Effect of Some Modifier Ions in CuO Doped Sodium Borosilicate Antibacterial Bioglass

A set of sodium borosilicate glasses mixed with different modifier oxides, viz., Li2O, MgO, CaO and ZnO, doped with antimicrobial oxide viz. CuO were synthesized. The structural (FT-IR spectroscopy, SEM and XRD) and bioactivity studies of the glasses were carried out before and after 30 days of immersion in simulated body fluid (SBF) under static conditions. Optical absorption spectra of all the glasses exhibited a broad absorption band identified due to 2B1g→2B2g octahedral transition of Cu2+ ions. Glass microstructure is analyzed using SEM images and XRD patterns to authenticate glass bioactivity (viz. to confirm whether there is formation of hydroxyapatite (HAp) layer on the surface). For further confirmation of the formation of HAp on the surface of the post immerse samples, the FTIR spectra were recorded. The spectra revealed some vibrational peaks of calcium phosphate. Solubility (weight loss due to immersion in SBF) percentage is found to be different for different modifiers mixed glasses containing antibacterial CuO. SEM results confirm apparent nodular calcium phosphate microcrystalites. It is observed that the addition of antimicrobial oxide has a positive effect on the bioactivity of glass and make these glasses as fourth-generation biomaterials, which are being extensively used to heal the wounds in the human body by facilitating the growth of soft tissues.

A medium range order structural connection to the configurational heat capacity of borate–silicate mixed glasses

Intermediate range order (IRO) structures have a major impact on the composition dependence of the configurational heat capacity of glass.

Multilevel Tunnelling Systems and Fractal Clustering in the Low-Temperature Mixed Alkali-Silicate Glasses

The thermal and dielectric anomalies of window-type glasses at low temperatures (T<1 K) are rather successfully explained by the two-level systems (2LS) standard tunneling model (STM). However, the magnetic effects discovered in the multisilicate glasses in recent times, magnetic effects in the organic glasses, and also some older data from mixed (SiO2)1−x(K2O)xand (SiO2)1−x(Na2O)xglasses indicate the need for a suitable extension of the 2LS-STM. We show that—not only for the magnetic effects, but also for the mixed glasses in the absence of a field—the right extension of the 2LS-STM is provided by the (anomalous) multilevel tunnelling systems (ATS) proposed by one of us for multicomponent amorphous solids. Though a secondary type of TS, different from the standard 2LS, was invoked long ago already, we clarify their physical origin and mathematical description and show that their contribution considerably improves the agreement with the experimental data. In spite of dealing with low-temperature properties, our work impinges on the structure and statistical physics of glasses at all temperatures.

A MAS-NMR and Combined Rietveldt Study of Mixed Calcium/Strontium Fluorapatite Glass-Ceramics

Strontium is one of the most common substituents in apatite crystals. The presence and behavior of Sr in apatite-group phases are of considerable significance in biology. The present paper investigates the substitution of strontium for calcium in a glass-ceramic of the following composition 4.5SiO23Al2O31.5P2O54CaO1CaF2. The glasses were characterized using Differential Thermal Analysis (DTA), X-ray powder diffraction (XRD), neutron diffraction (ND) and 19F Resonance Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR). The all calcium glass crystallized to calcium fluorapatite (Ca5(PO4)3F). Substituting strontium partially for calcium resulted in the formation of a mixed strontium/calcium fluorapatites. In contrast complete substitution resulted in the formation of strontium fluorapatite. MAS-NMR showed the the F to be present as F-Ca(3) representing a fluoride ion surrounded by three Ca2+ ions in the all calcium glass and was present as F-Sr(3) in the all strontium glass. In the mixed glasses fluorine was present as FCa( 3), F-Ca(2)Sr, F-CaSr(2) and F-Sr(3). Ca had a higher tendency to occupy the F-M(3) sites than Sr which may reflect the higher charge to size ratio of Ca2+ relative to Sr2+ and its greater affinity for F- ions.

The Delayed Fluorescence of Indole in Alcohol-Alkane Mixed Glasses at 77 K

Using a phosphoroscope and a pulsed light-signal integrator, the effect of alcohol on the delayed fluorescence of indole was investigated in alcohol-isopentane mixed glasses at 77 K. The delayed fluorescence intensity was strongly depended on the alcohol concen-tration and the polarity of alcohol. Trapped electrons causing the delayed fluorescence were separated into two species utilizing the scavenge effect of CCl4; shallow trapped-electrons sensitive to CCl4 and deep trapped-electrons insensitive to CCl4. The former electrons seem to be responsible for the delayed fluorescence at low alcohol concentrations, whereas the latter for the delayed fluorescence at higher alcohol concentrations. The delayed fluorescence decayed exponentially at low alcohol concentrations, but it decayed with the Debye-Edwards law of t-1 at higher alcohol concentrations. The recombination mechanism of trapped electrons with parent cations was discussed. The structure of shallow traps was also estimated.