For four years, inventing a new toilet bowl freshener has been a sideline pursuit for Michael Lefenfeld, a 25-year-old graduate student in molecular electronics at Columbia. Mr. Lefenfeld's doctoral research focuses on the structure of molecules in nanoscale devices like transistors. But his quest for a new freshener - a search inspired by his grandfather's wish for a quick way to neutralize smelly toilets - led to a surprising discovery, a way to encase sodium and other explosive alkaline metals in a powdered form of silicon gel, making them much safer to handle. The powdery materials, researchers say, could eventually...