Sub-100-nm STIM imaging and PIXE quantification of rare earth elements in algae cells

Abstract

The uptake of rare earth elements (REEs) such as Nd3+, Gd3+, and Er3+ by Euglena gracilis 848 algae cells has been studied using nuclear microprobe techniques at the Centre for Ion Beam Applications (CIBA), National University of Singapore. The cell imaging facility recently constructed at CIBA allows scanning transmission ion microscopy (STIM) down to the sub-100-nm level and provides energy loss images of whole intact cells. Helical coiling of the pellicle strips of the algae cells was observed, as was Rutherford backscattering spectrometry (RBS) images showing the distribution of erbium in the cell. Quantification of the REEs was carried out using a combination of nuclear techniques such as proton-induced X-ray emission, RBS, and STIM. Our results indicate significant variability in the uptake of REEs by algae cells. The amount of erbium absorbed was nearly one order of magnitude higher than that of neodymium, whereas the Gadolinium uptake was below the detection limit of 200ppm. © 2013 John Wiley & Sons, Ltd.