Control of the exact size and morphology of nanoparticles is key to their successful application in optical grade composites. In this work, dynamic light scattering (DLS) and ultrasound nanoparticle sizing (UNPS) have been used to follow the growth of nanoparticles from molecular precursors in a pilot scale reactor. DLS is a standard tool for sizing of nanoparticles in solution. The principle is based on the correlation of photons scattered from the sample and detected by a suitable photon detector. It requires that only single scattered photons arrive at the detector. While the criterion of single scattering imposes no problems for solutions of low turbidity, it renders measurement of turbid solution impossible, because this results in undetectable systematic errors. Since dilution may modify the sample this needs to be reduced as much as possible. This can be done with the 3D modulation technology which suppresses multiple scattering to filter out only the single scattering. We show that real-time measurements of particle size, using a bypass loop and flow cell, can be performed directly on turbid reaction mixtures without need for dilution, as a result of the design of the setup. Nanoparticles in dispersion change the speed and attenuation of ultrasonic waves in the dispersion. The size of the change depends amongst others on the particle size and concentration of the nanoparticles. This dependency is used in the developed measurement method. Using the known values of the speed and attenuation of the ultrasonic wave in the dispersing medium, the frequency dependent change in speed and attenuation can be obtained. An inversion process tries to fit these changes in speed of sound and attenuation by estimating the mean particle size and concentration of the particles. Figure 1 shows the basics of both the DLS and UNPS methods used. We show that real-time measurements of particle size and concentration using a bypass loop and flow cell can be performed directly on turbid reaction mixtures without need for dilution, by using the newly developed analytical tools. This is demonstrated using a size-tunable reaction system of nano-silica in dispersion.

Synthesis of nanoparticles in dispersion: Flow cell coupled analytics as a way to follow particle growth

2019 Fall National Meeting

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