Particle鈥揗atrix Interaction in Cross-Linked PAAm-Hydrogels Analyzed by M枚ssbauer Spectroscopy

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• 作者：Joachim Landers ; Lisa Roeder ; Soma Salamon ; Annette M. Schmidt ; Heiko Wende
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：September 3, 2015
• 年：2015
• 卷：119
• 期：35
• 页码：20642-20648
• 全文大小：480K
• ISSN：1932-7455

文摘

The constrained motion of spindle-shaped hematite nanoparticles of about 400 nm in PAAm-hydrogels with different degrees of cross-link density is measured utilizing the line broadening observable in M枚ssbauer spectra at 265鈥?93 K. A slight decrease of nanoparticle mobility is observed upon increasing cross-link density. M枚ssbauer spectra of the same nanoparticles in 60 wt % sucrose solution, used as reference material, display line broadening of the same magnitude as the hydrogel samples, indicating a similar degree of motion at the atomic scale and the time scale of the M枚ssbauer experiment. AC (alternating current) susceptibility data indicate that the magnetic relaxation of the nanoparticles in sucrose solution mainly occurs by Brownian motion, while the absence of magnetic loss within the investigated frequency range observed in measurements on hydrogel samples reveals very limited particle mobility. This apparent contradiction between results on particle dynamics in hydrogels by M枚ssbauer spectroscopy and AC susceptibility measurements is explained in terms of constrained particle mobility at atomic scales.