Dynamic Light Scattering (DLS) is the fastest and most straightforward process among various particle size measuring methods. It can measure nanoparticles and submicrons from 10μmto 1 nm in dimension. DLS can also be called Quasi-Elastic Light Scattering and Photon Correlation Spectroscopy. Today, this light scattering technique is used on polymers, emulsions, micelles, colloids, and proteins. How does this technique work? A laser beam is shone at the sample in the liquid, and a photon sensor detects the movement of the scattered light. Old DLS instruments could measure particles at a fixed angle. Due to this, you could only interpret the average size, limiting the study of the size range.
However, due to its multi-angle detection capabilities, a modern DLS instrument can monitor a sample’s full range of particle size diffusion. The light is scattered by the particles in a liquid sample, influenced by Brownian motion. The movement of particles also impacts the scattered light pattern. These variations in the diffused light reveal the speed of the moving particles, which becomes a data source for the instrument to analyze the particle size. Typically, large particles move slowly, while tiny ones flow faster.
- Measurement quality
An instrument’s ability to measure particle size dimensions correctly depends on many factors, such as the quality of the correlator, detector, and laser. Some indirect factors can also influence the process, though. Let’s look at them.
- Capturing the scattered light from different angles
The fading of the scattered light depends on the angle at which it was scattered. Different particle sizes will move at different speeds based on the scattering angle. Every particle size tends to have a specific detection angle. You can capture it all and produce high-quality analysis using multi-angle DLS equipment. Using advanced models is even more necessary when handling polydisperse samples that contain a wide range of particle size distributions. Otherwise, data analysis will be challenging as some particles with higher scattering intensities can completely overshadow the motion of the other particles and their light-scattering signals. DLS instruments with fixed-angle capability can be helpful in only limited scenarios. You should choose one that offers multi-angle tracking for particle size distributions for better results.
- Analyzing DLS data
The three standard DLS data analyzing techniques are CONTIN, CORENN, and CUMULANT. CUMULANT is considered highly reliable for its ability to gauge the distribution width. However, it can only study the average particle size. Samples with bi-modal particle diffusion can be analyzed through the CONTIN algorithm. The only challenge is that this technique is sensitive to data noise levels. For the best results, a researcher has to make additional assumptions. The third algorithm, CORENN, can offer credible results even with noisy data. You don’t need to add assumptions or restrictions, too.
Nevertheless, DLS equipment can be used to profile a chosen solution. You can depend on this method for its non-invasive nature, speed, versatility, extensive measurement range, and ease of use. This instrument allows you to work with various materials needed in different industries. You can use it as a tool for polymer synthesis, colloidal examination, protein size characterization, quantum dot profiling, and more. Ensure that you buy your product from only a trusted manufacturer, though.
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