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

Patterning defect-free nanocrystal films with nanometer resolution

New process developed at MIT could enable better LED displays, solar cells and biosensors -- and foster basic physics research

2012-08-21
(Press-News.org) Films made of semiconductor nanocrystals — tiny crystals measuring just a few billionths of a meter across — are seen as a promising new material for a wide range of applications. Nanocrystals could be used in electronic or photonic circuits, detectors for biomolecules, or the glowing pixels on high-resolution display screens. They also hold promise for more efficient solar cells.

The size of a semiconductor nanocrystal determines its electrical and optical properties. But it's very hard to control the placement of nanocrystals on a surface in order to make structurally uniform films. Typical nanocrystal films also have cracks that limit their usefulness and make it impossible to measure the fundamental properties of these materials.

Now, researchers at MIT say they have found ways of making defect-free patterns of nanocrystal films where the shape and position of the films are controlled with nanoscale resolution, potentially opening up a significant area for research and possible new applications.

"We've been trying to understand how electrons move in arrays of these nanocrystals," which has been difficult with limited control over the formation of the arrays, says physicist Marc Kastner, the Donner Professor of Science, dean of MIT's School of Science and senior author of a paper published online in the journal Nano Letters.

The work builds on research by Moungi Bawendi, the Lester Wolfe Professor of Chemistry at MIT and a co-author of this paper, who was one of the first researchers to precisely control nanocrystal production. Such control made it possible, among other things, to produce materials that glow, or fluoresce, in a range of different colors based on their sizes — even though they are all made of the same material.

In the initial phases of the new work, postdoc Tamar Mentzel produced nanoscale patterns that emit invisible infrared light. But working on such systems is tedious, since each fine-tuning has to be checked using time-consuming electron microscopy. So when Mentzel succeeded in getting semiconductor nanocrystal patterns to glow with visible light, making them visible through an optical microscope, it meant that the team could greatly speed the development of the new technology. "Even though the nanoscale patterns are below the resolution limit of the optical microscope, the nanocrystals act as a light source, rendering them visible," Mentzel says.

The electrical conductivity of the researchers' defect-free films is roughly 180 times greater than that of the cracked films made by conventional methods. In addition, the process developed by the MIT team has already made it possible to create patterns on a silicon surface that are just 30 nanometers across — about the size of the finest features possible with present manufacturing techniques.

The process is unique in producing such tiny patterns of defect-free films, Mentzel says. "The trick was to get the film to be uniform, and to stick" to the silicon dioxide substrate, Kastner adds. That was achieved by leaving a thin layer of polymer to coat the surface before depositing the layer of nanocrystals on top of it. The researchers conjecture that tiny organic molecules on the surface of the nanocrystals help them bind to the polymer layer.

Such nanocrystal patterns could have many applications, Kastner says. Because these nanocrystals can be tuned not only to emit but also to absorb a wide spectrum of colors of light, they could enable a new kind of broad-spectrum solar cell, he says.

But Kastner and Mentzel's personal interest has more to do with basic physics: Since the minuscule crystals behave almost like oversized atoms, the researchers aim to use the arrays to study fundamental processes of solids, Mentzel says. The success of this technique has already enabled new research on how electrons move in the films.

Such materials could also be used to develop sensitive detectors for tiny amounts of certain biological molecules, either as screening systems for toxins or as medical testing devices, the researchers say.

INFORMATION:

The research was supported by the U.S Army Research Office, the Department of Energy and Samsung.

Written by: David L. Chandler, MIT News Office

END



ELSE PRESS RELEASES FROM THIS DATE:

Politics and prejudice -- insights from Psychological Science

2012-08-21
New research from Psychological Science explores factors operating in political attitudes that could explain why political ideology and prejudice are often linked. Liberals and Conservatives Both Prejudiced Against Groups with Opposing Values Research has associated political conservatism with prejudice toward various stereotyped groups. But research has also shown that people select and interpret evidence consistent with their own pre-existing attitudes and ideologies. In this article, Chambers and colleagues hypothesized that, contrary to what some research might ...

Scientist finds new way to predict heat layer troublemaker

Scientist finds new way to predict heat layer troublemaker
2012-08-21
Researchers at a recent worldwide conference on fusion power have confirmed the surprising accuracy of a new model for predicting the size of a key barrier to fusion that a top scientist at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL) has developed. The model could serve as a starting point for overcoming the barrier. "This allows you to depict the size of the challenge so you can think through what needs to be done to overcome it," said physicist Robert Goldston, the Princeton University professor of astrophysical sciences and former PPPL ...

Specific toxic byproduct of heat-processed food may lead to increased body weight and diabetes

2012-08-21
Researchers at Mount Sinai School of Medicine have identified a common compound in the modern diet that could play a major role in the development of abdominal obesity, insulin resistance, and type 2 diabetes. The findings are published in the August 20, 2012 issue of the Proceedings of the National Academy of Sciences. The research team, led by Helen Vlassara, MD, Professor and Director of the Division of Experimental Diabetes and Aging, found that mice with sustained exposure to the compound, methyl-glyoxal (MG), developed significant abdominal weight gain, early insulin ...

UCSB scientists examine effects of manufactured nanoparticles on soybean crops

2012-08-21
(Santa Barbara, Calif.) –– Sunscreens, lotions, and cosmetics contain tiny metal nanoparticles that wash down the drain at the end of the day, or are discharged after manufacturing. Those nanoparticles eventually end up in agricultural soil, which is a cause for concern, according to a group of environmental scientists that recently carried out the first major study of soybeans grown in soil contaminated by two manufactured nanomaterials (MNMs). The team was led by scientists at UC Santa Barbara's Bren School of Environmental Science & Management. The team is also affiliated ...

Information overload in the era of 'big data'

Information overload in the era of big data
2012-08-21
Botany is plagued by the same problem as the rest of science and society: our ability to generate data quickly and cheaply is surpassing our ability to access and analyze it. In this age of big data, scientists facing too much information rely on computers to search large data sets for patterns that are beyond the capability of humans to recognize—but computers can only interpret data based on the strict set of rules in their programming. New tools called ontologies provide the rules computers need to transform information into knowledge, by attaching meaning to data, ...

Stroke disrupts how brain controls muscle synergies

2012-08-21
CAMBRIDGE, MA -- The simple act of picking up a pencil requires the coordination of dozens of muscles: The eyes and head must turn toward the object as the hand reaches forward and the fingers grasp it. To make this job more manageable, the brain's motor cortex has implemented a system of shortcuts. Instead of controlling each muscle independently, the cortex is believed to activate muscles in groups, known as "muscle synergies." These synergies can be combined in different ways to achieve a wide range of movements. A new study from MIT, Harvard Medical School and the ...

Nanoparticles added to platelets double internal injury survival rate

2012-08-21
Nanoparticles tailored to latch onto blood platelets rapidly create healthy clots and nearly double the survival rate in the vital first hour after injury, new research shows. "We knew an injection of these nanoparticles stopped bleeding faster, but now we know the bleeding is stopped in time to increase survival following trauma," said Erin Lavik, a professor of biomedical engineering at Case Western Reserve University and leader of the effort. The researchers are developing synthetic platelets that first responders and battlefield medics could carry with them to stabilize ...

Breast density does not influence breast cancer death among breast cancer patients

2012-08-21
The risk of dying from breast cancer was not related to high mammographic breast density in breast cancer patients, according to a study published August 20 in the Journal of the National Cancer Institute. One of the strongest risk factors for non-familial breast cancer is elevated mammographic breast density. While women with elevated mammographic breast density have a higher risk of developing breast cancer, it is not established whether a higher density indicates a lower chance of survival in breast cancer patients. In order to determine if higher mammographic breast ...

NASA satellites capture 3 days of Hurricane Gordon's Atlantic track

NASA satellites capture 3 days of Hurricane Gordons Atlantic track
2012-08-21
NASA's Terra and Aqua satellite have captured Hurricane Gordon over three days as it neared the Azores Islands in the eastern Atlantic Ocean. Gordon weakened to a tropical storm on August 20. The Moderate Resolution Imaging Spectroradiometer, or MODIS, is an instrument that flies onboard NASA's Terra and Aqua satellites and provides high-resolution imagery to users. When NASA's Terra satellite flew over Gordon on August 17 at 9:30 a.m. EDT it was a tropical storm and did not have a visible eye. It was followed up by a fly over of NASA's Aqua satellite on August 18 at ...

First evidence discovered of planet's destruction by its star

First evidence discovered of planets destruction by its star
2012-08-21
The first evidence of a planet's destruction by its aging star has been discovered by an international team of astronomers. The evidence indicates that the missing planet was devoured as the star began expanding into a "red giant" -- the stellar equivalent of advanced age. "A similar fate may await the inner planets in our solar system, when the Sun becomes a red giant and expands all the way out to Earth's orbit some five-billion years from now," said Alexander Wolszczan, Evan Pugh Professor of Astronomy and Astrophysics at Penn State University, who is one of the members ...

LAST 30 PRESS RELEASES:

Avalanches: user-carried safety device increases survival time fivefold

It’s all in your head: Select neurons in the brainstem may hold the key to treating chronic pain

Time-restricted eating can boost athletes' health and performance

Burning issue: study finds fire a friend to some bees, a foe to others

Insights from 15 years of collaborative microbiome research with Indigenous peoples in the Peruvian Amazon

Designing polymers for use in next-generation bioelectronics

Losing Nemo: Almost all aquarium fish in the US are caught in the wild

Revisiting minimum case volume recommendations for complex surgery in contemporary practice

Medicaid innovation models improve care for moms, but design matters

Cannabis use among individuals with psychosis after state-level commercial cannabis legalization

Open-label placebos as adjunct for the preventive treatment of migraine

Moon's biggest impact crater made a radioactive splash

Smoking and biological sex shape healthy bladder tissue evolution, offering clues to cancer risk

Improved genetic tool reveals hidden mutations that can drive cancer

Hidden evolution in sperm raises disease risk for children as men age

Women portrayed as younger than men online, and AI amplifies the bias

Engineered bacterial therapy activates immune response in cancer preclinical studies

Energy flexibility is reshaping Finland’s electricity market

Individuals with sickle cell disease face long delays to pain care in emergency department

Association for Molecular Pathology develops standardized biomarker report template for providers

Making regular GPS ultra-precise

Webb Telescope unveils doomed star hidden in dust

UT Southwestern preventive cardiologist to receive the 2025 Chairman’s Award

Slime mold metabolites are a promising, eco-friendly repellent of root-knot nematodes

Pathological mechanism of mechanosensitive cells driving the growth of keloids

First large-scale Alzheimer disease study in brain tissue from African American donors implicates roles for many novel genes

In a nasal spray, gold “nanoparticles” deliver a targeted treatment to the brain. A potentially revolutionary approach to mental disorders and neurodegenerative diseases already has a patent

Current and recommended diets in the USA have embedded forced labor risk

AI breakthrough helps astronomers spot cosmic events with just a handful of examples

New vaccine shows promise against typhoid and invasive salmonella in first human trial

[Press-News.org] Patterning defect-free nanocrystal films with nanometer resolution
New process developed at MIT could enable better LED displays, solar cells and biosensors -- and foster basic physics research