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

New process isolates promising material

Molybdenum disulfide has emerged as a leading successor to graphene

2014-11-13
(Press-News.org) After graphene was first produced in the lab in 2004, thousands of laboratories began developing graphene products worldwide. Researchers were amazed by its lightweight and ultra-strong properties. Ten years later, scientists now search for other materials that have the same level of potential.

"We continue to work with graphene, and there are some applications where it works very well," said Mark Hersam, the Bette and Neison Harris Chair in Teaching Excellence at Northwestern University's McCormick School of Engineering and Applied Science, who is a graphene expert. "But it's not the answer to all the world's problems."

Part of a family of materials called transition metal dichalcogenides, molybdenum disulfide (MoS2) has emerged as a frontrunner material for exploration in Hersam's lab. Like graphene, it can be exfoliated into atomically thin sheets. As it thins to the atomic limit, it becomes fluorescent, making it useful for optoelectronics, such as light-emitting diodes, or light-absorbing devices, such as solar cells. MoS2 is also a true semiconductor, making it an excellent candidate for electronics, and it historically has been used in catalysis to remove sulfur from crude oil, which prevents acid rain.

Hersam's challenge was to find a way to isolate atomically thin sheets of this promising material at a larger scale. For the past six years, his lab has developed methods for exfoliating thin layers of graphene from graphite, using solution-based methods.

"You would think it would be easy to do the same thing for molybdenum disulfide," he said. "But the problem is that while the exfoliation is similar to graphene, the separation is considerably more challenging."

Hersam's research is described in the paper "Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted gradient ultracentrifugation," which was published in the Nov. 13 issue of Nature Communications.

To sort graphene layers, Hersam used centrifugal force to separate materials by density. To do this, he and his group added the material to a centrifuge tube along with a gradient of water-based solution. Upon centrifugation, the denser species move toward the bottom, creating layers of densities within the centrifuge tube. Graphene sorts into single layer sheets toward the top, then bilayer sheets, trilayer, and so on. Because graphene has a relatively low density, it easily sorts compared to higher density materials.

"If I use the exact same process with molybdenum disulfide, its higher density will cause it to crash out," Hersam said. "It exceeds the maximum density of the gradient, which required an innovative solution."

Hersam needed to take the inherently dense material and effectively reduce its density without changing the material itself. He realized that this goal could be achieved by tuning the density of the molecules used to disperse MoS2. In particular, the use of bulkier polymer dispersants allowed the effective density of MoS2 to be reduced into the range of the density gradient. In this manner, the sheets of MoS2 floated at layered positions instead of collecting as the bottom of the centrifuge tube. This technique works not just for MoS2, but for other materials in the transition metal dichalcogenides family.

"Now we can isolate single layer, bilayer, or trilayer transition metal dichalcogenides in a scalable manner," Hersam said. "This process will allow us to explore their utility in large-scale applications, such as electronics, optoelectronics, catalysis, and solar cells."

INFORMATION:



ELSE PRESS RELEASES FROM THIS DATE:

High blood pressure puts 1 in 4 Nigerians at risk, study says

2014-11-13
High blood pressure - already a massive hidden killer in Nigeria - is set to sharply rise as the country adopts western lifestyles, a study suggests. Researchers who conducted the first up-to-date nationwide estimate of the condition in Nigeria warn that this will strain the country's already-stretched health system. Increased public awareness, lifestyle changes, screening and early detection are vital to tackle the increasing threat of the disease, they say. High blood pressure - also known as hypertension - is twice as high in Nigeria compared with other East ...

African Americans at greater risk from stroke and other cerebrovascular diseases

2014-11-13
Researchers at The University of Texas have found that compared to Caucasian Americans, African Americans have impaired blood flow regulation in the brain that could contribute to a greater risk of cerebrovascular diseases such as stroke, transient ischaemic attack ("mini stroke"), subarachnoid haemorrhage or vascular dementia. These findings were published in Experimental Physiology, the journal of The Physiological Society. Cerebrovascular diseases can result from reduced blood flow in affected areas of the brain. It is still unclear why African Americans are at higher ...

Tiny needles offer potential new treatment for two major eye diseases

Tiny needles offer potential new treatment for two major eye diseases
2014-11-13
Needles almost too small to be seen with the unaided eye could be the basis for new treatment options for two of the world's leading eye diseases: glaucoma and corneal neovascularization. The microneedles, ranging in length from 400 to 700 microns, could provide a new way to deliver drugs to specific areas within the eye relevant to these diseases. By targeting the drugs only to specific parts of the eye instead of the entire eye, researchers hope to increase effectiveness, limit side effects, and reduce the amount of drug needed. For glaucoma, which affects about 2.2 ...

Novel cancer vaccine approach for brain tumors

2014-11-13
(PHILADELPHIA) - Glioblastoma is the most common aggressive primary brain tumor, and despite advances in standard treatment, the median survival is about 15 months (compared to 4 months without treatment). Researchers at Thomas Jefferson University have been working on a cancer vaccine that would extend that survival by activating the patient's immune system to fight the brain tumor. A study published online November 13th in the journal Cancer Immunology, Immunotherapy drilled down to the cellular and molecular mechanisms behind the vaccine, paving the way for further development ...

Premature infants exposed to unsafe levels of chemical in medical products

2014-11-13
Hospitalized premature infants are exposed to unsafe levels of a chemical found in numerous medical products used to treat them, raising questions about whether critically ill newborns may be adversely affected by equipment designed to help save their lives. The chemical, di(2-ethylhexyl)phthalate (DEHP), is used to increase flexibility of many plastic devices. These products, made from polyvinyl chloride (PVC), include most intravenous tubing, catheters, endotracheal tubes, and fluid and blood product bags. DEHP doesn't bind chemically to PVC, and is able to leach into ...

Use of private social media affects work performance

Use of private social media affects work performance
2014-11-13
In a new study, Use of Social Network Sites at Work: Does it Impair Performance?, Postdoctoral Fellow Cecilie Schou Andreassen and colleagues at the University of Bergen's (UiB) Department of Psychosocial Science looked at the consequences of the use of social media during working hours. Every day, more than one billion people worldwide use social media. This habit has also invaded the workplace, as some research reports that four out of five employees use social media for private purpose during working hours. Surprisingly, although this type of distraction may potentially ...

Genetic testing could improve breast cancer prevention

2014-11-13
Scientists used mathematical models to show that analysing genetic data, alongside a range of other risk factors, could substantially improve the ability to flag up women at highest risk of developing breast cancer. Their study showed that prevention strategies could be improved by testing not only as currently for major cancer predisposition genes such as BRCA1 and BRCA2 - which identify a small percentage of women at very high risk - but also by factoring in data on multiple gene variants that individually have only a small effect on risk, but are more common in the ...

How the breast cancer cells transform normal cells into tumoral ones?

How the breast cancer cells transform normal cells into tumoral ones?
2014-11-13
Researchers at the Bellvitge Biomedical Research Institute of Bellvitge, the Catalan Institute of Oncology and the University Hospital of Bellvitge have participated in an international study published in the journal Cancer Cell that describes how exosomes secreted by tumor cells contain protein and microRNA molecules capable of transform neighboring cells into tumoral cells promoting tumor growth. What are exosomes? Exosomes are small vesicles which are secreted by all cells and contain proteins and messenger RNAs and microRNAs. At first it was thought that only functioned ...

Combatting illegal fishing in offshore marine reserves

2014-11-13
Researchers at the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University in Australia have found a way to predict illegal fishing activities to help authorities better protect marine reserves. Marine reserves are the most common strategy used to protect and maintain marine ecosystems around the world. The International Convention of Biological Diversity aims to have 10 per cent of the world's marine areas protected by 2020. Many countries are contributing to this target by protecting remote, offshore areas. For example, the United ...

National study provides insights into childhood head injuries

2014-11-13
(SACRAMENTO, Calif.) -- This week's issue of the New England Journal of Medicine features an article that highlights an unprecedented analysis of the nation's childhood head injuries. The study, authored by physicians at UC Davis School of Medicine and Washington University School of Medicine, analyzed more than 43,000 children who were evaluated for head trauma at 25 emergency departments around the United States. In the accompanying supplements, detailed information about these children, their presentations and results will be useful to doctors and helpful to policy makers ...

LAST 30 PRESS RELEASES:

Program takes aim at drinking, unsafe sex, and sexual assault on college campuses

Inability to pay for healthcare reaches record high in U.S.

Science ‘storytelling’ urgently needed amid climate and biodiversity crisis

KAIST Develops Retinal Therapy to Restore Lost Vision​

Adipocyte-hepatocyte signaling mechanism uncovered in endoplasmic reticulum stress response

Mammals were adapting from life in the trees to living on the ground before dinosaur-killing asteroid

Low LDL cholesterol levels linked to reduced risk of dementia

Thickening of the eye’s retina associated with greater risk and severity of postoperative delirium in older patients

Almost one in ten people surveyed report having been harmed by the NHS in the last three years

Enhancing light control with complex frequency excitations

New research finds novel drug target for acute myeloid leukemia, bringing hope for cancer patients

New insight into factors associated with a common disease among dogs and humans

Illuminating single atoms for sustainable propylene production

New study finds Rocky Mountain snow contamination

Study examines lactation in critically ill patients

UVA Engineering Dean Jennifer West earns AIMBE’s 2025 Pierre Galletti Award

Doubling down on metasurfaces

New Cedars-Sinai study shows how specialized diet can improve gut disorders

Making moves and hitting the breaks: Owl journeys surprise researchers in western Montana

PKU Scientists simulate the origin and evolution of the North Atlantic Oscillation

ICRAFT breakthrough: Unlocking A20’s dual role in cancer immunotherapy

How VR technology is changing the game for Alzheimer’s disease

A borrowed bacterial gene allowed some marine diatoms to live on a seaweed diet

Balance between two competing nerve proteins deters symptoms of autism in mice

Use of antifungals in agriculture may increase resistance in an infectious yeast

Awareness grows of cancer risk from alcohol consumption, survey finds

The experts that can outsmart optical illusions

Pregnancy may reduce long COVID risk

Scientists uncover novel immune mechanism in wheat tandem kinase

Three University of Virginia Engineering faculty elected as AAAS Fellows

[Press-News.org] New process isolates promising material
Molybdenum disulfide has emerged as a leading successor to graphene