The pristine and carbon,silicon or germanium-substituted (10, 0) BN nanotube: A computational DFT study of NMR parameters

The geometrical structure and nuclear magnetic resonance (NMR) parameters of the pristine as well as carbon, silicon and germanium-doped (10, 0) boron-nitride (BN) nanotubes have been studied using a DFT-B3LYP method for the first time. When either a Ge, C or Si atom is substituted for a single B or N in the BN nanotube, the dopant atom extends outward from the surface of the nanotube. Our results show that Ge extends more from the surface than C or Si. It was found that the NMR parameters are significantly changed for those B and N nuclei that bond directly to C, Si or a Ge dopant. The calculations were carried out using the Gaussian 03 software package.     

Solubility of H2S in ionic liquids [hmim][PF6], [hmim][BF4], and [hmim][Tf2N]

The solubility of hydrogen sulphide in three ionic liquids, viz. 1-hexyl-3-methylilmidazolium hexafluorophosphate ([hmim][PF₆]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim][BF₄]), and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([hmim][Tf₂N]), at temperatures ranging from 303.15 K to 343.15 K and pressures up to 1.1 MPa were determined. The solubility values were correlated using the Krichevsky–Kasarnovsky equation and Henry’s constants were obtained at different temperatures. Partial molar thermodynamic functions of solvation such as standard Gibbs free energy, enthalpy, and entropy were calculated from the solubility results. Comparison of the values obtained show that the solubility of H₂S in these three ionic liquids was in the sequence: [hmim][BF₄] > [hmim][PF₆] ≈ [hmim][Tf₂N].     

Spectrophotometric and conductometric study of complexation of salophen and some transition metal ions in nonaqueous polar solvents

The complexation reaction between Cu(2+), Co(2+) and Ni(2+) metal cations with N,N'-bis(salicylidene)-1,2-phenylenediamine (salophen), in three nonaqueous polar solvents such as: acetonitrile (AN), dimethyl sulfoxide (DMSO), methanol (MeOH) and two binary mixtures of AN:DMSO and AN:MeOH at 25 degrees C were studied by spectrophotometric and conductometric methods. All investigated metal ions form 1:1 ML complex which their stability constants were determined and increase as Irving-Williams stability order of Co(2+)相似文献   

Picosecond wavelength conversion using semiconductor optical amplifier integrated with microring resonator notch filter

Optical and Quantum Electronics - In this paper, we analyse the picosecond wavelength conversion using semiconductor optical amplifier (SOA) with a novel technique. For an accurate and precise...     

Functionalization of BN nanosheet with N2H4 may be feasible in the presence of Stone–Wales defect

Following recent experimental works, herein we investigated chemical functionalization of a BN graphene-like sheet with hydrazine (N₂H₄) molecule based on the density functional theory. We found that the functionalization of the pristine sheet is not possible; while the presence of some structural defects such as Stone–Wales is essential to make it feasible. Functionalization energy of the defected sheet is calculated to be in the range of ?6.1 to ?7.4 kcal/mol at B3LYP/6-31G (d) level. Based on the obtained results, the functionalized BN sheet is found to be more soluble in water in comparison with the pristine sheet which is in good agreement with previous experimental reports. Also, it was found that the electronic properties of the defected sheet are slightly changed upon the chemical functionalization.     

A Theoretical Study of OH and OCH3 Free Radical Adsorption on a Nanosized Tube of BC2N

By using density functional theory calculations, we have investigated the adsorption of OH and OCH₃ free radicals on a BC₂N nanotube based on the energetic, electronic and geometric properties. The adsorption of radicals on the top of a B atom is more favorable than that on the other sites and reaction energies have been calculated to be in the range of ?0.57 to ?1.48 eV for OH and ?0.27 to ?1.19 eV for OCH₃. It was found that the adsorption of radicals may facilitate the electron emission from the BC₂N nanotube surface by decreasing the work function due to the charge transfer which occurs between the tube and radicals. Also, HOMO/LUMO gap of the tube is significantly decreased, which may result in the increase of the electrical conductivity of the tube.     

Design and optimization of high-performance microring-based uni-traveling carrier photodiode for WDM optical systems

This paper presents the design principles of a novel optimized microring-based uni-traveling carrier photodiode (MR-UTC-PD), for wavelength division multiplexing (WDM) optical systems. The fundamental parameters for output characteristics such as quantum efficiency and 3-dB bandwidth of MR-UTC-PD are discussed. We analyze the effects of basic parameters as effective ring radius, definite coupling condition and the suitable cross section on the MR-UTC-PD main characteristics for high performance of the device. It is shown that the maximum quantum efficiency and most efficient performance of the device can be obtained at critical coupling condition. We show that the maximum 3-dB bandwidth and an efficient approach for high bandwidth-efficiency product can be achieved at overcoupling condition. In this regard, some design curves are presented for the optimized MR-UTC-PD.