Surface functionalization of nanodiamond with phenylphosphonate

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Nanodiamonds (NDs) possess unique properties but often require surface functionalization for specific applications.
• Oxidized nanodiamond (OND) and carboxylated nanodiamond (CND) offer reactive sites for surface modification.

Purpose of the Study:

• To explore the arylation of OND and CND with phenylphosphonate (PPA) to create PPA-grafted nanodiamond (PPA@ND).
• To investigate the influence of reaction conditions on PPA grafting efficiency and mode.
• To evaluate the impact of PPA functionalization on nanodiamond properties, including thermal stability and dispersibility.

Main Methods:

• Grafting of PPA onto OND and CND surfaces.
• Characterization using 31P MAS NMR, FTIR, XPS, and TGA.
• Evaluation of dispersibility in organic solvents using dynamic light scattering.

Main Results:

• Successful grafting of PPA onto both OND and CND was confirmed, with evidence of primarily bidentate grafting.
• PPA grafting on OND was independent of reactant ratio, heat, or sonication, while grafting on CND was significantly lower.
• Grafted PPA enhanced the thermal stability of both OND and CND.
• PPA functionalization rendered OND surfaces hydrophobic, preventing dispersion in water.
• Sonication was crucial for achieving good dispersion of PPA@OND in organic solvents like DMF and toluene.

Conclusions:

• Phenylphosphonate can be effectively grafted onto oxidized and carboxylated nanodiamonds.
• PPA functionalization improves thermal stability and modifies surface hydrophilicity/hydrophobicity.
• Optimized grafting conditions, including sonication, are essential for achieving desired dispersibility in organic solvents.