[1] Rice Univ, Dept Mat Sci & NanoEngn, Houston, TX 77005 USA
[2] Univ Fed Minas Gerais, Dept Quim, Av Antonio Carlos 6627, BR-31270901 Belo Horizonte, MG, Brazil
[3] Indian Inst Sci, Mat Res Ctr, Bangalore 560012, Karnataka, India
[4] Univ Estadual Campinas, Dept Fis Aplicada, BR-13083959 Campinas, SP, Brazil
[5] Univ Fed Rio Grande do Norte, Dept Fis Teor & Expt, BR-59072970 Natal, RN, Brazil