Abstract: A diamond electrode and a diamond microelectrode array for biosensors and electroanalytical applications, such as electrochemical impedance spectroscopy (EIS), are disclosed. The electrode comprises a layer of ultra-smooth conductive nanocrystalline diamond (NCD) having a resistivity of >0.05 ?cm and a surface roughness of <20 nm Ra. Preferably, the diamond layer comprises boron or nitrogen-doped ultrananocrystalline diamond (UNCD) having an average grain size <10 nm and a surface roughness <10 nm Ra. It may be patterned to define a microelectrode array with a plurality of individually addressable electrodes, each having a diameter in the range from 100 nm to 100 ?m. The surface of each microelectrode is hydrogen-terminated before bio-functionalization, i.e. modifying with sensing molecules for detection of a specific biological or chemical target and coating with a blocker for reducing non-specific binding.

Abstract: Conductive diamond micro-electrode sensors and sensor arrays are disclosed for in vivo chemical sensing. Also provided is a method of fabrication of individual sensors and sensor arrays. Reliable, sensitive and selective chemical micro-sensors may be constructed for real-time, continuous monitoring of neurotransmitters and neuro-active substances in vivo. Each sensor comprises a conductive microwire, having a distal end comprising a tip, coated with nanocrystalline or ultrananocrystalline conductive diamond, and an overlying insulating layer. Active sensor areas of the conductive diamond layer are defined by openings in the insulating layer at the distal end. Multiple sensor areas may be defined by a 2 or 3 dimensional pattern of openings near the tip. This structure limits interference from surrounding areas for improved signal to noise ratio, sensitivity and selectivity.