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Block copolymer micelles and vesicles are mostly prepared by the solvent mixing method, where the block copolymer is first dissolved in a common solvent for both blocks, which is then mixed with a selective solvent, mostly water, to induce self-assembly into the desired structure. Using a combination of microfluidic flow-focusing and capillary interdiffusion experiments combined with in-situ small-angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (cryo-TEM) we investigated the structural evolution during solvent mixing from single block copolymers into spherical and cylindrical micellar intermediate structures into vesicles. We find that micelle formation is very fast and diffusion-limited, occurring on time scales of a few milliseconds. The development of an ordered lyotropic micellar phase is completed within 1 s. The structural transformation into cylindrical micelles occurs over several hours, which subsequently evolve into vesicles over time scales of days. Whereas the first two steps are transport-limited, the two latter processes involve large activation energies related to micellar fusion against the sterically stabilizing micellar coronas, which corresponds to much longer time scales of self-assembly.

The synthesis of ZnO nanoparticles proceeds through a complex sequence of precursor reactions, nucleation, and growth processes. For further advancement and control of nanoparticle synthesis, a detailed understanding of the mechanisms and kinetics is essential. With the recent advancement in X-ray scattering and spectroscopy methods, in situ experiments during nanoparticle synthesis can be performed, which provide important new insights into reaction and growth mechanisms. Here we use in situ small- and wide-angle X-ray scattering (SAXS, WAXS) coupled with UV-vis spectroscopy to investigate the nucleation and growth process of an oleate-based ZnO nanoparticle synthesis yielding narrowly disperse nanoparticles over the complete time scale from 30 s to 18 h. We find that the nucleation and early growth period during the first 1000 s can be quantitatively described by a classical homogeneous nucleation and growth mechanism. Furthermore, we identified a second growth phase where nanoparticle crystallization occurs, as indicated by the appearance of higher-order Bragg peaks and a pronounced shift of the absorption edge in the UV-vis spectra. The results are in very good agreement with recent studies on the use of the ZnO alkali hydroxide hydrolysis route. Thus, a very good understanding of the nucleation and growth mechanisms and kinetics of the most important ZnO synthesis routes has been established.

Strong and tough fibers Dragline spider silk is known for its combination of strength and toughness, but this combination has been hard to replicate in synthetic fibers. Liao et al. electrospun polyacrylonitrile- co -methyl acrylate fibers modified with a small amount of poly(ethylene glycol) bisazide (PEG-BA) (see the Perspective by Fox). After collecting the electrospun yarn, it was annealed under tension that both aligned the small fibers and cross-linked them together via the PEG-BA. As hoped, the overall properties were comparable to those of spider silk. Science , this issue p. 1376 ; see also p. 1314

The defined assembly of nanoparticles (NPs) in polymer matrices is an important prerequisite for next-generation functional materials. A promising approach to control NP positions in polymer matrices at the nanometer scale is the use of block copolymers. It allows the selective deposition of NPs in nanodomains, but the final defined and ordered positioning of the NPs within the domains has not been possible. This can now be achieved by coating NPs with block copolymers. The self-assembly of block copolymer-coated NPs directly leads to ordered microdomains containing ordered NP arrays with exactly one NP per unit cell. By variation of the grafting density, the inter-nanoparticle distance can be controlled from direct NP surface contact to surface separations of several nanometers, determined by the thickness of the polymer shell. The method can be applied to a wide variety of block copolymers and NPs and is thus suitable for a broad range of applications.

In biological fluids, proteins bind to particles, forming so-called protein coronas. Such adsorbed protein layers significantly influence the biological interactions of particles, both in vitro and in vivo. The adsorbed protein layer is generally described as a two-component system comprising "hard" and "soft" protein coronas. However, a comprehensive picture regarding the protein corona structure is lacking. Herein, we introduce an experimental approach that allows for in situ monitoring of protein adsorption onto silica microparticles. The technique, which mimics flow in vascularized tumors, combines confocal laser scanning microscopy with microfluidics and allows the study of the time-evolution of protein corona formation. Our results show that protein corona formation is kinetically divided into three different phases: phase 1, proteins irreversibly and directly bound (under physiologically relevant conditions) to the particle surface; phase 2, irreversibly bound proteins interacting with preadsorbed proteins, and phase 3, reversibly bound "soft" protein corona proteins. Additionally, we investigate particle-protein interactions on low-fouling zwitterionic-coated particles where the adsorption of irreversibly bound proteins does not occur, and on such particles, only a "soft" protein corona is formed. The reported approach offers the potential to define new state-of-the art procedures for kinetics and protein fouling experiments.

Truly spherical silver nanoparticles are of great importance for fundamental studies including plasmonic applications, but their direct synthesis in aqueous media is not feasible. Using the commonly employed copper-based etching processes, an isotropic plasmonic response can be achieved by etching well-defined silver nanocubes. Whilst spherical-like shape is typically prevailing in such processes, we established that there is a preferential growth toward silver rhombicuboctahedra, which is the thermodynamically most stable product of this synthesis. The rhombicuboctahedral morphology is further evidenced by comprehensive characterization with small-angle X-ray scattering in combination with transmission electron microscopy (TEM) tomography and high-resolution TEM. We also elucidate the complete reaction mechanism based on UV–vis kinetic studies, and the postulated mechanism can also be extended to all copper-based etching processes.

Nanoscale 11(9), 3847-3854 (2019). doi:10.1039/C8NR10018G, Published by RSC Publ., Cambridge

Microflows constitute an important instrument to control particle dynamics. A prominent example is the sorting of biological cells, which relies on the ability of deformable cells to move transversely to flow lines. A classic result is that soft microparticles migrate in flows through straight microchannels to an attractor at their center. Here, we show that flows through wavy channels fundamentally change the overall picture. They lead to the emergence of a second, coexisting attractor for soft particles. Its emergence and off-center location depends on the boundary modulation and the particle properties. The related cross-stream migration of soft particles is explained by analytical considerations, Stokesian dynamics simulations in unbounded flows, and Lattice-Boltzmann simulations in bounded flows. The novel off-center attractor can be used, for instance, in diagnostics, for separating cells of different size and elasticity, which is often an indicator of their health status.

Small-K Advanced DIffractometer (SKADI is a Small-Angle Neutron Scattering (SANS) instrument to be constructed at the European Spallation Source (ESS). SANS instruments allow investigations of the structure of materials in the size regime between Angstroms up to micrometers. As very versatile instruments, they usually cater to the scientific needs of communities, such as chemists, biologists, and physicists, ranging from material and food sciences to archeology. They can offer analysis of the micro- and mesoscopic structure of the samples, as well as an analysis of the spin states in the samples, for example, for magnetic samples. SKADI, as a broad range instrument, thus offers features, such as an extremely flexible space for the sample environment, to accommodate a wide range of experiments, high-flux, and optimized detector-collimation system to allow for an excellent resolution of the sample structure, short measurement times to be able to record the internal kinetics during a transition in the sample, as well as polarized neutron scattering. In this manuscript, we describe the final design for the construction of SKADI. All of the features and capabilities presented here are projected to be included into the final instrument when going into operation phase.

Collagens are widely used as biomaterials in drug-delivery and tissue engineering applications due to their biodegradability, biocompatibility and hypoallergenicity. Besides gelatin-based materials, collagen microfibers are in the focus of biomedical research. Commonly, man-made fibers are produced by wet-spinning yielding fiber diameters higher than 8 μm. Here, assembly and continuous production of single collagen type I microfibers were established using a microfluidic chip. Microfluidics-produced microfibers exhibited tensile strength and Young's modulus exceeding that of fibers produced in classical wet-spinning devices and even that of natural tendon and they showed lower diameters. Their structural orientation was examined by polarized Fourier transform infrared spectroscopy (FTIR) showing fibril alignment within the microfiber. Cell culture tests using the neuronal cell line NG108-15 showed cell alignment and axon growth along the microfiber axes inaugurating potential applications in, for example, peripheral nerve repair.

Herein, we fabricate hollow silica nanoparticles with exceptionally narrow size distributions that inherently possess two distinct length scales—tens of nanometers with regards to the shell thickness, and hundreds of nanometers in regards to the total diameter. We characterize these structures using dynamic and static light scattering (DLS and SLS), small angle X-ray scattering (SAXS), and transmission electron microscopy (TEM), and we demonstrate quantitative agreement among all methods. The ratio between the radius of gyration (SLS) and hydrodynamic radius (DLS) in these particles equals almost unity, corresponding to ideal capsule behavior. We are able to resolve up to 20 diffraction orders of the hollow sphere form factor in SAXS, indicating a narrow size distribution. Data from light and X-ray scattering can be combined to a master curve covering a q-range of four orders of magnitude assessing all hierarchical length scales of the form factor. The measured SLS intensity profiles noticeably change when the scattering contrast between the interior and exterior is altered, whereas the SAXS intensity profiles do not show any significant change. Tight control of the aforementioned length scales in one simple and robust colloidal building block renders these particles suitable as future calibration standards.

We describe the room-temperature synthesis and characterization of needle-like lanthanide phosphate (LnPO4) nanocrystals in water, based on in situ precipitation of LnPO4 using functional aqueous microgels as a soft nanoreactor. The poly(NIPAm/VCL/MAA) microgels were prepared by the copolymerization of N-isopropylacrylamide, N-vinylcaprolactam, and methacrylic acid. Our goal was to prepare Ln-encoded microgels suitable for bead-based biological assays employing mass cytometry. The low solubility of nanocrystalline LnPO4 avoids the problem of Ln ion leakage from the microgels. The main challenge was to find appropriate conditions to confine the LnPO4 precipitate to the interior of the microgels. Various sources of phosphate ions led to precipitation of LnPO4 on the exterior of the microgels. One approach worked. It involved three steps: neutralization of the MAA groups in the microgels with NaOH, ion exchange with a lanthanide salt, followed by treatment with a large excess of PBS buffer at pH 7.4. In this...

Nowadays there is a high demand for specialized functional materials for specific applications in sensors or biomedicine (e.g. fMRI). For their implementation in devices, nanostructuring and integration in a composite matrix are indispensable. Spin crossover complexes are a highly promising family of switchable materials where the switching process can be triggered by various external stimuli. In this work, the synthesis of nanoparticles of the spin crossover iron(II) coordination polymer [Fe(L)(bipy)]n (with L = 1,2-phenylenebis(iminomethylidyne)bis(2,4-pentanedionato)(2-) and bipy = 4,4′-bipyridine) is described using polystyrene-poly-4-vinylprididine blockcopolymer micelles as the template defining the final size of the nanoparticle core. A control of the spin crossover properties can be achieved by precise tuning of the crystallinity of the coordination polymer via successive addition of the starting material Fe(L) and bipy. By this we were able to synthesize nanoparticles with a core size of 49 nm and a thermal hysteresis loop width of 8 K. This is, to the best of our knowledge, a completely new approach for the synthesis of nanoparticles of coordination polymers and should be easily transferable to other coordination polymers and networks. Furthermore, the use of blockcopolymers allows a further functionalization of the obtained nanoparticles by variation of the polymer blocks and an easy deposition of the composite material on surfaces via spin coating.

Organogels based on hydrogen-bond reinforced ordered micellar assemblies, having a very well-defined nanoscale structure and dynamic behaviour, are synthesized and investigated. The organogels consist of block copolymer micelles with covalently linked hydrogen bonding groups at their periphery which mediate attractive interactions between adjacent micelles. The structure and the viscoelastic properties of the organogels were systematically investigated by small-angle X-ray scattering and dynamic-mechanical measurements. We find with increasing number of hydrogen bonding groups an increase of the storage modulus, an increase of the melting temperature, and the development of a yield point. We show that the macroscopic viscoelastic properties of the organogels can be described by two theoretical models allowing a direct relation to the nanoscale organogel structure, the number of hydrogen bonds and the hydrogen bond lifetimes. The high-modulus transparent organogels undergo a reversible melting transition which allows them to be processed into well-defined micron-sized shapes.

Recent progress in microfluidic technology allows fabricating microfluidic devices to produce liquid microjets with unprecedented control of the jet diameter and velocity. Here it is demonstrated that microfluidic devices based on the gas dynamic virtual nozzle principle can be excellently used for micro solution blow spinning to continuously fabricate microfibers with excellent control of the fiber diameter and the internal crystalline alignment that determines the mechanical properties. Fiber spinning experiments with small‐ and wide‐angle X‐ray scattering are combined to directly relate the macroscopic spinning conditions to the bulk and molecular structure of the resulting fibers. The elongational rate is shown as the relevant parameter that transduces the nozzle flow conditions to the local macromolecular structure and orientation, and thus the mechanical properties of the resulting fiber. It is observed that the spinning process results in very uniform microfibers with a well‐defined shish–kebab crystal structure, which evolves into an extended chain crystal structure upon plastic deformation. Thus, the presented microfluidic spinning methodology has great implications for a precisely controlled production of microfibers using miniaturized spinning devices.

Plastic crystals are a promising candidate for solid state ionic conductors. In this work, quasielastic neutron scattering is employed to investigate the center of mass diffusive motions in two types of plastic crystalline cyclic alcohols: cyclohexanol and cyclooctanol. Two separate motions are observed which are attributed to long-range translational diffusion (α-process) and cage rattling (fast β-process). Residence times and diffusion coefficients are calculated for both processes, along with the confinement distances for the cage rattling. In addition, a binary mixture of these two materials is measured to understand how the dynamics change when a second type of molecule is added to the matrix. It is observed that, upon the addition of the larger cyclooctanol molecules into the cyclohexanol solution, the cage size decreases, which causes a decrease in the observed diffusion rates for both the α- and fast β-processes.

We studied the controlled growth of triangular prismatic Au nanoparticles with different beveled sides for surface-enhanced Raman spectroscopy (SERS) applications. First, in a seedless synthesis using 3-butenoic acid (3BA) and benzyldimethylammonium chloride (BDAC), gold nanotriangles (AuNTs) were synthesized in a mixture with gold nanooctahedra (AuNOCs) and separated by depletion-induced flocculation. Here, the influence of temperature, pH, and reducing agent on the reaction kinetics was initially investigated by UV-vis and correlated to the size and yield of AuNT seeds. In a second step, the AuNT size was increased by seed-mediated overgrowth with Au. We show for the first time that preformed 3BA-synthesized AuNT seeds can be overgrown up to a final edge length of 175 nm and a thickness of 80 nm while maintaining their triangular shape and tip sharpness. The NT morphology, including edge length, thickness, and tip rounding, was precisely characterized in dispersion by small-angle X-ray scattering and in dry state by transmission electron microscopy and field-emission scanning electron microscopy. For sensor purposes, we studied the size-dependent SERS performance of AuNTs yielding analytical enhancement factors between 0.9 × 10

This chapter describes the synthesis and some characteristics of magnetic iron oxide nanoparticles, mainly nanocubes, and focuses on their self-assembly into crystalline cuboids in dispersion. The influence of external magnetic fields, the concentration of particles, and the temperature on the assembly process are experimentally investigated.

Eine neue, Templat-gestutzte Synthese monodisperser Nanopartikel stellt keine Anforderungen an die Selbstorganisation und ist hoch reproduzierbar. Hierzu werden masgeschneiderte Polymerkafige fur die Synthese von Nanopartikeln verwendet, die aus vernetzten Makromolekulen mit Thiolendgruppen bestehen. Goldnanopartikel (AuNPs) wurden in verschiedenen Verhaltnissen von Polymerkafig zu Gold in situ in den Polymerkafigen synthetisiert. Die Polymerkafige zeichneten sich dabei durch eine definierte Beladungskapazitat aus, mit exzellenter Kontrolle uber Form und Grose. Dagegen zeigten Kontrollversuche mit linearen Diblockcopolymeren einen linearen Anstieg der Partikelgrosen mit steigendem Goldanteil. Das unterschiedliche Wachstumsverhalten der AuNPs wird durch die Vernetzungsgrad-abhangige Flexibilitat der Polymerketten erklart. Des Weiteren wird die Polymerkafig-gesteuerte In-situ-Synthese auf Silber- (AgNPs), Palladium- (PdNPs) und Platinnanopartikel (PtNPs) ubertragen.

Polymer nanocomposites for optical applications require high optical transparency at high filling ratios of nanoparticles. The nanoparticles provide optical functionality but unfortunately have a strong tendency to aggregate in polymer matrices leading to strong turbidity and reduced optical transmission, particularly at high filling ratios. We report a general route to nonaggregated highly filled, optically transparent polymer nanocomposites. It is based on using nanoparticles that have been coated with polymers forming spherical brushlike layers providing thermodynamic miscibility with the polymer matrix over the complete range of nanoparticle volume fractions. The polymers are attached via a versatile ligand exchange procedure which enables to prepare a wide range of optically transparent polymer nanocomposites up to weight fractions of 45%. This is demonstrated for a broad range of metal and semiconductor nanoparticles in optically transparent polymer matrices relevant for selective light/UV absorptio...

Inspired by an increasing demand for stimuli-controlled assembly of nanostructures, mechano-responsive nanocomposites are designed with tremendous scope in material applications. Providing switchable properties by means of mechanical stimulation, elastomer-incorporated gold nanorods (AuNR) are presented herein. Stepless and reversible control over the orientational AuNR alignment – and therefore over macroscopic anisotropy – is exerted by uniaxial film elongation. In context of optical applications, substantial impact on the plasmonic properties within adjustable spectral ranges is demonstrated. Mechano-responsive nanocomposites with high thermal colloidal stability are prepared via a facile hetero-phase ligand exchange procedure where complete coverage of the AuNR surface with hydrophobic ligands is achieved.

Nanocomposites based on molybdenum disulfide (MoS2) and different carbon modifications are intensively investigated in several areas of applications due to their intriguing optical and electrical properties. Addition of a third element may enhance the functionality and application areas of such nanocomposites. Herein, we present a facile synthetic approach based on directed thermal decomposition of (Ph4P)(2)MoS4 generating MoS2 nanocomposites containing carbon and phosphorous. Decomposition at 250 degrees C yields a composite material with significantly enlarged MoS2 interlayer distances caused by in situ formation of Ph3PS bonded to the MoS2 slabs through MoS bonds and (Ph4P)(2)S molecules in the van der Waals gap, as was evidenced by P-31 solid-state NMR spectroscopy. Visible-light-driven hydrogen generation demonstrates a high catalytic performance of the materials.

Funktionale Molekule lassen sich mit einem neuen Verfahren zwischen zwei 1 nm dunnen Schichten verkapseln, die ahnlich wie Glas transparent und chemisch inert sind. Geordnete Wechsellagerungen von alternierenden organischen und osmotisch quellfahigen Na+-Zwischenschichten delaminieren spontan zu Doppelschichten bestehend aus zwei Silicatschichten, welche die organische Zwischenschicht einschliesen. Die neue Technik ist geeignet, um hydrophobe, funktionale Molekule zu maskieren und vollstandig in Wasser dispergierbar zu machen. Die Doppelschichten besitzen durch die laterale Ausdehnung von 5000 nm und die Dicke von 4.5 nm ein Aspektverhaltnis von >1000. Die Kombination aus strukturimmanenter Anisotropie der Silicatschichten und der aus dem begrenzten Raum zwischen den Schichten resultierenden Vorzugsorientierung eingelagerter Molekule erlaubt es, Nanokompositfilme mit einer definierten Orientierung der eingekapselten Molekule herzustellen, die sich in der Folge durch anisotrope optische Eigenschaften auszeichnen.

Amphiphilic diblock copolymers can spontaneously form integral asymmetric isoporous membranes by evaporation-induced self-assembly. The critical structural evolution steps occur within the first hundred seconds after solvent casting. By using synchrotron X-ray scattering employing a specially designed solvent casting apparatus, we were able to follow the kinetics of the structural evolution in situ. At an initial time of 20 s after solvent-casting we observe the first structural features on length scales d of 30–70 nm, signaled by a weak maximum in the low-q region of the measured scattering curves. During the subsequent period the length scales increase continuously until after around 100 s they reach a plateau value d∞ of 80–120 nm, the size depending on the molecular weight of the block copolymer. Interestingly, the time evolution of the characteristic length scales follow a simple exponential saturation curve for all block copolymers, irrespective of molecular weight, composition, and addition of ioni...

The chemical structure and high aspect ratio of carbon nanotubes (CNTs) give rise to numerous exceptional physical properties but are also the origin for their intrinsic tendency to agglomerate. Since the full potential of CNTs is harnessed in homogeneous dispersions, e.g. in a polymer matrix, bundling of CNTs must be suppressed by compatibilizing unfavorable interfaces. We present a robust, noncovalent functionalization of multiwalled CNTs via physical grafting of polystyrene-block-polyethylene-block-poly(methyl methacrylate) (SEM) triblock terpolymers to the CNT surface in organic media. In an ultrasound-assisted approach at ambient temperature, the polyethylene (PE) middle block of SEM strongly adsorbs to the CNTs surface, yielding long-term stable dispersions of well-separated 1D hybrids with up to 3 wt % CNT content. Importantly, the strong affinity of PE toward CNTs prevents polymer desorption irrespective of the solvent conditions. The incompatible polystyrene (PS) and poly(methyl methacrylate) (PM...

Because of strong Coulomb interactions, the delamination of charged layered materials becomes progressively more difficult with increasing charge density. For instance, highly charged sodium fluorohectorite (Na0.6Mg2.4Li0.6Si4O10F2, Na-Hec) cannot be delaminated directly by osmotic swelling in water because its layer charge exceeds the established limit for osmotic swelling of 0.55 per formula unit Si4O10F2. Quite surprisingly, we found that this hectorite at the border of the smectite and vermiculite group can, however, be utterly delaminated into 1-nm-thick platelets with a high aspect ratio (24 000) in a two-step process. The hectorite is first converted by partial ion exchange into a one-dimensionally ordered, interstratified heterostructure with strictly alternating Na+ and n-butylammonium (C4) interlayers. This heterostructure then spontaneously delaminates into uniform single layers upon immersion in water whereas neither of the homoionic phases (Na-Hec and C4-Hec) swells osmotically. The delaminat...

Spin-crossover compounds are a class of materials that can change their spin state from high spin (HS) to low spin (LS) by external stimuli such as light, pressure or temperature. Applications demand compounds with defined properties concerning the size and switchability that are maintained when the compound is integrated into composite materials. Here, we report the synthesis of [Fe(Leq)(Lax)]n coordination polymer (CP) nanoparticles using self-assembled polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) micelles as template. Variation of the solvent (THF and toluene) and the rigidity of the axial ligand Lax (Lax = 1,2-di(pyridin-4-yl)ethane) (bpea), trans-1,2-di(pyridin-4-yl)ethene (bpee), and 1,2-di(pyridin-4-yl)ethyne) (bpey); Leq = 1,2-phenylenebis(iminomethylidyne)-bis(2,4-pentanedionato)(2−)) allowed the determination of the preconditions for the selective formation of nanoparticles. A low solubility of the CP in the used solvent and a high stability of the Fe–L bond with regard to ligand exchange are necessary for the formation of composite nanoparticles where the BCP micelle is filled with the CP, as in the case of the [FeLeq(bpey)]n@BCP. Otherwise, in the case of more flexible ligands or ligands that lead to high spin complexes, the formation of microcrystals next to the CP–BCP nanoparticles is observed above a certain concentration of [Fe(Leq)(Lax)]n. The core of the nanoparticles is about 45 nm in diameter due to the templating effect of the BCP micelle, independent of the used iron complex and [Fe(Leq)(Lax)]n concentration. The spin-crossover properties of the composite material are similar to those of the bulk for FeLeq(bpea)]n@BCP while pronounced differences are observed in the case of [FeLeq(bpey)]n@BCP nanoparticles.

Fast concentration-induced diffusion-limited lyotropic phase transitions can be studied in situ with millisecond time resolution using continuous flow microfluidics in combination with microfocus small-angle X-ray scattering. The method was applied to follow a classical self-assembly sequence where amphiphiles assemble into micelles, which subsequently assemble into an ordered lattice via a disorder/order transition. As a model system we selected the self-assembly of an amphiphilic block copolymer induced by the addition of a nonsolvent. Using microchannel hydrodynamic flow-focusing, large concentration gradients can be generated, leading to a deep quench from the miscible to the microphase-separated state. Within milliseconds the block copolymers assembly via a spinodal microphase separation into micelles, followed by a disorder/order transition into an FCC liquid-crystalline phase with late-stage domain growth and shear-induced domain orientation into a mesocrystal. A comparison with a slow macroscopic near-equilibrium kinetic experiment shows that the fast structural transitions follow a direct pathway to the equilibrium structure without the trapping of metastable states.

The selective cross-linking of individual domains in block copolymer bulk morphologies represents an elegant strategy to generate nanostructured materials of tunable size and geometry. We demonstrate the preparation of highly periodic nanoporous sheets and core–shell cylinders from a stimuli-responsive triblock terpolymer, polybutadiene-block-poly(tert-butyl methacrylate)-block-poly(2-(dimethylamino)ethyl methacrylate) (PB-b-PtBMA-b-PDMAEMA). By blending the terpolymer with different types and amounts of homopolymers, a variety of bulk morphologies is accessible, including rarely found examples such as tetragonally perforated lamellae and double gyroid networks. Selective cross-linking of the PB domains of the generated morphologies followed by sonication-assisted dispersion allows the preparation of well-defined nanostructures in nonselective solvents. Because of the PDMAEMA corona, the cross-linked structures are soluble in aqueous media. The high regularity of the pore diameter in combination with a tu...

We present a versatile approach to produce macroscopic, substrate-supported arrays of plasmonic nanoparticles with well-defined interparticle spacing and a continuous particle size gradient. The arrays thus present a "plasmonic library" of locally noncoupling plasmonic particles of different sizes, which can serve as a platform for future combinatorial screening of size effects. The structures were prepared by substrate assembly of gold-core/poly(N-isopropylacrylamide)-shell particles and subsequent post-modification. Coupling of the localized surface plasmon resonance (LSPR) could be avoided since the polymer shell separates the encapsulated gold cores. To produce a particle array with a broad range of well-defined but laterally distinguishable particle sizes, the substrate was dip-coated in a growth solution, which resulted in an overgrowth of the gold cores controlled by the local exposure time. The kinetics was quantitatively analyzed and found to be diffusion rate controlled, allowing for precise tuning of particle size by adjusting the withdrawal speed. We determined the kinetics of the overgrowth process, investigated the LSPRs along the gradient by UV-vis extinction spectroscopy, and compared the spectroscopic results to the predictions from Mie theory, indicating the absence of local interparticle coupling. We finally discuss potential applications of these substrate-supported plasmonic particle libraries and perspectives toward extending the concept from size to composition variation and screening of plasmonic coupling effects.

We systematically investigated the structure formation pathways and transient morphologies involved in the formation of mesoporous membranes by the self-assembly of block copolymers during nonsolvent-induced phase separation. Using AFM, SEM, and in situ synchrotron SAXS, we mapped the topological paths and characteristic transient structures into a ternary phase diagram. We focused on the stability region of an ordered pore phase which is relevant for the generation of integral asymmetric isoporous membranes. We could identify several characteristic morphologies, i.e., spinodal networks, sphere percolation networks, ordered pore structures, and disordered and ordered cylinder arrangements together with transient structures connecting their stability regions. With given evaporation rates for the pure solvents, we calculated the corresponding composition trajectories in the phase diagram to identify suitable experimental conditions in terms of initial polymer volume fraction, solvent composition, and immers...

Optimizing the reinforcement of polymers with nanoplatelets requires optimization of the aspect ratio and the moduli of the filler while providing a complete stress transfer. Employing a novel shear-stiff, nano-mica with large aspect ratio, we focus on maximizing the interfacial interaction between filler and matrix. External surfaces of the nano-mica were selectively modified by a polycationic macro-initiator and two PMMA-polymer brushes of length below and above critical entanglement length, respectively, and the mechanical properties of the three PMMA nanocomposites were measured. The multiple electrostatic anchoring groups of the macro-initiator not only provide reliable adhesion but at the same time allow the variation of the degree of protonation providing a local match between the charge densities of the clay surface and the adsorbed macro-initiator. PMMA coating of the nano-mica via surface initiated polymerization yielded long-term stable suspensions in THF that showed birefringence of a nematic phase. Solution blending of the PMMA coated nano-mica allows for dispersing single clay tactoids in the translucent PMMA nanocomposites at 5 wt% clay loading as determined by transmission electron microscopy (TEM). Although significantly improved mechanical properties could be achieved as compared to nanocomposites made with conventional clay fillers, the full potential – as expressed by Halpin–Tsai equations – of the PMMA coated nano-mica can still not be completely utilized. This is attributed to the non-wetting character of the densely packed PMMA brushes attached to planar nanoplatelets.

We report an efficient, robust and up-scalable synthetic route to small, spherical, well stabilized, narrow disperse, crystalline ZnO nanoparticles. The synthesis utilizes Zn-oleate or Zn-stearate as precursors, which are hydrolyzed in polar organic solvents to obtain ZnO nanoparticles in diameters in the range of 3–5 nm on multi-gram scales. The synthesis exploits the use of oleates and stearates as good precursors and stabilizing agents together with the hydrolysis route to obtain small ZnO nanoparticles in a well-controlled way. The nanoparticles show the characteristic bright green fluorescence emission, and can be precipitated, dried, and redispersed in common organic solvents without aggregation. Because of their good steric stabilization and hydrophobic coating, these nanoparticles are very suitable for applications in polymer nanocomposites for UV-absorption and opto-electronic applications.

Severe quality defects of a well-established preservation oil ranging from improper viscosity values to the formation of calcium carboxylate precipitates led to detailed investigations on the origin of these failures. Chemical analyses employing spectroscopic and chromatographic techniques focusing on the product's additives were performed. Thereupon, a mechanism for precipitate formation based on a delicate interaction between solubilizer, carboxylates, sulfonates and calcium ions was proposed. For this mechanism, ligand properties of sulfonates play a vital role: In contrast to monosulfonates, disulfonates seem to impede precipitation of calcium carboxylates. Copyright © 2014 John Wiley & Sons, Ltd.

We present microfluidic chip based devices that produce liquid jets with micrometer diameters while operating at very low flow rates. The chip production is based on established soft-lithographical techniques employing a three-layer design protocol. This allows the exact, controlled and reproducible design of critical parts such as nozzles and the production of nozzle arrays. The microfluidic chips reproducibly generate liquid jets exiting at perfect right angles with diameters between 20 μm and 2 μm, and under special circumstances, even down to 0.9 μm. Jet diameter, jet length, and the domain of the jetting/dripping instability can be predicted and controlled based on the theory for liquid jets in the plate-orifice configuration described by Gañán-Calvo et al. Additionally, conditions under which the device produces highly reproducible monodisperse droplets at exact and predictable rates can be achieved. The devices operate under atmospheric and under vacuum conditions making them highly relevant for a wide range of applications, for example, for free-electron lasers. Further, the straightforward integration of additional features such as a jet-in-jet is demonstrated. This device design has the potential to integrate more features based on established microfluidic components and may become a standard device for small liquid jet production.

DPDAK is a software for simple and fast on- and offline reduction and analysis of X-ray scattering data. It is an open-source software with a plug-in structure allowing tailored extensions., X-ray scattering experiments at synchrotron sources are characterized by large and constantly increasing amounts of data. The great number of files generated during a synchrotron experiment is often a limiting factor in the analysis of the data, since appropriate software is rarely available to perform fast and tailored data processing. Furthermore, it is often necessary to perform online data reduction and analysis during the experiment in order to interactively optimize experimental design. This article presents an open-source software package developed to process large amounts of data from synchrotron scattering experiments. These data reduction processes involve calibration and correction of raw data, one- or two-dimensional integration, as well as fitting and further analysis of the data, including the extraction of certain parameters. The software, DPDAK (directly programmable data analysis kit), is based on a plug-in structure and allows individual extension in accordance with the requirements of the user. The article demonstrates the use of DPDAK for on- and offline analysis of scanning small-angle X-ray scattering (SAXS) data on biological samples and microfluidic systems, as well as for a comprehensive analysis of grazing-incidence SAXS data. In addition to a comparison with existing software packages, the structure of DPDAK and the possibilities and limitations are discussed.

Nowadays there is a high demand for specialized functional materials for specific applications in sensors or biomedicine (e.g. fMRI). For their implementation in devices, nanostructuring and integration in a composite matrix are indispensable. Spin crossover complexes are a highly promising family of switchable materials where the switching process can be triggered by various external stimuli. In this work, the synthesis of nanoparticles of the spin crossover iron(ii) coordination polymer [Fe(L)(bipy)]

Compartmentalization is a major prerequisite for the origin of life on earth according to Wächtershäuser "Iron-Sulfur-World". The hypothesis is mainly based on an autocatalytic inorganic energy reproducing redox system consisting of iron and sulfur as requirement for the subsequent synthesis of complex organic structures. Here, we modified [FeFe]-hydrogenase models by means of covalent coupling to either oleic acid or the amphiphilic block copolymer polybutadiene-polyethyleneoxide (PB-PEO) and incorporated those into the membranes of vesicles composed of phospholipids (liposomes) or the unmodified amphiphilic polymer (polymersomes). We employed a [2Fe-2S] cluster as a hydrogenase model, since these structures are known to be suitable catalysts for the generation of H2 in the presence of weak acids. Successful incorporation was confirmed by spectrophotometric iron quantification and the vesicles formed were characterized by size determination (photon correlation spectroscopy (PCS)), and zeta potential as well as by cryo-transmission electron microscopy (Cryo-TEM). The modified models could be incorporated into liposomes or polymersomes up to molar proportions of 3.15% and 28%, respectively. Due to the immobilization in vesicular bilayers the [FeFe]-hydrogenase models can even exhibit catalytic action under the particular conditions of the intravesicular microenvironment. Our results suggest that the vesicular systems described may be applied as a nanoreactor for the reduction of encapsulated substances by generating hydrogen and thus as a minimal cell model.

Zur erfolgreichen Gestaltung einer angemessenen Lernumgebung gehört eine effiziente Klassenführung. Eine wesentliche Voraussetzung dafür ist die Fähigkeit, klassenführungsrelevante Ereignisse im Unterricht erkennen, angemessen einschätzen und mögliche Handlungsalternativen benennen zu können. In der vorliegenden Evaluationsstudie wird untersucht, inwiefern sich solch eine professionelle Wahrnehmung in der universitären Lehramtsausbildung anhand der angeleiteten Analyse von Unterrichtsvideos vermitteln lässt. In Lehrseminaren trainierten Studierende im Umfang von 60 Stunden in Partnerarbeit die Analyse ausgewählter Unterrichtsausschnitte hinsichtlich der Klassenführungsdimensionen Allgegenwärtigkeit, Strukturierung des Unterrichtsverlaufs und Gruppenfokus. Es nahmen insgesamt 120 Studierende an der Studie mit einem Prä-Post-Kontrollgruppendesign teil. In Kovarianzanalysen zeigten sich signifikante Effekte der Gruppe in der erwarteten Richtung, wobei sich für die Facette Strukturierung des Unterrichtsverlaufs eine kleine und für die Facette Gruppenfokus eine mittlere Effektstärke ergab, während für die Facette Allgegenwärtigkeit keine Effekte gefunden wurden. Der Einfluss des Fachsemesters, aber auch Erfahrungen mit Unterrichtsanalysen und Klassenführung hatten keinen signifikanten Einfluss auf die professionelle Wahrnehmung klassenführungsrelevanter Unterrichtsereignisse.

We present the efficient synthesis of a new molecular spoked-wheel structure (MSW-3). Two derivatives with diameters of approximately 4 nm have been prepared. By highlighting the importance of pseudo-high-dilution conditions during cyclization, we were able to access the compounds on a several hundred milligram scale. In addition to the standard characterization (NMR spectroscopy, MS), we describe a detailed investigation of the optical properties of the fluorescent MSWs by comparison with appropriate model chromophores. Furthermore, a comprehensive study of the structure in solution by means of light- and X-ray scattering experiments has been conducted. Scanning tunneling microscopy (STM) revealed the two-dimensional organization of the molecules on highly oriented pyrolytic graphite and emphasized the spoked-wheel structure. The diameter of these molecules measured by small-angle X-ray scattering is in very good agreement with that obtained from STM and matches the results of molecular modeling. This confirms the rigidifying effect of the spokes, which results in highly shape-persistent nanometer-sized oblate organic compounds.

We present a bottom-up assembly route for a large-scale organization of plasmonic nanoparticles (NPs) into three-dimensional (3D) modular assemblies with core/satellite structure. The protein-assisted assembly of small spherical gold or silver NPs with a hydrophilic protein shell (as satellites) onto larger metal NPs (as cores) offers high modularity in sizes and composition at high satellite coverage (close to the jamming limit). The resulting dispersions of metal/metal nanoclusters exhibit high colloidal stability and therefore allow for high concentrations and a precise characterization of the nanocluster architecture in dispersion by small-angle X-ray scattering (SAXS). Strong near-field coupling between the building blocks results in distinct regimes of dominant satellite-to-satellite and core-to-satellite coupling. High robustness against satellite disorder was proved by UV/vis diffuse reflectance (integrating sphere) measurements. Generalized multiparticle Mie theory (GMMT) simulations were employed to describe the electromagnetic coupling within the nanoclusters. The close correlation of structure and optical property allows for the rational design of core/satellite nanoclusters with tailored plasmonics and well-defined near-field enhancement, with perspectives for applications such as surface-enhanced spectroscopies.

Ordered heterostructures of layered materials where interlayers with different reactivities strictly alternate in stacks offer predetermined slippage planes that provide a precise route for the preparation of bilayer materials. We use this route for the synthesis of a novel type of reinforced layered silicate bilayer that is 15 % stiffer than the corresponding monolayer. Furthermore, we will demonstrate that triggering cleavage of bilayers by osmotic swelling gives access to a generic toolbox for an asymmetrical modification of the two vis-a-vis standing basal planes of monolayers. Only two simple steps applying arbitrary commercial polycations are needed to obtain such Janus-type monolayers. The generic synthesis route will be applicable to many other layered compounds capable of osmotic swelling, rendering this approach interesting for a variety of materials and applications.

Fabrication of anisotropic hydrogels exhibiting direction-dependent structure and properties have attracted great interest in biomimicking, tissue engineering and bioseparation. Herein, we report a single-step freeze casting-based fabrication of structurally and mechanically anisotropic aerogels and hydrogels composed of hydrazone cross-linked poly(oligoethylene glycol methacrylate) (POEGMA) and cellulose nanocrystals (CNCs). We show that by controlling the composition of the CNC/POEGMA dispersion and the freeze casting temperature, aerogels with fibrillar, columnar, or lamellar morphologies can be produced. Small-angle X-ray scattering experiments show that the anisotropy of the struc- ture originates from the alignment of the mesostructures, rather than the CNC building blocks. The composite hydrogels show high structural and mechanical integrity and a strong variation in Young's moduli in orthogonal directions. The controllable morphology and hydrogel anisotropy, coupled with hydrazone cross-linking and biocompatibility of CNCs and POEGMA, provide a versatile platform for the preparation of anisotropic hydrogels.

Monoguanidinato titanium complexes are efficient catalysts to make OH end-group-functionalized polyethylene (PE-OH) by a catalyzed version of Ziegler's "Aufbaureaktion". This PE-OH can be structured to mesoporous polyethylene or polyethylene nanofibers/ribbons through diblock copolymer synthesis, microphase separation, and etching of the sacrificial polylactide block.

Nanoparticles can self-assemble into highly ordered two- and three-dimensional superlattices. For many practical applications these assemblies need to be integrated into polymeric matrices to provide stability and function. By appropriate co-assembly of nanoparticles and polymers it has become possible to tailor the nanoparticle superlattice structure via the length and stiffness of the polymer chains. The present article outlines and discusses established routes to nanoparticle-polymer superlattices. Recent progress has been remarkable so that the integration into functional devices has become the next challenge.

Analytical expressions for the scattering patterns of ordered nano- and mesoscopic materials are derived and compared to measured scattering patterns. Ordered structures comprising spheres (fcc, bcc, hcp, sc, and bct), cylinders (hex and sq), lamellae (lam) and vesicles, as well as bicontinuous cubic structures (Ia3d, Pn3m, and Im3m) are considered. The expressions take into account unit cell dimensions, particle sizes and size distributions, lattice point deviations, finite domain sizes, orientational distributions, core/shell-structures as well a variety of peak shapes. The expressions allow to quantitatively describe, model and even fit measured SAXS and SANS-patterns of ordered or oriented micellar solutions, lyotropic phases, block copolymers, colloidal solutions, nanocomposites, photonic crystals, as well as mesoporous materials.

Micelles are the simplest example of self-assembly found in nature. As many other colloids, they can self-assemble in aqueous solution to form ordered periodic structures. These structures so far all exhibited classical crystallographic symmetries. Here we report that micelles in solution can self-assemble into quasicrystalline phases. We observe phases with 12-fold and 18-fold diffraction symmetry. Colloidal water-based quasicrystals are physically and chemically very simple systems. Macroscopic monodomain samples of centimeter dimension can be easily prepared. Phase transitions between the fcc phase and the two quasicrystalline phases can be easily followed in situ by time-resolved diffraction experiments. The discovery of quasicrystalline colloidal solutions advances the theoretical understanding of quasicrystals considerably, as for these systems the stability of quasicrystalline states has been theoretically predicted for the concentration and temperature range, where they are experimentally observed. Also for the use of quasicrystals in advanced materials this discovery is of particular importance, as it opens the route to quasicrystalline photonic band gap materials via established water-based colloidal self-assembly techniques.