1. Department of Chemistry, University of North Bengal, Darjeeling 734013, West Bengal, India
2. Department of Chemistry, National Institute of Technology, Durgapur 713209, India
3. Department of Chemistry, Gorubathan Government College, Kalimpong 735231, India
4. Department of Botany, University of North Bengal, Darjeeling 734013, India
5. Department of Chemistry, Alipurduar University, Alipurduar 736122, West Bengal, India