Influence of ultraviolet irradiation and heat treatment on the morphology of silver nanoparticles in photothermorefractive glasses

This paper reports on the experimental results of the investigation into the influence of ultraviolet irradiation and heat treatment on the absorption spectra of photothermorefractive glasses containing silver nanoparticles. It is demonstrated using numerical simulation methods that the spectral shift and the modification of the absorption bands associated with the plasmon resonances of silver nanoparticles are determined primarily by the variations observed in the shape of silver nanoparticles and by the formation of “core-shell” nanostructures.     

Fluorophosphate glasses activated by rare-earth ions and AgBr

Analysis of the absorption band position for colloidal silver in fluorophosphate glasses of the composition (0.95 ? x ? y)(MgCaBaSrAl₂F₁₄)-0.05Ba(PO₃)₂-xPbF₂-yLnF₃ (where Ln = Eu, Ce, Sm, Tb; 0 ?? x ?? 0.2; y = 0.01, 0.02) with small additives of AgBr (0.04 wt % above 100%) has been performed. It has been shown that joint introduction of AgBr and EuF₃ with additional heat treatment of the glasses below the temperature of the onset of crystallization leads to a rise of the plasmon absorption band of silver nanoparticles. It has been assumed that the reason for the observed shift of the plasmon absorption band is the formation of a ??0.5-nm-thick shell of AgBr on the surface of a metallic Ag _n ⁰ -cluster.     

Photo-Thermo-Refractive Glasses: Effects of Dopants on Their Ultraviolet Absorption Spectra

Data accumulated on the UV spectra of photo-thermo-refractive glasses known to be a new class of photo-sensitive materials for nanophotonics is discussed. The paper is aimed to providing specialists in the applied photonics with a complete self-consistent block of the latest information on the UV spectral manifestations of various oxidation states of dopants and on the redox balance between these states. For all oscillators related to the oxidation states of dopants such as cerium, silver, and antimony, the spectroscopic parameters are computed and analyzed. Intercomparison of the data is conducted in terms of the redox reactions between particular oxidation states of dopants. The effects of bromine in the matrix glass composition on the parameter magnitudes for the Ag⁺ and Ce⁴⁺ states are demonstrated and the origin of the effects is discussed. The roles of atomary silver and antimony in the Sb³⁺ state as strong reducers with respect to cerium in the Ce⁴⁺ state are analyzed. Estimates for the molar fractions of Ce³⁺ and Ce⁴⁺ states in the glasses with various dopant combinations are discussed. A possibility to reconstruct the absorption spectrum of commercial photo-thermo-refractive glass using data obtained on the parameter magnitudes for the oxidation states of dopants is shown.     

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 T _g , 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?C85°C.