Nanoscience and nanotechnology are based on materials with a characteristic size smaller than 100 nm. The average size and the size distribution of the nanomaterials are critical for their properties and applications. Although the characteristic size of the nanomaterials is small, they can appear in the forms of fine powder, thin film, solution, suspension, gel, or bulk. Small angle X-ray scattering (SAXS) is one of the most appropriate techniques to determine the size and size distribution of the nanomaterials. SAXS does not require complicated sample preparation and is often able to provide the information in the natural setting of the nanomaterials.
Rigaku's SmartLab® multi-purpose diffractometer has the capability to characterize nanomaterials in virtually all forms. Shown below is a SAXS curve measured from semiconducting CdSe nanoparticles in areogel for optoelectronic applications. Aerogel is a low-density solid-state material in which the liquid component of a gel has been replaced with gas. The result is an extremely low density solid with several remarkable properties, most notably its effectiveness as an insulator.
The sample was held in a 0.5 mm capillary tube and the entire scan took only 15 min. By fitting the measured curve with Rigaku's NanoSolver software, we determine that the CdSe particles have an average size of 3.52 nm. The dispersion of the CaSe particle size is also very small (10%). In addition, about 29% of these particles are closely packed, forming an ordered structure with a preferred interparticle distance about 4.36 nm. Moreover, as shown in the results table, there exist pores in the gel with an average size of 26.73 nm. These pores, in contrast to the nanoparticles, show a large dispersion ( ~ 59%).