Trading carats for nanometers - and defective diamonds for crystal clear microscopy

Mar 02, 2009
Unlike conventional microscopy (left) which renders a featureless image, the super-resolving STED microscope reveals individual luminescent atomic defects inside the diamond crystal (center). The position of each defect (right) can subsequently be determined with atomic scale precision (0.15 nanometer). Before STED microscopy such recordings were considered to be practically impossible. (Picture: Rittweger & Hell, MPIbpc)

(PhysOrg.com) -- Large, perfect diamonds are precious to almost all of us but to some scientists, it is the defects that really matter. This is because defects can form nanoscopic color centers, which play a key role in the development of both quantum computing and quantum cryptography. A research team at the Max Planck Institute for Biophysical Chemistry in Göttingen has now probed these color centers inside the crystal with unprecedented resolution using an optical microscope. Using STED microscopy, the scientists identified even densely packed color centers and determined their position inside the crystal with a precision better than 0.15 nanometers, corresponding to the dimension of an atom. (Nature Photonics, 22nd February 2009).

Diamonds are brilliant not only as gem stones but scientists are also increasingly interested in these precious crystals. As the perfect jewel, the colorless variant glitters brilliantly - but in science it is the much cheaper fluorescent diamonds that cause the sensation. Their color comes from impurities, such as nitrogen atoms, in the diamond lattice. If a nitrogen atom sits next to a vacancy in the crystal lattice, a luminescent defect of atomic size is formed. Electrons of these color centers can - similar to dye molecules - be excited by laser light. When they return to the ground state, the excitation energy is converted to fluorescence light. This fluorescence glowing and their ability to form atomically small magnets render color centers in diamond extremely interesting.

Researchers hope to use diamond color centers as small processors in quantum computing to speed up specific arithmetic operations, and their suitability for encoding highly sensitive data is currently being explored. However, there is a crucial drawback for observing these color centers inside the crystal: single defects can only be recognized with a fluorescence microscope, but only if they are further apart than approximately 200 nanometers (millionth of a millimeter) because this is the resolution limit of a standard optical microscope.

Trading carats for nanometers - and defective diamonds for crystal clear microscopy
Sharp focus: Recordings of lattice defects in diamond crystals are 28 times sharper with the super resolving STED microscope than with conventional fluorescence microscopy methods, namely 8 nanometers. (Picture: Rittweger & Hell, MPIbpc)

Stefan Hell's group at the Max Planck Institute for Biophysical Chemistry in Göttingen succeeded in recording the first images of densely packed individual color centers employing STED (Stimulated emission depletion) microscopy. They pushed the current resolution limit of STED down to a few nanometers. Diamond color centers closer than a tiny fraction of the resolution limit could be separated and their position determined with a precision of 0.15 nanometers. Scientists have now a method at hand to individually address densely packed color centers - with conventional lenses and focused light. For the ongoing research and application of these color centers this is a major breakthrough. This work is also important for the field of crystallography, which now has another method at hand to study crystal structures locally.

That nitrogen-vacancies fluoresce after excitation with laser pulses also makes them attractive for a different research field: biological fluorescence nanoscopy. Scientists plan to reveal a live cell's secrets using fluorescent diamonds, requiring tiny diamond nano particles which can be used for labeling cells."Organic fluorescent dyes, which we routinely use for STED, have the disadvantage that they blink and eventually bleach", says Eva Rittweger, a PhD student in the department. "However, color centers in diamonds are extremely photostable even when observed for hours in the STED microscope."

Research groups in Würzburg, Stuttgart, as well as in Asia and America are working on applying the nanocrystals to biological and medical fundamental research. "If we are successful in exploiting this property in nanodiamonds, one would have a new class of fluorescent markers and a form of fluorescence nanoscopy without bleaching. This could, in combination with the nanometric resolution of STED microscopy, improve imaging of the cell at the nanoscale", says Stefan Hell.

More information: Eva Rittweger, Kyu Young Han, Scott E. Irvine, Christian Eggeling, and Stefan W. Hell. STED microscopy reveals crystal colour centres wit nanometric resolution. (Nature Photonics, Online Publication, February 22, 2009) | doi:10.1038/nphoton.2009.2

Provided by Max Planck Institute for Biophysical Chemistry

Explore further: Yellowstone's thermal springs—their colors unveiled

add to favorites email to friend print save as pdf

Related Stories

Yellowstone's thermal springs—their colors unveiled

Dec 19, 2014

Researchers at Montana State University and Brandenburg University of Applied Sciences in Germany have created a simple mathematical model based on optical measurements that explains the stunning colors of ...

DNA sheds light on why largest lemurs disappeared

Dec 16, 2014

Ancient DNA extracted from the bones and teeth of giant lemurs that lived thousands of years ago in Madagascar may help explain why the giant lemurs went extinct. It also explains what factors make some surviving ...

Genes tell story of birdsong and human speech

Dec 11, 2014

His office is filled with all sorts of bird books, but Duke neuroscientist Erich Jarvis didn't become an expert on the avian family tree because of any particular interest in our feathered friends. Rather, ...

International team maps 'big bang' of bird evolution

Dec 11, 2014

The genomes of modern birds tell a story of how they emerged and evolved after the mass extinction that wiped out dinosaurs and almost everything else 66 million years ago. That story is now coming to light, ...

Recommended for you

Yellowstone's thermal springs—their colors unveiled

Dec 19, 2014

Researchers at Montana State University and Brandenburg University of Applied Sciences in Germany have created a simple mathematical model based on optical measurements that explains the stunning colors of ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.