Electro- and photo-catalytic performance of sono-assisted biogenicgold nanoparticles towards industrial contaminant: malachite green

The present study demonstrates a facile and rapid method for green synthesis of gold nanoparticles (AuNPs). This method
utilizes an unreported Citrus grandis peel extract as an eco-friendly reducing and stabilizing agent in a sonocatalysis
process under the influence of ultrasonics waves (40 kHz at 50 W). The sono-assisted synthesis of AuNPs took only
5 min at 37 °C. The formation of AuNPs was confirmed by surface plasmon resonance (SPR) band located at 561 nm
and the morphology, crystallinity, purity, and stability were characterized by FESEM, TEM, XRD, EDX and zeta potential
analysis. The as-synthesized AuNPs was then investigated for the electrocatalysis and photocatalysis against an industrial
contaminant malachite green (MG). DPV analysis of AuNPs modified glassy carbon electrode (AuNPs/GCE) shows a
moderate dynamic range over 1 to 40 µM for MG with a limit of detection (LoD) of 298 nM and a sensitivity of 0.373
µA µM−1 cm−2. Further, AuNPs as a heterogeneous catalyst exhibits a photocatalytic reduction of MG in the presence of
NaBH4. The reduction of MG follows first-order kinetic model with an estimated apparent reduction rate of 4.51×10−2
min−1. This result highlights the potential use of green synthesized AuNPs in wastewater management.