The increase in particle dimension is ascribed to the longer reaction time, which allows and promotes the crystal growth after nucleation in the hydrothermal process. Images of isolated nanocrystals at higher magnification
(HRTEM, Figure 1d) further confirm the DMXAA concentration crystallinity and phase purity of the as-synthesized cobalt ferrites. The well-defined two-dimensional lattice fringes of 10-nm nanocrystal indicate good crystallinity and lack of structural defects. The plane distance is measured as 2.99 Å, in good agreement with the (220) interplane spacing of the reported CoFe2O4 lattice. Figure 1 TEM image, EDX spectra, XRD pattern, and HRTEM of CoFe 2 O 4 nanocrystals. Low magnification TEM image (a) of CoFe2O4 nanocrystals synthesized via a solvothermal process and its corresponding EDX spectra (b). (c) XRD patterns of the CoFe2O4 nanocrystals reacted for 10 and 20 h. (d) High-resolution TEM image. Inset, corresponding its fast Fourier MRT67307 cell line transform indicating the particle is oriented along the zone axis [100]. Considering that the magnetic properties of the nanocrystal were to be compared that of the known bulk
behavior of CoFe2O4, unequivocal identification of the crystal phase, symmetry, and composition of an individual nanocrystal was highly desirable. To further verify the crystal structure, the samples were studied by high angle annular dark field (HAADF) STEM and compared with a calculated model. Figure 2a illustrates the projection of the atomic structure model of CoFe2O4 along the <110 > zone axis, with oxygen Carnitine palmitoyltransferase II atoms removed. Figure 2b shows the HAADF-STEM image of the as-synthesized nanocrystals, where the bright dots Go6983 supplier are Co and Fe atoms. The calculated positions of the transition metal atoms are superposed on the HAADF-STEM image, indicating that the elements and positions suggested in the model precisely fit those observed by STEM. As the intensity of the STEM pattern is proportional to Z 2[23], where Z is the atomic number, O atoms are not visible, while Co and Fe atoms are present. Since the atomic numbers of Co (Z
= 27) and Fe (Z = 26) are similar, it would be difficult to distinguish one from the other in the HAADF-STEM image. However, some Co columns exhibit stronger contrast than other Co/Fe columns in Figure 2b. This is because the former Co columns have twice the number of Co atoms as the dimmer ones. In addition, the measured interplane distance of (111) planes (4.80 Å) is consistent with the reported CoFe2O4 crystal information. Figure 2 Projection of the inverse spinel structure and the HAADF-STEM image of CoFe 2 O 4 nanoparticles. (a) Projection of the inverse spinel structure of CoFe2O4 along the <110> zone axis. Red balls represent iron atoms; green balls represent cobalt atoms; oxygen atoms have been removed for clarity. (b) Atomic resolution HAADF-STEM image of CoFe2O4 nanoparticles. Bright balls correspond to cobalt and ferrite atoms.