Measurements on Aqueous Silica Spheres Using a Continuous-Flow Setup
The properties of materials with structural features on the nanometer scale largely depend on the size of these objects. Small-angle X-ray scattering (SAXS) is a commonly used method to measure both the size and the shape of such structures, in the size range from 1 to 300 nm. This report shows a beamstop-less SAXS study of silica spheres dispersed in water with a nominal size of 213 nm. To prevent particle sedimentation during data acquisition, the meas-urement was performed using a continuous-flow setup where the sample was continuously redispersed.
Nanoparticles and nanoparticle solutions have a very wide range of applications. The properties of such materials largely depend on their size. Also, these nano-sized materials may have an impact on the environment (e. g., plastic nanoparticles in the sea). Thus, fast and reliable screening methods are required. Small-angle X-ray scattering (SAXS) is an effective technique to characterize both the shape and the size of nanoparticulate systems.1 While it is relatively easy in SAXS to measure small to medium-sized particles (<200 nm), it becomes experimentally more difficult to measure larger nanostructures, due to the extremely small scattering angles involved.
The resolution of any SAXS experiment is mainly defined by the size of the primary beam, since it directly influences the smallest scattering angle (qmin) that can be evaluated. Due to the high intensity of the primary beam in contrast to the photons scattered by the sample, the primary beam is usually attenuated or blocked by a so-called beamstop. Thus, the size of the used beamstop directly determines the qmin of the experiment, potentially blocking photons that could be detected if no beamstop was present. Modern X-ray detectors such as the EIGER2 R detectors by Dectris can be operated in a beamstop-free mode as long as the X-ray flux is reasonably small (which is usually the case in laboratory instruments). This does not only potentially increase the resolution for measuring larger particles but also makes the SAXS experiments simpler since no alignment of the beamstop is required.
In this study we show measurements of SiO2 nanospheres with a size around 213 nm, using the compact high-resolution laboratory SAXSpoint 5.0 instrument by Anton Paar in a beamstop-free mode. To avoid possible sedimentation, the sample solution is measured in a continuous flow-through setup.
1. Schnablegger, H.; Singh, Y., The SAXS Guide – Getting acquainted with the principles. 4th ed.; Anton Paar GmbH: Graz, Austria, 2017.
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