Direct analysis of engineered iron nanotubes and platinum nanorods: A challenge for single particle inductively coupled plasma mass spectrometry

The use of inductively coupled plasma mass spectrometry in single particle mode (SP-ICP-MS) for the characterization of micro and nanostructured materials is a growing field of research. In this work, the possibility of expanding the boundaries to anisotropic structures including solid Pt-nanorods and hollowed Fe₂O₃-nanotubes is presented. The obtained structures are evaluated by scanning electron microscopy (SEM), high-resolution electron microscopy (HR-TEM) and SP-ICP-MS techniques. Solid Pt-nanorods (191 ± 18 nm in diameter) showed important heterogeneity in their length, ranging 42-72 nm, due to sample preparation difficulties. The analysis by SP-ICP-MS confirmed the presence of two different populations of Pt/nanorods at 19 ± 4 fg and 41 ± 5 fg, respectively, yielding a mean value of 23 ± 12 fg Pt/rod and a length range of 38-67 nm, in agreement with TEM measurements. In the case of the two different sized double-walled Fe₂O₃-nanotubes of 900 nm and 1800 nm in length, the SP-ICP-MS measurements provided results of 16 ± 10 and 25 ± 4 fg Fe/nanotube, respectively. Out of this data, the layer thickness of the Fe₂O₃ nanotube wall was calculated, reporting values ranging between 20 ± 6 and 17 ± 4 nm, respectively, in good agreement with the TEM estimations (18 ± 4 nm). Considering the complexity of the highly anisotropic nano and micro-structures analyzed, SP-ICP-MS technique can be seen as a novel tool to evaluate the fabrication process of non-spherical nanomaterials as well as the sample preparation strategies, complementary to microscopic techniques and with higher sample throughput.