Experimental and theoretical studies of Boron Nitride Nanotubes: Electric arc discharge and DFT calculations.

Abstract

We present a joint experimental and theoretical study dedicated to analyze the properties of Boron-Nitride (BN) nanotubes. First, multi-walled boron-nitride (MWBN) nanotubes were prepared by means of a modified electric arc discharge technique using boron-nitride powder. In a first stage, the BN powder was subjected to a ball milling process for about 100 hours in an atmosphere of ammonia. Later on, BN nanoparticle formation took place after the preparation of a pressed pellet at 300 °C to 25 kPa which was sintered in a furnace at approximately 1000 °C in nitrogen atmosphere for 15 hrs. The pellets were subsequently incorporated to the electrical arc discharge set up to obtain the MWBN nanotubes. The as-prepared MWBN nanotubes samples were characterized by scanning electron microscope, X-ray photoelectron spectroscopy, and micro RAMAN spectroscopy. Second, and in order to understand the measured data, extensive density functional theory calculations were performed. We present low energy atomic configurations for model finite-length armchair, zigzag, and chiral single-walled BN nanotubes, as well as for two-dimensional BN sheets. We calculate the vibrational spectra and the optical gap of each one of our considered structures and reveal how precise details of the local atomic environment can be revealed. Finally, we consider BN nanotubes functionalized with NH₂, glycine and S-H molecules. We present the structural characteristics of the adsorbed configurations, charge transfer effects, and the electronic behavior. We conclude by underlining the crucial role played by molecular functionalization in order to tune the properties of these kinds of systems.