Tegene Desalegn | Adama Science and Technology University (original) (raw)

Papers by Tegene Desalegn

Social Science Research Network, 2022

Starch-starke, Nov 4, 2014

A new method for the preparation of epoxy fatty acid esters of cassava starch (starch vernolates)... more A new method for the preparation of epoxy fatty acid esters of cassava starch (starch vernolates) is presented based on the reaction of cassava starch with vernonia oil methyl ester (epoxy ester) using only 1‐butyl‐3‐methylimidazolium chloride, [C4C1im]Cl, ionic liquid as a reaction medium and a cheap inexpensive base such as pyridine as a catalyst. Under the reported reaction conditions, a high degree of substitution of 1.03 was achieved, at a reaction temperature of 110°C and 24 h reaction time. The new starch vernolates were characterized by infrared spectroscopy (FTIR) and solid state NMR (CP/MAS 13C NMR). Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) showed that the new product is an amorphous material with a continuous and shapeless morphology. The melting point measured by differential scanning calorimetry (DSC) is 111.4°C. The new synthetic method makes the synthesis of starch vernolates less time consuming and more inexpensive. The differences in melting point and degree of substitution with previously synthesized starch vernolates using enzymatic catalysis suggest a difference in reaction selectivity via this new reaction path.

ACS omega, Jan 27, 2022

Herein, we report novel Co(II) and V(IV) complexes synthesized from an (E)-2-(((2-((2-hydroxyethy... more Herein, we report novel Co(II) and V(IV) complexes synthesized from an (E)-2-(((2-((2-hydroxyethyl)amino)quinolin-3-yl)methylene)amino)ethan-1-ol ligand (L), cobalt(II) chloride hexahydrate, and vanadyl(IV) sulfate in methanolic solutions. The ligand and the complexes were characterized by 1 H NMR spectroscopy, 13 C NMR spectroscopy, UV−visible spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy−energy dispersive X-ray spectroscopy (SEM−EDX), mass spectroscopy (MS), thermal analysis, and molar conductance. The FT-IR spectral data showed that the ligand adopted a tridentate fashion when binding with the metal ions via the nitrogen atoms of the imine (CN) and amine (N−H), and the oxygen atom of the hydroxyl group (O−H). The PXRD and SEM results indicated that the complexes are amorphous in nature. The density functional theory (DFT) calculated absorption and IR spectra agree very well with the corresponding experimental results. The antibacterial activities of the free ligand and its complexes were evaluated using a paper disk diffusion method. The complexes have better percent activitiy index than the free ligand. The cobalt complex exhibited a more recognizable antibacterial activity than the vanadium complex, specifically against Pseudomonas aeruginosa with a mean inhibition zone of 18.62 ± 0.19 mm, when compared with the positive control, ciprofloxacin, with a mean inhibition zone of 22.98 ± 0.08 mm at the same concentration. Furthermore, the antioxidant activities of the free ligand and its metal complexes were also determined in vitro using 2,2-diphenyl-1-picrylhydrazyl. The ligand exhibited less in vitro antioxidant activity than its transition metal complexes, in which the cobalt complex has a better antioxidant activity with half-inhibitory concentrations (IC 50 of 16.01 μg/ mL) than the ligand and the vanadium complex. Quantum molecular descriptors from the DFT calculations further support the experimental results. Molecular docking analysis also shed more light on the biological activities of the novel cobalt and vanadium complexes.

American Journal of Applied Chemistry, 2017

In this study epoxidized vernonia oil (EVO) was synthesized by the epoxidation of vernonia oil us... more In this study epoxidized vernonia oil (EVO) was synthesized by the epoxidation of vernonia oil using peroxyformic acid, formed in situ by the reaction of hydrogen peroxide and formic acid in the presence of an acidic ion exchange resin (Amberlite IR-120 hydrogen form) as the catalyst. This method of epoxidation has resulted in product with about 78% conversion. Acid exchange resin catalyzed epoxidation reactions are found to be promising in minimizing oxirane ring opening.

Journal of Chemistry, Sep 27, 2022

Recently, heteroleptic coordination between essential metallic elements with semicarbazone-based ... more Recently, heteroleptic coordination between essential metallic elements with semicarbazone-based derivatives attracts more consideration for the varied ranges of bioactivities. Semicarbazone-based moiety holding azomethine (C N) group become exible ligands, forming stable complexes. rough a stirring and re ux technique, a novel heteroleptic complex of copper (II) was synthesized by reacting two semicarbazone-based derivative ligands, ortho-phthalaldehyde disemicarbazone (L 1) and dehydrozingerone semicarbazone (L 2), with copper chloride salt in 1 : 1 : 1 molar ratio. Magnetic moment measurement, elemental analyzer, thermogravimetric (TGA) analysis, and several spectroscopic techniques were applied to describe the prepared compounds. e disc di usion and DPPH methods were actually used to investigate the antibacterial and antiradical potentials, respectively. e obtained data indicates the ligand (L 1) has good mean inhibition zones on Staphylococcus aureus (12.42 ± 0.00 mm) and S. pyogenes (11.64 ± 0.12 mm) bacteria. e heteroleptic [Cu(L 1) (L 2)] complex displayed higher antibacterial actions (13.67 ± 0.52 mm) on Streptococcus pyogenes bacteria. e [Cu(L 1) (L 2)] complex also shows better antiradical potential (63.7%). Furthermore, the docking result of prepared compounds on S. aureus gyrase con rms the ligands (L 1 and L 2) and the complex potential molecules possess the smallest binding potential of −8.0 to −8.4 kcal/mol. A higher value was achieved by [Cu(L 1) (L 2)] complex (−8.4 kcal/mol). us, this study indicates an insight towards combining semicarbazone form derivatives of natural source origin with a synthetic compound as ligands through metal coordination could enhance bioactivity.

International Journal of Chemical Studies, 2018

Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with L-phenylalanine and maleic acid... more Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with L-phenylalanine and maleic acid in the presence of Dimethylformamide-water mixtures in the concentration range of 0-50% v/v DMF has been studied pH-metrically at a temperature of 303K and at an ionic strength of 0.16 mol L −1. The selection of best fit chemical models is based on statistical parameters and residual analysis. The predominant species detected were ML, ML2, and ML2H2 for Co(II), Ni(II), and Cu(II). The appropriateness of the experimental conditions were verified by introducing errors deliberately. The models containing different numbers of species were refined by using the computer program MINIQUAD75. The chemical speciation was explained based on the distribution diagrams drawn using HYSS HYPERQUAD. The trend in variation of stability constants of the complexes with dielectric constant of the medium was attributed for the formation and possible structures of the complex species presented.

Metallic nanoparticles synthesized using a green synthetic route has been found to be harmful to ... more Metallic nanoparticles synthesized using a green synthetic route has been found to be harmful to pathogens. An attempt was made to synthesize copper nanoparticles (EcS-Cu NPs) using the root extract of Echinops sp., Ethiopian medicinal plant. The most advanced techniques were employed to characterize NPs. The presence of the highest absorbance at λ max =454 nm confirms the formation of EcS-Cu NPs. The role of biomolecules as capping agents for EcS-Cu NPs was authenticated by FT-IR spectra. The presence of a single weak peak in the XRD pattern of NPs confirmed the amorphous nature of the NPs. The purity of the NPs was corroborated by the SEM-EDAX analysis. TEM-HRTEM-SAED analysis authenticated the presence of partially crystalline natured copper NPs with the appearance of weak concentric SAED rings. The EcS-Cu NPs showed significant synergistic antibacterial influence verses S. aureus, E. coli, P. aeruginosa, and E. aerogenes. The uppermost inhibition zone of 13 mm was inscribed against S. aureus bacteria. EcS-Cu NPs exhibited better antibacterial activities against gram positive and gram negative bacteria.

American Journal of Applied Chemistry, 2016

In this study the synthesis of epoxy fatty acid esters of starch (starch vernolates) by the react... more In this study the synthesis of epoxy fatty acid esters of starch (starch vernolates) by the reaction of cassava starch with vernonia oil methyl ester (epoxy ester) using basic catalyst K 2 CO 3 and organic solvent, DMSO as a reaction medium is presented. Under current reaction conditions, a high degree of substitution of 1.24 was achieved, at a reaction temperature of 110°C and 12 hours of reaction time. The new starch vernolates were characterized by Scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicated that the new product is an amorphous material with a continuous and shapeless morphology. The melting point measured by differential scanning calorimetry (DSC) was 118°C. The new synthetic method makes the synthesis of starch vernolates less time consuming and more inexpensive. The differences in melting point and degree of substitution with previously synthesized starch vernolates using enzymatic and chemical catalysis suggest a difference in reaction selectivity via this new reaction path.

Applied Nanoscience, Nov 25, 2020

Ethiopian medicinal plant, Vernonia amygdalina Del. mediated green silver nanostructures (V-SNS) ... more Ethiopian medicinal plant, Vernonia amygdalina Del. mediated green silver nanostructures (V-SNS) were successfully synthesized for the first time. The surface amalgamation of biomolecules of plant leaf extract around Ag nanostructures has also been approved by the most advanced techniques which were employed to characterize the NSs. The presence of absorbance maxima, λ max at 454 nm confirms the formation of V-SNS. UV-DRS studies revealed the band gap of 2.09 eV for NSs. The role of biomolecules as capping agents for V-SNS was authenticated by FT-IR spectra. The presence of four sharp peaks in the XRD pattern of NSs confirmed the highly crystalline nature of NSs. The TGA-DTA studies revealed that Ag NS is thermally stable above 570 °C. The purity of the NSs was corroborated by SEM-EDAX analysis. The average particle size of V-SNS was deduced to be 35.24 nm. In addition, TEM micrographs revealed the presence of V-SNS with varieties of nano-sized shapes. TEM-HRTEM-SAED analysis authenticated the presence of silver NS with interplanar spacing values of 0.248 nm and 0.243 nm which conformed to Ag (111) lattice fringes of silver. The V-SNS showed significant synergistic antibacterial influence versus S. aureus, E. coli, P. aeruginosa, and E. aerogenes. The uppermost zone of inhibition of 18 mm was inscribed against P. aeruginosa bacteria. The better electrochemical properties of V-SNS electrode as revealed by cyclic voltammograms, Nyquist and Bode plots make it suitable for potential electrochemical sensor application. V-SNS exhibited better photocatalytic activities against Acid orange 8 and Acid red 88 dyes. Keywords Medicinal plants • Green synthesis • Vernonia amygdalina Del. • Silver nanostructure • Antibacterial activity • Photocatalysis Abbreviations NS Nanostructure NP Nanoparticle SNS Silver nanostructure V-SNS Vernonia amygdalina Del. mediated silver nanostructure XRD X-ray diffractometer UV-DRS Ultraviolet diffused reflectance spectra

Materials research express, May 1, 2020

The biogenic/green silver nanoparticles (g-Ag NPs) were synthesised by using the extract of indig... more The biogenic/green silver nanoparticles (g-Ag NPs) were synthesised by using the extract of indigenous medicinal plant of Ethiopia, Hagenia abyssinica (Brace) JF. Gmel. leaf extract for the first time, to investigate the synergistic effect of biomolecules towards the enhancement of electrochemical properties of NPs. The synthesized g-Ag NPs were characterized by UV-visible, UV-DRS, FT-IR, XRD, SEM, EDXA, TEM, HRTEM and SAED techniques. The maximum absorbance, λ max was found to be 461 nm for g-Ag NPs due to surface plasmon resonance. The energy gap, Eg of NPs, was found to be 2.31 eV. FTIR spectrum confirmed the presence of bioactive compounds responsible for possible capping and stabilisation of g-Ag NPs. The XRD analysis revealed that the g-Ag NPs are highly crystalline exhibiting sharp peaks for (111), (200), (220) and (311) planes in the diffraction pattern. SEM and TEM micrographs showed differently shaped Ag particles in addition to spherical shape. The average particle size of NPs was found to be 24.08 nm using imageJ analysis. EDX analysis confirmed the presence of Ag in the g-Ag NPs. In addition, the SAED pattern of g-Ag NPs presented concentric patterns for 4 major planes of crystalline silver. The d-spacing values of 0.2428 nm, 0.2126 nm, 0.1483 nm and 0.1263 nm corresponds to d111Ag, d200Ag, d220Ag and d311Ag lattice fringes respectively. The cyclic voltammetry (CV) results suggest that g-Ag NPs possess better electrochemical properties due to its lower charge transfer resistance value of 17 Ω. EIS studies too revealed better stability of g-Ag NPs as electrode materials.

Adsorption Science & Technology, Jan 10, 2022

Degradation of dye pollutants by the photocatalytic process has been regarded as the most efficie... more Degradation of dye pollutants by the photocatalytic process has been regarded as the most efficient green method for removal organic dyes from contaminated water. The current research work describes the synthesis of Fe 3 O 4 @SiO 2 @Ru hybrid magnetic composites (HMCs) and their photocatalytic degradation of two azo dye pollutants, methyl orange (MO) and methyl red (MR), under irradiation of visible light. The synthesis of Fe 3 O 4 @SiO 2 @Ru HMCs involves three stages, including synthesis of Fe 3 O 4 magnetic microspheres (MMSs), followed by silica (SiO 2) coating to get Fe 3 O 4 @SiO 2 MMSs, and then incorporation of presynthesized Ru nanoparticles (~3 nm) onto the surface of Fe 3 O 4 @SiO 2 HMCs. The synthesized HMCs were characterized by XRD, FTIR, TEM, EDS, XPS, BET analysis, UV-DRS, PL spectroscopy, and VSM to study the physical and chemical properties. Furthermore, the narrow band gap energy of the HMC photocatalyst is a significant parameter that provides high photocatalytic properties due to the high light adsorption. The photocatalytic activity of synthesized Fe 3 O 4 @SiO 2 @Ru HMCs was assessed by researching their ability to degrade the aqueous solution of MO and MR dyes under visible radiation, and the influence of various functional parameters on photocatalytic degradation has also been studied. The results indicate that the photocatalytic degradation of MO and MR dyes is more than 90%, and acid media favors better degradation. The probable mechanism of photodegradation of azo dyes by Fe 3 O 4 @SiO 2 @Ru HMC catalysts has been proposed. Furthermore, due to the strong ferromagnetic Fe 3 O 4 core, HMCs were easily separated from the solution after the photocatalytic degradation process for reuse. Also, the photocatalytic activity after six cycles of use is greater than 90%, suggesting the stability of the synthesized

Journal of Nanostructures, 2021

The medicinal plant, Syzygium guineense (Willd.) DC (Waterberry) mediated green copper oxide nano... more The medicinal plant, Syzygium guineense (Willd.) DC (Waterberry) mediated green copper oxide nanostructures (SyG-CuO NSs) were successfully synthesized for the first time in Ethiopia. The antibacterial activity of CuO NSs capped by biomolecules of the plant leaf extract has been investigated. The UV-visible, UV-DRS, FT-IR, XRD, TGA-DTA, SEM, EDXA, TEM, HRTEM and SAED techniques were employed to characterize the NSs. The presence of two absorbance maxima, λ max 1 and λ max 2 at 423 nm and 451 nm, respectively confirms a mixture of copper oxide (E g =1.93 eV). FTIR spectra confirmed the presence of biomolecules with SyG-CuO NSs. The XRD patterns of NSs confirmed the presence of CuO with high crystallinity. The purity of the NSs was confirmed by SEM-EDAX analysis. In addition, TEM-HRTEM-SAED analysis revealed the d-spacing value of 0.2854 nm which corresponds to CuO (111) lattice fringe. SyG-CuO NSs showed good antibacterial effect against both Gram-positive bacteria, S. aureus (12 mm), and Gram-negative bacteria, E. coli (12 mm), P. aeruginosa (10 mm), and E. aerogenes (12 mm). The bioactive compounds capped around the CuO NPs served the effective role in disrupting the cell wall of bacterial strains. The CV and EIS studies confirmed the better electrochemical properties for SyG-CuO with low charge transfer resistance value of 49 Ω. These CuO NSs exhibited multifunctional applications.

Journal of Molecular Structure

Journal of Chemistry, Sep 27, 2022

Recently, heteroleptic coordination between essential metallic elements with semicarbazone-based ... more Recently, heteroleptic coordination between essential metallic elements with semicarbazone-based derivatives attracts more consideration for the varied ranges of bioactivities. Semicarbazone-based moiety holding azomethine (C N) group become exible ligands, forming stable complexes. rough a stirring and re ux technique, a novel heteroleptic complex of copper (II) was synthesized by reacting two semicarbazone-based derivative ligands, ortho-phthalaldehyde disemicarbazone (L 1) and dehydrozingerone semicarbazone (L 2), with copper chloride salt in 1 : 1 : 1 molar ratio. Magnetic moment measurement, elemental analyzer, thermogravimetric (TGA) analysis, and several spectroscopic techniques were applied to describe the prepared compounds. e disc di usion and DPPH methods were actually used to investigate the antibacterial and antiradical potentials, respectively. e obtained data indicates the ligand (L 1) has good mean inhibition zones on Staphylococcus aureus (12.42 ± 0.00 mm) and S. pyogenes (11.64 ± 0.12 mm) bacteria. e heteroleptic [Cu(L 1) (L 2)] complex displayed higher antibacterial actions (13.67 ± 0.52 mm) on Streptococcus pyogenes bacteria. e [Cu(L 1) (L 2)] complex also shows better antiradical potential (63.7%). Furthermore, the docking result of prepared compounds on S. aureus gyrase con rms the ligands (L 1 and L 2) and the complex potential molecules possess the smallest binding potential of −8.0 to −8.4 kcal/mol. A higher value was achieved by [Cu(L 1) (L 2)] complex (−8.4 kcal/mol). us, this study indicates an insight towards combining semicarbazone form derivatives of natural source origin with a synthetic compound as ligands through metal coordination could enhance bioactivity.

Addis Ababa University, Jun 6, 2012

International Journal of Advanced Research, 2018

Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with Lphenylalanine and maleic acid ... more Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with Lphenylalanine and maleic acid in the presence of Dimethylformamidewater mixtures in the concentration range of 0-50% v/v DMF has been studied pH-metrically at a temperature of 303K and at an ionic strength of 0.16 mol L −1. The selection of best fit chemical models is based on statistical parameters and residual analysis. The predominant species detected were ML, ML 2 , and ML 2 H 2 for Co(II), Ni(II), and Cu(II). The appropriateness of the experimental conditions were verified by introducing errors deliberately. The models containing different numbers of species were refined by using the computer program MINIQUAD75. The chemical speciation was explained based on the distribution diagrams drawn using HYSS HYPERQUAD. The trend in variation of stability constants of the complexes with dielectric constant of the medium was attributed for the formation and possible structures of the complex species presented.

Environmental Engineering and Management Journal, 2020

Inorganic ceramic materials is receiving more attention in recent times due to their unique chara... more Inorganic ceramic materials is receiving more attention in recent times due to their unique characteristics which include different pore structures, hydrophilic surfaces, high chemical, thermal and mechanical stabilities that offer avenues for application in water treatment. In the present work, cost-effective clay ceramic water filters of different designs were developed from clay (50, 60, and 70) %, sawdust (15, 20, 25, and 35) %, grog (5, 10 and 15)% ratios plus 5% bone char by volume and sintered at temperature of 950ºC for 6 hrs. For the flow rate, fluoride and nitrite tests synthetic waters were used, while for Escherichia coli removal efficiency test of the filter diluted wastewater sample collected by purposive sampling methods from Modjo River was used. The analysis of the optimal performing sintered filter by X-ray diffraction revealed the existence of mixed phases such as quartz, mulite and ilite. The surface functional group analysis by infrared spectroscopy showed the presence of strong bands at 3696 cm-1 , 3622 cm-1 , 3450 cm-1 of hydroxyl linkages. Field emission scanning electron microscopy of fractured filter surfaces with better performance showed the formation of interconnected porous microstructure materials. The ceramic water filter developed from 50% clay, 15% grog, 35% sawdust, and 5% bone char, (C950-50-35-15), characterized with total porosity 36.33±0.05%, displayed flow rate 1.91±0.55L/h and E. coli, nitrite, and fluoride removal efficiencies of 99.91±0.09%, 76.00±0.22%, and 96.8±0.41% respectively.

Starch - Stärke, 2014

A new method for the preparation of epoxy fatty acid esters of cassava starch (starch vernolates)... more A new method for the preparation of epoxy fatty acid esters of cassava starch (starch vernolates) is presented based on the reaction of cassava starch with vernonia oil methyl ester (epoxy ester) using only 1-butyl-3-methylimidazolium chloride, [C4C1im]Cl, ionic liquid as a reaction medium and a cheap inexpensive base such as pyridine as a catalyst. Under the reported reaction conditions, a high degree of substitution of 1.03 was achieved, at a reaction temperature of 110°C and 24 h reaction time. The new starch vernolates were characterized by infrared spectroscopy (FTIR) and solid state NMR (CP/MAS 13C NMR). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that the new product is an amorphous material with a continuous and shapeless morphology. The melting point measured by differential scanning calorimetry (DSC) is 111.4°C. The new synthetic method makes the synthesis of starch vernolates less time consuming and more inexpensive. The differences in melting point and degree of substitution with previously synthesized starch vernolates using enzymatic catalysis suggest a difference in reaction selectivity via this new reaction path.

Social Science Research Network, 2022

Starch-starke, Nov 4, 2014

A new method for the preparation of epoxy fatty acid esters of cassava starch (starch vernolates)... more A new method for the preparation of epoxy fatty acid esters of cassava starch (starch vernolates) is presented based on the reaction of cassava starch with vernonia oil methyl ester (epoxy ester) using only 1‐butyl‐3‐methylimidazolium chloride, [C4C1im]Cl, ionic liquid as a reaction medium and a cheap inexpensive base such as pyridine as a catalyst. Under the reported reaction conditions, a high degree of substitution of 1.03 was achieved, at a reaction temperature of 110°C and 24 h reaction time. The new starch vernolates were characterized by infrared spectroscopy (FTIR) and solid state NMR (CP/MAS 13C NMR). Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) showed that the new product is an amorphous material with a continuous and shapeless morphology. The melting point measured by differential scanning calorimetry (DSC) is 111.4°C. The new synthetic method makes the synthesis of starch vernolates less time consuming and more inexpensive. The differences in melting point and degree of substitution with previously synthesized starch vernolates using enzymatic catalysis suggest a difference in reaction selectivity via this new reaction path.

ACS omega, Jan 27, 2022

Herein, we report novel Co(II) and V(IV) complexes synthesized from an (E)-2-(((2-((2-hydroxyethy... more Herein, we report novel Co(II) and V(IV) complexes synthesized from an (E)-2-(((2-((2-hydroxyethyl)amino)quinolin-3-yl)methylene)amino)ethan-1-ol ligand (L), cobalt(II) chloride hexahydrate, and vanadyl(IV) sulfate in methanolic solutions. The ligand and the complexes were characterized by 1 H NMR spectroscopy, 13 C NMR spectroscopy, UV−visible spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy−energy dispersive X-ray spectroscopy (SEM−EDX), mass spectroscopy (MS), thermal analysis, and molar conductance. The FT-IR spectral data showed that the ligand adopted a tridentate fashion when binding with the metal ions via the nitrogen atoms of the imine (CN) and amine (N−H), and the oxygen atom of the hydroxyl group (O−H). The PXRD and SEM results indicated that the complexes are amorphous in nature. The density functional theory (DFT) calculated absorption and IR spectra agree very well with the corresponding experimental results. The antibacterial activities of the free ligand and its complexes were evaluated using a paper disk diffusion method. The complexes have better percent activitiy index than the free ligand. The cobalt complex exhibited a more recognizable antibacterial activity than the vanadium complex, specifically against Pseudomonas aeruginosa with a mean inhibition zone of 18.62 ± 0.19 mm, when compared with the positive control, ciprofloxacin, with a mean inhibition zone of 22.98 ± 0.08 mm at the same concentration. Furthermore, the antioxidant activities of the free ligand and its metal complexes were also determined in vitro using 2,2-diphenyl-1-picrylhydrazyl. The ligand exhibited less in vitro antioxidant activity than its transition metal complexes, in which the cobalt complex has a better antioxidant activity with half-inhibitory concentrations (IC 50 of 16.01 μg/ mL) than the ligand and the vanadium complex. Quantum molecular descriptors from the DFT calculations further support the experimental results. Molecular docking analysis also shed more light on the biological activities of the novel cobalt and vanadium complexes.

American Journal of Applied Chemistry, 2017

In this study epoxidized vernonia oil (EVO) was synthesized by the epoxidation of vernonia oil us... more In this study epoxidized vernonia oil (EVO) was synthesized by the epoxidation of vernonia oil using peroxyformic acid, formed in situ by the reaction of hydrogen peroxide and formic acid in the presence of an acidic ion exchange resin (Amberlite IR-120 hydrogen form) as the catalyst. This method of epoxidation has resulted in product with about 78% conversion. Acid exchange resin catalyzed epoxidation reactions are found to be promising in minimizing oxirane ring opening.

Journal of Chemistry, Sep 27, 2022

Recently, heteroleptic coordination between essential metallic elements with semicarbazone-based ... more Recently, heteroleptic coordination between essential metallic elements with semicarbazone-based derivatives attracts more consideration for the varied ranges of bioactivities. Semicarbazone-based moiety holding azomethine (C N) group become exible ligands, forming stable complexes. rough a stirring and re ux technique, a novel heteroleptic complex of copper (II) was synthesized by reacting two semicarbazone-based derivative ligands, ortho-phthalaldehyde disemicarbazone (L 1) and dehydrozingerone semicarbazone (L 2), with copper chloride salt in 1 : 1 : 1 molar ratio. Magnetic moment measurement, elemental analyzer, thermogravimetric (TGA) analysis, and several spectroscopic techniques were applied to describe the prepared compounds. e disc di usion and DPPH methods were actually used to investigate the antibacterial and antiradical potentials, respectively. e obtained data indicates the ligand (L 1) has good mean inhibition zones on Staphylococcus aureus (12.42 ± 0.00 mm) and S. pyogenes (11.64 ± 0.12 mm) bacteria. e heteroleptic [Cu(L 1) (L 2)] complex displayed higher antibacterial actions (13.67 ± 0.52 mm) on Streptococcus pyogenes bacteria. e [Cu(L 1) (L 2)] complex also shows better antiradical potential (63.7%). Furthermore, the docking result of prepared compounds on S. aureus gyrase con rms the ligands (L 1 and L 2) and the complex potential molecules possess the smallest binding potential of −8.0 to −8.4 kcal/mol. A higher value was achieved by [Cu(L 1) (L 2)] complex (−8.4 kcal/mol). us, this study indicates an insight towards combining semicarbazone form derivatives of natural source origin with a synthetic compound as ligands through metal coordination could enhance bioactivity.

International Journal of Chemical Studies, 2018

Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with L-phenylalanine and maleic acid... more Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with L-phenylalanine and maleic acid in the presence of Dimethylformamide-water mixtures in the concentration range of 0-50% v/v DMF has been studied pH-metrically at a temperature of 303K and at an ionic strength of 0.16 mol L −1. The selection of best fit chemical models is based on statistical parameters and residual analysis. The predominant species detected were ML, ML2, and ML2H2 for Co(II), Ni(II), and Cu(II). The appropriateness of the experimental conditions were verified by introducing errors deliberately. The models containing different numbers of species were refined by using the computer program MINIQUAD75. The chemical speciation was explained based on the distribution diagrams drawn using HYSS HYPERQUAD. The trend in variation of stability constants of the complexes with dielectric constant of the medium was attributed for the formation and possible structures of the complex species presented.

Metallic nanoparticles synthesized using a green synthetic route has been found to be harmful to ... more Metallic nanoparticles synthesized using a green synthetic route has been found to be harmful to pathogens. An attempt was made to synthesize copper nanoparticles (EcS-Cu NPs) using the root extract of Echinops sp., Ethiopian medicinal plant. The most advanced techniques were employed to characterize NPs. The presence of the highest absorbance at λ max =454 nm confirms the formation of EcS-Cu NPs. The role of biomolecules as capping agents for EcS-Cu NPs was authenticated by FT-IR spectra. The presence of a single weak peak in the XRD pattern of NPs confirmed the amorphous nature of the NPs. The purity of the NPs was corroborated by the SEM-EDAX analysis. TEM-HRTEM-SAED analysis authenticated the presence of partially crystalline natured copper NPs with the appearance of weak concentric SAED rings. The EcS-Cu NPs showed significant synergistic antibacterial influence verses S. aureus, E. coli, P. aeruginosa, and E. aerogenes. The uppermost inhibition zone of 13 mm was inscribed against S. aureus bacteria. EcS-Cu NPs exhibited better antibacterial activities against gram positive and gram negative bacteria.

American Journal of Applied Chemistry, 2016

In this study the synthesis of epoxy fatty acid esters of starch (starch vernolates) by the react... more In this study the synthesis of epoxy fatty acid esters of starch (starch vernolates) by the reaction of cassava starch with vernonia oil methyl ester (epoxy ester) using basic catalyst K 2 CO 3 and organic solvent, DMSO as a reaction medium is presented. Under current reaction conditions, a high degree of substitution of 1.24 was achieved, at a reaction temperature of 110°C and 12 hours of reaction time. The new starch vernolates were characterized by Scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicated that the new product is an amorphous material with a continuous and shapeless morphology. The melting point measured by differential scanning calorimetry (DSC) was 118°C. The new synthetic method makes the synthesis of starch vernolates less time consuming and more inexpensive. The differences in melting point and degree of substitution with previously synthesized starch vernolates using enzymatic and chemical catalysis suggest a difference in reaction selectivity via this new reaction path.

Applied Nanoscience, Nov 25, 2020

Ethiopian medicinal plant, Vernonia amygdalina Del. mediated green silver nanostructures (V-SNS) ... more Ethiopian medicinal plant, Vernonia amygdalina Del. mediated green silver nanostructures (V-SNS) were successfully synthesized for the first time. The surface amalgamation of biomolecules of plant leaf extract around Ag nanostructures has also been approved by the most advanced techniques which were employed to characterize the NSs. The presence of absorbance maxima, λ max at 454 nm confirms the formation of V-SNS. UV-DRS studies revealed the band gap of 2.09 eV for NSs. The role of biomolecules as capping agents for V-SNS was authenticated by FT-IR spectra. The presence of four sharp peaks in the XRD pattern of NSs confirmed the highly crystalline nature of NSs. The TGA-DTA studies revealed that Ag NS is thermally stable above 570 °C. The purity of the NSs was corroborated by SEM-EDAX analysis. The average particle size of V-SNS was deduced to be 35.24 nm. In addition, TEM micrographs revealed the presence of V-SNS with varieties of nano-sized shapes. TEM-HRTEM-SAED analysis authenticated the presence of silver NS with interplanar spacing values of 0.248 nm and 0.243 nm which conformed to Ag (111) lattice fringes of silver. The V-SNS showed significant synergistic antibacterial influence versus S. aureus, E. coli, P. aeruginosa, and E. aerogenes. The uppermost zone of inhibition of 18 mm was inscribed against P. aeruginosa bacteria. The better electrochemical properties of V-SNS electrode as revealed by cyclic voltammograms, Nyquist and Bode plots make it suitable for potential electrochemical sensor application. V-SNS exhibited better photocatalytic activities against Acid orange 8 and Acid red 88 dyes. Keywords Medicinal plants • Green synthesis • Vernonia amygdalina Del. • Silver nanostructure • Antibacterial activity • Photocatalysis Abbreviations NS Nanostructure NP Nanoparticle SNS Silver nanostructure V-SNS Vernonia amygdalina Del. mediated silver nanostructure XRD X-ray diffractometer UV-DRS Ultraviolet diffused reflectance spectra

Materials research express, May 1, 2020

The biogenic/green silver nanoparticles (g-Ag NPs) were synthesised by using the extract of indig... more The biogenic/green silver nanoparticles (g-Ag NPs) were synthesised by using the extract of indigenous medicinal plant of Ethiopia, Hagenia abyssinica (Brace) JF. Gmel. leaf extract for the first time, to investigate the synergistic effect of biomolecules towards the enhancement of electrochemical properties of NPs. The synthesized g-Ag NPs were characterized by UV-visible, UV-DRS, FT-IR, XRD, SEM, EDXA, TEM, HRTEM and SAED techniques. The maximum absorbance, λ max was found to be 461 nm for g-Ag NPs due to surface plasmon resonance. The energy gap, Eg of NPs, was found to be 2.31 eV. FTIR spectrum confirmed the presence of bioactive compounds responsible for possible capping and stabilisation of g-Ag NPs. The XRD analysis revealed that the g-Ag NPs are highly crystalline exhibiting sharp peaks for (111), (200), (220) and (311) planes in the diffraction pattern. SEM and TEM micrographs showed differently shaped Ag particles in addition to spherical shape. The average particle size of NPs was found to be 24.08 nm using imageJ analysis. EDX analysis confirmed the presence of Ag in the g-Ag NPs. In addition, the SAED pattern of g-Ag NPs presented concentric patterns for 4 major planes of crystalline silver. The d-spacing values of 0.2428 nm, 0.2126 nm, 0.1483 nm and 0.1263 nm corresponds to d111Ag, d200Ag, d220Ag and d311Ag lattice fringes respectively. The cyclic voltammetry (CV) results suggest that g-Ag NPs possess better electrochemical properties due to its lower charge transfer resistance value of 17 Ω. EIS studies too revealed better stability of g-Ag NPs as electrode materials.

Adsorption Science & Technology, Jan 10, 2022

Degradation of dye pollutants by the photocatalytic process has been regarded as the most efficie... more Degradation of dye pollutants by the photocatalytic process has been regarded as the most efficient green method for removal organic dyes from contaminated water. The current research work describes the synthesis of Fe 3 O 4 @SiO 2 @Ru hybrid magnetic composites (HMCs) and their photocatalytic degradation of two azo dye pollutants, methyl orange (MO) and methyl red (MR), under irradiation of visible light. The synthesis of Fe 3 O 4 @SiO 2 @Ru HMCs involves three stages, including synthesis of Fe 3 O 4 magnetic microspheres (MMSs), followed by silica (SiO 2) coating to get Fe 3 O 4 @SiO 2 MMSs, and then incorporation of presynthesized Ru nanoparticles (~3 nm) onto the surface of Fe 3 O 4 @SiO 2 HMCs. The synthesized HMCs were characterized by XRD, FTIR, TEM, EDS, XPS, BET analysis, UV-DRS, PL spectroscopy, and VSM to study the physical and chemical properties. Furthermore, the narrow band gap energy of the HMC photocatalyst is a significant parameter that provides high photocatalytic properties due to the high light adsorption. The photocatalytic activity of synthesized Fe 3 O 4 @SiO 2 @Ru HMCs was assessed by researching their ability to degrade the aqueous solution of MO and MR dyes under visible radiation, and the influence of various functional parameters on photocatalytic degradation has also been studied. The results indicate that the photocatalytic degradation of MO and MR dyes is more than 90%, and acid media favors better degradation. The probable mechanism of photodegradation of azo dyes by Fe 3 O 4 @SiO 2 @Ru HMC catalysts has been proposed. Furthermore, due to the strong ferromagnetic Fe 3 O 4 core, HMCs were easily separated from the solution after the photocatalytic degradation process for reuse. Also, the photocatalytic activity after six cycles of use is greater than 90%, suggesting the stability of the synthesized

Journal of Nanostructures, 2021

The medicinal plant, Syzygium guineense (Willd.) DC (Waterberry) mediated green copper oxide nano... more The medicinal plant, Syzygium guineense (Willd.) DC (Waterberry) mediated green copper oxide nanostructures (SyG-CuO NSs) were successfully synthesized for the first time in Ethiopia. The antibacterial activity of CuO NSs capped by biomolecules of the plant leaf extract has been investigated. The UV-visible, UV-DRS, FT-IR, XRD, TGA-DTA, SEM, EDXA, TEM, HRTEM and SAED techniques were employed to characterize the NSs. The presence of two absorbance maxima, λ max 1 and λ max 2 at 423 nm and 451 nm, respectively confirms a mixture of copper oxide (E g =1.93 eV). FTIR spectra confirmed the presence of biomolecules with SyG-CuO NSs. The XRD patterns of NSs confirmed the presence of CuO with high crystallinity. The purity of the NSs was confirmed by SEM-EDAX analysis. In addition, TEM-HRTEM-SAED analysis revealed the d-spacing value of 0.2854 nm which corresponds to CuO (111) lattice fringe. SyG-CuO NSs showed good antibacterial effect against both Gram-positive bacteria, S. aureus (12 mm), and Gram-negative bacteria, E. coli (12 mm), P. aeruginosa (10 mm), and E. aerogenes (12 mm). The bioactive compounds capped around the CuO NPs served the effective role in disrupting the cell wall of bacterial strains. The CV and EIS studies confirmed the better electrochemical properties for SyG-CuO with low charge transfer resistance value of 49 Ω. These CuO NSs exhibited multifunctional applications.

Journal of Molecular Structure

Journal of Chemistry, Sep 27, 2022

Recently, heteroleptic coordination between essential metallic elements with semicarbazone-based ... more Recently, heteroleptic coordination between essential metallic elements with semicarbazone-based derivatives attracts more consideration for the varied ranges of bioactivities. Semicarbazone-based moiety holding azomethine (C N) group become exible ligands, forming stable complexes. rough a stirring and re ux technique, a novel heteroleptic complex of copper (II) was synthesized by reacting two semicarbazone-based derivative ligands, ortho-phthalaldehyde disemicarbazone (L 1) and dehydrozingerone semicarbazone (L 2), with copper chloride salt in 1 : 1 : 1 molar ratio. Magnetic moment measurement, elemental analyzer, thermogravimetric (TGA) analysis, and several spectroscopic techniques were applied to describe the prepared compounds. e disc di usion and DPPH methods were actually used to investigate the antibacterial and antiradical potentials, respectively. e obtained data indicates the ligand (L 1) has good mean inhibition zones on Staphylococcus aureus (12.42 ± 0.00 mm) and S. pyogenes (11.64 ± 0.12 mm) bacteria. e heteroleptic [Cu(L 1) (L 2)] complex displayed higher antibacterial actions (13.67 ± 0.52 mm) on Streptococcus pyogenes bacteria. e [Cu(L 1) (L 2)] complex also shows better antiradical potential (63.7%). Furthermore, the docking result of prepared compounds on S. aureus gyrase con rms the ligands (L 1 and L 2) and the complex potential molecules possess the smallest binding potential of −8.0 to −8.4 kcal/mol. A higher value was achieved by [Cu(L 1) (L 2)] complex (−8.4 kcal/mol). us, this study indicates an insight towards combining semicarbazone form derivatives of natural source origin with a synthetic compound as ligands through metal coordination could enhance bioactivity.

Addis Ababa University, Jun 6, 2012

International Journal of Advanced Research, 2018

Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with Lphenylalanine and maleic acid ... more Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with Lphenylalanine and maleic acid in the presence of Dimethylformamidewater mixtures in the concentration range of 0-50% v/v DMF has been studied pH-metrically at a temperature of 303K and at an ionic strength of 0.16 mol L −1. The selection of best fit chemical models is based on statistical parameters and residual analysis. The predominant species detected were ML, ML 2 , and ML 2 H 2 for Co(II), Ni(II), and Cu(II). The appropriateness of the experimental conditions were verified by introducing errors deliberately. The models containing different numbers of species were refined by using the computer program MINIQUAD75. The chemical speciation was explained based on the distribution diagrams drawn using HYSS HYPERQUAD. The trend in variation of stability constants of the complexes with dielectric constant of the medium was attributed for the formation and possible structures of the complex species presented.

Environmental Engineering and Management Journal, 2020

Inorganic ceramic materials is receiving more attention in recent times due to their unique chara... more Inorganic ceramic materials is receiving more attention in recent times due to their unique characteristics which include different pore structures, hydrophilic surfaces, high chemical, thermal and mechanical stabilities that offer avenues for application in water treatment. In the present work, cost-effective clay ceramic water filters of different designs were developed from clay (50, 60, and 70) %, sawdust (15, 20, 25, and 35) %, grog (5, 10 and 15)% ratios plus 5% bone char by volume and sintered at temperature of 950ºC for 6 hrs. For the flow rate, fluoride and nitrite tests synthetic waters were used, while for Escherichia coli removal efficiency test of the filter diluted wastewater sample collected by purposive sampling methods from Modjo River was used. The analysis of the optimal performing sintered filter by X-ray diffraction revealed the existence of mixed phases such as quartz, mulite and ilite. The surface functional group analysis by infrared spectroscopy showed the presence of strong bands at 3696 cm-1 , 3622 cm-1 , 3450 cm-1 of hydroxyl linkages. Field emission scanning electron microscopy of fractured filter surfaces with better performance showed the formation of interconnected porous microstructure materials. The ceramic water filter developed from 50% clay, 15% grog, 35% sawdust, and 5% bone char, (C950-50-35-15), characterized with total porosity 36.33±0.05%, displayed flow rate 1.91±0.55L/h and E. coli, nitrite, and fluoride removal efficiencies of 99.91±0.09%, 76.00±0.22%, and 96.8±0.41% respectively.

Starch - Stärke, 2014

A new method for the preparation of epoxy fatty acid esters of cassava starch (starch vernolates)... more A new method for the preparation of epoxy fatty acid esters of cassava starch (starch vernolates) is presented based on the reaction of cassava starch with vernonia oil methyl ester (epoxy ester) using only 1-butyl-3-methylimidazolium chloride, [C4C1im]Cl, ionic liquid as a reaction medium and a cheap inexpensive base such as pyridine as a catalyst. Under the reported reaction conditions, a high degree of substitution of 1.03 was achieved, at a reaction temperature of 110°C and 24 h reaction time. The new starch vernolates were characterized by infrared spectroscopy (FTIR) and solid state NMR (CP/MAS 13C NMR). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that the new product is an amorphous material with a continuous and shapeless morphology. The melting point measured by differential scanning calorimetry (DSC) is 111.4°C. The new synthetic method makes the synthesis of starch vernolates less time consuming and more inexpensive. The differences in melting point and degree of substitution with previously synthesized starch vernolates using enzymatic catalysis suggest a difference in reaction selectivity via this new reaction path.