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Quantitative high-throughput optical sizing of individual colloidal nanoparticles by wide-field imaging extinction microscopy
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Paper Abstract

We present a wide-field imaging technique recently developed by us to measure quantitatively the optical extinction cross section σext of individual nanoparticles. The technique is simple, high speed, and enables the simultaneous acquisition of hundreds of nanoparticles in the wide-field image for statistical analysis, with a sensitivity corresponding to the detection of a single gold nanoparticle down to 2nm diameter. Notably, the method is applicable to any nanoparticle (dielectric, semiconducting, metallic), and can be easily and cost-effectively implemented on a conventional wide-field microscope. Of specific significance for accurate quantification, we show that σext depends on the numerical aperture of the microscope illumination due to the oblique incidence, even for spherical particles in an isotropic environment. This "long shadow" effect needs to be taken into account when comparing σext to theoretical values calculated under plane wave illumination at normal incidence. Owing to the accurate experimental quantification of σext, one can then use it to determine the nanoparticle size, as demonstrated here on gold nanoparticles of 30nm nominal diameter. This technique thus has the potential to become a simple and cost-effective new tool for accurate size characterization of single small nanoparticles, complementing time consuming and expensive methods such as electron microscopy.

Paper Details

Date Published: 7 March 2019
PDF: 11 pages
Proc. SPIE 10892, Colloidal Nanoparticles for Biomedical Applications XIV, 108920J (7 March 2019); doi: 10.1117/12.2507632
Show Author Affiliations
Lukas M. Payne, Cardiff Univ. (United Kingdom)
Attilio Zilli, Cardiff Univ. (United Kingdom)
Yisu Wang, Cardiff Univ. (United Kingdom)
Wolfgang Langbein, Cardiff Univ. (United Kingdom)
Paola Borri, Cardiff Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 10892:
Colloidal Nanoparticles for Biomedical Applications XIV
Marek Osiński; Wolfgang J. Parak, Editor(s)

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