Low temperature scanning tunneling microscopy (STM) and density functional theory (DFT) were used to study the adsorption of water on a Ru(0001) surface covered with half monolayer of oxygen. The oxygen atoms occupy hcp sites in an ordered structure with (2x1) periodicity. DFT predicts that water is weakly bound to the unmodified surface, 86 meV compared to the ~;;200 meV water-water H-bond. Instead, we found that water adsorption causes a shift of half of the oxygen atoms from hcp sites to fcc sites, creating a honeycomb structure where water molecules bind strongly to the exposed Ru atoms. The energy cost of reconstructing the oxygen overlayer, around 230 meV per displaced oxygen atom, is more than compensated by the larger adsorption energy of water on the newly exposed Ru atoms. Water forms hydrogen bonds with the fcc O atoms in a (4x2) superstructure due to alternating orientations of the molecules. Heating to 185 K results in the complete desorption of the water layer, leaving behind the oxygen honeycomb structure, which is metastable relative to the original (2x1). This stable structure is not recovered until after heating to temperatures close to 260K.

In 1662, Roman editore Giovanni Giacomo de’ Rossi published an updated version of Antonio Tempesta’s famous 1593 bird’s-eye view of Rome. In many ways, this move was standard practice: important images of the city were commonly copied or reprinted, and Tempesta’s original had been reissued multiple times. De’ Rossi’s version of 1662 was more than an incrementally revised restrike, however. In the title, he claimed it to show Tempesta’s prototype “recut, embellished, and enlarged” (rintagliato, abbellito ed accresciutto), and for once this language seems to reflect more than a rhetorical flourish. This essay shows, rather, that it was a meaningful reflection of process—one that leads, in turn, to many new questions. What was the lasting value of Tempesta’s view: what made it worth painstakingly refashioning for the present? Where did resemblance leave off and rupture begin? This essay seeks answers to these questions in interfamilial feuds and in the cut-throat world of Roman publishers as they sought novel ways to hitch their own reputations to that of their city. Among other challenges, they had to balance Rome’s illustrious antiquity with its shape-shifting modernity, and to attract an increasingly international market while catering to their local patrons and protectors. Ultimately, the significance of Tempesta’s image transcends any original author and moment. Its complex afterlife suggests a web of competing interests, as well as a cycle of decline and renewal, very much like that of Rome itself.

In physiological fluids and seawater, adhesion of synthetic polymers to solid surfaces is impaired by high salt, pH, and hydration. However, mussels have evolved effective strategies for wet adhesion despite these impediments. Inspection of mussel foot proteins (Mfps) provides insights into adhesive adaptations. Catecholic Dopa (3,4-dihydroxyphenylalanine) and lysine residues are present in high mole percent in the interfacial Mfps. The siderophore cyclic trichrysobactin also contains high mole percent of catechol and lysine and serves as a simplified mimic of Mfps.

This work is focused on use of Mfp-mimetic siderophores and synthetic siderophore analogs as model systems for dissecting the chemical and physical interactions that enable wet adhesion. Variation in number and identity of functional groups appended to the synthetic siderophore analogs allows identification of the specific contributions of those functional groups to wet adhesion. Both catechol and amine functional groups are critical to strong wet adhesion. The primary amine of lysine and catechol cooperatively displace interfacial hydration and bind to the underlying substrate. Variation in the amine identity as well as the amine to catechol ratio within siderophore analogs also has a significant impact on wet adhesive performance.

Catechol undergoes a pH-dependent autoxidation in which higher pH leads to faster oxidation by dioxygen. This oxidation abolishes all adhesion of Mfps to mica by pH 7.5, yet many applications of synthetic wet adhesives require adhesion at physiological or oceanic pH. A better understanding of catechol redox chemistry is critical to the design of wet adhesives. To this end, the pH-dependent autoxidation of catechol and substituted catechols was investigated and results are consistent with a mechanism in which O2 oxidizes both the mono-deprotonated and di-deprotonated catechol. A linear Hammett correlation for the pH-independent second order rate constants for catechol autoxidation indicates that catechols become resistant to autoxidation when functionalized with electron withdrawing groups and more susceptible to autoxidation when functionalized with electron donating groups. Analysis of substituent effects through Hammett correlation allows for selection of functionalized catechols with redox properties ideally suited for a given application.