High Conformity and Large Domain Monocrystalline Anatase on Multiwall Carbon Nanotube Core–Shell Nanostructure: Synthesis, Structure, and Interface

Abstract

We report a new facile approach to achieve highly conformal thin layers (∼10 nm) of anatase TiO 2 on nonfunctionalized carbon nanotubes (CNTs) using atomic layer deposition (ALD). The method adopts an initial deposition of amorphous TiO 2 at a low temperature of 60 °C to ensure a good conformity followed by postdeposition annealing at 450 °C under vacuum to induce a complete phase transformation to crystalline anatase TiO 2 while retaining the structural integrity of the CNTs. This approach yields unprecedented sizes of monocrystalline anatase shell domains of up to 500 nm along the CNTs. The high quality of the anatase layer is evidenced directly by high-resolution transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Atomic-scale study of the nanostructure crosssection using electron energy loss spectroscopy provides direct evidence that bonding is formed at the interface after annealing. The low grain boundary anatase shell layer with a well-bonded interface to the CNTs has a high potential of significantly enhanced performance in photocatalysis, solar energy, and nanoelectronics.

Structural and Optical Properties of Nanocrystalline TiO2 with Multiwalled Carbon Nanotubes and Its Photovoltaic Studies Using Ru(II) Sensitizers

“…The existence of all these groups is beneficial for making the chemical bond formation between the TiO 2 lattice and MWCNTs, and the absence of the other peak at 281 eV indicates that elemental carbon is not doped in the TiO 2 lattice. 37…”

Atomic Layer Deposition of Titanium Oxide on Single-Layer Graphene: An Atomic-Scale Study toward Understanding Nucleation and Growth

“…Using this method, an ∼10 nm thin monocrystalline anatase TiO 2 –CNT core–shell nanostructure was achieved, in which a conformal anatase layer composed of large domains free of defects was formed to surround the CNTs. 21 The same procedure was applied here to the titanium oxide on SLG. A uniform coverage of amorphous titanium oxide on the SLG surface was first obtained after 180 ALD cycles at 60 °C, as shown in panels a and b of Figure 2.…”

Diffusion of dilute gas in arrays of randomly distributed, vertically aligned, high-aspect-ratio cylinders

“…Our recent study constitutes an example of the coating of vertically aligned carbon nanotubes (VACNTs) with monocrystalline anatase using ALD [14]. Arrays of nanocylinders are also used in gas sensing systems [15–16].…”