Synthesis, isolation, and redispersion of resorcinarene-capped anatase TiO2 nanoparticles in nonaqueous solvents.

C-undodecylcalix[4]-resorcinarene (C(11)-resorcinarene)-capped anatase TiO(2) nanoparticles have been synthesized and could be isolated and redispersed in different nonaqueous solvents. The adsorption of C(11)-resorcinarene onto the surface of TiO(2) nanoparticles led the shifting of the onset wavelength of the optical absorption in the visible range along with a broad band centered at 422 nm corresponding to ligand-to-metal charge transfer transition within the surface titanium(IV)-C(11)-resorcinarene complex. The interaction of TiO(2) nanoparticle with C(11)-resorcinarenes was investigated by photoluminescence (PL). Proton nuclear magnetic resonance ((1)H NMR) spectroscopy study revealed that the C(11)-resorcenarene molecules adsorbed chemically onto the surfaces of TiO(2) nanoparticles. The average particle diameter of bare anatase TiO(2) and C(11)-resorcinarene-capped TiO(2) was determined using transmission electron microscopy (TEM) and was found to be equal to ca. 5 nm.