We present the quantitative analysis of the photoluminescence (PL) obtained for semiconductor TOPO-capped CdSe/ZnS QDs in solutions at 77–293[Formula: see text]K. The PL bands are approximated more accurately when assuming the superposition of at least two Gaussian components differing considerably in the linewidth (FWHM) and having different nature.

The attachment of pyridyl substituted porphyrin molecule to the surface of CdSe/ZnS quantum dots in solutions is realized in the competition with capping ligand TOPO molecules resulting in the specific change of photoluminescence for the quantum dots across the temperature range of 77–290[Formula: see text]K. We have shown that fixation of alone quantum dots or quantum dot-porphyrin nanoassemblies on quartz substrate changes significantly temperature dependence of photoluminescence. In contrast to the samples in a glass-forming solution no phase transition of the TOPO capping layer was observed upon removal of the capping layer.

This chapter presents a reinvestigation of spectral-kinetic properties for Cadmium selenide (CdSe)/ZnS quantum dots (QD) in solvents being obtained in a wide temperature range. It focuses on ensemble experiments to unravel as many as possible subtle optical properties of core and surface-related electronic states, which will give new insights into several optical observables both with respect to a basic understanding of surface properties and with envisaged applications. The chapter summarizes the basic implications of the influence of temperature on photoluminescence (PL) spectral-kinetic parameters for core/shell CdSe/ZnS QDs. If successfully applied, the large variety of functional organic molecules at hand allows for a broad scenario for modification of optical QD properties. Investigations of single QDs reveal PL intermittency, which has been explained either by photoinduced charging or a multiple relaxation center model. Due to weak ergodicity breaking QD ensemble and time-averaging single-QD data cannot uniquely but qualitatively be related to each other.

Some new experimental data on the time development of ultrashort superfluorescence (SF) in the dye solution are presented. The correlation between temporal behaviour change and the change of the spectral and spatial intensity distribution gives direct evidence of the important role of the selffocusing phenomenon in the formation of the ultrashort SF pulse synchronized with the pumping one. The oriental relaxation of solvent molecules in the dye solution not only influences the duration of the dye SF via the selffocusing mechanism but also causes a temporal change of spontaneous emission spectrum. At least two different relaxation times were found in the fluorescence spectrum of the dye in several polar solutions.

As was demonstrated in [1], ultrafast superfluorescence pulses can be developed in a dye solution under pumping by a powerful picosecond mode-locked solid-state laser, though normally superfluorescence emission of dye has a rather broad spectrum and its frequency tuning is comparatively inconvenient (it requires changing the dye concentration in a solution). The extreme simplicity of the method makes it quite attractive and useful for some applications in picosecond spectroscopy.

Using picosecond spectroscopy technique the rotational relaxation time of rhodamine 4C in solutions both in the ground and excited states is measured to be the same and equal to 250 ps.