Surface Functionalized Titanium Nitride Electrode for CMOS Compatible Bioelectronic Devices

The development of bioelectronic devices is heading toward high throughput and high resolution. Yet, most electrode materials utilized in electrical biosensing are not compatible with the manufacturing techniques of semiconductor chips, which somehow hinders the integration and miniaturization of these devices. Titanium nitride (TiN) is a durable and economical material that is widely used in CMOS-based integrated circuits, bioelectronic systems, electrocatalytic systems, etc. Considering different application scenarios, new and efficient methods are required to functionalize TiN surface. In this study, a surface functionalization approach by covalent grafting of an organic thin film containing hydroxyl groups on TiN surface via electroreduction of diazonium salt 4-(2-hydroxyethyl)benzenediazonium was presented. Cyclic voltammetry (CV) procedures were carried out at the potential ranges of -0.8 V~0.5 V (vs Ag/AgCl) with varying numbers of potential cycles (i. e., 5, 25, and 50 cycles) in order to study the thickness of modification layer. Then, the electrochemical property, surface morphology, and chemical structures of the sample before and after modifications were investigated via multiple characterization techniques, such as CV, atomic force microscopy (AFM), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), etc., thereby confirming the successful grafting of hydroxyl groups onto the TiN surface. The experiments on DNA synthesis aimed to explore the potential of modified TiN electrode as a novel platform for DNA data storage applications and the corresponding proof-of-principle was accomplished by the process of coupling Cy3-phosphoramidite. Finally, the experiments were successfully reproduced on the randomly selected sites of the modified TiN microarray chips demonstrating the potential of technical protocol to extend applications in future bioelectronic devices, such as bio-sensing, high-throughput DNA synthesis, and molecular manipulation.