动态光散射技术的角度依赖性

Angular Dependence of Dynamic Light Scattering

与单角度动态光散射技术相比,多角度动态光散射(MDLS)颗粒测量技术能够提高颗粒粒度分布的测量准确性。但在MDLS技术中,测量角度的选择常常与被测颗粒体系的分布有关。对100nm、500nm的单峰模拟分布和300nm与600nm混合的双峰模拟分布的颗粒体系,分别在1、3、6、9个散射角条件下进行了测量。颗粒粒度反演结果表明,随着散射角个数的增大,颗粒粒度分布更趋于真实的颗粒粒度分布。对数量比为5:1的100nm与503nm双峰分布的聚苯乙烯颗粒,分别在1、3、5、10个散射角条件下进行了测量,实测结果表明采用单角度测量只能得到单峰分布,3个及更多散射角可得到双峰分布,并且双峰的数量比随散射角数量的增加逐渐趋近真实的数量比。因此,MDLS颗粒测量技术能够改善颗粒粒度分布的测量结果,但这种改善程度会随散射角的增多逐渐降低。由于散射角个数的增多会增加散射角的校准噪声和光强相关函数的测量噪声,因而会导致在有些情况下颗粒粒度分布的测量结果反而变差。

Multiangle dynamic light scattering（MDLS） technique can give better particle-size distribution（PSD） than single-angle dynamic light scattering（SDLS） technique.However,the choice of scattering angles is affected by the measuring particles in MDLS.Unimodal simulation distribution of 100 nm and 500 nm and bimodal simulation distribution of 300 nm and 600 nm are respectively measured at one,three,six and nine scattering angles and are inversed to obtain the PSD.This results show that MDLS can give better PSD with the increase of number of angles.Furthermore,the PSD has a little modification when there are more than one angle for 100 nm particles or more than three angles for 600 nm particles.A dilute bimodal suspension of polystyrene latex standard spheres mixed in a number ratio of 5：1 is measured at one,three,five and ten angles.The results show that one angle only can give one peak and more than three angles can give two peaks.The number ratio is closer to the true value with the increase of number of angles.Though MDLS can give better PSD than SDLS,the improvement of PSD become less obvious with the increase of number of angles.In some cases,the PSD may become worse with the increase of angle numbers because the calibration noise of scattering angle and measurement noise of light-intensity correlation function are added.