Light-emitting diodes, or LEDs, are the most efficient and environmentally friendly light bulbs on the market. But they come at a higher up-front price than other bulbs, especially the ones with warmer and more appealing hues. Researchers at the University of Washington have created a material they say would make LED bulbs cheaper and greener to manufacture, driving down the price. Their silicon-based nanoparticles soften the blue light emitted by LEDs, creating white light that more closely resembles sunlight. The company, LumiSands, started as a graduate student pr...