Visualizing chemical states and defects induced magnetism of graphene oxide by spatially-resolved-X-ray microscopy and spectroscopy.
This investigation studies the various magnetic behaviors of graphene oxide (GO) and reduced graphene oxides (rGOs) and elucidates the relationship between the chemical states that involve defects therein and their magnetic behaviors in GO sheets. Magnetic hysteresis loop reveals that the GO is ferromagnetic whereas photo-thermal moderately reduced graphene oxide (M-rGO) and heavily reduced graphene oxide (H-rGO) gradually become paramagnetic behavior at room temperature. Scanning transmission X-ray microscopy and corresponding X-ray absorption near-edge structure spectroscopy were utilized to investigate thoroughly the variation of the C 2p(π*) states that are bound with oxygen-containing and hydroxyl groups, as well as the C 2p(σ*)-derived states in flat and wrinkle regions to clarify the relationship between the spatially-resolved chemical states and the magnetism of GO, M-rGO and H-rGO. The results of X-ray magnetic circular dichroism further support the finding that C 2p(σ*)-derived states are the main origin of the magnetism of GO. Based on experimental results and first-principles calculations, the variation in magnetic behavior from GO to M-rGO and to H-rGO is interpreted, and the origin of ferromagnetism is identified as the C 2p(σ*)-derived states that involve defects/vacancies rather than the C 2p(π*) states that are bound with oxygen-containing and hydroxyl groups on GO sheets.
Department of Physics, Tamkang University, Tamsui 251, Taiwan.|Institute for Molecular Science, Okazaki 444-8585, Japan.
Y F
YF
Wang
Department of Physics, Tamkang University, Tamsui 251, Taiwan.|Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India.
Shashi B
SB
Singh
Department of Physics, Tamkang University, Tamsui 251, Taiwan.|Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India.
Mukta V
MV
Limaye
Department of Physics, Tamkang University, Tamsui 251, Taiwan.
Y C
YC
Shao
Department of Physics, Tamkang University, Tamsui 251, Taiwan.
S H
SH
Hsieh
Department of Physics, Tamkang University, Tamsui 251, Taiwan.
L Y
LY
Chen
Department of Physics, Tamkang University, Tamsui 251, Taiwan.
H C
HC
Hsueh
Department of Physics, National Tsinghua University, Hsinchu 300, Taiwan.
H T
HT
Wang
Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan.
J W
JW
Chiou
Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan.
Y C
YC
Yeh
Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan.
C W
CW
Chen
National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan.
C H
CH
Chen
Department of Physics, University of South Africa, Johannesburg 1710, South Africa.
Sekhar C
SC
Ray
Canadian Light Source Inc., University of Saskatchewan, Saskatoon S7N 2V3, Canada.
J
J
Wang
Department of Physics, Tamkang University, Tamsui 251, Taiwan.
W F
WF
Pong
Institute for Molecular Science, Okazaki 444-8585, Japan.
Y
Y
Takagi
Institute for Molecular Science, Okazaki 444-8585, Japan.
T
T
Ohigashi
Institute for Molecular Science, Okazaki 444-8585, Japan.
T
T
Yokoyama
Institute for Molecular Science, Okazaki 444-8585, Japan.
N
N
Kosugi
D006108:Graphite / Q000737:chemistry*; D008853:Microscopy / Q000379:methods; D008962:Models, Theoretical; D010087:Oxides / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy / Q000379:methods
D010087:Oxides; D006108:Graphite