Interaction of Carboxyl Groups with Rare Metal Ions on the Surface of Detonation Nanodiamonds

This paper reports on the grafting of rare‐earth metal ions onto particles of 4–5 nm carboxylated detonation nanodiamond (DND‐COOH). Aqueous solutions of acetates and nitrates (Ln(OOCCH₃)₃·4H₂O or Ln(NO₃)₃·6H₂O, Ln = Eu, Gd) were used for the grafting. The ion exchange reaction between rare metal ions and protons of surface carboxyl groups was first detected by conductometry and electrokinetic potential measurements. The equivalence point corresponds to the bond between Ln³⁺ and the three carboxylate anions of DND‐COOH. Thus, we have demonstrated an easy synthetic approach for obtaining nanodiamond particles DND‐COOH with surface grafted with a controlled amount of any rare‐earth metal ions (DND‐COO‐ {Ln}, Ln = Ce, Pr, Sm, Eu, Gd, Dy, Ho, Tm). The resulting hybrid material DND‐COO‐{Eu} exhibits photoluminescence properties arising from f‐f transitions of Eu³⁺ ion.