Isoscattering point in SANS contrast variation study of aqueous magnetic fluids

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ABSTRACT

Small-angle neutron scattering (SANS) is widely used in structural analysis of complex liquid dispersions. An essential feature of SANS experiments for such systems is hydrogen/deuterium isotopic substitution in liquid media, which makes it possible to change the neutron scattering length density of the solvents, thus providing the basis for the contrast variation technique. In some cases, for dispersed particles with near-spherical symmetry, one can observe in the scattering curves specific points at which the scattered intensity is independent of the scattering contrast between dispersed particles and solvent. These points are referred to as ‘isoscattering points’ and in monodisperse solutions related to the particle size. Here, we report this effect for rather polydisperse (above 40%) magnetic fluids with core-shell particles in a liquid medium (water). It is shown that the effective isoscattering point can be analyzed to some extent for polydisperse systems, which gives additional possibilities for structural characterization of complex solutions via SANS.

KEYWORDS:

• Small-angle neutron scattering
• isoscattering point
• magnetic fluids

Acknowledgments

We acknowledge Frank Laboratory of Neutron Physics (FLNP), JINR (Dubna, Russia) for granting access to the SANS spectrometer YuMO and for the provision of additional experimental facilities. We thank Prof. Ladislau Vékás (Romanian Academy – Timisoara Branch) for providing the MF samples. We thank Dr. Oleksandr Ivankov (FLNP JINR) for his help in measuring SANS. The authors are thankful to CMSMS`21 participants for fruitful discussions.

Disclosure statement

The authors declare that they have no competing interests.

Author contributions

O.V.T. designed and supervised the project, participated in SANS experiments and data treatment, analyzed the results and wrote the manuscript; M.V.A. made a significant contribution to data analysis and writing of the manuscript; L.A.B. was responsible for the funding acquisition, reviewed and edited the manuscript; all authors gave final approval of the version to be published.

Additional information

Funding

The study was supported by the Ministry of Education and Science of Ukraine through the project 20BF051-01 of the Taras Shevchenko National University of Kyiv.