Browsing by Author "Alzahrani, Sanaa Abdullah M"

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Bimetallic Nanoporous Sponges
(University of Technology Sydney, 2025-02-11) Alzahrani, Sanaa Abdullah M; Dowd, Annette Roslyn, Cortie, Michael Bernard, De Silva, Sujeewa Sujeewa Buddhimali
Nanoporous silver (np-S) is a promising nanomaterial with unique physical properties distinct from its bulk counterpart, including high surface area, enhanced chemical sensing and tuneable optical and electrical properties. This thesis explores the fabrication and characterisation of np-S thin films and bulk structures using the dealloying method. Ag-Al alloy precursors with varying aluminium content (24.6–72.6 at.%) were sputter-deposited as thin films and dealloyed in NaOH, resulting in a ligament-pore structure. Smaller ligament sizes (13 nm) increased electron scattering, increased electrical resistivity and altered optical behaviour toward less metallic characteristics. Additionally, gradient np-S thin films (G-np-S) were synthesized, showing systematic shifts in optical properties and enhanced Surface-Enhanced Raman Spectroscopy (SERS) activity with decreasing pore size. Antibacterial studies against Pseudomonas aeruginosa and Escherichia coli revealed that np-S films with smaller ligaments exhibited moderate antibacterial effects due to increased surface area. Heat treatment of bulk Al-Ag precursors affected morphology, increasing pore and ligament sizes, which improved antibacterial performance against E. coli due to structural homogenisation. This research demonstrates the potential of np-S for applications in biosensors, plasmonic photocatalysis, and optical devices, highlighting the role of preparation conditions in controlling morphology, in turn tuning its electrical, optical and antibacterial properties.
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Electrical resistance measurements of silver nanowire junctions using Conductive Atomic Force Microscopy
(Saudi Digital Library, 2017-09-25) Alzahrani, Sanaa Abdullah M; Hoxley, David; Langley, Daniel
Transparent conductive materials (TCMs) are in high demand for widespread applications, including organic light-emitting diode displays, touch panels, solar cells. TCMs have conventionally been made from indium tin oxide (ITO) as it offers high electrical conductivity and transparency. However, as a brittle ceramic, its usage in future applications in building flexible electronic devices has become limited. Networks of silver nanowires (AgNWs) are an alternative TCM material, displaying flexibility and high optical transmittance. However, their low sheet resistance relies on minimizing the contact resistance between individual silver nanowires, which remains a major challenge. We have used an Atomic Force Microscope (AFM) to measuring the electrical resistance of individual nanowire junctions and conducting pathways in networks deposited on glass substrates. It was found that mechanical pressing at room temperature improves the electrical conductivity of the AgNW networks, but considerable resistance remains. This is attributed to residual layer of organic contamination from the dispersants used in the films formation process. Possible treatments to reduce this are discussed.
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