Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mystery of Nanoparticles Concealed in the Blink of an Eye

19.07.2004


Scientists at the University of Chicago have discovered a better way to measure a confounding property of microscopic high-tech particles called quantum dots.



Quantum dots, also called nanocrystals, emit light in a rainbow of colors and are used in lasers, biological studies and other applications, but their tendency to blink hinders their technological value. Imagine the annoyance caused by a randomly flickering light bulb.

"A quantum dot might blink for just a millionth of a second or it might blink for 15 minutes," said Matthew Pelton, a Research Associate at the University of Chicago’s James Franck Institute. "This is one of the problems we have to solve if we want to engineer the properties of materials, particularly semiconductor materials, on the nanoscale."


Pelton has found a way to measure the blinking that is simpler and faster than the conventional method. He will describe the measurements in the Aug. 2 issue of Applied Physics Letters with co-authors David Grier, now of New York University, and Philippe Guyot-Sionnest of the University of Chicago.

Grier compares the light output or "noise" of a blinking group of quantum dots to the babble of a cocktail party conversation. "Even if everyone’s talking about the same thing you probably wouldn’t be able to figure out what they’re saying because they’re all starting their conversations at random times and there are different variations on their conversations," he said.

"Matt has discovered that for these blinking quantum dots, all the conversations are the same in a very special way, and that allows you to figure out an awful lot about what’s being said by listening to the whole crowd."

In previous studies, various research groups combined powerful microscopes with video cameras to record the blinking behavior of one quantum dot at a time, but that method is expensive, time-consuming and difficult to perform. It also required that the dots be placed on a microscope slide. Pelton’s method enables scientists to study the blinking patterns of large quantities of dots. And it can be done in just a few minutes with standard laboratory equipment under a variety of environmental conditions.

"Matt’s approach is applicable to situations where previous measurements could not be made," Guyot-Sionnest said.

The four components of Pelton’s system are a light source, a photodetector (a device that measures the intensity of light), an amplifier to boost the photodetector’s output, and an analogue-to-digital converter that translates the amplified output into a string of numbers for digital processing.

The system has already revealed new insights into the behavior of quantum dots. Pelton’s results contradict the conventional wisdom about the blinking dots, which states that environmental factors influence the behavior. Pelton made his finding by applying a mathematical tool commonly used by electrical engineers to the problem of blinking quantum dots. "The mathematical tool is almost 200 years old. No one had thought to apply it to this problem before," Grier said.

Studying quantum dots one at a time with microscopes and video cameras was limited by the capabilities of the camera. For example, a camera that takes 40 frames a second would miss any blinks that occur more rapidly.

But Pelton’s system includes a tool called a power spectrum to trace blinking behavior. This tool has established numerical recipes for handling the time resolution problem.

The research team cannot say how long it might take to crack the mystery of the blinking quantum dots. What is certain is that quantum dots will continue to generate interest in high-tech circles.

"Many scientists are trying to start up companies to make nanocrystals and to find a new use for them," Guyot-Sionnest said.

Quantum dot research at the University of Chicago is supported by the Materials Science and Engineering Research Center, the National Science Foundation and the American Chemical Society.

| newswise
Further information:
http://www.uchicago.edu

More articles from Process Engineering:

nachricht New manufacturing process for SiC power devices opens market to more competition
14.09.2017 | North Carolina State University

nachricht Quick, Precise, but not Cold
17.05.2017 | Fraunhofer-Institut für Lasertechnik ILT

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>