Mentha piperita-mediated synthesis of cobalt aluminate nanoparticles and their photocatalytic activity

Abstract

This paper introduces for the first time the preparation of cobalt aluminate (CoAl2O4) nanoparticles through a solution combustion method using a Mentha piperita leaves extract. The active constituents present in the mentha leaves extract act as both a chelating and a reducing agent. The isolated precursor was characterized by FTIR, UV–Vis, thermal analysis and XPS. Various techniques (XRD, SEM and TEM, XPS, FTIR and UV–Vis) were also used to characterize the cobalt aluminate spinel from the point of view of structure, morphology and surface chemistry. XRD confirmed the formation of a single-phase, crystalline cubic spinel structure with mean crystalline domain size of 19.5 nm. The TEM analysis showed rhombic and rectangular CoAl2O4 nanoparticles with unimodal particle size distribution and average particle size of about 35 nm. The characteristic peaks of the CoAl2O4 spinel were highlighted by the FTIR spectrum. The tetrahedral configuration of Co2+ ions in the CoAl2O4 spinel structure was illustrated by the absorbance and XPS spectra. Furthermore, XPS spectra reveal both tetrahedral and octahedral configurations of Al3+ ions. To evaluate the catalytic properties of the cobalt aluminate, the photocatalytic degradation of methylene blue (MB) was carried out under visible light irradiation.