Multifunctional iron oxide nanoparticles using Carica papaya fruit extract as antibacterial, antioxidant and photocatalytic agent to remove industrial dyes

Abstract

• C. papaya fruit extract-based Fe 2 O 3 NPs were synthesized and characterized. • Fe 2 O 3 NPs have shown significant antibacterial effects on Gram-negative bacteria. • Fe 2 O 3 NPs have shown H 2 O 2 radical scavenging activity. • Fe 2 O 3 NPs efficiently degraded the toxic methyl orange (MO) dye. In this work, C. papaya fruit extract coated Fe 2 O 3 NPs were green synthesized and bio-physically characterized by UV–visible spectroscopy (UV–vis), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX) techniques. In UV–vis spectroscopy, the absorbance spectra of Fe 2 O 3 NPs were recorded at 300–700 nm. A strong absorbance peak was noticed at 346 nm. XRD was employed to determine the crystalline form of NPs using powdered X-ray diffractometer. XRD reflected the pure crystalline form of NPs and the crystallite size measured 7.8 nm. The presence of various functional chemical groups in the reduction process was observed by FTIR spectroscopy from 4000 to 400 cm −1 . SEM and EDX of Fe 2 O 3 NPs were performed using Hitachi S-4500 (Germany). SEM analysis revealed the presence of agglomerated NPs. The mean size of Fe 2 O 3 NPs was 23.7 nm. The presence of elemental Fe was 51.06 % and O was 28.97 % as recorded in EDX analysis. The antibacterial effects of Fe 2 O 3 NPs were evaluated against Gram-positive ( B. subtilis and S. pyogenes ) and Gram-negative ( P. aeruginosa and E. coli ) bacteria by agar well diffusion method. Dimethyl sulfoxide (DMSO) was used as negative control while tetracycline was used as positive control. Fe 2 O 3 NPs have significantly inhibited Gram-negative bacteria. The inhibition of E. coli was 20.2 mm at 100 μg mL −1 . The inhibition was 17.5 mm at 100 μg mL −1 for P. aeruginosa . Fe 2 O 3 NPs exhibited radical scavenging activity against hydrogen peroxide (H 2 O 2 ). The percentage scavenging of H 2 O 2 was enhanced to 90 % at 100 μg mL −1 . Moreover, the as synthesized Fe 2 O 3 NPs at 1 mM concentration efficiently degraded methyl orange (MO) dye and was noticed by the reduction in the absorbance peak at 375 nm within 4 h of reaction compared to 0.5 mM Fe 2 O 3 NPs. The results suggested that the synthesized Fe 2 O 3 NPs could be used to treat microbial infections and oxidative damage. Further, Fe 2 O 3 NPs may be used as a better biocatalyst for the removal of harmful industrial dyes from the environment.