Investigations of suspension stability of iron oxide nanoparticles using time-resolved UV–visible spectroscopy

  • S. Vikram
  • R. Vasanthakumari
  • Takuya Tsuzuki
  • Murali RangarajanEmail author
Research Paper


This study examines the suspension stability of iron oxide nanoparticles of different sizes, magnetic susceptibility, and saturation magnetization over long time scales in dilute systems using time-resolved UV–visible spectroscopy. The effects of citric acid as a chelating agent and applied external magnetic field are also studied. UV–visible spectra are obtained at different times for citric-acid-stabilized nanoparticles dispersed in water, and the peak absorbance is tracked with time, in the presence and absence of external magnetic fields. It is seen that the nanoparticles sediment slowly even in the absence of chain formation, with the phenomenon occurring in two-to-three regimes for the systems studied. Sedimentation exhibits either exponential or power-law behavior of maximum absorbance with time. In the dilute dispersions studied, thermal dispersion is about two orders of magnitude stronger than van der Waals interactions, and chain formation is not easy. Yet, it is likely that local anisotropic structures of the nanoparticles form, through which the attractive interactions result in sedimentation. Citric acid gradually stabilizes the aggregating particles; after an initial faster sedimentation, electrostatic repulsion causes the particles to segregate, as observed by a linear increase in the concentration of the nanoparticles at long times. In the presence of magnetic field, stabilization effects are significantly reduced. It is seen that though the attractive force between the nanoparticles and the external field is smaller than Brownian forces, together with van der Waals interactions, these attractive forces likely act as directing agents facilitating sedimentation. This study demonstrates that aggregation-induced sedimentation of magnetic nanoparticles is likely to play a significant role in magnetic drug targeting even when the particles are stabilized with chelating agents.

Graphical abstract


Iron oxide nanoparticles Citric acid Suspension stability UV–Vis spectroscopy Magnetic field van der Waals interactions Brownian motion Sedimentation 









Fourier transform infrared spectroscopy




Scan data acquisition


Dynamic light scattering


Vibrating sample magnetometer


X-ray photoelectron spectroscopy


High magnetic field


Low magnetic field



The authors wish to acknowledge B. S. Abdur Rahman University and Amrita University for providing financial support and lab facilities for this work.

Supplementary material

11051_2016_3570_MOESM1_ESM.docx (2.4 mb)
Supplementary material 1 (DOCX 2443 kb)


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Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  • S. Vikram
    • 1
  • R. Vasanthakumari
    • 1
  • Takuya Tsuzuki
    • 2
  • Murali Rangarajan
    • 3
    • 4
    Email author
  1. 1.Polymer Nanotechnology CentreB. S. Abdur Rahman UniversityChennaiIndia
  2. 2.Research School of Engineering, College of Engineering and Computer ScienceAustralian National UniversityCanberraAustralia
  3. 3.Center of Excellence in Advanced Materials and Green Technologies, Amrita School of Engineering CoimbatoreAmrita UniversityCoimbatoreIndia
  4. 4.Department of Chemical Engineering and Materials Science, Amrita School of Engineering CoimbatoreAmrita UniversityCoimbatoreIndia

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