1. Nanotechnology and Integrated Bioengineering Centre; University of Ulster; Jordanstown Campus Newtownabbey BT37 0QB Northern Ireland UK
2. Department of Physics; School of Natural Sciences; Shiv Nadar University; Gautam Buddha Nagar 201314 Uttar Pradesh India
3. School of Physical Sciences; Jawaharlal Nehru University; New Delhi 110067 India