First identification of primary nanoparticles in the aggregation of HMF
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ORIGINAL PAPER
Open Access
First identification of primary nanoparticles in the aggregation of HMF Mu Zhang1, Hong Yang1*, Yinong Liu1, Xudong Sun2, Dongke Zhang1 and Dongfeng Xue3
Abstract 5-Hydroxymethylfurfural [HMF] is an important intermediate compound for fine chemicals. It is often obtained via hydrothermal treatment of biomass-derived carbohydrates, such as fructose, glucose and sucrose. This study investigates the formation of carbonaceous spheres from HMF created by dehydration of fructose under hydrothermal conditions. The carbonaceous spheres, ranging between 0.4 and 10 μm in diameter, have granulated morphologies both on the surface and in the interior. The residual solution is found to contain a massive number of primary nanoparticles. The chemical structure of the carbonaceous spheres was characterised by means of FTIR and NMR spectroscopies. Based on these observations, a mechanism involving the formation and aggregation of the nanoparticles is proposed. This mechanism differs considerably from the conventional understanding in the open literature. Keywords: saccharides, carbohydrate, HMF, nanoparticles, carbonaceous spheres
Introduction Hydrothermal treatment of saccharides (e.g. fructose, glucose, sucrose and starch) at elevated temperatures has attracted much attention in recent years for its technological and scientific interests [1-6]. In general, hydrothermal treatment of saccharides produces water-soluble organic substances and insoluble carbonaceous solids. The soluble organic substances have been the focus of early research, and understanding of the chemical reaction process and the products has been well established by earlier researchers [7,8]. In more recent years, the solid products, often referred to as humins in early studies, have attracted keen attention due to their potential for applications as functional nanomaterials or as nanotemplates for other materials [1,9-11]. Among these studies, several hypotheses have been suggested in the literature for the physical and chemical mechanisms for the formation of these carbonaceous solids, often in a spherical form. Earlier studies suggested that the carbonaceous spheres form via dehydration of saccharide molecules followed by aromatization under hydrothermal conditions. The carbonaceous spheres produced are thus expected to have a highly aromatic nucleus and a hydrophilic shell [1-5,9]. Another hypothesis * Correspondence: [email protected] 1 School of Mechanical and Chemical Engineering and Centre for Energy, The University of Western Australia, 35 Stirling Highway, Perth, Western Australia, 6009, Australia Full list of author information is available at the end of the article
proposed by Wang et al. [12] suggests that sucrose molecules form a kind of amphiphilic micelle compound under hydrothermal conditions, and as the concentration of this compound reaches a critical micelle concentration, spherical micelles develop. The carbonaceous spheres thus grow by the polymerization of sucrose molecules [12]. Yao et al. [2] proposed pr
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