2, Adamas Nanotechnologies, Raleigh, North Carolina, United States
3, NanoCarbon Research Institute, Ueda, , Japan
4, CSIRO, Melbourne, Victoria, Australia
Detonation nanodiamond (DND), diamond nanoparticles of size ranging 3-5nm, synthesized through detonation process, has recently demonstrated many exciting applications. It's small size, non-toxic and biocompatibility has drawn huge interests, particularly in the biomedical field. In order to capitalize the large total surface areas afforded by the small particle size, dispersing DND have been one of the endeavour for the better utilizing of DND for its applications.
DND has strong tendency to aggregate and form robust superstructures on the order of ~100 nm. Theoretical calculations have shown that such aggregation is due to both coherent (CICI) as well as incoherent (IICI) interfacial columbic interactions. The previous interaction should produce ordered configuration whereas the latter random aggregates.
Here we unambiguously demonstrate that DND in water, without any surface modifications, exhibits striking lacy network, formed by self-assembled chain-like superstructures. This was carried out by cryo-TEM imaging of cryo-plunged DND suspension samples. The cryo-plunge method immobilizes DND in water through rapid freezing of DND suspensions. Our analysis shows that the superstructure morphology has strong size and particle shape dependence. First principle calculations reveal that the origin of the superstructure formation is due to the electrostatic potential interaction from specific paring of surface facets of DNDs.
To further understand the relation of surface chemistry to the self-assemble behaviour, we have conducted further experiments using surface modified, hydrogenated and carboxylated DNDs. We found that surface chemistry has significant influence to the assembly as the sizes of the superstructures differ among the untreated, and surface modified DND.