Fluorescence anisotropy near-field scanning optical microscopy (FANSOM): a new technique for nanoscale...

A near-field scanning optical microscope system was implemented and adapted for nanoscale steady-state fluorescence anisotropy measurement. The system as implemented can resolve approximately 0.1 cP microviscosity variations with a resolution of 250 nm laterally in the near field, or approximately 10 microm when employed in a vertical scanning mode. The system was initially used to investigate the extent of microviscous vicinal water over surfaces of varying hydrophilicity. Water above a cleaved mica surface was found to have a decreased microviscosity, while water above a hydrophobic surface showed no change (detection limit approximately 0.1 cP at approximately 30 + nm from the surface).