Study On Angular Weighting For Multi-angle Dynamic Light Scattering

Dynamic light scattering is an effective method for measuring submicron and nanometer particles.The particle size and distribution can be obtained according to the continuous Brownian motion caused by particles in the liquid.Multi-angle dynamic light scattering technology can obtain more granularity information than single-angle dynamic light scattering technology,avoid the adverse results caused by improper selection of scattering angles of test samples,and can obtain more accurate granularity distribution.For self-correlation data measured from multiple angles,it is necessary to combine it into a data analysis.Angle-weighted determine the angle weight coefficient based on the contribution of scattering angles to the particle size distribution information to make up for the difference in the average scattering light intensity at different scattering angles.Using the weight coefficient of the nuclear matrix to represent the contribution of particles of different granularity to scattered light at the scattering angle,so as to better analyze the data of multiple angles and give full play to the advantages of multi-angle measurement.In this thesis,the angular weighting are studied.The effects of angular error,signal noise and other effects on the particle size distribution are explored.The noise suppression method and the appropriate angular weighting are given.The main contents include:1.The mechanism of multi-angle dynamic light scattering angular weighting is explored.The multi-angle dynamic light scattering angular weighting includes the selection of the angular weighting coefficient and the kernel matrix weighting coefficient.The angular weighting coefficient compensates for the difference of the average scattered light intensity of different scattering angles.The kernel matrix weighting coefficient characterizes the contribution of different particle size particles to the scattered light at the scattering angle.2.The mechanism of the angular error on the angular weighting is studied,and the influence of the optical intensity mean method and the iterative recursive method on the angular error is compared.The angular weighting method is different,and the action mechanism of the angular error is also different.By comparing the intensity intensities method and the iterative recursive method with the inversion results of the angular error,it is found that the light intensity mean method has greater influence on the angle error than the iterative recursive method,and the large particle ratio Small particles are affected greatly,and this phenomenon can be explained by the Mie scattered light intensity distribution.3.The effects of noise on the intensity mean method and the iterative recursive method are studied,and a truncated singular value noise suppression method based on kernel matrix expansion is proposed.Noise not only directly affects the measurement of autocorrelation data,but also affects the calculation of the angular weight coefficient,which in turn adversely affects the inversion results.Comparing the inversion results of the light intensity mean method and the iterative recursive method affected by noise,it is found that the iterative recursion method is less affected by noise than the intensity mean method,but the ability of both methods to suppress noise has certain limitations.Aiming at this phenomenon,a truncated singular value suppression noise method based on kernel matrix expansion is proposed to improve the system's ability to suppress noise.4.A composite angular weighting method based on Mie scattered light intensity is studied.In the analysis of the theoretical angular weighting method,it is found that it is difficult to balance the information utilization and anti-noise performance.A new composite angle weighting method based on Mie scattered light intensity is proposed.This method has a good balance between information utilization and anti-noise performance.Multi-angle dynamic light scattering can obtain a more accurate particle size distribution than single-angle dynamic light scattering.The angular weighting method is the key to fully exploit the multi-angle advantage and has an important impact on the inversion results.Through the study of the angular weighting mechanism,the influencing factors of the angle weighting method are explored,and a more accurate angle weighting method is proposed to better deal with the autocorrelation data of multiple angles,and to improve the performance of the multi-angle dynamic light scattering instrument.Accurate measurement of complex distribution submicron and nanoparticle systems is important.