Influence of ZnO Nanoparticles on the Behavior of the Short-Lived Products of the Pulse Photolysis of Fluorescein and Its Halogen Derivatives in Isopropanol

Rapid processes, which occur on photoexcitation of fluorescein and a series of its halogen derivatives in the presence of ZnO nanoparticles in isopropanol, have been studied by pulse photolysis. The short-lived intermediates have been identified and the kinetics of their destruction have been studied. It is shown that photoinduced transfer of an electron from the singlet and triplet excited molecules of the dyestuffs into the conduction zone of the semiconductor occurs in the presence of ZnO nanoparticles.     

Annealing-induced structural transformation of gelatin-capped Se nanoparticles

Selenium nanoparticles were obtained by a new facile synthetic route from gelatin-stabilized aqueous colloidal solutions. The dependence of structural and optical properties of the nanoparticles upon duration of post-synthesis thermal treatment of Se sols was studied by optical absorption, photoluminescence and Raman scattering. We have shown that ageing of colloidal Se solutions at elevated temperatures results in an enlargement and crystallization of selenium nanoparticles, accompanied with noticeable changes in their optical spectra: an enhancement of the photoluminescence of the NPs, incorporated in gelatin films; a “red” shift of both the absorption threshold and emission band maximum; appearance of new peaks in Raman spectra, attributed to the formation of the crystalline phase in the course of the ageing.     

Photocatalytic synthesis of ZnO/Ag nanostructure sensitized by methylene blue

The possibility of photochemical synthesis of ZnO/Ag nanoheterostructures by the action of visible light absorbed by methylene blue as sensitizer was established. It was shown that sensitization of the ZnO nanoparticles results from electron transfer from the singlet-excited molecules of the dye to the conduction band of the ZnO nanoparticles. A scheme for the mechanism of the photoprocesses that occur is proposed.__________Translated from Teoreticheskaya i Éksperimentalnaya Khimiya, Vol. 41, No. 1, pp. 12–16, January–February, 2005.     

Doping/Alloying Pathways to Lead-Free Halide Perovskites with Ultimate Photoluminescence Quantum Yields

Tailored modifications of halide lead-free perovskites (LFPs) via doping/alloying with metal cations have been recognized as a promising pathway to highly efficient inorganic phosphors with photoluminescence (PL) quantum yields of up to 100 %. Such materials typically display selective sensitivity to UV light, a broad PL range, and long PL lifetimes as well as a unique compositional variability and stability—an ideal combination for many light-harvesting applications. This Minireview presents the state-of-the-art in doped LFPs, focusing on the reports published mostly in the last two to three years. We discuss the factors determining the efficiency and spectral parameters of the broadband PL of doped LFPs depending on the dopant and host matrix, both in micro- and nanocrystalline states, address the most relevant challenges this rapidly developing research area is facing, and outline the most promising concepts for further progress in this field.     

Dynamics of the radiative recombination of charge carriers in CdS nanoparticles stabilized with polyethyleneimine

The dynamics of the radiative recombination of charge carriers in CdS nanoparticles stabilized in aqueous solutions of polyethyleneimine was studied. It was shown that decay of the photoluminescence of the nanoparticles is characterized by a set of time constants in the range of 10⁻¹-10²ns, while its rate depends on the energy of the radiation quanta. This relationship is interpreted as the result of competition between the processes of radiative recombination and vibrational dissipation of the excitation energy.