Bio-directed synthesis of gold nanoparticles using Ananas comosus aqueous leaf extract and their photocatalytic activity for LDPE degradation

Abstract

A bio-directed synthesis of gold nanoparticles (Au NPs) was developed via the reduction of hydrogen tetrachloroaurate (III) (HAuCl4·3H2O) solution by the aqueous leaf extract of Ananas comosus. The polyphenol stabilized Au NPs were characterized by UV–visible, Fourier transform infrared (FTIR), powder X-ray diffraction (PXRD)/selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDX) analyses. The HRTEM images revealed that Au NPs were well dispersed with spherical structures. The size ranges from 7.39 to 32.09 nm with average particle size of 18.85 ± 6.74 nm. The peaks of XRD analysis at (2θ) 37.96°, 44.06°, 64.54°, 77.50° and 81.73° were respectively assigned to (111), (200), (220), (311) and (222) planes of the face-centered cubic (fcc) lattice of gold. The photocatalytic potential of Au NPs was studied through the solid-phase degradation of low-density polyethylene (LDPE) film. The photoinduced degradation of LDPE@Au nanocomposite film was higher than that of the pure LDPE film. The weight loss of LDPE@Au (1.0 wt%) nanocomposite film steadily increased and reached 51.4 ± 4.8% in 240 h under solar light irradiation, compared to the photo-induced LDPE with only 8.6 ± 0.7%. However, LDPE film with 1.0% Au NPs gave a weight loss value of 4.72 ± 0.71 under the dark condition at the end of 240 h. Thus, LDPE film with 1.0% Au NPs showed a degradation efficiency of 90.8% under solar irradiation after 240 h. The sustainability of the nanoparticles was confirmed through reusability in the photocatalytic degradation reaction up to five consecutive cycles without substantial loss in its catalytic performance.