Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Graphene Quantum Dots May Someday Tell if It Will Rain on Mars

10.05.2013
The latest research from a Kansas State University chemical engineer may help improve humidity and pressure sensors, particularly those used in outer space.

Vikas Berry, William H. Honstead professor of chemical engineering, and his research team are using graphene quantum dots to improve sensing devices in a twofold project. The first part involves producing the graphene quantum dots, which are ultrasmall pieces of graphene. Graphene is a single-atom thick sheet of carbon atoms and has superior electrical, mechanical and optical properties. The second part of the project involves incorporating these quantum dots into electron-tunneling based sensing devices.


Kansas State University

Vikas Berry, Kansas State University professor of chemical engineering, and his research team are using graphene quantum dots to improve electron tunneling-based sensing devices.

To create the graphene quantum dots, the researchers used nanoscale cutting of graphite to produce graphene nanoribbons. T.S. Sreeprasad, a postdoctoral researcher in Berry's group, chemically cleaved these ribbons into 100 nanometers lateral dimensions.

The scientists assembled the quantum dots into a network on a hydroscopic microfiber that was attached to electrodes on its two sides. They placed the assembled quantum dots less than a nanometer apart so they were not completely connected. The assembling of dots is similar to a corn on the cob structure -- the corn kernels are nanoscale quantum dots and the cob is the microfiber.

Several researchers -- including four 2012 alumni in chemical engineering: Augustus Graham, Alfredo A. Rodriguez, Jonathan Colston and Evgeniy Shishkin -- applied a potential across the fiber and controlled the distance between the quantum dots by adjusting the local humidity, which changes the current flowing through the dots.

"If you reduce the humidity around this device, the water held by this fiber is lost," Berry said. "As a result, the fiber shrinks and the graphenic components residing atop come close to one another in nanometer scale. This increases the electron transport from one dot to the next. Just by reading the currents one can tell the humidity in the environment."

Decreasing the distance between the graphene quantum dots by 0.35 nanometers increased the device's conductivity by 43-fold, Berry said. Furthermore, because air contains water, reducing air pressure decreased its water content and caused the graphene quantum dots to get closer together, which increased conductivity. Quantum mechanics suggests that electrons have a finite probability to tunnel from an electrode to a nonconnected electrode, Berry said. This probability is inversely and exponentially proportional to the tunneling distance, or the gap between the electrodes.

The research has numerous applications, particularly in improving sensors for humidity, pressure or temperature.

"These devices are unique because, unlike most humidity sensors, these are more responsive in vacuum," Berry said. "For example, these devices can be incorporated into space shuttles, where low humidity measurements are required. These sensors might also be able to detect trace amounts of water on Mars, which has 1/100th of the earth's atmospheric pressure. This is because the device measures humidity at a much higher resolution in vacuum."

While the heart of the device is the modulation of electron tunneling, the response of the device is through the polymer microfiber, Berry said. His team also is looking at changing the polymer to find other applications for this research.

"If you replace this polymer with a polymer that is responsive to other stimuli, you can make a different kind of sensor," Berry said. "I envision this project to have a broad impact on sensing."

The research is supported by Berry's five-year, $400,000 National Science Foundation CAREER award. The research results appear in a recent issue of the journal Nano Letters in an article titled "Electron-tunneling modulation in percolating-network of graphene quantum dots: fabrication, phenomenological understanding, and humidity/pressure sensing applications."

Molecular machines
Berry's research team also is studying molecular machines interfaced with graphene. In this work, the researchers are able to mechanically actuate the molecules, which undergo a change in the electric field around them and influence the carrier density of the interfaced graphene. This work will appear in an upcoming issue of the journal Small in an article titled "Covalent functionalization of dipole-modulating molecules on trilayer graphene: an avenue for graphene-interfaced molecular machines."

The researchers have found that graphene responds sensitively to molecular motion. Phong Nguyen, a doctoral student in chemical engineering and lead author of the work, tethered actuating molecules on graphene and measured the device's response.

"The next phase of science beyond nanotechnology will be molecular technology," Berry said. "We are working on developing routes to incorporate molecular machines into devices."

Other Kansas State University researchers involved include: Sreeprasad; Kabeer Jasuja, 2011 doctoral graduate in chemical engineering; Nihar Mohanty, 2011 doctoral graduate in chemical engineering; Myles Ikenberry, doctoral student in chemical engineering, Manhattan; and Keith Hohn, professor of chemical engineering. Other researchers include Junwen Li, graduate student at the University of Pennsylvania, and Vivek B. Shenoy professor of materials science and engineering at the University of Pennsylvania.

Read more about the research at
http://www.k-state.edu/media/newsreleases/may13/berry5813.html
Vikas Berry
785-532-5519
vberry@k-state.edu

Vikas Berry | Newswise
Further information:
http://www.k-state.edu

More articles from Physics and Astronomy:

nachricht Temperature-controlled fiber-optic light source with liquid core
20.06.2018 | Leibniz-Institut für Photonische Technologien e. V.

nachricht New material for splitting water
19.06.2018 | American Institute of Physics

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Better model of water under extreme conditions could aid understanding of Earth's mantle

21.06.2018 | Earth Sciences

What are the effects of coral reef marine protected areas?

21.06.2018 | Life Sciences

The Janus head of the South Asian monsoon

21.06.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>