Iron‐Doped NiCo₂O₄ Nanoparticles: Synthesis via Homogeneous Precipitation Method and Studies on their Peroxidase‐like Activity

Abstract

The present study reports the synthesis of iron-doped NiCo 2 O 4 nanoparticles (Ni 1À x Fe x Co 2 O 4 ) using homogeneous precipitation method followed by calcination. The precursors (NiÀ Co layered double hydroxides) and iron-doped NiCo 2 O 4 nanoparticles were characterized using various analytical techniques. XRD results indicate formation of iron-doped NiCo 2 O 4 nanoparticles up to x = 0.5 and when x � 0.7, there is also formation of α-Fe 2 O 3 . TEM images show formation of nanorods composed of nanoparticles in the iron-doped NiCo 2 O 4 nanoparticles. DRS results demonstrate change in optical properties upon doping of iron in the NiCo 2 O 4 nanoparticles. MÀ H measurements show soft ferromag-netic behavior of pure and iron-doped NiCo 2 O 4 nanoparticles at 300 K. At 5 K, soft ferromagnetic behavior is observed up to x = 0.3 in Ni 1À x Fe x Co 2 O 4 nanoparticles, and when x = 0.7, strong ferromagnetic behavior is observed. When x = 0.5, "wasp-waist" behavior is observed. The ZFC-FC measurements show single blocking temperature up to x = 0.3 while two blocking temperatures are observed when x = 0.5. When x = 0.7, the blocking temperature is above room temperature. After characterization, the peroxidase-like activity using iron-doped NiCo 2 O 4 nanoparticles as catalyst was investigated using oxidation of 3,3',5,5'tetramethyl benzidine as substrate.