A novel one-pot pseudo-five-component condensation reaction towards bifunctional diazepine-tetrazole containing compounds: synthesis of 1H-tetrazolyl-1H-1,4-diazepine-2,3-dicarbonitriles and 1H-tetrazolyl-benzo[b][1,4]diazepines

A novel and efficient method has been developed for the one-pot synthesis of bifunctional diazepine-tetrazole containing compounds. 1H-Tetrazolyl-1H-1,4-diazepine-2, 3-dicarbonitrile and 1H-tetrazolyl-benzo[b][1,4]diazepine derivatives were synthesized in good yields using 2,3-diaminomaleonitrile or an aromatic diamine, ketones, trimethylsilyl azide, and an isocyanide in the presence of p-toluenesulfonic acid as a catalyst in methanol at room temperature.     

Improvement of performance of tetraphenylporphyrin-based red organic light emitting diodes using WO3 and C60 buffer layers

One of the porphyrin derivatives, meso-tetraphenylporphyrin (TPP), has been synthesized and examined as an emitter material (EM) for efficient fluorescent red organic light-emitting diodes (OLEDs). By inserting a tungsten oxide (WO₃) layer into the interface of anode (ITO) and hole transport layer N,N′-Di-[(1-napthyl)-N,N′-diphenyl]-(1,1′-biphenyl)-4,4′-diamine (NPB) and by using fullerene (C₆₀) in contact with a LiF/Al cathode, the performance of devices was markedly improved. The current density–voltage–luminance (J–V–L) characterizations of the samples show that red OLEDs with both WO₃ and C₆₀ as buffer layers have a lower driving voltage and higher luminance compared with the devices without buffer layers. The red OLED with the configuration ITO/WO₃ (3 nm)/NPB (50 nm)/TPP (60 nm)/BPhen (30 nm)/C₆₀ (5 nm)/LiF (0.8 nm)/Al (100 nm) achieved the high luminance of 6359 cd/m² at the low driving voltage of 8 V. At a current density of 20 mA/cm², a pure red emission with CIE coordinates of (0.65; 0.35) is observed for this device. Moreover, a power efficiency of 2.07 lm/W and a current efficiency of 5.17 cd/A at 20 mA/cm² were obtained for the fabricated devices. The study of the energy level diagram of the devices revealed that the improvement in performance of the devices with buffer layers could be attributed to lowering of carrier-injecting barrier and more balanced charge injection and transport properties.     

Observation of chimera patterns in a network of symmetric chaotic finance systems

The economic and financial systems consist of many nonlinear factors that make them behave as the complex systems. Recently many chaotic finance systems have been proposed to study the complex dynamics of finance as a noticeable problem in economics. In fact, the intricate structure between financial institutions can be obtained by using a network of financial systems. Therefore, in this paper, we consider a ring network of coupled symmetric chaotic finance systems, and investigate its behavior by varying the coupling parameters. The results show that the coupling strength and range have significant effects on the behavior of the coupled systems, and various patterns such as the chimera and multi-chimera states are observed. Furthermore, changing the parameters' values, remarkably influences on the oscillators attractors. When several synchronous clusters are formed, the attractors of the synchronized oscillators are symmetric, but different from the single oscillator attractor.     

Interaction of longitudinal phonons with discrete breather in strained graphene

We numerically analyze the interaction of small-amplitude phonon waves with standing gap discrete breather (DB) in strained graphene. To make the system support gap DB, strain is applied to create a gap in the phonon spectrum. We only focus on the in-plane phonons and DB, so the issue is investigated under a quasi-one-dimensional setup. It is found that, for the longitudinal sound waves having frequencies below 6 THz, DB is transparent and thus no radiation of energy from DB takes place; whereas for those sound waves with higher frequencies within the acoustic (optical) phonon band, phonon is mainly transmitted (reflected) by DB, and concomitantly, DB radiates its energy when interacting with phonons. The latter case is supported by the fact that, the sum of the transmitted and reflected phonon energy densities is noticeably higher than that of the incident wave. Our results here may provide insight into energy transport in graphene when the spatially localized nonlinear vibration modes are presented.     

Sonochemical synthesis of silver vanadium oxide micro/nanorods: Solvent and surfactant effects

In this investigation, a facile sonochemical route has been developed for the preparation of silver vanadium oxide (SVO) micro/nanorods by using silver salicylate and ammonium metavanadate as silver and vanadate precursor, respectively. Here, silver salicylate, [Ag(HSal)], is introduced as a new silver precursor to fabricate AgVO₃ nanorods. The effect of numerous solvents and surfactants on the morphology and sonochemical formation mechanism of AgVO₃ nanorods was studied. AgVO₃ nanorods were characterized by SEM and TEM images, XRD patterns, FT-IR, XPS, and EDS spectroscopy. SEM, TEM, and XRD results showed that AgO nanoparticles were formed onto AgVO₃ nanorods in the presence of ethanol, cyclohexanol, dimethylsulfoxide (DMSO), and acetone. By using polyethylene glycol (PEG-6000) and N,N-dimethylformamide (DMF) as organic additives, the thickness of AgVO₃ nanorods decreased.     

Coexistence of paramagnetism and ferromagnetism in Fe-TiO2 nanoparticle

Magnetic properties of pure and Fe doped rutile TiO₂ and TiO_2-ε are investigated using the first principle density functional theory. The results show that the considered systems are ferromagnetic. Furthermore, the origin of ferromagnetism is discussed and it is found that the double exchange and super-exchange are the main interactions in these compounds. Based on the calculations, the magnitude of the magnetic moment depends on the concentration of impurities and oxygen vacancies and the largest magnetic moment corresponds to the Fe_xTi_1-xO_2-ε. Moreover, using a model based on the bound magnetic polarons, the coexistence of ferromagnetic and paramagnetic phases can occur in Fe_xTi_1-xO₂ containing different impurity ions such as Fe⁺² and Fe⁺³ with different Curie temperatures. The finding may presents the potential application of the considered system as diluted magnetic semiconductor.     

Examining metal nanoparticle surface chemistry using hollow-core, photonic-crystal, fiber-assisted SERS

In this Letter, we demonstrate the efficacy of hollow core photonic crystal fibers (HCPCFs) as a surface-enhanced Raman spectroscopy (SERS) platform for investigating the ligand exchange process on the surface of gold nanoparticles. Raman measurements carried out using this platform show the capability to monitor minute amounts of surface ligands on gold nanoparticles used as an SERS substrate. The SERS signal from an HCPCF exhibits a tenfold enhancement compared to that in a direct sampling scheme using a cuvette. Using exchange of cytotoxic cetyltrimethylammonium bromide with α-methoxy-ω-mercaptopoly(ethylene glycol) on the surface of gold nanorods as an exemplary system, we show the feasibility of using HCPCF SERS to monitor the change in surface chemistry of nanoparticles.     

Tunable optical filter based on Sagnac phase-shift using single optical ring resonator

In this paper, a single optical ring resonator connected to a Sagnac loop is used to demonstrate theoretically a novel narrow band optical filter response that is based on Sagnac phase-shift Δφ. The given filter structure permits the Sagnac rotation to control the filter response. It is shown that by changing the Sagnac rotation rate, we can tune the filter response for desired bandwidths. To increase the wavelength selectivity of the filter, the Sagnac phase-shift should be as small as possible that is limited by the loop length. For Δφ=0.1 rad, the obtained FWHM is 2.63 MHz for tuning loop length of 2 m. The simulation response agrees fairly with the recently reported experimental result.     

Synthesis of Novel Chiral Ionic Liquid and Its Application in Reduction of Prochiral Ketones to the Corresponding Chiral Alcohols Using NaBH4

A novel chiral ionic liquid (CIL) based on nicotinium salt has been synthesized and used as an efficient asymmetric chiral catalyst for reduction of acetophenone derivatives with NaBH₄ in methanol at room temperature. The optically active alcohols were obtained in low to moderate enantiomeric excess in a short reaction time.