Electroanalytical performance of nitrogen-containing tetrahedral amorphous carbon thin-film electrodes

Tetrahedral amorphous carbon (ta-C) consists of a mixture of sp(3)- and sp(2)-bonded carbon ranging from 60 to 40% (sp(3)/sp(3)+sp(2)) depending on the deposition conditions. The physical, chemical, and electrochemical properties depend on the sp(2)/sp(3) bonding ratio as well as the presence of incorporated impurities, such as hydrogen or nitrogen. The ability to grow ta-C at lower temperatures (25-100 degrees C) on a wider variety of substrates as compared to CVD diamond is an advantage of this material. Herein, we report on the structural and electrochemical properties of nitrogen incorporated ta-C thin films (ta-C:N). The incorporation of nitrogen into the films decreases the electrical resistivity from 613 +/- 60 (0 sccm N-2) to 1.10 +/- 0.07 Omega-cm (50 sccm N-2), presumably by increasing the sp(2)-bonded carbon content and the connectedness of these domains. Similar to boron doped diamond, these materials are characterized by a low background voltammetric current, a wide working potential window (similar to 3 V), and relatively rapid electron transfer kinetics for aqueous redox systems, including Fe(CN)(6)(-3/-4) and Ru(NH3)(6)(+3/+2), without conventional pretreatment Additionally, there is weak molecular adsorption of polar molecules (methylene blue) on the ta-C surface. Overall, the properties of the ta-C and ta-C:N electrodes are such that they could be excellent new choices for electroanalytical measurements.