**Acknowledgements**

UKS would like to acknowledge the Indian National Science Academy (INSA), New Delhi, India, for providing INSA Visiting Scientist Fellowship (SP/VF-9/2014-15/273/01 April, 2014) under the guidance of BA at Bio-inspired Materials Science Laboratory, Department of Chemistry, Savitribai Phule Pune University, Ganeshkind, Pune, India. UKS would like to acknowledge the financial support received from the projects funded by the UGC, New Delhi (grant no. PSW-045/13-14-ERO) and UGC-DAE CSR, Kolkata centre, Collaborative Research Schemes (UGC-DAE-CSR-KC/CRS/13/RC11/0984/0988). UKS would like to thank all the authors and publishers of various journals and books (Elsevier, RSC, ACS, Springer, Techno Press, Intech Inc, and Indian Academy of Sciences) from which various figures and text portions has been reproduced in this chapter. Finally, special acknowledgement should be given to Techno Press, the publisher of the journal *Advances in Nano research* [7] from which some portion of the text has been reproduced.
