Green synthesized Zn-based mono and bi-metallic nanoparticles for improved micronutrient delivery: A futuristic study...

Hydroponic farming is gaining importance due to the rapid expansion of cities worldwide. However, the significance of nano-enabled nutrient delivery in hydroponic crop culture is still poorly understood. Therefore, ZnO monometallic and Zn-Cu bimetallic nanoparticles (MNP and BNP) were innovatively synthesized through green routes using alcoholic leaf extract (ALE) 1-10 % (w/v) of Chrysalidocarpus lutescens due to its enriched phytochemical profile, prolific radical scavenging efficiency, and reasonably high IC50 values. The structural uniformity and batch-wise yield of MNP and BNP were optimized following response surface methodology. The uniqueness of C. lutescens-derived phytochemicals facilitated the production of anisotropic and crystalline MNP and BNP. It was revealed that structural uniformity and yields were most significant at pH 9 with 3 % ALE for both MNP (Yield/batch -20.54 ± 0.15 g) and BNP (Yield/batch - 18.37 ± 0.30 g). Both nanoparticles were hexagonal 30-85 nm nanocrystals, stable at alkaline pH (∼9) with uniform pore volume, surface area, and surface charge. The hydroponic compatibility of the MNP and BNP were compared with non-nanoscale Zn and Cu by cultivating Cicer arietinum with different doses of MNP, BNP, and other treatments. Among all doses, 250 and 500 mg L^-1 doses of MNP and BNP significantly augmented C. arietinum germination by ∼40-45 % and plumule growth by ∼18-22 % and enhanced chlorophyll stability while reducing oxidative stress in the seedlings. The MNP and BNP were ecologically safe for microorganisms (Rhizobium sp. and Salmonella typhi) and were viable within 250 mg L^-1 to 2000 mg L^-1 of MNP and BNP doses. Overall, the study reveals that the green synthetic routes using C. lutescens phytoextract led to significant yield of productive, biocompatible, and organically rich Zn and Cu-based MNP and BNP that can be easily pursued and sustainably applied in hydroponics or other agriculture platforms.