Shape and size control as well as the control of the assembly of nanostructures are current challenges in nano sciences. Focussing on metal nanostructures all of these aspects have been addressed in the frame of the present work. It was possible to develop a new aqueous seeded growth method that produces gold nanoparticles with adjustable diameters over a large range of sizes. The spherical particles obtained show very low polydispersities and a good long term stability. Furthermore it was possible to reveal the growth mechanism of these particles utilizing electron microscopy and optical investigations coupled with theoretical calculations. It was found that there is a formation of small nucleation sites on the surface of the seeds in the beginning of the growth process. These sites then subsequently grow into "blackberry-like" intermediate particles. A final intraparticle ripening step leads to smooth and uniform spherical gold nanoparticles. By correcting the dielectric function of gold for charging and the free mean path effect and taking into account the particle size distribution it was possible to accurately model the optical properties of the gold sols obtained using Mie theory. By controlling the concentration of chloride ions it was possible to influence both the ripening of the "blackberry-like" shaped particles and the morphology of gold nanoparticles. An increased concentration of the chloride ions in the standard citrate reduction procedure leads to larger and elongated particles, whereas the complete removal of the chloride ions made it possible to obtain star shaped, decahedral and \"desert-rose\" shaped particle morphologies. Using the layer-by-layer technique gold nanoparticles of different sizes could be immobilized on glass substrates. The surface-enhanced Raman scattering intensity of these mixed films were about 60% higher than compared to a film made of a single particle size. The optical properties were further investigated by comparing experimentally obtained UV/Vis spectra with generalized Mie theory simulations. Additionally it could be shown that tetrazole and its derivatives are suitable stabilizing agents in the aqueous synthesis of silver nanoparticles. It was found that depending on the tetrazole derivative used the tendencies of the nanoparticles to agglomerate vary significantly. Different agglomeration stages have been investigated by UV/Vis and Raman spectroscopy. The removal of the ligands used and a resulting improvement of the applicability of the silver nanostructures as SERS substrates is still a challenge. In the last part of this work the focus was changed from the optical properties of noble metal nanoparticles to their catalytic properties. Therefore gold and palladium nanoparticles have been successfully immobilized on highly porous zinc oxide aerogels. It was possible to synthesize sponge-, flake-, and ribbon-like zinc oxide gels with high specific surface areas. The facile approach of generating mixed metal oxide/noble metal aerogels is very promising for the preparation of highly selective and highly active heterogenous catalysts. First catalytic investigations of a sponge-like palladium loaded zinc oxide aerogel toward the semi-hydrogenation of acetylene showed very high selectivities of up to 85%.

La0.6Ca0.4Mn0.8Ni0.2O3-, La0.6Ca0.4Mn0.8Fe0.2O3- und La0.75Ca0.25Mn0.5Fe0.5O3-Volumenmaterialien wurden im potentiometrischen Messaufbau bereits erfolgreich auf ihre NO-Sensitivität getestet. Keramischen Nanomaterialien werden generell eine Reihe neuer oder verbesserter Eigenschaften (verbessertes Sinterverhalten, erhöhte NOx-Sensitivität, höhere Leitfähigkeit) zugesprochen. La0.6Ca0.4Mn0.8Ni0.2O3, La0.6Ca0.4Mn0.8Fe0.2O3 und La0.75Ca0.25Mn0.5Fe0.5O3 wurden mittels PVA/Sucrose-Methode, Aktivkohlemethode und Fällungssynthese als Nanomaterialien sowie mit Festkörperreaktion als Volumenmaterialien dargestellt und mit typischen Charakterisierungsmethoden untersucht. Die Materialien wurden in verschiedenen Schichtdicken auf YSZ-Substrate aufgetragen und potentiometrisch sowie impedanzspektroskopisch auf ihre NO-Sensitivität und die Querempfindlichkeit gegenüber NO2 und Propylen geprüft. Potentiometrische Messungen im NO-Gasstrom ergeben eine Abhängigkeit der NO-Sensitivität von der Partikelgröße, der Schichtdicke und der Beschichtungsmethode. Impedanzspektroskopische Messungen an beidseitig beschichteten YSZ-Substraten zeigen ebenfalls eine Abhängigkeit des Zellwiderstands von der NO-Konzentration und der Partikelgröße. Die Nanomaterialien zeigen bei unterschiedlichen Sauerstoffpartialdrücken im untersuchten Temperaturbereich (300°C bis 850°C) höhere Leitfähigkeiten als die Volumenmaterialien gleicher Zusammensetzung. Dieses Verhalten wird mit dem höheren Sauerstoffaustausch der Nanomaterialien in Verbindung gebracht, der zur Erzeugung zusätzlicher Defekte in der Kristallstruktur führt. Die Nanostruktur und somit eine entsprechend hohe Leitfähigkeit bleiben bei hohen Sintertemperaturen (T > 1000°C), die der Herstellung gasdichter Presslinge dienen, erhalten. XANES- und Photoelektronenspektroskopie wurden verwendet, um die Punktdefekte zu definieren.

This thesis addresses the syntheses towards high quality CdSe and CdTe nanoparticles. Therefore, thermodynamic and kinetic aspects of the hot injection method are investigated. By means of the introduction of a thermodynamically less favored nuclei species the nucleation event of CdSe quantum dot synthesis is affected. Utilizing highly reactive tin or lithium silylamides, primarily formed SnSe or Li2Se nuclei undergo a cation exchange to the demanded CdSe particles. The further growth proceeds without the incorporation of the so called quasi-seed species. In this manner, the mechanism of the cation exchange-mediated nucleation is proven and optimized with respect to the required amount of the quasi-seed species. Furthermore, this protocol is applied to up-scaling attempts to reduce the efforts for optimization to a minimum. Following this, a successful laboratory batch up-scaling is achieved by increasing flask size as well as precursor concentrations by factors of 2 and 10, respectively. A further possibility to thermodynamically influence the hot injection synthesis is the activation of the precursor species. By altering the injection pathway, as compared to the standard synthesis, the precursor species are differently coordinated and hence possess different thermodynamic stabilities. Investigations on the system of CdTe quantum dots lead to the result of a cation activation by the use of the thermodynamically less stable carboxylate ligands instead of phosphonates. Additionally, anion activation is suggested due to a kind of aging of the phosphine ligands via their oxidation by phosphonic acids. Furthermore, it is found that the ratio of Cd-to-Te strongly influences the formation of so called magic-sized clusters. Following the results, the smallest detectable species is determined as a cluster species with a size of 1.8 nm. The role of the magic-sized clusters is not fully resolved, but the initial growth is assumed to occur via monomer deposition onto or the fusion of the observed clusters. On the other hand, cluster dissolution is thermodynamically forced by the decreasing monomer concentration and can simply be explained by the process of Ostwald ripening via the creation of a smaller cluster species. Mechanistically this is explained by the formation of configurational deviations from the ideal closed-shell structure. Finally the inorganic coating of the core quantum dots in investigated. Therefore, homoepitaxial coating is employed to overcome the limit in particle size by introducing additional monomer supply. As a result, following the classical crystallization theory, defined injections of precursor material during the diffusion limited growth regime allow a fine tuning of the final particle size. Nevertheless, homoepitaxial coating inevitably leads to photoluminescence quenching, whereas heteroepitaxial growth usually improves the optical quality. By means of a type I structure, CdSe/CdS/ZnS, the successive ion layer adsoption and reaction mechanism is discussed. Furthermore, alloy structures of CdSe/ZnSe with a radially gradated intermediate shell of CdZnSe are achieved by postsynthetic high temperature treatments. This annealing induces internal diffusion processes and allows exactly adjusting the emission wavelength due to defined shrinkage of the initial core size during the alloying process.

Die vorliegende Dissertation beschäftigt sich mit Wachstum und Aufbau von Fluorapatit-Gelatine-Nanokompositaggregaten. Diese Aggregate werden im sogenannten Doppeldiffusionsversuch biomimetisch erzeugt und ihre äußere Form bzw. Formentwicklung lässt sich anhand eines fraktalen Modells bis ins Detail nachvollziehen. Sie zeigen einen komplexen inneren Aufbau, in dem die Makromoleküle der organischen Komponente einerseits im Zentrum jeder Nanoeinheit und andererseits zu Strängen, den sogenannten Fibrillen, zusammengelagert am Aufbau der Kompositaggregate beteiligt sind. Im Fall des Kompositkeims ist die innere Architektur in hoher Detailstufe verstanden, auch wenn -- insbesondere bezüglich der späteren Wachstumsphasen -- eine Reihe ungeklärter Fragestellungen verbleibt. Ein zentrales Ergebnis der vorliegenden Arbeit bildet die Entdeckung eines weiteren Wachstumstypen, der im Vergleich zu den bekannten, fraktalen Kompositaggregaten grundsätzliche Unterschiede bezüglich des inneren und äußeren Aufbaus zeigt. Der Grund für die andersartige Formentwicklung liegt in der Versteifung der organischen Komponente durch eine vorangegangene Einlagerung von Calciumionen, wie sowohl experimentell als auch mit atomistischen Computersimulationen gezeigt werden konnte. Aufgrund der hohen Komplexität des Systems ist es bislang allerdings nicht möglich, lokale Ionen-Konzentrationen und pH-Werte vor bzw. während Nukleation und Wachstum der Kompositaggregate im Doppeldiffusionsversuch zu bestimmen. Deshalb wurde ein Ersatzversuch -- der sehr ähnlich strukturierte Aggregate erzeugt, sich aber mit rechnerischen Methoden analysieren lässt -- entworfen und untersucht. Anhand dieser Ergebnisse konnte erstmals die "Geschichte" von Fluorapatit-Gelatine-Nanokompositaggregaten detailliert nachvollzogen werden. Da über die Rolle der Gelatine beim Wachstum der Kompositaggregate nur wenig bekannt ist, wurde eine Reihe von Versuchen durchgeführt, in denen Gelatinen mit verschiedenen Molekülmassenverteilungen eingesetzt wurden. Es stellte sich heraus, dass für selbstorganisiertes und insbesondere fraktales Wachstum der Kompositaggregate lange, möglichst wenig gestörte Makromoleküle von zentraler Wichtigkeit sind. Um die Funktion der organischen Komponente für das Kompositwachstum näher zu untersuchen, wurden Oberflächen von Kompositkeimen mit rasterkraftmikroskopischen Methoden studiert. Durch Säuberung der Oberflächen konnten Austrittsstellen der organischen Komponente durch die Oberfläche der Kompositkeime identifiziert werden. Damit konnte gezeigt werden, dass die organische Komponente aus dem Inneren des Festkörpers teilweise durch die Oberfläche dringt und somit während des Wachstums weit in das Gel hineinreichen sollte. Für die mesoskopische Strukturbildung der Kompositaggregate spielen intrinsische elektrische Felder eine essenzielle Rolle. Deshalb wurde bislang eine Wirkung externer elektrischer Felder auf das Wachstum der Kompositaggregate vermutet. Im Rahmen der vorliegenden Arbeit wurde herausgearbeitet, dass es zwar zu keiner direkten Beeinflussung kommen kann, jedoch in den elektrodennahen Bereichen des Gels eine Ordnung der organischen Moleküle durch externe elektrische Felder zu erwarten ist. Dies könnte eine Wirkung auf wachsende Kompositaggregate zeigen. Da diese Effekte auch aufgrund der elektrischen Felder um die dipolaren Kompositaggregate zu erwarten sind, könnte eine ähnliche Strukturierung der Gelatine in der Nähe der wachsenden Kompositaggregate stattfinden. Insgesamt wurden in dieser Arbeit eine Reihe grundlegender Beiträge zur Erforschung der biomimetisch erzeugten Fluorapatit-Gelatine-Nanokompositaggregate geleistet. Es konnten neue Erkenntnisse zur inneren und äußeren Architektur der Kompositaggregate, zu Mechanismen der Morphogenese und deren wichtigsten Einflussgrößen sowie zum Verständnis der chemisch-physikalischen Vorgänge auf atomarer Größenskala gewonnen werden. Als besonders fruchtbar erwies sich die Verbindung von Experimenten mit theoretischen Untersuchungen, so dass dieser Weg auch in Zukunft grundlegende Erkenntnisse bei der Erforschung der Biomineralisation verspricht und weiterhin verfolgt werden sollte.

This thesis comprises detailed experimental and theoretical investigations of the transport properties of one-dimensional nanostructures. Most of the work is dedicated to the exploration of the fascinating effects occurring in single wall carbon nanotubes (SWCNT). These particular nanostructures gained an overwhelming interest in the past two decades due to its outstanding electronic and mechanical features. We have investigated the properties of a novel family of carbon nanostructures, named here as Y-shaped rings. The studies show that they present very interesting quantum interference effects. A high structural stability under tensile strain and elevated temperatures is observed. Within the semi-classical potential adopted, the critical strain values of structure rupture lie in the same range of their pristine SWCNT counterparts. This is directly verified by the first observations of these ring-like structures in a transmission electron microscopy. A merging process of asymmetric into symmetric rings is investigated in-situ under electron beam irradiation at high temperatures. The electronic properties of these systems are theoretically studied using Monte Carlo simulations and environment dependent tight-binding calculations. From our results, we address the possibility of double-slit like interference processes of counter-propagating electron waves in the ring-like structures. The nature of well defined, sharp peaks in the density of states are determined as the discrete eigenenergies of the central loop part. Furthermore, the formation and dispersion of standing waves inside the ring is shown to originate from the quantum-dot like confinement of each branch between the leads. The obtained dispersion relation is shown to be the same occurring in purely one-dimensional quantum dots of similar geometries. Furthermore, Fabry-Perot-like interferences are observed. We established at the IFW a bottom-up processing route to fabricate nanotube based electronic devices. The SWCNTs are grown by chemical vapor deposition and we present a detailed study of the different approaches to obtain individual nanotubes suitable for a successful integration into electronic devices. Wet-chemistry and ultra-thin films as well as ferritin were employed as catalyst particles in the growth of SWCNT samples. By adjusting the optimized process parameters, we can control the obtained yield from thick nanotube forests down to just a couple of free-standing individual SWCNTs. The nanotubes are localized, contacted by standard e-beam lithography and characterized at ambient- as well as liquid helium temperatures. We usually obtain quite transparent contacts and the devices exhibit metallic or a mixed metallic/semiconducting behavior. The well-known memory effect upon gate voltage sweeping as well as single electron tunneling in the Coulomb blockade regime are addressed.

This work refers to the area of bio-nanotechnology and concerns the selective immobilization of DNA or other bio-template on microstructured gold contacts and which then permit a coordinated cooperation of several of these nanotemplate, e.g., within a microreactor. The immobilization of such nano-objects should be realized through functional thin polymer films which provide binding groups. Thus, the main aim of this work was the development of polymeric materials for thin functional films which permit to deposit on different substrates a wide variation of functional elements or metal structures and to achieve a pattern formation using optical grid methods. In order to realize this concept it was necessary to design and develop a polymer system based on suitable photolabile units and in addition having anchoring groups which attach on specific substrates like gold. In this terpolymer concept was aimed for which consists of three components with particular functions in suitable molar ratios, which allow the tune the properties of the materials, and provide: amino photolabile protected groups for the photolithographic creation of patterned areas with free amino groups, which are available for further modifications like attachment of colloids, metallization or attachment of DNA strands; disulfide derivative anchor groups providing anchoring capacity for gold surface and spacer groups for adjusting the film quality. These multifunctional terpolymers should be synthesised by free radical polymerisation of suitable monomers. Although these techniques are successful, they are limited by their complexity, rigorous synthetic demands, as well as incompatibility with many functional termolabile and highly reactive functionalities. To overcome these difficulties a polymerisation technique based on “living” free radical polymerisation has been used in this work. A highly efficient polymer-analogous modification allows to introduce the functionalities after the polymer construction reaction. The production of suitable prepolymers [poly(styrene-r-4-propargyl-oxystyrene)] was carried out with the help of a controlled synthesis methodology “nitroxide mediate radical polymerization" followed by polymer analogous reaction using one of the most efficient click reactions, the Cu(I) catalyzed Huisgen 1,3-dipolar cycloaddition between terminal acetylenes and azides to attach further functionalities through the formation of a stable 1,4-disubstituted 1,2,3-triazol ring . The combination of nitroxide mediated radical polymerization (NMRP) and click chemistry was used to produce well-defined random copolymer. It could already be shown that also block copolymers can be prepared which give the chance to combine nanostructure formation in block copolymers with special functionality. Thus, the special properties of these functional polymers like the capability for photopatterning and anchoring onto gold substrates make them very interesting for nanotechnology applications. / Diese Arbeit bezieht sich auf das Gebiet der Bionanotechnologie und betrifft ein neuartiges Verfahren zur selektiven Immobilisierung der DNA oder anderer Biomoleküle auf mikrostrukturierten Goldkontakten, welche dann ein koordiniertes Zusammenwirken von einzelnen Nanomolekülen ermöglichen, z.B. in einem Mikroreaktor. Die Immobilisierung solcher Nanoobjekte soll durch dünne Funktionsschichten realisiert werden, die die Anbindungsgruppen liefern. Folglich war das Hauptziel dieser Arbeit die Entwicklung von Polymermaterialien für dünne Funktionsschichten, die die Aufbringung einer großen Vielzahl von Funktionselementen oder metallischen Strukturen auf verschiedenen Substraten gestatten und die Strukturierung durch den Einsatz von lithographischen Methoden ermöglichen. Um dieses Konzept zu realisieren, war es notwendig, ein Polymersystem zu gestalten und zu entwickeln, welches auf geeignete photolabile Einheiten basiert und zusätzlich Ankergruppen hat, die mit spezifischen Substraten wie Gold verbunden ist. Dieses Terpolymerkonzept wurde gezielt aus drei Komponenten mit speziellen Funktionen in entsprechenden molaren Verhältnissen gebildet, die eine Abstimmung der Materialeigenschaften ermöglicht und folgendes bereitstellt: photolabile geschützte Aminogruppen für die photolitographische Strukturerzeugung mit freien Aminogruppen, welche für weitere Modifikationen verfügbar sind wie das Anhängen von Kolloiden, die Metallisierung oder Anfügung von DNA-Strängen; disulfide Derivate für die kovalente Anbindung auf der Goldoberfläche und Spacer-Gruppe für Verbesserung der Schichtenbildung. Diese multifunktionalen Terpolymere sollen durch eine freie radikalische Polymerisation von entsprechenden Monomeren synthetisiert werden. Obwohl diese Techniken erfolgreich sind, sind sie eingeschränkt durch ihre Komplexität, den strengen synthetischen Anforderungen, sowie der Inkompatibilität mit vielen funktionalen thermolabilen und hochreaktiven Funktionalitäten. Um diese Schwierigkeiten zu überwinden wurde eine Polymerisationstechnik für diese Arbeit genutzt, die auf der „lebenden“ freien radikalischen Polymerisation basiert. Eine hoch effiziente polymeranaloge Modifizierung erlaubt die Einführung von Funktionalitäten nach der Polymeraufbaureaktion. Die Herstellung von entsprechenden Präpolymeren Poly(Styrol-r-4-Propargyl-oxystyrol) wurde mittels einer kontrollierten Synthesemethodik „Nitroxid-mediated controled radical polymerisation“ (NMRP) durchgeführt, gefolgt von der Polymeranalogreaktion, die eine der effizientesten Click-Reaktion - die Cu(I) katalysierte 1,3-dipolar Cycloaddition von terminalen Alkinen an Aziden nach Huisgen nutzt, um weiter Funktionalitäten durch die Bildung eines stabilen 1,4-disubstituierten-[1,2,3]-Triazolringes anzufügen. Die Kombination von NMRP und Click-Chemie wurde zur Herstellung eines exakt definierten Random Copolymers genutzt. Es konnte bereits gezeigt werden, dass auch Blockcopolymere geschaffen werden können, die eine Möglichkeit zur Kombination von Nanostrukturformationen in Blockcopolymeren mit speziellen Funktionaltäten bieten. Folglich sind die speziellen Eigenschaften dieser Funktionalpolymere wie die Fähigkeit zur Photostrukturierung und Verankerung auf Goldsubstraten für nanotechnologische Anwendungen sehr interessant.

In the present work new methods were developed for preparation of novel nanosized and nanostructured ceramic materials. Ordered mesoporous silica SBA-15 was found to be useful as a hard template for the nanocasting of silicon carbide and allowed the preparation of high temperature stable mesoporous silicon carbide ceramics. Chemical vapor infiltration of SBA-15 with dimethyldichlorosilane at elevated temperatures yields SiC/SBA-15 nanocomposites. The subsequent HF treatment of those composites resulted in silica removal and preparation of mesoporous silicon carbide with surface areas between 410 and 830 m2g-1 and high mesopore volume (up to 0.9 cm3g-1). The pore size (between 3 and 7nm in diameter) and surface area of mesoporous silicon carbide were controlled by adjusting the infiltration conditions (time, atmosphere). The mesoporous silicon carbide prepared via this method showed high structural thermal stability at 1300 oC, exceeding that of the SBA-15 template. However, the ordering on the mesoscopic scale was low. Nevertheless, highly ordered mesoporous silicon carbide materials were obtained via polymer melt infiltration in SBA-15. The low molecular weight polycarbosilane used as a preceramic precursor was converted at 1300 oC to silicon carbide inside the SBA-15, and after subsequent silica removal by HF, a highly ordered mesoporous material was obtained. Ordered mesoporous silicon carbide prepared by the methods reported here, may be an interesting material as a support due to its high temperature stability, chemical inertness, high thermal conductivity and semiconductor properties. In contrast to the nanocasting approach, based on the complete pore filling, also a new in-situ procedure for the preparation of finely dispersed metal and metal oxide particles inside ordered mesoporous silica was developed. A swelling agent (toluene) was used to deliver a hydrophobic platinum precursor into the surfactant micelles before addition of silica source. Such an in-situ method resulted in very high platinum incorporation (80-100%), not achieved for any other in-situ preparation procedures. Additionally, the presence of platinum allowed to decrease the template removal temperatures. Moreover, the method was also extended to other metal or metal oxide/ordered mesoporous silica systems. This may be especially interesting for the preparation of ordered mesoporous materials with low melting points, where typically the structure collapses during the high temperature calcinations process. The in-situ synthesized V2O5/MCM-41 materials were used to prepare VN/MCM-41 composites via nitridation in ammonia at 800oC. This method allowed to prepare highly dispersed, X-ray amorphous vanadium nitride species, with high activity in the propane dehydrogenation. Compared to nitridation of supported vanadium oxide prepared via the ex-situ procedure, in-situ synthesized materials showed similar catalytic activity, in spite of having significantly lower vanadium loading. As an alternative for the preparation of supported nitride materials, a novel preparation procedure of bulk not supported nanocrystalline vanadium nitride with high surface area was presented. Instead of pure oxide powder (which was typically used in the preparation of high surface area vanadium nitride catalysts), a macroporous amine intercalated V2O5 was used as the starting material. The obtained nitride consisted of small crystallites and had a surface area up to 198 m2g-1. Moreover, this foam-derived VN showed significantly improved activity as a catalyst in propane dehydrogenation. This novel preparation method could also be extended to other systems such as ternary VMoxNy nitrides.

The main goal of this work is design and synthesis of novel composite hydrogel-based core-shell microparticles and their application for fabrication of coatings, which provide the “inverse-switching” behaviour to the surface, namely, to become more hydrophobic in water environment. Since contact angle of heterogeneous surfaces is dependent on the nature and ratio of surface components, an increase of amount of more hydrophobic component on the surface will cause the reducing of surface wettability. It was suggested that core-shell particles having water-swellable hydrogel core and hydrophobic, but permeable for water shell when deposited on the hydrophilic substrate should increase the total amount of hydrophobic component on the surface when the cores of particles will swell in water. During the work different approaches to obtain freely dispersed and surface-immobilized core-shell particles with required structure were developed. Obtained particles were applied for preparation of coatings with ability to display “inverse-switching” behaviour. It was demonstrated that properly designed and properly prepared core-shell particles could be successfully used for creation of smart adaptive coatings having the ability to alter the surface properties upon changing of the environment.

In der vorliegenden Arbeit soll das weit gefächerte Thema der chemischen Nanotechnologie um neue Resultate bereichert werden. Im Einzelnen handelt es sich um neue Synthesemethoden für magnetische Nanorods (Nanoteilchen mit länglicher Form) und Nanoshells (oxidische Nanokristalle mit einer Hülle aus Edelmetall), ein Verfahren zur Modifizierung diverser Oberflächen mit heterogenen Polymerbürsten durch kontrollierte binäre radikalische Polymerisation, neuartige Copolymere zur Stabilisierung und Funktionalisierung von Nanopartikeln und Herstellung von amphiphilen Nanopartikeln durch Oberflächenbehandlung mit Niotensiden. Es sollen ferner die möglichen Anwendungen diskutiert werden. Die Abb. 1 illustriert die Zusammenhänge der bearbeiteten Thematik.

The assembly of nanostructures into “multi”-dimensional materials is one of the main topics occurring in nanoscience today. It is now possible to produce high quality nanostructures reproducibly but for their further application larger structures that are easier to handle are required. Nevertheless during their assembly their nanometer size and accompanying properties must be maintained. This challenge was addressed in this work. Lead chalcogenides have been chosen as an example system because they are expected to offer great opportunities as thermoelectric materials. Three different ways to achieve assemblies of lead chalcogenide nanostructures were used and the resulting structures characterized with respect to their potential application as thermoelectric material. The first means by which a “multi”-dimensional assembly of lead chalcogenide quantum dots can be produced is the formation of porous structures such as aerogels and xerogels. A procedure, where the addition of an initiator such as oxidizers or incident radiation is unnecessary, is introduced and the formation process studied by absorption spectroscopy. The time-consuming aggregation step could be significantly reduced by employing a slightly elevated temperature during gelation that does not lead to any observable differences within the resulting gel structures. After either supercritical or subcritical drying, highly porous monolithic gel structures can be achieved. During the gel formation the size and the shape of the particles changed and they were directly linked together. Nevertheless the resulting porous structures remain crystalline and size dependent effects of the optical properties could be shown. Gels produced from a mixture of PbS and PbSe QDs show a homogenous distribution of both materials but it is not clear to what extent they form an alloy. Although the particles are directly linked together the resulting porous structures possess a very high resistivity and so it was not possible to characterize the semiconductor aerogels with regard to their thermoelectric properties. To achieve an enhanced conductivity porous structures containing PbS and Au nanoparticles have been produced. As has been seen for the pure semiconductor gels the size of the PbS quantum dots has increased and elongated particles were formed. In contrast to the PbS QDs the Au nanoparticles did not change their size and shape and are unevenly distributed within the PbS network. Through the use of the gold nanoparticles the conductivity could be increased and although the conductivity is still quite small, it was possible to determine Seebeck coefficients near room temperature for a mixed semiconductor-metal gel. The second means by which QD solids could be formed was by the compaction of the QD building blocks into a material that is still nanostructured. Therefore the synthesis of PbS was optimized to achieve sufficient amounts of PbS quantum dots. The ligands used in the synthesis of the QDs unfortunately act as an insulating layer resulting in QD solids with resistivities as high as 2 Gigaohm. For this reason different surface modification strategies were introduced to minimize the interparticle distance and to increase the coupling between the QDs so as to increase the conductivity of the resulting quantum dot solids. One very promising method was the exchange of the initial ligands by shorter ones that can be destroyed at lower temperatures. By such heat treatments the resistivity could be decreased by up to six orders of magnitude. For the pressing of the quantum dots two different compaction methods (SPS and hydraulic pressing) were compared. While the grain growth within the SPS pressed samples is significantly higher the same densification can be achieved by a cold hydraulic pressing as well as by SPS. The densification could be further increased through the use of preheated PbS QDs due to the destruction of the ligands. Samples which had been surface modified with MPA and subsequently thermally treated show the best results with respect to their thermopower and resistivities. Nevertheless the conductivity of the QD solids is still too high for them to be used as efficient thermoelectric materials. The final assembly method does not involve QDs but instead with one dimensional nanowires. Therefore a synthesis was developed that enables the formation of PbS nanowires of different diameters and one that is easy up-scalable. By the use of a less reactive sulfur precursor and an additional surfactant the formation of nuclei is significantly retarded and within an annealing time of two hours nanowires can be formed presumably by an oriented attachment mechanism. Single crystalline nanowires with a diameter of 65-105 nm could be achieved with the longest axes of the nanowires being parallel to [100]. The resulting nanowires were used as building blocks for film formation on glass substrates by an easily implemented method that requires no special equipment. To characterize the films with a view to their possible application as a thermoelectric material, surface modifications of the films were performed to improve the charge transfer in the films and the Seebeck coefficients of the resulting films measured. Therefore the previous approach of using MPA was applied and a subsequent thermal treatment demonstrated very promising results. In addition an crosslinking ligand was used for surface treatment that leads to similar results as was observed for the thermally treated MPA approach. Both approaches lead to an order of magnitude decrease in the resistivity and due to the fewer grain boundaries present in the films composed of nanowires as compared to the QD assemblies the conductivity is significantly higher. The Seebeck coefficient measurements show that the thermal treatment only slightly affects the Seebeck coefficients. Therefore a significantly higher power factor could be achieved for the nanowire films than for the QD solids.