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Synthesis, Characterization and Application of Silver Allied Nanobimetallic particles for Catalysis

Adekoya , J. A (2014) Synthesis, Characterization and Application of Silver Allied Nanobimetallic particles for Catalysis. ["eprint_fieldopt_thesis_type_phd" not defined] thesis, Covenant University, Ota.

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The synthesis of seed mediated AgM (M = Co, Ni, Ru, Pd and Pt) allied nanobimetallic particles was successfully carried out by simultaneous reduction in aqueous and non-aqueous solutions. The formation of novel monodispersed and unaggregated bimetallic nanoparticles capped by polymer and organic chelating agents was desirable for catalysis and photonic applications. As a result, wet chemical approach was successfully deployed to produce some novel bimetallic silver allied nanoparticles distinct in morphology from their monometal analogues. Optical and morphological investigation of the nanoparticles revealed that the shape, size and size distribution of the silver allied nanoparticles depended on the stabilizer or capping agent, mole ratio of inorganic sources, temperature and time of reaction. The analyses of the nanoparticles also showed that formation of uniformly distributed, highly crystalline and monodispersed/polydispersed silver allied bimetallic nanocomposites of different dimensions within the quantum realm had been achieved. Consequently, the alloy or core-shell crystalline structure of nanocomposites was also established. Furthermore, X-ray photoelectron spectrometer (XPS) scan established the surface elemental composition and the binding energy of the nanocomposites. As a result, a new morphology described as hybrid quasi nanocubes entangled in nanowebs was discovered for polyvinylpyrrolidone (PVP) stabilized AgPt nanoparticles passivated by diethylene glycol (DEG) and ethylene glycol (EG) which evolved a core-shell structure. The mean size of the nanocubes was 30.45 6.23 nm, while XRD analysis strongly suggested that the nanocubes pertained to {111} plane of face-centered cubic Ag. Meanwhile, the nanoweb was formed as a result of phase contraction by Pt. Likewise, electron micrographs of Ag/Ru nanoparticles capped by dodecanethiol/polyol at 200⁰C; 3h showed the presence of novel well-ordered core-shell structures with particle size in the range of 8.2 ± 0.7-11.4 ±1.3 nm. In addition, novel core-shell nanoparticles of AgPt capped by hexadecylamine (HDA) were discovered from their electron micrographs. The X-ray diffraction spectra suggested dominance of face-centered cubic structure with 2θ reflections slightly shifted from silver peaks. This is reminiscent of noble metals forming alloy or core-shell morphology with silver. Similarly, AgCo and AgNi nanoparticles passivated by polyol particularly revealed the formation of nearly uniform, monodispersed core-shell structure which proved to be optically active by characteristic surface plasmon resonance band blue shifted for pentaerythritol (PET) and trisodium citrate trihydrate (SC) derived nanoparticles. Further optical characterization also revealed the fluorescent potential of AgCo, AgNi, AgPt, AgPd and AgRu sols as a result of their S1-S0 xxvii vibrational mode relaxation with appreciable emission of appropriate quantum yield. Finally, the catalytic potential of the nanocomposites investigated using 4-nitrophenol in the presence of sodium borohydride at 299 K indicated a pseudo-first-order kinetics which gave AgPd/PVPGLY a rate constant of 5.4 x 10-3 s-1. This value is significantly higher than 2.8 x 10-3 s-1 reported for poly(ethylenimine)-stabilized Ag nanoparticles (Ag-HNP), but relatively lower than 9.2 ± 1.7 × 10-3 s-1 recorded for AuAg-HNP due to the fact that Au/Ag bimetallic nanoparticles have been shown to exhibit greater quantum size effect. These results strongly indicate the application of these materials for catalysis and optoelectronics.

Item Type: Thesis (["eprint_fieldopt_thesis_type_phd" not defined])
Subjects: Q Science > QD Chemistry
Divisions: Faculty of Engineering, Science and Mathematics > School of Chemistry
Depositing User: Mrs Patricia Nwokealisi
Date Deposited: 21 Jan 2015 22:03
Last Modified: 21 Jan 2015 22:03

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