title: All-optical sensing of a single-molecule electron spin.
abstract: We demonstrate an all-optical method for magnetic sensing of individual molecules in ambient conditions at room temperature. Our approach is based on shallow nitrogen-vacancy (NV) centers near the surface of a diamond crystal, which we use to detect single paramagnetic molecules covalently attached to the diamond surface. The manipulation and readout of the NV centers is all-optical and provides a sensitive probe of the magnetic field fluctuations stemming from the dynamics of the electronic spins of the attached molecules. As a specific example, we demonstrate detection of a single paramagnetic molecule containing a gadolinium (Gd(3+)) ion. We confirm single-molecule resolution using optical fluorescence and atomic force microscopy to colocalize one NV center and one Gd(3+)-containing molecule. Possible applications include nanoscale and in vivo magnetic spectroscopy and imaging of individual molecules.
authors.affiliation: Department of Physics, ‡Department of Chemistry and Chemical Biology, §School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: A O
authors.initials: AO
authors.lastname: Sushkov
authors.forename: N
authors.initials: N
authors.lastname: Chisholm
authors.forename: I
authors.initials: I
authors.lastname: Lovchinsky
authors.forename: M
authors.initials: M
authors.lastname: Kubo
authors.forename: P K
authors.initials: PK
authors.lastname: Lo
authors.forename: S D
authors.initials: SD
authors.lastname: Bennett
authors.forename: D
authors.initials: D
authors.lastname: Hunger
authors.forename: A
authors.initials: A
authors.lastname: Akimov
authors.forename: R L
authors.initials: RL
authors.lastname: Walsworth
authors.forename: H
authors.initials: H
authors.lastname: Park
authors.forename: M D
authors.initials: MD
authors.lastname: Lukin
keywords: Nitrogen vacancy center; all-optical; diamond; magnetometry; single-molecule spin