TY - JOUR
T1 - Formation mechanism and shape control of monodisperse magnetic CoFe 2O 4 nanocrystals
AU - Bao, Ningzhong
AU - Shen, Liming
AU - An, Wei
AU - Padhan, Prahallad
AU - Turner, C. Heath
AU - Gupta, Arunava
PY - 2009/7/28
Y1 - 2009/7/28
N2 - The formation mechanism and shape control of monodisperse magnetic cobalt ferrite CoFe 2O 4 nanocrystals produced by thermolysis of a stoichiometric Co 2+Fe 2 3+ 3+-oleate complex in organic solution has been investigated. Synthesis of the pure ternary CoFe 2O 4 inverse spinel phase, without formation of any intermediate binary cobalt and iron oxides, is favored by the close thermal decomposition temperature of the Co2+-oleate and Fe3+-oleate precursors. For reaction temperatures between 250 and 320 °C, the nucleation and growth dynamics dictate the size and shape evolution of the nanocrystals. Prenucleation of CoFe 2O 4 occurs at 250-300 °C but without any growth of nanocrystals, because the monomer concentration is lower than the critical nucleation concentration. For temperatures in the range of 300-320 °C,which is above the thermolysis temperature of the mixed Co 2+Fe 2 3+ 3+-oleate complex, the monomer concentration increases rapidly resulting in homogeneous nucleation. Atomic clusters of CoFe 2O 4 with size<2 nm are initially formed at 314 °C that then grow rapidly when the temperature is raised to 320 °C in less than a minute. The shape of the CoFe 2O 4 nanocrystals can be reproducibly controlled by prolonging the aging time at 320 °C, evolving from initial spherical, to spherical-to-cubic, cubic, corner-grown cubic, or starlike shapes. Thus, with careful choice of reaction parameters, such as the precursor concentration and the heating rate, it is possible to achieve large-scale synthesis of shape-controlled monodisperse CoFe 2O 4 nanocrystals with high yield.
AB - The formation mechanism and shape control of monodisperse magnetic cobalt ferrite CoFe 2O 4 nanocrystals produced by thermolysis of a stoichiometric Co 2+Fe 2 3+ 3+-oleate complex in organic solution has been investigated. Synthesis of the pure ternary CoFe 2O 4 inverse spinel phase, without formation of any intermediate binary cobalt and iron oxides, is favored by the close thermal decomposition temperature of the Co2+-oleate and Fe3+-oleate precursors. For reaction temperatures between 250 and 320 °C, the nucleation and growth dynamics dictate the size and shape evolution of the nanocrystals. Prenucleation of CoFe 2O 4 occurs at 250-300 °C but without any growth of nanocrystals, because the monomer concentration is lower than the critical nucleation concentration. For temperatures in the range of 300-320 °C,which is above the thermolysis temperature of the mixed Co 2+Fe 2 3+ 3+-oleate complex, the monomer concentration increases rapidly resulting in homogeneous nucleation. Atomic clusters of CoFe 2O 4 with size<2 nm are initially formed at 314 °C that then grow rapidly when the temperature is raised to 320 °C in less than a minute. The shape of the CoFe 2O 4 nanocrystals can be reproducibly controlled by prolonging the aging time at 320 °C, evolving from initial spherical, to spherical-to-cubic, cubic, corner-grown cubic, or starlike shapes. Thus, with careful choice of reaction parameters, such as the precursor concentration and the heating rate, it is possible to achieve large-scale synthesis of shape-controlled monodisperse CoFe 2O 4 nanocrystals with high yield.
UR - http://www.scopus.com/inward/record.url?scp=67651113777&partnerID=8YFLogxK
U2 - 10.1021/cm901033m
DO - 10.1021/cm901033m
M3 - 文章
AN - SCOPUS:67651113777
SN - 0897-4756
VL - 21
SP - 3458
EP - 3468
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 14
ER -