2019 Volume 3 Issue 1 Pages 113-119
We investigate the effect of the ionic strength of surrounding NaCl solutions of an iron-oxide chitosan hydrogel (FeOx-CH) on magnetic relaxation of the FeOx NPs. The magnetic relaxation of the FeOx NPs is examined using dynamic magnetic susceptibility measurement. Swelling ratio (SR) is also measured after the FeOx-CH is immersed to various NaCl concentrations. SR of the FeOx-CH decreases as the NaCl concentration increases. This trend is explained by considering the osmotic water flow in the FeOx-CH. The peak in frequency dependence of the imaginary part of the susceptibility (χ ”) is found around 200 Hz. In addition, the position of the χ ” peak frequency shifts to lower frequencies as the NaCl concentration increases. The observed frequency shift is inferred to be due to the suppression of the Brownian relaxation caused by the decrease of SR of the FeOx-CH as the NaCl concentrations increases. An effective viscosity change of 6.8% due to the change in the NaCl concentration is also estimated via analytical calculation.
