Synthesis and characterization of iron nanoparticles using banana peels extracts and their application in aptasensor

Abstract

Bio-inspired Iron nanoparticles were successfully synthesized by reduction of ferric chloride solution using aqueous solution of banana peel extract (BPE). The method was non-lethal, simple, eco-accommodating and relatively inexpensive. The resulting iron nanoparticles were characterized by physical colour changes, Fourier-transform infrared (FTIR) spectroscopy, UV-Vis spectroscopy, transmission electron microscopy (TEM), Energy Dispersive X-Ray (EDX), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The reaction mixture of aqueous ferric chloride and BPE displayed observable colours confirming the synthesis of Iron nanoparticles. UV–Vis spectra showing an absorption band at 276nm characteristic of the iron nanoparticles in deed revealed the presence of nanoparticles. Images of the biosynthesized Iron nanoparticles at different magnifications from SEM showed that the particles were round in shape with smooth surfaces. The TEM images revealed the nanoparticles were granular in nature with sizes in the range of 20-50 nm. EDX had strong iron signals at 182, 215, 424 and 458 energies, thus confirming the synthesis of Iron nanoparticles. X-ray diffraction investigations of the BPE synthesized Iron nanoparticles revealed that the nanoparticles were amorphous in nature with crystal planes at (110), (200) and (112) characteristic for iron nanoparticles. Fourier transform infrared (FTIR) spectroscopy showed the contribution of phenols, nitriles and carboxylic groups in the synthesis procedure. An aptasensor was developed using cyclic voltammetry as a transducer for the detection of microcystin-LR (MC-LR) by immobilizing MC-LR targeting aptamers onto electro-deposited polyaniline (PANI) doped with synthesised iron nanoparticles (FeNPs). Aptamer microcystin binding event was monitored and recorded by cyclic voltammetry. The linear range (LR) and the limit of detection (LOD) of the aptasensor were from 0.2 – 1 μgL-1 and 0.06 μmolL-1 respectively. The World Health Organization (WHO) has set a concentration limit of 1μmol L-1 for MC-LR in drinking water while the method developed in this work could easily detect MC-LR with good sensitivity and linearity down to the nanomolar range.