Study On Measurement Of High Concentration Nanoparticle Size Based On Backscattering Method

In the research of particle measurement technology,dynamic light scattering has become a standard method for characterizing ultrafine particles in dilute solutions.It is currently a commonly used method for nanoparticle size measurement in my country.However,for the measurement of high concentration nanoparticles,due to multiple scattering effects The traditional dynamic light scattering method cannot be accurately measured.Based on the traditional dynamic light scattering measurement principle,this paper studies the particle size measurement method of high-concentration nanoparticles,and proposes a high-concentration nano-particle size measurement method based on backscattering,which realizes the adaptive measurement of high-concentration nano-particle size.The main research contents of this paper include:1.The current methods for solving the problem of high-concentration nano-particle size measurement have been researched and analyzed,and it is confirmed that the multiple scattering effect is the main reason that affects the accuracy of the traditional dynamic light scattering method for the measurement of high-concentration nanoparticles,and the factors of multiple scattering effects on this basis have been studied in depth.2.By analyzing the basic principles of dynamic light scattering,the strength of multiple scattering effects can be characterized according to the optical thickness.To further analyze the influencing factors of the optical thickness,the backscattering method can be used to reduce the optical path of the scattered light to reduce the optical thickness,thereby achieving the purpose of weakening the effect of multiple scattering.3.According to the analysis,an experimental device for measuring the size of high-concentration nanoparticles based on backscattering was built.The device changes the position of the scattering center by adjusting the lens position to find the optimal scattering light path,effectively suppressing or weakening the influence of the multiple scattering effect,thereby realizing the measurement of the particle size of high-concentration nanoparticles.4.The particle size measurement experiments of samples with different concentrations were carried out.The optical thickness of the tested sample and the intercept of the correlation function were comprehensively considered.The criterion for the best optical path of backscattering was proposed.The lens position was adjusted adaptively according to the sample concentration to select the best scattered light path.In this paper,it is found through the results of side scattering experiments that as the concentration of the sample to be tested increases,the optical thickness continues to increase,and the multiple scattering effect becomes stronger,resulting in a continuous decrease in the correlation function intercept.When the optical thickness is greater than 0.3,the correlation function intercept is low at 0.8,the measured particle size is much smaller than the nominal value,and the measurement result is unacceptable.Therefore,the criterion for determining the optimal scattered optical path is: the optical path at an optical thickness of 0.3 is used as the optimal backscattered light The intercept of the correlation function is used as an auxiliary judgment criterion.According to the adjustment step,the scattered light optical path and the optical path range are controlled,and the optical path adaptive measurement of particle size is realized,and the particle size of high-concentration nanoparticles can be effectively measured.