Um, Myoung-Chul; Jang, Junhyuk; Kang, Jihoon; Hong, Jung-Pyo; Yoon, Do Yeung; Lee, Seong Hoon; Kim, Jang-Joo; Hong, Jong-In Journal of Materials Chemistry, 2008 , vol. 18, # 19 p. 2234 - 2239