A Discussion of Noise in Dynamic Light Scattering for Particle Sizing

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AbstractIn order to acquire high quality measurement data from DLS (Dynamic Light Scattering) experiments, serious attention has to be paid to minimizing the noise involved. In this paper, the noise in DLS for particle sizing is addressed for four parts of the measurement system. The first is the noise caused from the low quality of sample preparation and the scattering medium containing too high or too low concentration of analyte. The second is from the view of optics, i.e., the laser must have sufficient power, be stable under all expected conditions, and usually be restricted to a single transverse mode, in case it causes distortion in measurement data. In addition, if the energy of the incident light is too high, strong absorption occurs, which will induce thermal blooming. The optical components must be carefully chosen and designed to minimize noise from the unit itself. The detection area should be calculated to reach the best signal‐to‐noise ratio and an entrance lens with magnification that is too high and that causes distortion in the ACF (Auto Correlation Function) should be avoided. Some new components such as fiber optics and graded‐index may also introduce new noise. The third factor is the photodetector, which must have adequate speed and sensitivity and possess suitably low internal correlations and noise. In addition, the quantum noise from the detector should be subtracted. The fourth factor is that the correlator should be chosen carefully. In some cases, equipment with a higher speed and more channels should be chosen to minimize the statistical noise.