with the Program of New Century Excellent Talents in Uni-versity (NCET-10-0416) is gratefully acknowledged. Y.S.thanks for a support as visiting scientist at the Carl vonOssietzky University of Oldenburg. The authors thank the Analyti-cal and Testing Centre at the HUST for performing characterizationof various samples.Appendix A. Supplementary dataSupplementary material related to this article can be found,in the online version, at http://dx.doi.org/10.1016/j.electacta.2014.02.115.