The spheres were fire-polished but not pre-etched prior to coating. Polished spheres were immersed in 3% mercaptopropyltrimethoxy saline (MPTS) in methanol for 30-40 minutes under a nitrogen atmosphere. They were then removed into room air and washed 3-4 times with methanol. Images were measured directly after preparation and then after the sphere remained in ambient air for 5 hours.
AFM image of fused silica quartz slide directly after cleaning. The line profile shows a defect in the surface that is approximately 10 nm in height. Streaks in the image are a result of vibrations in the quartz rod used for mounting.
AFM image of quartz bead after exposure to air for 5 hours. The areas of contamination have heights of approximately 100 nm.
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