Carbon-TiO 2 Nanostructures: Flame Synthesis and Characterization
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Carbon-TiO2 Nanostructures: Flame Synthesis and Characterization Gianluigi De Falco1, Mario Commodo2, Paola Pedata3, Patrizia Minutolo2, Andrea D’Anna1 1
Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università degli Studi di Napoli Federico II, P.le Tecchio 80, 80125, Napoli, Italy. 2
Istituto di Ricerche sulla Combustione, CNR, P.le Tecchio 80, 80125, Napoli, Italy
3
Dipartimento di Medicina Sperimentale – Sezione di Igiene, Medicina del Lavoro e Medicina Legale, Seconda Università di Napoli, Via L. De Crecchio 7, 80138 Napoli, Italy ABSTRACT The synthesis of pure titania and carbon-titania nano-powders in a premixed atmospheric fuel-rich flame was studied. The variation of the flame C/O ratio allows to produce both pure titania and carbon-TiO2 nanoparticles. Raman Spectroscopy, X-ray Diffraction, Atomic Force Microscopy, Electrical Low Pressure Impactor and Scanning Electron Microscopy were used to characterize the synthesized nano-powders, in terms of crystallinity, phase content, size and morphology. Produced nano-powders with a dimension of 25-40 nm are composed by both rutile and anatase phases, with rutile being the predominant one. Reactive Oxygen Species analysis performed on the synthesized nano-powders showed that the inclusion of carbon in the nanopowders results in a reduced adverse health effect, in terms of ROS production. INTRODUCTION Titanium dioxide (TiO2) nanoparticles posses unique properties in terms of structural, chemical, electronic and optical characteristics [1], which made TiO2-based nanomaterials suitable for a wide range of applications, spanning from photocatalysis and dye-sensitized solar cells [2, 3] to food and personal care products [4]. Compared to other nano-titania synthesis methods, such as wet-chemical routes and chemical vapor deposition, flame synthesis offers a continuous and low-cost process with fine control over cristallinity and phase purity, avoiding any post-processing treatment [5]. A large variety of flame synthesis configurations, with different fuels and temperature ranges, have been developed during last decades for the synthesis of TiO2, including co-flow and counter flow diffusion flame [6, 7], premixed [8] and swirl [9]. Commonly used precursors were titanium chloride (TiCl4) and titanium tetraisopropoxide (TTIP). Among several diffuse applications, nano-powdered TiO2 is extensively employed, together with nano-ZnO, as physical filters in commercial sunscreens, due to its large band gap and its capability to adsorb and scatter both UVA and UVB radiations [10]. Health implications of the use of nano-TiO2 in sunscreens are related to the high oxidative potential of titania under UV illumination, which can lead to the formation of free radicals (reactive oxygen species— ROS), claimed to be responsible for skin damages [11]. Coating and doping of TiO2 nanoparticles with organic and inorganic additives represent a possible way to reduce those health implications. In such regards, when TiO2 is coated with carbon, its photocata
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