Electron micrograph of iron oxide nanocubes and their bottled dispersion as new CRM BAM-N012
Source: Sarah-Luise Abram (BAM, Division Biophotonics 1.2)
Nanomaterials are increasingly being used in industrial and medical applications as well as in daily products. In order to utilize and rationally design new nanomaterials with further improved function, the reliable characterization of their physico-chemical properties is highly important, especially with respect to the assessment of their environmental, biological, and toxicologic impact. Such considerations have led to challenging regulatory requirements for the marketing of nanomaterials that create an urgent need for reference methods and nanoscale reference materials that are essential for the validation and standardization of measurement methods used for the precise characterization of particle key properties such as size, size distribution, shape or surface chemistry. However, their availability is limited to very few materials such as polymer, silica, or Au with mainly ideal spherical shapes which offer only limited comparability to more complex nanoparticles with non-ideal shapes from real applications. This encouraged us to develop a non-spherical nanoscale reference material of very small size consisting of 8 nm iron oxide nanocubes (BAM-N012) that has been certified for particle sizing by electron microscopy.
The areas of the nanocubes’ 2D projections were measured in the electron microscope and the equivalent cube edge length and the area equivalent circular diameter were determined with a relative expanded uncertainty of less than 9%. By calibrating the electron microscope via the silicon lattice spacing, the traceability of the measurement results to a precisely known natural constant is guaranteed. Additionally, uncertified values from small-angle X-ray scattering measurements (SAXS) enable comparison with a complementary method that also allows the calculation of the cubes’ edge lengths. BAM-N012 qualifies therefore for the estimation of precision and trueness, validation and quality assurance of particle size and shape measurements with electron microscopy and SAXS as well as other sizing methods suitable for nanomaterials. The publication describes the production, characterization, and certification of BAM-N012 including the individual steps to ensure homogeneity, short- and long-term stability and the determination of the complete uncertainty budgets.
Iron Oxide Nanocubes as a New Certified Reference Material for Nanoparticle Size Measurements
Sarah-Luise Abram, Paul Mrkwitschka, Andreas Thünemann, Jörg Radnik, I. Häusler, Harald Bresch, Vasile-Dan Hodoroaba, Ute Resch-Genger
Published in Analytical chemistry, Volume 95, Issue 33, Pages 12223 -12231.
BAM Analytical Chemistry, Reference Materials
BAM Biophotonics