Synthesis and Characterization of CeO2 Nanoparticles via Solution Combustion Method for Photocatalytic and Antibacterial Activity Studies

Abstract

CeO2 nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO2 nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450 °C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO2 having crystallite size of 35 nm. The infrared spectrum shows a strong band below 700 cm(-1) due to the Ce-O-Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302 nm. The photoluminescence spectrum shows characteristic peaks of CeO2 nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42 nm. CeO2 nanoparticles exhibit photocatalytic activity against trypan blue at pH 10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO2 nanoparticles also reduce Cr(VI) to Cr(III) and show antibacterial activity against Pseudomonas aeruginosa.

Keywords: antibacterial; cerium oxide; nanoparticles; photocatalysis; solution combustion.

Figure 1

Characterization of CeO₂ nanoparticles prepared via solution combustion method. a)  Powder XRD pattern; b)  FTIR spectrum; c) UV/Vis spectrum; d) Phospholuminescence (PL) spectrum.

Figure 2

Microscopy images of CeO₂ nanoparticles prepared via solution combustion method. a) SEM image (Scale bar: 20 μm); b) SEM image (Scale bar: 10 μm.); c) TEM image.

Figure 3

N₂ gas adsorption–desorption isotherm of CeO₂ nanoparticles. Figure insert: pore diameter of CeO₂ nanoparticles prepared via solution combustion method.

Figure 4

Effect of a) dye concentration, b)  catalytic load, c)  pH, and d) light source on the photocatalytic activity of CeO₂ nanoparticles.

Figure 5

Effect of recyclability of CeO₂ on photocatalytic activity.

Figure 6

Comparison of the photocatalytic degradation of trypan blue by CeO₂ nanoparticles and bulk CeO₂.

Figure 7

Kinetics of the photocatalytic degradation of trypan blue by CeO₂ nanoparticles.

Figure 8

Photochemical reduction of Cr^VI to Cr^III using CeO₂ nanoparticles.

Figure 9

Phospholuminescence (PL) spectra for the detection of hydroxyl radicals.

Figure 10

Antibacterial activity of CeO₂ nanoparticles using the agar well diffusion method. A) P. aeruginosa with CeO₂ (500, 750, and 1000 μg per 50 μL in well), s: Ciprofloxacin (standard, positive control), c: water (negative control); B) S. aureus with CeO₂ (500, 750, and 1000 μg per 50 μL in well).

Figure 11

Antibacterial activity of CeO₂ nanoparticles using the broth dilution method. P. aeruginosa treated with A)  water (negative control); B) Ciprofloxacin (positive control); C) 200 μg mL⁻¹ CeO₂; D)  400 μg mL⁻¹ CeO₂ nanoparticles.

Scheme 1

Conversion of disodium salt of EDTA to pure EDTA.