ZnO Nanostructures: Low-Temperature Synthesis, Characterisation, Their Potential Application as Gene-Delivery Tools

Among metal oxide nanomaterials, zinc oxide (ZnO) nanostructures are one of the most important nanomaterials in today’s nanotechnology research. Over the past several decades, ZnO nanostructures have been extensively investigated for their extraordinary physical and chemical characteristics and also for their prominent performance in various novel applications such as photonics, optics, electronics, drug delivery, cancer treatment, bio-imaging, etc. However, the functionality of theses nanomaterials is eventually dictated by the capability to govern their properties including shape, size, position, and crystalline structure on the nanosized scale. This thesis investigates the solution-based synthesis of ZnO nanostructures and their morphological and structural properties. Importantly, in order to achieve the promising structure of ZnO, a systematic investigation of the influence of processing parameters, including solution concentration, time and temperature of growth reaction on the resultant materials was addressed. The other main point for this work is not only to effectively control the morphology, size, uniformly distribution, and orientation of ZnO nanomaterials, but also to build a good comprehension of the mechanism of the fabrication process to raise their performance in future nanoscale applications. Furthermore, the catalytic effect of RF sputtered gold (Au) thin layer on Si substrate prior to ZnO growth was investigated to demonstrate the contributory for the remarkable catalytic activity of Au nanoparticles in the formation of high-quality ZnO nanostructures. Furthermore, we introduce an effective, inexpensive lithographic patterning method to consistently control the position of solution-processed ZnO nanowires. Nanosphere lithography technique (NSL) utilizes a catalyst-assisted pattern generated by employing colloidal self-assembled crystal of polystyrene spheres (PS) on the substrate surface to guide the hydrothermal growth of ZnO nanowires. Further, we fabricate 3D NFs and branched NFs of ZnO on a silicon substrate via a simple and cost-effective solution growth method, incorporating with seed ZnO nanoparticles deposition. The synthesis of 3D branched ZnO nanostructure could potentially exploit for applications in optoelectronics, catalysis, sensing, and photovoltaics. In addition to the synthesis of 1D and 3D ZnO nanostructures, their morphology and distribution have been analysed via scanning electron microscopy (SEM) while the surface topography was analysed by atomic force microscopy (AFM). The crystalline structure, phase purity, and particle size of ZnO nanomaterials have been investigated using X-ray diffraction (XRD). The outcomes from all these efforts have been integrated for cellular investigation via fluorescence microscopy technique (FM) to demonstrate the potential application of ZnO nanostructures as a gene delivery/-tissue engineering tool in different expression systems.