| Dynamic light scattering(DLS) technology has angular dependence,increasing the measurement angle can provide more particle size distribution(PSD)information.However,the increase of measurement information was related to not only the number of scattering angles but also the combinations of scattering angles.In addition,as the scattering angle increases,the angular error also increases,which result in the accuracy of the measurement results does not increase with the increase of the scattering angle.It has great theoretical and practical significance to study the influence mechanism of angular error,further explore the effective method to reduce the influence of angular error on the accuracy of measurement results.Based on the analysis of the estimate process of light intensity autocorrelation function baseline and angular weight coefficients,the influence mechanism and path of the angular error were studied.Based on the analysis of the Mie-scattering theory,the influence of the angular combination on the PSD was studied,which consists of,1.Influence mechanism of angular error on PSD measurement was analyzed.Based on the theory of multiangle dynamic light scattering measurement,analyzed the influence of angular error on the baseline and angular weight coefficients.The baseline value has an important effect on the accurate granularity distribution of the extracted attenuation information,which can be obtained by the mean of the intensity autocorrelation function.The angular weighting coefficient is a measure of the contribution for each scattering angle to the measured PSD information which depended on the mean value of the light intensity or measurement of baselines.The effect of angular error on the PSD result was generated by the path of baseline calculation and weight coefficient estimation.2.Influences of angular error on PSD measurement by the baseline was studied.In order to analysis the the direct and indirect influence of angular error by baseline calculation,simulated broad unimadal(82nm,350 nm,865nm),narrow unimadal(104nm,431 nm,816nm),bimodal(137/601 nm,242/750 nm,470/895nm)particle system and 306/974 nm bimodal suspension of polystyrene latex standard spheres were measured.The results show that the effect of the angular error on the PSD inversion results from the baseline calculation was generated by a direct and indirect path.The effect of indirect factors on performance error was significantlygreater than the direct factor.The influence of the direct factor on the peak error was slightly less than the indirect factor at the small particle narrow peak particle system.In other cases,the influence of the indirect factor on the peak error was greater than the direct factor.3.Influences of angular error on PSD measurement by the angular weight coefficient was studied.Angular weight coefficients can be estimated by both the baseline and Mie scattered light intensity.In order to analysis the influence of angular error by two kinds of estimation method,simulated broad unimadal(86nm,415 nm,649nm),narrow unimadal(110nm,460 nm,697nm),bimodal(137/425 nm,202/673 nm,441/890nm)particle system and 306/974 nm bimodal suspension of polystyrene latex standard spheres were measured.The results show that,the PSD results get by two weighted methods has little difference when there was no angular error.When there was angular error,the effect of intensity method on the PSD was larger than that of the baseline method and the influence on the large particles was more significant than the small,medium particles.4.Influence of angular combination on multiangle dynamic light scattering measurement was studied.In order to analysis the influence of the angular combination on the DLS measurement,five groups of simulated bimodal particle system(114/457 nm,202/800 nm,307/541 nm,433/721 nm and 600/900nm)were measured at different combinations of three,four,five and six scattering angles respectively.The results show that the accuracy of the measurement results was not only related to the number of measured scattering angle,but also to the combination of the selected scattering angles.When selected angles corresponding to the points of Mie-scattering intensity were different significantly,especially including the maximum and minimum points,the more accurate measurement results can be gotten.The mechanism of angular error and the influence of the angular combination on the measurement results are the focus of the angular dependence in the DLS measurement.This work can improve the accuracy of the measurement results by exploring the angular error source,Which provides theoretical guidance for improving the performance of dynamic light scattering measuring instruments. |
PDF Full Text Request