Navigation Links
Graphene quantum dots: The next big small thing
Date:1/12/2012

A Rice University laboratory has found a way to turn common carbon fiber into graphene quantum dots, tiny specks of matter with properties expected to prove useful in electronic, optical and biomedical applications.

The Rice lab of materials scientist Pulickel Ajayan, in collaboration with colleagues in China, India, Japan and the Texas Medical Center, discovered a one-step chemical process that is markedly simpler than established techniques for making graphene quantum dots. The results were published online this month in the American Chemical Society's journal Nano Letters.

"There have been several attempts to make graphene-based quantum dots with specific electronic and luminescent properties using chemical breakdown or e-beam lithography of graphene layers," said Ajayan, Rice's Benjamin M. and Mary Greenwood Anderson Professor of Mechanical Engineering and Materials Science and of Chemistry. "We thought that as these nanodomains of graphitized carbons already exist in carbon fibers, which are cheap and plenty, why not use them as the precursor?"

Quantum dots, discovered in the 1980s, are semiconductors that contain a size- and shape-dependent band gap. These have been promising structures for applications that range from computers, LEDs, solar cells and lasers to medical imaging devices. The sub-5 nanometer carbon-based quantum dots produced in bulk through the wet chemical process discovered at Rice are highly soluble, and their size can be controlled via the temperature at which they're created.

The Rice researchers were attempting another experiment when they came across the technique. "We tried to selectively oxidize carbon fiber, and we found that was really hard," said Wei Gao, a Rice graduate student who worked on the project with lead author Juan Peng, a visiting student from Nanjing University who studied in Ajayan's lab last year. "We ended up with a solution and decided to look at a few drops with a transmission electron microscope."

The specks they saw were bits of graphene or, more precisely, oxidized nanodomains of graphene extracted via chemical treatment of carbon fiber. "That was a complete surprise," Gao said. "We call them quantum dots, but they're two-dimensional, so what we really have here are graphene quantum discs." Gao said other techniques are expensive and take weeks to make small batches of graphene quantum dots. "Our starting material is cheap, commercially available carbon fiber. In a one-step treatment, we get a large amount of quantum dots. I think that's the biggest advantage of our work," she said.

Further experimentation revealed interesting bits of information: The size of the dots, and thus their photoluminescent properties, could be controlled through processing at relatively low temperatures, from 80 to 120 degrees Celsius. "At 120, 100 and 80 degrees, we got blue, green and yellow luminescing dots," she said.

They also found the dots' edges tended to prefer the form known as zigzag. The edge of a sheet of graphene -- the single-atom-thick form of carbon -- determines its electrical characteristics, and zigzags are semiconducting.

Their luminescent properties give graphene quantum dots potential for imaging, protein analysis, cell tracking and other biomedical applications, Gao said. Tests at Houston's MD Anderson Cancer Center and Baylor College of Medicine on two human breast cancer lines showed the dots easily found their way into the cells' cytoplasm and did not interfere with their proliferation.

"The green quantum dots yielded a very good image," said co-author Rebeca Romero Aburto, a graduate student in the Ajayan Lab who also studies at MD Anderson. "The advantage of graphene dots over fluorophores is that their fluorescence is more stable and they don't photobleach. They don't lose their fluorescence as easily. They have a depth limit, so they may be good for in vitro and in vivo (small animal) studies, but perhaps not optimal for deep tissues in humans.

"But everything has to start in the lab, and these could be an interesting approach to further explore for bioimaging," Romero Alburto said. "In the future, these graphene quantum dots could have high impact because they can be conjugated with other entities for sensing applications, too."


'/>"/>
Contact: David Ruth
david@rice.edu
713-348-6327
Rice University
Source:Eurekalert

Related biology technology :

1. Graphene pioneers follow in Nobel footsteps
2. New graphene-based material clarifies graphite oxide chemistry
3. Researchers discover method for mass production of nanomaterial graphene
4. Light-speed nanotech: Controlling the nature of graphene
5. Scientists prove graphenes edge structure affects electronic properties
6. Graphene yields secrets to its extraordinary properties
7. Graphene may have advantages over copper for IC interconnects at the nanoscale
8. Bilayer graphene gets a bandgap
9. Material world: Graphenes versatility promises new applications
10. UCR scientists manipulate ripples in graphene, enabling strain-based graphene electronics
11. Researchers design new graphene-based, nano-material with magnetic properties
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/21/2017)... 2017   Boston Biomedical , an industry leader ... cancer stemness pathways, today presented data from two clinical ... 2017 American Society of Clinical Oncology (ASCO) Gastrointestinal Cancers ... In a Phase Ib/II study of napabucasin ... cancer stemness pathways by targeting STAT3 – colorectal cancer ...
(Date:1/20/2017)... ... January 20, 2017 , ... ... Technologies, announced today the next evolution in spinal fusion, the MISquito Percutaneous ... contrast to the competition, SpineFrontier is focused on technique driven product solutions ...
(Date:1/19/2017)... Research and Markets ... announced the addition of the "Implantable Biomaterials Market ... report to their offering. Report Highlights: ... analysis on current and future market trends to identify the investment opportunities ... the base numbers Key market trends across the business ...
(Date:1/19/2017)... 19, 2017 AquaBounty Technologies, Inc. (AIM: ABTU; ... in aquaculture and a majority-owned subsidiary of Intrexon Corporation ... completed the listing of its common shares on the ... Intrexon. "AquaBounty,s listing on NASDAQ represents an ... exposure to the U.S. markets as we advance plans ...
Breaking Biology Technology:
(Date:1/18/2017)... Jan. 18, 2017  In vitro diagnostic (IVD) companies ... and acquisitions (M&A), and Kalorama Information expects that trend ... have been shifting. Generally, uncertainty in reimbursement and healthcare ... U.S. has changed the acquisitions landscape. Instead of looking ... companies buying partners outside of their home country and ...
(Date:1/12/2017)... PORTLAND, Oregon and PUNE, India , January 12, 2017 ... Technology Market: Opportunities and Forecasts, 2015 - 2022," projects that the global biometric technology ... CAGR of 19.4% from 2016 to 2022. Continue Reading ... ... ...
(Date:1/6/2017)... , Jan. 5, 2017  Delta ID Inc., ... iris scanning technology for automotive at CES® 2017. Delta ... GNTX ) to demonstrate the use of iris scanning ... and authenticate the driver in a car, and as ... the driving experience. Delta ID and Gentex ...
Breaking Biology News(10 mins):