Development of the Multi Wavelength Light Extinction Technique for the characterization of nanoparticles - Data inversion

During the past decades, the number of applications of nanoparticles and that of the related research increased considerably. Unfortunately, a sufficiently flexible measurement technique is still not available for the online characterization of the size and concentration of nanoparticles . The present paper is dedicated to the development of the Multi Wavelength Light Extinction (MWLE) technique, which is a potential technique for real-time and online nanoparticle characterization. The technique reconstructs the particle properties from the light transmittance spectrum of the cloud of investigated particles. The paper reports the first step of the development, which is related to the data inversion algorithm. The latter is important for solving the arising Fredholm integral equation of the first kind, which is an ill-conditioned inverse problem. The first section describes an inversion algorithm, which ensures the retrieval of the size distribution function and concentration of the particles. The following chapters contain the results of a numerical test campaign, which was performed for evaluating the computational requirements, accuracy, robustness and the measurement limitations of the technique. The utmost importance of the information content of the measurement data was recognized and a criterion was found to ensure its maximization. The paper provides further guidelines to MWLE experiments and the corresponding data inversion process. Keywords— nanoparticle sizing, extinction, inversion