Modern technologies cannot be imagined without electronic devices, as e.g. the success stories of transistors and diodes illustrate. The performance of these electronic devices has tremendously increased during the last decades through a process known as downscaling: Minimizing structural units allows for extremely high densities of electronic modules. This entails an increase of speed as well as an enhanced performance. Today’s photonic devices, however, are still rather large. The reason therefore can be found in the nature of light: Diffraction sets a lower limit for the scales of photonic devices and therefore prevents densely packed photonic components. The diffraction limit can be, however, overcome by so called ’Surface Plasmon Polaritons’ (SPPs): These are oscillations of the conducting electrons in a metallic nanoparticle induced by an incoming electromagnetic field with a suitable frequency. By this conversion of the optical mode to surface plasmons, the electromagnetic energy can be localized to regions of merely several tens of nanometers. This property is highly desirable for the construction of future optoelectronic devices: Chains of metallic nanoparticles, for example, are promising waveguides with lateral confinements below the diffraction limit.

DNA is a potential pattern material for constructing nanostructures as it can be synthesized in almost arbitrary lengths in the nanometer scale and also allows for modifications that make site-specific reactions possible. Its inherent scaling limit is determined by the distance of two neighbored basepairs: This length is only 0.34nm and therefore much below the diffraction limit. Moreover, it seems very appealing to exploit the self-recognition properties of DNA to build functional nanostructures by self-assembly processes. Among all possible template-directed material syntheses, metallization of DNA is particularly interesting for photonic devices as it makes a controlled growth of metal nanoparticles with defined size and shape along the DNA template possible. Furthermore the use of DNA as a pattern promises to achieve a defined arrangement of the particles relative to each other.

Experiments concerning metallization of DNA have been done for approximately a decade now. Most experiments, however, have concentrated on investigating the electrical conductance of the DNA. Absorption spectra have merely been recorded for verifying the existence of metallized DNA in the solution. The optical properties of metallic nanoparticles grown on DNA templates have remained almost completely unexplored up to now.

Thus it is the main topic of this thesis to investigate the optical properties of metallized DNA structures, i.e. their absorption as well as scattering characteristics. Therefore two different metallization methods are applied and the resulting metallized particles are compared. Varying synthesis parameters, such as concentrations of the reagent or the reaction time systematically and analyzing the optical data, provides an understanding on what variables the metallization depends on. Changes in optical properties are related to changes in the size or structure of the nanoparticles. This information is extracted from polarized Dynamic Light Scattering experiments as well as Atomic Force Microscopy. Moreover Dynamic Light Scattering allows for direct monitoring of the nanoparticle growth; thereby the particle sizes as well as intensities are observed. These results are necessary to understand the DNA metallization process in detail and to be able to optimize the synthesis conditions on the way to a defined growth of metallic nanoparticles. Using various seed densities for site-specific DNA metallization and analyzing the resulting optical properties is a fist step to a defined arrangement of nanoparticles.

This thesis is structured as follows: After a brief introduction into theory about the properties of metallic nanoparticles and about DNA in chapter 2, chapter 3 explains the two different methods of metallization that are used for synthesis. Chapter 4 addresses absorption spectrometry: After a short description of the working principle, absorption spectra of metallized DNA samples are shown for numerous varied parameters and analyzed. The results are finally discussed and compared with two different theories about nanoparticle absorption. Chapter 5 is about Dynamic Light Scattering: In a theoretical part, simulations are done for a later comparison with experimental data. The second half of the chapter presents first results for the various metallized DNA samples. In chapter 6 the necessity for stabilizers and their working principle is explained before some experimental data is shown. Chapter 6 handles with metallization of ring-like DNA structures. In chapter 8 micrographs recorded with an Atomic Force Microscope are presented and analyzed.Afterward the obtained results of this thesis are concluded and an outlook for future investigations is given.