[1] Univ Malaya, Fac Sci, Dept Phys, Low Dimens Mat Res Ctr, Kuala Lumpur 50603, Malaysia
[2] Univ Putra Malaysia, Fac Sci, Dept Chem, Upm Serdang 43400, Selangor Darul, Malaysia
[3] Univ Kebangsaan Malaysia, Fac Sci & Technol, Sch Appl Phys, Bangi 43600, Selangor Darul, Malaysia
[4] Univ Nottingham, Fac Engn, Sch Chem & Environm Engn, Semenyih, Selangor Darul, Malaysia
[5] Multimedia Univ, Chancellery Off, Cyberjaya, Selangor Darul, Malaysia