1. Department of Chemistry, Mahila Mahavidyalaya, Banaras Hindu University, Varanasi 221 005, India
2. Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki-Aza-Aoba, Aoba-Ku, Sendai 980-8578, Japan
3. School of Materials Science and Engineering, Nankai University, Tianjin 300350, China