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Appropriate salt concentration of nanodiamond colloids for electrostatic self-assembly seeding of mono-sized individual diamond nanoparticles on silicon dioxide surfaces Taro Yoshikawa, Verena Zuerbig, Fang Gao, René Hoffmann, Christoph E. Nebel, Oliver Ambacher, and Vadim Lebedev Langmuir, Just Accepted Manuscript • Publication Date (Web): 03 May 2015 Downloaded from http://pubs.acs.org on May 4, 2015
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Langmuir
Appropriate salt concentration of nanodiamond colloids for electrostatic self-assembly seeding of mono-sized individual diamond nanoparticles on silicon dioxide surfaces
Taro Yoshikawa*,1,2, Verena Zuerbig1, Fang Gao1, René Hoffmann1, Christoph E. Nebel1, Oliver Ambacher1,2, and Vadim Lebedev1 1
Fraunhofer Institute for Applied Solid State Physics, Tullastraße 72, 79108, Freiburg, Germany
2
Department of Microsystems Engineering - IMTEK, University of Freiburg, Georges-KöhlerAllee 103, 79110 Freiburg, Germany
KEYWORDS Diamond nanoparticles; Electrostatic self-assembly; Seeding; DLVO theory; Nanocrystalline diamond growth
ABSTRACT
Mono-sized (~4 nm) diamond nanoparticles arranged on substrate surfaces are exciting candidates for single photon sources and nucleation sites for ultra-thin 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
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different substrate materials such as Si, SiO2, Cu, and AlN. However, the self-assembled nanoparticles tend to form small (typically a few tens of nanometer or even larger) aggregations on any 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 insert electrolyte and examined for the 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 based on the Derjaguin-LandauVerwey-Overbeek (DLVO) theory. From these investigations, it became clear that the appropriate salt concentration suppresses the formation of small aggregations during the seeding process owing to the modified electrostatic repulsive interaction between nanoparticles. Finally, mono-sized (
