Appropriate Salt Concentration of Nanodiamond Colloids for Electrostatic Self-Assembly Seeding of Monosized Individual Diamond Nanoparticles on Silicon Dioxide Surfaces

Abstract

Monosized (∼4 nm) diamond nanoparticles arranged on substrate surfaces are exciting candidates for single-photon sources and nucleation sites for ultrathin nanocrystalline diamond film growth. The most commonly used technique to obtain substrate-supported diamond nanoparticles is electrostatic self-assembly seeding using nanodiamond colloidal suspensions. Currently, monodisperse nanodiamond colloids, which have a narrow distribution of particle sizes centering on the core particle size (∼4 nm), are available for the seeding technique on different substrate materials such as Si, SiO2, Cu, and AlN. However, the self-assembled nanoparticles tend to form small (typically a few tens of nanometers or even larger) aggregates on all of those substrate materials. In this study, this major weakness of self-assembled diamond nanoparticles was solved by modifying the salt concentration of nanodiamond colloidal suspensions. Several salt concentrations of colloidal suspensions were prepared using potassium chloride as an inserted electrolyte and were examined with respect to seeding on SiO2 surfaces. The colloidal suspensions and the seeded surfaces were characterized by dynamic light scattering and atomic force microscopy, respectively. Also, the interaction energies between diamond nanoparticles in each of the examined colloidal suspensions were compared on the basis of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. From these investigations, it became clear that the appropriate salt concentration suppresses the formation of small aggregates during the seeding process owing to the modified electrostatic repulsive interaction between nanoparticles. Finally, monosized (<10 nm) individual diamond nanoparticles arranged on SiO2 surfaces have been successfully obtained.

Nanodiamond arrays on glass for quantification and fluorescence characterisation

“…Recently published work 41 suggests an optimal nanodiamond solution concentration to minimise agglomeration. Other researchers 47 have demonstrated ways to prevent agglomeration of nanodiamonds in solution and control their zeta potential, but they add 4/10 degrees of complexity such as chemical processing and additive surface modification.…”

Hydroxylation and self-assembly of colloidal hydrogenated nanodiamonds by aqueous oxygen radicals from atmospheric pressure plasma jet

“…Another aim in modifying the surface of NDs' is to tune their physico-chemical properties, like the surface potential or hydrophilicity/hydrophobicity. Such a tuning might, for instance, control the NDs' aggregation, 6 electrostatically-driven attachment to various substrates [7][8][9] or efficiency of lling the composites. 10,11 A plasma chemical approach as a surface chemistry modication tool brings several benets over other more conventional methods represented by wet chemistry or thermal treatments.…”

“…The DLS mean size around 3 nm has been indeed reported several times for hydrogenated DNDs. 6,7,48 Although the exact origin of this discrepancy remains unclear, several important factors can be still discussed. First, this is an effect of ND hydration shell which is involved in the measured DLS size.…”

Enhanced Diamond Nucleation on Cemented Carbide Cutting Tools by Employing Electrostatic Self-Assembly Seeding

“…The measured size value is larger than 5 nm (producer's value), which we ascribe to agglomeration of ND in suspensions. [21,22]. Fig.…”