259 research outputs found
Structural and physical studies of PVC/PVDF doped Nano lithium salt for electrochemical applications
Polymer blend of poly (vinyl chloride) and poly(vinylidene fluoride) of nominal composition (30PVC/70PVDF) wt:wt were prepared in the form of thin films using casting technique. Samples of the same composition doped with gradient concentration of nano lithium salt (LTO) were prepared and studied. Proposed filler was characterized using Fourier transform infrared spectroscopy (FTIR), UV/vis. optical absorption, X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Electron diffraction (ED). Obtained data approve the crystalline nano structure of filler with a cubic structure of average size (25-30 nm). Prepared nano composites were then investigated using different spectroscopic methods. XRD reveals the amorphous nature of the base polymer blend with tendency for increase in crystallinity with increasing the content of lithium salt. FTIR shows a preservation of the main vibrational spectral bands in their position with small variation in the area and intensity of some spectral bands related to the interaction between polymer and filler.
 
Structural and optical characteristics of poly(vinyl alcohol)/carboxymethyl cellulose/ curcumin nanocomposites
ABSTRACT. Curcumin nanoparticles (CurNP’s) were successfully synthesized, characterized, and used as a cross-linking dopant of polyvinyl alcohol/ sodium carboxymethyl cellulose (PVA/CMC) semi-natural polymer blend. Synthesized nanocomposite films of (PVA/CMC/CurNP’s) were characterized using Fourier transforms infrared FTIR spectroscopy and tested for their resistance of different bacterial grams. Obtained data shows that studied PVA polymerized and cross-linked with CMC as a result for hydrogen bonding between the carboxylic groups and with the non-substituted hydroxyl groups of the cellulose molecule. The optical energy gap was found to be sensitive for the CurNP’s doping level, and the indirect transition was dominant in the studied samples. The addition of CurNP’s appears to increase the activity index of all samples against both gram-negative and positive bacteria, and their activity increases with increasing dopant level until a specific optimal concentration.
KEY WORDS: Curcumin nanoparticles, Semi-natural polymer blend, Antibacterial, FTIR, Optical energy gap
Bull. Chem. Soc. Ethiop. 2021, 35(3), 615-624.
DOI: https://dx.doi.org/10.4314/bcse.v35i3.1
Molecular structure and optical attributes of (Na-CMC/SA) natural polymer blend
ABSTRACT. Biopolymers are referred to the bio-degradable polymer that is derived from living organisms in nature or synthesized from renewable materials but needs polymerization. There are consisting of monomeric units that bond together through a covalent bond to obtain large molecules. A biopolymeric blend of sodium carboxymethyl cellulose/sodium alginate (Na-CMC/SA) film was prepared by the casting/solvent evaporation method. In addition to the molecular structure, the optical and molecular geometry of the collected films were characterized. XRD of binary blend investigated the interaction and miscibility among two biopolymers. FTIR of the blend spectrum explicated the conferring of the two polymer group’s vibrations. UV/Vis and optical studies appeared a peak in the binary at the wavelength (227 nm) which explained the high combination between two polymers. Molecular geometry clarifies the assignment of vibrational spectra of pure polymers which implied the important role of the (C=O) group as eventful regions for the two polymers.
KEY WORDS: Sodium carboxymethyl cellulose, Sodium alginate, Na-CMC/SA, FTIR, XRD, UV/Vis
Bull. Chem. Soc. Ethiop. 2022, 36(3), 707-716.
DOI: https://dx.doi.org/10.4314/bcse.v36i3.19  
Corrosion mechanism and bioactivity of borate glasses analogue to Hench’s bioglass
Bioactive borate glasses (from the system Na2O-CaO-B2O3-P2O5) and corresponding glass-ceramics as a new class of scaffold material were prepared by full replacement of SiO2 with B2O3 in Hench patented bioactive glass. The prepared samples were investigated by differential thermal analysis (DTA), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis. The DTA data were used to find out the proper heat treatment temperatures for preparation of the appropriate glass-ceramics with high crystallinity. The prepared crystalline glass-ceramics derivatives were examined by XRD to identify the crystalline phases that were precipitated during controlled thermal treatment. The FTIR spectroscopy was used to justify the formation of hydroxyapatite as an indication of the bioactivity potential or activity of the studied ternary borate glasses or corresponding glass-ceramics after immersion in aqueous phosphate solution. The corrosion results are interpreted on the basis of suggested recent views on the corrosion mechanism of such modified borate glasses in relation to their composition and constitution
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Antecedents and consequences of intellectual capital: a systematic review, integrated framework, and agenda for future research
Data availability:
Data available on request from the authors.JEL Classifcation: M40 · G34.This study systematically reviews the fragmented field of Intellectual Capital (IC) to clarify its antecedents and outcomes. Using a hybrid method that combines bibliometric analysis and a framework-based approach, it examines 170 peer-reviewed articles, focusing on key articles, authors, countries, journals, and themes in IC research. The study introduces a comprehensive framework, summarizing the core elements of IC and providing a foundation for future theoretical, empirical, and conceptual research. Six main clusters were identified through co-citation analysis: three related to IC antecedents, particularly board gender diversity, and three concerning IC consequences, notably firm performance. This research maps out existing gaps in the literature and suggests integrated pathways for advancing IC knowledge. It contributes significantly to IC studies by synthesizing a vast array of literature into an integrated framework, offering new insights that both challenge and complement existing narratives. This framework not only elucidates IC's foundational aspects but also sets a strategic direction for future investigations. The findings underscore the evolving nature of IC research and highlight crucial antecedents and consequences. The study bridges academic research with practical applications, emphasizing IC's role in boosting firm competitiveness and value creation. While recognizing its methodological limitations, the study calls for a diversified perspective in future IC research, aiming to deepen the understanding of IC.Not applicable
Preparation and Characterization of Silver and Gold Nanoparticles and Study Influence on Physical Properties of PVA/PVP nanocomposites
Gold nanoparticles (Au NPs) and Silver nanoparticles (Ag NPs) ware prepared by green synthesis extraction using the Chenopodium murale leaf extract, the obtained (Ag NPs and Au NPs) were investigated by UV/Vis. absorption spectroscopy, transmission electron microscopy, Zetasizer, XRD. The plant extraction leads to produce nanoparticles of spherical shape with size range from 4 to 22 nm. Polyvinyl alcohol (PVA) and polyvinyl Pyrolidone (PVP) blend with mixed silver and gold nanoparticles were prepared by casting method. Amorphous feather of doping polymers blend was characterized by X-ray diffraction. Significant changes within the polymer matrix were monitored from infrared spectroscopy which indicates the interaction between polymer blend and mixed nanoparticles. Both indirect and direct optical energy gaps are calculated and discussed
Copper-based glass-ceramic as an efficient catalyst in the synthesis of pyrazolo[1,5-a] pyrimidineunder solvent-free condition with docking validation as Covid-19 main protease (Mpro) inhibitor
Copper-based oxide glass-ceramic was successfully synthesized through the single-step melt annealing technique. Synthesized glass-ceramics was characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) supported with energy dispersive X-ray (EDX) and mapping. Pyrazolo[1,5-a]pyrimidines 5a-f were synthesized via the reaction of 5-amino-1H-pyrazole-4-carboxamide (1) with enaminones 2a-f in the presence of synthesized oxide glass-ceramic catalyst powder under solvent-free condition. The molecular docking study demonstrated that the COVID-19 main protease (MPro) inhibitor.
KEY WORDS: Pyrazolopyrimidine, Enaminones, Copper-based catalysis, Solvent-free, COVID-19
Bull. Chem. Soc. Ethiop. 2021, 35(1), 185-196.
DOI: https://dx.doi.org/10.4314/bcse.v35i1.1
Effect of aluminum oxide on the structure and conduction behaviors of silver borate glasses
ABSTRACT. The current study focuses on glass preparation and characterization in the glass system of chemical formula xAl2O3 (35-x) Ag2O.65B2O3 (0≤x≤35 mol%), where Ag2O is replaced with Al2O3. To examine a wide range of both structure and morphology of the prepared glasses, nuclear magnetic resonance (NMR) of 27Al nuclei, X-ray diffraction (XRD) spectroscopy, and transmission electron microscopy (TEM) are used. In Al2O3-rich glass, the well-formed AlO6, AlO5, and AlO4 structural groups are the well-formed units. In samples of (20 and 30 mol % Al2O3), tetrahedral AlO4 and traces from AlO6 units could be detected. At lower concentrations of Al2O3 (10 mol%), the dominant forming unit is only AlO4 groups containing non-bridging oxygen bonds (NBO). The XRD spectra confirm the amorphous nature of the glasses of Al2O3 ˂20 mol% while glasses of higher Al2O3 concentrations contain crystalline Ag2Al2B2O7 formed due to the higher oxygen packaging of the mixed AlO5 and AlO4 compared with that of glasses containing only AlO4 species only. The morphology of crystalline units is confirmed from TEM to differ from that of an amorphous composition. The increase of activation energy and the hardness number of the glasses led to an increase in the durability of the investigated glasses.
KEY WORDS: Aluminum borate glass, NMR, Coordination of aluminum atom, Conductivity, Crystallization process
Bull. Chem. Soc. Ethiop. 2022, 36(3), 597-606.
DOI: https://dx.doi.org/10.4314/bcse.v36i3.9  
Effect of MWCNT doping on the structural and optical properties of PVC/PVDF polymer blend
Thin film samples of pristine polyvinyl chloride (PVC), poly vinyldine fluoride (PVDF) in combination with their blend in addition to samples containing factorial mass fraction of multi wall carbon nano-tubes (MWCNTs) in the dopant level were prepared via routine casting technique using tetrahydrofurane (THF) as a common solvent. X-ray diffraction and transmission electron microscopy (TEM) depict the nano-scale (15-25 nm) of functionalized MWCNTs with no surface damage results from functionalization process.X-ray diffraction (XRD) shows a semi-crystalline nature of PVDF with evidence for more than one phase namely a and b phases. The fraction of b phase was calculated and correlated to the dopant content. FTIR optical absorption spectra revels a preservation of the main vibrational bands before and after addition of MWCNTs in the doping level with a presence of new small band 1151 cm-1 assigned for the interaction and complexation between constituents
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