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We present a new method using a simultaneous AFM-STM setup to define the concept of distance as a tunneling tip first approaches and then penetrates an organic film on a solid surface. This provides a method to investigate the imaging of low intrinsic conductivity organic material with an STM. In a lipid film using small tip-to-sample voltages, on the order of 1 V, we find an upper thickness limit for tunneling of 30 A. However using higher voltages, on the order of 6 V, we measure a current through a lipid thickness of several 100 A.

Coadsorption of two different carboxylic acids, benzenetribenzoic acid and trimesic acid, was studied at the liquid-solid interface in two different solvents (heptanoic and nonanoic acid). Independent alteration of both concentrations in binary solutions resulted in six nondensely packed monolayer phases with different structures and stoichiometries, as revealed by means of scanning tunneling microscopy (STM). All of these structures are stabilized by intermolecular hydrogen bonding between the carboxylic acid functional groups. Moreover, phase transitions of the monolayer structures, accompanied by an alteration of the size and shape of cavity voids in the 2D molecular assembly, could be achieved by in situ dilution. The emergence of the various phases could be described by a simple thermodynamic model.

Les derives nitro de compose aromatiques se lient selectivement avec l'(aminopropyl)triethoxysilane attache de facon covalente sur la surface en quartz d'un capteur a onde acoustique de surface. La selectivite est associee aux liaisons hydrogene fermees et est etudiee par la methode de calcul des orbitales moleculaires AM1

We present a preparation method for self-assembled supra-molecular monolayers of unsubstituted organic semiconductors and pigments on a solid substrate, applicable under ambient conditions. The deposition is based on a solid-solid wetting phenomenon, whereas the subsequent layer growth proceeds according to standard models. Molecular adsorption results from direct contact of the compound in a nanocrystalline state with the solid surface. Based on complementary force field calculations, we propose that molecules disintegrate from the crystalline state and adsorb on the surface because of a gain in binding energy. The preparation method is exemplified by means of a linear hydrogen-bonded system, namely quinacridone (QAC) on graphite. In addition, the chosen system allows us to actively guide the self-assembly after deliberate removal of molecules from a predefined area.

Nanotechnology is entering a phase where the involvement of the public is becoming crucial in terms of public acceptance, market potential and political governance. This chapter reviews the issues involved in communicating about nanotechnology with the broader public: its novelty, ethical, legal and social aspects, and comparison with debates surrounding other new technologies such as genetic modification. It also covers ongoing activities, best practices and further research needs. The chapter also presents three projects currently funded by the European Commission in this area: NanoDialogue, Nanologue and Nanobio-RAISE

Cu3O7-δ films have been patterned by means of an arrangement employed in scanning near-field optical microscopy (SNOM). Standard SNOM probes were modified to achieve high transmission for direct writing by oxygen depletion in N2 atmosphere. The written lines are about 1.5 μm wide and show a semiconductor-like resistivity behavior (δ≥0.5). The morphology of illuminated regions is about the same as that of the YBCO films.

The temporal evolution of domain boundaries of hydrogen-bonded molecular monolayers at the liquid–solid interface is evaluated by recording series of subsequent scanning tunneling microscopy (STM) images. Comparison of dissimilar benzene carboxylic acids reveals a clear distinction between one- and two-dimensional H-bonded network structures. Trimesic acid forms a two-dimensionally H-bonded networked structure, whereas terephthalic acid organizes in a dense packing of H-bonded linear chains on a graphite surface. In addition, TMA forms a sixfold lattice on a threefold graphite substrate, whereas TPA exhibits only a twofold lattice, causing a high grain-boundary line energy for the latter. In the case of TMA the nanostructure was mostly stable during the observation time. For TPA, Ostwald ripening—that is, the growth of larger islands at the expense of smaller islands—was observed. To explain the various experimentally observed timescales of the dynamics occurring at grain boundaries, molecular mechanics simulations were applied to calculate the binding energy of edge molecules, that is, the line energy, of finite islands of both trimesic and terephthalic acid on a graphite substrate.

Stable adsorption of 1,3,5-tris(4-pyridyl)-2,4,6-triazine (TPT) molecules from the liquid phase was only observed in binary solutions, that is, in the presence of a second (adsorptive) species. The process of mediated coadsorption of a molecular species at the liquid-solid interface was accomplished through complexation of TPT with a second type of molecule acting as a "molecular glue" via hydrogen bonds. Scanning tunneling microscopy (STM) was utilized to investigate the structure of the coadsorbed monolayers at the liquid-solid interface. Trimesic acid (TMA) and terephthalic acid (TPA)--both benzene rings with disposed carboxylic acid groups-were appropriate to precipitate the stable adsorption of TPT. According to the different symmetry and number of carboxylic acid groups, various networks were observed.

We present a new tool for the estimation of the age of bloodstains, which could probably be used during forensic casework. For this, we used atomic force microscopy (AFM) for high-resolution imaging of erythrocytes in a blood sample and the detection of elasticity changes on a nanometer scale. For the analytic procedure we applied a fresh blood spot on a glass slide and started the AFM detection after drying of the blood drop. In a first step, an overview image was generated showing the presence of several red blood cells, which could easily be detected due to their typical "doughnut-like" appearance. The consecutively morphological investigations in a timeframe of 4 weeks could not show any alterations. Secondly, AFM was used to test the elasticity by recording force-distance curves. The measurements were performed immediately after drying, 1.5 h, 30 h and 31 days. The conditions were kept constant at room temperature (20 degrees C) and a humidity of 30%. The obtained elasticity parameters were plotted against a timeline and repeated several times. The elasticity pattern showed a decrease over time, which are most probably influenced by the alteration of the blood spot during the drying and coagulation process. The preliminary data demonstrates the capacity of this method to use it for development of calibration curves, which can be used for estimation of bloodstain ages during forensic investigations.

Nanomedicine is the application of nanotechnology to the prevention and treatment of diseases in human body. The discipline is in its infancy. It has the potential to change medical science dramatically in the 21/sup st/ century. The most elementary nanomedical devices are used for diagnosis. Chemical tests exist for this purpose; nanomachines could be employed to monitor the internal chemistry of the body. The combination of high resolution microscopy, such as atomic force microscopy (AFM), and laser-based microdissection provides a direct approach for the investigation and isolation of biological specimen.

In this paper, we report on a new method for the investigation and manipulation of single molecules by STM without the explicit need for experimentally challenging UHV techniques. The controlled manipulation of single molecules becomes possible, since an organic template preadsorbed on the substrate introduces a hexagonal grid of stable adsorption sites with a next nearest neighbor distance of approximately 1.6 nm.

The taphonomic nanostructure of acritarch cell walls from the c. 650 million years old Chichkan Formation was studied with optical microscopy (OM), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The integration of high-resolution methods and classical optical microscopy allows for the assessment of the relationship of the fossil to the embedding chert and of the authenticity of the fossil. Partial etching of paleontological (150 μm) and petrographic (30 μm) thin sections rather than maceration of the semi-stable cell structures served as the preparation method suitable for AFM and SEM studies. Focussed Ion Beam (FIB) preparation of sections normal to cell walls, yielded stable thin foils of the same thin sections and microfossils as investigated by OM, AFM and SEM. Unicells that appeared excellently preserved by optical microscopy standards, consisted of disconnected kerogen particles, dispersed in the cryptocrystalline quartz matrix and arranged in stacks of variable spacing on micro- to nanometer scale. The density of carbon particles was found to be correlative to the stability of cell walls and to inhomogeneities in the chert. SEM and AFM images of cell cross-sections are directly comparable at the same scale of magnification, but AFM offers higher resolution possibilities and 3-D information on the arrangement of particulate carbon within the cell. Whereas the microscopic appearance of cells was highly variable within the same rock unit, from the same locality in the Chichkan Formation, the nanoscopic structure of kerogen was found to be similar in all cells, consisting of multi-laminated (sheeted) amorphous carbon films, built up of layers with measured thickness between 10 and 20 nm, as revealed by TEM and AFM.

Plasmacytoid dendritic cells (PDC) represent a highly specialized immune cell subset that produces large quantities of the anti-viral cytokines type I interferons (IFN-alpha and IFN-beta) upon viral infection. PDC employ a member of the family of toll-like receptors, TLR9, to detect CpG motifs (unmethylated CG dinucleotides in certain base context) present in viral DNA. A certain group of CpG motif-containing oligodeoxynucleotides (CpG ODN), CpG-A, was the first synthetic stimulus available that induced large amounts of interferon-alpha (IFN-alpha) in PDC. However, the mechanism responsible for this activity remained elusive. CpG-A is characterized by a central palindrome and poly(G) at the 5' and 3' end. Here we demonstrate that CpG-A self-assembles to higher order tertiary structures via G-tetrad formation of their poly(G) motifs. Spontaneous G-tetrad formation of CpG-A required the palindrome sequence allowing structure formation in a physiological environment. Once formed, G-tetrad-linked structures were stable even under denaturing conditions. Atomic force microscopy revealed that the tertiary structures formed by CpG-A represent nucleic acid-based nanoparticles in the size range of viruses. Similarly sized preformed polystyrene nanoparticles loaded with a CpG ODN that is otherwise weak at inducing IFN-alpha (CpG-B) gained the potency of CpG-A to induce IFN-alpha. Higher ODN uptake in PDC was not responsible for the higher IFN-alpha-inducing activity of CpG-A or of CpG-B-coated nanoparticles as compared with CpG-B. Based on these results we propose a model in which the spatial configuration of CpG motifs as particle is responsible for the virus-like potency of CpG-A to induce IFN-alpha in PDC.

Fluorescence in situ hybridization (FISH) plays an essential role in research and clinical diagnostics. The versatility and resolution of FISH depends critically on the probe set used. Here, we describe an improved approach for the generation of specific DNA probes from single copies of chromosomes. Single chromosomes or single chromosomal regions were microdissected by laser pressure catapulting and amplified using linker-adaptor PCR. The probes were labeled and tested in various scenarios including multicolor-FISH experiments employing up to seven different fluorochromes. FISH confirmed the specific and even staining of the respective chromosomal regions. Furthermore, the capability of these probes to detect even small translocations (

The detailed understanding of the nuclear cell functions requires an accurate knowledge of the spatial organization of their structures. For many years the study of human metaphase chromosomes was conducted with light microscopy after staining protocols disturbing the native chromosomal structure. The approach by scanning electron microscopy (SEM) provides higher resolution as compared with light microscopy and permits surface analysis of the chromosomal structure, which cannot be adequately obtained from transmission electron microscopy. Nevertheless, to obtain high resolution in SEM observations, the use of a high electron accelerating voltage (up to 30 kV) is required (1). With these experimental conditions, the sputter coating or a conductive staining of the samples is generally required (1,2). Both procedures allow electron-charging dispersion from the sample but may obscure fine details and produce sample alterations (3).

We present possible applications of Atomic Force Microscopy (AFM) as a force spectroscopy tool in genomics and proteomics. AFM applications in these fields have opened new opportunities for studying the mechanical properties of biomolecules and their interactions in their native environment, as well as in determining the binding affinity of DNA proteins in dependence with the target DNA sequence for further correlative studies on physical affinity and biological relevance of the controlled gene. Furthermore, force spectroscopy is a powerful analytical tool to investigate structural and functional features of biomolecules. Altogether, these tools have revealed useful application in genomics and proteomics.

Atomic force microscopy (AFM) nowadays can be used not only as a high-resolution imaging tool for precise cytogenetic studies but, at the same time, for mechanical measurements and manipulation of genetic material. This combination allows, for the first time, identification of the sample area, microdissection and nanoextraction of genetic material for further biomedical and biochemical studies. In this review, we examine AFM techniques like cutting, gripping and extracting biomaterial at the submicron scale under high-resolution image control and potential applications in cytogenetics.

Therapies for liver diseases with stem and progenitor cells will require a detailed knowledge of the molecular mechanisms driving the in vivo differentiation process toward adult hepatic tissue. We applied quantitative gene expression methods to analyze the differentiation process of fetal liver progenitor cells after transplantation into an animal model of liver regeneration. Enhanced green fluorescent protein (EGFP)-transgenic liver progenitor cells were isolated from fetal mouse liver at stage embryonic day 13.5 and transplanted into uPA/RAG-2 mice. Two, 4, and 6 weeks after cell transplantation cryosections of liver tissue were analyzed for EGFP-positive regeneration nodules. RNA from laser-microdissected EGFP-positive tissue was isolated and used as template for quantitative real-time reverse transcriptase-polymerase chain reaction. Phenotypic differentiation was analyzed by staining of the canalicular marker enzyme dipeptidyl-peptidase IV. Proliferation in regenerative nodules and surrounding tissue was monitored with the BrdU incorporation assay. Alpha fetoprotein gene expression had already decreased 2 weeks after transplantation in EGFP-positive regeneration nodules compared to pretransplantation values and was not detectable after 4 and 6 weeks, whereas albumin slightly increased in transplanted cells indicating differentiation into a mature phenotype. The dipeptidyl-peptidase IV antigen was associated with some liver progenitor cells 2 weeks after transplantation and in virtually all cells after 4 and 6 weeks. Cell proliferation index in transplanted cells was maximally increased (4.8% BrdU-positive cells) after 2 weeks and decreased (0.4%) after 6 weeks to normal levels. Our results demonstrate that gene expression in liver progenitor cells changes from fetal to adult phenotype within 4 to 6 weeks after transplantation despite ongoing proliferation of the transplanted cells in a mouse model of liver regeneration. Quantitative gene expression profiles as shown here will have important implications in our understanding of the in vivo differentiation process of stem cells.

Atomic force microscopy (AFM) is a technique used routinely in material science to image substances at a submicron (including nm) scale. We apply this technique to analysis of the fine structure of organic-walled Precambrian fossils, microscopic sphaeromorph acritarchs (cysts of planktonic unicellular protists) permineralized in approximately 650-million-year-old cherts of the Chichkan Formation of southern Kazakhstan. AFM images, backed by laser-Raman spectroscopic analysis of individual specimens, demonstrate that the walls of these petrified fossils are composed of stacked arrays of approximately 200-nm-sized angular platelets of polycyclic aromatic kerogen. Together, AFM and laser-Raman spectroscopy provide means by which to elucidate the submicron-scale structure of individual microscopic fossils, investigate the geochemical maturation of ancient organic matter, and, potentially, distinguish true fossils from pseudofossils and probe the mechanisms of fossil preservation by silica permineralization.

Transient forces between nanoscale objects on surfaces govern friction, viscous flow, and plastic deformation, occur during manipulation of matter, or mediate the local wetting behavior of thin films. To resolve transient forces on the (sub) microsecond time and nanometer length scale, dynamic atomic force microscopy (AFM) offers largely unexploited potential. Full spectral analysis of the AFM signal completes dynamic AFM. Inverting the signal formation process, we measure the time course of the force effective at the sensing tip. This approach yields rich insight into processes at the tip and dispenses with a priori assumptions about the interaction, as it relies solely on measured data. Force measurements on silicon under ambient conditions demonstrate the distinct signature of the interaction and reveal that peak forces exceeding 200 nN are applied to the sample in a typical imaging situation. These forces are 2 orders of magnitude higher than those in covalent bonds.

The adsorption of the aromatic molecule hexabenzobenzene (coronene) on an HOPG(0001) surface was investigated under UHV conditions by means of variable temperature scanning tunneling microscopy (STM) and spectroscopy (STS). Imaging on a mesoscopic scale showed a distribution of coronene islands. These islands are mobile on the surface and can be pinned at step-edges. Zooming in on areas apart from the islands reveals an hexagonal arrangement of coronene molecules in a closed layer. Submolecular resolved molecules consist of bright spots with varying intensity. This variation in intensity is explained with the commensurability of the adlayer. STS investigations were performed for various tip-sample distances, adjusted by the tunneling current setpoint. A gap can be seen for every setpoint, but its width is dependent on the setpoint. The gap for the largest tip-sample distance and therefore the smallest tip-sample interaction is compared with the theoretical value.

Nanoarchitectonics is a new interdisciplinary field within the NanoSciences, which investigates the principles responsible for the formation of higher-ordered functional structures starting from their nanoscopic building blocks like atoms and molecules. Such a bottom up approach is new within the field of contemporary technology, which has used very successfully the top down strategy for the miniaturization of fabrication processes during the last hundred years. However, nature has always worked bottom up, where the principles of self-assembly lead to crystal growth in the inorganic world, and, via molecular self-assembly, to functional structures in biology. For instance, the three-dimensional architecture of a nanomachine called the ribosome comprises the natural molecular assembler, which organizes the transition from the DNA informational blueprint into polypeptides and other functional units. To understand and make technological use of the underlying mechanism of this process is one of the major goals of modem Proteomics, where the relation between the DNA base sequence and the respective protein must be mastered. One approach to this question is to simplify the process by transferring it into a two-dimensional scenario, thus reducing the complexity of the three-dimensional architecture to an in-plane problem. Such a reduced coordination space may also be adequate for a primordial soup scenario, where the spontaneous self-assembly of abiotic ally produced organic compounds may be facilitated. The formation of highly ordered monolayers of the purine and pyrimidine DNA bases through physisorption mediated molecular self-assembly at a solid-liquid mineral interface and the subsequent stereospecific adsorption of amino acids is an example for the spontaneous creation of nanoscale order. We have proposed a functional role of this process for the emergence of life that may also lead towards the construction of genetically based supramolecular architectures for modem technical applications [1-4].

The formation of highly ordered monolayers of organic molecules through physisorption-mediated molecular self-assembly at the solid-liquid interface is an example of the spontaneous creation of order. The resulting two-dimensional molecular crystal structures can be determined using the combination of scanning tunneling real-space analysis and diffraction methods together with molecular modeling. Here we present examples ranging from liquid crystals to heterocyclic organic molecules like trimesic acid, representative of a molecular host-guest system. In the case of DNA molecules we have proposed a functional role for this process of spontaneous self-organization for the emergence of terrestrial life, which may also lead towards the construction of genetically based supramolecular architectures for modern technical applications, such as heterogeneous catalysis.

Scanning force microscopy was used to analyze banded human chromosomes and in situ hybridization patterns of biotinylated DNA probes. In standard human GTG-banded metaphase chromosome preparations (where GTG is G-banding with trypsin-Giemsa), chromosomal morphology and banding patterns were well preserved during the scanning procedure. The smallest identifiable features were in the range of about 100 nm and are similar to the typical structures seen by electron microscopy. In addition, in situ hybridization of human DNA probes of known chromosomal localization was used to map specific hybridization signals. Imaging of the precipitated crystals at the hybridization site clearly demonstrates the superior resolution of scanning force microscopy compared to conventional microscopy.

In torsional overtone microscopy, a dynamic atomic force microscopy technique, antisymmetric vibration modes of a v-shaped cantilever are used to investigate the elastic properties of the tip-sample contact. In order to minimize the vibration amplitude, no external excitation is added in the passive overtone mode. In this mode, the thermomechanical noise of the surface coupled cantilever at room temperature is analyzed. This allows the shear stiffness of the tip-sample contact to be extracted from the analysis of the power spectrum of the photodiode signal. The load dependence of the first torsional vibration on silicon, aluminum, and cadmium telluride surfaces is compared with a theoretical mechanical model.

We have calculated the thermal noise of a v-shaped AFM cantilever (Microlever, Type E, Thermomicroscopes) by means of a finite element analysis. The modal shapes of the first 10 eigenmodes are displayed as well as the numerical constants, which are needed for the calibration using the thermal noise method. In the first eigenmode, values for the thermomechanical noise of the z-displacement at 22°C temperature of 〈u 1 2 〉 =0.627 A / c cant and the photodiode signal (normal-force) of 〈S 1 2 〉 =0.558 A / c cant were obtained. The results also indicate a systematic deviation of the spectral density of the thermomechanical noise of v-shaped cantilevers as compared to rectangular beam-shaped cantilevers.

The adsorption of organic molecules onto the surfaces of inorganic solids has long been considered a process relevant to the origin of life. We have determined the equilibrium adsorption isotherms for the nucleic acid purine and pyrimidine bases dissolved in water on the surface of crystalline graphite. The markedly different adsorption behavior of the bases describes an elutropic series: guanine > adenine > hypoxanthine > thymine > cytosine > uracil. We propose that such differential properties were relevant to the prebiotic chemistry of the bases and may have influenced the composition of the primordial genetic architecture.

Guanine, one of the four DNA bases, has been observed by tunneling microscopy to form a two-dimensional ordered structure on two crystalline substrates, graphite and MoS2. The two-dimensional lattice formed by guanine is nearly identical on the two surfaces, and heteroepitaxy appears to be the growth mechanism in both cases. Although the resolution of molecular details is superior for the graphite substrate, the simpler results on MoS2 are not only easier to interpret but also facilitate the understanding of the more complex images on graphite. We propose that the interfacial structure is composed of linear chains of hydrogen-bonded molecules aligned into a closely packed two-dimensional array.

A variety of microscope techniques have been used to study surficial phenomena on the fracture surfaces of the Martian meteorite ALH84001. The aim of the investigation was to determine the most useful microscopy methods in the search for morphological signs of biogenic activity. Emphasis was placed on scanning electron microscopy (SEM) using secondary, backscatter and cathodoluminescence modes combined with observation of samples at a variety of accelerating voltages. High resolution SEM imaging was compared with atomic force microscopy. These techniques revealed a number of structures of possible abiotic and biotic origin: (1) a large, fibrous-looking carbonaceous structure, (2) fine, flaky films coating pyroxene surfaces, (3) finely granular calcium carbonate deposit is associated with the fine film, and (4) lacy-structured, mineralized polymers on the pyroxene surface. Another sample contains further evidence of water-lain deposits in a cracked, iron oxide coat on a fracture surface.

The optical micromanipulation systems UV(ultraviolet)-Laser Microbeam and Optical Tweezers Trap, already proven to be powerful tools for ‘non-contact’ micro-manipulation of gametes, cells and organelles, have now made their way into the nanocosmos of genes and molecules. Force measurements of DNA transcription have been performed and selective DNA molecule micromanipulation gives insight into single molecule behaviour. Retrivement of selected single cells without contamination is an important prerequisite for further processing with modern methods of molecular biology. Laser micro-dissection allows to precisely eliminate any unwanted material or to isolate pieces of chromosomes or single cells of interest with high accuracy and efficiency. This enables the cell or chromosome specific molecular analysis of genes and genetic defects underlying disease, such as cancer or infection. This review article gives an overview of current topics of laser microbeam application in biological or medical research and advanced molecular diagnosis.

Due to the complexity of living matter on the nanometer scale, Sir Neville Mott’s above cited prediction will be a real challenge for crossdisciplinary teamwork in physics, chemistry and biology within the next decade. More specifically, the evolving discipline of nanotechnology, today still in its infancy, will become one of the key technologies of the 21st century. Nanotechnology deals with the direct visualization, the control and the manipulation of matter on the nanometer scale, i.e. down to the size of proteins, molecules and single atoms. What is so new about this concept? Today’s technology tries to reach smaller dimensions in manufacturing (e.g. in the area of microchips and biosensors) by starting with a huge piece of matter and physically dividing it to the desired size (“scaling down”). This approach has its physical limits, for example in the wavelength of light used for lithographic structuring of integrated circuits. A radically new approach is to start from the elementary building blocks of matter, like atoms and molecules, and to assemble them piece by piece into entities with desired functionality (“scaling up”). This method is not really so new at all, in fact there are many outstanding examples in nature. For example, molecular nanomachines in the form of ribosomes in the cell of living organisms assemble proteins from amino acids through the coded information stored in the RNA. The genetic code of the DNA-double helix is translated by means of a molecular reading machine into the proteins’ language.

The adsorption geometry of 1,3,5-tris(4-mercaptophenyl)benzene (TMB) on Cu(111) is determined with high precision using two independent methods, experimentally by quantitative low energy electron diffraction (LEED-I(V)) and theoretically by dispersion corrected density functional theory (DFT-vdW). Structural refinement using both methods consistently results in similar adsorption sites and geometries. Thereby a level of confidence is reached that allows deduction of subtle structural details such as molecular deformations or relaxations of copper substrate atoms., 7 pages, 3 figures

The polymerization of 1,4-diethynylbenzene was studied on a Cu(111) surface using scanning tunneling microscopy (STM) under ultra-high vacuum conditions. Thermal activation yielded disordered covalent networks, where distinct basic structural motifs indicate different coupling reactions.

‘Covalent self-assembly’, i.e. the on-surface synthesis of covalent organic aggregates and networks, has received considerable attention. This review covers recent scanning tunnelling microscopy (STM) based studies on intermolecular reactions carried out on solid substrates that resulted in surface-confined covalently interlinked organic nanostructures. Experiments showed that their defect density crucially depends on the targeted dimensionality: while zero-dimensional aggregates and one-dimensional chains and ribbons can be synthesized on surfaces with utmost structural perfection, i.e. without any topological defects, realization of long-range ordered two-dimensional (2D) covalently interlinked organic networks has revealed itself as a paramount challenge for on-surface chemists. Different types of reactions, foremost condensation and addition reactions have been proven suitable as polymerization reactions for 2D cross-linked covalent networks. Yet, the emergence of topological defects during the polymerization is difficult to avoid. However, the combined experience and creativity of chemists and surface scientists has yielded encouraging first results which may open up ways for realization of extended, long-range ordered 2D polymers. This review summarizes and compares different approaches, i.e. reaction types, monomers, environments and conditions, for the on-surface synthesis of covalent organic nanostructures. The focus on STM as an analytical tool appears justified, since its unique capabilities render the STM an ideal instrument to study and even control covalent coupling reactions of organic molecules on surfaces.

Self-assembly of melem on Ag(111) as studied by Scanning-Tunneling-Microscopy (STM) in ultra-high vacuum revealed a great structural variety. In total, five porous and two densely packed monolayer polymorphs were observed. All structures are stabilized by intermolecular hydrogen bonds, where melem–melem arrangements are based on very few basic motifs. Six out of seven polymorphs can be described by a unified concept.

The on surface synthesis of a two-dimensional (2D) covalent organic framework from a halogenated aromatic monomer under ultra-high vacuum conditions is shown to be dependent on the choice of substrate.

Between 1982 and 1988, 11 patients with congenital penile curvature without hypospadia or chordee were operated according to the technique originally described by Nesbit. In all these patients the operative results were reevaluated after a period of 1 1/2 to 7 years (average 3 3/4 years). Normal sexual intercourse was possible for all 11 men, and good long-term cosmetic results were noted. In contrast to formerly published results, histological examination of the segments resected from the tunica albuginea showed fibrotic tissue in some cases, which could play an important role in the etiology and/or pathogenesis of congenital penile curvature.

A scanning plasmon near-field microscope has been used to image dye clusters on a silver surface. This demonstrates the potential of optical near-field microscopy for the investigation of surfaces and non-conducting adsorbate layers. Images recorded in parallel with the conventional scanning tunneling microscope show the underlying conductive substrate.

The surface of a decagonal Al-Ni-Fe quasicrystal was investigated by overtone AFM, a special type of force modulation microscopy (FMM), where the cantilever is driven at a frequency higher than the fundamental flexural mode of the cantilever in contact with the surface. The resonance behaviour of the cantilever sample system was studied with finite element analysis (FEA). Using the excitation frequency of a torsional vibration of the cantilever, an image contrast could be obtained, which is dominated by the shear stiffness of the material. Differently orientated decagonal grains, as well as lamellae structures of different phases could be resolved on the quasicrystalline specimen. It is shown that the elastic anisotropy of the material gives rise to the contrast formation in overtone microscopy.

Ring‐like structures of two different sizes on a nanometer scale have been found on natural molybdenum disulfide (MoS2). Investigation by scanning tunneling and scanning force microscopy as well as secondary‐ion mass spectroscopy indicate that these rings might originate from included molecules. Synthetic compared to natural MoS2 shows characteristic differences. The origin of these striking structures could be the morphology of organic or even remnants of biological material included at the geological time when the mineral was formed and could therefore be regarded as a result of a molecular fossilization process. The alternative explanation that the ring structure is a nonmorphological and purely electronic effect caused by a point defect like a dopant is also discussed.