Investigating approaches to enhance sensing capabilities of nitrogen-vacancy centres in nanodiamond
The nitrogen-vacancy (NV) centre in diamond has proven to be an excellent tool to probe electro-magnetic fields and temperature. It has a number of unique features: High sensitivity and resolution, long coherence and lifetimes, the ability to operate from cryogenic temperatures to hundreds of Kelvin, chemical inertness and addressability via optics and microwaves. Recent progress includes the detection of NMR and spectroscopy of single proteins on a diamond surface and in-vivo temperature measurements.
However, while the NV centre in bulk diamond has received a lot of attention, the nitrogen-vacancy in nanodiamond has not been investigated extensively due its widely seen inferior properties. It is only very recently that problems with the stability of photoluminescence and short coherence times have been overcome. The NV centre in nanodiamond is thus increasingly seen as an interesting tool for research requiring nanoscale sensors, e.g. in cells.
The findings of this thesis facilitate applications of the NV centre in nanodiamond and demonstrate its high potential for future research. Most notably, the nuclear host spin, which is intrinsic to the point defect, can be used to enhance sensitivity and resolution of measurements. In addition, the sensitivity can be improved by time-tagging the emission from the NV centre. Furthermore, the graphite layer covering nanodiamonds can be removed by annealing. This does not have negative effects on the spin properties of the hosted NV centres but enables functionalisation of the surface and therefore advanced in-vivo measurements. Finally, the capabilities of the NV centre in nanodiamond in investigating the formation of magnetic domains are demonstrated at low temperatures.
These results enable and motivate the use of the NV centre in nanodiamond for future research, most especially in biological systems.