Nanoparticles illuminate

The lighting systems in use today—especially ordinary, everyday light bulbs—may not be as common in the future, if a team of chemical engineers led by Mark T. Swihart, assistant professor of chemical engineering, has its way. Today’s incandescent light bulbs have good color and poor efficiency, while fluorescent tubes have better efficiency and poorer color. Take a break, light bulbs: Solid state lighting based on silicon nanoparticles, with potential applications in such devices as ceiling squares, promises to offer both better color and higher efficiency than traditional lighting systems.

These luminescent nanoparticles have exciting potential applications in bioimaging as well. In biomedicine, fluorescent organic dyes are currently used as diagnostic tools. The dyes go to sites of interest and serve as beacons to enable clinicians and technicians to make diagnoses. Unfortunately, even though the dyes bleach quickly and stop fluorescing after unreasonably short periods of time, this technology is the best we have. In contrast, Swihart and UB Engineering researchers envision replacing these organic dyes with semi-conductor nanoparticles whose fluorescence is stable considerably longer.

Swihart’s team is preparing silicon nanoparticles to emit light under varying controlled conditions. Changing particle size and preparing particles in different ways can manipulate particle electronic properties to produce different colors.

Silicon nanoparticles (less than 5 nm in diameter) with bright visible photoluminescence have been prepared by a new combined vapor-phase and solution-phase process, using only inexpensive commodity chemicals. The wavelength of maximum photoluminescence intensity can be controlled by controlling processing conditions and methods, over a range that includes the entire visible spectrum. The particle surfaces can even be treated with organic chemicals or polymers to control their chemistry. Using these approaches, stable dispersions of silicon nanoparticles have been prepared in both polar and nonpolar solvents. These surface treatments can also stabilize the photoluminescence spectrum. The functionalized nanoparticles can then be attached to surfaces, biomolecules, or other sites, or incorporated into conducting polymer matrices. Two areas where this technology is expected to have applications are lighting systems and bioimaging.

Swihart and his team interface with his colleagues in chemical and electrical engineering and the UB Institute for Lasers, Photonics and Biophotonics to extend their technology to other systems and to pursue device fabrication.