Raman study of magnetite (Fe₃O₄): laser‐induced thermal effects and oxidation

Raman spectroscopy investigation of magnetite nanoparticles in ferrofluids

“…The shift spans between 10 cm À 1 for the lowest peak position to 40 cm À 1 for the two-magnon scattering feature at 1320 cm À 1 . These shifts are temperature dependent and in good agreement with those observed by Shebanova and Lazor [10]. Also there, a laser power of 2-3 mW had no effect on a magnetite sample with average size of particles 0.6 mm, whereas in our experiment 1.95 mW produced complete phase transition for our nanosized samples.…”

“…In this paper, we focus on Raman micro-spectroscopy investigation of magnetite nanoparticles dispersed in two types of ferrofluids. Contributions to Raman spectroscopy investigations of nanosized iron oxides have already been reported, with some special emphasis on the works of da Faria et al [9] and Shebanova and Lazor [10]. Some ferrofluid investigations involving this vibrational spectroscopy have also been made, where the preparative techniques yield either dried [11], precipitated [12], or frozen [13] samples to be measured.…”

Bifunctional Fe3O4/Ag nanoparticles obtained by two-step laser ablation in pure water

“…3. The typical Raman band of magnetite (Fe 3 O 4 ) occurs at 665 cm À1 , in agreement with the results reported in the literature [30,31]; the Raman band of maghemite (c-Fe 2 O 3 ) around 720 cm À1 [32] is not appreciably observed, even if the oxidation of magnetite to maghemite, which is also ferromagnetic, is likely to occur [33,34]. The typical Raman bands of hematite (a-Fe 2 O 3 ) [35], which is the most stable form of ferric oxide, that should occur at 292, 411, 612 cm À1 , are completely absent.…”

El arte rupestre esquemático del Arroyo Barbaón (Parque Nacional de Monfragüe, Cáceres): contextualización arqueológica y caracterización de pigmentos

“…Teniendo en cuenta que el láser altera drásti-camente la estructura de los probables óxidos de hierro de los pigmentos (Shebanova y Lazor, 2003;El Mendili et al, 2011), su potencia fue reducida hasta un grado de 0,2mW, con 30 s de tiempo de exposición.…”

“…Las bandas Raman de los diversos tipos de óxi-dos de hierro son recogidas de forma bastante ambigua en la bibliografía especializada, de modo que diferentes bandas pueden aparecer relacionadas con una determinada variante de óxido férrico (Faria et al, 1997;Clark y Curri, 1998;Cornell y Schwertmann, 2003;Shebanova y Lazor, 2003;Hanesch, 2009). Estas variaciones pueden responder al empleo de diferentes potencias de láser en la obtención de los espectros de dichos óxidos, pues la aplicación de potencias inadecuadas puede provocar las alteraciones de las fases minerales, si bien los picos o bandas características de cada fase mineral de óxido de hierro, ya sean férricas, ferrosas o mixtas, resultan independientes del tipo de láser que se use.…”