The Perfect Sphere: An Investigation of Monodisperse Hollow SiO2

The properties of materials with structural features on the nanometer scale largely depend on the size of these features. Small-angle X-ray scattering is a commonly used method to measure both the size and the shape of such structures. This report shows a SAXS study on very large hollow silica nanoparticles with well-defined diameter and shell thickness.


The capability to produce nanoparticles with a defined structure and high monodispersity allows the development of a variety of new functional materials. Such materials have potential application in fields such as energy conversion, energy storage, catalysis, and separation.1

These particles can be synthesized in the form of dense spheres, but recently also hollow, core/shell-type particles are seeing major interest in research. Such particles are produced either by top-down or bottom-up approaches. In either approach the deviation from uniformity in the structure or size (polydispersity) is detrimental to the desired properties. Thus, having access to fast and accurate characterization methods for measuring the dimension of such materials is of high importance.

Small-angle X-ray scattering (SAXS) is an effective technique to characterize both the shape and the size of such particle systems2. While it is relatively easy to measure smaller particle sizes (<200 nm), it becomes experimentally difficult to measure larger nanostructures, especially when using laboratory SAXS instruments.

Recent developments in laboratory instrumentation have pushed the upper limit in structural size that can be investigated with SAXS, to significantly larger dimensions.

Here we show measurements on hollow SiO2 spheres of a size bigger than 200 nm, using the Anton Paar SAXSpoint 5.0 instrument. Having two different, well defined length scales (overall size and shell thickness) allows the use of such materials as a reference material for different scattering methods like SAXS.

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