resumo
Mn-doped TiO2 nanocrystals encapsulated in a carbon layer (Ti1-xMnxO2@ C) were synthesized by the one-pot RAPET (reaction under autogenic pressure at elevated temperature) technique. Manganese was doped into the body-centered tetragonal TiO2 anatase phase to give a Mn:Ti atomic ratio of 1%, 5% and 10%. The surface modification by carbon was achieved in order to make the cubic/ tetragonal nanocrystals non-toxic and biocompatible. Electron paramagnetic resonance (EPR) studies revealed a broad resonance (centered at g = 1.9977 due to the interacting spins in the oxide matrix) with increased dopant concentration and the resonance due to carbon. Manganese is mainly present as + II or + III oxidation states. The magnetic behavior was found to be very dependent on the manganese concentration with a ferromagnetic behavior of the 1% doped sample due to the coupling between carriers and manganese spins. A predominant paramagnetic behavior was observed for the higher Mn-doped samples. This study opens up a new dimension for the carbon encapsulation of room-temperature ferromagnetic diluted magnetic semiconductor (DMS) nanomaterials.
palavras-chave
PHASE-TRANSITION; TITANIUM; DIOXIDE; TEMPERATURE; FERROMAGNETISM; SEMICONDUCTORS; NANOPARTICLES; RESONANCE; IMPLANTS; COATINGS
categoria
Science & Technology - Other Topics; Materials Science; Physics
autores
Bhattacharyya, S; Pucci, A; Zitoun, D; Gedanken, A
Grupos
agradecimentos
DZ acknowledges the Fame NOE ( Network of Excellence) for a fellowship for AP. AP acknowledges FCT for the doctoral grant SFRH/BD/45177/2008.