Highlight Publications 2017

Photocatalytically Active Lubricant-Impregnated Surface
Sanghyuk Wooh and Hans-Jürgen Butt
Photocatalytically Active Lubricant-Impregnated Surface
We designed a new lubricant-impregnated surface which possesses photocatalytic activity as well as improved liquid repellency. This photocatalytically active lubricant-impregnated surface (PALIS) was fabricated by simple polydimethylsiloxane (PDMS) brush grafting reaction via illumination. Liquid drops slide on the PALIS by the PDMS lubricant swelled PDMS brush layer. By the combination effect of photocatalytic activity and liquid-repellency, the PALIS exhibits enhanced self-cleaning property for both dusts and organic contaminations.
© WILEY-VCH (2017)
The photocatalytically active lubricant-impregnated surface was introduced by PDMS grafting reaction on mesoporous metal-oxide photocatalysts.
Heteroatom-Doped Perihexacene from a Double Helicene Precursor: On-Surface Synthesis and Properties
Xiao-Ye Wang, Thomas Dienel, Marco Di Giovannantonio, Gabriela Borin Barin, Neerav Kharche, Okan Deniz, José I. Urgel, Roland Widmer, Samuel Stolz, Luis Henrique De Lima, Matthias Muntwiler, Matteo Tommasini, Vincent Meunier, Pascal Ruffieux, Xinliang Feng, Roman Fasel, Klaus Müllen, and Akimitsu Narita
Heteroatom-Doped Perihexacene from a Double Helicene Precursor: On-Surface Synthesis and Properties
Periacenes, which comprise two laterally peri-fused linear acenes, are an important class of zigzag-edged nanographene molecules with intriguing electronic and magnetic properties. However, the synthesis of periacenes, especially peritetracene and higher homologues, has been severely hampered by their poor stability. Herein, we report the surface-assisted synthesis of the hitherto longest periacene analogue with oxygen-boron-oxygen (OBO) segments on the zigzag edges, that is, a heteroatom-doped perihexacene. The structure was clearly visualized by scanning tunneling microscopy and noncontact atomic force microscopy. X-ray photoelectron spectroscopy and Raman spectroscopy on both the precursor and the perihexacene analogue provided further insights into the cyclodehydrogenation process. It is found that the conformation of the double helicene is highly influenced by the metal surface and the self-assembly structures. Furthermore, both the precursor and the perihexacene analogue form one-dimensional superstructures on surfaces by virtue of OBO units. The intermolecular interactions resulted from OBO segments indicate great potential for fabricating tailor-made graphene nanoarchitectures in the future.
© JACS (2017)
Heteroatom-Doped Perihexacene from a Double Helicene Precursor
Nanoparticle amount, and not size, determines chain alignment and nonlinear hardening in polymer nanocomposites
H. Samet Varol, Fanlong Meng, Babak Hosseinkhani, Christian Malm, Daniel Bonn, Mischa Bonn, Alessio Zaccone, and Sapun H. Parekh
Nanoparticle amount, and not size, determines chain alignment and nonlinear hardening in polymer nanocomposites
Polymer nanocomposites—materials in which a polymer matrix is blended with nanoparticles (or fillers)—strengthen under sufficiently large strains. Such strain hardening is critical to their function, especially for materials that bear large cyclic loads such as car tires or bearing sealants. Although the reinforcement (i.e., the increase in the linear elasticity) by the addition of filler particles is phenomenologically understood, considerably less is known about strain hardening (the nonlinear elasticity). Here, we elucidate the molecular origin of strain hardening using uniaxial tensile loading, microspectroscopy of polymer chain alignment, and theory. The strain-hardening behavior and chain alignment are found to depend on the volume fraction, but not on the size of nanofillers. This contrasts with reinforcement, which depends on both volume fraction and size of nanofillers, potentially allowing linear and nonlinear elasticity of nanocomposites to be tuned independently.
© Hasan Samet Varol (2017)
Strain hardening in polymer nanocomposites is a function of inorganic “filler” particle amount and surprisingly independent of filler size. A cancellation of filler size effects is observed because of inter-particle polymer chain alignment.
Mitochondria Targeted Protein-Ruthenium Photosensitizer for Efficient Photodynamic Applications
Sabyasachi Chakrabortty, Bikram Keshari Agrawalla, Anne Stumper, Naidu M Vegi, Stephan Fischer, Christian Reichardt, Michael Kögler, Benjamin Dietzek, Michaela Feuring-Buske, Christian Buske, Sven Rau, and Tanja Weil
Mitochondria Targeted Protein-Ruthenium Photosensitizer for Efficient Photodynamic Applications
Organelle-targeted photosensitization represents a promising approach in photodynamic therapy where the design of the active photosensitizer (PS) is very crucial. In this work, we developed a macromolecular PS with multiple copies of mitochondria-targeting groups and ruthenium complexes that displays highest phototoxicity toward several cancerous cell lines. In particular, enhanced anticancer activity was demonstrated in acute myeloid leukemia cell lines, where significant impairment of proliferation and clonogenicity occurs. Finally, attractive two-photon absorbing properties further underlined the great significance of this PS for mitochondria targeted PDT applications in deep tissue cancer therapy.
© American Chemical Society (2017)
A novel plasma protein based phototoxic, biodegradable, mitochondria targeted macromolecular photosensitizer showing significantly enhanced photodynamic behavior
The Cassie-Wenzel transition of fluids on nanostructured substrates: Macroscopic force balance versus microscopic density-functional theory
Nikita Tretyakov, Periklis Papadopoulos, Doris Vollmer, Hans-Jürgen Butt, Burkhard Dünweg und Kostas Daoulas
The Cassie-Wenzel transition of fluids on nanostructured substrates: Macroscopic force balance versus microscopic density-functional theory
Classical density functional theory is applied to investigate the validity of a phenomenological force-balance description of the stability of the Cassie state of liquids on substrates with nanoscale corrugation. A bulk free-energy functional of third order in local density is combined with a square-gradient term, describing the liquid-vapor interface. The bulk free energy is parameterized to reproduce the liquid density and the compressibility of water. The square-gradient term is adjusted to model the width of the water-vapor interface. The substrate is modeled by an external potential, based upon the Lennard-Jones interactions. The three-dimensional calculation focuses on substrates patterned with nanostripes and square-shaped nanopillars. Using both the force-balance relation and density-functional theory, we locate the Cassie-to-Wenzel transition as a function of the corrugation parameters. We demonstrate that the force-balance relation gives a qualitatively reasonable description of the transition even on the nanoscale. The force balance utilizes an effective contact angle between the fluid and the vertical wall of the corrugation to parameterize the impalement pressure. This effective angle is found to have values smaller than the Young contact angle. This observation corresponds to an impalement pressure that is smaller than the value predicted by macroscopic theory. Therefore, this effective angle embodies effects specific to nanoscopically corrugated surfaces, including the finite range of the liquid-solid potential (which has both repulsive and attractive parts), line tension, and the finite interface thickness. Consistently with this picture, both patterns (stripes and pillars) yield the same effective contact angles for large periods of corrugation.
© AIP Publishing (2017)
The Cassie-to-Wenzel transition is located for striped (left) and pillared (right) substrates as a function of the corrugation parameters a and cx. Parts of the corrugations re-enter the calculation box through periodic boundary conditions.
Periodic potentials in hybrid van der Waals heterostructures formed by supramolecular lattices on graphene
Marco Gobbi, Sara Bonacchi, Jian X. Lian, Yi Liu, Xiao-YeWang, Marc-Antoine Stoeckel, Marco A. Squillaci, Gabriele D’Avino, Akimitsu Narita, Klaus Müllen, Xinliang Feng, Yoann Olivier, David Beljonne, Paolo Samorì & Emanuele Orgiu
Periodic potentials in hybrid van der Waals heterostructures formed by supramolecular lattices on graphene
The rise of 2D materials made it possible to form heterostructures held together by weak interplanar van der Waals interactions. Within such van der Waals heterostructures, the occurrence of 2D periodic potentials significantly modifies the electronic structure of single sheets within the stack, therefore modulating the material properties. However, these periodic potentials are determined by the mechanical alignment of adjacent 2D materials, which is cumbersome and time-consuming. Here we show that programmable 1D periodic potentials extending over areas exceeding 104 nm2 and stable at ambient conditions arise when graphene is covered by a self-assembled supramolecular lattice. The amplitude and sign of the potential can be modified without altering its periodicity by employing photoreactive molecules or their reaction products. In this regard, the supramolecular lattice/graphene bilayer represents the hybrid analogue of fully inorganic van der Waals heterostructures, highlighting the rich prospects that molecular design offers to create ad hoc materials.
© Macmillan Publishers Limited (2017)
Calculated differential electrical potential induced by a self-assembled supramolecular lattice on graphene. The supramolecular lattice is superimposed for clarity. The electrical potential is periodically modulated, with negative values in the region below the molecular heads. Carbon atoms are shown in grey, hydrogen in white, nitrogen in red, fluorine in light blue and chlorine in green.
 
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