Professor: 436
Graduate office: 435B
Department of Chemistry
Yonsei University
Shinchon-dong, Seodaemun-Gu
Seoul 03722, Korea
  Batch growth process of carbon nanotube produces carbon nanotubes with inhomogeneous physical properties. Therefore, sorting carbon nanotubes according to identical properties would impact various applications such as electronic devices, nanocatalyst, and photovoltaics. We are trying to sort carbon nanotube using binding affinity between surfactant and carbon nanotubes. Recently, we demonstrated selection of single chirality nanotube from more than 23 different nanotubes in reknown journal(Nature Nanotech, 3, 356(2008)). More recently, we sorted out enantiomer of carbon nanotube using right-handed supramolecular assembly (J. Am. Chem. Soc., 134 (32), 13196 (2012)). On top of this cutting-edge technique, we try to develop mature method and utilize it to regrow single chirality tubes as a bulk quantity. Later on stage of the research, photophysics and application such as photovoltaics will be considered for their utilization. Recently, sorting method such as density gradient ultracentrifugation (DGU) are actively pursued to sort out all nanotube chiralities.

Figure 1. Various degree of carbon nanotube separation. (Far left) metallic vs semiconducting, (left) chirality, (right) handedness, and (far right) length.
  Graphene and carbon nanotubes are 2D membrane and 1D rolled-up cylinder, respectively. These nanomaterials possess exceptional electical, optical, and mechanical properties, on top of large surface area. These properties can be utilized for various applications such as supercapacitor and lithium ion battery. In order to make these application affordable, solution process to make these materials is important. Our lab exploits vitamin B2 derivatives to disperse these materials and demonstrated that carbon nanotubes wrapped by this surfactant can boost their photoluminescence quantum efficiency upto 20%. In addition, vitamine B2 can unzip graphene to produce graphene nanoribbon in solution (Carbon, 81, 629 (2014)). Usign this method, we are trying to prepare porous materials for various applications.
  2D nanomaterials such as graphene and MoS2 have been studied mainly by ensemble measurement of optical methods. Recently-developed widefield Raman and Rayleight spectroscopies offer high throughput optical method to characterize individual 2D materials using their global illumination. (Nano Lett. 11, 1-7 (2010) & ACS Nano, 6, 373-380 (2012)). Utilizing these optical methods, one can monitor various chemical events in real time and correlate with spatial and spectral resolutions. Especially, heterogeneity of graphene such as doping, number of layers, and relative rotation can be immediately obtained by these methods. As a parallel effort, we synthesize graphenes and MoS2 with various properties in both solution and solid states.

Figure 2. Graphene image obtained by reflection microscope.