Dihexadecyl phosphate monolayer supported [Ru(bpy)(3)](2+) crystallites investigated by near-field scanning optical microscopy

Surface pressure (II) vs surface area (A) isotherms of dihexadecyl phosphat e (DHP) monolayers floating on aqueous tris(2,2'-bipyridyl)ruthenium(II) ch loride ([Ru(bpy)(3)][Cl-2]) solutions have established the formation of liq uid expanded (LE), liquid condensed (LC), and solid condensed (SC) phases. Repeated compression and expansion cycles lead to the irreversible formatio n of a SC phase. Horizontal lifting of a hydrophilic substrate through the monolayer resulted in the transfer of a layer of DHP-coated [Ru(bpy)(3)](2) microcrystallites. Additional layers of DHP/[Ru(bpy)(3)](2+) micocrystall ites have been transferred by Schaefer's method. The presence of [Ru(bpy)(3 )](2+) microcrystallites in the transferred multilayers has been establishe d by absorption and fluorescence spectroscopies. The absorption and emissio n spectra of [Ru(bpy)(3)](2+) microcrystallites, grown under the DHP monola yers, had their maxims red-shifted and blue-shifted with respect to those o bserved for [Ru(bpy)(3)][Cl-2] in aqueous solution. Near-field scanning opt ical microscopy (NSOM) has been employed to spatially and spectrally resolv e, at a submicron resolution, the presence of isolated seed crystals and th eir growth into differently shaped [Ru(bpy)(3)](2+) microcrystallites. NSOM also provided information on domain boundaries and on the partitioning of the fluorescent species into the various phases in the monolayer. Site-reso lved near-field fluorescence spectroscopy provided evidence for the presenc e of [Ru(bpy)(3)](2+) microcrystallites in the circular domains formed unde r a DHP monolayer.