Determination of size distribution of silica nanoparticles: A comparison of scanning electron microscopy, dynamic light scattering, and flow field-flow fractionation with multiangle light scattering methods

Methods for the accurate determination of the size and size distribution of nanomaterials are essential for nanoand biotechnology. Among the methods available, flow field-flow fractionation with multiangle light scattering and UV absorption detectors (FFFF-MALS-UV) is considered to be a more effective method than field emission scanning electron microscopy (FE-SEM) and dynamic light scattering (DLS) for determining the size and size distribution of nanomaterials. However, the raw values of size and size distribution obtained using these three methods are number-, volume-, and z-averaged, respectively. In order to compare the size and size distribution determined using different measurement methods, it is necessary to transform the raw values into the same dimensionality of length. In this study, we transformed the raw values obtained using the above mentioned three methods into the same dimensionality and found that the results for averaged size and size distribution were qualitatively similar despite the differences between the measurement methods. However, even though the obtained values were transformed to have the same dimensionality, the values obtained using FFFF-MALS-UV were found to be weighted more heavily by larger particles than those obtained using FE-SEM. Furthermore, the results obtained using DLS were weighted more heavily by larger particles than those obtained using FFFF-MALS-UV. This result was due to the observed physicochemical phenomena utilized by these two measurement methods, namely, UV absorption in the case of FFFF-MALS-UV and light scattering intensity in the case of DLS.