Purification and Tailored Functionalities in Detonation Nanodiamond

Abstract

Nanodiamonds (NDs) offer immense potential in various fields, but graphitic or metal-based impurities hinder their widespread adoption. Conventional purification methods often employ harsh chemicals or high temperatures, raising concerns about ND integrity and surface properties. Herein, we compared various strategies to purify and tailor the surface functional groups in the detonation-derived nanodiamonds. A facile two-step purification strategy combining salt-assisted air oxidation (SAAO) and Fenton chemistry is particularly interesting for efficient and selective removal of graphitic impurities while preserving the diamond lattice structure. SAAO selectively burns off graphitic impurities at 450 °C under controlled oxygen flow, minimizing damage to the diamond core. Subsequently, Fenton's reagent (H2O2/Fe2+) introduces hydrophilic functional groups onto the ND surface, further enhancing diamond purity and promoting subsequent functionalization. This synergistic approach enables i) highly efficient removal of graphitic impurities while preserving ND morphology and crystal structure, ii) controlled introduction of surface functionalities, and iii) improved colloidal stability of purified NDs. This green and efficient purification protocol is beneficial for tailoring ND properties and unlocking their full potential in diverse applications ranging from biomedicine and electronics to catalysis and quantum technologies.