Project DiaNanoRa: Diamond scanning probes for novel imaging techniques in the life sciences

Impurities in diamond as sensors

A single nitrogen atom replaces a carbon atom and form together with a vacancy the NV center.

Atomic impurities in diamond, so called color centers, form artificial atoms: bound inside the crystal, they absorb and emit light similar to atoms. Electrons bound to the color center lead to magnetic moments (spins), the color centers are long-term stable and can be used even at room temperature. Their light emission is so bright, that single centers can be observed in confocal laser fluorescence microscopy.  The most prominent color center in diamond is the nitrogen vacancy (NV) center (see figure).

Color centers are versatile sensors: their electronic spins react highly sensitive to magnetic fields; for NV centers the spin state can be read out optically via the fluorescence of the color center. The presence of e.g. dye molecules or other dipoles (e.g. graphene) in the vicinity of the color center (distance < 50 nm) also changes the light emission (lifetime changes). Due to their sub-nm size (atomic size), color centers can be used for high spatial resolution imaging (potentially down to nm resolution) as the sensor size will never limit the resolution. However, the color center has to be brought very close to the sample to enable high resolution imaging.

 

 

Literature:

First observation single NV: C. Kurtsiefer et al  Phys. Rev. Lett.,  85, 290-293 (2000), Link 

 

Review Magnetic Sensing using NV centers: L. Rondin et al Rep. Prog. Phys. 77 056503 (2014) Link

 

Near field interaction NVs: J. Tisler et al ACS Nano 10 7893 (2011) Link

Diamond scanning probes for the life sciences

Schematic Representation of a diamond scanning probe (nanowire and plattform. Scanning electron microscope image of diamond nanowires array.

 

To harness the full potential of diamond color centers for nano-imaging, we embed the color centers into single-crystal scanning probe nanostructures. Such an all-diamond scanning probe consists of a 2 µm long diamond nanowire on a holding platform (see Figure). Color centers are formed close to the end facet of the nanowire, e.g. via ion-implantation. With this device, the color center can be brought very close to the sample surface. The nanowire channels the color center emission and enables efficient collection of the fluorescence light. The nanostructures are fabricated in highly pure, synthetic diamond. In a combined setup consisting of a confocal microscope and an atomic force microscope (AFM), the probes can be used for scanning probe imaging, whereas the AFM enables scanning in close contact with the sample. The technique has been used variously in physics and material sciences. In life science color center are considered as promising, novel sensors for electrical currents and the near field of molecules.

 

Literature:

 

First Realization of all diamond scanning probes: P. Maletinsky et al Nature Nanotechn. 7, 320 (2012) Link

 

Scanning Probe imaging using near field energy transfer J. Tisler et al., Nanoletter 7, 3152 (2013) Link

 

Diamond Nanowires E. Neu et al. Appl. Phys. Lett. 104, 153108 (2014) Link

 

NV Sensing in biology: L.T. Hall et al. MRS Bulletin 38, 162 (2014) Link

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