[1] Anna Univ, Dept Med Phys, Chennai, Tamil Nadu, India
[2] Sathyabama Inst Sci & Technol, Chennai, Tamil Nadu, India
[3] SRM Inst Sci & Technol, Dept Phys & Nanotechnol, Kattankulathur, India
[4] Univ Madras, Natl Ctr Nanosci & Nanotechnol, Chennai, Tamil Nadu, India