Broad distributions can be sized with DLS

Dynamic Light Scattering if often disparaged for not being able to handle broad distributions. This is not the case.


It is true that the deconvolution algorithms used to convert correlation functions into particle size distributions will produce a stylized graph. For example, in Figure A, the PSD of a re-constituted nano-powder is shown. The PSD consists of three separate peaks. Considering the sample, the expectation would be that the actual PSD should consist of a continuous distribution. That is not what is displayed. However, the three peaks can be identified as the primary particle size followed by two peaks that are proxies for the continuous tail of aggregates that are present in the sample. From this graph we learn that the actual PSD consists of a primary peak at 40 nm followed by a shelf of large particles extending out to 7 microns. The relative amount of that shelf can be determined by the relative heights of the peaks. DLS was able to produce a PSD that extended more than two orders of magnitude which by anyone’s definition is broad.