Dynamic Light Scattering (DLS)

Dynamic light scattering (DLS) is an optical analysis method for particle sizes in solutions. It is a well-established method in many areas that focus on nanoparticles, such as colloid and polymer science, pharma and food industries, and cosmetic and paint product development. DLS allows for fast and non-invasive verification of sample quality and ensures a stable production process. One can see within seconds if the measured size of the dissolved nanoparticles is within expectations. And therefore, if the tested sample is suitable or if unwanted agglomeration of the particles has occurred. DLS can measure nanoparticles as small as one nanometer and as big as a few microns.

Nanoparticles inside a solution undergo random movements, the so-called Brownian motion. DLS measures these fluctuating motions and their characteristic time scale, which can then be related to the nanoparticle size distribution. Shining coherent laser light onto the sample results in scattering by the particles, and a speckle pattern is visible. Detecting the speckle pattern with a single photon detector at a fixed angle and tracking the intensity of the scattered photons with the Time Tagger, one can observe a fluctuating intensity time trace corresponding to the Brownian motion of the nanoparticles.

The Time Tagger software calculates a fully logarithmic autocorrelation on the detected photon time trace. Because large particles have higher friction and move more slowly in a liquid, the autocorrelation of the photon time trace decays more slowly than for small particles. One can thus determine the particle size from an exponential fit to the autocorrelation and its decay time.

Most commercial DLS systems calculate the correlation directly in hardware with a fixed number of channels and lag times, returning only the correlation curve. The Time Tagger, on the other hand, offers all the benefits of a software correlator. You have access to the full measurement data, allowing easy storing and post-processing of your raw photon counts. In addition, you can later change your autocorrelation parameters, investigate different time scales more closely, or compare different segments of your time trace in detail. All of this is possible without having to repeat the physical measurement. With the many inputs of the Time Tagger, you can also easily scale your DLS setup to many detection channels and integrate it into more sophisticated experiments.

Your benefits from a Swabian Instruments' DLS system

Logarithmic software autocorrelation, spanning from ps times to days

Don't worry about sampling time, dynamic range, or the number of correlation channels. With the Time Tagger software, you can specify arbitrary start and stop times for your logarithmic histogram - from ps to days, while keeping a high resolution and without losing statistical confidence either.

Data processing on the fly

Tired of waiting for your measurements to finish before you see the first results? No problem with the Time Tagger. You can have CONTIN and Cumulant fitting for the analysis of your sample on the fly and see the first size estimates within the first seconds of measuring.

Access to the raw time tags and post processing options

How often do intensity spikes due to dirt distort your measurement? Have you always wanted the possibility to exclude these parts of the data? The Time Tagger software allows you to do precisely this and reanalyze the undisturbed time periods again without performing a new measurement.

Simultaneous measurement on a multitude of angles and detectors

A full goniometer DLS setup is too bulky for your lab, but you don't want to forgo the increased accuracy and angle-dependence either? A Time Tagger DLS setup combines both advantages: A small DLS device with several detectors at different angles. Measure up to 8 detectors simultaneously with only one Time Tagger

Are you searching for a custom-built DLS device?
Do you need a certain wavelength, want to measure at a specific angle, or include a special analysis algorithm? Our modular DLS system enables us to accommodate your experimental demands. We'd love to learn about your wishes.

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