Making use of novel organic/inorganic synthesis, we achieved two-dimensional positioning in chromophores, which were confined to the interlayer of luminous silicate nanofilms synthesized with organoalkoxysilane precursors. Time-resolved photoluminescence demonstrated efficient energy transfer from a donor dye (coumarin) to an acceptor dye (cyanine) with a characteristic time of less than 5 ps. The copresence of slow radiative energy transfer, associated with emission and reabsorption of photons, was also confirmed in the acceptor emission decay. The relative efficiency of the slow and fast energy transfers was quantified, and found to depend on the molecular concentration.

Quantized energy levels of nanoscopic concentric double rings are identified by means of micro photoluminescence spectroscopy. High-yield emissions from a single quantum structures are observed. The spectra show several discrete lines reflecting the carrier confinement in the rings. Effective mass calculation is performed to characterize the quantized motion of carriers with rotational and orbital degrees of freedoms. Excellent agreement between the observed spectra and the numerical ones is found.

The relaxation dynamics of a multiple exciton complex (multiexciton) confined in a semiconductor quantum dot has been investigated. Emission signals from a single self-organized GaAs/Al0.3Ga0.7As quantum dot are temporally resolved with picosecond time resolution. The emission spectra consisting of the multiexciton structures are observed to depend on the delay time and the excitation intensity. Quantitative agreement is found between the experimental data and the calculation based on a model describing the successive relaxation of multiexcitons.