Thiol-capped CdTe nanocrystals with cubic zinc blende structure are synthesized in aqueous solution. Their steady-state and time-resolved luminescence characteristics are studied at room and liquid nitrogen temperatures. A strong exciton luminescence peak at 2.3 eV dominates the emission spectrum of CdTe nanocrystals at room temperature, whereas the trap band centered at 2.0 eV undergoes substantial temperature quenching. Luminescence excitation spectra reveal different channels leading to radiative recombination via either excitons or traps. The mean luminescence decay time of CdTe nanocrystals at room temperature decreases from 120 ns at 1.94 eV to 20 ns at 2.43 eV. Luminescence decay kinetics of CdTe nanocrystals are strongly nonexponential and are described by extremely broad lifetime distributions lying within the range from a few hundred picoseconds to a few hundred nanoseconds.

We report on the photonic band gap phenomenon in the visible range in a three-dimensional dielectric lattice formed by close-packed spherical silica clusters. The spectral position and the spectral width of the optical stop band depend on the direction of light propagation with respect to the crystal axes of opal, and on the relative cluster-to-cavity refraction index n. Manifestations of the photonic pseudogap have been established for both transmission and emission spectra. The stop band peak wavelength shows a linear dependence on n. Transmission characteristics of the lattice have been successfully simulated by numerical calculations within the framework of a quasicrystalline approximation. ͓S1063-651X͑97͒13805-3͔

Nanojet-induced modes (NIMs) and their attenuation properties are studied in linear chains consisting of tens of touching polystyrene microspheres with sizes in the 2-10 micro m range. To couple light to NIMs we used locally excited sources of light formed by several dye-doped fluorescent microspheres from the same chain of cavities. We directly observed the formation and propagation of NIMs by means of the scattering imaging technique. By measuring attenuation at long distances from the source, we demonstrate propagation losses for NIMs as small as 0.5 dB per sphere.

Abstract-Photonic crystals based on silica colloidal crystals (artificial opals) exhibit pronounced stopbands for electromagnetic wave propagation and the corresponding modification of the photon density of states in the visible range. These spectrally selective features can be enhanced by impregnating opals with higher refractive materials like, e.g., polymers. Doping of these structures with dye molecules, semiconductor nanoparticles (quantum dots), and rare-earth ions provides a possibility to examine the challenging theoretical predictions of the inhibited spontaneous emission in photonic bandgap (PBG) materials. First experiments are discussed in which pronounced modification of spontaneous emission spectra and noticeable changes in decay kinetics were observed.