V. A. Tsekhomskii

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.

Nonlinear optical effects in glasses containing copper chloride nanocrystals

Nonlinear optical properties of various glasses containing copper chloride nanocrystals have been studied at wavelengths of 532 and 1064 nm. It is established that the nonlinear optical response is manifested by the optical limiting of transmitted radiation and consists of two, low- and high-threshold parts. The low-threshold response is related to a self-defocusing of the radiation, while the high-threshold response is related to the phenomena of two-photon absorption, color center photogeneration, and thermal lens formation.

Effect of electron irradiation on the formation of silver nanoclusters in photothermorefractive glasses

The dynamics of formation of silver nanocrystals under the action of an electron beam in the near-surface layer of photothermorefractive glasses containing Ag+ ions has been experimentally studied. It is shown that the irradiation by electrons leads to the field-induced diffusion of Ag+ ions and the appearance of primary silver nanoclusters. The role of nanostructures of the core-shell type in the formation of these nanoclusters and the subsequent growth of metallic silver nanoparticles with plasmon resonances is determined.

Precipitation of Nanosized Crystals CuBr and CuCl in Potassium Aluminoborate Glasses

The precipitation of nanosized crystals CuBr and CuCl in potassium aluminoborate glasses containing additives of jointly introduced Cu and Br, as well as Cu and Cl, respectively, has been studied by the methods of small-angle X-ray scattering (SAXS) and X-ray powder diffraction (XRPD) analysis. It has been found that, upon thermal treatments at temperatures close to the glass transition temperature Tg, halide phases precipitate in the form of liquid drops containing CuBr and KBr or CuCl and KCl. The presence of nanocrystals CuBr or CuCl, respectively, has been established in the samples at room temperature by the XRPD method. Liquidus, solidus, and crystallization onset temperatures in the regions of precipitated halide phases in heat treated glass samples have been determined from the temperature dependences of SAXS intensity. The liquid released upon the heat treatment inside a matrix of potassium aluminoborate glass remains in the state of a supercooled liquid at temperatures essentially below the solidus temperature. At the drop sizes of the order of 10 nm, crystallization processes in them start at temperatures of 40–85°C.

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.

Influence of ionizing radiation on the spectral properties of photo-thermo-refractive glass containing silver nanoparticles

Experimental results on the investigation into the influence of ultraviolet, X-ray, and γ-radiation on the absorption spectra of photo-thermo-refractive glass containing silver nanoparticles have been presented. It is established that the peak position of the silver plasmon absorption band shifts depending on the ionizing radiation type. The observed changes are explained by changes in the particle size and refraction index of the layer surrounding the nanoparticles.

The effect of gold nanoparticles on crystallization processes in photostructured lithium-silicate glass

The surface plasmon resonance of gold nanoparticles (NP) is investigated, allowing their sizes before and after X-ray irradiation to be determined. It is shown that X-ray irradiation results in the growth of NP, while their heat treatment results in their reduction. The quasi-atomic structure of gold NP is assumed, leading to the entrapment of electrons on unoccupied orbitals upon X-ray irradiation. An explanation of the crystallization and amorphization of photostructured glass in the lithium-silicate system is suggested based on the fact that gold NP are negatively charged.

Electron-beam modification of the near-surface layers of photosensitive glasses

Electron-beam treatment of photosensitive silicate glasses doped with silver or copper ions leads to the formation of metal nanoparticles in the near-surface layer of a sample. The characteristics of this layer depend on the type of metal ions, pre- and postirradiation heat treatments, charge distribution, and conditions for the removal of electrons from the surface. A certain spatial profile of charge distribution can lead to the formation of lenslike structures with a thickness of 200–400 nm.

Effect of the size of CuBr nanocrystals formed in potassium-aluminum-borate glass on the phase transformation temperature

At thermal treatment of samples of potassium-aluminum-borate glass containing Cu and Br, a heterogeneous nanophase is formed as drops of the liquid containing CuBr and KBr. At room temperature, the phase contains CuBr and K2CuBr3 nanocrystals. The effect of sizes of nanophase areas on the temperatures of phase transformations (liquidus, solidus, and crystallization) at heating and cooling has been investigated. At the sizes of CuBr crystals equal to 10 nm, the solidus temperature is close to that shown on the state diagram of the KBr-CuBr system. The decrease of the sizes of CuBr crystals from 10 to 4.5 nm results in the decrease of the solidus temperature from 170 to 95°C and the liquidus temperature from 208 to 120°C: in other words, the dimensional effect is manifested almost identically on the values of the solidus and liquiddus temperatures. The decrease of the sizes of the liquid drops from 19 to 7 nm results in the decrease of the crystallization temperature from 100 to 70°C.

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.