Photo-responsive antibacterial surfaces combining both on-demand photo-switchable activity and sustained biocidal release were prepared using sequential chemical grafting of nano-objects with different geometries and functions. The multi-layered coating developed incorporates a monolayer of near-infrared active silica-coated gold nanostars (GNS) decorated by silver nanoparticles (AgNP). This modular approach also enables us to unravel static and photo-activated contributions to the overall antibacterial performance of the surfaces, demonstrating a remarkable synergy between these two mechanisms. Complementary microbiological and imaging evaluations on both planktonic and surfaceattached bacteria provided new insights on these distinct but cooperative effects.The development of smart on-demand antimicrobial surfaces has become a critical research area, addressing the issue of indiscriminate use of biocides implicated in the global emergence of antimicrobial resistance 1 . A significant challenge in this field is the need to combine on-demand antimicrobial functions at surfaces with static long-lasting effects. Static antibacterial surfaces are generally based on the release of metal cations with intrinsic biocidal properties 2 , e.g. sustained Ag + release from surface-attached silver nanoparticles [3][4][5] . In this area we have recently demonstrated that after 24 h such surfaces can reduce the colony forming units (CFU) of planktonic Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) by 5-7 orders of magnitude 4 and reduce the surviving fraction of Staphylococcus epidermidis (S. epidermidis) biofilms by 5 orders of magnitude 5 . Alternatively, the use of light-activated antimicrobial surfaces provides a route towards responsive systems that can be triggered remotely and on-demand 6 . Translation of such technology to in vivo applications (e.g. on the surfaces of prostheses and implants) needs to be restricted to systems responding in the narrow near-infrared (NIR) spectral window (750-900 nm) in which water and living tissues are transparent and, therefore, not susceptible to damage [7][8][9][10][11] . In this context, photothermal conversion by non-spherical plasmonic nanoparticles (e.g. nanorods 12 or nanostars) 7 is becoming particularly interesting, allowing the use of local hyperthermia activated by NIR radiation to kill bacteria. In 2014, the first example of combined use of biocidal metal cations and photothermal conversion of light was published 13 , using biomimetically-coated Au/Ag core/shell nanorods, and demonstrating a synergistic antibacterial effect against planktonic E. coli and S. epidermidis bacteria upon NIR irradiation. More recently, we have developed a different approach, specially designed for surfaces, where glass substrates bearing monolayers of non-coated Ag nanoplates 14 or Ag nanotriangles 15 displayed antibacterial effects significantly enhanced upon NIR irradiation with respect to the intrinsic biocidal effects due to the release of Ag + cations. Remarkably, the amou...

Adsorption of thymine on a defined Cu(110) surface was studied using reflection-absorption infrared spectroscopy (RAIRS), temperature programmed desorption (TPD), and scanning tunnelling microscopy (STM). In addition, density functional theory (DFT) calculations were undertaken in order to further understand the energetics of adsorption and self-assembly. The combination of RAIRS, TPD, and DFT results indicates that an upright, three-point-bonded adsorption configuration is adopted by the deprotonated thymine at room temperature. DFT calculations show that the upright configuration adopted by individual molecules arises as a direct result of strong O-Cu and N-Cu bonds between the molecule and the surface. STM data reveal that this upright thymine motif self-assembles into 1D chains, which are surprisingly oriented along the open-packed [001] direction of the metal surface and orthogonal to the alignment of the functional groups that are normally implicated in H-bonding interactions. DFT modelling of this system reveals that the molecular organisation is actually driven by dispersion interactions, which cause a slight tilt of the molecule and provide the major driving force for assembly into dimers and 1D chains. The relative orientations and distances of neighbouring molecules are amenable for π-π stacking, suggesting that this is an important contributor in the self-assembly process.

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