Our main experimental technique is scattering. We have access to a wide range of length scales and time scales through use of three different instruments: a classic light scattering apparatus built by ALV-Laser (ALV), a small-angle light scattering instrument built in-house (SALS), and a small angle x-ray scattering instrument (SAXSLab) that is housed in 4D Labs.
Figure 1 compares the range of scattering wavevector available to these three instruments. For light scattering, the scattering wavevector is defined
where θ is the scattering angle and λ is the wavelength of the light in the scattering medium. By varying the wavelength and the scattering angle, different ranges of q can be achieved. The range of each instrument that we use is shown as a horizontal bar. For comparison, the form factors for spherical particles 1000 Å and 40 Å are also shown.
Figure 1. q-ranges of different instruments compared to form factors for 1000 Å and 40 Å spherical particles
Static and Dynamic Light Scattering (SLS, DLS)
Figure 2 shows a photo of the ALV instrument. This instrument allows us to measure the scattered intensity at angles from 20 to 150 degrees. We use it to measure particle sizes ranging from 40 nm to 300 nm, as well as dynamics at time scales of micro seconds to seconds.
Figure 2. Light Scattering Instrument (ALV LSE)
Small Angle Light Scattering (SALS)
Figure 3 shows a photo of our SALS instrument. This instrument measures light scattering at angles less than 10 degrees and is appropriate for studying particles of 1 micro meter or larger.
Figure 3. Small Angle Light Scattering (David Lee, MSc Thesis)
Small, Medium and Wide Angle X-Ray Scattering (SAXS, MAXS, WAXS)
4D Labs has recently commissioned a lab-based SAXS instrument - the Ganesha 300 XL built by SAXSLab. This instrument includes a detector that moves within a vacuum chamber and provides capability for SAXS, MAXS, WAXS and GISAXS/GIWAXS measurements. For more information, see the 4D Labs website.
Figure 4. Small Angle X-Ray Scattering Instrument (SAXSLab Ganesha)