Quaternary‐ammonium‐compounds are potent cationic antimicrobials used in everyday consumer products. Surface‐immobilized, quaternary‐ammonium‐compounds create an antimicrobial contact‐killing coating. We describe the preparation of a shape‐adaptive, contact‐killing coating by tethering quaternary‐ammonium‐compounds onto hyperbranched polyurea coatings, able to kill adhering bacteria by partially enveloping them. Even after extensive washing, coatings caused high contact‐killing of Staphylococcus epidermidis, both in culture‐based assays and through confocal‐laser‐scanning‐microscopic examination of the membrane‐damage of adhering bacteria. In culture‐based assays, at a challenge of 1600 CFU/cm2, contact‐killing was >99.99%. The working‐mechanism of dissolved quaternary‐ammonium‐compounds is based on their interdigitation in bacterial membranes, but it is difficult to envisage how immobilized quaternary‐ammonium‐molecules can exert such a mechanism of action. Staphylococcal adhesion forces to hyperbranched quaternary‐ammonium coatings were extremely high, indicating that quaternary‐ammonium‐molecules on hyperbranched polyurea partially envelope adhering bacteria upon contact. These lethally strong adhesion forces upon adhering bacteria then cause removal of membrane lipids and eventually lead to bacterial death.

Monolayers of fluorinated light-driven molecular motors were synthesized and immobilized on gold films in an altitudinal orientation via tripodal stators. In this design the functionalized molecular motors are not interfering and preserve their rotary function on gold. The wettability of the self-assembled monolayers can be modulated by UV irradiation.

Two types of graphene-based hybrid materials, graphene-TPP (TPP=tetraphenylporphyrin) and graphene-PdTPP (PdTPP=palladium tetraphenylporphyrin), were prepared directly from pristine graphene through one-pot cycloaddition reactions. The hybrid materials were characterized by thermogravimetric analysis (TGA), by TEM, by UV/Vis, FTIR, Raman, and luminescence spectroscopy, and by fluorescence/phosphorescence lifetime measurements. The presence of the covalent linkages between graphene and porphyrin was confirmed by FTIR and Raman spectroscopy and further supported by control experiments. The presence of TPP (or PdTPP) in the hybrid material was demonstrated by UV/Vis spectroscopy, with TGA results indicating that the graphene-TPP and graphene-PdTPP hybrid materials contained approximately 18 % TPP and 20 % PdTPP. The quenching of fluorescence (or phosphorescence) and reduced lifetimes suggest excited state energy/electron transfer between graphene and the covalently attached TPP (or PdTPP) molecules.

Self-assembled monolayers of a 6-nitro BIPS spiropyran (SP) modified with a disulfide-terminated aliphatic chain were prepared on polycrystalline gold surfaces and characterized by UV/vis absorption, surface-enhanced Raman scattering (SERS), and X-ray photoelectron spectroscopies (XPS). The SAMs obtained are composed of the ring-closed form (i.e., spiropyran) only. Irradiation with UV light results in conversion of the monolayer to the merocyanine form (MC), manifested in the appearance of an N(+) contribution in the N 1s region of the XPS spectrum of the SAMs, the characteristic absorption band of the MC form in the visible region at 555 nm, and the C-O stretching band in the SERS spectrum. Recovery of the initial state of the monolayer was observed both thermally and after irradiation with visible light. Several switching cycles were performed and monitored by SERS spectroscopy, demonstrating the stability of the SAMs during repeated switching between SP and MC states. A key finding in the present study is that ring-opening of the surface-immobilized spiropyrans can be induced by irradiation with continuous wave NIR (785 nm) light as well as by irradiation with UV light. We demonstrate that ring-opening by irradiation at 785 nm proceeds by a two-photon absorption pathway both in the SAMs and in the solid state. Hence, spiropyran SAMs on gold can undergo reversible photochemical switching from the SP to the MC form with both UV and NIR and the reverse reaction induced by irradiation with visible light or heating. Furthermore, the observation of NIR-induced switching with a continuous wave source holds important consequences in the study of photochromic switches on surfaces using SERS and emphasizes the importance of the use of multiple complementary techniques in characterizing photoresponsive SAMs.

The epitaxial growth of graphene on catalytically active metallic surfaces via chemical vapor deposition (CVD) is known to be one of the most reliable routes toward high-quality large-area graphene. This CVD-grown graphene is generally coupled to its metallic support resulting in a modification of its intrinsic properties. Growth on oxides is a promising alternative that might lead to a decoupled graphene layer. Here, we compare graphene on a pure metallic to graphene on an oxidized copper surface in both cases grown by a single step CVD process under similar conditions. Remarkably, the growth on copper oxide, a high-k dielectric material, preserves the intrinsic properties of graphene; it is not doped and a linear dispersion is observed close to the Fermi energy. Density functional theory calculations give additional insight into the reaction processes and help explaining the catalytic activity of the copper oxide surface.