PNNL

Abstract

Azides on the periphery of nanodiamonds (NDs) are of great utility as they have been shown to undergo Cu-catalyzed and Cu-free cycloaddition reactions with structurally diverse alkynes affording particles tailored for applications in biology and materials science. However, current methods employed to access NDs featuring azide groups typically require either harsh pretreatment procedures or multiple synthetic steps and use surface linking groups that may be susceptible to undesirable cleavage. Here we demonstrate an alternative single-step approach to produce linker-free, azide-functionalized NDs. Our method was first applied to low-cost, detonation derived ND powders where surface carbonyl groups undergo silver-mediated decarboxylation and radical substitution with azide. Azide-terminated NDs were then treated with a variety of aliphatic, aromatic, and fluorescent alkynes to afford 1-(ND)-4-substituted-1,2,3-triazole materials under standard copper catalyzed cycloaddition conditions. Surface modification steps were characterized by characteristic infrared absorptions and elemental analyses. High loadings of triazole surface groups (up to 0.85 mmol g-1) were obtained as determined from thermogravimetric analysis. Decarboxylative azidation was also extended successfully to valuable high-pressure high-temperature (HPHT) fluorescent NDs containing nitrogen-vacancy centers. The azidation procedure disclosed is envisioned to become a valuable initial transformation in numerous future applications of NDs.