| Abstract |
The objective of this master thesis was the synthesis of ZnO micro and nanostructures by a hydrothermal method on various substrates, including glass and seeded glass with Zn or ZnO layers and the control of basic characteristics of these structures through growth parameters, such as crystallinity, morphology, dimensions and hydrophobicity / hydrophilicity.
Zn and ZnO thin layers were deposited on glass substrates using DC Magnetron Sputtering and Aerosol Spray Pyrolysis aiming to study the effect of these different techniques on the characteristics of the deposited structures. The Hydrothermal method applied, leads to nanostructures with different morphologies through the use of (ZnNO3)2 solutions at low temperatures (95o C), subject to parameters such as temperature, concentration of solution, substrate, pH and growth time.
We observed that deposition on glass substrates results in the formation of flower - like microstructures consisting of nanopetals or nanorods with different crystallographic orientations. In addition, the length or diameter of these structures are mainly affected by the concentration of the solution. Glass substrates seeded with Ζn or ZnO layers were necessary in order to produce highly c – axis oriented ZnO nanorods/columns or wires which followed the crystallographic orientation of the substrate, perpendicularly to the (002) plane. Increase of growth time, (varied from 4h to 24h), resulted in improved crystallinity samples.
The study of the effect of these micro-nanostructures on the initial hydrophilicity of the substrates showed that contact angle increases and the substrate converts to hydrophobic. We also observed the variation of contact angle during the UV irradiation of the sample and found that exhibits a remarkable reversible transition from hydrophobic to superhydrophilic behavior before and after exposure to UV light, resulting in reversible efficient wettability changes. Such capability may be useful for self–cleaning applications in the industry.
|
Ανάπτυξη και μελέτη ZnO νανοδομών διαφορετικής μορφολογίας μέσω υδατικών διαλυμάτων και η επίδραση του υποστρώματος
