T. A. Shakhverdov

Influence of UV irradiation and heat treatment on the luminescence of molecular silver clusters in photo-thermo-refractive glasses

The luminescence spectra of photo-thermo-refractive (PTR) glasses containing cerium, silver, and antimony ions before and after UV irradiation and after heat treatment have been thoroughly investigated for the first time. It is shown that silver is present in the initial PTR glass in the form of ions and positively charged molecular clusters. After UV irradiation into the absorption band of cerium ions, silver partially passes to the neutral state in the form of atoms and neutral molecular clusters Ag2, Ag3, and Ag4, which exhibit bright luminescence in the visible spectral range. Subsequent heat treatment at a temperature below the glassformation temperature leads to an increase in the luminescence intensity due to the increase in the concentration of neutral molecular clusters. Heat treatment at a temperature above the glass-formation temperature leads to the formation of silver nanocrystals and luminescence quenching. It is proposed to use PTR glasses with molecular silver clusters as phosphors for converting UV radiation into the visible range for solar power engineering and white LEDs.

Luminescence of molecular silver clusters in oxyfluoride glasses

Luminescence spectra of silver-containing oxyfluoride glasses have been investigated in the excitation spectral range of 360–480 nm. Analysis of the luminescence spectra shows that silver in oxyfluoride glasses that contain no strong reducers and were subjected to heat treatment affecting redox processes exists in the form of neutral atoms and neutral molecular Ag2, Ag3, and Ag4 clusters.

Broadband copper luminescence in potassium-aluminum borate glasses

Broadband luminescence in the visible spectral range has been investigated for copper-containing potassium-aluminum borate glasses. It is shown that the luminescence in initial glasses (before their heat treatment) is due to the presence of molecular clusters Cun (n < 10) in them. Chemical reactions during heat treatment lead to the formation of CunClx and CunOx clusters with luminescence bands lying in the spectral range of 450–600 nm.

Formation of luminescent centers in photo-thermo-refractive silicate glasses under the action of UV laser nanosecond pulses

It is shown experimentally that the result of the UV nanosecond laser irradiation of the silver-containing photo-thermo-refractive (PTR) glasses depends on the pre-history of glass. If the PTR glass was preliminary irradiated by the UV radiation by UV mercury lamp into the absorption band of Ce3+ ions the laser irradiation results in the silver molecular clusters (MCs) luminescence quenching. If the PTR glass was not preliminary irradiated by the UV radiation the UV nanosecond laser irradiation action results in the silver MCs luminescence appearance. The subsequent thermal treatment below the glass transition temperature results to the increase of the luminescence intensity. The thermal treatment above the glass transition temperature led to the silver nanoparticles formation and to luminescence quenching.

Specific features of the luminescence of silicate glasses with silver introduced by ion exchange

The luminescence spectra of silicate glasses with silver introduced by ion exchange have been investigated. It is shown that silver introduced into glass by ion exchange exists not only in the form of ions, but also as neutral atoms and charged and neutral molecular clusters, which provide intense luminescence in the visible spectral range. Cerium ions in glass facilitate the formation of neutral molecular silver clusters, due to which the luminescence intensity increases. It is shown that Agn-Cex+ complexes can be formed in glass containing cerium ions and neutral molecular silver clusters.

Photoinduced electron transfer involving radical ions in multicomponent solutions

A phenomenological study of a specific radical ion mechanism of formation of metastable products is presented. Energy level diagrams of fullerene C60, tetramethylbenzidine, perylene, and radical ion pairs in toluene and benzonitrile are constructed. The possibility for obtaining fast optical switching and limiting in solutions of C60 fullerene, tetramethylbenzidine, and perylene in toluene is analyzed.

Luminescent properties of fluorophosphate glasses with molecular cadmium selenide clusters

It is experimentally shown that, prior to the formation of CdSe quantum dots in fluorophosphate glasses with cadmium and selenium ions in the process of synthesis, subnanosized molecular clusters (CdSe)n are formed, which exhibit luminescence in the visible spectral region upon UV excitation. Heat treatment of the glasses increases the size of molecular clusters and makes their optical properties closer to the optical properties of CdSe semiconductor quantum dots. An increase in the sample temperature from 20 to 250°C leads to reversible thermal quenching of the luminescence.

Luminescent glass fiber sensors for ultraviolet radiation detection by the spectral conversion

Abstract. It is shown that glass fibers doped with luminescent molecular clusters of silver, cadmium and lead chalcogenides, or copper (I) can be used for the efficient radiation conversion of ultraviolet (UV) radiation to the visible spectral region. The advantages of radiation trapping in fibers by the luminescent centers and of spectral conversion are discussed. The excitation and luminescence spectra of luminescent fibers are presented. Analysis of application areas of the luminescent glasses and fibers is performed. The construction of the sensitive element for sensor models for electrical spark and UV radiation detection is described. The characteristics of the models of sensors for electrical spark and UV radiation detection are presented.

The effect of temperature on the luminescence spectra of potassium-aluminum borate and silicate glasses with copper(I) and silver ions

Luminescence and luminescence-excitation spectra of potassium-aluminum borate glasses containing copper(I) and silver ions have been investigated in the temperature range of 20–300°C. It is shown that the luminescence thermochromic effect, which manifests itself in a blue spectral shift of the luminescence bands with an increase in temperature, occurs in glasses of all types, reaching a value of 100 nm. Heating leads to a red shift of luminescence-excitation bands by 20 nm and their broadening. Luminescence quenching occurs in glasses exhibiting photochromic effect at room temperature. An increase in temperature leads to weakening and, finally, disappearance of the photochromic effect in these glasses with subsequent occurrence of the luminescence thermochromic effect.

Luminescent properties of molecular clusters (CdS)n in fluorophosphate glass

It is shown experimentally that subnanodimensional molecular clusters (CdS)n are formed by synthesis in fluorophosphate glass containing cadmium and sulfur ions. They possess an intense luminescence in the visible region of the spectrum when being excited by UV radiation. Thermal treatment of such glass results in an increase in the size of the molecular clusters and makes their optical properties approach those of semiconductor CdS quantum dots. Luminescent fluorophosphate glass with (CdS)n clusters can find applications in spectral down-converters of solar UV radiation in solar energetics, in light-emitting diodes of white radiation, and in luminescent detectors and sensors.