Electrochemical performance of micro/nano-structured boron-doped diamond electrodes for sensing applications

In this work, we will address the utilisation of novel micro/nano structures created by bottom-up and top-down approaches on the surface of highly conductive nanocrystalline boron-doped diamond films for the enhancement of electrochemical detection in aqueous media. Boron-doped diamond (BDD) films have been used since many years as electrodes in environments that require high electrode stability, robustness and reproducibility, such as in water purification systems, due to diamond's resistance to corrosion and to fouling. More recently, diamond has been applied as electrodes for (bio)electrochemical sensing, due to its large potential window (~3 V for O-terminated diamond surface), low background current and inherent biocompatibility. Diamond sensors that can be miniaturised and incorporated in lab-on-chip devices for analysis and point-of-care diagnosis are of particular relevance in the medical field. Additionally, there is currently substantial research efforts to use diamond for cell/neuron stimulation in the form of miniaturised electrode arrays. Typically, most of the applications described above make use of as-grown BDD films, which consist of relatively flat surfaces with almost 1:1 effective area to geometric area [1]. A few reports on nanostructured BDD films have already demonstrated substantial performance gains in electrochemical sensing and cell stimulation when the surface area increases many-fold [2, 3]. However, structuring all-diamond electrode surfaces involves complex cleanroom processing (e.g. lithography, reactive ion etching) that are costly and time-consuming, and therefore new fabrication routes are desirable. In this work, we will describe novel, simple and straightforward fabrication techniques for diamond surface structuring that do not require complex and long-flow manufacturing procedures. The electrochemical sensing performance of the fabricated BDD electrodes will be evaluated with standard, typically employed redox couples, and contrasted with as-grown electrodes. Finally, novel sensing application will be explored. The electrochemical characterisation will be done by cyclic voltammetry and electrochemical impedance spectroscopy. The base material consists of ~4 µm thick conductive (B-doped) nanocrystalline diamond films. References 1.Yang, N., J. Hees, and C.E. Nebel, Diamond Ultramicro- and Nano-electrode Arrays, in Novel Aspects of Diamond: From Growth to Applications, N. Yang, Editor. 2015, Springer International Publishing: Cham. p. 273-293. 2.Hébert, C., et al. Carbon, 2015. 90: p. 102-109. 3.Yang, N., J.S. Foord, and X. Jiang. Carbon, 2016. 99: p. 90-110.