[1] Sikkim Manipal Univ, Ctr Mat Sci & Nanotechnol, Sikkim Manipal Inst Technol, Rangpo 737136, East Sikkim, India
[2] Sikkim Univ, Sch Phys Sci, Dept Chem, Gangtok 737102, Sikkim, India
[3] Sikkim Manipal Univ, Sikkim Manipal Inst Technol, Dept Phys, Rangpo 737136, East Sikkim, India
[4] Sikkim Manipal Univ, Sikkim Manipal Inst Technol, Dept Chem, Rangpo 737136, East Sikkim, India
[5] Natl Inst Technol, Dept Phys, Langol, Manipur, India