Novel orange-emitting Ba2LaNbO6:Eu3+ nanophosphors for NUV-based WLEDs and photocatalytic water purification

Energy conservation and environmental safety are the key requirements in the modern world. We report novel orange-emitting double perovskite Ba₂LaNbO₆:Eu³⁺ (BLN:Eu³⁺) nanophosphor fabricated using a citrate sol-gel method for use in general illumination and photocatalysis. After annealing at 800?℃, the particles exhibited a nanorod-like morphology with monoclinic structure. The photoluminescence emission spectra exhibited an intense ⁵D₀→⁷F₁ transition at 594?nm and a moderate ⁵D₀→⁷F₂ transition at 615?nm, demonstrating that the Eu³⁺ ions occupied the La³⁺ sites with inversion symmetry. The optimal concentration of Eu³⁺ ions was found to be about 5?mol% for the BLN host lattice. Energy transfer from the NbO₆^7- octahedrons to the Eu³⁺ ions was clearly witnessed when the BLN:Eu³⁺ nanophosphors were excited with both the characteristic excitation bands of Eu³⁺ (⁷F₀→⁵L₆) and NbO₆^7- octahedrons at 392 and 380?nm, respectively. The thermal quenching temperature of 5?mol% Eu³⁺ ions doped BLN nanophosphors was found to be 183?℃, indicating that these nanophosphors are very stable at high temperatures. In addition, the dye removal efficiency of the proposed BLN nanophosphors was verified using Rhodamine B (RhB) dye as a model pollutant under UV irradiation. Compared to a commercial nano-ZnO catalyst, our synthesized BLN nanophosphors showed superior RhB de-colorization efficiency. Therefore, the proposed BLN:Eu³⁺ nanophosphors are promising multifunctional materials for photocatalysis and general lighting applications.     

Preparation of cerium oxide nanoparticles in Salvia Macrosiphon Boiss seeds extract and investigation of their photo-catalytic activities

Cerium oxide nanoparticles (CNPs) with desired particle size and spherical morphology were prepared from cerium nitrate in bio media of Salvia macrosiphon Boiss seeds extract, as a green synthesis route. Then they were characterized by XRD, UV–Vis and FTIR spectroscopies, FESEM and TGA. Band gap energy of the prepared powders was also determined which was found in the range of 2.5–3.5?eV. Determination of DLS and zeta potential were showed that CNPs had the small size and unique colloidal stability, respectively. Then the photo-catalytic activity of them was investigated by degradation of Rhodamine B (RhB) dye as a model of waste water pollutants, under UV-irradiation and optimum conditions were evaluated. Results showed that decreasing the particle size increased the rate of photo-catalytic reaction remarkably but ascending the band gap energy, in contrast. The photo-catalytic mechanism was also studied by using different scavengers.     

Improvement in phase-change hybrid nanocomposites material based on polyethylene glycol/epoxy/graphene for thermal protection systems

Polyethylene glycol (PEG) is established as an organic solid–liquid phase-change material (PCM) offering a wide range of enthalpies and phase transition temperatures as a function of its molecular weight. PCMs are known for their high-energy absorbance; however, they also have two main drawbacks of leakage and enthalpy reduction during melting. In this work, polyethylene glycol as a phase-change material and graphene oxide (GO), expanded graphene (EG), and epoxy resin (EP) as shape stabilizing materials were used and designed based on experimental design—Taguchi method to find the composition with the least molten PEG leakage and the highest enthalpy of melting. Based on improvements made on main drawbacks, two samples were introduced, while their only difference was epoxy content. The results showed that the epoxy resin and graphene oxide caused a significant reduction in molten PEG leakage by hydrogen bonding and trapping of PEG between GO plates and the barrier effect. Also, the expanded graphene by heterogeneous nucleation of molten PEG in a cooling cycle caused a dramatic increment in crystallinity and enthalpy of melting. Among the achievements of this research is the attainment of hybrid nanocomposites samples without leakage (less than 5 wt%) and samples with enthalpy of melting more than that of pure polyethylene glycol (8%).

     

Oxidation of polypropylene in a solution of monochlorobenzene

The oxidation of polypropylene (PP) was performed in a solution of monochlorobenzene using tetrabutyl ammonium permanganate either in the presence or absence of purified air and dodecanol‐1. The experiments were conducted under atmospheric pressure at 128–130°C. The oxidized PP was found to contain polar groups such as carboxylates, carboxylic acids, ketones, esters, etc. as determined by Fourier transform infrared, ultraviolet, nuclear magnetic resonance, and electron spectroscopy for chemical analysis. The presence of the MnO₂ formed upon the decomposition of tetrabutyl ammonium permanganate was determined by electron spectroscopy for chemical analysis. The dodecanol‐1 was used as an accelerator for the oxidation reaction of PP in presence of air. Solubility trials of oxidized PP in toluene and methyl ethyl ketone were performed. A reaction mechanism is proposed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3417–3424, 1999     

Controlling the electronic properties of Gd: MoS<Subscript>2</Subscript> monolayer with perpendicular electric field

A systematic computational study to demonstrate electric field dependence of electronic properties of Gd doped MoS₂monolayer is being reported. Density functional theory (DFT) based calculated were performed using ADF-BAND package to investigate the effects of applied electric field on pure and Gd doped monolayer of MoS₂using supercell approach. A detailed analysis of electric field dependence of host and dopant related states in the monolayers was carried out and discussed to explore the possible implications in devices. The findings on the basis of calculated results indicate that band gap of the monolayer decrease with increase in value of applied electric field. A model indicating this behaviour is also reported. It was further revealed that the formation energy of the monolayers exhibits a consistent decrease with increase in electric field.     

Time evolution of current density in conducting single-walled carbon nanotubes

In the present work, we study the trembling motion known as Zitterbewegung in a conducting single-walled carbon nanotube by using the long-wave approximation. The Heisenberg representation is used to derive an analytical expression for the current density operator along the axial and spiral direction, which describes the current induced by the motion of the electronic wave packet in the carbon nanotubes. We have considered a number of parameters to describe the Gaussian wave packet, such as: the values of the initial pseudo-spin polarization, the initial carrier wave vector and the width of the localized packet along the axial and spiral coordinates. As a result, we show that the oscillation in current density can be controlled not only by the initial parameters of the wave packet, but mainly by choosing the up and low components of the localized quantum state. The analysis of the interference between the conduction and valence bands of quantum states is emphasized as the possibility of the emergence of the transient or aperiodic temporal oscillations in the average value for the current density in the conducting single-walled carbon nanotubes.     

A New High Step-Up DC/DC Converter Structure by Using Coupled Inductor with Reduced Switch-Voltage Stress

In this paper, a new high step-up DC/DC converter for renewable energy systems is proposed, which provides high voltage gain by using a coupled inductor without having to have high-duty cycle and high-turn ratio. Moreover, the voltage gain increased by using capacitors charging techniques. In the proposed converter, the energy of leakage inductors of the coupled inductor is recycled to the load. This feature not only reduces stress on main switch but also increases the converter efficiency. Also, due to the configuration of the proposed structure, the voltage stress on the main switch is significantly reduced. Since the stress is low in this topology, low voltage switch with small ON-state resistance value can be used to reduce the conduction losses. As a result, losses decrease and the efficiency increases. Meanwhile, the main switch is placed in series with the source and it can control the flow of energy from source to load. The operating principles and steady-state analysis of the proposed converter are discussed in details. Finally, the prototype circuit with 12 V input voltage, 300 V output voltage, and 60 W output power is operated to verify its performance.     

Design and analysis of a high-performance CNFET-based Full Adder

This article presents a high-speed and high-performance Carbon Nanotube Field Effect Transistor (CNFET) based Full Adder cell for low-voltage applications. The proposed Full Adder cell is composed of two separate modules with identical hardware configurations which generate the Sum and C _out signals in a parallel manner. The great advantage of the proposed structure is its very short critical path which is composed of only two carbon nanotube pass-transistors. This design also takes advantage of the unique properties of metal oxide semiconductor field effect transistor-like CNFETs such as the feasibility of adjusting the threshold voltage of a CNFET by adjusting the diameter of its nanotubes to correct the voltage levels as well as to achieve a high performance. Comprehensive experiments are performed in various situations to evaluate the performance of the proposed design. Simulations are carried out using Synopsys HSPICE with 32-nm Complementary Metal Oxide Semiconductor (CMOS) and 32-nm CNFET technologies. The simulation results demonstrate the superiority of the proposed design in terms of speed, power consumption, power delay product, and less susceptibility to process variations, compared to other classical and modern CMOS and CNFET-based Full Adder cells.