Department of Biological Sciences
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Item Catalytic degradation of methylene blue by iron nanoparticles synthesized using Galinsoga parvifora, Conyza bonariensis and Bidens pilosa leaf extracts(Springer Nature Switzerland, 2019-09) Makhanu, David Sujee; Kareru, Patrick Gachoki; Wanakai, Sammy Indire; Madivoli, Edwin Shigwenya; Maina, Ernest Gachui; Nyabola, Augustine OtienoGreen synthesized metallic nanoparticles are environmentally friendly, bio-compatible, and highly stable. The aim of this study was to synthesize iron nanoparticles (FeNPs) from FeCl3 solution using aqueous leaf extracts of Galinsoga parvifora (Gp), Conyza bonariensis (Cb) and Bidens pilosa (Bp) and use them in degradation of methylene blue dye. The iron nanoparticles were characterized using UV–Vis spectrophotometer, FT-IR spectrophotometer, X-ray Fluorescence (EDXRF), X-ray difractometer (XRD), and scanning electron microscope (SEM). Phytochemical screening for presence of secondary metabolites revealed presence of phenolics, phytosterols and favonoids. The total phenolic and favonoid content in Galinsoga parvifora, Conyza bonariensis and Bidens pilosa leaf extracts were 57.67±1.27, 117.13±0.03, 126.27±0.013 mg Gallic Equivalent/g of Dry Weight (mg GAE/g DW) and 39.00±0.56, 45.50±0.59, 33.13±0.81 mg Rutin Equivalent/g of Dry Weight (mg RE/g DW) respectively. The UV–Vis spectrum of FeCl3 had a shoulder at 320 nm, which disappeared upon addition of G. parvifora, C. bonariensis and B. pilosa extracts confrming formation of iron nanoparticles. Evaluation of iron content of the synthesized nanoparticles revealed that the iron content in G. parvifora, C. bonariensis and B. pilosa extracts was 51, 47 and 44% respectively. XRD data revealed presence of a large amorphous coating that masked iron peaks, though 2 theta values observed have been reported to be of iron oxides. Methylene blue degradation studies revealed that CbNPs, BpNPs and GpNPs synthesized were good biocatalysts as they degraded the dye by 86, 84.3 and 92% respectively. Therefore, green synthesized iron nanoparticles is cost efective and environmentally safe in providing insight in the environmental removal of dyes.Item Phytofabrication of Iron Nanoparticles and their Catalytic Activity(Springer Nature Switzerland AG 2019, 2019-06-20) Edwin, Shigwenya Madivoli; Kareru, Patrick Gachoki; Gachanja, Anthony Ngure; Mugo, Samuel Mutuura; Makhanu, David SujeeMetallic nanoparticles that have photocatalytic activity can be synthesized using aqueous plant extracts. The aim of this study was to synthesize iron nanoparticles using Lantana trifolia extracts and to evaluate their ability to degrade Congo red dye. The nanoparticles were characterized using UV–Vis spectrophotometer (UV–Vis), Fourier transform infrared spectrophotometer, wide angle X-ray diffractometer, dynamic light scattering, transmission electron microscopy (TEM), and thermal gravimetric analyzer to determine the functional groups, thermal properties, crystalline phases and diameter distribution of the particles. Cyclic voltammetry was used to evaluate the redox potential of the extracts while photocatalytic activity of the nanoparticles was evaluated using a UV–Vis spectrophotometer. Functional groups analysis revealed presence of secondary metabolites having OH and C=C groups while a redox potential of + 0.3 V was an indication that the extracts can reduce iron. The presence of sharp peaks at 2θ values of 19.87°, 20.22°, 22.88°, 28.81°, 32.73°, 35.32°, 38.45°, 40.23° and 41.08° correspond to cubic crystal system of iron nanoparticles while particle aggregation was observed on TEM micrographs which also indicated that they were less than 200 nm. In the presence of H2O2, the nanoparticles catalyzed degradation of Congo red dye in a first order reaction that was temperature dependent. In conclusion, secondary metabolites in L. trifolia can reduce metallic ion to iron nanoparticles which can degrade Congo red dye.