I-SURF : Inorganic surfactants with multifunctinal heads
- FB Chemie
|(2019): Molecular Semiconductor Surfactants with Fullerenol Head and Colored Tails for Photoconversion of Carbon Dioxide Angewandte Chemie International Edition ; 2019. - ISSN 0570-0833. - eISSN 1521-3773|
Molecular Semiconductor Surfactants with Fullerenol Head and Colored Tails for Photoconversion of Carbon Dioxide
The leaf is paramount for a material converting waste (CO2) to value with maximum sustainability. As the most important constituent, it contains the coupled photosystems II and I imbedded in the cellular membrane of chloroplasts. Can key functions of the leaf be packed in soap? We present next generation surfactants, which self-assemble to bilayer vesicles (similar to the cellular membrane), are able to absorb photons of two different VIS-wavelengths and exchange excited charge carriers (similar to the photosystems), followed by conversion of CO2 (in analogy to the leaf). The amphiphiles contain five dye molecules as the hydrophobic entity attached exclusively to one hemisphere of a polyhydroxylated fullerene (Janus-type). The manuscript reports surfactant, optical, electronic and catalytic properties. Photons adsorbed by the dyes become transferred to the fullerenol head, where they are able react with different species like with CO2 to formic acid.
|(2018): Sweet surfactants : packing parameter-invariant amphiphiles as emulsifiers and capping agents for morphology control of inorganic particles Soft Matter ; 14 (2018), 35. - S. 7214-7227. - ISSN 1744-683X. - eISSN 1744-6848|
Sweet surfactants : packing parameter-invariant amphiphiles as emulsifiers and capping agents for morphology control of inorganic particles
Surfactants are not only pivotal constituents in any biological organism in the form of phospholipids, they are also essential for numerous applications benefiting from a large, internal surface, such as in detergents, for emulsification purposes, phase transfer catalysis or even nanoparticle stabilization. A particularly interesting, green class of surfactants contains glycoside head groups. Considering the variability of glycosides, a large number of surfactant isomers become accessible. According to established models in surfactant science such as the packing parameter or the hydrophilic lipophilic balance (HLB), they do not differ from each other and should, thus, have similar properties. Here, we present the preparation of a systematic set of glycoside surfactants and in particular isomers. We investigate to which extent they differ in several key features such as critical aggregation concentration, thermodynamic parameters, etc. Analytical methods like isothermal titration calorimetry (ITC), tensiometry, dynamic light scattering (DLS), small angle-X-ray scattering (SAXS), transmission electron microscopy (TEM) and others were applied. It was found that glycosurfactant isomers vary in their emulsification properties by up to two orders of magnitude. Finally, we have investigated the role of the surfactants in a microemulsion-based technique for the generation of zinc oxide (ZnO) nanoparticles. We found that the choice of the carbohydrate head has a marked effect on the shape of the formed inorganic nanocrystals.
|(2017): Hybrid Surfactants with N-Heterocyclic Carbene Heads as a Multifunctional Platform for Interfacial Catalysis Chemistry - A European Journal ; 23 (2017), 72. - S. 18129-18133. - ISSN 0947-6539. - eISSN 1521-3765|
Hybrid Surfactants with N-Heterocyclic Carbene Heads as a Multifunctional Platform for Interfacial Catalysis
Processing of substrates with different solvent compatibility is a persistent problem in homogeneous catalysis, in particular when one starting compound is water soluble and the other is not. A promising concept reported in the literature is micellar catalysis. However, the process of developing catalysts that are surfactants at the same time is still in its early stages. We report the synthesis of a new surfactant system with an N-heterocyclic carbene (NHC) moiety as a head group. Characteristic surfactant properties such as the formation of micelles or liquid crystals is documented. The new surfactant ligand forms coordination compounds with various metals, most importantly Pd2+ , in square planar geometry. In addition, the Pd-NHC compound shows surfactant features, and can be used successfully for C-C cross-coupling reactions (Suzuki, Heck). The boost in catalytic activity by one order of magnitude compared to analogous but non-amphiphilic species is reported.
|(2017): Magneto-Adaptive Surfactants Showing Anti-Curie Behavior and Tunable Surface Tension as Porogens for Mesoporous Particles with 12-Fold Symmetry Angewandte Chemie International Edition ; 56 (2017), 20. - S. 5475-5479. - ISSN 1433-7851. - eISSN 1521-3773|
Magneto-Adaptive Surfactants Showing Anti-Curie Behavior and Tunable Surface Tension as Porogens for Mesoporous Particles with 12-Fold Symmetry
Gaining external control over self-organization is of vital importance for future smart materials. Surfactants are extremely valuable for the synthesis of diverse nanomaterials. Their self-assembly is dictated by microphase separation, the hydrophobic effect, and head-group repulsion. It is desirable to supplement surfactants with an added mode of long-range and directional interaction. Magnetic forces are ideal, as they are not shielded in water. We report on surfactants with heads containing tightly bound transition-metal centers. The magnetic moment of the head was varied systematically while keeping shape and charge constant. Changes in the magnetic moment of the head led to notable differences in surface tension, aggregate size, and contact angle, which could also be altered by an external magnetic field. The most astonishing result was that the use of magnetic surfactants as structure-directing agents enabled the formation of porous solids with 12-fold rotational symmetry.
|(2016): Passing Current through Electrically Conducting Lyotropic Liquid Crystals and Micelles Assembled from Hybrid Surfactants with π-Conjugated Tail and Polyoxometalate Head ACS Nano ; 10 (2016), 11. - S. 10041-10048. - ISSN 1936-0851. - eISSN 1936-086X|
Passing Current through Electrically Conducting Lyotropic Liquid Crystals and Micelles Assembled from Hybrid Surfactants with π-Conjugated Tail and Polyoxometalate Head
The solvent-mediated ability for molecularly encoded self-assembly into states of higher order (micelles, lyotropic liquid crystals) embodies the basis for many applications of surfactants in science and society. Surfactants are used frequently in recipes for nanoparticle synthesis. Because ordinary surfactants comprise insulating constituents (alkyl groups as side-chains and charged organic heads), such nanostructures are wrapped in an electrically inactive barrier, and this is a large disadvantage for future developments in nanotechnology. Implications of micelles with electrically conducting walls made from either "metallic" or "semiconducting" surfactants are huge, also in other areas such as nanoelectrocatalysis or micellar energy storage. We cross this frontier by replacing not only the hydrophilic chain but also the hydrophilic head by electronically conducting entities. We report the synthesis of surfactants with oligo para-phenylene-ethynylene as a π-conjugated side-chain attached to a redox-active, inorganic polyoxometalate cluster as charged head. It is proven that electronic communication between head and tail takes place. Hybridization on the molecular level leads to the emergence of advanced surfactant features such as semiconductor properties (Egap = 2.6 eV) in soft lyotropic systems (micelles, liquid crystals).
|(2016): Maximizing Headgroup Repulsion : Hybrid Surfactants with Ultrahighly Charged Inorganic Heads and Their Unusual Self-Assembly Langmuir ; 32 (2016), 42. - S. 10920-10927. - ISSN 0743-7463. - eISSN 1520-5827|
Maximizing Headgroup Repulsion : Hybrid Surfactants with Ultrahighly Charged Inorganic Heads and Their Unusual Self-Assembly
Non-equilibrium states of matter are arousing huge interest based on outstanding possibilities to generate unprecedented structures with novel properties. Self-organizing soft-matter is the ideal object of study as it unifies periodic order and high dynamics. Compared to settled systems it becomes vital to realize more complex interaction patterns. A promising and intricate approach is implementing controlled balance between attractive and repulsive forces. We try to answer a fundamental question in surfactant science: How are processes like lyotropic liquid crystals and micellization affected, when head group charge becomes so large that repulsive interactions are inevitable? A particular challenge is that size and shape of the surfactant must not change. We could realize the latter by means of new hybrid surfactants with a heteropolyanion head [EW11O39]n- (E = PV, SiIV, BIII; n = 3, 4, 5). Among the unusual self-assembled structures we report about micelles of a new type with dumbbell morphology.
|Europäische Union||447/14||no information|
|Period:||01.03.2014 – 28.02.2019|