Near-field time-resolved fluorescence studies of poly(phenylmethyl silane) with subwavelength resolution.

We present an example of the first time-correlated single-photon counting (TCSPC) near-field optical measurement. The aperture size of our prepared aluminun-coated fiber-optic probe was approximately 50 nm, which represents a spatial resolution of λex/7 for our UV measurements. Near-field fluorescence decays of poly(phenylmethyl silane) in solid thin films excited in the range 325-360 nm were obtained and the steady-state excitation spectra compared with the excitation spectral information obtained in the far field. Fluorescence decays showed single exponential lifetimes ranging from 45 to 277 ps, which was dependent on the excitation wavelength and the selected near-field tip. The proximity of the metal-coated tip to the sample may be the reason for the modulation in fluorescence lifetime.