Abstract: Owing to Mössbauer spectroscopy, an advanced characterization technique for iron-containing materials, the present study reveals previously unknown possibilities using l-amino acids for the generation of magnetic particles. Based on our results, a simple choice of the order of l-amino acids addition into a reaction mixture containing ferrous ions leads to either superparamagnetic ferric oxide/oxyhydroxide particles, or magnetically strong Fe0-Fe2O3/FeOOH core-shell particles after chemical reduction. Conversely, when ferric salts are employed with the addition of selected l-amino acids, only Fe0-Fe2O3/FeOOH core-shell particles are observed, regardless of the addition order. We explain this phenomenon by a specific transient/intermediate complex formation between Fe2+ and l-glutamic acid. This type of complexation prevents ferrous ions from spontaneous oxidation in solutions with full air access. Moreover, due to surface-enhanced Raman scattering spectroscopy we show that the functional groups of l-amino acids are not destroyed during the borohydride-induced reduction. These functionalities can be further exploited for (i) attachment of l-amino acids to the as-prepared magnetic particles, and (ii) for targeted bio- and/or environmental applications where the surface chemistry needs to be tailored and directed toward biocompatible species.
Keywords: γ-Fe2O3; FeOOH; zero-valent iron; NZVI; Mössbauer spectroscopy; SERS; arginine; arginate; glutamic acid; glutamate; nanomagnetism
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Šišková, K.M.; Machala, L.; Tuček, J.; Kašlík, J.; Mojzeš, P.; Zbořil, R. Mixtures of l-Amino Acids as Reaction Medium for Formation of Iron Nanoparticles: The Order of Addition into a Ferrous Salt Solution Matters. Int. J. Mol. Sci. 2013, 14, 19452-19473.
Šišková KM, Machala L, Tuček J, Kašlík J, Mojzeš P, Zbořil R. Mixtures of l-Amino Acids as Reaction Medium for Formation of Iron Nanoparticles: The Order of Addition into a Ferrous Salt Solution Matters. International Journal of Molecular Sciences. 2013; 14(10):19452-19473.
Šišková, Karolína M.; Machala, Libor; Tuček, Jiři; Kašlík, Josef; Mojzeš, Peter; Zbořil, Radek. 2013. "Mixtures of l-Amino Acids as Reaction Medium for Formation of Iron Nanoparticles: The Order of Addition into a Ferrous Salt Solution Matters." Int. J. Mol. Sci. 14, no. 10: 19452-19473.