Synthesis, Characterization and Applications of Metal Oxides Nanostructures

Muhammad Tariq Jan, . (2015) Synthesis, Characterization and Applications of Metal Oxides Nanostructures. Doctoral thesis, INTERNATIONAL ISLAMIC UNIVERSITY, ISLAMABAD.

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Metal oxides (MOs) nanostructures represent new class of materials which have been explored for various applications such as solar cells, sensors, fuel cells, microelectronic circuits, photocatalysts, antibacterial agents and piezoelectric devices due to their unique physiochemical properties. MOs nanostructures have changed or enhanced characteristics in contrast to their bulk counterparts. Various physiochemical properties of MOs nanostructures are hugely dependent on their particle size and shape. Fabrication of MOs nanostructures with strict control over the above mentioned parameters, exploration of their unique physiochemical characteristics and applications have attracted enormous interest in various fields of science and technology. In this thesis, first of all different MOs nanostructures such as ZnO, CuO, SnO2 and CeO2 have been synthesized by chemical co-precipitation technique and characterized by XRD, SEM, FTIR and UV-visible spectroscopy analysis. XRD results reveal the single-phase formation of all MOs. Spherical nanoparticles are observed in case of ZnO, SnO2 and CeO2 samples, while hierarchal nanostructures are observed in case of CuO sample. The average particle sizes obtained from SEM images are 25 nm, 28 nm and 30 nm for ZnO, SnO2 and CeO2 nanostructures, respectively. The antibacterial characteristics of four different MOs nanostructures against E. coli bacterium has been assessed by agar disc method. The order of antibacterial activity for different MOs nanostructures is found to be the following: ZnO>SnO2>CeO2>CuO. Among these, the most efficient antibacterial agent ZnO has been selected and an effort is made to tailor its various physical properties by tuning its morphology, particle size and selective chemical doping in order to enhance its antibacterial potency. SnxZnO1-x (where x = 0, 0.02, 0.04 and 0.06) nanostructures have been prepared via co-precipitation meth0d. The detailed study has depicted the prepared SnxZnO1-x samples have hexagonal wurtzite structure. The shift in the main diffraction peak (101), increase in the particle size, modification in morphology, and tailoring in the excitation absorption peak with increases in Sn concentration into ZnO clearly demonstrate the successful substitution of Sn dopant into the host matrix. It is observed from the antibacterial tests that Sn doping enhances the antibacterial activity of ZnO nanostructures. It is found that shape and size of ZnO nanostructures along with the percentage Sn dopant remarkably manipulate its antibacterial potency. In the next step, AgxZnO1-x (where x = 0, 0.02 and 0.04) nanorods have been prepared via chemical route and their structural, morphological, Raman, optical properties and antibacterial activity are studied. Structural analysis has revealed that Ag doping cannot deteriorate the structure of ZnO and wurtzite phase is maintained. Scanning electron microscopy results have demonstrated the formation of ZnO nanorods. These nanorods have observed to have average diameter of 96 nm and length of 700 nm, respectively. Raman spectroscopy results suggest that the Ag doping enhances the number of defects in ZnO host matrix. It has been found from optical study that Ag doping results in positional shift of band edge absorption peak. This is attributed to the successful incorporation of Ag dopant into ZnO host matrix. The surface defects have been observed to play major role to enhance antibacterial activity of Ag doped ZnO nanorods as compared to undoped ZnO. Moreover, NixZnO1-x (where x = 0, 0.02, 0.04 and 0.06) nanorods have been synthesized via same procedure as used for the synthesis of AgxZnO1-x nanorods. It has been found that though Ni dopant is not able to alter the wurtzite structure of ZnO nanorods but strongly influence the length and diameter of the nanorods. Raman spectroscopy results show that the E1LO phonons mode band shifts to the higher values with Ni doping, which is attributed to large amount of crystal defects. Ni doping is also found to tune the optical properties of ZnO nanorods. Ni doping has also greatly enhanced the antibacterial potency of ZnO nanorods. Finally, CuO nanostructures doped with Ce at different concentration levels have been synthesized via a simple co-precipitation technique. Structural studies exhibit the presence of a monoclinic structure of CuO for CexCuO1-x (where x = 0, 0.02, 0.04 and 0.06) samples without any additional impurity phases. SEM images have revealed the rod-like morphology with an average diameter of 30 nm for undoped CuO. The optical band gap of CuO has been observed to be decreased with doping which is assigned to the integration of the impurity band with the conduction band of CuO. The Ce doping induced effects on the antibacterial activity of the prepared CexCuO1-x nanostructures have been examined by recording the growth curves of bacteria in the presence of prepared nanostructures. It has been observed that S. aureus bacterium may be completely eradicated by the use of Ce doped CuO nanostructures. The cytotoxicity analysis of all the prepared nanostructures has shown that the synthesized nanostructures are biocompatible and non-toxic towards the human cell line SH SY5Y cells. The bio-safe and biocompatible nature of the synthesized nanostructures along with the tunable optical properties and significant antibacterial potency make them potential for various applications in industrial, environmental and health sector.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Synthesis,Characterization,Metal Oxides
Subjects: Q Science > QC Physics
Depositing User: Ms Maryam Saeed
Date Deposited: 26 Oct 2017 04:08
Last Modified: 26 Oct 2017 04:08

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