Particle Sedimentation Behaviors in a Density Gradient

  • Pengsong Li
Part of the SpringerBriefs in Molecular Science book series (BRIEFSMOLECULAR)


Density gradient centrifugation, as an efficient separation method, is widely used in the purification of nanomaterials including zero, one-, and two-dimensional nanomaterials, such as FeCo@C nanoparticles, gold nanoparticles, gold nanobar, graphene, carbon nanotubes, hydrotalcite, zeolite nanometer sheet (the examples can be found in Chap.  5). Each system needs separation parameter optimization, which comes from tremendous research experiments. When particles are put on the top of density gradient medium, they will have a definite settling rate under centrifugal force (Fc) [1], which is influenced by their net density, size, and shape. In a sufficiently intense centrifugal field, the particle motion held quietly free from gravity and vibration [2]. This is the principle of the density gradient ultracentrifuge. Based on the above principle, we discussed the particle sedimentation behaviors and built the kinetic equation in a density gradient media. The kinetic equation could apply to zero, one-, and two-dimensional nanomaterials, within its variation form accordingly. We found that the separation parameters could be optimized based on the kinetic equation. A MATLAB program was further developed to simulate and optimize the separation parameters. The calculated best parameters could be deployed in practice to separate given nanoparticles successfully.


Density gradient centrifugation Sedimentation mechanism Sedimentation kinetics Mathematical model Separation parameters Optimization calculation 


  1. 1.
    Ma X, Kuang Y, Bai L, Chang Z, Wang F, Sun X, Evans DG (2011) Experimental and mathematical modeling studies of the separation of zinc blende and wurtzite phases of CdS nanorods by density gradient ultracentrifugation. ACS Nano 5(4):3242–3249CrossRefGoogle Scholar
  2. 2.
    Mcbain JW (2002) Opaque or analytical ultracentrifuges. Chem Rev 2:289–302Google Scholar
  3. 3.
    Lin Y (2008) Centrifugal Separation(Modern separation science and technology books). Chemical Industry Press. 林元喜 (2008) 离心分离(现代分离科学与技术丛书). 化学工业出版社Google Scholar
  4. 4.
    Price CA (1982) Centrifugation in density gradients. Academic PressCrossRefGoogle Scholar
  5. 5.
    Svedberg T, Pedersen KO (1940) The Ultracentrifuge. The UltracentrifugeGoogle Scholar
  6. 6.
    Sun X, Tabakman SM, Seo WS, Zhang L, Zhang G, Sherlock S, Bai L, Dai H (2009) Separation of nanoparticles in a density gradient: FeCo@C and gold nanocrystals. Angew Chem Int Edit 121(5):957–960CrossRefGoogle Scholar
  7. 7.
    Kuang Y, Song S, Huang J, Sun X (2015) Separation of colloidal two dimensional materials by density gradient ultracentrifugation. J Solid State Chem 224:120–126CrossRefGoogle Scholar
  8. 8.
    Bai L, Ma X, Liu J, Sun X, Zhao D, Evans DG (2010) Rapid separation and purification of nanoparticles in organic density gradients. J Am Chem Soc 132(7):2333–2337CrossRefGoogle Scholar
  9. 9.
    Li P, Huang J, Luo L, Kuang Y, Sun X (2016) Universal parameter optimization of density gradient ultracentrifugation using CdSe nanoparticles as tracing agents. Anal Chem 88(17):8495CrossRefGoogle Scholar

Copyright information

© The Author(s) 2018

Authors and Affiliations

  • Pengsong Li
    • 1
  1. 1.State Key Laboratory of Chemical Resource EngineeringBeijing University of Chemical TechnologyBeijingChina

Personalised recommendations