After the soya bean plants had been grown to maturity in greenhouses, the distribution of zinc and cerium throughout the plants was studied. The use of microscopic synchrotron X-ray beams at the European Synchrotron Radiation Facility (ESRF) and the Stanford Synchrotron Radiation Lightsource (SSRL), enabled scientists to determine the chemical form of these metals, i.e. whether they were still bound to nanoparticles or had dissolved and bound with plant tissue. "We used X-ray beams 1000 times thinner than a human hair, and the way in which they are absorbed tells us whether, at the microscopic spot they hit, zinc and cerium were present, and whether they formed part of a nanoparticle in the plant or not." says Hiram Castillo, a scientist at the ESRF in Grenoble.
Cerium was shown to be present not only in the nodules close to the soil but had also reached the plant pods. A detailed spectral analysis of the X-ray signals showed that the cerium in the nodules and pods was in the same chemical state as in the nanoparticles. However, part of the cerium had changed its oxidation state from Ce(IV) to Ce(III) which can alter the chemical reactivity of the nanoparticles.
Zinc was detected in nodules, stems and pods in concentrations higher than in a control group of plants. The spectral analysis did not show the presence of zinc in the plants bound as ZnO nanoparticles which means that the zinc in the nanoparticles had been biotransformed. The spectra suggest that organic acids present in the plants such as citrate, are the probable ligands for the zinc.
"As zinc is present in most pl
|Contact: Claus Habfast|
European Synchrotron Radiation Facility