Browsing by Author "Olabemiwo OM"

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    Green synthesis of silver nanoparticles using stem bark extract of Annona senegalensis: Characterization and its antibacterial potency
    (2021) Olabemiwo OM; Akintelu SA; Waheed AA; Okunlola DS; Akinwale DR; Adeyinka GC; Adeniji TW; Adebisi SA
    The green synthesis of nanoparticles has been a vital aspect in the search for novel antimicrobial agents. This research aimed at biosynthesis, characterization and preliminary evaluation of the antibacterial properties of silver nanoparticles (AgNPs) from the back extract of Annona senegalensisis. The bark of Annona senegalensis was scraped from the stem, washed, air-dried, pulverised and extracted. Four millilitre (4 ​ml) of the extract was pipetted into 36 ​mL (36 ​ml) of silver nitrate solution (5 ​mM AgNO3) in a conical flask. The resulting solution was subjected to magnetic stirring at room temperature (28 ​°C ​± ​2) till AgNPs were formed. The synthesized AgNPs were filtered, washed with deionized water and dried in oven at 40 ​°C. Fourier transform infrared (FTIR) analysis was carried out on the synthesized AgNPs. The AgNPs synthesized was also characterized with UV–visible spectrophotometer (UV), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy to ascertain the physico-chemical and morphological properties of the AgNPs. The antimicrobial investigation was carried out following standard method. The observation of colour change (pale yellow to dark brown) during the synthesis and maximum absorbance at wavelength 431.19 ​nm in the UV spectrum confirmed the formation of AgNPs. The FTIR analysis showed that the biomolecules responsible for the reduction of silver ion contain O–H functional groups. The electron microscopy studies indicated that the AgNPS are spherical in shape with nanoparticles sizes of 11–24.76 ​nm. EDX analysis showed that the AgNPs contain high amount of silver and few other elements. The antimicrobial study showed high zones of inhibition 22.75–33.75 against tested bacteria. The simplicity of the synthesis of AgNPs from the extract of the stem bark of Annona senegalensisis and relatively high zones of inhibitions shown by the AgNPs are strong evidences of the possible application of Annona senegalensisis in the synthesis of novel therapeutic agent against infections from bacteria and fungi.
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    The effects on oxidative aging, physical and flow properties of Agbabu natural bitumen modified with silver nanoparticles
    (2020) Olabemiwo OM; Lateef A; Agunbiade FO; Akanji SB; Bakare HO
    The quest for improvement in service life and performance of road pavement via reduction of oxidative aging failure of bitumen, led us to the investigation of novel application of Silver nanoparticles (AgNPs) as potential anti-oxidative material for Agbabu natural bitumen (ANB). The raw ANB was purified to form the base and the base modified in a stainless reactor using AgNPs via melt blend technique at temperature of 120 °C under stirring at 1200rpm. The proportions of AgNPs used for the modification were 1.5, 3.0 and 4.5 wt% and long-term aging was thermally simulated on the base and modified base samples at 60 °C. The aged samples were then subjected to Fourier Transform Infrared (FTIR) Spectroscopic Analysis to study the changes in the size of the peaks of the oxidation-related compounds. Physical and flow parameters (PFPs) of the base and modified base samples were characterized using softening point temperature, kinematic viscosity, penetration index, flash and fire points, penetration, kinematic viscosity and Oscillatory disc Rheometer (ODR) test. FTIR analysis showed that the AgNPs incorporation into ANB at 1797 cm−1, 1217 cm−1, 1300 cm−1 and 1097 cm−1 in the spectrum of the base sample. The sulphoxide peaks at 1031 cm−1 was completely obliterated. There was progressive reduction in the area of the carbonyl peak at 1693 cm−1 implying progressive lowering of the carbonyl index value with increasing in the amount of AgNPs used in the modification. These changes are attributable to the anti-oxidative potential of the AgNPs. The mechanism of the anti-oxidative effect of AgNPs is proposed to be due to scavenging of the free radical produced in the oxidation process. The values of softening point temperature, kinematic viscosity, penetration index, and flash and fire points increased while that of penetration and specific gravity reduced as the quantity of AgNPs in the base increased. The ODR test showed that, the modified samples compared to base sample at lower and higher road pavement temperatures are less prone to fatigue cracking and rutting, respectively. Thus, this study provides preliminary information about the novelty of AgNPs as potential antioxidant for improving the durability/performance of bitumen in pavements.