The use of biological agents to synthesize bimetallic nanoparticles (NPs) has gained popularity due to its cost-effectiveness, environmental friendliness, and ease of scaling up without utilization of lot of energy and use of harmful chemicals (Khan et al., 2020; Padilla-Cruz et al., 2021). Plant extract-based NP biosynthesis is more stable and has a higher rate of synthesis than other biological processes. It also doesn't require cell culture care and can be stepped up for large-scale synthesis (Gour et al., 2019). Researchers have recently begun concentrating on the production of bimetallic nanoparticles in order to investigate the potential of two metals for a variety of applications (Sharma et al., 2019). Furthermore, there are only a few recent studies on biological synthesis core and shell bimetallic nanoparticles, from aqueous plant extracts; to name a few Ag–Fe nanoparticles synthesized using Gardenia jasminoides leaf extract (Padilla-Cruz et al., 2021), silver-platinum nanoparticles biogenically synthesized using Schinusmolle L. leaf extract (Mares-Briones et al., 2019) and Au–Ag nanoparticles synthesized using weed Antigonon leptopus which is of no value (Ganaie et al.,2016).
The dye industry's wastewater is the second most dangerous industrial effluent, with around 100 tonnes of dye released each year (Benkhaya et al., 2020). Because of their synthetic origins and intricate structures, dye discoloration is difficult (Mozzoli et al., 2021). Nanoparticles are increasingly being used to treat dye effluents due to their qualities such as greater nano-adsorptive capabilities, faster attainment of equilibrium, and large surface area (Homaeigohar et al., 2020). Adsorption, photocatalytic degradation, and adsorption plus degradation are all mechanisms for hazardous dye elimination by nanoparticles (Alkaykh et al., 2020). Textile effluents are known to have detrimental effects on plants by bioaccumulation/disrupting photosynthesis mechanism in aquatic flora (plants and algae) (Berradi et al., 2019). Since degradative products of dyes can sometimes be much more mutagenic and carcinogenic than the parent compounds, understanding the toxicity of nano-remediated water on plant growth is important (Lellis et al., 2019). Keeping this in view, the study was undertaken to see the effect of dye and nano-remediated dye solution on germination and growth of Vigna radiata.
The current study, thus, focuses on biological plant based synthesis of bimetallic Au-Ag nanoparticles from Ocimum tenuiflorum (Krishna tulsi) leaf extract (OTAuAgNPs). Holy basil, or Ocimum tenuiflorum, is a plant native to the Indian subcontinent that is widely cultivated across the Southeast Asian tropics (Mousaviwt al., 2018). Although it is known to have potential health benefits such as antimicrobial (Yamani et al., 2016), anti-diabetic (Mousaviwt al., 2018), antioxidant and protection of DNA from damage (Sarkar et al.,2014), there are no reports on biosynthesis of bimetallic gold-silver nanoparticles using this plant for the applications of environmental remediation. Synthesized OTAuAgNPs were depicted by UV-Visible spectrophotometry, particle size and zeta sizer, Fourier Transform Infrared Spectroscopy (FT-IR) and X-Ray diffraction (XRD) analysis. This is the first report on CBB adsorption by bimetallic Au-AgNPs produced from Ocimum tenuiflorum, with focus on understanding the kinetics of adsorption and understanding the toxicity of the metabolite (nano-catalyst treated water) on Vigna radiata (green gram) germination and growth.