Tag Archives: David Awschalom

Nanodiamonds as imaging devices

Two different teams have recently published studies in Science magazine (Feb. 1, 2013 issue) about their work with nanodiamonds, flaws, and imaging in what seems to be a case of synchronicity as there are no obvious connections between the teams.

Sabrina Richards writes in her Jan. 31, 2013 article for The Scientist about the possibility of taking snapshots of molecules at some time in the future (Note: Links have been removed),

A miniscule diamond flaw—just two atoms different—could someday enable researchers to image single molecules without resorting to time-consuming and technically exacting X-ray crystallography. The new approach, published today (January 31 [sic]) in Science, relies on a single electron to detect perturbation in molecular magnetic fields, which can provide clues about the structures of proteins and other molecules.

The work was inspired by magnetic resonance imaging (MRI), which uses electromagnetic coils to detect the magnetic fields emitted by hydrogen atom protons.  But traditional MRI requires many trillions of protons to get a clear image—of a brain, for example—preventing scientists from visualizing anything much smaller than millimeters-wide structures. To detect just a few protons, such as those of a single molecule, scientists would need an atomic-scale sensor.

To construct such a sensor, physicists Daniel Rugar at IBM Research and David Awschalom at the University of California, Santa Barbara, turned to diamonds. A perfect diamond, made entirely of carbon atoms covalently bonded to each other, has no free electrons and therefore no magnetic properties, explained Hammel. But a special kind of defect, known as a nitrogen-vacancy (NV) center, confers unique magnetic properties.

Jyllian Kemsley’s Jan. 31, 2013 article for C&EN (Chemical and Engineering News) discusses the work from both teams and describes the technique they used,

To downscale NMR [aka MRI], both groups used a detector made of diamond with a site defect called a single nitrogen-vacancy (NV) center, in which a nitrogen atom and a lattice hole replace two adjacent carbon atoms. Prior work had determined that NV centers are sensitive to the internal magnetic fields of the diamond. The new research demonstrates that the fluorescence of such centers can be used to detect magnetic fields emanating from just outside the diamond. Both groups were able to use NV centers to detect nuclear polarization of hydrogens in poly(methyl methacrylate) with a sample volume lower limit of about (5 nm)3. Further development is necessary to extract structural information.

Still, nothing much has happened with this technique as Richards notes in her article,

So far, the study is “just a proof of principle,” noted Awschalom. The researchers haven’t actually imaged any molecules yet, but simply detected their presence. Still, Awschalom said, “we’ve shown it’s not a completely ridiculous idea to detect external nuclear magnetic fields with one electron.” …

Here’s a citation and a link to the article,

Nanoscale Nuclear Magnetic Resonance with a Nitrogen-Vacancy Spin Sensor by H. J. Mamin, M. Kim, M. H. Sherwood, C. T. Rettner, K. Ohno, D. D. Awschalom, D. Rugar. Science 1 February 2013: Vol. 339 no. 6119 pp. 557-560 DOI: 10.1126/science.1231540

The other research is described in a Feb. 14, 2013 news item on Azonano,

Magnetic resonance imaging (MRI) reveals details of living tissues, diseased organs and tumors inside the body without x-rays or surgery. What if the same technology could peer down to the level of atoms? Doctors could make visual diagnoses of a person’s molecules – examining damage on a strand of DNA, watching molecules misfold, or identifying a cancer cell by the proteins on its surface.

It is remarkably  similar work as Kemsley notes not helped by the fact that the one line description for both articles in Science magazine’s Table of Contents is identical.  (One line description: The optical response of the spin of a near-surface atomic defect in diamond can be used to sense proton magnetic fields.) The City College of New York City Feb. 13, 2013 news release, which originated the Azonano news item about the other team, offers more details,

 … Dr. Carlos Meriles, associate professor of physics at The City College of New York, and an international team of researchers at the University of Stuttgart and elsewhere have opened the door for nanoscale MRI. They used tiny defects in diamonds to sense the magnetic resonance of molecules. They reported their results in the February 1 [2013] issue of Science.

“It is bringing MRI to a level comparable to an atomic force microscope,” said Professor Meriles, referring to the device that traces the contours of atoms or tugs on a molecule to measure its strength. A nanoscale MRI could display how a molecule moves without touching it.

“Standard MRI typically gets to a resolution of 100 microns,” about the width of a human hair, said Professor Meriles. “With extraordinary effort,” he said, “it can get down to about 10 microns” – the width of a couple of blood cells. Nanoscale MRI would have a resolution 1,000 to 10,000 times better.

To try to pick up magnetic resonance on such a small scale, the team took advantage of the spin of protons in an atom, a property usually used to investigate quantum computing. In particular, they used minute imperfections in diamonds.

Diamonds are crystals made up almost entirely of carbon atoms. When a nitrogen atom lodges next to a spot where a carbon atom is missing, however, it creates a defect known as a nitrogen-vacancy (NV) center.

“These imperfections turn out to have a spin – like a little compass – and have some remarkable properties,” noted Professor Meriles. In the last few years, researchers realized that these NV centers could serve as very sensitive sensors. They can pick up the magnetic resonance of nearby atoms in a cell, for example. But unlike the atoms in a cell, the NVs shine when a light is directed at them, signaling what their spin is. If you illuminate it with green light it flashes red back.

“It is a form of what is called optically detected magnetic resonance,” he said. Like a hiker flashing Morse code on a hillside, the sensor “sends back flashes to say it is alive and well.”

“The NV can also be thought of as an atomic magnet. You can manipulate the spin of that atomic magnet just like you do with MRI by applying a radio frequency or radio pulses,” Professor Meriles explained. The NV responds. Shine a green light at it when the spin is pointing up and it will respond with brighter red light. A down spin gives a dimmer red light.

In the lab, graduate student Tobias Staudacher — the first author in this work — used NVs that had been created just below the diamond’s surface by bombarding it with nitrogen atoms. The team detected magnetic resonance within a film of organic material applied to the surface, just as one might examine a thin film of cells or tissue.

“Ultimately,” said Professor Meriles, “One will use a nitrogen-vacancy mounted on the tip of an atomic force microscope – or an array of NVs distributed on the diamond surface – to allow a scanning view of a cell, for example, to probe nuclear spins with a resolution down to a nanometer or perhaps better.”

Here’s a citation and a link to this team’s study,

Nuclear Magnetic Resonance Spectroscopy on a (5-Nanometer)3 Sample Volume by T. Staudacher, F. Shi, S. Pezzagna, J. Meijer, J. Du, C. A. Meriles, F. Reinhard1, J. Wrachtrup. Science 1 February 2013: Vol. 339 no. 6119 pp. 561-563 DOI: 10.1126/science.1231675

Both articles are behind paywalls.

Nanoscience: the next 50 years?

Tomorrow, Jan. 15 2011, there’s going to be a Kavli Futures Symposium titled, Plenty of Room in the Middle: Nanoscience – The Next 50 Years. This a symposium is being hosted (as you may have guessed) by the Kavli Nanoscience Institute at the California Institute of Technology where (from the Jan. 12, 2011 news item on Nanowerk),

… an assembly of pioneering scientists will gather to focus on four key topics in nanoscience: atomic-scale assembly and imaging, mesoscopic quantum coherence, the “nano/bio nexus” and nanotechnology frontiers. Co-chairing the symposium are Michael Roukes, co-director of the Kavli Institute of Nanoscience at the California Institute of Technology, and IBM scientist Donald Eigler.

Unfortunately, they do not seem to be webcasting this event but there’s a transcript of a recent teleconference amongst three of the pioneering nanoscientists who will be gathering to discuss Feynman, his legacy, and the future. (The transcript is embedded in the news item on Nanowerk.)  The three scientists are:

  • IBM scientist Don Eigler
  • Angela Belcher Massachusetts Institute of Technology (MIT) materials scientist
  • David Awschalom University of California physicist

Here’s an excerpt from the transcript which gives you a preview of what they’ll be talking about tomorrow. This bit is where David Awschalom is discussing convergence in the sciences,

I believe that the broad umbrella of nanoscience is rapidly dissolving the traditional barriers between these disciplines, and maybe wiring them a bit together with the idea that now people are thinking about atoms and materials as arbitrary forms, not in the historical sense. Physicists are now using biological systems, and biologists are exploiting solid state devices and microfluidic devices within a myriad of research efforts. People are thinking much more broadly than in the past and, as Don [Eigler] says, I think it’s the discoveries in science that are driving this direction. When I look at the students who are entering the university system, they’re highly motivated by the idea of breaking down the normal barriers and focusing on the new scientific opportunities that emerge. I agree with Don. I think the idea of labeling things is wrong. This merging is going to happen very naturally. It’s already happening. For example, some researchers are thinking about photosynthesis as a quantum process, and [asking] whether photosynthesis is driven quantum mechanically in certain plants – exploring the concept of coherent energy transfer in biology. If so, it is possible to control this flow with exquisite precision. When you look in the literature, there are growing numbers of laboratories working in these cross-disciplinary areas; not because they’re suddenly interested in biology but they realize that biological systems could be tuned and engineered to explore unique scientific missions. So yes, I do believe that this merge is inevitable. I don’t think it’s going to be because of funding, or because of labeling, as Don says, but it’s where the interest is, and it where the new frontiers are in science.

I find this to be very interesting since it fits in very well with a recent presentation that MIT researchers made at a forum hosted by the American Association for the Advancement of Science (AAAS) earlier this month. From the Jan. 5, 2011 news item on Azonano,

A new model for scientific research known as “convergence” offers the potential for revolutionary advances in biomedicine and other areas of science, according to a white paper issued today by 12 leading MIT researchers.

The report, “The Third Revolution: The Convergence of the Life Sciences, Physical Sciences and Engineering,” noted the impact that convergence is already having in a broad array of fields.

Just as advances in information technology, materials, imaging, nanotechnology and related fields — coupled with advances in computing, modeling and simulation — have transformed the physical sciences, so are they are beginning to transform life science. The result is critical new biology-related fields, such as bioengineering, computational biology, synthetic biology and tissue engineering.

At the same time, biological models (understanding complex, self-arranged systems) are already transforming engineering and the physical sciences, making possible advances in biofuels, food supply, viral self assembly and much more.

What’s fascinating to me is that there doesn’t seem to any consideration of the societal implications of all this boundary crossing or convergence. Frankenfoods (genetically modified food) created a major panic because people were not comfortable with crossing certain types of boundaries. Once you take the ideas being proposed by the Kavli nanoscientists and the MIT researchers from theory to application, another dimension can open up.

Not all applications are hugely upsetting to society but some have the potential to cause havoc and they don’t necessarily have to cross boundaries. For example, computers created huge problems. I once had a technical writer tell me that she found bullet casings in some of the computerized equipment they received back from some small towns in northern British Columbia (Canada). People were afraid for their jobs. And, when I was working in the library system at the University of British Columbia, a librarian tried to sabotage the system; she didn’t use a gun or a rifle. Instead, when they were transferring information from card catalogues to online catalogues the librarian [started] taking large chunks of catalogue cards home with her, effectively hiding the information.

Stories like the one about the librarian might seem amusing now but there was genuine anguish and panic over the advent of the computer into daily life. Personally, I think the changes these nanoscientists are discussing are more profound and potentially disturbing.