**Acknowledgements**

The authors gratefully acknowledge the support of Rastriya Shikshana Samithi Trust, Bangalore. The authors would also like to acknowledge Department of Materials Engineering, IISc, Bangalore, India, for the help in carrying out the XRD, Raman and SEM analysis. In addition, we acknowledge Aravind K. of Intelli Biotechnologies, Bangalore for helping in microbiological assays.
