A. N. Babkina

The effect of temperature on the exciton absorption of copper chloride and copper bromide nanocrystals in potassium-aluminum-borate glass

The absorption spectra of nanosized crystals of copper (I) halides distributed in the potassium-aluminum borate glass system were investigated in the region of the exciton absorption band in the temperature range from 20 to 300°C. The temperature dependences of the exciton absorption band of CuHal (Hal = Cl, Br) nanocrystals, which were obtained upon the heating and cooling of the sample, have a form of hysteresis. The melting (140–240°C) and crystallization (35–105°C) temperatures of copper (I) halide nanocrystals contained in the potassium-aluminum borate glass were determined by the optical spectroscopy method.

Luminescence properties of potassium aluminoborate glasses with copper(I) ions at cryogenic temperatures

Luminescence spectra of potassium aluminoborate glasses with copper(I) ions have been recorded in the temperature range from +20 to −196°C. It is shown that a decrease in the glass temperature gives rise to thermochromic luminescence, which manifests itself as a red shift of the luminescence band, a value of which reaches 95 nm. This spectral shift is accompanied by a decrease in the luminescence-band amplitude by 30%.

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.

Spectral properties of copper halide nanocrystals in glasses of fluorine-phosphate matrix

The absorption spectra of glasses of fluorine-phosphate matrix in the near-UV spectral region have been investigated in the temperature range from 20 to 420°C. It is shown that the absorption bands in this spectral region are exciton absorption bands of copper chloride(I) nanocrystals. Results of X-ray diffraction analysis of the glasses are presented. It is shown that the temperature dependences of the exciton absorption bands of CuCl nanocrystals, obtained upon heating and cooling samples, have a a form of hysteresis.

A study of the effect of lithium oxide on the spectral properties of potassium-aluminoborate glass activated by chromium ions

The results of designing and studying of potassium-aluminoborate glass activated by chromium and lithium ions are discussed. Changes in the absorption and luminescence spectra of glass after the isothermal treatment are demonstrated. X-ray diffraction data showed the presence of Li(Al7B4O17) and Cr2O3 nanocrystals with an average size of 20 and 15 nm, respectively. Analysis of the luminescence spectra showed that the Cr3+ ions are in a crystalline environment. The luminescence quantum yield was 20–50%, which indicates the prospects for using such materials as a basis for fiber amplifiers in information transmission systems and laser biomedical technologies.

Specific features of the optical properties of potassium–aluminum borate glasses with copper chloride nanocrystals at high temperatures

It is shown that heating of potassium–aluminum borate glasses with CuCl nanocrystals above 80°C leads to the disappearance of exciton absorption peaks, whereas cooling below 50°C gives rise to these peaks. These effects are related, respectively, to the melting of nanocrystals and crystallization of nanophase.

UV Pulsed Laser Irradiation Effect on Spectral Properties of Borosilicate and Phosphate Glasses with CuCl Nanocrystals

The results of the study of the pulsed UV laser radiation effect on the spectral properties of the borosilicate and the phosphate glasses doped with the copper chloride nanocrystals with the mean size of 26-70 Å are discussed. The changes of the exciton absorption spectra of the CuCl nanocrystals with various mean sizes induced by different duration of the laser exposure are studied. The effect of the phosphate glass transmission reduction in the visible region upon pulsed UV laser irradiation is obtained for the first time. The nature of the transmission reduction is discussed. The assumption is made that the transmission reduction is carried out through the formation of the color centers consisted of the Cun (n>13) clusters which have the absorption bands in the visible region. In conclusion the presence of the irreversible photochromism in the phosphate glass is stated.

On the size and temperature dependence of the energy gap in cadmium-selenide quantum dots embedded in fluorophosphate glasses

The temperature and size dependences of the energy gap in CdSe quantum dots with diameters of 2.4, 4.0, and 5.2 nm embedded in fluorophosphate glasses are investigated. It is shown that the temperature coefficient of the band gap dEg/dT in the quantum dots differs from the bulk value and depends strictly on the dot size. It is found that, furthermore, the energy of each transition in these quantum dots is characterized by an individual temperature coefficient dE/dT.

Luminescent properties of cadmium selenide quantum dots in fluorophosphate glasses

The optical properties of fluorophosphate glasses with CdSe quantum dots are studied. Secondary heat treatment at a temperature exceeding the glass transition temperature resulted in the formation of quantum dots with sizes of 3.7–6.2 nm. The influence of the semiconductor component concentration on the spectral-luminescent characteristics of glasses is shown. It is experimentally demonstrated that glasses with a lower CdSe concentration have a higher absolute luminescence quantum yield.

Photoluminescent temperature sensor based on borate and phosphate glasses doped with copper clusters

The research of the luminescent properties of the inorganic glasses doped with copper molecular clusters that can be used as a sensitive medium of the temperature sensors is presented. The luminescent spectra of the borate and phosphate glasses in the temperature range 77-623 K are examined. The big luminescent thermochromism for borate glasses is observed: from 293K to 623K the luminescent band shift is found out to be 110nm.