composed of lead, cadmium and, more recently, silicon. But these materials have raised concerns over potential toxicity and environmental harm. As a result, scientists have begun to look for more benign compounds for making quantum dots.

Researchers have known for some time that carbon nanoparticles, due partly to their enormous surface area, have unusual chemical and physical properties quite different from their bulk form. Using nanoparticles produced from graphite, Sun and his associates demonstrated that when these carbon nanoparticles are covered with special polymers, they glow brightly when exposed to light, behaving as tiny light bulbs. The dots glow continuously as long as a light source is present, they say.

The scientists believe that this photoluminescence may be due to the presence of "pockets" or holes on the surface of the carbon dots that trap energy. The polymer coating acts as a "molecular band-aid," enabling light emission from the inside of the polymer casing, they say. Scientists believe that metal-based quantum dots emit light by a somewhat different mechanism.

The two-sided polymer coating allows researchers to attach antibodies or other labeling materials to the carbon dot, says Sun. This could lead to improved dyes for medical imaging and also the development of sensors that light up in the presence of a target, such as anthrax or even food-borne pathogens. In lab studies, the researchers successfully labeled anthrax-like spores with luminescent carbon dots, resulting in glowing spores that were easily viewed under a microscope.

Source: American Chemical Society

Explore further: Scientists use nanoparticles to shut down mechanism that drives cancer growth

Related Stories

Graphene quantum dot LEDs

Jun 15, 2015

The first graphene quantum dot light-emitting diodes (GQD-LEDs), fabricated by using high-quantum-yield graphene quantum dots through graphite intercalation compounds, exhibit luminance in excess of 1,000 ...

Recommended for you

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 ...

Better memory with faster lasers

Jul 02, 2015

DVDs and Blu-ray disks contain so-called phase-change materials that morph from one atomic state to another after being struck with pulses of laser light, with data "recorded" in those two atomic states. ...

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.