Investigation of hydrogen induced fluorescence in C60 and its potential use in luminescence down shifting applications

Herein the photophysical properties of hydrogenated fullerenes (fulleranes) synthesized by direct hydrogenation utilizing hydrogen pressure (100 bar) and elevated temperatures (350 °C) are compared to the fulleranes C₆₀H₁₈ and C₆₀H₃₆ synthesized by amine reduction and the Birch reduction, respectively. Through spectroscopic measurements and density functional theory (DFT) calculations of the HOMO-LUMO gaps of C₆₀H_x (0 ≤ x ≤ 60), we show that hydrogenation significantly affects the electronic structure of C₆₀ by decreasing conjugation and increasing sp³ hybridization. This results in a blue shift of the emission maximum as the number of hydrogen atoms attached to C₆₀ increases. Correlations in the emission spectra of C₆₀H_x produced by direct hydrogenation and by chemical methods also support the hypothesis of the formation of C₆₀H₁₈ and C₆₀H₃₆ during direct hydrogenation with emission maxima of 435 and 550 nm respectively. We also demonstrate that photophysical tunability, stability, and solubility of C₆₀H_x in a variety of organic solvents make them easily adaptable for application as luminescent down-shifters in heads-up displays, light-emitting diodes, and luminescent solar concentrators. The utilizization of carbon based materials in these applications can potentially offer advantages over commonly utilized transition metal based quantum dot chromophores. We therefore propose that the controlled modification of C₆₀ provides an excellent platform for evaluating how individual chemical and structural changes affect the photophysical properties of a well-defined carbon nanostructure.

Hydriding characteristics of NaMgH2F with preliminary technical and cost evaluation of magnesium-based metal hydride materials for concentrating solar power thermal storage

An economic assessment is performed on NaMgH₂F and magnesium-based metal hydrides as heat storage materials for concentrating solar thermal power.

Venous thromboembolism and the utility of the Padua Prediction Score in patients with sepsis admitted to internal medicine departments

BACKGROUND

Sepsis is prevalent in internal medicine (IM) departments. Elderly patients with sepsis and chronic medical conditions are at an increased risk for venous thromboemolism (VTE). The objective of this study was to assess the rate of VTE and the accuracy of the Padua Prediction Score (PPS) to predict VTE in patient with sepsis admitted to IM departments.

METHODS

We prospectively collected data on septic patients admitted to IM departments in a community-based medical center. Additionally, we retrospectively collected VTE risk factors and events throughout a 1-year post hospitalization period. We computed the PPS for every patient, and analyzed the data accordingly.

RESULTS

In total, 1080 patients were included in the study. The mean age was 74.68 ± 16.1 years. The average PPS was 4.86 ± 2.26, and 71.2% of the patients had a positive PPS. Only 17.8% of the patients received anticoagulant prophylaxis during their hospital stay. Seven patients had VTE on admission, 14 (1.29%) acquired in-hospital VTE, and 7 (0.65%) had VTE post discharge throughout 1 year. In all, 21.9% patients died during hospitalization, and the overall survival rate was 64%. PPS was not correlated with anticoagulant administration (P = 0.36), in-hospital VTE (P = 0.23) or 1-year VTE (P = 0.40), but was significantly associated with in-hospital death and survival (P < 0.0001).

CONCLUSION

The rate of VTE in medical patients with sepsis in IM departments is low, and PPS lacks granularity in detecting patients at risk of acquiring it. In this population, a positive PPS is highly associated with death, and may reflect a more general co-morbidity and disease severity index.

Synthesis and thermoelectric power of nitrogen-doped carbon nanotubes

We have previously shown that high-purity multiwalled carbon nanotubes (pristine MWNTs) can be prepared from a mixture of xylene-ferrocene (99 at% C:1 at% Fe) inside a quartz tube reactor operating at approximately 700 degrees C. In a similar process, approximately 3 g of melamine (C3H6N6) was introduced during the growth of MWNTs to prepare nitrogen-doped nanotubes. The structural and electronic properties of nitrogen-doped MWNTs were determined by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and thermopower measurements. The individual nitrogen-doped nanotube exhibits a bamboo-like structure and comprises 6-16 tube walls, as evidenced by HRTEM studies. The EELS measurements yielded an average nitrogen content of approximately 5 at% in the doped tubes. The thermoelectric power data of nitrogen-doped MWNTs remained negative even after exposure to oxygen for an extended period of time, suggesting that nitrogen doping of MWNTs renders them n-type, consistent with scanning tunneling spectroscopic studies on similar nanotubes.