Bactericidal copper nanostructures by chemical dealloying

Healthcare acquired infections (HAIs), particularly bacterial infections, are a significant threat to the lives of patients in healthcare environments. This issue is amplified by the ever-increasing rise of antibiotic resistance and insufficient new and effective antibiotics currently in development. HAIs are most commonly transmitted to patients through exposure to high traffic "touch surfaces", requiring more effective infection prevention and control measures such as the introduction of intrinsically bactericidal surfaces into healthcare environments. The recent discovery of bactericidal nanostructured surfaces found in nature has prompted the design of bactericidal nanostructured surfaces made from various biocompatible materials. Additionally, the resurgence of the long-known antimicrobial metal copper (Cu) has also seen the development of surfaces made from Cu and Cu-based alloys. Unfortunately, these surfaces have shown the requirement for long exposure times in order to effectively eliminate these pathogenic bacteria. A promising solution to this is through the fabrication of nanostructured Cu surfaces with potential synergistic bactericidal potency, rapidly eliminating bacteria before transmission can occur. However, the cost-effective and scalable fabrication of nanostructured Cu surfaces has yet been demonstrated. Arguably the most promising large-scale Cu nanofabrication technique is known as "dealloying", a selective dissolution process which removes a metal(s) from a precursor alloy, leaving behind a nanoporous structure enriched in the less reactive Cu metal. However, issues of poor mechanical integrity due to stress incurred during the dealloying process has inhibited the promising production and application of robust bulk Cu nanostructures. This thesis addresses these issues by critically examining the influence of precursor alloy microstructure design in the development and accommodation of dealloying-induced stresses. Systematic characterisation of alloy specimen microstructures before and after dealloying using a hydrochloric acid (HCl) solution was performed through a variety of techniques including X-ray diffraction (XRD), scanning electron microscropy (SEM) and transmission electron microscopy (TEM). Using an optimized dealloying design explained within, the bactericidal performance of robust Cu nanostructures was tested against common and life-threatening Staphylococcus aureus (S. aureus) bacteria.