Direct Analysis of Engineered Iron Nanotubes and Platinum Nanorods: A Challenge for Single Particle Inductively Coupled Plasma Mass Spectrometry

Abstract

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 SiO2/Fe2O3/SiO2 nanotubes exhibiting a three-layered structure were deposited inside the nanopores of alumina templates by atomic layer deposition. For the solid Pt-nanorods, a multi-stepped electrochemical pulsed deposition process by employing the nanoporous alumina membranes as templates was used. The obtained structures were evaluated by scanning electron microscopy (SEM), high-resolution electron microscopy (HR-TEM) and SP-ICP-MS techniques. Solid Pt-nanorods (191 ± 18 nm width and 100 ± 20 nm long according to  HR-TEM) were obtained providing an estimated Pt mass of 30 ± 10 fg Pt/nanorod. The analysis by SP-ICP-MS revealed similar average results and, additionally, the presence of two populations with 19 ± 4 fg Pt/nanorod and 41 ± 5 fg Pt/nanorod respectively. In the case of the two different sized double-walled Fe2O3-nanotubes, the SP-ICP-MS measurements (11 ± 4 and 25 ± 4 fg Fe/nanotube, respectively) were also in relatively good agreement with the TEM results (17 ± 7 and 35 ± 19 fg Fe/nanotube, respectively). Considering the complexity of the analysed nano and micro-structures and the magnification of the uncertainties to transform length into mass and vice versa, SP-ICP-MS can be seen as a novel tool to evaluate the fabrication process of non-spherical nanomaterials, complementary to microscopy-based techniques.

Keywords: single particle ICP-MS, anisotropic nanostructures, Pt-nanorods, double layer Fe-nanotubes.