Catalytic degradation of organic dyes using Allium paradoxum extract mediated gold nanoparticles

This study investigated a simple, facile, eco-friendly, and cost-effective method for synthesizing gold nanoparticles using Allium paradoxum (A. paradoxum) extract (AP@AuNPs). The “X-ray diffraction analysis” analysis showed the face-centered cubic structure of the synthesized AP@AuNPs. The “energy dispersive X-ray” profile confirmed that the highest elementary composition was gold. “Field emission scanning electron microscopy” and “Transmission electron microscopy” images presented a spherical shape, and the histogram obtained from the SEM image exhibited an average size of 26.2 nm for AP@AuNPs. “Fourier transform infrared spectroscopy” spectrum indicated various functional groups involved in the reduction and capping of the prepared AP@AuNPs. The “thermogravimetry differential thermal analysis” curve of AP@AuNPs showed about 21% weight loss at about 200–500 ºC, indicating desorption of related capping biomolecules on the surface of AP@AuNPs. The catalytic investigation of the prepared AP@AuNPs to reduce Methyl orange, Methylene blue, and 4-Nitrophenol evidently showed that the addition of a catalytic amount of AP@AuNPs to NaBH₄ solution increased the dye degradation rate. The reduction reaction was determined by following pseudo-first-order kinetics with various concentrations of AuNPs. In addition, AP@AuNPs (550 µg/ml) at 10, 20, and 40 µl presented rate constants of 0.2032, 0.2513, and 0.3685 min⁻¹ for the reduction of MO, at 10, 20, and 30 µl, rate constants were 0.0549, 0.1756, and 0.5028 min⁻¹ for MB, and finally at 5 and 10 µl showed the rate constants of 0.1266 and 0.3919 min⁻¹ for 4-NP.