No abstract

We report in situ scanning tunneling microscopy (STM) results of underpotential deposition (UPD) of copper at well-ordered Pt(111) and Rh(111) electrodes in sulfuric acid solutions. Cyclic voltammograms of Pt(111) at 1 mV/s in 0.05 M H2SO4 and 5 mM CuSO4 reveal two well-defined UPD peaks at 0.65 and 0.61 V, whereas one doublet UPD peak at 0.44 V is observed for Rh(111). Real-time STM imaging revealed that the two sharp UPD features for Pt(111) correspond to the formation of a ( 3 × 3)R30°structure and a disorder phase, respectively. A long-range ordered ( 3 × 7)oblique structure was imaged after a full monolayer of Cu was deposited, tentatively assigned to the (bi)sulfate anions lying atop the Cu adlayer. In contrast, a monolayer of Cu was deposited in a single step on Rh (111), where (bi)sulfate anions also actively participated in the process. In situ STM revealed a well-ordered ( 3 × 7)oblique structure throughout the deposition process, likely because of the coadsorbed (bi)sulfate anions. A series of timedependent in situ STM images were acquired to unveil the deposition processes of Cu. Deposition of Cu preferentially began at defect sites, particularly upper step ledges. Lateral growth and coalescence of Cu islands followed to cover nearly the whole surface. Decreasing potential to the bulk deposition region led to the formation of local Cu islands with a thickness of 4-5 layers of Cu, on which a well-ordered ( 3 × 7)oblique structure was still observed. All the STM results indicate that sulfate anions were heavily involved in the UPD processes of Cu at these two electrodes. The different adsorption energies of Cu adatoms on Pt and Rh electrodes also affect the deposition processes.

No abstract

Although the role of 3,4-dihydroxyphenyl-L-alanine­(DOPA)­in mussel foot proteins (mfps) in the realization of underwater bonding has been widely recognized, the role of the polarity of the polymer was largely overlooked. Here, by systematically comparing the underwater bonding properties of four mussel-inspired adhesives with different amide/lactam contents but similar catechol contents and molecular weights, we came to the conclusion that the polarity of the polymers also contributes to the strong underwater bonding. With the increase in the amide/lactam contents, the polarity of the polymeric adhesive increases, which correlates to the improved underwater bonding strength. A dielectric constant is introduced to evaluate the polarity of the polymer, which may be used as a guidance for the design of mussel-inspired adhesives with even better underwater bonding properties.