Ionic to electronic conductivity studies of lithium-​borate ruby-​glass-​ceramics containing gold nano particles

Glass-​ceramics contg. Au nanoparticles have been synthesized in the glass compn. 30Li2O-​70B2O3 with HAuCl4.3H2O as dopant. The characteristic ruby color has been obsd. which is attributed to the surface plasmon resonance of the Au nanoparticles, uniformly embedded in the glass matrix. The imparted red color due to the presence of gold nanoparticles has been confirmed by studying the optical absorption spectra using UV-​VIS spectrometer in the visible range (400-​1000 nm) which show a characteristic absorption peak at ∼560 nm. In order to check the crystn.​/amorphous nature, the samples were powd. and characterized using X-​ray diffraction (XRD)​. The microstructural modifications in the samples due to the addn. of Au have been recorded using SEM (SEM)​. Further, the ESR (ESR) studies reveal that the electronic state of gold is either Au0 or Au+. AC cond. studies have been performed at room temp. over a frequency range 100 to 10 MHz. The ac cond. data is fitted by Almond-​West law with power exponent "s". The dc cond. is found to be increasing with the increase of temp. for a typical ruby glass, but almost const. with dopant concn

Transport properties of Li2O-MnO2-B2O 3 glasses

Lithium borate containing MnO2 glasses have been synthesized by melt quenching technique over a wide composition range. Frequency and temperature dependent conductivity measurements have been carried out in the range of 10 Hz to 13 MHz and at a temperature range of 298 K-523 K respectively. The impedance plots show only one semicircle indicating the presence of one type of conduction mechanism. The analysis of dc conductivity show that the conductivity is dominated by Li+ ions and the presence of MnO 2 has negligible effect. The ac conductivity data has been analysed by fitting the data into Almond-West type power law behaviour Ï = Ï(o) + AÏs. The power law exponent s is also determined and it is found to decrease with increase of temperature. We have also carried out the scaling behaviour of the ac conductivity and it is seen that all the curves coalesce on to a master curve suggesting that the ion transport mechanism remains unaffected at all temperatures. The results are discussed in the light of the structure of borate glass network. © 2005 Elsevier B.V. All rights reserved

Electrical conductivity studies of AgI-​Ag2O-​B2O3-​TeO2 glasses

The Ag ion conducting borotellurite glasses were prepd. by melt quenching technique. The cond. and dielec. measurements were carried out on these glasses as a function of frequency from 10 Hz to 10 MHz between 298-​328 K. The anal. of cond. measurement shows that the Ag ions are the main charge carriers, which are considered to be the predominant factor playing the role of enhancing the cond. The power law exponent s and stretched exponent β are found to be insensitive to both temp. and compns. A.c. cond. and dielec. relaxation behavior of these glasses were also studied and the results are discussed in view of the structure of borate and tellurite network

Elastic properties of lead-phosphate glasses doped with samarium trioxide

A series of ternary lead-phosphate glasses doped with samarium trioxide, xSm2O3-(40-x)PbO-60 P2O5 (where x=0.1 to 0.5 mol) have been prepared by using conventional melt quenching method and their elastic properties have been studied at room temperature. Results from the studies show that both longitudinal and transverse sound velocities decrease by increasing the Sm2O3 content. Elastic moduli, Poisson's ratios decrease with increase of Sm2O3 composition up to 0.3 mol and then there is a slight increasing trend observed at 0.4 mol. The densities of these glasses have been measured by using displacement method. The variations of these parameters have been discussed with respect to samarium trioxide concentration. © 2009 Elsevier Ltd. All rights reserved

Optical, physical and structural studies of vanadium doped P 2O5-BaO-Li2O glasses

Glasses in the compositions (Li2O)25–(BaO)25–(P2O5)50−x–(V2O5)x (with x=0.5,1.0,1.5,2.0,2.5, and 3.0 mol%) have been prepared by the conventional melt quenching technique. X-ray powder diffractrogram show broad peaks which conforms glassy nature of the sample. Differential scanning calorimetry (DSC) thermograms show characteristic glass transition temperature (Tg) and it increases with increasing substitution of V2O5 for P2O5. The measured physical parameters like density, refractive index, ionic concentration and electronic polarizability are found to vary linearly with increasing x. Infrared spectra exhibits few bands, which are attributed to (P=O)AS, (P=O)S, (V=O), (P–O–P)AS,P–O–V, (P–O–P)AS and O–P–O vibrations. The optical absorption spectra of VO2+ ions in these glasses show three bands and are assigned to the 2B2→ 2E,2B2→ 2B1 and 2B2→ 2A1 transitions. Electron paramagnetic resonance spectra of all the glass samples exhibit resonance signals characteristic of VO2+ ions. The values of Spin-Hamiltonian parameters indicate that the VO2+ ions are present in octahedral sites with tetragonal compression and belong to C4V symmetry

Characterization and structural studies of lithium doped lead zinc phosphate glass system

Glasses in the system (PbO) 30(P 2O 5) 40(ZnO) 30-x(Li 2O) x (where x = 0, 15, 20, 25, 30 mol) and (PbO) 30(P 2O 5) 50(ZnO) 20-x(Li 2O) x (where x = 0, 5, 10, 15, 20 mol) were prepared by conventional melt quenching technique. XRD and DSC measurements were performed to confirm their amorphous nature. Thermal stability factor (S) has been evaluated using the values of T g and T c. The refractive indices of these glasses lie in the range of 1.40-1.45. IR spectra of these glasses show absorption peaks in the range 1233-1247 cm -1, 1076-1087 cm -1, 905-894 cm -1, 735-731 cm -1 and 531-556 cm -1 corresponding to PO, PO -, (POP) AS, (POP) S and OPO vibrations respectively. The peak corresponding to PO, shows red shift with increasing Li 2O content indicating depolymerization of phosphate network. © 2012 Elsevier B.V

EPR and Optical Studies of Mo5+ Ions in Lithium Molybdoborate Glasses

Electron paramagnetic resonance (EPR) and optical absorption studies of Li2O–MoO3–B2O3 with varying concentrations of Li2O, MoO3 and B2O3 have been carried out at room temperature. Two series of glasses, one with constant MoO3 (CM) and another with constant borate (CB), have been investigated. Characteristic EPR spectra of Mo5+ have been observed centered around g ≅ 2.00, which are attributed to Mo5+ ion in an octahedral coordination sphere with an axial distortion. The spectra also show strong dependence on the concentration of Li2O and B2O3. Spin concentrations (N) and magnetic susceptibilities (χ) have been calculated. In the CM series, the N values decrease with increasing Li2O content up to 30 mol%, while in the CB series variation of N is found to increase initially up to 20 mol%, and with further increase in the Li2O content the N values tend to decrease. The variation of magnetic susceptibilities is almost similar to that observed with the variation of N. From the optical absorption spectra, an absorption edge (α) has been evaluated. In the CM series, the values of α show a blueshift. On the other hand, in the CB series a redshift is observed. The observed variations in spectral parameters are explained by considering the molybdoborate network. Addition of Li2O to the CM and CB series results in modification of [MoO6/2]0 → [MoOO5/2]− and [BO3/2]0 → [BO4/2]− → [BOO2/2]− groups, respectively, leading to creation of nonbridging oxygens. The optical basicity of the glasses has been evaluated in both the CM and the CB glasses. The optical basicity can be used to classify the covalent-to-ionic ratios of the glass, since an increasing optical basicity indicates decreasing covalency. It is observed that the covalency between Mo5+ ions and oxygen ligands increases in the CB series, whereas in the CM series the covalency between Mo5+ ions and oxygen ligands decreases

EPR and optical absorption studies of Fe3 ions in sodium borophosphate glasses

Electron paramagnetic resonance (EPR) and optical absorption spectral investigations have been carried out on Fe3 ions doped sodium borophosphate glasses (NaH2PO4B2O 3Fe2O3). The EPR spectra exhibit resonance signals with effective g values at g=2.02, g=4.2 and g=6.4. The resonance signal at g=4.2 is due to isolated Fe3 ions in site with rhombic symmetry whereas the g=2.02 resonance is due to Fe3 ions coupled by exchange interaction in a distorted octahedral environment. The EPR spectra at different temperatures (123295 K) have also been studied. The intensity of the resonance signals decreases with increase in temperature whereas linewidth is found to be independent of temperature. The paramagnetic susceptibility (Ï) was calculated from the EPR data at various temperatures and the Curie constant (C) and paramagnetic Curie temperature (θp) have been evaluated from the 1/Ï versus T graph. The optical absorption spectrum exhibits bands characteristic of Fe3 ions in octahedral symmetry. The crystal field parameter (Dq) and the Racah interelectronic repulsion parameters (B and C) have also been evaluated and discussed. © 2010 Elsevier Ltd

Spectroscopic Properties of Sm3+-Doped Lanthanum Borogermanate Glass

Ultraviolet–visible–near infrared (UV–vis–NIR) absorption and photoluminescence of (25-x) La2O3–25B2O3–50GeO2 glass series have been studied with different concentrations (x=0.1–1.0 wt%) of Sm2O3 as an optically active dopant. The values of Judd–Ofelt (JO) parameters (Ot) follow the trend O2>O4>O6. Visible emission and decay times from the 4G5/2 level and its relative quantum efficiencies are measured. Intense reddish-orange emission corresponding to 4G5/2?6H7/2 transition has been observed in these glasses under 488 nm excitation. A decrease in the quantum yield is observed with increasing Sm3+ ion concentration beyond 1% doping level

Cardiorenal syndrome: Resistant to diuretics, sensitive to ultraflitration

Cardiac and renal diseases are becoming increasingly common today, and are seen to frequently coexist, thus causing a significant increase in the mortality rate, morbidity, complexity of treatment and cost of care. Syndromes describing the interaction between heart and kidney have been defined and classified; however, never as a result of a consensus process. Though the incidence of cardiorenal syndrome is increasing, the associated pathophysiology and effective management are still not well understood. For many years, diuretics and ultrafiltration, have been the mainstay of treatment for cardiorenal syndrome, although a significant proportion of patients develop resistance to diuretics, and even deteriorate while on diuretics. Here, we will discuss one such patient who failed to respond to the optimum doses of diuretics; however, his blood urea and serum creatinine touched the baseline levels post-ultrafiltration