Biogenic gold nanoparticles for reduction of 4‐nitrophenol to 4‐aminophenol: an eco‐friendly bioremediation

The present study investigated the synthesis of gold nanoparticles (AuNPs) using mangrove plant extract from Avicennia marina as bioreductant for eco‐friendly bioremediation of 4‐nitrophenol (4‐NP). The AuNPs synthesised were confirmed by UV spectrum, transmission electron microscopy (TEM), X‐ray diffraction, Fourier transmission infrared spectroscopy (FTIR), dynamic light scattering (DLS), and zeta potential. The AuNPs were found to be spherical in shape with size ranging from 4 to 13 nm, as evident by TEM and DLS. Further, the AuNPs were encapsulated with sodium alginate in the form of gold nano beads and used as heterogeneous catalyst and degrading agent to reduce 4‐NP. This reduction in 4‐NP into 4‐aminophenol was confirmed by UV and FTIR. The aqueous solution of 4‐NP peaked its absorbance at 320 nm, and shifted to 400 nm, with an intense yellow colour, appeared due to formation of 4‐nitrophenolate ion. After the addition of AuNps, the 4‐NP solution became colourless and peaked at 400 nm and reduced to 290 nm corresponding to the formation of 4‐aminophenol. Hence, the present work suggested the AuNPs as the potent, eco‐friendly bionanocomposite catalyst for bioremediation of 4‐NP.Inspec keywords: gold, nanoparticles, nanobiotechnology, nanofabrication, ultraviolet spectra, transmission electron microscopy, X‐ray diffraction, Fourier transform spectra, infrared spectra, electrokinetic effects, catalysts, nanocomposites, biochemistryOther keywords: biogenic gold nanoparticles, 4‐nitrophenol, 4‐aminophenol, eco‐friendly bioremediation, mangrove plant extract, Avicennia marina, bioreductant, UV spectrum, transmission electron microscopy, TEM, X‐ray diffraction, Fourier transmission infrared spectroscopy, FTIR, dynamic light scattering, DLS, zeta potential, degrading agent, 4‐nitrophenolate, bionanocomposite catalyst, size 4 nm to 13 nm, wavelength 400 nm, wavelength 290 nm, Au