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Myosin II is the main force generating motor during muscle contraction. Myosin II exists as different isoforms, involved in diverse physiological functions. The outstanding question is whether the myosin heavy chain (MHC) isoforms alone account for the distinct physiological properties. Unique sets of essential and regulatory light chains (RLCs) assembled with specific MHCs raises an interesting possibility of specialization of myosin functions via light chains (LCs). Here, we ask whether different RLCs contribute to the functional diversification. To investigate this, we generated chimeric motors by reconstituting MHC fast isoform (MyHC-IId) and slow isoform (MHC-I) with different light chain variants. As a result of RLCs swapping, actin filament sliding velocity increased by ∼ 10 fold for the slow myosin and decreased by >3 fold for the fast myosin. Ensemble molecule solution kinetics and single molecule optical trapping measurements provided in-depth insights into altered chemo mechanical properties of the myosin motors, thereby affecting the sliding speed. We find that both slow and fast myosins mechanical output is sensitive to the RLC isoform and propose that RLCs are crucial in fine-tuning of the myosin function.

The recently reported ferroelectric phase in doped hafnium oxide films enabled various devices ranging from non-volatile applications to negative capacitance field effect transistors. This study analyses the structural and electrical changes in ferroelectric Hf1xZrxO2 based metal-insulator-metal capacitors. Planar metal-ferroelectric-metal stacks of different composition, thickness and purge times were prepared by atomic layer deposition for the Hf1xZrxO2 films with metal organic precursors, water as oxygen source and reactive physical vapor deposition of TiN electrodes. With the optimization of the process route it was possible to improve the endurance and the remanent polarization of the ferroelectric capacitor. The analysis proved that the reduction of the impurities in the film is decreasing the non-ferroelectric monoclinic phase fraction with increasing purge time. An increase of the annealing temperature from 500 to 800C resulted in a higher amount of the ferroelectric orthorhombic phase fraction, but also caused a reduced endurance. Impedance spectroscopy indicated the existence of an interfacial dead layer and its widening with higher anneal temperatures. Display Omitted Atomic layer deposition and anneal conditions were improved to optimize the Hf1xZrxO2 ferroelectric capacitor performance.Dielectric relaxation and impedance spectroscopy measurements have been performed to study the TiN/Hf1xZrxO2-interface.Hf1xZrxO2 film thicknesses in the range of 10 to 15nm are favorable for the ferroelectric orthorhombic phase.High anneal temperatures increases remanent polarization and reduces the wake up but decreases the endurance.The thickness of the TiN/Hf1xZrxO2-interface is increasing with increasing anneal temperature.

The unexpected ferroelectric properties of nanoscale hafnia-zirconia are considered to be promising for a wealth of applications including ferroelectric memory, field effect transistors, and energy-related applications. However, the reason why the unexpected ferroelectric Pca21 phase can be stabilized has not been clearly understood although numerous extensive theoretical and experimental results have been reported recently. The ferroelectric orthorhombic phase is not a stable phase under processing conditions from the viewpoint of bulk free energy. Although the possibility of stabilization of the ferroelectric phase due to the surface energy effect has been theoretically suggested, such a theoretical model has not been systematically compared with actual experimental results. In this study, the experimental observations on polymorphism in nanoscale HfO2–ZrO2 solid solution thin films of a wide range of film compositions and thicknesses are comprehensively related to the theoretical predictions based on a thermodynamic surface energy model. The theoretical model can semi-quantitatively explain the experimental results on the phase-evolution, but there were non-negligible discrepancies between the two results. To understand these discrepancies, various factors such as the film stress, the role of a TiN capping layer, and the kinetics of crystallization are systematically studied. This work also reports on the evolution of electrical properties of the film, i.e. dielectric, ferroelectric, anti-ferroelectric, and morphotropic phase changes, as a function of the film composition and thickness. The in-depth analyses of the phase change are expected to provide an important guideline for subsequent studies.

Extensive research has been performed in the past to understand the mechanisms responsible for the instabilities during electric field cycling of ferroelectric HfO2. In this chapter, the wake-up, imprint, and fatigue effect of fluorite structure-type ferroelectrics will be comprehensively reviewed based on the existing literature. The most likely root cause of the wake-up effect is identified as a local imprint mechanism. The constricted hysteresis in the pristine state is caused by the random orientation of domains. The imprint itself is likely generated by charge trapping. Electrons trapped into oxygen vacancies are pinning the domain seeds, which inhibit the ferroelectric switching. Lastly, the fatigue effect is examined. A generation and/or redistribution of oxygen vacancies during ferroelectric switching is occurring. These oxygen vacancies lead to domain wall pinning and finally to the forming of a conductive filament causing dielectric breakdown.

Recently simulation groups have reported the lanthanide series elements as the dopants that have the strongest effect on the stabilization of the ferroelectric non-centrosymmetric orthorhombic phase in hafnium oxide. This finding confirms experimental results for lanthanum and gadolinium showing the highest remanent polarization values of all hafnia-based ferroelectric films until now. However, no comprehensive overview that links structural properties to the electrical performance of the films in detail is available for lanthanide-doped hafnia. La:HfO₂ appears to be a material with a broad window of process parameters, and accordingly, by optimization of the La content in the layer, it is possible to improve the performance of the material significantly. Variations of the La concentration leads to changes in the crystallographic structure in the bulk of the films and at the interfaces to the electrode materials, which impacts the spontaneous polarization, internal bias fields, and with this the field cycling behavior of the capacitor structure. Characterization results are compared to other dopants like Si, Al, and Gd to validate the advantages of the material in applications such as semiconductor memory devices.

This value is achieved due to a very low interface trap density of below 1010 eV–1 cm–2 and a fixed charge density of (2–3) × 1012 cm–2. In contrast, plasma ALD-grown Al2O3 layers only reach carrier lifetimes of about 1 ms. This is mainly caused by a more than 10 times higher density of interface traps, and thus, inferior chemical passivation. The strong influence of the deposition parameters is explained by the limitation of hydrogen transport in Al2O3 during low-thermal budget annealing. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Chiral concave imidazolinium salts 4·Cl– with different ring sizes were synthesized as precursors of chiral concave N-heterocyclic carbenes, starting from di-ortho-substituted anilines 5 and 2,7-disubstituted aminonaphthalenes 6. The terminal alkene groups of the substituents were cyclized by ring-closing metathesis to give bimacrocyclic axially chiral concave imidazolinium salts 14·Cl–, and, after hydrogenation of the double bonds, 4·Cl–. The overall yields of bimacrocycles 4b·Cl– and 4c·Cl– were 54 and 39 %, starting from amino-substituted arenes 5 and 6, respectively. Racemic mixtures of the three concave NHC precursors 4a–c·Cl– were separated by chiral HPLC techniques, and their absolute stereochemistry was assigned by comparison of simulated and experimental CD spectra.

Ferroelectric random access memories (FRAM) are nonvolatile memories which allow a fast access time and a low power consumption. State-of-the-art devices are based on the perovskite lead zirconate titanate (PZT), which suffers from CMOS incompatibility resulting in scaling issues. The discovery of the ferroelectricity in doped hafnium oxide enabled scaled 3D memory devices. A variety of dopants has already been found to stabilize the orthorhombic phase, responsible for ferroelectric switching. Interestingly, among the variety of dopants only a mixed hafnium zirconium oxide (HZO) enabled a wide process window together with a large memory window. Here, we compare PZT with HZO and show that despite different dielectric properties similar memory relevant performance can be achieved. Additionally, analogous wake-up and degradation behavior can be observed in both materials. Moreover, we show experimental proof that a thermally driven wake-up in both material systems is caused by diffusion of ionic charges. Extracted activation energy hints to oxygen vacancy movement as the main cause for the wake-up effect in HZO.

We present a simulation procedure based on optical ray-tracing in order to optimize the angular homogeneity of the light emitted from the color conversion element (CCE) in a phosphor conversion-based white LED. The blue LED and the yellow CCE light have rather different emission characteristics; so the geometry of the CCE as well as its phosphor concentration have to be carefully adjusted in order to achieve equal irradiance and/or radiant intensity distributions on a photo-detector surrounding the LED. The simulations identify the optimal CCE geometries and material compositions in order to obtain angular homogeneity for a broad range of color temperatures.

We report on the micro-fabrication of diffractive optical elements (DOEs) such as 1D, 2D and concentric grating structures inside the volume of thin silicone films by femtosecond laser direct writing. In addition, we show that such structures can also be integrated into silicone films that act as encapsulation layers of high power light-emitting diodes. The latter strategy opens new possibilities to homogenize and to control the light emitted from such devices.

Calix[4]pyrrole-chloride interactions are affected not only by the choice of countercation in halogenated solvents, but show a specific dependence on the way in which these cations are bound within the electron rich, bowl-like calix[4]pyrrole cavity formed upon chloride anion complexation. In dichloromethane, the affinities of simple meso-octamethylcalix[4]pyrrole (1) for methyl-, ethyl-, and n-butylammonium chlorides are on the order of 10(5), 10(4), and 10(2) M(-1), respectively, as determined from isothermal titration calorimetry (ITC) analyses. These cation-dependent anion affinity effects, while clearly evident, are less pronounced in other halogenated solvents, such as 1,2-dichloroethane. Support for the proposed cation complexation selectivity is provided by solid state X-ray crystallographic analyses.

The bicyclic hexahydropyrimidino[1,2a]pyrimidine cationic scaffold has a well-known capacity to bind a variety of oxoanions (phosphates, carboxylates, squarates, phosphinates). Based on this feature, the parent host was supplemented with sec-carboxamido substituents to generate compounds 1-3 in an effort to improve the anion-binding affinity and selectivity and to learn about the role and magnitude of entropic factors. Bicyclic guanidinium compounds were prepared by a convergent strategy via the corresponding tetraester 22 followed by catalytic amidation. Host-guest binding studies with isothermal titration calorimetry in acetonitrile probed the behavior of artificial hosts 1-3 in comparison with the tetraallylguanidinium compound 4 on binding p-nitrobenzoate, dihydrogenphosphate, and 2,2'-bisphenolcyclophosphate guests that showed enhanced affinities in the 10(5)-10(6) M(-1) range. Contrary to expectation, better binding emerges from more positive association entropies rather than from stronger enthalpic interactions (hydrogen bonding). In an NMR spectroscopy titration in DMSO, o-phthalate was sufficiently basic to abstract a proton from the guanidinium function, as confirmed by an X-ray crystal structure of the product. The novel carboxamide-appended anchor groups also bind carboxylates and phosphates, but not hydrogen sulfate in methanol with affinities in excess of 10(4) M(-1). The energetic signature of the complexation in methanol is inverted with respect to acetonitrile solvent and shows a pattern of general ion pairing with strong positive entropies overcompensating endothermic binding enthalpies. This study provides an example of the fact that bona fide decoration of a parent guanidinium anchor function with an additional binding functionality may provide the desired enhancement of the host-guest affinity, yet for a different reason than that implemented by design as guided by standard molecular modeling.

A novel synthetic route to the versatile chiral bicyclic guanidinium building block is described making use of l-methionine as a starting material from the natural chiral pool. Furthermore, the synthetic elaboration of this building block is shown in the construction of macrocyclic and open chain hosts, respectively. The host design employs urea functions as the connecting units and supplementary anchor groups for the complexation of anions. The binding studies of these hosts with various chiral and achiral oxoanions are performed by isothermal titration calorimetry. A trend analysis of the binding energetics in an ensemble of structurally similar guests discloses the importance of geometrical confinement of the guest. Association entropy rather than free energy (affinity) is identified as an indicator of structural uniqueness needed to distinguish configurational isomers in the recognition of enantiomeric carboxylates by the chiral guanidinium hosts.

With the goal to improve host–guest binding affinity, while retaining guest selectivity, the parent calixpyrrole artificial receptor unit was decorated with four sulfonium moieties (e.g.3b) placed rigidly in symmetrical fashion remote from the core binding site. The determination of binding constants using isothermal titration calorimetry (ITC), in conjunction with trend analyses in a series of related anions, reveals the occurrence of several specific and unspecific binding steps. The former predominate in affinity by 20–1000 fold depending on guest charge and structure. The dissection of the free energy of association into its enthalpic and entropic parts, in combination with structural variation in the guest anion, offers insight into the nature and diversity of the guest binding modes. On these grounds, the supplementation of parent host scaffolds with rigidly positioned positive charge centers, holds promise as a general concept for anion binding in competitive media.

The principles and conceptual basis of the design of molecular hosts for anions is examined. Starting from general considerations on the fundamentals of supramolecular binding and selectivity the role of the underlying model is illuminated. Turning to an agenda to be followed in the construction of concrete anion hosts the aspects of function, the guest to be bound, the competition situation and the strategic feasibility are discussed. Finally, arguments to include various facets of association entropy are presented that were unraveled by recent experimental studies. As a conclusion, the necessity to consider entropic influences in host design is emphasized. Although this adds to the complexity of the design task an optimistic prospect for success is voiced in view of recent progress in computational prediction and the support from experimental entropy data.

Supplementing bicyclic guanidinium anion receptors with four sec-carboxamido groups leads to enhanced affinity for oxoanions, however, for a different reason than originally planned. Calorimetric analysis reveals that better binding is due to higher association entropies rather than more negative enthalpies. Thus, molecular design following geometric and functional complementarity principles may misguide supramolecular constructions aimed at a unique host-guest binding mode, as required, e.g., by self-assembly or catalysis.

An attempt to experimentally estimate the role of binding-mode diversity (structural fuzziness) on the molecular recognition seen in the prominent guanidinium-oxoanion host-guest pair is described. The global heat response as measured by isothermal titration calorimetry in acetonitrile, which was obtained from the interaction of five different but structurally closely related guanidinium hosts with three rigid phosphinate guests of decreasing accessibility of their binding sites, is correlated to provide a trend analysis. All host-guest associations of 1:1 stoichiometry in this series are strongly enthalpy-driven. The change in complexation entropy can be related to the tightness of the mutual fit of the host-guest partners, which approaches a minimum limit and is interpreted as the unique lock-and-key binding mode. The ordinary host-guest complexation in this ensemble features substantial positive entropy changes that correlate inversely with the binding interface area. This finding excludes desolvation effects as the major cause of entropy production, and provides evidence for the existence of a broad variety of complex configurations rather than a single binding mode to represent the associated host-guest pair. This result bears on the molecular design of systems that vitally depend on structural fidelity, such as nanoassemblies or homogeneous catalysis.

We report on the morphological aspects of thin films prepared from a blue–green light-emitting conjugated polymer, (methyl-substituted ladder-type poly(p-phenylene, mLPPP)), blended with a solid-state electrolyte composed either by a crown ether, dicyclohexano-18-crown-6 (DCH18C6), or a high-molecular-weight poly(ethylene oxide) (HMWPEO), and a Li salt, lithium trifluoromethanesulfonate (LiCF3SO3, Li triflate (LiTf)), as they have been successfully applied in light-emitting electrochemical cells (LECs). The surface morphologies of the blend layers were investigated using atomic force microscopy (AFM) in tapping mode, and the ion distribution was probed using X-ray analysis by means of energy-dispersive X-ray spectrometry (EDXS) in the scanning electron microscope (SEM). We show that the two different phase-separation processes, the complexation tendencies of the ionic species as well as the ionic transport numbers, have tremendous influence on the performances of the corresponding LECs, revealing either rectifying or symmetric optoelectronic characteristics in forward and reverse bias directions. This opens up new possibilities for tuning the optoelectronic properties of ion-supported organic electronic devices.

The formation of structurally defined bioconjugates of proteins hinges on their regioselective modification. Toward this goal a novel method is described here using the commercial IgA protease to attach a nonnatural peptidic moiety to the N-terminus of predisposed proteins by means of a kinetically controlled reverse proteolysis in water. The process requires an H-Ala-Pro N-terminal sequence and then furnishes a selectively modified conjugate under nondenaturing and nondestructive conditions in acceptable yield. The method lends itself to the N-terminal introduction of orthogonal moieties that may be elaborated further.

Polyfluorenes are possibly the most attractive class of conjugated polymers for blue polymer light emitting devices. Derivatives with dendron side chains have been found to significantly improve the color stability of the devices. Using a quasi-cw photoinduced absorption technique we present a qualitative and quantitative analysis of lifetimes and deactivation mechanisms for the triplet excited states in a dendronically substituted derivative. The triplet lifetimes increase by one order of magnitude in the dendronic derivative compared to those in a standard poly(dialkylfluorene), which has been characterized for comparison. The temperature dependence of triplet lifetimes is interpreted in terms of migration assisted deactivation of triplet excitations. We conclude that the dendrons inhibit the Dexter-transfers of triplet excitations between the polymer chains and so strongly hinder triplet migration.

Ab initio calculations of the Raman spectra of ladder type oligo (p-phenylenes) (LOPP) were done in order to study the influence of the side chains attached on the methine bridge and the aromatic rings. We found that the aromatic CC stretching modes and the interring CC stretching modes are significantly influenced. Due to the attachment of an aromatic side chain on the methin bridge, an additional strong mode appears in the interring CC stretching region. Side chains on the aromatic rings cause a splitting of the aromatic CC stretching mode.

We report on Raman spectra of ladder type oligo(p-phenylenes) of different chain lengths (5LOPP and 7LOPP) and make a comparison to the Raman spectrum of the corresponding polymer, ladder type poly(p-phenylene) (LPPP). For a better understanding of the vibrational behavior of LPPP, several LPPPs with different substituents (methyl, allyl, n-butyl, 1-adamantyl) were investigated. The recorded Raman spectra of these LPPPs show significant changes in the interring CC stretching regions. An experimental analysis of the frequencies, intensities and line-shapes of significant modes is given in dependence on the substituents and chain lengths.

Contrary to common expectation, calorimetric measurements do not corroborate the preference of calix[4]pyrrole for fluoride over chloride in acetonitrile solution.