Graphitic Carbon Nanoparticles from Asphaltenes
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Graphitic Carbon Nanoparticles from Asphaltenes Christophe Danumah, Andrew J. Myles and Hicham Fenniri National Institute for Nanotechnology and Department of Chemistry, Alberta Edmonton, Alberta T6G 2M9, Canada
ABSTRACT We report preliminary studies on the preparation of carbon nanoparticles (CNPs) of ~ 20 nm in diameter derived from asphaltenes under mild conditions. This transformation occurred upon heating a thin film of asphaltenes cast on a carbon coated copper grid under both nitrogen and oxygen atmosphere. The resulting CNPs were characterized by thermogravimetric analysis (TGA), scanning/transmission electron microscopy (SEM/STEM), transmission electron microscopy (TEM), elemental analysis (EA) and Auger electron spectroscopy (AES). The findings point towards asphaltenes, a crude oil by-product, as a potential source for carbon nanomaterials. INTRODUCTION Carbon nanomaterials are of great industrial interest for applications in electronics [1], bio-imaging [2], catalysis, materials science and engineering [3] due to their high surface area, large pore volume, high conductivity [4], mechanical strength and thermal properties [1]. Several synthetic routes to carbon nanomaterials have been reported with the goal of reducing overall cost and avoiding harsh, non-scalable conditions [5, 6]. For example, inexpensive carbon sources such as candle soot [7], natural gas soot [8], sawdust [9] and biomass processed through hydrothermal carbonization [6] have been used for generating carbon nanomaterials. Asphaltenes have also been investigated in this regard and carbon nanoparticles (CNPs) were successfully generated using electron beam irradiation [9] and chemical vapor deposition [10]. The major aim in the area of carbon nanomaterial preparation is the cost and scalability, which are required for any industrial application. Thus, our ultimate goal is to develop a simple, energy efficient and cost-effective processing methodology for fabricating CNPs from asphaltenes, which is a class of oilsands by-product. Our preliminary investigations have shown that upon heating of a thin film of asphaltenes cast on a carbon coated copper grid under both nitrogen and oxygen atmosphere, graphitic CNPs are formed. The resulting CNPs are ca. 20 nm in size and have been characterized using TGA, SEM/STEM, TEM, EA, and AES. EXPERIMENTAL DETAILS General Experimental C7-Asphaltenes samples used as carbon stock in this work were prepared in our laboratory from the Athabasca Crude Oil [11]. Reagent grade toluene was purchased from Fisher Scientific.
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Preparation of colloidal solutions of Asphaltenes A stock solution was prepared by dissolving asphaltenes (1 mg/mL) in toluene using a heat gun for few seconds followed by sonication with a Branson ultrasonic Cleaner (Model 1510R-MT) for 2 min. The heating/sonication process was repeated twice to ensure maximum solubilization of asphaltenes. The resulting stock solution was allowed to stand for 2-3 days. Aliquots from this solution were then diluted to the desired concentrations (0.0001
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