Fabrication of luminescent silver doped PbS nanowires in polymer

We report here fabrication of silver (0 to 1.76 mol%) doped PbS nanowires (radius r approximately 1.75 nm) in polymer by a simple wet chemical process. An X-ray photoelectron spectroscopy study clearly confirms the possibility of silver (Ag) doping in PbS nanowires. Both absorption and photoluminescence spectra reveal very strong quantum confinement effect in PbS nanowires as expected for a r/Bohr radius ratio approximately 0.0972 nm. Visible excitonic emission is observed at room temperature in the photoluminescence spectra of undoped and silver doped PbS nanowires in polymer. The excitonic emission is appreciably blue-shifted when doped by silver (1.76 mol%) indicating strong modification of the electronic states by magnetic silver ions. While Ag2+ centers at the substitutional lattice site show an emission band around 525 nm, Ag0 at the interstitial site act as nonradiative recombination centers. Effect of silver doping on the luminescence intensity is also discussed.     

Arsenic adsorption mechanism on clay minerals and its dependence on temperature

In the present study, the As(V) removal efficiency of different clay minerals was investigated as a function of solution pH, time, As(V) concentration, and temperature. Arsenic mobility was also investigated by determining the As(V) released from the loaded samples by leaching with various aqueous solutions. The kinetics of adsorption was observed to be fast and reached equilibrium within 3 h. As(V) adsorption on studied clays was pH dependent and maximum adsorption was achieved at pH 5.0. The maximum adsorption capacity was calculated by fitting the Langmuir equation to the adsorption isotherms and found to be 0.86, 0.64, and 0.52 mg As(V)/g of kaolinite, montmorillonite, and illite, respectively. The negative effect of temperature on As(V) adsorption showed the interactions to be exothermic. Based on the results, it was found that among the studied clay minerals, kaolinite was the best As(V) adsorbent and montmorillonite had strong retention capacity. The electrokinetic behavior of kaolinite and montmorillonite was modified in the presence of As(V), indicating that adsorption involves inner sphere surface complexation and strong specific ion adsorption.     

Structure and scintillation of Eu-activated solid solutions in the BaBr2-BaI2 system

We report the structure and scintillation of Eu²⁺-activated solid solutions in the BaBr₂-BaI₂ system. Samples were synthesized in the form of ∼1 mm size crystals by melting the reactants in a sealed quartz tube followed by slow cooling. The solid solutions form an orthorhombic PbCl₂-type crystal structure with an ordered arrangement of the anions. Upon optical and X-ray excitation, the Eu²⁺-activated samples show an intense emission centered between 410 and 423 nm. The samples exhibit a fast decay characteristic of Eu²⁺, with the primary decay time between 315 and 600 ns for ∼75% of the total emitted light. Light yields for the compositions are compared to a newly discovered scintillator, BaBrI:Eu²⁺, measured under identical conditions.     

Enhancing the Microstructure and Tribological Performance of Spray Formed Al Alloy by Cryorolling

Silicon - In the present study, the microstructure and tribological performance of Al alloy has been enhanced by cryorolling. The Al-6 wt.% Si alloy has been selected as Al alloy which has...     

A novel CoN4-driven self-assembled molecular engineering for oxygen reduction reaction

The poor kinetics of oxygen reduction reaction (ORR) invites a quest for the development of low-cost and efficient non-Pt electrocatalysts for fuel cells. Herein, a nanocomposite (g-[Co₂N₈]) was synthesized by coordination assembly of CoN₄ macrocyclic moieties on graphene surface. The CoN₄ macrocyclic complex was characterized by UV–Vis, FT-IR, Mass, ¹H NMR and ¹³C NMR spectral studies, whereas UV–Vis, FT-IR, and Mass spectral, Raman, XRD and TEM studies were utilized to characterize the nanocomposite g-[Co₂N₈]. The results suggested that [CoN₄] units are present in self-assembled [Co₂N₈] species. Further, the nanocomposite g-[Co₂N₈] was examined for ORR activity by employing cyclic and linear sweep voltammetry and found that the formal potential (E_1/2) of g-[Co₂N₈] (+0.90 V) was more positive than 20% Pt/C (+0.86 V), indicating a remarkable ORR performance of g-[Co₂N₈] in comparison to 20% Pt/C, followed by 4e-mechanism. Moreover, the nanocomposite (g-[Co₂N₈]) displayed better ORR activity in comparison to [CoN₄] complex which can be attributed to the synergistic incorporation of endo and exo N₄–Co²⁺ moieties in the [Co₂N₈] species. In addition, g-[Co₂N₈] electrocatalyst exhibited a comparable stability to 20% Pt/C catalyst after 5000 cycles. This work will help to design multi-metallic coordination polymers with similar or different metal ions in N₄-arrangement for various energy related electrocatalysis.     

In vitro regulation of enzymatic release of glucose and its uptake by Fenugreek microgreen and Mint leaf extract

Fenugreek microgreen and mint leaf displayed antidiabetic potential during in vitro assays including cell line‐based analysis. Aqueous fenugreek microgreen extract (FME) (2 mg mL^?1) inhibited α‐amylase by 70%. It also enhanced glucose uptake in L6 cells by 25% at 10 mg mL^?1 which further improved to 44% in the presence of insulin. On the other hand, fresh mint leaf extract (MLE) inhibited α‐glucosidase up to 90% and increased glucose uptake by 15% in HepG2 cells. Besides, both these extracts also inhibited nonenzymatic glycation of protein. FME and MLE were also found to have high levels of total phenolics, flavonoids and antioxidants which could play a possible role in the observed antidiabetic activity. As blood glucose levels in diabetes can be regulated by inhibition of enzymes regulating carbohydrate metabolism and improving glucose uptake in cells, the findings indicate a complimentary therapeutic role of these two dietary herbs in diabetes.     

Co-oxidation in the auto-ignition of primary reference fuels and n-heptane/toluene blends

Auto-ignition of fuel mixtures was investigated both theoretically and experimentally to gain further understanding of the fuel chemistry. A homogeneous charge compression ignition (HCCI) engine was run under different operating conditions with fuels of different RON and MON and different chemistries. Fuels considered were primary reference fuels and toluene/n-heptane blends. The experiments were modeled with a single-zone adiabatic model together with detailed chemical kinetic models. In the model validation, co-oxidation reactions between the individual fuel components were found to be important in order to predict HCCI experiments, shock-tube ignition delay time data, and ignition delay times in rapid compression machines. The kinetic models with added co-oxidation reactions further predicted that an n-heptane/toluene fuel with the same RON as the corresponding primary reference fuel had higher resistance to auto-ignition in HCCI combustion for lower intake temperatures and higher intake pressures. However, for higher intake temperatures and lower intake pressures the n-heptane/toluene fuel and the PRF fuel had similar combustion phasing.     

Effect of localised charges on nanoscale cylindrical surrounding gate MOSFET: Analog performance and linearity analysis

The paper presents a simulation study of Nanoscale Cylindrical Surrounding Gate (SRG) MOSFET with localised interface charges. The objective of the present work is to study the performance degradation due to hot carrier induced/radiation induced/stress induced damage in the form of localised/fixed charges at the semiconductor/oxide interface of the device. Impact of fixed charges has been studied on the characteristics such as drain current, transconductance and its higher order terms, device efficiency and linearity FOMs. Effect of nature and extension of interface fixed charges has been discussed in detail through extensive simulation. Circuit reliability issues of the device are discussed in terms of DC bias point degradation.     

Characterization of user activity and traffic in a commercial nationwide Wi-Fi hotspot network: global and individual metrics

This paper presents the characterization of a commercial nationwide Wi-Fi hotspot network. We examine a 5 month long log of user activity and traffic volume collected by a wireless network service provider operating hotspots in restaurants, serviced apartments, hotels and airports all over Australia. We categorize users based on their account time limits to analyze the impact of account stratification on the overall user behavior. A similarity index is developed to compare two datasets of unknown distributions which we then use to quantitatively compare how similar or different various types of accounts are. The user population of the network is found to be highly fluctuating, hence user specific, population independent metrics are proposed to account for this transience. We also introduce metrics to measure account time and data utilization. Key user and traffic statistics are presented for reference.