Assembly and application of metal and metal oxide nanowires
Date of Issue2013
School of Physical and Mathematical Sciences
Institute of Materials Research and Engineering (IMRE)
This thesis contains three parts. In the first part, highly SERS active 3D multi-layered wood pile like silver nanowires (AgNW) substrate was prepared using Langmuir Blodgett (LB) via a layer by layer approach. The assembled 3D nanowire substrate has higher and more homogenous SERS enhancement than the 2D monolayer of AgNW due to the increased in hot spots created by vertical stacking of the nanowires layers as shown by Raman mapping results. However, when the number of nanowire layers was increased beyond three layers of AgNW, the increased in SERS signal plateaued off. This can be attributed to the laser penetration depth. In addition, the multilayer AgNW substrate showed an angle independent SERS intensity and had a larger SERS depth cross section, allowing the multilayer AgNW to be more reliable and versatile for future sensing applications. In the second part, highly SERS active free standing silver nanowires (FS AgNW) film was prepared using vacuum filtration technique. The high SERS enhancement effect is due to the increase in SERS hot spots formed at the junctions of the overlapping AgNW within the free standing networks. A lack of correlation between thickness of the prepared free standing Ag NW and the SERS intensity measured was observed. This could be due to the excessive thickness of the FS AgNW. In the final part, we fabricated anatase TiO2 nanowires via hydrothermal method. Acid washing of the initial synthesized sodium titanate nanowires played an important role in determining the final crystal structure of the synthesized nanowires. Incomplete ion exchanged of sodium ions with hydrogen ions during the acid washing process led to the formation of Na2Ti6O13 nanowire instead of the desired anatase nanowire after calcination. Calcination of the synthesized nanowire will increased their photocatalytic rate and the anatase nanowire had the highest photocatalytic rate among all the synthesized nanowires.