Synthesis, structural and photo-physical studies of transition metal complexes with Mannich bases derived from 2-mercaptobenzimidazole

Two Mannich base ligands, [1-(di-n-butylamine-N-methyl)mercapto-1H-benz-imidazole] (L1) and [1-(diphenylamine-N-methyl)mercapto-1H-benzimidazole] (L2)have been synthesized and further reacted with Co(II), Ni(II), Cu(II) and Zn(II) ionsto afford their respective complexes. The progress of the reaction was monitored by thin layer chromatography. The structural elucidation of Mannich base ligands and their metal complexes was done by Fourier Transform Infrared (FTIR), UV-Visible, Nuclear Magnetic Resonance spectroscopy (1H NMR & 13C NMR) and Atomic absorption spectroscopy (AAS) / Inductively coupled plasma emission spectroscopy (ICPES). FTIR and NMR studies supported the monoanionic bidentate coordination mode of L1 and L2 while tetrahedral geometries of metal complexes were proposed on the basis of AAS/ICP, magnetic moment and electronic spectroscopic data. The synthesized compounds were also investigated for their luminescent behavior which exhibited broad emission bands indicating charge transfer nature of the involved transitions.               KEY WORDS: Metal complexes, Mannich bases, 2-Mercaptobenzimidazole, Luminescence Bull. Chem. Soc. Ethiop. 2018, 32(3), 481-490.DOI: https://dx.doi.org/10.4314/bcse.v32i3.

Defect engineering for improved photocatalytic performance of reduced lead titanate (PbTiO3) under solar light irradiation

Lead titanate (PbTiO3) nanoparticles were prepared successfully by template free hydrothermal  method. Size, crystallinity, morphology and phase determination of the nanoparticles were made by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and field-emission scanning electron microscopy (FESEM). FESEM results had shown that all nanoparticles were in the range between 20 to 40 nm size and found in the form of agglomerates. The average crystallite size of PbTiO3 nanoparticles was calculated to be nearly 35 nm. PbTiO3 nanoparticles were reduced by hydrogenation at high temperature to make the material active for visible light. Furthermore, optical absorbance of PbTiO3 nanoparticles was determined by applying ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. By using Davis-Mott model, the direct optical band gap of 2.65 eV was acquired. Methyl orange (MO) was used as pollutant to check the photocatalytic activity of reduced PbTiO3 nanoparticles under solar light irradiation. Photocatalytic activity of reduced PbTiO3 nanoparticles increased 2.6 times more than that of pure PbTiO3 nanoparticles for methyl orange (MO) under solar light irradiation.               KEY WORDS: Lead titanate (PbTiO3), Photocatalytic performance, Hydrothermal growth, Solar light, Irradiation Bull. Chem. Soc. Ethiop. 2019, 33(2), 373-380.DOI: https://dx.doi.org/10.4314/bcse.v33i2.1

Synthesis, Characterization and Biological Properties of Anions of Bivalent Transition Metal [Co(II) and Ni(II)] Complexes With Acylhydrazine Derived ONO Donor Schiff Bases

Some acylhydrazine derived ONO donor Schiff bases and their Co(II) and Ni(II) complexes have been prepared having the same metal ion (cation) but different anions. These synthesized metal(II) complexes have been characterized on the basis of their elemental analyses, magnetic moment, molar conductance, and IR and electronic spectral data. All of the Schiff base ligands function as tridentates and the deprotonated enolic form is preferred for coordination. In order to evaluate the effect of anions on the bactericidal activity, these synthesized complexes, in comparison to the uncomplexed Schiff bases have been screened against bacterial species., Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa and the results are reported

Studies on the effect of chlorpyrifos (organophosphate) and cypermethrin (synthetic pyrethroid) on the growth of Paramecium

Interest in the toxicity of pesticides has increased as they enter waterways from agricultural and urban runoffs and may end up in aquatic environment and bioaccumulate in the food chain. The aim of this study was to determine the effect of two insecticides; Chlorpyrifos and Cypermethrin on aquatic protozoa (Paramecium). The test was carried out in laboratory, where Monoxenic culture of Paramecium was used to test the effect of Chlorpyrifos and Cypermethrin at 50, 25, 12.5, 6.25, 3.125, 1 respectively, at time interval of 24, 48, and 72 hours. The effect of Chlorpyrifos on Paramecium growth showed significant different with P value 0.0228, while for Cypermethrin, there was no significant difference with P value of 0.1333. The damage was more at 24hrs interval, as the number of population growth increased with time. Hence, the effect of the insecticides reduced. Conclusively, both insecticides showed harmful effect to Paramecium and may disturb the aquatic ecosystem.Keywords: Chlorpyrifos, Cypermethrin, Paramecium, Monoxenic culture, Toxicit

Band gap engineering for improved photocatalytic performance of CuS/TiO2 composites under solar light irradiation

ABSTRACT. Nanoparticles of CuS, TiO2 and CuS/TiO2 composites were prepared by template free hydrothermal method. Prepared nanoparticles were characterized by X-ray diffraction (XRD) and electron dispersive X-ray spectroscopy to confirm the formation of nanoparticles. Field emission scanning electron microscopy (FESEM) was applied to investigate the morphology and particle size of the nanoparticles which were measured in the range of 30–40 nm. Photocatalytic performance of CuS, TiO2 and Cus/TiO2 were measured by degradation of methyl orange (MO) under solar light irradiation. Coupling of n-type TiO2 (3.2 eV) with p-type CuS (1.9 eV) showed efficient degradation of the contaminants under the solar light irradiation. Photocatalytic performance of CuS/TiO2 composite improves 1.4 times than CuS for the degradation of methyl orange (MO) under solar light irradiation.               KEY WORDS: CuS/TiO2 composites, Photocatalytic performance, Hydrothermal growth, Solar light, Irradiation Bull. Chem. Soc. Ethiop. 2019, 33(3), 561-571.        DOI: https://dx.doi.org/10.4314/bcse.v33i3.1

Compact Polarization Diversity Antenna for 28/38 GHz Bands

In this paper, design and analysis of a millimeter wave dual- and dual-polarized antenna for 5G millimeter communications system is presented. The proposed design has a compact structure with size of 5 × 5 mm 2 . It consists of a rectangular patch with a crossed-slot etched off in the patch to reduce the interference between the two targeted 5G bands of 28 and 38 GHz. To achieve dual polarization performance, the radiating patch is fed by two different 50-Ω microstrip transmission lines. The antenna has -10dB impedance bandwidths of 2.6GHz (26.8-29.4 GHz) and 2.5GHz (37.7-40.2GHz) to cover 28/38 GHz mobile communication bands respectively. The antenna has the merits of miniaturized dimensions, stable broadside radiation patterns with high gains and low cross polarization in both bands of operation

RESPIRATORY SYNDROME: A MAJOR THREAT TO THE LIVESTOCK FARMERS AND ITS ECONOMIC IMPACT

Epidemiology of a respiratory syndrome was studied at Landhi Dairy Colony (LDC), Karachi, Pakistan and its economic impact was estimated. Among 5889 buffaloes examined, 2.3% animals were suffering from this syndrome. From some of the sick animals, Pasteurella multocida, the causative agent of haemorrhagic septicaemia, was isolated. In the present study, an average loss of Rs. 0.2 million per farm was calculated and the extrapolated values for 0.2 and 0.8 million animals present in LDC and other dairy colonies in Karachi were Rs. 225.6 and Rs. 1128.1 million, respectively

EPIDEMIOLOGICAL INVESTIGATIONS OF A PESTE DES PETITS RUMINANTS (PPR) OUTBREAK IN AFGHAN SHEEP IN PAKISTAN

Epidemiological and virological investigations were carried out during an outbreak of Peste des petits ruminants (PPR) in Afghan (Bulkhi) sheep in Pakistan. The overall morbidity, mortality and case fatality rates were 41.0, 1.2 and 3.0%, respectively. The epidemic curve was plotted and the values for basic reproductive number (R0) and herd immunity threshold (HIT) for the affected flock were estimated to be 6.85 and 85.4%, respectively. The morbid material analysis by immuno-capture ELISA (Ic-ELISA) and haemagglutination assay (HA) revealed the presence of PPR virus. The PPR virus was isolated and identified through cytopathic effects, Ic-ELISA and transmission electron microscopy (TEM)

EBSD mapping of herringbone domain structures in tetragonal piezoelectrics

Herringbone domain structures have been mapped using electron backscatter diffraction (EBSD) in two tetragonal piezoelectrics, lead zirconate titanate, [Pb(Zr,Ti)O<sub>3</sub>] and bismuth ferrite – lead titanate, [(PbTi)<sub>0.5</sub>(BiFe)<sub>0.5</sub>O<sub>3</sub>]. Analysis of the domain misorientations across the band junctions shows that the structures correspond very well to crystallographic models. High resolution mapping with a 20 nm step size allowed the crystal rotation across one of these band junctions in lead zirconate titanate to be studied in detail and allowed an improved estimation of the peak strain at the junction, of 0.56 GPa. The significance of this for crack nucleation and propagation in such materials is discussed