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PP5.03 - On the Possibility of Intercalation under the Graphitic Surface of Primary Particles of Detonation Nanodiamond (PPDND) 
April 23, 2014   2:15pm - 2:30pm

When small particles of detonation nanodiamond (DND) with 4-5 nm in diameter were found dissolved in water in 2005, we were much surprised and sought to explain the unlikely phenomenon in terms of the surface interaction with water. Korobov first presented evidence for particularly strong hydration with the surface of disintegrated DND by observing an endothermic peak at -8 degrees centigrade by DSC. In the same year Barnard found strong negative Mulliken charges mainly on the spontaneously graphitized {111} facets, which should provide a good proton-accepting sites for H-bonding with water molecules.Then there arose two pieces of inconsistencies against the OH…e solvation theory. One difficulty is to assign continuously polarized hydration layer near the surface to a single and separate DSC endothermic peak. The other is good performance of our DDS experiments using DND as the drug carrier. Bonding between doxorubicin drug molecule and carrier particle has been considered similarly Coulombic N+…e, where N+ represents hydrochloride of primary amino group in the drug molecule. However, no side effect by the notorious drug was ever observed, which would be unlikely if the drug molecules were carried through polar blood while simply bound by electrostatic force to the surface of DND.Our recent success in isolating, producing and characterizing the true primary particles of DND, 3.0±0.6 nm in diameter (PPDND) , allowed us to straighten the confusion on the surface structure and its interactions. Larger DND particles used in the earlier stages of our work proved to have been mixtures of oligomers with the primary particles having large particle-size distribution with standard deviation of about 6nm. Thus, we are now ready to solve a number of pending problems.As a part of our study directed towards straightening the long confusion in the research of DND, here we propose that intercalation in the space created by graphitization of one (or two) layers of carbon atoms on the {111} facets of PPDND, takes place with solvent and solute molecules through holes created in the graphitic surface. The existence of holes for intercalation has not been proved by experimental approaches but geometry optimization of real-size models of PPDND provides supporting evidence. The intercalation hypothesis well explains new DSC results of PPDND and also fits the DDS performace. On the other hand, diffuse hydration layer on the surface must be responsible for dissolution of PPDND in water. It is also suggested that black color of aqueous colloid is caused by the layer of intercalated water beneath the graphene (oxide) surface.

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