Carbon materials such as graphite, diamond, fullerene, carbon nanotubes, graphene, carbon fibers, activated carbon, diamond-like carbon, carbon black, graphite oxide, exfoliated graphene, and so forth are materials which are composed of mainly carbon atoms . These carbon materials have been utilized for reinforced materials (airplane, automobile, sporting goods, tire), catalyst supports, electrodes (dry cells, fuel cells), molecular sieves, adsorbents for water purification, deodorants, shampoo, cosmetics, face mask, coating surfaces, electromagnetic interference shielding, heat dissipation, candies, medicines as adsorbents, and so forth.

           Fullerene                           Nanotube                                Graphene


Interests of our researches
Carbon materials include various defects such as functional groups, vacancy defects, and 5, 7 rings. All the defects affect the properties of carbon materials. Controlling and analyzing these defects in detail will improve the properties of carbon materials.

(1) Analyses of defect structures on graphene
(1-1) Analyses by spectroscopy and microscopy
Nano carbon materials include functional groups, vacancy defects, pentagons, and heptagons (Fig. 1-1). We analyze the defective structures of several-layered graphene using XPS, IR, TEM(Fig. 1-2), and Raman(Fig. 1-3).

Fig. 1-1 Types of defects on graphene         Fig. 1-2 TEM image of graphene  Fig. 1-3 Raman spectrum of graphene

(1-2)Defective structure analysis using DFT calculation(XPS・IR):

Various defects such as functional groups and point defects exixt on edges and in the basal plane of carbon materials. Complete understanding of these defects is essential to maximize the properties of carbon materials. We have conducted simulation of XPS and IR spectra for oxygen-containing functional groups (Fig. 1-2-1)[1-2-1,1-2-2], nitrogen-containing functional groups [1-2-3], and other defects.

Fig.1-2-1 Graphene with OH groups [1-2-1]      Fig.1-2-2 Simulated C1s XPS spectra of the left restructure [1-2-1]

[1-2-1] Y. Yamada, et al., "Analysis of heat-treated graphite oxide by X-ray photoelectron spectroscopy", J Mater Sci 48 (2013) 8171-8198.
[1-2-2] J. Kim, Y. Yamada, et al., "Pyrolysis of epoxidized fullerenes analyzed by spectroscopies", J Phys Chem C, accepted.
[1-2-3] Y. Yamada, et al.,"Nitrogen-containing graphene analyzed by X-ray photoelectron spectroscopy", Carbon 70(2014)59-74.

(2) Elimination of defects from nanocarbon materials

Defects influence on the mechanical, electronic, thermal properties of carbon materials. Our goal is to heal defects in nano carbon materials.

(3) Controlling the amount of defects and size of nano carbon materials

Carbon materials contain the basal plane and edges. We introduced vacancy defects in the basal plane (Fig. 3-1), and analyzed the defect structure [3-1].

Fig.3-1 Process to introduce vacancy defects

          Fig.3-2 Sub-nanometer vacancy defects introduced on graphene by oxygen gas

[3-1] Y. Yamada, K. Murota, et al., "Subnanometer vacancy defects introduced on graphene by oxygen gas", J Am Chem Soc 136(6)(2014)2232-2235.

(4) Graphene complex

We have prepared metal ion coordinated graphene (Fig. 4), and analyzed the agglomeration mechanisms of coordinated metal ions on graphene [4-1, 4-2].

Fig. 4 Introduction of hetero atoms at vacancy defects and coordination of metal ions and STEM image of metal ion coordinated graphene [4-1]

[4-1] Y. Yamada, M. Miyauchi, et al., "Exfoliated graphene ligands stabilizing copper cations", Carbon 49 (2011) 3375-3378.
[4-2] Y. Yamada,Y. Suzuki,H. Yasuda,et al.,"Functionalized graphene sheets coordinating metal cations", Carbon 75 (2014) 81-94.

(5) Dehydrogenation reaction of poly aromatic hydrocarbons

We have prepared carbon materials by dehydrogenation of various poly aromatic hydrocarbons.

(6) Clarification of mechanisms for migration of functional groups and their gasification

Carbon materials contain functional groups in the basal plane and on edges. We have attempted to understand the mechanisms of migration of functional groups and their gasification upon heat treatment [6-1,6-2].

                  Fig. Pyrolysis of epoxidized fullerenes (Calculated by Gaussian03)

[6-1] J. Kim, Y. Yamada*, et al., "Oxygen migration and selective CO and CO2 formation from epoxidized fullerenes", J Phys Chem C 118(13)(2014)7085-7093.
[6-2] J. Kim, Y. Yamada*, et al., "Pyrolysis of epoxidized fullerenes analyzed by spectroscopies", J Phys Chem C 118(13)(2014)7076-7084.

----- Updated in April 2014 -----