Bimetallic Nanoporous Sponges

Abstract

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.