Electroless plating is a metal deposition technique widely used in the coating industry. It is the method of choice to plate substrates with complex geometries and nonconductive surfaces, such as polymers and ceramics, since it is based on a chemical reduction in solution rather than on an external electrical energy source like the electroplating method. Among others, examples of well-established applications are the electroless deposition of decorative metal coatings such as gold and silver, wear and corrosion resistant nickel coatings, particularly to coat drive shafts, rotors, and bathroom fixtures, as well as the electroless deposition of copper in electronic devices as diffusion barriers and conductive circuit elements. In the academic research, electroless plating is extensively used thanks to its low cost, simple equipment and versatility that allow rapid prototyping. Two common applications are the coating of small particles and the selective plating of flat surfaces. Metal coated ceramic particles are of enormous interest in many scientific fields, e.g. fluorescent diagnostics in biochemistry, catalysis, and fabrication of photonic crystals. Metal coated ceramic nanoparticles and microparticles are also gaining attention as potential candidates in the fabrication of higher quality metal matrix Composites, which is one of the applications addressed by this work. Metal coated ceramic particles are easier to integrate in metal matrix composites, avoiding aggregation caused by the low wettability of the particles by the matrix metal, and are potentially shielded from oxidation and undesired chemical reactions that take place at the interface between the particles and the metal Matrix. Electroless plating is an autocatalytic process, meaning that the deposited metal atoms catalyze the deposition of further metal. In order to achieve the first stable metal seeds on a surface, the latter has to be functionalized. Without this functionalization the metal ions in the electroless plating bath are not reduced or are simply reduced to metal nanoparticles in solution. The traditional activation step for nonconductive surfaces is performed by immersion of the substrate in palladium based solutions, which is very time-consuming and extremely expensive. In particular for nanoparticles, previous work showed that at least 1015 Pd atoms/cm2 are required for a uniform activation of a surface, meaning that in the case of nanoparticles with a surface area of about 100 m2/g are necessary 6.4 g of palladium for each gram of substrate. Assuming a price of about 150 €/g (laboratory scale) for palladium nanoparticles and palladium precursors used for surface activation, it results that the activation of 1 g of nanoparticles costs around 1000 €. Such costs are suboptimal considering the typical production scale, and therefore alternative functionalization methods are desired. In this work, new organic-based functionalization methods based on (3-mercaptopropyl)triethoxysilane to functionalize oxide particles, 3-aminopropylphosphonic acid to activate carbide particles and a substrate-independent method based on the bioinspired polydopamine are developed and investigated in detail, together with the respective electroless plating baths, which often have to be specifically tailored regarding the different reactivity of the different molecules and substrates. Furthermore, in the fabrication of metallic patterns on substrates by electroless plating, new, simple, and cost-effective activation and metal deposition processes are desired. In this work, two new methods are presented, one based on the printing of (3-mercaptopropyl)triethoxysilane by microcontact printing, the other based on the capillary force lithography of polymethylmethacrylate.

The use of DNA-based therapeutics requires efficient delivery systems to transport the DNA to their place of action within the cell. To accomplish this, we investigated multiwalled carbon nanotubes (pristine MWCNT, p-MWCNT) functionalized with hydroxyl groups via 1,3-dipolar cycloaddition. In this way, we have obtained MWCNT-f-OH with improved stability in aqueous dispersions which is an advantageous property for their use in cellular environments. Afterwards, a carrier strand oligodeoxynucleotide (CS-ODN) was adsorbed to MWCNT-f-OH followed by hybridization with a therapeutic antisense oligodeoxynucleotide (AS-ODN). The amount of adsorbed CS-ODN, as well as the complementary AS-ODN and a non-complementary oligodeoxynucleotide (NS-ODN) as reference, was directly measured by radionuclide labeling of ODNs. We show that subsequent release of AS-ODNs and NS-ODNs was possible for MWCNT-f-OH above the melting temperature of AS-ODNs at 80 °C and under physiological conditions at different pH values at 37 °C. We also show a very low influence of p-MWCNT and MWCNT-f-OH on the cell viability of the bladder carcinoma (BCa) cell line EJ28 and that both MWCNT types were internalized by EJ28. Therefore, MWCNT-f-OH represents a promising carrier able to transport and release AS-ODNs inside cells.

Nanographene oxide particles (NGO) were produced via oxidative exfoliation of graphite. Three different sizes of NGO (300 nm, 200 nm and 100 nm) have been separated by using probe sonication and sucrose density gradient centrifugation. There is great interest in functionalized NGO as a nanocarrier for in vitro and in vivo drug delivery, in order to improve dispersibility and stability of the nanocarrier platforms in physiological media. In this study, the NGO particles were covalently functionalized with zero generation polyamidoamide (PAMAM-G0) and with gelatin via noncovalent interaction. Spectroscopic techniques have been used to discriminate the chemical states of NGO prior and after functionalization. The X-ray photoelectron spectroscopy (XPS) revealed a clear change in the chemical state of NGO after functionalization, for both covalent and noncovalent approaches. Raman spectroscopy gave obvious insight after oxidation of graphite and functionalization of NGO particles depending on the variation of intensity ratios between D, G and 2D bands. The Fourier transform infrared spectroscopy (FTIR) exhibited the presence of oxygen containing functional groups distributed onto graphene sheets after oxidation of graphite. Furthermore, the FTIR is complementary with the XPS which performed a strong reduction in the oxygen contents after functionalization. UV visible spectroscopy was used to understand the binding capacity of gelatin coated NGO particles. The Microscopy tools, scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to estimate the dimensions of NGO particles (thickness and lateral width). The nanohybrid systems (NGO-PAMAM and Gelatin-NGO) loaded with carboplatin (CP) were sought for anticancer activity investigation in HeLa and neuroblastoma cancer cells respectively. Mesenchymal stem cells (hMSCs) were used as a model of normal cells. On HeLa cells, the pristine NGO particles with average widths of 200 nm and 300 nm showed a cytotoxic effect at low (50 g.ml−1) and high (100 g.ml−1) concentrations. While the pristine NGO sample with an average width of 100 nm revealed no significant cytotoxicity at 50 g.ml−1, and only recorded a 10% level at 100 g.ml−1. The mesenchymal stem cells showed less than 35% viability for all size distributions. After functionalization with PAMAM, the carrier was found to be able to deliver carboplatin to the cancer cells, by enhancing the drug anticancer efficiency. Moreover, the carboplatin loaded NGO carrier shows no significant effect on the viability of hMSCs even at high concentration (100 g.ml−1). On neuroblastoma cells, the cell viability assay validated gelatin-NGO nanohybrids as a useful nanocarrier for CP release and delivery, without obvious signs of toxicity. The nano-sized NGO (200 nm and 300 nm) did not enable CP to kill the cancer cells efficiently, whilst the CP loaded gelatin-NGO 100 nm resulted in a synergistic activity through increasing the local concentration of CP inside the cancer cells.

In recent years supramolecular chemistry has established as one of the most active fields of science. The most significant feature of supramolecular chemistry is the use of building blocks which reversibly held together by intermolecular forces, electrostatic or H-bonding. Therefore, the synthesis of supramolecular systems using different non-covalent assemblies provides some unique architectures and features which are extremely difficult to be obtained via covalent synthesis. One main application of such influencing supramolecular systems is the preparation of self-healing materials. Among various approaches to self-healing effects, reversible bond formation has become prominent in the last years. To achieve both acceptable mechanical performance and self-healing behaviour from a polymeric material, proper balance between covalent and non-covalent bonding is important. The covalent bonding gives a basic strength to the material while the non-covalent bonding generates self-healing effects in the case of damage. The main aim of this study was to synthesize an organic moiety which is capable of forming supramolecular assemblies in the presence of suitable counterparts, followed by its incorporation on to polymer matrix and investigation of the final properties. For reversible bond forming technique H-bonding is exploited in this work. 4-substituted-2,6-diaminopyridine is selected as the organic moiety as it has a clear DAD (donor-acceptor-donor) structure and thus able to undergo self-association or triple hydrogen bonded complex formation with respective counterparts. Chichibabin reaction was utilised for the synthesis and 4-hydroxy-2,6-diamido pyridine was synthesised as the key compound. Initially different derivatives of 4-hydroxy-2,6 diamino pyridine was synthesized and utilised towards the formation of supramolecular network with a suitable monomeric counterpart. Poly (butadiene-co-maleic anhydride) is used as the base polymer as it has the possibility to introduce non-covalent bonding sites through grafting reactions on the double bonds or on maleic anhydride groups. The free amine group present in the main compound was grafted onto the backbone of poly (butadiene-co-maleic anhydride) via reaction of amine with maleic anhydride group. The main design of supramolecular self-assembly within poly (butadiene-co-maleic anhydride) with a suitable counterpart poly (butadiene-co-maleimide), is prepared and used in this thesis. The miscibility of the two polymers is proven by the presence of a single Tg in the DSC results of the mixture and also by the formation of homogeneous films with no phase separation in AFM. However the formation of hydrogen bonding within the monomer was proven by 1H NMR, IR studies. Further formation of complex between two polymers was established from the results of viscosity. Also the interactions between the complexes exert a distinct influence on the rheological behavior of the blend. Lastly the reversibility of this supramolecular blend was assured by temperature dependent viscosity values. In the final part of this work, bromobutyl rubber (BIIR) is selected as the model elastomer which has vast application in the tire industry; as the inner-liner that holds the air in the tire and also used as rubber stoppers for sealing medicine vials and bottles The bromine functionality can be substituted with an amine group making it more susceptible towards the incorporation of different organic moieties. In this way, the derivative of 2,6-diaminopyridine having a pendant amine group is incorporated in BIIR. As a counterpart uracil is used as its H-bond forming ability with diaminopyridine moieties is well established and supported by different previous research works. The supramolecular network formed between these two monomers help to generate self-healing effects within BIIR rubber. Fig. 2 represents the supramolecular network formed between chains of BIIR. The self-healing effect of the rubber material is examined through the stress-strain experiments where up to 82% healing was observed when heated up to 70 °C. With increasing temperature better healing was observed whereas at room temperature a 40% healing tendency was noticed. It is also interesting to note that the thermal and dynamic mechanical properties of this tailor made self-healing BIIR is identical with sulphur cured conventional BIIR.

Polymer magnetic composite (PMC) nanoparticles have gained a large attention due to their potential use in several biomedical applications from biomedical to engineering field. Among the different heterogeneous polymerization techniques that are generally used to prepare hybrid polymer particles, miniemulsion polymerization is proved to be an efficient one. The occurrence of preferential droplet nucleation in case of miniemulsion polymerization results in a 1:1 copy of monomer droplets to the polymer particles and such a mechanistic pathway offers a suitable environment for the preparation of hybrid polymer nanoparticles in the range between 50 to 500 nm. The surfactant in miniemulsoin plays a significant role to stabilize the droplets/particles and also in the encapsulation of nanoparticles. In the present study, a new class of surfactant, called amphiphilic ionic liquid, has been employed in the field of miniemulsion. The amphiphilic ionic liquid has amazing ability to impart surface tunable characteristics to the polymer particles when present on the surface of the particles. Thus the aim of the present work is to synthesize polymer magnetic composite nanoparticles with good colloidal stability, high content of magnetic nanoparticles as well as the chance for further surface functionality. Such magnetic nanoparticles may find applications in various fields. At first, the aim of the work was to establish a suitable recipe with ionic liquid as surfactant for the execution of miniemulsion polymerization. Monodisperse polystyrene nanoparticles were possible to be synthesized reproducibly. The established recipe was utilized to carry out the synthesis of PMC nanoparticles. Iron oxide (Fe3O4) was taken as magnetic nanoparticles (MNP) and it was hydrophobized with oleic acid to disperse in styrene. The concentration of feed MNP was varied to observe its influence on the characteristics of PMC nanoparticles. Stable dispersion of magnetic polystyrene particles was possible to be synthesized up to 8 wt% feed MNP. But feeding 12 wt% MNP resulted in the development of large amount of coagulum associated with instability in the dispersion. TGA investigation confirmed a significantly lower MNP content (8.2 wt%) of the composite compared to the feed amount. TEM investigation showed inhomogeneous distribution of MNP among polystyrene particles and agglomeration of MNP was observed on the surface of polystyrene particles. Considering the inability of the single step miniemulsion polymerization for the preparation of high MNP content polymer particles, it was aimed to find a new strategy which can produce such material. Inspired from the affinity of carboxylic acid group towards the surface of MNP, it was aimed to synthesize carboxyl functionalized polystyrene which was expected to improve the interaction between polymer and magnetic nanoparticles. For this purpose, RAFT mediated miniemulsion polymerization was performed in presence of a carboxyl functionalized chain transfer agent (CTA). The colloidal stability was much better compared to the previous case of non-RAFT experiments. From a feed MNP of 8 wt%, a high final MNP content up to ~27 wt% could be achieved and all the dispersions were highly stable. The higher MNP content in the final composites compared to the feed ratio was a result of the low monomer conversion and could be adjusted by a proper tuning of AIBN to CTA mole ratio. Another significant influence of the carboxyl functionalized CTA was observed on the morphology of the composite nanoparticles. The MNP were distributed homogeneously among the PS particles. Regarding the dispersion of MNP in the individual polystyrene particles, it was observed that higher amount of CTA resulted in a homogeneous dispersion of MNP whereas higher amount of initiator ended up producing asymmetric Janus like morphology. Apart from that, due to the involvement of CTA in the polymerization, much lower molecular weight of the polystyrene chains was developed compared to the free radical process and the molecular weight distribution of PS in the composite nanoparticles became much narrower through the RAFT polymerization. Thus a relatively good control over the polymerization process was achieved through RAFT polymerization which was confirmed by a nearly linear increase of molecular weight (Mn) with time of polymerization and thus, monomer conversion. In the recipe of miniemulsion, costabilizer plays an important role to retard monomer diffusion from smaller to larger droplets. Hexadecane, being the most frequently used costabilizer for miniemulsion, has been employed in this study so far. But its volatile nature restricts its utilization in several applications. For the replacement of hexadecane, a carboxyl functionalized polystyrene is employed as a costabilizer as well as a macro CTA in miniemulsoin polymerization of styrene. For this purpose, low molecular weight carboxyl bi-functionalized polystyrene (9000 g/mole) was synthesized by thermal bulk RAFT polymerization. The carboxylated polystyrene worked successfully as a costabilizer in miniemulsion and molecular weight investigation confirmed the integration of the carboxyl functionalized macro CTA into the developing polystyrene chain via RAFT polymerization. This strategy was employed successfully to synthesize stable dispersion of PMC nanoparticles with a reasonable content of MNP in the system. A homogeneous morphology was observed regarding the distribution of MNP among the polystyrene particles. The strategy of using macro CTA as costabilizer can be utilized to synthesize various functional copolymers with control architecture without any added monomer and CTA in the system. Moreover, presence of functionality within the monomer droplets can be effective to encapsulate several nanomaterials using miniemulsion polymerization.

The long-lived fission product 126Sn (105 years) (Weast (1972)) is of substantial interest in the context of nuclear waste disposal in deep underground repositories. However, the prevalent redox state, the aqueous speciation as well as the reactions at the mineral-water interface under the expected anoxic conditions are a matter of debate. Therefore, in this PhD thesis I present work on the reactions of SnII with three Fe-bearing minerals as a function of pH, time, and SnII loading under anoxic condition with O2 level < 2 ppmv. The first mineral, goethite, contains only trivalent Fe (FeIIIOOH), the second, magnetite, contains both FeII and FeIII (FeIIFeIII2O4), and the third, mackinawite (FeIIS), contains only divalent Fe. The uptake behavior of the three mineral surfaces was investigated by batch sorption studies. Tin redox state was investigated by Sn-K X-ray absorption near-edge structure (XANES) spectroscopy, and the local, molecular structure of the expected Sn surface complexes and precipitates was studied by extended X-ray absorption fine-structure (EXAFS) spectroscopy. Selected samples were also investigated by transmission electron microscopy (TEM) to elucidate the existence and nature of secondary, Fe- and /or Sn containing solids, and by Mössbauer spectroscopy to study FeII and FeIII in the minerals. Based on the such-obtained molecular-level information, surface complexation models (SCM) were fitted to the batch sorption data to derive surface complexation constants. In the presence of the FeIII-bearing minerals magnetite and goethite, I observed a rapid uptake and oxidation of SnII to SnIV. The local structure determined by EXAFS showed two Sn-Fe distances of about 3.15 and 3.60 Å in line with edge and corner sharing arrangements between octahedrally coordinated SnIV and the Fe(O,OH)6 octahedra at the magnetite and goethite surfaces. While the respective coordination numbers suggested formation of tetradentate inner-sphere complexes between pH 3 and 9 for magnetite, bidentate inner-sphere complexes (single edge-sharing (1E) and corner-sharing (2C)) prevail at the goethite surface at pH > 3, with the relative amount of 2C increasing with Sn loading. The interfacial electron transfer between sorbed SnII and structural FeIII potentially leads to dissolution of FeII and transformation to secondary FeII/FeIII oxide minerals. There is no clear evidence to confirm the reductive dissolution in the Sn/ magnetite system, Rietveld refinement of XRD patterns, however, indicates an increase of FeII/FeIII ratio in the magnetite structure. For the Sn/goethite system, dissolved FeII increased with SnII loading at the lowest pH investigated, indicative of reductive dissolution. At pH >5, spherical and cubic particles of magnetite were observed by TEM, and their number increased with SnII loading. Based on previous finding, this secondary mineral transformation of goethite should proceed via dissolution and recrystallization. The molecular structure and oxidation state of sorbed Sn were then used to fit the batch sorption data of magnetite and goethite with SCM. The sorption data on magnetite were fit with the diffuse double layer model (DLM) employing two different complexes, the first ( = -14.97±0.35) prevailing from pH 2 to 9, and the second ( = -17.72±0.50), which forms at pH > 9 by co-adsorption of FeII, thereby increasing sorption at this high pH. The sorption data on goethite were fitted with the charge distribution–multisite complexation model (CD-MUSIC). Based on the EXAFS-derived presence of two different bidentate inner-sphere complexes ((≡FeOH)(≡Fe3O)Sn(OH)3 (1E) and (≡FeOH)2Sn(OH)3) (2C)), sorption affinity constants of 15.5 ±1.4 for the 1E complex and of 19.2 ±0.6 for the 2C complex were obtained. The model is not only able to predict sorption across the observed pH range, but also the transition from a roughly 50/50 distribution of the two complexes at 12.5 µmol/g Sn loading, to the prevalence of the 2C complex at higher loading, in line with the EXAFS data. The retention mechanism of SnII by mackinawite is significantly dependent on the solution pH, reflecting the transient changes of the mackinawite surface in the sorption process. At pH <7, SnII is retained in its original oxidation state. It forms a surface complex, which is characterized by two short (2.38 Å) Sn-S bonds, which can be interpreted as the bonds towards the S-terminated surface of mackinawite, and two longer Sn-S bonds (2.59 Å), which point most likely towards the solution phase, completing the tetragonal SnS4 innersphere sorption complex. Precipitation of SnS or formation of a solid solution with mackinawite could be excluded. At pH > 9, SnII is completely oxidized by an FeII/FeIII (hydr)oxide, most likely green rust, forming on the surface of mackinawite. Six O atoms at 2.04 Å and 6 Fe atoms at 3.29 Å demonstrate a structural incorporation by green rust, where SnIV substitutes for Fe in the crystal structure. The transition between SnII and SnIV and between sulfur and oxygen coordination takes place between pH 7 and 8, in accordance with the transition from the mackinawite stability field to more oxidized Fe-bearing minerals. The uptake processes of SnII by mackinawite are largely in line with the uptake processes of divalent cations of other soft Lewis-acid metals like Cd, Hg and Pb. Very different Sn retention mechanisms were hence active, including oxidation to SnIV and formation of tetradentate and bidentate surface complexes of the SnIV hydroxo moieties on goethite and magnetite, and in the case of mackinawite a SnII sulfide species forming a bidentate surface complex at low pH, and structural incorporation of SnIV by an oxidation product, green rust, at high pH. In all three mineral systems and largely independent on the retention mechanisms, inorganic SnII was strongly retained, with Rd values always exceeding 5, across the relatively wide pH range relevant for the near and far-field of nuclear waste respositories. For the goethite and magnetite systems, the retention could be well modeled with surface complexation models based on the molecular structural data. This is an important contribution to the safety case for future nuclear waste repositories, since such SCMs provide reliable means for predicting the radioactive dose released by 126Sn from nuclear waste into the biosphere across a wide range of physicochemical conditions typical for the engineered as well as natural barriers.

Considering the worldwide growing discharge of minor actinides and the current need for geological disposal facilities for radioactive waste, this work provides a contribution to the safety case concerning Np transport if it would be released from deep repository sites and moving from alkaline cement conditions (near-field) to more neutral environmental conditions (far-field). The reducing conditions in a nuclear waste repository render neptunium tetravalent, which is assumed to be immobile in aqueous environment due to the low solubility solution of Np(IV). For tetravalent actinide nuclides, the most significant transport should occur via colloidal particles. This work demonstrates the formation of intrinsic neptunium dioxide nanocrystals and amorphous Np(IV) silica colloids under environmentally relevant conditions. The dissociation of the initial soluble Np(IV) complex (i.e. [Np(IV)(CO3)5]6-) induces the intrinsic formation of nanocrystalline NpO2 in the solution phase. The resulting irregularly shaped nanocrystals with an average size of 4 nm exhibit a face-centered cubic (fcc), fluorite-type structure (space group ). The NCs tend to agglomerate under ambient conditions due to the weakly charged hydrodynamic surface at neutral pH (zetapotential ~0 mV). The formation of micron-sized agglomerates, composed of nanocrystals of 2-5 nm in size, and the subsequent precipitation cause immobilization of the major amount of Np(IV) in the Np carbonate system. Agglomeration of NpO2 nanocrystals in dependence on time was indicated by PCS and UV-vis absorption spectroscopy with the changes of baseline characteristics and absorption maximum at 742 nm. Hitherto, unknown polynuclear species as intermediate species of NpO2 nanocrystal formation were isolated from solution and observed by HR-TEM. These polynuclear Np species appear as dimers, trimers and hexanuclear compounds in analogy with those reported for other actinides. Intrinsic formation of NpO2 (fcc) nanocrystals under ambient environmental conditions is prevented by admixing silicic acid: amorphous Np(IV) silica colloids are formed when silicate is present in carbonate solution. Herein, the initial molar ratio of Si to Np in solution lead to the formation of Np(IV) silica particles of different composition and size where Si content determines the structure and stability of resulting colloids. Implications for different electronic structures of Np(IV) in dependence on Si content in the solid phase are given by the shift of the absorption maximum at 742 nm characteristic for Np(IV) colloids, silica excess of 5 times the magnitude of Si to Np reveal a redshift up to 6 nm in the colloidal UV-vis spectrum. Precipitation of Np(IV) particles in the ternary system results in a different coordination sphere of Np(IV) compared to the binary system, and the incorporation of Si into internal structure of Np(IV) silica colloids in coffinite-like structure is confirmed by EXAFS. TEM confirms different kinds of particle morphologies in dependence on the silica content. Silica-poor systems reveal porous particles in the micron-range which consist of irregular cross-linked hydrolyzed Np(IV) silica compartments with pores <15 nm. In contrast, long-term stabilized and silica-enriched systems are characterized by isolated particles with an average particle size of 45 nm. Agglomerates of such isolated Np(IV) silica particles appear as consolidated amorphous solids with a densely closed surface and exhibit no internal fractures. The latter mentioned morphology of Np(IV) silica particles might facilitate the migration behavior of Np(IV) in a stabilized colloidal form under environmental conditions. The silica-enriched particles with densely closed surface are long-term stabilized as colloidal dispersion (>1 year) due to repulsion effects caused by significant surface charge. Particles synthesized from Si/Np = 9/1 carry exclusively negative surface charge in nearly the whole pH range from pH 3 to pH 10 with zetapotential = (-) 5 to (-) 30 mV. The zeta potentials of all particle systems containing silica are significantly shifted to more negative values below pH 7 where the isoelectrical point shifts from pH = 8.0 to 2.6 effecting negative charge under ambient conditions which supports electrostatic stabilization of Np(IV) particles. Particle surface charge at the slipping plane, particle size and shape necessarily depend on the initial magnitude of Si content in solution during particle formation. Particular changes of the morphology and internal structure of different Np(IV) silica colloids by aging are indicated by TEM and XPS. The composition and the crystallinity state of the initially formed amorphous phases partially changed into well-ordered nanocrystalline units characterized with fcc structure. The presence of silicate under conditions expected in a nuclear waste repository significantly influences the solubility of Np(IV) and provoke the stabilization of waterborne Np(IV) up to concentrations of 10-3 M, exceeding Np´s solubility limit by a factor of up 10.000. Neptunium and silicate significantly interact with each other, and thereby changing their individual hydrolysis and polymerization behavior. Silicate prevents the intrinsic formation of NpO2 NCs in fcc-structure, and at the same time, Np(IV) prevents the polymerization of silicate. Both processes result in the formation of Np(IV) silica colloids which possibly influence the migration behavior and fate of Np in the waste repositories and surrounding environments. For tetravalent actinides in general, the most significant transport in the environment would occur by colloidal particles. Therefore, Np(IV) silica colloids could have a significant implication in the migration of Np, the important minor actinide in the waste repositories, via colloidal transport.

Seit 2002 kam ein neues Interesse an Germanium als Material für CMOS-Bauelemente auf, angetrieben durch die höhere Beweglichkeit der Ladungsträger im Vergleich zu Silizium. Für die Herstellung von Germanium MOSFETs bestehen allerdings noch einige Herausforderungen. Speziell die Problematik der hohen n-Dotierung für die Source- und Draingebiete der PMOS-Transistoren hat sich dabei als potentieller Roadblocker herauskristallisiert. Die geringe Aktivierung und die hohe Diffusivität der Donatoren in Germanium stellen ein Problem für die Herstellung von CMOS-Schaltkreisen aus Germanium dar. Als ursächlich dafür wurden Vakanzen identifiziert (Bracht et.al.). Um das Diffusions- und das Aktivierungsverhalten von Arsen und Phosphor in Germanium zu untersuchen, wurden p-Typ Germaniumwafer durch Ionenimplantation mit beiden Spezies dotiert und anschließend durch Rapid-Thermal-Annealing und/ oder Flash-Lamp-Annealing ausgeheilt. Zusätzlich wurden Experimente mit kodotierten und P-dotierten Proben mit verringerter Schichtkonzentration durchgeführt. Untersuchungen mit Rutherford-Backscattering-Spektroskopie und Transmissions-Elektronen-Mikroskopie werden durchgeführt, um die strukturellen Eigenschaften der Proben infolge der Implantation und der Ausheilung festzustellen. Mittels Sekundärionen-Massen-Spektroskopie wird die Dotandenkonzentration bestimmt. Es folgen elektrische Messungen des Schichtwiderstandes bei Raumtemperatur und in geeigneten Fällen bei Temperaturen unterhalb 10K. An ausgewählten Proben werden Hallmessungen durchgeführt. Die Gesamtheit der Analyseverfahren ermöglicht eine Analyse des Rückwachsverhaltens, der Diffusion und der elektrischen Aktivierung der Dotanden unter den verschiedenen Implantations- und Ausheilbedingungen. Die nach verschiedenen Methoden bestimmten Größen wie die Ladungsträgerkonzentration und -mobilität werden betrachtet und im Hinblick auf die Parameter der Probenpräparation analysiert und mit der Literatur verglichen. Abschließend werden mögliche Mechanismen zur Deaktivierung von Donatoren in Germanium erörtert.

Nanomaterials have attracted considerable attention during the past decades due to their unique and fascinating properties. However, this class of materials is not an invention of modern age. People have been using nanomaterials for centuries, although unwittingly. Probably the most famous example for the usage of nanomaterials in ancient times is the Lycurgus Cup, a Roman glass cage cup created in the 4th century which changes the colour of its glass from green to ruby depending on the illumination conditions. The foundation for the development of the field of nanotechnology was laid by the speech of Feynman “There is plenty of room at the bottom” in 1959, in which he spoke about the principles of miniaturisation as low as to the atomic level. Today, modern nanotechnology made it its business to purposefully develop and synthesise nanomaterials as well as to face their applications in various fields, such as microelectronics, catalysis or biomedicine. However, the term “nanomaterials” does not solely involve the nanoparticulate units itself, but also their arrangement into two- or three-dimensional structures. Thereby, the maintenance of the nanoscale properties is one of the main challenges. This task was focussed by this work implied the preparation and macroscale arrangement of fluorescent QDs while preserving their optical properties. The main achievement of this work was the development of a novel aerogel material with non-quenching PL behaviour by using silica coated QDs as nanoparticulate building units. In comparison to other monolithic silica-QD structures or aerogels from pure QDs, a defined and controllable distance between the fluorescent QDs is provided in these structures by the silica shell. The spacing was shown to efficiently disable energy transfers so that no spectral shifts, lifetime shortening or PL QY losses are observed during the colloid to gel transition. The silica shell, established by a standard reverse microemulsion approach, was found to exhibit a certain porosity, which was proven by gas adsorption measurements. Existing cavities in the micro- and mesoporous range were found to allow small species such as metal ions to pass through the shell and interact with the QD core causing a detectable change of the PL intensity, which makes these materials suitable for future sensing applications. The gel preparation was based on a metal ion assisted complexation approach, which requires tetrazole functionalisation of the nanoparticulate building units. A major development in this work that permitted this gelation approach for silica-QDs was the development of a novel tetrazole-silane ligand. TMSPAMTz was specifically designed to bind to the silica surface of silica-QDs in aqueous solution and was prepared by a covalent coupling of an alkyl chained silane with a 5-subsituted tetrazole ring. Network formation is subsequently achieved by the interconnection of negatively charged tetrazole rings with metal ions, which allows for a broad spectrum of aerogel materials from different NP species as well as their mixtures as long as tetrazole capping is provided. Considering this diversity and the disabling of energy transfers, straightforward colour tuning was demonstrated herein by mixing differently emitting silica-QD species which gives great prospects for lighting applications. Furthermore, the possibility of plasmon enhanced emission was presented for mixed Au NP/silica-QD gels. With respect to future sensing applications, thin porous films from silica-QDs gels were prepared, which showed a promising concentration dependant PL quenching for the model analyst hydrogen peroxide. However, the film reproducibility of the applied drop-cast coating method was insufficient. As a suggestion to this, a LbL method was presented, wherein a gel is subsequently grown with the metal ion assisted complexation approach. In addition to the tetrazole ligands on the NP surface, tetrazole-silane ligands were used in this approach to functionalise the glass substrate surface. By this, homogeneous gel films of distinct thickness can be grown while the use of organic polymers can be completely avoided. Besides the preparation of NP assemblies, standard Cd-based QD materials as well as Au NPs of different sizes and shape, recent progresses in the synthesis of InP-based QDs were presented in this work. A thorough investigation and understanding of the growth influencing parameters allowed for the establishment of preparation routes for In(Zn)P/GaP/ZnS core/shell/shell QDs with emission wavelengths tuneable within a large range from 500 to 650 nm, narrow peak widths of 45 to 70 nm and PL QYs up to 60%. Successful incorporation of these QDs into salt matrices was further demonstrated. The resulting composite materials are very photostable and suitable as colour conversion materials for solid state lighting, as was clearly pointed out by a self-prepared WLED that met the standard commercial LEDs.

Ice accretion on various surfaces can cause destructive effect of our lives, from cars, aircrafts, to infrastructure, power line, cooling and transportation systems. There are plenty of methods to overcome the icing problems including electrical, thermal and mechanical process to remove already accumulated ice on the surfaces and to reduce the risk of further operation. But all these process required substantial amount of energy and high cost of operation. To save the global energy and to improvement the safety issue in many infrastructure and transportation systems we have to introduce some passive anti-icing coating known as ice-phobic coating to reduce the ice-formation and ice adhesion onto the surface. Ice-phobic coatings mostly devoted to utilizing lotus-leaf-inspired superhydrophobic coatings. These surfaces show promising behavior due to the low contact area between the impacting water droplets and the surface. In this present study we investigate systematically the influence of chemical composition and functionality as well as structure of surfaces on wetting properties and later on icing behavior of surfaces. Robust anti-icing coating has been prepared by using modified silica particles as a particles film. Polymer brushes were synthesized on flat, particle surfaces by using Surface initiated ATRP. We have also investigated the effect of anti-icing behavior on the surfaces by varying surface chemistry and textures by using different sizes of particles. This approach is based on the reducing ice accumulation on the surfaces by reducing contact angle hysteresis. This is achieved by introducing nano to micro structured rough surfaces with varying surface chemistry on different substrates. Freezing and melting dynamics of water has been investigated on different surfaces by water vapour condensation in a high humidity (80%) condition ranging from super hydrophilic to super hydrophobic surfaces below the freezing point of water. Kinetics of frost formation and ice adhesion strength measurements were also performed for all samples. All these experiments were carried out in a custom humidity and temperature controlled chamber. We prepared a superhydrophobic surface by using Poly dimethyl siloxane (PDMS) modified fumed silica which display very low ice-adhesion strength almost 10 times lower than the unmodified surface. Also it has self-cleaning behavior after melting of ice since whole ice layer was folded out from the surface to remove the ice during melting. Systematic investigation of the effect of three parameters as surface energy, surface textures (structure, geometry and roughness) and mechanical properties of polymers (soft and stiff) on icing behavior has also been reported.