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Silver nanoparticles (AgNPs) conjugated with polymers are well-known for their powerful and effective antimicrobial properties. In particular, the incorporation of AgNPs in biocompatible catecholamine-based polymers, such as polydopamine (PDA), has recently shown promising antimicrobial activity, due to the synergistic effects of the AgNPs, silver(I) ions released and PDA. In this study, we generated AgNPs-PDA-patterned surfaces by localised electrochemical depositions, using a double potentiostatic method via scanning electrochemical cell microscopy (SECCM). This technique enabled the assessment of a wide parameter space in a high-throughput manner. The optimised electrodeposition process resulted in stable and homogeneously distributed AgNP-microspots, and their antimicrobial activity against Escherichia coli was assessed using atomic force microscopy (AFM)-based force spectroscopy, in terms of bacterial adhesion and cell elasticity. We observed that the bacterial outer membrane underwent significant structural changes, when in close proximity to the AgNPs, namely increased hydrophilicity and stiffness loss. The spatially varied antimicrobial effect found experimentally was rationalised by numerical simulations of silver(I) concentration profiles. [ABSTRACT FROM AUTHOR]

The coadsorption of CO and hydrogen on a structurally well-defined Pt35Ru65/Ru(0001) monolayer surface alloy and, for comparison, on Ru(0001) were investigated by temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRAS). The data reveal distinct modifications in the hydrogen adsorption behavior and also in the CO adsorption properties compared to adsorption of the individual components both on the mono-metallic and on the bimetallic surface. These modifications are discussed on an atomic scale, in a picture that involves adsorbate–adsorbate interactions and site-specific variations in the (local) adsorption properties of the bimetallic surface, due to electronic ligand and strain effects and geometric ensemble effects. [ABSTRACT FROM AUTHOR]

The coadsorption of CO and hydrogen on a structurally well-defined Pt35Ru65/Ru(0001) monolayer surface alloy and, for comparison, on Ru(0001) were investigated by temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRAS). The data reveal distinct modifications in the hydrogen adsorption behavior and also in the CO adsorption properties compared to adsorption of the individual components both on the mono-metallic and on the bimetallic surface. These modifications are discussed on an atomic scale, in a picture that involves adsorbate–adsorbate interactions and site-specific variations in the (local) adsorption properties of the bimetallic surface, due to electronic ligand and strain effects and geometric ensemble effects. [ABSTRACT FROM AUTHOR]

The stability of three ultrathin TiOx/Pt(111) films with different stoichiometry and defectivity and the corresponding Au/TiOx/Pt(111) model catalysts in CO or a CO–O2(1 : 1) gas mixture up to a pressure of 100 mbar has been investigated. According to previous studies, the ultrathin films proved to be effective substrates to deposit in UHV Au nanoparticles with specific morphologies and lateral sizes ranging between 1 and 6 nm. The films have been characterized before and after the exposure using X-ray photoemission spectroscopy (XPS), low-energy electron diffraction (LEED) and scanning tunnelling microscopy (STM). Additional in situmeasurements of the CO chemisorption behavior were performed using polarization-modulation infrared reflection–absorption spectroscopy (PM-IRAS). A fully oxidized film is stable in CO and CO–O2(1 : 1) ambient, while the reduced films undergo an oxidative dewetting process at RT in the latter atmosphere. This process ultimately produces a nano-composite surface, where very tiny (from 0.5 to 3 nm lateral sizes) titania nanograins are mixed with open, uncovered areas of the Pt substrate. IRAS measurements on the corresponding Au/TiOx/Pt(111) model catalysts demonstrated that the CO chemisorption strongly depends on the Au nanoparticle size and morphology, while the actual Ti oxidation state of the oxide support does not seem to play a significant role. [ABSTRACT FROM AUTHOR]