Nature455, 648-651 (2 October 2008) | doi:10.1038/nature07278; Received 23 April 2008; Accepted 18 July 2008
Nanoscale imaging magnetometry with diamond spins under ambient conditions
Gopalakrishnan Balasubramanian1, I. Y. Chan2,6, Roman Kolesov1, Mohannad Al-Hmoud1, Julia Tisler1, Chang Shin3, Changdong Kim3, Aleksander Wojcik3, Philip R. Hemmer3, Anke Krueger4, Tobias Hanke5, Alfred Leitenstorfer5, Rudolf Bratschitsch5, Fedor Jelezko1 & Jörg Wrachtrup1
3 Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany
Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454, USA
Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas 77843, USA
Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
University of Konstanz and Center for Applied Photonics, 78457 Konstanz, Germany
Present address: 3 Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany.
Magnetic resonance imaging and optical microscopy are key technologies in the life sciences. For microbiological studies, especially of the inner workings of single cells, optical microscopy is normally used because it easily achieves resolution close to the optical wavelength. But in conventional microscopy, diffraction limits the resolution to about half the wavelength. Recently, it was shown that this limit can be partly overcome by nonlinear imaging techniques1, 2, but there is still a barrier to reaching the molecular scale. In contrast, in magnetic resonance imaging the spatial resolution is not determined by diffraction; rather, it is limited by magnetic field sensitivity, and so can in principle go well below the optical wavelength. The sensitivity of magnetic resonance imaging has recently been improved enough to image single cells3, 4, and magnetic resonance force microscopy5 has succeeded in detecting single electrons6 and small nuclear spin ensembles7. However, this technique currently requires cryogenic temperatures, which limit most potential biological applications8. Alternatively, single-electron spin states can be detected optically9, 10, even at room temperature in some systems11, 12, 13, 14. Here we show how magneto-optical spin detection can be used to determine the location of a spin associated with a single nitrogen-vacancy centre in diamond with nanometre resolution under ambient conditions. By placing these nitrogen-vacancy spins in functionalized diamond nanocrystals, biologically specific magnetofluorescent spin markers can be produced. Significantly, we show that this nanometre-scale resolution can be achieved without any probes located closer than typical cell dimensions. Furthermore, we demonstrate the use of a single diamond spin as a scanning probe magnetometer to map nanoscale magnetic field variations. The potential impact of single-spin imaging at room temperature is far-reaching. It could lead to the capability to probe biologically relevant spins in living cells.