Diamond sensor

-9. (canceled)

(canceled)

(canceled)

A single crystal diamond comprising:

• a surface which is configured, in use, to contact a fluid, the surface comprising a sensing surface region, wherein the single crystal diamond comprises a plurality of quantum spin defects in proximity to the sensing surface region;
• the surface further comprising at least one electrode region, the at least one electrode region configured, in use, to generate an electric field proximate to the sensing surface region, the electric field being sufficient to generate oxidising species in the fluid for removing contaminant material from the sensing surface region.

-18. (canceled)

(canceled)

(canceled)

A method of using a sensor assembly, the sensor assembly comprising single crystal diamond material, a first electrode and a second electrode, the single crystal diamond material comprising a sensing surface region comprising a plurality of quantum spin defects, the method comprising:

• allowing a fluid to pass over the sensing surface region of the single crystal diamond material;
• and
• generating an electric field between the first electrode and the second electrode and proximate to the sensing surface region, such that the field generates oxidising species in the fluid, the oxidising species for removing contaminant material from the sensing surface region.

(canceled)