Table of ContentsOverviewIntroductionMaterials and MethodsDLS of Silica SamplesResults and DiscussionConclusionsAbout Horiba
The applications of silica nanoparticles are often determined by the particle size. Dynamic light scattering provides quick, precise and repeatable nanoparticle size data and therefore is an essential tool for the nanoparticle technologist. Here, two different size silica particles are characterized with the Horiba SZ-100 in order to demonstrate the precision and utility of the instrument.
One may comfortably sip on a cold beer while listening to a MP3 player without pausing for a moment to think about those miniscule silica nanoparticles that were used to clarify the beer. Also note that the silicon wafers that constitute critical components in the mp3 player were polished flat using silica chemical mechanical polishing (CMP) nanoparticle slurries. In both these applications and many more, the size of the silica nanoparticles is a critical factor. In beer clarification, the silica is used to bind suspended haze-creating particles such as protein or yeast together forming large flocs that can be removed by settling or filtration resulting in a clear liquid. It is important that the silica particles used for CMP are not very large so as to scratch the delicate silicon wafers. However, they must be large enough to remove material quickly and cost-effectively.
Dynamic light scattering (DLS) is a preferred method for studying particles in the nano size range. Characteristics of the technique include:
- Rapid measurements, typically taking just a few minutes
- High repeatability
- Coefficient of variation on the z-average size is higher than 5% for a large number of samples
- High accuracy and is able to discern shifts in the z-average size of only a few percent
In this application note, the particle sizes of two different silica dispersions are studied to demonstrate the utility of the Horiba SZ-100 for both suppliers and users of such materials.
Figure 1. SZ-100 Nanoparticle Size Analyzer.
Materials and Methods
The samples used for the experiment include the following:
- Sample 1 used was Ludox TM 50, colloidal silica of nominal size 30 nm (narrow size distribution).
- Sample 2 was a more broadly distributed and larger-sized (nominal 500 nm) aqueous SiO2 suspension. Both materials were obtained from Sigma Aldrich. Each suspension was diluted with 10 mM KCl (aq) prior to measurement.
Figure 2. Fumed silica. The small size, hardness and inert nature of silica make it a very versatile and useful material for a wide range of applications and ideal for size analysis by DLS with the SZ-100.
DLS of Silica Samples
Dynamic light scattering information was gathered and studied with a SZ-100 particle size analyzer. Measurements were repeated five times in order to calculate the coefficient of variation, the standard deviation and mean of the measurements.
Figure 3. Sand dune. These larger silica particles, while beautiful in the aggregate, are typically analyzed by laser diffraction (HORIBA LA-950) or image analysis (HORIBA PSA300). Image courtesy of Florence Devouard and Wikimedia Commons.
Results and Discussion
The z-average diameters obtained with the SZ-100 are listed in Tables 1 and 2.
Table 1. Measurement of the Ludox TM50 colloidal silica. Here, results from two different laboratories are compared. The agreement is excellent showcasing the measurement reproducibility of the SZ-100 providing the user with confidence in multiple site installations. The SZ-100 has standardized measurement protocols which automate measurement and calculation to ensure maximum operator-to-operator and site-to-site reproducibility.
||Mean determined z-average size (nm)
Dynamic Light Scattering with SZ-100, laboratory 1
Dynamic Light Scattering with SZ-100, laboratory 2
Table 2. Measurement results for nominal 500 nm silica suspension. The two different techniques agree to within 5%, which is very good. Evident from the COV values, the measurement repeatability of the SZ-100 is superior to that the disc centrifuge.
||Particle Diameter (nm)
Manufacturer certificate (by disc centrifuge)
Dynamic Light Scattering with SZ-100
The results of these measurements show that the Horiba SZ-100 dynamic light scattering particle size analyzer can be used to characterize silica and other nanoparticle materials.
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This information has been sourced, reviewed and adapted from materials provided by Horiba.
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