Structural, EPR, optical and magnetic properties of a-Fe 2 O 3 nanoparticles A.A. Jahagirdar a , N. Dhananjaya b , D.L. Monika c , C.R. Kesavulu d , H. Nagabhushana c,⇑ , S.C. Sharma c , B.M. Nagabhushana e , C. Shivakumara f , J.L. Rao d , R.P.S. Chakradhar g a Department of Chemistry, Ambedkar Institute of Technology, Bangalore 560 056, India b Department of Physics, B.M.S. Institute of Technology, Bangalore 560 064, India c C.N.R. Rao Centre for Advanced Materials Research, Tumkur University, Tumkur 572 103, India d Department of Physics, Sri Venkateswara University, Tirupathi 517 502, India e Department of Chemistry, M.S. Ramaiah Institute of Technology, Bangalore 560 054, India f Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India g CSIR-National Aerospace Laboratories, Bangalore 560 017, India highlights " Dumbbell shaped a-Fe 2 O 3 nanoparticles with rhombohedral phase have been prepared. " Spectroscopic investigations on a- Fe 2 O 3 nanoparticles were carried out. " From TL glow peaks trapping parameters were evaluated and discussed. graphical abstract Packing diagram of a-Fe 2 O 3 nanoparticles. article info Article history: Received 29 April 2012 Received in revised form 18 September 2012 Accepted 22 September 2012 Available online 2 October 2012 Keywords: Nanostructures Chemical synthesis Crystal structure Electron microscopy Luminescence abstract a-Fe 2 O 3 nanoparticles were synthesized by a low temperature solution combustion method. The struc- tural, magnetic and luminescence properties were studied. Powder X-ray diffraction (PXRD) pattern of a-Fe 2 O 3 exhibits pure rhombohedral structure. SEM micrographs reveal the dumbbell shaped particles. The EPR spectrum shows an intense resonance signal at g  5.61 corresponding to isolated Fe 3+ ions sit- uated in axially distorted sites, whereas the g  2.30 is due to Fe 3+ ions coupled by exchange interaction. Raman studies show A 1g (225 cm 1 ) and E g (293 and 409 cm 1 ) phonon modes. The absorption at 300 nm results from the ligand to metal charge transfer transitions whereas the 540 nm peak is mainly due to the 6 A 1 + 6 A 1 ? 4 T 1 (4G) + 4 T 1 (4G) excitation of an Fe 3+ –Fe 3+ pair. A prominent TL glow peak was observed at 140 °C at heating rate of 5 °Cs 1 . The trapping parameters namely activation energy (E), frequency factor (s) and order of kinetics (b) were evaluated and discussed. Ó 2012 Elsevier B.V. All rights reserved. Introduction In recent years, the synthesis of oxide nanoparticles have re- ceived considerable attention due to its unique electrical, optical and magnetic properties [1,2] and has become the focus of modern 1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2012.09.069 ⇑ Corresponding authors. Tel.: +91 9945954010. E-mail address: bhushanvlc@gmail.com (H. Nagabhushana). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 104 (2013) 512–518 Contents lists available at SciVerse ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa