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Number concentration measurement of spherical particles in suspension


Innovative materials based on nanoscale and submicrometre particles are playing an increasingly important role in the development of new products across many fields. Applications range from battery electrodes to nanomedicine to quantum dots, which recently gained attention through the Nobel Prize in Chemistry 2023 which was awarded for their discovery and synthesis. Currently, only two methods are available for the traceable measurement of the number concentration of such particles in suspension. Single-particle inductively coupled plasma mass spectrometry (spICP-MS) can measure individual particles by evaporation and subsequent counting, while for small angle X-ray scattering (SAXS) the suspension is irradiated with monochromatic X-rays and the angle-resolved scattered intensity is analyzed.

PTB has established SAXS for determining the number concentration and made significant contributions to the corresponding ISO standard (ISO 23484:2023). Such measurements are now also offered as a product in the service portfolio of PTB for particles in a size range from 3 nm to 300 nm, provided that the particles have a narrow size distribution (FWHM smaller than about 50% of the mean size) and their composition and density are known.

Link: Product ID 7.2-1.15 in Measurements and Calibration Capabilities Division 7


C. Gollwitzer, 7.21, e-mail: christian.gollwitzer(at)ptb.de


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