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Phase transitions of amphiphilic copolymer solutions can be achieved by irradiating aqueous solutions of this polymer with an IR-laser beam. As a result, a single microparticle up to 15 μm is formed, whereas thermal heating of the solution results in submicrometer particles. Both the photo-thermal effect (due to absorption of 1064 nm by the H2O overtone) and the radiation force cause the unusual large particle formation (up to 15 μm). Furthermore, the present study shows that the conformational distribution and associations of polymers in solution can be controlled with the radiation force of a focused laser beam.

Synthetic details and stationary and time-resolved photophysical properties of five BODIPY derivatives containing chalcogen atoms are presented. The photophysical data are compared to those of a chlorine atom containing BODIPY, acting as a reference. A strong impact in the HOMO–LUMO transition energy is achieved via nucleophilic substitution with chalcogen based units. Going from oxygen to tellurium a bathochromic shift in both absorption and emission spectra from the green to the near infrared region was observed. By employing fluorescence single photon timing experiments in two solvents of different polarity, the excited state dynamics and their solvent dependence indicate the presence of a mechanism involving a photoinduced charge transfer that dramatically affects the optical radiative processes of these derivatives.

Transmission and confocal fluorescence microscopy, and time-resolved fluorescence spectroscopy combined with a laser trap: Investigation of optically trapped block copolymer micelles

This paper describes the essential photophysical properties of a newly synthesized 1-cetyl-4-(p-NN-dimethylamino styryl)-pyridinium bromide and its parent short-chain styrylcyanine dye. These dyes exhibit similar fluorescence behaviour and are characterized by extensive non-radiative processes. The observed main differences are related to the long-chain hydrocarbon group and are found to be an enhanced sensitivity of the organized surfactant molecules to solvent interactions. The influence of various macro-and micro-scopic solvent properties on the photophysical properties of the dyes is investigated, with particular focus on the interplay of dye structure and specific solvent-solute interactions that govern the competition between radiative and non-radiative decay. It is found that specific interactions by hydrogen-bonding solvents are the key controlling factors in the relaxation processes. The results are expressed in terms of linear and multilinear relationships. Correlating the experimental results with theory (CNDO and PPP-SCF-CI calculations) provides a better insight into the excited-state properties of these dyes.

Difluorenylcalcium (Fl2Ca) has been studied by absorption and emission spectrometry in tetrahydrofuran (THF) and in tetrahydropyran (THP). The absorption spectrum shows the presence of both contact and solvent-separated ion-pairs. The solvation of Fl2Ca in THF is probably a stepwise process. In THP only contact ion-pairs are found. The emission spectrum in THF is independent of the excitation wavelength and of the concentration, and the relative intensities within the emission band do not change in the range of +20 to –40 °C. The excitation spectrum shows only one maximum, at 373 nm.The emission may be caused by an excited-state cation solvent relaxation process and appears to occur from a separated ion pair in the ion triplet. The emission spectrum of Fl2Sr was examined in order to compare the characteristics of the Ba, Sr, and Ca salts; it depends on the excitation wavelength. The excitation spectrum also shows one maximum. The emission is probably due to a mechanism similar to that for Fl2Ca.