Nanotech 2010

Early Stages of Particle Formation by in-situ UV-Vis and HRS

B. Schürer, D. Segets, W. Peukert
University of Erlangen-Nuremberg, DE

Keywords: UV-Vis, Hyper Rayleigh Scattering, Second Harmonic Generation, ZnO, optics, in-situ, nanoparticle, precipitation

Abstract:

We present a new approach for the study of early states of particle formation that can be applied also for precipitation processes that occur on a millisecond timescale. A T-shaped micro-mixer is used to precipitate nanoparticles at steady state conditions. The synthesis of nanoparticles occurs in a capillary. For monitoring the growth of the nanoparticles Hyper Rayleigh Scattering and UV/Vis absorbance spectra are recorded simultaneously. By changing the measurement position along the capillary, different reaction states can be studied in detail. As the precipitation is performed at steady state the integration time for recording signals is not limited by the reaction kinetics of the precipitation process. With this approach the signal-to-noise ratio can be improved significantly so that it is also possible to study the formation of crystals with a weak nonlinear response. For the precipitation of ZnO particles we were able to characterize particles as small as 1.6 nm. The particle sizes and size distributions were calculated from the absorbance spectra. The HRS intensities can be used to derive the actual solid concentration of precipitated ZnO.
 
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