Abstract
Both in design and production of nanoparticles and nanocomposites it is of vital importance to have information about their size and concentration. During the formation of nanoparticles, real-time monitoring of particle size and concentration during bottom-up synthesis in liquids allows for a detailed study of nucleation and growth. This provides valuable insights into the formation of nanoparticles that can be used for process optimization and scale up. In the production of nanoparticles, real-time monitoring enables intervention to minimize the number of off-spec batches. In this paper we will qualify an ultrasound nanoparticle sizer (UNPS) as a real-time monitor for the growth of nanoparticles (or sub-micro particles) in the 100 nm–1 µm range. Nanoparticles affect the speed and attenuation of ultrasonic waves in the dispersion. The size of the change depends, amongst other things, on the size and concentration of the nanoparticles. This dependency is used in the UNPS method. The qualification of the UNPS was undertaken in two successful experiments. The first experiment consisted of static measurements on commercially available silica particles, and the second experiment was real-time monitoring of the size and concentration during the growth of silica nanoparticles in Stöber synthesis in a water–alcohol mixture starting from the molecular precursor tetraethyl orthosilicate. The results of the UNPS were verified by measurements of a dynamic light scattering device and a transmission electron microscope.
Highlights
Nanoparticles are used in products for a wide variety of applications ranging from performance polymers to pharmaceuticals, food ingredients, cosmetics and coatings and paints [1,2,3,4,5,6]
The methods used in this paper to measure dispersed nanoparticles are ultrasound spectroscopy, electron microscopy and dynamic light scattering
We first present the results of the static measurements, after which we will do the same for the real-time monitoring experiment
Summary
Nanoparticles are used in products for a wide variety of applications ranging from performance polymers to pharmaceuticals, food ingredients, cosmetics and coatings and paints [1,2,3,4,5,6]. The phase of the of sound and attenuation, we measure the temperature in the dispersion Both give detailed, complex thatspeed relate the speed and of soundwe and attenuation to the particle size concentration. We use these equations in our attenuation, measure the temperature inand the dispersion. We estimate the volume concentration of the particles per diameter bin, we deliberately do do notnot output a particle becausethe theaccuracy accuracyand andfrequency frequency bandwidth output a particlesize sizedistribution This is is done because bandwidth of the measured speed of sound and attenuation is more than enough to determine the mean of the measured speed of sound and attenuation is more than enough to determine thediameter, mean butdiameter, not enough estimate anestimate accuratean width of the particle size distribution.
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