Low-angle X-ray scattering for the determination of the size of mesoporous silica nanoparticles

Abstract

In the last two decades, Mesoporous Silica Nanoparticles (MSNs) were given a substantial interest due to their unique properties and wide range of applications. The size is a key feature which determines the use of MSNs. Transmission Electron Microscopy (TEM) is a standard technique for MSNs’ size determination. Despite reliable, yet it has some drawbacks, being time consuming, destructive and requires complex sample preparation. Therefore, this work aims at introducing Low-angle X-ray Scattering (LAXS) as a time-saving, non-destructive and inexpensive tool for the determination of the size of MSNs. Different sizes of MSNs are prepared using different concentrations of ammonium hydroxide (catalyst) and their corresponding LAXS profiles are recorded. LAXS profile parameters (peak position and area under peak) are found to exhibit a strong linear dependence on the size of MSNs determined using the standard TEM technique. Moreover, the pore sizes calculated from LAXS profiles show linear dependence on the size of MSNs. For MSNs in the range from 60 to 170 nm, two mathematical linear fitting equations are introduced for the determination of the size of MSNs by direct substitution using LAXS profile parameters. One more equation is introduced for the calculation of the size of MSNs directly from their pore size.