Tag Archives: diamonds

Quantum dots and graphene; a mini roundup

I’ve done very little writing about quantum dots (so much nano, so little time) but there’s been a fair amount of activity lately which has piqued my interest. In the last few days researchers at Kansas State University have been getting noticed for being able to control the size and shape of the graphene quantum dots they produce.  This one has gotten extensive coverage online including this May 17, 2012 news item on physorg.com,

Vikas Berry, William H. Honstead professor of chemical engineering, has developed a novel process that uses a diamond knife to cleave graphite into graphite nanoblocks, which are precursors for graphene quantum dots. These nanoblocks are then exfoliated to produce ultrasmall sheets of carbon atoms of controlled shape and size.

By controlling the size and shape, the researchers can control graphene’s properties over a wide range for varied applications, such as solar cells, electronics, optical dyes, biomarkers, composites and particulate systems. Their work has been published in Nature Communications and supports the university’s vision to become a top 50 public research university by 2025. The article is available online.

Here’s an image of graphene being cut by a diamond knife from the May 16, 2012 posting by jtorline on the K-State News blog,

Molecular dynamics snapshot of stretched graphene being nanotomed via a diamond knife.

Here’s why standardizing the size is so important,

While other researchers have been able to make quantum dots, Berry’s research team can make quantum dots with a controlled structure in large quantities, which may allow these optically active quantum dots to be used in solar cell and other optoelectronic applications. [emphasis mine]

While all this is happening in Kansas, the Econ0mist magazine published a May 12, 2012 article about some important quantum dot optoelectronic developments in Spain (an excellent description for relative beginners is given and, if this area interests you, I’d suggest reading it in full),

Actually converting the wonders of graphene into products has been tough. But Frank Koppens and his colleagues at the Institute of Photonic Sciences in Barcelona think they have found a way to do so. As they describe in Nature Nanotechnology, they believe graphene can be used to make ultra-sensitive, low-cost photodetectors.

A typical photodetector is made of a silicon chip a few millimetres across onto which light is focused by a small lens. Light striking the chip knocks electrons free from some of the silicon atoms, producing a signal that the chip’s electronics convert into a picture or other useful information. …

Silicon photodetectors suffer, though, from a handicap: they are inflexible. Nor are they particularly cheap. And they are not that sensitive. They absorb only 10-20% of the light that falls on to them. For years, therefore, engineers have been on the lookout for a cheap, bendable, sensitive photodetector. …

By itself, graphene is worse than silicon at absorbing light. According to Dr Koppens only 2.7% of the photons falling on it are captured. But he and his colleague Gerasimos Konstantatos have managed to increase this to more than 50% by spraying tiny crystals of lead sulphide onto the surface of the material.

So combining the ability to size quantum dots uniformly with this discovery on how to make graphene more sensitive (and more useful in potential products) with quantum dots suggests some very exciting possibilities including this one mentioned by Dexter Johnson (who’s living in Spain these days) in his May 16, 2012 posting on Nanoclast (on the Institute of Electrical and Electronics Engineers [IEEE] website),

The researchers offer a range of applications for the graphene-and-quantum-dot combination, including digital cameras and sensors.  [emphasis mine] But it seems the researchers seem particularly excited about one application in particular. They expect the material will be used for night-vision technologies in automobiles—an application I have never heard trotted out before in relation to nanotech.

You can get more insights, more precise descriptions if you want to follow up from the Econ0mist article,  and Dexter’s links to more information about the research in his posting.

In my final roundup piece, I received a news release (dated April 24, 2012) about a quantum dot commercialization project at the University of Utah,

One of the biggest challenges for advancing quantum dots is the manufacturing process. Conventional processes are expensive, require high temperatures and produce low yields. However, researchers at the University of Utah believe they have a solution. They recently formed a startup company called Navillum Nanotechnologies, and their efforts are gaining national attention with help from a team of M.B.A. students from the David Eccles School of Business.
The students recently won first place and $100,000 at the regional CU Cleantech New Venture Challenge. The student competition concluded at the University of Colorado in Boulder on Friday, April 20. The student team advances to the national championship, which will be held in June in Washington, D.C. Student teams from six regions will compete for additional prizes and recognition at the prestigious event. Other regional competitions were held at MIT, Cal Tech, the University of Maryland, Clean Energy Trust (Chicago) and Rice University. All the competitions are financed by the U.S. Department of Energy.

The students will be competing in the national Clean Energy Business Plan Competition taking place June 12-13, 2012 in Washington, D.C.  Here are a few more details from the national competition webpage,

Winners of the six regional competitions will represent their home universities and regions as they vie for the honor of presenting the best clean energy business plan before a distinguished panel of expert judges and invited guests from federal agencies, industry, national labs and the venture capital community.

Confirmed Attendees include:

The Honorable Steven Chu
Energy Secretary [US federal government]

Dr. David Danielson
Assistant Secretary, EERE  [US Dept. of Energy, energy efficiency and renewable energy technologies)

Dr. Karina Edmonds
Technology Transfer Coordinator [US Dept. of Energy]

Mr. Todd Park
Chief Technology Officer, White House

Good luck to the students!

Do you have any suggestions for the diamond engraved with Queen Elizabeth 2’s image?

The folks at the University of Nottingham’s Periodic Table of Videos have come up with a way to commemorate Queen Elizabeth II’s 60th anniversary (diamond) jubilee of her reign. Thanks to the April 11, 2012 posting by GrrlScientist on the Guardian science blogs I’ve gotten a really explanation of how a focused gallium ion beam can be used to engrave diamonds.  In my April 9, 2012 posting about computers in diamonds and a ring that’s 100% diamond, I noted my interest in focused ion beams and I’m delighted to include this video where scientist Martyn Poliakoff offers an explanation and demonstration,

If you do have any suggestions for what they could do with this diamond (I like Poliakoff’s suggestion of sending it to institutions that have diamond-jubilee themed exhibits for display), you can contact them via email periodicvideos@gmail.com or one of two twitter accounts @periodicvideos or @UniofNottingham.

Since posting on April 9, 2012 I’ve had this old pop song (‘This Diamond Ring’ by Gary Lewis and the Playboys) on a continuous loop in my brain,

I hope by placing the video here, the song will finally disappear. (I’m also hoping it doesn’t get replaced with ‘Diamonds are a girl’s best friend’.)

ETA April 16, 2012: There’s a bit more detail about the engraving process, which took place in the Nottingham Nanotechnology and Nanoscience Centre [NNNC] in this April 16, 2012 news item by Tara De Cozar on phyorg.com.

Entangling diamonds

Usually when you hear about entanglement, they’re talking about quantum particles or kittens. On Dec. 2, 2011, Science magazine published a paper by scientists who had entangled diamonds (that can be touched and held in human hands). From the Dec. 1, 2011 CBC (Canadian Broadcasting Corporation) news article by Emily Chung,

Quantum physics is known for bizarre phenomena that are very different from the behaviour we are familiar with through our interaction with objects on the human scale, which follow the laws of classical physics. For example, quantum “entanglement” connects two objects so that no matter how far away they are from one another, each object is affected by what happens to the other.

Now, scientists from the U.K., Canada and Singapore have managed to demonstrate entanglement in ordinary diamonds under conditions found in any ordinary room or laboratory.

Philip Ball in his Dec. 1, 2011 article for Nature magazine describes precisely what entanglement means when applied to the diamond crystals that were entangled,

A pair of diamond crystals has been linked by quantum entanglement. This means that a vibration in the crystals could not be meaningfully assigned to one or other of them: both crystals were simultaneously vibrating and not vibrating.

Quantum entanglement — interdependence of quantum states between particles not in physical contact — has been well established between quantum particles such as atoms at ultra-cold temperatures. But like most quantum effects, it doesn’t tend to survive either at room temperature or in objects large enough to see with the naked eye.

Entanglement, until now, has been demonstrated at very small scales due to an issue with coherence and under extreme conditions. Entangled objects are coherent with each other but other objects such as atoms can cause the entangled objects to lose their coherence and their entangled state. In order to entangle the diamonds, the scientists had to find a way of dealing with the loss of coherence as the objects are scaled up and they were able to achieve this at room temperature. From the Emily Chung article,

Walmsley [Ian Walmsley, professor of experimental physics at the University of Oxford] said it’s easier to maintain coherence in smaller objects because they can be isolated practically from disturbances. Things are trickier in larger systems that contain lots of interacting, moving parts.

Two things helped the researchers get around this in their experiment, Sussman [Ben Sussman, a quantum physicist at the National Research Council of Canada and adjunct professor at the University of Ottawa] said:

  • The hardness of the diamonds meant it was more resistant to disturbances that could destroy the coherence.
  • The extreme speed of the experiment — the researchers used laser pulses just 60 femtoseconds long, about 6/100,000ths of a nanosecond (a nanosecond is a billionth of a second) — meant there was no time for disturbances to destroy the quantum effects.

Laser pulses were used to put the two diamonds into a state where they were entangled with one another through a shared vibration known as a phonon. By measuring particles of light called photons subsequently scattered from the diamonds, the researchers confirmed that the states of the two diamonds were linked with each other — evidence that they were entangled.

If you are interested in the team’s research and can get past Science magazine’s paywall, here’s the citation,

“Entangling Macroscopic Diamonds at Room Temperature,” by K.C. Lee; M.R. Sprague; J. Nunn; N.K. Langford; X.-M. Jin; T. Champion; P. Michelberger; K.F. Reim; D. England; D. Jaksch; I.A. Walmsley at University of Oxford in Oxford, UK; B.J. Sussman at National Research Council of Canada in Ottawa, ON, Canada; X.-M. Jin; D. Jaksch at National University of Singapore in Singapore. Science 2 December 2011: Vol. 334 no. 6060 pp. 1253-1256 DOI: 10.1126/science.1211914

All of the media reports I’ve seen to date focus on the UK and Canadian researchers and I cannot find anything about the contribution of the researcher based in Singapore.

I do wish I could read more languages as I’d be more likely to find information about work which is not necessarily going to be covered in English language media.