PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Researchers use graphene quantum dots to detect humidity and pressure

2013-05-09
(Press-News.org) MANHATTAN, KAN. -- 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."

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.


ELSE PRESS RELEASES FROM THIS DATE:

Study shows that people organize daily travel efficiently

2013-05-09
CAMBRIDGE, MA -- Studies of human mobility usually focus on either the small scale — determining the origins, destinations and travel modes of individuals' daily commutes — or the very large scale, such as using air-travel patterns to track the spread of epidemics over time. The large-scale studies, most of which are made possible by the vast data generated and collected by new technologies like sensors and cellphones, are very good at describing the big picture, but don't provide much detail at the individual level. Smaller-scale studies have the opposite characteristic: ...

Researchers find a way to make steel without greenhouse-gas emissions

2013-05-09
CAMBRIDGE, MA -- Anyone who has seen pictures of the giant, red-hot cauldrons in which steel is made — fed by vast amounts of carbon, and belching flame and smoke — would not be surprised to learn that steelmaking is one of the world's leading industrial sources of greenhouse gases. But remarkably, a new process developed by MIT researchers could change all that. The new process even carries a couple of nice side benefits: The resulting steel should be of higher purity, and eventually, once the process is scaled up, cheaper. Donald Sadoway, the John F. Elliott Professor ...

Engineers fine-tune the sensitivity of nano-chemical sensor

2013-05-09
Researchers have discovered a technique for controlling the sensitivity of graphene chemical sensors. The sensors, made of an insulating base coated with a graphene sheet--a single-atom-thick layer of carbon--are already so sensitive that they can detect an individual molecule of gas. But manipulating the chemical properties of the insulating layer, without altering the graphene layer, may yet improve their ability to detect the most minute concentrations of various gases. The finding "will open up entirely new possibilities for modulation and control of the chemical ...

Setting the standard for sustainable bioenergy crops

2013-05-09
URBANA – Bioenergy crops, such as Miscanthus and switchgrass, appear to be promising resources for renewable energy, but these new crops did not come with a manual on how to measure details on their sustainability impacts. Jody Endres, University of Illinois professor of energy and environmental law and chair of the Council on Sustainable Biomass Production (CSBP) says standards are needed so farmers, ethanol producers, and others in the biofuels industry will all be on the same page here in the United States as well as in Europe and Brazil. Endres believes that three ...

New malaria tool shows which kids at greatest risk

2013-05-09
Researchers at Michigan State University have identified a test that can determine which children with malaria are likely to develop cerebral malaria, a much more life-threatening form of the disease. The screening tool could be a game-changer in resource-limited rural health clinics where workers see hundreds of children with malaria each day and must decide which patients can be sent home with oral drugs and which need to be taken to hospitals for more comprehensive care. "Rural health workers have to make these decisions with very little objective data, and the consequences ...

Dietary flexibility may have helped some large predators survive after last ice age

2013-05-09
During the late Pleistocene, a remarkably diverse assemblage of large-bodied mammals inhabited the "mammoth steppe," a cold and dry yet productive environment that extended from western Europe through northern Asia and across the Bering land bridge to the Yukon. Of the large predators--wolves, bears, and big cats--only the wolves and bears were able to maintain their ranges well after the end of the last ice age. A new study led by researchers at the University of California, Santa Cruz, suggests that dietary flexibility may have been an important factor giving wolves ...

Spintronics discovery

2013-05-09
From powerful computers to super-sensitive medical and environmental detectors that are faster, smaller and use less energy — yes, we want them, but how do we get them? In research that is helping to lay the groundwork for the electronics of the future, University of Delaware scientists have confirmed the presence of a magnetic field generated by electrons which scientists had theorized existed, but that had never been proven until now. The finding, which is reported in the journal Nature Communications, expands the potential for harnessing the "spin" or magnetic properties ...

Exotic atoms hold clues to unsolved physics puzzle at the dawn of the universe

2013-05-09
ANN ARBOR---An international team of physicists has found the first direct evidence of pear shaped nuclei in exotic atoms. The findings could advance the search for a new fundamental force in nature that could explain why the Big Bang created more matter than antimatter---a pivotal imbalance in the history of everything. "If equal amounts of matter and antimatter were created at the Big Bang, everything would have annihilated, and there would be no galaxies, stars, planets or people," said Tim Chupp, a University of Michigan professor of physics and biomedical engineering ...

George Washington University biologist maps the family tree of all known snake and lizard groups

2013-05-09
WASHINGTON- A George Washington University biologist and a team of researchers have created the first large-scale evolutionary family tree for every snake and lizard around the globe. The findings were recently published in the journal BMC Evolutionary Biology. Alex Pyron, the Robert F. Griggs Assistant Professor of Biology in GW's Columbian College of Arts and Sciences, along with researchers from the City University of New York and Arizona State University, detail the cataloguing of 4,161 species of snakes and lizards, or squamates. "Squamates include all lizards ...

Many plastic surgeons view social media as important tool for promoting their practice

2013-05-09
Social media has revolutionized the way in which people and businesses interact, and it is taking on a growing role in the health care industry. A new UCLA study looking at the use of social media among plastic surgeons found that roughly half of these specialists use social media tools. Plastic surgeons have been leaders among medical specialists in the development of interactive websites to promote their practices and educate patients, said the study's principal investigator and senior author, Dr. Reza Jarrahy, an associate clinical professor of plastic and reconstructive ...

LAST 30 PRESS RELEASES:

Being consistently physically active in adulthood linked to 30–40% lower risk of death

Nerve pain drug gabapentin linked to increased dementia, cognitive impairment risks

Children’s social care involvement common to nearly third of UK mums who died during perinatal period

‘Support, not judgement’: Study explores links between children’s social care involvement and maternal deaths

Ethnic minority and poorer children more likely to die in intensive care

Major progress in fertility preservation after treatment for cancer of the lymphatic system

Fewer complications after additional ultrasound in pregnant women who feel less fetal movement

Environmental impact of common pesticides seriously underestimated

The Milky Way could be teeming with more satellite galaxies than previously thought

New study reveals surprising reproductive secrets of a cricket-hunting parasitoid fly

Media Tip Sheet: Symposia at ESA2025

NSF CAREER Award will power UVA engineer’s research to improve drug purification

Tiny parasitoid flies show how early-life competition shapes adult success

New coating for glass promises energy-saving windows

Green spaces boost children’s cognitive skills and strengthen family well-being

Ancient trees dying faster than expected in Eastern Oregon

Study findings help hone precision of proven CVD risk tool

Most patients with advanced melanoma who received pre-surgical immunotherapy remain alive and disease free four years later

Introducing BioEmu: A generative AI Model that enables high-speed and accurate prediction of protein structural ensembles

Replacing mutated microglia with healthy microglia halts progression of genetic neurological disease in mice and humans

New research shows how tropical plants manage rival insect tenants by giving them separate ‘flats’

Condo-style living helps keep the peace inside these ant plants

Climate change action could dramatically limit rising UK heatwave deaths

Annual heat-related deaths projected to increase significantly due to climate and population change

Researchers discover new way cells protect themselves from damage

Rivers choose their path based on erosion — a discovery that could transform flood planning and restoration

New discovery reveals dopamine operates with surgical precision, not as a broad signal

New AI tool gives a helping hand to x ray diagnosis

New Leicester study reveals hidden heart risks in women with Type 2 Diabetes

Over 400 different types of nerve cell have been grown – far more than ever before

[Press-News.org] Researchers use graphene quantum dots to detect humidity and pressure