“Click” dendrimer-Pd nanoparticle assemblies as enzyme mimics: catalytic o-phenylenediamine oxidation and application in colorimetric H2O2 detection

Abstract

Dendrimers have already been successfully used in nanoparticle (NP) catalysis for many years, particularly for Pd NP protection towards carbon–carbon coupling reactions. In this paper, assemblies between Pd nanoparticles and two generations of “click” dendrimers, with 27 (dendrimer-1) and 81 (dendrimer-2) triethylene glycol (TEG) termini, respectively, are examined for catalytic peroxidase-like oxidative activity. This catalysis is investigated with o-phenylenediamine (OPD) and H₂O₂ as the substrates in water, displaying different colours. The dendritic effect is negative upon increasing generation, i.e., dendrimer 1-Pd nanoparticles show the best results, providing values with a V_max of 1.49 × 10⁻⁹ M s⁻¹ and K_m of 3.02 mM as obtained with the Michaelis–Menten model. The detection limit is 0.5 μM of H₂O₂ detection with dendrimer-1-PdNPs, and both dendrimer-Pd nanocatalysts exhibit excellent robustness of catalytic activity, with a water-dispersive state being stable for at least 2 months, thus showing promise as a mimic for peroxidase catalysts.