Browsing by Author "Kassa, Yirga"

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    Synthesis and Characterization of Zinc Oxide Nanoparticles Conjugated With Ferulic Acid and Investigation of Optical Transition Properties of Ferulic Acid Using Spectroscopic Techniques.
    (Addis Ababa University, 2020-10-16) Kassa, Yirga; Gholap, Ashok (Professor); Mesf in, Belayneh (PhD)
    In this research, synthesis and characterization of zinc oxide nanoparticle (ZnO NP), transition optical properties, self-association properties and the binding of ferulic acid (FA) and ZnO NPs are investigated. ZnO NP was synthesized by sol-gel synthesis approach and its optical, structural properties and its purity were investigated using spectroscopic and microscopic techniques. Equal association constant (EK) dimer model, uorescence quenching method, the Stern-Volmer equation (model) and Van't Ho_ equation were utilized for analyzing and interpreting data. Our _nding revealed that the synthesized ZnO NPs exhibits hexagonal wurtzite structure with lattice parameters a = 0:3250677 nm and c = 0:5212783 nm. It has average grain size and band gap energy are 19:89 nm and 3:29 eV , respectively. It's surface consists of O-H stretching, C-O-H bending, C-O stretching, O-H bending and Zn-O stretching vibration. The mechanism of quenching is static quenching. Bimolecular binding constant decreases as temperature increases. Consequently, the uorescence quenching was initiated by the formation of non-uorescent FA-ZnO NP complex. Enthalpy and entropy changes were found to be 􀀀53:301 kJ=mol and 􀀀76:27 J=Kmol. Accordingly, Van der Waals and hydrogen bond forces play a major role in FA and ZnO NP interaction. The e_ciency of energy transfer between FA and ZnO NP was obtained to be 52.31%. Increasing FA concentration causes the molecules to aggregate and to shift the absorbance maxima. The enthalpy and entropy changes were obtained to 10:703 kJ=mol and 110:02 (J=Kmol), respectively at all temperatures and Gibbs free energy at the temperatures 298 K, 310 K and 320 K were 􀀀22:084, 􀀀23:405 and 􀀀24:505 (KJ=mol), respectively.