Laser flash photolysis study of Nb2O5/g-C3N4 heterostructures as efficient photocatalyst for molecular H2 evolution.

Improvements of visible light activity, slow recombination rate, stability, and efficiency are major challenges facing photocatalyst technologies today. Utilizing heterostructures of g-C3N4 (bandgap ∼2.7eV) with Nb2O5 (bandgap ∼3.4eV) as an alternative materials for the first time, we tried to overcome such challenges in this work. Heterostructures of Nb2O5/g-C3N4 have been synthesized via hydrothermal technique. And then a time-resolved laser flash photolysis of those heterostructures has been analyzed, focusing on seeking how to improve photocatalytic efficiency for molecular hydrogen (H2) evolution. The transient absorption spectra and the lifetime of charge carriers at different wavelengths have been observed for Nb2O5/g-C3N4, where g-C3N4 was used for a control. The role of hole scavenger (methanol) has also been investigated for the purpose of boosting charge trapping and H2 evolution. The long lifetime of Nb2O5/g-C3N4 heterostructures (6.54165 µs) compared to g-C3N4 (3.1651897 µs) has successfully supported the increased H2 evolution of 75 mmol/h.g. An enhancement in the rate of H2 evolution (160 mmol/h.g) in the presence of methanol has been confirmed. This study not only deepens our understanding of the role of scavenger, but also enables a rigorous quantification of the recombination rate crucial for photocatalytic applications in relation with efficient H2 production.

Relationship between phosphor properties and chromaticity of phosphor-in-glass.

SiO2-B2O3-ZnO-Li2O glass and four types of phosphors (Y3Al5O12:Ce3+, (Sr,Ba)Si2O2N2:Eu2+, CaAlSiN3:Eu2+, and Lu3Al5O12:Ce3+) with different spectral distributions and thermal properties were prepared to achieve the desired color point based on the relationship between the thermal properties of phosphors and the microstructure of the phosphor-in-glass (PIG). The glass frit was mixed with various contents of phosphors (2.5, 5.0, 7.5, and 10.0 vol%) and then sintered to form a PIG. It was confirmed that the different pore properties of each PIG, caused by the difference in phosphor thermal properties, have a strong influence on the optical properties of the PIG. As the mass change of the phosphor increases, the scattering coefficient of the PIG also increases based on the variations in both pore size and porosity inside the plate. It is apparent that the scattering coefficient is strongly related to the path of converted light and blue light from the light-emitting diode (LED) chip; therefore, the ratio of transmittance to reflectance of each PIG is different, even if each PIG has the same phosphor content. These results indicate that achieving the target LED chromaticity is closely related to the phosphor characteristics and PIG's pore properties.

Effect of transmittance on luminescence properties of phosphor-in-glass for LED packaging.

The transmittance of phosphor-in-glass (PIG) color converter material was studied as a factor affecting the luminescence properties of light emitting diode packaging; it is closely related to the residual pores of sintered glass. In this study, the correlation between porosity and optical properties of the glass and PIG plates was investigated. The transmittance, luminescence properties, and porosity were measured by UV-visible spectrometer, integrating sphere and scanning electron microscope, respectively. Transmittance of the sintered glass plate and the luminous efficacy of the PIG plate both increase with decreased porosity, while the light scattering coefficient decreases. Luminescence properties such as emission intensity and color coordinates are also influenced by transmittance of the PIG plate.

Effect of intravenous pamidronate treatment in children with osteogenesis imperfecta.

OBJECTIVE: To assess the beneficial effect of intravenous pamidronate treatment in children with osteogenesis imperfecta (OI). STUDY DESIGN: Experimental study. PLACE AND DURATION OF STUDY: Endocrine Unit at the National Institute of Child Health, Karachi, Pakistan, from January 2007 to December 2011. METHODOLOGY: All children diagnosed with osteogenesis imperfecta on the basis of repeated spontaneous fractures and typical radiological findings registered during the study period, were included in this study. Pamidronate therapy were offered to those with more than 3 fractures per year or had platyspondyly. Pamidronate disodium was diluted in isotonic saline and administered by slow ravenous infusion over 3 hours in a dosage 1 mg/kg/day for 3 consecutive days 3 monthly for 2 years. Fracture rate, bone mineral density (BMD), mobility score, wellbeing and pain episodes were evaluated at baseline and 2 years after the treatment. Good response was defined as less than 2 fractures per year or mobility score improvement and poor response as more than 2 fracture per year with mobility score less than 2. RESULTS: Seventy two patients were included in this study. There were 40 boys and 32 girls with mean age of 3.64 ± 3.2 years. The annual fracture rate decreased overall from 5.8 ± 1.61 to 0.6 ± 0.93 (p < 0.001). BMD Z-score improved from -5.3 ± 1.74 to -1.7 ± 0.72 (p < 0.001). Mobility score was 0.94 ± 1.30 at baseline and 2.5 ± 1.02 at the end of the treatment (p < 0.001). Wellbeing gained from 3.63 ± 1.44 to 7.8 ± 1.18 (p < 0.001) and pain episode improved from 24.1 ± 8.15 to 2.7 ± 8.31 (p < 0.001). Good response was noted in 92% of patients and poor response in 8% patients. CONCLUSION: Bisphosphonate seems to be an effective symptomatic treatment for children with osteogenesis imperfecta irrespective of severity of mutation or clinical phenotype. Cyclical bisphosphonate therapy has a positive effect on fracture rate, BMD, mobility score, wellbeing and pain episode.