Acknowledgments
We acknowledge the Start-Up Research Grant [F.20-1(28)/2012 (BSR)] of Dr. D. S. Ramakrishna [Faculty Research Promotion Schemes (FRPS)] funded by the University Grants Commission (UGC)-India. SRK thanks the Department of Science & Technology (DST), New Delhi, for funding in the form of a project (DST-FTYS CS-120/2014), IICT, Hyderabad, and the University of Hyderabad for spectral data assistance. SRK also thanks Dr M. Sridhar Reddy, IICT, Hyderabad, for useful discussions.
Disclosure statement
No potential conflict of interest was reported by the author(s).