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Enhanced Thermal Oxidation Stability of Reduced Graphene Oxide by Nitrogen Doping

Enhanced Thermal Oxidation Stability of Reduced Graphene Oxide by Nitrogen Doping

Stefania Sandoval, Nitesh Kumar, Dr.  A. Sundaresan, Prof. C. N. R. Rao*, Prof. Amparo Fuertes and Dr. Gerard Tobias*. Chemistry - A European Journal, Volume 20, Issue 38, pages 11999–12003, September 15, 2014

Valence change of praseodymium in Pr0.5Ca0.5CoO3 investigated by x-ray absorption spectroscopy

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11-07-2012 15-13-28


J. Herrero-Martín, J. L. García-Muñoz, S. Valencia, C. Frontera, J. Blasco, A. J. Barón-González, G. Subías, R. Abrudan, F. Radu, E. Dudzik, and R. Feyerherm 

©2011 American Physical Society

X-ray absorption spectroscopy measurements in Pr0.5Ca0.5CoO3 were performed at the Pr M4,5, Pr L3, and Ca L2,3 absorption edges as a function of temperature below 300 K. Ca spectra show no changes down to 10 K while a noticeable thermally dependent evolution takes place at the Pr edges across the metal-insulator transition. Spectral changes are analyzed by different methods, including multiple scattering simulations, which provide quantitative details on an electron loss at Pr 4f orbitals. We conclude that in the insulating phase a fraction [15(±5)%] of Pr3+ undergoes a further oxidation to adopt a hybridized configuration composed of an admixture of atomiclike 4f1 states (Pr4+) and f-symmetry states on the O 2p valence band (Pr3+L̲ states) indicative of a strong 4f-2p interaction.


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