Although on-surface metalation protocols of tetrapyrroles with 3d metals are well established, reports on the formation of lanthanide tetrapyrrole complexes are scarce. Here, we address the synthesis of lanthanide-tetrapyrrole units in detail, refining earlier findings. Specifically, the formation of cerium tetraphenylporphyrin (Ce-TPP) was induced on Ag(111) either by thermal annealing or by a manipulation procedure using a scanning tunneling microscope (STM) tip. While the self-assembled TPP arrays are not altered upon Ce metalation, our STM observations show distinct modifications of submolecular features reflecting a multistep reaction pathway. The metalation proceeds from an initial configuration with a 2H-TPP molecule sitting atop a Ce atom via an intermediate state, where the macrocycle is partially deprotonated, to metalated Ce-TPP. The hitherto elusive 1H species-hypothesized in several 3d metalation studies-is visualized directly. Our study provides novel insights into the on-surface synthesis of tetrapyrroles and lanthanide-based nanosystems.

A novel approach is introduced for the experimental determination of critical fiber length in carbon fiber reinforced carbon (CFRC) composites. Critical fiber length is investigated using double lap joint samples. The transition of failure mode from bonding failure to fiber fraction with increasing overlap length correlates with the critical fiber length. Tested overlap lengths were in the range of 4–100mm. For CFRC at hand, failure mode changes at an overlap length of 26±2mm. Hence critical fiber length is derived as lc=52±4mm.

For short fiber CFRP based on a phenol matrix the influence of fiber length in terms of tensile strength and shear strength is investigated. The effect of fiber length within a representative phenol matrix structure (high porosity) is studied by a double lap joint principle. Therefore, a laminate with three layers is manufactured in such a way that each layer exhibits a cut. The two outer layers have the joint at the same position; the middle layer's joint has an offset which is adequate to the overlap length. Specimens with an overlap length ranging from 4 mm to 100 mm are mechanically tested. The CFRP material shows a nonlinear increase in tensile strength for short overlaps. As the overlap length increases, tensile strength reaches an upper limit asymptotically. This overlap length behavior is already known from adhesive double lap joints. The transition point between the rise and the asymptotic region is to determine the optimal overlap length. Due to contrary effects in short fiber composites (e.g. heterogeneity with increasing fiber length), the optimum length for the overlap is not the same as for the continuous fiber composites. If the model system is appropriate for short fiber composites, the optimal overlap length corresponds to an upper limit fiber length. The double lap joint principle could be an effective way of determining a maximum fiber length for a specific fiber matrix combination with a realistic matrix structure.

We employed de novo synthesized porphyrin modules to construct discrete cyclic supramolecular architectures supported on a copper surface. The programmed geometry and functionality of the molecular modules together with their conformational flexibility and substrate interaction yields symmetric discrete assemblies, including dimers and chains as well as three- to six-membered cyclic structures. The area of the molecular cavities is extended by creating bicomponent structures combining building blocks with different symmetry.

We report the hierarchic design of homochiral 2D nanoporous networks under ultrahigh vacuum conditions on the Ag(111) surface by using a flexible porphyrin derivative as a primary unit. The conformational adaptation of the molecular module gives rise to two enantiomers upon 2D confinement, which self-assemble in enantiopure clusters made of three molecules reflecting chiral recognition, which constitute the secondary supramolecular building block mediating the formation of the tertiary complex open networks. Our results show that the creation of homochiral superstructures based on the hierarchical assembly of conformationally flexible molecular components constitutes a unique pathway toward the design of novel and functional chiral structures.

We employed a de novo synthesized porphyrin module to construct one-dimensional (1D) Cu-coordinated polymers on Cu(111) and Ag(111) surfaces. The programmed geometry and functionality of the molecular module together with its conformational flexibility and substrate interaction yields sinuous metal-organic polymeric assemblies, based on an unusual two-fold Cu-pyridyl coordination motif. An analysis of scanning tunneling microscopy (STM) data reveals the occurrence of two enantiomers, resulting from the surface confinement that deconvolutes the module in 2D-chiral conformational isomers. The stereoisomers exhibit site-specific surface anchoring, from whence three discrete orientations are possible for each species. Their sequence and mutual arrangement determine direction and curvature of the metal-organic chains. The Cu-coordinated polymers are very similar on both Cu(111) and Ag(111), where their formation is induced by intrinsic and coevaporated adatoms, respectively, which indicates that the lateral bonding motif is predominantly independent of the substrate. In addition, molecular manipulation experiments show the collective motion of entire segments of the Cu-coordinated multi-porphyrin polymers.

We studied the interaction of a highly ordered array of Co-tetraphenylporphyrin (CoTPP) with NO on Ag(111) by in situ scanning tunneling microscopy and X-ray photoelectron spectroscopy. Upon NO exposure, the initially quadratically ordered CoTPP layer reorganizes, showing a wealth of highly ordered NO+CoTPP coadsorbate phases with increasing size of the unit cell, interpreted as due to attractive lateral dipole-dipole interactions between the two species. The findings not only suggest a novel approach to control the arrangement of adsorbed porphyrins in particular but also should generally be considered in the production of functional layers from large organic molecules under ambient conditions or after exposure to small electronegative molecules.

Abstract. Advanced applications of materials need sophisticated measurement methods for research, process development and quality control. X-ray Computed Tomography (CT) is a very powerful method for non-destructive testing of materials. A CT-scanner generates a series of X-ray attenuation measurements, which are used to produce computed reconstructed images of an object. In the last years 3D-CT systems with matrix detectors have become more and more popular. In this paper we outline the extended possibilities of 3D Computed Tomography by using a 450 kV-macro focus x-ray source and a 225 kV micro-focus source within one CT system as well as the advantages by applying different CT-methods for the characterisation of one specimen. The possibility of using two different X-ray sources within one CT-device leads to considerable advantages at certain circumstances. If there are different materials in one specimen the application of two different energies can lead to a significant improvement of the contrast. Moreover, if bigger parts are scanned, the 450 kV-source can be used to get an overall image of the specimen and the 225 kV can be used to get a high resolution image of a detail. In the second section we discuss the limits of 3D-CT and apply an advanced CT-mode (region of interest CT) for the characterisation of flat parts and of selected details in large objects. With the ROI-CT-mode “zooming” is possible similar to optical microscopes and a resolution down to 1/10.000 of the part diameter can be reached. This is a much higher resolution as compared to usual 3D-CT.