Control of sp 2 /sp 3 Carbon Ratio and Surface Chemistry of Nanodiamond Powders by Selective Oxidation in Air

Department of Materials Science and Engineering, Drexel University, Filadelfia, Pennsylvania, United States
Journal of the American Chemical Society (Impact Factor: 12.11). 10/2006; 128(35):11635-42. DOI: 10.1021/ja063303n
Source: PubMed


The presence of large amounts of nondiamond carbon in detonation-synthesized nanodiamond (ND) severely limits applications of this exciting nanomaterial. We report on a simple and environmentally friendly route involving oxidation in air to selectively remove sp(2)-bonded carbon from ND. Thermogravimetric analysis and in situ Raman spectroscopy shows that sp(2) and sp(3) carbon species oxidize with different rates at 375-450 degrees C and reveals a narrow temperature range of 400-430 degrees C in which the oxidation of sp(2)-bonded carbon occurs with no or minimal loss of diamond. X-ray absorption near-edge structure spectroscopy detects an increase of up to 2 orders of magnitude in the sp(3)/sp(2) ratio after oxidation. The content of up to 96% of sp(3)-bonded carbon in the oxidized samples is comparable to that found in microcrystalline diamond and is unprecedented for ND powders. Transmission electron microscopy and Fourier transform infrared spectroscopy studies show high purity 5-nm ND particles covered by oxygen-containing surface functional groups. The surface functionalization can be controlled by subsequent treatments (e.g., hydrogenization). In contrast to current purification techniques, the air oxidation process does not require the use of toxic or aggressive chemicals, catalysts, or inhibitors and opens avenues for numerous new applications of nanodiamond.

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Available from: Gleb Yushin, Aug 27, 2015
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    • "Both processes lead to the formation of carbon–hydrogen bonds on the DND surface and the formation of positive zeta potential in colloidal solution of hydrogenated H-DNDs [9] [10]. Oxygen termination of DNDs is typically achieved by annealing in air at temperatures between 400–500 °C [11] [12]. In contrast to H-DNDs the formation of functional groups containing oxygen on the surface of DNDs leads to a negative zeta potential of oxidized O-DNDs in colloidal solution [10] [13]. "

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    • "The colour of the Pristine DND powder is Black and size of the DND clusters is below 500 nm as per the supplier's specifications. Pristine DND powder was oxidized at 435 C for 5 h to remove the impurities [20] [22]. These impurities include traces of metals and nondiamond (amorphous and graphitic) carbon content [23]. "
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    ABSTRACT: The aim of this study is the potential use of nanodiamond to make the lightweight and strong nanocomposites. Here, effects of size and surface modification of detonation nanodiamond (DND) on mechanical performance of epoxy based nanocomposites is presented. Our characterizations reveal that the process of functionalization not only removes the non-diamond content and impurities by significantly reducing DND's size but also introduces oxygen containing functional groups on its surface. The average size of functionalized DND aggregations could be decreased from 300 to 100 nm in contrast to pristine DND, which greatly benefits its homogeneous dispersion in epoxy matrix. In addition, strong chemical bonding among functionalized DND and epoxy resin due to functional groups leads to the formation of efficient interface. These interfaces overlap at high concentrations making a network which in turn significantly enhances the tensile properties. The enhancement in Young's modulus can reach up to 2.5 times higher than that of neat epoxy whereas the enhancement in tensile strength is about 1.5 times in functionalized DND/epoxy nanocomposites.
    Composites Part B Engineering 09/2015; 78. DOI:10.1016/j.compositesb.2015.04.012 · 2.98 Impact Factor
    • "Electrospun PAN and PA11 nanofibers with high contents of ND show dramatically improved mechanical properties [43]. ND used in this study was purified by air oxidation [33], followed by HCl treatment to reduce the content of metals and hydrolyze anhydrides and lactones formed on ND surface during oxidation in air in order to maximize the number of carboxylic groups on the surface, which was confirmed by Fig. 3. (a) Two major issues in polymer nanocomposites are related to poor dispersion (when nanoparticles gather together in large micron-sized agglomerates, creating defects in the polymer matrix rather than improving it) and weak interface between the nanoparticles (even if they are well dispersed) and the matrix, resulting in poor load transfer. Overcoming this issues, when nanoparticles become well dispersed and covalently bonded to the matrix, will result in superior composites with very high mechanical, thermal, and other properties; (b) schematic illustration of gas (red, left side of the panel) and wet (blue, right side of the panel) chemical modification techniques for nanodiamond [21]. "
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    ABSTRACT: Nanodiamond particles (NDs) are unique among different nanomaterials due to their specific features and benefits. ND, also known as ultra-dispersed diamond or ultra nanocrystalline diamond, is a member of a diverse family of nanocarbons that includes fullerenes, nanotubes, graphene, amorphous dense and porous networks. Unique characteristics combined with a moderate production cost and commercial availability favorably distinguish NDs from many other nanoparticles, which have been tried as fillers in polymer nanocomposites. Main advantages of ND particles for nanocomposites stem from unique properties, such as diamond structure that provides superior Young's modulus, hardness, high thermal conductivity and electrical resistivity, low coefficient of friction, chemical stability, and biocompatibility.
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