Dynamic Light Scattering (DLS)
Dynamic Light Scattering (DLS, also known as Photon Correlation Spectroscopy or Quasi-Elastic Light Scattering) is one of the most popular light scattering techniques because it allows particle sizing down to 1 nm diameter. Typical systems to characterize are emulsions, micelles, polymers, proteins, nanoparticles, or colloids.
Static Light Scattering (SLS)
Static Light Scattering (SLS) is an optical technique that measures the intensity of the scattered light in dependence of the scattering angle to obtain information on the scattering source.
A typical application is the determination of the weight average molecular weight Mw of a macromolecule such as a polymer or a protein. Other popular applications are the measurement of the radius of gyration Rg or the form and structure factor.
Diffusing Wave Spectroscopy (DWS)
Diffusing Wave Spectroscopy (DWS) is an advanced light scattering technique based on the measurement of multiple light scattering. It is primarily used to perform contact-free rheology, as well as particle sizing on a wide range of samples, such as suspensions, emulsions, pastes, or gels. DWS offers a powerful alternative to mechanical rheology, as the measurements are non-destructive, conducted on a sample in a sealable cuvette, and as fast as 30 seconds. This enables a wide range of applications such as rapid formulation screening, gelation monitoring, or long-term stability studies.
Rheology
Rheology is the science that studies the behavior of fluids subject to a flow or a deformation. One of its main objectives is to comprehend how the microstructure of a fluid effects the response of that fluid to a deformation.
Digital Correlator Technology
The technology underlying Dynamic Light Scattering (DLS), Diffusing Wave Spectroscopy (DWS) or Fluorescence Correlation Spectroscopy (FCS) relies on the detection and subsequent digitalization of the scattered signal. In such experiments, the fluctuating scattered light intensity directed toward a single-photon detector (e.g. a photomultiplier or an avalanche photodiode), results in the emission of electronic current pulses with a probability proportional to the scattered intensity. Within a single photon detector (SPD) a wide band amplifier then converts the output current pulses to voltage pulses.
Particle Characterization
There is a wide range of man-made particles and an even wider range of particles that can be found in nature. While quantum mechanics or even more complex theories are required to explain elementary particles such as neutrons, electromagnetic theory, and classic mechanical physics are typically sufficient to explain the fundamental behavior of particles larger than 1 nm. This does not mean that the behavior of such particles could easily be predicted. Scientists continue to encounter unexpected and sometimes dazzling behavior of particles on a nearly daily basis, as the huge number of scientific publications in this field can verify.