Darstellung, Modifizierung und elektrische Charakterisierung von Silizium-Nanopartikeln

This thesis is motivated by the idea, to implement functional building blocks with silicon nanoparticles by means of printable electronics. Hence, the topic of this work is the investigation of the charge transport in thin layers made of silicon nanoparticles. As model systems commercially available as well as self prepared silicon nanoparticles were used and modified with different organic surface functionalities. In the first part of this work the surface modification of commercially available silicon nanoparticles synthesized in the gas phase is described: Initially, the surface oxide of the 20 nm large nanoparticles was removed by means of etching with acidic fluorine-containing solutions. Subsequently, the resulting hydrogen-terminated surface was modified via hydrosilylation using different 1-alkenes. In the second part of this work the preparation of modified silicon nanoparticles in liquid phase is observed: Based on silicon tetrachloride hydrogen-terminated silicon nanoparticles with a size between 1.2 nm and 4.5 nm as well as chlorine-terminated silicon nanoparticles with a size between 2 nm and 6 nm wered synthesized as intermediate and subsequently modified using hydrosilylation or silanization, respectively. The electrical characterization of thin layers made of modified silicon nanoparticles was performed using impedance spectroscopy. With regard to apply modified silicon nanoparticles as active material using printable electronics it was shown that the electrical transport in thin and compact layers made of the nanoparticles is thermically activated and, in the relevant area of room temperature, could be described using an ARRHENIUS approach. The activation energies were in the range of a half electron volt and could be influenced by thickness and permittivity of the organic modification. As electron transport mechanism nearest neighbor hopping was identified, as it was expected for a statistically distribution of localized states in the considered temperature range

Effect of Novel Aspergillus and Neurospora Species-Based Additive on Ensiling Parameters and Biomethane Potential of Sugar Beet Leaves

Research on additives that improve the quality of silages for an enhanced and sustainable biogas production are limited in the literature. Frequently used additives such as lactic acid bacteria enhance the quality of silages but have no significant effect on biogas yield. This study investigated the effect of a new enzymatic additive on the quality of ensiling and BMP of sugar beet leaves. Sugar beet leaves were ensiled with and without the additive (Aspergillus- and Neurospora-based additive) in ratios of 50:1 (A50:1), 150:1 (B150:1), and 500:1 (C500:1) (gsubstrate/gadditive) for 370 days at ambient temperature. Results showed that silages with additive had lower yeast activity and increased biodegradability compared to silages without additive (control). The additive increased the BMP by 45.35%, 24.23%, and 21.69% in silages A50:1, B150:1, and C500:1 respectively, compared to silages without additive (control). Although the novel enzyme is in its early stage, the results indicate that it has a potential for practical application at an additive to substrate ratio (g/g) of 1:50. The use of sugar beet leaves and the novel enzyme for biogas production forms part of the circular economy since it involves the use of wastes for clean energy production

Effect of Novel <i>Aspergillus</i> and <i>Neurospora</i> Species-Based Additive on Ensiling Parameters and Biomethane Potential of Sugar Beet Leaves

Research on additives that improve the quality of silages for an enhanced and sustainable biogas production are limited in the literature. Frequently used additives such as lactic acid bacteria enhance the quality of silages but have no significant effect on biogas yield. This study investigated the effect of a new enzymatic additive on the quality of ensiling and BMP of sugar beet leaves. Sugar beet leaves were ensiled with and without the additive (Aspergillus- and Neurospora-based additive) in ratios of 50:1 (A50:1), 150:1 (B150:1), and 500:1 (C500:1) (gsubstrate/gadditive) for 370 days at ambient temperature. Results showed that silages with additive had lower yeast activity and increased biodegradability compared to silages without additive (control). The additive increased the BMP by 45.35%, 24.23%, and 21.69% in silages A50:1, B150:1, and C500:1 respectively, compared to silages without additive (control). Although the novel enzyme is in its early stage, the results indicate that it has a potential for practical application at an additive to substrate ratio (g/g) of 1:50. The use of sugar beet leaves and the novel enzyme for biogas production forms part of the circular economy since it involves the use of wastes for clean energy production

Two-Dimensional Structure of Disulfides and Thiols on Gold(111)

In order to find factors which determine the two-dimensional structure of self-assembled monolayers (SAMs), several classes of thiols and disulfides on gold (111) have been investigated by atomic force microscopy (AFM). SAMs were formed from a series of symmetrical and asymmetrical diethylalkanoate disulfides, -hydroxy- and -carboxyalkanethiols, diacetylene disulfides, and different anthracene terminated thiols and disulfides. In all the cases, two-dimensional crystalline structures could be resolved; even for an asymmetrical diethylalkanoate disulfide that had a chain length difference of five methylene units. The lattices were analyzed quantitatively. Two distinctly different types of crystalline structures were observed, namely, a hexagonal and a centered rectangular lattice. For the diethylalkanoate disulfides with short alkyl chains (n <- 10) both structural phases were observed, domains with a hexagonal lattice existing simultaneously with centered rectangular domains. The length of the alkyl chain determined the probability of finding disulfides in the hexagonal structure. This dependence on the shape of the molecules as well as the clear contrast of SAMs of asymmetric disulfides suggest that the AFM tip penetrates into the SAMs and probes, at least partially, the interior of the layers. With the atomic force microscope no difference was observed between SAMs formed from thiols and those from disulfides