Challenges in sample preparation for measuring nanoparticles size by scanning electron microscopy from suspensions, powder form and complex media

Commercial products containing nanomaterials are already a part of our everyday life. The dimensional parameters play an important role for identifying nanoparticles. Various techniques are available for measuring the particles size and shape. However, electron microscopy-based techniques are often considered as the preferred methods for characterizing their dimensional properties. Samples preparations remain a key step but no standardized protocol is currently available. Scanning electron microscopy measurements require well-dispersed particle population corresponding to a statistically representative sample. This work presents a new approach, to prepare samples based on spincoating technique in order to measure in a reliable manner the constituent particle size. This method consists of three key processing steps: (i) extraction from complex media, (ii) redispersion by means of probe sonication and (iii) deposition by spincoating. The approach combines several factors such as pH, zeta potential, duration, concentration, sonication and spin coater parameters, that can influence agglomeration state of nanoparticles.