Homogeneous catalytic activity of gold nanoparticles synthesized using turnip (Brassica rapa L.) leaf extract in the reductive degradation of cationic azo dye

초록

A new greener strategy for the synthesis and stabilization of gold nanoparticles using aqueous turnip leaf extract under ambient conditions is reported in this study. The formation of gold nanoparticles was monitored using a UV-Vis spectrophotometer and the maximum absorption peak (λ max) at 535 nm with a visual color change to pinkish-red confirmed the gold nanoparticles. Further characterization was conducted using Fourier-transform Infra-red spectrometry (FT-IR), powder X-ray diffractometry (XRD), transmission electron microscopy (TEM), and dynamic light scattering (DLS) with zeta potential at pH 7.5. The stability of the nanoparticles was due to the capping of nanoparticles with amine groups and ortho-substituted aromatic phytoconstituents, which exhibit higher negative values of zeta potential (ζ). XRD pattern revealed the formation of face-centered cubic (fcc) lattice crystals of gold nanoparticles, while TEM have demonstrated the size of gold nanoparticles ranging from 3 to 58 nm. The as-synthesized gold nanoparticles showed rapid catalytic reduction of methylene blue (MB) dye to leuco MB in the presence of sodium borohydride (NaBH4). The reduction reaction followed pseudo-first order kinetics with a reaction rate constant of 0.372 min−1. This process of nanoparticle synthesis is simple, nontoxic and environmentally benign compared to the chemical synthetic routes.

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