For scanning electron microscopy (SEM), dried hydrophilic and hydrophobic nanoparticles were attached to a piece of glass slide using double-sided carbon tape and further dried under vacuum for 1 h. The glass slide was then mounted on an SEM stub using copper tape and sputter coated with gold. An Agilent 8500 FE-SEM was used to obtain SEM images.
For transmission electron microscopy (TEM), dried hydrophilic and hydrophobic nanoparticles were suspended at a concentration of 100 µg/mL (in 50/50% v/v ethanol/water) and 2 µL of this suspension was added to a TEM grid. The sample was air dried overnight and then imaged with a JEOL JEM 1400 TEM microscope fitted with a GATAN UltraScan 1000 CCD camera. The ImageJ software [34 (link)] was used to size the diameters of individual nanoparticles from TEM images and aggregate sizes were measured from SEM images. In total, 240 individual nanoparticles were sized across 8 TEM images for both the hydrophilic and hydrophobic nanoparticles. For aggregate sizing, over 50 aggregates were sized from across 5 SEM images for both hydrophilic and hydrophobic nanoparticles.
For transmission electron microscopy (TEM), dried hydrophilic and hydrophobic nanoparticles were suspended at a concentration of 100 µg/mL (in 50/50% v/v ethanol/water) and 2 µL of this suspension was added to a TEM grid. The sample was air dried overnight and then imaged with a JEOL JEM 1400 TEM microscope fitted with a GATAN UltraScan 1000 CCD camera. The ImageJ software [34 (link)] was used to size the diameters of individual nanoparticles from TEM images and aggregate sizes were measured from SEM images. In total, 240 individual nanoparticles were sized across 8 TEM images for both the hydrophilic and hydrophobic nanoparticles. For aggregate sizing, over 50 aggregates were sized from across 5 SEM images for both hydrophilic and hydrophobic nanoparticles.