Trading carats for nanometers – and defective diamonds for crystal clear microscopy
Max Planck researchers reveal individual fluorescent color centers in diamonds using STED microscopy, a light microscope with conceptually unlimited resolution
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.
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."
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-Veröffentlichung, 22. Februar 2009) | doi:10.1038/nphoton.2009.2
Prof. Dr. Stefan W. Hell, Department of NanoBiophotonics
Max Planck Institute for Biophysical Chemistry, Göttingen
Phone: +49 551 201-2500, -2503
Fax: +49 551 201-2505