A diamond based electrochemical band sensor comprising: a diamond body; and a plurality of boron doped diamond band electrodes disposed within the diamond body, wherein at least a portion of each of the plurality of boron doped diamond band electrodes is doped with boron to a level suitable to achieve metallic conduction, the boron doped diamond electrodes being spaced apart by non-conductive intrinsic layers of diamond, wherein the diamond body comprises a front sensing surface with the plurality of boron doped diamond band electrodes being exposed at said sensing surface and extending in an elongate manner across said surface, and wherein each boron doped diamond electrode has a length/width ratio of at least 10 at the front sensing surface.