Volume 230, Issue 12

The title compound, 2-amino 4-picolinium 4-nitrobenzoate (2A4PNB), has been identified as a nonlinear optical material and its good quality single crystals were grown from methanol solution. It crystallizes in monoclinic system with the non-centro symmetric space group P c . Its structure and chemical compositions were confirmed by the X-ray diffraction and microanalysis studies, respectively. FTIR, UV-Visible-NIR, NMR and photoluminescence (PL) spectra have been recorded and extensive spectroscopic investigations have been carried out. The grown crystals have been subjected to micro hardness and photoconductivity studies to explore its physico chemical properties. The free radical scavenging activity of the complex has been determined against DPPH and H 2 O 2 radicals. In addition, the quantum chemical studies were performed on the isolated 2A4PNB molecule using DFT calculations at the B3LYP/6-311++G (d,p) basis set.

The FT-IR and FT-Raman spectra of 5-fluoro-2-methylbenzaldehyde (5F2MB) have been recorded in the regions 4000–400 cm −1 and 4000–100 cm −1 , respectively. Using the observed FT-IR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of vibrations of the compound were carried out. The optimum molecular geometry, vibrational frequencies and Raman scattering activities were calculated by density functional theory with B3LYP/6-311+G** basis sets. A close agreement was achieved between the calculated and observed frequencies by refinement of scale factors. Unambiguously normal modes of vibrational assignments have been made with the help of the GUASSVIEW 5.0 program and the potential energy distribution (PED) calculated by the density functional theory calculations. Natural bonding orbital (NBO) analyses were carried out to discuss the stability of the molecule. The molecular electrostatic potential (MEP) map and electron density map were drawn and analyzed. Using nuclear magnetic resonance (NMR) analysis, the chemical shifts of hydrogen atoms and carbon atoms were calculated. The charge distribution, Mullikan atomic charge values and HOMO–LUMO energy have been calculated to explore the reasons for the change in biological activity. Furthermore, the first hyperpolarizability and the dipole moment of the molecule have also been calculated.

A green and simple chemistry approach was demonstrated to prepare reduced graphene oxide (rGO) using sodium humate (SH) as the reducing agent. Without using toxic and harmful chemicals, this method is environmentally friendly and suitable for the large-scale production of graphene. At first, the improved Hummers method to oxidize graphite for the synthesis of graphene oxide (GO) was applied, and then the as-prepared GO was reduced by SH to form rGO. Characterization was performed using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectrometry (XPS) and Raman spectra. The intensity ratio of the D and G band (I D /I G ) of GO after reduction with SH increases from 0.96 (GO) to 1.11 (rGO), the results obtained from the Raman spectra proved high purity of the final products.

Porous powdered carbon nanomaterials [carbon nanotubes (CNT) and carbon nanoshells (CNS)] were compacted using spark plasma sintering (SPS) technique. High resolution transmission electron microscopy (HRTEM) and SEM images demonstrate the structural change: the increase of density and thickness of nanoshells stack, formation of interparticle bonds between nanotubes. Surface properties of original and sintered materials were studied by liquid nitrogen sorption and compared to the characteristics for real vapors sorption. The data collected for water, ethanol, acetonitrile and benzene show both physical adsorption and chemisorption. The mean pore diameter distribution calculated from nitrogen adsorption by density functional theory (DFT) approach shows the reduction of total pore volume in CNS pellet while for CNT pellet total pore volume does not differ dramatically from those for non-compacted samples. The isosteric heats of sorption for all chosed vapors were calculated.

In the present paper we show that nanocrystalline ZnO/Ag composites can be obtained via an ultrasonic-assisted approach in the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethylsulfonate. Different techniques including, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and ultraviolet-visible spectroscopy (UV-vis) were utilized to characterize the synthesized materials. The XRD results revealed the formation of ZnO wurtzite structure along with metallic Ag in the ZnO/Ag composite. The particle size was estimated from the XRD results to be about 35 nm. The UV spectrum of ZnO/Ag showed the characteristic absorption band of wurtzite crystal structure of ZnO, and the presence of Ag in the ZnO/Ag composite led to a slight red shift. The employed ionic liquid acts as a template leading to the formation of nanoparticles of ZnO and of ZnO/Ag.

Al 2 O 3 doped TiO 2 samples were prepared by the simple sol-gel method. The prepared samples were annealed at 400°C for 1 h in an open air atmosphere. The dielectric properties, AC electrical conductivity (σ ac ), dielectric constant (ε′), dielectric loss (ε″) and the loss tangent (tan δ) of the prepared Al 2 O 3 doped TiO 2 nanocomposites were studied under a wide frequency and temperature range. The dielectric loss values of the prepared samples were measured at 50 Hz and 5 MHz and the values were found to be in the range of 0.11–1.73 at 40°C and 0.13–4.39 at 100°C. The microstructures of the prepared samples were also studied using high-resolution transmission electron microscopy (HRTEM) analysis.

Molar conductances and viscosities of some tetraalkylammonium perchlorate salts (R 4 NClO 4 where R=methyl, ethyl, propyl, butyl) have been measured in the concentration range (30–500)×10 −4 M in the binary mixtures of acetonitrile (AN)+methanol (MeOH) containing 0, 20, 40, 60, 80 and 100 mol% methanol at 298.15 K. Conductance data was analyzed by the Shedlovsky equation and the viscosity data by Jones–Dole equation. The limiting ionic conductances ( λ o ± ) were used to calculate the solvated radii ( r i ) of the ions. The A and B coefficients of the Jones–Dole equation are positive in all salts. The A coefficients are in reasonably good agreement with the limiting theoretical values ( Aη ) calculated using Falkenhagen–Vernon equation. The variation of the actual solvated radii ( r i ) as well as the ionic B ± coefficients with solvent composition in AN+MeOH mixtures shows the preferential solvation of tetraalkylammonium ions by methanol-rich region of the mixtures. The extent of solvation of the tetraalkylammonium ions is in the order Me 4 N + >Et 4 N + >Pr 4 N + >Bu 4 N + .

In a continuation of previous studies, thermophysical properties of the systems containing aspirin (ASA), ionic liquid, 1-octyl-3-methylimidazolium bromide ([OMIM][Br]) and acetonitrile (MeCN) have been determined. These properties contain density, viscosity, speed of sound and refractive index measured at T =(288.15 K–318.15 K) and at atmospheric pressure. The measured data have been applied to calculate the apparent molar volumes at infinite dilution Vφ0,$V_\varphi ^0,$ transfer volumes ΔVφ0,$\Delta V_\varphi ^0,$ apparent molar isentropic compressibilities κ ϕ , to viscosity B -coefficients and solvation number. The positive values of ΔVφ0$\Delta V_\varphi ^0$ and Δκφ0$\Delta \kappa _\varphi ^0$ indicate that dominant interactions between ASA and ionic liquid are ion–polar and polar–polar interactions. From the obtained parameters, some information in regard with the solute–solvent interactions in the studied systems was obtained. The cosphere overlap model was used to interpret the positive transfer volume ΔVφ0.$\Delta V_\varphi ^0.$