Bioinspired bactericidal surfaces with polymer nanocone arrays.

Infections resulting from bacterial biofilm formation on the surface of medical devices are challenging to treat and can cause significant patient morbidity. Recently, it has become apparent that regulation of surface nanotopography can render surfaces bactericidal. In this study, poly(ethylene terephthalate) nanocone arrays are generated through a polystyrene nanosphere-mask colloidal lithographic process. It is shown that modification of the mask diameter leads to a direct modification of centre-to-centre spacing between nanocones. By altering the oxygen plasma etching time it is possible to modify the height, tip width and base diameter of the individual nanocone features. The bactericidal activity of the nanocone arrays was investigated against Escherichia coli and Klebsiella pneumoniae. It is shown that surfaces with the most densely populated nanocone arrays (center-to-center spacing of 200 nm), higher aspect ratios (>3) and tip widths <20 nm kill the highest percentage of bacteria (∼30%).

Overlayers on silver nanotriangles: Field confinement and spectral position of localized surface plasmon resonances.

We studied the spectral evolution of plasmon modes associated with silver nanotriangles as a function of dielectric overlayer thickness in the range of 5-300 nm. A substantial red-shift of the resonance is observed that oscillates with increasing over-layer thickness. We explain this previously unreported oscillation through the cavity quantum electrodynamical effect of the array of triangles combined with the dielectric overlayer. The red-shift, though substantial, is less than expected. Comparison with numerical models indicates that this discrepancy is due to very tight field confinement around the tips of the triangles.