Solid State Phenomena Vol. 161

Abstract: In the recent years, sol-gel films have been intensively used in optical sensors configurations. Due to its hydrophobic nature, ormosil films have been reported to be a promising supporting matrix for oxygen sensing dyes for measurements in aqueous media. In this work, the impact of the sol-gel host fabrication parameters in the characteristics of the resulting oxygen sensing membranes is thoroughly evaluated. Different combinations of organic-inorganic precursors, with different aging times, were tested as oxygen sensors. All the solution were doped with ruthenium complex Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline) to introduce oxygen sensitivity. Thin films were produced by dip coating of glass slides. The oxygen sensitive films were tested in aqueous phase in equilibrium with different oxygen gas compositions, using a phase-modulation technique. Sensor performance parameters such as Stern-Volmer constant, quenching efficiency and lifetime response are reported. The data obtained clearly indicates that increased aging times and longer organic groups produce sensors with the highest sensitivity to dissolved oxygen. From all sol-gel films produced, the BTEOS:TEOS (1:1) mixture is the most promising for sensor construction.

Abstract: We report here on the preparation and optical characterization of certain rare earth (Nd3+,Tb3+,Pr3+ &Tm3+ each in 0.2 mol %) ions doped in two new series glasses in the following composition: Series A: 69.8 B2O3 – 10 P2O5 – 10(ZnO/CdO/TeO2) – 10 AlF3 Series B: 69.8 B2O3 – 10 P2O5 – 10(ZnO/CdO/TeO2) – 10 LiF By applying the Judd-Ofelt intensity parameters of Nd3+: BFP glasses, radiative properties of the emission transitions ( 4F3/2 ®4IJ=9/2, 11/2 &13/2 ) at 906, 1079 and 1349nm have been evaluated. By applying the Judd-Ofelt intensity parameters, radiative properties for Er3+ ions doped glasses, the NIR emission (4I13/2 4I15/2 ) at 1547nm , and also visible green emission (4S3/2 4I15/2 ) at 547nm have been evaluated. Measured absorption spectra of Pr3+: BFP glasses have shown eight absorption bands at 443, 469, 481, 589 , 1008, 1419, 1523 and 1930 nm which correspond to the transitions 3H4 ®3P2, 3P1, 3P0, 1D2, 1G4,3F4, 3F3 and 3F2 respectively. Absorption spectra of Tm3+: glasses have revealed five absorption bands at 466, 685, 790, 1206 and 1644 nm which corresponding to the transitions 3H6®1G4, 3F3, 3H4, 3H5 and 3F4 respectively. Pr3+: glasses, with an excitation at 442nm (3H4 ®3P2), a orange-red emission at 600 nm (1D2® 3H4) has been observed. In the case of Tm3+: glasses, upon excitation with 355nm (3H6®1D2), blue emissions at 452 nm (1D2®3F4) and at 476 nm (1G4®3H6) are observed. From the measured NIR emission spectra of Pr3+: BFP glasses, an NIR emission at 1354nm (1G4®3H5) and form Tm3+: glasses, an NIR emission (3F4®3H6) at 1809 nm are observed with an Ar+ laser (514.5 nm) as the excitation source.

Abstract: Hollow-core photonic crystal glass fibers have a high potential for gas sensing applications, since large light-gas interaction lengths can be effectively attained. Nevertheless, in order to enhance effective diffusion of gas into the hollow-core fiber, multi-coupling gaps are often needed, which raise coupling loss issues that must be evaluated prior to the development of practical systems. In this paper, a study on the coupling losses dependence on lateral and axial gap misalignment for single-mode fiber and two different types of hollow-core photonic crystal glass fibers is carried out. In addition, an experimental technique on splicing these glass fibers is also described and some results are presented showing that low splice losses can be obtained with high reproducibility.

Abstract: Glasses having composition xLi2O∙(30-x)Fe2O3∙20Bi2O3∙50B2O3 (0 ≤ x ≤ 30, in mol%) have been prepared using normal melt-quench technique. The variation in density and molar volume with composition has been investigated in terms of the structural modification that takes place in the glass matrix on decreasing Fe2O3. Infrared spectra of these glasses were recorded over continuous spectral range (400-4000 cm-1) in an attempt to study their structure systematically. IR spectra show that with increase in Li2O/Fe2O3 ratio there is formation of more structural units (e.g. [FeO4/2]-Li+) in the glass network. Bi3+ cations are present as [BiO6] octahedral units and acts as modifier in this glass system. Further, the effect of transition metal ions (iron) on the dynamics of lithium bismuth borate glasses has been studied in the frequency range of 20 Hz - 1 MHz and in the temperature range 240 – 350 °C using impedance spectroscopy. Possible conduction mechanisms are discussed. Various AC and DC electrical and dielectric parameters have been calculated and analyzed. The results show that the contribution of electronic conduction towards conductivity decreases with decreasing iron concentration, which is understood to be due to hopping of electrons from Fe2+→Fe3+. The frequency dependent conductivity has been studied using both conductivity and modulus formalism. The absence of maximum observed in dielectric permittivity in the temperature and frequency range studied, indicate the non-ferroelectric behavior of the glasses.

Abstract: Ferroelectric materials of LiNb0.95RE0.05O3 (RE3+=Eu3+, Sm3+, Dy3+ & Pr3+) have been prepared by a conventional solid state method. From the measurement of excitation and emission spectra of the prominent emission bands, emission performances of these optical materials have been investigated. In addition, structural analysis of these materials has also been carried out based on the data obtained from X-ray diffraction (XRD), Fourier Transform Infra-red (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX). Lifetime measurements have also been carried out for the prominent emission transitions of these ceramic powders.

Abstract: Bony defects caused by periodontitis are often treated by regenerative therapy using autografts and/or allografts. Alloplasts such as hydroxyapatite or ceramics and bioactive glasses are used as osteoconductive materials that serve as scaffold for new bony ingrowth. The purpose of this study was to ascertain the possible regenerative capability of glass reinforced hydroxyapatite (Bonelike¬)¬¬¬ an osteoconductive synthetic graft in the treatment of human periodontal intrabony angular defects. The material was placed in 2 defects in 2 individual patients and clinical parameters such as probing depth (PD) and clinical attachment level (CAL) have been included. Bone fill was determined using an intra oral periapical radiograph (IOPA) and Autocad Software. After 3 months implantation period, there was an improvement in CAL and reduction in PD along with bone fill was observed.