Fagonia arabica extract-stabilized gold nanoparticles as a highly selective colorimetric nanoprobe for Cd2+ detection and as a potential photocatalytic and antibacterial agent

In the current study, polar leaves extract of the plant Fagonia arabica (FALE) from the Zygophyllaceae family was used to synthesize sunlight-assisted gold nanoparticles (FALE@AuNPs) with defined size and shape and of excellent colloidal stability. The effect of different physiochemical parameters (FALE dosage, Au3+ ions concentration, sunlight exposure time) on the formation of AuNPs was also studied. The synthesized FALE@AuNPs were characterized using UV-visible spectrophotometry, scanning electron microscopy-energy dispersive X-rays (SEM-EDX), Fourier-transform infrared spectroscopy (FTIR), powder XRD, zeta potential (ZP) and dynamic light scattering (DLS). The successful synthesis of FALE@AuNPs in solution was confirmed by the appearance of a localized surface plasmon resonance (LSPR) characteristic peak at 535 nm in UV-Vis spectra. The size estimated by UV-Vis (∼59 nm) was found in good agreement with that determined by SEM (∼60 nm) and DLS (∼61 nm). A zeta potential value of -28±1.5 mV confirms the colloidal stability of FALE@AuNPs. The FALE@AuNPs were utilized as a colorimetric nano-sensor for Cd2+ ion 15 nM limit of detection (LOD) and linear range detection of 0-600 nM. When utilized to identify Cd2+ ion in actual water samples, the nano-probe demonstrated high recovery rates of over 98% and a low relative standard deviation (RSD) of about 4%, demonstrating its dependability and efficiency in doing so. FALE@AuNPs were found to be antibacterial against gram-positive as well as gram-negative bacteria. An exceptionally high photocatalytic activity was shown by FALE@AuNPs with 80% efficiency of degradation examined against methylene blue and methyl orange dye.