1. Institute of Physics & IMN Macronano; Ilmenau University of Technology; Ilmenau 98693 Germany
2. Chair of Materials Science; Otto Schott Institute of Materials Research; Friedrich Schiller University Jena; Jena 07743 Germany
3. Institute of Nanochemistry and Nanobiology; School of Environmental and Chemical Engineering; Shanghai University; Shanghai 200444 P. R. China