Goldnanopartikel als Sensoren und Aktuatoren für photothermische Reaktionen

The spatial dimensions of nanoparticles resemble those of biomolecules. The properties of nanoparticles can be adjusted by chemical synthesis and the particles are good sensors and actuators of biomolecular processes. By attaching biomlecules to nanoparticles they can be marked selectively, signals can be tapped from and transmitted to them. Gold nanoparticles with a diameter of two up to circa 100 nm are characterised by their intensive light absorption which is caused by excitation of collective oscillations of valence band electrons, the so called plasmon resonance. The plasmon resonance wavelength is, amongst others, a function of the direct particle environment such that changes therein can be monitored spectroscopically. In this thesis, biomolecule gold nanoparticle hybrid materials are shown to not only be a sensor but also an actuator of biomolecular processes on the nanoparticle surface. Therefore, biomolecule nanoparticle suspensions were irradiated by continuous laser light and simultaneously monitored by UV/Vis spectroscopy. First, DNA double strand functionalized gold nanoparticles were investigated. The aim was to induce DNA dissociation by photothermally heating the particles but the temperature dependence of the optical properties of the applied aggregates was considered to low to give unambiguous results. Then, DNA double strand gold nanoparticle networks were analyzed. They exhibited a spectral blueshift of the plasmon resonance wavelength by several nm when heated a few °C. Here, DNA dissociation could be triggered photothermally without markedly damaging the DNA molecules. Using in situ UV/Vis spectroscopy this could be monitored and it was possible to quantify the photothermal temperature increase in DNA melting experiments. Also, first evidence was found that the photothermal temperature increase was a function of the goldnanoparticle network size. Further, using horse radish peroxidase functionalized gold nanoparticles an enzymatic oxidation reaction was successfully manipulated for the first time. Again, this was monitored using in situ UV/Vis spectroscopy and by comparing the activity of non-irradiated and irradiated enzyme nanoparticle suspensions the photothermal temperature increases was determined