The effect of particle aspect ratio on spatially and angularly resolved vis-NIR spectroscopy of suspensions

Stoliarskaia, Daria and Thomson, Kelly and Lue, Leo and Chen, Yi-Chieh; Ferraro, Pietro and Grilli, Simonetta and Ritsch-Marte, Monika and Hitzenberger, Christoph K., eds. (2019) The effect of particle aspect ratio on spatially and angularly resolved vis-NIR spectroscopy of suspensions. In: Proceedings of SPIE - The International Society for Optical Engineering. Society of Photo-Optical Instrumentation Engineers, Bellingham, Washington. ISBN 9781510627994 (

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The particle characteristics in a suspension affect the performance and quality of the end product of many chemical industries. The shape of the suspended particles can be influenced by changes in the manufacturing process conditions. Thus, there is a need for a robust method for continuous monitoring of particle characteristics through the process. This study investigates the feasibility of using spatially and angularly resolved diffuse reflectance measurements as a method of determining particle shape. A forward calculation was developed using the discrete dipole approximation to estimate optical properties of the single particle and the diffuse approximation for the reflectance of the particle suspension. The method was used to study aqueous suspensions of randomly-oriented polystyrene ellipsoids. Our objectives were to determine and elucidate the contribution of aspect ratio on optical measurement in vis-NIR spectra. The results suggest that the method is suitable for determining particle shape for suspensions where the particle and the solvent have significantly different optical properties. For these systems, the study suggests that diffusion reflectance measurements can be developed into an in-line method for particle shape determination