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Characterisation of Nanomagnetites Co-Precipitated in Inert Gas Atmosphere for Plant Nutrition

Our future aim is to ascertain the effects of selected nanoparticles on plants of agricultural importance. In the future study we intend (a) to prepare the nanoparticles containing iron and (b) to obtain data about iron metabolism in the plant(s) and (c) to propose different iron utilization strategies in agriculture. In this sense the experiments involving the plants grown in hydroponics or soil conditions will be conducted. In our previous work [1] we reported about iron(III)-oxyhydroxide and non-stoichiometric magnetite nanoparticles with the aim to use them as possible nutrition source for plants. 57Fe Mössbauer spectra of magnetite nanoparticles synthesized under different preparation conditions at ambient atmosphere showed that the magnetite nanoparticles are highly oxidized. In order to obtain more efficient magnetite nanoparticles with higher FeII content, magnetite nanoparticles were prepared in N2 gas atmosphere. The chemical co-precipitation method was utilized, starting with stoichiometric ratio of FeSO4 and FeCl3 solutions for magnetite formation. Then, ammonia solution was slowly and continuously added to the iron salts solution. After the reaction was completed, the precipitates were filtered, washed several times with deionized water and lyophilized. Citric acid coated nanoparticles were also prepared similarly, but adding the citric acid dissolved in deionized water before the addition of ammonia solution. 57Fe Mössbauer spectra (Fig. 1) of washed and lyophilized nanomagnetite prepared in inert gas atmosphere undoubtedly indicated the presence of considerable fraction of FeII, close to the stoichiometric magnetite composition, both at room temperature (RT) and at 80K. XRD pattern of the same sample corresponded to nanomagnetite crystal structure. Mössbauer spectra in Fig. 1 also showed that after lyophilization the unwashed citric acid coated samples contained some FeII which disappeared when the sample was washed before lyophilisation. The washed samples, however, showed a poorly crystalline character.

iron nanoparticles, plant nutrition, XRD, 57Fe Moessbauer spectroscopy

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