A new certified reference material for size and shape analysis of nanorods using electron microscopy

Abstract

A new certified reference material (CRM) for size and shape analysis of elongated nanoparticles has been developed by the European Commission’s Joint Research Centre. The CRM consists of titanium dioxide nanorods dispersed in 1-butanol, was coded ERM-FD103 and has been certified for different electron microscopy–based operationally defined measurands such as the modal and median values of the particle number-weighted distributions of the minimum and maximum Feret diameter, the maximum inscribed circle diameter, the area-equivalent circular diameter and the aspect ratio. The nanorods have nominal dimensions of 15 nm in width and 55 nm in length. Homogeneity and stability measurements were performed using transmission electron microscopy. The relative standard uncertainty for homogeneity ranged from 0.3 to 1.7%. No significant instability was detected for a shelf life of 18 months and a storage temperature of 18 °C. The certified values have been determined from the results of an interlaboratory comparison in which qualified expert laboratories participated with scanning and transmission electron microscopy. The certified values are traceable to the unit of length in the International System of Units, the metre, and the relative expanded uncertainties (confidence level of approximately 95%) range from 4 to 6%. These properties allow the CRM to be used for quality assurance and calibration of electron microscopy methods for nanoparticle size and shape analysis in ranges relevant for the implementation of EU legislation related to nanomaterials. The presented study discusses the purpose and results of the different steps that were followed to turn an industrially relevant raw titanium dioxide nanorod material into a fit-for-purpose CRM. Graphical abstract

Customizing New Titanium Dioxide Nanoparticles with Controlled Particle Size and Shape Distribution: A Feasibility Study Toward Reference Materials for Quality Assurance of Nonspherical Nanoparticle Characterization

“…Moreover, it should be noticed that a certified reference material of the same matrix (TiO 2 ), of roughly similar particle shape and quality, is made commercially available. [ 16 ] The exact morphological and structural characterization of this type of material remains complex; see the detailed description of Figure 2c and 4.…”

“…[11,12] The present article intends to give an overview of the several developments of TiO 2 nanoparticles as reference materials with a focus on the morphologicalÀ structural properties, particle size, shape, and crystallinity on the background of general scarce availability of reference materials. Currently, there is a big lack of nanoparticles as certified reference materials, [11] solely gold, silica, [13] and polystyrene [14] of spherical or close-to-spherical shape and monodispersed size distribution, and, recently, bimodal colloidal silica [15] and titania elongated nanoparticles [16] are commercially available. New measurement procedures are necessary to be codeveloped simultaneously with the controlled, reproducible synthesis of new nanoparticles as a certified reference material.…”

Evaluation of techniques used for visualisation of hydrogel morphology and determination of pore size distributions

“…2 This definition of the pore size is useful when the value is used to correlate diffusion of solid nanoscale objects through the hydrogel. It is, however, different to the Feret diameter 49 and depending on the shape of the pore, the pore size may be underestimated relative to that of the Feret diameter. To avoid introducing additional variables in the study, a common approach to extracting the pore size from the images generated from the different techniques was required.…”

Iron Oxide Nanocubes as a New Certified Reference Material for Nanoparticle Size Measurements

“…6,14 The first certified nanoRMs were simple monodisperse spherical gold, silica, and polystyrene NPs, 6 followed by spherical silver NPs (BAM-N008). 15 These nanoRMs, which mostly cover the size range roughly between 10 and 100 nm, were recently complemented by TiO 2 nanorods and bimodal silica NPs certified by the Joint Research Center of the European Commission (JRC; ERM-FD103 and ERM-FD102) 16 and gold nanocubes from Korea Research Institute of Standards and Science (KRISS). 6 These "nonideal" nanoRMs, coming along with certified size values of NPs with highly nonspherical, but still relatively monodisperse shape, better match the irregular shape and size of most nanomaterials used in research and industrial applications.…”