Nanoparticle aggregation and relaxation effects in ferrofluids: studied through anisotropic light scattering

Corneliu Rablau; Prem Vaishnava; Chandran Sudakar; Ronald Tackett; Gavin Lawes; Ratna Naik

doi:10.1117/12.791987

26 August 2008 Nanoparticle aggregation and relaxation effects in ferrofluids: studied through anisotropic light scattering

Corneliu Rablau, Prem Vaishnava, Chandran Sudakar, Ronald Tackett, Gavin Lawes, Ratna Naik

Author Affiliations +

Proceedings Volume 7032, Plasmonics: Metallic Nanostructures and Their Optical Properties VI; 70320Z (2008) https://doi.org/10.1117/12.791987
Event: NanoScience + Engineering, 2008, San Diego, California, United States

Abstract

We have investigated the aggregation and dissociation dynamics of 6-nm size Fe₃O₄ nanoparticles coated by tetra methyl ammonium hydroxide (TMAH) and the same size γ-Fe₂O₃ nanoparticles precipitated inside an alginate hydrogel matrix, both in aqueous suspensions, using dc magnetic-field-induced time-dependent light scattering patterns. For the Fe₃O₄ ferrofluid, a strong anisotropy in light scattering was observed for light propagating perpendicular to the magnetic field. This behavior is attributed to the aggregation of the nanoparticles into chain-like and column-like structures oriented parallel to the magnetic field. A significantly different behavior is observed for the aqueous suspension of γ-Fe₂O₃ nanoparticles precipitated in alginate hydrogel, for which the application of the dc magnetic field produced little to no change in the light scattering patterns. We attribute this difference to the constrained random distribution of γ-Fe₂O₃ nanoparticles precipitated in the alginate matrix. Correlating the results from this investigation with our previous study of magneto-thermal measurements in ac fields [Vaishnava et al., J. Appl. Phys. 102, 063914 (2007)], we conclude that for a ferrofluid to exhibit significant thermal effects under an ac magnetic field, it should exhibit optical anisotropy by developing a chain like structure under the influence of a dc magnetic field.

Citation Download Citation

Corneliu Rablau, Prem Vaishnava, Chandran Sudakar, Ronald Tackett, Gavin Lawes, and Ratna Naik "Nanoparticle aggregation and relaxation effects in ferrofluids: studied through anisotropic light scattering", Proc. SPIE 7032, Plasmonics: Metallic Nanostructures and Their Optical Properties VI, 70320Z (26 August 2008); https://doi.org/10.1117/12.791987

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