Topic: Controlling Defects and Morphology of Nanotubes and Graphene during Growth: The Role of Dopants

Speaker: Prof. Mauricio Terrones
         Department of Physics, Department of Chemistry,
         Department of Materials Science and Engineering and Center for 2D Layered Materials. 
         The Pennsylvania State University, USA. & Shinshu University, Nagano, Japan

Time: 10:30-12:00 AM., (Fri.) May 16, 2014

Venue: Room 403, Shi Changxu Building, IMR CAS

Abstract

In this talk, we will first describe the synthesis of carbon nanotubes and nanotube networks using different dopants during chemical vapor deposition. In particular, we will discuss the effects of sulfur, boron and nitrogen. It will be shown that these dopants are responsible for significant changes in the nanotube morphology and electronic properties. For example, sulfur induces the formation of pentagons and heptagons, whereas boron aids the growth of heptagonal carbon rings, and nitrogen promotes the formation of pentagonal cusps. It will be demonstrated that it is indeed possible to assemble/grow carbon nanotube networks if a careful control of dopants is achieved during chemical vapor deposition (CVD) growth. High resolution electron energy loss spectroscopy (HR-EELS) studies on these nanotube materials will be presented, and the locations of boron, sulfur and nitrogen within nanotubes will also be shown. First principles theoretical calculations on nanotubes containing pentagon, hexagons and heptagons in the presence of these dopants will be discussed. Recent experiments on different doped graphene layers will also be presented. We will discuss the citotoxicity and applications as molecular sensors of these doped nanocarbons.

The talk will also discuss the synthesis of large-area, high-quality monolayers of nitrogen- and boron-doped graphene sheets on Cu foils using ambient-pressure chemical vapor deposition (AP-CVD). Scanning tunneling microscopy (STM) and spectroscopy (STS) reveal that the defects in the doped graphene samples arrange in different geometrical configurations exhibiting different electronic properties. Interestingly, these doped layers could be used as efficient molecular sensors and electronic devices. In addition, the synthesis of hybrid carbon materials consisting of sandwich layers of graphene layers and carbon nanotubes have been synthesized by a self assembly route. These films are novel, energetically stable and could well find important applications as field emission sources, catalytic supports, gas adsorption materials and super capacitors.

References