Optical Sensing with CdSe Quantum Dots in Condensed Phase Media

The next generation of sensors built upon nanotechnology is rapidly coming to the forefront of scientific applications, with particular application to contemporary global concerns including counterterrorism and device miniaturization. The challenge of incorporating these materials as a stable sensor package is discussed, with special emphasis on condensed phase media, particularly sol-gels, porous glasses and organic solutions. Specifically, incredibly stable, strongly emitting CdSe quantum dots have been incorporated into several glasses and plastics, and are able to detect the presence of organic moieties, the most notorious of which is TNT, through photoluminescence quenching. The mechanism by which this operates is a through-space, long-range resonant transfer of electronic excitation energy, which is further enhanced by a strong binding affinity of the various analytes to the quantum dot surface. New sensor technology based upon quantum-confined, optically-active semiconductor nanomaterials represents an important step in realizing small-scale, highly sensitive and smart sensors.