Georg R. J. Artus

Patterned superfunctional surfaces based on a silicone nanofilament coating

We demonstrate that a recently developed coating comprised of silicone nanofilaments can be selectively functionalized to yield well defined superhydrophobic, superhydrophilic, superoleophobic or superoleophilic domains on a single substrate, constituting a simple and versatile toolbox for surface scientists to create and study surfaces with extreme wetting properties.

Superhydrophobic Silicone Nanofilament Coatings

We present recent work on a method for depositing silicone nanofilament coatings on surfaces under mild conditions in the gas or solvent phase. The coating shows exceptional properties in an application as a superhydrophobic coating. It can be applied to a variety of substrates, is optically transparent and intrinsically superhydrophobic with typical water contact angles of more than 160° and sliding angles below 20°. It shows exceptional long term stability towards solvents and aqueous solutions of varying pH as well as natural and artificial weathering. We review the coating techniques as well as the results of our studies on the structure and properties of a silicone nanofilament coating.

The Chemistry of New Nitrosyltungsten Complexes with Pyridyl-Functionalized Phosphane Ligands

The coordination chemistry of pyridylphosphanes, such as 2-(6-tert-butylpyridyl)diphenylphosphane (Ph2P-tert-Bupy) (6) and 2-(6-tert-butylpyridyl)dimethylphosphane (Me2P-tert-Bupy) (7) towards a number of nitrosyltungsten complexes is reported. Displacement of the loosely coordinated MeCN from [W(CH3CN)3(CO)2(NO)][BF4] led to the following cationic compounds incorporating mono- and bidentate coordinated phosphane ligands: cis,cis-[W(CO)2(NO)(Ph2PR)(η2-Ph2PR)][BF4], [R = 2-pyridyl (9a), 2-picolyl (11)], cis,cis-[W(CO)(NO)(η2-Ph2Ppy)2][BF4] (20), trans,trans-[W(CO)(NO)(η2-Ph2Ppy)2][BPh4] (21), fac-[W(CO)2(NO)(Me2Ppy)3][BF4] (16), fac-[W(CO)2(NO)(Me2P-tert-Bupy)3][BF4] (18), cis,cis-[W(CO)2(NO)(Me2Ppy)(η2-Me2Ppy)][BF4] (22), and cis,cis-[W(CO)2(CH3CN)(NO)(Me2P-tert-Bupy)2][BF4] (23a). The cationic complex cis,mer-[W(CO)3(NO)(Ph2P-tert-Bupy)2][PF6] (14) has been prepared by nitrosylation of cis/trans-W(CO)4(Ph2P-tert-Bupy)2 (13). Reactions of 9a, 11, 14, 16, and 18 with hydride transfer reagents afforded trans,trans-HW(CO)2(NO)(Ph2Ppy)2 (10), trans,trans-HW(CO)2(NO)(Ph2Ppic)2 (12), trans,trans-HW(CO)2(NO)(Ph2-tBupy)2 (15), cis/trans-HW(CO)2(NO)(Me2Ppy)2 (17), and cis/trans-HW(CO)2(NO)(Me2P-tert-Bupy)2 (19), respectively. Reactivity experiments with acetic acid, hydroiodic acid, carbon dioxide, and acetylenedicarboxylic acid were performed, and were found to afford trans-W(CO)(NO)(Ph2Ppy)2(η2-CH3CO2) (24), trans,trans-IW(CO)2(NO)(Ph2Ppy)2 (25), trans-W(HCO2)(CO)2(NO)(Ph2Ppy)2 (26), and trans-W{η2-(Z)-C(CO2Me)=CH[C(O)OMe]}(CO)(NO)(Ph2Ppic)2 (27), respectively. The influence of the pyridyl substituent in 10 was probed by a comparative H/D exchange experiment in which 10 and the analogous complex HW(CO)2(NO)(PPh3)2 were treated with MeOD. The deuterated complex trans,trans-WD(CO)2(NO)(Ph2Ppy)2 (28) could be isolated. The structures of 9a, 11, 14, and 20 have been determined by single-crystal X-ray diffraction analysis.

One-dimensional silicone nanofilaments.

A decade ago one-dimensional silicone nanofilaments (1D-SNF) such as fibres and wires were described for the first time. Since then, the exploration of 1D-SNF has led to remarkable advancements with respect to material science and surface science: one-, two- and three-dimensional nanostructures of silicone were unknown before. The discovery of silicone nanostructures marks a turning point in the research on the silicone material at the nanoscale. Coatings made of 1D-SNF are among the most superhydrophobic surfaces known today. They are free of fluorine, can be applied to a large range of technologically important materials and their properties can be modified chemically. This opens the way to many interesting applications such as water harvesting, superoleophobicity, separation of oil and water, patterned wettability and storage and manipulation of data on a surface. Because of their high surface area, coatings consisting of 1D-SNF are used for protein adsorption experiments and as carrier systems for catalytically active nanoparticles. This paper reviews the current knowledge relating to the broad development of 1D-SNF technologies. Common preparation and coating techniques are presented along with a comparison and discussion of the published coating parameters to provide an insight on how these affect the topography of the 1D-SNF or coating. The proposed mechanisms of growth are presented, and their potentials and shortcomings are discussed. We introduce all explored applications and finally identify future prospects and potentials of 1D-SNF with respect to applications in material science and surface science.

Superficial Dopants Allow Growth of Silicone Nanofilaments on Hydroxyl-Free Substrates

We report new types of silicone nanostructures by a gas-phase reaction of trichloromethylsilane: 1-D silicone nanofilaments with a raveled end and silicone nanoteeth. Filaments with a raveled end are obtained on poly(vinyl chloride), which is superficially doped with the detergent Span 20. Silicone nanoteeth grow on sodium chloride using dibutyl phthalate as superficial dopant. Without dopants, no structures are observed. The dopants are identified by mass spectroscopy and the silicone nanostructures are analyzed by infrared spectroscopy and energy-dispersive analysis of X-rays. The growth of silicone nanostructures on a hydrophobic substrate (poly(vinyl chloride)/Span 20) and a substrate free of hydroxyl groups (sodium chloride/dibutyl phthalate) questions the currently discussed mechanisms for the growth of 1-D silicone nanofilaments, which is discussed. We suggest superficial doping as an alternative pretreatment method to oxidizing activation and prove this principle by the successful coating of copper, which is superficially doped with Span 20.

Directed in situ shaping of complex nano- and microstructures during chemical synthesis

Chemical composition and shape determine the basic properties of any object. Commonly, chemical synthesis and shaping follow each other in a sequence, although their combination into a single process would be an elegant simplification. Here, a pathway of simultaneous synthesis and shaping as applied to polysiloxanes on the micro- and nanoscale is presented. Complex structures such as stars, chalices, helices, volcanoes, rods, or combinations thereof are obtained. Varying the shape-controlling reaction parameters including temperature, water saturation, and the type of substrate allows to direct the reaction toward specific structures. A general mechanism of growth is suggested and analytical evidence and thermodynamic calculations to support it are provided. An aqueous droplet in either gaseous atmosphere or in a liquid organic solvent serves as a spatially confined polymerization volume. By substituting the starting materials, germanium-based nanostructures are also obtained. This transferability marks this approach as a major step toward a generally applicable method of chemical synthesis including in situ shaping.