High-silica Porous Glass Research Articles

Influence of the chemical composition of the porous matrix and sintering atmosphere on the luminescent properties of bismuth-containing composites

The spectral-optical and luminescence properties of bismuth-containing composite materials based on matrices of high-silica porous glasses are investigated. Luminescence spectra, luminescence excitation spectra, infrared transmission spectra (8000-4000 cm-1) depending on the composition of different types of matrices and sintering atmosphere (nitrogen, argon) of bismuth-containing composite materials were examined. It was found that the samples of bismuth-containing composite materials are characterized by UV (λem=350 nm), blue-green (λem=410-550 nm) and orange-red (λem=600-725 nm) luminescence due to the presence of various bismuth active centers. The analysis of the spectra obtained by near-infrared spectroscopy demonstrates the formation of Bi2+ dimers of bismuth and bismuth active centers associated with silicon. Keywords: Bismuth-containing composite materials, high-silica porous glass, near-infrared spectroscopy, luminescence, bismuth active centers.

Влияние химического состава пористой матрицы и атмосферы спекания на люминесцентные свойства висмутсодержащих композиционных материалов

The spectral-optical and luminescence properties of bismuth-containing composite materials based on matrices of high-silica porous glasses are investigated. Luminescence spectra, luminescence excitation spectra, infrared transmission spectra (8000–4000 cm-1) depending on the composition of different types of matrices and sintering atmosphere (nitrogen, argon) of bismuth-containing composite materials were examined. It was found that the samples of bismuth-containing composite materials are characterized by UV (λem = 350 nm), blue-green (λem = 410–550 nm) and orange-red (λem = 600–725 nm) luminescence due to the presence of various bismuth active centers. The analysis of the spectra obtained by near-infrared spectroscopy demonstrates the formation of Bi2+ dimers of bismuth and bismuth active centers associated with silicon.

Infrared Spectroscopy of Composite Materials Based on High-Silica Porous Glasses Activated by Bismuth and Yttrium Ions

Infrared Spectroscopy of Composite Materials Based on High-Silica Porous Glasses Activated by Bismuth and Yttrium Ions

Study of the toxicity of high-silica porous glasses

The toxicity of high-silica porous glasses in relation to Paramecium caudatum was investigated. The test results showed a generally acceptable toxicity range. The toxicity of porous glasses varies depending on the concentration and time of contact of the fine powder with water which may be is associated with the presence of sodium ions, fluoride and phosphate ions in an aqueous solutions.

Structural and Electrokinetic Characteristics of High-Silica Porous Glasses in Nickel Chloride Solutions

Structural and Electrokinetic Characteristics of High-Silica Porous Glasses in Nickel Chloride Solutions

Studying the Toxicity of High-Silica Porous Glass by Biotesting

The article presents the results of a study of the biological activity of porous high-silica glass obtained based on two-phase alkali borosilicate glass. The test results show that the toxicity of the investigated porous glass (PG) in relation to Paramecium caudatum varies depending on the concentration and time of contact of the finely dispersed PG powder with water. It is assumed that the revealed pattern is related to, first of all, the extraction of alkaline ions into an aqueous solution.

Spectral-Luminescent Properties of Nanocomposite Materials Based on Porous Silicate Glasses Doped by Silver and Copper Bromides

A series of nanocomposite materials (NCMs) doped by silver and copper bromides are synthesized based on high-silica porous glasses (PG matrices). The concentrations of silver and copper oxides in the synthesized samples are 0.32–1.06 wt % Ag2O and 0.005–0.025 wt % CuO, respectively. The samples are thermally treated in a wide temperature range of 120–750°C. It is found that samples of the 100Ag/10Cu series (120°C) exhibit blue–green (λlum = 424–560 nm), yellow–orange (λlum = 584–588 nm), and red (λlum = 658–732 nm) luminescence. A study is conducted using the method of near infrared spectroscopy in the frequency range 7500–4000 cm–1. It is found that the dehydroxylation of the NCM surface and an increase in the transmittance in the entire specified frequency range occur with an increase in the temperature. The NCM samples have absorption bands in the range of 4190–4171 cm–1, which are caused by the absorption of Cu2+ ions. Energy-dispersive X-ray spectroscopy shows that the porous structure of the PG matrix has an effect on the concentration distribution of elements over the thickness of the samples.

Influence of the Heat Treatment Conditions on the Elemental Composition and Spectral Properties of Composite Materials Based on Silicate Porous Glass Doped by AgI and Er3+ Ions

Composite materials (CMs) doped by AgI and Er3+ ions are synthesized based on high-silica porous glass matrices. The structures of the CMs are investigated by IR spectroscopy in the frequency range 1100–400 cm–1. The IR transmission spectra of the CMs exhibit bands corresponding to vibrations of the Ag–O, Ag–O–Ag, Er–O–H, and Er–O bonds. In addition, bands that are caused by the presence of Ag2O, AgI, and Er2O3 are found. Energy-dispersive X-ray spectroscopy shows that the conditions of treatment of CMs with heat have an effect on the concentration distribution of elements over the thickness of the samples.

Features of the Formation of Adsorption Centers of Thermally Modified High-Silica Porous Glasses

The results are presented on studies of the content of Lewis and Bronsted centers on the internal surface of high-silica porous glass (PG) obtained by the through chemical etching of alkali-borosilicate glass with the two-frame structure, including the one modified by an isothermal treatment in an electric furnace in air in the temperature range from 120 to 750°C. The content of the active surface centers is determined by the adsorption of the acid-base indicators with different рKа values. For all samples under investigation, the predominance of hydroxyl groups over siloxane ones is established, which indicates a high degree of surface hydroxylation; and the extreme dependence of the content of surface centers on the heat treatment temperature with the pronounced maximum at 650°C is found.

Electrokinetic Characteristics of Bismuth-Containing Materials Based on Porous Glasses

Bismuth-containing composite materials based on high-silica porous glasses (PGs) of various types are prepared. Their structural parameters and electrokinetic potential in 10–2 М KNO3 solutions in the pH range 1.5–8.5 are studied. The results are compared with the analogous properties of matrices not modified with bismuth oxide, as well as the pH dependence of the zeta-potential for SiO2 particles and the sols of synthesized and industrial bismuth(III) oxide. It is determined that modification of larger-pore particles not containing secondary silica with bismuth(III) oxide results in the deviation of the form of the ζ–рН dependences from those intrinsic for high-silica PG and SiO2 particles.

The content of the adsorption centers of high-silica porous glasses

Changes in the specific surface, pore size and content of Lewis (siloxane) and Brønsted (silanol) surface groups for high-silica nanoporous glass with a sponge-corpuscular structure depending on their thickness and storage time are studied and interpreted in terms of porous structure features, hydration and aging effects.

Infrared Spectroscopy of Bismuth-Containing Composites Based on Porous High-Silica Glass

Bismuth-containing composite materials (BCMs) are synthesized by the impregnation of matrices of thermally modified high-silica porous glasses (PGs) in aqueous solutions of bismuth nitrate (0.5 M) followed by heat treatment in a wide temperature range from 50 to 875°C. The obtained materials are studied by the infrared spectroscopy method in the frequency range 1100–400 cm–1 depending on the PG modification (120, 400, and 600°C) and BCM treatment temperatures. At a temperature above 570°C, bands associated with the vibrations of νas (Bi–O–Si) and νs (Bi–O) bonds in [BiO3] and [BiO6] groups and the possible existence of α‑Bi2O3 in composites are observed.

Influence of Heat-Treatment Conditions on the Optical Properties of Bismuth-Containing Composites Based on High-Silica Porous Glass

Bismuth-containing composite materials are synthesized by the impregnation of matrices of thermally modified porous glass (PG) in 0.5 M aqueous solutions of bismuth nitrate followed by heat treatment. The optical density spectra of the obtained materials are studied depending on the heat treatment temperature (400–870°C). When the temperature of the heat treatment is increased, the distribution of bismuth in the samples becomes more homogeneous. The heat treatment in the range of 650 to 870°C leads to the degree of bismuth oxidation changing from Bi3+ to Bi2+ ions with the formation of dimers and clusters of bismuth.

Synthesis and spectral-optical properties of composite materials based on high-silica porous glasses doped by iodides of silver and erbium

Composite materials (CMs) doped by iodides of silver and erbium were synthesized on the base of the thermally modified high-silica porous glasses (PGs) with small additions of P2O5 and fluoride ions. CMs were manufactured by two-stage impregnation of the PGs first with AgNO3 aqueous solution (with or without Er(NO3)3), next in the halide salt (0.6 M KI) aqueous solution. Then the samples of composites were heat treated at the temperatures from 120 to 870°C up to their sintering and closing of the pores. The structure of composites was studied by X-ray powder diffraction (XRD) technique. According to XRD data the CMs doped by iodides of silver and erbium contain the AgI phase. Spectral-optical properties of CMs were investigated by UV-VIS-NIR spectroscopy. Optical density spectra in UV-VIS region have the bands corresponded with the absorption of silver molecular clusters. Peaks at 377, 448, 450–453, 485, 611–622, 647, 668–684 nm answered to the absorption of erbium ions were found. According to NIR transmission spectra, bands caused by the absorption of Si–OH, B–OH and Na–OH groups are found.

High emission cross-section YVO4:Nd nanocrystalline glass prepared by high-silica porous glass

In this study, YVO4:Nd nanocrystals embedded in sintered high-silica porous glass are synthesized. XRD and Raman spectroscopy analyses confirm that YVO4:Nd nanocrystals are dispersed in sintered high-silica glass, and the average size of the nanoparticles is 24 nm. Absorption, emission intensities, and radiation quantum efficiency of Nd3+ ions are obviously enhanced after crystallization. The stimulated emission cross-section of Nd3+ ions 4F3/2 → 4I11/2 transition reaches 5.2 × 10−20 cm2, which is the largest in silicate glasses.

Structural and Electrosurface Properties of Iron-Containing Porous Glasses in NaCl Solutions. II. Surface Charge and Electrokinetic Potential of Porous Glasses

Equilibrium electrosurface characteristics (surface charge and electrokinetic potential) have been determined for porous glasses with different compositions (magnetite-containing and magnetite-free glasses) in solutions of an indifferent electrolyte (NaCl). It has been revealed that the incorporation of iron oxide into the glass matrix increases the absolute value of the surface charge of the composite material relative to high-silica porous glass obtained from basic sodium borosilicate glass. The electrokinetic potentials determined from a set of experimental data on the streaming potential, electrophoretic mobility of porous glass particles, their specific electrical conductivity, and the structure of the pore space have been analyzed. It has been found that freshly prepared iron-containing glass samples and those exposed in electrolyte solutions for a long time have different electrokinetic characteristics.

Effect of Formation Conditions on the Functional Composition of the Surface of High-Silica Porous Glass

The possibility of controlling the content and ratio of Bronsted acid to Lewis base centers on the surface of high-silica porous glass (PG) with various compositions based on two-phase alkali-borosilicate glass by varying the conditions of the preparation of PG during the acid work-up of the initial glass is shown. The results demonstrate the possibility to control the features of the surface of the PG, and in particular, the ratio of silanol to siloxane structures.

Spectral properties of the high-silica porous glasses doped by silver halides

Photochromic quartz-like glasses were synthesized by an impregnation of the high-silica porous glasses with mixture of the Ag/Cu-Hal compounds (where Hal = Cl, Br, I; Cu2+ is sensitizer) from water-salt solutions. UV/VIS/NIR optical density and visible luminescence spectra of synthesized glassy composites have been obtained. It was shown that UV radiation of these materials causes luminescence of the silver centers in a visible spectral region (450–620nm). The assumption that the photochromic quartz-like glasses based on the matrixes from silicate nanoporous glasses are promising materials for solar engineering has been stated on the grounds of obtained results.

Ultrafast laser-induced birefringence in various porosity silica glasses: from fused silica to aerogel

We compare a femtosecond laser induced modification in silica matrices with three different degrees of porosity. In single pulse regime, the decrease of substrate density from fused silica to high-silica porous glass and to silica aerogel glass results in tenfold increase of laser affected region with the formation of a symmetric cavity surrounded by the compressed silica shell with pearl like structures. In multi-pulse regime, if the cavity produced by the first pulse is relatively large, the subsequent pulses do not cause further modifications. If not, the transition from void to the anisotropic structure with the optical axis oriented parallel to the incident polarization is observed. The maximum retardance value achieved in porous glass is twofold higher than in fused silica, and tenfold greater than in aerogel. The polarization sensitive structuring in porous glass by two pulses of ultrafast laser irradiation is demonstrated, as well as no observable stress is generated at any conditions.

Viscosity of quartz-like glass containing cesium cations

The results of the measurements of the viscosity of quartz-like glass formed based on the high-silica alkali-borosilicate porous glass are presented in this work. The porous glass is impregnated by aqueous solutions containing cesium ions and then thermally treated until the pores collapse and a quartz-like glass is formed.