4. Nano and Bio Photonics and Electronics

Nanophotonics The objective has so far been focussed on designing nanostructured materials by incorporating nanoparticles showing quantum confinement (like quantum dots) in order to address fundamental issues limiting current photonic technologies. We also research the other outstanding property of nanoparticles. the plasmonic effect, and study excitonic and surface-plasmonic polaritons in nanostructures including inorganic semiconducting and metallic nanoparticles as well as organic molecules in terms of active photonic materials. We try to apply new design strategies for electromagnetic properties in order to reduce the optical loss and the spatial dimensions of optical components. Here the concept of metamaterials (.man-made materials.) is of relevance. The project aims to design photonic components with extraordinary optical properties, like low- or zero-loss high-index of refraction and low- or zero-loss metallic behaviour (negative epsilon).

Biophotonics Nanostructures for high-sensitivity photo-detection are developed for bio-medical technologies based on the principles of quantum confinement, plasmonics and upconversion. We take account of the general notion of nano-particle based biophotonics that combine nano-particle technology, biochemistry and integrated photonics for use in biomedicine (disease detection). We have demonstrated some new opportunities of quantum nano-particles for applications for protein tracking, and explored the potential for diagnosis through specially synthesized nanoparticle labelled DNA molecular probes. Other applications have concerned nanoparticle assisted tracking of proteins for early stage detection of atherosclerosis.

Nanoelectronics One direction of our electronics research program is to understand electron transport in a single molecule sandwiched between electrodes. This is driven by the ever growing demand for miniaturization of electronic components in modern information society. Single molecular electronic devices could be the ultimate solution for future information technology since molecules are the smallest stable quantum species. We have developed our own computational programs based on bottom-up quantum chemistry approaches that can accurately determinate molecular conformations, molecule-electrode interface structure and molecular excited state properties. Several devices with specific functions have been designed. We have, for instance, studied the electro luminance of molecules in a nano-cavity activated by plasmonic excitation, a new phenomenon that has many significant applications.

Bioelectronics A good understanding of electron transport in molecules can be extremely valuable for the development of bio-electronics, which takes advantage of highly sensitive electronic read-out techniques to determine some important properties of biological systems. The first thing that comes to mind is the design of bio-sensors. The specific interaction between the biological molecules and the electrodes result in the change of the current, which can be used to study the conductance of different DNA base-pairs, and to sequence DNA that way. Theoretical modelling is the first step towards the success of all such applications.

3rd Generation Nanostructured Solar Cells The third .nano. application area concerns design and fabrication of solar cell materials and architectures, by employing nanoparticles and hybrid nanostructures. The nanoparticle based micro structures have hetero-composition tailored for effective exciton generation and carrier separation and extraction, while also designed to depress various quenching mechanisms. We fabricate (in the Nano lab, see below) and study multiple core shell quantum dots and rods, and conjugate them in various ways. We study in particular the interface problem for the cells. A new direction is dye sensitized solar cells containing upconversion nanocrystals and plasmonic nanostructures for energy harvesting in the near infrared wavelength range and upconversion of the harvested energy to visible range. The goal is to catch in as much as possible of the 50 % solar energy which falls in the IR region.

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