RESUMO
Results of reflection microscopy and local reflection spectroscopy of J-aggregates of two pseudoisocyanine dyes in a thin film polymer matrix are reported. The individual J-aggregates assemble into fibre-like shapes of large structural heterogeneity. Reflectance spectra obtained at different samples, different locations on one sample and even at different positions of the same aggregate fibre reveal a wide distribution of optical properties. The shapes and absolute reflectivities of the spectra are suggested to originate from varying strengths of exciton-photon interaction and from the effect of finite thickness of the aggregate fibres. Polarization dependence measurements of local reflectivities provide orientations of the exciton transition dipole moments at 572 nm and 540 nm with respect to the orientation of the aggregate fibres. Furthermore, modified synthesis of capped semiconductor nanocrystals of CdSe is presented. The method yields high quality quantum dots suitable for microscopic imaging and spectroscopy.