1. Department of Chemistry, Pukyong National University, 599-1 Daeyeon-3-dong, Nam-gu, Pusan 608-737, Korea
2. Department of Physics, Pukyong National University, 599-1 Daeyeon-3-dong, Nam-gu, Pusan 608-737, Korea
3. Department of Chemical Engineering and Material Science, University of California, Davis, California 95616