Size and Size Distribution of Gold Nanoparticles by SAXS

Gold nanoparticle dispersions were measured with the SAXSpace system. SAXS proved to be a well-suited method for determining the size distribution of a binary mixture of two dispersions with very similar particle size.

Determining particle size with SAXS

Many materials gain their properties from the grain size of their constituting particles. Examples are the activity of catalysts and enzymes, the mechanical stability of ceramics and the thermal, electrical and optical properties of nanoparticles.

Aggregate formation and imperfect redispersion may lead to an effective particle size in suspension much larger than the primary particle size. Coalescence is one of the main break-down processes in emulsions.

SAXS is a powerful technique to characterize particle suspensions, emulsions and protein solutions with respect to their colloidal stability, aggregation and coalescence. This is due to the fact that large particles scatter a lot and are thus easily detectable. The SAXSpace system has proven to deliver excellent data well suited for particle sizing.

Experimental and Results

Two gold nanoparticle dispersions  with  different size (diameter: 6 nm and 14 nm) and a binary mixture of these dispersions (1:1) were measured with the SAXSpace system in line-collimation mode. The background-subtracted scattering curves are shown in Figure 1.

Fig. 1 Background-subtracted scattering curves

Data evaluation was performed with the GIFT software1 in order to determine the particle size and the size distribution of the dispersions.
The SAXS curves were converted into volume-weighted size distributions as shown in Figure 2.

Fig. 2 Volume-weighted size distributions

The two populations with a particle radius of 3 nm and 7 nm respectively, can be well resolved. In addition the relative amount of each fraction is reflected well.

1    O. Glatter, J. Phys.: Condens. Matter 18 (2006) 2403

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