Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Space Travel News .




SPACE TRAVEL
Researchers use graphene quantum dots to detect humidity and pressure
by Staff Writers
Manhattan KS (SPX) May 10, 2013


Vikas Berry, William H. Honstead professor of chemical engineering, and his research team are using graphene quantum dots to improve electron tunneling-based sensing devices. For a larger version of this image please go here.

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.

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."

The research is dedicated to Vasanta Pallem, a postdoctoral researcher who was involved in the work and died in a recent apartment fire.

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 the abstract "Covalent functionalization of dipole-modulating molecules on trilayer graphene: an avenue for graphene-interfaced molecular machines." here.

.


Related Links
Kansas State University
Space Tourism, Space Transport and Space Exploration News






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





SPACE TRAVEL
Success Continues as NASA's Orion Parachute Tests Get More Difficult
Yuma AZ (SPX) May 07, 2013
A test version of NASA's Orion spacecraft landed safely during a simulation of two types of parachute failures Wednesday, May 1. In the test, conducted in Yuma, Ariz., the mock capsule was traveling about 250 mph when the parachutes were deployed. That is the highest speed the craft has experienced as part of the test series designed to certify Orion's parachute system for carrying humans. ... read more


SPACE TRAVEL
NASA Awards Contract to Modify Mobile Launcher

Angara Rocket Launch Delayed to 2014

ESA's Vega launcher scores new success with Proba-V

European Vega rocket launch delayed due to weather

SPACE TRAVEL
NASA Curiosity Rover Team Selects Second Drilling Target on Mars

Opportunity Making Smallest Turn Yet, As Dust Storm Affects Rover

More than 78,000 people apply for one-way trip to Mars

Austria Aims For Mars Via Morocco

SPACE TRAVEL
Northrop Grumman Completes Lunar Lander Study for Golden Spike Company

Scientists Use Laser to Find Soviet Moon Rover

Characterizing The Lunar Radiation Environment

Russia rekindles Moon exploration program, intends setting up first human outposts there

SPACE TRAVEL
'Vulcan' wins Pluto moon name vote

Public to vote on names for Pluto moons

The PI's Perspective: The Seven-Year Itch

New Horizons Gets a New Year's Workout

SPACE TRAVEL
NASA's Hubble Space Telescope Finds Dead Stars Polluted with Planet Debris

The Great Exoplanet Debate

NASA's Spitzer Puts Planets in a Petri Dish

Two New Exoplanets Detected with Kepler, SOPHIE and HARPS-N

SPACE TRAVEL
Boeing X-51A WaveRider Sets Record with Successful Fourth Flight

AFOSR-funded research key to revolutionary 'green' spacecraft propellant

Air Force's experimental scramjet aircraft hits Mach 5.1 -- 3,880 mph

SNC's Hybrid Rocket Engines Power SpaceShipTwo on its First Powered Flight Test

SPACE TRAVEL
China launches communications satellite

On Course for Shenzhou 10

Yuanwang III, VI depart for space-tracking missions

Shenzhou's Shadow Crew

SPACE TRAVEL
Dawn On Route From Vesta to Ceres

Nine-Year-Old Names Target of UA-led NASA Mission

Asteroid Could Fly 8,600 Km From Earth in 2026

Astronomer: Asteroid could make close flyby in 2026




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement