TY - JOUR
T1 - Growth of nano Co encapsulated in carbon-shell
AU - Kang, H. Y.
AU - Wang, H. Paul
AU - Lin, W. K.
AU - Sun, I. W.
AU - Jou, C. J.G.
AU - Jeng, U. Ser
AU - Chang, S. G.
N1 - Funding Information:
The financial supports of the Taiwan National Science Council, Ministry of Economic Affairs (Project #: 101-EC-17-A-10-S1-187), Bureau of Energy, and National Synchrotron Radiation Research Center are gratefully acknowledged. We also gratefully thank Dr. F.C. Chang for assisting the experiments of magnetic properties.
PY - 2012/12
Y1 - 2012/12
N2 - Nanostructured cobalt is one of the key elements in catalysis and therapeutic drug delivery. To design and prepare nanosize-controllable cobalt, a better understanding of its growth mechanism is essential. Growth of Co nanoparticles encapsulated in carbon-shell (Co@C) during temperature-programmed carbonization of the Co2+-β-cyclodextrin (CD) complex at 363-573 K was, therefore, studied by in situ synchrotron small-angel X-ray scattering and X-ray absorption near edge structure spectroscopy. The carbon-shell having a thickness of about 2 nm can prevent the core Co from being aggregated and oxidized. A relatively slow reduction of Co(II) to Co is observed at 393-423 K (stage I) prior to a particle growth transition-state possessing Co of 2.2 nm in diameter at 423-483 K. At 483-513 K (stage II), an increasing Co(II) reduction rate coupled with a rapid fusion and coalescence of Co nanoparticles is found. The average growth rates of Co at stages I and II are about 27 and 98 atoms/min, respectively. The most-probable particle diameter of the ripened Co is 5.9 nm. The carbon-shell can be removed by steam reforming to yield the Co nanoparticles. This work also exemplifies the possible temperature-controllable growth of Co@C, especially in the Co size range of 2-6 nm in diameter.
AB - Nanostructured cobalt is one of the key elements in catalysis and therapeutic drug delivery. To design and prepare nanosize-controllable cobalt, a better understanding of its growth mechanism is essential. Growth of Co nanoparticles encapsulated in carbon-shell (Co@C) during temperature-programmed carbonization of the Co2+-β-cyclodextrin (CD) complex at 363-573 K was, therefore, studied by in situ synchrotron small-angel X-ray scattering and X-ray absorption near edge structure spectroscopy. The carbon-shell having a thickness of about 2 nm can prevent the core Co from being aggregated and oxidized. A relatively slow reduction of Co(II) to Co is observed at 393-423 K (stage I) prior to a particle growth transition-state possessing Co of 2.2 nm in diameter at 423-483 K. At 483-513 K (stage II), an increasing Co(II) reduction rate coupled with a rapid fusion and coalescence of Co nanoparticles is found. The average growth rates of Co at stages I and II are about 27 and 98 atoms/min, respectively. The most-probable particle diameter of the ripened Co is 5.9 nm. The carbon-shell can be removed by steam reforming to yield the Co nanoparticles. This work also exemplifies the possible temperature-controllable growth of Co@C, especially in the Co size range of 2-6 nm in diameter.
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U2 - 10.1016/j.elspec.2012.11.010
DO - 10.1016/j.elspec.2012.11.010
M3 - Article
AN - SCOPUS:84871771421
SN - 0368-2048
VL - 185
SP - 567
EP - 572
JO - Journal of Electron Spectroscopy and Related Phenomena
JF - Journal of Electron Spectroscopy and Related Phenomena
IS - 12
ER -