Synthesis, structure, and biocompatibility of pulsed laser-deposited TiN nanowires for implant applications

A bottom-up based pulsed laser deposition technique has been used to grow titanium nitride (TiN) nanowires on single crystalline substrates. The first step of this method is the dissolution of laser ablated gaseous TiN material in the nanodimensional catalytic gold (Au) liquid islands located on the substrate surfaces. The continuous dissolution of TiN results in the supersaturation of liquid Au with TiN followed by extrusion of solid TiN material in the nanowire form at the liquid/solid interface. The growth of TiN nanowires continues as long as its dissolution rate into the catalyst Au matches the extrusion rate of solid TiN. This bottom-up approach gives rise to a one-dimensional TiN nanowire structures (length: 200-300 nm and diameter: 20-30 nm) capped with Au. The ascent of Au nanodots to the top of TiN nanowires can be explained based on breaking of weaker bonds and building of stronger bonds. The TiN nanowires are provided vertical alignment by selecting a plane of the substrate that provides the least lattice mismatching to the (111) plane of TiN which has lower surface energy than its other planes: (100) or (110). After the successful formation and structural characterization, a lactate dehydrogenase (LDH) release assay has been used to confirm the biocompatibility and cytotoxicity of these nanowires.