Actively manipulating electronic excitations in nanocrystals

Colloidal nanocrystals made of semiconductor materials resemble fluorescent beads that are only a few nanometres in diameter. Their optical emission properties can be tuned from ultraviolet to infrared wavelengths by suitably choosing the material and adjusting their size and shape. To date, nanocrystals have been exploited in areas ranging from genomic and proteomic bio-assays, cell-staining and high-throughput screening, where they serve as fluorescence markers and more applications have been envisaged in LEDs, lasers, optical switches, photovoltaics, data storage devices, catalysis, drug delivery and other biomedical assays. Compared to self-assembled quantum dots made by molecular beam epitaxy, colloidal nanocrystals can be produced by comparatively simple and inexpensive solution methods, and are freely suspended in a solvent or matrix, while retaining a high optical and electronic stability. The precisely controlled size and shape of nanocrystals, such as in quantum dots, rods or even tetrapods, renders them promising building blocks for nanoscience and nanotechnology. Furthermore, shape control in the synthesis of colloidal nanocrystals offers unprecedented abilities to tune the interaction of solid state quantum structures with the environment, opening up the possibility of performing nanoscale manipulations of the optical and electronic properties. This 'First Grant' proposal aims for key experimental studies on the fundamental properties of colloidal nanocrystals. The overall plan is to develop novel applications based on the active manipulation of the optoelectronic properties of nanocrystals and on self-assembly methods for their alignment in large array device configurations. The ultimate applications range from electric-field nanosensors, single photon tunable sources to optical memory elements and all optical parallel processing.