1. College of Physics; Qingdao University; Qingdao 266071 China
2. School of Materials Science and Engineering; University of Jinan; Jinan 250022 China
3. Institute for Integrative Nanosciences; IFW-Dresden; Helmholtzstrasse 20 01069 Dresden Germany
4. Department of Electronic Engineering; Chemistry and Industrial Engineering; University of Messina; Contrada di Dio 98166 Messina Italy
5. Institut für Chemie; Humboldt-Universität zu Berlin; Brook-Taylor-Str. 2 12489 Berlin Germany