The DLS technique can be used for investigating suspensions in a wide range of sample buffers, over a relatively big range of temperatures and concentrations, as well. Some other methods that are used in the type of investigations mentioned above include analytical ultra-centrifugation, which requires a bigger amount of sample small angle X-ray scattering (SAXS), which requires a longer acquisition time, in the order of hours in lack of a synchrotron and static light scattering, which again requires time averaging to compensate for the dynamic light scattering effect. The DLS technique has been shown to be appealing for biomedical applications, such as studying homogeneity of proteins, ribonucleic acid (RNA), and their complexes as it has certain advantages over other experimental methods. The physical method that uses the dependence between the speckle dynamics and the particles diffusion caused by the Brownian motion is called dynamic light scattering (DLS), traditionally known as photon correlation spectroscopy (PCS) The physical explanation of the method can be found in many works, such as, to name just a few.ĭLS is widely used to analyze the size and size distributions of nanoparticles, colloids and proteins in the suspension of various solvents. Using the variation of the above mentioned parameters for particle sizing in dynamic processes where both the SC diameter and number of SCs can change in time is not a good choice. Several articles investigated the variation of physical parameters, such as the average intensity, speckle size and speckle contrast, with the size and the concentration of the SCs, references being an example. The particles in suspension undergo a complex motion, which confers a dynamic character to the far interference field, giving it the aspect of “boiling speckles”. If the light source is coherent the scattered waves are coherent, as well, therefore, they will interfere in the far-field. The particles become scattering centers (SC). When an incident light beam has a fluid containing suspended particles as target, each particle scatters light and therefore becomes a secondary light source as elastic or, more precisely, quasi-elastic scattering occurs. The results indicate that the procedure can be used to identify the presence of bigger particles and to assess their size, in aqueous suspensions used in the food industry. Results of monitoring the long-time variation of the size of the Saccharomyces cerevisiae during fermentation are presented, including the 10 h between dissolving from the solid form and the start of multiplication, as an application of the proposed procedure. The procedure proved to be much faster regarding time-series processing and easier to use than fitting a function to the experimental data using a minimization algorithm.
#Dynamic light scattering with applications to chemistry series#
A DLS time series processing procedure based on an artificial neural network is presented with details regarding the design, training procedure and error analysis, working over an extended particle size range. Although it has been very well established for quite some time, improvement can still be brought in simplifying the experimental setup and in employing an easier to use data processing procedure for the acquired time-series. Dynamic light scattering (DLS) is an essential technique used for assessing the size of the particles in suspension, covering the range from nanometers to microns.
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