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Salt-assisted deaggregation of nanodiamond
Nanodiamond deaggregation into single particles is a notoriously difficult task. The existing protocols make use of zirconia microbeads propelled by mechanical energy or cavitation. They are expensive and leave behind difficult-to-remove debris of zirconia. In K. Turcheniuk, C. Trecazzi, C. Deeleepojananan, V. N. Mochalin Salt-Assisted Ultrasonic Deaggregation of Nanodiamond, ACS Applied Materials & Interfaces, 8 (38), 25461–25468 (2016) we have developed a new facile, inexpensive, and contaminant-free salt-assisted ultrasonic deaggregation (SAUD) of nanodiamond into single-digit particles stable in aqueous colloidal solution in a wide pH range. The technique utilizes the energy of ultrasound in a salt slurry. In contrast to current deaggregation techniques, which introduce zirconia contaminants, the single-digit nanodiamond colloids produced by SAUD have no toxic or difficult-to-remove impurities and are well-suited to produce nanodiamonds for numerous applications including theranostics, composites, and lubrication. Requiring only aqueous salt slurry and standard horn sonicator, and yielding highly pure well-dispersed nanodiamond colloids, the technique is an attractive alternative to current nanodiamond deaggregation protocols and can be easily implemented in any laboratory or scaled up for industrial use.
Modeling mechanical properties of MXenes
MXenes is the large familiy of novel 2D early transition metal carbides/nitrides. DFT modeling predicts a high Young’s modulus (500-700 GPa) for 2D titanium carbides: Tin+1Cn. This makes them promising materials for membranes, microelectromechanical systems (MEMS) or as reinforcement in composites. In V. N. Borysiuk, V. N. Mochalin, Y. Gogotsi Molecular dynamic study of the mechanical properties of two-dimensional titanium carbides Tin+1Cn (MXenes), Nanotechnology, 26 (26), 265705 (10pp) (2015) mechanical behavior of Tin+1Cn monolayers with n=1,2,3 is modeled in tension using large-scale classical molecular dynamics. All obtained strain-stress curves have a similar shape. They have an initial linear region related to elastic deformation and a threshold point of a yield stress. This is followed by a sharp drop associated with sample fracture. Calculations show that mechanical properties and evolution of the atomic structure of 2D carbides under tensile loading depend on the number of atomic layers.
Scrolling of graphene
Graphene nanoscrolls are formed by sonication of graphene sheets dispersed in solvents such as ethanol (see, for example, L. M. Viculis, J. J. Mack, R. B. Kaner A Chemical Route to Carbon Nanoscrolls, Science, 299 (5611), p.1361 (2003); M. V. Savoskin, V. N. Mochalin, A. P. Yaroshenko, N. I. Lazareva, T. E. Konstantinova, I. V. Barsukov, Y. G. Prokofiev Carbon Nanoscrolls Produced from Acceptor-type Graphite Intercalation Compounds, Carbon, 45 (14), p.2797-2800 (2007)). This molecular dynamics model reveals the intimate details of the nanoscroll formation. Graphene nanoscrolls may find applications in gas storage systems, electrochemical batteries, and supercapacitors.
Graphitization of nanodiamond
Thermal stability and temperature-induced transformations of nanodiamond clusters is an area of intense research (see, for example, V. N. Mochalin, O. Shenderova, D. Ho, Y. Gogotsi The Properties and Applications of Nanodiamonds (Review), Nature Nanotechnology, 7 (1), p.11-23 (2012); P. Ganesh, P. R. C. Kent, V. Mochalin Formation, Characterization and Dynamics of Onion-like Carbon Structures for Electrical Energy Storage from Nanodiamonds Using Reactive Force Fields, Journal of Applied Physics, 110 (7), 073506 (2011)). This ReaxFF molecular dynamics simulation shows progressive graphitization, melting, and evaporation of 2 nm diameter diamond cluster upon heating to 5000 K in vacuum. The numbers in the video show frame number, simulation time (ps), and temperature (K).