Colloidal suspensions of monodisperse diamond core-shells

Abstract

We report on an innovative method to synthesize monodispersed diamond core-shells stable in colloidal aqueous suspensions. Starting with an electrostatic seeding of silica particles by detonation nanodiamonds, carefully driven in terms of charge and proportion, we are able to initiate the growth of a carbon coating all around the seeded silica particles in a plasma MPCVD reactor dedicated to powder treatments. The crystalline structure of the carbon coating can be tuned by changing the MPCVD conditions: from nanocrystalline diamond for low methane content to graphite nanoflakes for high methane content. These materials are characterized by FE-SEM, HR-TEM, FTIR and Raman spectroscopy. Preliminary photoluminescence (PL) data are also provided. A chemical post-treatment of the core-shell particles is applied to obtain colloidal stability in neutral aqueous suspensions. The monodispersity and the colloidal stability are assessed using DLS and Zeta measurements. After the removal of the silica core, stable suspensions of diamond hollow spheres are obtained. This new class of diamond-based material may find promising applications in various fields, such as nanomedicine toward a versatile nanotool for drug delivery or biolabeling, catalysis thanks to its controllable porosity and carbon surface chemistry or photonics as an elemental block toward bottom-up ordered diamond structures.