Featured Research

from universities, journals, and other organizations

Coal yields plenty of graphene quantum dots

Date:
December 6, 2013
Source:
Rice University
Summary:
Coal is a cost-effective source of abundant graphene quantum dots for photovoltaic, medical, electronic and sensing applications.

An illustration shows the nanostructure of bituminous coal before separation into graphene quantum dots. The Rice University lab of chemist James Tour has developed a method to extract graphene quantum dots in bulk from several types of coal.
Credit: Tour Group/Rice University

The prospect of turning coal into fluorescent particles may sound too good to be true, but the possibility exists, thanks to scientists at Rice University.

Related Articles


The Rice lab of chemist James Tour found simple methods to reduce three kinds of coal into graphene quantum dots (GQDs), microscopic discs of atom-thick graphene oxide that could be used in medical imaging as well as sensing, electronic and photovoltaic applications.

The find was reported today in the journal Nature Communications.

Band gaps determine how a semiconducting material carries an electric current. In quantum dots, band gaps are responsible for their fluorescence and can be tuned by changing the dots' size. The process by Tour and company allows a measure of control over their size, generally from 2 to 20 nanometers, depending on the source of the coal.

There are many ways to make GQDs now, but most are expensive and produce very small quantities, Tour said. Though another Rice lab found a way last year to make GQDs from relatively cheap carbon fiber, coal promises greater quantities of GQDs made even cheaper in one chemical step, he said.

"We wanted to see what's there in coal that might be interesting, so we put it through a very simple oxidation procedure," Tour explained. That involved crushing the coal and bathing it in acid solutions to break the bonds that hold the tiny graphene domains together.

"You can't just take a piece of graphene and easily chop it up this small," he said.

Tour depended on the lab of Rice chemist and co-author Angel Martí to help characterize the product. It turned out different types of coal produced different types of dots. GQDs were derived from bituminous coal, anthracite and coke, a byproduct of oil refining.

The coals were each sonicated in nitric and sulfuric acids and heated for 24 hours. Bituminous coal produced GQDs between 2 and 4 nanometers wide. Coke produced GQDs between 4 and 8 nanometers, and anthracite made stacked structures from 18 to 40 nanometers, with small round layers atop larger, thinner layers. (Just to see what would happen, the researchers treated graphite flakes with the same process and got mostly smaller graphite flakes.)

Tour said the dots are water-soluble, and early tests have shown them to be nontoxic. That offers the promise that GQDs may serve as effective antioxidants, he said.

Medical imaging could also benefit greatly, as the dots show robust performance as fluorescent agents.

"One of the problems with standard probes in fluorescent spectroscopy is that when you load them into a cell and hit them with high-powered lasers, you see them for a fraction of a second to upwards of a few seconds, and that's it," Martí said. "They're still there, but they have been photo-bleached. They don't fluoresce anymore."

Testing in the Martí lab showed GQDs resist bleaching. After hours of excitation, Martí said, the photoluminescent response of the coal-sourced GQDs was barely affected.

That could make them suitable for use in living organisms. "Because they're so stable, they could theoretically make imaging more efficient," he said.

A small change in the size of a quantum dot -- as little as a fraction of a nanometer -- changes its fluorescent wavelengths by a measurable factor, and that proved true for the coal-sourced GQDs, Martí said.

Low cost will also be a draw, according to Tour. "Graphite is $2,000 a ton for the best there is, from the U.K.," he said. "Cheaper graphite is $800 a ton from China. And coal is $10 to $60 a ton.

"Coal is the cheapest material you can get for producing GQDs, and we found we can get a 20 percent yield. So this discovery can really change the quantum dot industry. It's going to show the world that inside of coal are these very interesting structures that have real value."

Co-authors of the work include graduate students Ruquan Ye, Changsheng Xiang, Zhiwei Peng, Kewei Huang, Zheng Yan, Nathan Cook, Errol Samuel, Chih-Chau Hwang, Gedeng Ruan, Gabriel Ceriotti and Abdul-Rahman Raji and postdoctoral research associate Jian Lin, all of Rice. Martí is an assistant professor of chemistry and bioengineering. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science.

The Air Force Office of Scientific Research and the Office of Naval Research funded the work through their Multidisciplinary University Research Initiatives.

Watch a video about graphene quantum dots from coal at http://youtu.be/X6rHW7RxcZQ


Story Source:

The above story is based on materials provided by Rice University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ruquan Ye, Changsheng Xiang, Jian Lin, Zhiwei Peng, Kewei Huang, Zheng Yan, Nathan P. Cook, Errol L.G. Samuel, Chih-Chau Hwang, Gedeng Ruan, Gabriel Ceriotti, Abdul-Rahman O. Raji, Angel A. Martí, James M. Tour. Coal as an abundant source of graphene quantum dots. Nature Communications, 2013; 4 DOI: 10.1038/ncomms3943

Cite This Page:

Rice University. "Coal yields plenty of graphene quantum dots." ScienceDaily. ScienceDaily, 6 December 2013. <www.sciencedaily.com/releases/2013/12/131206111709.htm>.
Rice University. (2013, December 6). Coal yields plenty of graphene quantum dots. ScienceDaily. Retrieved November 26, 2014 from www.sciencedaily.com/releases/2013/12/131206111709.htm
Rice University. "Coal yields plenty of graphene quantum dots." ScienceDaily. www.sciencedaily.com/releases/2013/12/131206111709.htm (accessed November 26, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Wednesday, November 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

NASA's First 3-D Printer In Space Creates Its First Object

NASA's First 3-D Printer In Space Creates Its First Object

Newsy (Nov. 26, 2014) — The International Space Station is now using a proof-of-concept 3D printer to test additive printing in a weightless, isolated environment. Video provided by Newsy
Powered by NewsLook.com
Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Reuters - Innovations Video Online (Nov. 26, 2014) — Innovative recycling project in La Paz separates city waste and converts plastic garbage into school furniture made from 'plastiwood'. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Blu-Ray Discs Getting Second Run As Solar Panels

Blu-Ray Discs Getting Second Run As Solar Panels

Newsy (Nov. 26, 2014) — Researchers at Northwestern University are repurposing Blu-ray movies for better solar panel technology thanks to the discs' internal structures. Video provided by Newsy
Powered by NewsLook.com
Today's Prostheses Are More Capable Than Ever

Today's Prostheses Are More Capable Than Ever

Newsy (Nov. 26, 2014) — Advances in prosthetics are making replacement body parts stronger and more lifelike than they’ve ever been. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins