The described study concentrated on the investigation of II-VI semiconductor quantum dots, prepared as colloidal species imbedded in phosphate glass, or chemically deposited on a substrate. The ultimate goal of the present research was concerned with the examination of the influence of the surface/interface quality on the optical properties of those quantum dots. This was examined by the utilization of optically detected magnetic resonance spectroscopy. This method reflected knowledge of the chemical identity of the surface/interface trapping site, and trapped electron and trapped hole recombination mechanism. It also distinguished between radiative and nonradiative processes, determined the spin−lattice relaxation, estimated the trapped electron−hole exchange mechanism and the distribution of defects at the surface.

A method is described for the preparation of hybrid organic/inorganic structures where the inorganic component comprises semiconductor nanoparticles aligned in periodic layers within three-dimensional (3-D) crystalline powders and Langmuir−Blodgett (LB) films. The preparation process comprises the organization of metal ions in the form of periodic arrays within 3-D crystals or the LB films, followed by a topotactic gas/solid reaction. The method is illustrated for the organization of CdS nanoparticles within alkanoic acids. The order of the nanoparticles is achieved by introducing site directing nucleation centers of Cd thioalkanoates within Cd alkanoates, in the form of solid solutions. The formed particles are attached to the organic matrix via −C(O)S−Cd−S− bonds. The structure of those supramolecular architectures has been characterized by a variety of complementary methods, including transmission electron microscopy (TEM) and electron diffraction (ED), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and other spectroscopic measurements.

CdS/HgS/CdS nanoparticles consist of a CdS core, epitaxially covered by one or two monolayers of HgS, and additional cladding layers of CdS. The luminescence spectrum of the studied materials contains a dominant exciton band located at the HgS layer and an additional nonexcitonic band, presumably corresponding to the recombination of trapped carriers. The present paper describes our efforts to identify the influence of CdS/HgS/CdS interfaces on the localization of the photogenerated species. These properties were investigated by the utilization of optically detected magnetic resonance spectroscopy. The results have shown the existence of two kinds of electron−hole recombination, trapped either at a twin packing of a CdS/HgS interface or at an edge dislocation of an epitaxial HgS or a CdS cladding layer.

In the frame of BMBF project "BioLiP", new physical treatment techniques aiming at medical treatment of the human skin have been developed. The acronym BioLiP stands for "Desinfektion, Entkeimung und biologische Stimulation der Haut durch gesundheitsfördernde Licht-und Plasmaquellen" (Disinfection, germ reduction and biological stimulation of the human skin by health promoting light and plasma sources). A source applying a low-temperature dielectric barrier discharge plasma (DBD) has been investigated on its effectiveness for skin disinfection and stimulation of biological material. Alternatively an atmospheric plasma source consisting of a microwave resonator combined with a solid state power oscillator has been examined. This concept which allows for a compact and efficient design avoiding external microwave power supply and matching units has been optimized with respect to nitrogen monoxide (NO) production in high yields. In both cases various application possibilities in the medical and biological domain are opened up. Light sources in the visible spectral range have been investigated with respect to the proliferation of human cell types. Intensive highly selective blue light sources based on LED technology can slow down proliferation rates without inducing toxic effects which offers new opportunities for treatments of so-called hyperproliferative skin conditions (e.g. with psoriasis or in wound healing) using UV-free light.

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