Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Evidence for a macroscopic electric field in the sedimentation profiles of charged colloids

Nature volume 429, pages 857–860 (2004)Cite this article

Abstract

The determination of molecular masses from barometric sedimentation profiles, a main topic in ultracentrifugal analysis, is thought to be quantitatively correct for non-interacting particles1,2. Whereas this expectation is justified for uncharged colloids or macromolecules at low volume fractions, early ultracentrifugation studies3 on charged particles had already indicated that the obtained masses might be much too low. More recently, expanded sedimentation profiles have been observed for charged particles4,5, sometimes inflated by orders of magnitude5 relative to the barometric prediction, which highlights a shortcoming in our understanding of centrifugation of even very dilute charged species5. Theory6 and simulations7, anticipated by various authors4,8,9, now propose that strongly non-barometric sedimentation profiles might be caused by an internal macroscopic electric field that, even for non-interacting particles, significantly decreases the buoyant particle mass. The existence of this field and its intriguing consequences still lack experimental verification. Here we report ultracentrifugation experiments on charged colloidal silica spheres, showing both the existence of such a macroscopic electric field and its drastic effects on the sedimentation profiles of very dilute dispersions at low ionic strength.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Experimental sedimentation–diffusion equilibrium profiles for dispersions of charged silica spheres in ethanol plotted as attenuance against the square of the radial distance from the centre of rotation.
Figure 2: Analysis of the experimental profiles from Fig. 1a.

Similar content being viewed by others

References

  1. Harding, S. E., Rowe, A. J. & Horton, J. C. (eds) Analytical Ultracentrifugation in Biochemistry and Polymer Science (Royal Society of Chemistry, Cambridge, 1993)

  2. Stryer, L. Biochemistry, 4th edn (Freeman, New York, 1995)

    Google Scholar 

  3. Svedberg, T. & Pederson, O. Die Ultrazentrifuge (Dresden, 1940)

    Google Scholar 

  4. Piazza, R., Bellini, T. & Degiorgio, V. Equilibrium sedimentation profiles of screened charged colloids: a test of the hard-sphere equation of state. Phys. Rev. Lett. 71, 4267–4270 (1993)

    Article  CAS  ADS  Google Scholar 

  5. Philipse, A. P. & Koenderink, G. H. Sedimentation-diffusion profiles and layered sedimentation of charged colloids at low ionic strength. Adv. Colloid Interface Sci. 100–102, 613–639 (2003)

    Article  Google Scholar 

  6. Van Roij, R. Defying gravity with entropy and electrostatics: sedimentation of charged colloids. J. Phys.: Condens. Matter 15, S3569–S3580 (2003)

    CAS  ADS  Google Scholar 

  7. Hynninen, A. P., Van Roij, R. & Dijkstra, M. Sedimentation profiles of charged colloids: Entropic lift and charge separation. Europhys. Lett. 65, 719–725 (2004)

    Article  CAS  ADS  Google Scholar 

  8. Biben, T. & Hansen, J. P. Sedimentation equilibrium in concentrated charged–stabilized colloidal suspensions. J. Phys.: Condens. Matter 6, A345–A349 (1994)

    CAS  ADS  Google Scholar 

  9. Löwen, H. The apparent mass in sedimentation profiles of charged suspensions. J. Phys.: Condens. Matter 10, L479–L485 (1998)

    ADS  Google Scholar 

  10. Hunter, R. J. Foundations of Colloid Science Vol I (Clarendon, Oxford, 1991)

    Google Scholar 

  11. Becker, W. M., Kleinsmith, L. J. & Mardin, J. The World of the Cell (Benjamin Cummins, San Francisco, 2000)

    Google Scholar 

  12. Meselson, M. & Stahl, F. W. The replication of DNA in Escherichia coli. Proc. Natl. Acad. Sci. USA 44, 671–682 (1958)

    Article  CAS  ADS  Google Scholar 

  13. Philipse, A. P. Remarks on the Donnan condenser in the sedimentation–diffusion equilibrium of charged colloids. J. Phys.: Condens. Matter (submitted)

  14. Philipse, A. P. & Vrij, A. Preparation and properties of nonaqueous model dispersions of chemically modified charged silica spheres. J. Colloid Interf. Sci. 128, 121–153 (1989)

    Article  CAS  ADS  Google Scholar 

  15. Philipse, A. P. & Vrij, A. Determination of static and hydrodynamic interactions between monodisperse silica spheres in an optically matching, organic solvent. J. Chem. Phys. 88, 6459–6470 (1988)

    Article  CAS  ADS  Google Scholar 

  16. Thies-Weesie, D. M. E., Philipse, A. P., Nägele, G., Mandl, B. & Klein, R. Non-analytical concentration dependence of sedimentation of charged silica spheres in an organic solvent. Experiments and calculations. J. Colloid Interf. Sci 176, 43–54 (1995)

    Article  CAS  ADS  Google Scholar 

  17. Rasa, M., Philipse, A. P. & Meeldijk, J. D. Heteroaggregation, repeptisation, and stability in mixtures of oppositely charged colloids. J. Colloid Interf. Sci.(in press)

Download references

Acknowledgements

We thank R. van Roij and G. Koenderink for discussions and collaboration, B. Erné for sharing insights and unpublished results on Donnan potentials, N. Zuiverloon for synthesizing the silica spheres, and D. Thies-Weesie for maintenance of the ultracentrifuge. This work was supported financially by The Netherlands Organization for Scientific Research (NWO/Stichting Chemische Wetenschappen).

Author information

Authors and Affiliations

  1. Van 't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, Utrecht, 3584 CH, The Netherlands

    Mircea Raşa & Albert P. Philipse

Authors
  1. Mircea Raşa
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Albert P. Philipse
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Albert P. Philipse.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Raşa, M., Philipse, A. Evidence for a macroscopic electric field in the sedimentation profiles of charged colloids. Nature 429, 857–860 (2004). https://doi.org/10.1038/nature02672

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature02672

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing