Skip to main content Accessibility help

Structure of Cobalt Nanosphere Superlattice Films by Small Angle X-ray Scattering

  • Michael Beerman (a1), Masato Ohnuma (a2), Yuping Bao (a1) and Kannan M. Krishnan (a1)


Cobalt nanocrystals, recently synthesized with narrow size distributions and controlled shapes, organize in a wide range of arrays as a function of shape, size and interparticle interactions. The nanocrystals (NCs) consist of a cobalt metal core with a nominal diameter of 11 nm, and an organic surfactant surface layer with a chain length of ∼1.7 nm. For the simplest case (ε-Co nanospheres, super-paramagnetic at room temperature) a hexagonal arrangement of NCs is observed in transmission electron microscope (TEM) images when precipitated from solution onto carbon films. For practical applications and for further understanding of the self-assembly process, long range order of the super lattice must be probed over regions that are greater in extent than may be examined by TEM. Hence, small angle x-ray scattering (SAXS) measurements were performed on cobalt nanospheres randomly dispersed in solution and assembled on glass substrates. Least squares fit to the intensity distribution as a function of the scattering vector q gave an average particle diameter of 11.0 ± 0.8 nm. Structure factor contribution to the intensity profile agrees well with a quasi-random model for scattering from a face centered cubic (FCC) superlattice composed of uniform radius cobalt spheres. The measured nearest neighbor interparticle spacing, 14.1 nm, agrees to within 2% of the predicted value of 14.4 nm based on a free energy model that governs the self-assembly of the nanoparticle system.



Hide All
1. Puntes, V.F., Krishnan, K.M. and Alivisatos, A.P., Science 291, 2115 (2001).
2. Poddar, P., Wilson, J. L., Srikanth, H., Farrell, D. F., and Majetich, S. A., Phys. Rev. B 68, 214409 (2003).
3. Luttinger, J.M. and Tisza, L., Phys. Rev. 70, 954 (1946).
4. Russier, V., J. Appl. Phys. 89, 1287 (2001).
5. Bao, Y., Beerman, M. and Krishnan, K. M., J. Magn. Magn. Mater. 266, L245 (2003).
6. Petit, C., Taleb, A., and Pileni, M.P., J. Phys. Chem. B. 103, 1805 (1999).
7. Pederson, J.S., Adv. Coll. Inter. Sci. 20, 171 (1997); Phys. Rev. B. 47, 657 (1993).
8. Hono, K. and Ohnuma, M., Magnetic Nanostructures (American Scientific Publishers, (2002).
9. Feigin, L., and Svergon, D., Structure Analysis by Small-Angle X-ray and Neutron Scattering (Plenum, New York, 1987).
10. Cullity, B. D., Elements of X-ray Diffraction, 2nd Ed. (Addison-Wesley, 1978).
11. Tadmor, R., Rosensweig, R.E., Frey, J. and Klein, J., Langmuir 16, 9117 (2000).
12. Tadmor, R., J. Phys.: Condens. Matter. 13, L195 (2001).
13. Israelachvili, J.N., Intermolecular and surface forces with applications to colloidal and biological systems (Academic Press, London, 1985).

Structure of Cobalt Nanosphere Superlattice Films by Small Angle X-ray Scattering

  • Michael Beerman (a1), Masato Ohnuma (a2), Yuping Bao (a1) and Kannan M. Krishnan (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed