Solution assembly of vertically aligned diamond nanotube arrays from diamond nanocrystals

A facile and cost-effective solution method is presented to fabricate vertically aligned diamond nanotube arrays. The acid-treated diamond nanoparticles were dispersed in the organic solvent and then assembled to diamond nanotubes with the aid of an anodic aluminum oxide template. Scanning electron microscope characterization confirmed the uniformity of the as-produced diamond nanotubes and the morphology evolution was a function of process parameters. X-ray diffractions and Raman spectroscopy characterization also confirmed the one-dimensional nanodiamond structures. Further field emission tests indicated that the diamond nanotube array showed the turn-on electric field at 1.67 V/μm, which was more than 10-fold lower than that of a diamond nanoparticle film. The emission current density of the diamond nanotube array at 2.3 V/μm was approximately 0.1 mA/cm ². Further optimization of the diamond nanotube structure and the interface between nanotubes and substrate will significantly improve the emitter properties. This approach opens a new avenue for mass-production of the vertically aligned diamond nanotube arrays for industrial applications.